Space Charge Properties of SiC/SiR Composites with Nonlinear Conductivity at Different Temperatures

Abstract

High voltage direct current (HVDC) cable accessory is the key equipment of the HVDC transmission system. HVDC cable accessory insulation suffers from charge accumulation caused by the non-uniform electric field distribution. Temperature intensifies charge injection and accumulation. This paper prepares silicone rubber (SiR) composites with nonlinear conductivity and studies the space charge transmission under thermal-electric field. The nonlinear conductivity of SiC/SiR composites is obtained at different temperatures. It is found that as the SiC content increases, the conductivity-temperature coefficient changes from positive to negative. This is mainly because the lattice vibration of SiC. The space charge properties of SiC/SiR composites under DC field at different temperatures are obtained. It is found that space charge accumulation is suppressed in SiC/SiR composites. The effect of charge accumulation suppression and fast dissipation increases with the SiC content. Besides, high temperature can also increase the conductivity and further suppress the space charge accumulation. Moreover, the conductivity-temperature coefficient of SiC/SiR composites is smaller than that of SiR sample, which leads to a smaller decrease in space charge accumulation at high temperature.