Degradation of epoxy resin by partial discharges

Epoxy resins are used in the production of high-voltage insulation components. Partial discharges, inherent in high-voltage installations, degenerate the resinous material and cause degradation of the insulation thus reducing the working life of the component, An understanding of the nature of the chemical changes taking place under partial discharge stressing should allow the production of improved insulation systems and/or identification of diagnostic methods for monitoring the state of existing equipment. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) microspectroscopy is used to determine the chemical changes to the surface of a bisphenol-A based epoxy resin resulting from partial discharge stressing in an air environment. Differences in stressed resin surface chemistry are found to be dependent upon the humidity of the stressed air. The variation in degradation products occurring in dry and in moist air are discussed and possible reactions to explain these differences are presented.