Study on the Partial Discharge Characteristics of Epoxy Insulation Surface after Repeated Lightning Impulses in SF6Gas

The effect of the repeated lightning impulses accumulative effect on partial discharges (PDs) characteristics of epoxy insulation surface is experimentally investigated in SF
₆
gas. After the epoxy insulation specimen is subjected by 0, 200, 400, 600, 800 times of lightning impulses ( 1.2/50μs), respectively, PDs on epoxy insulation surface are measured. The surface morphology of the epoxy insulation specimen is observed by the scanning electron microscopy (SEM) after impulse. The amplitude of the impulse is about twice the PD inception voltage (PDIV). PDIV, average PD pulse number and average PD magnitude per cycle of the AC voltage are counted and analyzed after impulse. Results show that with the increase of the number of impulse, the PDIV under AC voltage is gradually decreases. Average PD pulse number and PD magnitude is increase. PDs in the negative half-cycle of the AC voltage is more intense than the positive half-cycle. The area of the epoxy insulation surface close to the high-voltage electrode becomes rougher as the number of the impulse increases.