PD characteristics in void in series with fissure-like interface

The partial discharge (PD) characteristics in void in series with fissure-like interface between insulation material were studied at room temperature. The interface between needle-plane electrodes was formed by two insulating plates of epoxy resin. The minute interfacial gap and the surface roughness of the plates were changed artificially. By the decrease of the interfacial gap from 400 pm to 0 /spl mu/m the charge of positive PD pulses become smaller significantly and the PD tends to occur around the zero cross phase of applied ac voltage. The experimental results also show that PD characteristics are affected by the surface roughness of interface. The limited discharge spaces along the interface and the charge deposited to the interface walls by PD are considered to exert intense influences on the PD characteristics.