bhel - training report punnet
TRANSCRIPT
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INDUSTRIAL TRAINING REPORT
BHARAT HEAVY ELECTRICALS LIMITED
RANIPUR, HARIDWAR
AREA OF TRAINING: ROTOR AND STATOR WINDING ASSEMBLY OF THRI
AND LSTG
Submitted to the
Department of Electrical Engineering
in partial fulfillment of the requirements for the degree of
Bachelor of Technology
in
Electrical Engineering
JSS Academy of Technical Education, NOIDA
U.P. Technical University
SUBMITTED BY: SUBMITTED TO:
Puneet Kapoor Mr. Nirmal Kr. Aggarwal
(1109120122) (Indust. Training Presentation Coordinator)
VII-EE-B Electrical Engg. Deptt.
JSSATE, NOIDA
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ACKNOWLEDGEMENT
Training has an important role in exposing the real life situation in an industry. It was
a great experience for me to work on training at BHARAT HEAVY
ELECTRICALS LIMITED through which I could learn how to work in aprofessional environment.
Now, I would like to thank the people who guided me and have been a constant
source of inspiration throughout the tenure of my summer training.
I am sincerely grateful to MR. RAJ SINGH (Manager)at HRDC, BHEL Haridwar
who allowed me to pursue my summer training at the plant and rendered me his
valuable assistance, constant encouragement and able guidance which made this
training actually possible.
I wish my deep sense of gratitude to MR. SANJAY KUMAR (Asst. GeneralManager) whose affectionate guidance has enabled me to complete this training
successfully. I wish my deep sense of gratitude to Dr. V. K CHANDNA (HOD: EE
Department)whose guidance and encouragement made my training successful.
Puneet Kapoor
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CONTENTS
Topic Page No.
1.
BHELAn Overview. 1
2.
HEAVY ELECTRICAL EQUIPMENT PLANT (HEEP). 5
3. ELECTRICAL MACHINES (BLOCK1) 11
I. TURBO-GENERATOR. 12
II.
LARGE SIZE TURBO-GENERATOR. 13
III. COMPONENTS OF TURBO-GENERATOR. 14
a)
STATOR
1)
STATOR CORE.
2) STATOR WINDING.
3)
END COVERS.
b) ROTOR
1) STEPS IN ROTOR MACHINING.
IV. EXCITATION SYSTEM. 19
a)
EXCITER.
V.
BAY-4 (SMALL AND MISCALLANEOUS COMPONENTS) 20
VI. TEST STANDS. 26
VII. LSTG TEST STANDS. 26
VIII.
TESTING. 26
a) HELIUM LEAK TESTS
b) HYDROGEN TESTING AND PNEUMATIC TESTING.
4. CONCLUSION 27
5. REFERENCES 27
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1. BHELAN OVERVIEW
Bharat Heavy Electricals Limited(BHEL) owned by Government of India, is apower plant equipment manufacturer and operates as engineering and manufacturing
company based in New Delhi, India. Established in 1964, BHEL is India's largest
engineering and manufacturing company of its kind. The company has been earning
profits continuously since 1971-72 and paying dividends uninterruptedly since 1976-
77.
BHEL caters to core sectors of the Indian Economy viz., Power Generation's &
Transmission, Industry, Transportation, Telecommunication, Renewable Energy,
Defense, etc. The wide network of BHEL's 14 manufacturing division, four power
Sector regional centres, over 150 project sites, eight service centres and 18 regional
offices, enables the Company to promptly serve its customers and provide them with
suitable products, systems and servicesefficiently and at competitive prices. BHEL
has already attained ISO 9000 certification for quality management, and ISO 14001
certification for environment management.
POWER GENERATION
Power generation sector comprises thermal, gas, hydro and nuclear power plant
business as of 31.03.2001, BHEL supplied sets account for nearly 64737 MW or 65%
of the total installed capacity of 99,146 MW in the country, as against nil till 1969-70.
BHEL has proven turnkey capabilities for executing power projects from concept to
commissioning, it possesses the technology and capability to produce thermal setswith super critical parameters up to 1000 MW unit rating and gas turbine generator
sets of up to 240 MW unit rating. Co-generation and combined-cycle plants have been
introduced to achieve higher plant efficiencies. to make efficient use of the high-ash-
content coal available in India, BHEL supplies circulating fluidized bed combustion
boilers to both thermal and combined cycle power plants.
The company manufactures 235 MW nuclear turbine generator sets and has
commenced production of 500 MW nuclear turbine generator sets.
Custom made hydro sets of Francis, Pelton and Kapian types for different head
discharge combination are also engineering and manufactured by BHEL.
In all, orders for more than 700 utility sets of thermal, hydro, gas and nuclear have
been placed on the Company as on date. The power plant equipment manufactured byBHEL is based on contemporary technology comparable to the best in the world and
is also internationally competitive.
The Company has proven expertise in Plant Performance Improvement through
renovation modernisation and uprating of a variety of power plant equipment besides
specialised know how of residual life assessment, health diagnostics and life
extension of plants.
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POWER TRANSMISSION & DISTRIBUTION (T & D)
BHEL offer wide ranging products and systems for T & D applications. Products
manufactured include power transformers, instrument transformers, dry type
transformers, seriesand stunt reactor, capacitor tanks, vacuumand SF circuitbreakers gas insulated switch gears and insulators.
A strong engineering base enables the Company to undertake turnkey delivery of
electric substances up to 400 kV level series compensation systems (for increasing
power transfer capacity of transmission lines and improving system stability and
voltage regulation), shunt compensation systems (for power factor and voltage
improvement) and HVDC systems (for economic transfer of bulk power). BHEL has
indigenously developed the state-of-the-art controlled shunt reactor (for reactive
power management on long transmission lines). Presently a 400 kV Facts (Flexible
AC Transmission System) project under execution.
INDUSTRIES
BHEL is a major contributor of equipment and systems to industries. Cement, sugar,
fertilizer, refineries, petrochemcials, paper, oil and gas, metallurgical and other
process industries lines and improving system stability and voltage regulation, shunt
compensation systems (for power factor and voltage improvement) and HVDC
systems (for economic transfer of bulk power) BHEL has indigenously developed the
state-of-the-art controlled shunt reactor (for reactive power management on long
transmission lines). Presently a 400 kV FACTS (Felxible AC Transmission System)
projects is under execution.
ACTIVITY PROFILE
PRODUCTS - Industrial Fans
Power Generation & Transmission - Seamless steel Tubes
- Steam Turbine-Generator Sets &
Auxiliaries
- Fabric Filters
- Boiler and Boiler Auxiliaries - AC DC Motors, Variable speed
- Once-through Boilers - AC Drive
- Nuclear Power Generation Equipment - Electronic Control Gear &
Automation
- Hydro Turbine-Generator Sets & Auxiliaries - Equipment- Mini/Micro Hydro Generator Sets - DDC for Process Industry
- Gas Turbine-Generator Sets - Thruster Equipment
- Waste Heat Recovery Boilers - Power Devices
- Heat Exchangers - Energy Meters
- Condensers - Transformer
- Bowi Mills and Tube Mills - Switch gear
- Gravimetric Feeders - Insulator
- Regenerative Air Pre-Heaters - Capacitors
- Electrostatic Precipitators - Broad Gauge AC, AC/DC Loco
Motives
- Bag Filters - Diesel-Electric ShuntingLocomotives
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- Valves - Traction Motors & Control
Equipment
- Pumps - Electric Trolley Buses
- Electrical Machines - AC/DC Electric Multiple Units
- Piping Systems - Drives and Controls for Metro
Systems- Power, Distribution & Instrument Transformers - Battery-Operated Passengers
Vans
- Reactors - X-Mas Trees and Well Heads
- Synchronous Condensers - Cathodic Protection Equipment
- Switchgear - Digital Switching Systems
- Control gear - Rural Automatic Exchange
- Distributed Digital Control for Power
Stations
- Simulators
- Bus Ducts - Wind Electric Generators
- Rectifiers - Solar Powered Water Pumps
- Porcelain Insulators - Solar Water Heating Systems- Ceralin - Photo Votaic Systems
- Defense Equipment
Industries/Transportation/Oil & Gas/ - Reverse Osmoses Desalination
Plants
Telecommunication/Renewable Energy SYSTEMS & SERVICES- Steam Turbine-Generator Sets - Turkey Utility Power Stations/
EPC
- Gas Turbine-Generator Sets - Contracts
- Diesel Engine-Based Generators - Captive Power Plants
- Industrial Steam Generators - Co-generation Systems
- Heat Recovery Steam Generators - Combined Cycle Power Plants
- Fluidised Bed Combustion Boilers - Modernisation & Renovation of
Power
- Drive Turbine Stations and FLA Studies
- Manne Turbines - Switch yards and Substations
- Industrial Heat Exchangers - HVDC Transmission Systems
- Centrifugal Compressor - Shorts sines condensation
Systems
- Industrial Valves - Power system analysis
- Reactors - Electron comissionly and
Operation- Columns - Consultancy services
- Pressure Vessels - Consultancy Services
- Pumps
SUMMARY OF BHEL'S CONTRIBUTION TO VARIOUS CORE SECTORS
POWER GENERATION
THERMAL RATING (MW) NO. OF
SETS
TOTAL
CAPACITY (MW)500 30 15000
250 9 2250210/200 138 28570
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120/125/130 20 2420
195 1 195
110 38 4180
100 6 600
70/67.5 6 410
60 14 84030 5 150
TOTAL
(THERMAL)
267 54615
GAS FRAME SIZE/
SCOPE
NO. OF
SETS
TOTAL
CAPACITY (MW)9 5 730
6 17 580
5 13 309
3 6 48
V 94.2 2 2866FA 3 207
STG 24 1190
GEN 4 87
TOTAL (GAS) 74 3437
NUCLEAR RATING (MW) NO. OF
SETS
TOTAL
CAPACITY (MW)500 2 1000
220 10 2200
TOTAL
(NUCLEAR)
12 3200
TOTAL (THERMAL+GAS+NUCLEAR) 353 61252
HYDRO 402 18735
GRAND TOTAL 755 79987
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2. HEAVY ELECTRICAL EQUIPMENT PLANT (HEEP)
At Hardwar, against the picturesque background of Shivalik Hills, two
important manufacturing units of BHEL are located viz. Heavy Electrical Equipment
Plant (HEEP) & Central Foundry Forge Plant (CFFP). The hum of the construction
machinery working started under Shivalik Hills during early 60s and sowed the seeds
of one of the greatest symbol of Indo Soviet Collaboration Heavy Electrical
Equipment Plant.
Consequent upon the technical collaboration between India and USSR in
1959, BHELs prestigious unit, Heavy Electrical Equipment plant (HEEP), was
established in October, 1963, at Hardwar. It started manufacturing thermal sets in
1967 and now thermal sets of 210, 250 and 500 MW, including steam turbines, turbo-
generators, condensers and all associated equipments, are being manufactured. This
unit is capable of manufacturing thermal sets up to 1000 MW. HEEP-manufactured
gas turbines, hydro turbines and generators, etc., are not only successfully generating
electrical energy within and outside the country, but have also achieved a historic
record of the best operational availability and plant load factor.
The Company is embarking upon an ambitions growth path through clearvision, mission and committed values to sustain and augment its image as a world
class enterprise.
VISION
World-class, innovative, competitive and profitable engineering enterprise providing
total business solutions.
MISSION
The leading Indian engineering enterprise providing quality products systems and
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services in the fields of energy, transportation, infrastructure and other potential areas.
VALUES
Meeting commitments made to external and internal customers.
Foster learning creativity and speed of response.
Respect for dignity and potential of individuals.
Loyalty and pride in the company.
Team playing
Zeal to excel.
Integrity and fairness in all matters.
ESTABLISHMENT AND DEVELOPMENT STAGES
Established in 1960s under the Indo-Soviet Agreements of 1959 and 1960 in the area
of Scientific, Technical and Industrial Cooperation.
DRRprepared in 1963-64, construction started from October '63
Initial production of Electric started from January, 1967.
Major construction / erection / commissioning completed by 1971-72 as per original
DPR scope.
Stamping Unit added later during 1968 to 1972.
Annual Manufacturing capacity for Thermal sets was expanded from 1500 MW to
3500 MW under LSTG. Project during 1979-85 (Sets up to 500 MW, extensible to
1000/1300 MW unit sizes with marginal addition in facilities with the collaboration of
M/s KWU-Siemens, Germany.
Motor manufacturing technology updated with Siemens collaboration during 1984-87.
S.No. Area/ Block Major Facilities Products
1. BlockI
(Electrical
Machines)
Machine Shop., Windings bar
preparation assembling, painting
section, packing& preservation,
over speed balancing, test bed test
stand, babbiting, micalastic
impregnation etc.
Turbo Generator,
Generator exciters,
motors (AC& DC)
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2. BlockII
(Fabrication
Block)
Markings, welding ,Cutting,
straightening, gas cutting press, ,
grinding, assembly, heat
treatment, cleaning & Shotblasting, machining, fabrication of
pipe coolers, painting
Large size fabricated
assemblies/
components for power
equipments
3. BlockIII
(Turbines &
Auxiliary Block)
Machining, facing wax melting,
broaching, assembly preservation
& packing, test stands/ station,
painting grinding, milling,
polishing etc.
Stem turbines, hydro
turbines, gas turbines,
turbine bladders,
special tooling.
4. BlockIV
(Feeder Block)
Bar winding, mechanical
assembly, armature winding,
sheet metal working marching,
copper profile drawing
electroplating, impregnation,
machining & preparation of
insulating components plastic
molding, press molding
Windings for turbo
generators, hydro
generators insulation
for AC & DC motors,
insulating components
for TG, HG & Motors
control panel, contact
relays master control
etc.
5. BlockV Fabrication, pneumatic hammer
for forgings, gas fired furnaces,
hydraulic manipulators
Fabricated parts of
steam turbine, water
box, storage tankhydro turbine parts,
hydro turbines
assemblers &
Components
6. BlockVI Welding, drilling, shot blasting,
CNC flame cutting ,CNC deep
Fabricated parts of
steam turbine water
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(Fabrication) drilling, Shot basting, sheet metal
work, assembly
box, stronger tanks,
hydro turbine parts,
Hydro turbines
assemblies &components,
7. Block- VI
(Stamping & Die
Manufacturing)
Machining, turning, grinding, jig
boring stamping presses, de
varnishing, degreasing & de
rusting, varnishing sport welding,
painting.
Wooden packing,
spacers etc.
8. Block- VII (wood
working)
Wood Cutting, machines,
grinding , packing
Wooden packing,
spacers etc.
9. BlockVIII Drilling ,turning, saw, cutting,
welding, tig welding
LP Heater ejectors
glad, steam cooler oil
coolers, ACG collers,
oil tanks, bearing
covers.
10. Services plat TPS : Power generation
equipment & auxiliaries plat
capacity 12 MW
Power generation
PGP Plat : Boiler Type gasgenerators
Producer gas
Acetylene Plat : A fully
automated plant for acetylene
generation & filling in cylinder
Acetylene gas
Compressor House: 4 No.
Compressors of rating 100 m2 /
min
Compressed air
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Oxygen Plat : 3 air separation unit
4 air compressors
Oxygen gas
Nitrogen gas
132 KV substation : 2 Nose 16.7
MVA/ 11 KV, one no. 20 MVA
& one no. 12.5 MVA 132/6.6 KV
transformer & other allied
equipment
Power supply
11. Motor transport A fleet of vehicles comprising of
cars, jeeps trekkers, buses, mini
buses motorcycles , fire tenders
trucks etc.
Transport service
12. Telecommunication A 2000 line main exchange for
internal communication
3 no Satellite exchange
Telephone service
13. Hydro Turbine Lab 3 test beds with electronic
instrumentation. It consists of
cavitations test bed for reactions
turbine & hydrodynamic test bed
for Impulse turbines facilities for
carrying out filed test at hydro
power sets.
Testing of turbine
models
14. HRDC Class room with audiovisual
facilities workshop with facilities
for turnings fitting machining,
weeding, electrical work
carpentry work
Training to
Employees, VTs
Apprentices,
Contractors &
Customers
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CLIMATIC AND GEOGRAPHICAL CONDITIONS
Hardwar is in extreme weather zone of the Western Uttar Pradesh of India and
temperature varies from 2oC in Winter (December to January) to 45oC in Summer
(April-June); Relative humidity 20% during dry season to 95-96% during rainyseason.
Longitude 78o3' East, Latitude 29o55'5" North.
Height above Mean Sea Level = 275 meters.
Situated within 60 to 100 KMs of Foot-hills of the Central Himalayan Ranges;
Ganges flows down within 7 KMs from the Factory area.
HEEP is located around 7 KMs on the Western side of Hardwar city.
POWER & WATER SUPPLY SYSTEM
40 MVA sanctioned Electric Power connection from UP Grid (132 KV / 11KV / 6.6
KV) (Connected loadaround 185 MVA)
26 deep submersible Tube Wells with O.H. Tanks for water supply.
A 12 MW captive thermal power station is located in the factory premises.
15. Engineering CAD Work stations, personal
computer reprographic facilities
like ammonia printing, semi dry
printing machine, Xerox process,micro filming facilities
Design and drawings
of all products
16. Computer Center ICIMs series 39 DX level 270-
320 computer system HCL
magnum mini compute system ,
ESPL SM32 mini computer
Nexus3500 CAE work station,
PCs etc.
IT services
17. CPL (Central plant
Lab.)
Testing Lab for new materials &
sample components
Testing of components
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3. ELECTRICAL MACHINES BLOCK (BLOCK-I)
INTRODUCTION
Block-I is designed to manufacturing Turbo Generators, Hydro generators and
large and medium size AC and DC Electrical machines.
The Block consist of 4 bays: Bay-1 (36*482 meters), Bay-2 (36*360 meters) and
Bay-3 and Bay-4 of size 24 *360 meters each. For handling and transporting the
various components over-head Crane facilities are available, depending upon the
products manufactured in each Bay. There are also a number of self-propelled
electrically-driven transfer trolleys for the inter-bay movement of components
/assemblies.
Conventional bay -wise broad distribution of products is as follows :
BAY1 ROTOR
SHAFT
MACHINI
NG
ROTOR SHAFT
SLOTTING
ROTOR
WINDING
OVER SPEED
AND
BALANCING
TUNNEL
LARGE SIZE
TURBO
GENERATOR
S
BAY2 EXCITER
SHAFT
MACHINI
NG
STATOR BODY
MACHINING
STATOR
WINDING
TOTAL
IMPREGNATION
TEST BED
BAY--3 ROTOR
SUPPORT
BEARING
SHAFT SEAL
BODY
DC
MOTOR
WINDING
(EARLIER)
BAY--4 COOLING
FANS
MACHINI
NG
ARRANGEMEN
T AND OTHER
PARTS
BASIC TRAINING DEPARTMENTS: -
MACHINE SHOP.
T/G ROTOR WINDING.
H/G IRON ASSEMBLY.
EXCITER. T/G STATOR WINDING.
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TOTAL IMPREGNATION TECHNIQUE.
T/G IRON ASSEMBLY.
T/G MAIN ASSEMBLY.
L.S.T.G ROTOR WINDING.
L.S.T.G STATOR WINDING.
L.S.T.G MAIN ASSEMBLY. TEST BED.
I. TURBO GENERATOR
Turbo generator or A.C. generators or alternators operates on the fundamental
principles of ELECTROMAGNETIC INDUCTION. In them the standard
construction consists of armature winding mounted on stationary element called stator
and field windings on rotating element called rotor. The stator consists of a cast-iron
frame , which supports the armature core , having slots on its inner periphery for
housing the armature conductors. The rotor is like a flywheel having alternating north
and south poles fixed to its outer rim. The magnetic poles are excited with the help of
an exciter mounted on the shaft of alternator itself. Because the field magnets are
rotating the current is supplied through two slip rings. As magnetic poles are
alternately N and S, they induce an e.m.f and hence current in armature conductors.
The frequency of e.m.f depends upon the no. of N and S poles moving past a
conductor in 1 second and whose direction is given by Fleming s right hand rule.
SYNOPSIS OF THE FUNCTION OF T.G.:
1.
The generator is driven by a prime mover which is steam turbine in this case.2.
The other side of generator is provided by a rotating armature of an exciter which
produces A.C. voltage. This is rectified to D.C. by using a rotating diode wheel.
3. The rear end of above exciter armature is mounted by a permanent magnet
generator rotor.
4.
As the above system is put into operation, the PMG produces A.C. voltage.
5. The voltage is rectified by thyristor circuit to D.C.
6.
This supply is given to exciter field. This field is also controlled by taking
feedback from main generator terminal voltage, to control exciter field variation by
automatic voltage regulator. The rectified DC supply out of exciter is supplied to
turbo generator rotor winding either through brushes or central which will be
directly connected to turbo generator. This depends on the type of exciter viz. DCcommutator machines or brushes exciter.
7. The main A.C. voltage is finally available at the stator of Turbo Generator.
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LSTG AREA
II. LARGE SIZE TURBO GENERATOR (LSTG)
In these types of generators steam turbine does the function of prime mover which
rotates the rotor of LSTG and the field winding is supplied D.C. by an exciter.
Main types of T.G. are:-
1. THRI2.
TARI
3. THDI
4. THDD
5. THDF
6. THFF
1stLETTER= (here-T)
= 3-phase turbo generator
2nd
LETTER= (here H or A)
=Medium present for generator cooling
(H= hydrogen, A or L=air)
3rdLETTER=type of rotor cooling employed
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R= radial,
F= direct water cooling
D= direct axial gas cooling)
4th
LETTER= type of as used for stator winding cooling
I= indirect gas cooling
D= direct gas cooling
F= direct water cooling
III. COMPONENTS OF T.G. :-
STATOR
1. Stator frame
2. Stator core
3. Stator winding
4. End covers.
ROTOR
1.
Rotor shaft
2. Rotor windings
3.
Rotor retaining rings
BEARINGS
COOLING SYSTEM
EXCITATION SYSTEM
STATOR
The generator stator is a tight construction supporting and enclosing stator winding,
core and hydrogen cooling medium. Hydrogen is contained within the frame and
circulated by fans mounted at either end of rotor. The generator is driven by a direct
coupled steam turbine at the speed of 3000 rpm.
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The generator is designed for continuous rated output. Temperature detector or other
devices installed or connected within the machine, permits the winding core and
hydrogen temperature, pressure and purity in machine.
STATOR FRAME
The stator frame is used for housing armature conductors. It is made of cylindrical
section with two end shields which are gas tight and pressure resistant. The stator
frame accommodates the electrically active parts of stator i.e. the stator core and the
stator winding.
The fabricated inner cage is inserted in the outer frame after the stator has been
constructed and the winding completed.
STATOR CORE
The stator core is stacked from the insulated electrical sheet steel lamination and
mounted in supporting rings over the insulated dovetail guide bars. In order to
minimize eddy current losses core is made of thin laminations. Each lamination layer
is made of individual sections. The ventilation ducts are imposed so as to distribute
the gas accurately over the core and in particularly to give adequate support to the
teeth.
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The main features of core are
1. To provide mechanical support.
2.
To carry efficiently electric, magnetic flux.
3. To ensure the perfect link between the core and rotor.
STATOR WINDING
Each conductor must be capable of carrying rated current without over heating.
The stator winding consists of two layers made up of individual bars. Windings for
the stators are made of 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 placed in the stator slots and held in with wedges to form the end
turns. These end turns are rigidly placed and packed with blocks of insulation material
to withstand heavy pressure.
The stator bar consists of hollow (in case of 500 MW generators) solid strands
distributed over the entire bar cross-section, so that good heat dissipation is ensured.
In the straight slot portion the strands are transposed by 540 degrees. The
transposition provides for mutual neutralization of the voltage induced in the
individual strands due to slot cross field and end winding flux leakage and ensure that
minimum circulating current exists. The current flowing through the conductors is
thus uniformly distributed over the entire cross section so that the current dependent
losses will be reduced.
The alternate arrangement of one hollow strand and two solid strands ensures
optimum heat removal capacity and minimum losses. The electrical connection
between top and bottom bars is made by connecting sleeve.
Class F insulation is used.
The no. of layer of insulation depends on machine voltage. The bars are brought under
vacuum and impregnated with epoxy resin, which has very good penetration property
due to low viscosity. After impregnation bars are subjected to pressure with nitrogen
being used as pressurizing medium (VPI process). The impregnated bars are formed
to the required shape on moulds and cured in an oven at high temperature to minimize
the corona discharge between the insulation and slot wall a final coat of
semiconducting varnish is applied to the surface of all bars within the slot range. Inaddition all bars are provided with an end corona protection to control the electric
field at the transition from the slot to end winding. The bars consist of a large no. of
separately insulated strands which are transposed to reduce the skin effect.
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INSULATION OF BARS
A. Vacuum pressed impregnated micaclastic high voltage insulation:-
The voltage insulation is provided according to the proven resin poor mice base of
thermo setting epoxy system. Several half overlapped continuous layer of resin poor
mica tape are applied over the bars. The number of layers or thickness of insulation
depends on the machine voltage. To minimize the effect of radial forces windingshold and insulated rings are used to support the overhang.
B. Corona Protection:-
To prevent the potential difference and possible corona discharge between the slot
wall and the insulation, the section of bars are provided with outer corona protection.
The protection consists of polyester fluce tape impregnated in epoxy resin with carbon
and graphite as fillers. At the transition from the slot to the end winding portion of the
stator bars a semiconductor tape is impregnated.
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C. Resistance Temperature Detector:-
The stator slots are provided with platinum resistant thermometer to record and watch
the temperature of stator core and tooth region and between the coil sides of machine
in operation. All AC machines rated for more than 5 MVA or with armature core
longer, the machine is to be provided with at least 6 resistance thermometers. The
thermometer should be fixed in the slot but outside the coil insulation. When thewinding has more than one coil side per slot, the thermometer is to be placed between
the insulated coil sides. The length of resistance thermometer depends upon the length
of armature. The leads from the detector are brought out and connected to the terminal
board for connection onto temperature meter or relays. Operation of RTD is based on
the prime factor that the electric resistance of metallic conductor varies linearly with
temperature
END COVERS:-
The end covers are made up of fabricated steel or aluminum castings. They are
employed with guide vans on inner side for ensuring uniform distribution of air or
gas.
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IV. EXCITATION SYSTEM:-
EXCITER:-
EXCITER ROTOR
The basic use of given exciter system is to produce necessary DC for
turbo generator system. Principal behind this is that PMG is mounted on the
common shaft which generates electricity and that is fed to yoke of main
exciter. This exciter generates electricity and this is of AC in nature. This ACis that converted into DC and is that fed to turbo generator via C/C bolt. For
rectifying purpose we have RC block and diode circuit. The most beautiful
feature is of this type of exciter is that is automatically divides the magnitude
of current to be circulated in rotor circuit. This happens with the help of AVR
regulator which means automatic voltage regulator. A feedback path is given
to this system which compares theoretical value to predetermine and than it
sends the current to rotor as per requirement.
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The brushless exciter mainly consists of:-
1. rectifier wheels
2. three phase main exciter
3. three phase pilot exciter
4.
Metering and supervisory equipment.
The brushes exciter is an AC exciter with rotating armature and
stationery field. The armature is connected to rotating rectifier bridges forrectifying AC voltage induced to armature to DC voltage. The pilot exciter is a
PMG (permanent magnet generator). The PMG is also an AC machine with
stationery armature and rotating field. When the generator rotates at the rated
speed, the PMG generates 220 V at 50 hertz to provide power supply to
automatic voltage regulator.
A common shaft carries the rectifier wheels the rotor of main exciter
and the permanent magnet rotor of pilot exciter. The shaft is rigidly coupled to
generator rotor and exciter rotors are than supported on these bearings.
V. BAY IV (SMALL AND MISCELLANEOUS COMPONENTS)
Facilities available in the various sections are as follows:-
MACHINE SECTION:-
The machine section of Bay-4 is equipped with small and medium sizeCNC & conventional machine tools like centre lathes, milling, radial drilling,
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cylindrical grinding, slotting, copy turning lathe, internal grinding and surface
grinding machines. Small-size and miscellaneous components for Turbo-
generators, Hydro generators and Motors are machined in this section.
POLE COIL SECTION
COILING SECTION
This section is equipped with baking oven , pneumatic shearingmachines , semi-automatic winding machines , pole straightening installations
, electric furnace for bright annealing of copper , tinning installation and
hydraulic press (800 Ton capacity ) for manufacturing Pole Coils of DC
motors , AC synchronous motors and hydro generators . Pole assembly is also
carried out in this section.
Manufacturing of coils (hydro generators) taken in this section.
German copper coils are initially in the form of rolls. These rolls are then
undergoes following processes to change into copper coils which are then
mounted with poles-
1. ANNEALING PROCESS:-
This is the process of hardening or softening any metal.
Initially copper rolls are hard & if it undergoes annealing then it may
breaks so firstly to make it soft so that it can easily change to winding.
This process is carried out in the annealing furnace.
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WINDING PROCESS:-
This process undergo following steps:-
Take out the softened copper rolls for pole coil winding. Winding is done with the help of change plate & winding template so
ensure major working dimensions of change plate & winding template
with respect to tool drawing.
Adjust & set the winding machine as per the product standards using
gear rack, change plate & winding template. Ensure parallelity of
winding template with respect to machine platform. Maintain height of
winding template with platform. Wind the coil in anticlockwise
direction.
NOTE:-
The joint in the copper coil shall be located in the straight part of
longer side.
If required heating by gas torch of copper profile at corner zone at
temperature between 100-150 degree centigrade is allowed. This is
to make easier bending.
2. BRAZING:-
Braze the joint with brazing alloy Ag40Cd.
Remove the coil with machine with 2 to 3 turns extra than the actual
number of turns for preparation of end-half turns.
3. Carry out bright annealing of the coil. Take out the coil from the oven
after annealing.
4.
PRESSING:-
Pressing of coil is done by hydraulic pressure of 800 tons.
This process is carried out in order to remove wrinkles from the coil.
This process is carried out after every process. In this process, set the
coil on the mandrel for pressing then slide the coil under press and
press the coil.
Take out the coil from press.
5.
FIXING:-
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Fix the accessory on the stretching machine.
Put the coil on the stretching machine& pull the coil to the drawing
dimensions.
Dress the conductors along periphery & take out the coil.
Check window dimensions as per drawing.
6. SEPARATION:-
Remove the buckling of each coil manually.
Grind the bulging of the copper at place of binding (inner side) with
pneumatic grinder.
Check the thickness of the profiled copper with the gauge. Grinding
shall be uniform & of smooth finish.
Round of sharp edges.
** Again press the coil as in pt.5 & take out the coil from the press.
7. PICKLING:-
Send the coil for pickling to block 4 & check the quality of pickling.
Press the coil again after pickling then remove pressure and take out
the coil.
8. Prepare end half turn as per drawing with template.
9. Braze item 2 & 3 corresponding to the variant with end half turn with
brazing alloy
Ag 40 Cd.
Remove extra material, clean and check with gauge.
Adjust the end half turn with top & bottom turn of coil braze the joint.
Remove extra material and check thickness of the gauge.
Check the distance from center axis of pole coil as per drawing.
10. FINISHING:-
Hang the coil on stand and separate out turns
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Remove black spots, burrs the sharp edges and clean the coil turns with
cotton dipped in thinner.
Press the coil again and check the height of the coil under press to
check dimensions as per drawing.
11.Take out the coil from the press and send for insulation.
12. INSULATION:-
Hang the coil on stand and separate out the turn.
Clean each turn with cotton dipped in thinner.
Apply Epoxy varnish on both sides of each turn with brush uniformly
all over the leaving top & bottom turn.
Cut strips of Nomax paper as per contour of coil with technologicalallowance 3 to 5 mm on either side.
Stick two layers of Nomax strips between each turn.
Coat varnish layer between two layers of Nomax also.
Let the excess varnish to flow out some time
13. BAKING AND PRESSING OF COIL:-
Place the coil on mandrel putting technological washer at top & bottom
of the coil.
Heat the coil by DC up to 100 +/-5o C , and maintain for 30 to 40
minutes.
Switch off the supply and elongate the coil and tight the pressing
blocks from sides.
Start heating coil again and raise temperature gradually in steps up to
130 +/- 5o C , with in 10 +/- 10 minutes.
Apply 110 tones pressure and maintain for 20 to 30 minutes. Then after
every half an hour, increases the pressure and temperature according to
product requirement.
Stop heating and then allow cooling the coil under pressure below 50oC, and taking out the coil from the press.
14.CLEANING AND DRYING:-
Clean outer and inner surface of projected insulation by means of shop
made scrubber.
Flow dry compressed air after cleaning.
Check height and window dimensions as per drawing.
Check no gap between the turns.
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Test the coil from inter turn test at 116 volts AC at a pressure of 480
tons in 5 minutes.
15.Coat the coil with two layers of epoxy red gel.
TURBO ROTOR COIL SECTION:-
This section is equipped with copper straightening and cutting
machines, edge bending machines, installation for forming and brazing, 10-
block hydraulic press and installation for insulation filling. Rotor coils for
water cooled generators (210 /235 MW) are manufactured in this section.
IMPREGNATION SECTION:-
This section is equipped with electric drying ovens, Air drying booths,
Bath for armature / rotor impregnation. Rotors / armatures of AC and DC
motors are impregnated in this section.
BABBITING SECTION:-
This section is equipped with alkaline degreasing baths, hot and cold
rinsing baths, pickling baths, tinning bath, and electric furnaces and centrifugal
Shot Blasting
babbitting machines, Babbitting of bearing liners for Turbo generators,
Turbines, Hydro generators, AC motors and DC motors is carried out in this
section.
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VI. TEST STANDS:-
Turbo-generators Test Bed -The Test Bed for Turbo-generators and Heavy
motors is equipped with one no. 6 MW drive motor and a test pit for carrying
out testing of Turbo-generators and Heavy motors. Open circuit, short circuit,temperature rise, hydraulic and hydrogen leakage test etc., are carried out here
for Turbo-generators. AC motors up to 11 MVA capacity and DC machines up
to 5000 amps and 850 volt can also be tested. Two DC drive motors of 2200
KW and one of 1500 KW are available for type testing of motors. Data
logging equipment is also available.
VII. LARGE SIZE TURBO GENERATOR TEST STAND (LSTG):-
It is equipped with a 12 MW drive motor and two number test pits. Open
circuit ,short circuit , sudden short circuit , temperature rise , hydraulic &hydrogen leakage tests are carried out here Large size Turbo-generators. This
test bed can presently test Tgs of unit capacity up to 500 MW. With certain
addition in facilities (Higher capacity Drive motor and EOT cranes and
modification in controls and auxiliary systems), Turbo-generators of unit size
up to1000 MW can be tested.
HELIUM LEAK TEST
PURPOSE
To check any leakage of gas from stator and rotor as if there is any leakage of
gas used for cooling such as hydrogen then it may cause an explosion.
VIII. Testing of stator frame involves two types of testing:
HYDRAULIC TESTING AND PNEUMATIC TESTING
Hydraulic testing involves in empty stator frame with attached end shields and
terminal box is subjected to a hydraulic test at 10 bar to ensure that it will be
capable of withstanding maximum explosion pressure.
The pneumatic testing involves filling of hydrogen in the sealed stator frame
and then soap water is used to check the leakage of welding.
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4. CONCLUSION
The Vocational training at BHEL Hardwar helped me in improving my practical
knowledge and awareness regarding Turbo Generator to a large extent.
Here I came to know about the technologies and material used in manufacturing ofturbo generators. Besides this, I also visualized the parts involved or equipments used
in the power generation.
Here I learnt about how the electrical equipments are being manufactured and how
they tackle the various problems under different circumstances. At least I could say
that the training at BHEL Hardwar is great experience for me and it really helped me
in making or developing my knowledge about turbo generator and other equipment
used in power generation.
5.REFERENCES
1. Material provided by the training Incharge.
2. Internet