Discharge pattern discrimination in vacuum interrupter with non-contact measurement of shield potential

Vacuum interrupter has a composite insulation system. When an internal insulation fails, the discharge has complex and various patterns. Previously, based on the discharge development characteristics, we proposed a discrimination method for the discharge pattern in vacuum interrupter. We measured the applied voltage, anode current, and shield potential waveforms, respectively. From the analysis of the measured waveforms, we can estimate the discharge patterns and discharge path lengths. In this paper, a non-contact shield potential measurement was proposed when the shield potential cannot be measured directly. Furthermore, verification tests with this measurement method were conducted and the effectiveness of the discrimination method was confirmed.