Analysis of surface discharge activity in epoxy nanocomposites in liquid nitrogen under AC voltage

A marginal increase in surface discharge inception voltage is observed with increase in percentage of clay in epoxy nanocomposites in liquid nitrogen medium. The flashover voltage of epoxy nanocomposites increases with increase in percentage of clay in epoxy resin up to 3 wt% and above which a slight reduction is observed but much higher than the pure epoxy resin.The intercalated and exfoliated properties were analyzed through TEM studies.Contact angle marginally vary with percentage of clay in epoxy resin. The surface variations of epoxy nanocomposites analysed through surface roughness measurement and by attenuated total reflectance Fourier transform infra-red spectroscopy (ATR-FTIR).The rise time of injected current pulse due to surface discharge process is measured to be 800 ps. The UHF signal generated due to surface discharge (at the point of inception and propagation) formation on epoxy resin with different percentage of clay in liquid nitrogen medium have dominant frequency near 1 GHz. The PRPD pattern obtained at the point of inception of surface discharges, the magnitude of discharges is nearly same in both half cycle of the applied AC voltage. Surface discharge occurs in the rising part of the applied AC voltage. When the applied voltage magnitude is increased, the higher magnitude discharges occurs at the positive half cycle of the applied AC voltage.