Overvoltages of 40.5 kV vacuum circuit breaker switching off shunt reactors

To investigate the reason of the severe overvoltage failures of 40.5 kV vacuum circuit breakers during switching off shunt reactors, a series of field tests were carried out. The transient process is analyzed, and the magnitude and the characteristics of the transient recovery voltages (TRV) are analyzed. The experiment results indicate that multi-reignition in 35 kV system is much more serious than that in 10 kV system, and the inter-phase overvoltage is especially critical. Additionally, the relationship between the breakdown voltage and the operating moment is exponentially fitted. The result could be used to simulate the overvoltage process when vacuum circuit breakers switch off shunt reactors.