Inclined Plane Test for Erosion of Polymeric Insulators under AC and DC Voltages

In this paper a study on effects of AC and DC dry band arcing on silicone rubber insulators surface is presented. The insulators tested are commercially available, having as their main material silicone rubber with alumina trihydrate as an additive. In addition to literature analysis, experiments were performed following the inclined plane test method described in the ASTM D2303. It was found that the voltage type (AC or DC) and polarity (positive or negative) influence not only the damage caused by the dry band arcing, but also the average value and the behavior of the leakage current. The voltage type that caused the most damage on the insulating material was DC with positive polarity, followed by DC with negative polarity, then AC. According to other studies, the difference in the results obtained with different voltage types are mainly caused by the ion release on the electrodes, behavior of the contaminant under the electric field and the length and duration of the dry band arcs. This shows that silicone rubber insulators should not be utilized in DC systems with same voltage as the ones that are designed to withstand AC, unless modifications are made in the material properties or in the insulators design.