This paper deals with the comparison of partial discharge (PD) characteristics of three kinds of insulating sheets produced by the local industry in Saudi Arabia; namely polycarbonate (PC), poly-methylmetacrylate (PMMA) and phenoplast resin (Bakelite). These were exposed to PDs under the IEC (b) electrode system, and the comparison was judged by the discharge onset; discharge propagation area, PD magnitude, surface erosion and elemental analysis of eroded zones. Results show that PD inception voltage is inversely proportional to the sample's relative permittivity. For higher permittivity samples, the eroded area under a constant voltage is larger, while PD activity is also augmented significantly. The erosion depth was found to be deeper in Bakelite. In this case, the scanning electron microscope images show a larger concentration of scattered debris of the base material on the eroded area. Whereas, EDX elemental analysis of these areas exhibits presence of the native matrix for PC and PMMA sheets, a large content of copper and zinc was found on the Bakelite sheet, which also displays the erosion of the electrode.

Keywords: Surface discharge, Polymer insulating sheets, Partial discharge, EDX analysis, Surface erosion.