共查询到20条相似文献,搜索用时 31 毫秒
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Akihiro Ametani Nobuhiro Kuroda Toru Tanimizu Hiroshi Hasegawa Hideki Inaba 《Electrical Engineering in Japan》2001,134(3):44-52
An analytical formula for the transient recovery voltage and its derivative dv/dt across a circuit breaker has been derived for the case of a transformer secondary fault. A comparison of the calculated results with field test and EMTP simulation results has demonstrated it to have satisfactory accuracy. By applying the formula, the effects of various circuit parameters on the transient recovery voltage and its derivative dv/dt are elucidated. The derivative dv/dt, defined conventionally as the ratio of the crest value and the time to the crest, is found to be about two‐thirds of the maximum value of dv/dt given as a function of time. In addition, a formula for the critical circuit parameters at which dv/dt across a vacuum circuit breaker reaches the critical condition, that is, the circuit breaker fails to interrupt a fault current, is derived. © 2000 Scripta Technica, Electr Eng Jpn, 134(3): 44–52, 2001 相似文献
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Case study of HTS resistive superconducting fault current limiter in electrical distribution systems
《Electric Power Systems Research》2007,77(5-6):534-539
As electric power systems grow and become more interconnected, the fault current levels increase. Superconducting fault current limiters (SFCL) can limit the prospective short-circuit currents to lower levels, so that the underrated switchgears can be operated safely. In order to introduce SFCL into the electric power system, we need a way to conveniently predict the limiting characteristics in a given situation. We have developed an Electromagnetic Transient Program (EMTP) model of high temperature resistive type SFCL based on the electric field (E)–current density (J) characteristic of the superconductor. The SFCL in series with a circuit breaker could be practically used in electrical distribution systems. Case studies of EMTP simulations show that the SFCL cannot only limit the fault current to an acceptable value, but also reduce voltage decrease and the rise rate of the transient recovery voltage. In order to ensure the safe and proper usage of SFCL, some future considerations on the interaction between SFCL and power systems are presented as well. 相似文献
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Diah Permata Naoto Nagaoka 《IEEJ Transactions on Electrical and Electronic Engineering》2014,9(Z1):S37-S43
A method to measure a small capacitance with its loss resistance using a set of transient current waveforms is proposed in this paper. The parameters are obtained from the time constants in the time domain. The method has high resistance to extraneous noise, because a time‐to‐frequency transformation, which is sensitive to noise, is not required. The transient current waveforms are obtained by a voltage or current source, a current transformer, and a waveform recorder. The measured capacitance by the proposed method is not affected by the capacitance of the voltage probe, because it is obtained without any voltage information. The sheath surge impedance of the current injection cable, which is indispensable for the transient measurement, is corrected. The application of the method has the advantage in that it allows the modeling of a fast transient of a power apparatus, comparing it with the steady‐state measurement using an impedance measuring instrument. The proposed method is applied to create an equivalent circuit between electrodes implanted into a piece of wood, and its reliability is confirmed by comparison between the measured and calculated results. Stray capacitances of a miniature circuit breaker are also measured, and the results show that the proposed method is applicable to equipment in power systems. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. 相似文献
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This paper deals with a modeling of components and calculation of transient overvoltages that build up on the transformer primary terminals after the transformer has been switched off by a vacuum circuit breaker (VCB). The transformer is connected to the circuit breaker by a cable. The transient overvoltages are calculated for different cable lengths, and the cumulative probability of different arc angles is investigated. In this study two cases are considered: transient overvoltages due to steady-state magnetizing current switching, and transient overvoltages due to inrush current switching. It is shown that the case of inrush current switching is worse, as virtual current chopping is possible. The cable is modeled by pi sections, whereas the transformer model is based on a terminal impedance. The VCB re-ignitions are modeled by means of withstand voltage characteristics and high-frequency quenching capability. Due to shortage of field tests, this work uses only literature references to compare the results with actual measurements 相似文献
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Toshihiko Noguchi Satoshi Yajima Hiroyoshi Komatsu 《Electrical Engineering in Japan》2011,176(4):52-60
This paper describes a gate drive circuit which is capable of driving an ultrahigh‐speed switching device and of suppressing high‐frequency noise caused by its high dV/dt ratio of 104 V/μs order. SiC (silicon carbide)‐based power semiconductor devices are very promising as next‐generation ultrahigh‐speed switching devices. However, one of their application problems is how to drive them with less high‐frequency noise without sacrificing their ultrahigh‐speed operation capability. The paper proposes a new gate drive circuit specialized for such devices, which charges and discharges the input capacitance of the device by using an impulse voltage generated by inductors. This ultrahigh‐speed switching operation causes a high‐frequency common‐mode noise current in the gate drive circuit, which penetrates an isolated power‐supply transformer due to the parasitic capacitance between the primary and the secondary windings. In order to overcome this secondary problem, a toroidal multicore transformer is also proposed in the paper in order to reduce the parasitic capacitance drastically. By applying the former technique, the turn‐on time and turn‐off time of the power device were shortened by 50% and by 20%, compared with a conventional push‐pull gate drive circuit, respectively. In addition, the latter technique allows reduction of the peak common‐mode noise current to 25%, compared with the use of a conventional standard utility power‐supply transformer. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 176(4): 52–60, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21124 相似文献
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合闸750kV空载变压器引起的系统电压暂降现场实测与计算分析 总被引:1,自引:0,他引:1
结合新疆与西北750 kV联网工程乌北变电站合闸750 kV空载变压器现场实施情况,分析了合闸空载变压器引起系统工频电压暂降现象的机制,提出励磁涌流及系统短路容量是影响合空变电压暂降的主要因素。并利用EMTP工具对合空变引起的电压暂降进行仿真建模分析,得出的合空变励磁涌流及系统电压暂降特性与现场实测基本一致,验证了仿真方法的有效性。提出了采取断路器装设合闸电阻的措施可以有效抑制合空变操作引起的系统电压暂降,另外采取系统调压、调整系统运行方式、消除剩磁等措施也有助于缓解合空变电压暂降对系统运行造成的不利影响。 相似文献
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Toshiro Matsumura Toshiyuki Uchii Yasunobu Yokomizu 《Electrical Engineering in Japan》1999,127(1):31-38
This paper proposes a new type of fault current limiter (FCL), which consists of a high‐TC superconducting (HTS) element and two coils wound on the same core without any leakage magnetic flux. In this FCL, either the limiting impedance or the initial limiting current level can be controlled by adjusting the inductances and the winding direction of the coils. Therefore, this FCL could relax the material restrictions on high‐TC superconducting FCL. A current‐limiting experiment by a model FCL was carried out, and the limiting performance was observed. The initial limiting current level of the model FCL was 1.7 times higher than the critical current of the HTS element, and the fault current is suppressed to 52% immediately after the short‐circuit in the test. Considering voltage–current characteristics of a high‐TC superconductor in a computer simulation, the calculated results almost agreed with the experimental results. © 1999 Scripta Technica, Electr Eng Jpn, 127(1): 31–38, 1999 相似文献
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混合式高压直流断路器(DC Circuit Breaker, DCCB)的本质是分断故障电流。分断暂态过程中的电气参数是决定断路器分断性能的核心所在。在分析DCCB拓扑结构的基础上,将断路器分断暂态过程划分为三个阶段。通过建立带DCCB的直流电网故障等效电路和断路器分断各暂态阶段的系统级等效电路,来分析分断过程中断路器自身的暂态特性。将断路器自身参数与直流系统参数联合起来,分别对断路器的两次换流过程进行详细分析。建立了断路器分断电流、暂态电压和开断时间的数学模型,推导断路器分断全过程中的分断电流以及最大暂态电压的计算表达式,并分析了断路器参数对分断性能的影响情况。利用PSCAD/EMTDC软件,搭建系统级混合式DCCB仿真模型,验证了所建立的断路器暂态模型的正确性及参数选取对断路器开断性能的影响。 相似文献
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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 230 kV 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. 相似文献
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采用内桥接线方式的110kV芦都站2号主变差动保护高压侧装设两组CT,一组位于线路侧,另一组在桥联断路器处。当线路断路器重合到永久性故障时,线路的二次电流波形严重畸变,而桥联二次电流则为标准的正弦量,出现了同一型号的CT在同一电流下表现出了不同特性的问题,由此导致差动保护误动作。采用大电流试验与模拟剩磁效应的方法证实,电流波形畸变的原因在于剩磁的影响,剩磁使CT处于暂态饱和状态、暂态饱和导致传变特性变坏进而造成二次电流的畸变。采取抗饱和措施后问题得到解决。 相似文献
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高厂变分支开关误合闸引起的发电机误上电事故分析 总被引:2,自引:0,他引:2
发电机误上电故障有2种发生形式:一种是由发电机组的主开关误合闸引起,另一种是由厂用电系统开关误合闸引起。由厂用电系统开关误合闸引起的发电机误上电事故的故障电流小于由发电机组主开关误合闸的故障电流,计算分析表明普通误上电保护的整定思想对于由厂用电开关误合闸导致的误上电故障没有灵敏度。通过对发电厂厂用电系统负荷配置的分析,及对发电厂高压工作厂用变压器分支过流保护整定原则的分析探讨,通过对一起故障实例的计算分析,认为高厂变分支过流保护合适的整定定值将对保护此类误上电事故起到有效作用。同时分析了由厂用电系统开关误合闸导致发电机组误上电的几种情况,提出了几种有效的防范措施。 相似文献
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500kV罐式断路器电流互感器二次回路接线错误的分析及对策 总被引:2,自引:0,他引:2
介绍了一起因500 kV罐式断路器电流互感器二次回路接线错误而产生的重大隐患,当500 kV罐式断路器本体发生故障时,由于线路保护与母线保护使用的电流互感器绕组接线未实现交叉,使得两者的保护范围没有交叉,存在保护死区,从而会导致主保护拒动。通过对全站500 kV系统保护用电流互感器绕组接线的检查和分析,发现造成保护死区主要是设计和安装两方面的原因,针对这两方面原因,提出了加强规范管理,在设计施工阶段加强一二次施工人员的配合以及施工、验收和日常维护时注重对该部分的检查等一系列具体的反事故措施,为今后罐式断路器继电保护用电流互感器绕组的设计、安装调试以及现场验收及维护提供了借鉴。 相似文献
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35kV真空断路器开断空载变压器时过电压的研究 总被引:2,自引:0,他引:2
切除空载变压器是真空断路器操作过电压问题最严重的情况,文中在真空断路器开断交流电流真空间隙介质恢复的物理过程的基础上,建立了灭弧室介质强度恢复的数学模型,采用Saber软件的MAST语言编程,对真空断路器开断空载变压器的一个完整过程进行了仿真计算。根据计算结果。分析了暂态过程,过电压的特点 及变压器,真空断路器参数对过电压的影响,并与平均恢复速度计算结果进行了比较,表明本文建立的灭弧室计算模型更接近于实测恢复特性。 相似文献
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Tadashi Koshizuka Takeshi Shinkai Susumu Nishiwaki Satoru Yanabu Yoshihiro Kawaguchi 《Electrical Engineering in Japan》2002,141(4):25-33
This paper shows the calculation of SLF interrupting performance for two serially connected Mayr‐type arc models with different arc parameters by using EMTP‐ATP Models. Arc model 1, assuming an air circuit breaker, has large arc time constant and large arc power loss. Arc model 2, assuming a vacuum circuit breaker, has small arc time constant and small arc power loss. It was not possible for arc model 1 to interrupt 300 kV‐63 kA‐90% SLF by itself. However, by connecting these arc models in series, interruption became successful, even if arc model 2 was reignited at low voltage a few microseconds after current zero. These computations suggested that serial connection of the two circuit breakers with different breaking characteristics would give a totally excellent circuit breaker by making the best use of advantages of each circuit breaker. EMTP‐ATP Models were very useful in solving the arc models, which are expressed by differential equations and coupled with the electric circuit. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(4): 25–33, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10020 相似文献