Summer brings higher temperatures, greater humidity and increased energy demands. With it comes heat stress on utility substations, which can impact the performance of substation transformers.

When transformer performance suffers, utilities may be forced to derate, potentially resulting in unscheduled brownouts, power outages or single phasing (phase failure), which can damage equipment. Brownouts and outages can in turn lead to angry customers and a damaged reputation.

United Rentals has developed temporary climate control solutions to help utilities overcome seasonal temperature limitations while avoiding or delaying a capital expenditure or major repairs.

When one substation in the eastern United States was facing 50,000 gallons of overheated transformer oil due to an overloaded transformer, United Rentals knew that a typical 208V/240V cooling application would not be sufficient to provide the temperature drop needed.

To solve the problem, its engineers developed a portable trailer-mounted motor cooling rental system designed to operate with multiple station power ratings. The solution was much more economical than relying on generators, which would have increased operating costs and also emissions.

Compared to the cost of derating by 20% to 30%, which could run tens of thousands of dollars per day, it was a small investment, one that helped the utility not only avoid derating but also stave off a potential increase in customer average interruption duration index (CAIDI) scores due to outages.

“While this solution is not intended to be permanent, it offsets the impact of deferred maintenance and limited capital investment,” said Eric Bateman, regional product development manager for the Power & HVAC group at United Rentals.

The transformer and motor cooling package was subsequently deployed across the utility’s network of substations to keep the lights—and air conditioning—on for its customers.

“Utility providers right now are asked to do much more with much less,” said Bateman. “A tremendous amount of load growth in certain areas is straining older energy infrastructure. This affects transformers as well as transmission and distribution lines, which are being taxed with doing more than they were designed to do.”