WRANGELL — A power outage left Ketchikan and Wrangell without power for about an hour Friday afternoon.
Lights and signs all along Front Street and throughout town abruptly shut off at about 4 pm. Power had been restored to most of the town by about 5 p.m. Lights remained on at businesses with back-up generators, most powered by either diesel fuel or propane. Petersburg reportedly suffered some temporary fluctuations about the same time, but never lost power entirely.
Some businesses, like radio station KSTK, Alaska Island Community Services, and City Market, switched over to back-up generators.
Most people seemed to treat the short-duration outage as a minor inconvenience.
The problem started in Ketchikan, when a fault occurred in an underground wire near the Bailey Diesel plant, said Andy Donato, a system manager with Ketchikan Public Utilities.
“About four o’clock Friday afternoon, we reacted to an underground fault in some underground cable in our Bailey Substation,” he said.
The fault occurred as a result of aging infrastructure for the generators at the plant, and caught operators of the power grid connecting Ketchikan, Wrangell, and Petersburg off-guard, Donato said. Ketchikan briefly switched over to diesel generation to resolve the issue.
“It turns out we have a finite number of underground cables,” Donato said. “We’ll check the integrity of those and replace what’s necessary with new, and this hopefully won’t surface again for a long time.”
However, beyond the fact of the fault, officials haven’t yet determined the precise reason why this caused power to go off in Ketchikan. The likely explanation is a change in the frequency of electricity flowing through the wires in the transmission system tying Ketchikan to Wrangell and Petersburg, known as the Swan-Tyee Intertie. This may explain in part why lights went off in Ketchikan and Wrangell, but may have only dimmed or brightened in Petersburg, Donato said.
“The reason why is because we all three have different protection systems,” he said. “It’s very much like you drive a Nissan, I drive a Ford, and Petersburg drives a Jeep.”
The hour-long duration in Wrangell was primarily because the process of re-energizing the grid isn’t as simple as flipping a switch, according to power superintendent Clay Hammer. The grid has to be energized in portions called feeders. The process of starting up each of the feeders is called sectionalizing, Hammer said. The biggest feeder – Feeder 4 – runs from the end of Peninsula Street to the end of Zimovia Highway.
“If we would just throw the switch in town and re-energize that in one chunk, it would throw everything into the black,” he said. “It would just be too much, like trying to start the car up, and trying to start the car out in fourth gear.”
Meanwhile, the number of outages is decreasing in frequency, since the construction of the Swan-Tyee Intertie, Hammer said.
“We used to have an anomaly in Wrangell with the sawmill that would take both us and Petersburg off the air,” he said.
Power officials from utilities in all three communities will meet Nov. 18 in Petersburg to discuss the outage as part of a regularly scheduled reliability meeting.