Impact of Electrode Surface Roughness on Electric Field Homogeneity, Conduction Current, and DC Breakdown in Air

This paper investigates the impact of electrode surface roughness on electric field homogeneity, conduction current, and DC breakdown behavior in air gaps. Stainless-steel plane-plane electrodes with four controlled roughness levels (A-D) were fabricated and characterized. DC breakdown tests were performed in atmospheric air for a fixed gap distance, while pre-breakdown conduction current was recorded as the applied voltage was increased. Finite-element simulations using FEMM 4.2 were employed to evaluate electric field distribution and to derive a homogeneity index and field enhancement factor for each roughness condition. The results show that increasing surface roughness leads to a more non-uniform electric field, with the homogeneity index decreasing from 0.99 (smooth electrode A) to 0.28 (rough electrode D). Rougher surfaces exhibit higher conduction currents and lower breakdown voltages; the average breakdown voltage decreases from 24.35 kV for electrode A to 22.96 kV for electrode D. These findings demonstrate a clear correlation between surface roughness, electric field inhomogeneity, and DC breakdown strength, and highlight the importance of surface treatment in the design and maintenance of high-voltage equipment employing air insulation.