Between Bassecourt and Mühleberg, the voltage on the existing line will be increased from 220 kilovolts to 380 kilovolts. This will improve the security of supply in Greater Bern when the Mühleberg nuclear power plant is decommissioned at the end of 2019.
The planned decommissioning of the Mühleberg nuclear power plant from 2019 will result in the removal of a large part of the energy feed-in at the 220 kV grid level in Mühleberg. To ensure security of supply in the Greater Berne area, the missing energy must primarily be imported via Northwest Switzerland. To do so, Swissgrid is modernising and reinforcing the grid infrastructure. It is increasing the voltage of the transmission line between Mühleberg (BE) and Bassecourt (JU) from 220 to 380 kV and installing a transformer in the Mühleberg substation. The Bassecourt – Mühleberg extra-high voltage line, with a length of 45 kilometres, was already approved for an operating voltage of 380 kV by the Federal Inspectorate for Heavy Current Installations (ESTI) in 1978, but is currently only operated at a voltage of 220 kV.
The future operation of the line at a voltage of 380 kV requires construction measures to ensure compliance with the applicable limit values for the electric field as well as the Ordinance on Electric Lines and Cables. The grid project's impact on the environment and the landscape are minimal. The noise emissions are below the target figures specified by law. This ensures that the most stringent statutory precautionary values pursuant to the Noise-Protection Ordinance (LSV) are observed.
The Bassecourt – Mühleberg extra-high voltage line, with a length of 45 kilometres, was constructed in 1978. It was approved and set up for an operating voltage of 380 or 220 kilovolts per circuit. Since then, the 380 kV circuit has been operated at 220 kV and the 220 kV circuit has been operated at 132 kV. The circuit operated at 220 kV will be upgraded for a power transmission of 380 kV. This will occur in compliance with the applicable limit values in the Ordinance on Protection against Non-Ionised Radiation (NISV) as well as the Noise-Protection Ordinance.
The increase in voltage will not impact on the landscape. The increase in voltage and modernisation of the line will take place on existing pylons. The line's route will remain the same. Construction work will take place on 54 of the total of 142 pylons.
| 2nd quarter 2017 | Start of the planning approval procedure ESTI |
| 2nd quarter 2019 | Construction permit / tenders |
| 3rd quarter 2019 | Construction and civil engineering / pylon and cable assembly |
| 2020 | Start of operation |
The planned decommissioning of the Mühleberg nuclear power plant (KKM) by no later than 2019 and the corresponding withdrawal of up to 370 MW of feed-in at the 220 kV level at the Mühleberg site results in an additional import requirement to supply the Greater Berne area and Central Switzerland. As a replacement, Swissgrid is planning to install an 800 MVA 380/220 kV transformer in Mühleberg. Connection to the 380 kV grid is expected to occur via the existing Bassecourt – Mühleberg line, which is currently operated at 220 kV. This will also relieve the burden on the transformer in Bassecourt, which could not be operated safely without a line increase in Mühleberg (n-1). The tense energy and grid situation in the winter of 2015/2016 clearly illustrated the urgency of the feed-in into the 220 kV grid, including in the region of Berne.
