WorldWideScience

Sample records for autotransformers

  1. Equipment set for protection of autotransformers

    Energy Technology Data Exchange (ETDEWEB)

    Nadel, L.A.; Lint, M.G.; Ribel, N.E.

    1985-08-01

    An equipment set for protection of 500+ kV power autotransformers has been developed. The entire equipment is contained in three cabinets. The first cabinet Sh2101 houses differential protection of an autotransformer and of its low-voltage busbars, one or two (depending on the voltage class) lead high-voltage insulation testers, protective devices for two-phase operation, circuits for automatic acceleration of backup action, overload relays, an alarm circuit signaling a short to ground on the low-voltage side, and tripping circuits. The second cabinet Sh2102 houses two 2-step distance relays and two directional zero-sequence current relays, one of each kind for the low-voltage side and another for the intermediate-voltage side, and circuits for manual acceleration of backup action. The third cabinet Sh2103 houses backup differential protection of an autotransformer as well as of its high-voltage and intermediate-voltage busbars, peak-current relays with holding elements for the low-voltage side, protection of the reactive branch on the low-voltage side, gas-leak protection circuitry, and tripping circuits. Reliability of the entire equipment is ensured by continuous operational monitoring of all meters and periodic spot-check testing of each cabinet, with appropriate logic and interlocking.

  2. 18-Pulse Converter Using 3/9 Auto-Transformer

    Directory of Open Access Journals (Sweden)

    Ahmad Hoteit

    2012-09-01

    Full Text Available This paper focuses to 3/9 phase auto-transformer with multiple windings per phase is powered a 9-phase AC to DC converter this type of transformer has 40o phase shift between the output voltages, it is supplied from a three phase AC source with star or delta connection, to use this type of transformer in aerospace the operation frequency should be at 400Hz in addition to reduce the current harmonic distortion through a three phase line reactor are connected after three phase AC source in this case the current harmonic distortion decreases to value less than 5% and it can be less than 3% level by using an additional suppression devices (Chokes at the output of the converter, this autotransformer includes three sections each spaced 120o electrically apart. Each section comprises a main winding and a pair of phase shift windings, it is a main element in 18 pulse converters, the multiphase rectification can be analyzed by using orcad simulation software, and shown the comparisons between the odd phases so that the 9 phases has a lower value of the ripple factor which is 0.763 %.

  3. High-Freqeuncy Analysis of Three-Winding Autotransformers 400/121/34 kV

    Directory of Open Access Journals (Sweden)

    Miroslav Gutten

    2008-01-01

    Full Text Available This article deals with a description of methods of an experimental analysis concerning the actual condition of windings and magnetic circuit of the autotransformer, which is required in power transmission companies all over the world.

  4. Measurements at autotransformer system Prenzlau-Stralsund; Messungen am Mehrspannungssystem Prenzlau-Stralsund

    Energy Technology Data Exchange (ETDEWEB)

    Levermann-Vollmer, D. [DB Energie GmbH, Frankfurt a.M. (Germany); Thiede, J. [Balfour Beatty Rail GmbH, Power Systems, Offenbach am Main (Germany)

    2002-10-01

    After conversion of Prenzlau-Stralsund line in 2002 to autotransformer supply measurements have shown advantages of this system by lower impedances and interference voltages compared to the conventional system and delivered decision criterias for future projects. (orig.) [German] Die Strecke Prenzlau-Stralsund wurde im Jahr 2002 auf Speisung mit Autotransformern umgestellt. Messungen haben die Vorteile dieses Systems in Form niedrigerer Impedanzen und Beeinflussungsspannungen gegenueber der herkoemmlichen Speisung bestaetigt und Entscheidungshilfen fuer kuenftige Projekte geliefert. (orig.)

  5. Ultra-Step-Up DC-DC Converter with Integrated Autotransformer and Coupled Inductor

    DEFF Research Database (Denmark)

    Siwakoti, Yam Prasad; Blaabjerg, Frede; Loh, Poh Chiang

    2016-01-01

    duty cycle. Further, an integrated passive regenerative circuit recycles the leakage energy of the coupled magnetics and transfer the leakage energy to the load, which helps to avoid high voltage spikes across the switch. This feature along with low stress on the switching device enables the designer......This paper introduces a new single-switch nonisolated dc-dc converter with very high voltage transfer ratio and reduced semiconductor voltage stress. The converter utilizes an integrated autotransformer and a coupled inductor on the same core to achieve a high step-up voltage gain without extreme...

  6. INVESTIGATION OF SPECIAL ASYMMETRICAL MODES OF THREE-PHASE THREE-LEG AUTOTRANSFORMERS

    Directory of Open Access Journals (Sweden)

    Bosneaga V.A

    2014-04-01

    Full Text Available the base of earlier proposed model calculations were made and were investigated peculiarities of special asymmetric modes of three-phase three legs autotransformer (AT with tertiary winding, connected in triangle. Calculations were carried out taking into account the electromagnetic coupling of coils, located on different legs. Modules and angles of currents and voltages vectors in autotransformer windings were calculated at breakage of one of the phases of the supply voltage and its simultaneous fault to ground at the side of AT. Based on these data vector diagrams were constructed, which give a visual representation of specific features of such regimes. Considered mode at grounded neutral is characterized by the occurrence of significant currents of the same value in all windings, app. equal to nominal current. Voltage of the windings varies slightly from the nominal values, except for the short-circuited phase. Furthermore, there is a considerable flow of the zero sequence flux, which may lead to additional heating of AT. At ungrounded neutral in this particular mode and absence of load on the secondary AT side, only a small magnetizing currents flows and neutral is significantly displaced. If the load is present, despite of the absence of the current in the neutral, currents in the windings, comparable with the nominal one appeared, also zero sequence flux appeared. In the general case, the currents of this failure (as in the previous case are much smaller, than the usual short-circuit currents, so are insufficient to trigger the relay protection, this may require additional measures to protect AT against such damage.

  7. 多端口直流-直流自耦变压器%Multiport DC-DC Autotransformer

    Institute of Scientific and Technical Information of China (English)

    林卫星; 劲宇; 程时杰

    2015-01-01

    该文提出了一种多端口直流–直流自耦变压器的拓扑,该多端口直流自耦变压器用于互联多个直流电压等级不同的直流系统。提出了多端口直流自耦变压器的潮流直接分析法以及潮流分解分析法,推导了多端口直流自耦变压器中各换流器额定电压与额定功率设计方法,设计了多端口直流自耦变压器的控制策略。以一个三端口直流自耦变压器为测试算例,在PSCAD/EMTDC下仿真验证了多端口直流自耦变压器的技术可行性。以互联±250、±320 kV和±400 kV直流系统为例,假设±250 kV 和±320 kV 系统的额定输入/输出功率分别为500 MW和1000 MW,采用常规的多端口直流–直流变换器技术所需要的换流器总容量为3000 MW,而采用多端口直流自耦变压器技术所需要总的换流器仅为775 MW,所使用的换流器总容量仅为现有技术的26%,显著节省了成本,降低了运行损耗。%This paper proposed a multiport DC-DC autotransformer to interconnect multiple DC grids with different DC voltages. Decomposed power flow analysis and direct power flow analysis for the multiport DC auto were proposed. Methods of dimensioning the voltage and power rating of each of the VSC converters in the multiport DC auto were derived. Controllers were designed to keep stable operation of the multiport DC auto. Simulation results of a 3-port DC auto demonstrated the technical feasibility of the multiport DC-DC autotransformer. Taking a 3-port DC auto interconnecting ±250, ±320 and ±400 kV DC grids as an example, suppose the power rating for each of the port is 500, 1 000 and 1 500 MW respectively, the 3-port DC auto only needs 775 MW VSC converters while a total of 3 000 MW VSC converters is required for conventional technology. The multiport DC auto can save significant amount of investment compared with conventional DC-DC technology.

  8. 基于零序电流分布的自耦变压器电流保护分析%Analysis of Current Protection for Auto-Transformer Based on Zero-Sequence Current Distribution

    Institute of Scientific and Technical Information of China (English)

    张连杰

    2011-01-01

    文中基于自耦变压器零序电流的分布特点,探讨了自耦变压器零序电流保护的构成及整定原则,重点分析了自耦变压器零序差动保护。%Based on zero-sequence current distributed characteristics of auto-transformer,the construction and setting principle of zero-sequence current protection is discussed in this paper.Particularly analyses zero-sequence current different protection of auto-transformer.

  9. Study on Feed Line Protection Disposition Plan of All-Parallel Autotransformer Power Supply System%全并联自耦变压器供电系统馈线保护配置方案研究

    Institute of Scientific and Technical Information of China (English)

    汪琪

    2012-01-01

    根据全并联自耦变压器(AT)供电系统的特点,给出了一种可以有效减少故障影响范围的馈线保护方案,研究了每部分的保护配置以及整定计算方法,通过对牵引网不同位置短路点短路故障的分析,给出了各保护之间的时限配合关系,满足了瞬时性故障时尽快恢复供电,永久性故障时尽可能的减少停电范围,使故障线路退出运行的要求。%According to the features of all-parallel autotransformer power supply system, this paper gave a feed line protection plan which could effectively reduce coverage of fault influence and studied the method of each part's protection disposition and setting calcu- lation. Via analysis to short circuit faults of traction electric network at short circuit points of different positions, time limit coordination relation was given between each protection, meeting the requirements of recovering power supply as soon as possible at instantaneous fault, reducing power off range as less as possible at permanent fault and making fault line go from operation.

  10. Auto-Transformation from IDEF0 to CPN%IDEF0与CPN的自动转换方法研究

    Institute of Scientific and Technical Information of China (English)

    周小舟

    2012-01-01

    在大型工程系统的建模与分析中,将系统的静态IDEF0模型转换为动态CPN模型的方法得到大量的应用,但是人工转换既繁琐也容易出错.该文在IDEF0和CPN模型的形式化表示分析的基础上,提出两种模型自动转换的一般步骤和方法.%In the practice of the modeling and analysis of the large-scale engineering system, transformation from the IDEFO models, applied for the static descriptions of the systems, to the CPN models which describe the dynamic attributes of the systems have been widely applied. Usually the manual transformations are trivial and prone to making mistakes. Based on the formal analysis and representation of the IDEFO and CPN models, a method is proposed to automate this process.

  11. Reducing the Risk of Damage to Power Transformers of 110 kV and Above Accompanying Internal Short Circuits

    International Nuclear Information System (INIS)

    Methods of increasing the operating reliability of power transformers, autotransformers and shunting reactors in order to reduce the risk of damage, which accompany internal short circuits and equipment fires and explosions, are considered

  12. Zero sequence blocking transformers for multi-pulse rectifier in aerospace applications

    DEFF Research Database (Denmark)

    Yao, Wenli; Blaabjerg, Frede; Zhang, Xiaobin;

    2014-01-01

    The power electronics technology plays an even more important role in the aerospace applications of More Electric Aircrafts (MEA). AutoTransformer Rectifier Units (ATRU) have been widely adopted in aircrafts due to its simplicity and reliability. In this paper, Zero Sequence Blocking Transformers...

  13. A-Source Impedance Network

    DEFF Research Database (Denmark)

    Siwakoti, Yam Prasad; Blaabjerg, Frede; Galigekere, Veda Prakash;

    2016-01-01

    A novel A-source impedance network is proposed in this letter. The A-source impedance network uses an autotransformer for realizing converters for any application that demand a very high dc voltage gain. The network utilizes a minimal turns ratio compared to other Magnetically Coupled Impedance S...... with an example single-switch 400 W dc-dc converter. For the closed-loop control design and stability assessment, a small signal model and its analysis of the proposed network are also presented in brief.......A novel A-source impedance network is proposed in this letter. The A-source impedance network uses an autotransformer for realizing converters for any application that demand a very high dc voltage gain. The network utilizes a minimal turns ratio compared to other Magnetically Coupled Impedance...

  14. The development of coil short circuits when transformer windings become contaminated with metal-containing colloidal particles

    International Nuclear Information System (INIS)

    The radiational-thermal development of coil short circuits due to the action of partial discharges of the first kind when the windings of transformers, autotransformers and shunting reactors become contaminated with metal-containing colloidal particles, formed in the transformer oil as a result of the interaction of the oil with the constructional materials (the copper of the windings, the iron of the tank, the core etc.) is considered. Acriterion of dangerous contamination of the coil insulation of the windings by metal-containing colloidal particles is proposed, namely, 3% of the mass content of copper and iron in it, which, if exceeded, may serve as a basis for recognizing the state of transformers, autotransformers and shunting reactors at a voltage of 110 kV and above the limit. It is shown that filters for continuously cleaning the oil play a considerable role in prolonging the life of transformer equipment.

  15. AC system stabilization via phase shift transformer with thyristor commutation

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Jose Carlos de; Guimaraes, Geraldo Caixeta; Moraes, Adelio Jose [Uberlandia Univ., MG (Brazil); Abreu, Jose Policarpo G. de [Escola Federal de Engenharia de Itajuba, MG (Brazil); Oliveira, Edimar Jose de [Juiz de Fora Univ., MG (Brazil)

    1994-12-31

    This article aims to present initially the constructive and operative forms of a phase-shift autotransformer which provides both magnitude and phase angle change through thyristor commutation, including a technic to reduce the number of thyristors. Following, it is proposed a control system to make such equipment an efficient AC system stabilizing tool. It is presented some simulation results to show the operation of this transformer in an electrical system. (author) 3 refs., 11 figs., 3 tabs.

  16. State-space average modelling of 18-pulse diode rectifier

    OpenAIRE

    Griffo, Antonio; Wang, J B; Howe, D.

    2008-01-01

    The paper presents an averaged-value model of the direct symmetric topology of 18-pulse autotransformer AC-DC rectifiers. The model captures the key features of the dynamic characteristics of the rectifiers, while being time invariant and computationally efficient. The developed models, validated by comparison of the resultant transient and steady state behaviours with those obtained from detailed simulations can, therefore, be used for stability assessment of electric power syste...

  17. Transformer regulated self-stabilizing chopper

    Science.gov (United States)

    Raposa, F. L. (Inventor)

    1969-01-01

    A self-stabilizing voltage regulator is described. Direct current voltage regulation employing a series transistor rendered conductive during various portions of a cycle is controlled by saturation of an autotransformer. The constant volt-second capacity of the transformer provides conduction time inverse to the input voltage whereby average output voltage is maintained constant. Conduction commenced in response to short gate signals, and resistor feedback for degenerative turn-off of the transistor was after transformer saturation. Standard output filters are also included.

  18. Modern distance relays for protection of electric transmission lines

    Energy Technology Data Exchange (ETDEWEB)

    Shneerson, E.M.; Fedorov, E.K.; Virt, A.N.

    1985-08-01

    The already commercially produced protective distance relaying equipment of the latest design includes PDE 2001 panel replacing the DZ-503 panel for 500-750 kV transmission lines, ShDE 2801/2 cabinets replacing EPZ-1636 and PZ-201 panels, module BRE 2801 of impedance relays replacing KRS-2/3 sets, and module BRE 2701 of distance relays replacing the PZ-3 set for protection against any kind of short-circuit along 10-35 kV transmission lines, also a set of distance relays in the Sh2102 cabinet for protection of 330 kV autotransformers. Any of these new 3-step distance relays is designed for any kind of interphase short-circuit. The panels and the cabinets are designed to coordinate the operation of all protective relaying devices by proper interconnection and circuit matching, with inclusion of necessary reserve capacity.

  19. Interfacing transformer for a pulsed load current exceeding 1 MA

    International Nuclear Information System (INIS)

    In much pulsed power experimentation a capacitor bank is discharged into an inductive load, but although sufficient energy may be available in the capacitors their voltage rating may considerably exceed that necessary for the load and the current delivered during the experiment may accordingly be too low. This paper describes a novel design of air-cored transformer that has been used as an interfacing or matching device in such a situation, where peak load currents between 1 and 2 MA were required. Design considerations led to the use of an air-cored autotransformer connection wound with copper sheet conductors. Although thick wide conductors and clamping are needed to prevent deformation due to high magnetic pressure, the transformer is nevertheless relatively simple, easy to make, lightweight and inexpensive. This paper describes the design and the winding arrangement of the transformer that was constructed, and presents typical experimental results

  20. Interfacing transformer for a pulsed load current exceeding 1 MA

    CERN Document Server

    Cliffe, R J; Brown, J

    2003-01-01

    In much pulsed power experimentation a capacitor bank is discharged into an inductive load, but although sufficient energy may be available in the capacitors their voltage rating may considerably exceed that necessary for the load and the current delivered during the experiment may accordingly be too low. This paper describes a novel design of air-cored transformer that has been used as an interfacing or matching device in such a situation, where peak load currents between 1 and 2 MA were required. Design considerations led to the use of an air-cored autotransformer connection wound with copper sheet conductors. Although thick wide conductors and clamping are needed to prevent deformation due to high magnetic pressure, the transformer is nevertheless relatively simple, easy to make, lightweight and inexpensive. This paper describes the design and the winding arrangement of the transformer that was constructed, and presents typical experimental results.

  1. Harmonic Domain Modelling of Transformer Core Nonlinearities Using the DIgSILENT PowerFactory Software

    DEFF Research Database (Denmark)

    Bak, Claus Leth; Bak-Jensen, Birgitte; Wiechowski, Wojciech

    2008-01-01

    This paper demonstrates the results of implementation and verification of an already existing algorithm that allows for calculating saturation characteristics of singlephase power transformers. The algorithm was described for the first time in 1993. Now this algorithm has been implemented using...... the DIgSILENT Programming Language (DPL) as an external script in the harmonic domain calculations of a power system analysis tool PowerFactory [10]. The algorithm is verified by harmonic measurements on a single-phase power transformer. A theoretical analysis of the core nonlinearities phenomena...... in single and three-phase transformers is also presented. This analysis leads to the conclusion that the method can be applied for modelling nonlinearities of three-phase autotransformers....

  2. THE METHODS AND THE RESULTS OF THE TESTING OF AN ASYNCHRONOUS GENERATOR WITH SIX PHASE ZONES

    Directory of Open Access Journals (Sweden)

    Bogatyrev N. I.

    2016-03-01

    Full Text Available The article contain the peculiarities of testing asynchronous generator with sixzone winding on the basis of the asynchronous motor series 4A100S4 and analysis of obtained characteristics. Circuit parameters of the stator winding can significantly affect the characteristics of the asynchronous generator. Asynchronous generator was tested with a stator winding connected star, autotransformer and sectional winding. Use chastising windings opens the possibility of applying various circuits of capacitors and the load to asynchronous generators, which in turn affect the efficiency and stabilizing properties of the electric machine. Asynchronous generators to test with sectional winding by confirmation of theoretical calculations for determine the most optimal scheme under connect capacitors and load, testing the stator winding. The volume of testing for asynchronous generators standard is not defined, so we proposed testing method, taking into account the design features of the stator winding. Asynchronous generators were tested with the help of special equipment with the use of analyzer of energy power quality. Article contains characteristics of idling, short circuit and others, considered the heat mode. On the basis of the results we have determined the parameters of the circuit, the efficiency and power factor of induction generator

  3. Adjustment of RVA-62 automatic field-current regulator

    Energy Technology Data Exchange (ETDEWEB)

    Petrov, A.A.; Karkazov, E.I.

    1985-08-01

    While the RVA-62 automatic field-current regulator performs adequately with small and medium-size turbogenerators, its stability margin being often sufficiently large to compensate design inaccuracies, a refinement is nevertheless recommended to ensure reliability under no-load as well as during parallel operation of generators into a common busbar group. The procedure is based on necessary adjustments of over 40 units and applies to redesign, measurements, breadboard simulation, settings, reassembly, and testing. First it is necessary to determine the correct number of primary and secondary turns in the universal controlled phase-compounding transformer, taking into account the parameters of associated equipment (autotransformer, filter choke, power rectifier, current transformer) as well as various modes of generator instability and the use of automatic field suppression. Revisions in testing circuitry and procedure are proposed, including more precise and some extra measurements, also replacement of selenium rectifiers with silicon diodes. Adjustments according to this scheme have been made in the RVA-62 regulators for 6-60 kW generators with VT exciters and 3000-12,000 kW generators, including Skoda, Siemens-Schuckert GmbH, Parsons Ltd units.

  4. Motor Starting Control Circuit Fault Diagnosis and Elimination Methods%电动机启动控制线路的故障诊断与排除方法

    Institute of Scientific and Technical Information of China (English)

    胡永春

    2015-01-01

    电动机直接启动控制线路的常见故障有:按启动按钮后电动机不能启动;接通电源无须启动按钮控制,电动机自行运转;电动机启动运转后,手离开按钮电动机便停转;按下停机按钮,电动机不能停转,等等。本文阐述了Y-△降压启动控制线路的故障诊断与排除,自耦变压器降压启动线路的故障排除等问题。%the direct motor starting control circuit common fault are the main press the start button motor can not be started;the power supply is switched on without the start button control, motor bike;electric motor starts to work, the motor stops rotating hands off button; press the stop button, the motor can not stop etc.. This paper mainly introduces Y- reduced voltage starting control circuit fault diagnosis and elimination, autotransformer fault step-down start line to eliminate the problem.

  5. 变压器整流电压输出受电压不平衡输入影响的分析

    Institute of Scientific and Technical Information of China (English)

    臧桂美; 刘焕秀

    2015-01-01

    在变压器整流电路中,输出电压的不平衡对设备的影响是是相当大的,因此分析输入电压不平衡对输出电压的影响是非常重要的。在本文中将定量的分析隔离式变压器和自耦变压器不对称和输入电压不平衡对整流系统的影响,通过数据分析来详细的分析不同变压器参数与电压不平衡的关系。%In the transformer rectifier circuit, unbalance of the output voltage of the device is quite large, so the analysis input voltage imbalance on the output voltage is very important. This article wil be a quantitative analysis of isolation transformers and autotransformers asymmetries and imbalances affect the input volt-age of the rectifier system, through data analysis to a detailed analysis of the relationship between different parameters of transformer voltage imbalance.

  6. High voltage pulse generator. [Patent application

    Science.gov (United States)

    Fasching, G.E.

    1975-06-12

    An improved high-voltage pulse generator is described 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 the first rectifier connected between the first and second 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. The output voltage can be readily increased by adding additional charging networks. The circuit allows the peak level of the output to be easily varied over a wide range by using a variable autotransformer in the charging circuit.

  7. Chemistry of Stable Carbenes and «Green» Technologies

    Directory of Open Access Journals (Sweden)

    Korotkikh, N.I.

    2015-11-01

    Full Text Available Brief analysis of fundamental research in the chemistry of stable carbenes and applications in the field of «green» chemistry on their basis carried out at the L.M. Litvinenko Institute of Physical Organic & Coal Chemistry of NAS of Ukraine over the last decade is given. Carbene versions of ester Claisen condensation to form zwitterionic compounds, the Leuckart-Wallach reaction with the autoreduction of carbenoid azolium salts, Hofmann cleavage of aminocarbene insertion products, an induced tandem autotransformation of 1,2,4-triazol-5-ylidenes into 5-amidino-1,2,4-triazoles were found. New carbene reactions of ad dition, deesterification, oxidation and complexation were revealed. Effective methods of obtaining stable carbenes and carbenoids were suggested. New types of carbenes, namely benzimidazolylidenes, superstable conjugated biscarbenes and new types of carbenoids were synthesized. The existence of hypernucleophilic carbenes was theoretically predicted and experimentally confirmed. The prospects of the use of carbenes and their derivatives, in particular, carbene complexes of transition metals in catalysis of organic reactions and the search of biologically active compounds were shown.

  8. Evaluation of the schemes of protections of Sistema Nacional Interconectado of year 2014 by analyzing the transient stability

    International Nuclear Information System (INIS)

    The elaboration of a study of transient stability is seen as part of the planning process associated with the Plan de Expansion de la Transmision. Studies have historically contemplated the calculation of critics times of release of failures without allowing to obtain conclusive information about the performance of protection systems. An evaluation of the protection schemes of substations is determined make of the Sistema Nacional Interconectado of year 2014. Analysis of transient stability was used to verify compliance with the ''Criterios de Seguridad para la Planificacion, Diseno y Operacion del Sistema Electrico Nacional'' and ''Criterios de Calidad, Seguridad y Desempeno'' of the Reglamento del Mercado Electrico Regional in order to determine the necessary improvements. A methodology is proposed for simulating the behavior of protection systems using the software PSS/E, which has replaced the methodology based on the calculation of critical times. The presence of 42 substations were determined in which the release of failures for remote backup has caused unstable conditions of the system. 174 improvements have identified as necessary among which are: the implementation of distance relays in autotransformers, differential protections in reactors, differentials of lines and overcurrents of definite time in lines, duplication of differentials in bars, the replacement of pole breakers for monopolar and duplication of breakers of link bars. The current criteria have been recommended to supplement with probabilistic criteria to avoid incurring unnecessary investments. (author)

  9. 变压器整流电压输出受电压不平衡输入影响的分析

    Institute of Scientific and Technical Information of China (English)

    臧桂美; 刘焕秀

    2015-01-01

    In the transformer rectifier circuit, unbalance of the output voltage of the device is quite large, so the analysis input voltage imbalance on the output voltage is very important. This article wil be a quantitative analysis of isolation transformers and autotransformers asymmetries and imbalances affect the input volt-age of the rectifier system, through data analysis to a detailed analysis of the relationship between different parameters of transformer voltage imbalance.%在变压器整流电路中,输出电压的不平衡对设备的影响是是相当大的,因此分析输入电压不平衡对输出电压的影响是非常重要的。在本文中将定量的分析隔离式变压器和自耦变压器不对称和输入电压不平衡对整流系统的影响,通过数据分析来详细的分析不同变压器参数与电压不平衡的关系。

  10. 带多脉波整流的级联逆变器研究%Research on Cascaded Inverter With Multiple Pulse Waveform Rectifier

    Institute of Scientific and Technical Information of China (English)

    徐海波; 朱忠尼; 陈元娣; 王永攀

    2012-01-01

      This paper presents a combined converter circuit of high power inverter consisted of multiple pulse waveform rectifier with autotransformer and cascaded inverter, by combining the advantages of multiple pulse waveform rectifier and cascaded inverter. In view of the problem that the triggering angle control algorithm of the current cascaded inverter with staircase control can only apply to a constant voltage difference mode and not be on line calculation, this paper proposes an easy algorithm that can be applied to a varying voltage differential mode and the on line calculation of triggering angle implemented. Finally, by the experimental results, the correctness of the theoretical analysis is verified, which shows the proposed combinative converter circuit is of higher utility value for high power inverter.%  将多脉波整流和级联逆变器两者的优点相结合,提出了一种采取带自耦变压器的多脉波整流和级联逆变器构成大功率逆变器的组合式变换电路。针对目前阶梯波控制级联逆变器的触发角控制算法仅适用于等电压差模式且不能在线计算的问题,提出了一种适用于电压级差不等模式且可实现触发角在线计算的简易算法。最后通过实验结果验证了理论分析的正确性。该组合式变换电路在大功率逆变器应用中具有较高的实用价值。

  11. Tissue Microarray Study of Vasculogenic Mimicry in Bi-directional Differentiated Malignant Tumors

    Institute of Scientific and Technical Information of China (English)

    XishanHao; BaocunSun; ShiwuZhang; XiulanZhao

    2004-01-01

    OBJECTIVE To determine if vasculogenic mimicry (VM) exists in bi-directional differentiated malignant tumors. METHODS The blood supply models for bi-directional differentiated tumors were studied with immunohistochemical and PAS double-staining techniques. New sections were made from 158 paraffin-embedded bi-directional malignant-tumor samples, including melanoma (high malignancy n=30, low malignancy n=30); synoviosarcoma(SS) (high malignancy n=26, low malignancy n=13); acinar rhabdomyosarcoma (All) (high malignancy n=16,low malignancy n=13); malignant mesothelioma (MM) (n=26), and epithelioid sarcoma (ES)(n=4). Tissue microarrays were made. The representative points in the paraffin sections were labeled and two tissue microarrays were made, one included 60 cases of melanoma, and the other included the other tumors. Immunohistochemical staining of the platelet-endothelial cell adhesive molecule(CD31 antigen) and periodic acid Schiff(PAS) staining were conducted. The areas were calculated of vessel-like channels consisting of CD31 antigen-positive tumor cells and of PAS positive materials. The VM was studied using the data obtained. RESULTS Some of these bi-directional tumor cells secreted PAS-positive materials and 0D31 positive materials. The walls of the VM consisted of PAS-positive materials lined with CD31 negative tumor cells with red blood cells inside the channel, whereas the walls of the epithelium-dependent vessels were comprised of CD31 positive materials. The positive areas of CD31 were significantly less than that of PAS (P<0.01). The number of cases with VM in highly malignant tumors was greater than that found in the lowly malignant tumors. CONCLUSIONS Bi-directional differentiated malignant tumor cells have the ability to auto-transform and might interact with the extracellular matrix to form a vessel channel system which mimics blood vessels for transporting blood. That process is called VM. Results in this study show that bi

  12. A Novel Full-Size Power Converter for Wind Energy Conversion System%一种新型的风力发电全功率变流器

    Institute of Scientific and Technical Information of China (English)

    陈杰; 龚春英; 陈家伟; 张方华; 严仰光

    2012-01-01

    Abstract A novel full-size power converter which consists of a machine side auto-transformer rectifier unit (ATRU) and grid side Z-source inverter(ZSI)is proposed in this paper. The power converter owns the merits of simple structure, high reliability, and high efficiency, which could cater for the off shore wind turbines where high reliability is required. The operational principle of the ATRU and ZSI is briefly introduced. Some design rules are concluded based on the feasibility analysis of applying ATRU to variable speed wind turbines. Then, the relationship between input voltage and dc link voltage of ZSI is carefully discussed, which decides the design requirements of PMSG and inverter A control strategy including the functions of maximum power point tracking (MPPT) function and dc link voltage stabilizing is devised for the wind energy conversion system (WECS), based on the proposed full-scale power converter, and the input voltage feed forward control method is adopted for the ZSI. to improve the dynamic performance of do link peak voltage. Finally, a simulation case is implemented, and the simulation results show the correctness and feasibility of the proposed power converter and its control strategy.%提出了一种新型的风力发电全功率变流器,由电机侧自耦调压整流器(ATRU)和网侧z源逆变器(ZSI)组成,具有结构简单、可靠性高、转换效率高等优点,为风力发电系统提供了一种可选的解决方案。文中首先简要地介绍了ATRU和ZSI的基本工作原理,对ATRU在变速风电机组中应用的可行性展开了推导分析,提出了相关设计要求。随后,针对网侧ZSI,详细地分析了其输入电压和直流链电压之间的内在关系,揭示了发电机和逆变器之间的参数匹配要求。设计了一种系统控制策略,实现了机组的最大功率跟踪,并提出了一种基于输入电压前馈的逆变器直流链电压控制方法,保证机组在各

  13. 交流传动机车与直流传动机车混合运用条件下牵引网电压控制技术%Traction Network Voltage Control Techniques under the Condition of Hybrid Application of AC Drive and DC Drive Locomotives

    Institute of Scientific and Technical Information of China (English)

    李强; 吴命利

    2014-01-01

    在大秦重载铁路上,担当万吨和两万吨重载列车牵引任务的即有 HXD1型、HXD2型交流传动电力机车,也有S S4型直流传动电力机车。由于这两种电力机车具有不同的电气负荷特性,在大秦线的部分区段,保持牵引变电所母线电压处在适当水平成为一个需要解决的技术问题。结合算例,本文给出因S S4型电力机车功率因数低而导致的网压降低和 HXD1型电力机车再生制动引起的网压升高的仿真计算结果,分析电源短路容量、牵引变压器、无功补偿装置以及牵引网阻抗对网压变动的影响。对包括使用有载调压牵引变压器、有载调压自耦变压器、晶闸管控制串联变压器、串联电容器和功率平衡调节器等在内的不同改善网压技术方案进行比较。基于现代电力电子技术的功率平衡调节器不但能有效稳定网压还能综合治理电能质量,有望为该问题提供最佳解决方案。%Both the AC drive locomotives , HXD1 and HXD2 , and the DC drive locomotive , SS4 , are designated for 10 000 t and 20 000 t heavy-duty haul on the Datong-Qinhuangdao Heavy-haul Railway Line . Due to the distinct electric loading characteristics of these two types of locomotives , how to maintain the bus bar voltage in traction substations in some sections of the Line at an appropriate level has become a technical issue to be handled .By a numerical example , the voltage drop caused by the low power factor of Locomotive SS4 and the voltage rise caused by the regenerative braking of Locomotive HXD1 were computed . The influences of the power source capacity , the traction transformer , the reactive power compensator and the impedance of the traction network on the voltage variations were analyzed . Different voltage improving schemes , including those schemes with use of the on-load tap changing traction transformer , the on-load voltage regulating auto-transformer , the thyristor

  14. Analysis and design of modular three-phase power factor correction schemes for utility interface

    Science.gov (United States)

    Hahn, Jae-Hong

    The extensive use of non-linear and electronically switched loads in power system has lead to higher incidences of harmonic distortion of the voltage and current waveforms. Harmonic currents degrade power quality and are considered the main source of many system malfunctions. Technical guidelines and standards regarding suppressions of system harmonic contents have been enacted. This dissertation proposes several new three-phase power factor correction (PFC) schemes using single-phase PFC modules. An integrated single-switch approach is first proposed. This is essentially an add-on solution to standard ASD's. This approach is based on circulating third harmonic current between neutral and DC mid-point by utilizing a lossless resistor. Single-phase PFC emulates this resistor to control the amplitude of the current, which is implemented by the dynamic breaking chopper available in standard adjustable speed drives (ASD's). This approach is also capable of reducing harmonic distortion in multiple drives. Analysis, design and simulations are conducted to determine the performance of the proposed scheme with different line impedances and with and without dc-link inductance in the ASD. Experimental results are presented using commercial ASD retrofitted with the proposed approach. Second scheme proposes a three-phase PFC using two standard single-phase PFC modules. In this approach, three-phase input is transformed into two-phase by means of 0.14 pu autotransformer. Two standard single-phase PFC modules are employed to process two-phase power to do output. Split inductors and diodes are employed to limit the interaction between the two phases. A method to eliminate the interaction between phases is also described. Due to cascade operation of two PFC stages, low frequency (120Hz) ripple in dc-link is cancelled. An active interphase transformer (IPT) scheme is proposed to draw sinusoidal input line currents, in the third study. This scheme utilizes a unique combination of a