Traffic lights, businesses and homes darkened briefly Tuesday morning when tens of thousands of electric utility customers from the Kenai Peninsula to Fairbanks lost power.
The cause: An Anchorage Municipal Light & Power plant went offline, triggering a domino effect of outages elsewhere on the Railbelt’s interconnected electric grid for just under a half hour.
Along with ML&P, Chugach Electric, Homer Electric Association, Matanuska Electric Association and Golden Valley Electric Association all reported outages starting just before 9 a.m. that cut power to more than 25,000 households.
Several utilities, including Homer Electric and Golden Valley, also dealt with much smaller outages from snow-loaded power lines Tuesday.
An ML&P spokeswoman said its Plant 2A off the Glenn Highway in Muldoon “briefly tripped” and went offline. ML&P had about 5,000 customers without power for about 25 minutes, spokeswoman Julie Harris said.
Chugach had about 6,000 people without power briefly, according to spokeswoman Julie Hasquet.
More than 8,000 Matanuska Electric households were without power for about 20 minutes Tuesday morning, spokeswoman Kierre Childers said.
Homer Electric Association reported nearly 7,000 offline. Golden Valley reported smaller outages.
The Railbelt utilities are interconnected, representatives of several explained Tuesday. When one loses generation, a drop in frequency results through the system. Utilities “shed” electrical load -- customers lose power -- to prevent additional generators from going offline and to divert power to essential systems.
Then other generation has to be brought back on.
ML&P ran two reserve units to make up for the lost generation, Harris said.
MEA brought two engines online at its Eklutna Generating Station, Childers said.
At Chugach, officials ramped up other Southcentral Alaska sources like Bradley Lake hydroelectric and Beluga natural gas, Hasquet said.
“It was all over within a few minutes,” she said.