Interfacial breakdown between dielectric surfaces determined by gas discharge

This paper examines the influence of the elastic modulus and applied contact pressure on the tangential AC breakdown strength (BDS) of polymer solid-solid interfaces theoretically and experimentally. In the experiments, three different materials with different elastic moduli, namely cross-linked polyethylene (XLPE), cured end product of epoxy resin (EPOXY), and polyether ether ketone (PEEK) were employed under various contact pressures. The BDS of each interface increased as the contact pressure was augmented. As the contact pressure became threefold, the interfacial BDS rose by a factor of 2.4, 1.7, and 1.8 in the case of the PEEK, EPOXY, and XLPE interface in a sequence following the decrease of the elastic modulus. Under the same contact pressure, it was observed that the lower the elastic modulus, the higher the BDS. The proposed theoretical approach tested two different mechanisms in determining the gas pressure inside the cavities. Both mechanisms suggested decreasing BDS values as the elastic modulus was augmented; however, the estimated results deviated widely from the experimental data as the pressure was significantly increased in the case of first proposed mechanism whereas the second mechanism correlated with the experimental data much better.