Partial discharge degradation of solid insulators with an air-filled void at liquid nitrogen temperature

Degradation and lifetime characteristics of solid insulators with an artificial air-filled void were investigated experimentally at liquid nitrogen temperature. As a result, it was found that the lifetime of a test sample decreased suddenly with increase in applied voltage. Observation of the PD characteristics showed that the decrease in lifetime at a higher applied voltage had a close relationship with the PD activity. The void surface subjected to the PDs was observed with SEM, and the degradation mechanism was discussed taking the experimental results into consideration