CREEPAGE DISCHARGE PROPAGATION IN AIR AND SF6 GAS INFLUENCED BY SURFACE-CHARGE ON SOLID DIELECTRICS

Influence of surface charging on creepage discharge propagation in air and SF6 gas was investigated. We have employed a surface charging sys tem using corona discharges, which permitted the deposition of surface charge on solid dielectrics with a given density distribution. By app lying a lightning impulse across the charged surface of polyester film , we measured the discharge extension length as a function of surface potential generated by the surface charge. It was found that the impul se creepage discharges along the charged surface under a potential of 2 to 3 kV, extended a distance which was maximum 6x longer than the ca se of the uncharged surface both in air and SF6 gas. Experimental resu lts were also discussed from the viewpoint of the specific capacitance , permitting their application to actual HV apparatus such as GIS.