Development of 550 kV and 362 kV synchronous switching gas circuit breakers

550 kV and 362 kV synchronous switching gas circuit breakers (GCBs) have been developed. In the closing operation of a GCB, making voltage depends on the rate of decrease of dielectric strength (RDDS) and the mechanical scatter of the operating time. No delay is caused by the operation after a long idle time up to 1000 hours, therefore optimal closing targets for different rated voltages can be determined by measurements on these characteristics of GCBs. Optimal target points for maximum and minimum making voltage are also given as functions of the RDDS and deviations of the operating time. The distribution of experimental maximum and minimum making voltages of synchronous closing with 550 kV and 362 kV GCBs shows good agreement with those calculated by the proposed method. A series of performance tests show that 550 kV and 362 kV GCBs can be applied for synchronous closing for transformer, reactor, capacitor, and line applications. The successful closing tests demonstrated the EMC of a synchronous switching controller mounted in a 550 kV GCB cabinet