An official with the Indian Point plant in Buchanan says there were no injuries in Sunday's incident.
The plant is owned by Entergy Corp. Company spokesman Jerry Nappi told the Journal News that no radioactive materials leaked.
He said the transformer was outside and not near the reactor.
Indian Point 2 was shut down after the 6:39 p.m. explosion.
Indian Point 3 was operating normally.
An alert was declared and the Nuclear Regulatory Commission notified.
Nappi said he didn't know how long Unit 2 would be offline.
The power plant is 24 miles north of the city.