Commissioning and operation of variable speed units at the 1000 MW Linthal pumped-storage plant

The Linthal 2015 scheme in Switzerland is equipped with single stage pump-turbines operating with the highest head in Europe; between 560 and 709 m. The units have large double-fed asynchronous motor-generators and power converters allowing for a power variation in the pump mode of approximately 30 per cent and minimum power generation, also at 30 per cent, in the turbine mode. This paper reports on recent progress and lessons learnt during commissioning and trial operation of the first 250 MW variable speed unit.