Buffalo Substation Expansion

Harding County, SD, USA

Substation & Switchyard

Project Highlights

  • Expanded 69 kV bus for new 69 kV line terminal.
  • Replaced control building shell while substation remained energized.
  • Updated substation from 48 VDC to 120 VDC.

As retained engineer for Grand Electric Cooperative (GEC), ECI prepared a complete design package for multiple upgrades for the Buffalo distribution substation near Buffalo, South Dakota. Work at this facility included expansion of the 69 kV bus to accommodate a transmission line terminal bay, which included one (1) 69 kV SF6 gas power circuit breakers, two (2) 69 kV disconnect switches, three (3) of combo metering units and one (1) new relay panel. This additional bay required yard expansion and interface with the existing lattice box structure. Work also entailed replacing an existing 69 kV oil-blast breaker with an SF6 breaker, adding reliability to an important switching device in GEC’s system.

The work at this facility posed a couple of unique challenges. One such challenge was the need to upgrade the facility from a control voltage of 48 VDC to 125 VDC. Extensive analysis was performed of all DC equipment in the existing station to determine which equipment and cabling could be reused in an effort to reduce project costs. All relays, RTU and the battery and charger were replaced as a result. Another unique challenge was the replacement of the outdated control building with a larger building while the station remained online. This work involved pouring the floor expansion around the existing building, removing all equipment mounted to the building wall and ceiling, hoisting the old building shell off of its foundation, installing the new building shell on the pad and then re-mounting/updating the equipment inside the new shell.

ECI was responsible for all physical and electrical design of the substation upgrades.

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