Hydro Power Plant - Electrical C & V


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31 March 2020

Hydro Power Plant

Hydro Power Plant

In the Hydroelectric station kinetic gravity energy developed due to gravity, the water falls from the high to the lower head to rotate a turbine to produce electricity. The potential energy stored in water at the upper water level will be released as kinetic energy when it falls to the lower water level. This turbine rotates when the low water hits the turbine blade. Hydroelectric power stations are usually built in hilly areas to achieve a head differential of water. On the way to the river in hilly areas, an artificial dam is constructed to make the required water head. From this dam, water flows downstream in a controlled manner to the turbine blades. As a result, the turbine rotates due to the force of water applied to its blades and hence the alternator rotates since it is coupled with the alternator shaft.

Hydro Power Plant
Hydro electric power plant

The main advantage of an electric power plant is that it does not require any fuel. It requires only a water head which is naturally available after the construction of the required dam.

No fuel means no cost of fuel, no combustion, no generation of any type of gases, and no pollution in the atmosphere. Due to the absence of fuel combustion, the hydroelectric power plant itself is very clean and hygienic. Additionally, it does not cause any pollution to the atmosphere. Even from a creative point of view, it is simpler than any thermal and nuclear power plant.
The constructive cost of hydroelectric power plant is probably higher than other conventional thermal power plant because of the construction of a huge dam in the flowing river. In addition to the construction cost in a hydroelectric plant, the engineering cost is also high. Another disadvantage of this plant is that it cannot be constructed anywhere according to load centers.
So, long transmission lines are required to transmit the generated power to the load centers.
Thus transmission costs can be quite high.

Despite that, the water stored in the dam can also be used for irrigation and other similar purposes. Sometimes by constructing such dams in the path of the river, the occasional flood in the river flow can be controlled to a great extent.
Hydroelectricity factory

Hydro Power Plant
Hydro electric power plant

Only six primary components are required to build a hydroelectric plant. These are dams, pressure tunnels, surge tanks, valve houses, penstock and power plants.
The dam is an artificial concrete barrier constructed in the way of the river. The catchment area behind the dam forms a huge reservoir.

The pressure tunnel carries water from the dam to the valve house.
In the valve house, there are two types of valves available. The first is the main sluiling valve and the second is an automatic isolating valve. The tilt valve controls the water flowing to the drift and the automatically separating valve stops the flow of water when the electrical load is suddenly thrown from the plant. The automatic isolating valve is a safety valve that plays no direct role in controlling the flow of water in the turbine. It only operates during an emergency to protect the system from burst out.

The penstock is a steel pipeline of suitable diameter between the valve house and the powerhouse. Water only flows through this penstock from the upper valve house to the lower powerhouse.
Water turbines and alternators are connected in the power station, with transformer and switchgear systems connected to facilitate the generation and then power supply.
Finally, we will come to the surge tank. Surge tank is also a protective auxiliary device connected with hydroelectric power plant. It is located just before the valve house. The height of the tank should be higher than the head of the water stored in the reservoir behind the dam. It is an open top water tank.

The purpose of this tank is to protect the penstock from the burst when the water turbine refuses to take water. At the entry point of the turbines, there are turbine gate controls by the governors. The governor opens or closes the turbine gate according to fluctuations in electrical load. If the electrical load is suddenly thrown from the plant, the governor closes the turbine gates and the water in the penstock is blocked. A sudden stoppage of water can cause severe bursting of the penstock pipeline. The surge tank absorbs this back pressure by swinging the level water in this tank.

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