Transmission line inspections for vegetation management and other purposes are essential in ensuring grid reliability and resilence. They are generally performed by manned helicopters or by a ground crew. Data is collected with cameras and analyzed to detect diseased trees that could fall and hit a powerline (fall ins) or trees that were encroaching on powerlines (grow ins). These inspections are mandated by NERC in North America and are not optional. Beyond visual line of sight (BVLOS) drones (UAVs) and software analytics using machine learning has made it possible to approach completely automating this expensive process. Automating transmission line inspections for vegetation management using BVLOS drones not only saves money but also could improve the resiliency and reliability of the transmission grid.
Mapping transmission lines with BVLOS UAVs
At ILMF 2019 in a very interesting talk Paolo Guzzini of Delair described how BVLOS drones has been deployed to map transmission lines in remote areas of Iceland. Delair conducted two surveys on behalf of EFLA Consulting Engineers, a general engineering and consulting company. EFLA needed to map existing power lines and survey an area where Landsnet, the main transmission system operator in Iceland, planned to build a new power line between two cities. Iceland's airspace regulations allows BVLOS UAVs to be used in areas that are not densely populated. Delair deployed fixed-wing drones to gather two types of data: photography and LiDAR. The drones were programmed to fly a predetermined flight plan so the pilot had to only monitor the drone's progress and be available for emergencies. Delair’s drones were able to capture comprehensive data along the planned route and deliver the processed results to the client the next day — all at a fraction of the cost of hiring a helicopter or ground crew. UAVs with a range of 110-120 minutes flew for up to 10 km per flight. In one case the UAV flew a total of 70 km with a 21.4 megapixel photo camera to capture a corridor of 200 m width to an accuracy of 0.5 m vertical and 0.2 m horizontal accuracy. The actual vertical accuracy achieved was 0.15 m. In a second mission a UAV flew at 100 m a corridor 10 km in length with a LiDAR camera to capture a corridor 200 m wide with the objective of vertical accuracy of 0.5 m and horizontal accuracy of 0.2 m. The actual accuracy achieved was 4 cm horizontally and 2 cm vertically. The advantage of using LiDAR is that it can achieve better accuracy in location especially in the vertical dimension. In addition the LiDAR approach was able to detect detect conductors and poles. In both cases the range of the flights was limited by weather conditions, radio range (15 km), and weight of the camera payloads.
Reality capture for vegetation management of transmission lines with BVLOS UAVs
Periodic transmission line inspection is mandated for North American transmission lines by NERC. Inspections are currently carried out by manned helicopter or ground crews which are expensive and for that reason not done more often than is required by NERC. Full automation, which is possible with BVLOS UAVs and automated feature extraction of lines, pylons, vegetation and ground, would dramatically reduce the cost of inspection and enable more frequent flyovers. The major benefits would be lower costs and a reduction in the number and length of outages resulting from vegetation transmission line interactions.
In the U.S. on July 15, 2016, President Obama signed the FAA Extension, Safety, and Security Act of 2016. The 2016 Act requires the FAA to establish a process to allow certain UAV operations related to utilities, pipelines, and oil and gas production to be conducted beyond the visual line of sight (BVLOS) of the operator and either in the daytime or nighttime. As a result FAA rules permit beyond visual line of sight (BVLOS) UAVs through Part 107 waivers. I blogged over a year ago about Xcel Energy which obtained one of the first three waiver to fly UAVs for beyond visual line of sight operations. Paolo related that 32 of these waivers have been granted and that more than 20 companies are operating beyond BVLOS drones but still with some restrictions. Paolo related that the FAA very recently began allowing BVLOS operation using radar to track the location of the UAV. Paolo expects to see many long-distance UAV operations in the near future, making drones fully competitive against helicopters.
Over 20 countries have regulations that permit BVLOS UAV flights. In some areas of the world, Delair has even been able to control flights via a 3G data connection, allowing a drone to inspect up to 30 miles in a single flight.
Post-processing
Paolo told me that Delair's post processing software uses a combination of machine learning and other technologies to classify LiDAR point clouds with 85 to 90 % reliability in order to identify potential vegetation encroachments. I have blogged about Enview and other companies that also offer software solutions for this problem.
Conclusion
Rapidly evolving regulation to permit BVLOS operations, Delair's successful deployment of BVLOS drones with radio or 3G communications and automated post-processing, often cloud-based, to identify potential vegetation encroachment indicate that we are on the cusp of being able to completely automate this type of transmission line inspection. Using drones and automated feature extraction software not only dramatically reduces the cost of these inspections but makes possible more frequent inspections including on-demand - for example immediately after storms - which would impact positively the reliability and resilience of the transmission grid.
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