Conversion of overhead line Eglisau-Wilchingen

The replacement of pylon number 63 is part of the voltage conversion project being implemented in Axpo’s transregional distribution grid in the Schaffhausen West region. 

It’s warm in the freshly cut field, situated in the small town of Wilchingen, at the heart of the rural Schaffhausen. Concrete pylon number 63 stands in front of a field of blossoming sunflowers. It was replaced by a new pylon at the end of July 2022. 

Go-ahead from the grid control centre

Staff from the Distribution Division’s operations are on site in Wilchingen as early as 7.00 am. The pylon replacement process was precisely planned in advance. Every employee knows what they have to do. The Axpo grid control centre in Baden and the control centre of the Canton of Schaffhausen electricity utility in Schaffhausen have complete control over both operation and switching of the Eglisau – Wilchingen line. It disconnects the Eglisau – Wilchingen line first of all, then informs the team on site. Now the construction work can commence.

Safety takes priority

Safety is the top priority when performing work like this, which is why it always takes precedence over everything else. ‘Nobody is allowed on a pylon unless it has been secured first,’ commented Dieter Reichelt, Head of the Distribution Division. After the switch-off, the line is earthed so work can be carried out safely. Staff also wear personal protective equipment designed to protect them against falls from height, including a helmet, steel toe capped boots, work clothes and gloves. 

Goodbye to the old pylon

This is where the work really starts. The six overhead line conductors are detached from the old pylon and laid on the ground in the field in no time at all. 

The pylon is then dismantled. To that end, it first had to be cut off at the base and set down on the ground with a crane. Dismantled old pylons are collected by an external company and disposed of or recycled. 

Hello to the new pylon

Once the old pylon is on the ground, the new one can be moved into the recess from the existing foundation. First of all, the recess is covered with concrete so that the pylon is anchored in the foundation. The team takes its own material (packed in advance) along with them for this purpose.

Wearing their helmets and protective equipment, and with the material in their pockets, two men climb up the pylon secured to the narrow conductor. This is a job that requires more than just strength and stamina. You need a head for heights too. 

Once at the top, the jibs are mounted and later set in concrete. Now pulleys (which six overhead line conductors are hooked into) are attached to the support pylons. The overhead line conductors are hooked in by simply pulling them up from the meadow, one after the other. The last step is installing the insulator chains. 

Here you can see how the overhead line conductors are pulled up and hooked in:

Adolf Keller, an overhead transmission line installation engineer, is satisfied with the work that’s been done. Everything went well, and the pylon was replaced quickly. 

Corrosion detection drones

The lines are checked periodically. Someone has to climb the pylons to perform this inspection. Nowadays, drones fitted with a high-resolution camera are being used on a trial basis to fly over the pylon structures and take pictures. A team checks the lines using these pictures. On the outsides of the pylon, for example, all is well as long as the lichens are green. But if they are darker and redder in colour, there is a risk of corrosion. Axpo’s specialists are currently examining how artificial intelligence could be used to interpret the many pictures and automatically detect damage.

Read more about the topic of drones at Axpo

A well-coordinated team

The maintenance team is made up of 50 members in total. Many of them are long-standing employees. At least four people are needed on site to replace one pylon. The team always sticks together, and everyone acts in unison because they all want to do a good job. This type of work is performed in all weathers and in all sorts of locations, which makes the job a challenging one. During the coronavirus lockdowns, the team was given warm soup in Thermos^® flasks on cold days because restaurants were closed. ‘Their wellbeing and safety are top priority,’ emphasised Dieter Reichelt.

Read more about the topic of grids