Abstract
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 the breakdown voltage of it 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 of the charge accumulation. Therefore, the conductivity of the insulator is also measured, and the influence of the surface conductivity on the charge accumulation is examined from both sides of experiment and numerical computation. It is confirmed that nonuniformity in the surface conductivity is responsible for the charge accumulation and the conductivity of insulator in atmospheric pressure SF6 is estimated to around σ = 1×10-18Ω-1.
