HYDRO-ELECTRIC POWER STATION

HYDRO-ELECTRIC POWER PLANT

 A generating station that utilizes the potential energy of water at a high level for the generation of electrical energy is known as a hydroelectric power station.

Hydroelectric power stations are generally located in hilly areas where dams can be built conveniently and large water reservoirs can be obtained. In a hydroelectric power station, the water head is created by constructing a dam across a river or lake. From the dam, water is led to a water turbine. The water turbine captures the energy in the falling water and changes the hydraulic energy (i.e., a product of head and flow of water) into mechanical energy at the turbine shaft. The turbine drives the alternator which converts mechanical energy into electrical energy. Hydroelectric power stations are becoming very popular because the reserves of fuels (i.e., coal and oil) are depleting day by day. They have the added importance for flood control, storage of water for irrigation, and water for drinking purposes.

Schematic Arrangement of Hydr-electric Power Station

 Although a hydroelectric power station simply involves the conversion of hydraulic energy into electrical energy, yet it embraces many arrangements for proper working and efficiency.

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 is brought to the valve house at the start of the penstock. The valve house contains main valves and automatic isolating valves. The former controls the water flow to the powerhouse and the latter cuts off the supply of water when the penstock bursts. From the valve house, water is taken to a water turbine through a huge steel pipe known as a 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 is built just before the valve house and protects the penstock from bursting in case the turbine gates suddenly close due to the 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 an increase in its level of water.