Investigations on SF6-Free Gas Circuit Breaker Adopting CO2 Gas as an Alternative Arc-Quenching and Insulating Medium

SF6 gas has widely been used for high-voltage and large-capacity electric power equipment such as gas insulated switchgears (GIS) and gas circuit breakers (GCB) due to its excellent insulating and arc-quenching capability. Although SF6 gas strongly contributes to achieve compactness and high reliability of the equipment, it has been recognized as one of the potent greenhouse gases and was designated to reduce the emissions at COP3 at Kyoto in 1997. At present, strategic effort to reduce the emissions is being made, which actually pan out.1 Over the long term, however, it is certainly preferable to reduce the consumption itself, because its atmospheric life time is observed to be quite long, thus the amount of SF6 gas on the earth will inevitably get increasing in the future unless artificial destruction.