Abstract
SF6 gas has excellent dielectric strength and current interruption performance. For these reasons, it has been widely used for gas insulated switchgear (GIS). Today, such global environmental problems as global warming are important issues of concern. SF6 gas is known as a greenhouse gas with a long atmospheric lifetime, and has global warming potential of 23,900. SF6-free 72kV GIS was recently developed by using high pressure air and a gas/solid hybrid structure. But an alternating current disconnecting switch (DS) has yet to be not developed thus making this type of SF6-free 72kV GIS unsuitable for double bus-bar application. Consequently, the development of a high pressure air-insulated DS corresponding to bus-transfer current switching has been expected. The bus-transfer current is the highest among all current interruption requirements for the DS. To develop an alternating current DS, efforts must be made to reduce arcing damage to the electrode. This paper describes the fundamental characteristics of current interruption in the plain break type and the magnetic field driven type. Then, average arcing time of the magnetic field driven type was estimated by magnetic flux density. Finally, two types of DS which were a high speed plain break and a low speed magnetic field driven, were confirmed to comply with bus-transfer current switching requirements on JEC standard.
