Effect of arc time on the current breaking capability of vacuum interrupters

Vacuum interrupters on medium voltage power systems need to interrupt short-circuit currents over a wide range of arc times. Synthetic testing allows the careful study of the interruption performance over arc times ranging from 0 to 13.3ms for a 50Hz system. Comparing the interruption performance as a function of arc time observed in single- and three-phase direct testing and single- phase synthetic testing gives good agreement. This agreement extends over different rating points, different contact designs, and different arc control methods. Additional tests compared synthetic tests with and without re-ignition for arc times greater than 10ms.