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Seattle’s Denny Substation sets new design standard for urban substations

July 2019

SEATTLE (July 19, 2019) ‒ Ceremonies held July 20 will officially introduce Seattle City Light’s first new substation in 30 years to the Emerald City, the stunning Denny Substation, which sets a new standard for urban substation design.

Seattle City Light used state-of-the-art technology, skilled and diverse engineering and a community-focused public involvement program to deliver a new high-voltage substation compatible with its densely populated neighborhood. Denny’s double-cantilever walls shimmer in the sunlight and its translucent glass panels emit a soft glow when illuminated at night. The substation provides spaces for people to not only view the workings of the substation, but also to meet, play, eat and enjoy outdoor art.

Behind its pretty face, the substation transforms high-voltage energy from SCL’s mostly renewable sources into lower voltages used by the growing number of South Lake Union and Denny Triangle residences and businesses. The substation supports Amazon’s headquarters, University of Washington School of Medicine’s biotechnology and medical research hub, the Fred Hutchinson Cancer Research Center, the Seattle Cancer Care Alliance, the Bill & Melinda Gates Foundation, the global health organization PATH and the Washington State Convention Center.

Denny’s design invites people to the site and offers them engaging things to do. The substation includes 44,000-square-feet of open space, an off-leash pet park and a quarter-mile walking loop that rises 16 feet above street level to provide pedestrians views of a public park, a landscaped terrace and the city skyline. The substation cuts across a block and a half, but its size doesn’t overpower passersby, thanks to walls that angle inward to lower its profile.

POWER Engineers Incorporated (POWER) served as SCL’s consultant team project manager, coordinated the work of 30 consultants and performed the electrical design needed to build the cutting-edge substation.

“Constructing Denny Substation required a lot of coordination and cooperation among elected officials, public agencies, design teams and many others, as well as input from citizens,” said Jay Keeling, vice president of program management at POWER. “Successfully meeting public needs and design challenges allows Seattle City Light to achieve its mission of service to its customers and to also give Seattle a substation design that celebrates its place in the Emerald City.”

POWER’s services included preliminary and detailed design of substation, transmission and distribution electrical systems. POWER also provided advanced substation automation design using modern communication networking, security and messaging protocols. Other services included electrical system studies and construction support.

Constructing the substation presented demanding technical and design puzzles because a lot of equipment and functions had to go into a relatively limited space that didn’t allow for a typical open-air insulated substation. Initial equipment includes four bays of 115 kV gas-insulated switchgear, three 115-13.8 kV power transformers, a 115 kV line inductor with integrated GIS, a 13.8 kV switchgear building with 72 interrupter positions, four 13.8 kV capacitor banks and three 13.8 kV grounding banks.