Parts of the Ketchikan Public Utilities grid lost power Tuesday. But crews got the lights back on in less than 30 minutes.
KPU Electric first reported the outage at 10:29 a.m. (Tuesday 9/10) on social media.
The system-wide outage affected areas from Ward Cove to Saxman to Mountain Point. At one point, only downtown Ketchikan had electricity, according to Andy Donato, KPU’s electric manager.
Donato said the town was relying on diesel generation because of maintenance on the Swan Lake hydropower plant. Technicians later blamed the blackout on a faulty sensor in a diesel generator at the Bailey Power Plant.
“If the pressures are right, it shuts the unit down to avoid a crank case explosion,” Donato said.
With that generator shut down, Donato estimates the system lost seven to eight megawatts of capacity.
“That’s too big a loss for the system to stay up, so it goes into something we call load-shed,” Donato said.
Load shedding occurs when generators can’t keep up with demand. When KPU lost a large portion of its generating capacity, it had to make up the difference by cutting the load. But in doing so, around 6,000 households and businesses went dark.
To make up for the loss, Donato says KPU fired up everything it had – four rental generators plus two more generators at the Bailey Power Plant. Donato says power was fully restored 24 minutes later.