Client: Seattle City Light
Location: Washington State

Seattle City Light is building its first new electrical power substation in 30 years to help relieve an overstressed electric grid that is seeing additional load and reliability requirements. The north downtown Seattle Denny substation and its related new transmission lines and distribution systems will serve high-load commercial users such as Amazon, Vulcan and the University of Washington as well as residential neighborhoods.

POWER’s Services

• Project management responsible for coordinating with the client and overseeing a team of 30 subconsultants
• Preliminary and detailed design of substation, transmission and distribution electrical systems
• Electrical system studies such as load flow, reactive compensation and short circuit
• Equipment technical specification development and evaluation support
• Construction support

Features

• Substation: 115 kV GIS switchgear (4 bays BAAH), 3-75 MVA 115/13.8 kV power transformers, 1-115 kV series inductor with integrated GIS, 13.8 kV arc resistant metal clad distribution switchgear (30 feeder positions) and 4-13.8 kV metal clad capacitor banks, complete UG of all transmission lines and distribution feeders.
• Distribution Network: Designed for up to 42 distribution feeders and associated 3.5 miles of underground duct bank systems, network configuration
• Substation Automation: SCADA/Automation system based on the IEC 61850 standard utilizing GOOSE and MMS
• Design: Community-lauded, aesthetically pleasing progressive design with a pedestrian walk-though above and an education center on ground level. Also includes off-leash pet park, integrated art, provisions for food trucks, meeting space, and interpretative walking paths
• Feasibility Study, Transmission Line: 3-mile, installed at 115 kV, built for 230 kV from Denny Substation to Massachusetts Substation
• Vertical screening: Increases public benefit to the surrounding open space by incorporating a dynamic architectural wall
• Expandable design for future 115 kV lines, 230 kV line and equipment as well as 26 kV future distribution

Challenges and Highlights

• A limited footprint within a highly urban environment. This presents several challenges: budget (urban costs are much higher); compact design; political influence; electrical load density changes; scheduling and planning; and community impact.
• Worked with the Seattle Design Commission, community stakeholders and City of Seattle departments to permanently vacate Pontious Avenue as part of the project. Used the Community Outreach Program to reach amicable public benefit back to the community.
• Successfully navigated a diverse range of area stakeholders. POWER’s team designed an aesthetically pleasing yet technically sound GIS substation design which met the interests of electrical high-load commercial users like Amazon, local residents, neighborhood groups and the Seattle Design Commission.
• Adaptable to future expansions. The transmission line enables flexibility and load shifting within the overall system as future needs evolve.