La Bâtiaz-Le Verney underground line - Start of work


June 15, 2020 | News

La Bâtiaz-Le Verney Underground Line

Start of work

On the Rhone plain in Martigny, construction has just begun on the third and final section of the ultra-high-voltage line connecting the Nant de Drance pumped-storage plant to the power grid.

Definitively approved by the Inspectorate of Heavy Current Installations (ESTI) in January 2020, this cable project, launched by Alpiq and taken over by Swissgrid in 2013, consists of drilling a tunnel with a diameter of about 2.5 meters at a depth of 12 to 20 meters between different layers of the water table for a distance of 1.2 km. The special geological conditions present at this location in the Rhone plain made this technological feat possible. The Bâtiaz - Le Verney will be the second underground line built by Swissgrid in Switzerland, but the first at a depth of more than one kilometer.

Preparations for the two site areas of Le Verney and La Bâtiaz have been underway since mid-May. Excavation work on the Le Verney shaft will begin in mid-June. The mini-milling machine will be installed in the main yard of the Le Verney site in August, and the tunnel drilling, which will take about eight months, will begin in September 2020, at the same time as the excavation of the La Bâtiaz shaft.

It will take about two years of work before this cable line, which will connect the La Bâtiaz substation to the Chamoson - Romanel very high voltage overhead line in Le Verney, can be put into service.

The Nant de Drance power plant is already connected to the grid.

Swissgrid is responsible for connecting the Nant de Drance power plant to the transmission grid. The power plant will be one of the most powerful pumped-storage plants in Europe and will produce about 2.5 billion kWh per year.

Two of the three sections of the Nant de Drance ultra-high voltage line have been in service since the end of November 2018. These are the 6.5-kilometer underground cable line, which connects the power plant to the Châtelard substation through the power plant access tunnel, and the 12.5-kilometer overhead line connecting the Châtelard and La Bâtiaz substations. Pending the construction of the third and final section, the power plant was connected to the grid with a temporary solution. In 2019, a voltage increase to 380 kV was carried out on one of the two overhead lines at La Bâtiaz - Le Rosel.

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