Comparative Inclined Plane Tests on Silicone and EPDM Elastomers under DC

The paper presents comparative inclined plane test results of high temperature vulcanized silicone rubber and EPDM elastomers filled with alumina trihydrate to 25 wt% under DC. Both the initial tracking voltage and the constant voltage test methods are employed to evaluate the relative tracking/erosion resistance of both elastomers. While insignificant differences between the tracking/erosion resistance of the two elastomers is observed, earlier failure occurs under -DC. A recognizable distinction is also found between the failure pattern and the corresponding dry-band arcing current. Shorter non-conduction periods in the leakage current are observed on the silicone rubber elastomer prior to failure, a result that indicates stable discharge activity, which is more evident under +DC than under -DC. Imbedded in the stable dry band arcing current are transient leakage current pulses due to probable ionization activity, which can be seen to enhance the intensity of the discharge. In contrast, intermittent dry band arcing current is found to be dominant for the EPDM elastomer.