Nonlinear conductivity characteristics of epoxy resin-impregnated nano-SiC-modified insulating paper

Epoxy resin-impregnated insulating paper (RIP) is the main insulation of the high-voltage direct-current (HVDC) dry bushing. In order to solve the problem of uneven radial electric field distribution of the bushing, the insulating paper was modified by nano-SiC with filling concentrations of 0-7wt% and impregnated with pure epoxy resin. The dispersibility of nanoparticles was observed by scanning electron microscope. Their conductivity, dielectric, and breakdown properties were tested. The results showed that the electrical conductivity of RIP could be improved by filling it with nano-SiC, and nano-SiC/RIP had obvious nonlinear conductivity characteristics. Comsol-Multiphysics was used to simulate the electric field of the HVDC dry bushing with 0-7wt% nano-SiC/RIP as the main insulation. The simulation results showed that the radial electric field uniformity decreased from 3.04 to 1.20 when concentrations increased from 0 wt% to 7 wt%. Finally, considering the comprehensive factor, 5wt% was considered the optimal doping concentration.