Testing of SF6- and vacuum generator circuit breakers

Generator circuit breakers differ in various aspects from standard distribution breakers. One of the main differences is in the electrical stresses during fault current interruption. This situation will be discussed in the present contribution, along with the standardization status and the backgrounds of these special requirements. An overview will be given on the testing issues that arise, given the very large current and the very steep rise of transient recovery voltages that are associated with generator supplied and system supplied faults. Test methods will be described for the testing of very large SF6 generator breakers, able to interrupt current in excess of 200 kA. In addition, the testing of vacuum generator circuit breakers will be described. Given the special dielectric features of vacuum interrupters an innovative circuit is introduced, being a hybrid of the conventional direct and synthetic test circuits. This circuit avoids any discussion on dielectric recovery. Results of tests will be included