Construction of transmission infrastructure in India faces enormous challenges such as cost and time overruns, owing to right-of-way (RoW) issues, technical difficulties in executing projects on tough topography and problems in land acquisition. The conventional methods of planning utilised for the installation of transmission lines include walkover surveys and other similar methodologies that have an oversized dependence on human intervention. Nonetheless, these methods are time consuming and inaccurate, owing to errors in human assessment and an array of technical challenges that arise in the course of monitoring.
With the transmission segment set to witness a substantial expansion, encompassing construction of high-voltage, direct current lines, monopoles, etc., reliance on new technologies for tower erection, mapping and asset monitoring is becoming imperative.
One of the key strategies that transmission project managers can adopt for transmission tower planning is the use of unmanned aerial vehicles (UAVs) and drones before determining a suitable route and design for the proposed transmission lines. Small and remotely controllable drones have vast potential for use in tower design as their aerial vantage enable more meticulous data collection. In addition, drone-based tower planning and design costs several times less while terrain surveillance is much quicker. Consequently, utilising drones enables transmission utilities to realise cost and time gains exceeding their investment on these technologies, given the massive improvement in precision and speed of project execution.
Utilising drone-applications
Currently, in the transmission sector, aerial drones and UAVs are utilised for aerial surveys and monitoring and charting of land masses, in addition to more complicated operations such as delivery of materials and automated stringing.
Meanwhile, drones can be fitted with gimbal-mounted ultra-HD video cameras, capable of closely capturing high quality images and videos. Before drones perform inspections, it is necessary to set waypoints and photo task points on the inspection line. This process relies on the generated power line laser point cloud model or manually setting waypoints. According to the power inspection personnel’s experience and the actual situation, the drone’s bird nest usually exists in the tower body and the power cable part of the transmission line tower.
After drones and the onboard computer are turned on, the inspectors first preset the waypoint information of the line to be inspected and upload it to the system. This includes the photos that the drones need to take at each waypoint. According to the task and camera angle, the drone takes off autonomously according to the waypoint information and automatically takes pictures after arriving at the waypoint. These drones typically have pre-installed thermovision and highly sensitive visual cameras with GPS for precise monitoring of any possible defects/lacunae in conductor/earth wire/insulators, missing/damaged hardware, hot spots, etc. During this process, the onboard computer pulls the video stream of the drone’s camera gimbal in real time and obtains the photos taken. After the drone completes a single inspection mission according to the waypoint and lands, the detection software automatically generates a location record file and a photo, which can then be viewed in the map software. Also, infringement/encroachment issues along the RoW can be identified. Digitally recorded data/details can be monitored or analysed by experts to confirm the healthiness.
Use cases for drones in the project life cycle
Drones offer a number of advantages for project developers at various phases of the project life cycle. For companies, drones are a cost-effective, efficient and safe solution for the inspection of power lines. They also improve safety, increase reliability and reduce transmission system response time.
Bidding stage: At the bidding stage, drones are used by transmission utilities to assess potential site locations, design site layouts, generate 3D visualisations and make estimates for RoW. In the past few years, images captured by drones can be transformed and enhanced into 3D images, with better visuals aiding in improved perception of the tower pathway and the space that it will potentially occupy. Drones and UAVs, coupled with data analytics systems such as machine learning and artificial intelligence (AI), facilitate projection of future vegetation and RoW issues in advance.
Construction phase: Drones can be used by developers for a detailed line survey, pre-pilot rope pulling. In fact, drones mounted with LiDAR sensors can significantly improve surveys and are suitable for any kind of terrain. The data collected is very dense as the point density is much higher in LiDAR and is based on the actual ground data and not interpolation. They can also be used for timely mapping and monitoring of the progress of construction lines using drone imageries and this is a great tool for MIS reporting. Also, they enable monitoring of workers at the site by closely watching them remotely. Further, they are useful for RoW and hotspot area mapping, besides habitation analysis, which is more accurate compared to satellite imagery.
Operations and maintenance phase: Similarly, high voltage power lines in remote areas and high altitudes present difficult and dangerous obstacles, either when conducting routine inspections or surveying the damage after a storm. Such challenges could be eliminated by the use of drones. Moreover, visual inspections, thermal inspection of towers, conductors, insulators, etc., can be done using drones. Also, moving from tower to tower is much faster using drones when processing can take place while teams are traveling between assets. In addition, using a cloud inspection platform, multiple transmission towers can be processed at the same time, which makes the whole process even faster.
The way forward
Drones also give utilities the ability to identify threats to the energy grid quickly and efficiently. As a result of these developments, conventional methods of line patrolling based on monkey patrolling and on-ground techniques are considered demonstrably less efficient, more expensive and time consuming than deploying aerial surveillance as well as remote airborne inspection and scanning systems. Further, combining these imageries can help in creating intelligent digital twins integrated with AI, which can accurately recreate power lines, which is vital for digital twins of transmission towers and thus, help optimise asset maintenance and records.
Several power utilities have been and are planning the adoption of drone technology. For example, Power Grid Corporation has commenced drone-based patrolling of important transmission lines using in-house micro-category drones (in line with communication from the Ministry of Civil Aviation and the Ministry of Power regarding no restriction on flying drones under the green zone up to 400 feet height). The Transmission Corporation of Telangana initiated a pilot project using drones and UAVs for surveying and monitoring transmission lines in November 2021. Meanwhile, Maharashtra State Electricity Transmission Company has been using drones with video cameras and thermo-vision cameras to check faults on power transmission lines across Maharashtra. Private transmission developer, Sterlite Power, has also deployed drones for stringing of transmission lines in its projects in live line conditions. Madhya Pradesh Power Transmission Company Limited is planning to deploy drones to monitor 10,000 high voltage towers in the state beginning October 2022.
Going forward, as changing regulatory requirements call for faster execution times and higher uptime of assets, using drones for surveillance, patrolling, and operations and maintenance can significantly enhance the operational efficiency of transmission assets by minimising unexpected equipment downtime and help deliver projects in a time-bound manner.