Maintain the safe zone around pad‑mounted transformers By Derrill Holly
Jordan Overbee was driving to work when he saw them. The elementary students were waiting for the school bus, but they were sitting on a big green metal box. Inside was vital electrical equipment, distributing electricity to several homes on the street.
“It was a bad place for a school bus stop,” Overbee recalled. “There were five kids gathered there to wait for a bus, sitting, talking and playing for a few minutes because it was between driveways.”
As manager of operations for Wake Electric Membership Corp., Overbee knows a lot about pad-mounted transformers. They make up about half of the transformers used across the North Carolina-based co-op’s system.
“Transformers change voltage from higher levels to voltages people use in their homes.” said Overbee. “Each of our transformers can be vital to providing electricity to several homes.”
After seeing the kids waiting at that same transformer several days in a row, Overbee pulled over and talked to some parents. He explained that high voltage electricity flowed through the transformer inside the casing and encouraged them to move a safer distance away. “The parents hadn’t thought much about it, so once I explained the risks, they were happy to move to another driveway,” Overbee said.
While overhead power lines are mounted on utility poles and substations are protected by security fences, pad-mounted transformers, switch boxes and pedestals are at ground level. “We have about 5,400 pad mounted transformers on our system,” said Van Crawford, vice president of operations at Peace River Electric Cooperative, headquartered in Florida. “Of that number, 4,800 of them are located in the western district of our service territory.”
In many newer residential areas, overhead lines are no longer an option. Burying power lines also reduces potential system damage from high winds and storms. While consumers seldom see technicians working on the transformers unless there are power outages, they are regularly inspected by co-op crews.
“We can see fault indicators from the road,” said Crawford, adding that one of the biggest concerns is safe access when repairs or adjustments must be made. “That’s why it’s important that landscaping and other barriers be kept clear of co-op equipment.”
Co-op technicians need at least 10-feet clearance at the opening side of a pad-mounted transformer. Approximately four feet of open space is preferable at the rear and sides of the metal housing.
That distance allows for tool use, including hot sticks—typically eight feet in length, used to work with energized equipment. It also ensures that the technicians working on a transformer have space to maneuver should they have to back away if problems occur.
Pad-mounted transformers are connected to primary high voltage lines, and secondary lines can extend in several directions to distribute power to homes and businesses. That’s why it’s important to check with Clay Electric Co-operative before planting shrubs or trees, setting fence posts, installing sprinkler systems and digging where it might damage underground lines.
“Clay Electric Co-operative recommends that you contact the Illinois One Call, JULIE at 811 for a site assessment and marking before proceeding with projects that might disrupt utility service,” said Luke Johnson, operations manager at Clay Electric. While pad-mounted transformers in developed, suburban or urban areas are regularly inspected for damage from vehicles, many utilities use marking sticks or pennants to alert tractor, snow plow or heavy equipment operators of their locations.
Clay Electric also encourages public works and transportation departments to keep equipment, supplies and road debris at least 15 feet away from pad-mounted transformers. Derrill Holly writes on cooperative issues for the National Rural Electric Cooperative Association, the Arlington, Va.-based service arm of the nation’s 900-plus consumer-owned, not-for-profit electric cooperatives.