Pressure dependence of interfacial breakdown between two solid dielectrics: Effects of environmental humidity while assembling and interfacial angle

Solid insulation system without SF 6 gas or with dry-air has become a promising technology for environmental friendly high voltage insulation. One of the problems of the solid insulation is breakdown along the interface between two solid dielectrics. In this paper, we investigated the effects of environmental relative humidity while assembling of a test piece, distance between electrode and interface length to the breakdown strength under non-uniform AC electric field. The results are as follows: (1) breakdown voltage increased with decreasing environmental relative humidity while assembling because streamer propagation was suppressed by high surface resistivity, (2) at the same applied pressure, the increase of the breakdown strength is prominent at large interfacial angle, and (3) the tangential breakdown strength is not influenced by the distance between electrodes and the interface length.