Study on naturally aged polymer insulators and weathersheds

The authors describe an analysis of suspension-type polymer insulators made of ethylene-propylene monomer which had been in service for more than ten years on transmission lines with nominal voltages up to 500 kV. To assess the level of performance degradation during service, a number of tests were performed. These included tests on the complete insulators, as received from the field, and tests on weathersheds subsequently removed from the insulators. The tests examined both the overall electrical, mechanical, and material characteristics and the aging of the polymer materials. Electrical tests on the entire units indicated no deviation from the originally catalogued values. The mechanical strengths of the assemblies were not noticeably reduced from those anticipated, compared to the catalog values. Results obtained indicate that twelve years of field exposure have not significantly degraded the materials