On a hot summer afternoon in 2011, cascading power outages spread across the North American Southwest. Over 5 million people in Southern California -- including all of San Diego -- Arizona and Mexico were left without power for up to 12 hours. This week a federal investigation into the outage was partially resolved by a $3.25 million settlement with Arizona Public Service Company.
According to a joint report by the staffs of the Federal Energy Regulatory Commission and the North American Electric Reliability Corporation
, the September 8, 2011 outage started when a 500-kilovolt transmission line owned by APS tripped. The Hassayampa - N. Gila line serves as a major transmission corridor that transports power in an east-west direction, from generators in Arizona into the San Diego area. The line's failure triggered significant voltage deviations and equipment overloads, causing transformers, transmission lines, and generating units to trip offline through automatic load shedding. In all, 7,835 megawatts of customer load lost power -- over 30,000 megawatt-hours of energy -- primarily in the San Diego Gas and Electric service territory and in Baja California.
Following the outages, both the Commission's Office of Enforcement
and NERC launched an investigation into the incident. That investigation, which has been ongoing since 2011, focused on APS and five other entities believed to have been involved: the California Independent System Operator, the Imperial Irrigation District, Southern California Edison, the Western Area Power Administration, and the Western Electricity Coordinating Council Reliability Coordinator.
The investigation concluded that APS had violated NERC's mandatory Reliability Standards. APS's role and liability was ultimately resolved this week when the Commission accepted a stipulation between APS, the Commission's Office of Enforcement and NERC
Through that stipulation, APS agreed to pay a civil penalty of $3.25 million. Of this amount, $1 million will go to the U.S. Treasury, $1 million will go to NERC, and $1.25 million will be invested in reliability enhancement measures that go beyond mitigation of the violations and the requirements of the mandatory Reliability Standards. In finding the settlement to be in the public interest, the Commission cited APS's cooperation in the investigation as well as its voluntary mitigation efforts.
With APS's role in the outage settled, joint FERC/NERC investigations into other entities' roles continue. While some targets of investigation choose to settle their cases, others insist to exercise their full legal rights. Will the 2011 Southwest blackouts lead to further stipulations and penalties?