Basics of DAM - Hydroelectric Power Station

The dam is a structure which uses potential energy of water and generates electricity. In this article, you'll learn about the basics of DAM.

After reading this post you'll be able to learn:
  • How a DAM works
  • Construction of DAM
  • Features of hydroelectric power station

How it works?

Water is stored in the dam at a certain height. Technically the height is also known as the head. This water moves down through the pipes (pen stock) and hits the turbines. These turbines are synchronized with the alternator thus causing it to rotate and produce electricity at the output.

Construction of Hydroelectric Power Station

Let's start our learning from the diagram of the station:

Catchment area

The catchment area collects water and sends it to the reservoir. Mostly the reservoir is constructed by building a concrete dam which acts as a barrier and controls the water.


A dam is made of concrete, stone masonry, rock or solid, as explained earlier it acts a s barrier and controls the water.


Gates are constructed inside the dam structure and they can be opened or closed to control the water.

Surge tank

Water from dam flows down through the penstock. A pen stock can be a closed pipe as well as it can be an open conduit. In the case of the open conduit, the pressure of flowing water doesn't create a problem. However, a closed pipe can face abnormal pressure. For this reason, a surge tank is constructed with the pipes. This surge tank is opened from the upper side and it allows water to escape through it.


Water turbines convert the potential energy of falling water to the mechanical energy. These turbines are also known as hydro-turbines. There are two basic types of turbines:
  1. Impulse turbines
  2. Reaction turbines
Impulse turbines are used for the low and medium heads whereas reaction turbines are used for high heads. This video by Learn and Grow explains impulse and reaction turbines in detail:


Alternator (Synchronous generator) is synchronized with the turbine, it rotor rotates and the electrical power is generated at the output.


A transformer connects next to alternator and steps up the ac voltages for distribution purposes.

Features of Hydroelectric Power Station

A hydroelectric power station is a clean source of producing electricity. Unlike fuel reservoir, there is no fear of depletion associated with it. Dams provide multiple benefits such as water control against floods, irrigation and power generation. An overview of advantages and disadvantages is given below:

Advantages of Dam

  1. A clean source which causes no environmental pollution
  2. Very small running charges as compared to Nuclear, coal and diesel plants.
  3. Has long life
  4. Requires little maintenance
  5. Multi-purpose plant (As explained above)

Disadvantages of Dam

  1. The initial cost of constructing the dam is very high.
  2. The hydroelectric station is a very large structure and is constructed far away from the population, Thus there is a need of constructing the longer transmission lines which increase the expenses
So that was all about Dam.
Learn more about Basics of Electrical Engineering


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