Nant de Drance: advances in the commissioning

The pumped storage project at Nant de Drance entered its commissioning phase in 2018. Thanks to the specialised skills of its staff in managing and operating hydroelectric plants, HYDRO Exploitation was mandated to supervise and monitor this essential stage of the project.

The commissioning stages for the six 150MW pump turbine units, to which the staff from HYDRO Exploitation called out on site have significantly contributed, primarily include:

  • Functional check of the auxiliary systems
  • Functional check of the protection scheme and electric locking systems
  • Energising the transformers and busbars
  • Dry run operational check of the gates and control systems for the units
  • Filling the two water channels
  • First submersion of turbine pumps in water and first rotation by hydraulic power
  • Electrical tests and grid synchronisation tests
  • Turbine load test
  • Pump load test
  • Safety and overall test

Even though the tests on the six units have not been run in full yet, several steps have already been successfully completed. Some of the units have progressed sufficiently in the turbine and pump tests for the plant to actively check the level of water in the Vieux Emosson reservoir and advance it towards its future role as a renewable energy supply.

This test sequence reached a new level in April 2021, with the white water shut-off test of one of the two head valves. This safety test, performed at reduced flow rates, ensures it is fully functional in its capacity to isolate the plant from the upper basin in the event that the water channels are damaged.

HYDRO Exploitation SA
Rue de l’Industrie 10
CP 315 - CH-1951 Sion
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HYDRO Exploitation SA
Rue de l’Industrie 10 CP 750 - CH-1951 Sion +41 (0)27 328 44 11
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