Eversource schedules its helicopters to fly over major electricity transmission lines and equipment four times a year (most recently in late December, late February and late this month — starting about now or sometime soon).
We asked a utility spokesman why that happens so often, and here’s what we found out:
Frank Poirot, a spokesman for Eversource, said the electric utility conducts two different types of regular inspections over major equipment, including transmission lines, each twice a year.
Two trips each year are done with infrared, heat-sensing equipment to see whether lines are especially hot — a sign that the equipment is breaking down. The choppers will fly over the equipment once in the winter and once in the summer.
“In the winter, we’ll see the greatest temperature differential, so that hot spot will show up right away,” Poirot said.
But it’s also useful to use the heat-sensing equipment in the summer, even though that temperature difference is less, because that’s the time of year that demand is highest.
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During peak-demand time, he said, it’s better to check when the equipment is under more stress to see “if there’s any electrical resistance in the line caused by metal fatigue or another issue.”
Checking the Vegetation
The other two annual trips are to look for trees and limbs that might need to be removed so they don’t fall and cause damage and an outage, he said.
Those fly-overs are best done when there aren’t leaves on the trees, he said — that’s when it’s better to see the trunks and limbs.
Why can’t Eversource combine the vegetation-checking flights with the infrared flights?
Because the infrared equipment and the staffer who operates it take up a lot of the interior space of the helicopter, Poirot said.
Some Other Times
Along with those four, scheduled flights, the helicopters might come at other, unscheduled times if needed. For instance, sometimes they help place wires for transmission lines. For those projects, they may even transport workers.
Another time is after a severe storm.
“There, we’re looking for any trees that have recently fallen or trees that could potentially contact with our lines.
Darien’s major transmission line is along the New Haven railroad line, he said.