Temporary voltage increase on the Bickigen – Chippis line (Gemmi line)
The Federal Council has enacted various measures to strengthen security of supply in the short term. These measures are ready to be implemented in the coming winter in order to deal with extraordinary and critical situations. They include plans for temporary voltage increases on the Bickigen – Chippis (Gemmi line) and Bassecourt – Mühleberg transmission lines.
To prevent congestion in the transmission system in the coming winter, the Federal Council is allowing a temporary increase in the operating voltage of the two transmission lines between Bickigen and Chippis (Gemmi line) and Bassecourt and Mühleberg from 220 kilovolts (kV) to 380 kV in the period from January to April 2023. This will relieve congestion in the Swiss transmission grid so that the energy from the pumped storage power plants in the Alps can be transported in full to Central Switzerland. In an emergency, Swissgrid can increase the transfer capacity of the extra-high-voltage grid on the basis of criteria set by the federal government.
Test operation at a voltage of 380 kV
Swissgrid is making the necessary technical preparations to operate the Bickigen – Chippis and Bassecourt – Mühleberg lines at a voltage of 380 kV on a temporary basis in the event of a tense supply situation. The measure is only planned for the period between January and April 2023. Test operations will take place on both lines between mid-December 2022 and the end of February 2023. This will involve temporarily changing the voltage of the existing lines from 220 kV to 380 kV. The test operation with 380 kV will only be carried out if the grid situation allows it. The combined test operations will verify the lines from an operational point of view. The two voltage increases influence each other and can shift congestion depending on grid utilisation. The scope and duration of the test operations were approved by the Federal Inspectorate for Heavy Current Installations (ESTI).
Renovation work on the existing line
Swissgrid is making the necessary technical preparations to operate the existing Bickigen – Chippis 220 kV line at 380 kV on a temporary basis. Two 220 kV lines are currently connected via the electricity pylons along the Bickigen – Chippis route. For the temporary voltage increase, all phases will be shifted by one position so that the 220 kV line is on the lowest cantilever. The line systems on four electricity pylons in the vicinity of the Bickigen, Chippis and Wimmis substations have been transposed especially for this purpose. The line lead-ins to the Bickigen and Chippis substations have also been modified. This will minimise the impact on people and the environment as much as possible and ensure that the safety distances between the conductors and the ground, houses or cableways can be observed. The voltage change will slightly increase the noise level. The planned line modifications required for the permanent voltage conversion to 380 kV are currently in the approval process.
Two 220 kV lines are currently connected via the electricity pylons along the Bickigen – Chippis route. A line consists of three phases of alternating current that run one above the other on the three pylon cantilevers. The ground conductor runs at the top of the pylons and is for grounding, which means that it protects against direct lightning strikes. For the temporary voltage increase, the live conductors of the 380-kV line were transposed so that the 220-kV line is on the lowest cantilever. This will minimise the impact on people and the environment as much as possible and ensure that the safety distances between the conductors and the ground, houses or cableways can be observed.