Experimental Comparisons of Susceptibilities to Long-term Action of AC Corona and Ozone of Non-ceramic Outdoor Insulation Materials

Paper in proceeding, 2009

By utilizing the multiple-needle electrode system selected by CIGRE working group WG D1.14, the influences of long-term AC corona discharge and ozone on the surface and volume resistivities as well as on the dielectric response of well defined non-ceramic outdoor insulation material samples were experimentally investigated and compared. The polymeric specimens concerned were obtained from five various materials used as housings of composite insulators, namely liquid silicone rubber (LSR), high temperature vulcanized silicone rubber (HTV), ethylene propylene diene monomer (EPDM) rubber and ethylene-vinyl acetate (EVA) rubber and hydrophobic cycloaliphatic epoxy (HCEP resin). External mechanical stress was applied as additional stress factor during corona-ozone exposure of the elastomeric materials. It was found as a result of the testing that, the 100-hour long corona-ozone exposure had obvious effects on both surface and volume resisitivities for all the materials investigated; surface resistivity was more sensitive than volume resistivity. The permittivity as well as the dissipation factor values, both being the electrical properties of the material bulk, did not exhibit a high susceptibility to the exposure.