Schematic Arrangement of Hydro-electric Power Plant
Although the hydro-electric power station does the purpose of converting hydraulic energy into mechanical energy it requires much arrangements for proper working and efficiency.The schematic arrangement of a modern hydro-electric plant is shown below.
The dam is constructed across a river,lake or any other water body.Water from the catchment area collects at the back of the dam to form reservoir.A pressure tunnel is taken off from the reservoir and water brought to valve house at the start of 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 the water supply 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 converts hydraulic energy into mechanical energy.the turbine drives the alternator which converts mechanical energy into electrical energy.
A surge tank(open from the top)is built just before the valve house and protects the penstock from bursting in the case the turbine gates suddenly close(the opening and closing of governor depends on electrical load)due to electrical loading being thrown off.When the gate close,there is a sudden stopping of water at the lower end of penstockand consequently the penstock can burst like a paper log.The surge tank absorbs this pressure swing by increase in its level of water.