Influence of Surface-Conductivity Nonuniformity on Charge Accumulation of GIS Downsized Model Spacer under DC Field Application

When a DC voltage is applied to an insulating spacer, the electric field distribution around it is determined by the resistivity of the material. Consequently, charges are accumulated on the surface of the insulator, and its breakdown voltage may become low. In this paper, the charge density distribution of the insulator is measured. The measured data indicate that the surface conductance is the main factor in charge accumulation. Therefore, the conductivity of the insulator is also measured, and the influence of the surface conductivity on charge accumulation is examined both experimentally and by numerical computation. It is confirmed that nonuniformity of surface conductivity is responsible for charge accumulation and the conductivity of the insulator in atmospheric-pressure SF6 is estimated to be sigma = 1 x 10(-18) Omega(-1). (C) 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 181(2): 29-36, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22272