Several 380 kilovolt overhead lines and underground cables between Nant de Drance and the Rhone plain near Martigny are required to connect the Nant de Drance pumped storage power plant. Without these connections, the energy of around 1 gigawatt cannot be fully transported
As part of this project, the Nant de Drance pumped storage power plant was connected to the extra-high-voltage grid. Connection to the power plant entails three projects:
Construction of a new 2 x 380 kV cable line to replace the existing 220 kV line that runs through the Rhone Valley for a distance of 1.2 km. In operation since 1 April 2022.
Construction of a new 12.5 km 2 x 380 kV line to replace the 220 kV line. In operation since 2018.
Construction of a new 6.5 km 2 x 380 kV cable line in the cave in order to connect the power plant at Nant de Drance with the Châtelard substation. In operation since 2018.
The project consists of three substations: the substation at Nant de Drance (380 kV) located in the cave, the substation at Châtelard equipped with a 380/220 kV transformer, and the substation at La Bâtiaz equipped with 380 kV installations. These three substations have been in operation since 2018.
The Nant de Drance pumped storage power plant connection project involves the construction of several 380 kV overhead and underground lines between Nant de Drance and Martigny in the Rhône valley, Swiss Federal Railways (SBB) 132 kV power lines between Châtelard and Vernayaz, and 220 kV lines between Châtelard and Vallorcine. All these installations are now in operation and the old 132/220 kV Le Châtelard – La Bâtiaz overhead line was dismantled in 2019.
The new SBB line is part of the Swissgrid project for the construction of the extra-high-voltage line that connects the Nant de Drance power plant to the electricity transmission grid. The new line will be overhead from Le Trétien to Les Combasses, then underground from Les Combasses to Vernayaz. Construction work began in July 2022. The cabling of the new SBB line from Les Combasses to Vernayaz and the dismantling of the existing overhead SBB line are part of the compensatory measures linked to the construction of the new Le Châtelard – La Bâtiaz extra-high-voltage overhead line. It should be noted that no work will be carried out on the Le Châtelard – Le Trétien section. This overhead section of the Le Châtelard – Vernayaz SBB line will remain unchanged.
Construction work on the new Le Châtelard – Vernayaz SBB line started in July 2022. The project is expected to be completed by the end of 2024 with the dismantling of the existing SBB overhead line.
Representatives of the main parties involved in the project to connect the Nant de Drance power plant give their views on the subject:
The new 380 kV Châtelard – La Bâtiaz overhead line has been constructed in the Gorges du Trient at an altitude of 800 metres at the edge of the forest. It was brought into service in 2018, enabling the dismantling of the old 220 kV overhead line crossing the village of Salvan. Following the planned dismantling of the old 132 kV SBB overhead line, there will no longer be any overhead electrical line on the Salvan plateau, as the new SBB line will be buried from the lower part of Les Marécottes until Marcot.
The burying of the La Bâtiaz – Le Verney 1.3 km section will eventually enable the dismantling of the old line crossing the Rhone Valley between La Bâtiaz and Le Rosel.
Revitalisation of dry grassland of high natural value in the Salvan municipality. This revitalisation encourages the proliferation of rare or endangered species of flowers.
Creation of ponds in the Salvan municipality to encourage the development of amphibians such as the European common frog, common toad and Alpine newt.
The burden on the population will be reduced by the greater distance of the line to the settlements. The limit of 1 μT for electromagnetic radiation will be complied with across the board, with some areas reporting values well below this limit. The noise burden will be significantly reduced thanks to the use of the latest technologies and triple conductors.
Videos of the construction
