Puget Sound Energy substation project
Mount Si substation, switching station and transmission lines
Summer 2010 project updates
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Puget Sound Energy expects to begin the permitting phase in fall 2010
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We plan to begin construction in 2011
Project overview
To meet current and future demand for power and maintain electrical system reliability, PSE has an immediate need to build a new distribution substation in the Snoqualmie Ridge area. Currently, the distribution circuits serving Snoqualmie Ridge are nearing capacity during winter months, and future growth in the area is expected to increase significantly.
We plan to construct a new distribution substation, located near the intersection of Southeast Douglas Street and 356th Avenue Southeast in Snoqualmie, to add capacity and accommodate growth. When complete, the substation will include one 25 megavolt ampere transformer, with space to add a second 25 MVA transformer, allowing PSE to double the capacity in the future without changing the substation footprint.
Our plans also include the construction of transmission switching facilities, where three 115 kilovolt transmission lines will converge, providing redundancy for the new substation and greater operational flexibility and efficiency in delivering power to our customers. In the future, our plans for this utility site include additional transmission facilities to meet projected local and regional electric needs.
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.
What is a switching station?
A switching station is a transmission substation where the utility can switch or reroute power flow from one line or path to another to allow the power to be isolated to clear a fault (e.g., a fallen tree in the wires) or to take the power line out of service for maintenance. It also may act as a point of interconnection between two different transmission operators (e.g., Bonneville Power Administration and PSE). Unlike a substation with a transformer service neighborhood circuitry, switching stations do not step power up or down; they integrate power from one or more transmission sources on the regional and local grid to serve neighborhood substations.
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.
Committed to keeping you informed
PSE will continue to provide updates to the community. We will notify residents and businesses near the project area when construction will occur. We aim to complete the work with as little disruption as possible.
Download the information
Project map
(311 KB PDF)
Annexation presentation to Snoqualmie City Council, May 24, 2010
(1 MB PDF)
Annexation presentation to City of Snoqualmie Planning Commission, March 1, 2010
(2 MB PDF)
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