Surveillance techniques help determine the number of transmission towers required for laying a transmission line through the shortest possible route. These techniques also aid in selecting the right tower foundations based on the topography and soil type of the area.
Conventional surveying techniques including walk-over survey, which entails going over to the proposed transmission line route, are both time-consuming and inaccurate. Therefore, utilities are adopting advanced technological tools for tower mapping. These include aerial patrolling solution, geographic information system (GIS) mapping and light detection and ranging (LiDAR). Tower-top patrolling devices using unmanned aerial vehicles (UAVs)/drones eliminate the need to physically visit the tower site. These UAVs are equipped with gimbal-mounted ultra-HD video cameras that can take close, high resolution photographs and videos. The use of helicopters/drones equipped with gimbal-mounted LIDAR thermo-vision cameras and high resolution video and digital cameras to provide high-resolution images of towers, lines and the project site is fast gaining traction. These methods are cost-effective and more efficient than the conventional solutions deployed by utilities.
Drone patrolling provides detailed information about the tower-top portion, that is, the condition of insulators, earth peak and earth wire. The advantage of using drones in operations is that they are a cost-effective, efficient and safe. Drones are also being used by transmission utilities to assess potential site locations, design site layouts, generate 3D visualisations and make right-of-way (RoW) estimations. Power Grid Corporation of India Limited is using drones for transmission line and tower patrolling and survey purposes.
LiDAR is used for carrying out aerial surveys to optimise route corridors for transmission lines and determine the position of towers through topographic mapping with the help of an aircraft. The data processed through a LiDAR survey can be directly linked to modelling software, which can provide options for alignments, tower designs and tower positions at minimum cost. In addition, LiDAR captures natural and artificial objects under and around the transmission lines. This information is extremely useful for understanding tower locations, the structural quality of towers, determining catenary models of lines, undertaking vegetative critical distance analysis, and carrying out repair and planning work in a transmission line corridor. Thermo vision cameras help in identifying loose connections, load imbalances and corrosion, which lead to an increase in temperature, resulting in component failure, possible power outages and system losses. The hot spots caused by these defects can be easily located by a thermal imager. Powergrid is undertaking aerial patrolling of its transmission lines using helicopter equipped with gimbal mounted LIDAR, thermo-vision camera, corona camera, high resolution video and digital camera to identify the defects.
GIS-based corridor mapping
GIS tools are being used for transmission asset mapping, route alignment during the planning of new transmission lines, vulnerability analysis during events like floods and fires, post-tripping analysis, study of changes in river courses (for monitoring the safety of lines and towers located near rivers), and disaster management studies. Recently, during the cyclones that impacted Odisha and Gujarat, the GIS platform was used to identify the transmission lines that came in the path of the cyclones and take adequate measures. Powergrid started undertaking GIS mapping of its assets in 2017 and aims to complete the process by December 2019. The utility has integrated GIS mapping of its assets on the BHUVAN server.
Mobile app-based inspection solutions help locate and monitor the complex electrical grid in real time, from the point of generation to consumption, as well as in case of a malfunction. Such an app allows towers to be identified based on their GPS location, besides providing biometrics-based authentication for maintenance engineers. It allows issues to be reported in real time. Data can also be captured offline and uploaded subsequently. In March 2019, Powergrid, through its Patrosoft software, had started patrolling close to 0.28 million towers. The software dashboard displays scheduled patrolling and patrolled line towers as well as highlights critical towers and emergency actions needed, if any. Tower patrolling and defect rectification are being ensured through the application.
New and emerging survey and patrolling techniques such as the use of UAVs/ drones and GIS-based corridor mapping enhance the operational efficiency of transmission assets by minimising unexpected equipment downtime. Besides, these help in accurate and detailed pre-construction surveys that are useful for minimising right-of-way requirements, which are one of the major constraints in transmission network expansion.