Grand Haven Board of Light and Power General Manager Annette Allen said approximately 9,400 customers south of the river lost power just before 11:30 p.m. on Thursday.
Allen said the Sims Plant on Harbor Island was generating power when the terminator failed, tripping off the plant itself.
Backup power which would normally have come in through the power grid was not available because Wolverine Power had their line down for upgrades, Allen said.
BLP employees worked through the night to connect a bypass line to a spare cable under the Grand River.
Power was restored to all customers between 4:20 and 4:30 a.m., she said.
See today's print or electronic edition of the Grand Haven Tribune for more on this story.