Each of the submitted versions has specific advantages and disadvantages with respect to regional planning, the environment, technology and economic viability. Overhead lines offer advantages in efficiency and the duration of repairs, while underground cables have advantages with regard to aesthetics, scenery and acceptance. On the other hand, the technical challenges in the extra-high-voltage grid increase with the number of sections of cable that are laid underground. Besides this, the costs of a line section are higher when underground cables are used.
The tunnel version incorporates the use of existing power plant tunnels for the underground cabling as well as the construction of new tunnels. Swissgrid is aware of the advantages of bundling large, linear infrastructures, especially with regard to landscape conservation, and checks for potential synergies in all its line projects. The proposed combination of the rail tunnel and underground cable is a sub-version that takes account of the particular circumstances that exist for the Grimsel Pass. In a feasibility study (2015) and in a detailed technical analysis (2019), Grimselbahn AG showed that the project involving a multi-functional tunnel is fundamentally technically feasible and has the potential of attaining approval.
Considerable relief for residential areas
The one thing common to all of the potential corridors submitted by Swissgrid is the relief they provide for residential areas in and around Innertkirchen, Guttannen and Obergesteln. In some cases, the existing line leads right through the centre of these villages and restricts their development. By contrast, the new line will bypass the residential areas – irrespective of the transmission technology used. Besides this, the burden on Innertkirchen will be eased by two additional Swissgrid projects, the planning and technology of which are closely linked to the Innertkirchen – Ulrichen project.
Firstly, Swissgrid is planning a new line connection for the Innertkirchen substation. Three overhead lines currently run through the centre of the village from the north. In future, they will be bundled and routed to the substation in an underground tunnel. The associated corridor versions are currently being reviewed in a separate sectoral plan process. Swissgrid is planning to commission the new line connection by the end of 2026 and then dismantle the overhead lines that pass through Innertkirchen by the end of 2027.
Secondly, Swissgrid will be replacing the outdated outdoor switching substation in Innertkirchen with a modern gas-insulated substation (GIS). It will be prepared for all technical versions of the new line between Innertkirchen and Ulrichen (underground cable or overhead line). The new 220 kV GIS – the largest in Switzerland – is expected to start operation in the autumn of 2020 and the existing outdoor switching substation will be dismantled by April 2021.
In dialogue with the public
Dialogue with the citizens, municipalities, authorities and associations is very important to Swissgrid. Swissgrid and Grimselbahn AG will be holding information events on the project on Thursday, 17 September in Innertkirchen (BE) and on Friday, 18 September in Oberwald (VS).