Swissgrid is making the necessary technical and operational preparations to operate the Bickigen – Chippis and Bassecourt – Mühleberg lines at 380 kV on a temporary basis in the event of a critical supply situation. Test operations at a voltage of 380 kV will take place on both lines between 15 December 2022 and 18 January 2023. The measure is only planned for the period between January and April 2023.
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. As the operator of a critical infrastructure, Swissgrid works closely with the federal authorities. Ensuring secure grid operation is an absolute priority for Swissgrid.
To prevent congestion in the transmission system, 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 coming winter. This measure will enable Swissgrid to relieve congestion in the Swiss transmission grid and make it possible for the energy from the pumped storage power plants in the Alps to be transported in full to Central Switzerland.
Test operation at a voltage of 380 kilovolts
The voltage increase is only planned for the period from January to April 2023, and the federal government has set out corresponding criteria. Test operations will take place on both lines between 15 December 2022 and 18 January 2023. This will involve temporarily changing the voltage of the existing lines from 220 kV to 380 kV. The 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 Bickigen – Chippis line
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.
Swissgrid had already successfully tested the operation of the Bassecourt – Mühleberg line and the transformer in Mühleberg at a voltage of 380 kV in autumn 2021. This means that Swissgrid will be technically ready to operate this line at 380 kV on a temporary basis in the event of a critical supply situation. The planned construction measures necessary for the permanent voltage change to 380 kV are being carried out in two stages from mid-August 2022 until the end of 2023.