FARMINGTON — Just as Farmington elementary schools released their children on Monday, stop lights in the city stopped working.

A power outage caused by a failed lightning arrestor swept from Main Street to Pinon Hills Boulevard cut power to businesses and about 2,950 Farmington Electric Utility System customers for about an hour, said Rodney Romero, assistant utility director of system operations.

The outage began at 2:41 p.m. and power was restored at 3:43 p.m., he said.

"Everything happened as designed," he said. "It's just hard to explain why the lightening arrestor failed."

College Substation, where the failure occurred, powers all of the East Main Street area. When its lightning arrestor failed, the station transferred power to the city's other substations to prevent further equipment damage, he said.

Four utility crews were dispatched to the substation, and another four crews each drove to the four tie points to restore power, he said.

It is unknown why the arrestor failed, he said. The equipment protects the substation from lightning strikes by grounding electricity surges, he said. This summer's lightning storms may have weakened it, causing its failure, he said. It is the first arrestor failure in five years, he said.