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Concorde Specialty Gases was contracted by National Grid to assist in the decommissioning of Tewksbury 22A 345 kV Gas Insulated Substation. Tewksbury GIS reached the end of its service life and needed to be decommissioned to make way for a new GIS.

Tewksbury 22A GIS was built in the 1970s and serves customers in cities and towns in eastern Massachusetts. Two 345 kilovolt lines come into the station, bringing power from generating stations; four other transmission lines deliver power from the substation to other facilities in the area.

The existing substation is part of the first generation of gas-insulated substations, which were built completely outdoors. This left them exposed to the New England weather, which sometimes features extreme cold and heat, along with ice and biting winds.

National Grid utilized Concorde’s expertise in recovering the SF6 gas.

• Over 8,000 lbs. of SF6 gas recovered
• 10 Isolation Zones
• 5 High Voltage Circuit Breakers
• Each isolation zone was brought down below 1 Torr