Suppression Measures for Overvoltage Caused by Vacuum Circuit Breaker Switching Off 10-kV Shunt Reactor

During the process in which a vacuum circuit breaker (VCB) switches off the shunt reactor (SR), an overvoltage with high amplitude and high frequency (HF) will occur because of current chopping and multireignition. To reproduce this switching overvoltage faithfully, the voltage and current characteristics of the VCB were analyzed in this work, based on the field test data from a 220-kV substation in Chongqing, China. Then, typical parameters of three basic factors mentioned in Helmer's VCB model, chopping current value, dielectric dynamic insulation strength, and HF current quenching capability, were selected after statistical analysis and an arc reignition model of VCB was established. Based on this presented model, the influences of the surge arrester, the resistor–capacitor (RC) snubber, and the installation positions and quantities of these protective devices on overvoltage suppression performance were studied in simulation. In addition, the field test using the surge arrester and the RC snubber as the suppression measures was performed again in the same substation. Finally, we derived the conclusion that the most suitable suppression scheme for overvoltage caused by VCB switching off 10-kV SR is installing two 12/32.4 kV surge arresters at the terminals of the cables for the SR and the substation transformer (ST).