Power increase improves electricity supply in the Untere Aaretal

Axpo is increasing the voltage on its power lines in the Untere Aaretal in the canton of Aargau from 50 to 110 kilovolts in order to secure the future energy supply. In preparation for the voltage increase, various works are being carried out on the high-voltage lines and substations. The region will thus benefit from a sustainable energy supply.

The expansion of the grid infrastructure is the basis for a secure electricity supply. In order to meet the growing demands, Axpo is successively increasing the operating voltage of its supraregional distribution grid from 50 to 110 kilovolts (kV). A higher voltage ensures a more efficient transport of electricity. As part of the final phase of these voltage conversions and modernisation measures in the Untere Aaretal region, several projects are currently being implemented:

• Beznau-Klingnau line: The power line between Beznau and the Klingnau power plant will be laid almost entirely in the ground. On the northern bank of the Aare at Beznau to the Klingnau substation, the 4.7 km long section along the Klingnau reservoir will be wired mainly along paths and roads. The Aare landscape requires special consideration of environmental aspects, bird protection (breeding periods, migratory bird resting periods), amphibian protection and soil protection. With the dismantling of the existing overhead line section, the local recreation area around the Klingnau reservoir will be enhanced.
  
  Civil engineering for the cable conduit block started on 22 May 2023.
  
  The cycle path near the dog racing track will be temporarily relocated directly adjacent during the ongoing construction work. There may be isolated restrictions to the passage of dirt roads. The construction activities will continue until 2024.
• Beznau-Rekingen line: The conversion of the existing overhead line between Beznau and Rekingen began on 22 May 2023 with the setting up of the construction site and the civil engineering work for the new mast foundations. From July onwards, the overhead line work will follow together with the line partner AEW Energie AG, which is expected to last until autumn 2023. The voltage changeover is being closely coordinated with AEW as the operator of the medium voltage grid.
• Klingnau-Rekingen line: The existing overhead line from the Klingnau hydropower plant to the Rekingen-Eicheracher substation has already been largely converted for 110 kV operation. The remaining section from the Klingnau power station to the Koblenzer fields and a short overhead line section before the Rekingen-Eicheracher substation still have to be converted for operation at 110 kV.
  
  From the Klingnau power plant to the future gravel extraction area Hard/Härdli, the line route will be cabled in a pipe block about 1.8 km long. Two new cable terminal poles are required to connect the cable line to the existing overhead line. The cantonal road will be undercut by means of a flush borehole and the railway lines by means of underpressure, so that traffic restrictions can be greatly minimised. Axpo is bundling infrastructure measures with AEW and the municipality of Klingnau for this project.
  
  The civil engineering work starting from the hydropower plant for the cable conduit block began at the beginning of May 2023 and will be completed by autumn of this year. Subsequent work, such as the installation of the new 110 kV cables, will be carried out in 2024. Once the Klingnau substation has been completed, the transmission line will be connected to the new switchgear, which is also currently being built, and put into operation. The overhead line section upstream of the Rekingen-Eicheracher substation will be converted to 110 kV operation over the last seven spans near Rekingen. The start of construction is currently planned for 2024 or 2025.
• Leibstadt-Klingnau line: The line between Leibstadt and Klingnau power station will also be converted from 50 to 110 kV. The existing infrastructure will continue to be used. The one-kilometer-long underground cable from Leibstadt will be replaced in the existing pipe system. Following the underground cable, the overhead line section up to Klingnau power station will be equipped with new insulator chains. The road network along the line will be used by various construction machines during the conversion work from August 2023 to January 2024. Minor restrictions on road traffic are unavoidable. The adjacent country lanes will be obstructed or closed for a short time.
• Villnachern substation: The existing switchgear of the Villnachern substation in the building of the Wildegg-Brugg hydropower plant is being replaced due to its age and the voltage changeover. The new 110 kV switchgear will be housed in a new building next to the wastewater treatment plant in Villnachern. The planning work for this is in progress.
• Beznau substation: The Beznau substation will be completely renewed due to its age and the voltage will also be increased from 50 to 110 kV.
• Klingnau substation: In the Klingnau substation, the outdoor switchgear is being replaced by a new switchgear due to the voltage changeover and for age reasons, and is being constructed in a new space-saving building next to the Aare power plant Klingnau. Construction work began in February and is expected to be completed by the end of 2023. This will be followed by assembly, commissioning and dismantling of the facilities in 2024.

As soon as all conversion measures in the region have been completed, the overhead line sections that are no longer needed will be dismantled.

Consultation with authorities, communities and interest groups

Conversion measures are always carried out after careful examination and consideration of numerous criteria. In addition to the applicable electricity supply and environmental legislation, these also take into account technical aspects of feasibility as well as questions of spatial development, environmental compatibility and economic efficiency. Furthermore, regional and local conditions must be taken into account. Within the framework of this overall assessment, the best possible solution is determined in consultation with authorities, municipalities, landowners and interest groups, such as nature conservation, water protection and bird protection. Each project undergoes an official planning approval procedure with the Federal Inspectorate for Heavy Current Installations ESTI.