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Sample records for voltage transient protection

  1. Surge protective device response to steep front transient in low voltage circuit

    Energy Technology Data Exchange (ETDEWEB)

    Marcuz, J.; Binczak, S.; Bilbault, J.M. [Universite de Bourgogne, Dijon (France)], Emails: jerome.marcuz@ laposte.net, stbinc@u-bourgogne.fr, bilbault@u-bourgogne.fr; Girard, F. [ADEE Electronic, Pont de Pany (France)

    2007-07-01

    Surge propagation on cables of electrical or data lines leads to a major protection problem as the number of equipment based on solid-state circuits or microprocessors increases. Sub-microsecond components of real surge waveform has to be taken into account for a proper protection even in the case of surges caused by indirect lightning effects. The response of a model of transient voltage suppressor diode based surge protection device (SPD) to fast front transient is analytically studied, then compared to simulations, including the lines connected to the SPD and to the protected equipment. (author)

  2. Transient Voltage Recorder

    Science.gov (United States)

    Medelius, Pedro J. (Inventor); Simpson, Howard J. (Inventor)

    2002-01-01

    A voltage transient recorder can detect lightning induced transient voltages. The recorder detects a lightning induced transient voltage and adjusts input amplifiers to accurately record transient voltage magnitudes. The recorder stores voltage data from numerous monitored channels, or devices. The data is time stamped and can be output in real time, or stored for later retrieval. The transient recorder, in one embodiment, includes an analog-to-digital converter and a voltage threshold detector. When an input voltage exceeds a pre-determined voltage threshold, the recorder stores the incoming voltage magnitude and time of arrival. The recorder also determines if its input amplifier circuits clip the incoming signal or if the incoming signal is too low. If the input data is clipped or too low, the recorder adjusts the gain of the amplifier circuits to accurately acquire subsequent components of the lightning induced transients.

  3. Transient voltage sharing in series-coupled high voltage switches

    Directory of Open Access Journals (Sweden)

    Editorial Office

    1992-07-01

    Full Text Available For switching voltages in excess of the maximum blocking voltage of a switching element (for example, thyristor, MOSFET or bipolar transistor such elements are often coupled in series - and additional circuitry has to be provided to ensure equal voltage sharing. Between each such series element and system ground there is a certain parasitic capacitance that may draw a significant current during high-speed voltage transients. The "open" switch is modelled as a ladder network. Analy­sis reveals an exponential progression in the distribution of the applied voltage across the elements. Overstressing thus oc­curs in some of the elements at levels of the total voltage that are significantly below the design value. This difficulty is overcome by grading the voltage sharing circuitry, coupled in parallel with each element, in a prescribed manner, as set out here.

  4. Electrode voltage fall and total voltage of a transient arc

    Science.gov (United States)

    Valensi, F.; Ratovoson, L.; Razafinimanana, M.; Masquère, M.; Freton, P.; Gleizes, A.

    2016-06-01

    This paper deals with an experimental study of the components of a transient arc total voltage with duration of a few tens of ms and a current peak close to 1000 A. The cathode tip is made of graphite whereas the flat anode is made either of copper or of graphite; the electrodes gap is a few mm. The analysis of the electrical parameters is supported and validated by fast imaging and by two models: the first one is a 2D physical model of the arc allowing to calculate both the plasma temperature field and the arc voltage; the second model is able to estimate the transient heating of the graphite electrode. The main aim of the study was to detect the possible change of the cathode voltage fall (CVF) during the first instants of the arc. Indeed it is expected that during the first ms the graphite cathode is rather cool and the main mechanism of the electron emission should be the field effect emission, whereas after several tens of ms the cathode is strongly heated and thermionic emission should be predominant. We have observed some change in the apparent CVF but we have shown that this apparent change can be attributed to the variation of the solid cathode resistance. On the other hand, the possible change of CVF corresponding to the transition between a ‘cold’ and a ‘hot’ cathode should be weak and could not be characterized considering our measurement uncertainty of about 2 V. The arc column voltage (ACV) was estimated by subtracting the electrode voltage fall from the total arc voltage. The experimental transient evolution of the ACV is in very good agreement with the theoretical variation predicted by the model, showing the good ability of the model to study this kind of transient arc.

  5. Coupling capacitor voltage transformer: A model for electromagnetic transient studies

    Energy Technology Data Exchange (ETDEWEB)

    Fernandes, D.; Neves, W.L.A. [Department of Electrical Engineering, Federal University of Campina Grande, Av. Aprigio Veloso, 882 Bodocongo, 58.109-970 Campina Grande, PB (Brazil); Vasconcelos, J.C.A. [Companhia Hidro Eletrica do Sao Francisco, Rua Delmiro Gouveia, 333 Bongi, 50.761-901 Recife, PE (Brazil)

    2007-02-15

    In this work, an accurate coupling capacitor voltage transformer (CCVT) model for electromagnetic transient studies is presented. The model takes into account linear and nonlinear elements. A support routine was developed to compute the linear 230kV CCVT parameters (resistances, inductances and capacitances) from frequency response data. The magnetic core and surge arrester nonlinear characteristics were estimated from laboratory measurements as well. The model is used in connection with the electromagnetic transients program (EMTP) to predict the CCVT performance when it is submitted to transient overvoltages, as are the cases of voltages due to the ferroresonance phenomenon and circuit breaker switching. The difference between simulated and measured results is fairly small. Simulations had shown that transient overvoltages produced inside the CCVT, when a short circuit is cleared at the CCVT secondary side, are effectively damped out by the ferroresonance suppression circuit and the protection circuit. (author)

  6. Plasma response to transient high voltage pulses

    Indian Academy of Sciences (India)

    S Kar; S Mukherjee

    2013-07-01

    This review reports on plasma response to transient high voltage pulses in a low pressure unmagnetized plasma. Mainly, the experiments are reviewed, when a disc electrode (metallic and dielectric) is biased pulsed negative or positive. The main aim is to review the electron loss in plasmas and particle balance during the negative pulse electrode biasing, when the applied pulse width is less than the ion plasma period. Though the applied pulse width is less than the ion plasma period, ion rarefaction waves are excited. The solitary electron holes are reviewed for positive pulsed bias to the electrode. Also the excitation of waves (solitary electron and ion holes) is reviewed for a metallic electrode covered by a dielectric material. The wave excitation during and after the pulse withdrawal, excitation and propagation characteristics of various electrostatic plasma waves are reviewed here.

  7. Transient sodium current at subthreshold voltages: activation by EPSP waveforms.

    Science.gov (United States)

    Carter, Brett C; Giessel, Andrew J; Sabatini, Bernardo L; Bean, Bruce P

    2012-09-20

    Tetrodotoxin (TTX)-sensitive sodium channels carry large transient currents during action potentials and also "persistent" sodium current, a noninactivating TTX-sensitive current present at subthreshold voltages. We examined gating of subthreshold sodium current in dissociated cerebellar Purkinje neurons and hippocampal CA1 neurons, studied at 37°C with near-physiological ionic conditions. Unexpectedly, in both cell types small voltage steps at subthreshold voltages activated a substantial component of transient sodium current as well as persistent current. Subthreshold EPSP-like waveforms also activated a large component of transient sodium current, but IPSP-like waveforms engaged primarily persistent sodium current with only a small additional transient component. Activation of transient as well as persistent sodium current at subthreshold voltages produces amplification of EPSPs that is sensitive to the rate of depolarization and can help account for the dependence of spike threshold on depolarization rate, as previously observed in vivo.

  8. Global Transient Stability and Voltage Regulation for Multimachine Power Systems

    DEFF Research Database (Denmark)

    Gordon, Mark; Hill, David J.

    2008-01-01

    This paper addresses simultaneously the major fundamental and difficult issues of nonlinearity, uncertainty, dimensionality and globality to derive performance enhancing power system stability control. The main focus is on simultaneous enhancement of transient stability and voltage regulation...... law is implemented to coordinate transient stabilizer and voltage regulator for each machine. Digital simulation studies show that global control scheme achieves unified transient stability and voltage regulation in the presence of parametric uncertainties and significant sudden changes in the network...... of power systems. This problem arises from the practical concern that both frequency and voltage control are important indices of power system control and operation but they are ascribed to different stages of system operation, i.e. the transient and post transient period respectively. The Direct Feedback...

  9. A Distance Protection Scheme Not Affected by Transient Characteristic of Capacitor Voltage Transformer for HV Long Transmission Line%不受电容式电压互感器暂态特性影响的距离保护

    Institute of Scientific and Technical Information of China (English)

    焦在滨; 齐倩; 杨黎明; 王优胤; 宁荣

    2014-01-01

    受电容式电压互感器(capacitive voltage transformer, CVT)暂态特性的影响,高压输电线路距离保护易发生暂态超越而误动,影响电力系统的安全稳定运行。提出了一种不受 CVT 暂态特性影响的距离保护新原理。该原理以 CVT能够正确传变工频量为基础,通过基于矩阵束的准确工频量提取方法计算保护安装处电压电流的工频量,利用贝瑞龙模型计算长距离输电线路整定点处的电压和电流,最终以整定点为观测点,通过传统的距离保护算法与方向元件配合确定故障点的位置,该原理不受CVT暂态特性的影响,同时考虑了长距离输电线路分布参数效应对距离保护的影响,具有较好的性能,仿真结果验证了所提算法的有效性。%Affected by transient characteristic of capacitor voltage transformer (CVT), the distance protection for HV transmission line is easily to mal-operate due to transient overreach, thus the secure and stable operation of power grid is affected. A new distance protection scheme that is not affected by the transient characteristics of CVT is proposed and its principle is as following:firstly, on the basis that the CVT can transmit and transform power frequency phasor, by means of the matrix pencil based accurate power frequency phasor extraction method the power frequency phasors of voltage and current at the position where the protection is installed are calculated;secondly, the voltage and current at the position of the long distance transmission line, where the protection is set, are calculated by Bergeron model; finally, coordinating with directional element and taking the setting point as the observation point, the fault point is located by traditional distance protection algorithm. The proposed principle is not affected by transient characteristic of CVT and the impacts of distributed parameters of the long distance transmission line are taken into account, thus the

  10. VOLTAGE MONITORING INSTRUMENT WITH FAST-TRANSIENTS CAPTURE CAPABILITY

    Directory of Open Access Journals (Sweden)

    M. Gracida-Aguirre

    2003-09-01

    Full Text Available A monitoring instrument aimed at recording the voltage levels at residential installations is described. Its main feature is the capability ot recording short transients, lasting less than one cycle, while requiring a rather modest amount of memory for long monitoring periods. The instrument uses synchronous sampling of the voltage waveform, and its response to outages has been optimized.

  11. Over-voltage protection system and method

    Energy Technology Data Exchange (ETDEWEB)

    Chi, Song; Dong, Dong; Lai, Rixin

    2017-05-02

    An over-voltage protection system includes an electronic valve connected across two terminals of a circuit and an over-voltage detection circuit connected across one of the plurality of semiconductor devices for detecting an over-voltage across the circuit. The electronic valve includes a plurality of semiconductor devices connected in series. The over-voltage detection circuit includes a voltage divider circuit connected to a break-over diode in a way to provide a representative low voltage to the break-over diode and an optocoupler configured to receive a current from the break-over diode when the representative low voltage exceeds a threshold voltage of the break-over diode indicating an over-voltage condition. The representative low voltage provided to the break-over diode represents a voltage across the one semiconductor device. A plurality of self-powered gate drive circuits are connected to the plurality of semiconductor devices, wherein the plurality of self-powered gate drive circuits receive over-voltage triggering pulses from the optocoupler during the over-voltage condition and switch on the plurality of semiconductor devices to bypass the circuit.

  12. WAVELET BASED CLASSIFICATION OF VOLTAGE SAG, SWELL & TRANSIENTS

    Directory of Open Access Journals (Sweden)

    Vijay Gajanan Neve

    2013-05-01

    Full Text Available When the time localization of the spectral components is needed, the WAVELE TRANSFORM (WT can be used to obtain the optimal time frequency representation of the signal. This paper deals with the use of a wavelet transform to detect and analyze voltage sags, voltage swell and transients. It introduces voltage disturbance detection approach based on wavelet transform, identifies voltage disturbances, and discriminates the type of event which has resulted in the voltage disturbance, e.g. either a fault or a capacitor-switching incident.Feasibility of the proposed disturbance detection approach is demonstrated based on digital time-domain simulation of a distribution power system using the PSCAD software package, and is implemented using MATLAB. The developed algorithm has been applied to the 14-buses IEEE system to illustrate its application. Results are analyzed.

  13. Early Prediction of Transient Voltage Sags caused by Rotor Swings

    DEFF Research Database (Denmark)

    Weckesser, Johannes Tilman Gabriel; Jóhannsson, Hjörtur; Van Cutsem, Thierry

    2014-01-01

    The paper investigates various methods to predict voltage sags at load buses caused by large generator rotor swings and following a transient disturbance. Three different prediction methods are proposed, which all use real-time measurements from PMUs. One of the methods uses a slightly extended v...

  14. Measuring voltage transients with an ultrafast scanning tunneling microscope

    DEFF Research Database (Denmark)

    Keil, Ulrich Dieter Felix; Jensen, Jacob Riis; Hvam, Jørn Märcher

    1997-01-01

    We use an ultrafast scanning tunneling microscope to resolve propagating voltage transients in space and time. We demonstrate that the previously observed dependence of the transient signal amplitude on the tunneling resistance was only caused by the electrical sampling circuit. With a modified...... circuit, where the tunneling tip is directly connected to the current amplifier of the scanning tunneling microscope, this dependence is eliminated. Ail results can be explained with coupling through the geometrical capacitance of the tip-electrode junction. By illuminating the current...

  15. Step voltage transient currents in poly(vinylidene fluoride)

    Science.gov (United States)

    Kaura, T.; Nath, Rabinder

    1983-10-01

    The step voltage current transient characteristics have been studied in poly(vinylidene flouride) as a function of field, temperature, and time. The current peaks have been observed in the current-time characteristics. These peaks have been attributed to the space-charge injection phenomena. Using the space-charge-limited model of current transients the mobility has been estimated to 2.2±0.2×10-9 cm2 v-1 s-1 at 301 K. The analysis of the temperature dependence of mobilities establishes that charge carrier transport in extended states involving trapping is predominant.

  16. A Generalised Fault Protection Structure Proposed for Uni-grounded Low-Voltage AC Microgrids

    Science.gov (United States)

    Bui, Duong Minh; Chen, Shi-Lin; Lien, Keng-Yu; Jiang, Jheng-Lun

    2016-04-01

    This paper presents three main configurations of uni-grounded low-voltage AC microgrids. Transient situations of a uni-grounded low-voltage (LV) AC microgrid (MG) are simulated through various fault tests and operation transition tests between grid-connected and islanded modes. Based on transient simulation results, available fault protection methods are proposed for main and back-up protection of a uni-grounded AC microgrid. In addition, concept of a generalised fault protection structure of uni-grounded LVAC MGs is mentioned in the paper. As a result, main contributions of the paper are: (i) definition of different uni-grounded LVAC MG configurations; (ii) analysing transient responses of a uni-grounded LVAC microgrid through line-to-line faults, line-to-ground faults, three-phase faults and a microgrid operation transition test, (iii) proposing available fault protection methods for uni-grounded microgrids, such as: non-directional or directional overcurrent protection, under/over voltage protection, differential current protection, voltage-restrained overcurrent protection, and other fault protection principles not based on phase currents and voltages (e.g. total harmonic distortion detection of currents and voltages, using sequence components of current and voltage, 3I0 or 3V0 components), and (iv) developing a generalised fault protection structure with six individual protection zones to be suitable for different uni-grounded AC MG configurations.

  17. Arc Conductance and Flow Velocity Affected by Transient Recovery Voltage

    Science.gov (United States)

    Fukuoka, Reo; Ishikawa, Yuya; Ono, Seisui; Sato, Ken; Yamamoto, Shinji; Iwao, Toru

    2016-09-01

    Recently, the stable supply of electric power is indispensable. The GCB (Gas Circuit Breaker) can prevent the spread of the fault current. However, it should have the reliability more. Therefore the GCB has been researched for performance improvement of the arc interruption of abnormal fault current without the fail. Therefore, it is important to prevent the breakdown such as the re-ignition and thermal re-ignition of arc after the arc interruption. It is necessary to reduce the arc conductance in order to prevent the re-ignition of arc. The arc conductance is derived from the temperature distribution and the volume of the arc. The temperature distribution of the arc is formed by convection. In this research, the arc conductance and flow velocity affected by transient recovery voltage are elucidated. The flow rate and temperature distribution of the arc is calculated with changing transient recovery voltage. In addition, the arc conductance is calculated in order to know the extinguish arc ability. As a result, when the transient recovery voltage increases, the probability of re-ignition increases. Therefore, the arc temperature and the arc conductance were increased.

  18. Protection of Low Voltage CIGRE distribution Network

    DEFF Research Database (Denmark)

    Mustafa, Ghullam; Bak-Jensen, Birgitte; Bak, Claus Leth

    2013-01-01

    the inverters used for Photovoltaic (PV) and battery applications. The disconnection of the PV solar panels when in island mode is made by proposing switch dis-connecting devices. ABB is currently using these kinds of disconnection devices for the purpose of protecting solar panels against over voltages...

  19. Wind Power Impact to Transient and Voltage Stability of the Power System in Eastern Denmark

    DEFF Research Database (Denmark)

    Rasmussen, Joana; Jørgensen, Preben; Palsson, Magni Thor

    2005-01-01

    Voltage stability, transient stability and reactive power compensation are extremely important issues for largescale integration of wind power in areas distant from the main transmission system in Eastern Denmark. This paper describes the application of a dynamic wind farm model in simulation...... studies for assessments of a large wind power penetration. The simulation results reveal problems with voltage stability due to the characteristic of wind turbine generation as well as the inability of the power system to meet the reactive power demand. Furthermore, the established model is applied...... to analyse challenges in system protection as means to reduce the risk of widespread blackouts....

  20. Inrush Transient Current Analysis and Suppression of Photovoltaic Grid-Connected Inverters During Voltage Sag

    DEFF Research Database (Denmark)

    Li, Zhongyu; Zhao, Rende; Xin, Zhen

    2016-01-01

    The Inrush Transient Current (ITC) in the output of the photovoltaic grid-connected inverters is usually generated when grid voltage sag occurs, which can trigger the protection of the grid-connected inverters, and even destroy the semiconductor switches. Then, the grid-connected inverters...... will thus fail to ride through the voltage sag and even further cause more serious grid faults. This paper analyzes the generation principle of ITC and explores its influence factors, upon which, the suppression approaches are presented. Simulation and experimental results validate the theoretical analysis...

  1. Voltage transients elicited by sudden step-up of auxin

    Science.gov (United States)

    Pickard, B. G.

    1984-01-01

    It is hypothesized (i) that the molecular mechanism for the reception of friction and flexure and the mechanism by which auxin enhances ethylene production have in common a release of free calcium into the cytosol, (ii) that elevated cytosolic calcium initiates vesicle exocytosis, and (iii) that the vesicles release a factor or set of factors which depolarizes the plasmalemma and promotes ethylene synthesis. One consequence of such exocytosis should be small, extracellularly observable voltage transients. Transients, ranging in size up to 600 microvolts and possessing risetimes (10-90%) of approximately 200 ms, are known to be elicited in etiolated stems of Pisum sativum L. by friction and are here shown to be elicited by sudden increase of auxin concentration and also by a Ca2+ ionophore.

  2. 通信机房设备直流电源端口电压瞬变防护%Protection of the Voltage Transient on DC Power Port in Telecommunication Site

    Institute of Scientific and Technical Information of China (English)

    祝捷

    2012-01-01

    The voltage transient on DC power port may cause equipment outage in telecommunication site.The related requirements defined in NEBS,ETSI and GB standards are all analyzed.Meanwhile,according to practical experiences,some suggestions on the related equipment design and engineering are provided.%直流电源端口的电压瞬变会导致通信现场设备退出服务。文章比较了美标、欧标和国标相关的规范要求。根据实践经验给出了现场工程实施方面的一些建议。

  3. Strategies for Voltage Control and Transient Stability Assessment

    Energy Technology Data Exchange (ETDEWEB)

    Hiskens, Ian A.

    2013-09-25

    As wind generation grows, its influence on power system performance will becoming increasingly noticeable. Wind generation di ffers from traditional forms of generation in numerous ways though, motivating the need to reconsider the usual approaches to power system assessment and performance enhancement. The project has investigated the impact of wind generation on transient stability and voltage control, identifying and addressing issues at three distinct levels of the power system: 1) at the device level, the physical characteristics of wind turbine generators (WTGs) are quite unlike those of synchronous machines, 2) at the wind-farm level, the provision of reactive support is achieved through coordination of numerous dissimilar devices, rather than straightforward generator control, and 3) from a systems perspective, the location of wind-farms on the sub-transmission network, coupled with the variability inherent in their power output, can cause complex voltage control issues. The project has sought to develop a thorough understanding of the dynamic behaviour of type-3 WTGs, and in particular the WECC generic model. The behaviour of such models is governed by interactions between the continuous dynamics of state variables and discrete events associated with limits. It was shown that these interactions can be quite complex, and may lead to switching deadlock that prevents continuation of the trajectory. Switching hysteresis was proposed for eliminating deadlock situations. Various type-3 WTG models include control blocks that duplicate integrators. It was shown that this leads to non-uniqueness in the conditions governing steady-state, and may result in pre- and post-disturbance equilibria not coinciding. It also gives rise to a zero eigenvalue in the linearized WTG model. In order to eliminate the anomalous behaviour revealed through this investigation, WECC has now released a new generic model for type-3 WTGs. Wind-farms typically incorporate a variety of

  4. Transient demonstration of exciton behaviours in solid state cathodoluminescence under different driving voltage

    Institute of Scientific and Technical Information of China (English)

    Zhang Fu-Jun; Zhao Su-Ling; Xu Zheng; Huang Jin-Zhao; Xu Xu-Rong

    2007-01-01

    In the solid state cathodoluminescence (SSCL), organic materials were excited by hot electrons accelerated in silicon oxide (SiO2) layer under alternating current (AC). In this paper exciton behaviours were analysed by using transient spectra under different driving voltages. The threshold voltages of SSCL and exciton ionization were obtained from the transient spectra. The recombination radiation occurred when the driving voltage went beyond the threshold voltage of exciton ionization. Prom the transient spectrum of two kinds of luminescence (exciton emission and recombination radiation), it was demonstrated that recombination radiation should benefit from the exciton ionization.

  5. Transient Voltage Stability Analysis and Improvement of A Network with different HVDC Systems

    DEFF Research Database (Denmark)

    Liu, Yan; Chen, Zhe

    2011-01-01

    the theoretical analysis and the improved control method, real time simulation model of a hybrid multi-infeed HVDC system based on western Danish power system is established in RTDS™. Simulation results show that the enhanced transient voltage stability can be achieved.......This paper presents transient voltage stability analysis of an AC system with multi-infeed HVDC links including a traditional LCC HVDC link and a VSC HVDC link. It is found that the voltage supporting capability of the VSC-HVDC link is significantly influenced by the tie-line distance between...... the two links and the size of loads. In order to improve the transient voltage stability, a voltage adjusting method is proposed in this paper. A voltage increment component has been introduced into the outer voltage control loop under emergency situation caused by severe grid faults. In order to verify...

  6. Effect of state feedback coupling on the transient performance of voltage source inverters with LC filter

    DEFF Research Database (Denmark)

    Federico, de Bosio; Pastorelli, Michele; Antonio DeSouza Ribeiro, Luiz

    2016-01-01

    State feedback coupling between the capacitor voltage and inductor current deteriorates notably the performance during transients of voltage and current regulators in stand-alone systems based on voltage source inverters. A decoupling technique is proposed, considering the limitations introduced ...... by system delays. Laboratory experiments were executed in compliance with the normative for Uninterruptible Power Supply systems to prove the developed analysis....

  7. Investigation and Improvement of Transient Response of DVR at Medium Voltage Level

    DEFF Research Database (Denmark)

    Blaabjerg, Frede; Wei Li, Yun; Chaing Loh, Poh;

    2007-01-01

    An area of interest for dynamic voltage restorer (DVR) research is the damping of transient oscillations initiated at the start and at the recovery instant from a voltage sag. Nonlinear loads, with harmonic currents close to the DVR filter resonance frequency, can also excite the resonance...... oscillations. To compensate voltage sags and dampen high-frequency oscillations simultaneously, an investigation of the transient response of DVR is first carried out. Possible control schemes and their effects on the oscillation attenuation are also studied. Such studied control schemes include the commonly...... used single voltage loop control, voltage feedback plus reference feedforward control, and double-loop control with an outer voltage loop and an inner current loop. Subsequently, an effective and simple resonance damping method is proposed by employing a closed-loop control with an embedded two...

  8. Decentralized Adaptive Overcurrent Protection for Medium Voltage Maritime Power Systems

    DEFF Research Database (Denmark)

    Ciontea, Catalin-Iosif; Bak, Claus Leth; Blaabjerg, Frede;

    2016-01-01

    control unit. The new adaptive protection method is based on communication between the overcurrent relays and the equipment that could affect the protection system, such as circuit breakers and generators. Using PSCAD, the proposed method is implemented in a test medium voltage maritime power system...

  9. Simulation Research of Transient Over-voltage on High-voltage Shunt Capacitor Banks

    Institute of Scientific and Technical Information of China (English)

    HU Quan-wei; ZHOU Xing-xing; SI Wen-rong; ZHANG Yang; LI Jur-hao; LI Yan-ming

    2011-01-01

    With the development of power systems,a large number of shunt capacitors are used to improve power quality in the distribution network.The shunt capacitor banks are operated much frequently,as a result,the capacitor banks will bear large numbers of over-voltage inevitably.If the over-voltage exceeds certain amplitude,the capacitor will be damaged.This paper aims at the capacitor banks in the 35 kV side of Shanghai Xu-xing 500 kV substation,and applies ATP-EMTP to simulate the over-voltages generated by operating the switches under different angles of the source.Finally,according to the results of simulation and theoretical analysis,a best choice (i.e.angles of the source) to switch on capacitor banks is proposed.In this case the over-voltage on the capacitor will be limited to lowest.

  10. Sensitivity based Assessment of Transient Voltage Sags caused by Rotor Swings

    DEFF Research Database (Denmark)

    Weckesser, Johannes Tilman Gabriel; Jóhannsson, Hjörtur; Østergaard, Jacob;

    2014-01-01

    The paper introduces an approach to investigate voltage sags, which are caused by large generator rotor swings following a transient disturbance. Therefore, the method exploits sensitivities derived from the algebraic network equations. These provide information on the impact of a generator on th...

  11. Derivation and application of sensitivities to assess transient voltage sags caused by rotor swings

    DEFF Research Database (Denmark)

    Weckesser, Johannes Tilman Gabriel; Jóhannsson, Hjörtur; Østergaard, Jacob;

    2015-01-01

    The paper introduces an approach to investigate voltage sags, which are caused by large generator rotor swings following a transient disturbance. Therefore, the method exploits sensitivities derived from the algebraic network equations. These provide information on the impact of a generator on th...

  12. Implementationof Single Phasing, Over Voltage, Under Voltage, Protection of Three Phase Appliances without Using Microcontroller

    Directory of Open Access Journals (Sweden)

    Girish Chandra Thakur

    2015-05-01

    Full Text Available This paper tends to develop for protection for costly appliances which require three-phase AC supply for operation. Failure of any of the phases or sudden change in voltage makes the appliance prone to erratic functioning and may even lead to failure. Hence it is of paramount importance to monitor the availability of the three-phase supply and proper voltage supply and switch off the appliance in the event of failure of one or two phases or if required voltage level is not available. The power to the appliance should resume with the availability of all phases of the supply with proper voltage level. The main advantage of this protector circuit is that it protects three-phase appliances from failure of any phase as well as from fluctuation of voltage. The concept in future can be extended to developing a mechanism to send message to the authority via SMS by interfacing GSM modem. Details description of all types of faults is given below.

  13. Protection Distance of Surge Protective Devices in Low Voltage Distribution Systems

    Institute of Scientific and Technical Information of China (English)

    ZHANG Dong; FU Zheng-cai; ZHAO Gang; SUN Wei

    2008-01-01

    Protection distance of surge protective devices (SPDs) is an important problem in designing a good location scheme of SPDs in low voltage distribution systems for protecting electrical equipments against overvoltage caused by lightning stroke. The simplified lumped-parameter circuit model and the circuit method were used to study the protection distance problem of SPDs. The analytical solutions of the load voltage and generale quations of the protection distance of SPDs under different load conditions were given. Simulation results of examples proved the validity of the proposed analytical method.

  14. Control and Protection Cooperation Strategy for Voltage Instability

    DEFF Research Database (Denmark)

    Liu, Zhou; Chen, Zhe; Sun, Haishun;

    2012-01-01

    Most cascaded blackouts are caused by unexpected backup relay operations due to low voltage or overload state caused by post fault load restoration dynamics. If such state can be sensed and adjusted appropriately prior to those relay actions, system stability might be sustained. This paper proposed...... a control and protection cooperation strategy to prevent post fault voltage instability. The multi-agent technology is applied for the strategy implementation; the criteria based on wide area measured apparent impedances are defined to choose the control strategy, such as tap changer adjusting or load...

  15. IGBT Fuses for Protection Against Explosion in Voltage Source Converters

    DEFF Research Database (Denmark)

    Blaabjerg, Frede; Iov, Florin; Rasmussen, H.

    2004-01-01

    The consequences of electrical faults can be severe; not only to the equipment, but also in the worse case, to people if safety principles are not observed. Every year new applications based on DC-link Voltage Source Converters are added and the demand for protection of power electronics increases...... regarding the high-power IGBT modules. Due to the fact that the power level increases more energy is stored in the DC-link and even with an active protection, a high-power IGBT still has a risk of case rupture (explode) when a circuit failure condition occurs. A possible solution is a protection...... of the converter with standard High Speed Fuses or High Speed IGBT fuses. It is discussed that protection can be achieved by introduction of IGBT fuse located in the DC-link. Experiments show that explosion can be avoided by use of High Speed Fuse protection and the added inductance of standard High Speed...

  16. Analysis of a Microgrid under Transient Conditions Using Voltage and Frequency Controller

    Directory of Open Access Journals (Sweden)

    Monika Jain

    2012-01-01

    Full Text Available This paper presents an investigation of voltage-and-frequency-(VF- based battery energy storage system (BESS controller used in micro grid for analyzing the optimum capability of plant. Microgrid is formed by using three hydropower plants feeding three-phase four-wire load. The proposed controller is used for load balancing, harmonic elimination, load leveling, and neutral current compensation. The proposed BESS controller permits the selection of an optimum voltage level of battery and allows independent current control of each phase. The main emphasis is given on maintaining constant voltage and frequency within the micro grid during transient conditions. Micro grid with power plant and its controller is modeled in MATLAB/Simulink using Power System Blockset (PSB toolboxes.

  17. 30 CFR 77.901 - Protection of low- and medium-voltage three-phase circuits.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Protection of low- and medium-voltage three... WORK AREAS OF UNDERGROUND COAL MINES Low- and Medium-Voltage Alternating Current Circuits § 77.901 Protection of low- and medium-voltage three-phase circuits. (a) Low- and medium-voltage circuits supplying...

  18. 30 CFR 77.802 - Protection of high-voltage circuits; neutral grounding resistors; disconnecting devices.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Protection of high-voltage circuits; neutral... AND SURFACE WORK AREAS OF UNDERGROUND COAL MINES Surface High-Voltage Distribution § 77.802 Protection of high-voltage circuits; neutral grounding resistors; disconnecting devices. High-voltage...

  19. Temperature and voltage coupling to channel opening in transient receptor potential melastatin 8 (TRPM8).

    Science.gov (United States)

    Raddatz, Natalia; Castillo, Juan P; Gonzalez, Carlos; Alvarez, Osvaldo; Latorre, Ramon

    2014-12-19

    Expressed in somatosensory neurons of the dorsal root and trigeminal ganglion, the transient receptor potential melastatin 8 (TRPM8) channel is a Ca(2+)-permeable cation channel activated by cold, voltage, phosphatidylinositol 4,5-bisphosphate, and menthol. Although TRPM8 channel gating has been characterized at the single channel and macroscopic current levels, there is currently no consensus regarding the extent to which temperature and voltage sensors couple to the conduction gate. In this study, we extended the range of voltages where TRPM8-induced ionic currents were measured and made careful measurements of the maximum open probability the channel can attain at different temperatures by means of fluctuation analysis. The first direct measurements of TRPM8 channel temperature-driven conformational rearrangements provided here suggest that temperature alone is able to open the channel and that the opening reaction is voltage-independent. Voltage is a partial activator of TRPM8 channels, because absolute open probability values measured with fully activated voltage sensors are less than 1, and they decrease as temperature rises. By unveiling the fast temperature-dependent deactivation process, we show that TRPM8 channel deactivation is well described by a double exponential time course. The fast and slow deactivation processes are temperature-dependent with enthalpy changes of 27.2 and 30.8 kcal mol(-1). The overall Q10 for the closing reaction is about 33. A three-tiered allosteric model containing four voltage sensors and four temperature sensors can account for the complex deactivation kinetics and coupling between voltage and temperature sensor activation and channel opening.

  20. Determining the mobility of ions by transient current measurements at high voltages.

    Science.gov (United States)

    Kohn, Peter; Schröter, Klaus; Thurn-Albrecht, Thomas

    2007-08-24

    We present polarization and transient current experiments that allow an independent determination of the charge carrier density and the mobility of ions in polymer electrolytes at low charge carrier density. The method relies on a complete depletion of ions in the bulk electrolyte achieved by applying high voltages. Based on a qualitative model for the charge dynamics in this nonlinear regime, the method is exemplarily applied to a system of polymethylmethacrylate doped with small amounts of a lithium salt. The independently obtained values for the ionic mobility, the charge carrier density, and the conductivity are consistent for all salt concentrations studied. Criteria for the applicability of the method are discussed.

  1. Neural-net based calculation of voltage dips at maximum angular swing in direct transient stability analysis [of power systems

    Energy Technology Data Exchange (ETDEWEB)

    Djukanovic, M. (Inst. ' Nikola Tesla' , Belgrade (Yugoslavia)); Sobajic, D.J.; Yohhan Pao (Case Western Reserve Univ., Cleveland, OH (United States). Dept. of Electrical Engineering and Applied Physics Case Western Reserve Univ., Cleveland, OH (United States). Dept. of Computer Engineering and Science AI WARE inc., Cleveland, OH (United States))

    1992-10-01

    In heavily stressed power systems, post-fault transient voltage dips can lead to undesired tripping of industrial drives and large induction motors. The lowest transient voltage dips occur when fault clearing times are less than critical ones. In this paper, we propose a new iterative analytical methodology to obtain more accurate estimates of voltage dips at maximum angular swing in direct transient stability analysis. We also propose and demonstrate the possibility of storing the results of these computations in the associative memory (AM) system, which exhibits remarkable generalization capabilities. Feature-based models stored in the AM can be utilized for fast and accurate prediction of the location, duration and the amount of the worst voltage dips, thereby avoiding the need and cost for lengthy time-domain simulations. Numerical results obtained using the example of the New England power system are presented to illustrate our approach. (Author)

  2. Investigation of transient overvoltages in heavily meshed low-voltage underground distribution networks

    Science.gov (United States)

    Salcedo Ulerio, Reynaldo Odalis

    The analysis of overvoltages in electrical distribution networks is of considerable significance since they may damage the power system infrastructure and the associated electrical equipment. Overvoltages in distribution networks arise due to switching transients, resonance, lightning strikes and ground faults, among other causes. The operation of network protectors (NWP), low voltage circuit breakers with directional power relay, in a secondary network prevents the continuous flow of reverse power. There are three modes of operation for the network protectors: sensitive, time delayed, and insensitive. In case of a fault, although all of the network protectors sense the fault at the same time, their operation is not simultaneous. Many of them open very quickly with opening times similar to those of the feeder breaker. However, some operate a few cycles later, others take several seconds to open and a few might even fail to operate. Therefore, depending on the settings of the network protectors, faults can last for significantly long time due to backfeeding of current from the low voltage (LV) network into the medium voltage (MV) network. In this work, low voltages are defined as 208V/460V and medium voltage are defined as 25kV/35kV. This thesis presents overvoltages which arise because of the occurrence of a single-line-to-ground (SLG) fault on the MV side (connected in delta) of the system. The thesis reveals that overvoltage stresses are imposed on insulation, micro-processor controlled equipment, and switching devices by overvoltages during current backfeeding. Also, it establishes a relationship between overvoltage magnitude, its duration, and the network loading conditions. Overvoltages above 3 p.u. may be developed as a result of a simultaneous occurrence of three phenomena: neutral displacement, Ferranti effect, and magnetic current chopping. Furthermore, this thesis exposes the possibility of occurrence of the ferro-resonance phenomena in a distribution

  3. Transient Receptor Potential Vanilloid 4-Induced Modulation of Voltage-Gated Sodium Channels in Hippocampal Neurons.

    Science.gov (United States)

    Hong, Zhiwen; Jie, Pinghui; Tian, Yujing; Chen, Tingting; Chen, Lei; Chen, Ling

    2016-01-01

    Transient receptor potential vanilloid 4 (TRPV4) is reported to control the resting membrane potential and increase excitability in many types of cells. Voltage-gated sodium channels (VGSCs) play an important role in initiating action potentials in neurons. However, whether VGSCs can be modulated by the activation of TRPV4 in hippocampal pyramidal neurons remains unknown. In this study, we tested the effect of TRPV4 agonists (GSK1016790A and 4α-PDD) on voltage-gated sodium current (I Na) in hippocampal CA1 pyramidal neurons and the protein levels of α/β-subunit of VGSCs in the hippocampus of mice subjected to intracerebroventricular (icv.) injection of GSK1016790A (GSK-injected mice). Herein, we report that I Na was inhibited by acute application of GSK1016790A or 4α-PDD. In the presence of TRPV4 agonists, the voltage-dependent inactivation curve shifted to the hyperpolarization, whereas the voltage-dependent activation curve remained unchanged. The TRPV4 agonist-induced inhibition of I Na was blocked by the TRPV4 antagonist or tetrodotoxin. Moreover, blocking protein kinase A (PKA) markedly attenuated the GSK1016790A-induced inhibition of I Na, whereas antagonism of protein kinase C or p38 mitogen-activated protein kinase did not change GSK1016790A action. Finally, the protein levels of Nav1.1, Nav1.2, and Nav1.6 in the hippocampus increased in GSK-injected mice, whereas those of Nav1.3 and Navβ1 remained nearly unchanged. We conclude that I Na is inhibited by the acute activation of TRPV4 through PKA signaling pathway in hippocampal pyramidal neurons, but protein expression of α-subunit of VGSCs is increased by sustained TRPV4 activation, which may compensate for the acute inhibition of I Na and provide a possibility for hyper-excitability upon sustained TRPV4 activation.

  4. Simulation Analysis of Transient Earth Voltages Aroused by Partial Discharge in Switchgear

    Directory of Open Access Journals (Sweden)

    Man Yuyan

    2014-01-01

    Full Text Available The authors investigated the properties of Transient Earth Voltages (TEV Aroused by Partial Discharge in Switchgear by Simulation. The mechanism of TEV aroused by partial discharge in switchgears is analyzed. The Finite Integration Theory (FIT was employed to simulate the propagation of TEV in the switchgear. The simulation results show that the pulse width of TEV increases as the pulse width of PD pulse increases and the amplitude of TEV is proportional to the PD pulse amplitude. There are time differences between the TEV signals of different detecting points when the TEV propagating on the switchgear’s surface. Based on the simulation, a method of locating the PD of switchgear is proposed by positioning multi-sensors on the external surface of switchgear.

  5. Transient Response of Organo-Metal-Halide Solar Cells Analyzed by Time-Resolved Current-Voltage Measurements

    Directory of Open Access Journals (Sweden)

    M. Greyson Christoforo

    2015-11-01

    Full Text Available The determination of the power conversion efficiency of solar cells based on organo-metal-halides is subject to an ongoing debate. As solar cell devices may exhibit very slow transient response, current-voltage scans in different directions may not be congruent, which is an effect often referred to as hysteresis. We here discuss time-resolved current-voltage measurements as a means to evaluate appropriate delay times (voltage settling times to be used in current-voltage measurements of solar cells. Furthermore, this method allows the analysis of transient current response to extract time constants that can be used to compare characteristic differences between devices of varying architecture types, selective contacts and changes in devices due to storage or degradation conditions.

  6. A Capacitor-Free, Fast Transient Response Linear Voltage Regulator In a 180nm CMOS

    DEFF Research Database (Denmark)

    Deleuran, Alexander N.; Lindbjerg, Nicklas; Pedersen, Martin K.

    2015-01-01

    A 1.8 V capacitor-free linear regulator with fast transient response based on a new topology with a fast and slow regulation loop is presented. The design has been laid out and simulated in a 0.18 µm CMOS process. The design has a low component count and is tailored for system-on-chip integration....... A current step load from 0-50 mA with a rise time of 1 µs results in an undershoot in the output voltage of 140 mV for a period of 39 ns. The regulator sources up to 50 mA current load.......A 1.8 V capacitor-free linear regulator with fast transient response based on a new topology with a fast and slow regulation loop is presented. The design has been laid out and simulated in a 0.18 µm CMOS process. The design has a low component count and is tailored for system-on-chip integration...

  7. Transient Recovery Voltages at the Main 132kV Line Bay GIS Circuit Breaker in a Windfarm

    OpenAIRE

    Arana Aristi, Iván; Okholm, J.; Holbøll, Joachim

    2011-01-01

    This paper presents the results of investigations of the Transient Recovery Voltage (TRV) across the terminals of the main 132kV Line Bay GIS circuit breaker (GIS CB) for Walney 2, second phase of the Walney Offshore Wind Farm. Several simulations were performed where the influence of different parameters in the network was evaluated during a fault in the onshore substation. The rate of rise of recovery voltage (RRRV) and the maximum crest voltage (Uc) of the TRV across the GIS CB were compar...

  8. Voltage-clamp studies of transient inward current and mechanical oscillations induced by ouabain in ferret papillary muscle.

    Science.gov (United States)

    Karagueuzian, H S; Katzung, B G

    1982-06-01

    1. We studied the effects of a toxic concentration of ouabain on transmembrane electrical activity and on mechanical behaviour of right ventricular papillary muscles from ferrets in a single sucrose-gap using current clamp and voltage clamp.2. Ouabain (1.4-1.8 muM) induced oscillatory after-potentials and after-concentrations in current-clamp experiments. Voltage clamp showed that the oscillatory after-potential was caused by a transient inward current, similar to that in Purkinje fibres.3. The transient current had a sigmoidal dependence on the preceding (activating) voltage step V1, with a treshold around -13 mV and a plateau between +10 and 20 mV. There was a decline in current amplitude for more positive clamps. When activated by a fixed V1 voltage step, and measured at different repolarization levels V2, the transient current manifested an inverse dependence on V2 between -50 and -10 mV. No outward transient current could be detected. Total replacement of Na in the bathing medium by Tris or by sucrose abolished the transient current.4. Ouabain caused an increase of phasic (twitch) tension responses to voltage steps at all potentials without shifting the curve relating these variables on the voltage axis. The drug evoked an even greater increase in the tonic tension responses.5. After prolonged exposure, oscillatory mechanical responses were frequently recorded during positive voltage steps. Unlike the after-contraction, these mechanical fluctuations were not consistently damped and were not accompanied by detectable synchronous current fluctuations. Catecholamines and dibutyryl cyclic AMP markedly reduced the amplitude of the tonic contraction and the mechanical oscillations but increased their frequency. Caffeine had no effect on the tonic contraction amplitude but abolished the fluctuations.6. These results support the proposal that Ca is transiently released from the overloaded sarcoplasmic reticulum in ouabain-intoxicated muscle and may evoke oscillatory

  9. Adaptive Voltage Stability Protection Based on Load Identification Using Phasor Measurement Units

    DEFF Research Database (Denmark)

    Liu, Leo; Bak, Claus Leth; Chen, Zhe

    2011-01-01

    collapse. In this paper, the online load identification using measurement-based approach based on Phasor Measurement Units (PMU) was proposed to evaluate the proximity to voltage instability in order to prevent voltage collapse. In the scenarios of disturbances, the proximity to voltage collapse...... with respect to load characteristics was evaluated. Based on different load characteristics, different control and protection schemes were implemented, i.e. shunt capacitor connection, on-load tap changer blocking and load shedding. The results showed that load-based adaptive voltage control and protection...... scheme based on PMUs is promising, as it prevented the voltage collapse and minimized the load shedding area....

  10. A NOVEL OVER—VOLTAGE PROTECTION METHOD FOR 600V SPIC

    Institute of Scientific and Technical Information of China (English)

    LanLei; YeXingning

    2002-01-01

    A novel over-voltage protection method for 600V BPIC(Smart Power IC) is proposed in this paper.The combining FFLRs(Floating Field Limiting Rings) system is designed to be a voltage detector.The detector's voltage can turn off the switch of the APFC(Active Power Factor Correction )Circuit and the bus voltage would fall from 600VDC to 300VDC,so the SPIC and power devices can be protected.The advantages of this design are that the total protection circuits are integrated in SPIC and technologically compatible with CMOS or BCD(Bipolar CMOS-DMOS) technology.

  11. A NOVEL OVER-VOLTAGE PROTECTION METHOD FOR 600V SPIC

    Institute of Scientific and Technical Information of China (English)

    Han Lei; Ye Xingning

    2002-01-01

    A novel over-voltage protection method for 600V SPIC (Smart Power IC) is proposed in this paper. The combining FFLRs (Floating Field Limiting Rings) system is designed to be a voltage detector. The detector's voltage can turn off the switch of the APFC (Active Power Factor Correction) circuit and the bus voltage would fall from 600VDC to 300VDC, so the SPIC and power devices can be protected. The advantages of this design are that the total protection circuits are integrated in SPIC and technologically compatible with CMOS or BCD(BipolarCMOS-DMOS) technology.

  12. Ultra-low-voltage-trigger thyristor for on-chip ESD protection without extra process cost

    Science.gov (United States)

    Yi, Shan; Jun, He; Wenyi, Huang

    2009-07-01

    A new thyristor is proposed and realized in the foundry's 0.18-μm CMOS process for electrostatic discharge (ESD) protection. Without extra mask layers or process steps, the new ultra-low-voltage-trigger thyristor (ULVT thyristor) has a trigger voltage as low as 6.7 V and an ESD robustness exceeding 50 mA/μm, which enables effective ESD protection. Compared with the traditional medium-voltage-trigger thyristor (MVT thyristor), the new structure not only has a lower trigger voltage, but can also provide better ESD protection under both positive and negative ESD zapping conditions.

  13. Ultra-low-voltage-trigger thyristor for on-chip ESD protection without extra process cost

    Energy Technology Data Exchange (ETDEWEB)

    Shan Yi [Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); He Jun; Huang Wenyi, E-mail: iamshanyi@163.co, E-mail: yi.shan@gracesemi.co [Grace Semiconductor Manufacturing Corporation, Shanghai 201203 (China)

    2009-07-15

    A new thyristor is proposed and realized in the foundry's 0.18-{mu}m CMOS process for electrostatic discharge (ESD) protection. Without extra mask layers or process steps, the new ultra-low-voltage-trigger thyristor (ULVT thyristor) has a trigger voltage as low as 6.7 V and an ESD robustness exceeding 50 mA/{mu}m, which enables effective ESD protection. Compared with the traditional medium-voltage-trigger thyristor (MVT thyristor), the new structure not only has a lower trigger voltage, but can also provide better ESD protection under both positive and negative ESD zapping conditions.

  14. Study on the instantaneous protection reliability of low voltage circuit breakers

    Institute of Scientific and Technical Information of China (English)

    LU Jian-guo; DU Tai-hang; LUO Yan-yan

    2007-01-01

    This paper outlines the significance of enhancing the instantaneous protection reliability of low voltage circuit breakers and describes their main failure modes. The instantaneous failure mechanism of low voltage circuit breakers was analyzed so that measures to improve instantaneous protection reliability can be determined. Furthermore, the theory of the instantaneous characteristics Calibration device for low voltage circuit breakers and the method of eliminating the non-periodic component of test current are given in detail. Finally, the test results are presented.

  15. Transient Fault Locating Method Based on Line Voltage and Zero-mode Current in Non-solidly Earthed Network

    Institute of Scientific and Technical Information of China (English)

    ZHANG Linli; XU Bingyin; XUE Yongduan; GAO Houlei

    2012-01-01

    Non-solidly earthed systems are widely used for middle voltage distribution network at home and abroad. Fault point location especially the single phase-to-earth fault is very difficult because the fault current is very weak and the fault arc is intermittent. Although several methods have been developed, the problem of fault location has not yet been resolved very well. A new fault location method based on transient component of line voltage and 0-mode current is presented in this paper, which can realize fault section location by the feeder automation (FA) system. Line voltage signal can be obtained conveniently without requiring any additional equipment. This method is based on transient information, not affected by arc suppression coil.

  16. Impact of the Voltage Transients after a Fast Power Abort on the Quench Detection System in the LHC Main Dipole Chain

    CERN Document Server

    Ravaioli, E; Formenti, F; Montabonnet, V; Pojer, M; Schmidt, R; Siemko, A; Solfaroli Camillocci, A; Steckert, J; Thiesen, H; Verweij, A

    2012-01-01

    A Fast Power Abort in the LHC superconducting main dipole circuit consists in the switch-off of the power converter and the opening of the two energy-extraction switches. Each energy-extraction unit is composed of redundant electromechanical breakers, which are opened to force the current through an extraction resistor. When a switch is opened arcing occurs in the switch and a voltage of up to 1 kV builds up across the extraction resistor with a typical ramp rate of about 80 kV/s. The subsequent voltage transient propagates through the chain of 154 dipoles and superposes on the voltage waves caused by the switch-off of the power converter. The resulting effect caused intermittent triggering of the quench protection systems along with heater firings in the magnets when the transient occurred during a ramp of the current. A delay between power converter switch-off and opening of the energy-extraction switches was introduced to prevent this effect. Furthermore, the output filters of the power converters were mod...

  17. Transient recovery voltage analysis for various current breaking mathematical models: shunt reactor and capacitor bank de-energization study

    Directory of Open Access Journals (Sweden)

    Oramus Piotr

    2015-09-01

    Full Text Available Electric arc is a complex phenomenon occurring during the current interruption process in the power system. Therefore performing digital simulations is often necessary to analyse transient conditions in power system during switching operations. This paper deals with the electric arc modelling and its implementation in simulation software for transient analyses during switching conditions in power system. Cassie, Cassie-Mayr as well as Schwarz-Avdonin equations describing the behaviour of the electric arc during the current interruption process have been implemented in EMTP-ATP simulation software and presented in this paper. The models developed have been used for transient simulations to analyse impact of the particular model and its parameters on Transient Recovery Voltage in different switching scenarios: during shunt reactor switching-off as well as during capacitor bank current switching-off. The selected simulation cases represent typical practical scenarios for inductive and capacitive currents breaking, respectively.

  18. 30 CFR 75.901 - Protection of low- and medium-voltage three-phase circuits used underground.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Protection of low- and medium-voltage three... Underground Low- and Medium-Voltage Alternating Current Circuits § 75.901 Protection of low- and medium-voltage three-phase circuits used underground. (a) Low- and medium-voltage three-phase alternating-current...

  19. Reversal transient laser-induced voltages in La2/3Ca1/3MnO3 films

    Institute of Scientific and Technical Information of China (English)

    Zhao Kun; He Meng; Lü Hui-Bin

    2007-01-01

    This paper reports that the transient laser-induced voltages have been observed in La2/3Ca1/3MnO3 thin films on MgO (001) in the absence of an applied current.A peak voltage of~0.15V Was detected in response to 0.015 J pulse of 308 nm laser.It is demonstrated that the signal polarity is reversed when the films are irradiated through the substrate rather than at the air/film interface.Off-diagonal thermoelectricity may support the inversion of the signal when the irradiation direction is reversed.

  20. A fully on-chip fast-transient NMOS low dropout voltage regulator with quasi floating gate pass element

    Science.gov (United States)

    Wang, Han; Gou, Chao; Luo, Kai

    2017-04-01

    This paper presents a fully on-chip NMOS low-dropout regulator (LDO) for portable applications with quasi floating gate pass element and fast transient response. The quasi floating gate structure makes the gate of the NMOS transistor only periodically charged or refreshed by the charge pump, which allows the charge pump to be a small economical circuit with small silicon area. In addition, a variable reference circuit is introduced enlarging the dynamic range of error amplifier during load transient. The proposed LDO has been implemented in a 0.35 μm BCD process. From experimental results, the regulator can operate with a minimum dropout voltage of 250 mV at a maximum 1 A load and {I}{{Q}} of 395 μA. Under full-range load current step, the voltage undershoot and overshoot of the proposed LDO are reduced to 50 and 26 mV, respectively.

  1. Systematic Review of the Exposure Assessment and Epidemiology of High-Frequency Voltage Transients

    Directory of Open Access Journals (Sweden)

    Frank eDe Vocht

    2016-03-01

    Full Text Available Conclusions of epidemiological studies describing adverse health effects as a result of exposure to electromagnetic fields are not unanimous and often contradictory. It has been proposed that an explanation could be that high frequency voltage transients (dirty electricity [DE] which are superimposed on 50/60Hz fields, but are generally not measured, is the real causal agent. DE has been linked to many different health and wellbeing effects, and on the basis of this an industry selling measurement and filtering equipment is growing. We reviewed the available peer-reviewed evidence for DE as a causal agent for adverse human health effects.A literature search was performed in the Cochrane Library, PubMed, Web of Science, Google Scholar and additional publications were obtained from reference lists and from the grey literature. This search resulted in 25 publications; 16 included primary epidemiological and/or exposure data. All studies were reviewed by both authors independently, and including a re-review of studies included in a review of data available up to July 31 2009 by one of the authors. DE has been measured differently in different studies and comparison data are not available. There is no evidence for 50 Graham/Stetzer (G/S units as a safety threshold being anything more than arbitrary. The epidemiological evidence on human health effects of DE is primarily based on, often re-used, case descriptions. Quantitative evidence relies on self-reporting in non-blinded interventions, ecological associations, and one cross-sectional cohort study of cancer risk which does not point to DE as the causal agent. The available evidence for DE as an exposure affecting human health at present does not stand up to scientific scrutiny.

  2. 30 CFR 75.802 - Protection of high-voltage circuits extending underground.

    Science.gov (United States)

    2010-07-01

    ... underground. 75.802 Section 75.802 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR COAL MINE SAFETY AND HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Underground High-Voltage Distribution § 75.802 Protection of high-voltage circuits extending underground. (a) Except as...

  3. Summary of transient high-voltage calculations for the FRX-C experiment

    Energy Technology Data Exchange (ETDEWEB)

    Kewish, R.W. Jr.; Rej, D.J.

    1982-06-01

    Calculations of the electrical circuit equations are performed over a wide range of parameters corresponding to the FRX-C field-reversed THETA-pinch experiment at Los Alamos. Without any plasma or external damping, serious voltage doubling and quadrupling of the main capacitor bank charge voltage are observed. These oscillating high voltages are found to be adequately suppressed by the strategic placement of external snubber circuitry. On the other hand, no doubling of the THETA-pinch preionization bank charge voltage is found. Calculations of the equations for the z-pinch preionization circuit are also performed.

  4. Novel substrate trigger SCR-LDMOS stacking structure for high-voltage ESD protection application

    Institute of Scientific and Technical Information of China (English)

    马金荣; 乔明; 张波

    2015-01-01

    A novel substrate trigger semiconductor control rectifier-laterally diffused metal–oxide semiconductor (STSCR-LDMOS) stacked structure is proposed and simulated using the transimission line pulser (TLP) multiple-pulse simulation method in a 0.35-µm, 60-V biploar-CMOS-DMOS (BCD) process without additional masks. On account of a very low holding voltage, it is susceptible to latch-up-like danger for the semiconductor control rectifier-laterally diffused metal–oxide semiconductor (SCR-LDMOS) in high-voltage electro-static discharge (ESD) protection applications. Although the conventional stacking structure has achieved strong latch-up immunity by increasing holding voltage, excessive high trigger voltage does not meet requirements for an ESD protection device. The holding voltage of the proposed stacked structure is proportional to the stacking number, whereas the trigger voltage remains nearly the same. A high holding voltage of 30.6 V and trigger voltage of 75.4 V are achieved.

  5. Hierarchical Control Scheme for Improving Transient Voltage Recovery of a DFIG-Based WPP

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jinho; Muljadi, Eduard; Kang, Yong Cheol

    2015-06-05

    Modern grid codes require that wind power plants (WPPs) inject reactive power according to the voltage dip at a point of interconnection (POI). This requirement helps to support a POI voltage during a fault. However, if a fault is cleared, the POI and wind turbine generator (WTG) voltages are likely to exceed acceptable levels unless the WPP reduces the injected reactive power quickly. This might deteriorate the stability of a grid by allowing the disconnection of WTGs to avoid any damage. This paper proposes a hierarchical control scheme of a doubly-fed induction generator (DFIG)-based WPP. The proposed scheme aims to improve the reactive power injecting capability during the fault and suppress the overvoltage after the fault clearance. To achieve the former, an adaptive reactive power-to-voltage scheme is implemented in each DFIG controller so that a DFIG with a larger reactive power capability will inject more reactive power. To achieve the latter, a washout filter is used to capture a high frequency component contained in the WPP voltage, which is used to remove the accumulated values in the proportional-integral controllers. Test results indicate that the scheme successfully supports the grid voltage during the fault, and recovers WPP voltages without exceeding the limit after the fault clearance.

  6. Modelación de sistemas de puesta a tierra para evaluación de sobretensiones transitorias; Modelling large grounding systems to evaluate transient voltages

    Directory of Open Access Journals (Sweden)

    Yandi Anibal Gallego Landera

    2015-04-01

    Full Text Available En plantas generadoras y en subestaciones se requieren sistemas de puesta a tierra (SPT espaciosos, con configuraciones complejas como parte del sistema de protección contra rayos. Las corrientes provocadas por una descarga atmosférica pueden causar altas tensiones en los cables de señales ubicados cerca de los SPT. Estas tensiones transitorias pueden causar falsas señales, las cuales provocan un mal funcionamiento de la instrumentación electrónica. Determinar medidas de protección contra rayos requiere del conocimiento de la máxima elevación de la tensión entre el SPT y la tierra remota. El presente trabajo propone una metodología para analizar el comportamiento transitorio de redes de tierra. La técnica se basa en considerar los diferentes segmentos de la malla de tierra como elementos de líneas de transmisión. Para desarrollar esta metodología se utilizó el software MATLAB-Simulink. Los resultados se validan por comparación con modelos basados en la teoría del campo electromagnético publicados en la literatura. In generating plants and substations spacious grounding systems with complex configuration as part of the protection system against lighting, are required. The current caused by an atmospheric discharge can cause high voltages in the signal cables located near the grounding systems. These transient voltages may be the reason for the occurrence of false signals, which can cause malfunctioning and of electronic instruments. The knowledge of maximum elevation of voltage between the grounding systems and the remote ground is required to determine protection against lightning. This paper proposes a methodology to analyze the transient behavior of grounding grid. The technique is based on considering the different segments of the ground grid as elements of transmission lines. For modeling the grounding systems behavior in its transient state faster, the MATLAB-Simulink software was used. The results were validated by

  7. Voltage control and protection in electrical power systems from system components to wide-area control

    CERN Document Server

    Corsi, Sandro

    2015-01-01

    Based on the author’s twenty years of experience, this book shows the practicality of modern, conceptually new, wide area voltage control in transmission and distribution smart grids, in detail. Evidence is given of the great advantages of this approach, as well as what can be gained by new control functionalities which modern technologies now available can provide. The distinction between solutions of wide area voltage regulation (V-WAR) and wide area voltage protection (V-WAP) are presented, demonstrating the proper synergy between them when they operate on the same power system as well as the simplicity and effectiveness of the protection solution in this case. The author provides an overview and detailed descriptions of voltage controls, distinguishing between generalities of underdeveloped, on-field operating applications and modern and available automatic control solutions, which are as yet not sufficiently known or perceived for what they are: practical, high-performance and reliable solutions. At th...

  8. The System Impact of Air-Conditioner Under-voltage Protection Schemes

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Ning; Yang, Bo; Huang, Zhenyu; Bravo, Richard

    2009-03-31

    This paper presents simulation results of evaluating an under-voltage protection scheme designed to take stalled air-conditioner (a/c) units offline such that the slow voltage recovery phenomena can be solved on areas heavily loaded with a/c motors during summer peak periods. A three feeder test-bed has been first used to quantify the effectiveness of the protection scheme and the sensitivity of the under-voltage relay settings. Then two real system events of the Western US power grid have been studied to evaluate the area impact of the protection scheme proposed by Southern California Edison. The study demonstrates that by taking all or most of the stalled a/c unit offline, the feeder voltage will recover in a few seconds, much quicker than the tens of seconds that the standard thermal relays imbedded in the motors need to trip the units. The drawback of the control scheme is that after the voltage recover, it settled at a higher voltage than before the faults because a large chuck of load has been shed.

  9. A Protection Circuit for DC-DC Converter with Voltage Doubler

    Directory of Open Access Journals (Sweden)

    D.Elangovan

    2012-12-01

    Full Text Available This paper proposes a method to obtain a protected voltage gain by employing a protection circuit for the voltage doubler or multiplier circuit in an isolated tyde DC-DC Converter. The entire set up consists of a phase shift converter with a protected bridge/voltage doubler rectifier on the output side. The operating frequency of the phase shift converter is 20-25kHz (depending on the requirement of the application which is high enough to improve the efficiency. Ferrite core transformer is used in place of ordinary air core transformer, which is small in size with number of turns of the transformer is reduced and the overall power density is increased. The doubler circuit consists of electrolytic capacitors, which are rated at 400V in order to comply with IEC65 requirements. This paper proposes an “electrolytic capacitor protection circuit”, which enables the voltage rating of the electrolytics to be reduced to 250V. This circuit results in cost savings of more than 50% in the price of the electrolytic filter capacitors. The circuits were simulated using PSPICE SOFTWARE and the following results were obtained. For an input voltage of 200V, an output of 200V and400V were obtained in bridge mode and doubler mode respectively.

  10. [Transient high frequency nodal rhythm after a high voltage electric shock. Report of one case].

    Science.gov (United States)

    Supervía, August; Del Baño, Francisco; Aguirre, Alfons; Membrilla, Estela

    2013-09-01

    Electrical shock can cause a direct myocardial damage and different types of arrhythmias, which are uncommon and occur more often when there is a high voltage exposure. We report a 19-year-old male that received a high voltage shock, falling thereafter from an altitude of four meters. On admission to the emergency room, he had second and third degree burns in the right hand and the left thigh. The electrocardiogram showed a nodal rhythm of 72 beats per minute. After four hours of monitoring, sinus rhythm returned spontaneously.

  11. A Capacitor-Free, Fast Transient Response Linear Voltage Regulator In a 180nm CMOS

    DEFF Research Database (Denmark)

    Deleuran, Alexander N.; Lindbjerg, Nicklas; Pedersen, Martin K.;

    2015-01-01

    A 1.8 V capacitor-free linear regulator with fast transient response based on a new topology with a fast and slow regulation loop is presented. The design has been laid out and simulated in a 0.18 µm CMOS process. The design has a low component count and is tailored for system-on-chip integration...

  12. Short-circuit protection of LLC resonant converter using voltages across resonant tank elements

    Directory of Open Access Journals (Sweden)

    Denys Igorovych Zaikin

    2015-06-01

    Full Text Available This paper describes two methods for the short-circuit protection of the LLC resonant converter. One of them uses the voltage across the capacitor and the other uses the voltage across the inductor of the resonant tank. These voltages can be processed (integrated or differentiated to recover the resonant tank current. The two circuits illustrated in the described methods make it possible to develop a robust LLC converter design and to avoid using lossy current measurement elements, such as a shunt resistor or current transformer. The methods also allow measuring resonant tank current without breaking high-current paths and connecting the measuring circuit in parallel with the inductor or capacitor of the resonant tank. Practical implementations of these indirect current measurements have been experimentally tested for the short-circuit protection of the 1600 W LLC converter.

  13. An improved GGNMOS triggered SCR for high holding voltage ESD protection applications

    Science.gov (United States)

    Zhang, Shuai; Dong, Shu-Rong; Wu, Xiao-Jing; Zeng, Jie; Zhong, Lei; Wu, Jian

    2015-10-01

    Developing an electrostatic discharge (ESD) protection device with a better latch-up immunity has been a challenging issue for the nanometer complementary metal-oxide semiconductor (CMOS) technology. In this work, an improved grounded-gate N-channel metal-oxide semiconductor (GGNMOS) transistor triggered silicon-controlled rectifier (SCR) structure, named GGSCR, is proposed for high holding voltage ESD protection applications. The GGSCR demonstrates a double snapback behavior as a result of progressive trigger-on of the GGNMOS and SCR. The double snapback makes the holding voltage increase from 3.43 V to 6.25 V as compared with the conventional low-voltage SCR. The TCAD simulations are carried out to verify the modes of operation of the device.

  14. An improved GGNMOS triggered SCR for high holding voltage ESD protection applications

    Institute of Scientific and Technical Information of China (English)

    张帅; 董树荣; 吴晓京; 曾杰; 钟雷; 吴健

    2015-01-01

    Developing an electrostatic discharge (ESD) protection device with a better latch-up immunity has been a challeng-ing issue for the nanometer complementary metal-oxide semiconductor (CMOS) technology. In this work, an improved grounded-gate N-channel metal-oxide semiconductor (GGNMOS) transistor triggered silicon-controlled rectifier (SCR) structure, named GGSCR, is proposed for high holding voltage ESD protection applications. The GGSCR demonstrates a double snapback behavior as a result of progressive trigger-on of the GGNMOS and SCR. The double snapback makes the holding voltage increase from 3.43 V to 6.25 V as compared with the conventional low-voltage SCR. The TCAD simulations are carried out to verify the modes of operation of the device.

  15. Computer simulation and experimental study of transient processes in a single-phase voltage transformer

    Science.gov (United States)

    Kruzhaev, A. V.; Elagin, I. A.; Pavleino, M. A.; Dmitriev, V. A.; Chaly, A. M.

    2015-02-01

    We perform simulation and experimental investigation of transient processes emerging in a single-phase transformer when it is connected to the network. The transformer model constructed taking into account the saturation of the steel of the core differs from standard models in detailed accounting for the magnetic flux leakage, which is required, for example, for a correct description of inrush current. Universality of the model for the type of transformers under study is ensured by the allowance for eddy current losses and calculation of the magnetic hysteresis in the steel core. The latter makes it possible to estimate the effect of residual magnetization of the core on the form of a transient process, which is studied in detail. The methods for computing model parameters are described and its experimental verification is carried out.

  16. Vacuum Circuit Breaker Modelling for the Assessment of Transient Recovery Voltages Under Various Network Configurations

    DEFF Research Database (Denmark)

    Bak, Claus Leth; Borghetti, Alberto; Glasdam, Jakob Bærholm

    2017-01-01

    for both VCB sizing and insulation coordination studies of the components nearby the switching device. In this respect, their accurate modelling, which is the object of the paper, becomes crucial. In particular, the paper presents (the concept of) a VCB model and two relevant applications showing the model......-known electromagnetic transient simulation environments, namely, EMTP-RV and PSCAD/EMTDC. The procedure adopted for the identification of the VCB model parameters is described....

  17. Characteristics of Overvoltage Protection with Cascade Application of Surge Protective Devices in Low-Voltage AC Power Circuits

    Directory of Open Access Journals (Sweden)

    RADULOVIC, V.

    2015-08-01

    Full Text Available Surge Protective Devices (SPDs are widely used for protection of the equipment in low-voltage AC power circuits against wide variety of surges. Cascade application of SPDs starting at the service entrance of a building and downstream toward near sensitive equipment is intended to ensure optimal energy distribution among installed SPDs, as well as proper equipment protection against surges. Characteristics of overvoltage protection with two-stage application of SPDs have been analyzed in the paper through performed measurements, followed by simulations and numerical modeling using the ATP/EMTP and MATLAB Simulink. Parametric analysis of the protection's characteristics in wide range of influencing factors has been performed in order to define a set of applicable solutions for proper selection and performance of SPDs.

  18. The effect of gas mixing and biased disc voltage on the preglow transient of electron cyclotron resonance ion source

    Energy Technology Data Exchange (ETDEWEB)

    Tarvainen, O.; Toivanen, V.; Komppula, J.; Kalvas, T.; Koivisto, H. [Department of Physics, University of Jyvaeskylae, Jyvaeskylae 40500 (Finland)

    2012-02-15

    The effect of gas mixing and biased disc voltage on the preglow of electron cyclotron resonance ion source plasma has been studied with the AECR-U type 14 GHz ion source. It was found that gas mixing has a significant effect on the preglow. The extracted transient beam currents and efficiency of the heavier species increase, while the currents and efficiency of the lighter species decrease when gas mixing is applied. The effect of the biased disc was found to be pronounced in continuous operation mode in comparison to preglow. The data provide information on the time scales of the plasma processes explaining the effects of gas mixing and biased disc. The results also have implications on production of radioactive ion beams in preglow mode for the proposed Beta Beam neutrino factory.

  19. Key Technologies Development of Transient Signals Based Protection Device Using DSP and S-Transform

    Science.gov (United States)

    Liu, Xingmao; Zheng, Gao

    2017-05-01

    The correctness of new principle of transient signal based protection used to be verified by simulating. In order to further introduce the dynamic simulation experiments for the transient signal based protection algorithm, the key technologies of transient signal based protection device were developed. The hardware of the synchronous multi-channel data acquisition and high-speed data processing was designed with kernel of high speed floating point digital signal processor TMS320C6748 and simultaneous sampling analog-to-digital converter. The sampling program reads the AD conversion data using DMA mode, which reduce the consumption of CPU time. The S transform was used to extract the fault traveling wave signals from the sampled data. The time consumption of algorithm which extract the traveling wave was analyzed when it ran on TMS320C6748. The test result shows that the hardware and software design is feasible.

  20. NBTI-Aware Transient Fault Rate Analysis Method for Logic Circuit Based on Probability Voltage Transfer Characteristics

    Directory of Open Access Journals (Sweden)

    Zhiming Yang

    2016-01-01

    Full Text Available The reliability of Very Large Scale Integration (VLSI circuits has become increasingly susceptible to transient faults induced by environmental noise with the scaling of technology. Some commonly used fault tolerance strategies require statistical methods to accurately estimate the fault rate in different parts of the logic circuit, and Monte Carlo (MC simulation is often applied to complete this task. However, the MC method suffers from impractical computation costs due to the size of the circuits. Furthermore, circuit aging effects, such as negative bias temperature instability (NBTI, will change the characteristics of the circuit during its lifetime, leading to a change in the circuit’s noise margin. This change will increase the complexity of transient fault rate estimation tasks. In this paper, an NBTI-aware statistical analysis method based on probability voltage transfer characteristics is proposed for combinational logic circuit. This method can acquire accurate fault rates using a discrete probability density function approximation process, thus resolving the computation cost problem of the MC method. The proposed method can also consider aging effects and analyze statistical changes in the fault rates. Experimental results demonstrate that, compared to the MC simulation, our method can achieve computation times that are two orders of magnitude shorter while maintaining an error rate less than 9%.

  1. A PMOS multipled LVTSCR device for ESD protection with a higher holding voltage

    Institute of Scientific and Technical Information of China (English)

    JIANG Tong-quan; WANG Yang; HUANG Wei; LUO Qi-yuan; JIN Xiang-liang

    2014-01-01

    A novel LVTSCR structure for 5 V on-chip protection against Electrostatic Discharge(ESD) stress at input or output pads is presented. Silvaco 2D TCAD software is used to simulate the device including electrical and thermal characteristics. The new device exchanges the diffusion region of N+ and P+ in N-WELL and introduces a PMOS-like structure to discharge ESD current before Low Voltage Triggering SCR(LVTSCR) starting to work. And the device simulation results show that it obtains a higher holding voltage(10.51 V) and a faster turn on speed(1.05×10-10 s) compared with LVTSCR, with the triggering voltage only increasing slightly from 12.45 V to 15.35 V. Also, in order to make sure that the PMOS structure will trigger first and will not cause thermal breakdown problem, nearly the same channel length as NMOS should be chosen for PMOS structure.

  2. Distance protection of multiple-circuit shared tower transmission lines with different voltages. Part I: Fault current magnitude

    DEFF Research Database (Denmark)

    Silva, Filipe Miguel Faria da; Bak, Claus Leth

    2017-01-01

    Multiple-circuit transmission lines combining different voltage levels in one tower present extra challenges when setting a protection philosophy, as faults between voltage levels are possible. This paper presents a detailed theoretical analysis of such combined faults, including the development...... of a formula for estimating the magnitude of the short-circuit current. It is demonstrated that if the faulted phase from the higher voltage level leads the faulted phase from the lower voltage level, a distance relay at the higher voltage level sees the fault in the forward direction, whereas a distance relay...... at the lower voltage level sees the fault in the reverse direction. The opposite happens if the lower voltage level leads the higher voltage level. It is also demonstrated that the magnitude of fault currents of combined faults is normally slightly larger than of equivalent single-phase-to-ground fault...

  3. A novel transient rotor current control scheme of a doubly-fed induction generator equipped with superconducting magnetic energy storage for voltage and frequency support

    Science.gov (United States)

    Shen, Yang-Wu; Ke, De-Ping; Sun, Yuan-Zhang; Daniel, Kirschen; Wang, Yi-Shen; Hu, Yuan-Chao

    2015-07-01

    A novel transient rotor current control scheme is proposed in this paper for a doubly-fed induction generator (DFIG) equipped with a superconducting magnetic energy storage (SMES) device to enhance its transient voltage and frequency support capacity during grid faults. The SMES connected to the DC-link capacitor of the DFIG is controlled to regulate the transient dc-link voltage so that the whole capacity of the grid side converter (GSC) is dedicated to injecting reactive power to the grid for the transient voltage support. However, the rotor-side converter (RSC) has different control tasks for different periods of the grid fault. Firstly, for Period I, the RSC injects the demagnetizing current to ensure the controllability of the rotor voltage. Then, since the dc stator flux degenerates rapidly in Period II, the required demagnetizing current is low in Period II and the RSC uses the spare capacity to additionally generate the reactive (priority) and active current so that the transient voltage capability is corroborated and the DFIG also positively responds to the system frequency dynamic at the earliest time. Finally, a small amount of demagnetizing current is provided after the fault clearance. Most of the RSC capacity is used to inject the active current to further support the frequency recovery of the system. Simulations are carried out on a simple power system with a wind farm. Comparisons with other commonly used control methods are performed to validate the proposed control method. Project supported by the National Natural Science Foundation of China (Grant No. 51307124) and the Major Program of the National Natural Science Foundation of China (Grant No. 51190105).

  4. Distance protection of multiple-circuit shared tower transmission lines with different voltages. Part II: Fault loop impedance

    DEFF Research Database (Denmark)

    Silva, Filipe Miguel Faria da; Bak, Claus Leth

    2017-01-01

    Multiple-circuit transmission lines combining different voltage levels in one tower present extra challenges when setting a protection philosophy, as faults between voltage levels are possible. In this paper, the fault loop impedance of combined faults is compared with the fault loop impedance...... of single-phase-to-ground faults at the higher voltage level of the multiple-circuit line and it is demonstrated that they are similar for high short-circuit powers; however, the fault loop impedance of a combined fault may increase substantially as the short-circuit power of the system decreases......-phase-to-ground faults are also capable of protecting the line against combined faults, being only advisable to increase the resistive limit of the protection zone if the network has lower short-circuit power. If the length of the line at lower voltage level is less than of the lien at higher voltage level...

  5. ASPECTS OF SURGE ARRESTERS’ MAXIMUM OPERATING VOLTAGE CHOICE FOR ELECTRICAL EQUIPMENT INSULATION PROTECTION IN 6-35 KV MAINS

    Directory of Open Access Journals (Sweden)

    Yu. N. Shumilov

    2013-09-01

    Full Text Available The paper shows that, in 6-35 kV mains, application of a non-linear surge arrester (SA with the maximum continuous admissible operating voltage which is 10% higher than the mains’ maximum operating voltage results in the SA protection from overheating and subsequent breakdown at nonnormable lifetime of single-phase arc faults.

  6. A Primary and Backup Protection Algorithm based on Voltage and Current Measurements for HVDC Grids

    OpenAIRE

    Abedrabbo, Mudar; Van Hertem, Dirk

    2016-01-01

    DC grids are susceptible to DC side faults, which lead to a rapid rise of the DC side currents. DC side faults should be detected in a very short time before fault currents cause damage to the system or equipment, e.g., exceed the maximum interruptible limits of DC circuit breaker. This paper presents a primary and backup protective data-based algorithm. The proposed algorithm depends on the local voltage and current measurements to detect and identify various kinds of faults in the HVDC grid...

  7. Reliability of semiconductor and gas-filled diodes for over-voltage protection exposed to ionizing radiation

    Directory of Open Access Journals (Sweden)

    Stanković Koviljka

    2009-01-01

    Full Text Available The wide-spread use of semiconductor and gas-filled diodes for non-linear over-voltage protection results in a variety of possible working conditions. It is therefore essential to have a thorough insight into their reliability in exploitation environments which imply exposure to ionizing radiation. The aim of this paper is to investigate the influence of irradiation on over-voltage diode characteristics by exposing the diodes to californium-252 combined neutron/gamma radiation field. The irradiation of semiconductor over-voltage diodes causes severe degradation of their protection characteristics. On the other hand, gas-filled over-voltage diodes exhibit a temporal improvement of performance. The results are presented with the accompanying theoretical interpretations of the observed changes in over-voltage diode behaviour, based on the interaction of radiation with materials constituting the diodes.

  8. Effects of Energy Storage Systems Grid Code Requirements on Interface Protection Performances in Low Voltage Networks

    Directory of Open Access Journals (Sweden)

    Fabio Bignucolo

    2017-03-01

    Full Text Available The ever-growing penetration of local generation in distribution networks and the large diffusion of energy storage systems (ESSs foreseen in the near future are bound to affect the effectiveness of interface protection systems (IPSs, with negative impact on the safety of medium voltage (MV and low voltage (LV systems. With the scope of preserving the main network stability, international and national grid connection codes have been updated recently. Consequently, distributed generators (DGs and storage units are increasingly called to provide stabilizing functions according to local voltage and frequency. This can be achieved by suitably controlling the electronic power converters interfacing small-scale generators and storage units to the network. The paper focuses on the regulating functions required to storage units by grid codes currently in force in the European area. Indeed, even if such regulating actions would enable local units in participating to network stability under normal steady-state operating conditions, it is shown through dynamic simulations that they may increase the risk of unintentional islanding occurrence. This means that dangerous operating conditions may arise in LV networks in case dispersed generators and storage systems are present, even if all the end-users are compliant with currently applied connection standards.

  9. Final Report - Durable Catalysts for Fuel Cell Protection during Transient Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Atanasoski, Radoslav [3M Company, St. Paul, MN (United States); van der Vliet, Dennis [3M Company, St. Paul, MN (United States); Cullen, David [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Atanasoska, Ljiljana [3M Company, St. Paul, MN (United States)

    2015-01-26

    The objective of this project was to develop catalysts that will enable proton exchange membranes (PEM) fuel cell systems to weather the damaging conditions in the fuel cell at voltages beyond the thermodynamic stability of water during the transient periods of start-up/shut-down and fuel starvation. Such catalysts are required to make it possible for the fuel cell to satisfy the 2015 DOE targets for performance and durability. The project addressed a key issue of importance for successful transition of PEM fuel cell technology from development to pre-commercial phase. This issue is the failure of the catalyst and the other thermodynamically unstable membrane electrode assembly (MEA) components during start-up/shut-down and local fuel starvation at the anode, commonly referred to as transient conditions. During these periods the electrodes can reach potentials higher than the usual 1.23V upper limit during normal operation. The most logical way to minimize the damage from such transient events is to minimize the potential seen by the electrodes. At lower positive potentials, increased stability of the catalysts themselves and reduced degradation of the other MEA components is expected.

  10. Voltage sags and transient detection and classification using half/one-cycle windowing techniques based on continuous s-transform with neural network

    Science.gov (United States)

    Daud, Kamarulazhar; Abidin, Ahmad Farid; Ismail, Ahmad Puad

    2017-08-01

    This paper was conducted to detect and classify the different power quality disturbance (PQD) using Half and One-Cycle Windowing Technique (WT) based on Continuous S-Transform (CST) and Neural Network (NN). The system using 14 bus bars based on IEEE standard had been designing using MATLAB©/Simulink to provide PQD data. The datum of PQD is analyzed by using WT based on CST to extract features and it characteristics. Besides, the study focused an important issue concerning the identification of PQD selection and detection, the feature and characteristics of two types of signals such as voltage sag and transient signal are obtained. After the feature extraction, the classified process had been done using NN to show the percentage of classification PQD either voltage sags or transients. The analysis show which selection of cycle for windowing technique can provide the smooth detection of PQD and the suitable characteristic to provide the highest percentage of classification of PQD.

  11. Electromagnetic transient analysis and Novell protective relaying techniques for power transformers

    CERN Document Server

    Lin, X; Tian, Q; Weng, H

    2015-01-01

    This book addresses the technical challenges of transformer malfunction analysis as well as protection. One of the current research directions is the malfunction mechanism analysis due to nonlinearity of transformer core and comprehensive countermeasures on improving the performance of transformer differential protection. Here, the authors summarize their research outcomes and present a set of recent research advances in the electromagnetic transient analysis, the application on power transformer protections, and present a more systematic investigation and review in this field. This research area is still progressing, especially with the fast development of Smart Grid. This book is an important addition to the literature and will enhance significant advancement in research. It is a good reference book for researchers in power transformer protection research and a good text book for graduate and undergraduate students in electrical engineering.

  12. Study of protection devices against the effects of electric discharges inside a very high voltage generator: the Vivitron accelerator; Etude de dispositifs de protection contre les effets des decharges electriques au sein d`un generateur de tres haute tension: l`accelerateur Vivitron

    Energy Technology Data Exchange (ETDEWEB)

    Nolot, E.

    1996-10-31

    The Vivitron tandem is a large electrostatic accelerator comprising a Van de Graaff generator designed to reach terminal voltages of around 30 MV. The machine is limited at rather lower nominal voltages (about 20 MV) due to the sensitivity of the insulating column structure to transient overvoltages. These are induced by electrical discharges in compressed SF{sub 6}. This thesis first aims at analysing the fundamental reasons of electrical discharges in order to limit the probability of their occurrence. Then we simulate the transient overvoltages induced and present some improvements which may lead to a stable behaviour of the Vivitron at nominal voltages higher than 20 MV. Initially we deduce discharge onset voltages and actual breakdown field limitations in the different gap geometries from analysis of possible breakdown mechanisms in compressed SF{sub 6}. In a second part, some electrical characteristics of the insulating column structure are measured at high voltage. Fast rising oscillating waves induced by sparking in the Vivitron, along with the associated energies,are determined in the third part. The last part deals with new surge protections of the insulating column structure. Spark gaps with precise onset voltage and optimized shielding electrodes are discussed. ZnO-based varistors designed for operation at very high fields have also been developed in order to reduce transient overvoltage values. (author). 122 refs.

  13. Voltage gated calcium channels negatively regulate protective immunity to Mycobacterium tuberculosis.

    Directory of Open Access Journals (Sweden)

    Shashank Gupta

    Full Text Available Mycobacterium tuberculosis modulates levels and activity of key intracellular second messengers to evade protective immune responses. Calcium release from voltage gated calcium channels (VGCC regulates immune responses to pathogens. In this study, we investigated the roles of VGCC in regulating protective immunity to mycobacteria in vitro and in vivo. Inhibiting L-type or R-type VGCC in dendritic cells (DCs either using antibodies or by siRNA increased calcium influx in an inositol 1,4,5-phosphate and calcium release calcium activated channel dependent mechanism that resulted in increased expression of genes favoring pro-inflammatory responses. Further, VGCC-blocked DCs activated T cells that in turn mediated killing of M. tuberculosis inside macrophages. Likewise, inhibiting VGCC in infected macrophages and PBMCs induced calcium influx, upregulated the expression of pro-inflammatory genes and resulted in enhanced killing of intracellular M. tuberculosis. Importantly, compared to healthy controls, PBMCs of tuberculosis patients expressed higher levels of both VGCC, which were significantly reduced following chemotherapy. Finally, blocking VGCC in vivo in M. tuberculosis infected mice using specific antibodies increased intracellular calcium and significantly reduced bacterial loads. These results indicate that L-type and R-type VGCC play a negative role in M. tuberculosis infection by regulating calcium mobilization in cells that determine protective immunity.

  14. Transient Recovery Voltages at the Main 132kV Line Bay GIS Circuit Breaker in a Windfarm

    DEFF Research Database (Denmark)

    Arana Aristi, Iván; Okholm, J.; Holbøll, Joachim

    2011-01-01

    parameters in the network was evaluated during a fault in the onshore substation. The rate of rise of recovery voltage (RRRV) and the maximum crest voltage (Uc) of the TRV across the GIS CB were compared against the standard values based on the type test results from the GIS. The investigations were...

  15. Comparison and analysis of transient performances for doubly fed induction generator wind turbine under grid voltage dip

    DEFF Research Database (Denmark)

    Li, H.; Ye, R.; Han, L.

    2010-01-01

    In order to entirely analyze the transient performances of a grid-connected doubly fed induction generator (DFIG) wind turbine under the different operational states, based on the transient models of DFIG, a two-mass wind turbine electrical equivalent model considering the torsional flexibility o...

  16. Transient thermal protection of film covering circular aperture by sublimation and weak decomposition

    Energy Technology Data Exchange (ETDEWEB)

    Havstad, Mark A.; Miles, Robin R.; Hsieh, Henry, E-mail: hsieh6@llnl.gov

    2015-03-15

    Highlights: • Precise sublimating layers can provide protection in transient thermal environments. • Sensitivity analysis shows that the uncertainty in properties has modest influence. • It is likely that methane layers are a good choice for IFE targets. - Abstract: Unwanted heating of sensitive surfaces in harsh thermal environments can be prevented by precise application of sacrificial materials such as sublimation layers and pyrolyzing films. The use of sublimation for the protection of circular polyimide membranes subjected to brief (∼100 ms) heating by infrared radiation and hot (6000 K) inert gas convection is analyzed. Selection of sublimation material and sublimation layer and membrane thickness is considered with emphasis on providing sufficient thermal protection yet negligible unwanted material remaining at the end of a specified heating period. Though the analysis here is general, the motivation is protection of the polyimide films covering the laser entrance holes on IFE (inertial fusion energy) hohlraums being injected into the hot gas (xenon) protecting IFE reactor chambers. Both one and two dimensional thermal models are used to develop a robust thermal concept. Sensitivity analyses (SA) methods are exercised to show where the design may be vulnerable and which input parameters have the greatest effect on performance and likelihood of success. For the design and conditions considered, methane sublimating layers are probably preferred over xenon or pentane.

  17. 基于集合Kalman滤波的暂态电压扰动检测%Transient voltage disturbances detection based on Ensemble-Kalman filtering

    Institute of Scientific and Technical Information of China (English)

    江辉; 邹崇杰; 谢兴; 彭建春

    2014-01-01

    With the increase of nonlinear loads in power system, power quality problems caused by transient voltage disturbance is more and more serious, the detection of transient voltage disturbance signal becomes the key to improve power quality. This paper proposes a transient voltage disturbance detection method based on Ensemble-Kalman filtering, the elements of Ensemble-Kalman filtering’s background ensemble are reformed according to the characteristics of transient voltage disturbance. The modified values of voltage state atk - 1 andk - 2 form the background ensemble, then the real-time voltage’s amplitude is obtained by recursive computation, thus the beginning and ending times of transient disturbances are positioned and abrupt amplitude is traced out. Simulation results show that the proposed method can quickly detect voltage’s sag/swell, precisely position the beginning and ending times of transient voltage disturbance, and track down the abrupt amplitude. The proposed method is more effective than the traditional Kalman filter (KF) and root-mean-square (RMS) algorithm. This work is supported by National Natural Science Foundation of China (No. 51177102).%随着电力系统中非线性负荷的增加,由暂态电压扰动引起的电能质量问题越来越严重,对暂态电压扰动信号的检测成为改善电能质量的关键。基于集合Kalman滤波方法进行暂态电压扰动检测分析,结合暂态电压扰动特点,构造了集合Kalman滤波的背景集合。由k-1,k-2时刻的电压状态修正值组成背景集合,然后进行递归运算,提取出实时的电压幅值,从而定位暂态扰动发生的起止时刻以及跟踪突变的幅值。仿真结果表明,所提方法能快速检测到电压暂降/突升、暂态电压脉冲信号发生的起止时刻,跟踪到突变幅值。其对谐波加电压暂降混合扰动信号的扰动起止时刻以及混合扰动信号中基波、谐波的幅值的跟踪也非常有效

  18. Transient loads identification for a standoff metallic thermal protection system panel.

    Energy Technology Data Exchange (ETDEWEB)

    Hundhausen, R. J. (Roy Jason); Adams, Douglas E.; Derriso, Mark; Kukuchek, Paul; Alloway, Richard

    2004-01-01

    Standoff thermal protection system (TPS) panels are critical structural components in future aerospace vehicles because they protect the vehicle from the hostile environment encountered during space launch and reentry. Consequently, the panels are exposed to a variety of loads including high temperature thermal stresses, thermal shock, acoustic pressure, and foreign object impacts. Transient impacts are especially detrimental because they can cause immediate and severe degradation of the panel in the form of, for example, debonding and buckling of the face sheet, cracking of the fasteners, or deformation of the standoffs. Loads identification methods for determining the magnitude and location of impact loads provide an indication of TPS components that may be more susceptible to failure. Furthermore, a historical database of impact loads encountered can be retained for use in the development of statistical models that relate impact loading to panel life. In this work, simulated inservice transient loads are identified experimentally using two methods: a physics-based approach and an inverse Frequency Response Function (FRF) approach. It is shown that by applying the inverse FRF method, the location and magnitude of these simulated impacts can be identified with a high degree of accuracy. The identified force levels vary significantly with impact location due to the differences in panel deformation at the impact site indicating that resultant damage due to impacts would vary with location as well.

  19. Adaptive Voltage Stability Protection Based on Load Identification Using Phasor Measurement Units

    DEFF Research Database (Denmark)

    Liu, Leo; Bak, Claus Leth; Chen, Zhe

    2011-01-01

    collapse. In this paper, the online load identification using measurement-based approach based on Phasor Measurement Units (PMU) was proposed to evaluate the proximity to voltage instability in order to prevent voltage collapse. In the scenarios of disturbances, the proximity to voltage collapse...

  20. Actions of a hydrogen sulfide donor (NaHS) on transient sodium, persistent sodium, and voltage-gated calcium currents in neurons of the subfornical organ.

    Science.gov (United States)

    Kuksis, Markus; Ferguson, Alastair V

    2015-09-01

    Hydrogen sulfide (H2S) is an endogenously found gasotransmitter that has been implicated in a variety of beneficial physiological functions. This study was performed to investigate the cellular mechanisms underlying actions of H2S previously observed in subfornical organ (SFO), where H2S acts to regulate blood pressure through a depolarization of the membrane and an overall increase in the excitability of SFO neurons. We used whole cell patch-clamp electrophysiology in the voltage-clamp configuration to analyze the effect of 1 mM NaHS, an H2S donor, on voltage-gated potassium, sodium, and calcium currents. We observed no effect of NaHS on potassium currents; however, both voltage-gated sodium currents (persistent and transient) and the N-type calcium current had a depolarized activation curve and an enhanced peak-induced current in response to a series of voltage-step and ramp protocols run in the control and NaHS conditions. These effects were not responsible for the previously observed depolarization of the membrane potential, as depolarizing effects of H2S were still observed following block of these conductances with tetrodotoxin (5 μM) and ω-conotoxin-GVIA (100 nM). Our studies are the first to investigate the effect of H2S on a variety of voltage-gated conductances in a single brain area, and although they do not explain mechanisms underlying the depolarizing actions of H2S on SFO neurons, they provide evidence of potential mechanisms through which this gasotransmitter influences the excitability of neurons in this important brain area as a consequence of the modulation of multiple ion channels.

  1. Lightning protection of mobile phone stations in high voltage towers; Blitzschutz bei Mobilfunkstationen auf Mittel- und Hochspannungsmasten. Schutz vor Ueberspannungen

    Energy Technology Data Exchange (ETDEWEB)

    Balzer, G. [TU Darmstadt (Germany); Richter, B. [ABB Hochpannungstechnik, Baden (Switzerland); Schmitt, O. [RWE Net AG, Siegen (Germany)

    2002-12-02

    Transmitter units for mobile phone networks are often installed in existing high voltage towers. In these cases a strict separation of the grounding systems is essential to avoid interferences between the high voltage area and the low voltage energy supply for the mobile phone transmitter station. In order to protect the safety transformer of the mobile phone installation against lightning surges a metall-oxide (MO-) surge arrester is necessary, which furthermore has to withstand the power frequency voltage in case of a single-phase fault in the high voltage power line. For a 110 kV system the power frequency voltage in case of a single-phase short circuit as well as the lightning current stress for a MO-surge arrester is calculated. (orig.) [German] Der weltweit zunehmende Ausbau der Mobilfunknetze erfordert eine grosse Anzahl von Standorten fuer Sende- und Empfangsanlagen. Dabei werden neben neuen Mobilfunkmasten auch Mittel- und Hochspannungsmaste genutzt. Zum Schutz der in den Mobilfunkanlagen eingesetzten Trenntransformatoren gegen moegliche Blitzeinwirkungen werden Metalloxid-Ueberspannungsableiter (MO-Ableiter) eingesetzt. Die Verfasser erlaeutern die geeignete Dimensionierung anhand praktischer Anwendungsbeispiele. (orig.)

  2. Calcium Transients in Dendrites of Neocortical Neurons Evoked by Single Subthreshold Excitatory Postsynaptic Potentials via Low-Voltage-Activated Calcium Channels

    Science.gov (United States)

    Markram, Henry; Sakmann, Bert

    1994-05-01

    Simultaneous recordings of membrane voltage and concentration of intracellular Ca2+ ([Ca2+]_i) were made in apical dendrites of layer 5 pyramidal cells of rat neocortex after filling dendrites with the fluorescent Ca2+ indicator Calcium Green-1. Subthreshold excitatory postsynaptic potentials (EPSPs), mediated by the activation of glutamate receptor channels, caused a brief increase in dendritic [Ca2+]_i. This rise in dendritic [Ca2+]_i was mediated by the opening of low-voltage-activated Ca2+ channels in the dendritic membrane. The results provide direct evidence that dendrites do not function as passive cables even at low-frequency synaptic activity; rather, a single subthreshold EPSP changes the dendritic membrane conductance by opening Ca2+ channels and generating a [Ca2+]_i transient that may propagate towards the soma. The activation of these Ca2+ channels at a low-voltage threshold is likely to influence the way in which dendritic EPSPs contribute to the electrical activity of the neuron.

  3. A new technique to study transient conductivity under pulsed monochromatic light in Cr-doped GaAs using acoustoelectric voltage measurement

    Science.gov (United States)

    Tabib-Azar, Massood

    1991-01-01

    The transient conductivity of high-resistivity Bridgman-grown Cr-doped GaAs under pulsed monochromatic light is monitored using transverse acoustoelectric voltage (TAV) at 83 K. Keeping the photon flux constant, the height and transient time constant at the TAV are used to calculate the energy dependence of the trap density and its cross section, respectively. Two prominent trap profiles with peak trap densities of approximately 10 to the 17th/cu cm eV near the valence and the conduction bands are detected. These traps have very small capture cross sections in the range of 10 to the -23 to 10 to the -21st cm sq. A phenomenon similar to the persistent photoconductivity with transient time constants in excess of a few seconds in high-resistivity GaAs at T = 83 K is also detected using this technique. These long relaxation times are readily explained by the spatial separation of the photo-excited electron-hole pairs and the small capture cross section and large density of trap distribution near the conduction band.

  4. Transient Analysis of Thermal Protection System for X-33 Aircraft using MSC/NASTRAN

    Science.gov (United States)

    Miura, Hirokazu; Chargin, M. K.; Bowles, J.; Tam, T.; Chu, D.; Chainyk, M.; Green, Michael J. (Technical Monitor)

    1997-01-01

    X-33 is an advanced technology demonstrator vehicle for the Reusable Launch Vehicle (RLV) program. The thermal protection system (TPS) for the X-33 is composed of complex layers of materials to protect internal components, while withstanding severe external temperatures induced by aerodynamic heating during high speed flight. It also serves as the vehicle aeroshell in some regions using a stand-off design. MSC/NASTRAN thermal analysis capability was used to predict transient temperature distribution (within the TPS) throughout a mission, from launch through the cool-off period after landing. In this paper, a typical analysis model, representing a point on the vehicle where the liquid oxygen tank is closest to the outer mold line, is described. The maximum temperature difference between the outer mold line and the internal surface of the liquid oxygen tank can exceed 1500 F. One dimensional thermal models are used to select the materials and determine the thickness of each layer for minimum weight while insuring that all materials remain within the allowable temperature range. The purpose of working with three dimensional (3D) comprehensive models using MSC/NASTRAN is to assess the 3D radiation effects and the thermal conduction heat shorts of the support fixtures.

  5. Circuits protection against interferences in high voltage substations; Protecao de circuitos contra interferencias em subestacoes

    Energy Technology Data Exchange (ETDEWEB)

    Hamada, Massayuki [Consultas e Aplicacoes de Engenharia Eletrica Ltda. (CAEEL) (Brazil)

    1989-12-01

    This paper makes a brief analysis of the different phenomena which may cause electromagnetic interference in high voltage substations and suggests adequate solutions to the problem according to the different events that may occur. 5 refs., 1 fig.

  6. Transient voltage-dependent potassium currents are reduced in NTS neurons isolated from renal wrap hypertensive rats.

    Science.gov (United States)

    Belugin, Sergei; Mifflin, Steve

    2005-12-01

    Whole cell patch-clamp measurements were made in neurons enzymatically dispersed from the nucleus of the solitary tract (NTS) to determine if alterations occur in voltage-dependent potassium channels from rats made hypertensive (HT) by unilateral nephrectomy/renal wrap for 4 wk. Some rats had the fluorescent tracer DiA applied to the aortic nerve before the experiment to identify NTS neurons receiving monosynaptic baroreceptor afferent inputs. Mean arterial pressure (MAP) was greater in 4-wk HT (165 +/- 5 mmHg, n = 26, P NTS neurons from NT and HT rats. At activation voltages from -10 to +10 mV, TOCs were significantly less in HT neurons compared with those observed in NT neurons (P NTS neurons from NT and HT rats and was not different comparing neurons from NT and HT rats. However, examination of the subset of NTS neurons exhibiting somatic DiA fluorescence revealed that DiA-labeled neurons from HT rats had a significantly shorter duration delayed excitation (n = 8 cells, P = 0.022) than DiA-labeled neurons from NT rats (n = 7 cells). Neurons with delayed excitation from HT rats had a significantly broader first action potential (AP) and a slower maximal downstroke velocity of repolarization compared with NT neurons with delayed excitation (P = 0.016 and P = 0.014, respectively). The number of APs in the first 200 ms of a sustained depolarization was greater in HT than NT neurons (P = 0.012). These results suggest that HT of 4-wk duration reduces TOCs in NTS neurons, and this contributes to reduced delayed excitation and increased AP responses to depolarizing inputs. Such changes could alter baroreflex function in hypertension.

  7. N- and L-type voltage-gated calcium channels mediate fast calcium transients in axonal shafts of mouse peripheral nerve.

    Directory of Open Access Journals (Sweden)

    Ruxandra eBarzan

    2016-06-01

    Full Text Available In the peripheral nervous system a vast number of axons are accommodated within fiber bundles that constitute peripheral nerves. A major function of peripheral axons is to propagate action potentials along their length, and hence they are equipped with Na+ and K+ channels, which ensure successful generation, conduction and termination of each action potential. However little is known about Ca2+ ion channels expressed along peripheral axons and their possible functional significance. The goal of the present study was to test whether voltage-gated Ca2+ channels (VGCCs are present along peripheral nerve axons in situ and mediate rapid activity-dependent Ca2+ elevations under physiological circumstances. To address this question we used mouse sciatic nerve slices, Ca2+ indicator Oregon Green BAPTA-1, and 2-photon Ca2+ imaging in fast line scan mode (500 Hz. We report that transient increases in intra-axonal Ca2+ concentration take place along peripheral nerve axons in situ when axons are stimulated electrically with single pulses. Furthermore, we show for the first time that Ca2+ transients in peripheral nerves are fast, i.e. occur in a millisecond time-domain. Combining Ca2+ imaging and pharmacology with specific blockers of different VGCCs subtypes we demonstrate that Ca2+ transients in peripheral nerves are mediated mainly by N-type and L-type VGCCs. Discovery of fast Ca2+ entry into the axonal shafts through VGCCs in peripheral nerves suggests that Ca2+ may be involved in regulation of action potential propagation and/or properties in this system, or mediate neurotransmitter release along peripheral axons as it occurs in the optic nerve and white matter of the central nervous system.

  8. N- and L-Type Voltage-Gated Calcium Channels Mediate Fast Calcium Transients in Axonal Shafts of Mouse Peripheral Nerve.

    Science.gov (United States)

    Barzan, Ruxandra; Pfeiffer, Friederike; Kukley, Maria

    2016-01-01

    In the peripheral nervous system (PNS) a vast number of axons are accommodated within fiber bundles that constitute peripheral nerves. A major function of peripheral axons is to propagate action potentials along their length, and hence they are equipped with Na(+) and K(+) channels, which ensure successful generation, conduction and termination of each action potential. However little is known about Ca(2+) ion channels expressed along peripheral axons and their possible functional significance. The goal of the present study was to test whether voltage-gated Ca(2+) channels (VGCCs) are present along peripheral nerve axons in situ and mediate rapid activity-dependent Ca(2+) elevations under physiological circumstances. To address this question we used mouse sciatic nerve slices, Ca(2+) indicator Oregon Green BAPTA-1, and 2-photon Ca(2+) imaging in fast line scan mode (500 Hz). We report that transient increases in intra-axonal Ca(2+) concentration take place along peripheral nerve axons in situ when axons are stimulated electrically with single pulses. Furthermore, we show for the first time that Ca(2+) transients in peripheral nerves are fast, i.e., occur in a millisecond time-domain. Combining Ca(2+) imaging and pharmacology with specific blockers of different VGCCs subtypes we demonstrate that Ca(2+) transients in peripheral nerves are mediated mainly by N-type and L-type VGCCs. Discovery of fast Ca(2+) entry into the axonal shafts through VGCCs in peripheral nerves suggests that Ca(2+) may be involved in regulation of action potential propagation and/or properties in this system, or mediate neurotransmitter release along peripheral axons as it occurs in the optic nerve and white matter of the central nervous system (CNS).

  9. A micro-power LDO with piecewise voltage foldback current limit protection

    Institute of Scientific and Technical Information of China (English)

    Wei Hailong; Liu Youbao; Guo Zhongjie; Liao Xue

    2012-01-01

    To achieve a constant current limit,low power consumption and high driving capability,a micro-power LDO with a piecewise voltage-foldback current-limit circuit is presented.The current-limit threshold is dynamically adjusted to achieve a maximum driving capability and lower quiescent current of only 300 nA.To increase the loop stability of the proposed LDO,a high impedance transconductance buffer under a micro quiescent current is designed for splitting the pole that exists at the gate of the pass transistor to the dominant pole,and a zero is designed for the purpose of the second pole phase compensation.The proposed LDO is fabricated in a BiCMOS process.The measurement results show that the short-circuit current of the LDO is 190 mA,the constant limit current under a high drop-out voltage is 440 mA,and the maximum load current under a low drop-out voltage is up to 800 mA.In addition,the quiescent current of the LDO is only 7 μA,the load regulation is about 0.56% on full scale,the line regulation is about 0.012%/V,the PSRR at 120 Hz is 58 dB and the drop-out voltage is only 70 mV when the load current is 250 mA.

  10. Mapping of sites facing aqueous environment of voltage-gated proton channel at resting state: a study with PEGylation protection.

    Science.gov (United States)

    Kurokawa, Tatsuki; Okamura, Yasushi

    2014-01-01

    Hv1 (also named, voltage-sensor only protein, VSOP) lacks an authentic pore domain, and its voltage sensor domain plays both roles in voltage sensing and proton permeation. The activities of a proton channel are intrinsic to protomers of Hv1, while Hv1 is dimeric in biological membranes; cooperative gating is exerted by interaction between two protomers. As the signature pattern conserved among voltage-gated channels and voltage-sensing phosphatase, Hv1 has multiple arginines intervened by two hydrophobic residues on the fourth transmembrane segment, S4. S4 moves upward relative to other helices upon depolarization, causing conformational change possibly leading to the formation of a proton-selective conduction pathway. However, detailed mechanisms of proton-selectivity and gating of Hv1 are unknown. Here we took an approach of PEGylation protection assay to define residues facing the aqueous environment of mouse Hv1 (mHv1). Accessibilities of two maleimide molecules, N-ethylmaleimide (NEM) and 4-acetamido-4'-maleimidylstilbene-2,2'-disulfonic acid (AMS), were examined on cysteine introduced into individual sites. Only the first arginine on S4 (R1: R201) was inaccessible by NEM and AMS in mHv1. This is consistent with previous results of electrophysiology on the resting state channel, suggesting that the accessibility profile represents the resting state of mHv1. D108, critical for proton selectivity, was accessible by AMS and NEM, suggesting that D108 faces the vestibule. F146, a site critical for blocking by a guanidinium-reagent, was accessible by NEM, suggesting that F146 also faces the inner vestibule. These findings suggest an inner vestibule lined by several residues on S2 including F146, D108 on S1, and the C-terminal half of S4. © 2013.

  11. ELABORATION OF HIGH-VOLTAGE PULSE INSTALLATIONS AND PROVIDING THEIR OPERATION PROTECTIVE MEASURES

    Directory of Open Access Journals (Sweden)

    А. М. Hashimov

    2016-01-01

    Full Text Available The article presents design engineering methods for the high-voltage pulse installations of technological purpose for disinfection of drinking water, sewage, and edible liquids by high field micro- and nanosecond pulsing exposure. Designing potentialities are considered of the principal elements of the high-voltage part and the discharge circuit of the installations towards assuring the best efficient on-load utilization of the source energy and safe operation of the high-voltage equipment. The study shows that for disinfection of drinking water and sewage it is expedient to apply microsecond pulse actions causing the electrohydraulic effect in aqueous media with associated complex of physical processes (ultraviolet emission, generation of ozone and atomic oxygen, mechanical compression waves, etc. having detrimental effect on life activity of the microorganisms. In case of disinfecting edible liquids it is recommended to use the nanosecond pulses capable of straight permeating the biological cell nucleus, inactivating it. Meanwhile, the nutritive and biological values of the foodstuffs are saved and their organoleptic properties are improved. It is noted that in elaboration process of high-frequency pulse installations special consideration should be given to issues of the operating personnel safety discipline and securing conditions for the entire installation uninterrupted performance. With this objective in view the necessary requirements should be fulfilled on shielding the high- and low-voltage installation parts against high-frequency electromagnetic emissions registered by special differential sensors. Simultaneously, the abatement measures should be applied on the high-voltage equipment operational noise level. The authors offer a technique for noise abatement to admissible levels (lower than 80 dB A by means of coating the inside surface with shielded enclosure of densely-packed abutting sheets of porous electro-acoustic insulating

  12. Study on Transient Voltage Stability of Wind Farm Incorporated System with Reactive Power Compensation Devices%含无功补偿装置的风电并网系统暂态电压稳定性研究

    Institute of Scientific and Technical Information of China (English)

    吴丽娜; 邵龙; 刘观起; 陶善宏

    2014-01-01

    ABSTRACT:To deal with the problem of transient voltage stability in the power system integrated with large-scale wind farms,this paper discusses the mechanism of transient voltage instability and the analysis method of transient voltage stability. Meanwhile,it introduces two important reactive power compen-sation devices that are SVC and STATCOM. The BPA software is used for the simulation analysis of an actual national power grid. The results show that wind speed variation and system short-circuit fault can affect transient voltage stability of power system,resulting in a reduction of the system voltage level. Both SVC and STATCOM can give support to the system voltage, and the support effect of STATCOM is more obvious.%针对大规模风电并网后系统的暂态电压稳定性问题,阐述了暂态电压失稳的机理以及暂态电压稳定性的分析计算方法,介绍了2种重要的无功补偿装置SVC和STATCOM。采用BPA软件对国内某一实际电网进行了仿真分析,结果表明,风速变化和系统发生短路故障均会对系统的暂态电压稳定性造成影响,导致系统的电压水平降低。装设SVC或STATCOM对系统电压均有支撑作用,且STATCOM对电压的支撑作用更加明显。

  13. A Dynamic Reactive Power Reserve Optimization Method to Enhance Transient Voltage Security%提高暂态电压安全水平的动态无功备用优化方法

    Institute of Scientific and Technical Information of China (English)

    孙全才; 程浩忠; 张健; 王琦; 宋越; 刘明松; 杨堤; 李诗旸

    2015-01-01

    Dynamic reactive power reserve of power system is vital to improve transient voltage security. An novel definition of reactive power reserve considering transient voltage security in transient procession was proposed. Correction coefficient to evaluate reactive power reserve's contribution to transient voltage security was given. Corrected reactive power reserve was computed through trace sensitivity method. Then an optimization model to enhance transient voltage security was built. It was solved by primal dual interior point method. Testing on IEEE 39-node system,it is indicated that three weight coefficients proposed are reasonable and effective. The evaluation method can give consideration both supporting capacity of one bus to the other and demand of reactive power reserve according to severity of faults. The system's transient voltage security is enhanced by the way of optimization of system's dynamic reactive power reserve. Hence, the method proposed can be used to prevent the happening of transient voltage collapse during system's fault.%电力系统动态无功储备对提高系统暂态电压安全水平具有重要作用,因此提出一种在系统暂态过程中考虑暂态电压安全的无功备用概念,并给出其对暂态电压安全贡献的评价方法及相应的修正系数.通过轨迹灵敏度方法实现对修正后的无功源动态无功备用的计算,建立提高系统暂态电压安全水平的无功备用优化模型,利用原对偶内点法进行求解.IEEE 39节点算例结果表明,所提3种权重系数合理、有效,通过该评价方式可以充分考虑到无功备用点对点的支撑能力以及故障严重性对无功备用的要求程度,通过系统动态无功备用的优化可提高系统的整体暂态电压安全水平,因此所提方法能够有效地预防系统故障时暂态电压安全问题的发生.

  14. Control and Protection in Low Voltage Grid with Large Scale Renewable Electricity Generation

    DEFF Research Database (Denmark)

    Mustafa, Ghullam

    of renewable energy based DGs are reduced CO2 emission, reduced operational cost as almost no fuel is used for their operation and less transmission and distribution losses as these units are normally built near to the load centers. This has also resulted in some operational challenges due to the unpredictable...... of the wind speed and solar irradiation fluctuations are tackled. The CIGRE Low Voltage (LV) network comprising two solar PV generating units of 3 kW and 4 kW, one 5.5 kW fixed-pitch fix speed WTG and two battery units each producing energy of 30kwh and 21kwh has been chosen for the study. The study...... the distribution system and the transmission grid has been proposed here. The algorithms, models and methodologies developed during this research study have been tested in a CIGRE low voltage distribution network. The simulation results show that they are able to correctly identify the states of the distribution...

  15. Evaluation results on the effectiveness of the corrosion protection system for underground pipelines, using the DC-voltage gradient technique

    Energy Technology Data Exchange (ETDEWEB)

    Ribeiro, Antonio Carlos [Petroquimica Uniao S.A., Santo Andre, SP (Brazil)

    2003-07-01

    A pipeline of diameter 6'' with 17.694 km of extension was evaluated how much to the integrity of its external covering and the effectiveness of the system of cathodic protection, using the method DC-Voltage Gradient. The Cathodic Protection in this pipeline is made by seven rectifiers. The gotten data indicate that the potential pipe-ground registered in some check points to the long one of the pipeline is extremely negative, what has led to a super protection of the pipeline for the CP. This if explains for the great proximity between the anodes and the pipeline. For km had been identified 917 failures with a mean density of 50,1 per Km. Beyond the analysis of the data, this work includes conclusions and recommendations detailed for the repairs of the covering of the pipeline and for improvement of the effectiveness of the CP. One sends regards to a combination of repairs in the covering and reevaluation of the CP, in way to improve the protection level and to assure the reduction of the risk of external corrosion. (author)

  16. Simulation of Transient Voltage Security of Large-Scale Power Grid Under Three-Level Voltage Control System and Its Control Strategy%三级电压控制体系下大电网暂态电压安全仿真及其控制策略

    Institute of Scientific and Technical Information of China (English)

    杨银国; 林舜江; 欧阳逸风; 刘明波; 温柏坚; 辛拓

    2013-01-01

      在Matlab环境下,借助电力系统分析工具箱(PSAT)实现了包含三级电压控制系统的大电网动态时域仿真,并分析其对广东电网暂态电压安全性的影响。结果表明该系统的二级电压控制紧急动作模式虽然有利于广东电网故障后的暂态电压恢复,但不能阻止暂态电压不安全事故的发生。进而,建立了针对暂态电压不安全故障的紧急切负荷控制优化模型,通过采用轨迹灵敏度法将动态优化模型转化为线性规划模型以获得紧急切负荷控制策略,动态仿真结果验证了所得控制策略能够使广东电网在严重故障后恢复暂态电压安全。%In Matlab environment and using power system analysis tools (PSAT) software, the dynamic time-domain simulation of large-scale power grid with three-level voltage control system is implemented, and the influences of three-level voltage control system on transient voltage security of Guangdong power grid are analyzed. Analysis results show that the emergency action mode of secondary voltage control in the three-level voltage control system contributes to the post-fault transient voltage recovery of load buses in Guangdong power grid, however it cannot prevent the occurrence of transient voltage insecurity. For this reason, in allusion to transient voltage insecurity accident an optimal control strategy for emergency load shedding, in which the trajectory sensitivity is utilized to turn the dynamic optimal model into linear programming model to achieve emergency load shedding control strategy, is established, and it is verified by dynamic simulation that after serious fault the transient voltage security of Guangdong power grid can be recovered by the achieved control strategy.

  17. Current interruption transients calculation

    CERN Document Server

    Peelo, David F

    2014-01-01

    Provides an original, detailed and practical description of current interruption transients, origins, and the circuits involved, and how they can be calculated Current Interruption Transients Calculationis a comprehensive resource for the understanding, calculation and analysis of the transient recovery voltages (TRVs) and related re-ignition or re-striking transients associated with fault current interruption and the switching of inductive and capacitive load currents in circuits. This book provides an original, detailed and practical description of current interruption transients, origins,

  18. Lightning, surge and transient protection. Citations from the NTIS data base

    Science.gov (United States)

    Reed, W. E.

    1980-06-01

    Techniques and devices for the protection of electronic and electrical equipment are presented in these Federally sponsored research reports. The citations include research on suppressors, limiters, lightning arresters, electromagnetic pulse protection devices, and overvoltage protection networks. Electromagnetic shielding is excluded. This updated bibliography contains 106 abstracts, 44 of which are new entries to the previous edition.

  19. A facile approach to derive binder protective film on high voltage spinel cathode materials against high temperature degradation

    Science.gov (United States)

    Chou, Wei-Yu; Jin, Yi-Chun; Duh, Jenq-Gong; Lu, Cheng-Zhang; Liao, Shih-Chieh

    2015-11-01

    The electrochemical performance of spinel LiNi0.5Mn1.5O4 cathode combined with different binders at elevated temperature is firstly investigated. The water soluble binder, such as sodium carboxymethyl cellulose (CMC) and sodium alginate (SA), is compared with the polyvinylidene difluoride (PVdF) binder used in non-aqueous process. The aqueous process can meet the need of Li-ion battery industry due to environmental-friendly and cost effectiveness by replacing toxic organic solvent, such as N-methyl-pyrrolidone (NMP). In this study, a significantly improved high temperature cycling performance is successfully obtained as compared to the traditional PVdF binder. The aqueous binder can serve as a protective film which inhibits the serious Ni and Mn dissolution especially at elevated temperature. Our result demonstrates a facile approach to solve the problem of capacity fading for high voltage spinel cathodes.

  20. The principle of elaboration of the relay protection against short circuits between the closely placed phases of high voltage electrical line

    Directory of Open Access Journals (Sweden)

    Kiorsak M.

    2015-12-01

    Full Text Available The article is devoted to the elaboration of the principle of relay protection against short circuits between the closely placed phases of higher voltage electrical line with self-compensation, based on the six phase’s symmetrical components. It is shown that the unsymmetrical short circuits between the closely placed phases are characterized by appearance of zero and tertiary sequences of symmetrical components. This fact can be used to choose them for relay protection. The electrical basic circuits and formulas for calculation of the passive parameters of zero and tertiary filters of currents (voltages are done. It is presented the structural-functional basic circuit scheme for relay protection against short circuits between the closely placed phases of higher voltage electrical line with self-compensation.

  1. An Unassisted Low-Voltage-Trigger ESD Protection Structure in a 0.18-µm CMOS Process without Extra Process Cost

    Science.gov (United States)

    Li, Bing; Shan, Yi

    In order to quickly discharge the electrostatic discharge (ESD) energy, an unassisted low-voltage-trigger ESD protection structure is proposed in this work. Under transmission line pulsing (TLP) stress, the trigger voltage, turn-on speed and second breakdown current can be obviously improved, as compared with the traditional protection structure. Moreover there is no need to add any extra mask or do any process modification for the new structure. The proposed structure has been verified in foundry's 0.18-µm CMOS process.

  2. Fault Transient Analysis and Protection Performance Evaluation within a Large-scale PV Power Plant

    Directory of Open Access Journals (Sweden)

    Wen Jinghua

    2016-01-01

    Full Text Available In this paper, a short-circuit test within a large-scale PV power plant with a total capacity of 850MWp is discussed. The fault currents supplied by the PV generation units are presented and analysed. According to the fault behaviour, the existing protection coordination principles with the plant are considered and their performances are evaluated. Moreover, these protections are examined in simulation platform under different operating situations. A simple measure with communication system is proposed to deal with the foreseeable problem about the current protection scheme in the PV power plant.

  3. Transient ischemic attack induced by melted solid lipid microparticles protects rat brains from permanent focal ischemia.

    Science.gov (United States)

    Tsai, M-J; Kuo, Y-M; Tsai, Y-H

    2014-09-01

    This study aims to develop a transient ischemic attack (TIA) model in conscious animals and uses this model to investigate the effect of TIA on subsequent permanent ischemia. TIA was induced by injecting designed temperature-sensitive melted solid lipid microparticles with a melting point around body temperature into male Wistar rats via arterial cannulation. Neurologic deficit was monitored immediately after the injection without anesthesia. According to the clinical definition of TIA, rats were divided into neurologic symptom durations ischemic stroke was induced 3d after the induction of TIA by injecting a different kind of embolic particle manufactured by blending chitin and PLGA. The ischemic stroke.

  4. 电力系统大扰动下暂态电压稳定的动态特征分析%Dynamic eigen analysis of transient voltage stability under large disturbance for power system

    Institute of Scientific and Technical Information of China (English)

    刘彦呈; 王川; 魏一

    2011-01-01

    A dynamic eigen analysis method is presented aiming at the defects that current voltage stability research results cannot give the explicit criterion about transient voltage stability information. First, this paper establishes an integrated mathematical model reflecting power system transient process with the consideration of speed-adjusting and excitation-control, i.e., Non-linear Differential Algebraic Equations (NDAE). Second, all the eigen values and left, right eigen vectors are solved by using implicit trapezoidal integration method to build Jacobian matrix dynamically in the process of step-by-step integration of NDAE. Finally, this paper calculates all the participating factors of eigen vectors corresponding with all status variables. Then, transient voltage instability criterion is proposed. Simulation results after comparing the method with time domain simulation demonstrate that the transient voltage instability criterion is correct. The paper provides a novel way to research power system transient voltage stability in terms of combining linear system theory with numerical integration.This work is supported by Natural Science Foundation of Liaoning Province (No. 20092148).%针对目前电力系统电压稳定性研究成果难以给出明确的暂态稳定判定信息的缺陷,提出一种电力系统大扰动下暂态电压稳定的动态特征分析方法.该方法首先建立反映电力系统暂态过渡过程的计及调速与励磁控制的综合数学模型,即非线性微分代数方程组(Non-linear Differential Algebraic Equations,NDAE);其次在运用隐式梯形积分法对NDAE进行逐步积分过程中动态生成Jacobian矩阵,并求解出全部特征根及左,右特征向量;最后计算出各个状态变量与之对应特征向量的相关因子,基于此给出暂态电压失稳的判据.该方法通过与时域仿真法的对比结果证明所提出系统暂态电压失稳判据的正确性,为今后从线性系统理论与数值积分

  5. Transient fault behavior in a microprocessor: A case study

    Science.gov (United States)

    Duba, Patrick

    1989-01-01

    An experimental analysis is described which studies the susceptibility of a microprocessor based jet engine controller to upsets caused by current and voltage transients. A design automation environment which allows the run time injection of transients and the tracing from their impact device to the pin level is described. The resulting error data are categorized by the charge levels of the injected transients by location and by their potential to cause logic upsets, latched errors, and pin errors. The results show a 3 picoCouloumb threshold, below which the transients have little impact. An Arithmetic and Logic Unit transient is most likely to result in logic upsets and pin errors (i.e., impact the external environment). The transients in the countdown unit are potentially serious since they can result in latched errors, thus causing latent faults. Suggestions to protect the processor against these errors, by incorporating internal error detection and transient suppression techniques, are also made.

  6. Amyloid Precursor Protein Protects Neuronal Network Function after Hypoxia via Control of Voltage-Gated Calcium Channels.

    Science.gov (United States)

    Hefter, Dimitri; Kaiser, Martin; Weyer, Sascha W; Papageorgiou, Ismini E; Both, Martin; Kann, Oliver; Müller, Ulrike C; Draguhn, Andreas

    2016-08-10

    Acute cerebral ischemia and chronic neurovascular diseases share various common mechanisms with neurodegenerative diseases, such as disturbed cellular calcium and energy homeostasis and accumulation of toxic metabolites. A link between these conditions may be constituted by amyloid precursor protein (APP), which plays a pivotal role in the pathogenesis of Alzheimer's disease, but has also been associated with the response to acute hypoxia and regulation of calcium homeostasis. We therefore studied hypoxia-induced loss of function and recovery upon reoxygenation in hippocampal slices of mice lacking APP (APP(-/-)) or selectively expressing its soluble extracellular domain (APPsα-KI). Transient hypoxia disrupted electrical activity at the network and cellular level. In mice lacking APP, these impairments were significantly more severe, showing increased rise of intracellular calcium, faster loss of function, and higher incidence of spreading depression. Likewise, functional recovery upon reoxygenation was much slower and less complete than in controls. Most of these deficits were rescued by selective expression of the soluble extracellular fragment APPsα, or by pharmacological block of L-type calcium channels. We conclude that APP supports neuronal resistance toward acute hypoxia. This effect is mediated by the secreted APPsα-domain and involves L-type calcium channels. Amyloid precursor protein (APP) is involved in the pathophysiology of Alzheimer's disease, but its normal function in the brain remains elusive. Here, we describe a neuroprotective role of the protein in acute hypoxia. Functional recovery of mouse hippocampal networks after transient reduction of oxygen supply was strongly impaired in animals lacking APP. Most protective effects are mediated by the soluble extracellular fragment APPsα and involve L-type calcium channels. Thus, APP contributes to calcium homeostasis in situations of metabolic stress. This finding may shed light on the physiological

  7. 恒压钳位高速关断瞬变电磁发射系统%Voltage stabilized clamping and fast turn-off transient electromagnetic transmitting system

    Institute of Scientific and Technical Information of China (English)

    赵海涛; 刘丽华; 吴凯; 张建国; 方广有

    2013-01-01

    Transient electromagnetic transmitter is an important part in transient electromagnetic detection equipment. In the aspects of high-power current steep pulse transmission, high precision synchronous control, falling-edge linearity , short turn-off time, turn-off time measurement and etc. , there are still a lot of problems to be solved urgently. This paper proposes a novel extra fast turn-off transient electromagnetic transmitting system, DSP and FPGA are used to work together and provide the system with reliable driving signals and protective measures. The system adopts a voltage stabilized clamping circuit and a damping resistance circuit, and has the characteristics of short turn-off time, high current falling-edge linearity and high transmission current; besides it can improve the speed of pulse current rising-edge. The system also adopts a novel turn-off time measurement circuit, which makes the measurement simple and accurate. A GPS synchronous controller is designed, which adopts a cooperative operation mode with a temperature compensated crystal, solves the GPS short-time failure problem and improves the reliability of the system. The transmitting system field experiment was carried out,experiment results show that the system features high transmission current, good current falling-edge linearity, accurate turn-off time measurement, and precise and reliable synchronous control. The system is easy to carry,convenient to operate,and has excellent performance.%瞬变电磁发射机是瞬变电磁探测设备中的重要组成部分,在大功率电流陡脉冲发射、高精度同步控制、下降沿线性度、短关断时间和关断时间测量等方面,有许多亟待解决的问题.提出了一种瞬变电磁发射系统,DSP和FPGA协同工作为系统提供可靠的驱动信号和保护措施;提出了恒压钳位电路,配合合适的阻尼吸收电路,具有关断时间短、电流下降沿线性度高和发射电流大的特点,并可提升脉冲

  8. Delayed administration of interleukin-1 receptor antagonist protects against transient cerebral ischaemia in the rat.

    Science.gov (United States)

    Mulcahy, Nicholas J; Ross, Jerard; Rothwell, Nancy J; Loddick, Sarah A

    2003-10-01

    The cytokine interleukin-1 (IL-1) has been implicated in ischaemic, excitotoxic and traumatic brain damage in rodents. The naturally occurring IL-1 receptor antagonist (IL-1ra) markedly reduces neuronal injury in these conditions. However, the effects of IL-1ra on focal, transient cerebral ischaemia in the rat, which is of major clinical relevance, have not been reported. The objectives of this study were to test the effects of IL-1ra on cell death after temporary cerebral ischaemia, and to investigate the therapeutic time window for IL-1ra treatment. Ischaemia was induced by temporary (60 min) occlusion of the middle cerebral artery (MCAO) in rats, via surgical insertion (and subsequent removal) of a thread into the internal carotid artery. Damage was quantified at various times after MCAO to investigate the temporal progression of damage and establish an appropriate time to assess the effects of IL-1ra on cell death. Cell death was complete 18-24 h after temporary MCAO. Intracerebroventricular injection of IL-1ra (10 microg) at the time of MCAO and 60 min later reduced the lesion volume measured 24 h (57% reduction) or 48 h (52% reduction) after MCAO. Cell death was also significantly reduced when IL-1ra (20 microg) was administered as a single injection, 1 h (47%), 2 h (57%) or 3 h (46%) after MCAO, when compared to vehicle. These data show that IL-1ra markedly reduces cell death even when administration is delayed until 3 h after induction of reversible, focal cerebral ischaemia in the rat, and support our proposal that IL-1ra may be of therapeutic benefit in stroke.

  9. A new ROIC with high-voltage protection circuit of HgCdTe e-APD FPA for passive and active imaging

    Science.gov (United States)

    Chen, Guoqiang; Zhang, Junling; Wang, Pan; Zhou, Jie; Gao, Lei; Ding, Ruijun

    2012-12-01

    HgCdTe electrons initiated avalanche photodiodes (e-APDs) in linear multiplication mode can be used for high speed applications such as active imaging. A readout integrated circuit of e-APD FPA is designed for dual mode passive/active imaging system. Unit cell circuit architecture of ROIC includes a high voltage protection module, a Sample-Hold circuit module, a comparator, output driver stage and a integrator module which includes a amplifier and three capacitors. Generally, APD FPA works at reversed bias such as 5V-15V in active imaging mode, and pixels' dark currents increase exponentially as the reverse-bias voltage is increased. Some cells of ROIC may be short to high voltage because of avalanche breakdown of diodes. If there is no protection circuit, the whole ROIC would be burnt out. Thus a protection circuit module introduced in every ROIC cell circuit is necessary to make sure the rest units of ROIC can still work. Conventional 5V CMOS process is applied to implement the high voltage protection with the small area other than LDMOS in high voltage BCD process in the limited 100μm×100μm pitch area. In integrator module, three integration capacitors are included in the ROIC to provide switchable well capacity. One of them can be shared in two modes in order to save area. Constraints such as pixel area and power lead us design toward a simple one-stage cascade operational transconductance amplifier (OTA) as pre-amplifier which can avoid potential instability caused by inaccuracy of MOSFET Model at 77K.

  10. THE MATHEMATICAL MODEL FOR DESCRIBING TRANSIENT CHARACTERISTICS OF TCSC BASED ON CAPACITOR VOLTAGE SYNCHRONIZATION MODE%电容电压同步下TCSC暂态特性的数学描述

    Institute of Scientific and Technical Information of China (English)

    葛俊; 童陆园; 耿俊成

    2001-01-01

    When the capacitor voltage is taken as synch-ronizing signal, there is obvious overshoot and oscillations in Thyristor Controlled Series Compensation(TCSC) tra nsients. However, the mechanism for this phenomenon is not explained in existing literatures yet. By the Topology method , this paper chooses conduction angle of thyristors as the object function an d builds a two-order difference equation mathematical model describing T CSC transient behaviors under capacitor voltage synchronization mode. Based on t he derived model, the factors affecting TCSC transient characteristics are discu ssed. Also the transient mechanism of TCSC is revealed under capacitor voltage synchronization mode.The model is verified by digital simulation results.%当选择电容电压作为同步信号时,可控串被(TCSC)的暂态过程会出现明显的超调和振荡,对于这一现象,前人还从未给出相应的机理解释。该文以晶闸管导通角为建模对象,采用拓扑建模法建立了能描述电容电压同步下TCSC暂态特性变化规律的二阶差分数学模型。借助该模 型可分析影响暂态过程的相关因素,进而从本质上揭示了电容电压同步下TCSC的暂态机理。 数字仿真结果验证了所建模型的正确性。

  11. A novel role of transient receptor potential mucolipin1 (TRPML1) in protecting against imidazole-induced cytotoxicity.

    Science.gov (United States)

    Liu, Zhenxing; Zhao, Shuan; Wu, Shuaishuai; Zhang, Jingyou; Nie, Zunyang; Zeng, Shenming

    2014-08-01

    Lysosomotropic amines cause serious side effects such as cytoplasmic vacuolation and cell death. TRPML1 (also known as mucolipin1), a member of the transient receptor potential (TRP) protein family, may regulate fusion/fission of vesicles along the endocytic pathway and some aspects of lysosomal ion homeostasis. Nevertheless, it is still unknown whether TRPML1 is involved in death of mammalian cells induced by lysosomotropic agents. In this study, imidazole was used as a model to investigate the role of TRPML1 in the cytotoxicity of lysosomotropic agents. Overexpression of wild-type TRPML1 inhibited imidazole-induced vacuole formation and cell death in human endometrial adenocarcinoma (HEC-1B) cells. In contrast, siRNA-mediated TRPML1 knockdown increased the cell death induced by imidazole. Bafilomycin A1 raises the pH of acidic organelles and therefore suppresses accumulation of weak bases in them. Similarly, lysosomal pH was raised in TRPML1-overexpressing cells; therefore, we inferred that TRPML1 protected against imidazole toxicity by regulating the pH of acidic organelles. We concluded that TRPML1 had a novel role in protecting against lysosomotropic amine toxicity.

  12. Frequency domain model for transient analysis of lightning protection systems of buildings.

    Science.gov (United States)

    Gómez, Pablo

    2016-10-01

    A frequency domain modeling approach for lightning protection systems (LPS) of buildings is described and validated in this paper. The model is based on a 2-port transmission line representation of each conductor, and the further assembling of a network representing the complete structure. Horizontal and vertical conductors are modeled using formulas based on the complex images method, in order to take into account frequency dependence. Variation of electrical parameters with height is also considered for vertical conductors. This is accomplished by means of a non-uniform modeling approach based on conductor subdivision and cascaded connection of chain matrices computed for each segment. The results from the model are validated by means of comparisons with measurements reported elsewhere, as well as simulations using PSCAD/EMTDC.

  13. Analysis on the Simulation of Interphase Power Controller Over-voltage and Its Protection%相间功率控制器过电压及其保护的仿真分析

    Institute of Scientific and Technical Information of China (English)

    李娟; 郑明; 张乐斌; 陈继军

    2011-01-01

    针对相间功率控制器(interphase power controller,IPC)在潮流控制过程中过电压及其保护的问题,基于相间功率控制器的基本结构原理,建立了电压与元件参数之间关系的数学模型,探讨了IPC过电压出现的原因及其保护系统的组成,并以两电网带IPC 240联络线为例采用Matlab中的Simulink搭建了仿真模型,进行了各种运行状态下的过电压及其保护的仿真分析.结果表明:正常运行时调节IPC的参数超过一定的范围会引起过电压;IPC端口开路时产生的谐振过电压是各种运行状态下最严重的;由于受断路器动作的影响,单相接地短路故障引起暂态过电压是各种短路故障中最严重的.在各种运行状态的过电压保护仿真中,IPC端口并联氧化物限压器(metal oxide varistors,MOV)及IPC电容、电感元件两端并联带触发间隙和旁路开关的MOV与断路器配合均能起到有效的过电压保护作用,严重情况下MOV并联的间隙电路被触发后能保护MOV.%The problem of over-voltage and its protection of interphase power controller (IPC) during controlling power flow were analyzed. A mathematical model of relationship between voltage and component parameters was established based on the basic theory of IPC construction, then the reasons of over-voltage and protection component were discussed. The simulation model of two networks with IPC 240 tie-line was established to analyze the problem using the Simulink model of MATLAB. The results show that over-voltage may be caused if adjusting the parameters of IPC beyond the certain scope , the resonance over-voltage values are maximal with IPC port opening, and the most severe transient over-voltage occurs on single phase to ground for action of breakers. Consequently, metal oxide varistors (MOV) are installed at the IPC port, and IPC capacitive and inductive branch are combined with circuit breakers parallel MOV with a triggered gap and bypass circuit

  14. High-Field Quench Behavior and Protection of $Bi_2 Sr_2 Ca Cu_2 O_x$ Coils: Minimum and Maximum Quench Detection Voltages

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Tengming [Fermilab; Ye, Liyang [NCSU, Raleigh; Turrioni, Daniele [Fermilab; Li, Pei [Fermilab

    2015-01-01

    Small insert coils have been built using a multifilamentary Bi2Sr2CaCu2Ox round wire, and characterized in background fields to explore the quench behaviors and limits of Bi2Sr2CaCu2Ox superconducting magnets, with an emphasis on assessing the impact of slow normal zone propagation on quench detection. Using heaters of various lengths to initiate a small normal zone, a coil was quenched safely more than 70 times without degradation, with the maximum coil temperature reaching 280 K. Coils withstood a resistive voltage of tens of mV for seconds without quenching, showing the high stability of these coils and suggesting that the quench detection voltage shall be greater than 50 mV to not to falsely trigger protection. The hot spot temperature for the resistive voltage of the normal zone to reach 100 mV increases from ~40 K to ~80 K with increasing the operating wire current density Jo from 89 A/mm2 to 354 A/mm2 whereas for the voltage to reach 1 V, it increases from ~60 K to ~140 K, showing the increasing negative impact of slow normal zone propagation on quench detection with increasing Jo and the need to limit the quench detection voltage to < 1 V. These measurements, coupled with an analytical quench model, were used to access the impact of the maximum allowable voltage and temperature upon quench detection on the quench protection, assuming to limit the hot spot temperature to <300 K.

  15. 基于DSP和小波变换的电压暂态扰动在线监测方法研究%Study of voltage transient disturbance on-line detection based on DSP and wavelet transform

    Institute of Scientific and Technical Information of China (English)

    王飞; 黄细霞; 张兵; 骆秀江

    2015-01-01

    A voltage disturbance detection device based on DSP2812 is designed in this paper. A method of transient voltage disturbance detection based on DSP and wavelet transform is studied. The system takes a Hall sensor and the parallel A/D con⁃verter chip as its acquisition circuit,and a kind of digital signal processing chip TMS320F2812 as its core information process⁃ing unit,by which the design of DSP and its peripheral circuit are achieved. The discrete wavelet transform(DWT)is adopted to detect transient voltage disturbance on line and realize wavelet algorithm in DSP. Software modules including the main pro⁃gram module,A/D module,interrupt module,communication module and so on were designed. Its simulation experiment was performed in Matlab to choose suitable wavelet functions and to locate disturbance position by utilizing DB4 wavelet in Matlab. The signal generator is used to produce the signal including transient voltage disturbance. The power acquisition and real⁃time analysis of transient voltage disturbance can be realized simultaneously by the strong operation ability of DSP and the effective DWT algorithm. The contrast test shows that the system has high precision,high data processing speed and perfect capability for real⁃time detection of transient voltage disturbance.%设计了一款基于DSP2812的电压暂态扰动在线检测装置,研究了基于DSP和小波变换的电压暂态扰动在线检测方法。该装置通过霍尔传感器和模数转换芯片采集电信号,以高性能数字信号处理芯片TMS320F2812为核心信息处理单元,完成了DSP及其外围电路设计。采用小波变换在线检测电压暂态扰动,并在DSP中实现了小波算法,软件还包括主程序模块、A/D采集模块、中断模块、上位机处理模块和通讯模块等设计。实验首先在Matlab中进行了仿真实验,选取合适的小波函数,利用Matlab中的DB4小波对扰动进行定位;然后再利用信号发生

  16. Cellular immunity confers transient protection in experimental Buruli ulcer following BCG or mycolactone-negative Mycobacterium ulcerans vaccination.

    Directory of Open Access Journals (Sweden)

    Alexandra G Fraga

    Full Text Available BACKGROUND: Buruli ulcer (BU is an emerging infectious disease caused by Mycobacterium ulcerans that can result in extensive necrotizing cutaneous lesions due to the cytotoxic exotoxin mycolactone. There is no specific vaccine against BU but reports show some degree of cross-reactive protection conferred by M. bovis BCG immunization. Alternatively, an M. ulcerans-specific immunization could be a better preventive strategy. METHODOLOGY/PRINCIPAL FINDINGS: In this study, we used the mouse model to characterize the histological and cytokine profiles triggered by vaccination with either BCG or mycolactone-negative M. ulcerans, followed by footpad infection with virulent M. ulcerans. We observed that BCG vaccination significantly delayed the onset of M. ulcerans growth and footpad swelling through the induction of an earlier and sustained IFN-γ T cell response in the draining lymph node (DLN. BCG vaccination also resulted in cell-mediated immunity (CMI in M. ulcerans-infected footpads, given the predominance of a chronic mononuclear infiltrate positive for iNOS, as well as increased and sustained levels of IFN-γ and TNF. No significant IL-4, IL-17 or IL-10 responses were detected in the footpad or the DLN, in either infected or vaccinated mice. Despite this protective Th1 response, BCG vaccination did not avoid the later progression of M. ulcerans infection, regardless of challenge dose. Immunization with mycolactone-deficient M. ulcerans also significantly delayed the progression of footpad infection, swelling and ulceration, but ultimately M. ulcerans pathogenic mechanisms prevailed. CONCLUSIONS/SIGNIFICANCE: The delay in the emergence of pathology observed in vaccinated mice emphasizes the relevance of protective Th1 recall responses against M. ulcerans. In future studies it will be important to determine how the transient CMI induced by vaccination is compromised.

  17. Cellular Immunity Confers Transient Protection in Experimental Buruli Ulcer following BCG or Mycolactone-Negative Mycobacterium ulcerans Vaccination

    Science.gov (United States)

    Fraga, Alexandra G.; Martins, Teresa G.; Torrado, Egídio; Huygen, Kris; Portaels, Françoise; Silva, Manuel T.; Castro, António G.; Pedrosa, Jorge

    2012-01-01

    Background Buruli ulcer (BU) is an emerging infectious disease caused by Mycobacterium ulcerans that can result in extensive necrotizing cutaneous lesions due to the cytotoxic exotoxin mycolactone. There is no specific vaccine against BU but reports show some degree of cross-reactive protection conferred by M. bovis BCG immunization. Alternatively, an M. ulcerans-specific immunization could be a better preventive strategy. Methodology/Principal Findings In this study, we used the mouse model to characterize the histological and cytokine profiles triggered by vaccination with either BCG or mycolactone-negative M. ulcerans, followed by footpad infection with virulent M. ulcerans. We observed that BCG vaccination significantly delayed the onset of M. ulcerans growth and footpad swelling through the induction of an earlier and sustained IFN-γ T cell response in the draining lymph node (DLN). BCG vaccination also resulted in cell-mediated immunity (CMI) in M. ulcerans-infected footpads, given the predominance of a chronic mononuclear infiltrate positive for iNOS, as well as increased and sustained levels of IFN-γ and TNF. No significant IL-4, IL-17 or IL-10 responses were detected in the footpad or the DLN, in either infected or vaccinated mice. Despite this protective Th1 response, BCG vaccination did not avoid the later progression of M. ulcerans infection, regardless of challenge dose. Immunization with mycolactone-deficient M. ulcerans also significantly delayed the progression of footpad infection, swelling and ulceration, but ultimately M. ulcerans pathogenic mechanisms prevailed. Conclusions/Significance The delay in the emergence of pathology observed in vaccinated mice emphasizes the relevance of protective Th1 recall responses against M. ulcerans. In future studies it will be important to determine how the transient CMI induced by vaccination is compromised. PMID:22413022

  18. The Protective Effects of Lycium Barbarum Polysaccharides on Transient Retinal Ischemia

    Directory of Open Access Journals (Sweden)

    Di Yang

    2011-05-01

    Full Text Available Retinal ischemia/reperfusion (I/R injury leads to irreversible neuronal death, glial activation, retinal swelling and oxidative stress. It is a common feature in various ocular diseases, such as glaucoma, diabetic retinopathy and amaurosis fugax. In the present study, we aimed to evaluate the effects of Lycium Barbarum Polysaccharides (LBP in a murine retinal I/R model. Mice were orally treated with either vehicle (PBS or LBP (1mg/kg daily for 1 week before induction of retinal ischemia. Retinae were collected after 2 hours ischemia and 22 hours reperfusion. Paraffin-embedded sections were prepared for immunohistochemical analyses. Significantly fewer viable cells were found in vehicle-treated retinae comparing to LBP group. This finding was further confirmed by TUNEL assay where significantly fewer apoptotic cells were identified in LBP-treated retinae. Additionally, retinal swelling induced by retinal I/R injury in the vehicle-treated group was not observed in LBP-treated group. Moreover, intense GFAP immunoreactivity and IgG extravasation were observed in vehicle-treated group but not in LBP treated group. The results showed that pre-treatment with LBP was protective in retinal I/R injury via reducing neuronal death, apoptosis, retinal swelling, GFAP activation and blood vessel leakage. LBP may be used as a preventive agent for retinal ischemia diseases.

  19. An Adaptive Load Shedding Scheme Based on a Novel Index of Transient Voltage Stability%基于暂态电压稳定性新指标的自适应紧急减载方案

    Institute of Scientific and Technical Information of China (English)

    李晔; 张保会

    2016-01-01

    Voltages and frequencies have mutual influences after large disturbance. The conventional under-voltage load shedding (UVLS) and under-frequency load shedding (UFLS) are adjusted respectively without full considerations on the time-space distribution character of voltages and the influences of induction motors on the system stability. From the two-node equivalent model, the influence of the slip ratio of the induction motor on transient voltage stability and load stability is analyzed, and a novel index of transient voltage instability which is composed of voltage drop and slip ratio increment is proposed. Furthermore, a wide area measurement system (WAMS) based adaptive load shedding scheme which is constructed by employing the novel index to determine the locations and magnitude of load curtailments is provided. This new scheme includes two control patterns including all nodes load shedding and partial nodes load shedding and it measures the transient voltage stability degree of the system more fully by using the novel index. Simulations on IEEE 39-bus system verify the effectiveness and the superiority of the proposed scheme on guaranteeing the voltage stability and frequency stability after large disturbance, comparing with the conventional control scheme.%频率和电压响应在大扰动后相互耦合,传统的低频、低压减载方案相互独立,未充分考虑电压的时空分布特性和感应电动机对系统稳定性的影响.从2节点系统出发,分析感应电动机转差率偏差值对负荷稳定性和暂态电压稳定性的影响,提出综合考虑感应电动机转差率偏差值和负荷母线电压跌落幅度的暂态电压失稳程度新指标;并基于广域信息条件,利用新指标选择切负荷地点,确定相应控制量以构建新的紧急切负荷方案.该方案利用新指标更加全面地衡量了系统暂态电压稳定程度,具有全网切负荷和局部切负荷两种控制模式.通过IEEE 39节点系统的仿真,

  20. 陶瓷输入电容器的副效应-瞬时过电压%Ceramic Input Capacitors Can Cause Over-voltage Transients

    Institute of Scientific and Technical Information of China (English)

    高兰·德里卡

    2002-01-01

    Ceramic capacitors are often chosen because of their small size, low equivalent series resistance (ESR)and high RMS current capability. However, Applying a voltage step to a ceramic capacitor causes a large current surge that stores energy. In the inductances of the power leads. A large voltage spike is created when the stored energy is transferred from these inductances into the ceramic capacitor. These voltage spikes can easily be twice the amplitude of the input voltage step.%陶瓷电容因其体积小、等效串联电阻小和具有较大的RMS电流而常被人们采用.然而,实际应用中的电压阶跃在陶瓷电容上可能产生较大的浪涌电流,并在电源电感中贮藏能量.当贮能从电感中转移到陶瓷电容时就会产生较大的峰值电压,其值往往可达到输入电压阶跃值的两倍.

  1. Protective effects of quercetin on rat pial microvascular changes during transient bilateral common carotid artery occlusion and reperfusion.

    Directory of Open Access Journals (Sweden)

    Dominga eLapi

    2012-03-01

    Full Text Available The aim of this study was to assess the in vivo effects of quercetin on pial microvascular responses during transient bilateral common carotid artery occlusion (BCCAO and reperfusion. Rat pial microcirculation was visualized by fluorescence microscopy through a closed cranial window. Pial arterioles were classified in five orders of branchings. Capillaries were assigned order 0, the smallest arterioles order 1 and the largest ones order 5. In ischemic rats, 30 min BCCAO and 60 min reperfusion caused arteriolar diameter decrease (by 14.5 ± 3.3% of baseline in order 2, microvascular leakage (0.47 ± 0.04 NGL: Normalized Grey Levels, leukocyte adhesion in venules (9 ± 2/100 µm venular length, v.l./30s and reduction of capillary perfusion (by 40 ± 7% of baseline. Moreover, at the end of BCCAO and reperfusion there was a significant increase in reactive oxygen species formation (ROS when compared with baseline. Quercetin highest dose determined dilation in all arteriolar orders (by 40 ± 4 % of baseline in order 2 and prevented microvascular permeability (0.15 ± 0.02 NGL, leukocyte adhesion (3 ± 1/100 µm v.l./30s as well as ROS formation, while capillary perfusion was protected. Inhibition of endothelial Nitric Oxide Synthase (NOS prior to quercetin reduced arteriolar dilation (order 2 diameter increase by 10.3 ± 2.5% of baseline and caused permeability increase (0.29 ± 0.03 NGL; inhibition of neuronal NOS or inducible NOS did not affect quercetin-induced effects. Inhibition of guanylyl cyclase prior to quercetin reversed the quercetin’s effects on pial arteriolar diameter and leakage. In conclusion, quercetin was able to protect pial microcirculation from ischemia-reperfusion damage inducing arteriolar dilation likely by nitric oxide release. Moreover, quercetin scavenger activity blunted reactive oxygen species formation preserving the blood-brain barrier integrity.

  2. carboxypeptidase E-ΔN, a neuroprotein transiently expressed during development protects embryonic neurons against glutamate neurotoxicity.

    Directory of Open Access Journals (Sweden)

    Xiao-Yan Qin

    Full Text Available Neuroprotective proteins expressed in the fetus play a critical role during early embryonic neurodevelopment, especially during maternal exposure to alcohol and drugs that cause stress, glutamate neuroexcitotoxicity, and damage to the fetal brain, if prolonged. We have identified a novel protein, carboxypeptidase E-ΔN (CPE-ΔN, which is a splice variant of CPE that has neuroprotective effects on embryonic neurons. CPE-ΔN is transiently expressed in mouse embryos from embryonic day 5.5 to postnatal day 1. It is expressed in embryonic neurons, but not in 3 week or older mouse brains, suggesting a function primarily in utero. CPE-ΔN expression was up-regulated in embryonic hippocampal neurons in response to dexamethasone treatment. CPE-ΔN transduced into rat embryonic cortical and hippocampal neurons protected them from glutamate- and H2O2-induced cell death. When transduced into embryonic cortical neurons, CPE-ΔN was found in the nucleus and enhanced the transcription of FGF2 mRNA. Embryonic cortical neurons challenged with glutamate resulted in attenuated FGF2 levels and cell death, but CPE-ΔN transduced neurons treated in the same manner showed increased FGF2 expression and normal viability. This neuroprotective effect of CPE-ΔN was mediated by secreted FGF2. Through receptor signaling, FGF2 activated the AKT and ERK signaling pathways, which in turn increased BCL-2 expression. This led to inhibition of caspase-3 activity and cell survival.

  3. Carboxypeptidase E-ΔN, a Neuroprotein Transiently Expressed during Development Protects Embryonic Neurons against Glutamate Neurotoxicity

    Science.gov (United States)

    Murthy, Saravana R. K.; Selvaraj, Prabhuanand; Loh, Y. Peng

    2014-01-01

    Neuroprotective proteins expressed in the fetus play a critical role during early embryonic neurodevelopment, especially during maternal exposure to alcohol and drugs that cause stress, glutamate neuroexcitotoxicity, and damage to the fetal brain, if prolonged. We have identified a novel protein, carboxypeptidase E-ΔN (CPE-ΔN), which is a splice variant of CPE that has neuroprotective effects on embryonic neurons. CPE-ΔN is transiently expressed in mouse embryos from embryonic day 5.5 to postnatal day 1. It is expressed in embryonic neurons, but not in 3 week or older mouse brains, suggesting a function primarily in utero. CPE-ΔN expression was up-regulated in embryonic hippocampal neurons in response to dexamethasone treatment. CPE-ΔN transduced into rat embryonic cortical and hippocampal neurons protected them from glutamate- and H2O2-induced cell death. When transduced into embryonic cortical neurons, CPE-ΔN was found in the nucleus and enhanced the transcription of FGF2 mRNA. Embryonic cortical neurons challenged with glutamate resulted in attenuated FGF2 levels and cell death, but CPE-ΔN transduced neurons treated in the same manner showed increased FGF2 expression and normal viability. This neuroprotective effect of CPE-ΔN was mediated by secreted FGF2. Through receptor signaling, FGF2 activated the AKT and ERK signaling pathways, which in turn increased BCL-2 expression. This led to inhibition of caspase-3 activity and cell survival. PMID:25426952

  4. Protection Principle for HVDC Transmission Lines Based on Fault Component of Voltage and Current%基于电压和电流突变量的高压直流输电线路保护原理

    Institute of Scientific and Technical Information of China (English)

    邢鲁华; 陈青; 付兆远; 高湛军; 于春光

    2012-01-01

    A new main protection principle is presented for high voltage direct current(HVDC) transmission lines.The principle is based on the variation characteristics of fault component of voltage and current,together with an indepth research on the transients caused by internal faults,external faults and lightning disturbances.By a set threshold for the ratio of amplitudes of the fault components of voltage at the same side relay location on bipolar lines,faults outside HVDC lines can be excluded,and the fault line can be distinguished.The polarities of the fault component of currents at the ends of the fault line are different for internal faults,while are the same for external faults.Accordingly,internal faults and external faults can be distinguished.Simulation results based on PSCAD/EMTDC for a practical HVDC transmission system demonstrate that the fault line can be rapidly selected and internal faults and external faults can be distinguished by the protection under bipolar neutral grounding at both ends mode.Lightning disturbances can be excluded by the proposed criterion.The protection criterion can move accurately for faults with high transition resistance and lightning induced faults,and can be also applied under one pole with 70% voltage and one pole with total voltage operation mode,anti-way power delivery operation mode,monopolar metallic return operation mode and one pole with maintenance outage.The calculation requirement of the protection criterion can be satisfied with sampling frequency in the range of 10~100 kHz.%在对高压直流输电线路区内、外故障和雷击等暂态过程研究的基础上,提出了一种基于电压、电流突变量变化特征的高压直流输电线路主保护原理。该原理对两极线路同侧保护安装处测得的电压突变量幅值的比值设定阈值,选出故障极;利用故障线路两端电流突变量的极性在线路保护区内故障时相异、在区外故障时相同,区分线路上保护区

  5. 暂态能量在高压网络中的散播%Spread of transient energy in high voltage network

    Institute of Scientific and Technical Information of China (English)

    孟祥侠; 蔡国伟

    2011-01-01

    By analyzing the change feature of branch phase-angle difference and transient energy distribution in different locations of network in time of one machine-infinite system losing stability, it is pointed out that transient energy is most liable to accumulate in the middle part of lines between groups or within a certain range in the vicinity.For multi-machines system network, based on network parameter, by means of coupling thinking, vulnerability location in network is identified, the relation between network structure vulnerability and transient energy distribution is further revealed.The results show that during system disturbance, more and more transient energy would accumulate in the middle part of vulnerability location in network or vicinity.Simulation and analysis on 6 machines system testify the validation of the proposed method.%通过分析单机无穷大系统失稳时网络中不同部位支路相角差及暂态能量的分布变化特点,指出暂态能量最易在失稳的群间联络线中部或其附近的某一范围内聚积.对多机系统网络,基于网络参数、利用耦合的思想识别网络中的脆弱环节,并进一步揭示网络结构脆弱性与暂态能量分布的关系.研究结果表明:在系统受扰动后的变化过程中,暂态能量越来越多地聚积到网络中脆弱环节的中部或其附近的某一范围内.对6机系统进行仿真分析,验证了所提方法的有效性.

  6. 暂态边界电压法在线测试全钒液流电池阻抗%On-line resistance measurement for all vanadium redox flow battery by transient-boundary voltage method

    Institute of Scientific and Technical Information of China (English)

    潘建欣; 廖玲芝; 谢晓峰; 王树博; 王金海; 尚玉明; 周涛

    2012-01-01

    国内首次采用暂态边界电压法在线研究了全钒液流电池(VRB)的特性,建立了由电压源、电阻以及一个电阻与电容并联的3部分串联而成的等效电路模型;研究了电流密度和荷电状态(SOC)对等效电路元件的影响。实验结果表明,极化阻抗随电流密度的增加有轻微下降,在充电初期和放电末期达到最大值。与极化阻抗相比,充、放电过程中的欧姆阻抗最大,是导致电压损失的主要因素,分别为1.905Ω.cm2和2.139Ω.cm2,暂态边界电压法是一种简单且有效的表征全钒液流电池性能的新方法。%A single cell of vanadium redox flow battery(VRB) was investigated on-line by the transient-boundary voltage method.An equivalent circuit model was established using the voltage source,resistor,and a resistor in parallel with the capacitance of three-part series.The effects of current density and state of charge(SOC) on equivalent circuit components values were investigated.The experimental results showed that the polarization resistance decreased slightly with increasing current density,and reached its maximum in the beginning of charge and the end of discharge.Compared with polarization resistance,ohm impedance in the charge/discharge process was the highest respectively 1.905 cm2and 2.139 cm2.It was the main factor leading to voltage loss.The transient boundary voltage method is a simple and effective way of characterizing performance of vanadium redox flow battery.

  7. Electromechanical Transient Modeling and Simulation for Voltage Source Converter Based HVDC Power Transmission%VSC-HVDC机电暂态仿真建模及仿真

    Institute of Scientific and Technical Information of China (English)

    刘昇; 徐政; 唐庚; 华文; 薛英林

    2013-01-01

    Based on the fundamental frequency mathematical model of VSC-HVDC power transmission in d-q rotating dq rotary coordinate system, the electromechanical transient mathematical equations of VSC-HVDC power transmission are summarized, afterwards a electromechanical transient model for VSC-HVDC power transmission is achieved based on user-defined function of PSS/E and the achieved model is compared with the precise electromagnetic transient model for VSC-HVDC power transmission in PSCAD, and simulation results show that the steady state power flows from the two models are very similar and their dynamic characteristics are highly consistent each other, thus the effectiveness and accuracy of the achieved electromechanical transient model for VSC-HVDC power transmission are verified. Finally, using the achieved model the application of VSC-HVDC power transmission in actual large-scale multi-infeed HVDC power transmission system is researched, and research results show that using VSC-HVDC power transmission technology the commutation failure occurred in traditional HVDC power transmission system can be radically resolved.%  以VSC-HVDC在dq旋转坐标系下的基频数学模型为基础,总结了 VSC-HVDC 的机电暂态数学方程。之后基于 PSS/E 自定义模型功能实现了 VSC-HVDC 机电暂态模型,并将该模型和PSCAD中VSC-HVDC电磁暂态精确模型进行了对比,仿真结果表明两者的稳态潮流十分接近,动态特性具有很好的一致性,从而验证了VSC-HVDC机电暂态模型的有效性和准确性。最后基于该模型对VSC-HVDC 在实际大规模多直流馈入系统中的应用进行了研究,结果表明 VSC-HVDC 从根本上解决了传统直流输电的换相失败问题。

  8. Networking sampling busbar protection based on voltage phase lock%基于电压锁相网络化采样的母线保护研究

    Institute of Scientific and Technical Information of China (English)

    韩冰; 汤汉松; 刘斌; 周东顶; 郑发林

    2015-01-01

    设计一种既具备结构简单、资源共享、扩展性好等优点,又不依赖于外部全局同步系统的采样值组网传输的母线保护,在数字化变电站的建设中具有十分重要的意义。介绍了数字化变电站母线保护的采样值传输系统,描述了基于绝对延时的点对点母线保护技术,提出了一种基于电压锁相的网络化母线保护方案。利用母线电压天然的同步性能特征,通过数字锁相环及采样重插值技术,消除网络化采样对同步信号的依赖性。测试表明,基于电压锁相的网络化母线保护采样同步性好,动作快速可靠,是数字化变电站母线保护的一种新思路。%A sampling value network transmission bus protection independent of outside global synchronization system is designed. The protection has the advantages of simple structure, resource sharing and good expansibility, so it has very important significance in the construction of digital substation. This paper introduces the sampling transmission system of bus protection in digital substation, describes a point-to-point bus protection technology based on absolute delay, and proposes a network bus protection using voltage phase lock. The synchronization performance of bus voltage, digital phase locked loop and resampling interpolation are used to eliminate the synchronization dependence in network sampling system. Experiments show that the bus protection based on voltage phase lock is well synchronous, fast and reliable. This method is a new solution for the bus protection of digital substation.

  9. Transient drainage summary report

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-09-01

    This report summarizes the history of transient drainage issues on the Uranium Mill Tailings Remedial Action (UMTRA) Project. It defines and describes the UMTRA Project disposal cell transient drainage process and chronicles UMTRA Project treatment of the transient drainage phenomenon. Section 4.0 includes a conceptual cross section of each UMTRA Project disposal site and summarizes design and construction information, the ground water protection strategy, and the potential for transient drainage.

  10. Boosting of synaptic potentials and spine Ca transients by the peptide toxin SNX-482 requires alpha-1E-encoded voltage-gated Ca channels.

    Directory of Open Access Journals (Sweden)

    Andrew J Giessel

    Full Text Available The majority of glutamatergic synapses formed onto principal neurons of the mammalian central nervous system are associated with dendritic spines. Spines are tiny protuberances that house the proteins that mediate the response of the postsynaptic cell to the presynaptic release of glutamate. Postsynaptic signals are regulated by an ion channel signaling cascade that is active in individual dendritic spines and involves voltage-gated calcium (Ca channels, small conductance (SK-type Ca-activated potassium channels, and NMDA-type glutamate receptors. Pharmacological studies using the toxin SNX-482 indicated that the voltage-gated Ca channels that signal within spines to open SK channels belong to the class Ca(V2.3, which is encoded by the Alpha-1E pore-forming subunit. In order to specifically test this conclusion, we examined the effects of SNX-482 on synaptic signals in acute hippocampal slices from knock-out mice lacking the Alpha-1E gene. We find that in these mice, application of SNX-482 has no effect on glutamate-uncaging evoked synaptic potentials and Ca influx, indicating that that SNX-482 indeed acts via the Alpha-1E-encoded Ca(V2.3 channel.

  11. GIS中金属氧化物避雷器对特快速暂态过电压的影响%Influence of Metal Oxide Arrester on Very Fast Transient Over-voltage in GIS

    Institute of Scientific and Technical Information of China (English)

    林莘; 王静; 徐建源; 王娜

    2012-01-01

    气体绝缘变电站(gas insulated substation,GIS)内部隔离开关切合空载短母线时产生的特快速暂态过电压(very fast transient over-voltage,VFTO)对电气设备构成严重的威胁。金属氧化物避雷器(metal oxide arrester,MOA)作为GIS中重要的保护设备之一,目前在VFTO计算中普遍采用对地电容模型或者非线性电阻模型,这忽略了VFTO暂态特性对MOA晶界层极化过程的影响。为此,结合MOA阀片的微观结构,通过分析交变电场下电介质的极化特性及其电流响应,提出了MOA暂态电路模型。以国内某550kV变电站为背景,采用EMTP软件对GIS中的VFTO进行了计算,分析了不同MOA模型下VFTO的差异,研究了MOA对VFTO波形、幅值和波前陡度的影响。结果表明,MOA暂态模型能很好地反映MOA在VFTO作用下的极化现象;MOA对VFTO有一定的抑制作用,它能使VFTO波形衰减,在一定程度上降低VFTO的幅值,并减缓VFTO的波前陡度。%The nonlinear resistance model and shunt capacitance are used for calculating very fast transient over-voltage(VFTO),which ignore the effect of VFTO transient characteristic on the polarization of the grain boundary layer in the MOA valve microstructure.Consequently,we established an improved metal oxide surge arrester(MOA) transient circuit model on the basis of the polarization theory in alternating electric field and the analysis of current response process of the grain boundary layer in high-frequency voltage.Taking a 550 kV GIS in China for example,we calculated its VFTO with EMTP.The difference among VFTO waveforms and spectrum distributions was analyzed in the three models to obtain the effects of MOA on VFTO waveform,amplitude,and tip steepness.The results show that,the presented MOA transient model can reflect the polarization under VFTO;in addition,MOA has inhibition effects on VFTO,of which the waveform is attenuated,the amplitude is reduced,and the tip steepness is slowed.

  12. Analysis on Transient Voltage Stability of Power System Including D-PMSG Wind Farm%含直驱机组风电场的电力系统暂态电压稳定分析

    Institute of Scientific and Technical Information of China (English)

    李江; 赵海岭; 常喜强; 宋联庆

    2012-01-01

    利用线路故障临界切除时间来表征电力系统暂态电压稳定性的量化指标,采取动态时域仿真法对WSCC3机9节点算例系统与基于直驱机组并网风电场接入该算例系统的暂态电压特性进行了仿真分析,研究结果表明,接入直驱机组风电场后算例系统的线路故障临界切除时间要比原算例系统的线路故障临界切除时间要长,因此,基于直驱机组风电场的接入算例系统能较好地改善原系统的暂态电压稳定性.%The transient voltage stabilities of a three—synchronous—generator and nine—bus power grid integrated with or without Direct-driven Permanent Magnet Synchronous Generator (D-PMSG) are simulated by dynamic time-domain method and compared by taking the fault critical clearing time as the quantitative indicator of transient voltage stability of power system. The results show that the fault critical clearing time of grid integrated with D-PMSG is longer than the grid without D-PMSG, and so the integration of D—PMSG into grid can improve the stability of grid.

  13. 晶闸管整流装置的瞬态电压及其保护%Analysis of Transient Overvoltage for Thyristor-converter and Its Protection

    Institute of Scientific and Technical Information of China (English)

    刘蜀宁

    2001-01-01

    本文分析了晶闸管变流装置中瞬态电压的产生机理及其相应的保护方法,并给出针对晶闸管变流装置换流过程产生的瞬态电压的保护电路参数的设计方法及具体计算实例。%Analysis the causes of transient overvoltage for thyristor-converter and schemes of protection,provides the method of choosing the parameters of protective circuit to deal with commutation spike,and gives an example in detail.

  14. The role of cathodic current in PEO of aluminum: Influence of cationic electrolyte composition on the transient current-voltage curves and the discharges optical emission spectra

    Science.gov (United States)

    Rogov, A. B.; Shayapov, V. R.

    2017-02-01

    In this paper, the influence of cationic electrolytes composition on electrical and optical responses of plasma electrolytic oxidation process of A1050 aluminum alloy under alternating polarization is considered. The electrolytes consist of 0.1 M boric acid with addition of one of the following hydroxides: LiOH, NaOH, KOH, tetraethylammonium hydroxide, Ca(OH)2 up to pH value 9.2. Coatings microstructure, elemental and phase compositions were studied by SEM, EDS and XRD. It was shown that the hysteresis of anodic current-voltage curve (specific feature of "Soft sparking" PEO) was clear observed in the presence of sodium and potassium cations. It was found that composition of microdischarges plasma is also affected by the nature of the cations. It was shown that there are a number of reciprocal processes, which take place under anodic and cathodic polarization.

  15. Fast turn-on of an NMOS ESD protection transistor: measurements and simulations

    NARCIS (Netherlands)

    Luchies, J.R.M.; Kort, de C.G.M.; Verweij, J.F.

    1995-01-01

    The transient turn-on of the parasitic bipolar transistor of an NMOS transistor was studied. The voltages appearing at internal nodes of protection and functional circuit after application of 350 ps rise-time pulses have been measured using electro-optic sampling. For very fast transients the trigge

  16. Fast Coordinated Control of DFIG Wind Turbine Generators for Low and High Voltage Ride-Through

    Directory of Open Access Journals (Sweden)

    Yun Wang

    2014-06-01

    Full Text Available This paper presents a fast coordinated control scheme of the rotor side converter (RSC, the Direct Current (DC chopper and the grid side converter (GSC of doubly fed induction generator (DFIG wind turbine generators (WTGs to improve the low voltage ride through (LVRT and high voltage ride through (HVRT capability of the DFIG WTGs. The characteristics of DFIG WTGs under voltage sags and swells were studied focusing on the DFIG WTG stator flux and rotor voltages during the transient periods of grid voltage changes. The protection schemes of the rotor crowbar circuit and the DC chopper circuit were proposed considering the characteristics of the DFIG WTGs during voltage changes. The fast coordinated control of RSC and GSC were developed based on the characteristic analysis in order to realize efficient LVRT and HVRT of the DFIG WTGs. The proposed fast coordinated control schemes were verified by time domain simulations using Matlab-Simulink.

  17. High voltage engineering

    CERN Document Server

    Rizk, Farouk AM

    2014-01-01

    Inspired by a new revival of worldwide interest in extra-high-voltage (EHV) and ultra-high-voltage (UHV) transmission, High Voltage Engineering merges the latest research with the extensive experience of the best in the field to deliver a comprehensive treatment of electrical insulation systems for the next generation of utility engineers and electric power professionals. The book offers extensive coverage of the physical basis of high-voltage engineering, from insulation stress and strength to lightning attachment and protection and beyond. Presenting information critical to the design, selec

  18. The involvement of PI3K-mediated and L-VGCC-gated transient Ca2+ influx in 17β-estradiol-mediated protection of retinal cells from H2O2-induced apoptosis with Ca2+ overload.

    Directory of Open Access Journals (Sweden)

    Yan Feng

    Full Text Available Intracellular calcium concentration ([Ca(2+]i plays an important role in regulating most cellular processes, including apoptosis and survival, but its alterations are different and complicated under diverse conditions. In this study, we focused on the [Ca(2+]i and its control mechanisms in process of hydrogen peroxide (H2O2-induced apoptosis of primary cultured Sprague-Dawley (SD rat retinal cells and 17β-estradiol (βE2 anti-apoptosis. Fluo-3AM was used as a Ca(2+ indicator to detect [Ca(2+]i through fluorescence-activated cell sorting (FACS, cell viability was assayed using MTT assay, and apoptosis was marked by Hoechst 33342 and annexin V/Propidium Iodide staining. Besides, PI3K activity was detected by Western blotting. Results showed: a 100 μM H2O2-induced retinal cell apoptosis occurred at 4 h after H2O2 stress and increased in a time-dependent manner, but [Ca(2+]i increased earlier at 2 h, sustained to 12 h, and then recovered at 24 h after H2O2 stress; b 10 μM βE2 treatment for 0.5-24 hrs increased cell viability by transiently increasing [Ca(2+]i, which appeared only at 0.5 h after βE2 application; c increased [Ca(2+]i under 100 µM H2O2 treatment for 2 hrs or 10 µM βE2 treatment for 0.5 hrs was, at least partly, due to extracellular Ca(2+ stores; d importantly, the transiently increased [Ca(2+]i induced by 10 µM βE2 treatment for 0.5 hrs was mediated by the phosphatidylinositol-3-kinase (PI3K and gated by the L-type voltage-gated Ca(2+ channels (L-VGCC, but the increased [Ca(2+]i induced by 100 µM H2O2 treatment for 2 hrs was not affected; and e pretreatment with 10 µM βE2 for 0.5 hrs effectively protected retinal cells from apoptosis induced by 100 µM H2O2, which was also associated with its transient [Ca(2+]i increase through L-VGCC and PI3K pathway. These findings will lead to better understanding of the mechanisms of βE2-mediated retinal protection and to exploration of the novel therapeutic strategies for retina

  19. Protection of transformers and low voltage secondary circuits; Protecao de transformadores e circuitos secundarios em baixa tensao

    Energy Technology Data Exchange (ETDEWEB)

    Bueno, Alexandre Francisco Maia; Bouissou, Jean Jacques [Companhia Energetica de Minas Gerais (CEMIG), Belo Horizonte, MG (Brazil)

    1994-12-31

    This work discusses two themes related to equipment and circuit protection, both of which are components of overhead electric power transmission networks. Two CEMIG`s, the electric power company of Minas Gerais State - Southeast Brazil, experiences are presented. The work also discusses the technical reliability of these two protection conceptions. The results obtained results are also presented and discussed 3 refs., 3 figs., 2 tabs.

  20. Pregnenolone sulfate activates basic region leucine zipper transcription factors in insulinoma cells: role of voltage-gated Ca2+ channels and transient receptor potential melastatin 3 channels.

    Science.gov (United States)

    Müller, Isabelle; Rössler, Oliver G; Thiel, Gerald

    2011-12-01

    The neurosteroid pregnenolone sulfate activates a signaling cascade in insulinoma cells involving activation of extracellular signal-regulated protein kinase and enhanced expression of the transcription factor Egr-1. Here, we show that pregnenolone sulfate stimulation leads to a significant elevation of activator protein-1 (AP-1) activity in insulinoma cells. Expression of the basic region leucine zipper (bZIP) transcription factors c-Jun and c-Fos is up-regulated in insulinoma cells and pancreatic β-cells in primary culture after pregnenolone sulfate stimulation. Up-regulation of a chromatin-embedded c-Jun promoter/luciferase reporter gene transcription in pregnenolone sulfate-stimulated insulinoma cells was impaired when the AP-1 binding sites were mutated, indicating that these motifs function as pregnenolone sulfate response elements. In addition, phosphorylation of cAMP response element (CRE)-binding protein is induced and transcription of a CRE-controlled reporter gene is stimulated after pregnenolone sulfate treatment, indicating that the CRE functions as a pregnenolone sulfate response element as well. Pharmacological and genetic experiments revealed that both L-type Ca(2+) channels and transient receptor potential melastatin 3 (TRPM3) channels are essential for connecting pregnenolone sulfate stimulation with enhanced AP-1 activity and bZIP-mediated transcription in insulinoma cells. In contrast, pregnenolone sulfate stimulation did not enhance AP-1 activity or c-Jun and c-Fos expression in pituitary corticotrophs that express functional L-type Ca(2+) channels but only trace amounts of TRPM3. We conclude that expression of L-type Ca(2+) channels is not sufficient to activate bZIP-mediated gene transcription by pregnenolone sulfate. Rather, additional expression of TRPM3 or depolarization of the cells is required to connect pregnenolone sulfate stimulation with enhanced gene transcription.

  1. Over-voltage surge arrester for lightning protection; Einsatz von Ueberspannungsableitern beim Blitzschutz. Notwendige Strombelastbarkeit von Varistoren in induktiv gekoppelten Schleifen

    Energy Technology Data Exchange (ETDEWEB)

    Haeberlin, H. [Berner Fachhochschule, Hochschule fuer Technik und Architektur (HTA), Burgdorf, (Switzerland)

    2001-07-01

    The article discusses the necessary loading characteristics of varistors that are used in inductively coupled loops to provide protection against over-voltages produced by lightning strikes. An overview of various types of commercially available surge arresters is presented; their function and their use in photovoltaic installations is discussed in detail. The calculation of the inductively induced currents is discussed in depth for loops with and without varistors. Diagrams with graphs of current against time and mathematical solutions for the representation of the induced currents are presented in detail. The article is supplemented by examples of the calculation of varistor current and a simplified procedure is presented for the definition of the varistor currents necessary for a particular application.

  2. Transient Thermal Analysis of Low-Voltage Electric Apparatus Contact and Its Application in Anti-Welding%低压电器触头瞬态热分析及其在抗熔焊中的应用

    Institute of Scientific and Technical Information of China (English)

    李衍川

    2012-01-01

      Discussion was made to a mathematical model of electric-contact transient thermal analysis of low-voltage electric apparatus contact. ANSYS was used to analyze the phase change problem of thermal process, so that in contact welding process temperatures followed time and the welding force could be calculated according to the change situation. Via changing contact material, simulating the mathematical model and calculating the corresponding welding force, the result shows that the method can effectively evaluate anti-welding performance of different materials, to ensure electric apparatus working reliably.%  探讨了低压电器触头电接触瞬态热分析的数学模型,利用ANSYS软件对热过程的相变问题进行分析,得出触头熔焊过程中温度随时间的变化情况,并由此计算熔焊力。通过改变触头材料,分别进行仿真和计算对应的熔焊力,结果表明该方法可有效估计不同材料的抗熔焊性能,确保电器可靠工作。

  3. Sevoflurane protects ventricular myocytes from Ca2+ paradox-mediated Ca2+ overload by blocking the activation of transient receptor potential canonical channels.

    Science.gov (United States)

    Kojima, Akiko; Kitagawa, Hirotoshi; Omatsu-Kanbe, Mariko; Matsuura, Hiroshi; Nosaka, Shuichi

    2011-09-01

    Volatile anesthetics produce cardioprotective action by attenuating cellular Ca2+ overload. The Ca2+ paradox is an important model for studying the mechanisms associated with Ca2+ overload-mediated myocardial injury, and was recently found to be mediated by Ca2+ entry through the transient receptor potential canonical channels upon Ca2+ repletion. This study investigated the effect of sevoflurane on cellular mechanisms underlying the Ca2+ paradox. The Ca2+ paradox was examined in fluo-3 or mag-fluo-4-loaded mouse ventricular myocytes using confocal laser scanning microscope, upon Ca2+ repletion after 15 min of Ca2+ depletion in the absence and presence of sevoflurane. The Ca2+ paradox was evoked in approximately 65% of myocytes upon Ca2+ repletion, as determined by an abrupt elevation of cytosolic Ca2+ accompanied by hypercontracture. The Ca2+ paradox was significantly suppressed by sevoflurane administered for 3 min before and during Ca2+ repletion (Post) or during Ca2+ depletion and repletion (Postlong), and Postlong was more beneficial than Post application. The sarcoplasmic reticulum Ca2+ levels gradually decreased during Ca2+ depletion, and the Ca2+ paradox was readily evoked in myocytes with reduced sarcoplasmic reticulum Ca2+ levels. Postlong but not Post application of sevoflurane prevented decrease in sarcoplasmic reticulum Ca2+ levels by blocking Ca2+ leak through ryanodine receptors. Whole cell patch-clamp recordings revealed that sevoflurane rapidly blocked thapsigargin-induced transient receptor potential canonical currents. Sevoflurane protects ventricular myocytes from Ca2+ paradox-mediated Ca2+ overload by blocking transient receptor potential canonical channels and by preventing the decrease in sarcoplasmic reticulum Ca2+ levels, which is associated with less activation of transient receptor potential canonical channels.

  4. Transient Voltage Stability Analysis of East China Receiving-End Power Grid With Multi-Infeed HVDC Transmission Lines%多直流馈入华东受端电网暂态电压稳定性分析

    Institute of Scientific and Technical Information of China (English)

    邵瑶; 汤涌; 郭小江; 周勤勇

    2011-01-01

    基于2015年“三华”特高压规划电网的丰大运行方式,利用短路比和多馈入短路比指标分析了华东受端电网的强度,并讨论了受端系统网架调整和直流系统落点位置对短路比/多馈入短路比的影响。采用PSD-BPA暂态稳定程序,分析了华东受端电网在各种故障下的暂态电压稳定性。结果表明:直流系统落点位置对华东受端电网强度的影响较大;交直流系统单一故障、受端特高压交流通道和逆变站换流母线附近线路发生三相永久性短路跳双回故障,大部分直流系统双极闭锁均不会导致华东受端电网暂态电压失稳;锦屏-同里、锡盟-金坛、复龙-奉贤和溪洛渡-浙西特高压直流发生双极闭锁故障后,送端电网需采取切机措施才能保持系统稳定。%Based on the summer peak load operation mode of the planned "North China-Central China-East China" UHV power grid in 2015, there will be 10 HVDC transmission lines feeding into East China power grid. The strength of East China receiving-end power grid is analyzed by short circuit ratio (SCR) and multi-infeed short circuit ratio (MISCR), and the impacts of network topology adjustment in receiving-end power grid and the positions where the multi-infeed DC transmission lines are connected with East China receiving-end power grid on SCR/MISCR are dissected. By use of PSD-BPA transient stability program, transient voltage stability of East China receiving-end power grid under various faults is analyzed. Analysis results show that the positions, where the multi-infeed DC transmission lines are connected with East China receiving-end power grid, greatly impacts the strength of the latter; all unipolar block faults occurred in DC systems, single faults occurred in AC/DC system, three-phase permanent short-circuit fault, which causes the tripout of two circuits, occurred in UHVAC transmission line of receiving-end system and that

  5. Suppression of Aluminum Current Collector Dissolution by Protective Ceramic Coatings for Better High-Voltage Battery Performance.

    Science.gov (United States)

    Heckmann, Andreas; Krott, Manuel; Streipert, Benjamin; Uhlenbruck, Sven; Winter, Martin; Placke, Tobias

    2017-01-04

    Batteries based on cathode materials that operate at high cathode potentials, such as LiNi0.5 Mn1.5 O4 (LNMO), in lithium-ion batteries or graphitic carbons in dual-ion batteries suffer from anodic dissolution of the aluminum (Al) current collector in organic solvent-based electrolytes based on imide salts, such as lithium bis(trifluoromethanesulfonyl) imide (LiTFSI). In this work, we developed a protective surface modification for the Al current collector by applying ceramic coatings of chromium nitride (Crx N) and studied the anodic Al dissolution behavior. By magnetron sputter deposition, two different coating types, which differ in their composition according to the CrN and Cr2 N phases, were prepared and characterized by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and their electronic conductivity. Furthermore, the anodic dissolution behavior was studied by cyclic voltammetry and chronocoulometry measurements in two different electrolyte mixtures, that is, LiTFSI in ethyl methyl sulfone and LiTFSI in ethylene carbonate/dimethyl carbonate 1:1 (by weight). These measurements showed a remarkably reduced current density or cumulative charge during the charge process, indicating an improved anodic stability of the protected Al current collector. The coating surfaces after electrochemical treatment were characterized by means of SEM and XPS, and the presence or lack of pit formation, as well as electrolyte degradation products could be well correlated to the electrochemical results.

  6. Protection of ischemic postconditioning against neuronal apoptosis induced by transient focal ischemia is associated with attenuation of NF-κB/p65 activation.

    Directory of Open Access Journals (Sweden)

    Jianmin Liang

    Full Text Available BACKGROUND AND PURPOSE: Accumulating evidences have demonstrated that nuclear factor κB/p65 plays a protective role in the protection of ischemic preconditioning and detrimental role in lethal ischemia-induced programmed cell death including apoptosis and autophagic death. However, its role in the protection of ischemic postconditioning is still unclear. METHODS: Rat MCAO model was used to produce transient focal ischemia. The procedure of ischemic postconditioning consisted of three cycles of 30 seconds reperfusion/reocclusion of MCA. The volume of cerebral infarction was measured by TTC staining and neuronal apoptosis was detected by TUNEL staining. Western blotting was used to analyze the changes in protein levels of Caspase-3, NF-κB/p65, phosphor- NF-κB/p65, IκBα, phosphor- IκBα, Noxa, Bim and Bax between rats treated with and without ischemic postconditioning. Laser scanning confocal microscopy was used to examine the distribution of NF-κB/p65 and Noxa. RESULTS: Ischemic postconditioning made transient focal ischemia-induced infarct volume decrease obviously from 38.6% ± 5.8% to 23.5% ± 4.3%, and apoptosis rate reduce significantly from 46.5% ± 6.2 to 29.6% ± 5.3% at reperfusion 24 h following 2 h focal cerebral ischemia. Western blotting analysis showed that ischemic postconditioning suppressed markedly the reduction of NF-κB/p65 in cytoplasm, but elevated its content in nucleus either at reperfusion 6 h or 24 h. Moreover, the decrease of IκBα and the increase of phosphorylated IκBα and phosphorylated NF-κB/p65 at indicated reperfusion time were reversed by ischemic postconditioning. Correspondingly, proapoptotic proteins Caspase-3, cleaved Caspase-3, Noxa, Bim and Bax were all mitigated significantly by ischemic postconditioning. Confocal microscopy revealed that ischemic postconditioning not only attenuated ischemia-induced translocation of NF-κB/p65 from neuronal cytoplasm to nucleus, but also inhibited the abnormal

  7. Modeling and simulation of the transient response of temperature and relative humidity sensors with and without protective housing.

    Directory of Open Access Journals (Sweden)

    Keller Sullivan Oliveira Rocha

    Full Text Available Based on the necessity for enclosure protection of temperature and relative humidity sensors installed in a hostile environment, a wind tunnel was used to quantify the time that the sensors take to reach equilibrium in the environmental conditions to which they are exposed. Two treatments were used: (1 sensors with polyvinyl chloride (PVC enclosure protection, and (2 sensors with no enclosure protection. The primary objective of this study was to develop and validate a 3-D computational fluid dynamics (CFD model for analyzing the temperature and relative humidity distribution in a wind tunnel using sensors with PVC enclosure protection and sensors with no enclosure protection. A CFD simulation model was developed to describe the temperature distribution and the physics of mass transfer related to the airflow relative humidity. The first results demonstrate the applicability of the simulation. For verification, a sensor device was successfully assembled and tested in an environment that was optimized to ensure fast change conditions. The quantification setup presented in this paper is thus considered to be adequate for testing different materials and morphologies for enclosure protection. The results show that the boundary layer flow regime has a significant impact on the heat flux distribution. The results indicate that the CFD technique is a powerful tool which provides a detailed description of the flow and temperature fields as well as the time that the relative humidity takes to reach equilibrium with the environment in which the sensors are inserted.

  8. Retinal protective effects of topically administered agmatine on ischemic ocular injury caused by transient occlusion of the ophthalmic artery

    Directory of Open Access Journals (Sweden)

    S. Hong

    2012-03-01

    Full Text Available Agmatine, an endogenous polyamine and putative neuromodulator, is known to have neuroprotective effects on various neurons in the central nervous system. We determined whether or not topically administered agmatine could reduce ischemic retinal injury. Transient ocular ischemia was achieved by intraluminal occlusion of the middle cerebral artery of ddY mice (30-35 g for 2 h, which is known to also induce occlusion of the ophthalmic artery. In the agmatine group (N = 6, a 1.0 mM agmatine-containing ophthalmic solution was administered four times daily for 2 weeks before occlusion. In the control group (N = 6, a 0.1% hyaluronic acid ophthalmic solution was instilled at the same times. At 22 h after reperfusion, the eyeballs were enucleated and the retinal sections were stained by terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL. Transient ocular ischemia induced apoptosis of retinal cells in the entire retinal layer, and topically administered agmatine can significantly reduce this ischemic retinal injury. The proportion of apoptotic cells was definitely decreased (P < 0.001; Kruskal-Wallis test. Overall, we determined that topical agmatine application effectively decreases retinal damage in an in vivo ocular ischemic injury model. This implies that agmatine is a good candidate as a direct neuroprotective agent for eyes with ocular ischemic diseases.

  9. Selective protection of human liver tissue in TNF-targeting of cancers of the liver by transient depletion of adenosine triphosphate.

    Directory of Open Access Journals (Sweden)

    Timo Weiland

    Full Text Available BACKGROUND: Tumor necrosis factor alpha (TNF is able to kill cancer cells via receptor-mediated cell death requiring adenosine triphosphate (ATP. Clinical usage of TNF so far is largely limited by its profound hepatotoxicity. Recently, it was found in the murine system that specific protection of hepatocytes against TNF's detrimental effects can be achieved by fructose-mediated ATP depletion therein. Before employing this quite attractive selection principle in a first clinical trial, we here comprehensively investigated the interdependence between ATP depletion and TNF hepatotoxicity in both in vitro and ex vivo experiments based on usage of primary patient tissue materials. METHODS: Primary human hepatocytes, and both non-tumorous and tumorous patient-derived primary liver tissue slices were used to elucidate fructose-induced ATP depletion and TNF-induced cytotoxicity. RESULTS: PHH as well as tissue slices prepared from non-malignant human liver specimen undergoing a fructose-mediated ATP depletion were both demonstrated to be protected against TNF-induced cell death. In contrast, due to tumor-specific overexpression of hexokinase II, which imposes a profound bypass on hepatocytic-specific fructose catabolism, this was not the case for human tumorous liver tissues. CONCLUSION: Normal human liver tissues can be protected transiently against TNF-induced cell death by systemic pretreatment with fructose used in non-toxic/physiologic concentrations. Selective TNF-targeting of primary and secondary tumors of the liver by transient and specific depletion of hepatocytic ATP opens up a new clinical avenue for the TNF-based treatment of liver cancers.

  10. Lightning-induced overvoltages in medium voltage distribution systems and customer experienced voltage spikes

    Energy Technology Data Exchange (ETDEWEB)

    Sabiha, N. A.

    2010-07-01

    In Finland, distribution transformers are frequently subjected to lightning strokes for which they are continuously protected by spark-gaps. So, the breakdown probability of medium voltage (MV) spark-gaps is modeled using the Gaussian distribution function under an impulse voltage test in accordance with the IEC 60060-1 standard. The model is presented in the form of the well-known Gaussian tail probability. Accordingly, a modified probabilistic model is proposed to study the effect of impulse voltage superimposed on the ac voltage on the breakdown probability of MV spark-gaps. The modified model is verified using experimental data, where the experimental setup is arranged to generate a range of impulse voltages superimposed on the ac voltages. The experimental verification shows evidence of the efficacy of the proposed probabilistic model. Furthermore, the proposed model is used to evaluate single-phase, two-phase and three-phase spark-gap breakdown probabilities in the case of lightning induced overvoltages. These breakdown probabilities are used along with the simplified Rusck expression to evaluate the performance of MV overhead lines above a perfectly conducting ground under lightning-induced overvoltages using a statistical approach. In order to study the overvoltages propagating through the transformer to its low voltage side, the high frequency model of the transformer is investigated. First, the investigation is carried out using model introduced by Piantini at no-load condition. This model is modified to take more than one resonance frequency into consideration. Therefore, the frequency response of the simulated transient voltage is improved. A verification of the modified model is carried out through the comparison between the experimental and simulation results, in which the time domain simulation is carried out using ATP/EMTP while MATLAB is used to identify the model parameters. As this model is found suitable only for unloaded transformer, an

  11. 锁相环电路中压控振荡器的SET响应研究%Research on Single-Event Transients in Voltage-Controlled Oscillators of Phase-Locked Loops

    Institute of Scientific and Technical Information of China (English)

    秦军瑞; 陈吉华; 赵振宇; 梁斌; 刘征

    2011-01-01

    Based on process calibration, single event transient in Voltage-Controlled Oscillators of high frequency Phase-Locked Loops in a 0.18μm bulk process is studied by the TCAD Mixed-mode simulation. The impact of voltage, LET and temperature on SET are studied. Our simulation results demonstrate that the max phase difference caused by the particles on VCO is weak when NMOS works in the cut-off region. The pulse error number caused by the particles on VCO increases linearly as LET increases, and when the device temperature increases, the max phase difference on VCO also generally increases.%空间辐射环境中的锁相环在SET作用下,将产生频率或相位偏差,甚至导致振荡中止,造成通信或功能中断.压控振荡器是锁相环中的关键电路,也是对SET最为敏感的部件之一.本文基于工艺校准的器件模型,采用TCAD混合模拟的方法,针对180nm体硅CMOS工艺下高频锁相环中的压控振荡器,研究了偏置条件、入射粒子的能量以及温度对压控振荡器SET响应的影响,通过分析失效机理,以指导抗辐照压控振荡器的设计.研究结果表明,当器件工作在截止区时,入射粒子引起压控振荡器输出时钟的最大相位差最小;压控振荡器的输出时钟错误脉冲数随着入射粒子LET的增加而线性增加;随着器件工作温度的升高,轰击粒子引起压控振荡器输出时钟的最大相位差也是增大的.

  12. Anthrax lethal factor (LF) mediated block of the anthrax protective antigen (PA) ion channel: effect of ionic strength and voltage.

    Science.gov (United States)

    Neumeyer, Tobias; Tonello, Fiorella; Dal Molin, Federica; Schiffler, Bettina; Orlik, Frank; Benz, Roland

    2006-03-07

    The anthrax toxin complex consists of three different molecules, protective antigen (PA), lethal factor (LF), and edema factor (EF). The activated form of PA, PA(63), forms heptamers that insert at low pH in biological membranes forming ion channels and that are necessary to translocate EF and LF in the cell cytosol. LF and EF are intracellular active enzymes that inhibit the host immune system promoting bacterial outgrowth. Here, PA(63) was reconstituted into artificial lipid bilayer membranes and formed ion-permeable channels. The heptameric PA(63) channel contains a binding site for LF on the cis side of the channel. Full-size LF was found to block the PA(63) channel in a dose- and ionic-strength-dependent way with half-saturation constants in the nanomolar concentration range. The binding curves suggest a 1:1 relationship between (PA(63))(7) and bound LF that blocks the channel. The presence of a His(6) tag at the N-terminal end of LF strongly increases the affinity of LF toward the PA(63) channel, indicating that the interaction between LF and the PA(63) channel occurs at the N terminus of the enzyme. The LF-mediated block of the PA(63)-induced membrane conductance is highly asymmetric with respect to the sign of the applied transmembrane potential. The result suggested that the PA(63) heptamers contain a high-affinity binding site for LF inside domain 1 or the channel vestibule and that the binding is ionic-strength-dependent.

  13. An analytic solution of the transient behavior of backscattering thermal protective coatings exposed to combined radiative and convective heating

    Science.gov (United States)

    Cornelison, Charles J.; Howe, John T.

    1991-01-01

    An analytic solution of the material response to combined radiative and convective heating is presented. The solution includes the equations of radiative transfer (within the material), coupled to a transient energy equation which contains both radiative and convective terms. The analysis allows for unlimited spectral detail, but assumes that within the range of applicability, the various material properties do not vary significantly with temperature. Also, to facilitate development of the analytic solution, it is assumed that scattering within the material dominates absorption, and the material exposed surface does not ablate. The exposed surface boundary condition includes convective heating and spectral radiation, some of which is absorbed by the surface and some which penetrates the surface.

  14. Effects of hydrogen, oxygen, and argon annealing on the electrical properties of ZnO and ZnO devices studied by current-voltage, deep level transient spectroscopy, and Laplace DLTS

    Science.gov (United States)

    Mtangi, W.; Auret, F. D.; Meyer, W. E.; Legodi, M. J.; Janse van Rensburg, P. J.; Coelho, S. M. M.; Diale, M.; Nel, J. M.

    2012-05-01

    Effects of annealing ZnO in hydrogen, oxygen, and argon have been investigated using deep level transient spectroscopy (DLTS) and Laplace-DLTS (LDLTS) measurements. Current-voltage (IV) measurements indicate a decrease in zero-bias barrier height for all the annealed samples. Conventional DLTS measurements reveal the presence of three prominent peaks in the un-annealed and annealed samples. A new peak with an activation enthalpy of 0.60 eV has been observed in the H2 annealed samples, while an estimated energy level of 0.67 eV has been observed in Ar annealed samples. O2 annealing does not introduce new peaks but causes a decrease in the concentration of the E3 peak and an increase in concentration of the E1 peak. The concentrations of all the intrinsic defects have decreased after H2 and Ar annealing; with Ar annealing giving peaks with the lowest concentrations. The E2 peak anneals out after annealing ZnO in Ar and H2 at 300 °C. From the annealing behaviour of E3, we have attributed to transition metal ion related defects, while E4 has been explained as a defect, whose formation favours oxygen deficient conditions. Laplace DLTS has successfully been employed to resolve the closely spaced energy levels in the E4 peak, splitting it into three peaks with energy levels, 0.68 eV, 0.58 eV, and 0.50 eV below the minimum of the conduction band for the Ar annealed sample.

  15. 550 kV双断口交流滤波器断路器暂态恢复电压仿真%Simulation of Transient Recovery Voltage of 550 kV AC Filter Breaker with Double Breaks

    Institute of Scientific and Technical Information of China (English)

    施健; 罗兵; 傅明利; 厉天威; 曾向君; 贾磊; 张福增

    2016-01-01

    直流换流站安装有不同滤波次数的交流滤波器(AC filter,ACF),ACF断路器频繁操作以满足换流站无功补偿的需要,在开断大容性电流后断口承受交直流混合电压的共同作用,断口直流分压按电阻分布,而断口等效电阻受外界环境的影响,因此断口承受的电压可能会超过其绝缘能力。以国内典型的550 kV瓷柱式双断口小组滤波器断路器为例,利用PSCAD建立暂态恢复电压(TRV)仿真电路模型,对影响断口TRV分布的环境因素进行了仿真,仿真结果显示外界环境因素(如湿度、污秽、干湿不均等)对断口TRV影响较大,在特定环境条件下当断口绝缘电阻下降较大且两断口电阻值差异较大时,断口最大TRV值会接近或超过规范要求值,从而可能造成断口电弧重燃或闪络故障。%AC filters (ACFs)for different harmonics are installed in HVDC stations,they switch on and off very often with circuit breakers for reactive power compensation. ACF breakers bear transient recovery voltages (TRV)comprising AC and DC voltages after switching off large capacitive current,because the DC voltage component is decided and divided by resistance which is influenced by the ambient environment of porcelain breaker external insulation,the TRV may exceed the insulation requirement. Using a typical 550 kV AC filter procelain breaker with two breaks used in HVDC stations as an example,a simulation model of TRV is established based on PSCAD to simulate the influencing factors of TRV. The simulation results show that the ambient environment,such as humidity, dirt and dry zone,can seriously affect the TRV of breaks. With specific ambient environment conditions,when the break resistance decreases and the diffence between the two break resistances is large,the maximum break TRV may approach or even exceed the theshhold value,which will result in breaker restrike or flashover.

  16. Protective effects of repetitive transcranial magnetic stimulation in a rat model of transient cerebral ischaemia: a microPET study

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Feng [Second Affiliated Hospital of Zhejiang University School of Medicine, Department of Nuclear Medicine, Hangzhou, Zhejiang (China); Second Affiliated Hospital of Zhejiang University School of Medicine, Department of Neurology, Hangzhou, Zhejiang (China); Zhejiang University Medical PET Center, Hangzhou, Zhejiang (China); Institute of Nuclear Medicine and Molecular Imaging of Zhejiang University, Hangzhou, Zhejiang (China); Key Laboratory of Medical Molecular Imaging of Zhejiang Province, Hangzhou, Zhejiang (China); Wang, Shuang; Guo, Yi; Lou, Min; Wu, Jimin; Ding, Meiping [Second Affiliated Hospital of Zhejiang University School of Medicine, Department of Neurology, Hangzhou, Zhejiang (China); Wang, Jing; Zhang, Hong [Second Affiliated Hospital of Zhejiang University School of Medicine, Department of Nuclear Medicine, Hangzhou, Zhejiang (China); Zhejiang University Medical PET Center, Hangzhou, Zhejiang (China); Institute of Nuclear Medicine and Molecular Imaging of Zhejiang University, Hangzhou, Zhejiang (China); Key Laboratory of Medical Molecular Imaging of Zhejiang Province, Hangzhou, Zhejiang (China); Tian, Mei [The University of Texas M.D. Anderson Cancer Center, Department of Experimental Diagnostic Imaging, Houston, TX (United States)

    2010-05-15

    Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive method to excite neurons in the brain. However, the underlying mechanism of its therapeutic effects in stroke remains unclear. The aim of this study was to investigate the neuroprotective effect of high-frequency rTMS in a rat model of transient cerebral ischaemia using positron emission tomography (PET). Sprague-Dawley rats (n=30) were anaesthetized with chloral hydrate and subjected to 90 min of intraluminal middle cerebral artery occlusion (MCAO) with subsequent reperfusion in three groups: control (n=10), rTMS (n=10), or sham-rTMS groups (n=10). In the rTMS group, rTMS was given 1 h after ischaemia and every 24 h for 7 days after MCAO. In all three groups, small-animal PET (microPET) imaging with {sup 18}F-FDG was used to evaluate brain glucose metabolism. Apoptotic molecules were measured in the infarct margin using immunohistochemical staining. The neurological scores of the rats in the rTMS group were higher than in those of the control group over the whole 7-day observation period. The total, cortical and striatal infarct volumes were significantly less in the rTMS group than in the control group, as measured by 2,3,5-triphenyltetrazolium chloride staining. {sup 18}F-FDG microPET images showed significantly higher standardized uptake values in the cortex and striatum in the rTMS group than in the control group in the affected hemisphere. The number of cells positive for caspase-3 was significantly lower in the rTMS group than in the control group, while the Bcl-2/Bax ratio was significantly higher in the rTMS group than in the control group. rTMS therapy increased glucose metabolism and inhibited apoptosis in the ischaemic hemisphere. {sup 18}F-FDG PET could be used to monitor rTMS therapy in transient cerebral ischaemia in animal studies and in future clinical trials. (orig.)

  17. A transient finite element study reveals the importance of the bycicle helmet material properties on head protection during an impact

    OpenAIRE

    Asiminei, Aida Georgeta; Van der Perre, Georges; Verpoest, Ignace; Goffin, Jan

    2009-01-01

    This paper is focused on understanding the mechanism that gives the bicycle helmet the role of protecting the head during an impact. The finite element method is used here as a first step in the helmet optimisation and improvement process. The relation between different helmet mechanical parameters and the risk of head injury during the impact is described using MSC Marc Mentat finite element software. The reduction in resulting head linear acceleration by more than 80% and in resulting stres...

  18. CAVE: A computer code for two-dimensional transient heating analysis of conceptual thermal protection systems for hypersonic vehicles

    Science.gov (United States)

    Rathjen, K. A.

    1977-01-01

    A digital computer code CAVE (Conduction Analysis Via Eigenvalues), which finds application in the analysis of two dimensional transient heating of hypersonic vehicles is described. The CAVE is written in FORTRAN 4 and is operational on both IBM 360-67 and CDC 6600 computers. The method of solution is a hybrid analytical numerical technique that is inherently stable permitting large time steps even with the best of conductors having the finest of mesh size. The aerodynamic heating boundary conditions are calculated by the code based on the input flight trajectory or can optionally be calculated external to the code and then entered as input data. The code computes the network conduction and convection links, as well as capacitance values, given basic geometrical and mesh sizes, for four generations (leading edges, cooled panels, X-24C structure and slabs). Input and output formats are presented and explained. Sample problems are included. A brief summary of the hybrid analytical-numerical technique, which utilizes eigenvalues (thermal frequencies) and eigenvectors (thermal mode vectors) is given along with aerodynamic heating equations that have been incorporated in the code and flow charts.

  19. Analyzing of Dynamic Voltage Restorer in Series Compensation Voltage

    Directory of Open Access Journals (Sweden)

    Naser Parhizgar

    2012-02-01

    Full Text Available The Dynamic Voltage Restorer (DVR is a series-connected compensator to generate a controllable voltage to against the short-term voltage disturbances. The technique of DVR is an effective and cost competitive approach to improve voltage quality at the load side. This study presents a single-phase and threephase DVR system with reduced switch-count topology to protect the sensitive load against abnormal voltage conditions. Most basic function, the DVR configuration consist of a two level Voltage Source Converter (VSC, a dc energy storage device, a coupling transformer Connected in shunt with the ac system This study presents the application of Dynamic Voltage Restorer (DVR on power distribution systems for mitigation of voltage sag at critical loads. DVR is one of the compensating types of custom power devices. The DVR, which is based on forced-commutated Voltage Source Converter (VSC has been proved suitable for the task of compensating voltage sags/swells. Simulation results are presented to illustrate and understand the performances of DVR in supporting load voltages under voltage sags/swells conditions.

  20. Protective effects of Galla Rhois, the excrescence produced by the sumac aphid, Schlechtendalia chinensis, on transient focal cerebral ischemia in the rat.

    Science.gov (United States)

    Lee, Kyungjin; Kim, Jinmo; Lee, Beom-joon; Park, Jea-Woo; Leem, Kang-Hyun; Bu, Youngmin

    2012-01-01

    Galla Rhois is formed by aphids, primarily Schlechtendalia chinensis Bell (Homoptera: Pemphigidae), on the leaf of sumac, Rhus javanica L. (Sapindales: Anacardiaceae). It is a tannin-rich herb that is widely used in traditional Korean medicine. Its various pharmacological effects, including its radical-scavenging effects, have been reported. The purpose of the current study was to determine if these radical-scavenging effects can be confirmed using in vitro assays and to investigate its neuroprotective effects, optimal dosage, mechanisms, and therapeutic time window in an animal model of stroke. Galla Rhois 85% methanol extract (GRE) exhibited potent and dose-dependent radical-scavenging effects on various radicals. Oral administration of GRE (300 mg/kg) in a transient focal cerebral ischemia rat model (two hours of occlusion followed by 22 hours of reperfusion) reduced the brain infarct volume by 37.5%. It also improved sensory motor function and reduced lipid-peroxidation in middle cerebral artery occlusion. However, it did not have any inhibitory effects on brain edema. The time window study revealed that pre- and co-treatment with GRE had protective effects, but post-treatment with GRE (three or six hours after ischemia) did not have protective effects. In conclusion, GRE had potent radical-scavenging activities and neuroprotective effects in a rat model of stroke when it was pre- and co-administered. The optimal dosage may be around 300 mg/kg for oral administration.

  1. 负荷模型选择对动态无功需求和暂态电压稳定的影响%Impact on Dynamic Reactive Power Demand and Transient Voltage Stability by Load Model Selection

    Institute of Scientific and Technical Information of China (English)

    张一荻; 管霖

    2014-01-01

    电力系统中的电源规划和静态无功补偿规划已经形成了相对成熟的理论和方法,但对于动态无功补偿的规划研究则尚未起步。利用 PSCAD/EMTDC软件,从动态无功需求分析和补偿容量选择原则两个方面进行仿真分析,研究感应电动机动态无功负荷的需求特性;给定负荷水平下不同的负荷模型和参数对负荷动态无功需求的影响;电网强弱和负荷模型对母线暂态电压稳定的影响。验证了依据动态无功需求测算来配置动态无功补偿装置补偿容量的可行性,并提出相应的规划方法。%There are comparatively mature theories and methods for power source planning and static var compensation plan-ning in power system but planning for dynamic reactive power compensation has not started up. By using PSCAD/EMTDC software and in aspects of analysis on dynamic reactive power demand and selection principle of compensation capacity,sim-ulation analysis was conducted for studying demand characteristics of dynamic reactive power load of the motor,impact on load dynamic reactive power demand by different load models and parameters with given load level and impact on transient voltage stability of the bus by strongness and weakness of the power grid and load models. Feasibility of deploying dynamic reactive power compensation device according to dynamic reactive power demand was verified and relevant planning methods were proposed.

  2. Low-dose alcohol consumption protects against transient focal cerebral ischemia in mice: possible role of PPARγ.

    Directory of Open Access Journals (Sweden)

    Hong Sun

    Full Text Available BACKGROUND: We examined the influence of low-dose alcohol consumption on cerebral ischemia/reperfusion (I/R injury in mice and a potential mechanism underlying the neuroprotective effect of low-dose alcohol consumption. METHODOLOGY/PRINCIPAL FINDINGS: C57BL/6 J mice were fed a liquid diet without or with 1% alcohol for 8 weeks, orally treated with rosiglitazone (20 mg/kg/day, a peroxisome proliferator-activated receptor gamma (PPARγ-selective agonist, or GW9662 (3 mg/kg/day, a selective PPARγ antagonist, for 2 weeks. The mice were subjected to unilateral middle cerebral artery occlusion (MCAO for 90 minutes. Brain injury, DNA fragmentation and nuclear PPARγ protein/activity were evaluated at 24 hours of reperfusion. We found that the brain injury and DNA fragmentation were reduced in 1% alcohol-fed mice compared to nonalcohol-fed mice. Rosiglitazone suppressed the brain injury in nonalcohol-fed mice, but didn't alter the brain injury in alcohol-fed mice. In contrast, GW9662 worsened the brain injury in alcohol-fed mice, but didn't alter the brain injury in nonalcohol-fed mice. Nuclear PPARγ protein/activity at peri-infarct and the contralateral corresponding areas of the parietal cortex was greater in alcohol-fed mice compared to nonalcohol-fed mice. Using differentiated catecholaminergic (CATH.a neurons, we measured dose-related influences of chronic alcohol exposure on nuclear PPARγ protein/activity and the influence of low-dose alcohol exposure on 2-hour oxygen-glucose deprivation (OGD/24-hour reoxygenation-induced apoptosis. We found that low-dose alcohol exposure increased nuclear PPARγ protein/activity and protected against the OGD/reoxygenation-induced apoptosis. The beneficial effect of low-dose alcohol exposure on OGD/reoxygenation-induced apoptosis was abolished by GW9662. CONCLUSIONS/SIGNIFICANCE: Our findings suggest that chronic consumption of low-dose alcohol protects the brain against I/R injury. The neuroprotective effect

  3. Cavity Voltage Phase Modulation MD

    CERN Document Server

    Mastoridis, Themistoklis; Molendijk, John; Timko, Helga; CERN. Geneva. ATS Department

    2016-01-01

    The LHC RF/LLRF system is currently configured for extremely stable RF voltage to minimize transient beam loading effects. The present scheme cannot be extended beyond nominal beam current since the demanded power would exceed the peak klystron power and lead to saturation. A new scheme has therefore been proposed: for beam currents above nominal (and possibly earlier), the cavity phase modulation by the beam will not be corrected (transient beam loading), but the strong RF feedback and One-Turn Delay feedback will still be active for loop and beam stability in physics. To achieve this, the voltage set point will be adapted for each bunch. The goal of this MD was to test a new algorithm that would adjust the voltage set point to achieve the cavity phase modulation that would minimize klystron forward power.

  4. CGP37157, an inhibitor of the mitochondrial Na+/Ca2+ exchanger, protects neurons from excitotoxicity by blocking voltage-gated Ca2+ channels.

    Science.gov (United States)

    Ruiz, A; Alberdi, E; Matute, C

    2014-04-10

    Inhibition of the mitochondrial Na(+)/Ca(2+) exchanger (NCLX) by CGP37157 is protective in models of neuronal injury that involve disruption of intracellular Ca(2+) homeostasis. However, the Ca(2+) signaling pathways and stores underlying neuroprotection by that inhibitor are not well defined. In the present study, we analyzed how intracellular Ca(2+) levels are modulated by CGP37157 (10 μM) during NMDA insults in primary cultures of rat cortical neurons. We initially assessed the presence of NCLX in mitochondria of cultured neurons by immunolabeling, and subsequently, we analyzed the effects of CGP37157 on neuronal Ca(2+) homeostasis using cameleon-based mitochondrial Ca(2+) and cytosolic Ca(2+) ([Ca(2+)]i) live imaging. We observed that NCLX-driven mitochondrial Ca(2+) exchange occurs in cortical neurons under basal conditions as CGP37157 induced a decrease in [Ca(2)]i concomitant with a Ca(2+) accumulation inside the mitochondria. In turn, CGP37157 also inhibited mitochondrial Ca(2+) efflux after the stimulation of acetylcholine receptors. In contrast, CGP37157 strongly prevented depolarization-induced [Ca(2+)]i increase by blocking voltage-gated Ca(2+) channels (VGCCs), whereas it did not induce depletion of ER Ca(2+) stores. Moreover, mitochondrial Ca(2+) overload was reduced as a consequence of diminished Ca(2+) entry through VGCCs. The decrease in cytosolic and mitochondrial Ca(2+) overload by CGP37157 resulted in a reduction of excitotoxic mitochondrial damage, characterized here by a reduction in mitochondrial membrane depolarization, oxidative stress and calpain activation. In summary, our results provide evidence that during excitotoxicity CGP37157 modulates cytosolic and mitochondrial Ca(2+) dynamics that leads to attenuation of NMDA-induced mitochondrial dysfunction and neuronal cell death by blocking VGCCs.

  5. Comprehensive Reactive Power Support of DFIG Adapted to Different Depth of Voltage Sags

    Directory of Open Access Journals (Sweden)

    Yangwu Shen

    2017-06-01

    Full Text Available The low voltage ride-through (LVRT capability of the doubly-fed induction generator (DFIG significantly impacts upon the integration of wind power into the power grid. This paper develops a novel comprehensive control strategy to enhance the LVRT and reactive power support capacities of the DFIG by installing the energy storage system (ESS. The ESS is connected to the DC-link capacitor of the DFIG and used to regulate the DC-link voltage during normal or fault operations. The unbalanced power between the captured wind power and the power injected to the grid during the transient process is absorbed or compensated by the ESS. The rotor-side converter (RSC is used to control the maximum power production and the grid-side converter (GSC is used to control the reactive power before participating in the voltage support. When the supply voltage continues to drop, the rotor speed is increased by controlling the RSC to realize the LVRT capability and help the GSC further enhance the reactive power support capability. The capacity of the GSC is dedicated to injecting the reactive power to the grid. An auxiliary transient pitch angle controller is proposed to protect the generator’s over speed. Both RSC and GSC act as reactive power sources to further enhance the voltage support capability with serious voltage sags. Simulations based on a single-machine infinite-bus power system verify the effectiveness of the developed comprehensive control strategy.

  6. Toll-like receptor agonist augments virus-like particle-mediated protection from Ebola virus with transient immune activation.

    Directory of Open Access Journals (Sweden)

    Karen A O Martins

    Full Text Available Identifying safe and effective adjuvants is critical for the advanced development of protein-based vaccines. Pattern recognition receptor (PRR agonists are increasingly being explored as potential adjuvants, but there is concern that the efficacy of these molecules may be dependent on potentially dangerous levels of non-specific immune activation. The filovirus virus-like particle (VLP vaccine protects mice, guinea pigs, and nonhuman primates from viral challenge. In this study, we explored the impact of a stabilized dsRNA mimic, polyICLC, on VLP vaccination of C57BL/6 mice and Hartley guinea pigs. We show that at dose levels as low as 100 ng, the adjuvant increased the efficacy of the vaccine in mice. Antigen-specific, polyfunctional CD4 and CD8 T cell responses and antibody responses increased significantly upon inclusion of adjuvant. To determine whether the efficacy of polyICLC correlated with systemic immune activation, we examined serum cytokine levels and cellular activation in the draining lymph node. PolyICLC administration was associated with increases in TNFα, IL6, MCP1, MIP1α, KC, and MIP1β levels in the periphery and with the activation of dendritic cells (DCs, NK cells, and B cells. However, this activation resolved within 24 to 72 hours at efficacious adjuvant dose levels. These studies are the first to examine the polyICLC-induced enhancement of antigen-specific immune responses in the context of non-specific immune activation, and they provide a framework from which to consider adjuvant dose levels.

  7. HEMP-induced transients in electric power substations

    Energy Technology Data Exchange (ETDEWEB)

    Wiggins, C.M.; Thomas, D.E.; Salas, T.M. (BDM International, Inc., Albuquerque, NM (United States))

    1992-02-01

    A nuclear detonation in or above the earth's atmosphere produces an intense electromagnetic pulse (EMP). A large portion of the EMP electromagnetic energy is within the RF spectrum. A detonation at high altitudes above 40 km produces an EMP called high-altitude EMP (HEMP). HEMP is a steep-front short duration transient with a rise time on the order of a few nanoseconds which decays to near zero in less than a microsecond. A single high-altitude burst can subject much of the continental United States to intense HEMP electric fields on the order of tens of kilovolts per meter. The intense transient HEMP will induce fast transients in high-voltage transmission lines and bus structures, instrumentation cables, and control wires in power transmission and distribution (T D) substations. A system of traveling wave coupling models for a 500 kV substation, including models for the high voltage primary bus, components (circuit breakers, disconnect switches, power transformers, and current and voltage instrument transformers), low voltage control wiring circuits, and a number of conducted and radiated interference coupling modes, had been developed earlier by EPRI. These EPRI served as the baseline for the present HEMP coupling investigations. The HEMP effects on protective relays were assessed for a nominal HEMP environment using several new field coupling models merged with the switching transient data. It is found that a representative solid state relay is unlikely to be damaged or to misoperate by the nominal HEMP threat with a peak field strength of 50 kV/m. However, it is possible for both DC control wires to flash over to ground simultaneously, causing fuses to blow and placing the relay in an inoperative state.

  8. HEMP-induced transients in electric power substations. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Wiggins, C.M.; Thomas, D.E.; Salas, T.M. [BDM International, Inc., Albuquerque, NM (United States)

    1992-02-01

    A nuclear detonation in or above the earth`s atmosphere produces an intense electromagnetic pulse (EMP). A large portion of the EMP electromagnetic energy is within the RF spectrum. A detonation at high altitudes above 40 km produces an EMP called high-altitude EMP (HEMP). HEMP is a steep-front short duration transient with a rise time on the order of a few nanoseconds which decays to near zero in less than a microsecond. A single high-altitude burst can subject much of the continental United States to intense HEMP electric fields on the order of tens of kilovolts per meter. The intense transient HEMP will induce fast transients in high-voltage transmission lines and bus structures, instrumentation cables, and control wires in power transmission and distribution (T & D) substations. A system of traveling wave coupling models for a 500 kV substation, including models for the high voltage primary bus, components (circuit breakers, disconnect switches, power transformers, and current and voltage instrument transformers), low voltage control wiring circuits, and a number of conducted and radiated interference coupling modes, had been developed earlier by EPRI. These EPRI served as the baseline for the present HEMP coupling investigations. The HEMP effects on protective relays were assessed for a nominal HEMP environment using several new field coupling models merged with the switching transient data. It is found that a representative solid state relay is unlikely to be damaged or to misoperate by the nominal HEMP threat with a peak field strength of 50 kV/m. However, it is possible for both DC control wires to flash over to ground simultaneously, causing fuses to blow and placing the relay in an inoperative state.

  9. Equivalent modeling of PMSG-based wind power plants considering LVRT capabilities: electromechanical transients in power systems.

    Science.gov (United States)

    Ding, Ming; Zhu, Qianlong

    2016-01-01

    Hardware protection and control action are two kinds of low voltage ride-through technical proposals widely used in a permanent magnet synchronous generator (PMSG). This paper proposes an innovative clustering concept for the equivalent modeling of a PMSG-based wind power plant (WPP), in which the impacts of both the chopper protection and the coordinated control of active and reactive powers are taken into account. First, the post-fault DC link voltage is selected as a concentrated expression of unit parameters, incoming wind and electrical distance to a fault point to reflect the transient characteristics of PMSGs. Next, we provide an effective method for calculating the post-fault DC link voltage based on the pre-fault wind energy and the terminal voltage dip. Third, PMSGs are divided into groups by analyzing the calculated DC link voltages without any clustering algorithm. Finally, PMSGs of the same group are equivalent as one rescaled PMSG to realize the transient equivalent modeling of the PMSG-based WPP. Using the DIgSILENT PowerFactory simulation platform, the efficiency and accuracy of the proposed equivalent model are tested against the traditional equivalent WPP and the detailed WPP. The simulation results show the proposed equivalent model can be used to analyze the offline electromechanical transients in power systems.

  10. Transient stability of DFIG wind turbines at an external short-circuit fault

    DEFF Research Database (Denmark)

    Sun, Tao; Chen, Zhe; Blaabjerg, Frede

    2005-01-01

    concentrates on the transient stability of variable speed wind turbines with doubly fed induction generators (DFIGs) at an external short-circuit fault. A simulation model of a MW-level variable speed wind turbine with a DFIG developed in PSCAD/EMTDC is presented and the control and protection schemes...... are described in detail. The transient process of grid-connected wind turbines with DFIGs at an external shortcircuit fault is analysed, and in critical post-fault situations a measure is proposed for the voltage recovery of DFIG wind turbines after fault clearance. Simulation results demonstrate...

  11. Protection of Large-scale Wind Power Integration

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    More and more large capacity wind power will be integrated into power system in the future, and certain technical challenges will emerge due to the fluctuation characteristics of wind power and the complex control of power electronic devices inside the wind turbines (e. g., low voltage ride through (LVRT)). By comparing a wind power integration grid with a hydropower integration grid, the special transient phenomena caused by the wind power integration is studied and simulation results are presented. Furthermore, the potential impacts on the traditional protection are discussed. Results show that the special transient phenomena can decrease the sensitivity, reliability and operation speed of conventional protections.

  12. Electromagnetic transients in power cables

    CERN Document Server

    da Silva, Filipe Faria

    2013-01-01

    From the more basic concepts to the most advanced ones where long and laborious simulation models are required, Electromagnetic Transients in Power Cables provides a thorough insight into the study of electromagnetic transients and underground power cables. Explanations and demonstrations of different electromagnetic transient phenomena are provided, from simple lumped-parameter circuits to complex cable-based high voltage networks, as well as instructions on how to model the cables.Supported throughout by illustrations, circuit diagrams and simulation results, each chapter contains exercises,

  13. 考虑感应电动机故障中电磁转矩变化的节点暂态电压评估方法%Assessment method of transient voltage stability of load bus considering the changing of induction motor electromagnetic torque in fault

    Institute of Scientific and Technical Information of China (English)

    宋帅; 张英敏; 李兴源

    2013-01-01

    The transient voltage stability has a close relationship with dynamic load characteristic. The load characteristic of induction motor is the important reason causing transient voltage stability. There have been studies on using the critical clearing time to assess transient voltage stability of load node, but the relevant research ignores the effect of the change of the electromagnetic torque of induction motor on the critical clearing time in fault. In order to obtain the critical clearing time accurately, the critical clearing time which considers the change of the electromagnetic torque of induction motor in fault is researched, the mathematical model of electromagnetic torque of induction motor is established, and the critical clearing time is obtained. The critical clearing time reflects transient voltage stability of load node. Simulation and comparison of EPRI36 node system are conducted in power system analysis software (PSASP), and the result verifies the effectiveness of this method. This work is supported by National Natural Science Foundation of China (No. 51037003) and National High-tech R&D Program of China (863 Program) (No. 2011AA05A119).%暂态电压稳定与负荷动态特性之间关系紧密,而感应电动机负荷特性是引起暂态电压稳定的重要原因。利用极限切除时间来评估负荷节点暂态电压稳定状况已有研究,但相关研究都忽略了故障中感应电动机电磁转矩的变化对极限切除时间的影响。为进一步准确求得极限切除时间,对计及故障中感应电动机电磁转矩的变化的极限切除时间进行了研究,建立了感应电动机电磁转矩的数学模型,求得了极限切除时间。极限切除时间反映了负荷节点暂态电压稳定状况,在综合程序(PSASP)中对EPRI36节点系统进行了仿真和对比,仿真结果验证了所述方法的有效性。

  14. A numerical algorithm to evaluate the transient response for a synchronous scanning streak camera using a time-domain Baum–Liu–Tesche equation

    Energy Technology Data Exchange (ETDEWEB)

    Pei, Chengquan [Key Laboratory for Physical Electronics and Devices of the Ministry of Education, Xi' an Jiaotong University, Xi’an 710049 (China); Tian, Jinshou [Xi' an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi' an 710119 (China); Wu, Shengli, E-mail: slwu@mail.xjtu.edu.cn [Key Laboratory for Physical Electronics and Devices of the Ministry of Education, Xi' an Jiaotong University, Xi’an 710049 (China); He, Jiai [School of Computer and Communication, Lanzhou University of Technology, Lanzhou, Gansu 730050 (China); Liu, Zhen [Key Laboratory for Physical Electronics and Devices of the Ministry of Education, Xi' an Jiaotong University, Xi’an 710049 (China)

    2016-10-01

    The transient response is of great influence on the electromagnetic compatibility of synchronous scanning streak cameras (SSSCs). In this paper we propose a numerical method to evaluate the transient response of the scanning deflection plate (SDP). First, we created a simplified circuit model for the SDP used in an SSSC, and then derived the Baum–Liu–Tesche (BLT) equation in the frequency domain. From the frequency-domain BLT equation, its transient counterpart was derived. These parameters, together with the transient-BLT equation, were used to compute the transient load voltage and load current, and then a novel numerical method to fulfill the continuity equation was used. Several numerical simulations were conducted to verify this proposed method. The computed results were then compared with transient responses obtained by a frequency-domain/fast Fourier transform (FFT) method, and the accordance was excellent for highly conducting cables. The benefit of deriving the BLT equation in the time domain is that it may be used with slight modifications to calculate the transient response and the error can be controlled by a computer program. The result showed that the transient voltage was up to 1000 V and the transient current was approximately 10 A, so some protective measures should be taken to improve the electromagnetic compatibility.

  15. A numerical algorithm to evaluate the transient response for a synchronous scanning streak camera using a time-domain Baum-Liu-Tesche equation

    Science.gov (United States)

    Pei, Chengquan; Tian, Jinshou; Wu, Shengli; He, Jiai; Liu, Zhen

    2016-10-01

    The transient response is of great influence on the electromagnetic compatibility of synchronous scanning streak cameras (SSSCs). In this paper we propose a numerical method to evaluate the transient response of the scanning deflection plate (SDP). First, we created a simplified circuit model for the SDP used in an SSSC, and then derived the Baum-Liu-Tesche (BLT) equation in the frequency domain. From the frequency-domain BLT equation, its transient counterpart was derived. These parameters, together with the transient-BLT equation, were used to compute the transient load voltage and load current, and then a novel numerical method to fulfill the continuity equation was used. Several numerical simulations were conducted to verify this proposed method. The computed results were then compared with transient responses obtained by a frequency-domain/fast Fourier transform (FFT) method, and the accordance was excellent for highly conducting cables. The benefit of deriving the BLT equation in the time domain is that it may be used with slight modifications to calculate the transient response and the error can be controlled by a computer program. The result showed that the transient voltage was up to 1000 V and the transient current was approximately 10 A, so some protective measures should be taken to improve the electromagnetic compatibility.

  16. Modeling of the Voltage Waves in the LHC Main Dipole Circuits

    CERN Document Server

    Ravaioli, E; Formenti, F; Steckert, J; Thiesen, H; Verweij, A

    2012-01-01

    When a fast power abort is triggered in the LHC main dipole chain, voltage transients are generated at the output of the power converter and across the energy-extraction switches. The voltage waves propagate through the chain of 154 superconducting dipoles and can have undesired effects leading to spurious triggering of the quench protection system and firing of the quench heaters. The phase velocity of the waves travelling along the chain changes due to the inhomogeneous AC behavior of the dipoles. Furthermore, complex phenomena of reflection and superposition are present in the circuit. For these reasons analytical calculations are not sufficient for properly analyzing the circuit behavior after a fast power abort. The transients following the switch-off of the power converter and the opening of the switches are analyzed by means of a complete electrical model, developed with the Cadence© suite (PSpice© based). The model comprises all the electrical components of the circuit, additional components simula...

  17. 46 CFR 111.01-17 - Voltage and frequency variations.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Voltage and frequency variations. 111.01-17 Section 111... ELECTRIC SYSTEMS-GENERAL REQUIREMENTS General § 111.01-17 Voltage and frequency variations. Unless... and +6 percent to −10 percent of rated voltage. This limitation does not address transient conditions....

  18. Modeling and Analysis of Holding Voltage in BJT-based ESD Protection Device%基于BJT的ESD保护器件中维持电压的建模与分析

    Institute of Scientific and Technical Information of China (English)

    梁海莲; 杨兵; 顾晓峰; 柯逸辰; 高国平

    2012-01-01

    The electro-static discharge (ESD) protection device based on the bipolar junction transistor (BJT) structure has been widely used due to its good bi-directional conduction ability and excellent protection performance. Since there is a little in-depth research on the production mechanism and modeling of the holding voltage under the negative resistor effect in such ESD protection device, we propose a modeling method for the holding voltage. By analyzing the impact of various modulation effects on the holding voltage, the modeling parameters are optimized first. Then, the structure and the electrical properties of NPN BJT are studied by simulation under the 0. 6 μm BiCMOS process, and a holding voltage estimation model is established by data fitting. Finally, two different BJT-based ESD protection devices are prepared and tested. The relative error range between the estimated and the measured data is about 12%~15%, indicating that the established holding voltage model is quite reliable.%基于双极晶体管(BJT)结构的静电放电(ESD)保护器件具有双向导通特性和良好的保护性能,在ESD保护中应用广泛.鉴于该类器件在负阻效应下维持电压的产生机理和建模方面的研究较少,提出了一种维持电压的数学建模方法.首先分析了多种调制效应对维持电压的影响,优化了模型参数;其次,基于0.6 μm BiCMOS工艺对NPN型BJT的结构及电学性能进行了仿真分析,通过数据拟合得到了维持电压的估算模型;最后,制备了两种不同结构的样品并进行了测试,实测数据与估算值的相对误差范围约12%~15%,表明建立的维持电压模型具有较高的可靠性.

  19. Influenza virus-like particles produced by transient expression in Nicotiana benthamiana induce a protective immune response against a lethal viral challenge in mice.

    Science.gov (United States)

    D'Aoust, Marc-André; Lavoie, Pierre-Olivier; Couture, Manon M-J; Trépanier, Sonia; Guay, Jean-Martin; Dargis, Michèle; Mongrand, Sébastien; Landry, Nathalie; Ward, Brian J; Vézina, Louis-P

    2008-12-01

    A strain-specific vaccine represents the best possible response to the threat of an influenza pandemic. Rapid delivery of such a vaccine to the world's population before the peak of the first infection wave seems to be an unattainable goal with the current influenza vaccine manufacturing capacity. Plant-based transient expression is one of the few production systems that can meet the anticipated surge requirement. To assess the capability of plant agroinfiltration to produce an influenza vaccine, we expressed haemagglutinin (HA) from strains A/Indonesia/5/05 (H5N1) and A/New Caledonia/20/99 (H1N1) by agroinfiltration of Nicotiana benthamiana plants. Size distribution analysis of protein content in infiltrated leaves revealed that HA was predominantly assembled into high-molecular-weight structures. H5-containing structures were purified and examination by transmission electron microscopy confirmed virus-like particle (VLP) assembly. High-performance thin layer chromatography analysis of VLP lipid composition highlighted polar and neutral lipid contents comparable with those of purified plasma membranes from tobacco plants. Electron microscopy of VLP-producing cells in N. benthamiana leaves confirmed that VLPs accumulated in apoplastic indentations of the plasma membrane. Finally, immunization of mice with two doses of as little as 0.1 microg of purified influenza H5-VLPs triggered a strong immune response against the homologous virus, whereas two doses of 0.5 microg of H5-VLPs conferred complete protection against a lethal challenge with the heterologous A/Vietnam/1194/04 (H5N1) strain. These results show, for the first time, that plants are capable of producing enveloped influenza VLPs budding from the plasma membrane; such VLPs represent very promising candidates for vaccination against influenza pandemic strains.

  20. Pre- and Posttreatment With Edaravone Protects CA1 Hippocampus and Enhances Neurogenesis in the Subgranular Zone of Dentate Gyrus After Transient Global Cerebral Ischemia in Rats

    Directory of Open Access Journals (Sweden)

    Shan Lei

    2014-11-01

    Full Text Available Edaravone is clinically used for treatment of patients with acute cerebral infarction. However, the effect of double application of edaravone on neurogenesis in the hippocampus following ischemia remains unknown. In the present study, we explored whether pre- and posttreatment of edaravone had any effect on neural stem/progenitor cells (NSPCs in the subgranular zone of hippocampus in a rat model of transient global cerebral ischemia and elucidated the potential mechanism of its effects. Male Sprague-Dawley rats were divided into three groups: sham-operated (n = 15, control (n = 15, and edaravone-treated (n = 15 groups. Newly generated cells were labeled by 5-bromo-2-deoxyuridine. Immunohistochemistry was used to detect neurogenesis. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling was used to detect cell apoptosis. Reactive oxygen species (ROS were detected by 2,7-dichlorofluorescien diacetate assay in NSPCs in vitro. Hypoxia-inducible factor-1α (HIF-1α and cleaved caspase-3 proteins were quantified by western blot analysis. Treatment with edaravone significantly increased the number of NSPCs and newly generated neurons in the subgranular zone (p < .05. Treatment with edaravone also decreased apoptosis of NSPCs (p < .01. Furthermore, treatment with edaravone significantly decreased ROS generation and inhibited HIF-1α and cleaved caspase-3 protein expressions. These findings indicate that pre- and posttreatment with edaravone enhances neurogenesis by protecting NSPCs from apoptosis in the hippocampus, which is probably mediated by decreasing ROS generation and inhibiting protein expressions of HIF-1α and cleaved caspase-3 after cerebral ischemia.

  1. Upregulation of the transient receptor potential ankyrin 1 ion channel in the inflamed human and mouse colon and its protective roles.

    Directory of Open Access Journals (Sweden)

    József Kun

    Full Text Available Transient Receptor Potential Ankyrin 1 (TRPA1 channels are localized on sensory nerves and several non-neural cells, but data on their functional significance are contradictory. We analysed the presence and alterations of TRPA1 in comparison with TRP Vanilloid 1 (TRPV1 at mRNA and protein levels in human and mouse intact and inflamed colons. The role of TRPA1 in a colitis model was investigated using gene-deficient mice. TRPA1 and TRPV1 expressions were investigated in human colon biopsies of healthy subjects and patients with inflammatory bowel diseases (IBD: ulcerative colitis, Crohn's disease with quantitative PCR and immunohistochemistry. Mouse colitis was induced by oral 2% dextran-sulphate (DSS for 10 days. For investigating the functions of TRPA1, Disease Activity Index (weight loss, stool consistency, blood content was determined in C57BL/6-based Trpa1-deficient (knockout: KO and wildtype (WT mice. Sensory neuropeptides, their receptors, and inflammatory cytokines/chemokines were determined with qPCR or Luminex. In human and mouse colons TRPA1 and TRPV1 are located on epithelial cells, macrophages, enteric ganglia. Significant upregulation of TRPA1 mRNA was detected in inflamed samples. In Trpa1 KO mice, Disease Activity Index was significantly higher compared to WTs. It could be explained by the greater levels of substance P, neurokinins A and B, neurokinin 1 receptor, pituitary adenylate-cyclase activating polypeptide, vasoactive intestinal polypeptide, and also interleukin-1beta, macrophage chemoattractant protein-1, monokine induced by gamma interferon-1, tumor necrosis factor-alpha and B-lymphocyte chemoattractant in the distal colon. TRPA1 is upregulated in colitis and its activation exerts protective roles by decreasing the expressions of several proinflammatory neuropeptides, cytokines and chemokines.

  2. Fault Characteristics and Control Strategies of Multiterminal High Voltage Direct Current Transmission Based on Modular Multilevel Converter

    Directory of Open Access Journals (Sweden)

    Fei Chang

    2015-01-01

    Full Text Available The modular multilevel converter (MMC is an emerging voltage source converter topology suitable for multiterminal high voltage direct current transmission based on modular multilevel converter (MMC-MTDC. This paper presents fault characteristics of MMC-MTDC including submodule fault, DC line fault, and fault ride-through of wind farm integration. Meanwhile, the corresponding protection strategies are proposed. The correctness and effectiveness of the control strategies are verified by establishing a three-terminal MMC-MTDC system under the PSCAD/EMTDC electromagnetic transient simulation environment.

  3. Research on Voltage Sag Protection Based on DC Power Supply Technology%基于直流供电技术的电压暂降保护系统研究

    Institute of Scientific and Technical Information of China (English)

    李江龙; 王丽; 陈文波

    2015-01-01

    The inverter is widely used for its obvious advantages in soft start, variable frequency speed control, optimal design, economic operation and so on. During voltage sag, the inverter will be tripped because of low voltage protection, which would cause the important motor driven by inverter to stop working. This will result in non planned outage in the continuous production enterprises, leading to huge economic losses and even personal safety accidents and environment problems. According to the characteristics of inverter’s AC-DC-AC structure and combining power electronics technology two kinds of voltage sag protection (VSP) systems are researched and developed based on DC power supply technology which take network residual voltage and batteries as energy source respectively. And through Boost DC/DC converter, the VSP system outputs a constant DC voltage, supporting inverter’s DC bus. Experimental data and field applications show that the two kinds of VSP system can ensure the normal operation of inverter during voltage sag which greatly improves the reliability on demand side and saves a lot of economic loss for users.%变频器在软启动、变频调速、优化设计、经济运行等方面具有明显优势,得到广泛应用。在电压暂降期间,变频器会因低压保护而跳闸,造成连续性生产企业非计划停运,带来巨大的经济损失和事故。根据变频器交-直-交的特性,结合电力电子技术,研究开发了两种基于直流供电技术的电压暂降保护系统。两种保护系统分别利用电网残压和蓄电池组作为能量来源,通过Boost DC/DC变换器,输出恒定的直流电压,为变频器直流母线提供恒定的直流电。实验数据和现场应用表明,该两种电压暂降保护系统可以确保变频器在电压暂降期间正常运行,大大提高了供电可靠性,为用户避免了大量的经济损失。

  4. Voltage-sharing Characteristics and Protection Value Setting of Modular Multilevel Converter at Static DC Charging State%MMC静态直流充电时电容均压特性研究和保护定值整定

    Institute of Scientific and Technical Information of China (English)

    李超; 唐志军; 林国栋; 邹焕雄; 翟博龙; 陈锦山

    2016-01-01

    A common problem in the static DC charging process of modular multilevel converter is voltage polarization.Some sub-modules”voltage sags even cause startup and shutdown repeatedly.In order to analyze the voltage-sharing characteristics of MMC,firstly,equivalent impedance of energy-absorbing source is introduced into the simulation model of sub-module;secondly,the mechanism of voltage polarization is studied based on the improved model;finally,a setting process of static DC charging tolerance time protection is proposed which can reduce the degree of voltage polarization.The static DC charging experiment and single tower test are conducted at Xiamen HVDC flexible transmission project and the results show consistence between simulation and experiment,which prove the feasibility of the improved simulation model of the sub-module,the mechanism analysis result of voltage polarization,the correction of static DC charging tolerance time protection value setting method.%模块化多电平换流器在静态直流充电时存在电容电压两极分化的问题,部分子模块甚至因电压跌落导致反复启动。先通过引入取能电源等效阻抗动态参数改进子模块等效模型,然后根据改进后模型仿真分析了电容电压两极分化的机理,最后在仿真基础上提出了静态直流充电耐受时间定值整定方法,通过优化保护定值降低电容电压两极分化程度。依托厦门柔性直流输电工程进行了静态直流充电和单个阀塔加压试验,试验结果与仿真结果基本一致,验证了所提子模块等效模型、电容电压两极分化机理分析和保护定值整定方法的正确性。

  5. High-voltage picoamperemeter

    Energy Technology Data Exchange (ETDEWEB)

    Bugl, Andrea; Ball, Markus; Boehmer, Michael; Doerheim, Sverre; Hoenle, Andreas; Konorov, Igor [Technische Universitaet Muenchen, Garching (Germany); Ketzer, Bernhard [Technische Universitaet Muenchen, Garching (Germany); Helmholtz-Institut fuer Strahlen- und Kernphysik, Bonn (Germany)

    2014-07-01

    Current measurements in the nano- and picoampere region on high voltage are an important tool to understand charge transfer processes in micropattern gas detectors like the Gas Electron Multiplier (GEM). They are currently used to e.g. optimize the field configuration in a multi-GEM stack to be used in the ALICE TPC after the upgrade of the experiment during the 2nd long shutdown of the LHC. Devices which allow measurements down to 1pA at high voltage up to 6 kV have been developed at TU Muenchen. They are based on analog current measurements via the voltage drop over a switchable shunt. A microcontroller collects 128 digital ADC values and calculates their mean and standard deviation. This information is sent with a wireless transmitting unit to a computer and stored in a root file. A nearly unlimited number of devices can be operated simultaneously and read out by a single receiver. The results can also be displayed on a LCD directly at the device. Battery operation and the wireless readout are important to protect the user from any contact to high voltage. The principle of the device is explained, and systematic studies of their properties are shown.

  6. Transient of power pulse and its sequence in power electronics

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Various failures and destructions occur in the applications of the power electronic converter. The real practice shows that these failures are connected with the con-centration of the transient power pulse. In allusion to the physical characteristics of power electronic converters,this paper proposed that the power pulse and its se-quence are the basis for power electronics in the perspective of electromagnetic energy. The authors analyzed the transient processes in the power semiconductors,electric conduction loops and controller system and illustrated the power pulse phenomena in high voltage and high power inverters. This investigation on the power pulse sequence is very meaningful for the failure analysis and device pro-tection and has become an important topic in power electronics.

  7. Transient of power pulse and its sequence in power electronics

    Institute of Scientific and Technical Information of China (English)

    ZHAO ZhengMing; BAI Hua; YUAN LiQiang

    2007-01-01

    Various failures and destructions occur in the applications of the power electronic converter, The real practice shows that these failures are connected with the concentration of the transient power pulse. In allusion to the physical characteristics of power electronic converters, this paper proposed that the power pulse and its sequence are the basis for power electronics in the perspective of electromagnetic energy. The authors analyzed the transient processes in the power semiconductors,electric conduction loops and controller system and illustrated the power pulse phenomena in high voltage and high power inverters. This investigation on the power pulse sequence is very meaningful for the failure analysis and device protection and has become an important topic in power electronics.

  8. High holding voltage segmentation stacking silicon-controlled-rectifier structure with field implant as body ties blocking layer

    Science.gov (United States)

    Yen, Shiang-Shiou; Cheng, Chun-Hu; Lan, Yu-Pin; Chiu, Yu-Chien; Fan, Chia-Chi; Hsu, Hsiao-Hsuan; Chang, Shao-Chin; Jiang, Zhe-Wei; Hung, Li-Yue; Tsai, Chi-Chung; Chang, Chun-Yen

    2016-04-01

    High electrostatic discharge (ESD) protection robustness and good transient-induced latchup immunity are two important issues for high voltage integrate circuit application. In this study, we report a high-voltage-n-type-field (HVNF) implantation to act as the body ties blocking layer in segmented topology silicon-controlled-rectifier (SCR) structure in 0.11 µm 32 V high voltage process. This body ties blocking layer eliminate the elevated triggered voltage in segmented technique. Using a large resistance as shunt resistor in resistor assisted triggered SCRs stacking structure, the double snapback phenomenon is eliminate. The series SCR could be decoupled a sufficient voltage drop to turned-on when a very low current flow through the shunt resistor. The holding voltage and the failure current of 22 V and 3.4 A are achieved in the best condition of segmented topology SCR stacking structure, respectively. It improves the latchup immunity at high voltage ICs application. On the other hand, the triggered voltage almost keep the same value which is identical to SCR single cell without using segmented topology.

  9. HPEM protection on HF transmission lines

    Directory of Open Access Journals (Sweden)

    R. Krzikalla

    2004-01-01

    Full Text Available Traditional protection concepts against electromagnetic interferences are combinations of nonlinear elements like spark gaps, varistors or suppressor diodes. Due to parasitic capacitances and inductivities and the general behavior of the elements, a trade off has to be made between the frequency bandwidth and the energy absorption capability of the protection circuit. For high frequency applications with signal frequencies above about 500MHz a sufficient protection can not be given without changing the transmitted signals itself. Additionally this kind of protection concept is designed and optimized against transient interferences with rise times down to some nanoseconds, for example the LEMP, the NEMP or the ESD. Current researches focus on transient interferences with rise times in the picosecond range and pulse widths of a few nanoseconds, the so called ultra wideband (UWB pulses, combined with a significant voltage amplitude of some kilovolts. In this paper investigations on nonlinear protection elements and linear filters against line-coupled UWB pulses with high voltage amplitudes will be done with special focus on the protection of high frequency data-lines.

  10. Accurate Switched-Voltage voltage averaging circuit

    OpenAIRE

    金光, 一幸; 松本, 寛樹

    2006-01-01

    Abstract ###This paper proposes an accurate Switched-Voltage (SV) voltage averaging circuit. It is presented ###to compensated for NMOS missmatch error at MOS differential type voltage averaging circuit. ###The proposed circuit consists of a voltage averaging and a SV sample/hold (S/H) circuit. It can ###operate using nonoverlapping three phase clocks. Performance of this circuit is verified by PSpice ###simulations.

  11. Suppressing capacity fading and voltage decay of Li-rich layered cathode material by a surface nano-protective layer of CoF2 for lithium-ion batteries

    Science.gov (United States)

    Chong, Shaokun; Chen, Yuanzhen; Yan, Wuwei; Guo, Shengwu; Tan, Qiang; Wu, Yifang; Jiang, Tao; Liu, Yongning

    2016-11-01

    Li-rich layered oxides have been regarded as valuable cathode materials for high energy density lithium-ion batteries. However, high initial irreversible capacity, bad rate capability, as well as serious capacity fading and voltage decay hinder their commercial application. In this paper, a nano CoF2 protective layer is coated on the surface of Li1.2Ni0.2Mn0.6O2 via a facial wet chemistry method. A high initial discharge capacity of 264.4 mAh g-1 is obtained for 0.5% CoF2-coated sample and 259.1 mAh g-1 for 1% CoF2-coated sample owing to the suppression of irreversible release of O2 and the contribution of electrochemical conversion of CoF2/LiF. Furthermore, 1% CoF2-coated sample exhibits the excellent rate capability of 167.5 mAh g-1 at 5 C rate, the superior cycling stability with the capacity retention of 241.0 mAh g-1 and the ameliorative voltage drop of 0.312 V at 0.1C after 100 cycles. The enhanced rate performance as well as stability of capacity and voltage can be attributed to the nano coatings which inhibit the electrolyte-electrode side reaction, enhance the electrochemical kinetics and mitigate structure transition from layered to spinel phase.

  12. Influencing Power Flow and Transient Stability by Static Synchronous Series Compensator

    Directory of Open Access Journals (Sweden)

    Md. Imran Azim

    2015-04-01

    Full Text Available In the present world, modern power system networks, being a complicated combination of generators, transmission lines, transformers, circuit breakers and other devices, are more vulnerable to various types of faults causing stability problems. Among these faults, transient fault is believed to be a major disturbance as it causes large damage to a sound system within a certain period of time. Therefore, the protection against transient faults, better known as transient stability control is one of the major considerations for the power system engineers. This paper presents the control approach in the transmission line during transient faults by means of Static Synchronous Series Compensator (SSSC in order to stabilize Single Machine Infinite Bus (SMIB system.  In this paper, SSSC is represented by variable voltage injection associated with the transformer leakage reactance and the voltage source. The comparative results depict that the swing curve of a system increases monotonically after the occurrence of transient faults However, SSSC is effective enough to make it stable after a while.

  13. Protection testing of a modernised medium-voltage switching station in accordance with IEC 61850. An experience report; Schutzpruefung einer erneuerten Mittelspannungsschaltanlage mit IEC 61850. Ein Erfahrungsbericht

    Energy Technology Data Exchange (ETDEWEB)

    Kroll, Karlheinz [MVV Energie AG, Netzschutz- und Stationsleittechnik, Mannheim (Germany); Schossig, Thomas [Omicron electronics GmbH, Product Management, Klaus (Austria)

    2009-08-15

    At MW Energie AG the protection of an installation was entirely renewed. Protection messages to the control system are transmitted in accordance with IEC 61850. Since not all testing signals are available in conventional wiring, the configuration has been extended to permit fast real-time communication with Goose.

  14. 低压船用电动机绝缘与绕组热保护%Insulation of the Low Voltage Marine Motor and Thermal Protection of Its Winding

    Institute of Scientific and Technical Information of China (English)

    王强; 陈金刚

    2013-01-01

      讲述低压船用三相异步电动机绝缘与绕组热保护。介绍了电机用防潮加热带、PTC热敏电阻、热电阻PT100和热电偶在低压船用三相异步电动机上的安装、测量及使用方法。明确电动机在潮湿环境下,绝缘电阻低时防潮加热带的作用,并阐述电机绕组热保护的控制原理以及电机线圈及轴承温度测量的方法和意义。%Insulation of the low voltage marine motor and thermal protection of its winding was described. Instal-lation, measurement and operation of the moisture-proof heating tape, PTC thermistor, thermal resistance PT100 and thermocouple in the low voltage marine three-phase asyn-chronous motor were introduced. The effect of the moisture-proof heating tape in condition that the motor operating under the moist environment was determined. The motor winding overheat protection control principle as well as the motor coil and bearing temperature measurement methods and significance were also discussed.

  15. Mechanistic Insight in the Function of Phosphite Additives for Protection of LiNi0.5Co0.2Mn0.3O2 Cathode in High Voltage Li-Ion Cells.

    Science.gov (United States)

    He, Meinan; Su, Chi-Cheung; Peebles, Cameron; Feng, Zhenxing; Connell, Justin G; Liao, Chen; Wang, Yan; Shkrob, Ilya A; Zhang, Zhengcheng

    2016-05-11

    Triethlylphosphite (TEP) and tris(2,2,2-trifluoroethyl) phosphite (TTFP) have been evaluated as electrolyte additives for high-voltage Li-ion battery cells using a Ni-rich layered cathode material LiNi0.5Co0.2Mn0.3O2 (NCM523) and the conventional carbonate electrolyte. The repeated charge/discharge cycling for cells containing 1 wt % of these additives was performed using an NCM523/graphite full cell operated at the voltage window from 3.0-4.6 V. During the initial charge process, these additives decompose on the cathode surface at a lower oxidation potential than the baseline electrolyte. Impedance spectroscopy and post-test analyses indicate the formation of protective coatings by both additives on the cathode surface that prevent oxidative breakdown of the electrolyte. However, only TTFP containing cells demonstrate the improved capacity retention and Coulombic efficiency. For TEP, the protective coating is also formed, but low Li(+) ion mobility through the interphase layer results in inferior performance. These observations are rationalized through the inhibition of electrocatalytic centers present on the cathode surface and the formation of organophosphate deposits isolating the cathode surface from the electrolyte. The difference between the two phosphites clearly originates in the different properties of the resulting phosphate coatings, which may be in Li(+) ion conductivity through such materials.

  16. Transient osteoporosis.

    Science.gov (United States)

    Korompilias, Anastasios V; Karantanas, Apostolos H; Lykissas, Marios G; Beris, Alexandros E

    2008-08-01

    Transient osteoporosis is characterized primarily by bone marrow edema. The disease most commonly affects the hip, knee, and ankle in middle-aged men. Its cause remains unknown. The hallmark that separates transient osteoporosis from other conditions presenting with a bone marrow edema pattern is its self-limited nature. Laboratory tests usually do not contribute to the diagnosis. Plain radiographs may reveal regional osseous demineralization. Magnetic resonance imaging is used primarily for early diagnosis and monitoring disease progression. Early differentiation from more aggressive conditions with long-term sequelae is essential to avoid unnecessary treatment. Clinical entities such as transient osteoporosis of the hip and regional migratory osteoporosis are spontaneously resolving conditions. However, early differential diagnosis and surgical treatment are crucial for the patient with osteonecrosis of the hip or knee.

  17. 基于RTDS的中压母线弧光保护试验研究%Experimental Study on Arc-flash Protection of Medium Voltage Busbar Based on RTDS

    Institute of Scientific and Technical Information of China (English)

    丁北平; 吴英俊; 陈琳灿; 林钧; 姚一军

    2013-01-01

    In order to realize the fast protection of MV(medium voltage) busbar, RTDS simulation test system is connected to the developed arc-flash protection device of MV busbar in accordance with operating parame-ters of field substation to establish the real-time closed-loop system for arc-flash protection of MV busbar. By setting different types of fault locations, various faults of MV busbar are simulated. The waves are recorded and action behavior of the protection is analyzed. The feasibility of arc-flash protection as fast protection of MV busbar is investigated, and the original intention of the design to meet the protection selectivity and sen-sitivity is verified.%为实现中压母线的快速保护,根据现场变电站运行参数,用RTDS仿真试验系统连接开发的中压母线快速弧光保护装置,构建了中压母线电弧光保护实时闭环系统模型。通过设置不同类型的故障点模拟中压母线的各类故障,录波并分析保护的动作行为,研究弧光保护作为中压母线快速保护的可行性,并验证了其满足保护选择性与灵敏性的设计初衷。

  18. Identification of Transient and Permanent Faults

    Institute of Scientific and Technical Information of China (English)

    李幼仪; 董新洲; 孙元章

    2003-01-01

    A new algorithm was developed for arcing fault detection based on high-frequency current transients analyzed with wavelet transforms to avoid automatic reclosing on permanent faults. The characteristics of arc currents during transient faults were investigated. The current curves of transient and permanent faults are quite similar since current variation from the fault arc is much less than the voltage variation. However, the fault current details are quite different because of the arc extinguishing and reigniting. Dyadic wavelet transforms were used to identify the current variation since wavelet transform has time-frequency localization ability. Many electric magnetic transient program (EMTP) simulations have verified the feasibility of the algorithm.

  19. Lowering of the firing voltage and reducing of the discharge delay time in alternating current plasma display panels by a discontinuous spin-coated LaB6 film on the MgO protective layer

    Directory of Open Access Journals (Sweden)

    Jiang Deng

    2014-03-01

    Full Text Available A spin coated LaB6 discontinuous film is covered on MgO protective layer to improve the discharge performance of alternating current plasma display panels. Under the premise of high transmittance of more than 90%, a very small amount of polycrystal LaB6 powders added in an organic solvent are chosen as the coating solution. The discharge characteristics results show that with 250 torr 5% Xe-Ne pressure, the firing voltage and discharge delay time of the test panel with LaB6/MgO double protective layer are decreased by 13.4% and 36.5%, respectively, compared with that of conventional MgO protective layer, likely owing to the low work function of LaB6. Furthermore, the aging time of the proposed structure is comparable to that of pure MgO protective layer. Therefore, it will not increase the production costs and is highly suitable to be applied for alternating current plasma display panels with low electrical power consumption.

  20. Lowering of the firing voltage and reducing of the discharge delay time in alternating current plasma display panels by a discontinuous spin-coated LaB{sub 6} film on the MgO protective layer

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Jiang, E-mail: dj78291@163.com [School of Physical Electronic, University of Electronic Science and Technology of China, No.4, Section 2, Jianshe North Road, 610054 Chengdu (China); Zeng, Baoqing [School of Physical Electronic, University of Electronic Science and Technology of China, No.4, Section 2, Jianshe North Road, 610054 Chengdu (China); Zhongshan Institute, University of Electronic Science and Technology of China, 528402 zhongshan (China); Wang, Xiaoju; Lin, Zulun; Qi, Kangcheng; Cao, Guichuan [School of Opto-electronic Information, University of Electronic Science and Technology of China, No.4, Section 2, Jianshe North Road, 610054 Chengdu (China)

    2014-03-15

    A spin coated LaB{sub 6} discontinuous film is covered on MgO protective layer to improve the discharge performance of alternating current plasma display panels. Under the premise of high transmittance of more than 90%, a very small amount of polycrystal LaB{sub 6} powders added in an organic solvent are chosen as the coating solution. The discharge characteristics results show that with 250 torr 5% Xe-Ne pressure, the firing voltage and discharge delay time of the test panel with LaB{sub 6}/MgO double protective layer are decreased by 13.4% and 36.5%, respectively, compared with that of conventional MgO protective layer, likely owing to the low work function of LaB{sub 6.} Furthermore, the aging time of the proposed structure is comparable to that of pure MgO protective layer. Therefore, it will not increase the production costs and is highly suitable to be applied for alternating current plasma display panels with low electrical power consumption.

  1. Transient tests on an MHD thruster

    Energy Technology Data Exchange (ETDEWEB)

    Pierson, E.S. (Purdue Univ., Hammond, IN (United States). Dept. of Engineering); Libera, J.; Petrick, M. (Argonne National Lab., IL (United States). Energy Systems Div.)

    1993-01-01

    Three different types of transient tests were made -- coast downs to zero voltage and current under open circuit and short circuit conditions, reverses where the applied voltage was reversed to the same or a different value, and jumps where the voltage applied to the thruster was increased without a change in polarity. Most except the coast downs were dons both quickly (voltage changes as fast as possible) and slowly (6 s to complete the voltage change). A few slower (12 s) transients were done. Transient runs were made for water conductivities of 16.2 and 5.09 S/m. In all cases steady-state conditions were established and several seconds of data taken before initiating the transients. Data were measured every 0.75 to 1 .5 second over the time interval of interest. Particular attention was paid to looking for evidence of gas bubbles, and to the chance of the voltage profiles between the electrodes. The data are interpreted based on the behavior of the power supply and the thruster.

  2. Quantitative evaluation of difference in impact of grounding accident on zero-phase voltage and zero-phase current in 6kV distribution system. Results of EMTP simulation; 6kV haiden keito deno chiraku jiko yoso no reiso den`atsu, reiso denryuha eno eikyo ni kansuru teiryoteki hyoka. EMTP (Electro Magnetic Transients Program) simulation kekka

    Energy Technology Data Exchange (ETDEWEB)

    Nagai, K. [Kansai Electric Power Co. Inc., Osaka (Japan)

    1997-10-10

    EMTP (electromagnetic transients program) analysis using accident spot models is conducted to disclose the different effect exerted on the zero-phase voltage and zero-phase current by different grounding accidents. An accident spot producing a near-delta waveform is represented by an equivalent circuit model No. 1 in which a switch simulating a discharge gap and the accident spot resistance are connected in series. In the case of an accident presenting a near-needle waveform, since it is supposed that the discharge is caused to be intermittent because the gap discharge start voltage is high and the accident spot resistance is low, it is presented by an equivalent circuit similar in configuration to model No. 1 with the constants altered. A leak-suggesting waveform with a current flowing even in the neighborhood of the zero cross point is represented by model No. 1 with a leak resistor added in parallel thereto, which circuit is shown as model No. 2. In the accidents represented by model No. 1, zero-phase current waveforms are grouped into three types, and the relations between the switch on-off circuit/grounding resistance and waveform configuration are disclosed. As for the accidents represented by model No. 2, it is found that the leak resistance values fall somewhere in the 200-2000 ohm range. 2 refs., 6 figs., 2 tabs.

  3. Development of a model of synchronous generator with a saturable transformer for the analysis of transient overvoltage in medium voltage systems; Desarrollo de un modelo de generador sincrono con transformador saturable para el analisis de sobrevoltajes transitorios en sistemas de mediana tension

    Energy Technology Data Exchange (ETDEWEB)

    Reyes Martinez, Oscar Alfonso

    2001-02-01

    In this work the problems of the transient overvoltage produced in the components that integrate the synchronous generators installed in industrial systems of medium voltage are approached. The development of a mathematical model in phase components for the synchronous generator is presented. The model includes a current saturation transformer, a system of static excitation and a scheme of grounding by low impedance through an energy cable. In the formulation the effect of the dampening windings is neglected since the interest is only to evaluate the effect of the initial transient overvoltage. Also, symmetry in the phases is considered and the saturation is neglected. The proposed mathematical model was evaluated through cases of simulation using real data of a typical industrial system. Also some tests were conducted in laboratories that, qualitatively, endorse the results obtained by simulation. Two real cases of electrical equipment fault by effect of transient overvoltage in industrial centers in Mexico were analyzed, with generators grounded through high impedance. [Spanish] En este trabajo se aborda la problematica de los sobrevoltajes transitorios producidos en los componentes que integran los generadores sincronos instalados en sistemas industriales de mediana tension. Se presenta el desarrollo de un modelo matematico en componentes de fase para el generador sincrono. El modelo incluye un transformador de corriente saturable, un sistema de excitacion estatica y un esquema de aterrizamiento por baja impedancia a traves de un cable de energia. En la formulacion se desprecia el efecto de los devanados amortiguadores debido a que solo interesa evaluar el efecto del sobrevoltaje transitorio inicial. Asi mismo, se considera simetria en las fases y se desprecia la saturacion. El modelo matematico propuesto fue evaluado a traves de casos de simulacion utilizando datos reales de un sistema industrial tipico. Tambien se realizaron algunas pruebas en laboratorios que

  4. A low voltage CMOS low drop-out voltage regulator

    Science.gov (United States)

    Bakr, Salma Ali; Abbasi, Tanvir Ahmad; Abbasi, Mohammas Suhaib; Aldessouky, Mohamed Samir; Abbasi, Mohammad Usaid

    2009-05-01

    A low voltage implementation of a CMOS Low Drop-Out voltage regulator (LDO) is presented. The requirement of low voltage devices is crucial for portable devices that require extensive computations in a low power environment. The LDO is implemented in 90nm generic CMOS technology. It generates a fixed 0.8V from a 2.5V supply which on discharging goes to 1V. The buffer stage used is unity gain configured unbuffered OpAmp with rail-to-rail swing input stage. The simulation result shows that the implemented circuit provides load regulation of 0.004%/mA and line regulation of -11.09mV/V. The LDO provides full load transient response with a settling time of 5.2μs. Further, the dropout voltage is 200mV and the quiescent current through the pass transistor (Iload=0) is 20μA. The total power consumption of this LDO (excluding bandgap reference) is only 80μW.

  5. Implementation of Dynamic Voltage Restorer for Mitigation of Voltage Sag

    Directory of Open Access Journals (Sweden)

    K.Vinod Kumar

    2013-07-01

    Full Text Available Power quality is one of major concerns in the present. It has become important, especially with the introduction of sophisticated devices, whose performance is very sensitive to the quality of power supply. The dynamic voltage restorer (DVR is one of the modern devices used in distribution systems to improve the power quality. In this paper, emergency control in distribution systems is discussed by using the proposed multifunctional DVR control strategy.Also, themultiloop controller using the Posicast and P+Resonant controllers is proposed in order to improve the transient response and eliminate the steady state error in DVR response,respectively.The proposed process is applied to some riots in load voltage effected by induction motors starting, and a three-phase short circuit fault. The three-phase short circuits, and the large induction motors are suddenly started then voltage sags areoccurred.The innovation here is that by using the Multifunctional Dynamic Voltage Restorer, improve the power quality in distribution side. Simulation results show the capability of the DVR to control the emergency conditions of the distribution systems by using MATLAB/Simulink software.

  6. Transient cooling during early reperfusion attenuates delayed edema and infarct progression in the Spontaneously Hypertensive Rat. Distribution and time course of regional brain temperature change in a model of postischemic hypothermic protection.

    Science.gov (United States)

    Kurasako, Toshiaki; Zhao, Liang; Pulsinelli, William A; Nowak, Thaddeus S

    2007-12-01

    The temperature threshold for protection by brief postischemic cooling was evaluated in a model of transient focal ischemia in the Spontaneously Hypertensive Rat, using an array of epidural probes to monitor regional brain temperatures. Rats were subjected to 90 mins tandem occlusion of the right middle cerebral artery (MCA) and common carotid artery. Systemic cooling to 32 degrees C was initiated 5 mins before recirculation, with simultaneous brain cooling to temperatures ranging from 28 degrees C to 32 degrees C within the MCA territory by means of a temperature-controlled saline drip. Rewarming was initiated at 2 h recirculation and was complete within 30 mins. Tissue damage and edema volume showed clear temperature-dependent reductions when evaluated at 3 days survival, with no protection evident in the group at 32 degrees C but progressive effects on both parameters after deeper cooling. A particularly striking effect was the essentially complete elimination of edema progression between 1 and 3 days. Temperature at distal sites within the MCA territory better predicted reductions in lesion volume, indicating that protection required effective cooling of the penumbral regions destined to be spared. These results show that even brief cooling can be highly protective when initiated at the time of recirculation after focal ischemia, but indicate a substantially lower temperature threshold for hypothermic protection than has been reported for other strains, occlusion methods, and cooling durations.

  7. ±800kV酒泉特高压直流入湘对湖南电网暂态电压稳定性的影响%Impacts of ±800 kV DC Power Transmission From Jiuquan to Hunan on Transient Voltage Stability of Hunan Power Grid

    Institute of Scientific and Technical Information of China (English)

    廖国栋; 谢欣涛; 侯益灵; 徐超

    2012-01-01

    基于湖南电网2015年规划数据,应用电力系统分析综合程序(power system analysis software package,PSASP)分析了±800kV滔泉特高压直流入湘对湖南电网暂态电压稳定性的影响。分析结果表明:±800kV酒泉直流入湘后湖南电网机组的开机数量和电容器组投切量均将相应减少,但湘东500kV环网的无功损耗将增加,同时扰动后酒泉直流还将从湘东500kV环网吸入大量无功,最终减弱了扰动后湖南电网电压的恢复能力,降低了湖南电网的暂态电压稳定水平。分析结果可为其他电网研究特高压直流对受端电网的影响提供参考。%According to the planned data of Hunan power grid for the year of 2015, the influence of transmitting power via ±800 kV HVDC transmission line from Jiuquan to Hunan power grid on transient voltage stability of Hunan power grid is simulated by power system analysis software package (PSASP) Simulation results show that under the power transmission from Jiuquan to Hunan via ±800 kV HVDC transmission line the number of being operated generating units in Hunan power grid as well as the capacity of switched over capacitor banks are reduced correspondingly, however the reactive power loss of 500 kV electromagnetic looped network in East Hunan will increase, and after the disturbance the ±800 kV HVDC system will absorb large amount of reactive power from 500 kV electromagnetic looped network in East Hunan, thus the ability of voltage recovery of Hunan power grid after the disturbance will be weakened and the transient voltage stability level of Hunan power grid will be decreased.

  8. Protective

    Directory of Open Access Journals (Sweden)

    Wessam M. Abdel-Wahab

    2013-10-01

    Full Text Available Many active ingredients extracted from herbal and medicinal plants are extensively studied for their beneficial effects. Antioxidant activity and free radical scavenging properties of thymoquinone (TQ have been reported. The present study evaluated the possible protective effects of TQ against the toxicity and oxidative stress of sodium fluoride (NaF in the liver of rats. Rats were divided into four groups, the first group served as the control group and was administered distilled water whereas the NaF group received NaF orally at a dose of 10 mg/kg for 4 weeks, TQ group was administered TQ orally at a dose of 10 mg/kg for 5 weeks, and the NaF-TQ group was first given TQ for 1 week and was secondly administered 10 mg/kg/day NaF in association with 10 mg/kg TQ for 4 weeks. Rats intoxicated with NaF showed a significant increase in lipid peroxidation whereas the level of reduced glutathione (GSH and the activity of superoxide dismutase (SOD, catalase (CAT, glutathione S-transferase (GST and glutathione peroxidase (GPx were reduced in hepatic tissues. The proper functioning of the liver was also disrupted as indicated by alterations in the measured liver function indices and biochemical parameters. TQ supplementation counteracted the NaF-induced hepatotoxicity probably due to its strong antioxidant activity. In conclusion, the results obtained clearly indicated the role of oxidative stress in the induction of NaF toxicity and suggested hepatoprotective effects of TQ against the toxicity of fluoride compounds.

  9. 厂外排水管道交流稳态干扰防护设计%Protection Design against AC Steady-state Interference for Water Pipeline near High-voltage Transmission Lines

    Institute of Scientific and Technical Information of China (English)

    程明; 牟华; 黄春蓉; 张平

    2013-01-01

    AC steady-state interference may affect the water pipeline near high-voltage transmission lines. Referring to some related standards, the mitigation objective and protection effect of the AC interference were analyzed, and the Right of Way (ROW) package was used to build modeling and calculation around the mitigation. The calculation results can guide the engineering design.%高压输电线路附近的厂外排水管道可能面临交流稳态干扰影响.结合相关标准要求,对交流干扰缓解目标和防护效果进行探讨分析,并利用自动计算软件包(ROW)分别对缓解前后进行建模计算分析.计算分析结果可以指导工程设计.

  10. Switching transients in a superconducting coil

    Energy Technology Data Exchange (ETDEWEB)

    Owen, E.W.; Shimer, D.W.

    1983-11-18

    A study is made of the transients caused by the fast dump of large superconducting coils. Theoretical analysis, computer simulation, and actual measurements are used. Theoretical analysis can only be applied to the simplest of models. In the computer simulations two models are used, one in which the coil is divided into ten segments and another in which a single coil is employed. The circuit breaker that interrupts the current to the power supply, causing a fast dump, is represented by a time and current dependent conductance. Actual measurements are limited to measurements made incidental to performance tests on the MFTF Yin-yang coils. It is found that the breaker opening time is the critical factor in determining the size and shape of the transient. Instantaneous opening of the breaker causes a lightly damped transient with large amplitude voltages to ground. Increasing the opening time causes the transient to become a monopulse of decreasing amplitude. The voltages at the external terminals are determined by the parameters of the external circuit. For fast opening times the frequency depends on the dump resistor inductance, the circuit capacitance, and the amplitude on the coil current. For slower openings the dump resistor inductance and the current determine the amplitude of the voltage to ground at the terminals. Voltages to ground are less in the interior of the coil, where transients related to the parameters of the coil itself are observed.

  11. 低压智能馈电开关漏电保护的故障分析与改造%Fault analysis of leakage protection of smart low-voltage feed switch and its reformation

    Institute of Scientific and Technical Information of China (English)

    管振翔; 王光生; 姜涛; 刘士刚; 翟东; 范新留

    2013-01-01

    针对南屯煤矿井下低压智能馈电开关漏电保护出现的故障,分析了漏电保护原理及故障原因,并提出了改造方案:在总开关处通过附加电容来增大零序电流,以便综合保护装置能够进行采集、判断,使漏电支路分开关可靠动作;在分开关漏电检测回路中串接一个断路器常闭辅助接点,使分开关合闸后能够将附加直流电源式原理检测回路完全切除,消除对总开关漏电检测的干扰.现场应用结果表明,改造后的低压供电系统漏电保护运行正常,总开关漏电动作时间由原来的2 s缩短到250 ms以内,分开关漏电保护动作灵敏、可靠.%For faults in leakage protection of smart low-voltage feed switch of Nantun Coal Mine, the paper analyzed leakage protection principle and causes of the faults, and proposed reformation schemes: increase zero sequence current by additional capacitance at the master switch, so that integrated protector can be used for acquisition and judgment, and sub switch of the leakage branch can operate reliably; connect a circuit breaker auxiliary contact normally closed in series in leakage detection circuit of sub switch, so that detection circuit based on additional DC power principle can be cut off completely after closing of the sub switch to eliminate interference to leakage detection of master switch. Field application results show that the improved leakage protection of the low-voltage power supply system operates normally, leakage action time is shortened from 2 s to less than 250 ms, and the leakage protection of sub switch acts sensitively and reliably.

  12. A combined uninterruptible power supply and dynamic voltage compensator using a flywheel energy storage system

    Science.gov (United States)

    Weissbach, Robert Stephen

    Due to recent technological advances in materials, power electronics, magnetic bearings and controls, the flywheel energy storage system has become a viable alternative to electrochemical batteries. The advantages of the flywheel system are its higher power density, insensitivity to environmental conditions, lack of hazardous materials and ease of checking the charge. One potential use is in a power distribution system. The flywheel energy storage system may be used as both an uninterruptible power supply as well as a means of dynamic voltage compensation to protect critical loads on radial distribution feeders. To perform dynamic voltage compensation, a comparison was performed which shows that the series injection of power is preferable to the shunt injection of power in utilizing the available kVA of the flywheel system motor/generator. The system was designed and modeled using the Electromagnetic Transients Program to ensure a proper dynamic response of the flywheel energy storage system in either mode of operation. The design incorporates a boost converter on the dc link to enable the load voltage to be maintained as the flywheel spins down. The same boost converter also allows for extended operation in the series compensation mode, by implementing a novel control scheme where sinusoidal pulse width modulation control is used for to compensate for smaller supply voltage dips, while the boost converter is used to control the compensation for larger supply voltage dips.

  13. Comparison of Single-Event Transients Induced in an Operational Amplifier (LM124) by Pulsed Laser Light and a Broad Beam of Heavy Ions

    Science.gov (United States)

    Buchner, Steve; McMorrow, Dale; Poivey, Christian; Howard, James, Jr.; Pease, Rom; Savage, Mark; Boulghassoul, Younis; Massengill, Lloyd

    2003-01-01

    A comparison of transients from heavy-ion and pulsed-laser testing shows good agreement for many different voltage configurations. The agreement is illustrated by comparing directly individual transients and plots of transient amplitude versus width.

  14. Voltage-dependent anion channels (VDACs) promote mitophagy to protect neuron from death in an early brain injury following a subarachnoid hemorrhage in rats.

    Science.gov (United States)

    Li, Jian; Lu, Jianfei; Mi, Yongjie; Shi, Zhao; Chen, Chunhua; Riley, John; Zhou, Changman

    2014-07-21

    The term mitophagy is coined to describe the selective removal of mitochondria by autophagy but the process itself is still contentious, especially in the early period following subarachnoid hemorrhage (SAH). In the present study, we investigated the role of mitophagy following 48h after SAH injury in rats. Specifically evaluating whether mitophagy, through voltage dependant anion channels (VDACs) interacting with microtubule-associated protein 1 light chain 3, could orchestrate the induction of apoptotic and necrotic cell death in neurons, a VDAC1siRNA and an activitor Rapamycian (RAPA), were engaged. One hundred and twelve male Sprague-Dawley rats were randomly divided into 4 groups: Sham, SAH, SAH+VDAC1siRNA, and SAH+RAPA. Outcomes measured included mortality rate, brain edema, BBB disruption, and neurobehavioral testing. We also used western blotting techniques to analyze the expressions of key mitophagic/autophagic proteins and pro-apoptotic protein such as ROS, VDAC1, LC-3II and Caspase-3. Rapamycin treatment significantly improved the mortality rate, cerebral edema, and neurobehavioral deficits; apoptotic and necrotic cell death in neurons were reduced by Rapamycin following SAH injury. However, VDAC1siRNA worsened the brain injury following SAH. Immunohistochemical staining and western blot analysis demonstrated a decreased expression of VDAC1, LC3II, and an increase of ROS and Caspase-3 followed by VDAC1siRNA administration. In conclusion, mitophagy induced by VDAC1 following SAH injury may in fact play a significant role in neuroprotection, the mechanism which may be through the attenuation of the apoptosic and necrosic molecular pathways. This translates a preservation of functional integrity and an improvement in mortality.

  15. Simulation and Characteristics Analysis of Very Fast Transient Overvoltage in Gas Insulated Substation with Ultra High Voltage%特高压GIS变电站中快速暂态过电压仿真及其特性分析

    Institute of Scientific and Technical Information of China (English)

    王娜; 林莘; 徐建源; 王飞鸣; 王静

    2012-01-01

    在计算快速暂态过电压(VFTO)时,建立准确的全封闭气体绝缘变电站(GIS)暂态电路模型是影响VFTO的关键。为此,将GIS内部暂态模型和GIS外壳传输特性模型相结合,建立了VFTO整体仿真模型。在GIS内部元件建模时,根据电弧的动态物理过程,建立隔离开关分段式动态电弧模型;结合交变电场下电介质极化原理,建立金属氧化物避雷器(MOA)暂态电路模型;并从GIS本体结构出发,通过三维电场分析,获得较准确的GIS元件暂态模型及参数;结合传输线理论和相模变换,获得GIS外壳暂态模型,并建立了考虑接地体问互感作用的暂态地网模型。最后结合国内某1100kV气体绝缘变电站,进行VFTO详细仿真。仿真结果表明,分段式动态电弧模型下VFTO幅值标幺值高达1.270(基准值取898kV),较指数时变电弧模型下的VFTO幅值标幺值增加了17.59%,当考虑了MOA的非线性特性时,VFTO的振荡幅值有不断减小的趋势,在仿真时间将近20μs时,VFTO标幺值振荡幅度至0.8。最后将仿真结果与实测波形进行对比分析,VFTO幅值标幺值相差0.2~0.4,证明了所建立的VFTO仿真整体模型的实用性。%In the computer simulation process of very fast transient overvoltage (VFTO), establishing an accurate model of gas insulated substation(GIS)component is a key factor that affects the accuracy of VFTO. Thus, a VFTO overall simulation model was established combining the inner transient model and the model of transmission characteristics of GIS enclosures. Moreover, A dynamic arcing model was proposed based on the arc physical process, and a metal oxide surge arrester(MOA) transient circuit model was established based on the polarization theory in alternating electric field. By 3D electric field analysis, an accurate GIS equipment equivalent model and its parameters were obtained based on the body structure

  16. Variable Current Transient Beam Loading Compensation

    Energy Technology Data Exchange (ETDEWEB)

    Farkas, Zoltan D

    2000-10-25

    The energy spread caused by transients during beam turn-on can be reduced by suitable timing of the beam turn-on[1]. If the beam is injected when the no-load voltage reaches the desired loaded voltage, then the energy spread is about 10%. To eliminate this energy spread, one can amplitude or phase modulate the section input power for one fill time, so that when the beam is turned on, the no-load voltage equals the desired loaded voltage and from then on, the change in no-load voltage tracks the beam induced voltage. It is known that for a constant gradient (CG) structure, and amplitude variation of the form E(t) = a{sub 0} + (1 - a{sub 0}) t{sub p} will reduce the energy spread to zero for a current that is determined by a{sub 0}. When one uses rf modulation for transient beam loading compensation, the beam is injected a fill time after the rf has been turned on, and one is forced to throw away a section's worth of rf energy. In addition, it requires extra components which use up additional rf energy. This note describes transient beam loading compensation with variable current. It will show that it increases the rf energy to beam energy transfer efficiency.

  17. Kinetics of transient electroluminescence in organic light emitting diodes

    Science.gov (United States)

    Shukla, Manju; Kumar, Pankaj; Chand, Suresh; Brahme, Nameeta; Kher, R. S.; Khokhar, M. S. K.

    2008-08-01

    Mathematical simulation on the rise and decay kinetics of transient electroluminescence (EL) in organic light emitting diodes (OLEDs) is presented. The transient EL is studied with respect to a step voltage pulse. While rising, for lower values of time, the EL intensity shows a quadratic dependence on (t - tdel), where tdel is the time delay observed in the onset of EL, and finally attains saturation at a sufficiently large time. When the applied voltage is switched off, the initial EL decay shows an exponential dependence on (t - tdec), where tdec is the time when the voltage is switched off. The simulated results are compared with the transient EL performance of a bilayer OLED based on small molecular bis(2-methyl 8-hydroxyquinoline)(triphenyl siloxy) aluminium (SAlq). Transient EL studies have been carried out at different voltage pulse amplitudes. The simulated results show good agreement with experimental data. Using these simulated results the lifetime of the excitons in SAlq has also been calculated.

  18. Adenosine Triphosphate (ATP) Inhibits Voltage-Sensitive Potassium Currents in Isolated Hensen's Cells and Nifedipine Protects Against Noise-Induced Hearing Loss in Guinea Pigs.

    Science.gov (United States)

    Ye, Rui; Liu, Jun; Jia, Zhiying; Wang, Hongyang; Wang, YongAn; Sun, Wei; Wu, Xuan; Zhao, Zhifei; Niu, Baolong; Li, Xingqi; Dai, Guanghai; Li, Jianxiong

    2016-06-13

    BACKGROUND There is increasing evidence that adenosine triphosphate (ATP), a well-known neurotransmitter and neuromodulator in the central nervous system, plays an important role as an extracellular chemical messenger in the cochlea. MATERIAL AND METHODS Using a whole-cell recording technique, we studied the effects of ATP on isolated Hensen's cells, which are supporting cells in the cochlea, to determine if they are involved in the transduction of ions with hair cells. RESULTS ATP (0.1-10 µM) reduced the potassium current (IK+) in the majority of the recorded Hensen's cells (21 out of 25 cells). An inward current was also induced by high concentrations of ATP (100 µM to 10 mM), which was reversibly blocked by 100 µM suramin (a purinergic antagonist) and blocked by nifedipine (an L-type calcium channel blocker). After the cochleas were perfused with artificial perilymph solutions containing nifedipine and exposed to noise, the amplitude increase in the compound action potential (CAP) threshold and the reduction in cochlear microphonics was lower than when they were exposed to noise alone. CONCLUSIONS Our results suggest that ATP can block IK+ channels at a low concentration and induce an inward Ca2+ current at high concentrations, which is reversed by purinergic receptors. Nifedipine may have a partially protective effect on noise-induced hearing loss (NIHL).

  19. A technique to reduce plasma armature formation voltage

    Energy Technology Data Exchange (ETDEWEB)

    Jamison, K.A. (Science Applications International Corp., Shalimar, FL (US)); Littrell, D.M. (Air Force Armament Lab., Eglin AFB, FL (United States))

    1991-01-01

    The initiation of a plasma armature by foil vaporization in a railgun is often accompanied by a large, fast, voltage transient appearing on both the breech and muzzle of the gun. For a railgun driven by an inductor/opening switch power supply, this voltage transient becomes a concern during current commutation from the switch to the railgun. To lessen the requirements on the opening switch, techniques must be found to reduce the armature formation voltage. This paper presents the experimental results from railgun firings at AFATL's Electromagnetic Launcher Basic Research Facility (Site A-15, Eglin Air Force Base, Florida) using different shapes of initiation foils. These foils have been designed to vaporize into a plasma armature with reduced transient voltages. A design criteria was developed to ensure that all portions of the foil vaporize at slightly different times.

  20. 基于站域集成的暂态电流极性比较保护方案%Transient Current Polarity Comparison Scheme Based on Substation Integrated Protection

    Institute of Scientific and Technical Information of China (English)

    张堃; 薄志谦; 杨通; 解海宁

    2015-01-01

    A transient current polarity comparison scheme based on substation integrated protection for distribution networks is presented. The technique is based on the detection and processing of fault generated transient current signals, in which specially designed integrated protection relays are installed at each substation of a distribution network. The relay detects the fault generated super-imposed current signals. The transient current polarity identification algorithm is then applied to the super-imposed signals to identify the polarity of the signal detected. The direction of a fault is determined by comparison of the polarity of the signals derived from all the line sections connected to the station. The actual fault line section is identified by comparing the directional information from all stations within the protected area. Simulation results presented demonstrate the feasibility of the scheme.%提出一种基于站域保护的暂态电流极性比较的保护方案.该技术运用安装在配电网中每个变电站中专门设计的集成保护继电器,实现检测、分析处理因故障产生的暂态电流信号.通过集成继电器检测出因故障产生的故障电流分量信号,运用暂态电流极性识别算法来检出信号的极性;之后,通过比较来自与站点相连接的所有线路上的电流信号的极性就可以确定故障的方向;最后,通过对比来自网络中各站点的方向信息便可以确定故障的线路.通过仿真证明该方案是切实可行的.

  1. Voltage stability analysis in the new deregulated environment

    Science.gov (United States)

    Zhu, Tong

    Nowadays, a significant portion of the power industry is under deregulation. Under this new circumstance, network security analysis is more critical and more difficult. One of the most important issues in network security analysis is voltage stability analysis. Due to the expected higher utilization of equipment induced by competition in a power market that covers bigger power systems, this issue is increasingly acute after deregulation. In this dissertation, some selected topics of voltage stability analysis are covered. In the first part, after a brief review of general concepts of continuation power flow (CPF), investigations on various matrix analysis techniques to improve the speed of CPF calculation for large systems are reported. Based on these improvements, a new CPF algorithm is proposed. This new method is then tested by an inter-area transaction in a large inter-connected power system. In the second part, the Arnoldi algorithm, the best method to find a few minimum singular values for a large sparse matrix, is introduced into the modal analysis for the first time. This new modal analysis is applied to the estimation of the point of voltage collapse and contingency evaluation in voltage security assessment. Simulations show that the new method is very efficient. In the third part, after transient voltage stability component models are investigated systematically, a novel system model for transient voltage stability analysis, which is a logical-algebraic-differential-difference equation (LADDE), is offered. As an example, TCSC (Thyristor controlled series capacitors) is addressed as a transient voltage stabilizing controller. After a TCSC transient voltage stability model is outlined, a new TCSC controller is proposed to enhance both fault related and load increasing related transient voltage stability. Its ability is proven by the simulation.

  2. Simulation Analysis of the Electro-Magnetic Transient on High Voltage Submarine Cable of the Offshore Wind Farms%海上风电场海底高压电缆电磁暂态过程的仿真分析

    Institute of Scientific and Technical Information of China (English)

    黄辉; 郑明; 蓝锦标; 李迪

    2012-01-01

    In order to better determine the selection requirements of the high voltage submarine cable of the wind farms, the corresponding submarine cable simulation model is built using PSCAD/EMTDC software. The simulation is made for frequency overvoltage, switching overvoltage and lightning overvaltage with different characteristics of the transient process. Effects of the three kinds of overvoltage on the cable insulation are also considered in different system conditions. For switching overvoltage, the study is focused on the influence of the closing resistance on the overvoltage, while for lightning overvoltage focused on the lightning intruding to transmission lines. The simulation results show that the submarine cable structure parameters of each layer exert different impacts on the submarine cable electro-magnetic transient, and the conductor layer, insulation layer and HDPE layer have more remarkable impacts. In addition, the material of the sheath layer and the main insulation layer have impacts on the electro -magnetic transient.%为了能更好地确定海上风电场海底高压电缆的选型要求,使用PSCAD/EMTDC软件建立相应的海上风电场仿真计算模型.针对海上风电场工频过电压、操作过电压和雷电过电压这3种电磁暂态过程的不同特点,进行仿真,并且考虑了不同的系统条件下上述3种过电压对电缆绝缘的影响.在操作过电压中,重点研究了合闸电阻对过电压的影响;而在雷电过电压中重点研究的是架空线路受雷电侵入波的过电压.仿真结果表明,海底电缆各层的结构参数对海底电缆的电磁暂态有着不同程度的影响,其中导体层、绝缘层、HDPE层对海底电缆的电磁暂态影响尤为明显.另外,海底高压电缆的护套层材料和主绝缘层材料也对电磁暂态有影响.

  3. Transient Fitting Restraint Characteristic Based Generator Differential Protection Scheme%基于暂态拟合制动特性的发电机差动保护算法

    Institute of Scientific and Technical Information of China (English)

    蔡超; 陆于平; 黄涛

    2015-01-01

    With an analysis of the change of excitation current for a current transformer with time and the change of operating characteristic for generator percentage differential protection with time when there is an external fault with current transformer saturation,this paper proposes a generator differential algorithm based on transient fitting restraint characteristic.The algorithm fits the slope K of restraint curve with the change of transient unbalanced current with time during current transformer saturation.The initial expression of slope K curve and its adjustment method are proposed.The proposed transient fitting restraint characteristic reflects both the transient unbalanced current characteristic with time during current transformer saturation period and the stable current transformer error characteristic enabling the operating threshold to envelop the unbalanced current to increase protection reliability.Meanwhile the restraint characteristic only needs to consider current transformer stable error when current transformer is working in linear condition and the slope K can be set lower than traditional percentage differential protection which makes this algorithm more sensitive than the traditional one.Theoretical analysis and simulation results based on MATLAB indicate that the algorithm proposed has better reliability during external faults with current transformer saturation and higher sensitivity during internal faults than traditional percentage differential protection.%从电流互感器饱和励磁电流和发电机差动保护工作点随时间变化特点分析入手,提出了一种基于暂态拟合制动特性原理的差动保护算法。算法通过拟合电流互感器饱和时差动不平衡电流随时间变化规律得到制动曲线斜率 K 随时间变化曲线,给出了初始 K 值曲线表达式及初始 K 值曲线的调整方法。该制动特性既反映了电流互感器饱和暂态过程引起的差动不平衡电流随时间变化

  4. 矿用高压开关柜的弧光监测与保护系统%Online monitoring and protection system for the arc fault of the mining high-voltage switchgear

    Institute of Scientific and Technical Information of China (English)

    张杰; 马宏伟

    2013-01-01

      煤矿工业现场特殊的生产环境对电气设备的安全运行提出了更高的要求,尤其是以故障电弧为主的电气故障蕴含着巨大的安全隐患。传统的故障电弧监测和保护手段一般基于电流、电压、弧光等单一信号的提取和判断,虽然组合式监测方法已被提出,但往往实现复杂,成本较高。提出电流和弧光双判据的监测方法,通过光敏三极管阵列的传感措施,结合专家系统的评估方法,可以有效判断并定位高压开关柜中的故障电弧,及时切除故障,进而提高设备的工作寿命和安全可靠性,为煤矿电力系统的安全稳定运行提供保障。%The specific on-site environment of the mining industry field puts forward higher request to the safe operation of electrical equipment. Especially the arc-fault is one of the most important causes of disasters in distribution system. The traditional methods of the arc-fault detection and protection are based on the extraction and diagnosis of the single signals such as electric current, voltage, arc light, etc. Though the combined methodology has been proposed, it is difficult to implement and the cost is increased. On the basis, a double-criterion monitoring and protection method is proposed, which takes both electric current and arc light as the monitoring parameters. By use of the sensing measures of photosensitive dynatron matrix and expert system evaluation method, arc-fault in the high-voltage switch cabinet can be effectively judged and located and the fault can be cut timely, then the service life and safety and reliability of switch apparatus can be enhanced, ensuring the safe and stable operation of the mining power system.

  5. Automatic voltage imbalance detector

    Science.gov (United States)

    Bobbett, Ronald E.; McCormick, J. Byron; Kerwin, William J.

    1984-01-01

    A device for indicating and preventing damage to voltage cells such as galvanic cells and fuel cells connected in series by detecting sequential voltages and comparing these voltages to adjacent voltage cells. The device is implemented by using operational amplifiers and switching circuitry is provided by transistors. The device can be utilized in battery powered electric vehicles to prevent galvanic cell damage and also in series connected fuel cells to prevent fuel cell damage.

  6. New longitudinal differential protection scheme for four-circuit transmission line with different voltage grades%不同电压等级的四回线的纵联差动保护方案

    Institute of Scientific and Technical Information of China (English)

    陈金熠; 范春菊; 刘玲

    2011-01-01

    To solve the problem that the traditional longitudinal differential protection used in four-circuit transmission line on the same pole with different levels will be seriously affected by coupling inductance, a new longitudinal differential protection scheme based on inverse-sequence negative sequence difference current is proposed. Four-circuit transmission lines with different voltage grades generally consist of two double circuit transmission lines at the same tower. However, when line parameters are symmetry, the inverted sequence current is zero when the system operates normally or external faults occur. Once internal faults occur, there is inverted current in the transmission line, and the sum of inverted current at both sides is large, so the differential protection based on inverted current can operate correctly. For this method, the reliability and sensitivity under big fault resistance can be kept. And it will not be affected by capacitive current when it is applied to the main protection of four-circuit transmission line with different voltage grades. The theoretical analysis and EMTP simulation results show that the proposed principle is correct and reliable.%为克服传统纵联差动保护运用在不同电压等级的同杆四回线中容易受到耦合电感的影响,提出了基于反序负序差电流的纵联差动保护方案.不同电压等级的四回线由两个不同电压的等级的同杆双回线构成.对于同杆双回线路,当线路参数完全对称时,系统正常运行或是外部故障时,反向电流分量为零;而当双回线内部故障时,反向环流量存在于双回线的内部,双回线两侧反向电流之和比较大,可以构成基于反向环流量的纵联差动保护.该保护方案不仅可以避开电容电流对于差动保护的影响,而且有较强的抗过渡电阻能力.将该保护方案应用到不同电压等级的四回线的主保护中,保护性能优越,不仅可以可靠动作,还避免了电容

  7. Mixed voltage VLSI design

    Science.gov (United States)

    Panwar, Ramesh; Rennels, David; Alkalaj, Leon

    1993-01-01

    A technique for minimizing the power dissipated in a Very Large Scale Integration (VLSI) chip by lowering the operating voltage without any significant penalty in the chip throughput even though low voltage operation results in slower circuits. Since the overall throughput of a VLSI chip depends on the speed of the critical path(s) in the chip, it may be possible to sustain the throughput rates attained at higher voltages by operating the circuits in the critical path(s) with a high voltage while operating the other circuits with a lower voltage to minimize the power dissipation. The interface between the gates which operate at different voltages is crucial for low power dissipation since the interface may possibly have high static current dissipation thus negating the gains of the low voltage operation. The design of a voltage level translator which does the interface between the low voltage and high voltage circuits without any significant static dissipation is presented. Then, the results of the mixed voltage design using a greedy algorithm on three chips for various operating voltages are presented.

  8. Equivalent Modeling of DFIG-Based Wind Power Plant Considering Crowbar Protection

    OpenAIRE

    Qianlong Zhu; Ming Ding; Pingping Han

    2016-01-01

    Crowbar conduction has an impact on the transient characteristics of a doubly fed induction generator (DFIG) in the short-circuit fault condition. But crowbar protection is seldom considered in the aggregation method for equivalent modeling of DFIG-based wind power plants (WPPs). In this paper, the relationship between the growth of postfault rotor current and the amplitude of the terminal voltage dip is studied by analyzing the rotor current characteristics of a DFIG during the fault process...

  9. The N-methyl-D-aspartate antagonist, MK-801, fails to protect against neuronal damage caused by transient, severe forebrain ischemia in adult rats.

    Science.gov (United States)

    Buchan, A; Li, H; Pulsinelli, W A

    1991-04-01

    The neuroprotective effects of dizocilipine maleate (MK-801), a noncompetitive antagonist of the N-methyl-D-aspartate (NMDA) receptor/channel, were tested in the 4-vessel occlusion rat model of forebrain ischemia. Adult Wistar rats, treated intraperitoneally with MK-801 or saline using several different treatment paradigms were subjected to 5 (n = 208) or 15 (n = 62) min of severe, transient forebrain ischemia. In saline-treated animals, 15 min of ischemia (n = 13) produced extensive and consistent loss of pyramidal neurons in the CA1 zone of hippocampus. The degree and distribution of cell loss were not reduced by single dose preischemic administration of MK-801 at 1 (n = 7), 2.5 (n = 4), or 5 mg/kg (n = 8). In other animals subjected to 15 min of forebrain ischemia, multiple doses of MK-801 (5, 2.5, and 2.5 mg/kg) given immediately and at approximately 8 and 20 hr after cerebral reperfusion (n = 5) did not alter CA1 injury compared to saline-treated controls (n = 5). Five minutes of forebrain ischemia in saline-treated animals, (n = 82) resulted in significantly fewer (p less than 0.001) dead CA1 pyramidal cells and a greater variance compared to animals subjected to 15 min of ischemia. Power analysis of the preliminary saline-treated animals subjected to 5 min of ischemia (n = 22) indicated that 60 animals per group were necessary to detect a 15% difference between MK-801 and vehicle-treated groups. Multidose treatment with MK-801 (1 mg/kg) given 1 hr prior to 5 min of ischemia (n = 60) and again at approximately 8 and 16 hr after recirculation failed to attenuate hippocampal injury.(ABSTRACT TRUNCATED AT 250 WORDS)

  10. Contribution of hypothermia and CB1 receptor activation to protective effects of TAK-937, a cannabinoid receptor agonist, in rat transient MCAO model.

    Directory of Open Access Journals (Sweden)

    Noriko Suzuki

    Full Text Available BACKGROUND: Cannabinoid (CB receptor agonists are expected to alleviate ischemic brain damage by modulating neurotransmission and neuroinflammatory responses via CB(1 and CB(2 receptors, respectively. In a previous study, TAK-937, a novel potent and selective CB(1 and CB(2 receptor agonist, was shown to exert significant cerebroprotective effects accompanied by hypothermia after transient middle cerebral artery occlusion (MCAO in rats. Sustained hypothermia itself induces significant neuroprotective effects. In the present studies, we examined the relative contribution of hypothermia and CB(1 receptor activation to the cerebroprotective effects of TAK-937. METHODOLOGY/PRINCIPAL FINDINGS: Using a multichannel brain temperature controlling system we developed, the brain temperature of freely moving rats was telemetrically monitored and maintained between 37 and 38°C during intravenous infusion of TAK-937 (100 µg/kg/h or vehicle for 24 h after 2 h MCAO. AM251, a selective CB(1 receptor antagonist, was administered intraperitoneally at 30 mg/kg 30 min before starting intravenous infusion of TAK-937 (100 µg/kg/h for 24 h. Rats were sacrificed and their brains were isolated 26 h after MCAO in both experiments. When the hypothermic effect of TAK-937 was completely reversed by a brain temperature controlling system, the infarct-reducing effect of TAK-937 was attenuated in part, but remained significant. On the other hand, concomitant AM251 treatment with TAK-937 completely abolished the hypothermic and infarct-reducing effects of TAK-937. CONCLUSIONS/SIGNIFICANCE: We conclude that the cerebroprotective effects of TAK-937 were at least in part mediated by induction of hypothermia, and mainly mediated by CB(1 receptor activation.

  11. Transient Ischemic Attack

    Medline Plus

    Full Text Available Transient Ischemic Attack TIA , or transient ischemic attack, is a "mini stroke" that occurs when a blood ... The only difference between a stroke and TIA is that with TIA the blockage is transient (temporary). ...

  12. Fast Diagnosis of Transient Plasma by Langmuir Probe

    Institute of Scientific and Technical Information of China (English)

    TANG En-ling; ZHANG Qing-ming; OUYANG Ji-ting

    2007-01-01

    A method for the fast measurement of electron temperature and density with temporal resolution in transient plasma has been implemented by Langmuir probe. The diagnostic system consists of a single Langmuir probe driven by a high frequency sinusoidal voltage. The current and voltage spectrum on the probe were detected synchronously by an oscilloscope with sampling rate being at least 5 times higher than the frequency of sweep voltage. The system has been used to diagnose the transient plasma generated by hypervelocity-impact of LY12 aluminum projectile into LY12 aluminum target.

  13. Voltage dependence of the Na-K pump.

    Science.gov (United States)

    De Weer, P; Gadsby, D C; Rakowski, R F

    1988-01-01

    Present evidence demonstrates that the Na-K pump rate is voltage dependent, whereas early work was largely inconclusive. The I-V relationship has a positive slope over a wide voltage range, and the existence of a negative slope region is now doubtful. Monotonic voltage dependence is consistent with the reaction cycle containing a single voltage-dependent step. Recent measurements suggest that this voltage-dependent step occurs during Na translocation and may be deocclusion of Na+. In addition, two results suggest that K translocation is voltage insensitive: (a) large positive potentials appear to have no influence on Rb-Rb exchange or associated conformational transitions; and (b) transient currents associated with Na translocation appear to involve movement of a single charge, which is sufficient for a 3Na-2K cycle. The simplest interpretation is that the pump's cation binding sites supply two negative charges. Pre-steady-state measurements demonstrate that Na translocation precedes the pump cycle's rate-limiting step, presumably K translocation. But, because K translocation seems voltage insensitive, the voltage dependence of the steady-state pump rate probably reflects that of the concentration of the intermediate entering this slow step. Further pump current and flux data (both transient and steady-state), carefully determined over a range of conditions, should increase our understanding of the voltage-dependent step(s) in the Na-K pump cycle.

  14. Transient global amnesia mimics: Transient epileptic amnesia

    Directory of Open Access Journals (Sweden)

    Nicolas Nicastro

    2014-01-01

    Full Text Available We describe the case of a 79-year-old patient referred for suspected transient global amnesia, after an episode of anterograde amnesia which lasted 90 min. An EEG, performed after the episode, showed bilateral temporal electrographic seizures, orienting the diagnosis toward a transient epileptic amnesia. Transient epileptic amnesia is defined by temporal lobe epilepsy characterized by recurrent transient amnestic episodes of 30–90 min in duration, sometimes associated with olfactory hallucinations or oral automatisms. Response to antiepileptic drugs is excellent. We would like to raise awareness toward this epileptic amnesia when facing atypical or recurrent transient amnestic episodes.

  15. Wind Farm Stabilization by using DFIG with Current Controlled Voltage Source Converters Taking Grid Codes into Consideration

    Science.gov (United States)

    Okedu, Kenneth Eloghene; Muyeen, S. M.; Takahashi, Rion; Tamura, Junji

    Recent wind farm grid codes require wind generators to ride through voltage sags, which means that normal power production should be re-initiated once the nominal grid voltage is recovered. However, fixed speed wind turbine generator system using induction generator (IG) has the stability problem similar to the step-out phenomenon of a synchronous generator. On the other hand, doubly fed induction generator (DFIG) can control its real and reactive powers independently while being operated in variable speed mode. This paper proposes a new control strategy using DFIGs for stabilizing a wind farm composed of DFIGs and IGs, without incorporating additional FACTS devices. A new current controlled voltage source converter (CC-VSC) scheme is proposed to control the converters of DFIG and the performance is verified by comparing the results with those of voltage controlled voltage source converter (VC-VSC) scheme. Another salient feature of this study is to reduce the number of proportionate integral (PI) controllers used in the rotor side converter without degrading dynamic and transient performances. Moreover, DC-link protection scheme during grid fault can be omitted in the proposed scheme which reduces overall cost of the system. Extensive simulation analyses by using PSCAD/EMTDC are carried out to clarify the effectiveness of the proposed CC-VSC based control scheme of DFIGs.

  16. A voltage-dependent persistent sodium current in mammalian hippocampal neurons

    OpenAIRE

    1990-01-01

    Currents generated by depolarizing voltage pulses were recorded in neurons from the pyramidal cell layer of the CA1 region of rat or guinea pig hippocampus with single electrode voltage-clamp or tight- seal whole-cell voltage-clamp techniques. In neurons in situ in slices, and in dissociated neurons, subtraction of currents generated by identical depolarizing voltage pulses before and after exposure to tetrodotoxin revealed a small, persistent current after the transient current. These curren...

  17. 40 CFR 86.1333-2010 - Transient test cycle generation.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 19 2010-07-01 2010-07-01 false Transient test cycle generation. 86... Exhaust Test Procedures § 86.1333-2010 Transient test cycle generation. (a) Generating transient test... engines: ER13JY05.001 Where: MaxTestSpeed = the maximum test speed as calculated in 40 CFR part 1065....

  18. Technological Aspects: High Voltage

    CERN Document Server

    Faircloth, D C

    2013-01-01

    This paper covers the theory and technological aspects of high-voltage design for ion sources. Electric field strengths are critical to understanding high-voltage breakdown. The equations governing electric fields and the techniques to solve them are discussed. The fundamental physics of high-voltage breakdown and electrical discharges are outlined. Different types of electrical discharges are catalogued and their behaviour in environments ranging from air to vacuum are detailed. The importance of surfaces is discussed. The principles of designing electrodes and insulators are introduced. The use of high-voltage platforms and their relation to system design are discussed. The use of commercially available high-voltage technology such as connectors, feedthroughs and cables are considered. Different power supply technologies and their procurement are briefly outlined. High-voltage safety, electric shocks and system design rules are covered.

  19. Artifical Excitation of Ferro-Resonance for Testing Electrotechnical Equipment in Distribution Devices with Increased Voltage

    Directory of Open Access Journals (Sweden)

    Ye. V. Dmitriev

    2006-01-01

    Full Text Available On the basis of the developed device for protection against of ferro-resonant and high-frequency cumulative over-voltages an algorithm for obtaining a voltage imitating ferro-resonant over-voltages is proposed in the paper. This algorithm presupposes to apply a voltage to the secondary transformer side from an extraneous source is proposed.

  20. 30 CFR 77.800 - High-voltage circuits; circuit breakers.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false High-voltage circuits; circuit breakers. 77.800... COAL MINES Surface High-Voltage Distribution § 77.800 High-voltage circuits; circuit breakers. High-voltage circuits supplying power to portable or mobile equipment shall be protected by suitable...

  1. 胡椒碱对H2O2所致兔心房肌细胞瞬时外向钾电流异常的保护作用%Protective effect of piperine on H2O2-induced abnormal transient outward potassium current in rabbit atrial myocytes

    Institute of Scientific and Technical Information of China (English)

    刘岩; 李泱; 林琨; 田苗; 王玉堂; 单兆亮

    2012-01-01

    目的 研究胡椒碱对H2O2引起的兔单个心房肌细胞瞬时外向钾电流(Ito)异常的保护作用.方法 采用全细胞膜片钳技术分析50μmol/L的H2O2对兔单个心房肌细胞Ito的影响,并研究预先应用7μmol/L的胡椒碱对其的保护作用.结果 7μmol/L胡椒碱对正常兔心房肌细胞Ito及其通道动力学无显著影响.在50μmol/L H2O2作用下,兔心房肌细胞Ito峰值由(39.3±5.4)pA/pF降低至(32.8±2.0)pA/pF(P<0.05),电流-电压曲线下移,通道稳态激活曲线右移,通道稳态失活曲线及恢复时间不变,关闭态失活加速.预先给予7 μ mol/L胡椒碱,明显减轻H2O2对Ito的抑制作用(P<0.01),并可减轻H2O2对瞬时外向钾通道动力学的异常影响.结论 胡椒碱可减轻氧化应激对心房肌细胞Ito的影响.%Objective To study the protective effect of piperine on H2O2-induced abnormal transient outward potassium current(Ito) in single rabbit atrial myocyte. Methods Effect of H2O2(50 μ mol/L) and piperine(7 μ mol/L) on Lto in single rabbit atrial myocyte was analyzed using the whole cell patch clamp technique. Results Piperine(7 μ mol/L) had no significant effect on Ito and its transient outward potassium channel dynamics. The peak value of IB in rabbit atrial myocytes decreased to (32.8 ± 2.0)pA/pF from (39.3 ± 5.4) pA/pF(P<0.05), the current-voltage curve of Ito was shifted down, the channel steady-state activation curve of Ito, was shifted to the right, the steady-state inactivation curve and the recovery time of Ito from inactivation did not change, the closed-state inactivation of Ito was accelerated, when H2O2(50 μ , mol/L) was applied. Piperine(7 μ mol/L) significantly alleviated the inhibitory effect of H2O2 on Lto and its transient outward potassium channel dynamics(P<0.01). Conclusion Piperine can alleviate H2O2induced abnormal Ito in rabbit atrial myocytes.

  2. Stray voltage mitigation

    Energy Technology Data Exchange (ETDEWEB)

    Jamali, B.; Piercy, R.; Dick, P. [Kinetrics Inc., Toronto, ON (Canada). Transmission and Distribution Technologies

    2008-04-09

    This report discussed issues related to farm stray voltage and evaluated mitigation strategies and costs for limiting voltage to farms. A 3-phase, 3-wire system with no neutral ground was used throughout North America before the 1930s. Transformers were connected phase to phase without any electrical connection between the primary and secondary sides of the transformers. Distribution voltage levels were then increased and multi-grounded neutral wires were added. The earth now forms a parallel return path for the neutral current that allows part of the neutral current to flow continuously through the earth. The arrangement is responsible for causing stray voltage. Stray voltage causes uneven milk production, increased incidences of mastitis, and can create a reluctance to drink water amongst cows when stray voltages are present. Off-farm sources of stray voltage include phase unbalances, undersized neutral wire, and high resistance splices on the neutral wire. Mitigation strategies for reducing stray voltage include phase balancing; conversion from single to 3-phase; increasing distribution voltage levels, and changing pole configurations. 22 refs., 5 tabs., 13 figs.

  3. High voltage test techniques

    CERN Document Server

    Kind, Dieter

    2001-01-01

    The second edition of High Voltage Test Techniques has been completely revised. The present revision takes into account the latest international developments in High Voltage and Measurement technology, making it an essential reference for engineers in the testing field.High Voltage Technology belongs to the traditional area of Electrical Engineering. However, this is not to say that the area has stood still. New insulating materials, computing methods and voltage levels repeatedly pose new problems or open up methods of solution; electromagnetic compatibility (EMC) or components and systems al

  4. Mitigation of Unbalanced Voltage Sags and Voltage Unbalance in CIGRE Low Voltage Distribution Network

    OpenAIRE

    Mustafa, Ghullam; Bak-Jensen, Birgitte; Mahat, Pukar; Cecati, Carlo

    2013-01-01

    Any problem with voltage in a power network is undesirable as it aggravates the quality of the power. Power electronic devices such as Voltage Source Converter (VSC) based Static Synchronous Compensator (STATCOM) etc. can be used to mitigate the voltage problems in the distribution system. The voltage problems dealt with in this paper are to show how to mitigate unbalanced voltage sags and voltage unbalance in the CIGRE Low Voltage (LV) test network and net-works like this. The voltage unbala...

  5. Current and Voltage Conveyors in Current- and Voltage-Mode Precision Full-Wave Rectifiers

    Directory of Open Access Journals (Sweden)

    J. Koton

    2011-04-01

    Full Text Available In this paper new versatile precision full-wave rectifiers using current and/or voltage conveyors as active elements and two diodes are presented. The performance of these circuit solutions is analysed and compared to the opamp based precision rectifier. To analyze the behavior of the functional blocks, the frequency dependent RMS error and DC transient value are evaluated for different values of input voltage amplitudes. Furthermore, experimental results are given that show the feasibilities of the conveyor based rectifiers superior to the corresponding operational amplifier based topology.

  6. Large Capacity SMES for Voltage Dip Compensation

    Science.gov (United States)

    Iwatani, Yu; Saito, Fusao; Ito, Toshinobu; Shimada, Mamoru; Ishida, Satoshi; Shimanuki, Yoshio

    Voltage dips of power grids due to thunderbolts, snow damage, and so on, cause serious damage to production lines of precision instruments, for example, semiconductors. In recent years, in order to solve this problem, uninterruptible power supply systems (UPS) are used. UPS, however, has small capacity, so a great number of UPS are needed in large factories. Therefore, we have manufactured the superconducting magnetic energy storage (SMES) system for voltage dip compensation able to protect loads with large capacity collectively. SMES has advantages such as space conservation, long lifetime and others. In field tests, cooperating with CHUBU Electric Power Co., Inc. we proved that SMES is valuable for compensating voltage dips. Since 2007, 10MVA SMES improved from field test machines has been running in a domestic liquid crystal display plant, and in 2008, it protected plant loads from a number of voltage dips. In this paper, we report the action principle and components of the improved SMES for voltage dip compensation, and examples of waveforms when 10MVA SMES compensated voltage dips.

  7. Long-term Aβ exposure augments mCa2+-independent mROS-mediated depletion of cardiolipin for the shift of a lethal transient mitochondrial permeability transition to its permanent mode in NARP cybrids: a protective targeting of melatonin.

    Science.gov (United States)

    Hsiao, Chia-Wei; Peng, Tsung-I; Peng, Alexander C; Reiter, Russel J; Tanaka, Masashi; Lai, Yiu-Kay; Jou, Mei-Jie

    2013-01-01

    Mitochondrial dysfunction is a hallmark of amyloid β-peptide (Aβ)-induced neurodegeneration of Alzheimer's disease (AD). This study investigated whether mtDNA T8993G mutation-induced complex V inhibition, clinically associated with neurological muscle weakness, ataxia, and retinitis pigmentosa (NARP), is a potential risk factor for AD and the pathological link for long-term exposure of Aβ-induced mitochondrial toxicity and apoptosis in NARP cybrids. Using noninvasive fluorescence probe-coupled laser scanning imaging microscopy and NARP cybrids harboring 98% mutant genes along with its parental 143B osteosarcoma cells, we demonstrated that Aβ-augmented mitochondrial Ca(2+) (mCa(2+))-independent mitochondrial reactive oxygen species (mROS) formation for a cardiolipin (CL, a major mitochondrial protective phospholipid)-dependent lethal modulation of the mitochondrial permeability transition (MPT). Aβ augmented not only the amount but also the propagation rate of mROS-induced mROS formation to significantly depolarize mitochondrial membrane potential (∆Ψ(m)) and reduce mCa(2+) stress. Aβ-augmented mROS oxidized and depleted CL, thereby enhances mitochondrial fission and movement retardation, which promoted the NARP-augmented lethal transient-MPT (t-MPT) to switch to its irreversible mode of permanent-MPT (p-MPT). Interestingly, melatonin, a multiple mitochondrial protector, markedly reduced Aβ-augmented mROS formation and therefore significantly reduced mROS-mediated depolarization of ∆Ψ(m), fission of mitochondria and retardation of mitochondrial movement to stabilize CL and hence the MPT. In the presence of melatonin, Aβ-promoted p-MPT was reversed to a protective t-MPT, which preserved ∆Ψ(m) and lowered elevated mCa(2+) to sublethal levels for an enhanced mCa(2+)-dependent O(2) consumption. Thus, melatonin may potentially rescue AD patients associated with NARP symptoms.

  8. Protection circuits for very high frequency ultrasound systems.

    Science.gov (United States)

    Choi, Hojong; Shung, K Kirk

    2014-04-01

    The purpose of protection circuits in ultrasound applications is to block noise signals from the transmitter from reaching the transducer and also to prevent unwanted high voltage signals from reaching the receiver. The protection circuit using a resistor and diode pair is widely used due to its simple architecture, however, it may not be suitable for very high frequency (VHF) ultrasound transducer applications (>100 MHz) because of its limited bandwidth. Therefore, a protection circuit using MOSFET devices with unique structure is proposed in this paper. The performance of the designed protection circuit was compared with that of other traditional protection schemes. The performance characteristics measured were the insertion loss (IL), total harmonic distortion (THD) and transient response time (TRT). The new protection scheme offers the lowest IL (-1.0 dB), THD (-69.8 dB) and TRT (78 ns) at 120 MHz. The pulse-echo response using a 120 MHz LiNbO3 transducer with each protection circuit was measured to validate the feasibility of the protection circuits in VHF ultrasound applications. The sensitivity and bandwidth of the transducer using the new protection circuit improved by 252.1 and 50.9 %, respectively with respect to the protection circuit using a resistor and diode pair. These results demonstrated that the new protection circuit design minimizes the IL, THD and TRT for VHF ultrasound transducer applications.

  9. Combined Digital Electronic Current and Voltage Transducer

    Institute of Scientific and Technical Information of China (English)

    段雄英; 邹积岩; 等

    2002-01-01

    A high-performance current and voltage measurement system has been developed in power system.The system is composed of two parts:one current measurement element and one voltage measurement element.A Rogowski coil and a capacitive voltage divider are used respectively for the line current and voltage measurements.Active electronic components are used to modulate signal,and power supply for these components is drawn from power line via an auxiliary current transformer,Measurement signal is transmitted y optical fibers,which is resistant to electromagnetic induction and noise,With careful design and the use of digital signal processing technology,the whole system can meet 0.5% accuracy for metering and provides large dynamic range coupled with good accuracy for protective relaying use.

  10. Voltage verification unit

    Science.gov (United States)

    Martin, Edward J.

    2008-01-15

    A voltage verification unit and method for determining the absence of potentially dangerous potentials within a power supply enclosure without Mode 2 work is disclosed. With this device and method, a qualified worker, following a relatively simple protocol that involves a function test (hot, cold, hot) of the voltage verification unit before Lock Out/Tag Out and, and once the Lock Out/Tag Out is completed, testing or "trying" by simply reading a display on the voltage verification unit can be accomplished without exposure of the operator to the interior of the voltage supply enclosure. According to a preferred embodiment, the voltage verification unit includes test leads to allow diagnostics with other meters, without the necessity of accessing potentially dangerous bus bars or the like.

  11. Temperature Induced Voltage Offset Drifts in Silicon Carbide Pressure Sensors

    Science.gov (United States)

    Okojie, Robert S.; Lukco, Dorothy; Nguyen, Vu; Savrun, Ender

    2012-01-01

    We report the reduction of transient drifts in the zero pressure offset voltage in silicon carbide (SiC) pressure sensors when operating at 600 C. The previously observed maximum drift of +/- 10 mV of the reference offset voltage at 600 C was reduced to within +/- 5 mV. The offset voltage drifts and bridge resistance changes over time at test temperature are explained in terms of the microstructure and phase changes occurring within the contact metallization, as analyzed by Auger electron spectroscopy and field emission scanning electron microscopy. The results have helped to identify the upper temperature reliable operational limit of this particular metallization scheme to be 605 C.

  12. Air Breakdown Behavior of Two Series Gaps for Composite Switching Impulse/Alternating Voltage

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    More and more high voltage transmission lines make use of rubber housed ZnO arresters in series with another air gap (for example, the insulator gap) as lighting protection elements. Many test results of ZnO arresters protection performance show that this insulation arrangement is suitable for practical lines according to results based on only simple impulse voltage. This paper uses a composite voltage (switching impulse voltage/alternating voltage) to determine the air breakdown behavior of the conductor-rod gap in series with the sphere gap. In the test, the switching impulse voltage is applied to the conductor while the alternating voltage is applied to the rod and one sphere and the other sphere is grounded. The results show that in some cases, the value of the U50% sparkover voltage for the conductor-rod gap with the composite voltage is nearly only half of that for just the simple impulse voltage.

  13. Performance of Three-Arm Ac Automatic Voltage Regulator

    Directory of Open Access Journals (Sweden)

    T. Papinaidu

    2014-04-01

    Full Text Available In this paper the design and simulation of automatic voltage regulator (AVR is proposed. The AVR provides voltage buck and boost capability to eliminate power problems created by under voltage or over voltage fluctuations. It also protects against minor and severe spikes and surges that comprise over 80% of power problems. Over heating of components due to voltage swell is also avoided by using AVR. The switching losses are also reduced as only one arm among three arms is maintained at higher power frequencies depending on mode of operation. Moreover, there is no need to use large capacitor as a result the overall size of converter is also reduced. Hence, the output voltage of the AVR can be maintained at the specified voltage. Hence, the AVR is cost can be reduced, and the efficiency of the power convertor can be extended.

  14. Associating ground magnetometer observations with current or voltage generators

    DEFF Research Database (Denmark)

    Hartinger, M. D.; Xu, Z.; Clauer, C. R.

    2017-01-01

    A circuit analogy for magnetosphere-ionosphere current systems has two extremes for driversof ionospheric currents: ionospheric elec tric fields/voltages constant while current/conductivity vary—the“voltage generator”—and current constant while electric field/conductivity vary—the “current generator.......”Statistical studies of ground magnetometer observations associated with dayside Transient High LatitudeCurrent Systems (THLCS) driven by similar mechanisms find contradictory results using this paradigm:some studies associate THLCS with voltage generators, others with current generators. We argue that mostof...... these two assumptions substantially alter expectations for magnetic perturbations associatedwith either a current or a voltage generator. Our results demonstrate that before interpreting groundmagnetometer observations of THLCS in the context of current/voltage generators, the location...

  15. Analysis of Transient Overvoltage Protection Circuits

    Science.gov (United States)

    1990-06-01

    breakdown In the port is greater than that across the input port at line-to-neutral capacitor Inside the filter. Dough t-mes .iear 4 and 8 us. ’here is no...gh and 2A w.i sour c n 2 ifrtl brAnch an 11= Alg measurement series inductances in Fig. 3 are negligible compared to the resistance values. The

  16. 现代架空线输电系统中的高压电缆段%Aspects of High Voltage Cable Sections in Modern Overhead Line Transmission Systems

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Electrical power transmission is dominated by overhead line systems at present. This is mainly based on more than hundred years of experience of utilities in running overhead lines. Furthermore, overhead lines have proven their operational reliability and functional assurance. In the past, cables were used in distribution networks in urban areas for the most part with the exception of direct current submarine cables. New developments of high voltage XLPE cables make it possible to use this technology for EHV level applications in transmission networks. Within this paper, mixed network configurations, consisting of overhead lines and high voltage cables, are investigated. An exemplary EHV transmission line with a total length of about 100 km, which is quite typical for Central Europe, has been studied. Several different line combinations are discussed with varied rates between overhead line sections and cable sections length in practice. The length of the cable sections are ranging from several kilometers up to lengths of 100 km. In this paper the work focuses on the transient behavior of combined 400 kV overhead and cable lines during switching processes and lightning impacts. A number of calculations were carried out to get an overview of the transient stress in numerous network nodes along the transmission system. Numerical programs like ATP/EMTP have been used for these simulations. Peak values and wave shapes of the transient voltage stress have been evaluated, based on different systems and within possible combinations. In respect of the insulation coordination and transient stress at network nodes, the voltage-time trends are also analyzed. The combination of high voltage overhead and cable transmission systems, especially such with lengths of more than about 50 km, are making tightened and extended demands to the network design, to the operational management and of course to the network protection also. As an output of this investigations, the results might

  17. Low voltage lightning arresters. Components. Low voltage grids; Parafoudres basse tension. Composants. Reseaux basse tension

    Energy Technology Data Exchange (ETDEWEB)

    Rousseau, A. [Assistance Protection System SAS, 94 - Cachan (France)

    2003-08-01

    Electrical equipments used in domestic and industrial applications are more and more sensible to overvoltages because of the massive use of electronic components in these equipments and appliances. Overvoltages do not propagate only with power lines but also through phone lines, coaxial cables, data networks, and even through grounding circuits. The informations about low voltage grids, useful for the selection of lightning arresters are presented in this article. In the ideal case, each possible way of input for overvoltage currents must be protected. The components used in lightning arresters have improved for a better reliability, a better energy resistance and a better protection level. These components are also presented in this article: 1 - technical and standard evolution: improvement of the understanding of low voltage phenomena, standards evolution, recall of basic definitions and data about lightning protection; 2 - components: varistors, spark gaps, silicon-based solid components, aging and end of life, decoupling components (thermistors, resistors, inductors); 3 - low voltage grids: different types of energy networks, transmission of overvoltages on low voltage networks (overvoltages due to lightning, or power station actuating, temporary overvoltages), influence of lightning conductors and lightning strikes close to the building structure, statistical data about lightning overvoltages on low voltage grids, protection and risk analysis. (J.S.)

  18. COTS Li-Ion Cells in High Voltage Batteries

    Science.gov (United States)

    Davies, Francis; Darcy, Eric; Jeevarajan, Judy; Cowles, Phil

    2003-01-01

    Testing at NASA JSC and COMDEV shows that Commercial Off the Shelf (COTS) Li Ion cells can not be used in high voltage batteries safely without considering the voltage stresses that may be put on the protective devices in them during failure modes.

  19. High Voltage Distribution

    Science.gov (United States)

    Norbeck, Edwin; Miller, Michael; Onel, Yasar

    2010-11-01

    For detector arrays that require 5 to 10 kV at a few microamps each for hundreds of detectors, using hundreds of HV power supplies is unreasonable. Bundles of hundreds of HV cables take up space that should be filled with detectors. A typical HV module can supply 1 ma, enough current for hundreds of detectors. It is better to use a single HV module and distribute the current as needed. We show a circuit that, for each detector, measures the current, cuts off the voltage if the current exceeds a set maximum, and allows the HV to be turned on or off from a control computer. The entire array requires a single HV cable and 2 or 3 control lines. This design provides the same voltage to all of the detectors, the voltage set by the single HV module. Some additional circuitry would allow a computer controlled voltage drop between the HV and each individual detector.

  20. High voltage engineering fundamentals

    CERN Document Server

    Kuffel, E; Hammond, P

    1984-01-01

    Provides a comprehensive treatment of high voltage engineering fundamentals at the introductory and intermediate levels. It covers: techniques used for generation and measurement of high direct, alternating and surge voltages for general application in industrial testing and selected special examples found in basic research; analytical and numerical calculation of electrostatic fields in simple practical insulation system; basic ionisation and decay processes in gases and breakdown mechanisms of gaseous, liquid and solid dielectrics; partial discharges and modern discharge detectors; and over

  1. Low-voltage gyrotrons

    Science.gov (United States)

    Glyavin, M. Yu.; Zavolskiy, N. A.; Sedov, A. S.; Nusinovich, G. S.

    2013-03-01

    For a long time, the gyrotrons were primarily developed for electron cyclotron heating and current drive of plasmas in controlled fusion reactors where a multi-megawatt, quasi-continuous millimeter-wave power is required. In addition to this important application, there are other applications (and their number increases with time) which do not require a very high power level, but such issues as the ability to operate at low voltages and have compact devices are very important. For example, gyrotrons are of interest for a dynamic nuclear polarization, which improves the sensitivity of the nuclear magnetic resonance spectroscopy. In this paper, some issues important for operation of gyrotrons driven by low-voltage electron beams are analyzed. An emphasis is made on the efficiency of low-voltage gyrotron operation at the fundamental and higher cyclotron harmonics. These efficiencies calculated with the account for ohmic losses were, first, determined in the framework of the generalized gyrotron theory based on the cold-cavity approximation. Then, more accurate, self-consistent calculations for the fundamental and second harmonic low-voltage sub-THz gyrotron designs were carried out. Results of these calculations are presented and discussed. It is shown that operation of the fundamental and second harmonic gyrotrons with noticeable efficiencies is possible even at voltages as low as 5-10 kV. Even the third harmonic gyrotrons can operate at voltages about 15 kV, albeit with rather low efficiency (1%-2% in the submillimeter wavelength region).

  2. Transient stability of DFIG wind turbines at an external short-circuit fault

    Science.gov (United States)

    Sun, Tao; Chen, Zhe; Blaabjerg, Frede

    2005-07-01

    The fast development of wind power generation brings new requirements for wind turbine integration into the network. After clearance of an external short-circuit fault, grid-connected wind turbines should restore their normal operation without power loss caused by disconnections. This article concentrates on the transient stability of variable speed wind turbines with doubly fed induction generators (DFIGs) at an external short-circuit fault. A simulation model of a MW-level variable speed wind turbine with a DFIG developed in PSCAD/EMTDC is presented and the control and protection schemes are described in detail. The transient process of grid-connected wind turbines with DFIGs at an external short-circuit fault is analysed, and in critical post-fault situations a measure is proposed for the voltage recovery of DFIG wind turbines after fault clearance. Simulation results demonstrate that in uncritical post-fault situations the control schemes are able to restore the wind turbine's normal operation without disconnections. It is also proved that the proposed measure is effective in re-establishing the voltage at the wind turbine terminal in critical post-fault situations. Copyright

  3. Wind Power Plant Voltage Stability Evaluation: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Muljadi, E.; Zhang, Y. C.

    2014-09-01

    Voltage stability refers to the ability of a power system to maintain steady voltages at all buses in the system after being subjected to a disturbance from a given initial operating condition. Voltage stability depends on a power system's ability to maintain and/or restore equilibrium between load demand and supply. Instability that may result occurs in the form of a progressive fall or rise of voltages of some buses. Possible outcomes of voltage instability are the loss of load in an area or tripped transmission lines and other elements by their protective systems, which may lead to cascading outages. The loss of synchronism of some generators may result from these outages or from operating conditions that violate a synchronous generator's field current limit, or in the case of variable speed wind turbine generator, the current limits of power switches. This paper investigates the impact of wind power plants on power system voltage stability by using synchrophasor measurements.

  4. Influence of System Parameters on Fuse Protection Use in Regenerative DC Drives

    Directory of Open Access Journals (Sweden)

    Isa Salman Qamber

    2009-06-01

    Full Text Available Current limiting fuses are widely used to protect the thyristors in DC drive systems. One very important problem is the choice of the correct voltage rating for fuses protecting regenerative DC drives, where many types of fault may occur, which makes fuse protection difficult. In the event of a commutation failure while regenerating, the fuses need to interrupt the loop supplied by the AC and DC voltages acting in series, which is the most difficult case for protection by fuses. In this paper a detailed study of the complete interruption process has been investigated by modeling of arcing process of the fuse protection against the regenerative circuit internal commutation fault. The effect of varying the motor time constant, supply impedance, number of fuses used to clear the fault and DC machine rating on the total transient response is studied. The model of a 200 A fuse is employed in this study. Fuses in series with both the semiconductor devices (F1 and fuses in AC lines (F2 are considered. Comparison was made between arc energy produced for fuses protecting the regenerative circuit if failure occurs, with the arc energy produced in a standard AC test in order to investigate the required voltage rating for the fuse.

  5. Dynamic Voltage Restorer Based on Space Vector Pulse Width Modulation Technique

    Directory of Open Access Journals (Sweden)

    B.N S P Venkatesh

    2011-07-01

    Full Text Available Power Quality problems encompass a wide range of disturbances such as voltage sags, swells, flicker,harmonics distortion and interruptions. The strategic deployment of custom power devices has been proposed asone of the means to protect sensitive loads from power quality problems such as voltage sags and swells. The Dynamic Voltage Restorer (DVR is a power electronic device that is used to inject 3-phase voltage in series and in synchronism with the distribution feeder voltages in order to compensate voltage sag and similarly itreacts quickly to inject the appropriate voltage component (negative voltage magnitude in order to compensate voltage swell. The principal component of the DVR is a voltage source inverter that generates three phase voltages and provides the voltage support to a sensitive load during voltage sags and swells. Pulse Width Modulation Technique is very critical for proper control of DVR. Sinusoidal Pulse Width Modulation (SPWM and Space Vector Pulse Width Modulation (SVPWM control techniques are used for controlling the DVR. Inthis work, the operation of DVR is presented and the control technique used for voltage source inverter is Space Vector PWM technique. Space vector PWM can utilize the better dc voltage and generates the fewer harmonic in inverter output voltage than Sinusoidal PWM technique. This work describes the DVR based on Space Vector PWM which provides voltage support to sensitive loads and is simulated by using MATLAB/SIMULINK. Simulation results show that the control approach is able to compensate for any type of voltage sags and swells.

  6. Device for monitoring cell voltage

    Science.gov (United States)

    Doepke, Matthias [Garbsen, DE; Eisermann, Henning [Edermissen, DE

    2012-08-21

    A device for monitoring a rechargeable battery having a number of electrically connected cells includes at least one current interruption switch for interrupting current flowing through at least one associated cell and a plurality of monitoring units for detecting cell voltage. Each monitoring unit is associated with a single cell and includes a reference voltage unit for producing a defined reference threshold voltage and a voltage comparison unit for comparing the reference threshold voltage with a partial cell voltage of the associated cell. The reference voltage unit is electrically supplied from the cell voltage of the associated cell. The voltage comparison unit is coupled to the at least one current interruption switch for interrupting the current of at least the current flowing through the associated cell, with a defined minimum difference between the reference threshold voltage and the partial cell voltage.

  7. The Effect of Current-Limiting Reactors on the Tripping of Short Circuits in High-Voltage Electrical Equipment

    Energy Technology Data Exchange (ETDEWEB)

    Volkov, M. S.; Gusev, Yu. P., E-mail: GusevYP@mpei.ru; Monakov, Yu. V.; Cho, Gvan Chun [National Research University “Moscow Power Engineering Institute,” (Russian Federation)

    2016-01-15

    The insertion of current-limiting reactors into electrical equipment operating at a voltage of 110 and 220 kV produces a change in the parameters of the transient recovery voltages at the contacts of the circuit breakers for disconnecting short circuits, which could be the reason for the increase in the duration of the short circuit, damage to the electrical equipment and losses in the power system. The results of mathematical modeling of the transients, caused by tripping of the short circuit in a reactive electric power transmission line are presented, and data are given on the negative effect of a current-limiting resistor on the rate of increase and peak value of the transient recovery voltages. Methods of ensuring the standard requirements imposed on the parameters of the transient recovery voltages when using current-limiting reactors in the high-voltage electrical equipment of power plants and substations are proposed and analyzed.

  8. High voltage pulse generator

    Science.gov (United States)

    Fasching, George E.

    1977-03-08

    An improved high-voltage pulse generator has been provided which is especially useful in ultrasonic testing of rock core samples. An N number of capacitors are charged in parallel to V volts and at the proper instance are coupled in series to produce a high-voltage pulse of N times V volts. Rapid switching of the capacitors from the paralleled charging configuration to the series discharging configuration is accomplished by using silicon-controlled rectifiers which are chain self-triggered following the initial triggering of a first one of the rectifiers connected between the first and second of the plurality of charging capacitors. A timing and triggering circuit is provided to properly synchronize triggering pulses to the first SCR at a time when the charging voltage is not being applied to the parallel-connected charging capacitors. Alternate circuits are provided for controlling the application of the charging voltage from a charging circuit to be applied to the parallel capacitors which provides a selection of at least two different intervals in which the charging voltage is turned "off" to allow the SCR's connecting the capacitors in series to turn "off" before recharging begins. The high-voltage pulse-generating circuit including the N capacitors and corresponding SCR's which connect the capacitors in series when triggered "on" further includes diodes and series-connected inductors between the parallel-connected charging capacitors which allow sufficiently fast charging of the capacitors for a high pulse repetition rate and yet allow considerable control of the decay time of the high-voltage pulses from the pulse-generating circuit.

  9. Dual-loop control strategy for DFIG-based Wind turbines under grid voltage disturbances

    DEFF Research Database (Denmark)

    Zhu, Rongwu; Chen, Zhe; Tang, Yi

    2016-01-01

    For a multimegawatts doubly-fed induction generator (DFIG), the grid voltage disturbances may affect the stator flux and induce the transient stator flux, due to the direct connection of the stator and the grid. The accumulation of the transient stator flux caused by the variations of the stator ...

  10. Protection of electronic circuits from overvoltages

    CERN Document Server

    Standler, Ronald B

    1989-01-01

    Practical rules and strategies designed to protect electronic systems from damage by transient overvoltages include symptoms and threats, remedies, protective devices and their applications, and validation of protective measures. 1989 edition.

  11. Mitigation of Voltage Swells by Static Series Compensator

    DEFF Research Database (Denmark)

    Awad, Hilmy; Blaabjerg, Frede

    2004-01-01

    is lower than a predetermined voltage level, the active power is employed to charge the ESC to this voltage level; 2) otherwise, the overvoltage protection of the SSC must operate. This paper also applies an overvoltage protection scheme based on a combination of a dc resistor with a chopper and the valves...... of the SSC. The design of the dc resistor is discussed. A 10 kV SSC experimental setup is exploited to carry out experiments in the case of balanced and unbalanced voltage swells at the grid side....

  12. Evaluation of lightning-induced voltages on low-voltage distribution networks

    Energy Technology Data Exchange (ETDEWEB)

    Silveira, Fernando H.; Visacro, Silverio [Federal University of Minas Gerais (LRC/UFMG), Belo Horizonte, MG (Brazil). Lightning Research Center], Emails: silveira@cpdee.ufmg.br, visacro@cpdee.ufmg.br

    2007-07-01

    This paper presents a set of evaluations concerning lightning-induced voltages on low-voltage networks. Such evaluations were performed by means of the Hybrid Electromagnetic Model, a frequency-domain code based on electromagnetic field equations. Sensitivity analyses were developed in order to investigate the role played by the most relevant line parameters on the voltages induced along the electrical system and at the consumer service entrance. The performance of two different low voltage line configurations (conventional versus multiplexed) usually adopted in Brazil was also investigated. The obtained results constitute a contribution to this theme and also provide elements to the development of protection practices to the electrical system and to the consumer against such phenomenon. (author)

  13. Voltage Regulators for Photovoltaic Systems

    Science.gov (United States)

    Delombard, R.

    1986-01-01

    Two simple circuits developed to provide voltage regulation for highvoltage (i.e., is greater than 75 volts) and low-voltage (i.e., is less than 36 volts) photovoltaic/battery power systems. Use of these circuits results in voltage regulator small, low-cost, and reliable, with very low power dissipation. Simple oscillator circuit controls photovoltaic-array current to regulate system voltage and control battery charging. Circuit senses battery (and system) voltage and adjusts array current to keep battery voltage from exceeding maximum voltage.

  14. TRANSIENT ELECTRONICS CATEGORIZATION

    Science.gov (United States)

    2017-08-24

    definitions of what it means to be transient. The purpose of this technical report is to provide a background of the issues related to transient...In this section, we will attempt to identify these parameters and provide preliminary definitions for categories of transience behavior. Transient...programmable lifetimes. Ideally , such materials with expiration dates will deconstruct themselves into harmless and invisible remnants. The technology base

  15. Studying Voltage Transformer Ferroresonance

    Directory of Open Access Journals (Sweden)

    Hamid Radmanesh

    2012-09-01

    Full Text Available This study studies the effect of Circuit Breaker Shunt Resistance (CBSR, Metal Oxide Vaistor (MOV and Neutral earth Resistance (NR on the control of ferroresonance in the voltage transformer. It is expected that NR can controlled ferroresonance better than MOV and CBSR. Study has been done on a one phase voltage transformer rated 100 VA, 275 kV. The simulation results reveal that considering the CBSR and MOV exhibits a great mitigating effect on ferroresonance overvoltages, but these resistances cannot control these phenomena for all range of parameters. By applying NR to the system structure, ferroresonance has been controlled and its amplitude has been damped for all parameters values.

  16. Automatic Voltage Control (AVC) System under Uncertainty from Wind Power

    DEFF Research Database (Denmark)

    Qin, Nan; Abildgaard, Hans; Flynn, Damian

    2016-01-01

    An automatic voltage control (AVC) system maintains the voltage profile of a power system in an acceptable range and minimizes the operational cost by coordinating the regulation of controllable components. Typically, all of the parameters in the optimization problem are assumed to be certain...... and constant in the decision making process. However, for high shares of wind power, uncertainty in the decision process due to wind power variability may result in an infeasible AVC solution. This paper proposes a voltage control approach which considers the voltage uncertainty from wind power productions....... The proposed method improves the performance and the robustness of a scenario based approach by estimating the potential voltage variations due to fluctuating wind power production, and introduces a voltage margin to protect the decision against uncertainty for each scenario. The effectiveness of the proposed...

  17. The Zwicky Transient Facility

    CERN Document Server

    Bellm, Eric C

    2014-01-01

    The Zwicky Transient Facility (ZTF) is a next-generation optical synoptic survey that builds on the experience and infrastructure of the Palomar Transient Factory (PTF). Using a new 47 deg$^2$ survey camera, ZTF will survey more than an order of magnitude faster than PTF to discover rare transients and variables. I describe the survey and the camera design. Searches for young supernovae, fast transients, counterparts to gravitational-wave detections, and rare variables will benefit from ZTF's high cadence, wide area survey.

  18. Coordination of Voltage and Frequency Feedback in Load-Frequency Control Capability of Wind Turbine

    DEFF Research Database (Denmark)

    Hoseinzadeh, Bakhtyar; Silva, Filipe Faria Da; Bak, Claus Leth

    2014-01-01

    regulation. The proposed scheme demonstrates remarkable improvement transient state of both voltage and frequency profiles in comparison with conventional LFC designs provided by Central Power Plants (CPP) or Wind Power Plants (WPP). Numerical simulations carried out in DigSilent Power- Factory confirm......, sufficient reserve capacity should be procured. This paper addresses the Load-Frequency Control (LFC) scheme offered by VSWT. Feedback loop of locally measured voltage and frequency data is employed to improve transient and permanent response to achieve faster and more efficient LFC action and voltage...

  19. Blockade or deletion of transient receptor potential vanilloid 4 (TRPV4 is not protective in a murine model of sepsis [v1; ref status: indexed, http://f1000r.es/57n

    Directory of Open Access Journals (Sweden)

    Claire A. Sand

    2015-04-01

    Full Text Available Sepsis is a systemic inflammatory response triggered by microbial infection that can cause cardiovascular collapse, insufficient tissue perfusion and multi-organ failure. The cation channel transient receptor potential vanilloid 4 (TRPV4 is expressed in vascular endothelium and causes vasodilatation, but excessive TRPV4 activation leads to profound hypotension and circulatory collapse - key features of sepsis pathogenesis. We hypothesised that loss of TRPV4 signaling would protect against cardiovascular dysfunction in a mouse model of sepsis (endotoxaemia. Multi-parameter monitoring of conscious systemic haemodynamics (by radiotelemetry probe, mesenteric microvascular blood flow (laser speckle contrast imaging and blood biochemistry (iSTAT blood gas analysis was carried out in wild type (WT and TRPV4 knockout (KO mice. Endotoxaemia was induced by a single intravenous injection of lipopolysaccharide (LPS; 12.5 mg/kg and systemic haemodynamics monitored for 24 h. Blood flow recording was then conducted under terminal anaesthesia after which blood was obtained for haematological/biochemical analysis. No significant differences were observed in baseline haemodynamics or mesenteric blood flow. Naïve TRPV4 KO mice were significantly acidotic relative to WT counterparts. Following induction of sepsis, all mice became significantly hypotensive, though there was no significant difference in the degree of hypotension between TRPV4 WT and KO mice. TRPV4 KO mice exhibited a higher sepsis severity score. While septic WT mice became significantly hypernatraemic relative to the naïve state, this was not observed in septic KO mice. Mesenteric blood flow was inhibited by topical application of the TRPV4 agonist GSK1016790A in naïve WT mice, but enhanced 24 h following LPS injection. Contrary to the initial hypothesis, loss of TRPV4 signaling (either through gene deletion or pharmacological antagonism did not attenuate sepsis-induced cardiovascular dysfunction

  20. Transients in reactors for power systems compensation

    Science.gov (United States)

    Abdul Hamid, Haziah

    This thesis describes new models and investigations into switching transient phenomena related to the shunt reactors and the Mechanically Switched Capacitor with Damping Network (MSCDN) operations used for reactive power control in the transmission system. Shunt reactors and MSCDN are similar in that they have reactors. A shunt reactor is connected parallel to the compensated lines to absorb the leading current, whereas the MSCDN is a version of a capacitor bank designed as a C-type filter for use in the harmonic-rich environment. In this work, models have been developed and transient overvoltages due to shunt reactor deenergisation were estimated analytically using MathCad, a mathematical program. Computer simulations used the ATP/EMTP program to reproduce both single-phase and three-phase shunt reactor switching at 275 kV operational substations. The effect of the reactor switching on the circuit breaker grading capacitor was also examined by considering various switching conditions.. The main original achievement of this thesis is the clarification of failure mechanisms occurring in the air-core filter reactor due to MSCDN switching operations. The simulation of the MSCDN energisation was conducted using the ATP/EMTP program in the presence of surge arresters. The outcome of this simulation shows that extremely fast transients were established across the air-core filter reactor. This identified transient event has led to the development of a detailed air-core reactor model, which accounts for the inter-turn RLC parameters as well as the stray capacitances-to-ground. These parameters are incorporated into the transient simulation circuit, from which the current and voltage distribution across the winding were derived using electric field and equivalent circuit modelling. Analysis of the results has revealed that there are substantial dielectric stresses imposed on the winding insulation that can be attributed to a combination of three factors. (i) First, the

  1. Mathematical Simulation of Transient Parameters of Vertical Grounding Electrodes

    Directory of Open Access Journals (Sweden)

    A. Dziaruhina

    2012-01-01

    Full Text Available The paper contains a mathematical simulation of transient parameters of vertical grounding electrodes for the first and subsequent short strokes of a lightning current. Results of the research show that transient resistances of grounding electrodes change appreciably in time. The transient resistances are always higher in the moment of voltage maximum then in the moment of current maximum. The dependences of transient resistances on grounding electrode length at different ground conductivity and lightning current parameters (first and subsequent short strokes are obtained in the paper. The paper proposes an approximate criterion for estimation of grounding electrode equivalent length at transient condition that considers short stroke parameters of the lightning current and ground conductivity.

  2. Transient regimes of the three-phase power transformers

    Directory of Open Access Journals (Sweden)

    Olivian Chiver

    2015-12-01

    Full Text Available The transient regimes of a three-phase power transformer will be studied in this paper. The transient currents in the windings will be determined both analytically and by finite elements method (FEM. The no load and short circuit regimes will be considered. The current dependence of the instantaneous phase voltage and of the initial current value will be highlighted, by FEM. In order to determine analytically the transient currents, for inductances the analytical and FEM values will be used. The inductances are determined with FEM through the simulation of experimental tests. With FEM, the transient currents will be determined using transient analysis. Finally, the FEM and analytical results will be compared and discussed.

  3. VOLTAGE REGULATORS ASYNCHRONOUS GENERATORS

    Directory of Open Access Journals (Sweden)

    Grigorash O. V.

    2015-06-01

    Full Text Available A promising is currently the use of asynchronous generators with capacitive excitation as a source of electricity in stand-alone power systems. Drive asynchronous generators may exercise as a thermal engine and wind wheel wind power plant or turbines of small hydropower plants. The article discusses the structural and schematics of voltage stabilizers and frequency of asynchronous generators with improved operational and technical specifications. Technical novelty of design solutions of the magnetic system and stabilizers asynchronous generator of electricity parameters confirmed by the patents for the invention of the Russian Federation. The proposed technical solution voltage stabilizer asynchronous generators, can reduce the weight of the block capacitors excitation and reactive power compensation, as well as to simplify the control system power circuit which has less power electronic devices. For wind power plants it is an important issue not only to stabilize the voltage of the generator, but also the frequency of the current. Recommend functionality stabilizer schemes parameters of electric power made for direct frequency converters with artificial and natural switching power electronic devices. It is also proposed as part of stabilization systems use single-phase voltage, three-phase transformers with rotating magnetic field, reduce the level of electromagnetic interference generated by power electronic devices for switching, enhance the efficiency and reliability of the stabilizer.

  4. Geomagnetism and Induced Voltage

    Science.gov (United States)

    Abdul-Razzaq, W.; Biller, R. D.

    2010-01-01

    Introductory physics laboratories have seen an influx of "conceptual integrated science" over time in their classrooms with elements of other sciences such as chemistry, biology, Earth science, and astronomy. We describe a laboratory to introduce this development, as it attracts attention to the voltage induced in the human brain as it…

  5. Control voltage and power fluctuations when connecting wind farms

    Energy Technology Data Exchange (ETDEWEB)

    Berinde, Ioan, E-mail: ioan-berinde@yahoo.com; Bălan, Horia, E-mail: hbalan@mail.utcluj.ro; Oros, Teodora Susana, E-mail: teodoraoros-87@yahoo.com [Technical University of Cluj-Napoca, Romania, Faculty of Electrical Engineering, Department of Power Engineering and Management (Romania)

    2015-12-23

    Voltage, frequency, active power and reactive power are very important parameters in terms of power quality. These parameters are followed when connecting any power plant, the more the connection of wind farms. Connecting wind farms to the electricity system must not cause interference outside the limits set by regulations. Modern solutions for fast and automatic voltage control and power fluctuations using electronic control systems of reactive power flows. FACTS (Flexible Alternating Current Transmision System) systems, established on the basis of power electronic circuits ensure control of electrical status quantities to achieve the necessary transfer of power to the power grid. FACTS devices can quickly control parameters and sizes of state power lines, such as impedance line voltages and phase angles of the voltages of the two ends of the line. Their use can lead to improvement in power system operation by increasing the transmission capacity of power lines, power flow control lines, improved static and transient stability reserve.

  6. 浅谈高压输电线路的运行维护与防雷措施%On the Running Maintenance and Lightning Protection Measures of High-voltage Transmission Line

    Institute of Scientific and Technical Information of China (English)

    赵登

    2014-01-01

    高压输电线路是电力系统的重要组成部分。由于地形复杂、距离长,高压输电线路在运行过程中难免出现故障,本文针对高压输电线路常见的故障,提出了有效的故障诊断和处理方法,为线路故障的诊断和维护提供了依据,具有重要的理论和实用价值。%The high-voltage transmission line is an important part of the power system. Because of the complex terrain and long distance, high-voltage transmission line will inevitably fail during operation. Aiming at the common faults of high-voltage transmission line, this paper proposes effective fault diagnosis and treatment methods, which provide basis, for fault diagnosis and maintenance and has important theoretical and practical value.

  7. Lightning transient analysis in wind turbine blades

    DEFF Research Database (Denmark)

    Candela Garolera, Anna; Holbøll, Joachim; Madsen, Søren Find

    2013-01-01

    The transient behavior of lightning surges in the lightning protection system of wind turbine blades has been investigated in this paper. The study is based on PSCAD models consisting of electric equivalent circuits with lumped and distributed parameters involving different lightning current...

  8. 30 CFR 75.800 - High-voltage circuits; circuit breakers.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false High-voltage circuits; circuit breakers. 75.800... § 75.800 High-voltage circuits; circuit breakers. High-voltage circuits entering the underground area of any coal mine shall be protected by suitable circuit breakers of adequate interrupting...

  9. Kinetics of transient electroluminescence in organic light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Shukla, Manju; Brahme, Nameeta [School of Studies in Physics, Pt. Ravishanker Shukla University, Raipur (Congo, The Democratic Republic of the) 492010 (India); Kumar, Pankaj; Chand, Suresh [Center for Organic Electronics, National Physical Laboratory, Dr K S Krishnan Road, New Delhi-110012 (India); Kher, R S [Department of Physics, Government Science PG College, Bilaspur (Congo, The Democratic Republic of the) 495006 (India); Khokhar, M S K [Department of Rural Technology, GuruGhasidas University Bilaspur (Congo, The Democratic Republic of the) 495009 (India)], E-mail: manjushukla2003@gmail.com

    2008-08-21

    Mathematical simulation on the rise and decay kinetics of transient electroluminescence (EL) in organic light emitting diodes (OLEDs) is presented. The transient EL is studied with respect to a step voltage pulse. While rising, for lower values of time, the EL intensity shows a quadratic dependence on (t - t{sub del}), where t{sub del} is the time delay observed in the onset of EL, and finally attains saturation at a sufficiently large time. When the applied voltage is switched off, the initial EL decay shows an exponential dependence on (t - t{sub dec}), where t{sub dec} is the time when the voltage is switched off. The simulated results are compared with the transient EL performance of a bilayer OLED based on small molecular bis(2-methyl 8-hydroxyquinoline)(triphenyl siloxy) aluminium (SAlq). Transient EL studies have been carried out at different voltage pulse amplitudes. The simulated results show good agreement with experimental data. Using these simulated results the lifetime of the excitons in SAlq has also been calculated.

  10. Novel Low Loss Active Voltage Clamp Circuit for Series Connection of RCGCT thyristors

    Science.gov (United States)

    Ito, Hiroshi; Suzuki, Akihiro; Iwata, Akihiko

    This paper describes novel low loss active voltage clamp circuits for the series connection of RCGCT thyristors. For high voltage converters the series connection of power semiconductor devices is an essential technique for direct switching of high voltages. Several protection circuits have been applied to the series connection of RCGCT thyristors such as CRD snubber circuits which suppress over-voltages across RCGCT thyristors, and voltage balancing resistors to equalize voltage sharing in steady states. However, significant losses in these protection circuits lower the converter’s efficiency. We propose novel low-loss protection circuits, which have active voltage clamp snubber circuits and static voltage balancing circuits. The clamp capacitor voltage of the active voltage clamp snubber circuits are designed to be higher than the equally divided DC-Link voltage. This method can reduce the loss of the clamp circuit to no more than 1/10 of that of the conventional CRD snubber. Also the static voltage balancing circuits compensate for the voltage imbalance generated by the difference in the leakage current between the series connection RCGCT thyristors.

  11. The transient behavior of electrorheological fluid in tensile flow

    Science.gov (United States)

    Tian, Yu; Zhang, Minliang; Zhu, Xuli; Jiang, Jile; Meng, Yonggang; Wen, Shizhu

    2009-12-01

    Transient behaviors of (ER) fluids in tensile flow and applied stepwise voltages were experimentally studied. The transient tensile stress rises exponentially with time. The characteristic rising time of tensile stress is independent of the amplitude of the applied voltage and the tensile velocity, while the amplitude of tensile yield stress is significantly affected by the two factors. The transient tension applied as a stepwise voltage is different from a stable tension pre-applied at constant voltage in different particle chain structure forming processes. Because of the chain aggregation during an intermittent voltage on-off test, the achieved tensile yield stress showed an exponent of 2.75 to the applied electric field at low separation velocities (0.2 mm s-1), higher than the square relationship predicted by traditional polarization models, and the exponent of 1.5 predicted by the conduction model. The results achieved in this study show that the mechanical properties of ER fluids are greatly affected by the method of applying the electric field, the strain rate, and the gap geometry between electrodes. These factors should be properly considered in the design and control of ER actuators.

  12. FUZZY LOGIC CONTROLLED CATHODIC PROTECTION CIRCUIT DESIGN

    OpenAIRE

    AKÇAYOL, M. Ali

    2010-01-01

    In this study, output voltage of automatic transformer-rectifier (TR) unit of impressed current cathodic protection has been controlled by using fuzzy logic controller. To prevent corrosion, voltage between the protection metal and the auxiliary anode has to be controlled on a desired level. Because soil resistance in the environment changes with humidity and soil characteristics, TRs must control the output voltage between protection metal and auxiliary anode automatically. In this study, a ...

  13. Analysis and Mitigation of Shunt Capacitor Bank Switching Transients on 132 kV Grid Station, Qasimabad Hyderabad

    Directory of Open Access Journals (Sweden)

    Sunny Katyara

    2015-10-01

    Full Text Available In this paper analysis and mitigation methods of capacitor bank switching transients on 132KV Grid station, Qasimabad Hyderabad are simulated through the MATLAB software (Matrix Laboratory. Analysis of transients with and without capacitor bank is made. Mathematical measurements of quantities such as transient voltages and inrush currents for each case are discussed. Reasons for these transients, their impact on utility and customer systems and their mitigation are provided.

  14. Analysis and Mitigation of Shunt Capacitor Bank Switching Transients on 132 kV Grid Station, Qasimabad Hyderabad

    OpenAIRE

    Sunny Katyara; Ashfaque Ahmed Hashmani; Bhawani Shankar Chowdhry

    2015-01-01

    In this paper analysis and mitigation methods of capacitor bank switching transients on 132KV Grid station, Qasimabad Hyderabad are simulated through the MATLAB software (Matrix Laboratory). Analysis of transients with and without capacitor bank is made. Mathematical measurements of quantities such as transient voltages and inrush currents for each case are discussed. Reasons for these transients, their impact on utility and customer systems and their mitigation are provided.

  15. Transients of Water Distribution and Transport in PEFCs

    KAUST Repository

    Hussaini, Irfan

    2008-01-01

    Response of PEM fuel cells to a step-change in load is investigated experimentally in this work. Voltage undershoot, a characteristic feature of such transient response, is shown to be due to transients of water distribution in membrane phase occurring at sub-second time scales. Use of humidified reactants as a means to control magnitude of voltage undershoot has been demonstrated. Constant stoichiometry operation under certain current-step conditions is found to result in reactant starvation, potentially leading to cell shut down. Further, response under step decrease in current density has been explored to determine existence of hysteresis. Under sufficiently humidified conditions, response under forward and reverse step changes are found to be symmetric, but under low RH conditions, voltage undershoot is found to be twice as large as the overshoot. © The Electrochemical Society.

  16. Transients of Water Distribution and Transport in PEM Fuel Cells

    KAUST Repository

    Hussaini, Irfan S.

    2009-01-01

    The response of polymer electrolyte membrane (PEM) fuel cells to a step change in load is investigated experimentally in this work. Voltage undershoot, a characteristic feature of transient response following a step increase in current, is due to transients of water distribution in the membrane and ionomers occurring at subsecond time scales. The use of humidified reactants as a means to control the magnitude of voltage undershoot is demonstrated. Further, the response under a step decrease in current density is explored to determine the existence of hysteresis. Under sufficiently humidified conditions, the responses under forward and reverse step changes are symmetric, but under low relative humidity conditions, voltage undershoot is twice as large as the overshoot. © 2009 The Electrochemical Society.

  17. Deployment of low-voltage regulator considering existing voltage control in medium-voltage distribution systems

    Directory of Open Access Journals (Sweden)

    Hiroshi Kikusato

    2016-01-01

    Full Text Available Many photovoltaic (PV systems have been installed in distribution systems. This installation complicates the maintenance of all voltages within the appropriate range in all low-voltage distribution systems (LVDSs because the trends in voltage fluctuation differ in each LVDS. The installation of a low-voltage regulator (LVR that can accordingly control the voltage in each LVDS has been studied as a solution to this problem. Voltage control in a medium-voltage distribution system must be considered to study the deployment of LVRs. In this study, we installed LVRs in the LVDSs in which the existing voltage-control scheme cannot prevent voltage deviation and performed a numerical simulation by using a distribution system model with PV to evaluate the deployment of the LVRs.

  18. High Voltage Charge Pump

    KAUST Repository

    Emira, Ahmed A.

    2014-10-09

    Various embodiments of a high voltage charge pump are described. One embodiment is a charge pump circuit that comprises a plurality of switching stages each including a clock input, a clock input inverse, a clock output, and a clock output inverse. The circuit further comprises a plurality of pumping capacitors, wherein one or more pumping capacitors are coupled to a corresponding switching stage. The circuit also comprises a maximum selection circuit coupled to a last switching stage among the plurality of switching stages, the maximum selection circuit configured to filter noise on the output clock and the output clock inverse of the last switching stage, the maximum selection circuit further configured to generate a DC output voltage based on the output clock and the output clock inverse of the last switching stage.

  19. Electromagnetic Transient Response Analysis of DFIG under Cascading Grid Faults Considering Phase Angel Jumps

    DEFF Research Database (Denmark)

    Wang, Yun; Wu, Qiuwei

    2014-01-01

    This paper analysis the electromagnetic transient response characteristics of DFIG under symmetrical and asymmetrical cascading grid fault conditions considering phaseangel jump of grid. On deriving the dynamic equations of the DFIG with considering multiple constraints on balanced and unbalanced...... conditions, phase angel jumps, interval of cascading fault, electromagnetic transient characteristics, the principle of the DFIG response under cascading voltage fault can be extract. The influence of grid angel jump on the transient characteristic of DFIG is analyzed and electromagnetic response...

  20. Mechanistic Insight in the Function of Phosphite Additives for Protection of LiNi 0.5 Co 0.2 Mn 0.3 O 2 Cathode in High Voltage Li-Ion Cells

    Energy Technology Data Exchange (ETDEWEB)

    He, Meinan; Su, Chi-Cheung; Peebles, Cameron; Feng, Zhenxing; Connell, Justin G.; Liao, Chen; Wang, Yan; Shkrob, Ilya A.; Zhang, Zhengcheng

    2016-05-11

    Triethlylphosphite (TEP) and tris(2,2,2-trifluoroethyl) phosphite (TTFP) have been evaluated as electrolyte additives for high-voltage Li-ion battery cells using a Ni-rich layered cathode material LiNi0.5Co0.2Mn0.3O2 (NCM523) and the conventional carbonate electrolyte. The repeated charge/discharge cycling for cells containing 1 wt% of these additives was performed using an NCM523/graphite full cell operated at the voltage window from 3.0 to 4.6 V. During the initial charge process, these additives decompose on the cathode surface at a lower oxidation potential than the baseline electrolyte. Impedance spectroscopy and post-test analyses indicate the formation of protective coatings by both additives on the cathode surface that prevent oxidative breakdown of the electrolyte. However, only TTFP containing cells demonstrate the improved capacity retention and Coulombic efficiency. For TEP, the protective coating is also formed, but low Li+ ion mobility through the interphase layer results in inferior performance. These observations are rationalized through the inhibition of electrocatalytic centers present on the cathode surface and the formation of organophosphate deposits isolating the cathode surface from the electrolyte. The difference between the two phosphites clearly originates in the different properties of the resulting phosphate coatings, which may be in Li+ ion conductivity through such materials.

  1. Increased voltage photovoltaic cell

    Science.gov (United States)

    Ross, B.; Bickler, D. B.; Gallagher, B. D. (Inventor)

    1985-01-01

    A photovoltaic cell, such as a solar cell, is provided which has a higher output voltage than prior cells. The improved cell includes a substrate of doped silicon, a first layer of silicon disposed on the substrate and having opposite doping, and a second layer of silicon carbide disposed on the first layer. The silicon carbide preferably has the same type of doping as the first layer.

  2. High Voltage Seismic Generator

    Science.gov (United States)

    Bogacz, Adrian; Pala, Damian; Knafel, Marcin

    2015-04-01

    This contribution describes the preliminary result of annual cooperation of three student research groups from AGH UST in Krakow, Poland. The aim of this cooperation was to develop and construct a high voltage seismic wave generator. Constructed device uses a high-energy electrical discharge to generate seismic wave in ground. This type of device can be applied in several different methods of seismic measurement, but because of its limited power it is mainly dedicated for engineering geophysics. The source operates on a basic physical principles. The energy is stored in capacitor bank, which is charged by two stage low to high voltage converter. Stored energy is then released in very short time through high voltage thyristor in spark gap. The whole appliance is powered from li-ion battery and controlled by ATmega microcontroller. It is possible to construct larger and more powerful device. In this contribution the structure of device with technical specifications is resented. As a part of the investigation the prototype was built and series of experiments conducted. System parameter was measured, on this basis specification of elements for the final device were chosen. First stage of the project was successful. It was possible to efficiently generate seismic waves with constructed device. Then the field test was conducted. Spark gap wasplaced in shallowborehole(0.5 m) filled with salt water. Geophones were placed on the ground in straight line. The comparison of signal registered with hammer source and sparker source was made. The results of the test measurements are presented and discussed. Analysis of the collected data shows that characteristic of generated seismic signal is very promising, thus confirms possibility of practical application of the new high voltage generator. The biggest advantage of presented device after signal characteristics is its size which is 0.5 x 0.25 x 0.2 m and weight approximately 7 kg. This features with small li-ion battery makes

  3. Mitigation of Voltage Sags in CIGRE Low Voltage Distribution Network

    DEFF Research Database (Denmark)

    Mustafa, Ghullam; Bak-Jensen, Birgitte; Mahat, Pukar;

    2013-01-01

    problems in the distribution system. The voltage problems dealt with in this paper are to show how to mitigate voltage sags in the CIGRE Low Voltage (LV) test network and networks like this. The voltage sags, for the tested cases in the CIGRE LV test network are mainly due to three phase faults....... The compensation of voltage sags in the different parts of CIGRE distribution network is done by using the four STATCOM compensators already existing in the test grid. The simulations are carried out in DIgSILENT power factory software version 15.0....

  4. Transient excitation boosting at Grand Coulee third power plant: Power system application and field tests

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, C.W.; Mechenbier, J.R.; Matthews, C.E. (Bonneville Power Administration, Portland, OR (United States))

    1993-08-01

    Transient excitation boosting (TEB) has been installed on the Grand Coulee Third Power Plant hydrogenerators (three 600 MVA units and three 700 MVA units). TEB is initiated for outages of the 3100 MW Pacific HVDC Intertie, and results in a decaying pulse input to the generator voltage regulators. TEB temporarily raises Pacific Northwest transmission voltages which increases voltage-sensitive loads. The increased load brakes Northwest generators which are accelerating because of the loss of HVDC Intertie power. Transient stability of the parallel Pacific AC Intertie is thus improved. Power system-wide commissioning tests were conducted on May 7, 1991. The authors describe the tests and compare test results with simulation results.

  5. Voltage Controlled Dynamic Demand Response

    DEFF Research Database (Denmark)

    Bhattarai, Bishnu Prasad; Bak-Jensen, Birgitte; Mahat, Pukar

    2013-01-01

    . An adaptive dynamic model has been developed to determine composite voltage dependency of an aggregated load on feeder level. Following the demand dispatch or control signal, optimum voltage setting at the LV substation is determined based on the voltage dependency of the load. Furthermore, a new technique...

  6. Charge-pump voltage converter

    Science.gov (United States)

    Brainard, John P.; Christenson, Todd R.

    2009-11-03

    A charge-pump voltage converter for converting a low voltage provided by a low-voltage source to a higher voltage. Charge is inductively generated on a transfer rotor electrode during its transit past an inductor stator electrode and subsequently transferred by the rotating rotor to a collector stator electrode for storage or use. Repetition of the charge transfer process leads to a build-up of voltage on a charge-receiving device. Connection of multiple charge-pump voltage converters in series can generate higher voltages, and connection of multiple charge-pump voltage converters in parallel can generate higher currents. Microelectromechanical (MEMS) embodiments of this invention provide a small and compact high-voltage (several hundred V) voltage source starting with a few-V initial voltage source. The microscale size of many embodiments of this invention make it ideally suited for MEMS- and other micro-applications where integration of the voltage or charge source in a small package is highly desirable.

  7. Inferring the correlation between lightning events and voltage dips in distribution networks

    Energy Technology Data Exchange (ETDEWEB)

    Nucci, C.A. [University of Bologna (Italy)], E-mail: carloalberto.nucci@unibo.it

    2007-07-01

    To appropriately infer the correlation between lightning events and flashover/voltage dips on real distribution networks, data coming from lightning location systems are certainly needed, but need to be complemented on the one hand by data coming from distributed measurement systems able to record both protection manoeuvres and lightning-originated transients, and on the other hand by accurate calculation results. Additionally, the analysis needs to be performed on a statistical basis. The paper illustrates the main concepts used in developing a procedure aimed at inferring the above mentioned correlation, which is based on the integrated use of experimental data obtained from the Italian lightning location system CESI-SIRF, a monitoring system of relay operation, a distributed monitoring system of lightning-induced transients and of calculations performed using the LIOV-EMTP code. The application of the procedure to the portion of a real distribution network located in Italy in a high level keraunic area is presented by making use of some CESI-SIRF-detected events. (author)

  8. Transient Ischemic Attack

    Medline Plus

    Full Text Available ... TIA , or transient ischemic attack, is a "mini stroke" that occurs when a blood clot blocks an ... a short time. The only difference between a stroke and TIA is that with TIA the blockage ...

  9. Transient Ischemic Attack

    Medline Plus

    Full Text Available ... TIA , or transient ischemic attack, is a "mini stroke" that occurs when a blood clot blocks an ... a short time. The only difference between a stroke and TIA is that with TIA the blockage ...

  10. Searches for radio transients

    CERN Document Server

    Bhat, N D R

    2011-01-01

    Exploration of the transient Universe is an exciting and fast-emerging area within radio astronomy. Known transient phenomena range in time scales from sub-nanoseconds to years or longer, thus spanning a huge range in time domain and hinting a rich diversity in their underlying physical processes. Transient phenomena are likely locations of explosive or dynamic events and they offer tremendous potential to uncover new physics and astrophysics. A number of upcoming next-generation radio facilities and recent advances in computing and instrumentation have provided a much needed impetus for this field which has remained a relatively uncharted territory for the past several decades. In this paper we focus mainly on the class of phenomena that occur on very short time scales (i.e. from $\\sim$ milliseconds to $\\sim$ nanoseconds), known as {\\it fast transients}, the detections of which involve considerable signal processing and data management challenges, given the high time and frequency resolutions required in the...

  11. Transient Ischemic Attack

    Medline Plus

    Full Text Available ... Ischemic Attack TIA , or transient ischemic attack, is a "mini stroke" that occurs when a blood clot blocks an artery for a short time. The only difference between a stroke ...

  12. Transient multivariable sensor evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Vilim, Richard B.; Heifetz, Alexander

    2017-02-21

    A method and system for performing transient multivariable sensor evaluation. The method and system includes a computer system for identifying a model form, providing training measurement data, generating a basis vector, monitoring system data from sensor, loading the system data in a non-transient memory, performing an estimation to provide desired data and comparing the system data to the desired data and outputting an alarm for a defective sensor.

  13. Transient multivariable sensor evaluation

    Science.gov (United States)

    Vilim, Richard B.; Heifetz, Alexander

    2017-02-21

    A method and system for performing transient multivariable sensor evaluation. The method and system includes a computer system for identifying a model form, providing training measurement data, generating a basis vector, monitoring system data from sensor, loading the system data in a non-transient memory, performing an estimation to provide desired data and comparing the system data to the desired data and outputting an alarm for a defective sensor.

  14. Improved Phasor Estimation Method for Dynamic Voltage Restorer Applications

    DEFF Research Database (Denmark)

    Ebrahimzadeh, Esmaeil; Farhangi, Shahrokh; Iman-Eini, Hossein;

    2015-01-01

    The dynamic voltage restorer (DVR) is a series compensator for distribution system applications, which protects sensitive loads against voltage sags by fast voltage injection. The DVR must estimate the magnitude and phase of the measured voltages to achieve the desired performance. This paper...... proposes a phasor parameter estimation algorithm based on a recursive variable and fixed data window least error squares (LES) method for the DVR control system. The proposed algorithm, in addition to decreasing the computational burden, improves the frequency response of the control scheme based...... on the fixed data window LES method. The DVR control system based on the proposed algorithm provides a better compromise between the estimation speed and accuracy of the voltage and current signals and can be implemented using a simple and low-cost processor. The results of the studies indicate...

  15. Effect of semiconductor-controlled voltage injection by UPFC and ULTC on power system stability

    Science.gov (United States)

    Alavian Mehr, Alireza

    Commercial availability of various power semiconductor switches indicates proliferation of power electronic based apparatus in utility power systems. Furthermore, existing power system apparatus, e.g. mechanical phase shifters and mechanical tap changing transformers, will be retrofitted to utilize higher switching speed of semiconductor switches. A group of these apparatus, i.e., unified power flow controller (UPFC), static phase shifter (SPS), under-load tap-changing (ULTC) transformer and static series capacitor (SSC), perform their respective functions by means of injecting series controlled voltages in power systems. This thesis demonstrates that fast series voltage injection, for dynamic power flow regulation, can result in voltage dynamics and even voltage instability. This indicates that fast voltage injection by means of power electronic based apparatus can couple voltage stability and angle stability phenomena. To investigate this coupling phenomena, the voltage dependency of the load must be adequately represented in the load model. The reported studies in this work are based on representing the load by a combination of static and dynamic loads. This thesis primarily investigates impacts of UPFC and semiconductor-controlled ULTC on voltage stability and angle stability phenomena. An eigen analysis approach is used for the studies. The eigen analysis results are validated by digital time-domain simulations using a transient stability software. Both the eigen analysis and the transient stability software tools are tailored to account for angle and voltage stability phenomena.

  16. No-Voltage Meter

    Science.gov (United States)

    1976-02-01

    VW- IKft, 1/4 H4 -Wv- IK!1, I/4W INTERNAL VOLTAGE NOTE ALL TRANSISTORS ARE 2N43A OR EQUIVALENT GERMANIUM ALLOY PNP AA ALKALINE BATTERY...D-,, regardless of polarity. This signal is then full-wave rectified by the diode-connected Germanium transistor bridge, T,, T-,, T3, and T4... Transistor T5 acts as a second current limiter. Resistor R2 was selected to give 90 f# of full-scale meter deflection with an input signal of 115 volts

  17. Benchmarking of Voltage Sag Generators

    DEFF Research Database (Denmark)

    Yang, Yongheng; Blaabjerg, Frede; Zou, Zhixiang

    2012-01-01

    The increased penetration of renewable energy systems, like photovoltaic and wind power systems, rises the concern about the power quality and stability of the utility grid. Some regulations for Low Voltage Ride-Through (LVRT) for medium voltage or high voltage applications, are coming into force...... to guide these grid-connected distributed power generation systems. In order to verify the response of such systems for voltage disturbance, mainly for evaluation of voltage sags/dips, a Voltage Sag Generator (VSG) is needed. This paper evaluates such sag test devices according to IEC 61000 in order...... to provide cheaper solutions to test against voltage sags. Simulation and experimental results demonstrate that the shunt impedance based VSG solution is the easiest and cheapest one for laboratory test applications. The back-to-back fully controlled converter based VSG is the most flexible solution...

  18. Modeling and Simulation of Transient Fault Response at Lillgrund Wind Farm when Subjected to Faults in the Connecting 130 kV Grid

    Energy Technology Data Exchange (ETDEWEB)

    Eliasson, Anders; Isabegovic, Emir

    2009-07-01

    The purpose of this thesis was to investigate what type of faults in the connecting grid should be dimensioning for future wind farms. An investigation of over and under voltages at the main transformer and the turbines inside Lillgrund wind farm was the main goal. The results will be used in the planning stage of future wind farms when performing insulation coordination and determining the protection settings. A model of the Lillgrund wind farm and a part of the connecting 130 kV grid were built in PSCAD/EMTDC. The farm consists of 48 Siemens SWT-2.3-93 2.3 MW wind turbines with full power converters. The turbines were modeled as controllable current sources providing a constant active power output up to the current limit of 1.4 pu. The transmission lines and cables were modeled as frequency dependent (phase) models. The load flows and bus voltages were verified towards a PSS/E model and the transient response was verified towards measuring data from two faults, a line to line fault in the vicinity of Barsebaeck (BBK) and a single line-to-ground fault close to Bunkeflo (BFO) substation. For the simulation, three phase to ground, single line to ground and line to line faults were applied at different locations in the connecting grid and the phase to ground voltages at different buses in the connecting grid and at turbines were studied. These faults were applied for different configurations of the farm. For single line to ground faults, the highest over voltage on a turbine was 1.22 pu (32.87 kV) due to clearing of a fault at BFO (the PCC). For line to line faults, the highest over voltage on a turbine was 1.59 pu (42.83 kV) at the beginning of a fault at KGE one bus away from BFO. Both these cases were when all radials were connected and the turbines ran at full power. The highest over voltage observed at Lillgrund was 1.65 pu (44.45 kV). This over voltage was caused by a three phase to ground fault applied at KGE and occurred at the beginning of the fault and when

  19. Impact Analyses of Wind Farm on Performances of Transmission Line Relay Protection

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    A simulation system for power grid with concentrated based on the electro-magnetic transient model of wind turbine (DFIG), which is built by real-time digital simulator (RTDS) large-scale wind farm integration is established equipped with doubly-fed induction generator Using the hardware communication interface of RTDS, a closed-loop testing experiment is accomplished to study the impacts of large-scale wind farms on the existing relay protection devices for wind farm outgoing transmission line. This paper points out problems existing in current relay protection devices as follows: fault phase selector can select unwanted phase due to the changes of fault features caused by special network connection of wind farms; blocking condition for distance protections needs to be re-examined due to the weak power-feed characteristics of wind farms; and power frequency parameter based relay protection devices cannot accurately operate due to the special transient voltage and current characteristics of wind farms during fault period. Results lay the foundation for improving the performances of the existing relay protection device and developing new principle relay protection.

  20. Numerical differential protection

    CERN Document Server

    Ziegler, Gerhard

    2012-01-01

    Differential protection is a fast and selective method of protection against short-circuits. It is applied in many variants for electrical machines, trans?formers, busbars, and electric lines.Initially this book covers the theory and fundamentals of analog and numerical differential protection. Current transformers are treated in detail including transient behaviour, impact on protection performance, and practical dimensioning. An extended chapter is dedicated to signal transmission for line protection, in particular, modern digital communication and GPS timing.The emphasis is then pla

  1. Improving Power System Transient Stability with Static Synchronous Series Compensator

    Directory of Open Access Journals (Sweden)

    Prechanon Kumkratug

    2011-01-01

    Full Text Available Problem statement: Modern power system consists of the complicated network of transmission lines and carries heavy demand. Thus they cause in the stability problem. One of the major interests of power utilities is the improvement of power system transient behavior. Approach: Static Synchronous Series Compensator (SSSC is a power electronic based device that has the capability of controlling the power flow through a line. This study applies the SSSC to improve transient stability of power system. To verify the effect of the SSSC on transient stability, the mathematical model and control strategy of a SSSC is presented. The SSSC is represented by variable voltage injection with associate transformer leakage reactance and the voltage source. The series voltage injection model of SSSC is modeled into power flow equation and thus it is used to determine its control strategy. This study uses machine speed deviation to control it. The swing curves of the three phase faulted power system without and with a SSSC is tested and compared in various cases. Results: The swing curve of system without a SSSC gets increases monotonically and thus the system can be considered as unstable whereas the swing curves of system with a SSSC can be considered as stable. Conclusion: SSSSC can improve transient stability of power system.

  2. Coordinated Voltage Control of Distributed PV Inverters for Voltage Regulation in Low Voltage Distribution Networks

    DEFF Research Database (Denmark)

    Nainar, Karthikeyan; Pokhrel, Basanta Raj; Pillai, Jayakrishnan Radhakrishna

    2017-01-01

    This paper reviews and analyzes the existing voltage control methods of distributed solar PV inverters to improve the voltage regulation and thereby the hosting capacity of a low-voltage distribution network. A novel coordinated voltage control method is proposed based on voltage sensitivity...... analysis, which is simple for computation and requires moderate automation and communication infrastructure. The proposed method is suitable for a hierarchical control structure where a supervisory controller has the provision to adapt the settings of local PV inverter controllers for overall system...

  3. Heat-pump performance: voltage dip/sag, under-voltage and over-voltage

    Directory of Open Access Journals (Sweden)

    William J.B. Heffernan

    2014-12-01

    Full Text Available Reverse cycle air-source heat-pumps are an increasingly significant load in New Zealand and in many other countries. This has raised concern over the impact wide-spread use of heat-pumps may have on the grid. The characteristics of the loads connected to the power system are changing because of heat-pumps. Their performance during under-voltage events such as voltage dips has the potential to compound the event and possibly cause voltage collapse. In this study, results from testing six heat-pumps are presented to assess their performance at various voltages and hence their impact on voltage stability.

  4. The Zwicky Transient Facility Camera

    Science.gov (United States)

    Dekany, Richard; Smith, Roger M.; Belicki, Justin; Delacroix, Alexandre; Duggan, Gina; Feeney, Michael; Hale, David; Kaye, Stephen; Milburn, Jennifer; Murphy, Patrick; Porter, Michael; Reiley, Daniel J.; Riddle, Reed L.; Rodriguez, Hector; Bellm, Eric C.

    2016-08-01

    The Zwicky Transient Facility Camera (ZTFC) is a key element of the ZTF Observing System, the integrated system of optoelectromechanical instrumentation tasked to acquire the wide-field, high-cadence time-domain astronomical data at the heart of the Zwicky Transient Facility. The ZTFC consists of a compact cryostat with large vacuum window protecting a mosaic of 16 large, wafer-scale science CCDs and 4 smaller guide/focus CCDs, a sophisticated vacuum interface board which carries data as electrical signals out of the cryostat, an electromechanical window frame for securing externally inserted optical filter selections, and associated cryo-thermal/vacuum system support elements. The ZTFC provides an instantaneous 47 deg2 field of view, limited by primary mirror vignetting in its Schmidt telescope prime focus configuration. We report here on the design and performance of the ZTF CCD camera cryostat and report results from extensive Joule-Thompson cryocooler tests that may be of broad interest to the instrumentation community.

  5. Voltage Swells Improvement in Low Voltage Network Using Dynamic Voltage Restorer

    Directory of Open Access Journals (Sweden)

    R. Omar

    2011-01-01

    Full Text Available Problem statement: Voltage disturbances are the most common power quality problem due to the increased use of a large numbers of sophisticated electronic equipment in industrial distribution system. The voltage disturbances such as voltage sags, swells, harmonics, unbalance and flickers. High quality in the power supply is needed, since failures due to such disturbances usually have a high impact on production cost. There are many different solutions to compensate voltage disturbances but the use of a DVR is considered to be the most cost effective method. The objective of this study is to propose a new topology of a DVR in order to mitigate voltage swells using a powerful power custom device namely the Dynamic Voltage Restorer (DVR. Approach: New configuration of a DVR with an improvement of a controller based on direct-quadrature-zero method has been introduced to compensate voltage swells in the network. Results: The effectiveness of the DVR with its controller were verify using Matlab/Simulinks SimPower Toolbox and then implemented using 5KVA DVR experimental setup. Simulations and experimental results demonstrate the effective dynamic performance of the proposed configuration. Conclusion: The implimentation of the proposed DVR validate the capabilities in mitigating of voltage swells effectiveness.During voltage swells, the DVR injects an appropriate voltage to maintain the load voltage at its nominal value.

  6. Isomerically Pure Tetramethylrhodamine Voltage Reporters.

    Science.gov (United States)

    Deal, Parker E; Kulkarni, Rishikesh U; Al-Abdullatif, Sarah H; Miller, Evan W

    2016-07-27

    We present the design, synthesis, and application of a new family of fluorescent voltage indicators based on isomerically pure tetramethylrhodamines. These new Rhodamine Voltage Reporters, or RhoVRs, use photoinduced electron transfer (PeT) as a trigger for voltage sensing, display excitation and emission profiles in the green to orange region of the visible spectrum, demonstrate high sensitivity to membrane potential changes (up to 47% ΔF/F per 100 mV), and employ a tertiary amide derived from sarcosine, which aids in membrane localization and simultaneously simplifies the synthetic route to the voltage sensors. The most sensitive of the RhoVR dyes, RhoVR 1, features a methoxy-substituted diethylaniline donor and phenylenevinylene molecular wire at the 5'-position of the rhodamine aryl ring, exhibits the highest voltage sensitivity to date for red-shifted PeT-based voltage sensors, and is compatible with simultaneous imaging alongside green fluorescent protein-based indicators. The discoveries that sarcosine-based tertiary amides in the context of molecular-wire voltage indicators prevent dye internalization and 5'-substituted voltage indicators exhibit improved voltage sensitivity should be broadly applicable to other types of PeT-based voltage-sensitive fluorophores.

  7. Implementation of a Capacitor Less Low Dropout Voltage Regulator on Chip (SOC

    Directory of Open Access Journals (Sweden)

    Shailika Sharma

    2014-06-01

    Full Text Available — In this paper we have implemented a linear voltage low drop out regulator for efficient power management considering the fact in mind that voltage regulators provide a constant voltage supply to the circuits. We replace the common drain by common source pass element to improve efficiency and reduce the voltage drop across the device. This research paper includes the process to remove the external capacitor allowing for greater power system (soc application. A compensation scheme is presented that provides both a fast transient response and full range alternating current (ac stability from 0 to 50 mA load current even if the output load is as high as 100 pf. A 2.7-v capacitorless LDO voltage regulator with a power supply 3 v was designed with a dropout voltage of 300 mv.

  8. A Case Study Of Turkish Transmission System For VoltageDips

    DEFF Research Database (Denmark)

    Inan, E.; Alboyaci, B.; Bak, Claus Leth

    2009-01-01

    Power quality problems usually appear in the form of voltage sags, transients and harmonics. From these three broad categories of power quality problems, voltage dips account the most disturbances experienced by industrial customers. Voltage dips generally refer to instantaneous short...... analysis of voltage dip performance of the whole transmission system, is used to compare with results constructed fault statics from SIMPOW DIPS analysis program real data. SIMPOW DIPS software enables to calculate dip frequency for all busses and lines.......-duration voltage variations. The aim of this paper is to have an idea about voltage dip performance of Turkey Transmission System. Turkey's transmission system has 21 regions. For simulations, 2nd region, which includes Istanbul city's area is heavy loaded, is selected. For purposes of early warning and later...

  9. Design and Simulation Test of an Open D-Dot Voltage Sensor

    Directory of Open Access Journals (Sweden)

    Yunjie Bai

    2015-09-01

    Full Text Available Nowadays, sensor development focuses on miniaturization and non-contact measurement. According to the D-dot principle, a D-dot voltage sensor with a new structure was designed based on the differential D-dot sensor with a symmetrical structure, called an asymmetric open D-dot voltage sensor. It is easier to install. The electric field distribution of the sensor was analyzed through Ansoft Maxwell and an open D-dot voltage sensor was designed. This open D-voltage sensor is characteristic of accessible insulating strength and small electric field distortion. The steady and transient performance test under 10 kV-voltage reported satisfying performances of the designed open D-dot voltage sensor. It conforms to requirements for a smart grid measuring sensor in intelligence, miniaturization and facilitation.

  10. Analysis of Doubly-Fed Induction Generator Low Voltage Ride Through Based on Crowbar Protection%基于Crowbar保护的双馈感应发电机组的低电压研究

    Institute of Scientific and Technical Information of China (English)

    张靠社; 王媛; 胡德海

    2011-01-01

    The influence of the crowbar resistors on the electrical behavior of the Doubly -Fed Induction Generator (DFIG) during the grid voltage dips is analyzed in this paper. According to the mathematical modal of DFIG, the current expressions of stator and rotator are deduced under the condition of symmetrical fault of generator, also the appropriate crowbar by-pass resistor is given by the maximum rotor current. In PSCAD/EMTDC, the different crowbar by-pass resistors and their impacts on the system are simulated, then the correctness of the formula is verified, and the reasonable time for removal of crowbar is confirmed by the simulations.%分析了双馈感应发电机组在电网电压跌落时Crowbar阻值变化对电网的影响.根据双馈感应发电机( Doubly-Fed Induction Generator,DFIG)的数学模型,推导出在发电机机端发生对称故障时,定子、转子电流的表达式,通过故障期间的最大转子电流,给出Crowbar阻值估算值.在PSCAD/EMTDC软件中仿真分析不同的Crowbar阻值对系统的影响,验证公式推导的正确性,并通过仿真试验确定合理的Crowbar切除出时间.

  11. Role of the adsorption phenomenon on the ionic equilibrium distribution and on the transient effects in electrolytic cells.

    Science.gov (United States)

    Barbero, Giovanni; Freire, Fernando C M; Scalerandi, Marco; Alexe-Ionescu, Anca L

    2006-09-14

    We analyze the influence of the adsorption of ions at the interfaces on the transient phenomena occurring in an electrolytic cell submitted to a steplike external voltage. In the limit of small amplitude of the applied voltage, where the equation of the problem can be linearized, we obtain an analytical solution for the bulk and surface densities of ions and for the electrical potential. We also obtain, in this limit, the relaxation time for the transient phenomena.

  12. Cooperation of relay protection for grid-connected wind power with low-voltage ride-through capability%具有低电压穿越能力的风电接入电力系统继电保护的配合

    Institute of Scientific and Technical Information of China (English)

    张保会; 王进; 李光辉; 郝治国; 刘志远; 薄志谦

    2012-01-01

    具备低电压穿越能力的风电机组要求在一定的故障条件下不脱网,需要相关继电保护与之配合.详细分析了风电场送出线以外输电系统元件故障、风电场送出线故障、风电场内部电网故障以及风电机组本体故障情况下,输电系统保护以及风电场内部保护应有的配合关系.进一步分析了当前集中式接入风电场的继电保护配置,指出风电机组保护及变流器保护选择性不强,在风电场内部保护或系统保护动作切除故障之前,风电机组已经脱网,而且将风电网等同于单侧电源的配电网,没有考虑风电机组对短路的贡献.最后分析了单风电机组本体保护、风电场主变保护、风电场送出线保护需要进行的改进,以保证低电压穿越能力的发挥,并指出各保护需要注意的问题.%The wind turbine with low-voltage ride-through capability is required not to disconnect from grid under certain fault conditions, for which the relevant relay protections should cooperate with it. The cooperation between the relay protection of transmission system beyond the wind farm outgoing line and the relay protection of wind farm is analyzed for different faults of transmission system components, wind farm outgoing line,wind farm internal grid and wind turbine. The current configuration of relay protection for the wind farm centrally connected to power grid is analyzed and it is pointed out that,the selectivity of wind turbine protection and converter protection is not enough,which leads to the disconnection of wind farm from grid before the fault is removed by wind farm internal relay protection or system relay protection, and the current configuration regards the wind power as a distribution network with single source,which neglects the contribution of wind turbine to short-circuit fault. Improvements are proposed for the relay protections of wind turbine,main transformer and outgoing line to ensure the successful

  13. Design of protective inductors for HVDC transmission line within DC grid offshore wind farms

    DEFF Research Database (Denmark)

    Deng, Fujin; Chen, Zhe

    2013-01-01

    This paper presents fault analysis and protective inductors design for an offshore wind farm, where the power collection system in the wind farm and the power transmission link to the grid adopt high-voltage direct-current (HVDC) technology. This paper focuses on dealing with short-circuit faults...... in the HVDC link between the offshore station and the onshore station. The transient characteristics of the transmission system are analyzed in detail. The criteria of selecting protective inductors are proposed to effectively limit the short-circuit current and avoid the damage to the converters. A dc grid...... offshore wind farm is simulated, and the results demonstrate the effectiveness of the proposed protective inductors design....

  14. Settings Calculation and Comparison of Unbalanced Current Protection of High Voltage Filter Capacitor Banks Connected as H and∏Circuits%H和Π接线高压滤波电容器组不平衡电流保护的定值计算及比较

    Institute of Scientific and Technical Information of China (English)

    肖遥; 夏谷林; 张楠

    2014-01-01

    提出了高压滤波电容器组不平衡电流保护的整定原则,从两方面通过数学逻辑分析了H型和∏型接线高压电容器组及其不平衡电流保护的优缺点:其一是部分电容器单元失效后滤波器所允许的失谐度,其二是余下完好电容器单元所承受的端电压。文中给出了不同电容器单元短路方式下的不平衡保护定值计算公式和整定值,得出了∏型接线优于H型接线的结论。为改进∏型接线电容器组的差电流检测精度,给出了差值电流检测电路的改进方案。%The paper proposed principles for calculating the settings of unbalanced current protection of high voltage filter capacitor banks, and analyzed the merits and demerits of“H-type” and “∏-type” connections of capacitor banks from perspective of mathematic logic in two ways. Of which one involved the permitted detuning of the filters after failure of some units, the other involved the withstand voltages on remaining perfect capacitor units. The formulations were deducted to calculate the settings of unbalanced current protection in cases when short circuit of some capacitor units occurred. It is concluded that ∏-type connection is better than the H-type connection. To improve the accuracy for detecting differential currents of ∏-type connection, a new unbalanced current transformer and its application are suggested.

  15. Anomalous current transients in organic field-effect transistors

    Science.gov (United States)

    Sharma, A.; Mathijssen, S. G. J.; Cramer, T.; Kemerink, M.; de Leeuw, D. M.; Bobbert, P. A.

    2010-03-01

    Here we study the origin of the gate bias-stress effect in organic p-type transistors. Based on water-mediated exchange between holes in the semiconductor and protons in the gate dielectric, we predict anomalous current transients for a non-constant gate bias, while ensuring accumulation. When applying a strongly negative gate bias followed by a less negative bias a back-transfer of protons to holes and an increase of the current is expected. We verify this counterintuitive behavior experimentally and can quantitatively model the transients with the same parameters as used to describe the threshold voltage shift.

  16. Voltage Dependence of Supercapacitor Capacitance

    Directory of Open Access Journals (Sweden)

    Szewczyk Arkadiusz

    2016-09-01

    Full Text Available Electronic Double-Layer Capacitors (EDLC, called Supercapacitors (SC, are electronic devices that are capable to store a relatively high amount of energy in a small volume comparing to other types of capacitors. They are composed of an activated carbon layer and electrolyte solution. The charge is stored on electrodes, forming the Helmholtz layer, and in electrolyte. The capacitance of supercapacitor is voltage- dependent. We propose an experimental method, based on monitoring of charging and discharging a supercapacitor, which enables to evaluate the charge in an SC structure as well as the Capacitance-Voltage (C-V dependence. The measurement setup, method and experimental results of charging/discharging commercially available supercapacitors in various voltage and current conditions are presented. The total charge stored in an SC structure is proportional to the square of voltage at SC electrodes while the charge on electrodes increases linearly with the voltage on SC electrodes. The Helmholtz capacitance increases linearly with the voltage bias while a sublinear increase of total capacitance was found. The voltage on SC increases after the discharge of electrodes due to diffusion of charges from the electrolyte to the electrodes. We have found that the recovery voltage value is linearly proportional to the initial bias voltage value.

  17. Analysis of Mechanical Stresses Due to Voltage Dips in Fixed-Speed Wind Turbines

    DEFF Research Database (Denmark)

    Veluri, Badrinath; Santos-Martin, David; Jensen, Henrik Myhre

    2011-01-01

    drivetrain components. An electro-mechanical model is built to simulate the grid disturbances that easily excite the asynchronous generator poorly damped stator flux oscillations, which cause high transients of the generator electromagnetic torque. This article focuses in estimating the resulting significant...... stresses transients that may have a detrimental effect on the fatigue life of drivetrain system due to voltage dips. A rainflow cycle counting method for the stress history during the voltage dip event, analyses mean and amplitudes of the counted cycles, their occurrence moment and time of duration....

  18. A Simple Control Strategy Using Speedy Transient Response for Multiphase Buck Converter

    Science.gov (United States)

    Sasikala, K.; Ravikumar, D.; Rubini, B.

    2017-03-01

    The high performance of recent originating digital processors requires power supply for transient output, firm voltage regulation and high current. Industry has taken up interleaved multiphase synchronous buck converters for meeting such demands. Application of the voltage mode (ripple) hysteretic strategy to multiphase Voltage Regulator Units (VRU) would help satisfying many of the upcoming digital processors and IC’s powering demands. This arises from the use of the various advantages that can be obtained from this technique. This current division method is known for several benefits it provides: easy accessibility in application to all control methods, with freedom from the prime control technique in voltage regulation loop, absence of any necessity for current reference, better accuracy in current division of equal magnitude at almost every load conditions in standstill and transients. As against this, there are several challenges that involve distribution of multiple control signals, current sharing and sensitivity to noise, high speed comparators, hysteretic band accuracy and stable at large load transients. In addition, application of the current division technique presented was made to a multiphase voltage mode ripple controlled Buck Converter that produced a novel and easy control strategy having minimum output voltage ripples and speedy transient output.

  19. Transient lingual papillitis.

    Science.gov (United States)

    Kornerup, Ida M; Senye, Mireya; Peters, Edmund

    2016-01-01

    A case of recurrent, clinically innocuous, but painful papules involving the tongue dorsum of a 25-year-old man is presented. The lesions were interpreted to represent a transient lingual papillitis. This a poorly understood, but benign and self-limited condition involving the tongue fungiform papillae, which does not appear to be widely recognized.

  20. Transient Heat Conduction

    DEFF Research Database (Denmark)

    Rode, Carsten

    1998-01-01

    Analytical theory of transient heat conduction.Fourier's law. General heat conducation equation. Thermal diffusivity. Biot and Fourier numbers. Lumped analysis and time constant. Semi-infinite body: fixed surface temperature, convective heat transfer at the surface, or constant surface heat flux...

  1. Transient tachypnea - newborn

    Science.gov (United States)

    ... or reabsorbing it. The first few breaths a baby takes after delivery fill the lungs with air and help to ... goes away within 24 to 48 hours after delivery. In most cases, babies who have had transient tachypnea have no further ...

  2. On Detecting Transients

    CERN Document Server

    Belanger, G

    2013-01-01

    Transient phenomena are interesting and potentially highly revealing of details about the processes under observation and study that could otherwise go unnoticed. It is therefore important to maximise the sensitivity of the method used to identify such events. In this article we present a general procedure based on the use of the likelihood function for identifying transients that is particularly suited for real-time applications because it requires no grouping or pre-processing of the data. The method is optimal in the sense that all the information that is available in the data is used in the statistical decision making process, and is suitable for a wide range of applications. We here consider those most common in astrophysics which involve searching for transient sources, events or features in images, time series, energy spectra and power spectra, and demonstrate the use of the method in the cases of a transient in a time series or in a power spectrum. We derive a fit statistic that is ideal for fitting a...

  3. The LOFAR Transients Pipeline

    NARCIS (Netherlands)

    Swinbank, J.; Staley, T.; Molenaar, G.; Rol, E.; Rowlinson, A.; Scheers, L.H.A.; Spreeuw, H.; Bell, M.E.; Broderick, J.; Carbone, D.; Garsden, H.; Horst, A. van der; Law, C.J.; Wise, M.W.; Breton, R.P.; Cendes, Y.; Corbel, S.; Eisloeffel, J.; Falcke, H.; Fender, R.P.; Griessmeier, J.-M.; Hessels, J.W.T.; Stappers, B.W.; Stewart, A.; Wijers, R.A.M.J.; Wijnands, R.; Zarka, P.

    2015-01-01

    Current and future astronomical survey facilities provide a remarkably rich opportunity for transient astronomy, combining unprecedented fields of view with high sensitivity and the ability to access previously unexplored wavelength regimes. This is particularly true of LOFAR, a recently-commissione

  4. Isolated Fast High-Voltage Switching Circuit

    Science.gov (United States)

    Rizzi, Anthony

    1992-01-01

    Electrically isolated switching circuit supplies pulses at potentials up to 6.5 kV and currents up to 6.5 A, lasting as long as few microseconds. Turn-on time about 40 ns; turn-off time about 3 microseconds. Electrically isolated from control circuitry by means of fiber-optic signal coupling and isolated power supply. Electrical isolation protects both technician and equipment. This and similar circuits useful in such industrial and scientific applications as high-voltage, high-frequency test equipment; electrostatic-discharge test equipment; plasma-laboratory instrumentation; spark chambers; and electromagnetic-interference test equipment.

  5. Compressive Transient Imaging

    KAUST Repository

    Sun, Qilin

    2017-04-01

    High resolution transient/3D imaging technology is of high interest in both scientific research and commercial application. Nowadays, all of the transient imaging methods suffer from low resolution or time consuming mechanical scanning. We proposed a new method based on TCSPC and Compressive Sensing to achieve a high resolution transient imaging with a several seconds capturing process. Picosecond laser sends a serious of equal interval pulse while synchronized SPAD camera\\'s detecting gate window has a precise phase delay at each cycle. After capturing enough points, we are able to make up a whole signal. By inserting a DMD device into the system, we are able to modulate all the frames of data using binary random patterns to reconstruct a super resolution transient/3D image later. Because the low fill factor of SPAD sensor will make a compressive sensing scenario ill-conditioned, We designed and fabricated a diffractive microlens array. We proposed a new CS reconstruction algorithm which is able to denoise at the same time for the measurements suffering from Poisson noise. Instead of a single SPAD senor, we chose a SPAD array because it can drastically reduce the requirement for the number of measurements and its reconstruction time. Further more, it not easy to reconstruct a high resolution image with only one single sensor while for an array, it just needs to reconstruct small patches and a few measurements. In this thesis, we evaluated the reconstruction methods using both clean measurements and the version corrupted by Poisson noise. The results show how the integration over the layers influence the image quality and our algorithm works well while the measurements suffer from non-trival Poisson noise. It\\'s a breakthrough in the areas of both transient imaging and compressive sensing.

  6. High voltage trapping effects in GaN-based metal-insulator-semiconductor transistors

    Science.gov (United States)

    Meneghesso, Gaudenzio; Meneghini, Matteo; Silvestri, Riccardo; Vanmeerbeek, Piet; Moens, Peter; Zanoni, Enrico

    2016-01-01

    This paper presents an analysis of the high voltage trapping processes that take place in high-electron mobility transistors based on GaN, with a metal-insulator-semiconductor (MIS) structure. The study is based on combined pulsed and transient measurements, carried out with trapping voltages in the range from 50 to 500 V. The results indicate that: (i) dynamic Ron is maximum for trapping voltages between 200 and 300 V, and decreases for higher voltage levels; (ii) Ron-transient measurements reveal the presence of a dominant trap with activation energy Ea1 = 0.93 eV and of a second trap with activation energy equal to Ea2 = 0.61 eV; (iii) the deep level transient spectroscopy (DLTS) signal associated to trap Ea1 is completely suppressed for high trapping voltages (VDS = 500 V). The results are interpreted by considering that the trap Ea1 is located in the buffer, and originates from CN defects. The exposure to high drain voltages may favor the depletion of such traps, due to a field-assisted de-trapping process or to the presence of vertical leakage paths.

  7. Research on Capacitive Current Automatic Compensation on Low Voltage Power Grid Leakage Protection of Coal Mine%煤矿低压电网漏电容性电流自动补偿研究

    Institute of Scientific and Technical Information of China (English)

    徐国萍

    2014-01-01

    In neutral insulation low voltage power supply lines of coal mine,due to distributed capacitance exists, the leakage currents or personal electric shock currents exceed the limited safety value, and the changes of distributed capacitance easily cause the original system overcompensation or under compensation. The automatic compensation scheme of combining inductance the coarse adjustment with the fine adjustment is proposed on base of the minimum leakage currents closed loop control theory. Using single chip microcomputer control relay automatic switching magnetic amplifier is to achieve multi tap AC winding inductance step adjustment. The currents of magnetic amplifier DC winding are changed by single chip microcomputer control step motor to adjust potentiometer. The system attains stepless regulation of the inductance, so that the currents of distributed capacitance are completely compensated by the inductor currents of the magnetic amplifier. It has many advantages of fast compensation speed, high precision, short cycle, safety and easy operation during compensation process.%针对煤矿井下中性点绝缘低压供电线路中,由于电网对地分布电容的存在,使漏电电流或人身触电电流超过极限安全值,并且电网分布电容的多变容易引起原系统过补偿或欠补偿的情况,提出基于最小漏电电流闭环控制理论的电感量粗调和细调相融合的自动补偿方案,采用单片机控制继电器自动切换磁放大器多抽头交流绕组实现电感量有级调节,通过步进电机调节电位器改变磁放大器直流绕组的电流,实现电感量无级调节,从而使流过磁放大器的电感电流完全补偿电网分布电容的电流。该系统补偿速度快、精度高、调整周期短,补偿过程操作方便、安全。

  8. System and method for quench protection of a superconductor

    Science.gov (United States)

    Huang, Xianrui; Sivasubramaniam, Kiruba Haran; Bray, James William; Ryan, David Thomas

    2008-03-11

    A system and method for protecting a superconductor from a quench condition. A quench protection system is provided to protect the superconductor from damage due to a quench condition. The quench protection system comprises a voltage detector operable to detect voltage across the superconductor. The system also comprises a frequency filter coupled to the voltage detector. The frequency filter is operable to couple voltage signals to a control circuit that are representative of a rise in superconductor voltage caused by a quench condition and to block voltage signals that are not. The system is operable to detect whether a quench condition exists in the superconductor based on the voltage signal received via the frequency filter and to initiate a protective action in response.

  9. High Performance of Space Vector Modulation Direct Torque Control SVM-DTC Based on Amplitude Voltage and Stator Flux Angle

    Directory of Open Access Journals (Sweden)

    Hassan Farhan Rashag

    2013-04-01

    Full Text Available Various aspects related to controlling induction motor are investigated. Direct torque control is an original high performance control strategy in the field of AC drive. In this proposed method, the control system is based on Space Vector Modulation (SVM, amplitude of voltage in direct- quadrature reference frame (d-q reference and angle of stator flux. Amplitude of stator voltage is controlled by PI torque and PI flux controller. The stator flux angle is adjusted by rotor angular frequency and slip angular frequency. Then, the reference torque and the estimated torque is applied to the input of PI torque controller and the control quadrature axis voltage is determined. The control d-axis voltage is determined from the flux calculator. These q and d axis voltage are converted into amplitude voltage. By applying polar to Cartesian on amplitude voltage and stator flux angle, direct voltage and quadratures voltage are generated. The reference stator voltages in d-q are calculated based on forcing the stator voltage error to zero at next sampling period. By applying inverse park transformation on d-q voltages, the stator voltages in &alpha and &beta frame are generated and apply to SVM. From the output of SVM, the motor control signal is generated and the speed of the induction motor regulated toward the rated speed. The simulation Results have demonstrated exceptional performance in steady and transient states and shows that decrease of torque and flux ripples is achieved in a complete speed range.

  10. High-Voltage, Low-Power BNC Feedthrough Terminator

    Science.gov (United States)

    Bearden, Douglas

    2012-01-01

    This innovation is a high-voltage, lowpower BNC (Bayonet Neill-Concelman) feedthrough that enables the user to terminate an instrumentation cable properly while connected to a high voltage, without the use of a voltage divider. This feedthrough is low power, which will not load the source, and will properly terminate the instrumentation cable to the instrumentation, even if the cable impedance is not constant. The Space Shuttle Program had a requirement to measure voltage transients on the orbiter bus through the Ground Lightning Measurement System (GLMS). This measurement has a bandwidth requirement of 1 MHz. The GLMS voltage measurement is connected to the orbiter through a DC panel. The DC panel is connected to the bus through a nonuniform cable that is approximately 75 ft (approximately equal to 23 m) long. A 15-ft (approximately equal to 5-m), 50-ohm triaxial cable is connected between the DC panel and the digitizer. Based on calculations and simulations, cable resonances and reflections due to mismatched impedances of the cable connecting the orbiter bus and the digitizer causes the output not to reflect accurately what is on the bus. A voltage divider at the DC panel, and terminating the 50-ohm cable properly, would eliminate this issue. Due to implementation issues, an alternative design was needed to terminate the cable properly without the use of a voltage divider. Analysis shows how the cable resonances and reflections due to the mismatched impedances of the cable connecting the orbiter bus and the digitizer causes the output not to reflect accurately what is on the bus. After simulating a dampening circuit located at the digitizer, simulations were performed to show how the cable resonances were dampened and the accuracy was improved significantly. Test cables built to verify simulations were accurate. Since the dampening circuit is low power, it can be packaged in a BNC feedthrough.

  11. Requirement of ultra-high voltage GIS arrester to voltage gradient of metal-oxide varistor

    Institute of Scientific and Technical Information of China (English)

    HE JinLiang; HU Jun; MENG BoWen; ZHANG Bo; ZHU Bin; CHEN ShuiMing; ZENG Rong

    2009-01-01

    The surge arrestor with excellent protection characteristics would decrease the overvoltage level ap-plied on the power apparatus to reduce their insulation levels and manufacturing bottleneck. The ar-restor for the 1000-kV ultra-high voltage ac power transmission system is designed as tank-type structure. The field-circuit combination numerical method combining the three-dimensional finite ele-ment method with circuit is proposed to analyze the potential distribution of GIS arrester. By comparing several design schemes, the most effective method to improve the potential distribution along the varistor column is to increase the voltage gradient of the ZnO varistor. Synthesizing several influential factors, the suitable voltage gradient of ZnO varistor should be controlled to 435 V/mm, and the re-sulted nonuniform degree of the potential distribution along the varistor column inside the GIS arrestor would be controlled smaller than 10%. The result in this paper provides the fundamental technical in-dex for the study of the high voltage gradient ZnO varistors.

  12. Requirement of ultra-high voltage GIS arrester to voltage gradient of metal-oxide varistor

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The surge arrester with excellent protection characteristics would decrease the overvoltage level ap- plied on the power apparatus to reduce their insulation levels and manufacturing bottleneck. The arrester for the 1000-kV ultra-high voltage ac power transmission system is designed as tank-type structure. The field-circuit combination numerical method combining the three-dimensional finite element method with circuit is proposed to analyze the potential distribution of GIS arrester. By comparing several design schemes, the most effective method to improve the potential distribution along the varistor column is to increase the voltage gradient of the ZnO varistor. Synthesizing several influential factors, the suitable voltage gradient of ZnO varistor should be controlled to 435 V/mm, and the resulted nonuniform degree of the potential distribution along the varistor column inside the GIS arrester would be controlled smaller than 10%. The result in this paper provides the fundamental technical index for the study of the high voltage gradient ZnO varistors.

  13. Coherent Transient Systems Evaluation

    Science.gov (United States)

    1993-06-17

    manuscript is submitted for publication with the understanding that the United States Government is authorized to reproduce and distribute reprints...for governmental purposes. 1.0 Introduction The continuous optical correlator presented here is based on the phenomena of coherent transients, also...Gating the Continuous Processor Programming the continuous processor is accomplished by illuminati , n, the material with ,.’ modulated light pulses: a

  14. The Rapid Transient Surveyor

    Science.gov (United States)

    Baranec, Christoph; Tonry, John; Wright, Shelley; Tully, R. Brent; Lu, Jessica R.; Takamiya, Marianne Y.; Hunter, Lisa

    2016-01-01

    The next decade of astronomy will be dominated by large area surveys (see the detailed discussion in the Astro-2010 Decadal survey and NRC's recent OIR System Report). Ground-based optical transient surveys, e.g., LSST, ZTF and ATLAS and space-based exoplanet, supernova, and lensing surveys such as TESS and WFIRST will join the Gaia all-sky astrometric survey in producing a flood of data that will enable leaps in our understanding of the universe. There is a critical need for further characterization of these discoveries through high angular resolution images, deeper images, spectra, or observations at different cadences or periods than the main surveys. Such follow-up characterization must be well matched to the particular surveys, and requires sufficient additional observing resources and time to cover the extensive number of targets.We describe plans for the Rapid Transient Surveyor (RTS), a permanently mounted, rapid-response, high-cadence facility for follow-up characterization of transient objects on the U. of Hawai'i 2.2-m telescope on Maunakea. RTS will comprise an improved robotic laser adaptive optics system, based on the prototype Robo-AO system (formerly at the Palomar 1.5-m and now at the Kitt Peak 2.2-m telescope), with simultaneous visible and near-infrared imagers as well as a near-infrared integral field spectrograph (R~100, λ = 850 - 1830 nm, 0.15″ spaxels, 8.7″×6.0″ FoV). RTS will achieve an acuity of ~0.07″ in visible wavelengths and automated detection and characterization of astrophysical transients during a sustained observing campaign will yield the necessary statistics to precisely map dark matter in the local universe.

  15. Universal Voltage Conveyor and Current Conveyor in Fast Full-Wave Rectifier

    Directory of Open Access Journals (Sweden)

    Josef Burian

    2012-12-01

    Full Text Available This paper deals about the design of a fast voltage-mode full-wave rectifier, where universal voltage conveyor and second-generation current conveyor are used as active elements. Thanks to the active elements, the input and output impedance of the non-linear circuit is infinitely high respectively zero in theory. For the rectification only two diodes and three resistors are required as passive elements. The performance of the circuit is shown on experimental measurement results showing the dynamic range, time response, frequency dependent DC transient value and RMS error for different values of input voltage amplitudes.

  16. Techniques for detecting proximity to voltage collapse in AC/DC systems

    Energy Technology Data Exchange (ETDEWEB)

    Canizares, Claudio A. [Escuela Politecnica Nacional, Quito (Ecuador); Long, Willis F.; Alvarado, Fernando L.; DeMarco, CChristopher L. [Wisconsin Univ., Madison, WI (United States)

    1992-12-31

    This paper describes three different techniques to detect proximity to voltage collapse (saddle-node bifurcation) in AC/DC systems; namely, direct (point of collapse) methods, continuation methods, and transient energy function methods. These techniques are compared among them, and also against the voltage sensitivity factor method using a 173 bus ac/dc test system. Various operational conditions are considered for this test system, so that transfer capabilities between areas and the effects of HVDC links can be analysed from the point of view of voltage collapse. 24 refs., 7 figs.

  17. Effects of constant voltage on time evolution of propagating concentration polarization.

    Science.gov (United States)

    Zangle, Thomas A; Mani, Ali; Santiago, Juan G

    2010-04-15

    We extend the analytical theory of propagating concentration polarization (CP) to describe and compare the effects of constant-voltage versus constant-current conditions on the transient development of CP enrichment and depletion zones. We support our analysis with computational and experimental results. We find that at constant voltage, enrichment and depletion regions spread as t(1/2) as opposed to the previously observed t(1) scaling for constant current conditions. At low, constant voltages, the growth and propagation of CP zones can easily be misinterpreted as nonpropagating behavior.

  18. Modeling and Simulation of the Single Phase Voltage Source UPS Inverter With Fourth Order Output Filter

    Directory of Open Access Journals (Sweden)

    Javad Faiz

    2011-01-01

    Full Text Available A UPS inverter operates in wide load impedance ranges from resistive to capacitive or inductive load. At the same time, fast transient load response, good load regulation and good switching frequency suppression is required. The variation of the load impedance changes the filter transfer characteristic and thus the output voltage value. In this paper, an analysis and simulation of the single phase voltage source uninterruptible power supply (UPS with fourth order filter (multiple-filter in output inverter, based on the state space averaging and small signal linearization technique, is proposed. The simulation results show the high quality sinusoidal output voltage at different loads, with THD less than %5.

  19. Transient Astrophysics Probe

    Science.gov (United States)

    Camp, Jordan

    2017-08-01

    Transient Astrophysics Probe (TAP), selected by NASA for a funded Concept Study, is a wide-field high-energy transient mission proposed for flight starting in the late 2020s. TAP’s main science goals, called out as Frontier Discovery areas in the 2010 Decadal Survey, are time-domain astrophysics and counterparts of gravitational wave (GW) detections. The mission instruments include unique imaging soft X-ray optics that allow ~500 deg2 FoV in each of four separate modules; a high sensitivity, 1 deg2 FoV soft X-ray telescope based on single crystal silicon optics; a passively cooled, 1 deg2 FoV Infrared telescope with bandpass 0.6-3 micron; and a set of ~8 small NaI gamma-ray detectors. TAP will observe many events per year of X-ray transients related to compact objects, including tidal disruptions of stars, supernova shock breakouts, neutron star bursts and superbursts, and high redshift Gamma-Ray Bursts. Perhaps most exciting is TAP’s capability to observe X-ray and IR counterparts of GWs involving stellar mass black holes detected by LIGO/Virgo, and possibly X-ray counterparts of GWs from supermassive black holes, detected by LISA and Pulsar Timing Arrays.

  20. Distribution Grid Fault Location Applying Transient Zero-mode Current

    Directory of Open Access Journals (Sweden)

    Yunchuan Zhang

    2012-09-01

    Full Text Available To aim at the puzzles on faults location in distribution grids, the paper analyzed the distributing characteristics of transient zero-mode currents as the faults occurred, with the aid of correlation theory, a new fault circuit-selection and fault-location method was proposed based on transient zero model current for power distribution grid faults. The method is based on such a fact that the RMS was maximum of fault line transient zero-mode current, and the inner products between it and other line transient zero-mode current were less than zero, in addition, the transient zero-model currents at two sides of the fault point possessed opposite polarity and diverse waveform, and as well as small correlation coefficient closer to zero. In the end, the simulation results show that the proposed method on circuit-selection and fault-location for power distribution grids fault based on transient zero- mode current is correct and effective, and not affected by voltage epoch angle, and grounding resistance, and as well as neutral-point grounding modes.

  1. Non-Pilot Protection of the HVDC Grid

    Science.gov (United States)

    Badrkhani Ajaei, Firouz

    This thesis develops a non-pilot protection system for the next generation power transmission system, the High-Voltage Direct Current (HVDC) grid. The HVDC grid protection system is required to be (i) adequately fast to prevent damages and/or converter blocking and (ii) reliable to minimize the impacts of faults. This study is mainly focused on the Modular Multilevel Converter (MMC) -based HVDC grid since the MMC is considered as the building block of the future HVDC systems. The studies reported in this thesis include (i) developing an enhanced equivalent model of the MMC to enable accurate representation of its DC-side fault response, (ii) developing a realistic HVDC-AC test system that includes a five-terminal MMC-based HVDC grid embedded in a large interconnected AC network, (iii) investigating the transient response of the developed test system to AC-side and DC-side disturbances in order to determine the HVDC grid protection requirements, (iv) investigating the fault surge propagation in the HVDC grid to determine the impacts of the DC-side fault location on the measured signals at each relay location, (v) designing a protection algorithm that detects and locates DC-side faults reliably and sufficiently fast to prevent relay malfunction and unnecessary blocking of the converters, and (vi) performing hardware-in-the-loop tests on the designed relay to verify its potential to be implemented in hardware. The results of the off-line time domain transients studies in the PSCAD software platform and the real-time hardware-in-the-loop tests using an enhanced version of the RTDS platform indicate that the developed HVDC grid relay meets all technical requirements including speed, dependability, security, selectivity, and robustness. Moreover, the developed protection algorithm does not impose considerable computational burden on the hardware.

  2. Analysis on a Mal-operation of Differential Protection for Ultra-high Voltage Transformer and Its Countermeasure%一起特高压变压器的差动保护误动分析及防范措施

    Institute of Scientific and Technical Information of China (English)

    郑涛; 张婕; 高旭

    2011-01-01

    通过建立MATLAB仿真模型,分析了在特高压交流试验示范工程投运调试过程中出现的一起由于中压侧空投主变压器产生励磁涌流而导致调压变压器差动保护误动作的案例。针对特高压变压器结构上的特殊性,分析了合闸角、剩磁等因素对励磁涌流的影响,仿真复现了现场故障录波波形。针对调压变压器差动电流中二次谐波含量较低可能引起的误动,从2个方面提出了相应的解决方案:指出二次谐波涌流闭锁判据宜采用三取二闭锁方式,但在某些特殊情况下,依然可能失效,进而提出了利用二次谐波变化趋势来识别励磁涌流和故障电流的辅助判据,并对综合判据进行了仿真验证;分析了调压变压器容量对励磁涌流的影响,提出在条件允许的情况下,适当增加调压变压器容量来避免励磁涌流可能引起的误动,为提高调压变压器差动保护可靠性提供了新思路。%A simulation model based on MATLAB is developed to analyze the mal-operation of differential protection in voltage regulating transformer(VRT) in an experiment project of ultra-high voltage system,which is caused by inrush current during energizing of the transformer from medium-voltage side.According to particular structure of ultra-high voltage transformers,the influence of closure angle and residual magnetism,etc.on inrush current is analyzed and the waveform of field failure is resembled with simulation.In order to solve mal-operation caused by less second harmonic in differential current of VRT,lock criteria for second harmonic of inrush current should adopt two-out-of-three principle,but it may not valid in some situation.Furthermore,auxiliary criteria with second harmonic tendency is proposed for identifying inrush current or faulty current.Besides,it analyzes the influence of VRT capacity on inrush current and also suggests that suitably increasing the capacity of VRT should be considered in

  3. A Versatile Control Scheme For Dynamic Voltage Restorer To Limit Downstream Fault Currents

    Directory of Open Access Journals (Sweden)

    A.Nagendra

    2014-12-01

    Full Text Available The Dynamic Voltage Restorer (DVR is a custom power device utilized to counteract voltage sags. It injects controlled three-phase ac voltages in series with the supply voltage, subsequent to voltage sag, to enhance voltage quality by adjusting the voltage magnitude, wave shape, and phase angle. The DVR is conventionally bypassed during a downstream fault to prevent potential adverse impacts on the fault and to protect the DVR components against the fault current. This paper proposes an augmented control strategy for the DVR that provides:1 voltage-sag compensation under balanced and unbalanced conditions and 2 a fault current interruption (FCI function. This paper introduces and evaluates an auxiliary control strategy for downstream fault current interruption in a radial distribution line by means of a dynamic voltage restorer (DVR. The proposed controller supplements the voltage-sag compensation control of the DVR. It does not require phaselocked loop and independently controls the magnitude and phase angle of the injected voltage for each phase. Fast least error squares digital filters are used to estimate the magnitude and phase of the measured voltages and effectively reduce the impacts of noise, harmonics, and disturbances on the estimated phasor parameters, and this enables effective fault current interrupting even under arcing fault conditions. The performance of the DVR for fault current interruption is analyzed by using MATLAB/SIMULINK software.

  4. Voltage Sensors Monitor Harmful Static

    Science.gov (United States)

    2009-01-01

    A tiny sensor, small enough to be worn on clothing, now monitors voltage changes near sensitive instruments after being created to alert Agency workers to dangerous static buildup near fuel operations and avionics. San Diego s Quasar Federal Systems received a Small Business Innovation Research (SBIR) contract from Kennedy Space Center to develop its remote voltage sensor (RVS), a dime-sized electrometer designed to measure triboelectric changes in the environment. One of the unique qualities of the RVS is that it can detect static at greater distances than previous devices, measuring voltage changes from a few centimeters to a few meters away, due to its much-improved sensitivity.

  5. Modeling and analysis of single-event transients in charge pumps

    Institute of Scientific and Technical Information of China (English)

    Zhao Zhenyu; Li Junfeng; Zhang Minxuan; Li Shaoqing

    2009-01-01

    It has been shown that charge pumps (CPs) dominate single-event transient (SET) responses of phaselocked loops (PLLs). Using a pulse to represent a single event hit on CPs, the SET analysis model is established and the characteristics of SET generation and propagation in PLLs are revealed. An analysis of single event transients in PLLs demonstrates that the settling time of the voltage-controlled oscillators (VCOs) control voltage after a single event strike is strongly dependent on the peak control voltage deviation, the SET pulse width, and the settling time constant. And the peak control voltage disturbance decreases with the SET strength or the filter resistance. Furthermore, the analysis in the proposed PLL model is confirmed by simulation results using MATLAB and HSPICE,respectively.

  6. Design of transient light signal simulator based on FPGA

    Science.gov (United States)

    Kang, Jing; Chen, Rong-li; Wang, Hong

    2014-11-01

    A design scheme of transient light signal simulator based on Field Programmable gate Array (FPGA) was proposed in this paper. Based on the characteristics of transient light signals and measured feature points of optical intensity signals, a fitted curve was created in MATLAB. And then the wave data was stored in a programmed memory chip AT29C1024 by using SUPERPRO programmer. The control logic was realized inside one EP3C16 FPGA chip. Data readout, data stream cache and a constant current buck regulator for powering high-brightness LEDs were all controlled by FPGA. A 12-Bit multiplying CMOS digital-to-analog converter (DAC) DAC7545 and an amplifier OPA277 were used to convert digital signals to voltage signals. A voltage-controlled current source constituted by a NPN transistor and an operational amplifier controlled LED array diming to achieve simulation of transient light signal. LM3405A, 1A Constant Current Buck Regulator for Powering LEDs, was used to simulate strong background signal in space. Experimental results showed that the scheme as a transient light signal simulator can satisfy the requests of the design stably.

  7. An improved control method of power electronic converters in low voltage micro-grid

    DEFF Research Database (Denmark)

    Xiaofeng, Sun; Qingqiu, Lv; Yanjun, Tian

    2011-01-01

    control of the voltage and frequency deviation added to power references could achieve secondary regulation of the voltage and frequency. In this paper, the authors take the steady and transient transition of grid connecting and disconnecting of the micro-grid as an example, and demonstrate...... the place. The conventional droop control can perform the energy management in grid-connected mode, but may not so effective when micro-grid transferring between grid-connected mode and island mode. The paper analysis the micro-grid in different modes (Conventional droop control, Voltage reference...... compensation, Constant power output mode, Phase adjustment mode), and then proposes an overall control strategy for the micro-grid. The voltage reference compensation would minimize the steady-state error on the nominated operation point; the coordinate control of voltage and frequency with a feed forward...

  8. Optimized Controller Design for a 12-Pulse Voltage Source Converter Based HVDC System

    Science.gov (United States)

    Agarwal, Ruchi; Singh, Sanjeev

    2017-08-01

    The paper proposes an optimized controller design scheme for power quality improvement in 12-pulse voltage source converter based high voltage direct current system. The proposed scheme is hybrid combination of golden section search and successive linear search method. The paper aims at reduction of current sensor and optimization of controller. The voltage and current controller parameters are selected for optimization due to its impact on power quality. The proposed algorithm for controller optimizes the objective function which is composed of current harmonic distortion, power factor, and DC voltage ripples. The detailed designs and modeling of the complete system are discussed and its simulation is carried out in MATLAB-Simulink environment. The obtained results are presented to demonstrate the effectiveness of the proposed scheme under different transient conditions such as load perturbation, non-linear load condition, voltage sag condition, and tapped load fault under one phase open condition at both points-of-common coupling.

  9. Transient Performance of Electrical System in a Military Vehicle

    Directory of Open Access Journals (Sweden)

    Zang Kemao

    2004-01-01

    Full Text Available Electrical system in a military vehicle is a low voltage (28 V dc system which is an unsymmetrical and nonlinear system made up of silicon-rectifying generator and a battery in parallel. Studies have been carried out using numerical method to calculate its transient performance. State variable and coordinate transformation have been adopted to express the functional modes and its transfer law of the silicon-rectifying generator; the battery is expressed as a simplified equivalent circuit according to its characteristics during transient process: Consequently, the general mathematical model of electrical system in a military vehicle is presented. Examples of electrical systems in somemilitary vehicles have been taken to carry out the calculation of transient performance and the findings have been compared with the test results of an actual vehicle to show that the numerical method designed works.

  10. Energy reduction through voltage scaling and lightweight checking

    Science.gov (United States)

    Kadric, Edin

    As the semiconductor roadmap reaches smaller feature sizes and the end of Dennard Scaling, design goals change, and managing the power envelope often dominates delay minimization. Voltage scaling remains a powerful tool to reduce energy. We find that it results in about 60% geomean energy reduction on top of other common low-energy optimizations with 22nm CMOS technology. However, when voltage is reduced, it becomes easier for noise and particle strikes to upset a node, potentially causing Silent Data Corruption (SDC). The 60% energy reduction, therefore, comes with a significant drop in reliability. Duplication with checking and triple-modular redundancy are traditional approaches used to combat transient errors, but spending 2--3x the energy for redundant computation can diminish or reverse the benefits of voltage scaling. As an alternative, we explore the opportunity to use checking operations that are cheaper than the base computation they are guarding. We devise a classification system for applications and their lightweight checking characteristics. In particular, we identify and evaluate the effectiveness of lightweight checks in a broad set of common tasks in scientific computing and signal processing. We find that the lightweight checks cost only a fraction of the base computation (0-25%) and allow us to recover the reliability losses from voltage scaling. Overall, we show about 50% net energy reduction without compromising reliability compared to operation at the nominal voltage. We use FPGAs (Field-Programmable Gate Arrays) in our work, although the same ideas can be applied to different systems. On top of voltage scaling, we explore other common low-energy techniques for FPGAs: transmission gates, gate boosting, power gating, low-leakage (high-Vth) processes, and dual-V dd architectures. We do not scale voltage for memories, so lower voltages help us reduce logic and interconnect energy, but not memory energy. At lower voltages, memories become dominant

  11. Increasing the dynamic range of a transient recorder by using two analog-to-digital converters.

    Science.gov (United States)

    Beavis, R C

    1996-01-01

    This article describes an algorithm for recording transient voltages with enhanced dynamic range by using two 8-bit analog-to-digital converters (ADCs). The method requires each transient to be recorded in both ADCs, with different input voltage gains. The transients then are compared and combined to produce a single signal that has less digitization noise and greater dynamic range than signals recorded by either ADC alone and with no decrease in the sampling rate of the ADCs. The selection of operating parameters is considered and guidelines are established for the performance of this type of transient recorder. The system described here was built as a data acquisition device for a time-of-flight mass spectrometer; however, the algorithm could be applied to other types of ADC-based applications to extend their dynamic range.

  12. Digitally Controlled Point of Load Converter with Very Fast Transient Response

    DEFF Research Database (Denmark)

    Jakobsen, Lars Tønnes; Andersen, Michael Andreas E.

    2007-01-01

    voltage mode control and very fast transient response. The DiSOM modulator is combined with a digital PID compensator algorithm is implemented in a hybrid CPLD/FPGA and is used to control a synchronous Buck converter, which is used in typical Point of Load applications. The computational time is only...... three clock cycles from the time the A/D converter result is read by the control algorithm to the time the duty cycle command is updated. A typical POL converter has been built and the experimental results show that the transient response of the converter is very fast. The output voltage overshoot...

  13. Low Voltage Power Supply Incorporating Ceramic Transformer

    CERN Document Server

    Imori, M

    2007-01-01

    A low voltage power supply provides the regulated output voltage of 1 V from the supply voltage around 48 V. The low voltage power supply incorporates a ceramic transformer which utilizes piezoelectric effect to convert voltage. The ceramic transformer isolates the secondary from the primary, thus providing the ground isolation between the supply and the output voltages. The ceramic transformer takes the place of the conventional magnetic transformer. The ceramic transformer is constructed from a ceramic bar and does not include any magnetic material. So the low voltage power supply can operate under a magnetic field. The output voltage is stabilized by feedback. A feedback loop consists of an error amplifier, a voltage controlled oscillator and a driver circuit. The amplitude ratio of the transformer has dependence on the frequency, which is utilized to stabilize the output voltage. The low voltage power supply is investigated on the analogy of the high voltage power supply similarly incorporating the cerami...

  14. Frequency-dependent Transient Response of an Oscillating Electrically Actuated Droplet

    OpenAIRE

    Dash, S.; Kumari, N; Garimella, S V

    2012-01-01

    The transient response of a millimeter-sized sessile droplet under electrical actuation is experimentally investigated. Under dc actuation, the droplet spreading rate increases as the applied voltage is increased due to the higher electrical forces induced. At sufficiently high dc voltages, competition between the electrical actuation force, droplet inertia, the retarding surface tension force and contact line friction leads to droplet oscillation. The timescale for the droplet to attain its ...

  15. Effect of voltage sags on digitally controlled line connected switched-mode power supplies

    DEFF Research Database (Denmark)

    Török, Lajos; Munk-Nielsen, Stig

    2012-01-01

    Different voltage disorders like voltage fluctuations, sags, frequency variations may occur in the power supply networks due to different fault conditions. These deviations from normal operation affects in different ways the line connected devices. Standards were developed to protect and ensure i...

  16. Modular High Voltage Power Supply

    Energy Technology Data Exchange (ETDEWEB)

    Newell, Matthew R. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-05-18

    The goal of this project is to develop a modular high voltage power supply that will meet the needs of safeguards applications and provide a modular plug and play supply for use with standard electronic racks.

  17. Reliability criteria for voltage stability

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, Carson W.; Silverstein, Brian L. [Bonneville Power Administration, Portland, OR (United States)

    1994-12-31

    In face of costs pressures, there is need to allocate scare resources more effectively in order to achieve voltage stability. This naturally leads to development of probabilistic criteria and notions of rick management. In this paper it is presented a discussion about criteria for long term voltage stability limited to the case in which the time frames are topically several minutes. (author) 14 refs., 1 fig.

  18. A Voltage Quality Detection Method

    DEFF Research Database (Denmark)

    Chen, Zhe; Wei, Mu

    2008-01-01

    This paper presents a voltage quality detection method based on a phase-locked loop (PLL) technique. The technique can detect the voltage magnitude and phase angle of each individual phase under both normal and fault power system conditions. The proposed method has the potential to evaluate vario...... power quality disturbances, such as interruptions, sags and imbalances. Simulation studies have been performed. The effectiveness of the proposed method has been demonstrated under the simulated typical power disturbances....

  19. Method and apparatus for controlling LCL converters using asymmetric voltage cancellation techniques

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Hunter; Sealy, Kylee Devro; Sharp, Bryan Thomas; Gilchrist, Aaron

    2016-01-26

    A method and apparatus for LCL resonant converter control utilizing Asymmetric Voltage Cancellation is described. The methods to determine the optimal trajectory of the control variables are discussed. Practical implementations of sensing load parameters are included. Simple PI, PID and fuzzy logic controllers are included with AVC for achieving good transient response characteristics with output current regulation.

  20. Simulation of Voltage Dip Event in Fixed-Speed Wind Turbines: Fatigue Evaluation

    DEFF Research Database (Denmark)

    Veluri, Badrinath; Santos-Martin, David; Jensen, Henrik Myhre

    2012-01-01

    transients affecting the fatigue life of drivetrain system due to voltage dips. A rainflow cycle counting method was developed to evaluate the fatigue life of the mechanical system. The methodology analyses the stress history and estimates the mean and amplitudes of the counted cycles, and time of duration...

  1. Automatic Distance Monitoring System of Contact Connections in High Voltage Equipment of Electric Power Lines

    Directory of Open Access Journals (Sweden)

    M. Diachenko

    2013-01-01

    Full Text Available The developed automatic distance monitoring system of contact connections in high voltage equipment is based on technology of sensor circuits. The paper shows application of control methodology for contact connections in accordance with time rate of conductor temperature changes and contact connection and also direct measurement of transient resistance.

  2. A matter of quantum voltages.

    Science.gov (United States)

    Sellner, Bernhard; Kathmann, Shawn M

    2014-11-14

    Voltages inside matter are relevant to crystallization, materials science, biology, catalysis, and aqueous chemistry. The variation of voltages in matter can be measured by experiment, however, modern supercomputers allow the calculation of accurate quantum voltages with spatial resolutions of bulk systems well beyond what can currently be measured provided a sufficient level of theory is employed. Of particular interest is the Mean Inner Potential (V(o))--the spatial average of these quantum voltages referenced to the vacuum. Here we establish a protocol to reliably evaluate V(o) from quantum calculations. Voltages are very sensitive to the distribution of electrons and provide metrics to understand interactions in condensed phases. In the present study, we find excellent agreement with measurements of V(o) for vitrified water and salt crystals and demonstrate the impact of covalent and ionic bonding as well as intermolecular/atomic interactions. Certain aspects in this regard are highlighted making use of simple model systems/approximations. Furthermore, we predict V(o) as well as the fluctuations of these voltages in aqueous NaCl electrolytes and characterize the changes in their behavior as the resolution increases below the size of atoms.

  3. Harnessing quantum transport by transient chaos.

    Science.gov (United States)

    Yang, Rui; Huang, Liang; Lai, Ying-Cheng; Grebogi, Celso; Pecora, Louis M

    2013-03-01

    Chaos has long been recognized to be generally advantageous from the perspective of control. In particular, the infinite number of unstable periodic orbits embedded in a chaotic set and the intrinsically sensitive dependence on initial conditions imply that a chaotic system can be controlled to a desirable state by using small perturbations. Investigation of chaos control, however, was largely limited to nonlinear dynamical systems in the classical realm. In this paper, we show that chaos may be used to modulate or harness quantum mechanical systems. To be concrete, we focus on quantum transport through nanostructures, a problem of considerable interest in nanoscience, where a key feature is conductance fluctuations. We articulate and demonstrate that chaos, more specifically transient chaos, can be effective in modulating the conductance-fluctuation patterns. Experimentally, this can be achieved by applying an external gate voltage in a device of suitable geometry to generate classically inaccessible potential barriers. Adjusting the gate voltage allows the characteristics of the dynamical invariant set responsible for transient chaos to be varied in a desirable manner which, in turn, can induce continuous changes in the statistical characteristics of the quantum conductance-fluctuation pattern. To understand the physical mechanism of our scheme, we develop a theory based on analyzing the spectrum of the generalized non-Hermitian Hamiltonian that includes the effect of leads, or electronic waveguides, as self-energy terms. As the escape rate of the underlying non-attracting chaotic set is increased, the imaginary part of the complex eigenenergy becomes increasingly large so that pointer states are more difficult to form, making smoother the conductance-fluctuation pattern.

  4. Thermal transient anemometer

    Science.gov (United States)

    Bailey, James L.; Vresk, Josip

    1989-01-01

    A thermal transient anemometer having a thermocouple probe which is utilized to measure the change in temperature over a period of time to provide a measure of fluid flow velocity. The thermocouple probe is located in the fluid flow path and pulsed to heat or cool the probe. The cooling of the heated probe or the heating of the cooled probe from the fluid flow over a period of time is measured to determine the fluid flow velocity. The probe is desired to be locally heated near the tip to increase the efficiency of devices incorporating the probe.

  5. DSN Transient Observatory

    Science.gov (United States)

    Kuiper, T. B. H.; Monroe, R. M.; White, L. A.; Garcia Miro, C.; Levin, S. M.; Majid, W. A.; Soriano, M.

    2016-11-01

    The Deep Space Network (DSN) Transient Observatory (DTO) is a signal processing facility that can monitor up to four DSN downlink bands for astronomically interesting signals. The monitoring is done commensally with reception of deep space mission telemetry. The initial signal processing is done with two CASPERa ROACH1 boards, each handling one or two baseband signals. Each ROACH1 has a 10 GBe interface with a GPU-equipped Debian Linux workstation for additional processing. The initial science programs include monitoring Mars for electrostatic discharges, radio spectral lines, searches for fast radio bursts and pulsars and SETI. The facility will be available to the scientific community through a peer review process.

  6. VOLTAGE COMPENSATION USING ARTIFICIAL NEURAL NETWORK

    African Journals Online (AJOL)

    VOLTAGE COMPENSATION USING ARTIFICIAL NEURAL NETWORK: A CASE STUDY OF RUMUOLA DISTRIBUTION NETWORK. ... The artificial neural networks controller engaged to controlling the dynamic voltage ... Article Metrics.

  7. Design and Control of a Dynamic Voltage Restorer

    DEFF Research Database (Denmark)

    Nielsen, John Godsk

    . The advantages and disadvantages are treated by inserting the DVR in either the medium voltage distribution system or in the low voltage distribution system. Different topologies for a DVR are investigated on a converter and system level and the protection issues are treated. The design of a DVR is treated...... and two prototype DVRs are designed and specified. The first DVR is a low voltage DVR (LV-DVR) rated for 10 kVA for insertion in a 400 V low voltage grid and the second DVR is a high voltage DVR (HV-DVR) rated for 200 kVA for insertion in a 10 kV medium voltage distribution system. The control issues...... in order to aid the design process and perform simulations on a DVR. The simulations have been compared with measurements in order to be able to test the validity of the models. A good agreement have been found between simulations and measurements, which indicates that the system is sufficiently modelled...

  8. A Voltage Instability Predictor Using Local Area Measurements. VIP++

    Energy Technology Data Exchange (ETDEWEB)

    Warland, Leif

    2002-07-01

    There has been a pressure to operate power systems closer to their security limits. This has partially been due to financial imperatives following the deregulating of markets. Other practical difficulties have been obtaining authorization from regulatory bodies to build power plants and transmission lines. In this situation it is essential to monitor the system and to have tools that can predict the distance to the point of collapse (PoC). Much effort has been put into research of the phenomenon voltage collapse, and many approaches have been explored. Both dynamic and steady-state behavior have been studied thoroughly, though very few protection and control schemes have been implemented. In this dissertation the possibility of an index based on local area measurements have been explored. Voltage stability can be classified as either a transient or a long-term stability problem, and the index proposed in this dissertation is based on long-term dynamics. The VIP algorithm is a method that uses the maximum load ability of a transmission network as the PoC, thus by estimating a Thevenin equivalent the method can track the distance to the PoC as this occurs when the two impedances are equal in absolute value. The problem of the VIP algorithm is that it is based on a system with two equations and four unknowns, thus it is not observable. In order to make it observable the assumption of constant Thevenin equivalent between two sets of measurements is made. When this is not the case the method will estimate a Thevenin impedance of the same size as the measured load impedance, but with a negative sign. Changes in the Thevenin equivalent can be traced to both angle variation in a remote generator area or to variations in load impedances on nearby buses. The problem of angle variations can be mitigated by the selection of an appropriate reference bus. A method to solve the second problem, of variation in load admittances, has been proposed in this dissertation and given the

  9. Fire protection electrical engineering

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Jung Min

    2000-03-15

    This book concentrates of electricity with current, voltage, power, ohms law, access of resistance, electrolytic analysis and battery, static on frictional electricity and electrostatic induction, coulomb's law, Gauss's law, condenser and capacity, magmatism on magnetic field and magnetic line of force, magnetic circuit, electromagnetic force, electromotive current, basic alternating current circuit, circuit network analysis, three-phase current, non-sinusoidal alternating current, transient phenomena, semiconductor, electric measurement on measurement over resistance, power, power rate and circuit tester, automatic control on introduction, term, classification, foundation of sequence control, logic circuit and basic logic circuit and electric equipment.

  10. Transient regional osteoporosis

    Directory of Open Access Journals (Sweden)

    F. Trotta

    2011-09-01

    Full Text Available Transient osteoporosis of the hip and regional migratory osteoporosis are uncommon and probably underdiagnosed bone diseases characterized by pain and functional limitation mainly affecting weight-bearing joints of the lower limbs. These conditions are usually self-limiting and symptoms tend to abate within a few months without sequelae. Routine laboratory investigations are unremarkable. Middle aged men and women during the last months of pregnancy or in the immediate post-partum period are principally affected. Osteopenia with preservation of articular space and transitory edema of the bone marrow provided by magnetic resonance imaging are common to these two conditions, so they are also known by the term regional transitory osteoporosis. The appearance of bone marrow edema is not specific to regional transitory osteoporosis but can be observed in several diseases, i.e. trauma, reflex sympathetic dystrophy, avascular osteonecrosis, infections, tumors from which it must be differentiated. The etiology of this condition is unknown. Pathogenesis is still debated in particular the relationship with reflex sympathetic dystrophy, with which regional transitory osteoporosis is often identified. The purpose of the present review is to remark on the relationship between transient osteoporosis of the hip and regional migratory osteoporosis with particular attention to the bone marrow edema pattern and relative differential diagnosis.

  11. Transient Black Hole Binaries

    CERN Document Server

    Belloni, T M

    2016-01-01

    The last two decades have seen a great improvement in our understand- ing of the complex phenomenology observed in transient black-hole binary systems, especially thanks to the activity of the Rossi X-Ray Timing Explorer satellite, com- plemented by observations from many other X-ray observatories and ground-based radio, optical and infrared facilities. Accretion alone cannot describe accurately the intricate behavior associated with black-hole transients and it is now clear that the role played by different kinds of (often massive) outflows seen at different phases of the outburst evolution of these systems is as fundamental as the one played by the accretion process itself. The spectral-timing states originally identified in the X-rays and fundamentally based on the observed effect of accretion, have acquired new importance as they now allow to describe within a coherent picture the phenomenology observed at other wave- length, where the effects of ejection processes are most evident. With a particular focu...

  12. Characterizing Nanoscale Transient Communication.

    Science.gov (United States)

    Chen, Yifan; Anwar, Putri Santi; Huang, Limin; Asvial, Muhamad

    2016-04-01

    We consider the novel paradigm of nanoscale transient communication (NTC), where certain components of the small-scale communication link are physically transient. As such, the transmitter and the receiver may change their properties over a prescribed lifespan due to their time-varying structures. The NTC systems may find important applications in the biomedical, environmental, and military fields, where system degradability allows for benign integration into life and environment. In this paper, we analyze the NTC systems from the channel-modeling and capacity-analysis perspectives and focus on the stochastically meaningful slow transience scenario, where the coherence time of degeneration Td is much longer than the coding delay Tc. We first develop novel and parsimonious models to characterize the NTC channels, where three types of physical layers are considered: electromagnetism-based terahertz (THz) communication, diffusion-based molecular communication (DMC), and nanobots-assisted touchable communication (TouchCom). We then revisit the classical performance measure of ϵ-outage channel capacity and take a fresh look at its formulations in the NTC context. Next, we present the notion of capacity degeneration profile (CDP), which describes the reduction of channel capacity with respect to the degeneration time. Finally, we provide numerical examples to demonstrate the features of CDP. To the best of our knowledge, the current work represents a first attempt to systematically evaluate the quality of nanoscale communication systems deteriorating with time.

  13. Strongly nonlinear dynamics of electrolytes in large ac voltages

    CERN Document Server

    Olesen, Laurits H; Bruus, Henrik

    2009-01-01

    We study the response of a model micro-electrochemical cell to a large ac voltage of frequency comparable to the inverse cell relaxation time. To bring out the basic physics, we consider the simplest possible model of a symmetric binary electrolyte confined between parallel-plate blocking electrodes, ignoring any transverse instability or fluid flow. We analyze the resulting one-dimensional problem by matched asymptotic expansions in the limit of thin double layers and extend previous work into the strongly nonlinear regime, which is characterized by two novel features - significant salt depletion in the electrolyte near the electrodes and, at very large voltage, the breakdown of the quasi-equilibrium structure of the double layers. The former leads to the prediction of "ac capacitive desalination", since there is a time-averaged transfer of salt from the bulk to the double layers, via oscillating diffusion layers. The latter is associated with transient diffusion limitation, which drives the formation and co...

  14. Voltage- and calcium-dependent motility of saccular hair bundles

    Science.gov (United States)

    Quiñones, Patricia M.; Meenderink, Sebastiaan W. F.; Bozovic, Dolores

    2015-12-01

    Active bundle motility, which is hypothesized to supply feedback for mechanical amplification of signals, is thought to enhance sensitivity and sharpen tuning in vestibular and auditory organs. To study active hair bundle motility, we combined high-speed camera recordings of bullfrog sacculi, which were mounted in a two-compartment chamber, and voltage-clamp of the hair cell membrane potential. Using this paradigm, we measured three types of bundle motions: 1) spontaneous oscillations which can be analyzed to measure the physiological operating range of the transduction channel; 2) a sustained quasi-static movement of the bundle that depends on membrane potential; and 3) a fast, transient and asymmetric movement that resets the bundle position and depends on changes in the membrane potential. These data support a role for both calcium and voltage in the transduction-channel function.

  15. Transient Performance Improvement Circuit (TPIC)s for DC-DC converter applications

    Science.gov (United States)

    Lim, Sungkeun

    Gordon Moore famously predicted the exponential increase in transistor integration and computing power that has been witnessed in recent decades [1]. In the near future, it is expected that more than one billion transistors will be integrated per chip, and advanced microprocessors will require clock speeds in excess of several GHz. The increasing number of transistors and high clock speeds will necessitate the consumption of more power. By 2014, it is expected that the maximum power consumption of the microprocessor will reach approximately 150W, and the maximum load current will be around 150A. Today's trend in power and thermal management is to reduce supply voltage as low as possible to reduce delivered power. It is anticipated that the Intel cores will operate on 0.8V of supply voltage by 2014 [2]. A significant challenge in Voltage Regulator Module (VRM) development for next generation microprocessors is to regulate the supply voltage within a certain tolerance band during high slew rate load transitions, since the required supply voltage tolerance band will be much narrower than the current requirement. If VR output impedance is maintained at a constant value from DC to high frequency, large output voltage spikes can be avoided during load cur- rent transients. Based on this, the Adaptive Voltage Position (AVP) concept was developed to achieve constant VR output impedance to improve transient response performance [3]. However, the VR output impedance can not be made constant over the entire frequency range with AVP design, because the AVP design makes the VR output impedance constant only at low frequencies. To make the output impedance constant at high frequencies, many bulk capacitors and ceramic capacitors are required. The tight supply voltage tolerance for the next generation of microprocessors during high slew rate load transitions requires fast transient response power supplies. A VRM can not follow the high slew rate load current transients, because

  16. Calculating transient rates from surveys

    CERN Document Server

    Carbone, Dario; Wijers, Ralph A M J; Rowlinson, Antonia

    2016-01-01

    We have developed a method to determine the transient surface density and transient rate for any given survey, using Monte-Carlo simulations. This method allows us to determine the transient rate as a function of both the flux and the duration of the transients in the whole flux-duration plane rather than one or a few points as currently available methods do. It is applicable to every survey strategy that is monitoring the same part of the sky, regardless the instrument or wavelength of the survey, or the target sources. We have simulated both top-hat and Fast Rise Exponential Decay light curves, highlighting how the shape of the light curve might affect the detectability of transients. Another application for this method is to estimate the number of transients of a given kind that are expected to be detected by a survey, provided that their rate is known.

  17. Calculating transient rates from surveys

    Science.gov (United States)

    Carbone, D.; van der Horst, A. J.; Wijers, R. A. M. J.; Rowlinson, A.

    2017-03-01

    We have developed a method to determine the transient surface density and transient rate for any given survey, using Monte Carlo simulations. This method allows us to determine the transient rate as a function of both the flux and the duration of the transients in the whole flux-duration plane rather than one or a few points as currently available methods do. It is applicable to every survey strategy that is monitoring the same part of the sky, regardless the instrument or wavelength of the survey, or the target sources. We have simulated both top-hat and Fast Rise Exponential Decay light curves, highlighting how the shape of the light curve might affect the detectability of transients. Another application for this method is to estimate the number of transients of a given kind that are expected to be detected by a survey, provided that their rate is known.

  18. Unbalanced Voltage Compensation in Low Voltage Residential AC Grids

    DEFF Research Database (Denmark)

    Trintis, Ionut; Douglass, Philip; Munk-Nielsen, Stig

    2016-01-01

    This paper describes the design and test of a control algorithm for active front-end rectifiers that draw power from a residential AC grid to feed heat pump loads. The control algorithm is able to control the phase to neutral or phase to phase RMS voltages at the point of common coupling....... The voltage control was evaluated with either active or reactive independent phase load current control. The control performance in field operation in a residential grid situated in Bornholm, Denmark was investigated for different use cases....

  19. The Zwicky Transient Facility

    Science.gov (United States)

    Kulkarni, Shrinivas R.

    2016-01-01

    The Zwicky Transient Facility (ZTF) has been designed with a singular focus: a systematic exploration of the night sky at a magnitude level well suited for spectral classification and follow up with the existing class of 4-m to 10-m class telescopes. ZTF is the successor to the Palomar Transient Factory (PTF). The discovery engine for ZTF is a 47 square degree camera (realized through 16 e2V monolithic CCDs) that fills the entire focal plane of the 48-inch Oschin telescope of the Palomar Observatory. Single 30-s epoch sensitivity is about 20.5 in g and R bands. The Infarared Processing & Analysis Center (IPAC) is the data center for ZTF. ZTF is a public-private partnership with equal contributions from a consortium of world-wide partners and an NSF MSIP grant. Forty percent of ZTF time is set aside for two major community surveys: a 3-day cadence survey of high latitudes (to mimic LSST) and a time domain survey of the entire Northern Galactic plane. We expect first light in February 2017 and begin a 3-year survey starting summer of 2017. The first year will be spent on building up deep reference images of the sky (a must for transient surveys). During the second year IPAC will deliver near archival quality photometric products within 12 hours of observations. By comparison to reference images photometric alerts will be sent out. Year 3 will see the near real-time release of image differencing products. A Community Science Advisory Committee (CSAC), chaired by S. Ridgway (NOAO), has been set up to both advise the PI and to ensure that the US community's interests are well served. Astronomers interested in getting a head start on ZTF may wish to peruse the data releases from PTF. Young people (or young at heart) may wish to attend the annual summer school on PTF/ZTF (August, Caltech campus). The Principal Investigator (PI) for the project is S. Kulkarni and the Project Scientist is Eric Bellm.For further details please consult http://www.ptf.caltech.edu/ztf

  20. Automated Voltage Control in LHCb

    CERN Document Server

    Granado Cardoso, L; Jacobsson, R

    2011-01-01

    LHCb is one of the 4 LHC experiments. In order to ensure the safety of the detector and to maximize efficiency, LHCb needs to coordinate its own operations, in particular the voltage configuration of the different subdetectors, according to the accelerator status. A control software has been developed for this purpose, based on the Finite State Machine toolkit and the SCADA system used for control throughout LHCb (and the other LHC experiments). This software permits to efficiently drive both the Low Voltage (LV) and High Voltage (HV) systems of the 10 different sub-detectors that constitute LHCb, setting each sub-system to the required voltage (easily configurable at run-time) based on the accelerator state. The control software is also responsible for monitoring the state of the Sub-detector voltages and adding it to the event data in the form of status-bits. Safe and yet flexible operation of the LHCb detector has been obtained and automatic actions, triggered by the state changes of the ...

  1. The joy of transient chaos

    Energy Technology Data Exchange (ETDEWEB)

    Tél, Tamás [Institute for Theoretical Physics, Eötvös University, and MTA-ELTE Theoretical Physics Research Group, Pázmány P. s. 1/A, Budapest H-1117 (Hungary)

    2015-09-15

    We intend to show that transient chaos is a very appealing, but still not widely appreciated, subfield of nonlinear dynamics. Besides flashing its basic properties and giving a brief overview of the many applications, a few recent transient-chaos-related subjects are introduced in some detail. These include the dynamics of decision making, dispersion, and sedimentation of volcanic ash, doubly transient chaos of undriven autonomous mechanical systems, and a dynamical systems approach to energy absorption or explosion.

  2. Dependence of transient performance on potential distribution in a static induction thyristor channel

    Institute of Scientific and Technical Information of China (English)

    Liu Chunjuan; Liu Su; Bai Yajie

    2012-01-01

    The impact of potential barrier distribution on the transient performance of a static induction thyristor (SITH) in a channel determined by geometrical parameters and applied bias voltage is studied theoretically and experimentally.The analytical expressions of potential barrier height and the Ⅰ-Ⅴ characteristics of the SITH are also derived.The main factors that influence the transient performance of the SITH between the blocking and conducting states,as well as the mechanism underlying the transient process,is thoroughly investigated.This is useful in designing,fabricating,optimizing and applying SITHs properly.

  3. A transient energy function for power systems including the induction motor model

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A construction method for power system transient energy function is studied in the paper, which is simple and universal, and can unify the forms of some current energy functions. A transient energy function including the induction motor model is derived using the method. The unintegrable term is dealt with to get an approximate energy function. Simulations in a 3-bus system and in the WSCC 4-generator system verify the validity of the proposed energy function. The function can be applied to direct transient stability analysis of multi-machine large power systems and provides a tool for analysis of the interaction between the generator angle stability and the load voltage stability.

  4. Transient osteoporosis of pregnancy.

    Science.gov (United States)

    Maliha, George; Morgan, Jordan; Vrahas, Mark

    2012-08-01

    Transient osteoporosis of pregnancy (TOP) is a rare yet perhaps under-reported condition that has affected otherwise healthy pregnancies throughout the world. The condition presents suddenly in the third trimester of a usually uneventful pregnancy and progressively immobilizes the mother. Radiographic studies detect drastic loss of bone mass, elevated rates of turnover in the bone, and oedema in the affected portion. Weakness of the bone can lead to fractures during delivery and other complications for the mother. Then, within weeks of labour, symptoms and radiological findings resolve. Aetiology is currently unknown, although neural, vascular, haematological, endocrine, nutrient-deficiency, and other etiologies have been proposed. Several treatments have also been explored, including simple bed rest, steroids, bisphosphonates, calcitonin, induced termination of pregnancy, and surgical intervention. The orthopedist plays an essential role in monitoring the condition (and potential complications) as well as ensuring satisfactory outcomes for both the mother and newborn.

  5. Transient Detection and Classification

    CERN Document Server

    Becker, Andrew C

    2008-01-01

    I provide an incomplete inventory of the astronomical variability that will be found by next-generation time-domain astronomical surveys. These phenomena span the distance range from near-Earth satellites to the farthest Gamma Ray Bursts. The surveys that detect these transients will issue alerts to the greater astronomical community; this decision process must be extremely robust to avoid a slew of ``false'' alerts, and to maintain the community's trust in the surveys. I review the functionality required of both the surveys and the telescope networks that will be following them up, and the role of VOEvents in this process. Finally, I offer some ideas about object and event classification, which will be explored more thoroughly by other articles in these proceedings.

  6. Stability of Ignition Transients

    Directory of Open Access Journals (Sweden)

    V.E. Zarko

    1991-07-01

    Full Text Available The problem of ignition stability arises in the case of the action of intense external heat stimuli when, resulting from the cut-off of solid substance heating, momentary ignition is followed by extinction. Physical pattern of solid propellant ignition is considered and ignition criteria available in the literature are discussed. It is shown that the above mentioned problem amounts to transient burning at a given arbitrary temperature distribution in the condensed phase. A brief survey of published data on experimental and theoretical studies on ignition stability is offered. The comparison between theory and experiment is shown to prove qualitatively the efficiency of the phenomenological approach in the theory. However, the methods of mathematical simulation as well as those of experimental studying of ignition phenomenon, especially at high fluxes, need to be improved.

  7. Transient heliosheath modulation

    Science.gov (United States)

    Quenby, J. J.; Webber, W. R.

    2015-10-01

    Voyager 1 has explored the solar wind-interstellar medium interaction region between the terminal shock and heliopause, following the intensity distribution of Galactic cosmic ray protons above 200 MeV energy. Before this component reached the expected galactic flux level at 121.7 au from the Sun, four episodes of rapid intensity change occurred with a behaviour similar to that found in Forbush Decreases in the inner Solar system, rather than that expected from a mechanism related to models for the long-term modulation found closer to the Sun. Because the mean solar wind flow is both expected and observed to be perpendicular to the radial direction close to the heliopause, an explanation is suggested in terms of transient radial flows related to possible heliopause boundary flapping. It is necessary that the radial flows are of the order either of the sound speed found for conditions downstream of the terminal shock or of the fluctuations found near the boundary by the Voyager 1 Low Energy Charged Particle detector and that the relevant cosmic ray diffusion perpendicular to the mean field is controlled by `slab' fluctuations accounting for about 20 per cent of the total power in the field variance. However, additional radial drift motion related to possible north to south gradients in the magnetic field may allow the inclusion of some diffusion according to the predictions of a theory based upon the presence of 2D turbulence. The required field gradients may arise due to field variation in the field carried by solar plasma flow deflected away from the solar equatorial plane. Modulation amounting to a total 30 per cent drop in galactic intensity requires explanation by a combination of transient effects.

  8. Development of a New Cascade Voltage-Doubler for Voltage Multiplication

    OpenAIRE

    Arash Toudeshki; Norman Mariun; Hashim Hizam; Noor Izzri Abdul Wahab

    2014-01-01

    For more than eight decades, cascade voltage-doubler circuits are used as a method to produce DC output voltage higher than the input voltage. In this paper, the topological developments of cascade voltage-doublers are reviewed. A new circuit configuration for cascade voltage-doubler is presented. This circuit can produce a higher value of the DC output voltage and better output quality compared to the conventional cascade voltage-doubler circuits, with the same number of stages.

  9. Low-Energy Real-Time OS Using Voltage Scheduling Algorithm for Variable Voltage Processors

    OpenAIRE

    Okuma, Takanori; Yasuura, Hiroto

    2001-01-01

    This paper presents a real-time OS based on $ mu $ITRON using proposed voltage scheduling algorithm for variable voltage processors which can vary supply voltage dynamically. The proposed voltage scheduling algorithms assign voltage level for each task dynamically in order to minimize energy consumption under timing constraints. Using the presented real-time OS, running tasks with low supply voltage leads to drastic energy reduction. In addition, the presented voltage scheduling algorithm is ...

  10. Simple buck/boost voltage regulator

    Science.gov (United States)

    Paulkovich, J.; Rodriguez, G. E.

    1980-01-01

    Circuit corrects low or high supply voltage, produces regulated output voltage. Circuit has fewer components because inductory/transformer combination and pulse-width modulator serve double duty. Regulator handles input voltage variation from as low as one half output voltage to as high as input transistor rating. Solar arrays, fuel cells, and thermionic generators might use this regulator.

  11. 30 CFR 18.47 - Voltage limitation.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Voltage limitation. 18.47 Section 18.47 Mineral... § 18.47 Voltage limitation. (a) A tool or switch held in the operator's hand or supported against his... particular voltage(s) are provided in the design and construction of the equipment, its wiring,...

  12. Commercial Building Motor Protection Response Report

    Energy Technology Data Exchange (ETDEWEB)

    James, Daniel P. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Kueck, John [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-06-17

    When voltages recover, motors may immediately reenergize and reaccelerate, or delay for a few minutes, or stay stalled. The estimated motor response is given for both the voltage sag magnitude and voltage sag duration. These response estimates are based on experience and available test data. Good data is available for voltage sag response for many components such as relays and contactors, but little data is available for both voltage sag and recovery response. The tables in Appendix A include data from recent voltage sag and recovery tests performed by SCE and BPA on air conditioners and energy management systems. The response of the motor can vary greatly depending on the type of protection and control. The time duration for the voltage sag consists of those times that are of interest for bulk power system modelers.

  13. Portable High Voltage Impulse Generator

    Directory of Open Access Journals (Sweden)

    S. Gómez

    2011-07-01

    Full Text Available This paper presents a portable high voltage impulse generator which was designed and built with insulation up to 20 kV. This design was based on previous work in which simulation software for standard waves was developed. Commercial components and low-cost components were used in this work; however, these particular elements are not generally used for high voltage applications. The impulse generators used in industry and laboratories are usually expensive; they are built to withstand extra high voltage and they are big, making them impossible to transport. The proposed generator is portable, thereby allowing tests to be made on devices that cannot be moved from their location. The results obtained with the proposed impulse generator were satisfactory in terms of time and waveforms compared to other commercial impulse generators and the standard impulse wave simulator.

  14. Voltage Dependence of Conformational Dynamics and Subconducting States of VDAC-1.

    Science.gov (United States)

    Briones, Rodolfo; Weichbrodt, Conrad; Paltrinieri, Licia; Mey, Ingo; Villinger, Saskia; Giller, Karin; Lange, Adam; Zweckstetter, Markus; Griesinger, Christian; Becker, Stefan; Steinem, Claudia; de Groot, Bert L

    2016-09-20

    The voltage-dependent anion channel 1 (VDAC-1) is an important protein of the outer mitochondrial membrane that transports energy metabolites and is involved in apoptosis. The available structures of VDAC proteins show a wide β-stranded barrel pore, with its N-terminal α-helix (N-α) bound to its interior. Electrophysiology experiments revealed that voltage, its polarity, and membrane composition modulate VDAC currents. Experiments with VDAC-1 mutants identified amino acids that regulate the gating process. However, the mechanisms for how these factors regulate VDAC-1, and which changes they trigger in the channel, are still unknown. In this study, molecular dynamics simulations and single-channel experiments of VDAC-1 show agreement for the current-voltage relationships of an "open" channel and they also show several subconducting transient states that are more cation selective in the simulations. We observed voltage-dependent asymmetric distortions of the VDAC-1 barrel and the displacement of particular charged amino acids. We constructed conformational models of the protein voltage response and the pore changes that consistently explain the protein conformations observed at opposite voltage polarities, either in phosphatidylethanolamine or phosphatidylcholine membranes. The submicrosecond VDAC-1 voltage response shows intrinsic structural changes that explain the role of key gating amino acids and support some of the current gating hypotheses. These voltage-dependent protein changes include asymmetric barrel distortion, its interaction with the membrane, and significant displacement of N-α amino acids.

  15. Transient Go: A Mobile App for Transient Astronomy Outreach

    Science.gov (United States)

    Crichton, D.; Mahabal, A.; Djorgovski, S. G.; Drake, A.; Early, J.; Ivezic, Z.; Jacoby, S.; Kanbur, S.

    2016-12-01

    Augmented Reality (AR) is set to revolutionize human interaction with the real world as demonstrated by the phenomenal success of `Pokemon Go'. That very technology can be used to rekindle the interest in science at the school level. We are in the process of developing a prototype app based on sky maps that will use AR to introduce different classes of astronomical transients to students as they are discovered i.e. in real-time. This will involve transient streams from surveys such as the Catalina Real-time Transient Survey (CRTS) today and the Large Synoptic Survey Telescope (LSST) in the near future. The transient streams will be combined with archival and latest image cut-outs and other auxiliary data as well as historical and statistical perspectives on each of the transient types being served. Such an app could easily be adapted to work with various NASA missions and NSF projects to enrich the student experience.

  16. The high voltage homopolar generator

    Science.gov (United States)

    Price, J. H.; Gully, J. H.; Driga, M. D.

    1986-11-01

    System and component design features of proposed high voltage homopolar generator (HVHPG) are described. The system is to have an open circuit voltage of 500 V, a peak output current of 500 kA, 3.25 MJ of stored inertial energy and possess an average magnetic-flux density of 5 T. Stator assembly components are discussed, including the stator, mount structure, hydrostatic bearings, main and motoring brushgears and rotor. Planned operational procedures such as monitoring the rotor to full speed and operation with a superconducting field coil are delineated.

  17. Series-connected substrate-integrated lead-carbon hybrid ultracapacitors with voltage-management circuit

    Indian Academy of Sciences (India)

    A Banerjee; R Srinivasan; A K Shukla

    2015-02-01

    Cell voltage for a fully charged-substrate-integrated lead-carbon hybrid ultracapacitor is about 2.3 V. Therefore, for applications requiring higher DC voltage, several of these ultracapacitors need to be connected in series. However, voltage distribution across each series-connected ultracapacitor tends to be uneven due to tolerance in capacitance and parasitic parallel-resistance values. Accordingly, voltage-management circuit is required to protect constituent ultracapacitors from exceeding their rated voltage. In this study, the design and characterization of the substrate-integrated lead-carbon hybrid ultracapacitor with co-located terminals is discussed. Voltage-management circuit for the ultracapacitor is presented, and its effectiveness is validated experimentally.

  18. Resilient architecture design for voltage variation

    CERN Document Server

    Reddi, Vijay Janapa

    2013-01-01

    Shrinking feature size and diminishing supply voltage are making circuits sensitive to supply voltage fluctuations within the microprocessor, caused by normal workload activity changes. If left unattended, voltage fluctuations can lead to timing violations or even transistor lifetime issues that degrade processor robustness. Mechanisms that learn to tolerate, avoid, and eliminate voltage fluctuations based on program and microarchitectural events can help steer the processor clear of danger, thus enabling tighter voltage margins that improve performance or lower power consumption. We describe

  19. Determination of the electronics transfer function for current transient measurements

    CERN Document Server

    Scharf, Christian

    2014-01-01

    We describe a straight-forward method for determining the transfer function of the readout of a sensor for the situation in which the current transient of the sensor can be precisely simulated. The method relies on the convolution theorem of Fourier transforms. The specific example is a planar silicon pad diode connected with a 50 $\\Omega $ cable to an amplifier followed by a 5 GS/s sampling oscilloscope. The charge carriers in the sensor were produced by picosecond lasers with light of wavelengths of 675 and 1060 nm. The transfer function is determined from the 1060 nm data with the pad diode biased at 1000 V. It is shown that the simulated sensor response convoluted with this transfer function provides an excellent description of the measured transients for the laser light of both wavelengths, at voltages 50 V above the depletion voltage of about 90 V up to the maximum applied voltage of 1000 V. The method has been developed for the precise measurement of the dependence of the drift velocity of electrons an...

  20. 30 CFR 77.704-5 - Installation of protective equipment.

    Science.gov (United States)

    2010-07-01

    ... high-voltage surface lines is begun, protective equipment shall be used to cover all bare conductors.... Such protective equipment shall be installed from a safe position below the conductors or...

  1. Mathematical simulation application for research of nonuniform distributed-parameter circuit transients

    Science.gov (United States)

    Kuleshova, E. O.; Plyusnin, A. A.; Shandarova, E. B.; Tikhomirova, O. V.

    2016-04-01

    This paper considers the simulation capability of nonuniform distributed-parameter circuit transients by using MatLab Simulink. This approach is capable of determining currents and voltages of nodes for power networks of any configurations and modes. The paper contains results of nonuniform line simulations in idle, short-circuit and load modes.

  2. OPTIMIZATION OF TRANSIENT FEEDING TO PARALLEL-PLATE TRANSMISSION LINES FROM COAXIAL LINE

    Institute of Scientific and Technical Information of China (English)

    Tian Chunming; Wang Jianguo; Meng Fenxia; Zhang Maoyu; Ge Debiao

    2001-01-01

    The transient feeding to parallel-plate transmission lines from coaxial line is optimized by using the Finite-Difference Time-Domain (FDTD) method and a simple FDTD feed model. Observing the reflected voltages, this letter presents the optimal feeding position and ratio of width to height for a given input impedance of the coaxial line.

  3. Transient charging and discharging of spin-polarized electrons in a quantum dot

    DEFF Research Database (Denmark)

    De Souza, Fabricio; Leao, S.A.; Gester, R. M.;

    2007-01-01

    We study spin-polarized transient transport in a quantum dot coupled to two ferromagnetic leads subjected to a rectangular bias voltage pulse. Time-dependent spin-resolved currents, occupations, spin accumulation, and tunneling magnetoresistance TMR are calculated using both nonequilibrium Green ...

  4. The MWA Transients Survey (MWATS).

    Science.gov (United States)

    Bell, M.; Murphy, T.; Kaplan, D. L.; Croft, S. D.; Hancock, P.; Rowlinson, A.; Wayth, R.; Gaensler, B.; Hurley-Walker, N.; Offringa, A.; Loi, C.; Bannister, K.; Trott, C.; Marquart, J.

    2017-01-01

    We propose the continuation of the MWA transients survey to search for and monitor low frequency transient and variable radio sources in the southern sky. This proposal is aimed at commensally utilising data from the GLEAM-X (G0008) project in semester 2017-A. The aim of this commensal data acquisition is to commission long baseline observations for transient science. In particular this will involve studying the impact of the ionosphere on calibration and imaging, and developing the techniques needed to produce science quality data products. The proposed drift scans with LST locking (see G0008 proposal) are particularly exciting as we can test image subtraction for transient and variable identification. This survey is targeted at studying objects such as AGN (intrinsic and extrinsic variability), long duration synchrotron emitters, pulsars and transients of unknown origin. The maps generated from this survey will be analysed with the Variables and Slow Transients (VAST) detection pipeline. The motivation for this survey is as follows: (i) To obtain temporal data on an extremely large and robust sample of low frequency sources to explore and quantify both intrinsic and extrinsic variability; (ii) To search and find new classes of low frequency radio transients that previously remained undetected and obscured from multi-wavelength discovery; (iii) To place rigorous statistics on the occurrence of both transients and variables prior to the Australian SKA era.

  5. Drosophila mushroom body Kenyon cells generate spontaneous calcium transients mediated by PLTX-sensitive calcium channels.

    Science.gov (United States)

    Jiang, Shaojuan Amy; Campusano, Jorge M; Su, Hailing; O'Dowd, Diane K

    2005-07-01

    Spontaneous calcium oscillations in mushroom bodies of late stage pupal and adult Drosophila brains have been implicated in memory consolidation during olfactory associative learning. This study explores the cellular mechanisms regulating calcium dynamics in Kenyon cells, principal neurons in mushroom bodies. Fura-2 imaging shows that Kenyon cells cultured from late stage Drosophila pupae generate spontaneous calcium transients in a cell autonomous fashion, at a frequency similar to calcium oscillations in vivo (10-20/h). The expression of calcium transients is up regulated during pupal development. Although the ability to generate transients is a property intrinsic to Kenyon cells, transients can be modulated by bath application of nicotine and GABA. Calcium transients are blocked, and baseline calcium levels reduced, by removal of external calcium, addition of cobalt, or addition of Plectreurys toxin (PLTX), an insect-specific calcium channel antagonist. Transients do not require calcium release from intracellular stores. Whole cell recordings reveal that the majority of voltage-gated calcium channels in Kenyon cells are PLTX-sensitive. Together these data show that influx of calcium through PLTX-sensitive voltage-gated calcium channels mediates spontaneous calcium transients and regulates basal calcium levels in cultured Kenyon cells. The data also suggest that these calcium transients represent cellular events underlying calcium oscillations in the intact mushroom bodies. However, spontaneous calcium transients are not unique to Kenyon cells as they are present in approximately 60% of all cultured central brain neurons. This suggests the calcium transients play a more general role in maturation or function of adult brain neurons.

  6. Over Voltage in a Multi-sectioned Solenoid during a Quenching

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Xinglong; Wang, Li; Pan, Heng; Wu, Hong; Liu, Xiaokun; Chen, Anbin; Green, M.A.; Xu, F.Y.

    2009-06-21

    Accurate analysis of over voltage in the superconducting solenoid during a quench is one of the bases for quench protection system design. Classical quench simulation methods can only give rough estimation of the over voltage within a magnet coil. In this paper, for multi-sectioned superconducting solenoid, based on the classical assumption of ellipsoidal normal zone, three-dimension al temperature results are mapped to the one-dimension of the wire, the temperature distribution along the wire and the resistances of each turn are obtained. The coil is treated as circuit comprised of turn resistances, turn self and mutual inductances. The turn resistive voltage, turn inductive voltage, and turn resultant voltage along the wire are calculated. As a result, maximum internal voltages, the layer-to-layer voltages and the turn-to-turn voltages are better estimated. Utilizing this method, the over voltage of a small solenoid and a large solenoid during quenching have been studied. The result shows that this method can well improve the over voltage estimate, especially when the coil is larger.

  7. VOLTAGE REGULATORS OF SYNCHRONOUS GENERATORS

    Directory of Open Access Journals (Sweden)

    Grigorash O. V.

    2015-06-01

    Full Text Available Synchronous generators are the primary source of electrical power autonomous electrosupply systems, including backup systems. They are also used in a structure of rotating electricity converters and are widely used in renewable energy as part of wind power plants of small, mini and micro hydroelectric plants. Increasing the speed and the accuracy of the system of the voltage regulation of synchronous generators is possible due to the development of combined systems containing more stabilizers. The article illustrates the functional schemes of circuit voltage stabilizers and frequency synchronous generators (with electromagnetic excitation and permanent magnet excitation and describes the features of their work, including two and three-aggregate rotating converters of electricity used in uninterruptible power supply systems. To improve the technical characteristics of the system of stabilization we have proposed functional solutions for stabilizers of synchronous generators made on the base of direct frequency converters and using a transformer with a rotating magnetic field. To improve the reliability of and to improve the operational characteristics of the autonomous independent sources of electricity we suggest creating the main functional blocks and the elements of the stabilization system in a modular way. The functional circuit solutions of voltage regulators of synchronous generators and the characteristics of their work considered in the article, are able to improve the efficiency of pre-design work in the development of new technical solutions for stabilizing the voltage and the frequency in synchronous generators of electrosupply autonomous systems

  8. Frequency-controlled voltage regulator

    Science.gov (United States)

    Mclyman, W. T.

    1980-01-01

    Converting input ac to higher frequency reduce size and weight and makes possible unique kind of regulation. Since conversion frequency is above range of human hearing, supply generated on audible noise. It also exploits highfrequency conversion features to regulate its output voltage in novel way. Circuit is inherently short-circuit proof.

  9. Design and control of single-phase dynamic voltage restorer

    Indian Academy of Sciences (India)

    AMIT MEENA; SHIRAZUL ISLAM; SANDEEP ANAND; YOGESH SONAWANE; SANJAY TUNGARE

    2017-08-01

    Dynamic voltage restorer (DVR) is a custom power device used in electrical distribution system for power quality improvement. It ensures regulated voltage supply to the sensitive loads, even in case of voltage sag and swell disturbances in the distribution network. It is a series connected device and compensates voltagesag and swell by injecting a voltage with the help of a series transformer. The injection of an appropriate voltage component in the event of a voltage disturbance requires a certain amount of real and reactive power. Conventionally,DVR consists of an energy storage device, which supplies the required power over the limited duration of the sags. Large magnitude and long duration of sags lead to heavy financial investment in energy storage unit. To overcome this limitation, a single-phase back-to-back converter-based DVR is implemented inthis work, which eliminates energy storage requirement. The integration of series and shunt converter makes the DVR capable of bidirectional flow of energy. Therefore, the key advantage of this topology is its capability to compensate for long-term voltage sag and swell. Modelling of the DVR and its controller design is included in this paper. The effectiveness of control schemes, protection schemes and starting sequence of operation of DVR is verified through detailed simulation studies. A scaled down laboratory prototype of DVR is developed. The viability of these schemes is confirmed by the experimental results generated from the laboratory prototype. Various challenges faced during the prototype development and corresponding solutions are also discussed in this paper.

  10. Improved direct power control of a grid-connected voltage source converter during network unbalance

    Institute of Scientific and Technical Information of China (English)

    Peng ZHOU; Wei ZHANG; Yi-kang HE; Rong ZENG

    2010-01-01

    This paper deals with an improved direct power control(DPC)strategy for the pulse width modulation(PWM)voltage source converter(VSC)under unbalanced grid voltage conditions.In order to provide enhanced control performance for the VSC,the resonant controllers tuned at the double grid frequency are applied in the DPC design to eliminate the power pulsations and dc link voltage ripples produced by the transient unbalanced grid faults.In this way,the output power and dc link voltage of the VSC can be directly regulated without positive and negative sequential decomposition.As a result,and as has been verified by experiment,the proposed method can provide fast dynamic response with easy implementation.

  11. Fast-responding short circuit protection system with self-reset for use in circuit supplied by DC power

    Science.gov (United States)

    Burns, Bradley M. (Inventor); Blalock, Norman N. (Inventor)

    2011-01-01

    A short circuit protection system includes an inductor, a switch, a voltage sensing circuit, and a controller. The switch and inductor are electrically coupled to be in series with one another. A voltage sensing circuit is coupled across the switch and the inductor. A controller, coupled to the voltage sensing circuit and the switch, opens the switch when a voltage at the output terminal of the inductor transitions from above a threshold voltage to below the threshold voltage. The controller closes the switch when the voltage at the output terminal of the inductor transitions from below the threshold voltage to above the threshold voltage.

  12. Voltage-gated Proton Channels

    Science.gov (United States)

    DeCoursey, Thomas E.

    2014-01-01

    Voltage-gated proton channels, HV1, have vaulted from the realm of the esoteric into the forefront of a central question facing ion channel biophysicists, namely the mechanism by which voltage-dependent gating occurs. This transformation is the result of several factors. Identification of the gene in 2006 revealed that proton channels are homologues of the voltage-sensing domain of most other voltage-gated ion channels. Unique, or at least eccentric, properties of proton channels include dimeric architecture with dual conduction pathways, perfect proton selectivity, a single-channel conductance ~103 smaller than most ion channels, voltage-dependent gating that is strongly modulated by the pH gradient, ΔpH, and potent inhibition by Zn2+ (in many species) but an absence of other potent inhibitors. The recent identification of HV1 in three unicellular marine plankton species has dramatically expanded the phylogenetic family tree. Interest in proton channels in their own right has increased as important physiological roles have been identified in many cells. Proton channels trigger the bioluminescent flash of dinoflagellates, facilitate calcification by coccolithophores, regulate pH-dependent processes in eggs and sperm during fertilization, secrete acid to control the pH of airway fluids, facilitate histamine secretion by basophils, and play a signaling role in facilitating B-cell receptor mediated responses in B lymphocytes. The most elaborate and best-established functions occur in phagocytes, where proton channels optimize the activity of NADPH oxidase, an important producer of reactive oxygen species. Proton efflux mediated by HV1 balances the charge translocated across the membrane by electrons through NADPH oxidase, minimizes changes in cytoplasmic and phagosomal pH, limits osmotic swelling of the phagosome, and provides substrate H+ for the production of H2O2 and HOCl, reactive oxygen species crucial to killing pathogens. PMID:23798303

  13. Transient regional osteoporosis.

    Science.gov (United States)

    Cano-Marquina, Antonio; Tarín, Juan J; García-Pérez, Miguel-Ángel; Cano, Antonio

    2014-04-01

    Transient regional osteoporosis (TRO) is a disease that predisposes to fragility fracture in weight bearing joints of mid-life women and men. Pregnant women may also suffer the process, usually at the hip. The prevalence of TRO is lower than the systemic form, associated with postmenopause and advanced age, but may be falsely diminished by under-diagnosis. The disease may be uni- or bilateral, and may migrate to distinct joints. One main feature of TRO is spontaneous recovery. Pain and progressive limitation in the functionality of the affected joint(s) are key symptoms. In the case of the form associated with pregnancy, difficulties in diagnosis derive from the relatively young age at presentation and from the clinical overlapping with the frequent aches during gestation. Densitometric osteoporosis in the affected region is not always present, but bone marrow edema, with or without joint effusion, is detected by magnetic resonance. There are not treatment guidelines, but the association of antiresorptives to symptomatic treatment seems to be beneficial. Surgery or other orthopedic interventions can be required for specific indications, like hip fracture, intra-medullary decompression, or other.

  14. Applied hydraulic transients

    CERN Document Server

    Chaudhry, M Hanif

    2014-01-01

    This book covers hydraulic transients in a comprehensive and systematic manner from introduction to advanced level and presents various methods of analysis for computer solution. The field of application of the book is very broad and diverse and covers areas such as hydroelectric projects, pumped storage schemes, water-supply systems, cooling-water systems, oil pipelines and industrial piping systems. Strong emphasis is given to practical applications, including several case studies, problems of applied nature, and design criteria. This will help design engineers and introduce students to real-life projects. This book also: ·         Presents modern methods of analysis suitable for computer analysis, such as the method of characteristics, explicit and implicit finite-difference methods and matrix methods ·         Includes case studies of actual projects ·         Provides extensive and complete treatment of governed hydraulic turbines ·         Presents design charts, desi...

  15. The Rapid Transient Surveyor

    CERN Document Server

    Baranec, Christoph; Wright, Shelley A; Tonry, John; Tully, R Brent; Szapudi, István; Takamiya, Marianne; Hunter, Lisa; Riddle, Reed; Chen, Shaojie; Chun, Mark

    2016-01-01

    The Rapid Transient Surveyor (RTS) is a proposed rapid-response, high-cadence adaptive optics (AO) facility for the UH 2.2-m telescope on Maunakea. RTS will uniquely address the need for high-acuity and sensitive near-infrared spectral follow-up observations of tens of thousands of objects in mere months by combining an excellent observing site, unmatched robotic observational efficiency, and an AO system that significantly increases both sensitivity and spatial resolving power. We will initially use RTS to obtain the infrared spectra of ~4,000 Type Ia supernovae identified by the Asteroid Terrestrial-Impact Last Alert System over a two year period that will be crucial to precisely measuring distances and mapping the distribution of dark matter in the z < 0.1 universe. RTS will comprise an upgraded version of the Robo-AO laser AO system and will respond quickly to target-of-opportunity events, minimizing the time between discovery and characterization. RTS will acquire simultaneous-multicolor images with a...

  16. The rapid transient surveyor

    Science.gov (United States)

    Baranec, C.; Lu, J. R.; Wright, S. A.; Tonry, J.; Tully, R. B.; Szapudi, I.; Takamiya, M.; Hunter, L.; Riddle, R.; Chen, S.; Chun, M.

    2016-07-01

    The Rapid Transient Surveyor (RTS) is a proposed rapid-response, high-cadence adaptive optics (AO) facility for the UH 2.2-m telescope on Maunakea. RTS will uniquely address the need for high-acuity and sensitive near-infrared spectral follow-up observations of tens of thousands of objects in mere months by combining an excellent observing site, unmatched robotic observational efficiency, and an AO system that significantly increases both sensitivity and spatial resolving power. We will initially use RTS to obtain the infrared spectra of 4,000 Type Ia supernovae identified by the Asteroid Terrestrial-Impact Last Alert System over a two year period that will be crucial to precisely measuring distances and mapping the distribution of dark matter in the z efficiency prism integral field unit spectrograph: R = 70-140 over a total bandpass of 840-1830nm with an 8.7" by 6.0" field of view (0.15" spaxels). The AO correction boosts the infrared point-source sensitivity of the spectrograph against the sky background by a factor of seven for faint targets, giving the UH 2.2-m the H-band sensitivity of a 5.7-m telescope without AO.

  17. Transient Performance Improvement of Static Series Compensator by Double Vector Control

    DEFF Research Database (Denmark)

    Awad, Hilmy; Blaabjerg, Frede

    2004-01-01

    control loop. The loop gains are determined according to the system stability analysis, carried out on the closed loop system. Also a review of the reported control techniques that have been implemented to control the injected voltage by the SSC is presented. A 10-kV SSC experimental setup is exploited......This paper presents the principle and verification of the double vector control (DVC) algorithm, which improves the transient performance of the Static Series Compensator (SSC). Both current and voltage controllers are incorporated by the DVC, with an inner current control loop and outer voltage...... to carry out experiments with different load types: static linear; dynamic linear and non-linear loads. Experiments have proved that the proposed algorithm is able to improve the transient response of the SSC compared to like using phasors of the sequence components, RMS calculations and even vector...

  18. Transient charge technique investigation of HgI/sub 2/ and CdSe nuclear detectors

    Energy Technology Data Exchange (ETDEWEB)

    Roth, M.; Burger, A.; Nissenbaum, J.; Schieber, M.

    1987-02-01

    The use of the Transient Charge Technique (TCT) for the evaluation of high resistivity Mercuric Iodide and Cadmium Selenide nuclear radiation detectors is suggested. It has been shown that the real values of mobilities and trapping times of electrons and holes in HgI/sub 2/ can be easily obtained from the analysis of the voltage transient response to drift of charge carriers created by alpha particles. This allows one to evaluate the bulk transport properties of the material and, additionally, to estimate accurately the surface recombination velocity of the carriers. Preliminary results on the shape of voltage transients in CdSe are also reported, and the limitations of the use of the TCT for characterization of both materials are discussed.

  19. THE EFFECT OF LIGHTNING ON HIGH VOLTAGE ELECTRICAL SUBSTATIONS’ LOW VOLTAGE SYSTEMS

    Directory of Open Access Journals (Sweden)

    M. I. Fursanov

    2016-01-01

    Full Text Available The article presents the results of studies of the effects of lightning on low voltage systems of high voltage electrical substations with outdoor switchgears of 110 kV. The topicality of research is associated with a wide spreading of such substations as well as with a high reliability requirements of their work and, also, with their widespread distribution and high probability of lightning strikes to the substation or around it. The highest probable and the most dangerous effects of lightning on low voltage systems of a substation are determined on the basis of critical review and special literature analysis and, also, of systematization of practical information that had been collected during the survey of operating substations. Adequate physical models were developed for the list of hazardous effects based on physical processes of lightning. A model of each effect was studied on the basis of the sensitivity theory. The accuracy and adequacy of the models were verified by means of comparison of calculation results for the models under investigation with the results of calculations fulfilled in accordance with specialized programs, as well as from practical or theoretical data obtained by other authors. The factors that had been included in the models were studied and were defined in accordance with their nature (natural or artificial, the range of possible values in a substation was determined; the coefficients of elasticity were calculated. The obtained results enable to ascertain the contribution of the factor in the effect of lightning and the ability to control the factor. The relationship between the factors and the effects of lightning are shown as graphs. For practical application the information, obtained as the result of the research, was organized in the form of checklists that can be applied when collecting baseline information to develop the lightning protection of the substation, to examine the existing lightning protection, to

  20. Computational reconstitution of spine calcium transients from individual proteins

    Directory of Open Access Journals (Sweden)

    Thomas Matthew Bartol

    2015-10-01

    Full Text Available We have built a stochastic model in the program MCell that simulates Ca2+ transients in spines from the principal molecular components believed to control Ca2+ entry and exit. Proteins, with their kinetic models, are located within two segments of dendrites containing 88 intact spines, centered in a fully reconstructed 5 x 5 x 6 µm cube of hippocampal neuropil. Protein components include AMPA- and NMDA-type glutamate receptors, L- and R-type voltage-dependent Ca2+ channels, Na+/Ca2+ exchangers, plasma membrane Ca2+ ATPases, smooth endoplasmic reticulum Ca2+ ATPases, immobile Ca2+ buffers, and calbindin. Kinetic models for each protein were taken from published studies of the isolated proteins in vitro. For simulation of electrical stimuli, the time course of voltage changes in the dendritic spine was generated with the desired stimulus in the program NEURON. Voltage-dependent parameters were then continuously re-adjusted during simulations in MCell to reproduce the effects of the stimulus. Nine parameters of the model were optimized within realistic experimental limits by a process that compared results of simulations to published data. We find that simulations in the optimized model reproduce the timing and amplitude of Ca2+ transients measured experimentally in intact neurons. Thus, we demonstrate that the characteristics of individual isolated proteins determined in vitro can accurately reproduce the dynamics of experimentally measured Ca2+ transients in spines. The model will provide a test bed for exploring the roles of additional proteins that regulate Ca2+ influx into spines and for studying the behavior of protein targets in the spine that are regulated by Ca2+ influx.

  1. DARHT-II Injector Transients and the Ferrite Damper

    Energy Technology Data Exchange (ETDEWEB)

    Waldron, Will; Reginato, Lou; Chow, Ken; Houck, Tim; Henestroza, Enrique; Yu, Simon; Kang, Michael; Briggs, Richard

    2006-08-04

    This report summarizes the transient response of the DARHT-II Injector and the design of the ferrite damper. Initial commissioning of the injector revealed a rise time excited 7.8 MHz oscillation on the diode voltage and stalk current leading to a 7.8 MHz modulation of the beam current, position, and energy. Commissioning also revealed that the use of the crowbar to decrease the voltage fall time excited a spectrum of radio frequency modes which caused concern that there might be significant transient RF electric field stresses imposed on the high voltage column insulators. Based on the experience of damping the induction cell RF modes with ferrite, the concept of a ferrite damper was developed to address the crowbar-excited oscillations as well as the rise-time-excited 7.8 MHz oscillations. After the Project decided to discontinue the use of the crowbar, further development of the concept focused exclusively on damping the oscillations excited by the rise time. The design was completed and the ferrite damper was installed in the DARHT-II Injector in February 2006. The organization of this report is as follows. The suite of injector diagnostics are described in Section 2. The data and modeling of the injector transients excited on the rise-time and also by the crowbar are discussed in Section 3; the objective is a concise summary of the present state of understanding. The design of the ferrite damper, and the small scale circuit simulations used to evaluate the ferrite material options and select the key design parameters like the cross sectional area and the optimum gap width, are presented in Section 4. The details of the mechanical design and the installation of the ferrite damper are covered in Section 5. A brief summary of the performance of the ferrite damper following its installation in the injector is presented in Section 6.

  2. Helioseismic Effects of Energetic Transients

    Indian Academy of Sciences (India)

    Ashok Ambastha

    2008-03-01

    Photospheric and chromospheric signatures related to large, energetic transients such as flares and CMEs, have been extensively reported during the last several years. In addition, energetic solar transients are expected to cause helioseismic effects. Some of the recent results are reviewed here; in particular, the helioseismic effects of the powerful flares in superactive region, NOAA 10486, including the 4B/X17 superflare of October 28, 2003. We also examine the temporal variations of power in low- modes during the period May 1995–October 2005, and compare with daily, disk-integrated flare- and CME-indices to infer the effect of transients on the scale of whole solar disk.

  3. TRANSIENT ANALYSIS OF NONUNIFORM TRANSMISSION LINES WITH NONLINEAR TERMINAL NETWORKS

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A semi-analytical method in time domain is presented for analysis of the transient response of nonuniform transmission lines. In this method, the telegraph equations in time domain is differenced in space domain first, and is transformed into a set of first-order differential equations of voltage and current with respect to time. By integrating these differential equations with respect to time, and precise computation, the solution of these differential equations can be obtained. This method can solve the transient response of various kinds of transmission lines with arbitrary terminal networks. Particularly, it can analyze the nonuniform lines with initial conditions, for which there is no existing effective method to analyze the time response so far. The results obtained with this method are stable and accurate. Two examples are given to illustrate the application of this method.

  4. Operation of grid-connected DFIG under unbalanced grid voltage condition

    NARCIS (Netherlands)

    Zhou, Y.; Bauer, P.; Ferreira, J.A.; Pierik, J.

    2009-01-01

    Doubly fed induction generator (DFIG) still shares a large part in today's wind power market. It provides the benefits of variable speed operation cost-effectively, and can control its active and reactive power independently. Crowbar protection is often adopted to protect the rotor-side voltage sour

  5. Variable speed wind turbine generator system with current controlled voltage source inverter

    Energy Technology Data Exchange (ETDEWEB)

    Muyeen, S.M., E-mail: muyeen0809@yahoo.co [Dept. of Electrical Engineering, Petroleum Institute, P.O. Box 2533, Abu Dhabi (United Arab Emirates); Al-Durra, Ahmed [Dept. of Electrical Engineering, The Petroleum Institute, P.O. Box 2533, Abu Dhabi (United Arab Emirates); Tamura, J. [Dept. of EEE, Kitami Institute of Technology, 165 Koen-cho, Kitami 090-8507 (Japan)

    2011-07-15

    highlights: {yields} Current controlled voltage source inverter scheme for wind power application. {yields} Low voltage ride through of wind farm. {yields} Variable speed wind turbine driven permanent magnet synchronous generator-operation and control. -- Abstract: The present popular trend of wind power generation is to use variable speed wind turbine (VSWT) driving a doubly fed induction generator (DFIG), wound field synchronous generator (WFSG) or permanent magnet synchronous generator (PMSG). Among them, stability analyses of DFIG type of VSWT have already been reported in many literatures. However, transient stability and low voltage ride through (LVRT) characteristics analyses for synchronous generator type of VSWT is not sufficient enough. This paper focuses on detailed LVRT characteristic analysis of variable speed wind turbine driving a PMSG (VSWT-PMSG) with current controlled voltage source inverter (CC-VSI). Modeling and suitable control strategies for overall system are developed to augment the low voltage ride through capability of variable speed wind generator, considering recent wind farm grid code. Both symmetrical and unsymmetrical faults are analyzed as network disturbances in this paper. The permanent fault due to unsuccessful reclosing of circuit breakers is taken into consideration, which is a salient feature of this study. Moreover, the dynamic characteristic is analyzed using real wind speed data measured in Hokkaido Island, Japan. The proposed control scheme is simulated by using the standard power system simulation package PSCAD/EMTDC and results are verified by comparing that of voltage controlled voltage source inverter scheme available in power system literature.

  6. Modified Quasi-Steady State Model of DC System for Transient Stability Simulation under Asymmetric Faults

    Directory of Open Access Journals (Sweden)

    Jun Liu

    2015-01-01

    Full Text Available As using the classical quasi-steady state (QSS model could not be able to accurately simulate the dynamic characteristics of DC transmission and its controlling systems in electromechanical transient stability simulation, when asymmetric fault occurs in AC system, a modified quasi-steady state model (MQSS is proposed. The model firstly analyzes the calculation error induced by classical QSS model under asymmetric commutation voltage, which is mainly caused by the commutation voltage zero offset thus making inaccurate calculation of the average DC voltage and the inverter extinction advance angle. The new MQSS model calculates the average DC voltage according to the actual half-cycle voltage waveform on the DC terminal after fault occurrence, and the extinction advance angle is also derived accordingly, so as to avoid the negative effect of the asymmetric commutation voltage. Simulation experiments show that the new MQSS model proposed in this paper has higher simulation precision than the classical QSS model when asymmetric fault occurs in the AC system, by comparing both of them with the results of detailed electromagnetic transient (EMT model of the DC transmission and its controlling system.

  7. Comparison of Harmony Search Algorithm and Particle Swarm Optimization for Distributed Generation Allocation to Improve Steady State Voltage Stability of Distribution Networks

    Directory of Open Access Journals (Sweden)

    Hamed Piarehzadeh

    2012-08-01

    Full Text Available In this study is tried to optimal distributed generation allocation for stability improvement in radial distribution systems. Voltage instability implies an uncontrolled decrease in voltage triggered by a disturbance, leading to voltage collapse and is primarily caused by dynamics connected with the load. The instability is divided into steady state and transient voltage instability Based on the time spectrum of the incident of the phenomena. The analysis is accomplished using a steady state voltage stability index which can be evaluated at each node of the distribution system. Several optimal capacities and locations are used to check these results. The location of DG has the main effect voltage stability on the system. Effects of location and capacity on incrementing steady state voltage stability in radial distribution systems are examined through Harmony Search Algorithm (HSA and finally the results are compared to Particle Swarm Optimization (PSO on the terms of speed, convergence and accuracy.

  8. Generator voltage stabilisation for series-hybrid electric vehicles.

    Science.gov (United States)

    Stewart, P; Gladwin, D; Stewart, J; Cowley, R

    2008-04-01

    This paper presents a controller for use in speed control of an internal combustion engine for series-hybrid electric vehicle applications. Particular reference is made to the stability of the rectified DC link voltage under load disturbance. In the system under consideration, the primary power source is a four-cylinder normally aspirated gasoline internal combustion engine, which is mechanically coupled to a three-phase permanent magnet AC generator. The generated AC voltage is subsequently rectified to supply a lead-acid battery, and permanent magnet traction motors via three-phase full bridge power electronic inverters. Two complementary performance objectives exist. Firstly to maintain the internal combustion engine at its optimal operating point, and secondly to supply a stable 42 V supply to the traction drive inverters. Achievement of these goals minimises the transient energy storage requirements at the DC link, with a consequent reduction in both weight and cost. These objectives imply constant velocity operation of the internal combustion engine under external load disturbances and changes in both operating conditions and vehicle speed set-points. An electronically operated throttle allows closed loop engine velocity control. System time delays and nonlinearities render closed loop control design extremely problematic. A model-based controller is designed and shown to be effective in controlling the DC link voltage, resulting in the well-conditioned operation of the hybrid vehicle.

  9. Large-signal transient response of a switching regulator

    Science.gov (United States)

    Harada, K.; Nabeshima, T.

    Analytical and experimental considerations on the large-signal transient-responses of the buck-type switching regulator are described. The behaviour under the large-signal operation is different from the case of small signal because of the saturation characteristics of the PWM feedback controller. The effect of this nonlinearity is analyzed by dividing its operation into three modes. As a result, the maximum peak values of the inrush current and output voltage are obtained analytically both for the start-up and for the step change of the load current.

  10. Transient Stability Performance Analysis of Power System Using Facts Devices

    Directory of Open Access Journals (Sweden)

    M. Srinivasa Rao

    2014-02-01

    Full Text Available Transient stability is increasingly important for secure loading. Transient stability evaluation of large scale power systems is an extremely intricate and highly non linear problem. An important function of transient evaluation is to appraise the capability of the power system to with stand serious contingency in time, so that some emergencies or preventive control can be carried out to prevent system breakdown, the fault current so produced is diverted to the capacitor by using dual-STATCOM controller, results proved that voltage is maintained nearly constant, surge currents decreased and oscillations in generator have damped and hence system stability and continuity of supply are enhanced. If for UPFC, replacing series controller with shunt controller, it works as dual STATCOM. It has advantages as series pulse controller is not required and same pulses can be given to both STATCOMs. The shunt controller is so designed to act as low impedance path for short circuit current, thereby surge currents can be diverted to VSC. A general program for transient stability studies to incorporate FACTS devices is developed using MATLAB/SIMULINK.

  11. Advances in high voltage engineering

    CERN Document Server

    Haddad, A

    2005-01-01

    This book addresses the very latest research and development issues in high voltage technology and is intended as a reference source for researchers and students in the field, specifically covering developments throughout the past decade. This unique blend of expert authors and comprehensive subject coverage means that this book is ideally suited as a reference source for engineers and academics in the field for years to come.

  12. High Voltage Pulse Testing Survey.

    Science.gov (United States)

    1985-10-01

    Cryogenic 23 E. Liquids 26 F. Solids 28 1. Polyethylene 28 2. Cross-Linked Polyethylene ( XLPE ) 29 3. Polyimide and Polyvenylchloride (PVC) 31 VI Benefits 35 A...Strength of XLPE Cables 29 vii * 4" I PROGRAM OBJECTIVES The Pulse Test Survey summarizes government, industry, and technical reports on high voltage pulse...system of silicone oil on a XLPE (cross-linked polyethylene) spacer tends to lower the impulse breakdown by approximately 10 percent. The negative impulse

  13. TRANSISTOR HIGH VOLTAGE POWER SUPPLY

    Science.gov (United States)

    Driver, G.E.

    1958-07-15

    High voltage, direct current power supplies are described for use with battery powered nuclear detection equipment. The particular advantages of the power supply described, are increased efficiency and reduced size and welght brought about by the use of transistors in the circuit. An important feature resides tn the employment of a pair of transistors in an alternatefiring oscillator circuit having a coupling transformer and other circuit components which are used for interconnecting the various electrodes of the transistors.

  14. Transient absorption and laser output of YAG : Nd

    Science.gov (United States)

    Kvapil, Jiří; Kvapil, Jos; Kubelka, J.; Kubeček, V.

    1981-06-01

    YAG : Nd grown under 98% Ar 2% H2 protective atmosphere free of nitrogen or hydrocarbons showed after UV irradiation broad absorption peaked at ˜1·9×104 cm-1 which disappeared relatively slowly at room temperature. It was more intensive in oxygen treated samples than in those annealed in hydrogsn. Transient absorption suppresses laser output by the increase of absorption at 0·94×104 cm-1 (1064 nm) and, particularly in CW mode, by the anomalous rod deformation. YAG : Nd containing Fe ions (≲2·10-4 wt%) showed no transient absorption.

  15. Internal voltage control of hydrogen-oxygen fuel cells: Feasibility study

    Science.gov (United States)

    Prokopius, P. R.

    1975-01-01

    An experimental study was conducted to assess the feasibility of internal voltage regulation of fuel cell systems. Two methods were tested. In one, reactant partial pressure was used as the voltage control parameter and in the other reactant total pressure was used for control. Both techniques were breadboarded and tested on a single alkaline-electrolyte fuel cell. Both methods were found to be possible forms of regulation, however, of the two the total pressure technique would be more efficient, simpler to apply and would provide better transient characteristics.

  16. Modeling and Stress Analysis of Doubly-Fed Induction Generator during Grid Voltage Swell

    DEFF Research Database (Denmark)

    Zhou, Dao; Song, Yipeng; Blaabjerg, Frede

    2016-01-01

    The Doubly-Fed Induction Generator (DFIG) based wind turbine system is presently dominant in the wind turbine market. Due to heavy load switch-off and faults in the power grid, voltage swells may occur and this phenomenon is currently given sufficient insights. This paper starts to describe...... the transient voltage swell and its recovery. It is concluded that although both higher swell level and higher rotor speed cause higher rotor electromotive force, the doubly-fed induction generator can successfully ride through the grid fault due to the relatively small swell level required by the modern grid...

  17. A test technique for measuring lightning-induced voltages on aircraft electrical circuits

    Science.gov (United States)

    Walko, L. C.

    1974-01-01

    The development of a test technique used for the measurement of lightning-induced voltages in the electrical circuits of a complete aircraft is described. The resultant technique utilizes a portable device known as a transient analyzer capable of generating unidirectional current impulses similar to lightning current surges, but at a lower current level. A linear relationship between the magnitude of lightning current and the magnitude of induced voltage permitted the scaling up of measured induced values to full threat levels. The test technique was found to be practical when used on a complete aircraft.

  18. Low voltage electron beam accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Ochi, Masafumi [Iwasaki Electric Co., Ltd., Tokyo (Japan)

    2003-02-01

    Widely used electron accelerators in industries are the electron beams with acceleration voltage at 300 kV or less. The typical examples are shown on manufactures in Japan, equipment configuration, operation, determination of process parameters, and basic maintenance requirement of the electron beam processors. New electron beam processors with acceleration voltage around 100 kV were introduced maintaining the relatively high dose speed capability of around 10,000 kGy x mpm at production by ESI (Energy Science Inc. USA, Iwasaki Electric Group). The application field like printing and coating for packaging requires treating thickness of 30 micron or less. It does not require high voltage over 110 kV. Also recently developed is a miniature bulb type electron beam tube with energy less than 60 kV. The new application area for this new electron beam tube is being searched. The drive force of this technology to spread in the industries would be further development of new application, process and market as well as the price reduction of the equipment, upon which further acknowledgement and acceptance of the technology to societies and industries would entirely depend. (Y. Tanaka)

  19. Transient or permanent fisheye views

    DEFF Research Database (Denmark)

    Jakobsen, Mikkel Rønne; Hornbæk, Kasper

    2012-01-01

    , about the benefits and limitations of transient visualizations. We describe an experiment that compares the usability of a fisheye view that participants could call up temporarily, a permanent fisheye view, and a linear view: all interfaces gave access to source code in the editor of a widespread......Transient use of information visualization may support specific tasks without permanently changing the user interface. Transient visualizations provide immediate and transient use of information visualization close to and in the context of the user’s focus of attention. Little is known, however...... programming environment. Fourteen participants performed varied tasks involving navigation and understanding of source code. Participants used the three interfaces for between four and six hours in all. Time and accuracy measures were inconclusive, but subjective data showed a preference for the permanent...

  20. Transient heating of moving objects

    Directory of Open Access Journals (Sweden)

    E.I. Baida

    2014-06-01

    Full Text Available A mathematical model of transient and quasistatic heating of moving objects by various heat sources is considered. The mathematical formulation of the problem is described, examples of thermal calculation given.

  1. A Pilot Directional Protection for HVDC Transmission Line Based on Relative Entropy of Wavelet Energy

    Directory of Open Access Journals (Sweden)

    Sheng Lin

    2015-07-01

    Full Text Available On the basis of analyzing high-voltage direct current (HVDC transmission system and its fault superimposed circuit, the direction of the fault components of the voltage and the current measured at one end of transmission line is certified to be different for internal faults and external faults. As an estimate of the differences between two signals, relative entropy is an effective parameter for recognizing transient signals in HVDC transmission lines. In this paper, the relative entropy of wavelet energy is applied to distinguish internal fault from external fault. For internal faults, the directions of fault components of voltage and current are opposite at the two ends of the transmission line, indicating a huge difference of wavelet energy relative entropy; for external faults, the directions are identical, indicating a small difference. The simulation results based on PSCAD/EMTDC show that the proposed pilot protection system acts accurately for faults under different conditions, and its performance is not affected by fault type, fault location, fault resistance and noise.

  2. Radiation Protection

    Science.gov (United States)

    ... EPA United States Environmental Protection Agency Search Search Radiation Protection Share Facebook Twitter Google+ Pinterest Contact Us Radiation Protection Document Library View and download EPA radiation ...

  3. Piezo Voltage Controlled Planar Hall Effect Devices

    OpenAIRE

    Bao Zhang; Kang-Kang Meng; Mei-Yin Yang; Edmonds, K. W.; Hao Zhang; Kai-Ming Cai; Yu Sheng; Nan Zhang; Yang Ji; Jian-Hua Zhao; Hou-Zhi Zheng; Kai-You Wang

    2015-01-01

    The electrical control of the magnetization switching in ferromagnets is highly desired for future spintronic applications. Here we report on hybrid piezoelectric (PZT)/ferromagnetic (Co2FeAl) devices in which the planar Hall voltage in the ferromagnetic layer is tuned solely by piezo voltages. The change of planar Hall voltage is associated with magnetization switching through 90° in the plane under piezo voltages. Room temperature magnetic NOT and NOR gates are demonstrated based on the pie...

  4. Fault Analysis of DC Voltage Dividers in Xiangjiaba--Shanghai ±800 kV UHVDC Project

    Institute of Scientific and Technical Information of China (English)

    LI Fengqi; SHE Zhengqiu; LOU Dianqiang; Rajendra Iyer; Urban Astrom

    2012-01-01

    Transient DC voltage measurement error has been observed several times ever since Xiangjiaba--Shanghai ±800 kV UHVDC project started its commercial operation. The measurement error causes considerable disturbances to the AC networks. By analyzing the time frequency record, simulating faults at different positions of the divider, and testing the gas in voltage dividers, the fault is located and then is proved to be some partial discharges inside DC voltage dividers. The reason of the internal flashes and the solution to the problem is also discussed in this paper. The conclusion is that instead of N2 , SF6 should be used for the internal insulation of high voltage DC voltage dividers.

  5. Activity of Palythoa caribaeorum Venom on Voltage-Gated Ion Channels in Mammalian Superior Cervical Ganglion Neurons

    Directory of Open Access Journals (Sweden)

    Fernando Lazcano-Pérez

    2016-05-01

    Full Text Available The Zoanthids are an order of cnidarians whose venoms and toxins have been poorly studied. Palythoa caribaeorum is a zoanthid commonly found around the Mexican coastline. In this study, we tested the activity of P. caribaeorum venom on voltage-gated sodium channel (NaV1.7, voltage-gated calcium channel (CaV2.2, the A-type transient outward (IA and delayed rectifier (IDR currents of KV channels of the superior cervical ganglion (SCG neurons of the rat. These results showed that the venom reversibly delays the inactivation process of voltage-gated sodium channels and inhibits voltage-gated calcium and potassium channels in this mammalian model. The compounds responsible for these effects seem to be low molecular weight peptides. Together, these results provide evidence for the potential use of zoanthids as a novel source of cnidarian toxins active on voltage-gated ion channels.

  6. High-Performance Harmonic Isolation and Load Voltage Regulation of the Three-Phase Series Active Filter Utilizing the Waveform Reconstruction Method

    DEFF Research Database (Denmark)

    Senturk, Osman Selcuk; Hava, Ahmet M.

    2009-01-01

    . The SAF-compensated system utilizing WRM provides highperformance load harmonic voltage isolation and load voltage regulation at steady-state and during transients compared to the system utilizing the synchronous reference-frame-based signal decomposition. In addition, reducing the line current sampling......This paper develops a waveform reconstruction method (WRM) for high accuracy and bandwidth signal decomposition of voltage-harmonic-type three-phase diode rectifier load voltage into its harmonic and fundamental components, which are utilized in the series active filter (SAF) control algorithms...

  7. 49 CFR 234.221 - Lamp voltage.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Lamp voltage. 234.221 Section 234.221 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION..., Inspection, and Testing Maintenance Standards § 234.221 Lamp voltage. The voltage at each lamp shall...

  8. Bootstrapped Low-Voltage Analog Switches

    DEFF Research Database (Denmark)

    Steensgaard-Madsen, Jesper

    1999-01-01

    Novel low-voltage constant-impedance analog switch circuits are proposed. The switch element is a single MOSFET, and constant-impedance operation is obtained using simple circuits to adjust the gate and bulk voltages relative to the switched signal. Low-voltage (1-volt) operation is made feasible...

  9. Ionospheric plasma flow over large high-voltage space platforms. I - Ion-plasma-time scale interactions of a plate at zero angle of attack. II - The formation and structure of plasma wake

    Science.gov (United States)

    Wang, J.; Hastings, D. E.

    1992-01-01

    The paper presents the theory and particle simulation results for the ionospheric plasma flow over a large high-voltage space platform at a zero angle of attack and at a large angle of attack. Emphasis is placed on the structures in the large, high-voltage regime and the transient plasma response on the ion-plasma time scale. Special consideration is given to the transient formation of the space-charge wake and its steady-state structure.

  10. Determination of Resistor Resistance According to Over-Voltage Criteria in 6–35 kV Mains

    Directory of Open Access Journals (Sweden)

    V. I. Glushko

    2010-01-01

    Full Text Available A new method has been developed  for selection of resistor type according to over-voltage criteria that includes methods for calculation of resistor resistance RN  and over-voltage ratio factor kп which are used for evaluation of protective resistance functions.

  11. Co-ordinated voltage control of DFIG wind turbines in uninterrupted operation during grid faults

    DEFF Research Database (Denmark)

    Hansen, Anca Daniela; Michalke, G.; Sørensen, Poul Ejnar

    2007-01-01

    is implemented in the power system simulation toolbox PowerFactory DIgSILENT. The DFIG wind farm ride-through capability and contribution to voltage control in the power system are assessed and discussed by means of simulations with the use of a transmission power system generic model developed and delivered......-side converter as long as it is not blocked by the protection system, otherwise the grid-side converter takes over the voltage control. Moreover, the article presents a DFIG wind farm model equipped with a grid fault protection system and the described co-ordinated voltage control. The whole DFIG wind farm model...... by the Danish Transmission System Operator Energinet.dk. The simulation results show how a DFIG wind farm equipped with voltage control can help a nearby active stall wind farm to ride through a grid fault, without implementation of any additional ride-through control strategy in the active stall wind farm....

  12. Gaia transient detection efficiency: hunting for nuclear transients

    CERN Document Server

    Blagorodnova, Nadejda; Harrison, Diana L; Koposov, Sergey; Mattila, Seppo; Campbell, Heather; Walton, Nicholas A; Wyrzykowski, Lukasz

    2015-01-01

    We present a study of the detectability of transient events associated with galaxies for the Gaia European Space Agency astrometric mission. We simulated the on-board detections, and on-ground processing for a mock galaxy catalogue to establish the properties required for the discovery of transient events by Gaia, specifically tidal disruption events (TDEs) and supernovae (SNe). Transients may either be discovered by the on-board detection of a new source or by the brightening of a previously known source. We show that Gaia transients can be identified as new detections on-board for offsets from the host galaxy nucleus of 0.1--0.5,arcsec, depending on magnitude and scanning angle. The Gaia detection system shows no significant loss of SNe at close radial distances to the nucleus. We used the detection efficiencies to predict the number of transients events discovered by Gaia. For a limiting magnitude of 19, we expect around 1300 SNe per year: 65% SN Ia, 28% SN II and 7% SN Ibc, and ~20 TDEs per year.

  13. Protection of Renewable-dominated Microgrids: Challenges and Potential Solutions

    Energy Technology Data Exchange (ETDEWEB)

    Elkhatib, Mohamed [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Ellis, Abraham [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Biswal, Milan [New Mexico State Univ., Las Cruces, NM (United States); Brahma, Sukumar [New Mexico State Univ., Las Cruces, NM (United States); Ranade, Satish [New Mexico State Univ., Las Cruces, NM (United States)

    2016-11-01

    In this report we address the challenge of designing efficient protection system for inverter- dominated microgrids. These microgrids are characterised with limited fault current capacity as a result of current-limiting protection functions of inverters. Typically, inverters limit their fault contribution in sub-cycle time frame to as low as 1.1 per unit. As a result, overcurrent protection could fail completely to detect faults in inverter-dominated microgrids. As part of this project a detailed literature survey of existing and proposed microgrid protection schemes were conducted. The survey concluded that there is a gap in the available microgrid protection methods. The only credible protection solution available in literature for low- fault inverter-dominated microgrids is the differential protection scheme which represents a robust transmission-grade protection solution but at a very high cost. Two non-overcurrent protection schemes were investigated as part of this project; impedance-based protection and transient-based protection. Impedance-based protection depends on monitoring impedance trajectories at feeder relays to detect faults. Two communication-based impedance-based protection schemes were developed. the first scheme utilizes directional elements and pilot signals to locate the fault. The second scheme depends on a Central Protection Unit that communicates with all feeder relays to locate the fault based on directional flags received from feeder relays. The later approach could potentially be adapted to protect networked microgrids and dynamic topology microgrids. Transient-based protection relies on analyzing high frequency transients to detect and locate faults. This approach is very promising but its implementation in the filed faces several challenges. For example, high frequency transients due to faults can be confused with transients due to other events such as capacitor switching. Additionally, while detecting faults by analyzing transients

  14. Acetylcholine modulates transient outward potassium channel in acutely isolated cerebral cortical neurons of rats

    Institute of Scientific and Technical Information of China (English)

    Lanwei Cui; Tao Sun; Lihui Qu; Yurong Li; Haixia Wen

    2009-01-01

    BACKGROUND:The neuronal transient outward potassium channel has been shown to be highly associated with acetylcholine.However,the influence of acetylcholine on the transient outward potassium current in cerebral cortical neurons remains poorly understood.OBJECTIVE:To investigate acetylcholine modulation on transient outward potassium current in rat parietal cortical neurons using the whole-cell patch-clamp technique.DESIGN,TIME AND SETTING:A neuroelectrophysiology study was performed at the Department of Physiology,Harbin Medical University between January 2005 and January 2006.MATERIALS:Wistar rats were provided by the Animal Research Center,the Second Hospital of Harbin Medical University;PC-IIC patch-clamp amplifier and IBBClamp data collection analysis system were provided by Huazhong University for Science and Technology,Wuhan,China;PP-83 microelectrode puller was purchased from Narrishage,Japan.METHODS:The parietal somatosensory cortical neurons were acutely dissociated,and the modulation of acetylcholine (0.1,1,10,100 μmol/L) on transient outward potassium channel was recorded using the whole-cell patch-clamp technique.MAIN OUTCOME MEASURES:Influence of acetylcholine on transient outward potassium current,potassium channel activation,and inactivation.RESULTS:The inhibitory effect of acetylcholine on transient outward potassium current was dose- and voltage-dependent (P<0.01).Acetylcholine was found to significantly affect the activation process of transient outward potassium current,i.e.,the activation curve of transient outward potassium current was left-shifted,while the inactivation curve was shifted to hyperpolarization.Acetylcholine significantly prolonged the time constant of recovery from inactivation of transient outward potassium current (P<0.01).CONCLUSION:These results suggest that acetylcholine inhibits transient outward potassium current by regulating activation and inactivation processes of the transient outward potassium channel.

  15. Analysis of trigger behavior of high voltage LDMOS under TLP and VFTLP stress

    Energy Technology Data Exchange (ETDEWEB)

    Zhu Jing; Qian Qinsong; Sun Weifeng; Liu Siyang, E-mail: zhj_seu@126.co [National ASIC System Engineering Research Center, Southeast University, Nanjing 210096 (China)

    2010-01-15

    The physical mechanisms triggering electrostatic discharge (ESD) in high voltage LDMOS power transistors (> 160 V) under transmission line pulsing (TLP) and very fast transmission line pulsing (VFTLP) stress are investigated by TCAD simulations using a set of macroscopic physical models related to previous studies implemented in Sentaurus Device. Under VFTLP stress, it is observed that the triggering voltage of the high voltage LDMOS obviously increases, which is a unique phenomenon compared with the low voltage ESD protection devices like NMOS and SCR. The relationship between the triggering voltage increase and the parasitic capacitances is also analyzed in detail. A compact equivalent circuit schematic is presented according to the investigated phenomena. An improved structure to alleviate this effect is also proposed and confirmed by the experiments. (semiconductor devices)

  16. An non-uniformity voltage model for proton exchange membrane fuel cell

    Science.gov (United States)

    Li, Kelei; Li, Yankun; Liu, Jiawei; Guo, Ai

    2017-01-01

    The fuel cell used in transportation has environmental protection, high efficiency and no line traction power system which can greatly reduce line construction investment. That makes it a huge potential. The voltage uniformity is one of the most important factors affecting the operation life of proton exchange membrane fuel cell (PEMFC). On the basis of principle and classical model of the PEMFC, single cell voltage is calculated and the location coefficients are introduced so as to establish a non-uniformity voltage model. These coefficients are estimated with the experimental datum at stack current 50 A. The model is validated respectively with datum at 60 A and 100 A. The results show that the model reflects the basic characteristics of voltage non-uniformity and provides the beneficial reference for fuel cell control and single cell voltage detection.

  17. Voltage Management in Unbalanced Low Voltage Networks Using a Decoupled Phase-Tap-Changer Transformer

    DEFF Research Database (Denmark)

    Coppo, Massimiliano; Turri, Roberto; Marinelli, Mattia

    2014-01-01

    The paper studies a medium voltage-low voltage transformer with a decoupled on load tap changer capability on each phase. The overall objective is the evaluation of the potential benefits on a low voltage network of such possibility. A realistic Danish low voltage network is used for the analysis...

  18. Estimating Voltage Asymmetry Making by One Phase Micro-generator in Low Voltage Network

    Directory of Open Access Journals (Sweden)

    Marian Sobierajski

    2014-12-01

    Full Text Available Connection of one phase micro-generator to the low voltage network increases voltage asymmetry. The voltage asymmetry is defined as the quotient of negative and positive voltage components. The mathematical background of exact and rough computation of the asymmetry quotient is presented in the paper. Considerations are illustrated by simple examples.

  19. 76 FR 70721 - Voltage Coordination on High Voltage Grids; Notice of Staff Workshop

    Science.gov (United States)

    2011-11-15

    ... Energy Regulatory Commission Voltage Coordination on High Voltage Grids; Notice of Staff Workshop Take notice that the Federal Energy Regulatory Commission will hold a Workshop on Voltage Coordination on High Voltage Grids on Thursday, December 1, 2011 from 9 a.m. to 4:30 p.m. This staff-led workshop will be...

  20. Improving transition voltage spectroscopy of molecular junctions

    DEFF Research Database (Denmark)

    Markussen, Troels; Chen, Jingzhe; Thygesen, Kristian Sommer

    2011-01-01

    Transition voltage spectroscopy (TVS) is a promising spectroscopic tool for molecular junctions. The principles in TVS is to find the minimum on a Fowler-Nordheim plot where ln(I/V2) is plotted against 1/V and relate the voltage at the minimum Vmin to the closest molecular level. Importantly, Vmin...... is approximately half the voltage required to see a peak in the dI/dV curve. Information about the molecular level position can thus be obtained at relatively low voltages. In this work we show that the molecular level position can be determined at even lower voltages, Vmin(α), by finding the minimum of ln...