Simultaneous measurement of high and low frequency pre-breakdown currents on HV vacuum interrupters

Abstract

Vacuum circuit breakers are well established in the distribution voltage level (U s ≤ 52 kV) due to their various advantages, e.g. frequent switching operations, low life-cycle-costs, excellent arc quenching capabilities and nearly maintenance free operation. In order to establish this technology at higher voltages, U s > 52 kV, the dielectric withstand reliability must be increased. In particular, the occurrence of restrikes, while switching off capacitive currents needs to be characterized and reduced. According to current theories, restrikes mainly occur due to the release of charged particles or due to field emission currents while the contacts are open after breaking the capacitive current. However, the possibility that both processes operate simultaneously is rarely included in theoretical models. In the past, investigations focused on one pre-breakdown phenomenon at the time. In this work, a possibility of a simultaneous measurement of high and low frequent pre-breakdown currents will be described. A specially designed test setup utilizing two different measurement principles at the same time will be presented. Furthermore, first results with the simultaneous measurement on a commercially available 72.5 kV vacuum interrupter will be presented.