Power plant overview_2

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POWER GENERATION AND
MAINTAINANCE
By
D.SRAVAN (314126514036)
E.SIVA SHANKAR (314126514041)
G.NARENDRA (314126514044)
G.G.CHAITANYA (314126514045)
PERIOD: 30/5/2016 to 13/06/2016
DATE:13/06/2016

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CERTIFICATE
ELECTRICAL MAINTAINANCE DEPARTMENT
SIMHADRI SUPER THERMAL POWER STATION
NTPC -VISAKHAPATNAM
This is to certify that the project work entitled
POWER GENERATION AND MAINTAINANCE
is a bonafide record of the work done by
D.SRAVAN (314126514036)
E.SIVA SHANKAR(314126514041)
G.NARENDRA (314126514044)
G.G.CHAITANYA (314126514045)
of Department of ELECTRICAL and ELECTRONICS Engineering, Anil
Neerukonda Institute of Technology and Sciences, affiliated to
Andhra University (AU), Visakhapatnam. They did this project
work under my supervision and guidance in partial fulfilment of
the requirement for the award of grade points in INDUSTRIAL
TRAINING, 2/4 - B.E,III- semester.

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SHRI
VIJAYA KUMAR,
DEPUTY GENERAL MANAGER (E.M),
NTPC SIMHADRI.
CERTIFICATE
NTPC -VISAKHAPATNAM
is a bonafide record of the work done by D.SRAVAN
(314126514036)of Department of ELECTRICAL and ELECTRONICS
Engineering, Anil Neerukonda Institute of Technology and
Sciences, affiliated to Andhra University (AU), Visakhapatnam. He
did this project work under my supervision and guidance in

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partial fulfilment of the requirement for the award of grade points
in INDUSTRIAL TRAINING, 2/4 - B.E, III- semester.
SHRI VIJAYA KUMAR,
NTPC SIMHADRI.

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CERTIFICATE
NTPC -VISAKHAPATNAM
is a bonafide record of the work done by E.SIVA SHANKAR
(314126514041) of Department of ELECTRICAL and ELECTRONICS
in INDUSTRIAL TRAINING, 2 /4 - B.E, III-semester.

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SHRI VIJAYA KUMAR,
NTPC SIMHADRI.

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CERTIFICATE
NTPC -VISAKHAPATNAM
is a bonafide record of the work done by G.NARENDRA

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CERTIFICATE
NTPC -VISAKHAPATNAM
is a bona fide record of the work done by G.G.CHAITANYA

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SHRI VIJAYA KUMAR,
NTPC SIMHADRI.
ACKNOWLEDGEMENT
My sincere thanks to our guide SHRI VIJAYA KUMAR , DEPUTY
GENERAL MANAGER (Electrical Maintenance), NTPC Simhadri for
his continuous help, encouragement and involvement in my mini
project.
With profound respect and gratitude, we take the opportunity to
convey thanks for permitting us to complete our training here.
We are extremely grateful to all the technical staff of STPP / NTPC
for their co-operation and guidance that has helped us a lot
during the course of training. We have learnt a lot working under

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them and we will always be indebted to them for this value
addition in us.
We would also like to thank H.O.D. of ANITS ENGINEERING
COLLLEGE and all the faculty members of electrical department
for their effort of constant co-operation, which have been a
significant factor in the accomplishment of our industrial training.
NTPC Overview
NTPC is India’s largest energy conglomerate with roots planted
way back in 1975 to accelerate power development in India. Since
then it has established itself as the dominant power major with
presence in the entire value chain of the power generation
business. From fossil fuels it has forayed into generating
electricity via hydro, nuclear and renewable energy sources. This
foray will play a major role in lowering its carbon footprint by
reducing green house gas emissions. To strengthen its core
business, the corporation has diversified into the fields of
consultancy, power trading, training of power professionals, rural
electrification, ash utilisation and coal mining as well.

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NTPC became a Maharatna company in May 2010, one of the only
four companies to be awarded this status. NTPC was ranked
400th in the ‘2016, Forbes Global 2000’ ranking of the World’s
biggest companies.
Growth of NTPC installed capacity and generation

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The total installed capacity of the company is 47,178 MW
(including JVs) with 18 coal based, 7 gas based stations and 1
Hydro based station. 9 Joint Venture stations are coal based and 9
renewable energy projects. The capacity will have a diversified
fuel mix and by 2032, non fossil fuel based generation capacity
shall make up nearly 28% of NTPC’s portfolio.
NTPC has been operating its plants at high efficiency levels.
Although the company has 17.73% of the total national capacity,
it contributes 24% of total power generation due to its focus on
high efficiency.
In October 2004, NTPC launched its Initial Public Offering (IPO)
consisting of 5.25% as fresh issue and 5.25% as offer for sale by
the Government of India. NTPC thus became a listed company in
November 2004 with the Government holding 89.5% of the equity
share capital. In February 2010, the Shareholding of Government
of India was reduced from 89.5% to 84.5% through a further
public offer. Government of India has further divested 9.5%
shares through OFS route in February 2013. With this, GOI's
holding in NTPC has reduced from 84.5% to 75%. The rest is held
by Institutional Investors, banks and Public.
NTPC is not only the foremost power generator; it is also among
the great places to work. The company is guided by the “People
before Plant Load Factor” mantra which is the template for all its
human resource related policies. NTPC has been ranked as “6th
Best Company to work for in India” among the Public Sector
Undertakings and Large Enterprises for the year 2014, by the

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Great Places to Work Institute, India Chapter in collaboration with
The Economic Times.
Vision and Mission
Vision
“To be the world’s largest and best power producer, powering
India’s growth”.

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Mission
“Develop and provide reliable power, related products and
services at competitive prices, integrating multiple energy sources
with innovative and eco-friendly technologies and contribute to
society”.
NTPC OBJECTIVE
 Business portfolio growth
 Customer Focus
 Agile Corporation
 Performance Leadership
 Human Resource Development

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 Financial Soundness
 Sustainable Power Development
 Research and Development
Core Values – BE COMMITTED
 B Business Ethics.
 E Environmentally & Economically Sustainable.
 C Customer Focus.
 O Organisational & Professional Pride.
 M Mutual Respect & Trust.
 M Motivating Self & others.
 I Innovation & Speed.
 T Total Quality for Excellence.
CONTENTS

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CHAPTER 1........................................................................................................23
NATIONAL THERMAL POWER CORPORATION (NTPC Ltd.).................23
1.1 INTRODUTION:........................................................................... 23
1.2 POWER STATIONS OF NTPC:.................................................... 24
1.2.1 Thermal Based Stations ........................................................ 24
1.2.2 Gas based stations: ............................................................... 27
1.2.3 Hydro based stations:........................................................... 28
CHAPTER 2........................................................................................................29
POWER PLANTS..........................................................................................29
2.1 Types of Power Plants.............................................................. 29
A. CONVENTIONAL PLANTS:................................................................................... 29
i. THERMAL POWER PLANTS:................................................................................. 29
ii. HYDAL POWER PLANTS:...................................................................................... 29
iii. NUCLEAR POWER PLANTS: ................................................................................. 30
B. NON CONVENTIONAL PLANTS: ......................................................................... 30
i. SOLAR PLANTS:.................................................................................................... 30
a) SOLAR PHOTO VOLTAICS (PV):.......................................................................... 30
b) SOLAR THERMAL PLANTS:.................................................................................. 30
ii. WIND POWER PLANTS: ........................................................................................ 30
CHAPTER 3........................................................................................................32
SIMHADRI SUPER THERMAL POWER PROJECT (STPP)..........................32
3.1 INTRODUCTION......................................................................... 32
3.2 GEOGRAPHY:.............................................................................. 32
3.3 UNITS OF STPP:.......................................................................... 32

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3.4 RESOURCES:................................................................................ 33
A. WATER:.................................................................................................................. 33
B. COAL: .................................................................................................................... 34
3.5 CUSTOMERS:............................................................................... 34
3.6 UNIQUE FEATURES:.................................................................... 34
3.7 PROCESS SCHEME OF POWER PLANT:.................................... 35
CHAPTER 4........................................................................................................38
POWER PLANT EQUIPMENT......................................................................38
4.1 CLASSIFICATION........................................................................ 38
CHAPTER 5........................................................................................................40
BOILER & AUXILIARIES ..............................................................................40
4.2 BOILER ......................................................................................... 40
4.3 BOILER TYPES ............................................................................. 40
4.4 CONTROLLING DRAFT:............................................................. 41
4.5 BOILER EQUIPMENT................................................................... 43
A) Super Heaters:......................................................................................................... 44
B) Re-Heaters:............................................................................................................. 44
C) Economizer:............................................................................................................. 45
4.6 BOILER AUXILIARIES .................................................................. 45
A) Coal Firing System:................................................................................................... 46
B) Coal Burners:........................................................................................................... 47
C) AIR PRE HEATER (APH) ............................................................................................. 47
CHAPTER 6........................................................................................................50
TURBINE & AUXILIARIES ...........................................................................50
6.1 TURBINE ...................................................................................... 50

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6.2 TYPES OF TURBINE .................................................................... 51
6.3 STAGES OF TURBINE ................................................................. 53
A) High Pressure (HP) Turbine:..................................................................................... 53
B) Intermediate Pressure (IP) Turbine:.......................................................................... 54
C) Low Pressure (LP) Turbine: ................................................................................ 54
6.4 TURBINE EQUIPMENT................................................................ 55
A) CONDENSER ............................................................................................................ 55
B) Low Pressure heater:............................................................................................... 57
C) DEAERATOR............................................................................................................. 59
6.5 TURBINE AUXILIARIES................................................................ 60
A) BOILER FEED WATER PUMP...................................................................................... 61
CHAPTER 7........................................................................................................63
GENERATOR ...............................................................................................63
7.1 TECHNICAL SPECIFICATION..................................................... 63
7.2 CONSTRUCTION......................................................................... 64
A) STATOR ................................................................................................................... 64
B) ROTOR .................................................................................................................... 65
C) STATOR WINDING.................................................................................................... 66
D) ROTOR WINDING..................................................................................................... 66
E) TEMPERATURE RISES ............................................................................................... 67
F) WINDING TEMPERATURE MONITORING................................................................... 68
G) VENTILATION & COOLING ........................................................................................ 68
H) COOLANT TEMPERATURE CONTROL.......................................................................... 69
I) SEAL OIL SYSTEM (DOUBLE FLOW SEAL).................................................................... 70
J) PRIMARY WATER SYSTEM........................................................................................ 71
K) BEARING AND SHAFT SEALS ..................................................................................... 71
L) HYDROGEN GAS COOLERS........................................................................................ 72
M) PRIMARY WATER TREATMENT SYSTEM..................................................................... 72
N) STATOR WINDING HOLLOW COPPER CORROSION..................................................... 73
O) Generator& Auxiliaries ............................................................................................ 74

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CHAPTER 8........................................................................................................75
TRANSFORMERS ........................................................................................75
8.1 INTRODUCTION......................................................................... 75
8.2 GENERATOR TRANSFORMER (GT)........................................... 76
8.3 UNIT TRANSFORMERS (UT)...................................................... 77
8.4 STANDBY TRANSFORMER (ST)................................................. 78
8.5 DG SETS....................................................................................... 79
CHAPTER 9........................................................................................................80
OFFSITE AREAS ..........................................................................................80
9.1 WATER SYSTEM.......................................................................... 80
A) Sea water pump house:........................................................................................ 80
B) CW system:.............................................................................................................. 80
C) Cooling Towers:....................................................................................................... 81
D) SweetWater Pump House:................................................................................... 81
E) Pre Treatment and DM Plant.................................................................................... 82
9.2 COAL HANDLING PLANT:......................................................... 83
9.3 ASH HANDLING PLANT............................................................. 83
9.4 FUEL OIL PUMP HOUSE ............................................................. 84
9.5 H2 PLANT.................................................................................... 84
CHAPTER 10......................................................................................................85
SWITCHYARD .............................................................................................85
10.1 INTRODUCTION...................................................................... 85
10.2 MAIN EQUIPMENTS USED IN SWITCH YARD:...................... 86
A) Bus bars: ................................................................................................................. 86
B) Solid Core Post Insulator.......................................................................................... 86
C) Capacitor Voltage Transformer (CVT): ...................................................................... 87

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D) CURRENT TRANSFORMERS (CT):............................................................................... 87
E) SURGE ARRESTERS (SA):........................................................................................... 88
F) ISOLATORS AND EARTH SWITCHES:.......................................................................... 89
G) CIRCUIT BREAKERS:.................................................................................................. 90
H) Overhead earth wire:............................................................................................... 92
I) Reactive power control devices:............................................................................... 92
J) Current Limiting Reactors:........................................................................................ 92
K) Batteries:................................................................................................................. 93
CONCLUSION....................................................................................................94

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CHAPTER 1
NATIONAL THERMAL POWER CORPORATION (NTPC Ltd.)
1.1INTRODUTION:
 NTPC Limited (formerly National Thermal Power
Corporation) (BSE: 532555, NSE: NTPC) which is founded
on 7 November 1975, is the largest Indian state-owned
electric utilities company based in New Delhi, India.
 NTPC is a Maharatna Status Company with a total installed
capacity of 43,039 MW (including Joint Ventures) with 17
coal based and 7 gas based stations, located across the
country. In addition, under JVs (Joint Venture), 7 stations
are coal-based, and another station uses naphtha/LNG as
fuel.
 It is listed in Forbes Global 2000 for 2014 at 424th rank
in the world.
 By 2017, the power generation portfolio is expected to
have a diversified fuel mix with coal based capacity of

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around 27,535 MW, 3,955 MW through gas, 1,328 MW
through Hydro generation, about 1400 MW from nuclear
sources and around 1000 MW from Renewable Energy
Sources (RES).
 The company has 18% of the total national capacity it
contributes 27% of total power generation due to its focus
on high efficiency.
 Every fourth home in India is lit by NTPC.
 NTPC is lighting every third bulb in India.
1.2POWER STATIONS OF NTPC:
1.2.1 Thermal Based Stations
Sr.
No.
Project State Capacity Units Status
1
Singrauli Super
Thermal Power
Station
Uttar
Pradesh
2,000
5x200 MW, 2x500
MW
All units functional
2 NTPC Korba
Chhattisg
arh
2,600
3x200 MW, 4x500
MW
3
NTPC
Ramagundam
Andhra
Pradesh
2,600
3x200 MW, 4x500
MW

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Sr.
No.
4
Farakka Super
Thermal Power
Station
West
Bengal
2,100
3x200 MW, 3x500
MW
5
NTPC
Vindhyachal
Madhya
Pradesh
4,260
6x210 MW, 6x500
MW
6
Rihand Thermal
Power Station
Uttar
Pradesh
3,000 6x500 MW All units functional
7
Kahalgaon
Super Thermal
Power Station
Bihar 2,340
4x210 MW, 3x500
MW
8 NTPC Dadri
Uttar
Pradesh
1,820
4x210 MW, 2x490
MW
9
NTPC
TalcherKaniha
Orissa 3,000 6x500 MW All units functional
10
Feroze Gandhi
Unchahar
Thermal Power
Plant
Uttar
Pradesh
1,050 5x210 MW All units functional
11
Talcher Thermal
Power Station
Orissa 460
4x60 MW, 2x110
MW
12 Simhadri Super
Thermal Power
Andhra
2000 4x500 MW All units functional

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Sr.
No.
Plant Pradesh
13
Tanda Thermal
Power Plant
Uttar
Pradesh
440 4x110 MW All units functional
14
Badarpur
Thermal Power
Station
Delhi 705
3x95 MW, 2x210
MW
15
Sipat Thermal
Power Plant
Chhattisg
arh
2980
2x500 MW, 3x660
MW
16
Mauda Super
Thermal Power
Station
Maharasht
ra
1000 2x500 MW
All units
functional [12]
17
Barh Super
Thermal Power
Station
Bihar 1980 3x660
(1x660 MW)
Running, two more
units of 660 MW
under
construction[13]
18
Kudgi Super
Thermal Power
Project
Karnataka 2400 MW 3x800 MW
Under construction.
One unit is
expected to be
commissioned by
2015 December.[14]
19
NTPC
Bongaigaon
Assam 750 MW 3x250 MW
Under construction.
One unit is
expected to be

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Sr.
No.
commissioned in
2014.[15]
20
LARA Super
Thermal Power
Project
Chhattisg
arh
4000 MW
2x800+3x800(Sta
ge-I +Stage-II)
MW
Under construction.
One unit is
expected to be
commissioned by
2015 December.
[16]
1.2.2 Gas based stations:
Sr. No. Project State
Installed Capacity in
Megawatt
1 NTPC Anta Rajasthan – Kota 413
2 NTPC Auraiya Uttar Pradesh 652
3 NTPC Kawas Gujarat 645
4 NTPC Dadri Uttar Pradesh 817
5 NTPC Jhanor Gujarat 648
6
NTPC
Kayamkulam
Kerala 350

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Sr. No. Project State
Installed Capacity in
Megawatt
7
NTPC
Faridabad
Haryana 430
8 RGPPL Ratnagiri
Maharashtra-
Ratnagiri
1967
1.2.3 Hydro based stations:
S.No Project State Installed
Capacity in
Megawatt
1 Loharinag Pala Hydro Power
Project
Uttarakhand state 600
2 TapovanVishnugad Joshimath town 520
3 LataTapovan upstream to Joshimath 130
4. Koldam Dam Himachal Pradesh 800
--*--*--

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CHAPTER 2
POWER PLANTS
2.1Types of Power Plants
Power plants can be broadly categorized based upon the
resource, as follows:
A. CONVENTIONAL PLANTS:
These plants operate on the resources that do not have the
capacity to renew on their own.
i. THERMAL POWER PLANTS:
The input to the power production is the coal which
serves as the fuel for the conversion of the feed water
into the steam, which is propelled onto the turbine.
The inputs for a thermal power plant are:
 water, which is being converted into steam the
working fluid of the power plant
 coal is ignited for the conversion of the water into
steam
 fuel oil is used to ignite the coal at the initial stages
of firing of the coal
ii. HYDAL POWER PLANTS:
The energy in the water which is present at some head is
used to rotate the turbine, which is coupled to the
generator for the electric power generation.

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iii. NUCLEAR POWER PLANTS:
The energy obtained by the chemical reactions of
radioactive elements is used to convert the water into
steam which is propelled onto the turbine.
B. NON CONVENTIONAL PLANTS:
Power plants utilize renewable energy resources which have
the capacity of renewing on their own on earth.
i. SOLAR PLANTS:
a) SOLAR PHOTO VOLTAICS (PV):
Electricity is produced from the solar energy by
photovoltaic solar cells, which convert the solar
energy directly to electricity. The dc power
generated from the PV cells is converted to ac with
the application of power electronic converters. These
Solar PV plants can either be grid connected or off-
grid type.
b) SOLAR THERMAL PLANTS:
Solar concentrators are used to receive solar energy
and are used to heat the oil flow through a set of
pipes, which in turn heat the water into steam in a
boiler and the steam generated is further used to
run the turbine.
ii. WIND POWER PLANTS:
The potential in the winds is being harnessed by placing
the wind turbines in the large scale commonly called as
wind farms.

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CHAPTER 3
SIMHADRI SUPER THERMAL POWER PROJECT (STPP)
3.1INTRODUCTION
Simhadri is the ambitious project of the NTPC intended to
provide the ever growing power needs of the state of Andhra
Pradesh.
STPP comes to the rescue of about 20 million units of power
consumed every day in Andhra Pradesh.
3.2GEOGRAPHY:
The Project was developed near Parawada and 3384 acres of
land was allocated for the construction of the Thermal plant.
The site is located between the latitude 17°35’ to 17° 37’north
and longitude 83°05’ to 83°8’E.
3.3UNITS OF STPP:

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STPP constitutes four operational units (each of 500MW).
Stage#1 includes Unit 1 & 2 and Stage#2 includes Unit 3 & 4.
Unit wise details along with commissioned date are tabulated
in the table below.
Stag
e
Unit
Numb
er
Installed
Capacity
(MW)
Date of
Commissioning
1st 1 500 2002 February
1st 2 500 2004 August
2nd 3 500 2011 March
2nd 4 500 2012 March
3.4RESOURCES:
A. WATER:
The water intake for the project for cooling is done by sea
water drawn from 8.9 kms away from the Bay of Bengal
through an intake-well sized 9100 cubic meters. This
intake-well is again the biggest well-constructed in the
entire India. The project also gets Sweet water from the
Yeluru canal.

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B. COAL:
The plant receives the coal from talcher, singareni and
mahanadhi coal fields and also the imported coal from
Indonesia. The imported coal is of high GCV when compared
to the native coal fields. The Coal for the project will be
coming to the plan with a special rail line setup. The Coal
transport for the NTPC Simhadri Project has begun in
December 2002.
3.5CUSTOMERS:
The produced power by the stage#1 is utilized by state of
Andhra Pradesh. The 85% of the power generated by the
stage#2 will be utilized by AP and the remaining 15% is given
to the central power grid.
3.6UNIQUE FEATURES:
 FIRST coastal based coal fired thermal power project of
NTPC
 Biggest sea water intake-well in India (for drawing sea water
fro, bay of Bengal)
 Use of sea water for condenser cooling and ash disposal
 Asia’s tallest natural cooling towers (165 mts)6th in the
world
 Use of fly ash bricks in the construction of all buildings

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 Coal based project of ntpc whose entire power is allocated
to home state (AP)
 Use of monitors as man machine interface (MMI’s) for
operating the plant
 Use of the distributed digital control and management
information systems (DDCMIS)
 Totally spring loaded floating foundation for all major
equipment including TG
 Use of INERGEN as fire protection system for the 1st time in
NTPC
 Flame analysis of boiler by dedicated scanners for all coal
burners the height of the Chimney is 275-feet - a record in
Asia for being the tallest factory chimney. Near to this are
the 165-meter two cooling towers.
3.7PROCESS SCHEME OF POWER PLANT:
The process scheme of the power plant is shown below.

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Generation of electricity comprises various processes listed
below.
 Coal cycle
 Water to steam cycle
 Flue gas cycle
 Electricity cycle
 Ash cycle
The Overview Diagram of The Stage#1’s Unit I is given below,
showing all process parameters.

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CHAPTER 4
POWER PLANT EQUIPMENT
4.1 CLASSIFICATION
Equipment in the power plant can be broadly classified into
A. Main plant equipment
I. Boiler & Boiler auxiliaries
II. Turbine & Turbine auxiliaries
III. Generator & Generator auxiliaries
IV. Transformers & transformer auxiliaries
B.Station common equipment
I. Switchyard
II.H2 plant
C. Offsite area equipment
I. Coal Handling Plant (CHP)
II.Ash handling system
a.Ash water system
b.Ash Extraction system
c.Ash water recirculation
III. De-mineralized/ Pre-treatment Water Plant
(DMPT)

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IV. Fuel Oil Pump House (FOPH)
V. Fire Water Pump House (FWPH)
The equipment in power plant is described in the following
chapters.
--*--*--

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CHAPTER 5
BOILER & AUXILIARIES
4.2 BOILER
A boiler is a closed vessel in which water or fluid is heated.
The heated or vaporized fluid exits the boiler for use in
various processes or heating applications.
4.3 BOILER TYPES
Boilers are of mainly two types
 Fire tube boilers
 Water tube boilers.
Fire tube boilers:
Here water partially fills a boiler barrel with a small volume
left above to accommodate the steam. The heat source is
inside a furnace or a fire box that has to be kept permanently
surrounded by the water in order to maintain the temperature
of the heating surface just below the boiling point. The
furnace can be situated at one of the fire tube which
lengthens the path of hot gases, thus augmenting the heating
surface which can be further increased by making the gases
reversed direction through a second parallel tube or bundle
of multiple tubes (two-pass or return flue boiler).
Alternatively the gases may be taken along the sides and then
beneath the boiler through flues. In the case of a locomotive
boiler a boiler barrel extends from the fire box and the hot

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gases passes through a bundle of fire tubes inside the barrel
which greatly increases the heating surface compared to a
single tube and further improves heat transfer. Fire tube
boilers usually have a comparatively low rate of steam
production, but high steam storage capacity. Fire tube boilers
mostly burn solid fuels, but are readily adaptable to those of
liquid or gas variety.
Water tube boilers:
In this type the water tubes are arranged inside a furnace in a
number of possible configurations. Often the water tubes
connect large drums, the lower half portion of the drum
contains water and the upper half contains steam. In other
cases such as mono-tube boilers water is circulated by a
pump through a succession of coils. This type generally gives
high steam production rates, but less storage capacity than
the above. Water tube boilers can be designed to exploit any
heat source including nuclear fission and are generally
preferred in high-pressure applications, since the high-
pressure water or steam is contained within narrow pipes
which can withstand the pressure within a thinner wall.
4.4 CONTROLLING DRAFT:
Most boilers now depend on mechanical draft equipment
rather than natural draft. This is because the natural draft is
subjected to outside air conditions and temperature of flue

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gases leaving the furnace, as well the chimney height. All
these factors make proper draft hard to attain and therefore
make mechanical draft equipment much more economical.
There are three types of mechanical drafts.
 Induced draft
 Forced draft:
 Balanced draft:
Induced draft:
This is obtained in one of the three ways, the first being the
stack effect of a heated chimney, in which the flue gas is less
dense than the ambient air surrounding the boiler. The more
dense column of ambient air forces combustion air into and
through the boiler. The second method is through use of a
steam jet. The steam jet oriented in the direction of flue gas
flow induces flue gases into the stack and allows for a greater
flue gas velocity increasing the overall draft in the furnace.
This method was common on steam-driven locomotive which
could not have tall chimneys. The third method is by simply
using induced draft fan which sucks flue gases out of the
furnace and up the stack. Almost all induced draft furnaces
have a negative pressure.
Forced draft:
Draft is obtained by forcing air into the furnace by means of a
fan (FD fan) and ductwork. Air is often passed through an air
heater, which, as name suggests, heats the air going into the
furnace in order to increase the overall efficiency of the

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boiler. Dampers are used to control the quantity of air
admitted to the furnace. Forced draft furnaces usually have a
positive pressure
Balanced draft:
Balanced draft is obtained through use of both induced and
forced draft. This is more common with larger boilers where
the flue gases have to travel a long distances through many
boiler passes. The induced draft fan works in conjunction
with the forced draft fan allowing furnace pressure.
Boilers in STPP in Stage#1 & 2 are highlighted as below.
MAKE TYPE
STAGE 1: BHEL Controlled circulation balanced
draft furnace type tangential firing.STAGE 2
4.5 BOILER EQUIPMENT
Boiler equipment is divided into
 Furnace
 Water walls
 Drum
 Super heater
 Re-heater

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 Economizer
A) Super Heaters:
The super heater is a device which is used to remove the
last traces of moisture from the saturated steam leaving
from the boiler drum and also to increase temperature
above saturation level temperatures. For this, the heat
from flew gases is used. There are three stages of super
heaters besides the side walls and extended sidewalls.
The first stage consists of horizontal super heater (LTSH
or PSH) of convection mixed flow type with upper and
lower banks located above economizer assembly in the
rear pass. Convective heat transfer superheats the steam
as the flue gases from the furnace pass through this
section. The upper bank terminates into hanger tubes,
which are connected to outlet header of the first stage
super heater. The second stage super heater consists of
pendant platen which is of radiant parallel flow type. The
third stage super heater is Platent (FSH) spaced is of
convection parallel flow type.
The outlet temperature and pressure of the steam coming
out from the super heater is 540° C and 157 kg/cm2
respectively.
B) Re-Heaters:

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The function of Re-heaters is to re-heat the partly
expanded steam from the HP Turbine to a temperature of
540°C. This is done so that the steam remains dry as far
as possible through the last stages of the turbine. The
input for the re heater is Cold Reheat line (CRH) from the
HP turbine output and the output of the re heater is Hot
Reheat Line (HRH) which goes to IP turbine input.
C) Economizer:
When the combustion gases leave the boiler after giving
most of their heat to the water tubes, super heater tubes
and re-heater tubes. But they still possess a lot of heat, if
not recovered, would go waste. Economizer is a device
which recovers the heat from the flue gases on their way
to chimney and raises the temperature of the feed water.
This increases the boiler efficiency by 10 to 12%.
4.6 BOILER AUXILIARIES
Boiler auxiliaries are divided into
 Boiler Water circulating pump (BCW)
 Coal firing

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 coal piping & burners
 Coal burners
 Oil firing
 Induced Draft fan (ID Fan)
 Forced Draft fan (FD Fan)
 Primary air fan (PA Fan)
 Scanner air fan
 Air pre-heaters
◦ Primary air pre-heaters (PAPH)
◦ Secondary air pre-heater (SAPH)
◦ Steam coil air pre-heater (SCAPH)
A) Coal Firing System:
Coal Firing System deals with the feeding of coal from the
bunkers. The coal firing system consists of the mills and
the Raw Coal Feeder. The mills pulverize the coal from
the bunkers.
MAKE TYPE Qty.
STAGE 1
bowl mill 9 mills/ unit
STAGE 2 10 mills/ unit

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B) Coal Burners:
The coal burner consists of Carbon Steel piping of 658.8
mm dia. The burners are tangential firing type. There are
a total of 36 burners per unit and the temperature of the
coal air mixture.
C) AIR PRE HEATER (APH)
The purpose of the air pre-heater is to recover the heat
from the boiler flue gas which increases the thermal
efficiency of the boiler by reducing the useful heat lost in
the flue gas. As a consequence, the flue gases are also
sent to the flue gas stack or chimney at a lower
temperature, allowing simplified design of the ducting
and the flue gas stack. It also allows control over the
temperature of gases leaving the stack (to meet emissions
regulations, for example).
Types
There are two types of air pre-heaters for use in steam
generators in thermal power stations:
 One is a tubular type built into the boiler flue gas
ducting and the other is a regenerative air pre-
heater. These may be arranged so the gas flows
horizontally or vertically across the axis of rotation.
 Another type of air pre-heater is the regenerator
used in iron or glass manufacture

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Regenerative air pre-heaters:
In this design the whole air pre-heater casing is
supported on the boiler supporting structure itself with
necessary expansion joints in the ducting.
The vertical rotor is supported on thrust bearings at the
lower end and has an oil bath lubrication, cooled by water
circulating in coils inside the oil bath. This arrangement is
for cooling the lower end of the shaft, as this end of the
vertical rotor is on the hot end of the ducting. The top
end of the rotor has a simple roller bearing to hold the
shaft in a vertical position.
The rotor is built up on the vertical shaft with radial
supports and cages for holding the baskets in position.
Radial and circumferential seal plates are also provided to
avoid leakages of gases or air between the sectors or
between the duct and the casing while in rotation.
For on line cleaning of the deposits from the baskets
steam jets are provided such that the blown out dust and
ash are collected at the bottom ash hopper of the air pre-
heater. This dust hopper is connected for emptying along
with the main dust hoppers or the dust collectors.
The rotor is turned by an air driven motor and gearing
and is required to be started before starting the boiler
and also to be kept in rotation for some time after the
booker is stopped, to avoid uneven expansion and
contraction resulting in wrapping or cracking of the rotor.

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The station air is generally totally dry (dry air is required
for instrumentation), so the air used to drive the rotor is
injected with oil to lubricate the air motor.
Safety protected inspection windows are provided for
viewing the pre-heaters internal operation under all
operating conditions.
The baskets are in the sector housings provided on the
rotor and are renewable. The life of the baskets depends
on the ash abrasiveness and corrosiveness of the boiler
outlet gases.

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CHAPTER 6
TURBINE & AUXILIARIES
6.1 TURBINE
A steam turbine is a mechanical device that extracts thermal
energy from pressurized steam, and converts it into useful
mechanical work.
Principle of operation
An ideal steam turbine is considered to be an isentropic
process or constant entropy process, in which the entropy of
the steam entering the turbine is equal to the entropy of the
steam leaving the turbine. No steam turbine is truly
“Isentropic”, however, with typical isentropic efficiencies
ranging from 20%-90% based on the application of the
turbine. The interior of the turbine is comprised of several
sets of blades or buckets as they are more commonly referred
to. One set of stationary blades is connected to the casing
and one set of rotating blades is connected to the shaft. The
sets intermesh with certain minimum clearances, with the
size and configuration of sets varying to efficiently exploit the
expansion of steam at each stage.
There are two types of steam prime movers viz., steam
engines and steam turbines. Steam turbines are generally

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classified into two types according to the action of steam on
moving blades viz.
 Impulse turbines
 Reactions turbines
In STPP, Turbine types in Stage#1 & 2 are highlighted as given
below.
MAK
E
DESIGN TYPE
STAGE 1
BHEL
KWU,
WEST
GERMANY
3 CYLINDER REHEAT
CONDENSED TURBINESTAGE 2
6.2 TYPES OF TURBINE
Turbine types include condensing, non-condensing, re-heat,
extraction and induction.
 Non-condensing or backpressure turbines are mostly
widely used for process steam applications. The
exhaust pressure is controlled by a regulating valve to
suit the needs of the process steam pressure. These
are commonly found at refineries, district heating
units, pulp and paper plants and desalination facilities
where large amounts of low pressure process steam
are available.
 Condensing turbines are most commonly found in
electrical power plants. These turbines exhaust steam

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un a partially condensed state, typically of a quality
near 90%, at a pressure well below atmospheric to a
condenser.
 Reheat turbines are also used almost exclusively in
electrical power plants. In a reheat turbine, steam flow
exits from a high pressure section of the turbine and is
returned to the boiler where additional superheat is
added. The steam then goes back into an intermediate
pressure section of the turbine and continues
expansion.
 Extracting type turbines are common in all
applications. In an extracting type turbine, steam is
released from various stages of the turbine and used
for industrial process needs or sent to boiler feed water
heaters to improve overall cycle efficiency. Extraction
flows may be controlled with a valve or left
uncontrolled. Induction turbines introduce low
pressure steam at an intermediate stage to produce
additional power.
Casing or Shaft arrangements
These arrangements include single casing, Tandem
compound and cross compound turbines. Single casing
units are the most basic style where a single casing and
shaft are coupled to a generator. Tandem compound are
used where two or more casings are directly coupled
together to drive a single generator. A Cross compound

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turbine arrangement features two or more shafts not in
line driving two or more generators that often operate at
different speeds. A Cross compound turbine is typically
used for many large applications.
6.3 STAGES OF TURBINE
Turbine is divided into 3 stages
 HPT-High pressure turbine
 IPT-Intermediate pressure turbine
 LPT-Low pressure turbine
First stage consists of IMPULSE type: for high speeds
The rest of the three stages consist of REACTION type: for low
speeds.
A) High Pressure (HP) Turbine:
The steam is initially passed through the HP Turbine.
Here, the steam loses some of its pressure and heat as it
comes in contact with the blades of the turbine. The
superheated steams from the super heaters enter the HP
turbine where it is freely expanded radially in all
directions and axially from a fixed point. From the HP
turbine outlet the expanded steam is again sent for
reheating. One extraction is taken from HP turbine, where

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the steam from CRH is sent to the HP heaters 6A & 6B to
heat the feed water. The HP turbine casing is designed as
a barrel type casing without axial joint.
B) Intermediate Pressure (IP) Turbine:
The IP turbine is split horizontally and is of double shell
and double flow construction. Steam from the reheat lines
enters the inner casing from the top and bottom through
two inlet nozzles flanged into the mid section of the outer
casing. The centre flow prevents the steam inlet
temperature from affecting the support brackets and
bearing sections. Two extractions take place in IP turbine,
where the steam from one extraction is sent to the
Deaerator and the boiler feed pump.
C) Low Pressure (LP) Turbine:
The LP turbine is of double flow and triple shell welded
casing. The steam from the IP turbine enters the LP
turbine and flows into the inner casing from both sides
through steam inlet nozzles before the LP blading. Three
extractions take place, where the extracted steam is sent
to the Three LP heaters.
There are different control valves at each stage like the main
stop and control valves such as re-heat stop and control
valve, swing check valve etc. All the three turbines are

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mounted on the same shaft and mechanically coupled to the
generator.
6.4 TURBINE EQUIPMENT
Turbine equipment is divided into following.
 Main turbine
 Turbine lube oil system
 Turbine control system (Control fluid system)
 Condenser
 LP Heater
 Dearator & FST
 HP Heater
A) CONDENSER
In thermal power plants, the primary purpose of a surface
condenser is to condense the exhaust steam from a
steam turbine to obtain maximum efficiency and also to
convert the turbine exhaust steam into pure water
(referred to as steam condensate) so that it may be
reused in the steam generator or boiler as boiler feed
water.
The steam turbine itself is a device to convert the heat in
steam to mechanical power. The difference between the
heat of steam per unit weight at the inlet to the turbine

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and the heat of steam per unit weight at the outlet to the
turbine represents the heat which is converted to
mechanical power. Therefore, the more the conversion of
heat per pound or kilogram of steam to mechanical power
in the turbine, the better is its efficiency. By condensing
the exhaust steam of a turbine at a pressure below
atmospheric pressure, the steam pressure drop between
the inlet and exhaust of the turbine is increased, which
increases the amount of heat available for conversion to
mechanical power. Most of the heat liberated due to
condensation f the exhaust steam is carried away by the
cooling medium (water or air) used by the surface
condenser.
Condensate Extraction Pump:
These pumps are run by constant speed motors through
a rigid coupling, vertical barrel, double barrel, double
section, multi stage, diffuser type. Condensate from the
hot well is pumped to deaerator by these pumps. These
pumps require Net Positive Suction Head (NPSH), as there
are negative levels.
Condensate polishing unit (CPU):
CPU is used for polishing the condensate to help in
regaining its properties if the properties are deteriorated.
Gland Steam Condenser:

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GSC is used for the condensation of the Leak off steam
from the turbine glands.GSC uses the leakage steam as
input which is coming from the sealing system provided
for the turbines which is used to avoid the leakage of
steam.
B) Low Pressure heater:
Before entering the Deaerator, the condensate gains some
temperature in Low pressure heaters (LPH). These are
special type of shell and tube heat exchangers, where the
condensate is heated by recovering the heat from a
turbine extracted steam. There are three heaters where
the drain from the first LP heater enters the second and
subsequent third one.
Corrosion
On the cooling water side of the condenser:
The tubes, the tube sheets and the water boxes may be
made up of materials having different compositions and
are always in contact with circulating water. This water,
depending on its chemical composition, will act as an
electrolyte between the metallic composition of the tubes
and water boxes. This will give rise to electrolytic
corrosion which will start from more anodic materials
first.

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‘Sea water based condensers’, in particular when sea
water has added chemical pollutants, has the worst
corrosion characteristics. River water with pollutants is
also undesirable for condenser cooling water.
The corrosive effect of sea or river water has to be
tolerated and remedial methods have to be adopted.
On the steam (shell) side of the condenser:
The concentration of undissolved gases is high over air
zone tubes. Therefore these tubes are exposed to higher
corrosion rates. Some tomes these tubes are affected by
stress corrosion cracking, if originally stress is not fully
relieved during manufacture. To overcome these effects
of corrosion some manufactures provide higher corrosive
resistant tubes in this area.
Effects of corrosion
As the tube ends get corroded there is the possibility of
cooling water leakage to the steam side contaminating
the condensed steam or condensate, which is harmful to
steam generators.
The other parts of water boxes may also get affected in
the long run requiring repairs or replacements involving
long duration shut-downs.
Protection from corrosion

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Cathodic protection is typically employed to overcome
this problem. Sacrificial anodes of Zinc (being cheapest)
plates are mounted at suitable places inside the water
boxes. These Zinc plates will get corroded first being in
the lowest range of anodes. Hence these Zinc anodes
require periodic inspection and replacements. This
involves comparatively less down time. The water boxes
made of steel plates are also protected inside by epoxy
paint.
C) DEAERATOR
A Deaerator is a device for air removal and is used to
remove dissolved gases (an alternate would be the use of
water treatment chemicals) from boiler feed water to
make it non-corrosive. A deaerator typically includes a
vertical domed deaeration section mounted on top of a
horizontal cylindrical vessel which serves as the deaerated
boiler feed water tank.
Necessity for Deaeration
A steam generating boiler requires that the circulating
steam, condensate and feed water should be devoid of
dissolved gases, particularly corrosive ones and dissolved
or suspended solids. The gases will give rise to corrosion
of the metal. The solids will deposit on the heating
surfaces giving rise to localized heating and tube ruptures
due to overheating. Under some conditions it may give
rise to stress corrosion cracking.

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Mounting arrangement
The feed tank is mounted horizontally at a sufficient
height above the boiler to provide the Net Positive Suction
Head (NPSH) to the boiler feed pump under all conditions
of the system operation.
Controls and monitoring
Normally, all the control and monitoring equipment for
startups, normal operation and alarms for out of
parameter operations are provided at the operator’s
console.
Deaerator level and pressure must be controlled by
adjusting control valves. The level is maintained by
regulating condensate flow and make-up water. Pressure
is maintained by regulating steam flow.
If operated properly, most deaerator vendors will
guarantee that oxygen in the deaerated water will not
exceed 7 ppb by weight (0.005cm^3/L)
6.5 TURBINE AUXILIARIES
Turbine auxiliaries are divided into the following
 Boiler Feed Pump (BFP)
 Booster Pump
 Vacuum raising system

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 TG equipment cooling water system
 Auxiliary Cooling Water System (ARCW)
 Condenser On load Tube cleaning system (COLTCS)
A) BOILER FEED WATER PUMP
A Boiler feed water pump is a specific type of pump used
to pump feed water into a steam boiler. The water may be
freshly supplied or returning condensate produced as a
result of the condensation of the steam produced by the
boiler. These pumps are normally high pressure units that
use suction from a condensate return system and can be
of the centrifugal pump type or positive displacement
type.
Feed water pumps range in size up to many horsepower
and the electric motor is usually separated from the pump
body by some form of mechanical coupling. Large
industrial condensate pumps may also serve as the feed
water pump. In either case, to force the water into the
boiler, the pump must generate sufficient pressure to
overcome the steam pressure developed by the boiler.
This is usually accomplished through the use of a
centrifugal pump.
Feed water pumps usually run intermittently and are
controlled by a float switch or other similar level-sensing
device energizing the pump when it detects a lowered
liquid level in the boiler. The pump then runs until the

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level in the boiler is substantially increased. Some pumps
contain a two-stage switch. As liquid lowers to the trigger
point of the first stage, the pump is activated. If the liquid
continues to drop (perhaps because the pump has failed,
its supply has been cut off or exhausted or its discharge
is blocked), the second stage will be triggered. This stage
may switch off the boiler equipment (preventing the
boiler from running dry and overheating), trigger an
alarm, or both.

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CHAPTER 7
GENERATOR
7.1 TECHNICAL SPECIFICATION
500 MW THDF 115/59 TG:
UNIT 1 TYPE: TG-HW-0500-2
SL.NO: 10526-P-129-01
UNIT 2 TYPE: TG-HW-0500-2
SL.NO: 10527-P-129-01
GENERATOR 500 MW, 588 MVA, 16.2 KA,
21 KV, 0.85 PF(lag),
FREQUENCY 50Hz
H2 PRESSURE 3.5 BAR.
EXCITATION 340 V, 4040 A.
CRITICAL SPEEDS: 864, 1806, 2388 RPM
SUBTRANSIENT REACTANCE Xd ‘’ 7.2 %
TRANSIENT REACTANCE Xd ’ 24.1 %
SYNCHRONOUS REACTANCE Xd 231 %
SHORT CIRCUIT RATIO 0.52
ZERO PF LAG CAPABILITY 433 MVA

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ZERO PF LEAD CAPABILITY 250 MVA
TOTAL LOSSES IN GENERATOR TOTAL TO 6920 KW,
BREAK UP AS FOLLOWS:
 IRON LOSSES 600 KW.
 SHORT CIRCUIT LOSSES 2800 KW.
 EXCITATION LOSSES 1390 KW.
 WINDAGE LOSSES 1680 KW
 BEARING & SEALS LOSSES 450 KW
EFFICIENCIES
AT FULL LOAD & AT 75% FULL LOAD: 98.63%
AT 50% FULL LOAD 98.44%.
AT 25% FULL LOAD 97.50%
7.2 CONSTRUCTION
A) STATOR
The generator has built in end shields bearings. Core
suspension system using flat - plate springs, keeps the
stator body vibrations low and within acceptable limits.
21 springs are provided at the machine bottom and at
both its sides. Mild steel pressure plates and axial studs
keep core tight. Core ends are shielded from end leakage

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magnetic fluxes by H2 cooled magnetic steel flux shields.
Stator core is insulated from the frame except for one
earthing core bar. Stator core is cooled by H2 flow in
radial ducts. All four cooler sections are vertically
mounted. A control valve on cold water flow side, based
on load, automatically adjusts cold water flow. This
ensures nearly uniform temperatures inside generator
irrespective of loads. Ring type double flow H2 shaft
seals, with separate air and Hydrogen side oil flows, are
reliable and give low H2 gas consumption. Distortion free
seal rings carriers are provided.
B) ROTOR
Rotor shaft forging is single piece vacuum cast and then
forged from low alloy steel to achieve high electro-
magnetic as well as mechanical properties. Both poles are
provided with cross pole slots for inertia equalization.
Rotor is fitted with 18Mn -18Cr non-magnetic steel
retaining rings for winding retention. The rings are
shrunk fitted and locked axially by snap rings. Seating
surfaces of rings and the shaft are silver coated. Class ‘F’
layers electrically insulate the rings from copper
underneath. Axial flow multi-stage fans/compressors
fitted on shaft at turbine end. Copper forged field leads
carry DC-rotor current from exciter to the rotor coils.

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C) STATOR WINDING
RESIATNACE IN OHMS AT 20°C U-X 0.001440 Ω, V-Y
0.001440 Ω, W-Z 0.001440 Ω
3 phase fractional pitch, 2 layer winding. Each slot has
Winding consists of polyester-mica splitting-epoxy resin,
having high electrical, mechanical and thermal / aging
properties. All bars are coated with semi-conducting
varnish in their slot portions. End corona protection is
provided in overhang portions. Slot bottom equalizing
strips are provided between the bars and stator slots. Top
and side ripple springs are provided.
D) ROTORWINDING
RESIATNACE IN OHMS AT 20°C F1-F2:0.06700 Ω.
The rotor winding consists of silver bearing copper
conductors for higher creep resistance and mechanical
strength. Trapezoidal slots are milled in the shaft for very
high shaft utilization and conductors are also trapezoidal.
Insulation between turns are made of class F laminated
glass - epoxy. Cu-Co-Be-Zr copper alloy slot wedges are
used in rotor slots. They also act as damper bars for
shaft circulating currents. Slot end wedges are Silver-
plated to improve conductivity of eddy currents that flow
on rotor surface in case of unbalanced or asynchronous

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machine operation. Wedges are snug fitted, permitting
thermal expansions. Rotor field leads get connected to
brushless exciter leads by silver plated multi contacts.
Current from field leads is transferred to rotor coils by
means of thread-less special current carrying bolts. Bolts
are sealed adequately, by rubber rings against escape of
Hydrogen gas via field leads.
E) TEMPERATURE RISES
IEC-34 permits maximum rotor winding Temp. Rise 62°C .
Actual expected rise is 31°C.
IEC-34 permits maximum stator winding Temp. Rise
37°C. Actual expected rise is 27°C.
IEC-34 permits maximum stator core Temp. Rise 77°C
based on RTDs. but actual as measured at hottest point in
type tests was only 41°C at teeth.
Magnetic flux density in both stator & rotor 2 - 2.5
Tesla.
Heat load for all H2 coolers 4424 KW.
Without one cooler full load permitted.67%
Machine is unloaded if H2 pressure < 3.1 bar.
Continuous unbalanced load of 8 % and on short time
basis, I2 ² t value of 10 is permitted.
Over-current is allowed for very brief spells as per O & M
manual. Thus for example, restricted operation is

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allowed for 90 sec at 120% rated current, or for 25 sec at
160 % rated current.
No operation is permitted without primary water flow in
winding.
Voltage-frequency combination variations in operation
permitted as per O&M manual.
F) WINDING TEMPERATURE MONITORING
Outlet water header has RTDs embedded in each outlet
hot water header nipple. These are thermally insulated
and connected to continuous monitoring system with
alarm provisions. Hot flow temperature monitoring
method gives accurate data vis a vis conventional slot
RTD method. Also flow monitoring of circuits is possible.
G) VENTILATION & COOLING
GENERATOR (GAS)VOLUME 80 m3.
CO2 FILLING QUANTITY 160M3 AT S.T.P
H2 FILLING QUANITY 480m3 AT S.T.P
Gas flow path 1 enters rotor on Turbine end and cools
rotor overhang and slots.
Gas flow path 2 cools stator core.
Gas flow 3 enters rotor on exciter end & cools rotor
overhang and rotor slots, as well as stator core end parts

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at both the ends.
Hot gas from all paths returns through air gap to
compressor and then to the gas coolers.
Hydrogen enters rotor ends and then into axial ducts
provided in rotor copper strip conductors in rotor slots.
Hot gas comes out from them radially, at barrel center
through number of radial holes provided in conductors
and in slot wedges. Gas also enters into winding
overhangs at both the barrel ends. Hot gas is then
collected in special chambers and then discharged into
the air-gap.
H) COOLANTTEMPERATURE CONTROL
Load changes lead to stresses. These are due to unequal
thermal expansion coefficients and unequal expansions
of winding copper, insulation and core iron. CW flow to
Hydrogen gas coolers is varied with load to achieve nearly
uniform machine temperatures. Secondary water flow
through primary water coolers is varied with load, also
towards maintaining uniform temperatures. With load,
cold coolant references are automatically reduced, such
that mean value of hot and cold remains nearly constant.
Cold gas temperature is changed with load by sensing
stator current; being a function of (Stator current)².
Parallel displacement of the cold gas curve is possible by
adjusting the set value of cold gas at no load. It is
theoretically possible either to keep mean of cold and hot

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gas temperatures constant, or maintain hot gas
temperature constant.
I) SEAL OIL SYSTEM (DOUBLE FLOW SEAL)
There are two separate seal oil systems in Generators.
One system runs saturated with Hydrogen and is at higher
pressure to prevent leaking of Hydrogen gas along the
shaft. Air side seal oil system caters to outer chamber in
shaft seals here outgoing oil gets mixed with bearing oil.
Air-side circuit has three oil pumps. Only one pump runs.
Air side oil is air - saturated. H2 side oil runs saturated
with H2 and have no air in it. Thus entry of air to H2
chamber is kept at minimum, so H2 purity is maintained.
H2 side has one pump only. If it fails, airside system
supplies oil to H2 side also. H2 purity goes down. If
prolonged, purity is improved by scavenging. Air-side
seal oil pressure is slightly higher than H2 side. Very
small quantity flows from air-side to H2 side.
Float valve in seal-oil tank returns excess oil to seal-oil
storage tank. Differential pressure regulating valve
controls sealing oil pressure above H2 pressure for AC
pumps. Another Differential pressure regulating valve
controls for 3rd standby, i.e. DC pump. For H2 side seal-
oil pressure, another differential press regulating valve is

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used, that takes signal from air-side seal oil pressure.
Constant differential pressure between air and H2 side oil
is controlled by separate pressure equalizing control
valves for each seal. Free movement of seal rings is
ensured by feeding ring relief press oil. It comes from air
side oil. Pressures for each seal are set separately at 8.5
mtr seal oil valve rack.
J) PRIMARY WATER SYSTEM
Primary water required for cooling the stator winding is
circulated in a closed system. In order to prevent
corrosion only copper stainless steels or similar corrosion
resistant material are used throughout the entire cooling
circuit.
K) BEARING AND SHAFTSEALS
Built in end shield bearings insulated on both TE and EE
from earth. Bearing bore is of elliptical shape i.e. having
greater clearances at sides than on top.
Clearance at maximum diameter of ellipse:
Horizontal clearance Sh (radial) = 0.88 - 0.94
Top clearance Sv (diametrical) = 0.52 - 0.63
Contact arc length of shaft with bearing liner babbbit B =
190 ± 10.

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Dia 'C' i.e. larger diameter of ellipse: 451.8 ± 0.04.
Shaft seals: Shaft Dia: 450 - 0.04.
Radial clearances between shaft and seal rings are 0.31 -
0.35.
Oil catcher radial clearances are = 0.17 - 0.30
L) HYDROGEN GAS COOLERS
 4 SECTIONS EACH RATED FOR 25%.
 GAS FLOW 33 CUM/SEC.
 HEAT DISSIPATION PER COOLER 5050 KW
 HOT / COLD GAS TEMP. 75.5 / 43.7 °C
 GAS PRESSURE DROP 620 Pa
 COOLING WATER FLOW 114 dm3/S CW
INLET / OUTLET TEMPS. 38.7/45.8 °C
 TUBES OF CuZn28Sn, FINS OF COPPER.
M) PRIMARY WATER TREATMENT SYSTEM
It is important that PW pumps have effective gland sealing
preventing air-suction. If air is sucked in, Oxygen ingress
increases and conductivity values shall go up. Also copper
corrosion rate goes up. Mixed bed ion exchanger is
provided to keep water conductivity low. 5 Micron filter is
provided in the system to arrest resin particles.
Integrating flow meter and conductivity meter are also
provided. Make up water quantity upstream and total

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make up volume is monitored. DM plant to give clean
water for the winding make up etc, free from iron oxides
to prevent deposits in winding. Whenever there is need to
test PW circuit, it should be done with 6 bar N2 pressure
in PW tank and the PW system full of water.
N) STATOR WINDING HOLLOW COPPER CORROSION
Corrosion of hollow conductors is harmful since it leads
to decrease in water flow. Oxygen corrodes copper - CuO
and Cu2O are formed. Corrosion is uniform along length
but deposits are more at conductor outlets. Each hollow
conductor is air checked for clear flow worthiness. Air /
water or mild acid flushing is followed by water flushing.
Flow is checked in each hollow conductor.
Very low or very high oxygen content in winding water
both give low corrosion levels of hollow copper. For 500
MW low oxygen levels 10 - 20 ppb are recommended.
NaOH added water with pH value of 8.5 - 9 gives
optimum results. Water conductivity at these pH values
tends to increase. Conductivity to be less than 10 micro
mho/cm, say : 0.5 micro mho/cm. CO2, Chlorides and
other anions to be minimum. CO2 content to be nil.
Conductivity after strongly acidic cation exchanger < 0.2
Micro mho/cm. Ammonia to be minimum. Test with
Nessler’s solution shall not cause change in color. Copper
and Iron in dissolved or undissolved form to be less than
20ppb. Ph value of 8.5 to 9 gives optimum results.

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Dilute 1 - 2% NaOH is added to obtain high pH levels.
Integrated alkalyzer unit is used. But conductivity shall
slightly increase.
O) Generator& Auxiliaries
Each alternator is coupled to a steam turbine and converts
mechanical energy of the turbine into electrical energy.
The alternator may be hydrogen or air or water cooled
where stator is water cooled and rotor is gas cooled. The
necessary excitation is provided by means of main and
pilot exciters directly coupled to the alternator shaft.
--*--*--

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CHAPTER 8
TRANSFORMERS
8.1 INTRODUCTION
A transformer is an energy transfer device. It has an input
side (primary) and an output side (secondary). Electrical
energy applied to the primary is converted to a magnetic field
which in turn, induces a current in the secondary which
carries energy to the load connected to the secondary. The
energy applied to the primary must be in the form of a
changing voltage which creates a constantly changing current
in the primary, since only a changing magnetic field will
produce a current in the secondary.
A transformer consists of at least two sets of windings wound
on a single magnetic core. There are two main purposes for
using transformers. The first is to convert the energy on the
primary side to a different voltage level on the secondary
side. This is accomplished by using differing turns counts on
primary and secondary windings. The voltage ratio is the
same as the turns ratio. The second purpose is to isolate the
energy source from the destination, either for personal
safety, or to allow a voltage offset between the source and
load.
Transformers are generally divided into two main types.
Power transformers are used to convert voltages and provide
operating power for electrical devices, while signal
transformers are used to transfer some type of useful
information from one form or location to another.

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Following are the Main Power transformers used in the
Simhadri power plant.
 Generator Transformer
 Unit Transformer
 Standby Transformer
8.2 GENERATOR TRANSFORMER (GT)
There are two Generator Transformers one to each of the
Generator. This Generator Transformer is connected between
generator and switch yard which steps up 21 KV to 400 KV. It
is connected in star-delta connection with the secondary star
neutral is solidly grounded.
Rating of Generator Transformer are as follows:
Phase: 3 x 1 phase
MVA rating: 120/160/200 MVA
KV rating: 420/sqrt (3)/21 KV
Current rating: 11000 Amps
Cooling: ONAN/ONAF/OFAF
Z = 13.5%, +/- 5% Tolerance at principle tap
Z min = 12% at maximum tap
Z max = 15% at minimum tap
Off circuit tap changer: +5 to -5% in steps of 2.5%

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8.3 UNIT TRANSFORMERS (UT)
It is a transformer which steps down the voltage from 21 KV
to 11 KV which is supplied to the other auxiliaries. There are
four Unit Transformers, two for each Generator.
These two Unit Transformers are connected to Generator to
supply auxiliary power to plant. Each Transformer supplies to
one 11KV switchgear. Four such switchgears are provided in
the station. Vacuum Circuit Breakers are used in the 11KV
Switchgear for feeding power supply to motor and
transformers.
Each Unit Transformer is connected in delta-star connection
with star side neutral resistively grounded.
If fault occurs in one Unit Transformer then loads connected
to that transformer will change over to 400KV/11KV Standby
Transformer .If there is a fault in one unit the loads
connected to that unit are fed by the 400KV/11KV Standby
Transformer.
Rating of UT are as follows:
Phase: 3-phase
MVA rating: 40/50 MVA
KV rating: 21/11.5 KV
Current rating:
Cooling: ONAN/ONAF
Z = 13% at principal tap
Z min = 10.5% at minimum tap

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Z max = 14% at maximum tap
On load tap changer: +7.5% to -12.5% in steps of 1.25% on
HV side
8.4 STANDBY TRANSFORMER (ST)
It is a transformer which steps down the voltage from 400 KV
to 11 KV supply. There is only one Standby Transformer in
the total plant. This transformer supplies power to the unit
switch gears whenever any one or both the Unit
Transformers fail. Standby Transformer is connected in star-
star fashion with both primary and secondary neutrals being
solidly grounded.
Rating of ST are as follows:
Phase:
MVA rating: 40/50 MVA
KV rating: 400/11.5 KV
Current rating:
Cooling: ONAN/ONAF
Z = 12.5% at principle tap
Z min = 9.5% at maximum tap
Z max = 16.5% at minimum tap
On load tap changer: +/- 10% in steps of 1.25% on HV side

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8.5 DG SETS
DG set is provided for the safe shutdown of the unit, in the
event of a grid failure. To safely shut down the unit, the
turbine has to be brought to rest gradually, and there are
several units like the generator seal oil system, emergency
lighting, and Data Acquisition Units, which have to be
constantly powered.
If the grid is active, then these loads are powered from the
grid by use of the Station Transformers. If the grid has failed,
the DG sets are used to run the loads till the unit is
completely turned off.
MAKE Rating
STAGE
1
Poweri
ca
415V, 3x1500
KVA
STAGE
2
Jackso
n
415V, 3x1250
KVA
There is 1 no. of DG per unit and 1 no. of standby per stage.
--*--*--

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CHAPTER 9
OFFSITE AREAS
9.1 WATER SYSTEM
The water system forms one of the vital systems of the Plant.
It constitutes the generation and circulation of de mineralized
(DM) water and cooling water. The water system mainly
consists of the following sections
A) Sea water pump house:
In NTPC Simhadri, Sea Water is used for cooling purposes.
A Sea Water Pump House is set up at 685 meters from
shore into sea. There are total of 2 pumps of 1 meter
diameter and ratings are 2500 litres/second and total
head of 43.3 meters and pump input is 1152.4 KW. The
pump motors are electrically mounted type. They have
the facility of electro chlorination to separate chlorine
from water through electrolysis.
B) CW system:
The CW pumps are used to circulate the sea water
through the plant from the Sea Water Reservoir. They are
a total of 5 pumps of concrete volute type. The pump
motors are squirrel cage.

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C) Cooling Towers:
The cooling towers are huge concrete structures used to
cool the hot sea water from the condenser and they use
natural draft. Sweetwater is used for the production of
steam in the boiler .In the heat exchanger in order to cool
this water, sea water is used as a heat exchange medium.
In the cooling tower to cool this hot water either natural
drought or forced drought cooling towers are used. In
Natural draft type design no pumps or fans are used to
circulate or cool the water. Where as in forced draft
cooling towers pumps and fans are used to circulate the
water. Here in NTPC Simhadri natural drought cooling
towers are used. In this type, scrubbers are arranged
through which hot sea water is forced to pass through.
While passing through these scrubbers, the water gets
cooled. As it is a closed loop the cooled water is again
sent back to the heat exchanger. There are two towers.
The height of each tower is 165 meters and hot water
temperature is 43.5 degrees and cool water temperature
is 32. 5 degrees.
E)Sweet Water Pump House:

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The Plant needs Sweet water for the Boiler. This
requirement is fulfilled by the Sweet Water Pump House.
The Pump House takes water from yelluru Canal.
D) Pre Treatment and DM Plant
The water used for generation of steam inside the boiler
should be free from any minerals or corroding materials
or else there is a high risk of chocking of tubes and this
may lead to damage of boiler. Hence, the water is being
de mineralized.
The impurities in the raw water input to the plant
generally consist of calcium and magnesium salts which
impart hardness to the water. Hardness in the make-up
water in the boiler will form deposits on the tube water
surface which leads overheating and failure of tubes.
Thus the salts have to be removed from the water and
that is done by water de-materialization treatment (DM).
A DM plant generally consists of cation, anion and mixed
bed exchangers. The final water from this process
consists essentially of hydrogen and hydroxide ions which
is the chemical combination of pure water. The DM water
being very pure becomes highly corrosive once it absorbs
oxygen.
The capacity of DM plant is decided by the type and
quantity of salts and raw water input. However some

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storage is essential as the DM plant may be down for
maintenance. For this purpose a storage tank is installed
from which DM water is continuously withdrawn for boiler
make-up. It is made up of material such as PVC. The
piping and valves are generally stainless steel. DM water
make-up is generally added at the steam space of the
surface condenser. This arrangement not only sprays
water but also DM water gets de-aerated, with the
dissolved gases being removed by the ejector of the
condenser itself.
9.2 COAL HANDLING PLANT:
Coal is stored in the coal storage plant. From the coal storage
plant, coal is delivered to the coal handling plant where it is
pulverized (i.e., crushed into small pieces) Pulverization is
done in order to increase its surface exposure, thus
promoting rapid combustion without using large quantity of
excess air.
9.3 ASH HANDLING PLANT
Ash produced may be to the tune of 10% to 15% of coal fired
.Ash slurry is made by wetting the fly ash and is pumped and
dumped in ash dykes which are located 10-15fkms away
from the power plant. The produced ash is pumped to sumps
in the form of wet ash and the fly ash is sent to the cement
companies.

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9.4 FUEL OIL PUMP HOUSE
For burning the coal at starting the oil is used and for safety
measures the fuel oil (HFO &LDO) tanks are placed at very far
away from the main plant. For pumping the fuel from there
fuel oil pump house is constructed where it employs drives
for pumping the fuel.
9.5 H2 PLANT
The Hydrogen plant of Simhadri has a capacity to generate
7.5 cubic meters of hydrogen per hour. The hydrogen is
produced by means of water electrolysis in the Electrolyser.
The electrolyser is filled with a solution of KOH in DM water
at a concentration of 25%. The electrolysis is achieved by the
passing of direct current from a rectifier through the cells
block. The oxygen generated in this electrolysis is vented out
to the atmosphere through a pressure balancing seal.There
are three important sections for this plant, namely the
Electrolyser section, the compressor section and the filling
station.
--*--*--

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CHAPTER 10
SWITCHYARD
10.1 INTRODUCTION
Switchyard as a main connecting link between the generating
plant and transmission systems has a large influence on the
security of supply. As the switchyard handles large amount of
power, it is considered essential that it remains secure and
serviceable to supply the outgoing transmission system even
under conditions of major equipment or busbar failure. The
choice of a bus switching scheme is governed by various
factors which ultimately aim at achieving the objective of the
security.
In all these regions there are switchgears. The switchgear in
generating stations can be classified as
 Main switchgear
 Auxiliary switchgear.
Main switchgear comprises of circuit-breakers, isolators, bus
bars, current transformers, potential transformers, etc. in the
main circuit of generator associated transformers of
transmission lines. It is generally of EHV and outdoor type.
Auxiliary switchgear is generally indoor type and controls the
various auxiliaries of the generator, turbine, boiler and the
station auxiliary.

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The functions of switch yard are as follows:
 Main link between generating plant and Transmission
system, which has a large influence on the security of the
supply.
 Step-up and/or Step-down the voltage levels depending
upon the Network Node.
 Switching ON/OFF Reactive Power Control devices, which
has effect on Quality of power.
10.2
AIN EQUIPMENTS USED IN SWITCH YARD:
A) Bus bars:
These are conducting bars to which a number of local
feeders or numbers of circuits are attached. They are of
hollow aluminum circular conductors. Bus bars are merely
convenient means of connecting switches and other
equipment into various arrangements. The usual
arrangements of connections in most of the substations
permits working on almost any piece of equipment
without interruption to incoming of outgoing feeders
B) Solid Core Post Insulator
They prevent any leakage current from conductor to
earth.

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C) Capacitor Voltage Transformer (CVT):
To step-down the high magnitude of voltage to a safe
value to incorporate Measuring and Protection logics .The
primary voltage is applied to a series of capacitors group.
The voltage across one of the capacitor is taken to
auxiliary PT. The secondary of the aux PT is taken for
measurement and protection.
D) CURRENT TRANSFORMERS (CT):
To step-down the high magnitude of current to a safe
value to incorporate Measuring and Protection logics .
Current transformers are used for the instrumentation,
protection or metering of power systems.

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Current transformers are divided into two groups they
are:
Protective current transformers: They are used in
association with relays, trip coils, pilot wires etc.
Measuring current transformers: They are used in
conjunction with ammeter, wattmeter etc.
Combined together PT’S and CT’S are called as instrument
transformers.
E) SURGE ARRESTERS (SA):

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Safe guards the equipment by discharging the high
currents due to Lightning and to discharge the high
voltage surges in the power system due to lightning to
the ground.
F) ISOLATORS AND EARTH SWITCHES:
Isolators are disconnecting switches, which operate under
no-load conditions and it is not designed to make a
circuit under load or short-circuit condition.
Earth switch is connected between the line conductor and
earth and it is earthed. Normally it is open and it is closed
to discharge the voltage trapped on the isolated or
disconnected line. When the line is disconnected from the
supply end there is some voltage on the line to which the
capacitance between the line and earth is charged. This
voltage is significant in hv systems. Before
commencement of maintenance work it is necessary that

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these voltages are discharged to earth by closing the ear
thing switch. Normally, the earthing switches are
mounted on the frame of the isolator.
Isolator cannot be opened unless the circuit breaker is
opened and circuit breaker cannot be closed unless the
isolator is closed and these two are interlocked to serve
the above functions.
G) CIRCUIT BREAKERS:
Makes or automatically breaks the electrical circuits under
loaded condition.
On the basis of type of current they may be classified as
 Ac circuit breakers
 Dc circuit breakers

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However, most general way of classification of circuit
breakers is on the basis of medium of arc extinction such
as
 Air-break circuit breakers
 Oil circuit breakers
 Minimum oil circuit breakers
 Air-blast circuit breaker
 Sulphur Hexafluoride circuit breaker
 Vacuum circuit breaker
But in NTPC all the breakers used in switch yard are SF6
Breakers because of following advantages.
 Minimum current chopping tendency at low
pressure and velocity
 High dielectric strength
 Outstanding arc quenching properties (small arcing
times)
 Not affected due to atmospheric conditions.

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H) Overhead earth wire:
Protects the over head transmission line from lightning
strokes.
I) Reactive power control devices:
Controls the reactive power imbalance in the grid by
switching ON/OFF the Shunt Reactors, Shunt Capacitors
etc
J) Current Limiting Reactors:
Limits the Short circuit currents in case of faulty
conditions.

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K) Batteries:
In electric power stations and large capacity sub stations,
the operating and automatic control circuits, the
protective relay systems, as well as emergency lighting
circuits, are supplied by station batteries. The latter
constitute independent sources of operative dc power and
guarantee operation of the above mentioned circuits
irrespective of any fault which occurred in the station or
sub- station, even in the event of complete disappearance
of the supply in the installation.
--*--*--

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CONCLUSION
The current generation of the electric power is unfortunately
unable to suit the emerging demands of the country. If “India -
2020 “vision is to be reached for the country becoming a major
superpower it is the power-sector which needs tremendous
growth.
Thermal power plants are catering to a great extent in the regard.
In the process, the NTPC is successful in powering India’s growth
by providing a world class integrated power major with innovative
and eco-friendly technologies, thus increasing global presence.
But still there is scope for improvement by installing thermal
power plants of larger MW-like 660 MW & 800 MW units. Also
there is need to exploit the vast hydro-power potential of about
1,50,000 MW available in the country and last but not the least
there is the need of the mighty “Nuclear power” which all
together will make India a real superpower
Thus increase in power will automatically aid to economic growth
which will give India the position in the world which it truly
deserves.

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NTPC is also successfully in adopting new technologies like VFD
system and that to first time in Simhadri which has been studied
here and it had been observed that it got less power
consumption when operating at different speeds and this is the
advantage when compared to its competitors like inlet guide vane
control, outlet damper control and flow control.
--*--*--

Power plant overview_2

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