Pad-mounted double-fused vacuum switchgear

Abstract

Pad-mounted double-fused switchgear especially adapted for use in underground distribution systems is provided which includes an oil tank having manually operable vacuum switch apparatus therein in conjunction with closely adjacent, series-connected, combination current limiting fuse-expulsion link protective fuse structure for maintaining the required momentary electrical rating of the overall switch apparatus notwithstanding of a relatively low-rated switch element, and for providing thermal protection for the switchgear. Double-fusing within the oil tank also serves to reduce electrical duty on upstream and downstream equipment, increases the interruption rating of the switchgear, and enhances overall system coordination. In preferred forms the expulsion link is temperature sensitive and is constructed to actuate only at relatively low fault current levels while remaining intact during high-level faults which actuate the backup current limiting fuse; in this manner effective total range fuse protection is maintained and the extent of attendant oil contamination is lessened since the expulsion link operates only during low level fault-clearing situations. Novel fuse well-double fuse assemblies adapted for use with pad-mounted electrical apparatus are also disclosed, along with structure for selectively holding the tank lid of such apparatus open against inadvertent closing thereof which can occur during high wind conditions.