Swissgrid is now able to use drone technology to detect damage to extra-high-voltage lines more quickly and in a more targeted manner, for example. Autonomous flights and intelligent image analysis make overhead line inspections more precise, safer and more sustainable – progress that saves time and money.

Markus pulls his safety jacket tighter around his body as he inspects the electricity pylon in front of him with a practised eye. A Grid Maintenance Manager has tasked him with carrying out an inspection. For years, it has been part of his job to detect damage to extra-high-voltage lines during routine ground inspections – even on terrain that is difficult to access. He notices a dark spot on a pylon element. A look through his binoculars confirms his suspicions: heavily rusted armature hangers on an insulator string. This indicates wear and could have critical consequences. If an insulator string breaks, this can trigger a grid disconnection. That’s when the real work begins: the results of the inspection are sent to the Grid Maintenance Manager, and Grid Strategy analyses the damage before commissioning repairs. To ensure that the work can be carried out safely, the entire affected section of line must be taken out of service. This shutdown has to be coordinated with Operational Planning – a complex process that must be carefully planned to avoid jeopardising grid stability. It can take days or even weeks until all the necessary steps have been completed and the line has been repaired.

All the advantages of automation

In the future, instead of having to use binoculars, drones will fly over the extra-high-voltage pylons. Automated flight planning makes this possible: drones can fly along their route independently and capture high-resolution inspection images of predefined locations. In the present case, this means that the problem can be recorded immediately and the inspection data sent promptly to the Grid Maintenance Manager and the department with operating responsibility. The only thing left to do after that is to check the availability of materials and service providers. But instead of losing weeks, it will only take a few days for repairs to be carried out – in a targeted and efficient manner and without unnecessary delays. Using a drone not only saves time and money, but may also prevent a grid disconnection.

The benefits of automated flight planning at a glance:

• Drones allow preventive screening and can detect damage to overhead lines at an early stage before it becomes critical.
• Predictive maintenance: the status of the grid can be continuously monitored and long-term trends analysed.
• In comparison with ground inspections, drones deliver highly precise and complete image data.
• Less human intervention is needed in areas that are difficult to access, increasing safety.
• Drones are particularly advantageous in mountainous regions because they can negotiate differences in height without any problems and without complex logistics.
• Efficiency can be increased due to continuous process automation.

Flights out of visual range: a milestone for Swissgrid

When a drone flies autonomously, it does so out of the pilot’s visual range. Swissgrid carried out a BVLOS (Beyond Visual Line of Sight) flight for the first time in 2024. BVLOS flights can be used to monitor long distances without direct visual contact – automation is a key advantage for the inspection of high-voltage lines because it enables a significant increase in efficiency.

Another innovative aspect is that the drones are equipped with LiDAR sensors (Light Detection and Ranging). Thanks to three-dimensional laser scans, these sensors provide high-precision image data that complements existing helicopter images and will even replace them in the long term. The positive results of the test flights are paving the way for the increased use of autonomous drones in the coming years. This will enable Swissgrid to further optimise its processes for maintaining the transmission grid, drive forward the digitalisation of grid inspections and ensure long-term security of supply on the grid side.