Discharge phenomena in low vacuum region of glass tube vacuum interrupter under AC applied voltage

In this paper, we experimentally investigated discharge phenomena inside vacuum interrupter at 1 to 20 Torr to simulate the vacuum leakage. We used glass type of vacuum interrupter where the internal pressure and the type of gasses can be varied according to requirement. The experiment is conducted under AC applied voltage and the experimental circuit is constructed to simulate the actual circuit used in cubical type insulated switchgear. We used two types of gases such as air and SF₆. The use of glass type vacuum interrupter allowed us to measure discharges occurring in vacuum interrupter optically. We measured and discussed the discharge occurring in both gases with a current transformer and ICCD camera. We also revealed that electromagnetic wave spectra emitted by the discharge have same frequency range for both gasses.