Principles of Anti-Fog Design for Polymeric Insulators

Electric field and leakage current density in the shank region of a polluted polymeric insulator may cause local dry-banding, with a risk of long-term degradation from partial-arc discharges. In a novel approach to dry-band control, the characteristics of silicone rubber surfaces with a textured finish are investigated and, depending on the geometry chosen for the texture, two useful objectives can be achieved. First, the increase of surface area can both reduce the leakage current density in the vulnerable shank region, and also increase the longitudinal creepage distance. Secondly, the damage arising from surface discharges can be mitigated. The principles of the proposed anti-fog design are described in details, and preliminary results from tests which show an improvement in performance are presented.