Capacitive current switching capability of 72.5 kV high-voltage vacuum interrupters

Vacuum circuit breakers offer various advantages such as frequent switching operations, low life-cycle-costs, excellent thermal arc quenching capabilities, and nearly maintenance free operation. On the other hand, the switching of loads followed by a very high voltage stress could be more challenging. In this context, the switching of capacitive loads, e.g. unloaded overhead lines or cables and capacitor banks, remains an issue for vacuum circuit breakers. The occurrence of restrikes while switching off capacitive currents is of statistical nature and is in general more pronounced for higher voltage levels. In this work we discuss the role of the circuit breaker closing velocity and the capacitive voltage factor on the restrike behavior of the vacuum interrupter. It is shown that a proper adjustment of all relevant parameters leads to sufficient capacitive switching performance of high-voltage vacuum circuit breakers. Therefore it is possible to meet the IEC requirements for capacitive current switching for class C2, i.e., a very low restrike probability.