Effect of void area on PD magnitude uniformity

Accumulated surface charges at the interface between solid dielectric and gas, resulting from former discharges plays an important role in the characters of subsequent ones during the partial discharge (PD) sequences. Specifically, it is assumed that variations in PD magnitude are associated with the discharge area. In our previous research, it was found that the diameter of discharge area can reach up to 1.5 mm due to the dielectric barrier. Based on this, different variation degree of discharge area was obtained via changing the void area in this paper. When the size of void was larger (diameter 5.0 mm), streamer could spread freely after it landed on the interface, so the discharge area varied in a large range, leading to the intense fluctuation of discharge magnitude. After the void diameter was reduced to 1.5 mm, the variation range of discharge magnitude is restricted by the void edge. As the void area became much smaller (diameter 0.7 mm), the uniformity of discharge magnitude increased.