Study on surface degradation of polymer insulating materials caused by leakage current

Some artificial aging tests were performed using test rods made of Silicone Rubber (SR) and Ethylene Propylene Rubber (EPDM), based on the Rotating Wheel Dip Test (RWDT) method and the Salt Fog Chamber Test (SFCT) method, and aspects of the surface degradation were evaluated. Following the tests, it was concluded that the surface degradation of polymer insulating materials is directly related to the partial discharge and that measurement of the cumulative charge of the leakage current is useful in evaluating the degradation. Moreover, an energized exposure test using prototype composite insulators was carried out for five years. The accelerating factor from the artificial aging test for actual use was estimated by comparing the amounts of cumulative charge in the artificial aging test and in the exposure test