SAN LUIS OBISPO, Calif. (AP) _ Diablo Canyon nuclear plant's Unit 1 reactor was shut down by an electrical malfunction Saturday, 11 days after it reached its full commercial operating level.

Ron Weinberg, spokesman for Pacific Gas & Electric Co., which owns the plant, said the shutdown occurred automatically because a sensor detected that a power supply regulator was not working.

He said workers were repairing a transformer and the reactor, which supplies 1.1 million kilowatts of electricity to customers throughout California, was expected to be back on line within a few days.

Meanwhile, dispatchers rerouted power from other plants so the shutdown would have no effect on customers, he said.

The U.S. Nuclear Regulatory Commission was notified immediately, as required by law, Weinberg added, although the fault was entirely electrical.

Diablo Canyon is about midway between Los Angeles and San Francisco. The plant has been the focus of a court case over its safety because of its location near earthquake faults.