Petersburg Pilot -

By Dan Rudy 

Swan Lake outage affects tri-borough grid

 


Power service went down to southern Southeast Alaska communities, following problems at the Swan Lake dam site on June 8.

The hydroelectric dam is one of two major producers utilized by Southeast Alaska Power Agency, primarily servicing the Ketchikan area. This year an effort is being made to raise the dam, a $10 million project which will increase active storage by 25 percent and yield between 6,000 and 12,000 megawatt hours

annually.

A five-megawatt load bank being used during the project experienced a problem with its cooling circuit, which ended up tripping the system’s failsafe. Wrangell Municipal Light and Power superintendent Clay Hammer likened the load bank to a large, “trailer-mounted toaster,” a device which generates additional load.

Ordinarily used to test out newly-installed generation, in Swan’s case the load bank was deployed in order to help maintain water levels in the lake. During this stage of the project, any excess water cannot be drained using the dam’s spillway, and so must be run through its turbines. Hammer explained that the load bank uses up the excess energy being produced as a result. At 4:30 a.m. the system failed, tripping power being provided to SEAPA’s member communities in Ketchikan, Wrangell and Petersburg.

Hammer recounted Wrangell’s backup diesel generators were fired up by 5:30 a.m., with the generators at Tyee Lake back online about 20 minutes later. Power also fluctuated just before noon on Sunday after a hiccup with the load bank, only briefly disrupting service.

The power provider’s CEO, Trey Acteson, explained engineers are still evaluating what went wrong, and expected a final report later this week. Need for the load bank at Swan may be passing, however, with energy-intensive fish processing soon to pick up and rainfall to become less frequent. In previous meetings of the power provider’s board, Acteson had identified the spring as the most crucial time to control water levels during the project.

 

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