Power frequency and impulse field calculation around a HV insulator with uniform or nonuniform surface pollution

HV outdoor insulators are always subjected to pollution of different nature and severity and the performance of a HV insulator under polluted conditions is quite different from that under pollution-free conditions. The present paper is concerned with the field distribution around a post-type insulator for different severities of surface pollution. The capacitive-resistive field distribution around the polluted insulator is calculated by a charge simulation method. The field calculations are carried out for power frequency voltage and also for lightning and switching impulse voltages. The effects of uniform or partial surface pollution and the presence of dry bands on the field distribution around a polluted post insulator are presented and discussed in detail.>