The device rolls at about three miles an hour along a high-lying “shield wire,” a wire that protects the main transmission lines below from lightning strikes. Initially, the plan to power the robot involved covering its surface with solar cells that would charge a lithium polymer battery inside. “We decided instead to harvest power flowing through the shield wire itself,” says Phillips, who explains that the shield wire picks up some power flow from the nearby transmission lines through electromagnetic induction. Solar cells will still be used for backup power, however.
In the most remote areas, raw data that has been collected will be sent back to the utility through a satellite link. Higher bandwidth information, such as digital images, will be transmitted through cell-phone signals when the robot gets closer to population centers. Phillips figures that each robot will be capable of covering 80 miles of line twice a year.
George Juhn, director of investment planning and asset management at Ontario transmission giant Hydro One, notes that aerial drones are also being tested by the industry as a way to collect data about remote power lines. “A device such as [the new robot] does need to go through extensive testing to ensure it provides reliable information,” he says, adding “It would definitely be of interest to us.”
Phillips says the problem with aerial drones is that the U.S. Federal Aviation Authority has strict rules on how and when they can be used because of the potential impact if they malfunctioned. A line-crawling robot poses less of a threat and can travel the lines all year and, if necessary, even at night.
But Phillips agrees that much more testing is needed. He says the first commercial test is expected to take place as early as 2014 along the Potomac-Appalachian Transmission Highline, a new 275-mile transmission corridor being built by Allegheny Energy and American Electric Power in Columbus, OH.