High Flying Act in Northern Minnesota

Insulators replaced on 500 kilovolt transmission line

An energy link between the United States and Canada got an upgrade recently.  Working in the air, and on the ground, crews replaced 576 polymer insulators on 32 dead-end structures on Xcel Energy’s only 500 kilovolt line.  The transmission line work took place between the Forbes and Chisago County Substations stretching about 300 miles from northwest of Warroad, Minn. which is on the Canadian border to North Branch, Minn. 

Xcel Energy Transmission Line Construction crews used bucket trucks to replace the insulators on structures within or near substations due to their easy accessibility, while an Xcel Energy Civil Construction crew worked to mat two structure locations and four landing zones. Helicopter companies Air2 and Haverfield Aviation took to the air in more remote areas.

“It was an outstanding effort by all of the crews to finish the project ahead of schedule” said Brendan Cohen, Project Manager. “The line’s outage was scheduled for two weeks without any options for extension, but crews finished in eight days.”

The insulators which were originally installed in 1992 were at the end of their lifespan and due to be replaced.

“We decided to proactively change out the insulators due to some things we discovered at another structure on the line where we had a failure of the fiber glass rod inside the insulator,” said Brian Long, Director, Transmission System Sustainability. “We are sending a sample of the insulators removed to Electric Power Research Institute (EPRI) to gain a better understanding of possible damage to the devices and what happens to them as they age.”