Transmission line engineers involved in planning new lines and upgrades use aerial surveillance techniques to determine routes, select right tower foundations, etc. Further, the routine monitoring and inspection of power transmission lines through aerial surveys is vital for ensuring uninterrupted electricity transmission. Conventional surveying techniques including walk over survey, which entails going over to the proposed transmission line route, are both labour-intensive and inaccurate and at best give results in approximations. Aerial surveys using helicopters are faster, but rely on human assessment.
Utilities are adopting advanced technological tools for monitoring transmission systems, to collect data via mobile and automated aerial devices. For instance, light detection and ranging (LiDAR) and patrolling devices, which use unmanned aerial vehicles (UAVs)/ drones, eliminate the need for physical visits to the tower site. The LiDAR data collection method offers a fast turnaround time from collection to delivery, and the ability to accurately map terrains and deliver high resolution images of towers. Meanwhile, UAVs are fitted with gimbal-mounted ultra-HD video cameras, capable of capturing high quality images and videos closely.
A look at the new and promising aerial surveillance technologies being adopted by transmission utilities…
LiDAR
LiDAR is used to conduct aerial surveys to enhance route corridors for transmission lines and determine the tower position through topographic mapping using an aircraft. The data processed through a LiDAR survey can be directly linked to modelling software, which can provide the least expensive options for alignments, tower designs and tower positions.
A key advantage of a LiDAR survey is the speed of data capture over conventional surveys. In addition, the data collected by a LiDAR survey can be connected directly to PLS-CADD. Models can be created in PLS-CADD using this data to assess the different criteria for the selection of the location of transmission lines and towers. Furthermore, LiDAR captures artificial and natural objects under and around transmission lines. This information is extremely useful for understanding tower locations and structural quality, determining catenary lines model, undertaking vegetative critical distance analysis, and performing repair and planning work in a corridor of transmission lines. Thermovision cameras help to detect loose connections, load imbalances and corrosion, leading to temperature changes, resulting in device malfunction, possible power outages and system losses. One thermal imager can accurately identify the hotspots caused by these defects.
India’s biggest power transmission utility Power Grid Corporation of India Limited (Powergrid) also uses helicopters equipped with gimbal-mounted LiDAR, thermo-vision cameras, corona cameras, and high resolution video and digital cameras to identify the defects of its transmission lines. With aerial patrolling, 100-150 route km can be covered in a single day by Powergrid. The infringement of safety clearances by trees/bushes, adjacent side objects and broken insulators are some of the faults that can be easily identified using aerial patrolling. Critical faults like hotspots can be identified using thermovision techniques. Another technology that Powergrid is using to ensure the health of its transmission assets is app-based patrolling. In March 2019, Powergrid had started patrolling nearly 0.28 million towers through its Patrosoft software. The software dashboard displays scheduled patrolling and patrolled line towers, and highlights critical towers and emergency actions required, if any. Tower monitoring and rectification of defects are being ensured through the application.
Private sector major Sterlite Power has deployed LiDAR technology for the construction of the Bhopal-Dhule transmission project, executed by its subsidiary Bhopal Dhule Transmission Company Limited to conduct topographical mapping. According to the company, LiDAR beams transmitted from the aircraft helped Sterlite Power in overcast and cloudy conditions, providing high precision at a high speed. With the use of these technologies, the risk of project execution was significantly reduced.
Drones
The increasing focus on delivering transmission projects in a timely manner pushes developers to deploy aerial technologies such as drones. 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. In addition, drones are used by transmission utilities to assess potential site locations, design site layouts, generate 3D visualisations, and make estimates for right of way (RoW). Remote areas of high voltage power lines present difficult and dangerous obstacles, either when conducting routine inspections or surveying the damage after storm. Such challenges could be removed with drones. Drones also give utilities the ability to identify threats to the energy grid quickly and efficiently.
Powergrid uses drones to patrol and survey its transmission line infrastructure. Drone patrolling provides the transco with detailed information about the tower-top portion, that is, insulator condition, earth peak and earth wire. A consolidated UAV patrol provides increased efficiency as a single survey flight enables data capture for the needs of network planning, engineering, maintenance planning, vegetation management and fire threat analysis, thereby reducing costs and the need for a routine patrol cycle. The technology will help in improving the reliability, resilience and safety of transmission networks.
For instance, Sterlite Power has entered into a partnership with a Finnish company for drone-based automated transmission line inspection. Long distance inspection will be provided through drone-based technology. This will increase the uptime of the grid, save the environment by conducting preventive maintenance and reduce deforestation along the line corridors.
Going forward, with the evolution in AI and machine learning, companies can expect upgrades in drone technology as algorithms generate more accurate results based on the large amounts of input data. In the future, an AI system may be able to quickly pinpoint problems and enable the utility to address them before failures occur. These potential usages go beyond the financial benefit and provide safety and reliability benefits to utilities across the board. Also, sensors are becoming cheaper and lighter while still retaining high power. These changes in the sensor market are expected to lead to higher volumes of data, more accurate results and actionable insights.
Conclusion
The focus on automated inspection and maintenance has significant value for high-value assets like power transmission lines. For instance, US electric companies collectively spend between $6 billion and $8 billion per year to inspect and maintain the vegetation surrounding their power lines, via helicopters and ground crews. Even with these inspection methods, it is hard for electric companies to survey long stretches of power lines at once, and access remote areas. Drones offer a safer and reliable way of inspection.
Net, net, the use of UAVs/drones enhances the operational efficiency of transmission assets by reducing the unexpected downtime of equipment. In addition, these help conduct accurate and detailed pre-construction surveys, thereby reducing RoW requirements, one of the major constraints in expanding the transmission network. It is expected that the use of these new technologies will increase as there is greater demand to execute transmission programmes under strict timelines, reduce implementation risks and optimise costs. Ultimately, given the long time period involved in the execution of transmission projects, including long-drawn clearance procedures, using the right technologies could reduce the design and execution time, generating overall savings for the project developer.