Types of Hydro-electric power plants on the basic of available head

         Types of Hydro-electric power plants on the basic of available head

The hydro electric power plants are mainly classified in to three types on the basis of available head of water, namely.

1.     High head plants.

2.     Medium head plants.

3.     Low head plants

High Head power plant:

If the head of water for power generation exceeds 100 meters, Then this type of power plant is known as head power plant. In this type of plant the water from the main reservoir is first carried by a tunnel up to surge tank and then it is carried through penstock (steel pipe) to the power house. In this system the surge tank will reduce theater hemmer effects on the penstock. 

                    

If the head available is above 500 meters then pelt on wheel turbine and for lower head Francis turbines are employed. Figure shows the high head power plant.

Medium Head plant

If the head of water lies between 30 to 100 meters then this type of power plant is known as medium head plant. The forebay is provided at the beginning of penstock serves as water reservoir. In this type of plants the water is generally carried in open canals from main reservoir to the forebay and then to the power house through the penstock. The forebay itself works as surge tank in this plant. In this type of plants Francis turbines are used. A medium head hydro-plant show in below fig. 

Low Head plants

If the head of water available is below 30 meters then this type of power plant is known as low head plant. In this type of plants a dam is built across the river to create the necessary head of water. The excess water is allowed to flow over the dam itself. Franc's is (or) Kaplan vertical shaft type turbines are used. A low head plant is as show fig.