Testing of 800 and 1200 kV class circuit breakers

The most critical transient a circuit breaker has to endure during its operation is the transient recovery voltage (TRV), initiated by the electric power system as a natural reaction on current interruption. For circuit breakers intended to operate in ultra-high voltage systems (with rated voltage above 800 kV), the realization of realistic transient recovery voltages in testing of these circuit breakers becomes a real challenge. In this contribution a new and proven method is described of creating adequate TRVs by a double stage synthetic test circuit. Due to the extremely high voltages to be applied immediately after interruption of very high fault current, a two-stage approach is necessary. This is the only way to perform full-pole testing, the realistic laboratory simulation of service conditions during fault current interruption.