Phenomena and Mechanism Analysis on Overvoltages Caused by 40.5-kV Vacuum Circuit Breakers Switching Off Shunt Reactors

In view of frequent and severe overvoltage failures of 40.5-kV vacuum circuit breakers (CBs) while switching off the shunt reactors in the 35-kV distribution systems in China, a series of field tests was carried out to determine the mechanism of this kind of disruption. The transient process and phenomena were analyzed and summarized based on the overvoltage waveforms obtained from the field tests. The experimental results indicated that the probability of reignition is greater for a 40.5-kV CB than in a 12 kV one. The interphase overvoltage was especially critical. The causes of severe overvoltages were analyzed, and it was indicated that the difference of CBs, multireignitions by the interphase coupling, and the different application conditions were the main effect factors. In addition, some suggestions were given.