The electrical performance of air or nitrogen gas with solid insulation and the application for switchgears

The electrical performance of air or N₂ insulated system could be improved by composite gas/polymer insulation. Extensive investigations on composite insulated system have shown the possibility of substitution for SF₆ insulated system. We applied the covered hemisphere-rod/plate electrode for studying the effect of composite insulated system for an application of switchgears. It was found in our studies that this system improved the dielectric strength up to maximum 1.5 times higher than that of air or N₂ insulated system at 0.2 MPa·G, using a liquid rubber as a cover of the rod. However, a liquid rubber cannot be applied in air as an insulated gas where oxidant degradation occurs in constant heat. On the other hand, it is presumably possible to utilize a liquid rubber in N₂ where oxidant degradation does not occur, since the examination of heat degradation showed that its electric characteristics was maintained. This paper presents the improvement effect for a composite insulated system with a liquid rubber, compared with some fundamental results about air or N₂ gas insulation performance.