The 27-kilometre-long line section between Innertkirchen (BE) and Ulrichen (VS) is to be replaced and increased from 220 to 380 kilovolts. Swissgrid has developed various technically feasible planning corridors. They include both overhead line and cable variants. The multifunctional Grimselbahn Tunnel is one of these cable variants.
Most of the around 27-kilometre high-voltage line between Innertkirchen and Ulrichen, which passes over the Grimsel Pass, is over 60 years old and must be brought in line with the current state of the art. At the same time, the voltage will be increased from today's 220 kilovolts (kV) to 380 kV throughout. The increase in power of the line between Mettlen (LU) and Ulrichen is an important project in Swissgrid's «Strategic Grid 2025».
The expansion of electricity production from hydropower is a central pillar of the Energy Strategy 2050; the replacement and power increase of the line between Innertkirchen and Ulrichen is important for transportation of the growing electricity production from the cantons of Berne, Valais and Ticino to the conurbations in the Swiss Central Plateau. The distribution of energy flows along several north-south axes also increases grid stability. In view of the federal government's energy strategy, the capacity increase is necessary to transport the growing electricity production from hydropower in the cantons of Bern, Valais and Ticino to the Swiss Central Plateau and to increase security of supply throughout Switzerland in the long term.
At the beginning of July 2020, Swissgrid submitted an application to the Swiss Federal Office of Energy (SFOE) for the definition of a planning corridor between Innertkirchen and Ulrichen in the Federal Transmission Lines Sectoral Plan. The first step was for Swissgrid to develop various corridor variants; these are geographical areas in which a route with a specific transmission technology—overhead line or underground cable—can be implemented once the project moves forward. Swissgrid has developed three main corridors, some of which include sub-variants:
The corridor runs underground from Innertkirchen to Obergoms—either in a new tunnel that will be built until Handegg and from there in mostly existing tunnels or in the multifunctional Grimselbahn Tunnel, which runs from Innertkirchen to Oberwald. Between Oberwald and Ulrichen, corridor variants are possible as overhead lines or underground cables.
The corridor runs to Handegg as an overhead line. Afterwards, the line will be laid as an underground cable in mostly existing tunnels all the way into Obergoms. There are five options for the tunnel portal on the Valais side between St. Niklaus and Ulrichen. From this point, the corridor is continued as an overhead line.
The overhead line corridor runs between Innertkirchen and Handegg in the area of the valley floor. It runs through high alpine terrain from Handegg to the east of Oberwald. On the Valais side of the Grimsel, the corridor crosses Obergoms in the St. Niklaus area and runs to Ulrichen on the southern side of the valley.
Swissgrid is aware of the advantages of bundling large, linear infrastructures, particularly in the area of landscape protection. It is examining the corresponding synergy potential in all line projects. With the proposal to combine a railway tunnel and an underground cable, a variant on the Grimsel is now available that is technically feasible and is suitable for approval. Grimselbahn AG has demonstrated this in a feasibility study (2015) and in an in-depth technical analysis (2019). For further information, visit www.grimseltunnel.ch
All the corridor options submitted by Swissgrid have one thing in common: they all reduce the burden on settlements in the Innertkirchen, Guttannen and Obergesteln areas. Today's 220 kV line runs partly through the middle of these villages and restricts their settlement development. This cable will removed in all variants.
Each of the variants submitted by Swissgrid has specific advantages and disadvantages in the areas of regional planning, environment, technology and economic viability. The SFOE is setting up a monitoring group to assess and evaluate these aspects as objectively as possible. It will conduct a comprehensive balancing of interests and recommend one of the corridor variants for implementation. This recommendation then goes into public consultation. At the end of the process, the Federal Council—on the basis of the monitoring group's recommendation and the results of the consultation—will decide on the planning corridor and the transmission technology between Innertkirchen and Ulrichen. Swissgrid will then draw up a corresponding construction project.
Swissgrid is planning a new line lead-in into the Innertkirchen substation to relieve the village of the current overhead lines. In addition, Swissgrid is replacing the ageing outdoor switchgear in the Innertkirchen substation with a modern, gas-insulated switchgear (GIS)—the largest in Switzerland.
Today Innertkirchen is heavily burdened by three overhead lines running through the middle of the village (Innertkirchen – Mettlen, Innertkirchen – Bickigen, Innertkirchen – Wimmis). Swissgrid is therefore looking into alternative routes for bundling the lines from the north to the Innertkirchen substation in an underground tunnel. Swissgrid has submitted this lead-in to a separate sectoral planning process in order to avoid any delays. The following corridor variants are currently being examined:
The «Bergschwendi» corridor envisages laying all overhead lines from the Innertkirchen substation to the northern edge of the planning perimeter in the ground. In the area where the Gadmerwasser is crossed, the three lines run first in a joint tunnel and then to the Innertkirchen substation in an existing underground tunnel.
The «Felskante» corridor provides for an underground cable route of 1.6 kilometres in length. The remaining overhead lines in the corridor have a length of 0.9 kilometres. The overhead lines merge into a joint tunnel at the transition structure north of the Gadmerwasser. They then run as underground cables to the Innertkirchen substation in an existing underground tunnel.
The «Wimmiserleitung Waldrand» corridor is a combination of the «Bergschwendi» and «Felskante» variants. The line Innertkirchen – Wimmis (Wimmiser line), which is closest to the buildings, will be laid underground in the Äppigen area. The remaining overhead lines in the Äppigen area will remain in this variant. Dismantling the Wimmiser line entails a significant reduction of electromagnetic fields in the hamlet of Äppigen.
These remaining overhead lines merge into a joint tunnel at the transition structure north of the Gadmerwasser. They then run as underground cables to the Innertkirchen substation in an existing underground tunnel.
Swissgrid plans to put the new line lead-in into operation by the end of 2026. The overhead lines running through Innertkirchen will probably be dismantled by the end of 2027.
Swissgrid is currently building a modern, gas-insulated 220 kV switchgear (GIS) at the Innertkirchen substation—the largest of its kind in Switzerland. It is being prepared for all technical variants of the new line from Innertkirchen (underground cable or overhead line). Housed in the building of the substation, the modern GIS system replaces the ageing outdoor switchgear, which further relieves the burden on Innertkirchen's landscape. The GIS system is set to be commissioned in Autumn 2020. The existing outdoor switchgear will be dismantled by April 2021.
