All electricians will tell you that the first thing they learned at the start of their training is to make sure the power was off before working. Since 1 October 2020, this is no longer entirely correct in Switzerland.

Since the 1980s, Airtelis, a subsidiary of RTE, Swissgrid’s French counterpart, has been developing a method and a technology that allows maintenance work to be carried out safety on extra-high-voltage lines in particular, without cutting off the power supply!

Airtelis’ expertise, which is widely recognised in Europe and around the world, has aroused Swissgrid’s interest. A first pilot project took place on 1 October in the Lausanne region. Swissgrid commissioned Airtelis to install an orange signal ball on the ground wire of the 380 kV Chamoson – Romanel line, a few hundred metres from the Romanel substation in the landing corridor of Lausanne-Blécherette airport.

On the morning of 1 October 2020, Swissgrid representatives Marcel Lenzin, Head of Grid Delivery; Rolf Tschampion, Head of Region West; and Cécile Jost, Grid Mainenance Manager welcomed the Airtelis/RTE team of around 15 professionals, on the tarmac at Lausanne Airport.

The helicopter, a Eurocopter EC135 with two turbines in RTE colours, was specially adapted for work under live extra-high-voltage lines and equipped, among other things, with numerous mirrors and an on-board camera. To facilitate the work of the two pilots and to allow them to check the position and the stability of the nacelle in flight with their own eyes, all the doors of the helicopter were removed before take-off.

A special nacelle was then connected to the helicopter by insulating non-rotation ropes. These ropes have a lifespan of two years and are checked after twelve months to ensure their insulating capacity. All insulating material is red in colour to facilitate control of the anchoring process. The two RTE employees responsible for setting up the signal from the nacelle were equipped with a suit specially designed for work under tension. Like a Faraday cage, this suit protects them and allows them to do their jobs safely. The French team was very vigilant and aware of the significance of their task. It took only 30 minutes to complete all the preparatory work according to a very precisely defined process that was strictly followed.

After a last briefing the work started. The helicopter took off at noon. Five minutes later, the two workers attached the signal ball to the guard wire of the 380 kV Chamoson – Romanel line without having switched it off beforehand. By 12.20 pm, the work was done, and the helicopter gently lowered the nacelle on the tarmac at Lausanne-Blécherette Airport.

The value of such technology is obvious. Currently, all maintenance work carried out on Swissgrid’s extra-high voltage grid requires the installation concerned to be taken out of service. This means a reduction in transmission capacity and an additional workload for Swissgrid employees at the Grid Control Centre, who are responsible for coordinating each shutdown. The results of this first pilot project for live maintenance work will now be analysed by Swissgrid. Will they lead to the implementation of this live working technology in Switzerland? Time will tell. In any case, thanks to the the Airtelis/RTE team. The job was done very well and in complete safety.