T&D World Magazine
Nation’s Largest Phase-Shifting Transformer Takes Up Residence in Monticello

Nation’s Largest Phase-Shifting Transformer Takes Up Residence in Monticello

Rocky Mountain Power’s Pinto substation outside Monticello just became home to the largest phase-shifting power transformer in the United States – the second largest in the world. Once fully assembled and on-line, the unit will weigh approximately 2.5 million pounds.

“Planning and development of this project began in 2012,” said Deb Dull, Rocky Mountain Power regional business manager. “The new transformer will increase the capacity on the system and enhance electric service reliability for our customers. This is a phase-shifting transformer that will give the company more control and flexibility for the entire system.”

The 400-MVA transformer is the third transformer to be placed in the Pinto substation and will allow more electricity to be transferred within the system. In addition, the new design of this transformer will better accommodate the variable nature of renewable generating resources that are seeking to interconnect to the electrical grid.

Preparing for the installation of the transformer, a concrete foundation three feet thick was constructed inside the substation. The transformer will measure 58 x 57 feet and 32 feet high and took seven months to construct. Because of its size, it was transported in two pieces. Each transformer piece made its way to Monticello on a 30-axle, 413-foot-long 20-foot-wide transport vehicle with 240 tires that was pulled by one or two trucks and pushed by five other trucks. The first piece arrived on Oct. 27; the second piece is scheduled to arrive before Thanksgiving. The two sections will be put in place on the foundation and joined together using a third piece and about 40 crates of parts and pieces. Once the units are attached together they will be connected to the electrical system.

“We expect to have the initial connections made and some preliminary testing done during December,” Dull said. “Work will continue for a few weeks and final integration onto the system is scheduled for mid-February.”

The Pinto substation was built in the mid-1970s and has been serving Monticello and southeastern Utah since that time as an integral part of the overall electric system. Rocky Mountain Power continually evaluates electrical system capacity and upgrades its system to keep pace with customer needs and technological advancements.

“This substation upgrade enables the company to continue its commitment to reliable customer service throughout the six-state service area,” Dull said.


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