Electric field analysis of 132kv EPDM insulator and correlation with ageing features

A COMSOL multiphysics electric field analysis of an ethylene-propylene rubber (EPDM) insulator is presented. The 132kV insulator is an inverted post insulator that is taken from a jumper loop. It has been in service in a severely polluted environment for eight years. The insulator´s surfaces are asymmetrically aged with organic dark deposits covering the insulator´s surface, and with additional surface markings. The insulator has a manufacturing artifact, known as the mold line, which forms an elongated protrusion along the length of the insulator. This artifact is introduced into the COMSOL model to investigate its effect on the local electrical field. The reason for this study is that the area surrounding the mold line is lighter in color, with markings that suggest discharge activity. The regions of the localized field enhancements are identified and correlated with the ageing features, such as hydrophobicity loss, surface roughness and discoloration observed after eight years in service. A discussion whether the environment or the electric field are dominating the ageing process of the insulator is included.