Pawnee-San Miguel 345-kV & 138-kV Overhead Transmission Line

Pawnee-San Miguel 345-kV & 138-kV Overhead Transmission Line

Location: Nursery, Texas

Client: South Texas Electric Cooperative

Completion Date: June 2002

Burns & McDonnell provided professional engineering and design services related to the Pawnee-San Miguel 345-kV Transmission Project, for South Texas Electric Cooperative. The San Miguel-Pawnee 345-kV Transmission Project consisted of approximately 35 miles of 345-kV double-circuit transmission lines, with one circuit initially installed; the new Pawnee 345/138-kV Substation; expansion of the existing 345-kV yard at the San Miguel Power Plant Substation; and modification of an existing 138-kV transmission line in order to loop it through the Pawnee 345/138-kV Substation.

  • Transmission design
  • Substation design
  • Equipment, material and construction specifications
  • Construction inspection

Initial construction of the Pawnee 345/138-kV Substation consisted of a 4-position, 6-breaker, breaker-and-a-half 345-kV Yard; one 345/138-kV, 150 MVA autotransformer; and a 3-position, 3-breaker, ring bus 138-kV Yard. The Pawnee 345/138-kV Substation is located northwest of El Oso, Texas. This site is served by a combination of all-weather, gravel and unimproved dirt roads.

Expansion of the existing San Miguel Power Plant Substation consisted of the addition of a 2-position bay to the existing breaker-and-a-half 345-kV Yard with 2-breakers and 1-position initially installed. This site is located southeast of Christine, Texas and is served by all-weather roads.

Burns & McDonnell's responsibilities included design and engineering services related to the selection of routes and sites, acquisition of properties and rights-of-way, environmental and geotechnical investigations, design and engineering studies, procurement and construction specifications, and other subcontract services directly related to the complete design of the project. Burns & McDonnell also performed construction observation in order to verify to STEC that the construction contractor performed in accordance with the plans and specifications. Construction was competed in June 2002.


  • Burns & McDonnell provided complete engineering services from route selection and environmental studies through design and construction inspection
  • STEC’s first 345-kV line and substation
  • Tubular steel structures with negative-shielding provided efficient design with shorter structures, improved lighting performance and better Land-owner acceptance