Partial Discharge Inception Phase and Light Emission Distribution of an Enclosed Void in Epoxy Resin

Degradation of epoxy resin caused by partial discharges (PDs) within enclosed voids has been investigated. To clarify the distribution of PD light emission in the void, we constructed an enclosed void-electrode system to measure PD light emission distribution at each phase of the AC voltage. The PD light emission distribution was different for each voltage phase in 14.4°. The intensity of the PD light emission decreased with time, whereas the PD light emission at the center of the void disappeared at all voltage phases within approximately 300 min. The surface of the epoxy resin on the void side deteriorated after voltage application. These results suggest that the time variation in the PD light emission distribution is related to the surface degradation of epoxy resin.