Report ntpc

INDUSTRIAL TRAINING REPORT
ON
BTPS, NTPC BADARPUR, NEW DELHI
A TRAINING REPORT IN PARTIAL FULFILMENT OF
REQUIREMENTS
FOR THE AWARD OF THE DEGREE OF
BACHELOR OF TECHNOLOGY
IN
ELECTRICAL AND ELECTRONICS ENGINEERING
SUBMITTED TO
DEPARTMENT OF ELECTRICAL AND ELETRONICS
ENGINEERING NORTHERN INDIA ENGINEERING COLLEGE
GGSIPU, NEW DELHI
BY
LAKSHAY BHAMBRI
00296204913
DEPARTMENT OF ELECTRICAL AND ELECTRONICS
ENGINEERING
NORTHERN INDIA ENGINEERING COLLEGE
FC-26, SHASTRI PARK, NEW DELHI-110053
INDIA
JUNE,2016

ACKNOWLEDGEMENT
It has been a great honor and privilege to undergo training at NTPC Limited, Badarpur, Delhi,
India. I am very grateful to Mr. KALYAN MANDAL (AGM C&I) & Mr. P.C. MAHAR
(DGM EMD) for giving their valuable time and constructive guidance in preparing the
internship report for Internship. It would not have been possible to complete this report in
short period of time without their kind encouragement and valuable guidance.

TABLE OF CONTENT
1. About NTPC 1
Vision & Mission 1
Evolution 2
Power Generation 2
NTPC Plants 3
Future Goals 6
2. About BTPS 7
Coal to Electric Process 8
Basic power plant cycle 10
Installed Units 11
3. Electrical Maintenance Division – 1 13
Coal Handling Plant 13
Switch Gear 15
4. Electrical Maintenance Division – 2 20
Generator 20
Transformer 26
5. Control & Instrumentation 28
6. Bibliography 32

TABLE OF FIGURES
Sr. No. Figure Page No.
1. NTPC’s share in total capacity of INDIA 3
2. Growth in installed capacity of NTPC 6
3. Typical diagram of a coal based thermal
power plant
7
4. Flow chart of coal to electricity 9
5. Components of coal fired thermal plant 11
6. Installed units of BTPS 11
7. Flow chart of a coal handling plant 13
8. Switch Gear 16
9. Cross sectional view of a Generator 20
10. Transformer 26
11. Control Unit 28

1
CHAPTER-1
ABOUT National Thermal Power Corporation
NTPC Limited is the largest thermal power generating company of India. A public sector
company, it was incorporated in the year 1975 to accelerate power development in the country
as a wholly owned company of the Government of India. At present, Government of India
holds 89.5% of the total equity shares of the company and FIIs, Domestic Banks, Public and
others hold the balance 10.5%. Within a span of 31 years, NTPC has emerged as a truly national
power company, with power generating facilities in all the major regions of the country.
VISION AND MISSION
Vision
“To be the world’s largest and best power producer, powering India’s growth.”
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.”
Core Values – BE COMMITTED
B Business Ethics
E Environmentally & Economically Sustainable
C Customer Focus
O Organizational & Professional Pride
M Mutual Respect & Trust
M Motivating Self & others
I Innovation & Speed
T Total Quality for Excellence
T Transparent & Respected Organization
E Enterprising
D Devoted

2
EVOLUTION
NTPC was set up in 1975 in 100% by the ownership of Government of
India. In the last 30 years NTPC has grown into the largest power utility
in India.
In 1997, Government of India granted NTPC status of ‘Navratna’ being
one of the nine jewels of India, enhancing the powers to the Board of
directors.
NTPC became a listed company with majority Government ownership of
89.5%. NTPC becomes third largest by market capitalisation of listed
companies.
The company rechristened as NTPC Limited in line with its changing
business portfolio and transforms itself from a thermal power utility to an
integrated power utility.
National Thermal Power Corporation is the largest power generation
company in India. Forbes Global 2000 for 2008 ranked it 317th in the
world.
NTPC has also set up a plan to achieve a target of 50,000 MW generation
capacities.
NTPC has embarked on plans to become a 75,000 MW company by 2017.
NTPC is the largest power utility in India, accounting for about 20% of India’s installed
capacity.
POWER GENERATION IN INDIA
NTPC’s core business is engineering, construction and operation of power generating plants.
It also provides consultancy in the area of power plant constructions and power generation to
companies in India and abroad. As on date the installed capacity of NTPC is 47,228 MW
through its 18 coal based (35,085 MW), 7 gas based (4,017 MW), 9 solar photovoltaic based
(360 MW), 1 hydro based (800 MW), and 9 Joint Venture Projects (6,966 MW).
1975
1997
2004
2005
2009
2012
2017

3
Figure 1: NTPC’s Share in total capacity of INDIA
NTPC PLANTS
1. Thermal-Coal based
S. NO. CITY STATE COMMISSIONED
CAPACITY(MW)
1. SINGRAULI UTTAR PRADESH 2000
2. KORBA CHATTISGARH 2600
3. RAMAGUNDAM TELANGANA 2600
4. FARAKKA WEST BENGAL 2100
5. VINDHYACHAL MADHYA
PRADESH
4760
6. RIHAND UTTAR PRADESH 3000
7. KAHALGAON BIHAR 2340
8. DADRI UTTAR PRADESH 1820
9. TALCHER ORISSA 3000
10. UNCHAHAR UTTAR PRADESH 1050
11. TALCHER ORISSA 460
12. SIMHADRI ANDHRA
PRADESH
2000
13. TANDA UTTAR PRADESH 440

4
14. BADARPUR DELHI 705
15. SIPAT CHHATTISGARH 2980
16. BONGAIGAON ASSAM 250
17. MAUDA MAHARASHTRA 1660
18. BARH BIHAR 1320
TOTAL 35085 MW
2. COAL BASED (Owned by JVs)
S.NO. CITY STATE COMMISSIONED
CAPACITY(MW)
1. DURGAPUR WEST BENGAL 120
2. ROURKELA ORISSA 120
3. BHILAI CHHATTISGARH 574
4. JHAJJAR HARYANA 1500
5. KANTI BIHAR 610
6. NABINAGAR BIHAR 250
7. VALLUR TAMIL NADU 1500
8. PUVNL(Patratu) JHARKHAND 325
TOTAL 4999 MW
3. GAS Based
CAPACITY(MW)
1. ANTA RAJSTHAN 419
2. AURAIYA UTTAR PRADESH 663
3. KAWAS GUJARAT 656
4. DADRI UTTAR PRADESH 829
5. JHANOR GUJARAT 657
6. KAYAMKULAM KERALA 359
7. FARIDABAD HARYANA 431
TOTAL 4017 MW

5
4. GAS Based (Owned by JVs)
CAPACITY(MW)
1. RGPPL MAHARASHTRA 1967
TOTAL 1967 MW
5. HYDRO Based
CAPACITY(MW)
1. BILASPUR(Koldam) HIMACHAL PRADESH 800
POWER BURDEN
India, as a developing country is characterized by increase in demand for electricity and as of
moment the power plants are able to meet only about 60–75% of this demand on an yearly
average. The only way to meet the requirement completely is to achieve a rate of power
capacity addition (implementing power projects) higher than the rate of demand addition.
NTPC strives to achieve this and undoubtedly leads in sharing this burden on the country.
OVERALL POWER GENERATION
UNIT 1997-98 2014-15 % OF
INCREASE
INSTALLED CAPACITY MW 16,847 47,228 180.33
GENERATION MUs 97,609 2,41,261 147.17
NO. OF EMPLOYEES NO. 23,585 22,496 -4.61
GENERATION/EMPLOYEE MUs 4.14 10.72 158.93

6
Figure 2: Growth in installed capacity of NTPC
FUTURE GOALS
NTPC has set an ambitious target of becoming a 1,28,000 MW capacity firm by 2032. NTPC
CMD Arup Roy Choudhury said at 35th Annual General Meeting that based on the demand
growth and project plans, the Corporate Plan target of 1,28,000 MW capacity by the end of the
15th Five Year Plan, the year 2032, appears well within reach. NTPC has signed a Joint Venture
Agreement with Ceylon Electricity Board (CEB) of Sri Lanka with 50:50 equity participation
for setting up the first overseas power project - scheduled to be commissioned by 2016. NTPC
is also exploring the possibility of setting up a 1,320 MW coal based power project in
Bangladesh through a 50:50 JV with Bangladesh Power Development Board (BPDB).

7
CHAPTER 2
ABOUT Badarpur Thermal Power Station
Badarpur Thermal Power Station is located at Badarpur area in NCT Delhi. The power plant is
one of the coal based power plants of NTPC. The National Power Training Institute (NPTI) for
North India Region under Ministry of Power, Government of India was established at Badarpur
in 1974, within the Badarpur Thermal power plant (BTPS) complex.
It is situated in south east corner of Delhi on Mathura Road near Faridabad. It was the first
central sector power plant conceived in India, in 1965. It was originally conceived to provide
power to neighbouring states of Haryana, Punjab, Jammu and Kashmir, U.P., Rajasthan, and
Delhi but since year 1987 Delhi has become its sole beneficiary.
Figure 3: Typical diagram of coal based thermal power plant
BADARPUR THERMAL POWER STATION
COUNTRY INDIA
LOCATION MATHURA ROAD, BADARPUR, NEW
DELHI
STATUS ACTIVE
COMISSION DATE 1973
OPERATOR(S) NTPC

8
POWER STATION INFORMATION
PRIMARY FUEL COAL-FIRED
GENERATION UNITS 5
INSTALLED CAPACITY 705 MW
COAL SOURCE JHARIA COAL FIELDS
WATER SOURCE AGRA CANAL
FROM COAL TO ELECTRICITY PROCESS
Coal to Steam
Coal from the coal wagons is unloaded in the coal handling plant. This Coal is transported up
to the raw coal bunkers with the help of belt conveyors. Coal is transported to Bowl mills by
Coal Feeders. The coal is pulverized in the Bowl Mill, where it is ground to powder form.
The mill consists of a round metallic table on which coal particles fall. This table is rotated
with the help of a motor. There are three large steel rollers, which are spaced 120degrees
apart. When there is no coal, these rollers do not rotate but when the coal is fed to the table it
pack up between roller and the table and this forces the rollers to rotate. Coal is crushed
by the crushing action between the rollers and the rotating table. This crushed coal is taken
away to the furnace through coal pipes with the help of hot and cold air mixture from P.A.
Fan.
P.A. Fan takes atmospheric air, a part of which is sent to Air-Preheaters for heating while a
part goes directly to the mill for temperature control. Atmospheric air from F.D. Fan is heated
in the air heaters and sent to the furnace as combustion air.
Water from the boiler feed pump passes through economizer and reaches the boiler drum.
Water from the drum passes through down comers and goes to the bottom ring header. Water
from the bottom ring header is divided to all the four sides of the furnace. Due to heat and
density difference, the water rises up in the water wall tubes. Water is partly converted to
steam as it rises up in the furnace. This steam and water mixture is again taken to the boiler
drum where the steam is separated from water.

9
Figure 4: Flow chart of Coal to Electricity
Water follows the same path while the steam is sent to superheaters for superheating. The
superheaters are located inside the furnace and the steam is superheated (540 oC) and finally
it goes to the turbine.
Flue gases from the furnace are extracted by induced draft fan, which maintains balance draft
in the furnace (-5 to –10 mm of wcl) with forced draft fan. These flue gases emit their heat
energy to various super heaters in the pent house and finally pass through air-preheaters and
goes to electrostatic precipitators where the ash particles are extracted. Electrostatic
Precipitator consists of metal plates, which are electrically charged. Ash particles are
attracted on to these plates, so that they do not pass through the chimney to pollute the
atmosphere. Regular mechanical hammer blows cause the accumulation of ash to fall to the
bottom of the precipitator where they are collected in a hopper for disposal.
Steam to Mechanical Power
From the boiler, a steam pipe conveys steam to the turbine through a stop valve (which can
be used to shut-off the steam in case of emergency) and through control valves that
automatically regulate the supply of steam to the turbine. Stop valve and control valves are
located in a steam chest and a governor, driven from the main turbine shaft, operates the
control valves to regulate the amount of steam used. (This depends upon the speed of the
turbine and the amount of electricity required from the generator).
Steam from the control valves enters the high pressure cylinder of the turbine, where it passes
through a ring of stationary blades fixed to the cylinder wall. These act as nozzles and direct
the steam into a second ring of moving blades mounted on a disc secured to the turbine shaft.
The second ring turns the shafts as a result of the force of steam. The stationary and moving

10
blades together constitute a „stage‟ of turbine and in practice many stages are necessary, so
that the cylinder contains a number of rings of stationary blades with rings of moving blades
arranged between them. The steam passes through each stage in turn until it reaches the end
of the high-pressure cylinder and in its passage some of its heat energy is changed into
mechanical energy.
The steam leaving the high pressure cylinder goes back to the boiler for reheating and returns
by a further pipe to the intermediate pressure cylinder. Here it passes through another series
of stationary and moving blades.
Finally, the steam is taken to the low-pressure cylinders, each of which enters at the centre
flowing outwards in opposite directions through the rows of turbine blades through an
arrangement called the „double flow‟- to the extremities of the cylinder. As the steam gives
up its heat energy to drive the turbine, its temperature and pressure fall and it expands.
Because of this expansion the blades are much larger and longer towards the low pressure
ends of the turbine.
Mechanical Power to Electrical Power
As the blades of turbine rotate, the shaft of the generator, which is coupled to that of the
turbine, also rotates. It results in rotation of the coil of the generator, which causes induced
electricity to be produced.
BASIC POWER PLANT CYCLE
The thermal (steam) power plant uses a dual (vapour + liquid) phase cycle. It is a close cycle
to enable the working fluid (water) to be used again and again. The cycle used is Rankine
Cycle modified to include superheating of steam, regenerative feed water heating and
reheating of steam. On large turbines, it becomes economical to increase the cycle efficiency
by using reheat, which is a way of partially overcoming temperature limitations. By returning
partially expanded steam, to a reheat, the average temperature at which the heat is added, is
increased and, by expanding this reheated steam to the remaining stages of the turbine, the
exhaust wetness is considerably less than it would otherwise be conversely, if the maximum
tolerable wetness is allowed, the initial pressure of the steam can be appreciably increased.
Bleed Steam Extraction: For regenerative system, nos. of non-regulated extractions is taken
from HP, IP turbine. Regenerative heating of the boiler feed water is widely used in modern
power plants; the effect being to increase the average temperature at which heat is added to
the cycle, thus improving the cycle efficiency.

11
Figure 5: Components of a coal fired thermal plant
On large turbines, it becomes economical to increase the cycle efficiency by using reheat,
which is a way of partially overcoming temperature limitations. By returning partially
expanded steam, to a reheat, the average temperature at which the heat is added, is increased
and, by expanding this reheated steam to the remaining stages of the turbine, the exhaust
wetness is considerably less than it would otherwise be conversely, if the maximum tolerable
wetness is allowed, the initial pressure of the steam can be appreciably increased.
Bleed Steam Extraction: For regenerative system, nos. of non-regulated extractions is taken
from HP, IP turbine. Regenerative heating of the boiler feed water is widely used in modern
power plants; the effect being to increase the average temperature at which heat is added to
the cycle, thus improving the cycle efficiency.
INSTALLED UNITS
Figure 6: Installed Units of BTPS
MAIN GENERATOR
Maximum continuous KVA rating 24700KVA
Maximum continuous KW 210000KW
Rated terminal voltage 15750V

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Rated Stator current 9050 A
Rated Power Factor 0.85 lag
Excitation current 2600 A
Slip-ring Voltage 310 V
Rated Speed 3000 rpm
Rated Frequency 50 Hz
Short circuit ratio 0.49
Efficiency 98.4%
Direction of rotation viewed Anti Clockwise
Phase Connection Star - Delta
Number of terminals brought out 9(6 neutral and 3 phases)
MAIN TURBINE DATA
Rated output of Turbine 210 MW
Rated speed of turbine 3000 rpm
Rated pressure of steam before emergency 130 kg/cm^2
Stop valve rated live steam temperature 535 o Celsius
Rated steam temperature after reheat at inlet to receptor valve 535 o Celsius
Steam flow at valve wide open condition 670 tons/hour
Rated quantity of circulating water through condenser 27000 cm^3/hour

13
CHAPTER 3
EMD – 1
Electrical Maintenance Division I
It is responsible for the maintenance of:
1. Coal Handling Plant (C.H.P) & New Coal Handling Plant (N.C.H.P)
The old coal handling plant caters to the need of units 2,3,4,5 and 1 whereas the latter supplies
coal to units 4 and V.O.C.H.P. supplies coal to second and third stages in the advent coal to
usable form to (crushed) form its raw form and send it to bunkers, from where it is send to
furnace.
Figure 7: Flow chart of a Coal handling plant
Major Components
1. Wagon Tippler: - Wagons from the coal yard come to the tippler and are emptied here. The
process is performed by a slip –ring motor of rating: 55 KW, 415V, 1480 RPM. This motor
turns the wagon by 135 degrees and coal falls directly on the conveyor through vibrators.
Tippler has raised lower system which enables is to switch off motor when required till is
wagon back to its original position. It is titled by weight balancing principle. The motor lowers
the hanging balancing weights, which in turn tilts the conveyor. Estimate of the weight of the
conveyor is made through hydraulic weighing machine.
2. Conveyor: - There are 14 conveyors in the plant. They are numbered so that their function
can be easily demarcated. Conveyors are made of rubber and more with a speed of 250-
300m/min. Motors employed for conveyors has a capacity of 150 HP. Conveyors have a

14
capacity of carrying coal at the rate of 400 tons per hour. Few conveyors are double belt, this
is done for imp. Conveyors so that if a belt develops any problem the process is not stalled.
The conveyor belt has a switch after every 25-30 m on both sides so stop the belt in case of
emergency. The conveyors are 1m wide, 3 cm thick and made of chemically treated vulcanized
rubber. The max angular elevation of conveyor is designed such as never to exceed half of the
angle of response and comes out to be around 20 degrees.
3. Zero Speed Switch:-It is safety device for motors, i.e., if belt is not moving and the motor
is on the motor may burn. So to protect this switch checks the speed of the belt and switches
off the motor when speed is zero.
4. Metal Separators: - As the belt takes coal to the crusher, No metal pieces should go along
with coal. To achieve this objective, we use metal separators. When coal is dropped to the
crusher hoots, the separator drops metal pieces ahead of coal. It has a magnet and a belt and
the belt is moving, the pieces are thrown away. The capacity of this device is around 50 kg.
The CHP is supposed to transfer 600 tons of coal/hr, but practically only 300-400 tons coal is
transfer.
5. Crusher: - Both the plants use TATA crushers powered by BHEL. Motors. The crusher is
of ring type and motor ratings are 400 HP, 606 KV. Crusher is designed to crush the pieces to
20 mm size i.e. practically considered as the optimum size of transfer via conveyor.
6. Rotatory Breaker: - OCHP employs mesh type of filters and allows particles of 20mm size
to go directly to RC bunker, larger particles are sent to crushes. This leads to frequent clogging.
NCHP uses a technique that crushes the larger of harder substance like metal impurities easing
the load on the magnetic separators.
NEW COAL HANDLING PLANT
Major Components
1. Wagon Tippler:
Motor Specification
(i) H.P 75 HP
(ii) Voltage 415, 3 phase

15
(iii) Speed 1480 rpm
(iv) Frequency 50 Hz
(v) Current rating 102 A
2. Coal feed to plant:
Feeder motor specification
(i) Horse power 15 HP
(ii) Voltage 415V, 3 phase
(iii) Speed 1480 rpm
(iv) Frequency 50 Hz
2. SWITCH GEAR
It makes or breaks an electrical circuit.
1. Isolation: - A device which breaks an electrical circuit when circuit is switched on to no
load. Isolation is normally used in various ways for purpose of isolating a certain portion when
required for maintenance.
2. Switching Isolation: - It is capable of doing things like interrupting transformer magnetized
current, interrupting line charging current and even perform load transfer switching. The main
application of switching isolation is in connection with transformer feeders as unit makes it
possible to switch out one transformer while other is still on load.
3. Circuit Breakers: - One which can make or break the circuit on load and even on faults is
referred to as circuit breakers. This equipment is the most important and is heavy duty
equipment mainly utilized for protection of various circuits and operations on load. Normally
circuit breakers installed are accompanied by isolators.
4. Load Break Switches: - These are those interrupting devices which can make or break
circuits. These are normally on same circuit, which are backed by circuit breakers.
5. Earth Switches: - Devices which are used normally to earth a particular system, to avoid
any accident happening due to induction on account of live adjoining circuits. These

16
equipments do not handle any appreciable current at all. Apart from this equipment there are a
number of relays etc. which are used in switchgear.
Figure 8 : Switch Gear
LT Switchgear
It is classified in following ways :-
1. Main Switch: - Main switch is control equipment which controls or disconnects the main
supply. The main switch for 3 phase supply is available for the range 32A, 63A, 100A, 200Q,
300A at 500V grade.
2. Fuses: - With Avery high generating capacity of the modern power stations extremely heavy
carnets would flow in the fault and the fuse clearing the fault would be required to withstand
extremely heavy stress in process.
It is used for supplying power to auxiliaries with backup fuse protection, rotary switch up to
25A. With fuses, quick break, quick make and double break switch fuses for 63A and 100A,
switch fuses for 200A, 400A, 600A, 800A and 1000A are used.
3. Contractors: - AC Contractors are 3 poles suitable for D.O.L Starting of motors and
protecting the connected motors.

17
4. Overload Relay: - For overload protection, thermal over relay are best suited for this
purpose. They operate due to the action of heat generated by passage of current through relay
element.
5. Air Circuit Breakers: - It is seen that use of oil in circuit breaker may cause a fire. So in all
circuits breakers at large capacity air at high pressure is used which is maximum at the time of
quick tripping of contacts. This reduces the possibility of sparking. The pressure may vary from
50-60 kg/cm^2 for high and medium capacity circuit breakers.
HT Switch Gear
1. Minimum oil Circuit Breaker: - These use oil as quenching medium. It comprises of simple
dead tank row pursuing projection from it. The moving contracts are carried on an iron arm
lifted by a long insulating tension rod and are closed simultaneously pneumatic operating
mechanism by means of tensions but throw off spring to be provided at mouth of the control
the main current within the controlled device.
Type-HKH 12/1000c
· Rated Voltage-66 KV
· Normal Current-1250A
· Frequency-5Hz
· Breaking Capacity-3.4+KA Symmetrical
· 3.4+KA Asymmetrical
· 360 MVA Symmetrical
· Operating Coils-CC 220 V/DC
§ FC 220V/DC
· Motor Voltage-220 V/DC
2. Air Circuit Breaker: - In this the compressed air pressure around 15 kg per cm^2 is used
for extinction of arc caused by flow of air around the moving circuit . The breaker is closed by
applying pressure at lower opening and opened by applying pressure at upper opening. When
contacts operate, the cold air rushes around the movable contacts and blown the arc.

18
Rated Voltage-6.6 KV
Current-630 A
Auxiliary current-220 V/DC
3. SF6 Circuit Breaker: - This type of circuit breaker is of construction to dead tank bulk oil
to circuit breaker but the principle of current interruption is similar o that of air blast circuit
breaker. It simply employs the arc extinguishing medium namely SF6 the performance of gas.
When it is broken down under an electrical stress, it will quickly reconstitute itself
· Circuit Breakers-HPA
· Standard-1 EC 56
· Insulation Level-28/75 KV
· Rated Frequency-50 Hz
· Breaking Current-40 KA
· Rated Current-1600 A
· Making Capacity-110 KA
· Rated Short Time Current 1/3s -40 A
· Mass Approximation-185 KG
· Auxiliary Voltage
. Closing Coil-220 V/DC
. Opening Coil-220 V/DC
· Motor-220 V/DC
· SF6 Pressure at 20 Degree Celsius-0.25 KG
· SF6 Gas Per pole-0.25 KG

19
4. Vacuum Circuit Breaker: - It works on the principle that vacuum is used to save the
purpose of insulation and it implies that pressure of gas at which breakdown voltage is
independent of pressure. It regards of insulation and strength, vacuum is superior dielectric
medium and is better that all other medium except air and sulphur which are generally used at
high pressure.
· Rated frequency-50 Hz
· Rated making Current-10 Peak KA
· Supply Voltage Closing-220 V/DC
· Rated Current-1250 A
· Supply Voltage Tripping-220 V/DC
· Insulation Level-IMP 75 KVP
· Rated Short Time Current-40 KA (3 SEC), Weight of Breaker-8 KG

20
CHAPTER 4
EMD – 2
Electrical Maintenance division II
This division is divided as follows
Generator and Auxiliaries
Generator Fundamentals
The transformation of mechanical energy into electrical energy is carried out by the Generator.
This Chapter seeks to provide basic understanding about the working principles and
development of Generator.
Figure 9 : Cross sectional view of a Generator
Working Principle
The A.C. Generator or alternator is based upon the principle of electromagnetic induction and
consists generally of a stationary part called stator and a rotating part called rotor. The stator
housed the armature windings. The rotor houses the field windings. D.C. voltage is applied to
the field windings through slip rings. When the rotor is rotated, the lines of magnetic flux (i.e.
magnetic field) cut through the stator windings. This induces an electromagnetic force (EMF)
in the stator windings. The magnitude of this EMF is given by the following expression.

21
E = 4.44 /Ø FN volts
Ø = Strength of magnetic field in Weber’s.
F = Frequency in cycles per second or Hertz.
N = Number of turns in a coil of stator winding
F = Frequency = P*n/120
Where P = Number of poles
n = revolutions per second of rotor.
From the expression it is clear that for the same frequency, number of poles increases with
decrease in speed and vice versa. Therefore, low speed hydro turbine drives generators have
14 to 20 poles were as high speed steam turbine driven generators have generally 2 poles.
Generator component
This deals with the two main components of the Generator viz. Rotor, its winding &
balancing and stator, its frame, core & windings.
Rotor
The electrical rotor is the most difficult part of the generator to design. It revolves in most
modern generators at a speed of 3,000 revolutions per minute. The problem of guaranteeing
the dynamic strength and operating stability of such a rotor is complicated by the fact that a
massive non-uniform shaft subjected to a multiplicity of differential stresses must operate in
oil lubricated sleeve bearings supported by a structure mounted on foundations all of which
possess complex dynamic be behavior peculiar to them. It is also an electromagnet and to
give it the necessary magnetic strength
The windings must carry a fairly high current. The passage of the current through the
windings generates heat but the temperature must not be allowed to become so high,
otherwise difficulties will be experienced with insulation. To keep the temperature down, the
cross section of the conductor could not be increased but this would introduce another
problems. In order to make room for the large conductors, body and this would cause
mechanical weakness. The problem is really to get the maximum amount of copper into the
windings without reducing the mechanical strength. With good design and great care in

22
construction this can be achieved. The rotor is a cast steel ingot, and it is further forged and
machined. Very often a hole is bored through the center of the rotor axially from one end of
the other for inspection. Slots are then machined for windings and ventilation.
Rotor winding
Silver bearing copper is used for the winding with mica as the insulation between conductors.
A mechanically strong insulator such as micanite is used for lining the slots. Later designs of
windings for large rotor incorporate combination of hollow conductors with slots or holes
arranged to provide for circulation of the cooling gas through the actual conductors. When
rotating at high speed. Centrifugal force tries to lift the windings out of the slots and they are
contained by wedges. The end rings are secured to a turned recess in the rotor body, by
shrinking or screwing and supported at the other end by fittings carried by the rotor body.
The two ends of windings are connected to slip rings, usually made of forged steel, and
mounted on insulated sleeves.
Stator
Stator frame: The stator is the heaviest load to be transported. The major part of this load is
the stator core. This comprises an inner frame and outer frame. The outer frame is a rigid
fabricated structure of welded steel plates, within this shell is a fixed cage of girder built
circular and axial ribs. The ribs divide the yoke in the compartments through which hydrogen
flows into radial ducts in the stator core and circulate through the gas coolers housed in the
frame. The inner cage is usually fixed in to the yoke by an arrangement of springs to dampen
the double frequency vibrations inherent in 2 pole generators. The end shields of hydrogen
cooled generators must be strong enough to carry shaft seals. In large generators the frame is
constructed as two separate parts. The fabricated inner cage is inserted in the outer frame
after the stator core has been constructed and the winding completed. Stator core: The stator
core is built up from a large number of 'punching" or sections of thin steel plates. The use of
cold rolled grain-oriented steel can contribute to reduction in the weight of stator core for two
main reasons:
a) There is an increase in core stacking factor with improvement in lamination cold Rolling
and in cold buildings techniques.

23
b) The advantage can be taken of the high magnetic permeance of grain-oriented steels of
work the stator core at comparatively high magnetic saturation without fear or excessive iron
loss of two heavy a demand for excitation ampere turns from the generator rotor.
Stator Windings
Each stator conductor must be capable of carrying the rated current without overheating. The
insulation must be sufficient to prevent leakage currents flowing between the phases to earth.
Windings for the stator are made up from copper strips wound with insulated tape which is
impregnated with varnish, dried under vacuum and hot pressed to form a solid insulation bar.
These bars are then place in the stator slots and held in with wedges to form the complete
winding which is connected together at each end of the core forming the end turns. These end
turns are rigidly braced and packed with blocks of insulation material to withstand the heavy
forces which might result from a short circuit or other fault conditions. The generator
terminals are usually arranged below the stator. On recent generators (210 MW) the windings
are made up from copper tubes instead of strips through which water is circulated for cooling
purposes. The water is fed to the windings through plastic tubes.
Generator Cooling System
The 200/210 MW Generator is provided with an efficient cooling system to avoid excessive
heating and consequent wear and tear of its main components during operation. This Chapter
deals with the rotor-hydrogen cooling system and stator water cooling system along with the
shaft sealing and bearing cooling systems.
Rotor Cooling System
The rotor is cooled by means of gap pick-up cooling, wherein the hydrogen gas in the air gap
is sucked through the scoops on the rotor wedges and is directed to flow along the ventilating
canals milled on the sides of the rotor coil, to the bottom of the slot where it takes a turn and
comes out on the similar canal milled on the other side of the rotor coil to the hot zone of the
rotor. Due to the rotation of the rotor, a positive suction as well as discharge is created due to
which a certain quantity of gas flows and cools the rotor. This method of cooling gives
uniform distribution of temperature. Also, this method has an inherent advantage of
eliminating the deformation of copper due to varying temperatures.

24
Hydrogen Cooling System
Hydrogen is used as a cooling medium in large capacity generator in view of its high heat
carrying capacity and low density. But in view of it’s forming an explosive mixture with
oxygen, proper arrangement for filling, purging and maintaining its purity inside the
generator have to be made. Also, in order to prevent escape of hydrogen from the generator
casing, shaft sealing system is used to provide oil sealing.
The hydrogen cooling system mainly comprises of a gas control stand, a drier, an liquid level
indicator, hydrogen control panel, gas purity measuring and indicating instruments,
The system is capable of performing the following functions:
I. Filling in and purging of hydrogen safely without bringing in contact with air.
II. Maintaining the gas pressure inside the machine at the desired value at all the times.
III. Provide indication to the operator about the condition of the gas inside the machine
i.e. its pressure, temperature and purity.
IV. Continuous circulation of gas inside the machine through a drier in order to remove
any water vapor that may be present in it.
V. Indication of liquid level in the generator and alarm in case of high level.
Stator Cooling System
The stator winding is cooled by distillate.
Turbo generators require water cooling arrangement over and above the usual hydrogen
cooling arrangement. The stator winding is cooled in this system by circulating demineralised
water (DM water) through hollow conductors. The cooling water used for cooling stator
winding calls for the use of very high quality of cooling water. For this purpose DM water of
proper specific resistance is selected. Generator is to be loaded within a very short period if
the specific resistance of the cooling DM water goes beyond certain preset values. The
system is designed to maintain a constant rate of cooling water flow to the stator winding at a
nominal inlet water temperature of 400C.

25
Rating of 95 MW Generator-
Manufacture by Bharat heavy electrical Limited (BHEL)
Capacity - 117500 KVA
Voltage - 10500V
Speed - 3000 rpm
Hydrogen - 2.5 Kg/cm2
Power factor - 0.85 (lagging)
Stator current - 6475 A
Frequency - 50 Hz
Stator winding connection - 3 phase
Rating of 210 MW Generator-
Manufacture by Bharat heavy electrical Limited (BHEL)
Capacity - 247000 KVA
Voltage (stator) - 15750 V
Current (stator) - 9050 A
Voltage (rotor) - 310 V
Current (rotor) - 2600 V
Speed - 3000 rpm
Power factor - 0.85
Frequency - 50 Hz
Hydrogen - 3.5 Kg/cm2
Stator winding connection - 3 phase star connection
Insulation class - B

26
Transformer
A transformer is a device that transfers electrical energy from one circuit to another by
magnetic coupling without requiring relative motion between its parts. It usually comprises
two or more coupled windings, and in most cases, a core to concentrate magnetic flux. An
alternating voltage applied to one winding creates a time-varying magnetic flux in the core,
which includes a voltage in the other windings. Varying the relative number of turns between
primary and secondary windings determines the ratio of the input and output voltages, thus
transforming the voltage by stepping it up or down between circuits. By transforming
electrical power to a high-voltage, _low-current form and back again, the transformer greatly
reduces energy losses and so enables the economic transmission of power over long
distances. It has thus shape the electricity supply industry, permitting generation to be located
remotely from point of demand. All but a fraction of the world’s electrical power has passed
through a series of transformer by the time it reaches the consumer.
Figure 10 : Transformer
Rating of transformer
Manufactured by Bharat Heavy Electrical Limited
No load voltage (HV) - 229 KV
No load Voltage (LV) -10.5 KV

27
Line current (HV) -315.2 A
Line current (LV) - 873.2 A
Temp rise - 45 Celsius
Oil quantity - 40180 lit
Weight of oil - 34985 Kg
Total weight - 147725 Kg
Core & winding - 84325 Kg
Phase -3
Frequency - 50 Hz

28
CHAPTER 4
CONTROL & INSTRUMENTATION
This division is basically brain of the power plant and this division is responsible for:
1. For controlling the entire process of boiler, turbine and generator.
2. Is responsible for protection of boiler turbine & generator & associated auxiliaries.
3. It is responsible for display of all the parameters to the operator for taking the manual
action in case of emergency.
4. Responsible for logging of sequence of events taking place in the control room
Figure 11 : Control Unit
This department is the brain of the plant because from the relays to transmitters followed by
the electronic computation chipsets and recorders and lastly the controlling circuitry, all fall
under this.

29
This division also calibrates various instruments and takes care of any faults occurring in any
of the auxiliaries in the plant provided for all the equipments. Tripping can be considered as
the series of instructions connected through OR GATE. When the main equipments of this
laboratories are relay and circuit breakers.
Objectives of Instrumentation & Control
1. Efficient Operation of the plant.
2. Economic Operation of the plant.
3. Safe operation of the plant.
This entire task is often taken up by control & instrumentation or simply instrumentation
system which has following functions :-
1. Measurement
2. Control
3. Operation
4. Monitoring
5. Protection
For a Plant Measurement system needs to be:
1. Very accurate
2. Reliable
3. Delays should be as small as possible
4. Should be switched on manually when overall control system fails.
Measurement Parameters & Variables
Sr. No. Parameters/
Variables
Measuring Points Type of Sensor/ Instrument
1. Pressure Boiler, Turbine,
Furnace
Bourdon Tube, Diaphgram,
Bell Gauges

30
2. Temperature Steam inlet & output
Feed water inlet
Air preheater
Flue gases
Bearing of turbine &
generator
Thermocouple
RTD
3. Flow High pressure steam
Feed water inlet
Orifice, Venturi,
Flow Nozzle
4. Level Boiler drum
Condensate tank
Water line
Differential Pressure Methods
5. Expansion Turbine shaft
Turbine casing
Relative displacement
Control and Instrumentation Department has following labs:
1. Manometry Lab
2. Protection and Interlocks Lab
3. Automation Lab
4. Electronics Lab
5. Water Treatment Plant
6. Furnaces Safety Supervisory System Lab
Instruments used for protection
1. Relay
It is a protective device. It can detect wrong condition in electrical circuits by constantly
measuring the electrical quantities flowing under normal and faulty conditions. Some
of the electrical quantities are voltage, current, phase angle and velocity.

31
2. Fuses
It is a short piece of metal inserted in the circuit, which melts when heavy current flows
through it and thus breaks the circuit. Usually silver is used as a fuse material.
3. Miniature Circuit Breaker
They are used with combination of the control circuits to enable the staring of plant and
distributors & protect the circuit in case of a fault. In consists of current carrying
contacts, one movable and other fixed. When a fault occurs the contacts separate and
are is stuck between them.

32
BIBLIOGRAPHY
Ashfaq Husain. Electrical Machines. Dhanpat Rai & Co. 2015.
S. L. Uppal. Electrical Power. Khanna Publishers. 13th edition 2003.
Badri Ram. Power System Protection and Switchgear. TMH Publications 2nd Edition.
D. Patranabis. Sensors and Transducers. PHI Learning Pvt. Ltd., 2nd edition.
Annual Report 2014-15, NTPC.
Useful Links :
http://www.ntpc.co.in/en
http://www.ntpc.co.in/en/power-generation

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