A. B. Chance Company

Harold D Haubein

George D Allen

Melvin B Goe, Jr

Robert W Harmon

Vance B Martin

Kenneth A Toeniskoetter

Edgar J Ramsey, Jr

Ronald C Pehle

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.

Pad-mounted double-fused vacuum switchgear

A rigid, unitary, externally mounted combination bus bar and current interrupter especially adapted for protecting pad-mounted transformers from the effects of fault currents is provided which precludes catastrophic transformer failures by ensuring that all energized parts within the transformer tank are on the protected load side of the current interrupter while also providing an external, insulated bus bar having strategically spaced, line-connecting, loop feed bushings which preclude arcing-over therebetween and permit the transformer to be safely system-installed according to established practices with preexisting feeder lines. The assembly preferably includes a rigid, encapsulated bus bar carrying a central conductor which electrically connects the spaced terminator-receiving bushings thereon in order to define an external electrical feed loop, with an integrally attached, oil-submersible high-range current limiting fuse extending from the bar and into the tank of the protected transformer. This construction permits safe, desirable double-fusing of the transformer with a series-related internal low-range expulsion-type fuse in order to enhance overall system coordination and ensure that only the easily replaceable expulsion fuse operates in the case of normally encountered low-range faults.

Externally bussed, encapsulated current limiting fuse for pad mounted

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Centralia, MO, United States of America

Harold D Haubein