Central Power Loop

Location: Nashville, Tenn.

Client: Nashville Electric Service

Completion Date: Phase I: 2000; Phase II: March 2002; Phase III: November 2002

The project consisted of approximately 10 miles of new 69- and 161-kV transmission line as part of the Central Power Loop around downtown Nashville, Tenn. It was designed and constructed in three phases: Phase I; between Sharondale, Battlefield and Craighead substations; Phase II; between West substation and Galloway substations and Phase III; between Galloway substation and Sharondale substation. The Central Power Loop project increased system reliability and increased capacity for future predicted loads.

  • Underground transmission line design
  • Overhead transmission line design
  • Transmission line routing
  • Facilitating Citizens Advisory Committee meetings
  • Transmission thermal upgrade studies
  • Substation design
  • Site development
  • On-site construction project management

Transmission Line Design

Burns & McDonnell was given complete responsibility for all transmission line design. Each phase of the project began with route study and analysis, and involved a Citizen’s Advisory Committee selected by local government to work with Burn & McDonnell to select the route. This process also included multiple open houses for additional public involvement.

Burns & McDonnell performed all aspects of transmission line design, including development of loading criteria, conductor sag and tension design, vibration analysis, insulation, clearance, structure spotting using PLS-CADD transmission line design software, and foundation design.

Other services included preparing the plans and specifications for procurement of materials and construction; review of shop drawings and submittals and full-time, on-site construction management, including engineering support as required.

Underground Transmission Line Design

As part of Phase I of the Central Power Loop, Burns & McDonnell designed a 69-kV underground transmission line through an established residential area of Nashville. This portion of the project included significant involvement of the Citizen’s Advisory Committee and the public.

Burns & McDonnell services include duct bank routing; reinforced concrete duct bank design; conductor pulling tension calculations; manhole design; riser structure loading diagrams and foundation design; and conductor bonding and grounding design. The project also included a horizontal boring beneath an existing box culvert. The horizontal boring design included a grout-filled steel casing to protect the duct bank.

Additional Burns & McDonnell services included plans and specifications for material and construction, and coordination with the Metropolitan Government of Nashville to limit street closures and utility interruptions.

Thermal Rating Study

Burns & McDonnell modeled existing 161 and 69-kV transmission lines using PLS-CADD software. This included a thermal rating study of the conductors to determine if the existing conductors could operate at higher electrical load and elevated temperatures without violating code clearances to the ground, other lines or structures. The thermal rating study also included conductor loss of strength calculations to determine how long the conductors can operate at elevated loads and temperature without experiencing loss of strength of other conductor damage.

Burns & McDonnell’s services include specifications for aerial and ground surveys to capture line data; coordinating and administering the aerial and ground surveys; PLS-CADD modeling of existing lines and structures; thermal rating analysis; and a final written report.

Substation Design

Burns & McDonnell performed substation site development for the 161-kV Airport Substation. This project included grading design using AutoCAD Land Development software, stormwater run-off calculations, cut and fill quantities, access road design and drainage structure design.

All storm water run-off calculations were performed in conformance with the Nashville Stormwater Management Manual. All calculations and drawings were submitted to the Metropolitan Nashville Government for approval. In addition, Burns & McDonnell coordinated with the Metropolitan Nashville Government to insure the site was constructed in accordance with public works requirements.