About 1,300 Superior residents were without power for at least 90 minutes Monday evening.
Superior Light & Power electric operations manager Bill Fennessy said the power went out around 8 p.m. in the city's Central neighborhood.
Power returned to half the customers by 9:30 p.m., with the rest restored by 10 p.m., Fennessy said.
He said an equipment failure on the system caused the blackout.
