Effect of Electric-Field Components on the Flashover Characteristics of Oil-Paper Insulation under Combined AC-DC Voltage

Flashover characteristics are closely related to the electrical field distribution on the surface of oil-paper insulation. In this study, the effects of electrical field on the creepage flashover characteristics of oil-paper insulation under combined AC-DC voltage (CADV) are investigated. The results demonstrate that when the DC voltage component is large, the flashover voltage under the influence of strong parallel electric field component is approximately 1.2 times higher than that under the influence of strong normal electric field component. When the DC voltage component value increases under the influence of strong normal electric field component, the value of corresponding AC voltage component of the creepage flashover voltage exhibits a decreasing trend. Under the influence of the DC voltage component and due to the presence of space charge on the insulating paper, the distribution shape of carbonized particles on the surface of the insulating paper after creepage flashover is different. Furthermore, the instantaneous energy release during creepage flashover under CADV is higher than that under AC voltage, and the greater the DC voltage component value, more severe is the damage to the fibers on the insulating paper surface.