Tuesday’s power outage in Alameda was the result of a misunderstanding between the Northern California Power Agency (NCPA) and the California Independent System Operator (CAISO), according to an NCPA press release.

NCPA is Alameda Municipal Power’s (AMP) electric load scheduler. They are a joint power agency that provides electrical energy purchasing, aggregation, scheduling and management to its 16 members including AMP. In its role as AMP’s electric load scheduler, NCPA has the authority to command AMP to lower its electrical load, which can be done by rotating power outages. NCPA is also responsible for communicating CAISO’s directives to AMP and the other public utilities in its network.

CAISO manages the flow of electricity across the high-voltage, long-distance power lines for the grid serving 80 percent of California. On Tuesday, Sept. 6, around 5:17 p.m., CAISO issued an Energy Emergency Alert (EEA) 3, due to the record heat and consumer demand.

“(Tuesday) was an extremely challenging day for California,” said Elliot Mainzer, President and CEO of CAISO in a video message on CAISO's YouTube page. “We endured the hottest triple-digit temperatures in a historic week-long heat wave. Demand on our electrical grid peaked at 52,061 megawatts, a level we have not seen in California.”

Under EEA 3, CAISO alerts grid operators like NCPA to prepare for possible rotating outages if supply gets low. However, dispatchers at NCPA took the alert as a directive to lower power consumption.

“At 5:53 pm, NCPA’s dispatch center was contacted by CAISO with an order our dispatcher understood as a request to shed 46.02 MW of load to help prevent widespread outages,” read the NCPA statement.

NCPA contacted AMP and the other public utilities in its network to begin preparation for rotating power outages. However, after NCPA made the rotating outage orders, they learned they made a mistake.

“Once the outages had been initiated, our dispatcher contacted CAISO to inform them that the curtailment action had been undertaken and was then notified there had been a misunderstanding of the initial order,” read NCPA’s statement.

NCPA began the process of returning the load back onto the system and notifying its public utilities, but by then it was too late.

AMP dropped two circuits in the first hour of the rotating outages, according to an AMP Twitter post. The two circuits affected residents and businesses located at the center of the city including Marina Village and the East End. The power was shut off from 6:05 to 7:05 p.m. About 1,400 customers were without power. AMP called off the rotating outages after the first hour. Outages also took place in Lodi, Santa Clara (Silicon Valley Power), Palo Alto, Healdsburg, and Ukiah.

AMP did not acknowledge publicly that the power outage was a mistake but did say they were taking steps to correct communication procedures in the future.

“In conjunction with NCPA working with the CAISO, we are working to clarify procedures to ensure unnecessary outages do not occur moving forward,” wrote AMP in a social media post. “We thank you all for your patience and support as we navigate these dynamic situations that change frequently.”

Mainzer said CAISO did not have to make the order for rotating outages because the organization saw about 2,000 to 2,500 megawatts of load reduction after the EEA 3 went into effect. Earlier in day, an EEA 2, or Flex Alert, was ordered for 4 to 9 p.m. An EEA 2 signals to participants to bid more energy into the market and allows CAISO to tap into emergency demand response programs.

AMP has not yet responded to Alameda Sun’s request for comment.