Investigation on Reignition Probability of Switching Overvoltage Caused by Vacuum Circuit Breaker in Offshore Wind Farms

The reignition probability of switching overvoltage caused by vacuum circuit breaker (VCB) switching off shunt reactor (SR) in offshore wind farm (OWF) is studied. Firstly, a model of OWF is developed in the environment of electromagnetic transient program. According to the switching time of VCB, a current period is divided into non-reignition zone, reignition zone and current chopping zone. Based on the analysis of overvoltage mechanism, a method for calculating critical arcing time and reignition probability is proposed. Then, the effects of resistor-capacitor (RC) snubber on reignition probability are discussed. The capacitance of RC snubber is optimized based on switching dispersibility of VCB and critical arcing time, and a new structure of RC snubber is developed. Finally, the hybrid method of RC snubber with new structure and phase-controlled switching is presented to suppress the switching overvoltage. The results indicate that the method can eliminate the reignitions and weaken the impact of overvoltage on the insulation of power apparatus.