What is a Hydroelectric Power Plant?


Hydropower plants capture the energy of falling water to generate electricity . A turbine converts the kinetic energy of falling water into mechanical energy. Then a generator converts the mechanical energy from the turbine into electrical energy

Site Selection for Hydropower Plants

Availability of Water: Run-off data for many years available

Water Storage: for water availability throughout the year

Head of Water: most economic head, possibility of constructing a dam to get required head

Geological Investigations: strong foundation, earthquake frequency is less

Water Pollution: excessive corrosion and damage to metallic structures

Sedimentation: capacity reduces due to gradual deposition of silt

Social and Environmental Effects: submergence of areas, effect on biodiversity (e.g.

western ghat), cultural and historic aspects

Access to Site: for transportation of construction material and heavy machinery new railway

lines or roads may be needed

Multipurpose: power generation, irrigation, flood control, navigation, recreation; because

initial cost of power plant is high because of civil engineering construction work

Types of Dams


Figure 1: Earth and Rockfill Dam


Figure 2: Arc Dam


Figure 3: Arc Gravity Dam

Classification of Hydropower Plants

According to water flow regulation:

  1. Runoff river plants without pondage

  2. Runoff river plants with pondage

  3. Hydroelectric plants with storage reservoir

According to Load:

  1. Base load plants

  2. Peak load plants

  3. Pumped storage plants

According to head:

  1. High head plants (>100m)

  2. Medium head plants (30-100 m)

  3. Low head plants (<30 m)

Components of a HPP


Figure 4: Schmatic of a Hydropower Plant

The various components of HPP are as follows:

  1. Catchment area

  2. Reservoir

  3. Dam

  4. Spillways

  5. Conduits

  6. Surge tanks

  7. Draft tubes

  8. Power house

  9. Switchyard for power evacuation


 Develops a reservoir to store water

 Builds up head for power generation


 To safeguard the dam when water level in the reservoir rises


 Contains trash racks to filter out debris which may damage the turbine


 Enlarged body of water just above the intake


Figure 5: Forebay

 Headrace is a channel which lead the water to the turbine

 Tailrace is a channel which carries water from the turbine

 A canal is an open waterway excavated in natural ground following its contour.

 A flume is an open channel erected on a surface above ground.

 A tunnel is a closed channel excavated through an obstruction.

 A pipeline is a closed conduit supported on the ground.

Penstocks are closed conduits for supplying water “under pressure” from head pond to the


Hydro Power Plant Auxiliaries

  1. Governing oils systems

  2. Lubricating oil pumps

  3. Coolant oil pumps

  4. Drainage pumps

  5. Pipes, fans, ventilation

  6. Air compressor

  7. Cooling oil pumps for transformers

  8. Head gates

  9. Drain valves

  10. Gantry cranes

  11. Station batteries

  12. Instrumentation system