Temperature effects on partial discharges in the combined system of a solid-liquid dielectric during lightning impulse voltage

The experimental work presented in this paper shows that the level of partial discharges in a solid-liquid dielectric increases with temperature. Partial discharge implications in the "metal-dielectric-metal" system were investigated using 1.2/50 /spl mu/s impulse voltages under environmental temperatures of 20/spl deg/C and 40/spl deg/C. Although the repeat rate of the partial discharges appears to be almost independent of temperature, the charge associated with these partial discharges shows a remarkable increase. Furthermore, the threshold electric field required for partial discharge initiation was found to be reduced significantly as the system's temperature was increased. The commonly accepted model of Gemant and Philipoff incorporating pre-existing defects or irregularities of the molecular structure in the solid-liquid dielectric and voids in the volume of the solid dielectric has been used for the interpretation of the obtained results. The approach of the solid-liquid dielectric to the above experimental results may imply a conductivity increase of the system in the high field region due to enhanced electron avalanche mechanism.