Field and laboratory aging of RTV silicone insulator coatings

The silicone-based coating applied to 345 kV post insulators in a substation on the shore of Long Island Sound has depolymerized over a period of about 7 years although no in-service failures have occurred. However, the increasing rate of depolymerization suggests that the coatings will have to be renewed in the near future. This paper reports comparisons of aging and material properties for a number of RTV silicone insulator coatings and measurements related to application of a new coating over an existing, field-aged coating.