A BPA outage for 6,000 customers? No, thank you.
Bonneville Power Administration will be replacing a 45-year-old circuit breaker at its Shelton substation on Olympic Highway North. The work will begin at 2:00 AM, September 8. They are estimating only a 30-minute outage, but PUD 3 is preparing for a two-hour interruption of service.
BPA’s circuit breaker B-1128 was originally put into service in 1974.
The circuit breaker feeds power to the PUD’s Mt. View Ring Bus, which distributes 115 kV transmission voltage to the Johns Prairie, Mountain View, and Mason substations.
PUD 3’s Mt. View Substation as seen from above. You can see the Ring Bus at the center of the picture. It’s the rectangle-shaped collection of equipment.
PUD 3 prides itself on the redundant design of its distribution system and substations.
If we allowed BPA’s work to de-energize three substations (Johns Prairie, Mountain View, Mason), about 6,000 customers would be without electricity for up to two hours. But that’s not how we do things!
Because nearly all our substations have been designed to have excess capacity, we will re-route power by utilizing a massive switching procedure involving seven substations to keep nearly all 6,000 customers online during BPA’s work.
Engineering wasn’t comfortable transferring the entirety of this load, so about 300 customers on Johns Prairie Road from Export Road up through Hiawatha Park, including the PUD 3 operations Center, will be without power during the planned outage. The PUD offices will be running on backup generation. Sierra Pacific will also be without power during this early-morning window.
The switching order to re-route power has a whopping 96 steps: 48 to transfer the power load from the Johns Prairie, Mountain View, and Mason substations to the other substations, and 48 to put things back the way they were.
We will use this brief downtime at the Mountain View switchyard to conduct maintenance on our ring bus equipment that hasn’t been de-energized through a planned outage since it was put into operation in 2009.
We manage power loads on our substations with the intent of keeping 40% of capacity set aside so we can do switching like this. When the extra capacity starts to shrink due to load growth (as in the Skookum Substation), we can use the PUD’s substation capacity revolving fund to pay for construction of new facilities (as in the currently under construction Totten Substation). This demonstrates wise financial and capital planning.
Mason PUD 3 is designated as a diamond level Reliable Public Power Provider by the American Public Power Association. Its future-focused financial and facility planning supports PUD’s mission of “…always providing safe, reliable, economical service, 24/7.”
If you have any questions about this outage or how the substations can help each other out, feel free to reach out to Tim, Mike Simmons, or Justin.