The agency that manages the state's electrical-service grid blamed its own personnel today for a blackout that left roughly a quarter-million San Diego County homes and businesses without power for about 45 minutes last week.
"We acted in good faith, but we made mistakes, first allowing this situation to occur by not maintaining adequate local generation in San Diego, and then applying operating requirements incorrectly," said Jim Detmers, vice president of operations for the California Independent System Operator.
Control-room personnel involved in the incident have been reassigned to other duties pending completion of an ongoing internal review, Cal-ISO officials said.
Just after midnight Thursday, employees of the state agency, headquartered near Sacramento, realized that insufficient power was being generated by private companies inside the San Diego-area service area, Cal-ISO spokesman Gregg Fishman said earlier.
The personnel asked San Diego Gas & Electric to address the emergency by "shedding load," and the local utility dropped some 290 megawatts of power. The cutback, similar to a "rolling blackout," left hundreds of thousands of addresses throughout the county without power.
The plug-pulling move brought the grid back into balance until more local generators could be brought on line to restore full service, which occurred about 1 a.m., Fishman said.
Preliminary findings from the in-house investigation revealed that the agency improperly allowed an Otay Mesa-area power plant to shut down, leading the state agency to violate a requirement that requires at least 25 percent of the San Diego area's power load be served by local generation.
The ISO then "inappropriately applied an operating requirement that ... called for load-shedding to reduce demand," according to a statement from the agency.
"This was unacceptable," Detmers said. "I am sorry it happened, and I apologize to the people of San Diego who were impacted by this outage. The ISO is doing everything we can to ensure this does not happen again."
Though the internal probe remains incomplete, the state agency announced that it already has begun taking the following actions to prevent such errors from recurring:
-- improving operating systems and control-room tools;
-- providing better "situational awareness" to operators;
-- adding to training regimens for all control-room crews; and
-- reviewing operating procedures to determine how they can be improved.
The ISO is cooperating with the Western Electric Coordinating Council in its review and "fully briefing" state and federal regulatory agencies, the governor's office and "key legislative leaders," according to the agency's statement.
