Surface Flashover Characteristic of EP/MWCNTS in Vacuum Under DC Voltage

The surface flashover voltage of the interface between solid and atmosphere is much lower than the breakdown voltage in the same atmosphere, which restricts the rapid development of ultra-high voltage electrical equipment. The modification of a solid insulating material can improve the flashover performance of the gas-solid insulation system. Consequently, we prepared the epoxy resins with multi-walled carbon nanotobes (MWCNTS) particles in 8 different mass fractions, which are 0%, 0.02%, 0.05%, 0.1%, 0.125%, 0.1%, 0.2%, 0.5%, respectively. Then, the experiments of microscopy morphology, glass transition temperature, dielectric constant, surface roughness, resistivity, surface potential decay (SPD), and DC flashover in vacuum were conducted. The experimental results show that the surface flashover voltage first increases and then decreases as filler loadings increases, and reaches the climax with the filler doping mass fraction of 0.1%, and the flashover voltage increases 23.1% compared with neat epoxy resin. It is found that the increase of the surface flashover voltage is related to the increase of the trap depth and the decrease of the dielectric constant when the filler doping mass fraction is low, while the decrease of flashover voltage results from the increasing of dielectric constant and the density of shallow traps at high filler doping mass fraction. It can be concluded that the dielectric constant will cause the electric field distortion, and the depth and density of the trap will affect the carrier transport process, both of which will affect the flashover voltage.