Impulse corona inception in dielectric covered rod-plane air gaps

This study presents investigations on corona inception in short dielectric covered-rod/plane gaps stressed by positive lightning and switching impulse voltages. Corona inception probability distributions were obtained and the salient characteristics of the corona discharge, namely inception time and voltage, were measured as influenced by the gap length, waveform of the applied impulse voltage and by the cover material. The electric field required for corona inception was calculated as electric field computations were performed via the Comsol multiphysics software package. Under lightning impulse voltages causing around 50% corona inception probability the corona inception field is lower for the dielectric covered rod-plane gaps; the opposite is true under switching voltages.