Application of dry-air insulating media in 170kV GIS

Dry-air is a promising insulating medium for substituting the SF6 gas in industrial devices. The lower insulating performance of dry-air was compensated by moderate increase of service pressure and careful optimization of electric field within high voltage gas insulated switchgears (GIS). In addition to the insulating feature the different heat-transport characteristics of dry-air were also considered. The electric field distribution was simulated and compared with impulse test results on a compressed dry-air insulated integrated disconnector-earthing switch unit. The aim of development was to find a technically and economically optimal solution, which is equivalent to the SF₆ gas insulated switchgear unit.