Dielectric Properties of highly - pressurized Dry Air and their Application to 550 kV DC Residual Current Switch

High voltage gas-insulated switchgear (GIS) using SF6 alternative gas insulation technologies has been developed to meet the global demand for reducing environmental impact. Dry air is an ideal candidate because its GWP equals zero, and its insulation technology has been widely utilized at low and medium voltages around the world. The authors have developed highvoltage rated equipment using dry air (80% N2 and 20% O2) [1] and, with a view toward expanding their applicability to DC equipment, have also advanced the development of a residual-current interrupter (RCS) for DC circuit breaker.