Schematic Arrangement of Hydro-electric Power Station

Schematic Arrangement of Hydro-electric Power Station:

Although a hydro-electric power station simply involves the conversion of hydraulic energy into electrical energy, yet it embraces many arrangements for  proper working and efficiency.The schematic arrangement of a modern hydro-electric plant is shown in given Fig.

Schematic Arrangement of Hydro-electric Power Station

The dam is constructed across a river or lake and water from the catchment area collects at the back of the dam to form a reservoir. A pressure tunnel is taken off from the reservoir and water brought to the valve house at the start of the penstock.The valve house contains main sluice valves and automatic isolating valves.The former controls the water flow to the power house and  the latter cuts off supply of water when the penstock bursts. From the valve house, water is taken to water turbine through a huge steel pipe known as  penstock.The water turbine converts hydraulic energy into mechanical energy.The turbine drives the alternator which converts mechanical energy into electrical energy.A surge tank (open from top) is built just before the valve house and protects the penstock from bursting in case the turbine gates suddenly close due to electrical load being thrown off. When the gates close, there is a sudden stopping of water at the lower end of the penstock and consequently the penstock can burst like a paper log.The surge tank absorbs this pressure swing by increase in its level of water.

Choice of Site for Hydro-electric Power Stations:

The following points should be taken into account while selecting the site for a hydro-electric power station :

(i) Availability of water. Since the primary requirement of a hydro-electric power station is the availability of huge quantity of water, such plants should be built at a place ( e.g ., river, canal) where adequate water is available at a good head.

(ii) Storage of water. There are wide variations in water supply from a river or canal during the year. This makes it necessary to store water by constructing a dam in order to ensure the generation of power throughout the year.The storage helps in equalizing the flow of water so that any excess quantity of water at a certain period of the year can be made available during times of very low flow in the river.This leads to the conclusion that site selected for a hydro-electric plant should provide adequate facilities for erecting a dam and storage of water.

(iii) Cost and type of land.The land for the construction of the plant should be available at a reasonable price.Further, the bearing capacity of the ground should be adequate to withstand the weight of heavy equipment to be installed.

(iv) Transportation facilities. The site selected for a hydro-electric plant should be accessible by rail and road so that necessary equipment and machinery could be easily transported.It is clear from the above mentioned factors that ideal choice of site for such a plant is near a river in hilly areas where dam can be conveniently built and large reservoirs can be obtained.