Restriction Of Shunt Reactor Overvoltage Caused By Vacuum Breaker In Switching Period

With the fast development of power electronics technology, the power electronic devices are widely used to supply the large and impactive load in industrial and mining enterprises where power quality is becoming a more and more prominent problem, especially the deficiency of reactive power. If the compensation hasn’t been undertaken, the reactive power of load will fluctuate and the capacity of electric equipment will not be fully utilized, which brings the consequences of decreased transmission ability and increased loss in power system. Therefore, necessary measures should be taken to compensate the reactive power. In 10-35kV distribution system compensation, referring to counterparts in long distance overhead transmission line, shunt reactor is usually used as local active power compensation through reactive voltage control system, which decides the number of energizing reactors according to the state of power system, and then cut in or out respective reactors by vacuum breaker. Vacuum breaker enjoys a preeminent arc extinguishing capability, which will cause cut-off overvoltage and restriking overvoltage in switching period. In recent years, several accidents have appeared because of operating overvoltage which is brought by cutting in and out shunt reactor. These accidents resulted in flashover of supplying transformers and switchgears. In more severe case, switchgear was burned down, which affected the secure operation of substation.In this thesis, shunt reactor overvoltage caused by vacuum breaker during switching period is theoretically analyzed and experimentally studied. Overvoltage mechanism and factors which may influent the level of overvoltage are studied as well. Between the year of 2011 and 2013 in Nanjing Power Grid, many accidents occurred in process of cutting in or out shunt reactors, leading to equipment fault eventually. After analyzing and resimulating these cases, measuring overvoltage of shunt reactor in the site, based on the data derived from the test, protective measures are put forward after combining experiment result and theoretical study in lab. Then the effect is verified by application in power system. The expanding plan is determined according to verification result, which eliminates the overvoltage causing by vacuum breaker in switching period completely.