Factors influencing the performance of polymeric insulating materials in contaminated environments

Abstract

The successful application of polymeric materials for outdoor insulation depends primarily on the capability of materials to suppress surface leakage current leading to dry band arcing which causes tracking or erosion. The widely used materials, namely, silicone rubber, ethylene propylene diene monomer (EPDM) rubber and epoxy resins are all hydrophobic initially thus suppressing leakage current, but only silicone rubber has shown the capacity to maintain its hydrophobicity for prolonged periods despite the accumulation of surface contamination. Although the EPDM and epoxy materials when filled with substantial inorganic fillers (> 40% by weight), have performed well in laboratory aging tests [1], their performance in the field has not been as good as that of silicone rubber and the reasons for this are not fully understood.