Abstract
It is well-known that a surface discharge is significantly affected by electrificated charge on the surface of an insulator. However, only limited information is available concerning the electric field strength of a surface discharge produced by the charge itself. This paper describes the relationship between a surface discharge inception field caused by the charge itself and the pressure. After the charge was electrificated on the surface of film covering a plane electrode by corona discharge using a needle electrode, this electrode system was placed in a vacuum chamber lowering the pressure. A weak discharge momentarily occurs at a critical pressure around the center of the electrificated charge. We obtained the relation between the maximum field strength and the critical pressure in the range of about 50 hPa-1000hPa. It should be emphasized that the inception electric field were 6-8kV/mm at the atmospheric pressure and the 0.5kV/mm at 50hPa. Finally, such results are discussed comparing the flashover voltage of the uniform field and the electric field of discharge inception obtained through the experiment with various altitude in the lightning cloud.
