Evaluation of EPDM rubber for high voltage insulator

This paper describes the fundamental characteristics of EPDM (ethylene propylene rubber) which is applied as a high voltage insulation material. Also recently, polymer compounds have been applied as high voltage insulation materials. EPDM rubber is inferior in weather resistance to silicone rubber. However, we found that the addition of carbon black results in an excellent weathering property of EPDM rubber without any degradation of tracking resistance. We also improved the electrical tracking resistance of EPDM rubber by adding alumina trihydrates (ATH) as fillers. The compound shows excellent physical properties and low cost in comparison with silicone rubber. We carried out a tracking test which followed IEC pub. 587 as a short term evaluation, and the rotating wheel dip test as a long term evaluation test. Furthermore, the xenon-arc radiation exposure test was carried out as an accelerated weathering test. From the results of the tracking test, we found that the tracking resistance is dependent upon the particle diameter of alumina trihydrates and the compound with a small particle filler has less weight loss than that with larger ones. As one of high voltage insulation applications, we applied EPDM to a polymer housing arrestor and evaluated the electrical characteristics of the polymer housing.