Effect of temperature on insulation properties of epoxy resin-impregnated paper bushings

Resin-Impregnated Paper (RIP) insulate system was widely used in transformer bushings and wall bushings. In order to study the effect of temperature on RIP bushings, the insulation properties such as insulation resistance, dielectric loss parameter (tato) and capacitance are tested and analyzed in different temperature from 20°C to 110°C. And RIP bushing samples are tested by the Frequency Domain Spectroscopy (FDS) method within 0.001Hz to 1000Hz which is based on the dielectric response theory. The results demonstrated that with the rising of temperature, the insulation resistance decrease exponentially. In general, tato and capacitance will be larger on the condition of high temperature and low frequency. And the tato increased with the frequency decrease and presents a platform area between 0.22Hz and 0.046Hz in the temperature of 30C. The dielectric loss frequency curves move towards higher frequency in higher temperature. And when the temperature is 110C, there has two platforms in the curve, the first one is near 10Hz and the second one is from 0.01Hz to 0.001Hz. The results can provide reference for RIP bushings' maintenance and insulation diagnostics.