An ultra-pure water system for a hydro-electric generator-motor

In 1979 the North of Scotland Hydro Electric Board and GEC Large Machines Ltd. agreed to co-operate in the development of UK´s first direct water-cooled hydro-electric generator-motor. The machine incorporates seven cooling water circuits, but only two require water of ultra-pure quality, i.e. having a conductivity of less than one micro Siemen per centimetre. These are the stator and rotor field winding circuits in which the cooling water is a direct connection between an electric potential and earth. Consequently the water has to be effectively nonconducting. The author describes the basic components of the system, the basic system concepts, hydraulic design, service experience and comparison with other systems