RAVINDER Report...Final

7/29/2019 RAVINDER Report...Final

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ACKNOWLEDGEMENT

An engineer with only theoretical knowledge is not a complete

engineer. Practical knowledge is very important to develop and

apply engineering skills. It gives me a great pleasure to have

an opportunityto acknowledge and to express gratitude to those

who were associated with me during my training at BHEL. Special

thanks to Mr. P.S. Jangpangi Sir for providing me with an opportunityto undergo training under his guidance. I am very grateful to our traning

officer Mr. Arup Chakrobarty for his support. I express my sincere

thanks and gratitude BHEL authorities for allowing me to undergo the

training in this prestigious organization. I will always remain indebted

to them for their constant interest and excellent guidance in my training

work, moreover for providing me with an opportunity to work and gain

experience.

RAVINDER SAINI

SGIMT | AHERA,BAGHPAT


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Table of Contents

BHEL:

AN OVERVIEW............................................................................................ 4

Power Generation............................................................................................ 6

Heavy Electrical Equipment Plant.................................................................12

ELECTRICAL MACHINES BLOCK(BLOCK-I) ...................................... 14

Introduction .................................................................................................. 14

Plant Details ................................................................................................. 15

Stator body 15Stator winding And insulation16

ROTOR ................................................ 18

Rotor .............................................................................................................22

Rotor winding............................................................................................... 23

Sliprings, Brushgears and shaft Earthing..27

Safety Precautions..30

Emergency Procedure....31

CONCLUSION ...............................................................................................32

Bibliography ............................................................................................ .......32



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BHEL: AN OVERVIEW

BHEL is the largest engine energy related/infrastructure sector. BHEL

was established more than 40 years ago, ushering in the indigenousHeavy Electrical Equipment industry in India, a dream which has beenmore than released with a well-recognized track record of performance.

It has been earning profits continuously since 1971-72.BHEL caters to

core sectors of India economy viz. Power Generation and Transmission,

Renewable Energy, Defense etc. The wide network of BHELs 14

manufacturing divisions, 4 power sector regional centers, 8 service

centers, 15 regional offices and a large number of projects sites spreadall over India and abroad enables the company to promptly serve as

customer and provide them with suitable products, systems and

services- efficiently and at competitive prices. BHEL has attained ISO

9001:2000 certifications for quality management and all themanufacturing units divisions of BHEL have been upgraded to the latest

ISO 9001:2000version. All the major units divisions of BHEL have

been awarded ISO 14001 certification for Environmental Management

System and OHSAS-18001 certification for Occupational Health and

Safety management System. BHEL become the first public sector

Company in the country to win the coveted prize for in Haridwar unit

under the CII Exim Award for the business excellence as per the

globally recognized model of European Foundation for quality

management. BHEL is the only PSU among the 12 Indian Companies to

figure in Forbes Asia Fabulous 50 list. It has also won the Business

standard star Public Sector Company Award 2006. The companyreceived MoU Excellence award for 2004-2005 and Merit Certificate

for MoU Excellence for 2005-2006.



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STATE OF PLANT :

Generator Erection complete and satisfactory.

All erection test results/log sheets available for the following :

- Mounting of embedded parts and foundation plates.

- Erection of stator.

- Gas tightness and Hydraulic tests.

- Measurement of insulation resistances of various parts of generator,

D.C. resistances and impedances.

- Continuity, D.C. resistance and IR checks of RTDs.

- Purge tests of rotor ventilation canals.

- Rotor insertion tests.

- Bearing adjustment tests.

- Alignment or generator rotor.

- Inclination or shaft journal test results.

- Coupling alignment results of generator and LP rotor.

- Magnetic Axis adjustment results.

- Fan and shield clearance results.

- DTI checks on generator rotor.

- Shaft seal adjustment results.

- Temperature monitoring system.

- Centering and offset-setting of brush gear.

- Fixing of brush holder and brushes.



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Following Testing/Commissioning schedules completed satisfactorily and

results/records available :

- Generator Gas Tightness Test.

- Hydraulic test and oil flushing of seal oil system.

- Seal Oil System Circulation

- Hydraulic test and flushing of primary water system.

All the systems mentioned in 7.2 are in totally normalised condition and

available for generator testing.

Fire protection system (CO2 system) is made available

Power Generation



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Power generation Sector comprises Thermal Gas, Hydrogen, Nuclear

power plant business. As of 31.3.2007. BHEL supplied sets accounts for

80,781 MW or nearly 65% of the total install capacity of 1, 25,414 MW

in the country. Significantly these sets contribute 73% of the total powergenerated in the country. BHEL has proven turnkey capabilities forexecuting power projects from concepts to commissioning. It possesses

the technology and capability to produce Thermal sets with super

critical parameters up to 1000 MW unit rating and gas turbine generator

sets of up to300 MW units rating. Co-generating 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 also supplies circulating Fluidized Bed Combustion (CFBC)

boilers for thermal plants.

The company has proven expertise in Plant Performance Improvement

through renovation, modernization and upgrading of a variety of Powerplant equipment, besides specialized know-how of residual life

assessment health diagnostics and life extension of plants. Overall,

BHEL built Thermal sets achieved the highest ever PLH of 78.3% in

2006-2007 which is 2.5% higher than the National average. The

combined operating availability of these sets was 84.7%.

In fig. is a reminder of the components of a turbine/generator system.

Here it includes the

exciter which provides DC current to the rotor of the generator.



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Synchronous Generator Theory

Synchronous means that the generators rotor runs at the constant

mains frequency as load

varies.



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Electromagnetic Induction

The instantaneous voltage induced in a stator conductor is given by;dB

e kldt

=

where;k= constantl= length of conductor

dB

dt= rate of change of magnetic flux density

Ife is to be a sinusoid, dB/dtmust also be sinusoidal. Excitation coils

are wound on the rotor

to produce a flux with a density which varies approximately

sinusoidally around the

circumference. A two-pole arrangement (one pole pair) is shown in Fig.

The magnitude of the flux density can be changed by varying the direct

current to the excitation coils on therotor.



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Production of sinusoidal voltage (from MPSP).

Speed, Frequency and Pole Pairs

Iff= frequency, Hzn = rotational speed, r/s

p = number of pole pairsThenf = pn

In Australia, generators are 2-pole (i.e.p = 1). Hence generators run at

3000 rpm.

Three-phase Windings



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Fig. shows how three phases are generated by having three winding

spaces on the stator.This is still a 2-pole generator. It is economical to have many statorconductors in parallel so

the individual conductor voltages are additive. Each go conductor is

connected to a return

conductor, acted on by the pole of opposite polarity, and thence to a

third conductor adjacent

to the first, and so on through the phase. The return conductors aredisposed in a layer

displaced radially from the go conductor, both in the slots and in the

end region. The

discrete nature of the windings gives rise to generation of harmonics.



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Arrangement of stator conductors (from MPSP).

Torque

The mechanical torque provided by the turbine is balanced by anelectromagnetic torque

caused by the interaction of the magnetic flux and the current flowing in

the stator windings



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Heavy Electrical Equipment Plant

BHEL's Heavy Electrical Equipment Plant (HEEP) was set up intechnical collaboration with USSR, for the manufacturing of power

plant equipment, AC/DC motors of various rating with associated

control equipment and started production in January 1967. In 1976,

BHEL entered into a collaboration agreement with M/s Kraftwerk

Union, AG of Germany for design, manufacturing, erection and

commissioning of large size steam turbines. More than40 percent of thecountry's electrical energy is generated from the power equipment

supplied by BHEL, Haridwar. BHEL offer wide ranging products and

systems for T & D applications. Products manufactured include power

transformers, instrument transformers, dry type transformers,series and stunt reactor, capacitor tanks, vacuum and SF circuit

breakers gas insulated switch gears and insulators. The products, which

are manufactured in HEEP, are: - Steam Turbines, Turbo Generators,

hydro turbines, Gas turbines, etc.



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ELECTRICAL MACHINES BLOCK(BLOCK-I)

Introduction

Turbo Generator

500MW Turbo generators at a glance-

2-poles machines with the following features:-

Direct cooling of stator winding with water.

Direct hydrogen cooling for rotor.

Micalastic insulation system.

Spring mounted core housing for effective transmission of vibrations.

Brushless Excitation System.

Vertical hydrogen cooler.

Salient technical data:

Rated output : 588MVA,500MW

Terminal voltage : 21KV

Rated stator current : 16KA

Rated frequency : 50Hz

Rated power factor : 0.855Lag

Efficiency : 98.55%

Important dimensions and weights:-

Heaviest lift of generator stator : 255TonsSGIMT | AHERA,BAGHPAT


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Rotor weight : 68Tons

Overall stator dimensions(L*B*H) : 8.83m*4.1m*4.02m

Rotor dimensions(Dia. And Length) : 1.15m and 12.11m

Total weight of turbo generator : 428 Tons

PLANT DETAILS :

The 500 MW generator is coupled to the 500 MW KWU turbine. The

rated parameters of the generator are listed in plant details (Section-1) ofTesting schedule for generator protection and generator bay. The design

and constructional features are outlined briefly below. Generator

manual supplied by the manufacturer may be referred for details of

above.

STATOR BODY :

The stator body is a totally enclosed gas tight fabricated structure

suitably ribbed internally to ensure high rigidity. Hydrogen coolers are

housed longitudinally inside the stator body. Rigid end shields close thecasing and support the fan shields.

STATOR CORE :

The stator core is made up of segmental varnish insulated punchings of

cold rolled grain oriented silicon gel and is assembled in an interleaved



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manner on core bars. Steel spacers for ventilating ducts are provided

for radial cooling of core by hydrogen.

The core is held pressed by means of heavy non-magnetic steel press

rings which are bolted to the ends of the core bars. Additional support

is provided to the teeth portion. In order to isolate the stator body and

thus the foundations from magnetic vibrations, the core bars are

designed to provide elastic suspension of the core in the stator frame.

STATOR WINDING AND INSULATION:

The stator has a three phase, double layer short corded bar type

windings having two parallel paths. Each coil side consists of glass

insulated solid and hollow conductors with cooling water passing

through the latter. The elementary conductors are Rosbel transposed inthe slot portion to minimize eddy current losses. The coil sides are

firmly held in position by fibrous slot wedges. The overhang portion of

the coil is securely lashed with glass chord to bondage rings and special

brackets of non-magnetic steel, which are in turn fixed to the core press

rings.



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DISTILLATE HEADERS:

Ring type water headers, made of copper are provided separately for

distillate inlet and outlet in the stator on turbine side. The headers are

supported on insulators and isolated from stator body. The winding ends

are solidly soldered into the coil legs which are then ultrasonically

tested. Individual bars are provided with water inlet/outlet connections

made of P.T.F.E Hoses, The bar heads are insulated by fiber molded

covers.

TERMINAL BUSHINGS:

Water cooled terminal bushings are housed in the lower part of the

stator on the slip ring side, Porcelain insulators are provided to insulate

the terminal bars from the stator body. Effective sealing is provided

between the terminal bushings and the stator body to avoid any possible

leakage of hydrogen. Terminal bushings are housed inside a chambermade of non-magnetic steel plates. Three phase terminals and three



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neutral terminals are brought out. The terminal plate of the end

terminals, where bus bar connections are made is silver plated.

ROTOR:

The rotor is of cylindrical type; the shaft and body being forged in one

piece from chromium nickel molybdenum and vanadium steel. The

rotor with all the details assembled is dynamically balanced to a high

degree of accuracy subjected to 20% over speed for 2 minutes.



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FIELD WINDING:

The field winding is made from hard drawn silver bearing copper. The

winding is held in position and by non-magnetic rotating ring in the

overhang portion. Gap pickup method is used for direct hydrogen

cooling of rotor.



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The main slot insulation is of glass cloth impregnated with Epoxy resin.

The inter turn insulation consists of layers of prepped glass cloth glued

to the bottom of each conductor. The end windings are packed withblocks of glass laminates to separate and support the coils and to restrict

their movement under stress. The end windings are insulated from the

retaining rings with the help of glass epoxy molded segments.

SHAFT MOUNTED FANS:-

For circulating the cooling gas inside the generator two propeller type

fans are shaft mounted on either end of the rotor body. Fan hubs are

made of alloy steel forging and are a shrunk fit on the rotor shaft. The

alloy steel cast fan blades are machined in the tail portion to suit the fan

hub and held in position with the help of conical pins.

The blades can be easily removed from or assembled in the fan hub. Fan

shields fixed to the end shields guide the gas flow.

RETAINING RINGS:



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The end windings are held in position by retaining rings of floating type

shrunk fit on the rotor body. The rings are screwed to prevent axial

movement by locking nuts.

SLIP RINGS:

The slip rings consists of helically grooved alloy steel rings shrunk on

the rotor shaft and insulated from it. They are mounted on a single,

common steel bush, which has an insulating jacket pre-molded on it.

The complete bush with sliprings are provided with inclined holes for

self ventilation. The helical grooves cut on the outer surface help

improve the brush performance.

FIELD LEAD:

The slip rings are connected to the field winding through semi-flexible

copper leads and current carrying bolts, placed radially in the shaft. Two

semicircular hard copper bars insulated from each other and from therotor shaft are placed in the central bore or the rotor joining the two sets

of current carrying bolts with special profiled precision conical threads.

GAS COOLERS:

Four longitudinally mounted gas coolers are mounted in the stator body.

They are made out of admiralty brass with coiled copper wire wound on

them staggered form so as to expose maximum surface area tohydrogen.



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BEARINGS:

Generator bearings are of pedestal type with spherical seating to allow

self alignment and are supported on a separate pedestal on slip ring sideand in the L.P casing on the turbine side, Bearing bush is of cast steel

lined with white metal. Oil catchers and deflectors are provided to

prevent axial leakage of oil. To prevent shaft currents slip ring side

bearing and connecting pipes are insulated from earth.

SHAFT SEALS:

In order to prevent leakage of hydrogen from the generator casing radial

thrust type shaft seals are provided on either side where the shaft

extends out from the generator. The seal consists of seal liner with

babbit pressing against the shaft caller of the rotor. Seals are defined in

testing schedule of seal oil system.

ROTOR:

The rotor must:

carry the excitation windings

provide a low reluctance path for the magnetic flux

transfer the rated torque from the turbine to the electromagnetic

reaction at the air

gap resist large centrifugal forces.



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Steel is the most suitable material. A steel

forging is used with machined slots (Fig.).

Rotor section

The winding slots are cut in diametrically opposite pairs over abouttwo-thirds of the circumference, leaving the pole faces without winding

slots (Fig.). Equalising slots are cut across the pole faces to avoid a

difference in stiffness in two orthogonal directions which

would produce a twice-per-revolution vibration.

The rotor shaft and the coupling must be designed to withstand four tofive times full-load torque in the event of a sudden short circuit.



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Journal bearings are used.

ROTOR WINDDING:

Full detail of the winding of a rotor is shown in Fig. Winding coils are

assembled into diametrically opposite pairs of rotor slots symmetrically

distributed about the pole axis, but in the opposite senses in the two

poles; i.e. clockwise current for the north pole and counterclockwisecurrent for the south pole.

Each coil must be assembled as a half-turn, with brazed joints in the endturns (end windings). There are usually one or two turns in the width of

a slot. Axial passages and radial holes in the copper conductors provide

for forced cooling with hydrogen. The high rotational speed causes

hydrogen to flow axially from both ends and radially outwards. Fans

mounted on the rotor, primarily to circulate hydrogen though the stator,help the flow through the rotor (Fig.). Insulation is achieved with slot

liners of glassfibre material Thick end rings are used to restrain the rotorend winding under the action of entrifugal force. The ends of the



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windings are connected to flexible leads and there are radial copper

studs to connect to the sliprings and thence to the exciter. The contents

of the winding slots are retrained by an aluminium wedge.

Rotor winding (from MPSP).



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SLIPRINGS, BRUSHGEAR AND SHAFT EARTHING:

For a 500 MW generator the excitation current is about 5000 A. This

must flow through sliprings with a large area (Figs). Brushes only last

about six months but they can be changed while running on-load.

In normal operation there is 10-50 volts between the two shaft ends of agenerator, due mainly to magnetic dissymmetry. To stop an axial



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current from flowing and damaging bearings, an insulation barrier is

provided at the exciter end.



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It is important that the shaft at the turbine end of the generator is

maintained at earth potential, using a pair of shaft-riding brushes

connected to earth through a resistor. The voltage at the exciter end is

monitored as an indication that insulation is intact.

TESTING OBJECTIVE :



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To test the generator equipment and make it ready for excitation and

synchronization.

PROPOSAL:

Tests as detailed in item-8 shall be carried out on generator, confirming the

manufacturers test reports.

Insulation resistance tests on generator rotor, stator and bearing pedestals

shall be carried out.

Winding resistances for both stator and rotor will be measured and

recorded.

Impedance of rotor windings shall be measured and recorded.

Checks/Tests shall be carried out all the embedded resistance temperature

detectors.

The brush gear assembly shall be checked tested as per its standard

checklist and test procedure.



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SERVICES REQUIRED

Laboratory equipments/test sets for measurement of electrical parameters

required in specific tests (5KV motorized megger, Kelvins bridge or micro

ohm meter).

Illumination at required locations.

240 V A.C power supply for testing.

Communication facility at test area.

S A F E T Y PRECAUTIONS:

The test area shall be clearly defined and cordoned off.

The test team leader is fully aware of the nature, ocation, and probable

duration of the tests.

The other agencies working in the test area are informed about the test in

progress.



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EMERGENCY PROCEDURE :

Shock treatment chart and first aid box shall be available.

Emergency telephone numbers of fire and hospital shall be prominently

displayed near by.

The test in progress shall immediately be stopped and all line apparatus

disconnected and equipment suitably earthed in case of a accident or

abnormality. Such instruction will be received from the team leader.

The test team is fully aware of measures to be taken in the event of injuries

to any personnel / damage to any machinery.



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CONSTRUCTIONAL FEATURES OF ROTOR

The rotor comprises of the following components:-

Rotor shaft

Rotor winding

Rotor wedge and other locating parts for winding

Retaining rings

Fans

Field lead connection.

CONCLUSION

The second phase of training has proved to be quite faithful.It proved anopportunity for encounter with such huge machines like turbo-generator hydro

generators etc.

The architecture of BHEL, the way various units are linked

and the way working of whole plants is controlled make the realize that

Engineering is not just structural description ,but greater part is planning and

management.It provides an opportunity to learn tech. Used at proper place and

time can save a lot of labor.However, training has proved to be satisfactory.It has allowed us an opportunity

to get an exposure of the practical implementation of theoretical fundamentals.



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BIBLIOGRAPHY

1. Electr ical machines by B.L. Threja .

2. Electrical Machines by V.K. Mehta.

3. Electr ical machines by Ashfaq Husain.

4. Electro Mechanical Energy Conversion by P.S.

Bhimra.

5. Electrical Engineering by B.L. Threja

RAVINDER Report...Final

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