Substation maintenance prevents outage
A sharp eye for detail and quick thinking prevented a |
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Wearing a safety harness for support, Lineworker John Frey takes apart the cracked bushing, or insulator, on a potential transformer at the North Bismarck Substation. The orange cables hanging from the bus work, known as personal protective grounds, protect John and the line crew from unwanted or unexpected voltage by grounding the circuit. |
power outage for Capital Electric members who live in north Bismarck, says Engineering Assistant Rich Dunn. On Wednesday, March 14, Lineworker John Frey spotted a small oil leak on the ground at the North Bismarck Substation on East Century Avenue. He reported the leak back to the cooperative, and the line department made immediate plans to fix the leak.
The oil appeared under one of the substation’s potential transformers, or PTs, which measure voltage for relaying. The transformer “steps down” or reduces the high voltage from 24,000 volts to 120 volts, which is then distributed to protective relaying equipment in the control building.
Rich Dunn, engineering assistant for Capital Electric, says oil insulates and cools the PTs. If the oil had continued to leak, the equipment would have eventually burned out and caused an outage.
“If the oil got down too low, it could catch on fire. Then it would short out and trip the breakers so all of north Bismarck would be out of power,” he says.
To fix the leak, a line crew of five worked together under the supervision of Les Vietz, crew foreman. On a blustery cold day, Lineworker Frey was hoisted up in a bucket truck to replace the culprit: a cracked insulator called a bushing. The line crew took apart the bushing, drained the oil, cleaned the corresponding parts, and replaced the bushing and gasket.
Prevention and maintenance are an important part of a lineworker’s job, says Wally Kalmbach, director of safety for the North Dakota Association of Rural Electric Cooperatives. On a monthly basis they perform substation checks, and on a daily basis they inspect lines, poles, equipment and facilities to prevent problems like the oil leak from happening.
“This problem could have been costly. It would have damaged equipment and inconvenienced our members,” Dunn says.
“Preventing outages and maintaining equipment are the keys to providing affordable and reliable electric service. In this case, John’s watchful eyes caught a minor problem and we were able to fix it before it became a major disaster.”