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Drones will help helicopters and ground crew inspect Eversource lines

  • Allen Tweed of Mesa Associates, an Eversource contractor, demonstrates the drones that will be used for power line inspections. David Brooks—Monitor Staff

  • These pictures show the zoom ability of inspection drones being used by Eversource. They are taken from the same location by a hovering drone. Courtesy—Eversource

  • Footage from a drone flown over Eversource power lines in Allenstown. Courtesy

  • Footage from a drone flown over Eversource power lines in Allenstown. Courtesy



Monitor staff
Thursday, September 06, 2018

Replacing expensive helicopters with drones seems like an obvious move for utilities that have to inspect thousands of miles of power lines every year, but even as Eversource rolls out its first drone program, it is aware the switch has limits.

“This is complementing, not replacing, helicopters,” said Carol Burke, manager for transmission inspection operations for Eversource.

Burke led a demonstration at a Hooksett substation of Eversource Wednesday, showing the first of four drones, each costing $15,000 to $20,000 depending on equipment, that will be used for annual inspections of transmission lines throughout the three states served by the company. In New Hampshire, Vermont and Massachusetts, Eversource has more than 4,270 miles of high-voltage transmission lines strung between towers that can be as tall as 160 feet.

Burke explained that the drones will be used to do visual inspections of lines, poles and hardware using high-end cameras with optical zoom lenses that can enlarge 30 times as the drone hovers relatively close to the lines.

“We look for defects, damage, aging equipment, rotting crossbars. We look at poles, insulators, all the hardware,” she said.

Eversource will continue to use helicopters for some inspections where the longer range is an asset and getting close to the lines is less important, such as during infrared examination that can spot problems in advance because of excess heat, or searching for damage after storms.

Eversource started testing inspection drones two years ago. It has hired Mesa Associates, an Alabama-based engineering firm, to operate the program.

One big shortcoming to inspection drones is that they must stay within sight of the operator, which means they can only travel along lines as fast as the people below can move along the right-of-way.

“We’d love to go further,” said Allen Tweed, senior utility consultant at Mesa. The Federal Aviation Administration is weighing whether to allow drones to travel out of the line of sight when doing power-line inspections.

Even if that happens, there’s another drawback: battery life.

The drones being used by Eversource, made by Chinese manufacturer DJI, last about 20 minutes before they must land and have their batteries replaced.

The drones can travel as fast as 40 mph, and can go higher than the legal limit of 400 feet above the ground, Tweed said. Each one weighs about 10 pounds.

Tweed said that companies are testing and the FAA is studying whether to allow the use of fixed-wing drones, of the sort used by the military, for power line inspections beyond the line of site. Batteries in these drones, which look like small airplanes, can last for hours, meaning they could do long-distance surveillance of power lines autonomously without human operators, replacing piloted-helicopter inspection or searching. Because fixed-wing drones can’t hover, however, quadrocopter drones or helicopters would still be needed.

Burke said that Eversource, like all utilities, has long been expanding the technologies used for line inspections. Initially, inspections were all done by people, on foot or using bucket trucks, which is effective but slow and usually requires that the power lines be turned off. Aerial inspections by small airplanes became common decades ago, and helicopter inspections became the norm in the past four or five years, although foot and airplane inspections are still used.

Drones are the latest step in that evolution, she said.

“All these methods have benefits,” said Tweed. “They complement each other.”

(David Brooks can be reached at 369-3313 or dbrooks@cmonitor.com or on Twitter @GraniteGeek.)