Performance of suspension insulators under flashover conditions

High-voltage outdoor insulators for power overhead line applications are subject to pollution by dirt and chemicals in industrial areas, and by salt deposits near the coast. In such a case, nonuniform heating of the pollution layer occurs at narrow sections of the insulators where the current density in the pollution layer is highest. Since almost the whole of the insulator voltage appears across these `dry bands´, air breakdown occurs, with the result of a quasistable gas discharge burn on the surface of the insulator, the current being limited by the series resistance of the pollution films. The author investigates this pollution flashover phenomenon by presenting a flat plate model for a cap and pin insulator. The dimensions of the suggested model are calculated. Using this model, the potential and field distribution on the polluted suspension insulator are determined