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Puget Sound Energy transmission line project

Thurston 230 kV transmission line project

Spring 2014 Project Updates

  • Construction on the transmission line (see project map) began in February 2014. Construction is expected to be complete, and the line energized, by the end of June 2014.
  • PSE completed related capacity upgrades to the St. Clair substation in Lacey in 2013.
Project overview

Puget Sound Energy is installing 3.2 miles of new 230 kilovolt transmission line between the St. Clair substation (9512 Pacific Highway SE in Olympia), and an interconnection point on the Bonneville Power Administration's South Tacoma-Olympia 230 kV transmission line (See map for location).

The new transmission line will bring 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 rest of the region. It's part of PSE's continuing efforts to improve system reliability and respond to the county's growing demand for power. 

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Project map
What is a transmission line?

Transmission lines are key elements in the electrical distribution system. The 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.