Corona Inception Phenomena in Solid-Air Composite Systems

60 Hz and dc corona inception voltage is measured in solid-air composite insulation systems under electrical fields of varying degree of non-uniformity. Residual field due to charges deposited on the insulator surface, using dc voltages, is also measured and its influence on corona inception phenomena is discussed. The charging phenomena of insulators in non-uniform fields is found to be distinctly different from that in uniform fields. A semi-empirical relationship is developed between the measured discharge inception voltages and field parameters.