Fundamental tests for 550 kV SF6 synchronous circuit breaker

Synchronous circuit breaker can close or open the circuit at some designated phase of the voltage or current to avoid serious transient overvoltage and surge current in power system. Synchronous circuit breaker can significantly improve the intelligent and automatic level of a substation. Rate of decrease dielectric strength (RDDS) and operation time stability are the first important parameters to determine if a circuit breaker can operate synchronously. This paper focuses on the characteristics of a 550 kV SF6 circuit breaker. The RDDS requirement was discussed and given out. The pre-breakdown tests have been carried, whose results showed that the RDDS of the circuit breaker is 83.34 kV/ms and matched quite well the requirement of 21.16 kV/ms to limit the overvoltage at 1.5 p.u. when close parallel capacitor. A series tests on the influence from operation voltage, hydraulic oil pressure and environment temperature to the operation time have been executed in a large amount, the results of which showed that the influence of these factors should be considered when make the controlling strategy for synchronous operation, while the disciplines of the influence are just simple and can be presented by basic functions. The tests results also indicated that the deviation of the operation time is less than ±1 ms, which means the circuit breaker is suitable for synchronous operation.