Human error, poor planning contributed to blackout, report finds
The massive blackout in Southern California in September 2011 began with a loss of a transmission line in Arizona, but rippled quickly westward due to a series of human errors and instances of "inadequate planning" by utility agencies, according to a report issued Tuesday by the Federal Energy Regulatory Commission and the North American Electric Reliability Corp.
“That line loss did not cause the blackout but it did initiate a sequence of events that led to the blackout, exposing grid operators’ lack of real-time situational awareness,” said a statement by the commission and corporation, based on an eight-month investigation.
More than 2.7 million customers were left without power in Southern California, Arizona and Baja California. The blackout lasted from the afternoon of Sept. 8 until early morning Sept. 9.
When the Hassayampa-North Gila transmission line, operated by Arizona Public Service, went down during maintenance and a day of heavy usage, it overloaded adjacent systems, starting with those operated by the Imperial Irrigation District, over the California border.
The overload then spread west, including to the San Onofre nuclear plant.
If power operators had studied their “real time contingency analysis results,” they could have taken steps to avoid the “cascading blackout,” said the report. Lack of coordination among agencies, and failure to update emergency plans caused the blackout to spread.
Some agencies failed to consider how problems outside their system could affect their customers, the report said.
“This report highlights the growing need for more coordination of grid operations in the west,” said FERC Chairman Jon Wellinghoff.
More review is needed, the report said, to determine, for example, how high-voltage lines leading south from the San Onofre plant were disconnected, leaving San Diego County largely in the dark.
-- Tony Perry in San Diego
Photo: Sidewalk restaurant customers dine by candlelight in San Diego's Gaslamp District during the Sept. 8, 2011, blackout. Credit: Robert Gauthier / Los Angeles Times