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Puget Sound Energy transmission line project

Tukwila underground 115 kV cable replacement project

Winter 2014 project updates

  • We're currently in the preliminary engineering and right of way review phase
  • We expect to complete engineering and permitting in 2014
  • Construction is expected to start in 2015

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Project map

Project overview

Customers in the Tukwila area will see continued electric reliability with Puget Sound Energy's planned replacement of the existing 115 kilovolt underground transmission cable. The cable connects the Nelson cable station (16210 West Valley Road in Tukwila), Southcenter substation (16801 Southcenter Parkway in Tukwila) and Tukwila cable substation (5186 S. 168th St. in SeaTac) (see project map).

The original underground cable was installed in 1974 (see photos of original installation below), with technology that provided an average cable life of 35-45 years. The existing cable is nearing the end of its useful life and is at an increased risk of failure. Today's cable is expected to last 75-100 years due to improvements in insulation materials and manufacturing techniques. Replacing the existing cable will enable PSE to provide continued reliability to customers in the Tukwila area now and well into the future.

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.