Nuclear Regulatory Commission spokesman Neil Sheehan said that the automatic switch to diesel generators worked the way it's designed to. He said the reactor, Indian Point 2 in Buchanan, remained at full power. Indian Point 3, the other reactor at the site, was unaffected.
Plant owner Entergy Nuclear said there was no emergency or release of radioactivity.
Sheehan said breakers at a switchyard sensed a fault and opened, cutting off electric power. He said the precise cause was not immediately known.
Entergy spokesman Jerry Nappi said electrical power was restored within about two hours.