Plants Based on Availability of Head

1. Hydro power plants are called as low head plants in case the available water head is less than 30 meters. In such plants the water is stored by constructing a dam across a river and the power plant is constructed at the base of the dam on the downstream side.
2. The excess water available is allowed to flow over the dam itself.
3. Such plants use Francis, propeller or Kaplan type of hydraulic turbines.
4. A low head plant is represented in Figure A.
5. In these plants no surge tank is used since the plant is located near the dam itself.

Figure A

Medium Head Plants :

1. Medium head plants are similar to low head plants but they work under a head of 30 m to 100 m.
2. Such a plant is shown in Figure B These plants generally use Francis turbine.

1. Hydro power plants are called high head plants in case the available water head is more than 100 meters.
2. In such plants, water is stored at high head due to rain or melting of snow.
3. Water is usually available throughout the year.
4. Such plants use Francis turbine upto the head of 300 m and Pelton wheel when head available is more than 300 m.
5. Such a plant has been shown in Figure C.