The effect of surface charge decay on variation of partial discharge location

The accumulation of surface charge generated by discharge at the solid-gas interface is an import factor that can affect PD characteristics. In this paper, the decay time of surface charge was measured by the surface charge measurement system based on Pockels effect, and the effect of surface charge decay on variation of partial discharge location was investigated by changing the cycle of applied voltage. As applied voltage cycle length increased, the coincidence rate of hetero-discharge location (CRHEL) before and after voltage zero-crossing point decreased. Besides, CRHEL from a void between two dielectric surfaces (called symmetrical electrode) was larger than that from a void between a dielectric surface and a metal surface (called asymmetrical electrode). Regarding asymmetrical electrode, CRHEL for the case with negative discharges occurring in the former half-cycle was larger than that with positive discharges occurring in the former half-cycle. However, there was almost no difference about CRHEL for these two cases when symmetrical electrode was used. After the applied voltage cycle length exceeded 500 ms, the coincidence phenomenon of homo-discharge location during negative half-cycle was observed in the usage of asymmetrical electrode, and the coincidence rate of homodischarge location (CRHOL) became larger with voltage cycle length increasing. As for symmetrical electrode, there was no coincidence of homo-discharge location. These results were attributed to the charge decay and difference of discharge initiation position.