GAIL(India)Ltd.,PATA Petrochemical Complex

1. i
GAIL, PATA
SUMMER INTERNSHIP REPORT
Submitted by
MIRAJALAM
(RA1411005010364)
in partial fulfillment for the award of the degree of
BACHELOR OF TECHNOLOGY
in
ELECTRICAL AND ELECTRONICS ENGINEERING
JUNE –JULY

2. ii
BONAFIDE CERTIFICATE
This is to certify that the in-plant training report entitled “INPLANT
TRAINING” submitted by MIRAJ ALAM to SRM University – Kattanlathur
Campus, in partial fulfillment of the requirement for the award of the degree of
BACHELOR OF TECHNOLOGY in ELECTRICAL AND ELECTRONICS
ENGINEERING is a record of bonafide in-plant training undertaken by him/her
under my supervision. The training fulfills the requirements as per the regulations of
this Institute and in my opinion meets the necessary standards for submission. The
contents of this report have not been submitted and will not be submitted either in
part or in full, for the award of any other degree or diploma in this institute or any
other institute or university.
Program Manager (B.TECH EEE)
Date:

3. iii
ACKNOWLEDGEMENT
It is with a feeling of profound gratitude and immense regard that I acknowledge the valuable
and expert guidance Mr.S.K MUSALGAONKAR HOD (Electrical),has provided me with this
training. I am indebted to him for his valuable suggestions and productive discussions from time
to time that have been instrumental in giving direction to this training.
AlsoIwouldliketothankMr. U N SINGH (CM) andMr.S K DIXIT (CM)
fortheirconstantguidance and greatsupport.
Itgives megreatpleasureto acknowledgemyhumble&sincere indebtnessto Mr.P.K
JAIN,forproviding encouragementandallhelp needed despiteofhismultifarious responsibilities.
Above all, I am deeply grateful to our Program Chair, Dr. Senthil Kumar for his consistent
support and motivation for doing this in-plant training program.
This work bears the impact of many persons who made significant contribution in formal
orinformalway.
Place : Chennai
MIRAJ ALAM
Date :

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TABLE OF CONTENTS
Serial no. TITLE PAGE NO.
Introduction Vii
Abstract Viii
List of tables Ix
1 Overview of the company X
1.1 Historyof company X
1.2 Growth of company XI
2 Substation and switchyard XIII
2.1 Substationandswitchyard XIII
2.2 Switchyard at Gail Pata XIII
2.3 Switchyard and its part XIII
2.4 Power distribution system XVI
3 Transformer XVIII
3.1 Transformer XX

5. v
3.2 Major equipment in transformer XX
3.3Generation in GAIL Pata XXIV
4 Electrical workshop XXVII
4.1 Motor XXVIII
4.2 Types of electric motor XXVIII
4.3 Types of induction motor XXIX
4.4 Three phase induction motor XXIX
4.5 Construction of 3 phase induction motor XXX
4.6 Squirrel cage induction motor XXXI
4.7 Slip ring induction motor XXXII
4.8 Coiling of induction motor XXXII
5 Conclusion XXXV

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INTRODUCTION
GAIL(India)Ltd.,PATAPetrochemicalComplex is located atDistrictAuraiyainUttar
Pradesh.Itisbasedonnaturalgasasfeedstockfrom GAIL’sHVJpipeline,whichhasbeenset
upinaccordancewithGAIL’smissiontomaximizethevalueadditionfrom eachfractionof natural
gas.
ThePlantconsistsoffivemajorunitsi.e.GasProcessingUnit(GPU),GasCrackerUnit (GCU),
HDPE unit, LLDPE Unit and LPG unit. Current capacity ofthe cracker plant is
440,000tonsperannum ofEthylene. Thisactsasafeedstockforthetwodownstream units with an
annual production capacity of 100,000TPAHDPEand210,000TPAofLLDPE/HDPE respectively.
HDPE and LLDPE are used by plastic processors to manufacture a large variety of
productsforindustrial,agriculturalanddomesticuses.ThePlantalsohasanLPGrecovery plant.
TheUpstream(GPU&GCU)andDownstream (LLDPE&HDPE)plants ofGAIL, PATAare
basedonthebesttechnologiesavailablein theworld.ThetechnologyfortheGCUhasbeen licensed by
Stone and Webstar, USA and theGPU by TFE. The technology for the HDPE unit has been
licensed by Mitsui of Japan and Nova Chemicals, Canada for Swing plant of HDPE &
LLDPEunit.Ethane,aconstituentofnaturalgasisconvertedintoethyleneasitsmainproduct
intheGCUusingthelatesttechnologyfrom USA.Ethyleneisfeedstockfordownstream units namely,
HDPE plant and Swing LLDPE/HDPE Plant. Butene-1 used as co-monomer in the production
of HDPE & LLDPE is produced in Butene-1 Plant licensed by M/s Axens, USA.

7. vii
ABSTRACT
The report presents how successfully the industrial training was done by me at GAIL, PATA.
The objective behind this training was to realize the theoretical concepts that were learnt through
academic courses and to experience the atmosphere of the industry.
It is with this objective that every student of B.Tech has to undergo four to six weeks of
summer training in the corporate world to get the first hand experience of working in an
organization. I was fortunate enough in doing my summer training at GAIL, PATA which is a
prestigious “MAHANAVARATNA STATUS” company.
LIST OF TABLES

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Table no Table title Page No.
3.1 Transformer rating in switchyard 10
3.2 Technical data of turbo generator (STG-1) 16
3.3 Technical data of turbo generator (STG-2) 17
4.1 Rating of three phase induction motor (LT) 24
4.2 Rating of three phase induction motor (HT) 25
4.3 Rating of transformer in electrical workshop 25
CHAPTER 1
OVERVIEW OF THE COMPANY

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Fig.1.1 GAIL power plant
1.1 History of Company
GAIL(INDIA)Ltd.was incorporated in August 1984 as a Central Public Sector
Undertaking (PSU) under the Ministry of Petroleum & Natural Gas (MoP&NG). The
company used to be known as Gas Authority of India Limited. It is India's principal gas
transmission and marketing company. The company was initially given the responsibility
of construction, operation & maintenance of the Hazira – Vijaypur – Jagdishpur (HVJ)
pipeline project. It was one of the largest cross-country natural gas pipeline projects in
the world. This 1750-kilometre-long pipeline was built at a cost of ₹17
billion (US$250 million) and it laid the foundation for development of market for natural
gas in India. GAIL commissioned the 1,750 kilometres (1,090 mi) Hazira-Vijaipur-
Jagdishpur (HVJ) pipeline in 1991. Between 1991 and 1993, three liquefied natural gas
(LPG) plants were constructed and some regional pipelines acquired, enabling GAIL to
begin its gas transportation in various parts of India.

10. x
GAIL began its city gas distribution in New Delhi in 1997 by setting up
nine compressed natural gas (CNG) stations.
GAIL today has reached new milestones with its strategic diversification into
Petrochemicals, Telecom and Liquid Hydrocarbons besides gas infrastructure. The
company has also extended its presence in Power, Liquefied Natural Gas re-gasification,
City Gas Distribution and Exploration & Production through participation in equity and
joint ventures. Incorporating the new-found energy into its corporate identity, Gas
Authority of India was renamed GAIL (India) Limited on 22 November 2002.
GAIL (India) Limited has shown organic growth in gas transmission through the
years by building large network of trunk pipelines covering length of around 10,700
kilometres (6,600 mi). Leveraging on the core competencies, GAIL played a key role as
gas market developer in India for decades catering to major industrial sectors like power,
fertilizers, and city gas distribution. GAIL transmits more than 160 mmscmd of gas
through its dedicated pipelines and have more than 70% market share in both gas
transmission and marketing.
1.2 Growth of company
GAILtodayhasreached newmilestoneswith itsstrategicdiversificationintoPetrochemicals,
TelecomandLiquidHydrocarbonsbesidesgasinfrastructure.Thecompanyhasalsoextended its

11. xi
presence in power, LNG regasification, City Gas Distribution andexploration and
productionthroughequityandjointventuresparticipations.
Withintheperiodof15 years GAILhasemergedandmaintained itsposition as theno.1gas
companyinIndia.Ithaswontheexcellent performanceawardsforthepastfiveyears
consecutivelyandalsosafetyawardsfrom theOilIndustrySafetyDirectorate(OISD)and British
Safety Council. It has an ISO-9002 certification for its pipeline system. LPG plants and
GasTechnologyInstituteandalsoISO-14001certificationforitsLPGplantsatVijaypur ,
VaghodiaandalongtheHVJPipelinemakingitthe1Indiancompanyinthepetroleumsector to secure
this certification.
Recently the running LPG plant at UPPCPATA was dedicated to the nation on 20thJune’01
by theHonorableOilandPetroleum ministerMr.R.Naik.AsaGAILsubsidiary,UPPCPATAis
anintegratedPetrochemicalComplexwithaninvestmentofRs.2500CroreitselfandLPGplant is
installed with a capital investment of Rs.460 Crore. This complex recovers ethane, propane
(C2/C3) from natural gas.
Ratnagiri Gas And Power Pvt. Ltd. (RGPPL) is a joint venture company between GAIL
(India) Ltd, NTPC Limited, Indian Financial Institutions (IFIs) and MSEB Holding Company
Limited. The promoters have incorporated and registered the company as a private limited
company on 8 July 2005. The authorised share capital of the company is 20 billion and the
shareholdings of GAIL, NTPC and IFI's are 28 1/3% each and MSEB 15%. The project is
located at Ratnagiri district of Maharashtra state about 340 km south of Mumbai. The project
has power generation capacity of 2150 MW along with an integrated 5 MMTPA LNG terminal.
Primary fuel for the power plant is natural gas.
CHAPTER 2
SUBSTATION AND SWITCHYARD

12. xii
2.1 SUBSTATION AND SWITCHYARD
Electricity is a necessity of modern life. Transmission and distribution (T&D) systems
provide electricity to consumers wherever and whenever it is needed. Two of the major
components of a typical T&D system are substations and switch yards.
2.2 SWITCHYARD AT GAIL, PATA
 Two Incomersare comingfromNTPCAuGPSwhichare at 220 KV.
 At switchyardtheyare steppeddownto33 KV bytwo transformersof 40 MVA.
 220 KV SF6typesCGL(five innumber) make outdoorcircuitbreakersare used.
 VacuumCircuitBreakersare usedat33 KV side of transformer.
 Thispowerisfedto SS#1, and there are 4 sectionof 33 KV bus.
 All the busbars are connectedinparallel sothatincase oneincomerfailsothercantake full load.
 15.6 MWSTG is connectedto33 KV bus section2.
 25.5 MWSTG is connectedto33 KV bus section 3.
 At SS#1, 33 KV voltage is stepped down to 6.6 KV with the help of 4 transformers of33/6.6 KV
25/31.5 MVA.
Power at6.6 KVlevelis fedto various substationall overthe plant through cables.
2.3 SWITCHYARD AND ITS PART
In switchyard (Gail- pata ) following equipments are used-:

13. xiii
POTENTIAL TRANSFORMER
Potential transformers are devices that reduce line voltage to a proportionally lower and safer
voltage for metering and relaying. A potential transformer, normally has a
large porcelain bushing that insulates the higher voltage conductor going into the
transformer. The transformer itself is usually enclosed in a metal housing. The output wires of
the transformers are enclosed in conduit to protect them. These wires connect to meters or
relaying equipment in a control house. Potential transformers come in many shapes and sizes.
They are sometimes difficult to distinguish from other devices such as some current transformers
and surge arrestors. For this reason, potential transformers are often identified in substations.
CURRENT TRANSFORMER
A current transformer(CT) is used for measurement of alternating electric currents. Current
transformers, together with voltage transformers (VT) (potential transformers (PT)), are known
as instrument transformers. When current in a circuit is too high to apply directly to measuring
instruments, a current transformer produces a reduced current accurately proportional to the
current in the circuit, which can be conveniently connected to measuring and recording
instruments. A current transformer isolates the measuring instruments from what may be very
high voltage in the monitored circuit. Current transformers are commonly used in metering and
protective relaysin the electrical power industry.
LIGHTNING ARRESTER
A lightning arrester is a device used on electrical powersystems and
telecommunicationssystems to protect the insulationand conductors of the system from the
damaging effects of lightning. The typical lightning arrester has a high-voltageterminal and a
ground terminal. When a lightning surge (or switching surge, which is very similar) travels along
the power line to the arrester, the current from the surge is diverted through the arrestor, in most
cases to earth.
If protection fails or is absent, lightning that strikes the electrical system introduces
thousands of kilovolts that may damage the transmission lines, and can also cause severe damage
to transformers and other electrical or electronic devices. Lightning-produced extreme voltage
spikes in incoming power lines can damage electrical home appliances.

14. xiv
EARTH SWITCH
The use of earth switches is to send any trapped charge in the line into ground after thelineis
switched off. Mainly what happens, when the line is switched off, some charges remain trapped
in line due to their own capacity and also due to influence of side by X-line. This trapped charge
is dangerous if someone goes for maintenance of that very line. So it is very much required to
neutralize that much charge and here comes the use of earth switches.
DISCONNECTOR
In electrical engineering, a dis-connector, disconnect switch or isolator switch is used to
ensure that an electrical circuit is completely De-energized for service or maintenance. Such
switches are often found in electrical distribution and industrial applications, where machinery
must have its source of driving power removed for adjustment or repair. High-voltage isolation
switches are used in electrical substations to allow isolation of apparatus such as circuit breakers,
transformers, and transmission lines, for maintenance. The dis-connector is usually not intended
for normal control of the circuit, but only for safety isolation. Dis-connector can be operated
either manually or automatically (motorized dis-connector).
Unlike load break switches and circuit breakers, dis-connectors lack a mechanism for
suppression of electric arc, which occurs when conductors carrying high currents are electrically
interrupted. Thus, they are off-load devices, intended to be opened only after current has been
interrupted by some other control device. Safety regulations of the utility must prevent any
attempt to open the dis-connector while it supplies a circuit. Standards in some countries for
safety may require either local motor isolators or lockable overloads (which can be padlocked).
Dis-connectors have provisions for a padlock so that inadvertent operation is not possible
(lockout-tagout). In high-voltage or complex systems, these padlocks may be part of a trapped-
key interlock system to ensure proper sequence of operation. In some designs, the isolator switch
has the additional ability to earth the isolated circuit thereby providing additional safety. Such an
arrangement would apply to circuits which inter-connect power distribution systems where both
ends of the circuit need to be isolated.

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CIRCUIT BREAKER
Electrical circuit breaker is a switching device which can be operated manually as well as
automatically for controlling and protection of electrical power system respectively. As the
modern power system deals with huge currents, the special attention should be given during
designing of circuit breaker to safe interruption of arc produced during the operation of circuit
breaker. This was the basic definition of circuit breaker.
INTRODUCTION TO CIRCUIT BREAKER
The modern power system deals with huge power network and huge numbers of associated
electrical equipment. During short circuit fault or any other types of electrical fault these
equipment as well as the power network suffer a high stress of fault current in them which may
damage the equipment and networks permanently. For saving these equipment and the power
networks the fault current should be cleared from the system as quickly as possible. Again after
the fault is cleared, the system must come to its normal working condition as soon as possible for
supplying reliable quality power to the receiving ends. In addition to that for proper controlling
of power system, different switching operations are required to be performed. So for timely
disconnecting and reconnecting different parts of power system network for protection and
control, there must be some special type of switching devices which can be operated safely under
huge current carrying condition. During interruption of huge current, there would be large arcing
in between switching contacts, so care should be taken to quench these arcs in circuit breakerin
safe manner. The circuit breaker is the special device which does all the required switching
operations during current carrying condition. This was the basic introduction to circuit breaker.
2.4 POWER DISTRIBUTION SYSTEM
 Power fed from two independent overhead lines from NTPC at 220KV.

16. xvi
 In-house generation capacity of 41 MW. Present generation of 16 MW From STG-
1(6MW) & STG-2(10MW) at 11KV.
 Import Power is approx 25-28MW from NTPC.
 Both the power is synchronized at 33KV.
 Present load of plant : 41MW(Average).
220KV/ 33 KV
SWITCHYARD
2x 220KV LINES FROM NTPC
33KV/ 6.6 KV
SUB-STATION-1
33 KV
11KV/ 33 KV STG-1 & 2
GAILPOWER PLANT
33KV
6.6 KV
SS-2 CT-
1&2
SS-3
STORAGE
6.6KV
SS-5
WORKSHOP
SS-7 WWTP SS-8 LPG
SS-12
HDPE/LLDPE
SS-4 RWTP-
1
SS-11
GPU/GCU
SS-4A RWTP-
2
SS-4B RWTP SS-6 POLYMER
BHAWAN
6.6 KV BUS6.6 KV BUS
SS-18
HDPE-2
Electrical Power Distribution System
220 KV
33 KV
GAILGAON
33 KV

17. xvii
CHAPTER 3
TRANSFORMER
3.1 TRANSFORMER
The principle parts of a transformer and their functions are:
• The core, which makes a path for the magnetic flux.
• The primary coil, which receives energy from the ac source.
• The secondary coil, which receives energy from the primary winding
and delivers it to the load.
• The enclosure, which protects the transformer from dirt, moisture, and
Mechanical damage.
1) Transformer Core
The composition of a transformer core depends on voltage, current, and frequency.
Commonly used core materials are air, soft iron, and steel. Each of these materials is suitable for
certain applications. Generally, air-core transformers are used when the voltage source has a high
frequency (above 20 kHz). Iron-core transformers are usually used when the source frequency is
low (below 20 kHz).
A soft-iron-core transformer is very useful where the transformer must be physically small,
yet efficient. The iron-core transformer provides better power transfer than does the air-core

18. xviii
transformer. A transformer whose core is constructed of laminated sheets of steel dissipates heat
readily; thus it provides for the efficient transfer of power.
The majority of transformers contain laminated-steel cores. These steel
Laminations are insulated with a nonconducting material, such as varnish, and then formed
into a core. It takes about 40 laminations to make a core of 2 cm thick.
The most efficient transformer core is one that offers the best path for the most lines of flux
with the least loss in magnetic and electrical energy.
Table 3.1
TRANSFORMER RATING IN SWITCHYARD
POWER RATING
SERIA
L NO.
SPECIFICATION RATINGS
1) POWER RATING
MVA 40
2) VOLTAGE RATING
KV(HV) 220
KV(LV) 34.5
3) CURRENT RATING
AMPERE (HV) 105
AMPERE(LV) 669.5
4) PHASE 4
5) FREQUENCY 50
6) TYPES OF COOLING ONAF/ONAN
7) RATING MVA 30/40
8) OC (Rise temperature) 50 celsius
9) WINDING 55 celsius

19. xix
10) TOTAL OIL 25000/28570
11) TOTAL MASS 89000KG
3.2) MAJOR EQUIPMENT IN TRANSFORMER
Fig 3.1 conservator tank of transformer
This is a cylindrical tank mounted on supporting structure on the roof the transformer main
tank. The main function of conservator tank of transformeris to provide adequate space for
expansion of oil inside the transformer.

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Function of Conservator Tank of a Transformer
When transformer is loaded and when ambient temperature rises, the volume of oil inside
transformer increases. A conservator tank of transformer provides adequate space to this
expanded transformer oil. It also acts as a reservoir for transformer insulating oil.
Construction of Conservator Tank
This is a cylindrical shaped oil container closed from both ends. One large inspection cover is
provided on either side of the container to facilitate maintenance and cleaning inside of the
conservator.
Conservator pipe, i.e., pipe comes from main transformer tank, is projected inside the
conservator from bottom portion. Head of the conservator pipe inside the conservator is provided
with a cap. This pipe is projected as well as provided with a cap because this design prevents oil
sludge and sediment to enter into main tank from conservator. Generally silica gel breather
fixing pipe enters into the conservator from top. If it enters from bottom, it should be projected
well above the level of oil inside the conservator. This arrangement ensures that oil does not
enter the silica gel breather even at highest operating level.
Working of Conservator Tank
When volume of transformer insulating oil increases due to load and ambient temperature,
the vacant space above the oil level inside the conservator is partially occupied by the expanded
oil. Consequently, corresponding quantity of air of that space is pushed away through breather.
On other hand, when load of transformer decreases, the transformer is switched off and when the

21. xxi
ambient temperature decreases, the oil inside the transformer contracts. This causes outside air to
enter in the conservator tank of transformer through silica gel breather.
SILICA GEL BREATHER OF TRANSFORMER
Fig.3.2 silica gel breather of transformer
Whenever electrical power transformeris loaded, the temperature of the transformer
insulating oilincreases, consequently the volume of the oil is increased. As the volume of the oil
is increased, the air above the oil level in conservator will come out. Again at low oil
temperature; the volume of the oil is decreased, which causes the volume of the oil to be
decreased which again causes air to enter into conservator tank. The natural air always consists
of more or less moisture in it and this moisture can be mixed up with oil if it is allowed to enter
into the transformer. The air moisture should be resisted during entering of the air into the
transformer, because moisture is very harmful for transformer insulation. A silica gel breather is
the most commonly used way of filtering air from moisture. Silica gel breather for transformer is
connected with conservator tank by means of breathing pipe.
WORKING PRINCIPLE OF BREATHER
Silica gel crystal has tremendous capacity of absorbing moisture. When air passes through
these crystals in the breather; the moisture of the air is absorbed by them. Therefore, the air
reaches to the conservator is quite dry, the dust particles in the air get trapped by the oil in the oil
seal cup. The oil in the oil sealing cup acts as barrier between silica gel crystal and air when there
is no flow of air through silica gel breather. The color of silica gel crystal is dark blue but, when

22. xxii
it absorbs moisture; it becomes pink. When there is sufficient difference between the air inside
the conservator and the outside air, the oil level in two components of the oil seal changes until
the lower oil level just reaches the rim of the inverted cup, the air then moves from high pressure
compartment to the low pressure compartment of the oil seal. Both of these happen when the oil
acts as core filter and removes the dust from the outside air.
BUCHHOLZ RELAY
Construction of Buchholz Relay
Buchholz relay in transformer is an oil container housed the connecting pipe from main tank
to conservator tank. It has mainly two elements. The upper element consists of a float. The float
is attached to a hinge in such a way that it can move up and down depending upon the oil level in
the Buchholz relay Container. One mercury switch is fixed on the float. The alignment of
mercury switch hence depends upon the position of the float.
The lower element consists of a baffle plate and mercury switch. This plate is fitted on a
hinge just in front of the inlet (main tank side) of Buchholz relay in transformer in such a way
that when oil enters in the relay from that inlet in high pressure the alignment of the baffle plate
along with the mercury switch attached to it, will change.
Fig 3.3 buchholz relay

23. xxiii
PRINCIPLE OF BUCHHOLZ RELAY
The Buchholz relay working principle of is very simple. Buchholz relay function is based
on very simple mechanical phenomenon. It is mechanically actuated. Whenever there will be a
minor internal fault in the transformer such as an insulation faults between turns, break down of
core of transformer, core heating, the transformer insulating oil will be decomposed in different
hydrocarbon gases, CO2 and CO. The gases produced due to decomposition of transformer
insulating oil will accumulate in the upper part the Buchholz container which causes fall of oil
level in it.
3.3 GENERATION IN GAIL-PATA
In Gail (pata) power is taken from ntpc and also generated here. For power generationtwo
generators which are synchronized with the grid.
1) There are twosteamturbine used -:
a) STG 1 have extraction type turbine in this turbine VHP steam at 105 kg/cm sq. is fed and HP
steamat 40 kg/cm sq.is extracted.The steamisusedinplantoperation
b) STG2 have condensate type turbine in which output steam is condensate and water is
recirculatedtoDM waterplant.
2) Power is generated at STG1 at 11kv level and then stepped to 33kv with the help of 20 MVA and
a 30 MVA transformer
3) STG is helpful inmaintainingthe powerfactorof plantloadabove 0 .95
4) The speed of STG-1 turbine is up to 8580 rpm and generator’s speed is 3000 rpm (speed
reducedusingGEARS) butin STG-2 speedof bothturbine andgeneratorissame.
5) Frequencyof Exciteris1500 rpm.

24. xxiv
Table 3.2
TECHNICAL DATA OF TURBO GENERATOR
STG-1 - 15.5 MW
SERIAL
NO.
SPECIFICATION RATING
1) APPARENT OUTPUT 19.375 MVA
2) ACTIVE OUTPUT 15.50 MW
3) RATED POWER FACTOR 0.8 LAG
4) STATOR (RATING)
RATED VOLTAGE 11000V
RATED CURRENT 1017A
RATED SPEED 3000RPM
5) ROTOR(RATING)
RATED VOLTAGE 33KV
RATED CURRENT 484A
6) FREQUENCY 50HZ
7) GENERATOR FIELD
RESISTANCE
.198 OHM
8) NO. OF GENERATOR
TERMINALS
6

25. xxv
Table 3.3
TECHNICAL DATA OF TURBO GENERATOR
STG 2 25.6MW
SERIAL NO. SPECIFICATION RATING
1) ACTIVE OUTPUT 25.6MW
2) RATED POWER FACTOR 0.8LAG
3) APPARENT OUTPUT 32MW
4) STATOR (RATING)
RATED VOLTAGE 11000V
RATED CURRENT 1680A
5) ROTOR(RATING)
RATINGVOLTAGE 181V
RATINGCURRENT 593A
6) FREQUENCY 50HZ

26. xxvi
CHAPTER 4
ELECTRICAL WORKSHOP
4.1)MOTOR
An electric motor is an electric machine that converts electrical energy into mechanical
energy.In normal motoring mode, most electric motors operate through the interaction between
an electric motor's magnetic field and winding currents to generate force within the motor. In
certain applications, such as in the transportation industry with traction motors, electric motors
can operate in both motoring and generating or braking modes to also produce electrical energy
from mechanical energy. Found in applications as diverse as industrial fans, blowers and pumps,
machine tools, household appliances, power tools, and disk drives, electric motors can be
powered by direct current (DC) sources, such as from batteries, motor vehicles or rectifiers, or by
alternating current (AC) sources, such as from the power grid, inverters or generators. Small
motors may be found in electric watches. General-purpose motors with highly standardized
dimensions and characteristics provide convenient mechanical power for industrial use. The
largest of electric motors are used for ship propulsion, pipeline compression and pumped-storage
applications with ratings reaching 100 megawatts. Electric motors may be classified by electric
power source type, internal construction, application, type of motion output, and so on.

27. xxvii
Devices such as magnetic solenoids and loudspeakers that convert electricity into motion but
do not generate usable mechanical power are respectively referred to as actuators and
transducers. Electric motors are used to produce linear force or torque (rotary).
In simple words we can say a device that produces rotational force is a motor. The very basic
principal of functioning of an electrical motor lies on the fact that force is experienced in the
direction perpendicular to magnetic field and the current, when field and electric current are
made to interact with each other. Ever since the invention of motors, a lot of advancements have
taken place in this field ofengineering and it has become a subject of extreme importance for
modern engineers.
The primary classification of motor or types of motor can be tabulated as shown below,
4.2) TYPES OF ELECTRIC MOTOR
The electric motor is a device which converts electrical energy to mechanical energy. There
are mainly three types of electric motor.
1) DC Motor.
2)Induction Motor.
3) Synchronous Motor.
All of these motors work in more or less same principle. Working of electric motor mainly
depends upon the interaction of magnetic field with electric current.
Now we will discuss the basic operating principle of electric motor one by one for better
understanding the subject.
Working of DC Motor
Working principle of DC Motor mainly depends upon Fleming Left Hand rule. In a basic dc
motor, an armature is placed in between magnetic poles. If the armature winding is supplied by
an external d c source, electric currentstarts flowing through the armature conductors. As the
conductors are carrying current inside a magnetic field, they will experience a force which tends
to rotate the armature. Suppose armature conductors under N poles of the field magnet, are
carrying current downwards (crosses) and those under S poles are carrying current upwards
(dots). By applying Fleming’s Left hand Rule, the direction of force F, experienced by the

28. xxviii
conductor under N poles and the force experienced by the conductors under S poles can be
determined. It is found that at any instant the forces experienced by the conductors are in such a
direction that they tend to rotate the armature. Again, due this rotation the conductors under N –
poles come under S – pole and the conductors under S – poles come under N – pole. While the
conductors go form N – poles to S – pole and S – poles to N – pole, the direction of current
through them, is reversed by means of commutator. Due to this reversal of current, all the
conductors come under N - poles carry current in downward direction and all the conductors
come under S – poles carry current in upward direction as shown in the figure. Hence, every
conductor comes under N – pole experiences force in same direction and same is true for the
conductors come under S – poles. This phenomenon helps to develop continuous and
unidirectional torque.
Working of Induction Motor
Working of electric motor in the case of induction motor is little bit different from dc motor.
In single phase induction motor, when a single phase supply is given to the stator winding, a
pulsating magnetic field is produced and in a three phase induction motor, when three phase
supply is given to three phase stator winding, a rotating magnetic field is produced. The rotor of
an induction motor is either wound type or squirrel cadge type. Whatever may be the type of
rotor, the conductors on it are shorted at end to form closed loop. Due to rotating magnetic field,
the flux passes through the air gap between rotor and stator, sweeps past the rotor surface and so
cuts the rotor conductor. Hence according to Faraday’s law of electromagnetic induction, there
would be a induced current circulating in the closed rotor conductors. The amount of induced
current is proportional to the rate of change of flux linkage with respect to time. Again this rate
of change of flux linkage is proportional to the relative speed between rotor and rotating
magnetic field. As per Lenz law the rotor will try to reduce the every cause of producing current
in it. Hence the rotor rotates and tries to achieve the speed of rotating magnetic field to reduce
the relative speed between rotor and rotating magnetic field.
4.3) Types Induction Motor

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SINGLE PHASE INDUCTION MOTOR
1) Splitphase inductionmotor
2) Capacitorstart inductionmotor
3) Capacitorstart capacitor runs inductionmotor
4) Shadedpole inductionmotor
4.4) THREE PHASE INDUCTION MOTOR
1) Squirrel cage inductionmotor
2) Slipringinductionmotor
We had mentioned above that single phase induction motoris not a self starting and three
phase induction motoris self starting. So what is self starting? When the machine starts running
automatically without any external force to the machine, then it is called as self starting. For
example we see that when we press the key the fan starts to rotate automatically, so it is self
starting. Point to be note that fan used in home appliances is single phase induction motorbut it is
self starting. How? We will discuss it how.
4.5) CONSTRUCTION OF THREE PHASE INDUCTION MOTOR
The three phase induction motor is the most widely used electrical motor. Almost 80% of the
mechanical power used by industries is provided by three phase induction motors because of its
simple and rugged construction, low cost, good operating characteristics, absence of commutator
and good speed regulation. In three phase induction motor the power is transferred from stator to
rotor winding through induction. The Induction motor is also called asynchronous motor as it
runs at a speed other than the synchronous speed.
Like any other electrical motor induction motor also have two main parts namely rotor and
stator
Stator: As its name indicates stator is a stationary part of induction motor. A stator winding is
placed in the stator of induction motor and the three phase supply is given to it.
Rotor: The rotor is a rotating part of induction motor. The rotor is connected to the mechanical
load through the shaft.
The rotor of the three phase induction motor are further classified as

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Squirrel cage rotor,
Slip ring rotor or wound rotor or phase wound rotor.
Depending upon the type of rotor construction used the three phase induction motor are
classified as:
Squirrel cage induction motor,
Slip ring induction motor or wound induction motor or phase wound induction motor.
The construction of stator for both the kinds of three phase induction motor remains the same
and is discussed in brief in next paragraph.
The other parts, which are required to complete the induction motor, are:
Shaft for transmitting the torque to the load. This shaft is made up of steel.
Bearings for supporting the rotating shaft.
One of the problems with electrical motor is the production of heat during its rotation.
In order to overcome this problem we need fan for cooling.
For receiving external electrical connection Terminal box is needed.
There is a small distance between rotor and stator which usually varies from 0.4 mm to 4 mm.
Such a distance is called air gap.
4.6) SQUIRREL CAGE INDUCTION MOTOR
The rotor of the squirrel cage three phase induction motor is cylindrical in shape and has slots
on its periphery. The slots are not made parallel to each other but are bit skewed (skewing is not
shown in the figure of squirrel cadge rotor beside) as the skewing prevents magnetic locking of
stator and rotor teeth and makes the working of motor more smooth and quieter. The squirrel
cage rotor consists of aluminum, brass or copper bars (copper bras rotor is shown in the figure
beside). These aluminum, brass or copper bars are called rotor conductors and are placed in the
slots on the periphery of the rotor. The rotor conductors are permanently shorted by the copper or
aluminum rings called the end rings. In order to provide mechanical strength these rotor
conductor are braced to the end ring and hence form a complete closed circuit resembling like a
cage and hence got its name as "squirrel cage induction motor". The squirrel cage rotor winding
is made symmetrical. As the bars are permanently shorted by end rings, the rotor resistance is
very small and it is not possible to add external resistance as the bars are permanently shorted.
The absence of slip ring and brushes make the construction of Squirrel cage three phase

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induction motor very simple and robust and hence widely used three phase induction motor.
These motors have the advantage of adapting any number of pole pairs. The below diagram
shows squirrel cage induction rotor having aluminum bars short circuit by aluminum end rings.
Advantages of squirrel cage induction rotor-
Its construction is very simple and rugged.
As there are no brushes and slip ring, these motors requires less maintenance.
Applications:
Squirrel cage induction motor is used in lathes, drilling machine, fan, blower printing machines
etc.
4.7) SLIP RING INDUCTION MOTOR
In this type of three phase induction motor the rotor is wound for the same number of poles
as that of stator but it has less number of slots and has less turns per phase of a heavier
conductor. The rotor also carries star or delta winding similar to that of stator winding. The rotor
consists of numbers of slots and rotor winding are placed inside these slots. The three end
terminals are connected together to form star connection. As its name indicates three phase slip
ring induction motor consists of slip rings connected on same shaft as that of rotor. The three
ends of three phase windings are permanently connected to these slip rings. The external
resistance can be easily connected through the brushes and slip rings and hence used for speed
control and improving the starting torque of three phase induction motor. The brushes are used to
carry current to and from the rotor winding. These brushes are further connected to three phase
star connected resistances. At starting, the resistance is connected in rotor circuit and is gradually
cut out as the rotor pick up its speed. When the motor is running the slip ring are shorted by
connecting a metal collar, which connect all slip ring together and the brushes are also removed.
This reduces wear and tear of the brushes. Due to presence of slip rings and brushes the rotor
construction becomes somewhat complicated therefore it is less used as compare to squirrel cage
induction motor.
Advantages of slip ring induction motor -

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It has high starting torque and low starting current.
Possibility of adding additional resistance to control speed.
Application:
Slip ring induction motor is used where high starting torque is required i.e. in hoists, cranes,
elevator etc.
4.8) COILING OF INDUCTION MOTOR
Induction motor coiling is done by NOMAX paper which has a insulation class F.
at first, running winding is coiled and then starting windingthe resistance difference between
the two should not be more than 10%insulation is must between running and starting coil to
avoid any touching of starting and running winding and hence reduces the faultcondenser is
needed to start the motor.
Table 4.1
THREE PHASE INDUCTION MOTOR IN GAIL PATA (LT)
SERIAL NO. SPECIFICATION RATING
1) TYPE MLA 5223B
2) OUTPUT 30KW
3) VOLTAGE 415V
4) FREQUENCY 50HZ
5) BEARING
D-END 6312C3
N-END 6212C3
6) INSULATION F
7) AMPERE 51
8) RPM 2940
9) POLES 2
10) COOLENT 42C

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Table 4.2
THREE PHASE INDUCTION MOTOR (HT)
SERIAL NO. SPECIFICATION RATING
1) OUTPUT 180KW
2) VOLTAGE 6.6KV
3) FREQUENCY 50HZ
4) INSULATION F
5) AMPERE 20
6) RPM 1478
7) CONNECTION STAR
Table 4.3
TRANSFORMER IN ELECTRICAL WORKSHOP
SERIAL NO. SPECIFICATION RATING
1) CONNECTION:
INPUT STAR
OUTPUT DELTA
2) POWER 2000KVA
3) VOLTAGE:

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H.V 6.6KV
L.V 433V
4) CURRENT:
H.V 14.9A
L.V 2666.7A
5) PHASES 3
6) FREQUENCY 50HZ
7) COOLING ONAN
8) TOTAL WEIGHT 6230KG
CONCLUSION
GAIL, PATA is an integrated plant. Everything depends on how fast it can complete its order
keeping in mind the quality of the product which it makes. As a huge plant it has taken some
majors to save the energy which must be there in a plant.
 Improve power factor by installing capacitor banks to reduce KVA demand chargers and
line losseswithinthe plant.
 Avoidrepeatedrewindingof motors.Rewoundmotors show efficiencylossof upto5
 Use of variable frequency drives, slip power recovery systems and fluid coupling for
variable speedapplicationslikefans,pumpshelptominimize the consumption.
 Replacing aluminum or fabricated steel fans by molded FRP fan with aerofoil design result
inelectrical savingupto15 to 40 %.

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