Gas-insulated switch for an underground power distrubution system

A self-contained and hermetically sealed gas-insulated switch for use in power distribution systems, said switch comprising, in combination:

• a conductive and hermetically sealed housing;
• at least one pair of insulated feed-through bushings fixedly mounted to said housing, each bushing having a first conductive portion thereof external of said housing for coupling to an underground conductor termination, and each bushing having a second conductive portion internal to said housing;
• first and second electrodes respectively coupled to said second conductive portions of said pair of bushings;
• means for moving said electrodes relative to one another during a switching operation to alternately engage and disengage said electrodes, wherein a circuit is completed when said electrodes engage and wherein an electric arc is drawn between said electrodes during a portion of said switching operation;
• an electronegative gas within said housing for extinguishing said arc, and for electrically insulating said electrodes from one another and from said conductive housing, wherein said gas is maintained within said conductive housing at a pressure within the range of 0 to 20 psig. thereby to prevent liquefication of said gas at relatively low ambient temperatures and to permit said housing to be sealed without necessitating an external gas containing storage reservoir;
• means including a casing internal to said housing and surrounding said electrodes and a portion of one of said bushings for directing a stream of said gas into said arc during said switching operation;
• and
• said casing having at least one opening therein wherein the internal portion of said casing communicates with the internal portion of said housing which is external to said casing whereby the normal pressure of said gas within said casing is equal to the pressure of said gas external to said casing.

A gas-insulated switch for use in a power distribution system, said switch comprising, in combination:

• a conductive housing;
• at least one pair of insulated feed-through bushings fixedly mounted to said housing, each bushing having a first conductive portion thereof external of said housing for coupling to a conductor termination, and each bushing having a second conductive portion internal to said housing;
• first and second electrodes respectively coupled to said second conductive portions of said pair of bushings;
• means for moving said electrodes relative to one another during a switching operation to alternately engage and disengage said electrodes, wherein a circuit is completed when said electrodes engage and wherein an electric arc is drawn between said electrodes during a portion of said switching operation;
• an electronegative gas within said housing for extinguishing said arc, and for electrically insulating said electrodes from one another and from said conductive housing, and wherein said gas is maintained within said conductive housing at a pressure sufficient to prevent liquefication of said gas at relatively low ambient temperatures;
• means including a casing internal to said housing and surrounding said electrodes and an insulated portion of one of said bushings for directing a stream of said gas into said arc during said switching operation;
• wherein at least the portion of said casing which surrounds said insulated portion of said one of said bushings comprises an insulating material;
• and,
• means for sealingly engaging the insulated portion of said casing with said insulated portion of said one of said bushings along a portion thereof which is spaced apart from said second conductive portion of said one of said bushings.