Variable Speed Turbines


The application of variable-speed generation schemes to hydroelectric power plants offers a series of advantages, based essentially on the greater flexibility of the turbine operation in situations where the flow or the head deviate substantially from their nominal values. Specifically, the following aspects may be emphasized:

  • In general, for variations in head and flow, the variable speed option would be more advantageous.
  • Running the turbine at a variable speed avoids cavitation and draft tube oscillations.
  • In hydro plants with reservoir, the operating range of head variations can be increased, thus reducing the need for flooded areas.
  • In the run-of-the-river hydro plants, the continuity of operation may be increased because of the higher range of allowable flows in the turbine.
  • A simulation performed on a run-of-the-river small hydro plant confirms that significant gains in generated energy may be obtained.
Variable Speed Francis and Propeller turbines


  • Higher Production (kWh)
  • Increased income from the Power Plant
  • Simple design, less operational problems, cheaper maintenance and less loss of production due to failures
  • High efficiency over the whole operational area