Stringing power line is faster with a helicopter -- but also distracting.
Motorists zipping along Interstate 94 just north of Monticello were doing double-takes on Thursday as they caught glimpses of a helicopter clattering overhead with a helmeted man in a harness dangling far below it. Not a daring rescue, but rather precise high-wire maneuvering along a new power line.
Twenty-eight miles of high-voltage line, to be exact, between Monticello and St. Cloud. Xcel Energy workers will spend the next two months stringing transmission line between 157 poles that were installed last year.
But instead of the homeowner equivalent of going up and down the ladder and moving it around to string outdoor holiday lights, Xcel has gone airborne to get it done faster and more efficiently.
In addition to rope-suspended workers causing traffic slowdowns, Xcel occasionally rattles passers-by with fireworks-caliber blasts -- accompanied by puffs of smoke and fire -- to fuse the new lines together. The work is so startling that signs and even a patrol car with flashing lights are deployed to warn motorists.
It's the utility's first new major power line in three decades and the first of three segments that will be built along 231 miles between Monticello and Fargo by mid-2015.
The utility uses helicopters regularly for maintenance but not for building a new line, said project manager Jerry Chezik. "This is the first time we've actually done this for stringing wire for new construction," he said.
A helicopter is in continuous motion, he said, and can perform tasks in minutes that would take hours if ground crews needed to set up aerial buckets at each transmission pole and move between them constantly. The poles are about 1,000 feet apart, or five per mile.
The new power line is needed to strengthen the grid and increase reliability, said Xcel spokesman Tim Carlsgaard. Demand for electricity is growing, especially in the St. Cloud, Alexandria and Fargo areas.
"We've had significant growth in the past 20 to 30 years since the last major [power line] expansion, and we're also looking out for the next 20 to 30 years," Carlsgaard said.
Much of future power will come from renewable sources, especially wind, he said, and four other utilities are partners in the project.
On Thursday, a worker tethered to a 75-foot line beneath the green underbelly of a helicopter was lowered onto the uppermost horizontal bar atop a 150-foot pole. He wrapped his legs around the bar, attached himself with safety gear, unhooked from the helicopter and shimmied out to the far end to install a pulley.
As the worker set about his tasks, the helicopter darted away like a dragonfly to pick up a second worker and ferried him to another pole to perform the same task. Then the pilot returned for the first worker.
Attaching pulleys to each of the four horizontal bars on each pole is the first step of helicopter work that ultimately leads to five different colored ropes being strung between the poles. Three are for power lines, one for a fiber optic line and one for a shield wire to protect against lightning strikes.
Later, ground crews will attach the ropes to wires and use machines to pull them back across the system. Those wires in turn will be attached to the thick conductor wires that, once they are pulled through the system, will be able to carry electricity on the 345-kilovolt line.
Workers suspended from the helicopter are used again at the end of the installation to remove the pulleys and "pin" the huge wires onto struts that keep the wire a safe distance from the poles.
Gawkers and stoppers
Helicopter pilot Michael Peters, who has worked on power lines around the country, said the Xcel job is somewhat tricky because it snakes along the curving highway, with more angles than is typical for transmission lines. Peters said he can't help noticing that his low-flying helicopter is a distraction for motorists. He has a bird's eye-view of how drivers behave.
"People stop or slow down to watch the helicopter and it just creates a nightmare," he said. "We've had traffic backed up for a long ways because people stop and gawk." Last week the slowdown was so serious on one afternoon that the helicopter stopped flying for awhile.
Another potential hazard is that crews installing the line occasionally use "implosive" devices as a way to splice and fuse the thick conductor line. The blasts are similar to large fireworks explosions, Carlsgaard said.
"We've had some trucks and cars pull over and people get out of their cars because they thought they had a flat tire," he said.
To prevent accidents, authorities have placed signs along the highway warning of a blasting zone ahead and portable signs with flashing messages: Emergency stopping only, Aerial work ahead."
To enforce that message further and prohibit curious onlookers from stopping, a State Patrol squad car was stationed on the highway near the work zone on Thursday with its warning lights flashing.
The installation of pulleys, cables, insulators, struts, bird diverters, vibration dampers and other devices will leapfrog northward toward St. Cloud and is expected to be finished in late October or early November. Utility officials expect the new transmission line to be fully "energized" by the end of the year.
Tom Meersman • 612-673-7388