Investigation on abnormal phenomena of contacts using disconnecting switch and detachable bus in 300 kV GIS

Using the disconnecting switch and the detachable bus of a gas-insulated switchgear (GIS), rated voltage 300 kV and rated current 2000 A, current and voltage-current tests were conducted in simulation of abnormal contact likely to occur in actual operations, yielding the following results: under the abnormal condition of the arcing contact of the disconnecting switch, continuous arcing occurs with a current above a certain level, resulting in a ground fault. Under the abnormal condition of the main contacts of the disconnecting switch, continuous arcing occurs, resulting in a ground fault if products decomposed by arcing are deposited on the contacts. In conductors of the detachable bus, arcing occurs with current above a certain level if there is a gap between the current-carrying surfaces even when bolts are used. The progress thereafter can be roughly divided into two categories. With narrow gaps between the current-carrying surfaces, the current-carrying surfaces are welded together with the molten metal produced by arcing. With wide gaps between the current-carrying surfaces, continuous arcing occurs. Rapid overheating or arcing at contacts is likely to occur not only when the current is raised by also when sunlight shifts