Grid project: Underground cable in the Gotthard Road Tunnel

The 220-kV overhead line over the Gotthard Pass was erected in the 1930s and requires a complete overhaul in the coming years. Carrying out this overhaul during construction of the second section of the Gotthard Road Tunnel gives Swissgrid the opportunity to create several synergies, including renewing the 220-kV line between Göschenen and Airolo, bundling the infrastructure inside the road tunnel, and further protecting the landscape in the surroundings of the tunnel.

Your contact for this grid project

Alessandro Cameroni
Alessandro Cameroni

Phone +41 58 580 21 11
info@swissgrid.ch

220 kV underground cabling
220 kV underground cabling
Dismantling
Dismantling
Existing line
Existing line
Substation
Substation

Overview

  • The Swiss Federal Roads Office (FEDRO) is planning a second Gotthard Road Tunnel.
  • The 220-kV Swissgrid line between Göschenen and Airolo, which runs as an overhead line over the Gotthard Pass, will soon be reaching the end of its useful life and needs to be renovated.
  • The construction of second tunnel offers the opportunity to bundle the infrastructure and to lay new extra-high-voltage lines in the service duct that will run under the carriageway.
  • The sections of line between the Airolo substation and the south portal of the tunnel, and between the north portal and the cable end pylon in Göschenen, will also be laid underground.
  • This means that Swissgrid will be implementing the longest underground extra-high-voltage line in Switzerland. Combining this kind of line with a road tunnel is also a first in Europe.
  • Swissgrid has been tasked with checking the options for bundling infrastructure for each grid project. The Gotthard Tunnel meets the criteria for this kind of bundling with regard to deadlines and technical synergies.
  • The costs for the new line between Airolo and Göschenen total CHF 107 million.
  • The works will be carried out in parallel with the construction of the road tunnel and the cabling will be ready for use in 2028.
Project video
Cabling of the 220-kV line at the Gotthard (in German)

Project

Background

The 220-kV high-voltage line between Airolo and Mettlen is crucial for grid stability and redundancy on the north-south axis as well as for the transfer of energy generated in the hydropower plants in the Alps. The Swiss voting public approved the construction of a second Gotthard Road Tunnel on 28 February 2016. The bundling of various infrastructure in and around the Gotthard Tunnel opens up new options for Swissgrid in the renewal of the line.

Extra high voltage in the road tunnel – a trailblazing project

FEDRO is planning to build a new service duct under the carriageway of the new tunnel. Swissgrid plans to lay the extra-high-voltage line between Airolo and Göschenen in this service duct. The plan is a trailblazing project – combining an extra-high-voltage line with a road tunnel is a first in Europe. The laying of such a long cable is a technical challenge which will allow Swissgrid to gain valuable experience. Various federal authorities have investigated the technical feasibility and the various safety aspects of the plans. Swissgrid will comply with all safety regulations and emission limit values at the Gotthard.

Adrian Häsler, Head of Grid Infrastructure
Robert Widmer, Grid Project Manager
Adrian Häsler, Head of Grid Infrastructure
1/2: In the interview: Adrian Häsler, Head of Grid Infrastructure (in German)
Robert Widmer, Grid Project Manager
2/2: In the interview: Robert Widmer, Grid Project Manager (in German)

Use of various cabling technologies

Various technologies are used for cabling the line between Airolo and Göschenen. Between the Airolo substation and the Gotthard Road Tunnel's south portal, the line runs for more than 300 metres in a conduit block laid in the ground. In the interior of the tunnel, in the part of the service duct that lies under the hard shoulder, it will be attached to cable racks. From the north portal, the cables will be re-laid into a subterranean conduit block running 800 metres up to the cable end pylon in Göschenen and directly connected with the overhead line at the pylon that continues on towards Mettlen.

General site plan of the Gotthard line
1/5: General site plan of the Gotthard line
Scheme Gotthard tunnel
2/5: For the cabling of the extra-high-voltage line in the road tunnel, the cables under the hard shoulder of the carriageway are attached to cable racks.
Separate service duct
3/5: The line runs in a separate service duct (known as «WELK») for 17 km
Airolo substation
4/5: The line will be fed from the Airolo substation to the south portal of the Gotthard Tunnel for 300 metres in a conduit block laid underground.
Cable end pylon Göschenen
5/5: From the north portal of the Gotthard Tunnel to the cable end pylon in Göschenen, the line will again runs in a conduit block laid underground.

Bundling of line infrastructures

For each grid project, Swissgrid is obliged to check possible overhead line and cable variants and, in so doing, to evaluate a wide range of technological, environmental, economic and regional planning factors. For each grid project, it has also been tasked by the Swiss Federal Office of Energy (SFOE) with conducting feasibility studies to examine the potential for bundling infrastructure. The Gotthard Tunnel meets the criteria for this kind of bundling. The situation is ideal – but it cannot be replicated exactly in other grid projects.

Easing the burden on the landscape at the Gotthard Pass

According to current schedules, the existing overhead line over the Gotthard Pass will be dismantled from 2029 onwards, following commissioning of the new cable through the Gotthard Road Tunnel. In all, more than 60 high-voltage pylons and 23 kilometres of overhead lines will be dismantled. This will noticeably ease the burden on the landscape surrounding the Gotthard Pass.

Dismantling of the 220-kV line Airolo – Göschenen
Dismantling of the 220-kV line Airolo – Göschenen

Sectoral plan obligation waiver, agreement with FEDRO

The sectoral plan transmission lines (SÜL) is Switzerland's superordinate planning and coordination tool for the construction or extension of high-voltage lines. After consultation with the responsible federal authorities, the SFOE decided that Swissgrid’s Gotthard project meets the criteria for a sectoral plan obligation waiver, as the planning corridor is already in place due to the construction of the tunnel. Following this decision and the conclusion of an agreement with FEDRO, Swissgrid may begin with detailed project planning.

Next steps

The works will be carried out in parallel with the construction of the road tunnel and the cabling is expected to be ready for use in 2028.

Technical details

Voltage of existing line 220 kV
Length of underground line between Airolo and Göschenen 18 kilometres
Length of overhead line to be dismantled 23 kilometres
Cable voltage 220 kV
Number of systems 1 x 220 kV
Number of cables in tunnel 3
Diameter of cable approx. 150 mm
Investment by Swissgrid CHF 107 million (total costs)

Downloads


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