03.03.2020 | For the first time, a 380-kilovolt high-voltage cable is being laid in the ground

A premiere for Swissgrid

Swissgrid is extending the existing power line between Beznau and Birr to 380 kV. Part of the line will run underground on a 1.3-kilometre section of the "Gäbihübel" near Bözberg/Riniken. This is a first for Swissgrid - in which Axpo is also involved. It plans the underground cabling for the national grid company.

The voltage increase in the line between Beznau (AG) and Mettlen (LU) from 220 kV to 380 kV is part of Swissgrid's "Strategic Grid 2025". It will help to increase security of supply in the Zurich conurbation and central Switzerland. There is still a 6.5-kilometre-long section between Beznau and Birr, which is now being upgraded and is scheduled to go into operation in the course of 2020.

This video from Swissgrid shows exactly where the pipeline runs through:

On a 1.3-kilometre section of the "Gäbihübel" near Bözberg/Riniken, Swissgrid is laying an extra-high voltage cable of a 380 kV line underground for the first time - a technically challenging project. This video explains exactly how this is done and what has to be taken into account for such a project (German version): 

Planning by Axpo

Axpo is also involved in the pioneering "Gäbihübel" project. It is responsible for planning the project. This business is one of Axpo's milestones in the strategically important third market business.

What are the challenges of this project? Thomas Jödicke, the project manager responsible for the Networks Division at Axpo, mentions the following points:

  • The general conditions: Due to the long planning process - the first plan submissions date back to 1988, when Axpo still owned the line - and due to objections from the local population, the general conditions changed, which led to many project changes. The planning had to be adjusted accordingly.
  • The technical challenges: The 12 cables laid on the section weigh over 300 tonnes in total. In addition, the cables are quite stiff with an outer diameter of 13.5 cm and a cross-section of the aluminium conductor of 2500 m2. Pulling in these cables in the cramped conditions of the transition structures and through the cable protection pipes was correspondingly challenging. In addition, as with any large construction site, there were surprises. For example, the subsoil in the area of the SBB railway line, which had to be crossed under, was much rockier than assumed, so that the drill head had to be replaced once during the drilling of two parallel 38 m long concrete pipes, each with a diameter of 2 m.

Construction work on the "Gäbihübel" started as early as August 2018, and it is expected that the construction of transition structures, cable trenches and overhead line connections will be completed by mid-2020 and the new line will be ready for operation. The current 220 kV overhead line will then be dismantled.

All pictures and videos in this article: @Swissgrid

Swissgrid figures

2006

Swissgrid was created in 2006 in view of the gradual liberalisation of the Swiss electricity market. Since 2008, the Electricity Supply Act (StromVG) has stipulated that the transmission system must be owned by the national grid company.

2009

As the national grid company, Swissgrid has been responsible for the operation, security and expansion of the extra-high voltage grid since 2009.

2013

In this year, Swissgrid took over the extra-high voltage grid - including from Axpo and CKW. Like all the other energy supply companies affected, they were compensated for this and are now the owners of Swissgrid.

31,44 %

This is how high Axpo (Power AG/Solutions AG)'s share of Swissgrid,is.

4,21 %

This is the amount of CKW's stake in Swissgrid. CKW is part of the Axpo group.

6700 km

This is the length of the Swissgrid extra-high voltage grid. This also includes 12,000 pylons. Less than one percent, 42 km, are underground lines.

By way of comparison: Axpo's distribution network (110kV/50kV/16kV) is around 2200 kilometres long and has around 8000 masts. It consists of 82 percent overhead lines and 18 percent cable lines. Axpo is open to both technologies and uses the one that makes the most sense based on objective criteria.

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