When the city of Palo Alto shut off power to about 1,700 customers in the Midtown, Old Palo Alto and Industrial Park neighborhoods on Tuesday afternoon, utilities officials believed they were following an urgent order to conserve power from a state agency that oversees independent utility operators.

Now, however, it appears that the power outage was premature, unnecessary and based on a dispatcher's misunderstanding. The outage, which came in the midst of a sweltering heat wave, hit Palo Alto customers at about 6:30 p.m. and lasted for about 30 minutes before city officials learned about the error and restored power.

Palo Alto was asked to cut off power by the Northern California Power Agency (NCPA), a not-for-profit organization that represents numerous municipal utilities and that serves as an intermediary between these utilities and the California Independent System Operator (CAISO), which manages electricity flow. At about 5:17 p.m., CAISO issued an order known as an "energy emergency alert 3 (EE3)," a step that indicates that power outages may need to be implemented.

In receiving the order, however, a dispatcher with the Northern California Power Agency misinterpreted it as a request to shed 46.02 megawatts of electricity to prevent widespread outages, according to a statement from the agency. The dispatcher then immediately communicated the directive to utility officials in Palo Alto, Alameda, Lodi, Santa Clara, Healdsburg and Ukiah, prompting them to turn off power.

Once the dispatcher contacted CAISO to inform them about the action, the individual was notified that there was a misunderstanding around the order. The NCPA then began the process of returning the load back into the system, according to its statement. The longest outages lasted about an hour, the NCPA reported.

In explaining the error, the NCPA noted that the issuance of the order represented the first time such an order had been declared in California. It describes a situation in which CAISO is "unable to meet minimum requirements and controlled power curtailments are imminent and in progress." The NCPA stated that it is conducting an internal inquiry into the disconnect and has taken "immediate measures" to make sure all protocols are clear to all involved.

It is also "closely coordinating with the CAISO to review the conversation that occurred between the dispatchers involved to avoid a miscommunication in the future."

NCPA General Manager Randy Howard said in a statement that the outage, while "very impactful to those directly affected," may have helped the state's stressed grid.

"The action taken yesterday by the NCPA member systems mentioned above, while inadvertent, helped to ultimately benefit and keep the overall grid stable through the most extreme heat of the day and a record CAISO load," NCPA General Manager Randy Howard said in a statement Wednesday.

Palo Alto received instructions to begin implementing rolling blackouts at about 5:45 p.m., according to an update that the city posted on its website Wednesday. The rolling blackouts were implemented "in a specific order to minimize customer impact," the city's announcement stated.

"We share NCPA's regret that this impacted our community and appreciate the patience and support provided through this challenging time," City Manager Ed Shikada said in a statement. "The City is continuing to work on minimizing customer impacts going forward."

The Tuesday outage was one of three that occurred in Palo Alto during this week's heat wave. On Monday night, more than 4,400 customers in south Palo Alto lost power for several hours because of a faulty transformer. On Wednesday, about the same number of customers in downtown Palo Alto lost power for about two hours after a squirrel made contact with an underground wire, according to utilities officials.