SAN DIEGO (AP) — A power outage that affected 7 million people last month in the Southwest U.S. and part of Mexico was not solely caused by a utility worker doing a minor repair job, as originally thought, utility officials said Wednesday.
Federal investigators and officials from California and Arizona utility companies said they still don't know exactly what happened the afternoon of Sept. 8, when power was knocked out for up to 12 hours from Arizona to southern California and into the northern part of Mexico's Baja California.
While the utility worker's repair of a transmission line at an Arizona substation was the first action in the chain of events, it should not have triggered a massive blackout because a complex system involving five electric grids is built to quickly compensate for such glitches and prevent the problem from spreading, utility officials said.
Investigators have discovered that at least 20 problems took place across the five grids — including one in Mexico — within an 11-minute period, said Stephen Berberich, president and CEO of the California Independent System Operator, or ISO, which operates the state's wholesale power system.
"This blackout should not have happened," Berberich said Wednesday during an oversight hearing of the California State Assembly Committee on Utilities and Commerce, and of the Joint Legislative Committee on Emergency Management, held in San Diego.
Donald Robinson, president and chief operating officer of Arizona Public Service Co., said it was wrong to pin the blame solely on a utility worker at his company's substation.
"There are still many things we do not know that happened on those days," he said.
But the probe over the past two months has revealed one fact, Robinson said: "This event was not caused by the actions of a single utility worker. That is an unfortunate perception that came out early in the process. The system is built to withstand an event like that."
The utility companies involved, under ISO's direction, have formed a joint task force to investigate. Berberich said it could take up to a year before investigators find the exact cause.
The Federal Energy Regulatory Commission and the North American Electric Reliabilty Corp. also have opened a joint inquiry into the outage.
The outage knocked out traffic lights, causing gridlock on the roads in the San Diego area. Two reactors at a nuclear power plant up the California coast went offline after losing electricity. Nearly 3.5 million gallons of sewage spilled into the water off San Diego, closing beaches in the eighth-largest U.S. city.
The National University System Institute for Policy Research has estimated the outage cost the San Diego-area economy more than $100 million.
Many people on both sides of the U.S-Mexico border had to spend the night struggling to fall asleep in high temperatures, which reached up to 115 degrees in the desert areas.
There were no reported deaths or injuries related to the outage.
The blackout was another reminder that U.S. transmission lines remain vulnerable to cascading power failures.
In 2003, a blackout knocked out power to 50 million people in the Midwest and the Northeast. And in 2005, a major outage struck the Los Angeles metropolitan area.
That same year, Congress required utilities to comply with federal reliability standards for the electric grid instead of self-regulation. Layers of safeguards and backups were intended to isolate problems and make sure power keeps flowing.
Berberich said some of the safeguards helped curb the problem.
As the lines were knocked out, power flows jumped to levels that were at or exceeded safety standards and triggered the San Onofre Nuclear Generation Station to be taken offline, as it is supposed to do, Berberich said. That kept the outage from spreading to Los Angeles.
Mexico also took power plants offline to contain the blackout.
Utility companies used Twitter and email to communicate with the public and learn of breakdowns in backup systems at hospitals, the airport and other critical customers, so officials could focus on restoring power to them first.
The companies are communicating more often with each other, Berberich said. ISO is putting in place operating procedures that monitor the transmission flows on the south line of the San Onofre Nuclear Generation Station, he said. That way, when power reaches certain levels officials will take immediate action, such as bringing up additional generation to alleviate a potential overload before a blackout occurs.
But the companies say pinpointing the cause is crucial.
"We think that the only way that we get better is if we understand exactly what took place and put in place steps that we can to prevent it from happening in the future," Robinson said.
If regulatory violations are found, the government could issue fines of up to $1 million per day for every violation, officials said.
This is a story update. A previous story is below.
SAN DIEGO (CNS) - Power industry officials said Wednesday they still don't have an answer for why the actions of one utility worker in Arizona triggered a cascade of outages that affected an estimated seven million California residents - including all of San Diego County - on Sept. 8.
Their testimony came in a hearing conducted by the Assembly Committee on Utilities and Commerce and the Joint Committee on Emergency Response at San Diego City Hall.
Mark Maher, chief executive officer of the Salt Lake City-based Western Electrical Coordinating Council, said what happened that day was known, and the timeline was established.
"The outstanding question we have to pursue is why this happened," Maher said. "We know what failed and in what sequence, but we don't know why."
Stephen Berberich, president and CEO of the California Independent System Operator, said the complex transmission system that carries power between various utilities should have absorbed the singular event of a worker in Arizona who switched lines out of sequence.
"This blackout should not have happened," Berberich said.
Instead, 20 separate events took place within 11 minutes to cause the widespread power outage, he said.
Among them, according to Berberich:
- a power plant in northern Mexico stopped operating, but it is unknown whether that was in reaction to the Arizona event;
- three power plants operated by the Imperial Irrigation District shut down in rapid succession;
- the energy flow between Arizona and California was cut off; and
- a transmission line south of San Onofre that connects San Diego Gas & Electric with Southern California Edison switched off, plunging San Diego County into a massive blackout.
The power industry officials said it could take anywhere from two months to one year to find out why the outage became as big as it did.
"Unfortunately, I feel a little less informed and a little confused," Assemblyman Ben Hueso, D-San Diego, said after their presentation.
The Western Electrical Coordinating Council assists various power system operators with the flow of electricity across 14 states, two provinces in Canada and part of Baja California Norte, according to Maher. Cal-ISO does the same within the state.
San Diego Gas & Electric President and CEO Michael Niggli credited customers for the return of power within 12 hours instead of two days, as originally estimated.
Niggli said unplugging air conditioners and other energy-hogging electronics allowed them to restart their system faster than expected.
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