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The purpose of this paper is to verify the aging characteristics of domestic polymer housed distribution surge arresters. In this study accelerated aging test equipment was developed to simulate field condition of the distribution polymer housed surge arresters. Polymeric housing of distribution surge arresters should be degraded by environmental stress and the interface between housing and inner module can be affected by moisture ingress. This moisture absorption should increase leakage current and make tracking damage at the interface. Proposed aging test equipment can simulate UV, temperature, humidity, voltage, salt fog and rain and it can monitor total and resistive leakage current of arresters. In addition we carried out field exposure test at the outdoor test yard and characteristic analysis of field operated arresters. And then electrical performance of arresters, insulation condition of housing material and surface condition of the housing were compared.

Because of environmental friendly and higher fire point, Natural ester fluids are widely used for transformer cooling materials. Natural ester has higher viscosity than that mineral oil. Top oil temperature and hottest temperature will be warmer when using natural ester fluid in transformers designed for conventional transformer oil. Although natural ester has less influence on deterioration of cellulose paper than mineral oil, an increased hottest temperature might have an effect on the aging of insulating paper in coil winding. When comparing natural ester with mineral oil at the same designed transformers up to 500 kVA. The deviation of hottest temperature between the two is increased with load. For preventing additional aging of insulation paper, design changes are required when substituting natural ester for conventional transformer oil.