Sabotage was ruled out.

The blackout started around 4am and affected people in Amado all the way to Nogales, with some customers not having power restored until around 5:30pm, shutting down local schools, government agencies and many businesses. Business closed for most of the day.

UniSource spokesperson Joe Barrios said the outage was caused by a fault in a conductor or wire on the main 138-kilovolt transmission line that supplies Santa Cruz County, and the remote location makes quick repair difficult. said it is.

“Everyone in Santa Cruz County is primarily serviced by the 138 (kilovolt) line, which is fairly remote and runs through rough terrain,” says Barrios. “It took time to inspect the line, find the problem, get to the site, get the people and materials there and start the repairs.”

Unisource Energy ServiceA sister company of Tucson Electric Power Co., serves more than 19,000 customers in Santa Cruz County and more than 80,000 customers in Mojave County.

By using a 46-kilovolt transmission line to power the utility’s Valencia substation north of Nogales, the utility could get some customers back online by mid-afternoon, Barrios said. It is said that it was possible. – megawatt Valencia power plant;

Barrios said these measures took some time, at which point the 46kv line was out of service due to an upgrade.

By 1 p.m., UES had restored service to about 6,000 customers, and by 2 p.m., 7,000 were still without power, Barrios said.

Lines were repaired by approximately 3:20pm and gradually brought online to avoid disruption, with power restored to all but about 2,100 by 4:00pm and the rest by approximately 5:30pm. He said it was online on

The cause of the conductor failure is still under investigation, but UNS has ruled out sabotage, Barrios said.

In 2014, saboteurs broke into the Valencia power plant and planted a makeshift bomb that exploded next to the valve assembly of a 50,000-gallon diesel fuel tank, but the tank did not explode. The FBI investigated, but no arrests were reported.

Due to the magnitude of the outage, UES is required to file a report on the incident. Arizona Corporation Commissionsaid Barrios.

UES has improved its system reliability rankings in recent years and has been in the top quartile of reliability among utilities nationwide for the past four years, Barrios said.

The average system-wide time UES customers were offline during an outage in 2021 was approximately 48 minutes, up from 43 minutes in 2020 and down from the three-year average of 50 minutes in 2019-2021.

In November, UES filed a rate lawsuit against Arizona, seeking a 14% increase in invoices to recover approximately $78 million in post-2019 system improvements.

Last year, UES installed a mobile substation next to Rio Rico’s Sonoita substation to quickly add capacity to meet summer demand peaks.