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Energy :: Traditional

7th Avenue Substation 115-kV Rebuild

Longview, WA

DEA (formerly TriAxis, a Division of David Evans and Associates) provided design services for the reconstruction of a complex distribution substation. Fed from three high-side line positions, the substation received a new 20/26.7/33.3 MVA, 115‑13.09/7.56 kV three-phase, two-winding power transformer with LTC. The existing substation was torn down and the new substation was constructed on the same site.

Design features included:

  • A 115-kV primary aluminum bus, surge arresters, a circuit switcher for over-current protection, power-circuit breakers, and provisions to serve a future second transformer
  • Complete design of oil retention system for the power transformer.
  • Foundation design of all high-side equipment (pull-offs, circuit breakers, switch stands, VT stands, bus supports, and circuit switcher), including anchor bolt calculations.
  • Dimensioned steel support concepts and loading requirements.
  • The existing ground grid was analyzed using CDEGS software to verify safe touch-and-step potentials inside and adjacent to the substation.
  • Design of all substation feeder getaways, including conduits, junction boxes, pull vaults, and equipment connections.
  • Fence design using a combination of concrete wall and chain-link, along with perimeter curbs, gates, and signs.
  • The 13.09-kV, 1200-amp bus design with 500-MVA-rated breakers consisting of rigid aluminum tubing, and aluminum and copper jumpers.


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