Diagnostic test of early stage degradation of polymer insulating materials

Abstract

Polymer as one of solid insulating materials that widely used for high voltage power system apparatus offer some advantages. The outdoor usage such as distribution and transmission lines causes multi factor stresses that cannot be avoided from any source that subjected to the insulator surface that will lead to ageing. An early stage degradation investigation is required to diagnose the condition of materials before it starts to degrade due to the insulation performance and lifetime expectancy. Hydrophobicity loss and increasing of leakage current as well as the appearance of surface partial discharge are important parameter related to the above purposes. Some methods that compatible for investigating these properties are by using Scanning Electron Microscope (SEM), contact angle measurement and leakage current measurement using Inclined Plane Tracking (IPT) test method. The early stage degradation condition of the specimens was obtained by exposing the specimens to outdoor environment for short time periods. The observation under IPT test based on IEC 587 which was employed to affect the material surface under strong discharge showed that it is not suitable method for early stage degradation investigation. The SEM observation and contact angle measurement result a good performance on the surface morphology study and loss of hydrophobicity property respectively. More observation on chemical properties of the tested insulating materials before and after subjected to strong discharge on their surfaces is required to result more accurate analysis.