Temperature dependent surface potential decay and flashover characteristics of epoxy/SiC composites

GIS spacers made of epoxy resin always suffer from the flashover due to surface charge accumulation. Therefore, it is important to seek a new method to improve the performance of epoxy resin. The epoxy/SiC composites have been proven to have nonlinear conductivity and the potential of being used in the spacer manufacture because of their field grading function under DC voltage. A high temperature rise on the central conductor of GIS can cause a large temperature gradient along the spacers. Exploring the effects of temperature on the electrical properties of the epoxy/SiC composites is helpful in the design the space dependent SiC filler content in GIS spacers. In this paper, three temperatures 20, 50 and 70 °C were studed on the temperature dependent surface potential decay (SPD) and flashover characteristics of the epoxy/SiC composites. At 20 °C, the epoxy/SiC composites, especially the 14 vol % samples, have much better SPD performances and higher flashover voltages than the pure epoxy. As the temperature increases, the SPD performances of all samples are greatly improved. The SPD rate of the 0 vol % samples approaches that of the 6 vol % samples at 50 °C and the 14 vol % samples at 70 °C. When the temperature is over 50 °C, flashover of the epoxy/SiC composites occur at lower voltages compared with the pure epoxy resin. With a further increase of temperature from 50 to 70°C, the flashover voltages of all samples have a significant drop, indicating that the temperature effects on flashover fault must be included in the spacer design and manufacture.