真空断路器开断并联电抗器保护措施仿真分析

Simulation Analysis on Overvoltage Protection of Shunt Reactors with Switching-off Vacuum Circuit Breakers

近年来中国中压配电系统中真空断路器切除并联电抗器时故障频发,如站用变压器及母联开关等设备闪络,甚至引发开关柜烧毁的严重事故。以某220 kV变电站的20 kV系统发生的该类故障为研究对象,运用PSCAD/EMTDC建立该变电站系统模型,仿真分析故障发生时系统的运行状态,并结合故障现象分析故障发生原因,提出相应措施,以抑制真空断路器切除电抗器时的操作过电压。仿真计算结果表明,由于真空断路器开断时发生截流、复燃且电抗器与杂散电容间发生谐振等多个方面原因,真空断路器切除电抗器时产生较高过电压,如果仅在电抗器侧安装避雷器与电容器,将无法有效抑制由于截流和复燃产生的过电压,需要在电抗器两端并联阻容保护装置。针对故障变电站的系统配置,建议电抗器并联的阻容装置电容值取0.2μF,电阻值取400Ω为宜。

In recent years,overvoltage accidents occur frequently in distribution networks of 10～35 kV when shunt reactors are switched off by vacuum circuit breakers,such as flashover on house-transformers and coupler bus switches,even burning out switchgears.On the basis of this kind of accidents in a 20 kV system in a 220 kV substation,the power system simulation model of this substation was built with the PSCAD/EMTDC software.The operating status of the system was simulated to analyze the cause of the accident,and then the measures of suppressing overvoltage were proposed and verified.The simulation results show that the high overvoltage is caused by the current chopping,reignition and resonance between the reactor and the stray capacitance when the breaker switched off the reactor.The overvoltage couldn＇t be suppressed effectively if there were only arrests and capacitors installed.Therefore,the resistor-capacitor protection is recommended.For the substation of this paper,the resistance and capacitance values of the resistor-capacitor should be 400 Ω and 0.2 μF to be suitable to suppress the overvoltage effectually.