Discrimination of Streamer / Leader Type Partial Discharge in SF6 Gas Based on Discharge Mechanism

Abstract

Since SF6 gas insulated power apparatus like gas insulated switchgears (GIS) have been widely used in high and middle voltage substations for electric power transmission and distribution, it is strongly needed to enhance the operational reliability of the apparatus.1 for example, insulation defects like metallic particles in GIS would be a cause of partial discharge (PD) and could lead to dielectric breakdown (BD).2 Thus, for the stable operation of GIS, it is very important to diagnose the insulation condition in service and to predict the BD using PD detection techniques.3-5 Therefore, it is crucial to clarify the PD mechanism in SF6 and to develop the BD prediction technique in GIS. Under ac voltage application, however, space charges generated by PD show complicated behavior and have an influence to PD themselves, due to the temporal change of the instantaneous value and the polarity of applied voltage.6 Thus, it is important to investigate the PD mechanism under ac voltage application. From these points of view, we have investigated the PD characteristics under ac voltage application in SF6 gas.