Increasing electric reliability and capacity on Bainbridge Island

The need

Bainbridge Island customers experience more power outages and for longer durations than many of our customers. This lower reliability occurs because of aging equipment, the lack of a second source of power without a looped system (redundancy), trees falling on transmission lines and difficult access.  

In addition, we increasingly rely on electricity to power our daily lives and islanders need more energy, especially during the coldest and hottest times of the year.

The hybrid solution 

PSE will combine new grid infrastructure and energy efficiency programs to improve transmission reliability and address distribution capacity. 

Reliability components 

The following projects will make the Island’s electric grid more resilient and reduce the impact of outages by adding redundancy to the system. 

Capacity components 

The following project and program will address the Island’s increasing power needs and reduce demand on the grid. 

  • Second transformer at Murden Cove Substation 
  • Flex Smart+ 
    • Flex Smart+ is a voluntary energy efficiency pilot program for residential customers on Bainbridge Island who heat with electricity. The program helps customers shift their energy use when our experts predict a higher than normal demand for electricity. This smooths out energy demand. 
    • Visit this page and sign into your PSE account to see if you’re eligible for the program. 

Other PSE projects on Bainbridge Island 

In addition to these hybrid solution projects, PSE is investing in other projects to improve Bainbridge Island’s transmission and distribution system reliability. Check out our full list of current projects here.  

Changes from the 2019 plan 

In 2019, PSE shared our proposed solution to meet Bainbridge Island’s identified electric reliability and capacity needs. Since 2019, we have more information and details that have helped us refine our solutions to meet the energy needs of the community.

We plan to install a second transformer (called a “bank”) within the existing Murden Cove Substation instead of a battery energy storage system (BESS) to provide more electric capacity to meet all of our customers’ energy needs. Learn more here.

Map of the hybrid solution projects 

Note: Map elements are not to scale and locations are approximate | Click map to enlarge. 

Schedule 

Below is our current schedule for the Flex Smart+ program and construction on our infrastructure projects. This schedule could change, depending on the permitting process. 

Click to enlarge

In 2019, PSE shared our needs assessment and proposed solution to meet Bainbridge Island’s identified electric reliability and capacity needs. Since 2019, we have more information and details that have helped us refine our needs analysis and solutions to meet the energy needs of the community. Therefore, the Needs Assessment and Solutions Report linked below are no longer our current plan. For our current plan, see PSE’s hybrid solution section above.

Bainbridge Island customers have been vocal in asking us to find solutions that improve electric reliability, meet this community’s growing energy needs and align with the community’s values. 

In 2019, PSE completed a detailed assessment on Bainbridge Island’s electric system needs. The Needs Assessment identified known and new issues. 

Read the Needs Assessment 

PSE and third-party experts then developed a Solutions Report to analyze potential solutions to meet these needs. The report studied the feasibility of both traditional wires solutions and innovative non-wires solutions. 

Read the Solutions Report 

The Need Assessment identified three key findings:

  • Poor transmission reliability
  • Aging infrastructure
  • Growth: ferry electrification and increased demand for power

Poor transmission reliability

A graphic illustrating why the power goes out at substations and what parts of the Island lose power.

The Needs Assessment affirmed that the island has a transmission reliability need. The study highlighted that Bainbridge Island customers experience more frequent and longer outages than the average PSE customer, and nearly half of those outage minutes are due to issues with the transmission system. Some specific challenges to reliability include:

  • Trees: Bainbridge transmission lines are heavily exposed to trees, and 64 percent of outages are caused by trees.
  • Radial transmission lines: Nearly two-thirds of Bainbridge customers are at risk of a prolonged outage. This is because their area is served by a substation – either Winslow or Murden Cove substation – that’s fed by a single transmission line with no back-up.
    • Customers served by the Winslow substation have the worst reliability on the island, and secondarily Murden Cove substation.
    • Nearly 70 percent of transmission customer minutes of service interruptions were from the Winslow Tap transmission line that feeds the Winslow substation.
Bainbridge Island transmission and substation outage summary, 2013 – 2022 (click to enlarge)

Aging infrastructure

Inspections determined that portions of the Winslow Tap circa-1960 transmission line are nearing the end of its useful life and needs to be replaced. In addition, the Winslow Tap is in a heavily vegetated corridor with difficult terrain, which makes finding and repairing outages challenging and results in longer outages.

a map of the existing Winslow Tap transmission line corridor including the three substations with two photos of wooden transmission poles on the right hand side.
Existing Winslow Tap transmission line corridor

Substation capacity need

Ferry electrification and the community’s growing energy needs are driving the need for additional substation capacity, particularly during winter peaks.

  • Increasing demand: The population of Bainbridge Island has increased significantly over the last few decades and electric demand has changed. Even with energy conservation, the electric demand residents place on the system has dramatically increased.
  • Ferry electrification: Soon Washington State Ferries will be electrified to cut carbon emissions and reduce pollution, which will require a charging system at Bainbridge Island and creates even more demand.
a graphic that displays to two houses one labeled 1960 with household appliances. The other house is labeled today and inside the house its shows more household appliances including a car. This graphics illustrates the increase of electric demand.