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Nant de Drance to be hooked up to extra-high-voltage grid after commissioning

The TV programme 10vor10 (SRF) broadcast a report on the Nant de Drance pump storage power plant and the expansion of the extra-high-voltage in Valais on Tuesday, 26 April. Following on from the broadcast, Swissgrid and Nant de Drance wish to clarify the situation with regard to the hook-up of the future pump storage power plant to the Swiss extra-high-voltage grid.

The commissioning of the Nant de Drance plant means the extra-high voltage grid between Châtelard (Finhaut) and the Rhone valley will have to be expanded. The project envisages replacing the existing 220-kV cable strand with 380-kV cable strands. This connection to the Swiss extra-high-voltage grid is in general progressing very well.

The hook-up of the power plant is divided into three line sections:

  • Nant de Drance power plant – Châtelard (Finhaut): construction of a new cable line as a connection between the Nant de Drance power plant and the Châtelard substation. The construction work is in progress.
  • Châtelard – La Bâtiaz: construction of a new 380-kV overhead line as a replacement for the existing 220-kV line. The line is under construction.
  • La Bâtiaz – Le Verney (Martigny): construction of a new 380-kV line as a replacement for the existing 220-kV line that crosses the Rhone valley. Planning permission is currently under examination by the Federal Inspectorate for Heavy Current Installations (ESTI).

As from the commissioning of the first part of Nant de Drance in 2018, the pump storage power plant will start transferring its production through to the Rhone valley and, depending on the capacities available at the time concerned, will be able to transfer it further via the extra-high-voltage grid already in existence.

Grid expansion is essential for hydropower in Valais
The tense situation in the extra-high-voltage grid in Canton Valais has been a concern for Swissgrid for several years. The commissioning of Nant de Drance, with its capacity of 900 MW, means the congestion situation already in existence will deteriorate further.

The adaptation of the extra-high-voltage grid, notably the sections between Chamoson and Chippis and between Chippis and Bickigen, is urgent and indispensable. The new overhead line will not only transfer the production of the major Valais hydropower plants but also hook up Valais to the Swiss extra-high-voltage grid already in place.

Swissgrid is assuming that due to the existing congestion, about one-third of the hydropower produced in Valais will not be able to be transferred without the upgrading of the line between Chamoson and Chippis to 380/220 kV. This affects all Valais hydropower plants. Swissgrid has to instruct the power plants affected in certain situations to reduce their production so that it can operate the grid safely.

Nant de Drance is working closely together with Swissgrid to assure the future hook-up of the pump storage power plant to the Swiss extra-high-voltage grid and support Swissgrid in its remit of guaranteeing the safety, operation and further development of the Swiss extra-high-voltage grid.



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