Evaluation of cumulative charge data of polymer insulator aging tests

Polymer insulators have been employed by the electric utility industry for the last three decades. The three main components of the polymer insulators are the high strength fiberglass core, the metal end fittings, and the weathershed housing. The housing is made of base polymers or elastomers, typically of silicone rubber, ethylene propylene diene monomer (EPDM), and alloys of EPDM and silicone rubber. Filler additives, such as alumina trihydrate, antidegradants and coupling agents, are also compounded with the base polymers. The range of electrical and material tests for polymer insulators over the years has become broader and more sophisticated. The purpose of such tests is to investigate the performance of polymer insulating materials and insulator designs, and to estimate the service life of a specific polymer insulator. This paper presents the results of a research project performed at The Ohio State University (OSU). This project utilized a salt fog chamber for material aging tests. Salt fog chamber application is one of the preferred aging tests, together with flashover tests and various material diagnostic techniques.