Commonwealth Edison Co., already under fire from critics who question whether the utility is capable of meeting heavy summer demand for electricity, reported a series of blackouts throughout the north and northwest suburbs Thursday after a large transmission line serving the area failed.
The outage, which ComEd officials said late Thursday that they still could not explain, left 63,000 businesses and homes without power for much of the day, idling air conditioners, snarling traffic at intersections with darkened signals and sending workers at some businesses home early.
The rough boundaries of the outage were Schaumburg to Deerfield to Lake Zurich, ComEd officials said.
ComEd spokeswoman Susana Leyva said customers lost power after a large transmission line connecting two electrical substations serving the north and northwest suburbs failed. ComEd declined to reveal the location of the two substations.
The line, which has the capacity to transmit 134 kilovolts, went down about 10:15 a.m., she said. But smaller outages from wires feeding the transmission line were reported as early as 8 a.m., Leyva said.
Power to all but 300 customers had been restored by Thursday evening, she said.
A report issued recently by the North American Electric Reliability Council, an industry group, predicted that ComEd would face difficulty during this peak-demand summer season because of problems with its generating and transmission equipment.
But the utility disputed those conclusions Thursday, as it did at a hearing June 10 before the rate-setting Illinois Commerce Commission.
“It’s always a concern if you get too many days of hot weather,” Leyva said. But because more of the company’s coal-burning and nuclear plants are on-line than last year, when 27,000 outages were reported, “we’re feeling comfortable,” she said.
Thursday’s outage occurred on one of the first sweltering days of the season. The temperature reached 89 degrees at 1:43 p.m. at O’Hare International Airport.
“You can’t work in here,” said Cindy Swinerton, manager at the Workbench furniture store in Schaumburg as she sat, looking hot and miserable, at her post. “You can’t shop in here. It’s too hot.”