The correlation of breakdown and partial discharge for SF6 needle-plate gap under power frequency and lightning impulse superimposed voltage

SF6 gas insulated switchgear (GIS) equipment is widely used in power substation, but its defects are difficult to detect and insulation accident appears sudden. In order to improve the research on the discharge characteristics of defects in GIS, SF6 needle-plate gap was used to simulate the spike defect in GIS and the relationship between the breakdown characteristics and the partial discharge (PD) under power-frequency voltage and lightning impulse superimposed voltage (AC+LI) was studied. On the one hand, it was found that partial discharge of the spike defect under power frequency voltage was the main reason that the breakdown voltage under AC+LI superimposed voltage deviated from single lightning breakdown voltage. On the other hand, the space charge generated from partial discharge under power frequency voltage had different polarity and density, which resulted in the difference of breakdown characteristics under uniform or opposite superimposition.