Environment Minister Sigmar Gabriel said the automatic shutdown, which was the result of a short-circuit in a transformer, called for "an examination of the electrical systems in all nuclear plants."
The incident at the Kruemmel plant in northern Germany switched off the majority of traffic lights across the city of Hamburg and affected thousands of private homes.
The power station's operator, Vattenfall, says the short-circuit was reminiscent of an accident two years ago when a fire put the station out of action for two years. It came back into service just two weeks ago. Vatenfall says it is too early to say when the reactor will be restarted.