Surface discharges on polymeric insulator shed surfaces

This paper describes results of an experimental investigation into surface discharges occurring on the surface of polymeric insulators. Discharges on partially hydrophobic surfaces were found to occur across well defined dry bands, while discharges on hydrophobic surfaces appeared as small points of light occurring between discrete water drops. These discharges were observed to produce a localized loss of hydrophobicity. It is shown that these discharges are stable atmospheric-pressure glow discharges. The discharges are characterized by a high cathode voltage fall, dependent on the electrical conductivity of the water drop, and a voltage gradient in the positive column, dependent on the discharge current. A technique is presented for measuring the rate at which surface hydrophobicity of polymeric materials is lost due to the action of this type of discharge. It was found that the loss of hydrophobicity occurred predominantly in the region near the cathode.