The California Independent System Operator Corp. has terminated the transmission emergency issued at the onset of the tragic Southern California firestorm that ravaged homes and knocked out of service a record number of high-voltage transmission lines. Some customers continue to be affected by distribution-related outages, but the wholesale transmission system is flowing smoothly today.

The California ISO would like to acknowledge the dedicated work performed by scores of utility line workers as they braved severe fire conditions to restore transmission facilities in order for the ISO to re-energize the system. San Diego Gas & Electric and Southern California Edison crews worked day and night, in coordination with the ISO control rooms in Folsom and Alhambra, to get the transmission system functional again. Pacific Gas and Electric also sent its line crews into Southern California to help with restoration.

“Disasters of this scale take a toll on all of us,” said California ISO President and CEO Yakout Mansour. “The ISO was saddened to watch the human suffering and loss of homes that came in the wake of the firestorms, but we are heartened by the industry’s strength as it worked feverishly to re-energize the power grid. We also want to thank Southern Californians for conserving electricity during the restoration process, even when their lives were turned upside down.”

Since Sunday, Oct. 21, when fires began in seven Southern California counties, more than two dozen different transmission lines have been out of service at one time or another—including the 500-kV Southwest Powerlink, the Pacific DC Intertie, and numerous other lines at the 230 and 138kV levels. On Wednesday, the San Diego area was hanging onto the western grid by only one 230kV line. Over one 24-hour period, several 230kV lines that link Southern California Edison and San Diego Gas & Electric at the San Onofre power plant tripped in and out of service at least 25 times.

Despite the numerous transmission line outages—some lasting almost four days—the California ISO operators worked around-the-clock to re-route power and dispatch generation to compensate for the loss of transmission.

“Contingency plans were put to the ultimate test,” said Mansour. “And, the good news is they worked. ISO operators were able to maintain reliability of the transmission grid with minimal interruptions to end use consumers.”

The California ISO would like to recognize the contributions made by power plant owners who quickly responded to the need for additional generation in Southern California in order to offset the transmission lines that were impacted by the multiple fires spreading across the southland. Emergency power was also supplied by Mexico’s Comisión Federal de Electricidad, which was critical to maintaining reliability on Wednesday when San Diego nearly disconnected from the larger western grid.