Aerial inspections with drones

The buzz can sometimes disturb a relaxing coffee break on the terrace: The use of drones has become more and more widespread. At Axpo Grids they make sense in order to ensure a reliable power grid. Thanks to drones, power masts and lines can be inspected more efficiently. Careful navigation along power lines requires precision – aside from being fun. The “Axpo pilots” also put their drones to work for other grid operators.

Power masts and lines are major assets for reliable power supply. Axpo’s 2100-kilometre long distribution and medium-voltage grid alone has about 7500 masts. Their flawless condition is the prerequisite for safe, reliable electricity transmission in Switzerland. Up to now the regular inspections of masts and transmission lines had to be performed by linesmen who had to climb up the masts. This required a great deal of time and manpower. Now the Axpo linesmen have support from the air:

We asked Roland Ziegler, Head of System Operations at Axpo Grids about the use of drones.

What are the advantages of using drones for line inspections?
The lines can remain switched on when making aerial inspections using drones. This increases line availability and ultimately saves costs. Drones also take high-resolution photos from the optimal perspective – particularly in areas that are difficult to access. The photos help to assess damages and define repair measures.

What sort of damage are we talking about here?
Lines and masts are inspected for cracks, flaking, corrosion or contamination. Timely detection and repair prevent, for example, frozen water from entering the cracks and causing major damage.

So, a digital device is now replacing manpower, that is the linesman?
No, certainly not. Linesmen are optimally supported by drones in their work. It is not always possible to perform work without climbing up the masts. When lines have accumulated a lot of moss or calcification, the damage cannot be seen from the air. Someone still has to climb the mast and remove the material by hand. However, most of the lines are in good condition and for these an aerial inspection is sufficient. However, linesmen are indispensable when it comes to making re-pairs.

Navigating drones takes practice. Can all the linesman operate drones?
Two of the Axpo linesmen have been professionally trained to pilot drones. It was a conscious decision to limit training to only two. The goal is that these two pilots can perform as many inspections as possible. Steering an aircraft is challenging and requires a great deal of routine in addition to professional training.

What are the greatest difficulties?
Navigation is precision work that requires a steady hand and high concentration. Narrow spaces, for example, in forests and alpine terrain with limited visibility are the greatest challenges. The pilot must have visual contact to the drone at all times. It is not possible to fly the drone in wind, rain or fog. 

Where are the drones being used?
The decision to use a drone is made on a case by case basis and depending on the condition of the lines. If possible, drones are used to inspect lines while they are connected to power. The Axpo service is already being used by other grid operators and will be expanded further.

Has the Federal Office of Civil Aviation (FOCA) made any stipulations on using drones?
Axpo follows the FOCA stipulated Regulations and questions relating to drones. With a weight of approx. 7 kg, our drones fall under the “light weight” category. As a rule, drones weighing less than 30 kilograms can be flown without a permit. The pilot must, however, have visual contact to the aircraft at all times and may not fly over crowds. The latter usually does not occur because power masts are usually located in remote areas far from civilisation.