The mechanisms of surface charging on downsized HVDC GIL spacers coated with non-uniform conductivity

摘要

Surface charging phenomena on DC GIL spacers is a complicated process affected by lots of factors, among which surface conductivity is an important dielectrics parameter. In this study, experimental and theoretical research are carried out to investigate the effects of non-uniform surface conductivity on surface charge accumulation behaviours of downsized HVDC GIL spacers. A SiC/epoxy layer is partially coated on alumina/epoxy spacers to form a non-uniform surface conductivity. The coating patterns include sector-shaped coating and ring-shaped coating. The applied stress is DC voltage. The accumulated surface charges show a rising first and then decreasing trend with the increase of $S$ iC contents in coated area. When surface conductivity is high enough, there is almost no charge accumulation. Bipolar charges, which are generally observed on raw alumina/epoxy spacers, are found to be preferable to accumulate at interface region between high and low surface conductivity. The orientation of bipolar charges is determined by the distribution of inhomogeneous surface conductivity. The corresponding mechanism is revealed on the basis of experiment and simulation results which would be helpful for designing highly reliable and stable HVDC GIL.