Field Coating of 765kV Transformer Bushings with RTV HVIC: Planning, Implementation and Results

This paper discusses the selection, planning, implementation and performance of RTV Coating on 765kV OIP transformer bushings that are part of a critical transmission grid requiring near-zero downtime performance. After several instances of pollution flashovers on bushings in foggy and humid conditions, various methods of reducing such outages were considered, including the application of two kinds of RTV Coatings – the first a Gen-3 coating and thereafter a Gen-4 RTV with Quartz Silica as the primary filler. Other than RTV Coating, no maintenance methods were successful or viable whereas after the application of RTV, the number of failures had dropped considerably with only one bushing failure reported on the Gen-3 coating and zero failures on the Gen-4 coating.