The water held by the Grande Dixence dam is transformed into electricity over two levels. The first level is the underground Fionnay plant. A 9 km tunnel with a slight gradient was constructed to transport the water to its turbines.
The Bieudron power plant is Switzerland’s most powerful hydroelectric power plant. It was built underground next to the Nendaz plant between 1993 and 1998, in order to more than double the output of the Grande Dixence complex. Within just a few minutes, it can feed in the equivalent output of a nuclear power station into the grid! The Bieudron plant holds three world records: for the height of its drop (1883 m), for the output of each Pelton turbine (3 x 423 MW) and for the output per pole of the alternating current generators (35.7 MVA).
After passing through the turbines of the Fionnay power station, the water from Grande Dixence is channelled through a 16 km headrace tunnel into the Péroua compensating basin, 1,000m above the Nendaz power plant. From there, it passes through a pressure shaft down to the Pelton turbines.