The type of machinery turns in one direction to pump the water up and the other to bring it down again. The machines are big and heavy. Every time they start up, the alternator's polar masses turn. “It's as if a wire were being continually bent,” explain the engineers Andrés Muñoz and Antonio Velasco, who are responsible for the Endesa power plant. Every so often the material has to be checked for signs of fracture. The last check was made three years ago, and with the help of the University of Stuttgart (Germany), the remaining useful life of the power station was predicted, with a fixed number of uses that could not be exceeded for safety reasons.
In the light of this a project was carried out with the help of the manufacturers of the turbines, Alstom, which involved removing and replacing the central body of the rotors (the cylindrical metal supports) where the polar masses rested. To do that, they had to remove the four alternators. Endesa invested five million euros in this recent project. Ten years ago another 15 million euros were spent to repair the stator coil, the stationary part of the alternators. After this upgrade, it is predicted that the hydro power station is ready to operate for at least another 35 years.