PUD 3’s Redundant Electrical System to Keep Customers Online

In the early morning hours of Sunday, September 8, Bonneville Power Administration (BPA) will replace a 45-year-old circuit breaker at its Shelton substation on Olympic Highway North. The work is scheduled to begin at 2:00 AM.

Normally, such an operation would mean a large-scale power outage, in this case affecting nearly 6,000 Mason PUD 3 customers in the Shelton area. PUD 3 has a better idea. It will keep the power on by using a massive switching procedure involving seven substations to keep almost all customers online during BPA’s work.

About 300 customers on Johns Prairie Road, including the PUD 3 operations center, will be without power during the planned outage. PUD offices will run on backup generation. Sierra Pacific will also be without power during the work.

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.

Mason PUD 3 strategically manages power loads on its substations to keep capacity set aside so it can do switching like this. The PUD’s distribution system allows for re-routing energy feeds for outage recovery and system maintenance. When the extra capacity shrinks because of load growth (as in the Skookum Substation), the PUD’s substation capacity revolving fund helps pay for new facilities (as in the currently-under-construction Totten Substation). This demonstrates wise financial and capital planning.

The circuit breaker that BPA is replacing 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 will use the brief downtime at the Mountain View switchyard to conduct maintenance on electrical equipment at that facility.

BPA’s work could take nearly two hours.

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.”