Control of potential insulator surfaces

To reduce radio interference caused by corona from pin insulators, adherent conducting coatings or films usually are applied to the central portions of the heads of the insulators, and metal thimbles or conducting coatings in the pin holes. By extending the coating to cover the entire head and by using a coating of the proper resistivity, the voltage at which corona occurs can be raised considerably without materially lowering the flashover voltage. This paper calls attention to the principle of controlling the potential distribution over surfaces of insulators by utilizing the resistance drop in potential resulting from the flow of charging current in high resistance films.