HYDROLOGY AND WATER
PRINCIPLE COMPONENTS OF HYDROELECTRIC POWER
ALAY MEHTA 141080106011
SHIVANI PATEL 141080106021
KAVIN RAVAL 141080106026
KUNTAL SONI 141080106028
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PRINCIPAL COMPONENT OF HYDROELECTRIC
The principal components of a hydroelectric scheme
are as under:
1. Intake structure
3. Surge tank
5. Conveyance systems
6. Power house
7. Draft tube
8. Tail race
1. INTAKE STRUCTURE
An intake is a structure constructed at the entrance of
the pipe or canal or tunnel through which water is
conveyed to the power house.
The intake serves the following functions:
i. It controls the flow of water into the conveyance
ii. It prevents the entry of debris, ice, boulders, etc.
into the conveyance systems by means trash racks.
iii. It prevents the heavy sediment load of the river
from entering the conveyance system with help of
silt traps and silt excluders.
iv. It provides a smooth, easy and turbulence free
entry of water into the conveyance system.
TYPES OF INTAKE
The type of intake most suitable for a particular
project will depend upon the type of storage or
diversion structure, the location of the power house,
the conveyance system, topography, etc.
Commonly used intakes are:
1. Dam intake
2. Run-of-river intake
3. Canal intake
4. Tower intake
5. Shaft intake
• A forebay is an enlarged body of water provided at the
downstream end of the canal just at the upstream of
penstocks to act as a small balancing reservoir or pond.
• The main function of the forebay is to store some water
to act as a regulating reservoir for the penstocks.
• The forebay should be provide with an outlet or spill way
to dispose of the water safety whenever required.
• A forebay is usually created by widening the downstream
and of the power canal into the form of a small basin.
• Sometimes a byepass is provided to convey water from
the forebay to the tailrace when the load is reduced.
3. SURGE TANK
If the conveyance system consists of a penstock under
a very high pressure, a surge tank is usually required
at the upstream of the powerhouse to reduce the
water hammer effect.
Functions of surge tank:
1. It provides a free reservoir surface just upstream
of the turbine intake to absorb and compensate
water hammer effects.
2. It reduces the length of the high pressure conduits
required to resist the water hammer effects.
3. It quickly dampens the water level fluctuations
following load changes.
Types of surge tanks:
Basically surge tanks are of three types:
1. Simple surge tank
2. Restricted entry surge tank
3. Differential surge tank
• Penstocks are the pressure pipes which convey
water from the intake to the turbines.
• If the power house is located at the toe of the
dam, penstocks are entirely embedded in the dam.
• When power house is located away from the dam,
penstocks are provided to take the water from the
dam to the power house.
• Sometimes, a canal is provided in initial reach
ending in a forebay and the penstocks are provided
in the remaining reach.
• When the distance between the forebay and the
power house is relarively short, a separate
penstock is provided for each turbine.
5. CONVEYANCE SYSTEMS
A conveyance system is required to carry the water from the
intake to the power house. It may consist of one of the
1. Canals 2. Closed conduits
3. Tunnels 4. Penstocks
• When the general topography of the terrain is moderate
and the discharge is large, canals are generally most
• The tunnel may have pressure flow or free flow. When
the ground is very steep and rugged, penstocks are more
• In the case of an open channel, a forebay is usually
provided at the end of the channel from which the water
is conveyed to the turbines through penstocks.
6. POWER HOUSE
A power house is a building constructed for housing
and protection of the various hydraulic and electrical
equipments required for the generation of power, such
as spiral casing, turbines, governors, draft tube,
The power house consists of three main components:
2. Intermediate structure
7. DRAFT TUBE
A draft tube is a pipe or passage of gradually increasing
cross-sectional area which connects the runner exit to the
It serves the following purposes:
1. It permits a negative or suction head to be established
at the runner exit, thus making it possible the placing of
wheel and connecting machinery at level above that of
water in the tail race under high-water flow conditions
of river, without loss of head.
2. It reduces the high velocity of the water discharged by
the turbine by gradually enlarging the cross-section and
thus converts the kinetic energy of the water leaving the
runner, into mechanical energy of the wheel. Thus it
acts as a recuperator of pressure energy.
8. TAIL RACE
• The tail race is the channel into which the water is
discharged after passing through the turbines, if
the power house is close to the stream, the outflow
may be discharged directly into the stream.
• On the other hand, if the power house is located
away from the stream, the tail race is formed by
constructing an artificial channel between the
power house and the stream.
• A draft tube of a reaction turbine discharged at a
level below the river bed. The upslope of the tail
race is usually kept 1 in 6, from the draft tube exit
to the river bed.
• For pelton wheels, a small rectangular or
trapezoidal tail race is provided because the
discharged is relatively small.