Drone inspection of power lines will be out of sight but not out of mind
When electric drones first hit the scene, they seemed like one of those tech that was going to change everything because they’re so cool.
But the reality is not science fiction; quadcopter air taxis and pizza delivery by drone remain far away. The main impact I have seen are aerial photos like the one that made the front page of The Monitor on Monday.
There are two reasons for this. One is energy density. The millions of years of organic matter compressed in a pound of gasoline or aviation fuel contain 20 to 30 times more potential energy than there is in a pound of lithium-ion batteries. Since weight is the enemy of flight, this extra weight limits what can be accomplished even though electric motors are lighter and more efficient than internal combustion engines.
The other, more important reason is regulation. Flying objects can do a lot of damage, so they must follow rules that may restrict their use.
Both limitations are reflected in a pilot project that Eversource New Hampshire is running this summer, using a six-rotor drone to inspect a transmission line between Franklin and Bristol.
Eversource has been experimenting for a few years with drones to inspect large wooden or metal structures that carry transmission lines across the country (those of at least 69 kilovolts that feed other lines rather than customers directly).
“There are a lot of things that you can’t really see from the ground. With drones you can get up close, see all angles… you can see the top of the posts is where you get the most rot, especially in the wooden posts, ”said Elizabeth Hall, Head of Eversource’s newly formed drone engineering team. “We are looking for anything that could pose a threat, cause an outage – pole conditions, rotting or cracking; all the material, the connecting parts, any fatigue on them, definitely wear and tear, especially if there is a lot of wind.
One specific concern about the wooden poles, she said: spike holes.
These inspections are usually carried out by helicopter, but it is expensive. Doing it by drone is cheaper and could be more flexible, but the Federal Aviation Administration requires them to remain in sight of the operator, which negates the whole premise. At this point, utilities use them sparingly, for tasks such as specific storm damage investigations.
This pilot project, which is slated to fly in July, is the first step beyond. The FAA has granted Eversource a waiver to fly the drone beyond the operator’s sight, the first such waiver for Eversource and “the first known to us over mountainous terrain.”
“Most of the rest are in Kansas where there is a strong line of sight. Flying through mountainous terrain is more difficult, ”Hall said.
The waiver, however, is quite limited. While the drone can fly beyond the sight of the person at the controls but not beyond the rest of the team, which means people must be spaced out along the right-of-way, ready to take over In case of problem. “There will always be someone with their eyes on the drone at all times,” Hall said.
In addition, the operator will not be able to see what the drone sees, in order to limit the possibility of radio interference. And the flight will be 200 to 400 feet above the ground, higher than usual. This adds to the safety margin but reduces its usefulness for inspections.
“Everything about this is very specific,” said Sam Johnson, director of UAS operations at ARE Corp., which operates the drones for Eversource. “The FAA is big on the crawl-walk-run approach. This is our exploration.
If all goes well and FAA fears prove to be unfounded, Eversource will petition to expand the program. He plans to do more and more useful drone inspections in the future. The utility has two drone pilots on staff for New Hampshire, part of Hall’s internal drone group that covers the three northern New England states.
As for the energy density problem, the hexacopter is cheating: it is powered by both a gasoline engine and a battery. which allows it to fly for up to 45 minutes, Jonson said, much longer than battery-only models.
Technology will eventually fix this as the batteries improve, but it will be a long time before an electric drone carries you and me.
(David Brooks can be reached at 369-3313 or email@example.com or on Twitter @GraniteGeek.)