They’re not electric vehicles, but they do get up and go and plug into the grid when needed.

Mobile substations play a crucial role in keeping the lights on for TEP customers, often in fast-growing areas with increasing energy needs. In addition to supporting reliability while permanent facilities are developed, these portable facilities also help us restore service and reduce outage times during emergencies.

Substations adjust voltage to appropriate levels and provide other support for our local energy grid. TEP has about 110 permanent substations throughout our service territory. Typically, it takes about five years to design, permit and build a permanent distribution substation. New transformers for those facilities can cost nearly $1.5 million each and take up to two years to build and install.

Mobile substations and skid-mounted transformers provide temporary solutions during periods of high energy usage, unexpected outages or ongoing upgrades to existing equipment. TEP has about a dozen of them. Once our permanent facilities are installed or repaired, mobile substations hit the road again to plug into the grid in another location.

“Mobile substations are designed to be reliable but flexible,” said Ernesto Ojeda, TEP Director of Equipment & Asset Management. “They allow us to continue serving customers while we’re working on improvements to our energy grid.”

Mobile substations played a crucial role in supporting reliability on Tucson’s east side this summer. In early June, while performing scheduled maintenance on an older transformer at our Wilmot Substation, crews determined that a transformer there was no longer suitable for service. TEP worked with the Jim Click Automotive Team, which provided space at no cost in a nearby overflow parking lot, to set up a temporary substation. Customers in the area experienced no outage and the temporary substation was in use for several weeks while crews installed a new permanent transformer at the Wilmot Substation. The new transformer was energized late last month and the temporary substation was removed.

On the northwest side, TEP customers have been served by the new Tangerine Mobile Substation since it was placed into service in May. The area has experienced rapid, significant growth over the last several years and TEP is working to develop a new, permanent substation in the area. Once complete, the new permanent substation will link to TEP’s 138-kV transmission infrastructure.

The Tangerine Mobile Substation, located at a decommissioned landfill, will continue to serve customers for the next few years. TEP invested about $700k to develop the site and connect it to our local energy grid. Once a suitable site for the mobile substation was secured, employees from multiple teams including Land Resources, Engineering, Design, Line Construction, Substations, Relay, & Communications C&M, Asset Management and System Control worked quickly and safely to get the unit up and running.

Another mobile substation has supported reliable service for customers near Interstate 19 and West Ajo Road over the last three years. Crews are working nearby to build the new 138-kV Cottonwood Substation, which is expected to be placed into service in October 2024.

In 2020, TEP completed an $8.4 million upgrade of the Country Club Substation near East Speedway Boulevard and North Country Club Road. Our crews replaced transformers, power poles and other equipment. To maintain reliable service to area homes and businesses, TEP installed a mobile substation on a nearby lot while new equipment was installed.

TEP crews will inspect and perform maintenance on mobile substations and transformers in between deployments to ensure each piece of equipment is ready for emergency use.

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