Partial Discharge at the Surface of 66kV Insulator Covered with Frost

摘要

Frost usually forms over the surface of a polymeric insulator installed at a transmission line in snowing area might affect the insulating performance for the period from late fall to early spring. If the partial discharge occurred in the surface of a polymeric insulator, the surface of the insulator would deteriorate to decrease its insulating performance. Therefore, it is necessary to confirm the occurrence of partial discharge during frost formation along the insulator surface. When frost formed on the surface of insulating plate, the leakage current increase and the lead phase angle decrease were confirmed by an indoor experiment using an insulating sheet. In this study, the period for frost formation was estimated from the data on the magnitude and lead phase angle of leakage current and climate condition in the outdoor exposure experiment carried out in 2008/2009 winter. The time variation of leakage current obtained under the fair weather and foggy condition was analyzed in comparison with the time variation of leakage current flowing through a frost layer artificially formed along the surface of silicone rubber and glass plate by an indoor experiment. In the indoor experiment, occurrence of partial discharge at the surface of the insulating plate was confirmed during a period of formation and melting of frost. The result suggests the possibility of occurrence of partial discharge at the surface of insulators installed at a practical transmission line by frost.