Effects of surface conductivity on current form of PD pulse in voids

The current form of partial discharge (PD) in a usual void was divided into fast and slow components, with short and long fall times, respectively. Comparing these with the current shape of PD in a void between two metal surfaces, in which the slow component was not observed, it is suggested that the formation of fast component in a usual void was due to the instantaneous discharge between the discharge areas of the PD, i.e. the region to which the carriers in a PD process can instantaneously propagate. And the slow one may be due to the low conductivity in the regions outside the discharge areas. An equivalent circuit was proposed to describe the effect. The simulation suggested that the effective surface conductivity in the region outside the PD discharge areas in a PD process is in the order of 10^-7 S