Page 297 - Electrician - TT (Volume 2)

ELECTRICIAN - CITS

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 given below.

Fig 2

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.

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CITS : Power - Electrician & Wireman - Lesson 106-116