The voltage between Bassecourt and Mühleberg may be increased

The increase in capacity of the high-voltage transmission line between Bassecourt and Mühleberg envisaged by Swissgrid does not violate federal legislation on environmental protection and line construction. The Federal Administrative Court has concluded that the legally established limits are being observed.

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The high-voltage transmission line between Bassecourt and Mühleberg was constructed between 1976 and 1977 and approved for operation with a voltage of 380 and 220 kilovolts (kV). Since it entered into operation, the 380 kV section has been operated at 220 kV and the 220 kV section at 132 kV.

Due to the decommissioning of the Mühleberg nuclear power plant at the end of 2019, the production loss associated with this and its impact on the Swiss transmission network, the network company Swissgrid Ltd was forced to increase the capacity of the said line by increasing the voltage. One of the aims of this is to secure electricity supply in the Bern region. Specifically, the 220 kV line section is to be increased to an operating voltage, approved at the time of construction, of 380 kV, while the 132 kV line section is to continue at the same voltage. This increase of the operating voltage would require several accompanying measures, such as an on-site increase in the cable winch tension, the installation of phase spacers, phase optimisation, and the uncontested adjustment of the cable routing near Bassecourt. The Swiss Federal Office of Energy (SFOE) granted the necessary planning approval for this in August 2019. The municipalities of Valbirse and Seedorf as well as 36 private individuals appealed to the Federal Administrative Court (FAC) against this decision.

Limits are being observed
The FAC finds that the increase in voltage does indeed increase the strength of the electrical field and the noise generated by the power lines. However, due to the relatively minor construction measures envisaged by the project that are not legally considered to be a significant change to the installation, the limits established by the environmental protection legislation are able to be upheld.

A distinction must be made between the electrical field and the magnetic field generated by electrical lines, whose non-ionising radiation may be harmful to health. In the planning approval procedure, the SFOE determined the strength of the current to be 1490 amps, as before, meaning that the magnetic field with phase optimisation stays the same even if the voltage increases and is thus legally compliant. The SFOE also obliged Swissgrid Ltd to monitor the operating data over the course of ongoing operations.

Overall, the increase in voltage is within the permissible limits. In addition, the FAC rules that the SFOE was right to reject the underground installation of the high-voltage transmission line or its relocation outside of the settlement areas of the municipalities of Valbirse and Seedorf. It therefore dismisses the three appeals, which were combined into a single judgment.

This judgment may be appealed to the Federal Supreme Court.

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