Outages blamed on human error

? A power failure that plunged large parts of Florida into the dark this week was caused primarily by human error, the state’s largest electric company said Friday.

Florida Power & Light issued a preliminary report saying that a field engineer was to blame for Tuesday’s failure, which affected more than 584,000 customers, or the equivalent of more than 1 million people.

The engineer was investigating a malfunctioning switch at one of the power company’s substations in west Miami when he disabled two levels of protection for the system, officials said.

While he was making measurements of the switch, a circuit shorted, making a loud noise and smoke that was reported as a fire. Normally, the protection system would have contained the consequences of the short circuit, but because both levels of protection had been removed, the problem cascaded to other parts of the system.