Green Valley Substation Rebuild

It took a team effort to rebuild the Green Valley Substation

Built in 1973, the Green Valley Substation (Green Valley Sub) needed an upgrade. So, in May 2022, Trico hired the firm TOR Engineering to come up with a plan for the rebuilding of the Green Valley Sub.

“Given the age of the substation, its limitations and the fact that we just finished rebuilding the 69 kV transmission line from the Bicknell Substation to Green Valley, it made sense to rebuild it,” said Roger Patnode, the Project Lead.

A decision was made to rebuild the whole substation.

“Starting with the Three Points Substation, we came up with a standard way of designing the 25 kV side of the substations,” Patnode said. “We’re using the same design for the new Adonis Substation and when we rebuild the Marana Substation.”

Like the SaddleBrooke Substation, Trico controls the 69 kV transmission line into the Green Valley Sub. At our other substations, Arizona Electric Power Cooperative Association (AEPCO) handles the 69 kV transmission line.

“At Green Valley, we designed the 69 kV side with a ring bus,” he said. “It provides us with more flexibility for expansion in the future.”

A ring bus configuration is an extension of the sectionalized bus arrangement and is accomplished by interconnecting the two open ends of the buses through another sectionalizing breaker. This results in a closed loop or ring with each bus section protected by a circuit breaker.

The rebuild was done in two phases. In July 2022, Trico started rebuilding the 25 kV side of the substation, south of the existing substation. The Green Valley Sub remained energized during this phase. In November 2022, the old substation was deenergized and demolished and the new 69 kV side was built during this phase.

“We picked up the Green Valley Sub circuits from Bicknell,” Patnode said. “We were able do it because loads are low in the winter.”

The Green Valley Sub was reenergized by May 2, 2023, just in time for summer. Patnode said a lot of work from different departments went into the rebuilding of the Green Valley Sub.

“It was a joint effort,” he said. “It starts with engineering. Then procurement – acquiring the needed equipment and materials. Operations and the Substation and Meter Technicians were also involved in the project. Kudos to everybody who worked on the project.”

Patnode said the two new 20 MVA transformers should last at least 30 years.

“The original transformer was 50 years old and still working when it was retired,” he said.