Effects of Temperature on Surface Charge and Flashover Characteristics of Epoxy/SiC Composites

The epoxy/SiC composites have been proved 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 causes a large temperature range along the spacers. Exploring the effects of temperature on the electrical properties of the epoxy/SiC composites is helpful to design the space- dependent SiC filler content in GIS spacers. In this paper, three temperatures (20/50/70 °C) were set to study 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 catches up with that of the 6 vol% samples at 50 °C and the 14 vol% samples at 70 °C. When the temperature is over 50 °C, the flashover faults of the epoxy/SiC composites occur under lower voltages compared with the pure epoxy resin. With the 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.