The Influence of Chromium Oxide Coating of Alumina Surface on Partial Discharge in Vacuum

Owing to its use of epoxy resin with high insulation performance, solid-insulated switchgear (SIS) is smaller than other switchgear. The molded vacuum interrupter for the switchgear is also smaller but has higher electric field intensity, which is likely to cause partial discharge in vacuum. This is attributable to by electric field electron and secondary electron emission, and it is necessary to suppress these electrons in order to reduce the occurrence of partial discharge. We focused on a way of suppressing secondary electron emission, namely, coating chromium oxide on the alumina ceramic surface. In this article, we investigated the effects on partial discharge in vacuum of coating the alumina ceramic surface with chromium oxide. As a result of evaluation, it was confirmed that partial discharge extinction voltage (PDEV) with the coating improved drastically, and the larger the coating region is, the higher these parameters are.