Characteristics of surface discharges on outdoor high voltage insulation

It was shown that discharges observed on the surfaces of wet insulators are not electric arcs but are a form of glow discharge operating at atmospheric pressure. These glows occur between electrodes consisting of water and contaminants forming an electrolyte. The resistance of an EPDM and a silicone rubber material to loss of hydrophobicity from surface discharge activity was evaluated using a novel technique. It was found that silicone rubber was less resistant to surface discharges than EPDM. It was also found that low current discharges with average currents of less than 2 mA produced more rapid loss of hydrophobicity than larger discharges