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 SF 6 is estimated to be σ = 1 × 10 -18 Ω -1 .
In the case of interrupting capacitive loads, the most challenging problem for vacuum interrupters is to withstand recovery voltage during opening operation. In addition, the field enhancement factor of vacuum contacts is assumed to be high due to the damage of contacts caused by making the inrush current. In this paper, simulated shunt capacitor switching tests are carried out and the field emission current across the contact gap is measured to research the influence of the inrush current on the breakdown phenomena during opening operation. All breakdowns occur before the gap spacing reaches the maximum value and it is determined that there is a correlation between the electric field breakdown and the field emission current measured before the breakdowns. Furthermore, the found correlation is independent of the amplitude of the inrush current. The electric field breakdown is nearly invariant under the condition that the measured field emission current is constant regardless of the inrush current. However, the field emission current tends to be high in the presence of a large inrush current. The difference in the expected field emission current is believed to affect the electric field breakdown.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.