Grid project Obfelden – Samstagern

Swissgrid is upgrading the 150-kilovolt line between Samstagern, Thalwil, Waldegg (Zurich) and Obfelden to 220 kilovolts (kV) in stages. By doing so, Swissgrid will strengthen the security of supply for the city of Zurich and the western shore of Lake Zurich in the long term.

Your contact for this grid project

Joshu Jullier
Joshu Jullier

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

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

Overview

  • The current 150 kV line between Samstagern (Richterswil), Thalwil, Waldegg (Zurich) and Obfelden operated by the electricity company of the city of Zurich, ewz (Elektrizitätswerk der Stadt Zürich), will be upgraded to 220 kV in stages.
  • Connecting the Thalwil and Waldegg (Zurich) substations to the extra-high-voltage grid will strengthen the security of supply for the city of Zurich and the western shore of Lake Zurich.
  • The work on the six sections and the dismantling of the existing lines is expected to take until 2030. The construction costs of the entire project amount to around CHF 170 million.
  • Construction work on the first section will begin in the Gattikon area in October 2022, and is expected to continue until the end of 2023. Afterwards, the current line, which partly runs through local recreation and residential areas, will be dismantled.

Project

Initial situation

Currently, the greater Zurich area is much better connected to the extra-high-voltage grid from the north than from the south. In the north, the 220 kV grid reaches as far as the city of Zurich via the Auwiesen and Fällanden substations. In the south, on the other hand, the Obfelden and Samstagern connection points are only connected to the city boundary via one 150 kV line each. Swissgrid is therefore planning to upgrade the line between Samstagern (Richterswil), Thalwil, Waldegg (Zurich) and Obfelden to 220 kilovolts (kV) in six sub-projects. The upgrade is part of Swissgrid’s Strategic Grid.

Why the project is important

With the connection of the Thalwil and Waldegg substations to the extra-high-voltage grid and the reinforcement of the lines between Obfelden and Samstagern, the extra-high-voltage grid will also reach the city of Zurich from the south. This will increase the transport capacity as well as the security of supply for the city and the entire Zurich region. The project is also very important for Swiss Federal Railways (SBB), as two 132 kV railway power lines will be carried on one of the sections. These two lines will connect the Sihlbrugg substation with the Zurich substation, significantly improving the security of supply for SBB in the greater Zurich area.

The extension of the high-voltage lines in the Zurich South area will strengthen the security of supply for the city of Zurich and the entire region.

The six sections of the project

The expansion of the line between Samstagern (Richterswil), Thalwil, Waldegg (Zurich) and Obfelden consists of six sub-projects. The construction costs of the entire project amount to around CHF 170 million. The work on the various sections and the dismantling of the existing line sections is expected to take until 2030.

Die sechs Abschnitte des Projekts zwischen Samstagern, Thalwil, Waldegg (Zürich) und Obfelden.
The six sections of the project between Samstagern, Thalwil, Waldegg (Zurich) and Obfelden.

Samstagern substation connection

At the Samstagern substation, modifications to the substation and line must be implemented in order to connect the line, which is currently operated at 150 kV, to the 220 kV grid.

Samstagern – Schweikrüti (Thalwil)

Between Samstagern and Schweikrüti (municipality of Thalwil), the line is already designed for extra-high voltage, but is only operated at 150 kV. Swissgrid is planning to increase the voltage to 220 kV. This will probably not require any major structural measures on the line.

Schweikrüti (Thalwil) – Kilchberg

A legally binding construction permit for a new overhead line along a modified route has been issued for this section. The construction of an underground cable is not possible on this section because two 132 kV SBB lines will be carried on the same pylons as the Swissgrid line. For technical reasons, the SBB lines must necessarily run above ground. The Thalwil substation, which is important for supplying the western shore of Lake Zurich, will be connected to the Schweikrüti – Kilchberg section. As soon as the Thalwil substation is connected to the extra-high-voltage grid, Axpo’s 110 kV Obfelden – Thalwil line (known as the Albis line), which served as an alternative measure, will be dismantled. This will substantially reduce the burden on the residential areas of Langnau and Gattikon.

Kilchberg – Waldegg (Zurich)

The new line from Kilchberg to Frohalp near Zurich Manegg station will be built underground along the motorway. It will then be routed through the conduit blocks built during the construction of the two tunnel tubes of the Uetliberg tunnel before continuing to the Waldegg substation via a two-kilometre underground tunnel (with a diameter of approx. four metres).

Waldegg (Zurich) underground substation

Swissgrid is planning a new underground substation with ewz. From here, electricity will flow into the city of Zurich. The substation will be built underground to minimise the impact on the landscape and the visibility for the neighbouring residential area.

Obfelden – Waldegg (Zurich)

The line between Obfelden and Waldegg (Zurich) is already designed for extra-high voltage, but is only operated at 150 kV. Swissgrid plans to increase the voltage to 220 kV by 2027, so that the Waldegg substation can then be connected to the transmission grid. This will probably not require any major structural measures on the line.


Start of construction on the first section

Construction work on the section between Schweikrüti and Kilchberg will start with the erection of six new pylons in the Gattikon area. The foundations will be built first, starting in October 2022. This will require 2,200 tonnes of concrete. The construction and installation sites will be set up as early as September. Concrete and construction machinery for the pylon foundations will be delivered in the area of Waldweiher and Gattikerweiher, and excavated material will be removed from the same place. It will be transported via the forest road towards Waldweier rather than via Schweikrütiweg to avoid the residential areas in Gattikon. We kindly ask for your understanding for the resulting construction noise and transport.

Erection of the construction and installation sites for the Schweikrüti (Thalwil) – Kilchberg section will begin in the Gattikon area in September 2022. Construction work will then start in October.

At the end of 2023, the new line between Schweikrüti and Sihlhalden will initially be put into operation at 150 kV, so that the old line on this section can be dismantled in 2024. This will free the Gattikerweiher recreation area and the residential area from the line.

1/4: The dismantling of the old line in Gattikon will provide noticeable relief for the residential area.
2/4: The dismantling of the old line in Gattikon will provide noticeable relief for the residential area.
3/4: The removal of the old line in Gattikon will free Gattikerweiher from the line.
4/4: The removal of the old line in Gattikon will free Gattikerweiher from the line.

The second part between Sihlhalden and Kilchberg will be built in 2025. Here, the new line will largely run along the existing route. According to current planning and assuming optimal project progress, the line from Samstagern to Thalwil will be put into operation at extra-high voltage at the end of 2025. Axpo’s 110 kV Obfelden – Thalwil line (known as the Albis line) can subsequently be dismantled. The upgraded line between Thalwil and Waldegg (Zurich) is scheduled to go into operation in 2030.


Timetable for the Schweikrüti – Kilchberg section, assuming optimal project progress.

Downloads


Further information

  • Approval process

    Swissgrid is responsible for the project planning for and implementation of the transmission lines.

    Learn more

  • Emissions

    It is hard to imagine our daily life without the numerous electronic gadgets and tools. However, we are much less aware that electric and magnetic fields are formed everywhere electricity is present: including in the generation, transmission and distribution of electric energy.

    Learn more

  • Grid technologies

    The decision on whether to install a high-voltage line as an overhead line or as an underground cable is based on objective criteria. That's why Swissgrid checks the cable and overhead line options for every grid project.

    Learn more

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