Condensation and AC pollution flashover characteristics of F-SiO2/RTV superhydrophobic coatings on epoxy resin

Under condensation and contamination conditions, conductive water paths can form on insulating components in enclosed electrical equipment, consequently deteriorating surface insulation performance. However, systematic studies linking pollution severity, condensation behavior, electric-field-induced droplet dynamics, leakage-current evolution, and AC flashover performance remain limited. In this study, epoxy resin (EP) is employed as the insulating substrate, and three surface conditions, namely bare EP, room-temperature-vulcanized (RTV) silicone-rubber-coated EP, and F-SiO 2 /RTV superhydrophobic (SHP)-coated EP, are comparatively investigated. Three-dimensional electrostatic finite-element simulations are first performed to evaluate the effects of droplet position and volume on the local electric-field distribution and Maxwell stress. Subsequently, static contact angle, condensation behavior, condensation mass, flashover voltage, leakage current, and electric-field-driven droplet dynamics are experimentally investigated under clean and different levels of pollution. The simulation results show that droplet displacement toward the electrode produces a stronger local electric-field enhancement than increasing droplet volume. At 20 kV, as a 15 μL droplet moves from d = 0 to 20 mm toward the HV electrode, the maximum electric-field strength increases from 16.27 to 33.86 kV/cm for EP, from 18.80 to 36.98 kV/cm for RTV, and from 10.76 to 26.28 kV/cm for SHP, with the SHP surface maintaining the lowest maximum field strength over the investigated displacement range. With increasing pollution severity, the static contact angles of all three samples decrease and the condensation mass increases. Under Level III pollution, the contact angle of the SHP surface remains 141.3°, while the condensation mass is 0.55 ± 0.03 g, compared with 0.86 ± 0.04 g for EP and 0.73 ± 0.04 g for RTV. The corresponding AC flashover voltage of the SHP surface reaches 14.8 ± 1.3 kV at a 5 cm electrode gap, which is 202.0 % and 78.3 % higher than those of EP (4.9 ± 0.85 kV) and RTV (8.3 ± 1.0 kV), respectively. During voltage application, droplets on the SHP surface can roll, coalesce, and partially shed, thereby suppressing continuous conductive paths and improving surface insulation performance.