Shaikh Zhayed University
Engineering Faculty
Electrical Engineering Department
Chapter 2
Hydro-Electric Power Plant
Teaching Assistant. Mohammad Muslim HAQANI
A Text Book of Power Plant Engineering fifth edition By
Dr. R.K. RAJPUT
Power plant Engineering , 1st edition by Dr. S.
Suyambazhahan
CONTENTS
 Introduction
 Application of hydro-electric plants
 Classification
 Layout of hydro-electric power plant
 Dams
 Selection of water turbines
 Advantages of hydro power plant
 Disadvantages of hydro power plant
 Selection of site for a hydro-electric plant.
2
INTRODUCTION
 In hydro-electric plants energy of water is utilised to move the
turbines which in turn run the electric generators.
 The power extracted from the water depends on the volume and
on the difference in height between the source and the water’s
outflow.
3
Cont.
 Hydro (water) power is a conventional renewable source of
energy which is clean, free from pollution and generally has a
good environmental effect.
 However the following factors are major obstacles in the
utilisation of hydro-power resources :
(i) Large investments
(ii) Long gestation period
(iii) Increased cost of power transmission.
 The hydro-electric power plants provide 30 per cent of the
total power of the world.
 The total hydro-potential of the world is about 5000 GW.
4
Introduction to Hydro Power Plant
5
CLASSIFICATION
According to Rating of the Plant
1: Micro hydro power plant: If the rating of the plant or we can
say the output of the plant is less than 100 kW or 0.1 MW, the plant
is called Micro Hydro Power Plant.
6
Cont..
Based on the Rating of the Plant cont…
2: Mini hydro power plant: If the rating of the plant or we can say
the output of the plant is more than 100 kW or 0.1 MW and is less
than 1 MW, the plant is called Mini Hydro Power Plant.
7
Cont..
Based on the Rating of the Plant
3: Small hydro power plant: If the rating of the plant or we can
say the output of the plant is less than 10 MW, the plant will come
under the Category of Small Hydro Power Plant.
8
Cont..
Based on the Technology Used
1: Impoundment hydro power plant: It is the most common
type of hydro power plant based on technological classification.
 Adam is constructed and water is stored behind dam and the
stored potential energy of water behind dam is used as fuel for
hydro power plant.
9
Cont..
Based on the Technology Used
2: Diversion hydro power plant: In case the water head is small
and the potential energy of water is not enough to drive a turbine
then a separate water flow is taken from river with high speed so that
it may produce enough current in the generator.
10
Cont..
Based on the Technology Used
3: Pumped hydro power plant: Sometimes when the demand of
power supply is not high then produced electricity is used to drive a
motor and water is pumped back to the dam and the potential energy
of this water is used to generate the electricity at the plant.
11
Pumped storage plant.
Cont..
According to the nature of load
1: Peak load power plant: There types of power plant supply power to
the load when there peak load period, only.
 Run - off –river plant may be use for peak load by providing
pondage.
1
0
Cont..
According to the nature of load
2: Base load hydro power plant: The plants which cater for
the base load of the system are called base load plants.
 Run-of-river plants without pondage may sometimes
work as baseload plant
13
Cont..
According on the availability of head
(i) High head power plants (head > 100 m)
(ii) Medium head power plants (30 m to 100 m)
(iii) Low head power plants (head < 30 m)
14
Cont..
(i) High head power plants
 Water is usually stored up in lakes on
high mountains during the rainy season
or during the reason when the snow
melts.
 This type of site might also be suitable
for an underground station.
 The Pelton wheel is the common prime
mover used in high head power plants
15
Cont..
ii. Medium Head Power Plants
 When the operating head of water lies between 30 to 100 meters,
the power plant is known as medium head power plant.
 This type of plant commonly uses Francis turbines.
16
Medium head power plant layout.
Cont..
iii. Low Head Power Plants
 These plants usually consist of a dam across a river.
 This type of plant uses vertical shaft Francis turbine or Kaplan
turbine.
17
Low head power plant layout.
Cont..
(i) Based on the quality of water available
(i) Run-of-river plant with pondage.
(ii)Run-of-river plant without pondage.
(iii)Plant with storage reservoirs.
(iv)Pumped storage plants.
(v)Mini and micro hydro plants.
18
Cont..
Run-of-River Plants Without Pondage
 A run-of-river plant without pondage, as the name indicates,
does not store water and uses the water as it comes.
 These plants without storage may sometimes be made to
supply the base load,
19
Cont..
Run-of-River Plant with Pondage
 Pondage usually refers to the collection of water behind a dam
at the plant and increases the stream capacity for a short
period, say a week.
20
Cont..
Storage Type Plants
 A storage type plant is one with a reservoir of sufficiently
large size to permit carry-over storage from the wet reason to
the dry reason, and thus to supply firm flow substantially
more than the minimum natural flow..
21
Three Gorges dam in china
Capacity (22.5GW)
LAYOUT OF HYDROELECTRIC POWER PLANT
22
Flow sheet of hydro-electric power plant
Different parts of hydroelectric power plant
1.Water reservoir:
 It stores the water received from the catchment areas during
monsoon period.
 Water surface in the storage reservoir is known as head race.
23
DAMS
 Adam is a man-made structure built across a river.
 Most dams are built to control river flow, improve navigation, and
regulate flooding.
 Hydroelectric power is produced as water passes through a dam,
and into a river below.
24
Classification of Dams
Types of Dams
(i) Based on their functions, dams can be classified as
(a) Storage dams
(b) Diversion dams
(c) Detention dams
(ii) Based on the shape, the dams are classified into
(a) Trapezoidal dams
(b) Arch dams
(iii) Based on the materials of construction
(a) Earth dams
(b) Rock pieces dam
(c) Stone masonry dams
(d) Concrete dams
(e) RCC dams
(f)Timber and rubber dam
25
Cont..
Types of Dams cont…
(iv) Based on hydraulic design
(a) Overflow type dam
(b) Non-overflow type dam
(v) Based on structural design
(a) Gravity dam
b) Arch dam
(c) Buttresses dam
26
Cont..
 In this Presentation we describe more important and
famous type of Dams.
A. Fill dams
1. Earth dams
2. Rock-fill dams.
B. Masonry dams
1. Solid gravity dams
2. Buttress dams
3. Arch dams.
C. Timber dams
27
Types of dams
A. Fill dams
1. Earth dams: suitable for small project,
Advantage:
• (i) It is usually cheaper than a masonry dam.
• (ii) It is suitable for relatively previous foundation.
• (iii) It blends best with the natural surroundings.
• (iv) It is the most permanent type of construction if protected
from corrosion.
28
Types of dams
Disadvantages of the earth dam are :
(i) It has greater seepage losses than most other types of dams.
(ii) Since this type of dam is not suitable for a spillway structure,
therefore it requires a supplementary spillway.
(iii) It is subject to possible destruction or serious damage from erosion
by water either overtopping
29
Types of dams
A. Fill dams
2. Rock-fill dams: A rock-fill dam consists of loose rock of all
sizes and has a trapezoidal shape with a wide base, with a
watertight section to reduce seepage.
30
Types of dams
B. Masonry dams :
1. Solid gravity dams.: This type of dam is more massive and
bulky than the other types since it depends on its weight for
stability.
31
Grand Dixence Dam a massive
concrete gravity dam in Switzerland
Types of dams
B. Masonry dams :
2. Buttress dam: A buttress dam has an inclined upstream face, so
that water pressure creates a large downward force which provides
stability against overturning or sliding.
Slab-and-buttress type.
32
Multiple-arch type
Types of dams
B. Masonry dams :
3. Arch dam :This type of dam resists the water force by being
braced against the canyon sides because of its curved shape.
33
Typical arch dam : (a) Plan (b) Section
Hoover Dam on the Colorado River,
Types of dams
C. Timber dams ::
When wood is plentiful and more durable materials are not
accessible timber is sometimes used for low dams upto 12 m.
Timber dams
34
Cont..
3. Spill way:
 A spillway as the name suggests could be called as a way for
spilling of water from dams.
 It is used to provide for the release of flood water from a dam.
 It is used to prevent over toping of the dams which could result
in damage or failure of dams.
35
Cont..
4. Pressure tunnel:
 It carries water from the reservoir to surge tank.
36
Cont..
5. Pen stock and tunnel:
 Penstocks are pipes which carry water from the reservoir to the
turbines inside power station.
 They are usually made of steel and are equipped with gate
systems.
37
Cont..
6. Surge tank:
 Surge tanks are tanks connected to the water conductor system.
 It serves the purpose of reducing water hammering in pipes
which can cause damage to pipes.
38
Cont..
Types of surge tanks
The different types of surge tanks in use are :
1. Simple surge tank
2. Inclined surge tank
3. The expansion chamber and gallery type surge
tank
4. Restricted orifice surge tank
5. Differential surge tank.
39
Types of surge tanks
1. Simple surge tank: A simple surge tank is a vertical stand
pipe connected to the penstock as shown in Fig.
Surge tank on ground level.
40
Types of surge tanks
2. Inclined surge tank: When a surge tank is inclined (Fig.)
to the horizontal its effective water surface increases and
therefore, lesser height surge tank is required of the same
diameter
Inclined surge tank.
41
Types of surge tanks
3. Expansion chamber surge tank: Refer to Fig. This type
of a surge tank has an expansion tank at top and expansion gallery
at the bottom
42
The expansion chamber surge tank
Types of surge tanks
4. Restricted orifice surge tank.: Restricted orifice surge tank
Refer to Fig. It is also called throttled surge tank.
5. Differential surge tank: A differential surge tank has a riser
with a small hole at its lower end through which water enters in it.
43
Differential surge tank
Restricted orifice surge tank.
Cont..
7. Power station:
 Power station contains a turbine coupled to a generator.
44
Cont..
8. Draft tube:
 It is connected to the outlet of the turbine. It allows the turbine to
be placed over tail race level.
45
Cont..
9.Tail race:
 It is a water way to lead the water discharged from the turbine to
the river.
46
HYDRAULIC TURBINES
 A hydraulic turbine converts the potential energy of water
into mechanical energy which in turn is utilised to run an
electric generator to get electric energy.
47
Classification of Hydraulic Turbines
(i) According to the head and quantity of water
available.
(ii) According to the name of the originator.
(iii) According to the action of water on the moving
blades.
(iv) According to the direction of flow of water in
the
runner.
(v) According to the disposition of the turbine shaft.
(vi) According to the specific speed N .
s
48
Cont..
1. According to the head and quantity of water available
(i) Impulse turbine—requires high head and small quantity of
flow.
(ii) Reaction turbine—requires low head and high rate of flow.
2. According to the name of the originator :
((i) Pelton turbine—named after Lester Allen Pelton
of California (USA).
ii) Francis turbine—named after James Bichens Francis. It is a
reaction type of turbine for medium high to medium low heads
and medium, small to medium large quantities of water.
(iii) Kaplan turbine—named after Dr. Victor Kaplan.
It is a reaction type of turbine for low heads and
large quantities of flow.
49
Cont..
50
Cont..
4. According to direction of flow of water in the runner :
(i) Tangential flow turbine (Pelton turbine)
(ii) Radial flow turbine (no more used)
(iii) Axial flow turbine (Kaplan turbine)
(iv) Mixed (radial and axial) flow turbine (Francis turbine)
 In tangential flow turbine of Pelton type the water strikes the
runner tangential to the path of rotation.
51
Cont..
 In axial flow turbine water flows parallel to the axis of the
turbine shaft.
 In mixed flow turbines the water
enters the blades radially and comes
out axially, parallel to the turbine
shaft.
52
Cont..
 5. According to the disposition of the turbine shaft :
Vertical shaft Turbine
Horizontal shaft Turbine
53
Cont..
 In axial flow turbine water flows parallel to the axis of the
turbine shaft.
 In mixed flow turbines the water
enters the blades radially and comes
out axially, parallel to the turbine
shaft.
54
Cont..
 6. According to specific speed :
• The specific speeds for the various types of runners are given below :
55
SELECTION OF WATER TURBINES
 The major problem confronting the engineering is to select the
type of turbine which will give maximum economy
 The hydraulic prime-mover is always selected to match the
specific conditions under which it has to operate and attain
maximum possible efficiency.
 The choice of a suitable hydraulic prime-mover depends upon
various considerations for the given head and discharge at a
particular site of the power plant.
56
Cont..
 The following factors have the bearing on the selection of the
right type of hydraulic turbine which will be discussed separately.
1. Rotational Speed
2. Specific Speed
3. Maximum Efficiency
4. Part load Efficiency
5. Head
6. Type of Water
7. Runaway Speed
8. Cavitation
9. Number of Units
10. Overall cost
57
Cont..
 The hydraulic power of a plant can be calculated using following
expression.
P = ρ g HQ
P: is the hydraulic energy inWatts
g : is acceleration due to gravity (9.81 m/s2)
ρ : is water density (1000 kg/m3)
Q: is the flow (or) discharge m3/s
H: is the height of fall of water or head in meter
58
Cont..
 The electric power produced in kWh.
W = 9.81 × 1000 × Q × H × η × t
W = 9.81 Q H η t KWh
t: is the operating time in hours (8760 hours/year)
Η: is the efficiency of the turbine-generator (0.5 to 0.9)
 The power developed depends upon the quantity of water (Q)
and the head (H) of water.
59
Governing of Hydraulic Turbines
 Governing of a hydraulic turbine means speed regulation.
1. Governing of impulse turbine. The quantity of
water rejected from the turbine nozzle and from striking
the buckets may be regulated in one of the following ways:
1. Spear regulation
2. Deflector regulation
3. Combined spear and deflector regulation.
60
Cont.
61
Governing of Pelton turbine
Cont.
2. Governing of reaction turbines
62
Cont.
Fig. 6.45 shows the speed governing systems for by hydraulic
turbines schematically.
63
AVERAGE LIFE OF HYDRO-PLANT COMPONENTS
The average life (approximate) of various components of
hydro-electric power plant is given below :
Components Average life (years)
1. Reservoirs 70–80
2. Dams
(i) Earthen, concrete or masonry 150
(ii) Loose rock 60
4. Powerhouse and equipment
3. Water ways
(i) Building 35–50
(i) Canals, tunnels 50–100
(ii) Generators 25
(ii) Penstocks
(iii) Transformers 30
(a) Steel 40–50
(iv) Turbines (hydraulic) 5
(b) Concrete 25–50
(v) Pumps 20–25
64
ELECTRICAL AND MECHANICAL EQUIPMENT IN A HYDRO-PLANT
A. Electrical equipment
In electrical equipment the following elements items are included :
(i) Generators
(ii) Exciters
(iii) Voltage regulators
(iv) Transformers
(v) Switchgear
(vi) Control room equipment.
65
Cont.
Generators. The generators employed in a hydro-plant are
usually 3-phase synchronous machines
• This generator have a vertical shaft arrangement or horizontal
shaft arrangement ; but vertical shaft arrangement is preferred.
• The power output of a 3-phase alternator is given by:
P = 3 VI cos 𝜙×10–6 MW
cos  = Power factor (varies from 0.9 to 0.95).
66
Cont..
Step up transformer:
 It is used to raise the voltage of the electrical power generated at
the generator terminal.
67
Cont.
Switchgear. A switchgear consists of switches, isolators, surge
arrestors and circuit breakers.
• Its main function is to make and break the circuits
Control room equipment. It performs the following functions :
(i) Machine starting and stopping,
(ii) Generator and system voltage control,
(iii) Machine loading control,
(iv) Frequency control,
(v) Hydraulic control,
(vi) Machine running control,
68
Cont.
B. Mechanical equipment
Mechanical equipment include the following :
(i) Compressors and air ducts
(ii) Shaft, coupling, bearings etc.
(iii) Braking equipment for the generator
(iv) The oil circuits and pumps
(v) Cranes and other lifting equipment
(vi) Ventilation and cooling systems
(vii) Equipment for water supply
(viii) Equipment for power house lighting.
69
Advantages of Hydropower plant
1. Water source is perennially available.
2. Running cost is very low.
3. Non-polluting.
4. Power generation can be switched on and off in a very short time.
5. Simple in concept and self-contained in operation.
6. Greater reliability.
7. Greater life (more than 50 years).
8. Other than power generation, it provides irrigation, flood control,
afforestation, navigation and aqua-culture.
9. High efficiency.
10. Suitable for spinning reserve.
11. Man power requirement is low.
12. Simple in design and operation.
70
Disadvantages of Hydropower
1. High capital investment and low rate of return.
2. Gestation period is very large.
3. Power generation depends on availability of water.
4. Plants are for away from load center hence cost of transmission and
losses are high.
5. Large hydro plants disturb the ecology of the area due to
deforestation.
71
FACTORS TO BE CONSIDERED WHILE SELECTING THE SITE FOR
HYDROELECTRIC POWER PLANT
1. Availability of water and water head.
2. Accessibility of site.
3. Water storage capacity.
4. Distance from the load center.
5. Type of land.
72
Practical Examples.
73
Practical Examples.
74
Practical Examples.
75
76
Practical Examples.
77
Cont.
78
Cont.
79
80
Cont.
81
Practical Examples.
82
Cont.
83
Practical Examples.
84
Cont.
85
Assignment-2
Please solve the incoming slide problems and the
problems list of chapter -2
Please solve all question from chapter two.
Final date and time for submission: 1404/02/29 before 12:00 AM
86
87