Improved calculations for no-load transformer switching surges

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     

真空断路器电磁瞬态仿真模型的研究与应用

由于真空断路器具有优良的开断和绝缘恢复性能，因此，可用来开断由于电弧不稳定而产生的高频电流。在一定的电网奈件下，在开断高频电流的过程中可能引起多次重燃和严重的过电压。本文的主要目的是用PSCAD建立真空断路器模型来展现断路器的真实特性。这个模型融合了燃弧时间、截流，介质恢复强度及断路器的熄弧能力等所有本质特性。采用开断实用的电炉用变压器来检验本文所开发的三相真空断路器的模型。并提供了检验结果。     

基于低能量直流的真空断路器短路开断能力评估

针对目前真空断路器无法在现场进行短路开断能力评估的问题,提出一种利用低能量直流对真空断路器短路开断能力的评估方法。首先分析真空断路器的基本结构和电弧开断原理,得出工程实践中真空断路器开断故障电流失败的原因;其次使用小容量直流高电压、直流大电流模拟真实情况,在断路器触头间注入可控的直流电流和直流电压,通过检测断路器分闸过程电气量变化时间来评估断路器的极限开断能力。对安徽某变电站VS1-12真空断路器进行现场测试,结果表明低能量直流法能有效评估真空断路器短路开断能力,适合现场对断路器短路开断能力的筛查评估。     

Application of controlled switching to 500-kV shunt reactor current interruption

To suppress reignition overvoltages caused when a 500-kV shunt reactor current is interrupted by a 550-kV one-break circuit breaker (CB), a study was carried out on controlled switching. Using a full-scale test circuit, reactor current interruption tests were carried out to obtain the relation between opening phase angle and generation of reignition. The results showed that even with the dispersion of CB operations taken into account, there were contact separation points free from high reignition overvoltages. It was also proved that no voltage escalations were caused by reignition and high-frequency arc extinction, and that overvoltages due to current chopping were at a safe level in terms of equipment insulation.     

Overvoltages due to switching off an unloaded transformer with avacuum circuit breaker

When a vacuum breaker is used to disconnect an unloaded transformer, high overvoltages may result on the secondary side. The phenomena of current chopping and multiple reignitions after contact opening, shortly before current zero, play a significant role in generating these overvoltages, Furthermore, the transient recovery voltage (TRV) is also influenced by virtual current chopping which may lead to fast interruptions and reignitions. The paper reports on a vacuum breaker model implemented in the ATP-EMTP program. Simulations have been performed to determine overvoltages generated by the vacuum breaker, before and after suppression. Network elements were simulated by simplified models of limited complexity     

真空断路器开断并联电抗器过电压试验研究

针对国内35kV与20kV系统真空断路器开断并联电抗器系统事故多发情况,开展35kV系统工况下的现场试验,分析了开断后的暂态过程及过电压的机理,并在实验室进行了20kV系统真空断路器在额定电流下投切电抗器的截流试验,研究截流值和过电压规律。结果表明:截流过电压幅值远小于重燃过电压,多次重燃过电压是真空断路器开断并联电抗器频繁出现高过电压的主要原因;在系统典型额定工况下,300A负载电流下的截流值比100A负载电流下小,真空断路器的截流值随着开断电流的增大而减小的理论在系统额定电流下同样成立。     

Clearing faults near shunt capacitor banks

Fault interrupting tests on high-voltage circuit breakers confirmed the problems of breaking a short-circuit current, which can occur in substations with shunt capacitor banks. Research was conducted on the behavior of different extinguishing media. Tests show that all types of circuit breakers (including the restrike-free breakers) have reignitions after the interruption of faults in the vicinity of a shunt capacitor bank. This is caused by the low rate of rise of the recovery voltage which gives the circuit breaker an opportunity to clear at short arcing times. Reignitions occur because of the low dielectric withstand capability of the small contact gap. Both tests and computer calculations show high overvoltages when the circuit breaker interrupts at one of the superimposed high-frequency current zeros which are created after reignition. Some breakers interrupt at a high-frequency current zero and thus create overvoltages. Other breakers do not interrupt at a high-frequency current zero and wait for a current zero of the power-frequency current, thus prolonging the arcing time. The overvoltages in three-phase circuits are higher than in single-phase circuits     

对1000kV电网操作过电压及相位控制高压断路器的讨论

根据500kV及750kV电网操作过电压的数据以及1000kV电网应有的过电压水平,指出了对于1000kV电网断路器关合开断可能引起的多种操作过电压(如开断并联电抗器及开断中小短路电流的的重燃过电压等)必须给予重视.近年来国外用以抑制操作过电压的装置除并联电阻的高压断路器及氧化锌避雷器以外,相位控制高压断路器日益得以广泛应用.文章介绍了国外相控高压断路器的应用情况,总结了相控高压断路器的关键技术,并对将其应用于我国1000kV电网提出了几点建议.     

10kV永磁断路器驱动电路设计及其脉宽调制仿真

永磁断路器作为过零投切开关使用是一个新的应用领域。针对目前普遍采取的直接电容对断路器线圈放电,断路器线圈开关电流不一致而导致永磁断路器开关动作存在分散性的问题,设计了一种新型永磁断路器驱动电路,跟踪给定线圈工作电流,保证线圈开关动作电流相同,并给出了的电路参数选择方法及适用范围,最后用软件进行了仿真,验证了方案的可行性。     

真空断路器操作过电压对电机产生的危害及对策

真空断路器开断电机回路时 ,会产生截流过电压、多次重燃过电压及三相同时截流过电压。因此 ,在电机回路中装设真空断路器时 ,必须有完善的保护设备来限制真空断路器的操作过电压 ,以保护主设备 ,使电力系统安全、可靠、经济地运行。特别是在发电机回路中使用真空断路器时 ,更要慎重 ,除具有完善的保护措施外 ,还要考虑其绝缘水平配合、发电机回路的电容电流、切断直流分量的要求等因素 ,使真空断路器的优良性能得到充分发挥     

Comparing direct and synthetic tests for interruption ofline-charging capacitive current

Using a validated arc model, this paper analyzes current distortion and voltage waveforms during both direct and synthetic tests for interruption of line-charging capacitive current by power circuit breakers. Although the voltage of the electric arc drawn between breaker contacts may produce significant current distortion, it is demonstrated that the most significant parameter affecting the breaking capacity of power circuit breakers in capacitive-current switching tests is the voltage jump appearing across breaker contacts immediately after current interruption. It is essential to correctly define the supply circuit impedances and the associated voltage jump so as not to reduce or increase this test severity unduly     

Steep fronts at transient recovery voltages appearing with the interruption of inrush currents of transformers

High lightning overvoltages do not appear in underground substations connected to transmission cables. Consequently, it is very important to thoroughly investigate switching overvoltages and to achieve rational insulation coordination for apparatus installed in such underground substations. This paper discusses the occurrence of steep fronts at transient recovery voltages (TRV) appearing at circuit breakers when the inrush currents of transformers are interrupted. Caused by a steep front at the TRV, reignitions occur at circuit breakers, resulting in the generation of high overvoltages with high frequencies. The overvoltages are among the highest switching overvoltages appearing at the terminal of a transformer. The authors clarified the mechanism of the generation of steep fronts at TRV by means of EMTP analysis, as well as by carrying out tests in a high‐power laboratory. © 2001 Scripta Technica, Electr Eng Jpn, 135(1): 24–32, 2001     

Application of 800-kV SF6 dead tank circuit breaker with transmission line surge arrester to control switching transient overvoltages

An 800-kV metal oxide transmission line surge arrester (TLA) has been developed, installed and tested on the AEP 765-kV Marysville-Kammer transmission line. The purpose of this TLA is to pave the way for the development, construction and application of an 800-kV SF/sub 6/ dead tank circuit breaker without closing resistors and free standing current transformers at American Electric Power's (AEP) 800-kV Orange station. Eight hundred kilovolts is the maximum design operating voltage, and 765 kV is the nominal operating voltage. Successful field test results of the TLAs ability to limit switching overvoltages emanating from circuit breaker operation to below the transmission line switching withstand are given. In addition, successful test results of the 800-kV dead tank circuit breaker design dielectric test are given in this paper.     

大中容量短路试验发电机主要设计特点

短路试验发电机又称冲击发电机,是一种专门用于短路试验的特殊发电机(电力系统的高压断路器、开关、变压器等元件进行短路电流开断、电强度、高瞬态电流等项试验).该机由小功率电动机拖动,当转速达到额定转速后,把空载电压下的机械能经短路后变为电能输送到被试品.本文围绕哈电机公司生产的短路试验发电机,介绍其主要设计特点.     

低压真空断路器的大电流开断技术

低压真空断路器具有无火灾爆炸危险、良好的环境适应性,以及寿命长、维护量小等一系列优点。低压真空断路器的开断能力与触头直径之间呈线性关系,其极限开断能力取决于电流过零时的触头表面温度。当它开断大的短路电流时,一般采用与电弧轴向垂直的横向磁场真空电弧控制技术,使集聚态真空电弧在触头表面上快速旋转,减轻时局部触头区域的烧蚀。在低压真空断路器中CuCr触头材料显示出最好的性能。低压真空断路器将在煤矿、化工、冶金、纺织、采矿等时断路器有较高环境要求的领域中占有一席之地。     

大容量发电机出口断路器选择

针对大容量发电机出口断路器的选择问题,依据GB/T 14824-2008、IEEE Std C37.013-1997和IEC 60909-0-2001中的计算方法,并结合发电机出口断路器型式试验报告的有关数据,以某百万千瓦级发电机组为例进行了比较计算,分析计算结果,提出了对发电机出口短路器短路电流开断能力不能采用百分比...     

基于分合闸电气量的真空断路器灭弧能力在线检测研究

高压真空断路器灭弧性能的退化易导致断路器触头动作过程中持续性电弧的产生,将会破坏触头表面粗糙度,导致滞后分合闸时间,严重时会引发击穿爆炸事故。因此,亟待开展高压真空断路器灭弧性能监测研究。现有对高压真空断路器灭弧性能的研究主要采用对灭弧室真空度的测量,但是存在测量周期较长、无法保证气密性等问题。通过分析灭弧室内熄弧原理,发现根据介质恢复时电弧电阻对电弧电流衰减特性的影响可以反演灭弧室内的熄弧水平。据此提取电弧电流趋势项作为灭弧能力的表征量,提出了一种仅基于电气量的高压真空断路器灭弧能力在线检测方法。该方法具有能够快速实时监测及测量手段安全的优势,现场实测数据及数字仿真验证了其有效性。     

有源配电网中的断路器应用研究

为解决有源网络的保护问题,对相关的断路器应用技术进行了研究。通过对电弧更有效的控制,实现直流断路器的开断能力与极性无关,使其满足光伏发电系统的保护需求。通过将真空灭弧技术与ACB操作机构相结合,提高断路器在AC690~1 140 V电压下的开断能力。通过对操作过程的有限元分析和优化设计,提高断路器的操作寿命,使其满足风力发电系统的保护需求。通过采用方向性的区域选择性联锁技术,解决了多电源系统中的选择性保护问题。运行经验表明,上述工作有效提高了有源网络运行的安全性。     

特高压断路器的瞬态恢复电压研究

结合晋东南—南阳—荆门1 000 kV特高压试验示范工程，研究了交流1100 kV断路器瞬态问题中的断路器开断短路电流或失步解列后的瞬态恢复电压(transient recovery voltage，TRV)内容。在此基础上提出了我国交流1100 kV特高压断路器的工作条件建议，分析了特高压断路器TRV问题的前景。认为我国特高压电网断路器在不采用分闸电阻的条件下，可满足IEC断路器扩展标准和正在修订的我国电力行业断路器标准中对TRV的要求。