Looped transmission will improve electric reliability on Bainbridge Island 

1/24/2023

Looped transmission system graphic.

On Friday, December 23, a tree fell into the transmission line serving the Winslow substation, taking out power to over 4,000 Bainbridge Island customers for approximately 10 hours while crews worked to make repairs. The Winslow substation is currently served by a single radial transmission line, referred to as a "tap". If the transmission line serving the substation goes out, then the substation and all customers served by that substation lose power.

As part of PSE's solution to improve reliability on the island, we’re planning to create a transmission loop by building a new 115 kV transmission line between the Winslow and Murden Cove substations. This means each substation will be connected to two transmission lines, reducing the frequency and duration of this type of outage. If one line goes out, the other line can still feed the substation and provide power to customers. If the new transmission line were in place, the outage on December 23 could have been avoided. The new transmission line could have kept power flowing to the Winslow substation, keeping the lights on for customers while crews repaired the other line. PSE has been engaging with the community since 2019 to site the new transmission line. The project is currently in the design and fieldwork phase with permitting expected to begin later this year.

We know outages are frustrating and disruptive, especially during the holidays. PSE’s investment in transmission infrastructure will make the island’s electric grid more resilient and reduce the impact of any single outage by focusing on redundancy. That is why the new Murden Cove – Winslow transmission line is a critical component of PSE’s plan to improve electric service reliability on Bainbridge Island.