SDG&E asked to cut power to 250,000 customers for 1 hour

Officials say power plant failed to generate enough electricity

More than 250,000 San Diego-area homes and businesses lost electrical power overnight when local power plants failed to generate enough power and long-distance transmission lines almost overloaded, officials said.

Two smaller, unrelated blackouts also hit the North County coastal areas later in the day.

Alarms went off just after midnight when the California Independent System Operator, headquartered near Sacramento, noticed not enough power was being generated by private companies inside the SDG&E service area, said Cal-ISO spokesman Gregg Fishman.

“We noticed too much reliance on the transmission grid, and we rely on a system where about 25 percent of the power used in San Diego has to be generated locally,” Fishman said.

“When that ratio gets too small, we start running a much higher risk of a greater outage,” he said.

Cal-ISO asked San Diego Gas & Electric to “shed load” and turn off electricity to 250,000 customer accounts just after midnight.

Some 290 megawatts of customer demand was dropped by SDG&E, bringing the grid back into balance until more local generators could be brought on line, and full service restored.

The cutback, similar to a “rolling blackout,” left the scattered addresses without power for less than an hour, and all affected customers were all back on line by about 1 a.m., Fishman said.

State engineers are reviewing what went wrong, and why not enough electricity was coming from local independent power companies to feed the SDG&E grid, Fishman said.

The problem was not related to the idling of the two nuclear generating units at San Onofre, he added.

The smaller outages happened later in the morning. The first, believed to have been caused by a problem with overhead electric lines, occurred shortly after 8 a.m. and affected 2,162 addresses in parts of Carlsbad, La Costa, western San Marcos and southern Vista, SDG&E reported.

Power was restored to those areas by late morning.

A traffic crash resulted in a third blackout about 9:15 a.m., leaving roughly 3,375 customers in parts of Cardiff, Encinitas and Olivenhain out of service, according to the utility company.

As of mid-afternoon, 1,277 of those addresses remained without electricity. They were expected to be back on line by early evening, SDG&E reported.