Characterization of Surface Discharge Used for Measuring Degradation Degree of Polymer Insulator

Polymer insulators with silicone rubber (SiR) insulation have unique properties and are installed all over the world. However, due to pollution deposits on the surface, the characteristics of polymer insulators become degraded. We have already investigated that the degradation degree of the polymer insulator can be evaluated by a 20-cycle salt-fog aging test or a surface discharge (SD) treatment. However, the decrease mechanism of the contact angle by such discharge treatment wasn't interpreted in detail. In this study, to characterize SD generated on the surfaces of SiR, we first measured the SD current. The observed maximum SD current did not significantly differ from that obtained during the 20-cycle-salt-fog aging test. In addition, the SD consisted of filamentary discharges. In measurements of optical emissions, emissions with wavelengths of less than 291 nm which can cut C-H bond of SiR weren't observed. Therefore, it is thought that the direct energy transfer from energetic particles with higher energy than the binding energy of C-H changes chemical characteristics and decreases the contact angle on the SiR surface.