Standardizing conductor surface roughness for DC gas-insulated equipment-a careful analysis on local morphology

Abstract

Abstract The gas ionization inside the gas-insulated electric power equipment increases the gas conduction current and introduces charges to the spacer surface, which results in local electric field enhancement and potentially triggers spacer flashover. In this letter, we demonstrated that micro protrusions in a finely finished conductor surface plays a significant role in inducing local gas ionization, resulting in an increased local gas conduction current. A gas conduction current using conductors with higher surface kurtosis S ku was found approximately 10 times higher than that using an electrode with a similar S a but a different machining procedure. The piecewise nonlinear relation between the maximum local field strength and the average roughness was calculated over different kurtosis ranges. A conductor surface roughness evaluation method which combines average height of peak S pa with extreme probability of deviation from mean height of peak S pku was put forward.