Nonceramic insulators for transmission lines

Progress in the development of nonceramic transmission line insulator technology is reviewed. The results of a survey of utilities in the United States are presented to indicate the range of applications, distribution by voltage class, appraisal of performance, and failure modes. It was found that the tracking, erosion, and mechanical problems of the first generation of nonceramic insulators have been reduced. Typical problems with nonceramic insulators in the past were discoloring, crazing, chalking, corona cutting and deterioration, water penetration and subsequent electrical failure, interface flashover, loosened end-fittings, and mechanical failures. Utilities have in general utilized these insulators in short lines, in trouble spots, and for data gathering. A number of utilities have valuable test facilities to verify both short and long-term insulator behavior. The major problem with nonceramic insulators is deterioration caused by contamination-induced discharges and poor electric-field distribution. Concerns expressed by utility representatives at a recent workshop are described, and future research standardization needs are presented