Insulation technology for medium voltage solid insulated switchgear

The authors have developed solid insulated switchgear that does not use SF₆ gas at all as an insulating medium. This paper describes the insulating material technology, diagnostic technology for partial discharge, insulation technology of the vacuum disconnecting switch and aerial composite insulation technology which are applied to this solid insulated switchgear. A new epoxy resin, which was dispersedly configured with spherical silica and rubber particles, was developed. The insulation performance of this resin is 50% higher compared with filling of alumina. Utilizing the features of the solid insulated switchgear, a diagnostic technology for partial discharge employing an acoustic emission (AE) sensor was developed. A vacuum disconnecting switch with high insulation reliability was developed applying Weibull distribution to dielectric breakdown in a vacuum. The insulated parts of insulating rods of circuit-breakers and disconnecting switches were miniaturized through composite insulation.