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Puget Sound Energy transmission line project

Thurston 230 kV transmission line project

Summer 2014 project completion

  • Construction on the transmission line began in February 2014 and was completed in June 2014.
  • PSE completed related capacity upgrades to the St. Clair substation in Lacey in 2013.
Project overview

Puget Sound Energy installed 3.2 miles of new 230 kilovolt (kV) transmission line between the St. Clair substation and an interconnection point on the Bonneville Power Administration's (BPA) South Tacoma-Olympia 230 kV transmission line.

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The new transmission line brings a new power source to the area, increasing the capacity and reliability of the elecric transmission system for the more than 120,000 customers in Thurston County and the surrounding region. The project was part of PSE's continuing efforts to improve system reliability and respond to the county's growing demand for power. 

What is a transmission line?

Transmission lines are key elements in the electrical distribution system. These lines safely transport high voltage electricity from power generation sources like dams and wind generating facilities to substations in local communities. Transmission normally takes place at voltages of 55 kV and higher.

What is a substation?

Substations are critical links in the electricity distribution system, containing utility circuit protection, voltage regulation, and equipment that steps down higher voltage to lower voltage. Before reaching homes and businesses, power is routed through our transmission system to a substation where it is changed to a lower voltage that can be utilized by customers.