Mesa transformer fire that cut power to 150,000 under investigation

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MESA, Ariz. - Investigators are trying to determine what sparked a massive transformer fire that cut power to about 150,000 Salt River Project customers in Mesa and Apache Junction.

SRP says power has been fully restored to all of its customers.

Scott Harelson, an SRP spokesman, said Friday that the utility might be asking customers east of Loop 101 and north of U.S. 60 to conserve power today if crews are unable to make the necessary repairs by the peak energy demand this afternoon.

A large transformer caught fire Thursday around 12:30 p.m. at the SRP East Mesa Service Center substation.

According to SRP, mineral oil that is used to cool down a transformer is what was burning. An explosion in a transformer caused the fire and the domino effect down the line that led to power outages in the afternoon across the East Valley.

Crews had to de-de-energize nearby transformers to avoid any further fires from starting at the plant located near University Drive between Sossaman and Power roads.

Officials say they had the fire contained shortly after it started, despite not being able to get foam trucks in to extinguish the blaze until over an hour after the blaze started.

After the other transformers were de-energized, crews were able to cool hot spots on nearby transformers and suppress the blaze using foam. The fire burned for about three hours.

Heavy black smoke and flames were seen coming from the area.

Power to nearby residents was briefly interrupted when the fire started, but SRP said they were able to switch to backup transformers.

With many transformers de-energized the strain put on during the heavy use of electricity in the summer months led to widespread rolling outages as transformers tripped.

At the peak of the outage, 150,000 customers in Mesa and Apache Junction were without power.

According to Mesa police the areas affected are predominately Dobson Road to the east of the city limits and from U.S. 60 to the northern city border.

SRP re-routed the power at the substations that were having problems. The utility said electricity was fully restored about 11:30 p.m. Thursday, some 11 hours later.

Due to the scattered power outages, the City of Mesa Energy Resources Department was asking its electric customers to conserve electricity; turn off all unnecessary electronic equipment, lighting and appliances and adjusting thermostats. 

SRP activated its bagged-ice plan to help people cool off. There were long lines as people picked up free ice at several Mesa stores.

SRP began distributing ice again early Friday morning at the Fry's stores at  Recker and McKellips roads and Ellsworth and Broadway roads.

It will be several weeks before investigators know exactly what happened, but SRP officials believe some kind of surge might be to blame for the huge fire.