Forced Commutation Performance of Vaccum Switches for HVDC Breaker Application

Tests were conducted to determine performance limits for vacuum switches under forced commutation conditions associated with a high- voltage dc (HVDC) breaker.* Circuit parameters were varied and both linear and saturable reactors were used. Single as well as two series breaks were tested. Both ac and dc recovery voltages were applied. Results confirm that the critical parameters are the current to be interrupted and the time to drive the switch current to zero. A linear reactor works nearly as well as a saturable reactor. Also, the magnitude of current injection need not be matched to the fault current; excess charge is preferred.