New wire provides reliability when it matters most

Imagine an electric system so resilient it can withstand 94 mile-per-hour winds, ice and severe weather to keep electricity reliable during even the worst storm. Great River Energy is piloting such a project in Federated Rural Electric Association’s service territory.

The southwest part of Minnesota, where Federated Rural Electric Association is located, is the area on Great River Energy’s transmission system that sees the most “galloping.” Galloping occurs when ice forms on overhead lines and the conductors — or wires — jump like a rope and sometimes contact each other, which can cause momentary outages. Sometimes galloping is so widespread that system operators will de-energize a line until the wind and ice have subsided.

A pulley system was used to string the lines on the project in Federated Rural Electric Association’s service territory.

The pilot project involves rebuilding a 69-kilovolt, 23-mile line with larger wood pole structures, steel switch structures and a “twisted pair” conductor, which is resistant to icing.

“This line needed to be rebuilt based on the age and condition of the line, but we also are taking the opportunity to use innovative conductor technology,” said Mark Peterson, manager of system operations at Great River Energy. “Our goal is to improve reliability in this area where we are at high risk for severe ice storms.”

These additional resiliency design features are expected to result in a hardened, more reliable system that can withstand 100-year storm events.

Peterson said transmission lines, especially those located south of the Interstate 94 corridor, have historically had damaging events related to freezing rain and ice.

“When a typical round conductor is subjected to freezing rain, ice forms around the conductor in the shape of a wing,” Peterson said. “As the wind blows across the conductor, the lines can start galloping, causing faults and potential damage to line equipment such as insulators and poles. The twisted pair conductor minimizes the galloping effects because it sheds ice due to its asymmetric shape, which causes the conductor to continuously rotate.”

Peterson said the pilot project will help Great River Energy understand if the benefits of the conductor will outweigh the extra effort needed to install and maintain it.

“The twisted pair conductor is installed differently,” Peterson said. “It can be more labor intensive, and our crews will need to gain experience maintaining the line once it’s constructed. Ultimately, the benefits should outweigh those issues. This investment in the part of the state where we see reliability issues due to icing will help ensure we can continue to keep the lights on for end-use members.”

This project is expected to be completed by spring 2022.