The influential factors on electric breakdown damage of insulator in electric pulse rock breaking drill bits

In the working process of the Electric Pulse rock Breaking (EPB) drill bit, the insulator will have electrical breakdown failure under the action of long-term strong voltage, resulting in the loss of rock breaking ability of the EPB drill bit. Based on the simplified circuit analysis and the electric breakdown PDM (Probability Development Model), numerical simulation and laboratory experiment were conducted to study the electric field strength distribution in the insulation and the evolution law of the breakdown path. In this paper, nylon (PA), epoxy resin (EP), crosslinked polyethylene (XLPE), polytetrafluoroethylene (PTFE) as the base material, boron nitride (BN), glass fiber (GFR) as the filler to construct 8 kinds of electrical insulation composite materials, considering the material properties of different components and particle size. The effects of different insulators, filling particles, load voltage and insulator thickness on the breakdown path, growth rate and deterioration area in the insulation were analyzed. The results show that the breakdown path of the electric branches develops along the direction of electric field distortion. Using GFR as filler can effectively inhibit the diffusion capacity and development speed of the breakdown channel, reduce the deterioration area, but the breakdown voltage will be reduced. The research results have certain guiding significance for the engineering application of EPB and the optimization design of EPB drill bit.