Modeling longitudinal breakdown strength of solid-solid interfaces using contact theory

The main purpose of this paper is to explore the impact of applied contact pressure, surface roughness and elastic modulus on the AC tangential breakdown strength (BDS) of dry and wet-mate solid-solid interfaces both experimentally and theoretically. Experiments were performed using samples made of cross-linked polyethylene (XLPE) and silicone rubber (SiR) at three different contact pressures. The average diameters of interface voids were estimated using results from surface roughness measurements combined with contact theory. The expected breakdown values were assumed to be determined by the gas discharges and to be proportional to the real contact area in case of dry and wet assembly, respectively. Both theory and experiments showed increasing tangential breakdown values with increasing contact pressure in case of both dry and wet-mate interfaces. The effect of reducing the elasticity modulus is to shrink the void size and increase the real contact area of the interface. The breakdown strength of interfaces between soft SiR materials was found to be 3–4 times higher than that of the harder XLPE materials.