Charge trapping and transport phenomenon in aged and unaged epoxy resin and polyethylene

Polymeric dielectrics are prone to space charge trapping within their volume. This in turn affects many of their dielectric properties including breakdown strength and charge transport. In the current paper, we attempt to characterise charge accumulation and transport in polymeric dielectrics under the application of DC field. Epoxy (EP) resin and polyethylene (PE) are chosen as the dielectric materials to be investigated on account of their prevalence in the high voltage industry. Pulsed electro-acoustic measurements are performed on EP resin and PE specimens. Further, effect of ageing on charge trapping is studied for both EP resin and PE, by thermally ageing the materials under controlled conditions. In addition, the dielectric materials are exposed to a humid environment over long periods and the effect of prolonged exposure to moisture on charge trapping studied. From the experimental results, density of trapped charge is obtained for the different cases. Fourier transform infrared spectroscopy is carried out to identify chemical changes in dielectric materials due to ageing, with an aim to relating physicochemical changes in the material to charge trapping. Copyright (c) 2014 John Wiley & Sons, Ltd.