Discharge mechanism in voids at sub-atmospheric pressures

The physical processes occurring during partial discharges (PD) in voids in solid dielectrics are complicated due to the lack of knowledge of void shape, location and gas pressure. Fast oscilloscopic techniques are needed to measure the build up and decay of current as a function of time for single discharges. The purpose of the present work is to investigate the mechanism of the discharge in artificial voids in thin polypropylene (PP) films at different sub-atmospheric pressures. Efforts have been made in this work to distinguish Townsend-like and streamer-like discharges on the basis of the discharge pulses recorded in terms of rise time, pulse width and peak current for the various void dimensions and pressures studied