The CapX power line between St. Cloud and Alexandria will undergo another four months of work this summer to correct an unforeseen condition caused by ice and high winds.

As crews were stringing the high-voltage transmission line along Interstate Highway 94 this winter, they noticed a phenomenon known as "galloping," said Tim Carlsgaard, Xcel Energy's spokesman for CapX. Dc Transformer

When ice forms on transmission lines, strong winds can cause the lines to start galloping, or bouncing wildly.

"It almost moves like a wave action up and down," Carlsgaard said.

Galloping lines can slap into each other, causing power outages and damage to the wires and structures.

CapX planners didn't anticipate galloping would be a problem, Carlsgaard said. While the condition has been an issue on some transmission lines in southern Minnesota, Xcel had not experienced it on its existing lines, he said.

CapX crews didn't find any damage, but took wind surveys and brought in another company to study the problem, Carlsgaard said.

The CapX utilities decided to install devices called interphase spacers between the lines on about half of the segment between St. Cloud and Alexandria, he said.

The spacers weigh 200 pounds and are 25 feet in length. There will be four per span, Carlsgaard said.

Crews are close to finishing work on the second phase of CapX. They have been using helicopters to string wire between I-94 and the new substation near St. Cloud, Carlsgaard said.

CapX plans to energize the line in late April to demonstrate that it works and would be available in a pinch, Carlsgaard said.

Then it will be de-energized so the interphase spacers can be installed from May until August, he said. The line should be energized again in late August.

The St. Cloud-to-Alexandria segment is the second phase of the 345-kilowatt transmission line, which will extend from Monticello to Fargo, N.D.

The first phase from Monticello to St. Cloud already is operating. The third phase from Alexandria to Fargo is under construction.

There have been no problems with galloping on the stretch between Monticello and St. Cloud, Carlsgaard said.

Photovoltaic Substation Follow Kirsti Marohn on Twitter @kirstimarohn.