Application Research of 35kv Switching Shunt Capacitor Banks with Phase-Controlled Circuit Breakers

Abstract

In recent years, two series reactor faults occurred when a 35kV shunt capacitor bank was cut by a circuit breaker in a 500kV substation in Shenzhen. The reason is analyzed that the large inrush current and overvoltage generated during the switching process caused interturn short circuit fault of the reactor, which seriously threatens the safe operation of the system. To avoid such faults, intelligent phase-controlled short-circuit breakers were used to suppress the closing inrush current and reduce the probability of reignition. To verify the effectiveness of the technology, this paper introduces the causes of switching inrush current and over-voltage and the principle of phase-controlled suppression technology, and then applies the technology to a 500kV substation in Shenzhen. Multiple switching tests are carried out on the intelligent and ordinary circuit breakers respectively. The results show that the maximum inrush current generated by the ordinary circuit breaker is 4.2p.u., and the overvoltage is 1.81p.u. While the maximum inrush current of the intelligent phase-controlled circuit breaker is 2.3p.u., and the overvoltage is 1.4p.u. The results confirm that the application of the intelligent phase-controlled switching technology can suppress the inrush current and overvoltage, thus fundamentally improving the reactive switching efficiency and system safety.