A substation replacement project years in the making is finally coming to a close in Upper Great Plains.
Brookings Substation, located in the South Dakota city of the same name, is being replaced with a state-of-the-art facility that will improve the reliability of electric service to the area.
“We’re putting a lot of people’s minds at ease with this project,” said Electrical Engineer Lesley Berg. “The extra reliability will help as South Dakota is prone to ice in the winter and storms in the summer.”
The 115-kilovolt substation carries several lines belonging to WAPA, the City of Brookings and East River Electric Power Cooperative. Originally built in the 1950s, time has worn away both equipment and the surrounding land.
“The substation is located in a swamp,” said Supervisory General Engineer Randy Diede. “We have cable trays that are full of water and sump pumps in the control building. This yard has had drainage issues for quite some time. Drainage paths from the original construction have long since eroded away.”
Among other improvements, the new yard will include drainage to prevent flooding. It is also more than double the size of the old yard and has extra space for East River to add a new bay as demand increases.
“The loads in southeast South Dakota have exploded,” said Berg. “Up and down the Interstate 29 corridor, there is a lot of growth.”
The old substation was a main and transfer scheme, in which a single breaker failure would result in multiple line outages. The new yard is a breaker-and-a-half scheme in which three breakers protect two lines.
Brookings, which depends on the substation, is the fourth largest city in South Dakota and is home to more than 22,000 people. It is also home to South Dakota State University, the state’s largest university, which adds another 12,000 residents during the school year.
The university, a 3M Health Care manufacturing facility, a Bel Brands USA cheese factory and Daktronics—a company that builds scoreboards for events such as the Olympics—represent the critical loads in the area.
“We’re improving reliability for a lot of people with this project,” said Diede.
The growing regional needs have kept UGP busy upgrading, rebuilding and replacing substations. The region just completed rebuilding the VT Hanlon Substation for the burgeoning East River load. Next year, UGP plans to rebuild Gregory Substation.
“Lots of substations were built in the 1950s and 60s and very little had been done to them since then,” said Berg.
A saga for the ages
The story of rebuilding Brookings Substation goes back more than a decade.
“The idea for this project has been around a long time,” said Berg. “We had a WAPA couple here and the wife said her husband, Bill Folk, couldn’t retire because Brookings substation hadn’t been rebuilt yet. He retired 15 years ago!”
Berg is also part of a WAPA couple. Her husband purchases transformers and conducts facility ratings in UGP.
When the project began in 2015, the original objective was to rebuild and expand Brookings Substation in the existing location.
“After joining the Southwest Power Pool we had significantly more interconnection requests,” said Diede. “As more of these requests went into the planning queue, studies identified several instances where we would not be able to maintain reliable service to our customers during the required construction outages. Because of these constructability issues, we had to scrap the idea of modifying the existing substation and start over designing a new substation directly adjacent to the existing yard.”
The project plan was 90% complete when that decision was made in January 2017. The new plan was completed in March 2018.
“This project has been a coordinated effort between Design, Maintenance, Operations, Planning, the City of Brookings and East River,” said Berg. “A lot of people needed to be on board to come up with a plan that makes everyone feel warm and fuzzy.”
With plans in hand, UGP was ready to tackle the project. Then Mother Nature got involved.
“By May, Southeast South Dakota had 200% of average precipitation for that time of year,” said Berg. “Construction was at least six months behind.”
The substation was supposed to be ready for testing and commissioning by WAPA electricians in May; instead, construction resumed in May when the site finally dried.
Criticality creates complications
“It’s a big job to get the outages to complete the substation work,” said Berg. “The planning group didn’t want to take lines out for long in the Brookings Substation during construction and commissioning. To keep the substation energized, we had to bring the lines up and over the old yard.”
Line crews installed temporary structures between the two yards while permanent approach structures were built outside the new yard, allowing for the substation to remain energized for nearly all of construction.
The project team is optimistic the substation construction will conclude in the fall, including moving the communications tower, capacitor banks and a station service transformer from the old yard into the new one.
“We still have to coordinate crew availability to do the commissioning work,” said Berg. “Electricians were slated to complete the work in May, not the fall, which squeezes their schedules. But it’s not that big of a problem. This project has waited 15 years; it can wait a few more months.”
Once the new substation is energized, there will be a new project to demolish the old substation infrastructure. The only equipment that will remain in the old yard will be takeoff structures, the control building slab and a station service transformer maintained by the local rural electric cooperative. ]
Note: Meiman is a public affairs specialist.