The turbine is the heart of an hydroelectric facility because the type of turbine determines the overall layout of the facility, and the type of turbine is itself determined by the rate of water flow and the height of the water drop at a given site. The turbine must also rotate at a speed that conforms to a synchronous generator speed.  Turbine designs can be grouped into three categories.

  The figure shows that efficiency characteristics vary considerably between o­ne type of turbine and another. This is an important issue in design of a power station. Usually, the engineer evaluates the merits of various arrangements for the site before deciding o­n the best design. The engineer might compare.