Why Do Insulators Prone to Pollution Flashover in Rain and Fog? Start with Hydrophobicity and Surface Leakage Current

High‑voltage insulators face elevated pollution flashover risk under rainy and foggy conditions. Priority shall be given to examining accumulated surface contamination, conductive behaviour upon wetting, hydrophobicity variation and local electric field distribution, rather than simply thickening the insulating coating. For substation post insulators, external insulation of transmission lines and other eligible power equipment, ELAPLUS SICOAT 9099R anti‑pollution‑flashover insulating coating may be evaluated, with focus on coating hydrophobicity, substrate adhesion, erosion resistance and adaptability for long‑term outdoor service. High‑voltage insulators achieve electrical isolation via solid insulation and creepage distance. During prolonged operation, they are subject to deposition of dust, salt and industrial contaminants. Under dry conditions, surface fouling may not trigger obvious abnormalities immediately; yet when rain, fog or condensation wets the contaminated layer, the electrical condition along the surface may alter. Accordingly, anti‑flashover design shall take into account the geometric configuration of external insulation, on‑site pollution environment and surface material performance. Insulating coating serves as one protective measure for external insulation, but it cannot substitute for structural design, operational maintenance and electrical safety assessment of the insulator itself. 1. Why Are Insulators More Vulnerable to Pollution Flashover in Rain and Fog? Salts, industrial dust and other pollutants accumulated over time on insulator surfaces may form a conductive wet layer once moistened. Under applied voltage, surface leakage current rises; heat generated by local current redistributes the water film and creates uneven dry and wet zones. Under certain conditions, local dry bands withstand high voltage and initiate dry‑band discharges. When discharges propagate along the insulating surface and meet relevant criteria, flashover occurs. Pollution flashover is governed by multiple factors, including contaminant type, deposition density, wetting severity, insulator profile, creepage distance and operating voltage. For silicone‑rubber‑based anti‑pollution‑flashover coatings, hydrophobicity restricts the formation of continuous water films. Nevertheless, satisfactory hydrophobicity does not eliminate flashover…