Temperature-dependent charge property of silicone rubber/SiC composites under lightning impulse superimposed DC voltage

Field grading materials (FGMs) with nonlinear conductivity, which can form a uniform local field in high-voltage direct current (HVDC) cables, have received considerable attention. This paper focuses on the temperature-dependent charge transport property of an FGM based on high-temperature vulcanized (HTV) silicone rubber (SiR). A nonlinearity in the conductivity is achieved by mixing silicon carbide (SiC) particles with the SiR matrix. The conductivities of the samples are measured at temperatures of 30–90 °C. In addition, the surface potential decay is analyzed. The experimental results show that the nonlinear conductivity is suppressed at high temperatures. Increased temperature can cause a lattice vibration, which scatters carriers and reduces the conductivity. With an increase in the homopolar impulse voltage, all samples experiences a rise in the initial surface potential. The increase in SiC content and the increase in impulse voltage can both accelerate the decay process. The heteropolar impulse voltage not only intensifies the accumulation of surface charge but also slows down the decay process. Neutralization occurs immediately between heterocharges. The positive charges are captured by traps, and the attraction between heterocharges is thought to be the reason for the observed phenomena.