Component of Hydro Power Plant

Component of Hydro Power Plant
Prepared by
Prof. S. G. Taji
Dept. of Civil Engineering
S.R.E.S’s Sanjivani College of Engineering,
Kopargaon

Prepared by: Prof. Taji S. G.
2
 Following Table gives the average monthly flow rate
of river corresponding to driest year in record:
 What should be the minimum storage capacity for power
generation at uniform rate of 85 m3/s?
 If the reservoir capacity is fixed at 270 cumec, what
uniform rate of withdrawal is possible?
Month
Average Monthly Discharge
(Cumec)
January 110
February 90
March 70
April 50
May 30
June 25
July 65
August 220
September 300
October 190
November 115
December 110
Cumulative Volume
(Cumec)
110
200
270
320
350
375
440
660
960
1150
1265
1375

3
0
200
400
600
800
1000
1200
1400
1600
January February March April May June July August September October November December
Cumulative Volume (Cumec)
A
B
190 Cumec Reservoir Capacity

4
0
200
400
600
800
1000
1200
1400
1600
January February March April May June July August September October November December
Cumulative Volume (Cumec)
270 Cumec
Slope of Line AB = 100 cumec
i.e. 100 cumec withdrawal is possible
A
B

Following table indicate the flow of river for low water
period. It is proposed to locate a dam at this site
where the losses and other requirement are given.
Calculate req storage
5
Month
Average Monthly
Discharge (Cumec)
Losses and
other
requirement
Demand
January 1500 1130 200
February 1430 1135 220
March 1350 1145 300
April 1280 1145 280
May 1220 1260 300
June 1180 1280 300
July 1350 1170 300
August 1900 1140 300
September 2010 1135 280
October 1520 1140 250
November 1430 1145 220
December 1240 1155 180

6
Month
Average
Monthly
Discharge
(Cumec)
Losses
and other
requireme
nt
Dema
nd
January 1500 1130 200
February 1430 1135 220
March 1350 1145 300
April 1280 1145 280
May 1220 1260 300
June 1180 1280 300
July 1350 1170 300
August 1900 1140 300
September 2010 1135 280
October 1520 1140 250
November 1430 1145 220
December 1240 1155 180
Remaining
water in river
for fulfill
demand
370
295
205
135
-40
-100
180
760
875
380
285
85
Req.
Storag
e
170
75
-95
-145
-340
-400
-120
460
595
130
65
-95
Cumul
ative
deman
d
--
--
-95
-240
-580
-980
-1100
--
--
--
--
--

7

8

9

10

11
 Flow Duration Analysis

12

Site Selection For HP Plant
13
 Availability of Water
 Storage of Water
 Head of Water
 Cost and Type of Land
 Transportation Facilities
 Accessibility to the Site

Components of HP Plant
14
1. Catchment Area
2. Reservoir
3. Dam
i. Fore bay
ii. Sluice Gate
iii. Spillway
4. Intake Structure
5. Penstock
6. Surge Tank
7. Power House
i. Turbines
ii. Generators
8. Draft Tube
9. Tail Race

15

1.Catchment Area
16
 The catchment area is the total area of
watershed that drains all water at dam
site or across which dam is built

2. Reservoir
17
 The function or purpose of
reservoir is to store the water
during rainy season and supply
the same during dry season
 either natural or artificial

3. Dam
18
 A dam is a barrier which confines or raise water
for storage or diversion to create a hydraulic
head.
 Dam’s are generally made of concrete, Stone
masonry, Rock fill or Timber
 The purpose of the dam is to store the water and
to regulate the out going flow of water.
 The dam helps to store all the incoming water.
 It also helps to increase the head of the water.
 In order to generate a required quantity of power
it is necessary that a sufficient head is available.

19
Types of Dam
1. Masonry Dams
2. Earth Dams
The masonry dams which are generally used
for HP generation, are of three major classes :
a) Gravity dam
b) Buttress dam
c) Arched dam

i. Spillway
20
 A spillway is an integral part of a Dam.
 A spillway is usually used to remove excess water from
a reservoir to prevent overflow

Overflow Spillways
21
 Overflow spillways are also called ogee-shaped (S-
shaped) spillways.
 This type of spillways allows the passage of the flood
wave over its crest (which is S-shaped).
 Can be classified under controlled or uncontrolled.
 Widely used on Gravity dams, Arch dams, and
Buttress dams.

Chute Spillways
22
 Chute spillways are common
and basic in design as they
transfer excess water from
behind the dam down a smooth
decline into the river below.
 The spillway’s slope and its sides
are lined with concrete.
 In case of having sufficient stiff
foundation conditions at the
spillway location, a chute
spillway may be used instead of
overflow spillway due to
economic consideration.

Side Channel Spillway
23
 It is employed when valley
is too narrow in case of
solid gravity dams and
when non rigid dams are
adopted.
 The side channel spillway
is different from chute
spillway in the sense that
after crossing over the
spillway crest.
 Water flows parallel to the
crest length in former,
whereas the flow is normal
to the crest in the later.

Saddle Spillway
24
 There may be natural
depressions or saddle
on the periphery of
the reservoir basin
away from the dam.
 The depressions may
be used as spillway.
 The bottom of the
depression should be
at full reservoir level.

Siphon Spillway
25
 Crest is fixed at Full Reservoir Level.
When the water level in the reservoir rises
over F.R.L water starts spilling over the
crest.

Conduit/Tunnel Spillway
26
 A conduit spillway consist of closed conduit to
carry flood water to the downstream of dam
 It may constructed in abutment or body of the
dam.

ii. Sluice/Intake Gate
27
 Sluice gate refers to a movable gate allowing
water to flow under it.
 Flap sluice gate
 A fully automatic type, controlled by the pressure
head across it; operation is similar to that of a check
valve.
 It is a gate hinged at the top. When pressure is from
one side, the gate is kept closed; a pressure from the
other side opens the sluice when a threshold
pressure is surpassed.
 Vertical rising sluice gate
 A plate sliding in the vertical direction, which may be
controlled by machinery.

28

29
 Radial sluice gate
 A structure, where a small part of a cylindrical
surface serves as the gate, supported by radial
constructions going through the cylinder's
radius. On occasion, a counterweight is
provided.
 Rising sector sluice gate
 Also a part of a cylindrical surface, which rests
at the bottom of the channel and rises by
rotating around its centre.

30

iii. Fore bay
31
 Enlarged body of water provided in front
of penstock.
 Provided in case of run off river plants
and storage plants.
 Main function to store water which is
rejected by plant.
 Power house located closed to dam
penstock directly take water from
reservoir, reservoir act as fore bay.

32

33

4. Intake Structure
34
 Water conveyed from forebay to penstocks
through intake structures.
 Main components are trash rack and
gate.
 Trash rack prevent entry of debris.

35

36
 It is designed such that the following points
are complied, as far as possible:
 There should be minimum head loss as water
enters from the reservoir behind a dam or the
pool behind a barrage into the water conducting
system.
 There should not be any formation of vortices
that could draw air into the water conducting
system.
 There should be minimum entry of sediment
into the water conducting system.
 Floating material should not enter the water
conducting system.

Types
37
 Run-of-river type intake
 Intakes adjacent to a diversion structure like a
barrage.
 Here, an intake for a tunnel is placed upstream
of the diversion structure to draw water from
the pool.
 For a canal intake, the head regulator
resembles that of an irrigation canal intake.

38

39
 Reservoir type intakes
 Intakes for concrete dams are located on the
upstream face of the dam.
 The face of the intake is rectangular and is
reduced to a smaller rectangular section
through a transitory shape known as the bell-
mouth.
 From the smaller rectangular section, another
transition is provided to change the shape to
circular.

40

5. Penstock
41
 Penstocks are the water conductor conduit of
suitable size connecting the surge shaft to main
inlet valve
 It allows water to the turbine through main inlet
valve.
 At the end of the penstock a drainage valve is
provided which drains water from penstock to the
draft tube.
 In case of long penstock and high head, butterfly
valve is provided just before the penstock.
 It takes off from the surge shaft in addition to
spherical valve at the end of the penstock acting
as the main inlet valve.

42
 Open or closed conduits
which carry water to the
turbines.
 made of reinforced concrete
or steel.
 Concrete penstocks are
suitable for low heads less
then 30mtrs.
 Steel penstocks are designed
for any head.
 Thickness of penstocks
increases with head or water
pressure

43
 The thickness of penstock depend on water
head and hoop stress allowed in the
material.
T = 𝑝𝑝.𝑑𝑑 / 2𝑓𝑓𝜂𝜂
Where,
 T= Penstock thickness
 d= Dia. of penstock
 𝑓𝑓= Permissible stress
 p= Pressure due to water including water
hammer.

Number of penstock
44
 A hydro Power Plant uses a number of turbine
which are to be supplied water through
penstock.
 The number of penstock may depends on
design considerations of plant , for example:
 use a single penstock for the whole a plant.
 use individual penstock for each turbine
separately.
 provide multiple penstock but each penstock
supplying water to at least two or more turbine.

Surge Tank
45
 A surge tank is small reservoir or tank in which water
level rises of falls to reduce the pressure swings so
that they are not transmitted in full to closed circuit.
1. They reduce the distance between the free water
surface and turbine thereby reducing water hammer
effect ( the change in in pressure rapidly above or
below normal pressure caused by sudden changes in
the rate of water flow through the pipe according to
the demand of the prime mover) on the penstock.
2. They serve as supply tank to the turbine in case of
increased load conditions, and storage tank in case of
low load conditions.

46

47
Water-hammer effect :
 The water hammer is defined as the
change in pressure rapidly above or below
normal pressure caused by sudden
change in the rate of water flow through
the pipe, according to the demand of
prime mover i.e. turbine

Inlet Valve
48
 Main inlet valve works as the gate valve or
isolating valve in the water conductor system.
 It is located before turbine and allows water
flow from penstock to turbine.
 Main Inlet Valve acts as closing valve and cuts
the flow of water during an emergency trip.
 They are of following type:
• Butterfly valve (upto 200 m head)
• Spherical valve (more than200m head)

Butterfly valve
49

Hydraulic Turbines
50
 Water flowing from the penstock is allowed
to enter the power generation unit, which
houses the turbine and the generator.
 When water falls on the blades of the
turbine the kinetic and potential energy of
water is converted into the rotational motion
of the blades of the turbine

51
 The principal types of turbines are:
1) Impulse turbine
2) Reaction Turbine

52
 Impulse turbines: mainly used in high head
plants.
 the entire pressure of water is converted into
kinetic energy in a nozzle and the velocity of
the jet drives the blades of turbine.
 The nozzle consist of a needle, and quantity of
water jet falling on the turbine is controlled this
needle placed in the tip of the nozzle.
 If the load on the turbine decreases, the
governor pushes the needle into the nozzle,
thereby reducing the quantity of water striking
the turbine.

53
 Examples of Impulse turbines are:
• Pelton Wheel.
• Turgo
• Michell-Banki (also known as the Cross
flow or Ossberger turbine)

54
 Reaction turbines : are mainly for low and
medium head plants.
 In reaction turbine the water enters the runner
partly with pressure energy and partly with
velocity head.
 Most water turbines in use are reaction
turbines and are used in low (<30m/98 ft) and
medium (30-300m/98–984 ft)head
applications.
 In reaction turbine pressure drop occurs in
both fixed and moving blades.

55
 In this turbine the runner blades changed with
respect to guide vane opening.
 As the sudden decrease of load takes place, the
guide vane limit decreases according to that
runner blade closes.
 Examples of reaction turbines are:
 Francis turbine
 Kaplan turbine

56

Impulse Turbine-Pelton Turbine
57
 Tangential flow impulse turbine.
 Rotor has equally spaced hemispherical
buckets, Water is transferred from high head
source through penstock pipes.
 All the available potential energy is converted
to kinetic energy before the jet strikes the
buckets.
 The pressure all over the wheel is constant
and equal to atmospheric pressure, energy
transfer occurs due to purely impulse action.

58

Francis Turbine
59
 It is an inward mixed flow reaction turbine i.e. water under
pressure, enters the runner form the guide vanes towards
the centre in the radial direction and discharges out of the
runner axially.
 It runs under medium heads and requires medium quantity
of water.
 Water is brought down to the turbine and directed to a
number of stationary guide vanes.
 The head acting on the turbine is partly transformed into
kinetic energy and rest remains as pressure head.
 The runner is always full of water. The movement of runner
is affected by the change of both the potential and the
kinetic energies of water.
 The water is then discharged to the tail race, through draft
tube.

60

Kaplan Turbine
61
 Propeller turbine is a reaction turbine used for
heads between 4m to 80 m and specific speed
of 300 to 1000.
 Axial Flow Type
 It consists of axial flow runner
 With 4-6 or max 10 blades of air foil shape
 In Propeller Runner blades are fixed and non
adjustable as in Francis Turbine.
 In Kaplan Turbine which is a modification of
propeller turbine the runner blades are
adjustable and can be rotated about pivots
fixed to the base.

62

Draft Tube
63
 It is a pipe or passage of gradually
increasing cross sectional area, which
connect to the exit to tail race.
 it reduces high velocity of water
discharged by the turbine.
 draft tube permits turbines to be installed
at a higher level than the tail race level,
which help the maintenances and repair
of turbines.

64
(1) Conical Draft Tube
 This is known as tapered draft tube and
used in all reaction turbines where
conditions permit.
 It is preferred for low specific speed and
vertical shaft Francis turbine.
 The maximum cone angle of this draft
tube is limited to 8° (a = 4°). The hydraulic
efficiency of such type of draft tube is
90%.

65
(2) Elbow Type Draft Tube
 The elbow type draft tube is often
preferred in most of the power
plants, where the setting of
vertical draft tube does not
permit enough room without
excessive cost of excavation.
 Mostly used, vertical portion is a
conical section which gradually
flattens in the elbow section and
then discharges horizontally.

Tail Race
66
 Tail race tunnel or channel are provided
to direct the used water coming out of
draft tube back to the river.
 Important criteria of designing the tail
race is kind of draft tube, the gross head
and geographical situation of the area.
 Tail race is designed in such a way that
water hammer is minimizes when water
leaves the draft tube.

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