All areas of Juneau lost power late Tuesday morning, with service restored about an hour later through Alaska Electric Light & Power’s backup generators. The city remained on generators for roughly two hours before returning to hydropower.
AEL&P identified a fault in a transmission line — which carries electricity between a power source and a substation — as the cause of the outage. The fault occurred on the line between Taku Inlet and the Thane substation, cutting the city off from all hydropower sources.
“We patrolled the line and were unable to identify a definitive cause,” AEL&P said in a Facebook post at 2 p.m. “This sometimes happens when the cause has cleared the line such as wildlife, a tree branch, or debris.”
Once crews confirmed that nothing was in contact with the line, nor was the line damaged, they could safely resume the flow of power and bring the whole system back onto hydropower, according to Debbie Driscoll, AEL&P’s vice president and chief people officer.
Driscoll said the company experiences a citywide outage less than once a year. But Tuesday’s response — shifting temporarily to backup generation while diagnosing the issue — was standard procedure.
In 2008 and 2009, major avalanches damaged transmission lines connecting Juneau to the Snettisham hydroelectric power plant. AEL&P restored power quickly through backup generators, but the city remained on fuel-based generation for weeks. Because of the economic recession, fuel prices were high, which caused electricity rates to skyrocket.
Those extended outages left a lasting impression on residents, Driscoll said. When the city switches to backup generation, customers often worry about fuel costs driving up rates. But Tuesday’s outage, she said, was no cause for alarm.
“If we’re on backup generation, we want people to know that, when it’s just on for an hour or two, it’s not going to impact folks’ rates,” Driscoll said.
Juneau has seen a string of smaller outages this fall, unrelated to Tuesday’s event, Driscoll said. September and October tend to come with more frequent outages, as fall storms take down the weak and dead trees, and trees aren’t yet stabilized by frozen ground.
Juneau operates on an isolated electrical grid, not connected to any outside power system. Under normal conditions, AEL&P’s power supply is 100% hydropower.
The Snettisham hydroelectric plant, which draws from mountain lakes east of Taku Inlet, provides about 70% of Juneau’s power, according to Driscoll. The Lake Dorothy plant supplies another 20%, with the remainder generated by local creeks. About 42 miles of transmission lines carry power from main hydro sources through rugged terrain to substations in town.
This time of year, as outages are more common, Driscoll encourages residents to be prepared. “Make sure that your cell phone is charged, you have an outage kit, that type of thing.”
