kanika nn12 ntpc

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Summer Training Report

JUNE-JULY 2010

SUBMITTED BY:-

KANIKA AGARWAL

B.TECH 2ndYear

ELECTRICAL & ELECTRONICS

ENGINEERING

Enrollment No: 0591484908

Maharaja Agrasen Institue of Technolog

Rohini Sec-22, Delhi-110086.


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TABLE OF CONTENTS

Certificate

Acknowledgement

Training at BTPS

1. Introduction NTPC Badarpur

Thermal Power Station

2. Operation .

3. Electrical Maintenance Division-I HT/LT Switch Gear HT/LT Motors,

Turbine & Boilers Side CHP/NCHP

4. Electrical Maintenance Division-II

Generator Transformer & Switchyard

Protection Lighting EP

5.Control & Instrumentation

Manometry Lab Protection and interlock

Lab Automation Lab Water Treatment

Plant Furnace Safeguard Supervisory

System Electronic Test Lab

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CERTIFICATE

This is to certify that KANIKA AGARWAL student of

Electrical & ElectronicsEngineering (2nd Year);

Maharaja Agrasen Institute of Technology has

successfully completed her industrial training at

Badarpur Thermal power station New Delhi lasting for

a period of (01st June to 10th July). She has completed

the whole training as per the training report submitted

by her.

Training Incharge

BTPS/NTPC NEW DELHI

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Acknowledgement

With profound respect and gratitude, I take this opportunity

to convey my heartfelt gratitude to various individuals

involved in making this training a truly learning and

enriching experience. I do extend my heartfelt thanks to Mrs.

Rachna Singh for providing me this opportunity to be a part

of this esteemed organization. I am extremely grateful to all

the technical staff of BTPS/NTPC for their co-operation

and guidance that helped me a lot during the course of

training. I have learnt a lot working under them and I will

always be indebted of them for this value addition in me. I

would also like to thank the training incharge of

NIT Trichy and all the faculty member of Electrical &

Electronics department for their effort and constant co-

operation which have been a significant factor in the

accomplishment of my industrial training.

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Training at BTPS

I was appointed to do six-week training at this esteemed organization from

01st June to 10th July 2010. In these six weeks I was assigned to visit various

division of the plant which were

1. Operation

2. Control and instrumentation (C&I)

3. Electrical maintenance division I (EMD-I)

4. Electrical maintenance division II (EMD-II)

This six-week training was like an educational adventure for me. It

was really amazing to see the plant by your self and learn how

electricity, which is one of our daily requirements of life, is produced.

This report has been made from self-experience at BTPS. The

material in this report has been gathered from my textbooks, senior

student reports, and trainer manual provided by training department.

The specification & principles have been learnt by me from the

employees of each division of BTPS.

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ABOUT NTPC

NTPC Limited is the largest thermal power generating

company of India. A public sector company, it was

incorporated in the year 1975 to accelerate power

development in the country as a wholly owned company of

the Government of India. At present, Government of India

holds 89.5% of the total equity shares of the company and

FIIs, Domestic Banks, Public and others hold the balance

10.5%. With in a span of 31 years, NTPC has emerged as a

truly national power company, with power generating

facilities in all the major regions of the country.

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POWER GENERATION IN INDIA

NTPCs core business is engineering, construction and operation of powergenerating plants. It also provides consultancy in the area of power plant

constructions and power generation to companies in India and abroad. As ondate the installed capacity of NTPC is 27,904 MW through its 15 coal based(22,895 MW), 7 gas based (3,955 MW) and 4 Joint Venture Projects (1,054MW). NTPC acquired 50% equity of the SAIL Power Supply Corporation Ltd.(SPSCL). This JV Company operates the captive power plants of Durgapur(120 MW), Rourkela (120 MW) and Bhilai (74 MW). NTPC also has 28.33%

stake in Ratnagiri Gas & Power Private Limited (RGPPL) a joint venturecompany between NTPC, GAIL, Indian Financial Institutions and Maharashtra

SEB Co Ltd.NTPC has set new benchmarks for the power industry both in the area of

power plant construction and operations. Its providing power at thecheapest average tariff in the country..

NTPC is committed to the environment, generating power at minimalenvironmental cost and preserving the ecology in the vicinity of the plants.The massive a forestation by NTPC in and around its Ramagundam Power

station (2600 MW) have contributed reducing the temperature in the areas by

about 3c. NTPC has also taken proactive steps for ash utilization. In1991, it set up Ash Utilization Division

A "Centre for Power Efficiency and Environment Protection (CENPEEP)"has been established in NTPC with the assistance of United States Agency for

International Development. (USAID). Cenpeep is efficiency oriented, eco-friendly and eco-nurturing initiative - a symbol of NTPC's concern towards

environmental protection and continued commitment to sustainable power

development in India. Through its Rehabilitation and Resettlementprogrammes, the company endeavors to improve the overall socio economic

status Project Affected Persons.NTPC was among the first Public Sector Enterprises to enter into a

Memorandum of Understanding (MOU) with the Government in 1987-88.NTPC has been placed under the 'Excellent category' (the best category)

every year since the MOU system became operative.

Environment Policy & EnvironmentManagement System

Driven by its commitment for sustainable growth of power,

NTPC has evolved a well defined environment managementpolicy and sound environment practices for minimizingenvironmental impact arising out of setting up of power

plants and preserving the natural ecology.

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National Environment Policy:

At the national level, the Ministry of Environment and Forests had prepared a

draft Environment Policy (NEP) and the Ministry of Power along with NTPC

actively participated in the deliberations of the draft NEP. The NEP 2006 has

since been approved by the Union Cabinet in May 2006.

NTPC Environment Policy:As early as in November 1995, NTPC brought out a comprehensive

document entitled "NTPC Environment Policy and EnvironmentManagement System". Amongst the guiding principles adopted in the

document are company's proactive approach to environment, optimumutilization of equipment, adoption of latest technologies and continual

environment improvement. The policy also envisages efficientutilization of resources, thereby minimizing waste, maximizing ash

utilization and providing green belt all around the plant for maintainingecological balance.

Environment Management, Occupational Health andSafety Systems:

NTPC has actively gone for adoption of best international practices onenvironment, occupational health and safety areas. The organization

has pursued the Environmental Management System (EMS) ISO 14001and the Occupational Health and Safety Assessment System OHSAS18001 at its different establishments. As a result of pursuing these

practices, all NTPC power stations have been certified for ISO 14001 &OHSAS 18001 by reputed national and international Certifying

Agencies.

Pollution Control systems:While deciding the appropriate technology for its projects, NTPC

integrates many environmental provisions into the plant design. Inorder to ensure that NTPC comply with all the stipulated environmentnorms, various state-of-the-art pollution control systems / devices as

discussed below have been installed to control air and water pollution.

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Electrostatic Precipitators:The ash left behind after combustion of coal is arrested in high

efficiency Electrostatic Precipitators (ESPs) and particulate emission iscontrolled well within the stipulated norms. The ash collected in the

ESPs is disposed to Ash Ponds in slurry form.

Flue Gas Stacks:Tall Flue Gas Stacks have been provided for wide dispersion of the

gaseous emissions (SOX, NOX etc) into the atmosphere.

Low-NOXBurners:In gas based NTPC power stations, NOx emissions are controlled by

provision of Low-NOx Burners (dry or wet type) and in coal firedstations, by adopting best combustion practices.

Neutralisation Pits:Neutralisation pits have been provided in the Water Treatment Plant(WTP) for pH correction of the effluents before discharge into Effluent

Treatment Plant (ETP) for further treatment and use.

Coal Settling Pits / Oil Settling Pits:In these Pits, coal dust and oil are removed from the effluents

emanating from the Coal Handling Plant (CHP), coal yard and Fuel OilHandling areas before discharge into ETP.

DE & DS Systems:Dust Extraction (DE) and Dust Suppression (DS) systems have been

installed in all coal fired power stations in NTPC to contain and extractthe fugitive dust released in the Coal Handling Plant (CHP).

Ash Dykes & Ash Disposal systems:Ash ponds have been provided at all coal based stations except Dadriwhere Dry Ash Disposal System has been provided. Ash Ponds have

been divided into lagoons and provided with garlanding arrangementsfor change over of the ash slurry feed points for even filling of the pond

and for effective settlement of the ash particles. Ash in slurry form isdischarged into the lagoons where ash particles get settled from theslurry and clear effluent water is discharged from the ash pond. Thedischarged effluents conform to standards specified by CPCB and thesame is regularly monitored. At its Dadri Power Station, NTPC has set

up a unique system for dry ash collection and disposal facility with AshMound formation. This has been envisaged for the first time in Asia

which has resulted in progressive development of green belt besides

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far less requirement of land and less water requirement as comparedto the wet ash disposal system.

Ash Water Recycling System:Further, in a number of NTPC stations, as a proactive measure, Ash

Water Recycling System (AWRS) has been provided. In the AWRS, theeffluent from ash pond is circulated back to the station for further ash

sluicing to the ash pond. This helps in savings of fresh waterrequirements for transportation of ash from the plant. The ash water

recycling system has already been installed and is in operation atRamagundam, Simhadri, Rihand, Talcher Kaniha, Talcher Thermal,

Kahalgaon, Korba and Vindhyachal. The scheme has helped stations tosave huge quantity of fresh water required as make-up water for

disposal of ash.

Dry Ash Extraction System (DAES):Dry ash has much higher utilization potential in ash-based products

(such as bricks, aerated autoclaved concrete blocks, concrete, Portlandpozzolana cement, etc.). DAES has been installed at Unchahar, Dadri,

Simhadri, Ramagundam, Singrauli, Kahalgaon, Farakka, TalcherThermal, Korba, Vindhyachal, Talcher Kaniha and BTPS.

Liquid Waste Treatment Plants & ManagementSystem:

The objective of industrial liquid effluent treatment plant (ETP) is todischarge lesser and cleaner effluent from the power plants to meet

environmental regulations. After primary treatment at the source oftheir generation, the effluents are sent to the ETP for further

treatment. The composite liquid effluent treatment plant has beendesigned to treat all liquid effluents which originate within the powerstation e.g. Water Treatment Plant (WTP), Condensate Polishing Unit

(CPU) effluent, Coal Handling Plant (CHP) effluent, floor washings,service water drains etc. The scheme involves collection of various

effluents and their appropriate treatment centrally and re-circulation ofthe treated effluent for various plant uses. NTPC has implemented such

systems in a number of its power stations such as Ramagundam,Simhadri, Kayamkulam, Singrauli, Rihand, Vindhyachal, Korba, JhanorGandhar, Faridabad, Farakka, Kahalgaon and Talcher Kaniha. Theseplants have helped to control quality and quantity of the effluents

discharged from the stations.

Sewage Treatment Plants & Facilities:Sewage Treatment Plants (STPs) sewage treatment facilities have been

provided at all NTPC stations to take care of Sewage Effluent from

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Plant and township areas. In a number of NTPC projects modern typeSTPs with Clarifloculators, Mechanical Agitators, sludge drying beds,

Gas Collection Chambers etc have been provided to improve theeffluent quality. The effluent quality is monitored regularly and treated

effluent conforming to the prescribed limit is discharged from the

station. At several stations, treated effluents of STPs are being used forhorticulture purpose.

Environmental Institutional Set-up:Realizing the importance of protection of the environment with speedy

development of the power sector, the company has constituteddifferent groups at project, regional and Corporate Centre level tocarry out specific environment related functions. The EnvironmentManagement Group, Ash Utilisation Group and Centre for Power

Efficiency & Environment Protection (CENPEEP) function from theCorporate Centre and initiate measures to mitigate the impact of

power project implementation on the environment and preserveecology in the vicinity of the projects. Environment Management andAsh Utilisation Groups established at each station, look after various

environmental issues of the individual station.

Environment Reviews:To maintain constant vigil on environmental compliance,

Environmental Reviews are carried out at all operating stations andremedial measures have been taken wherever necessary. As a

feedback and follow-up of these Environmental Reviews, a number of

retrofit and up-gradation measures have been undertaken at differentstations. Such periodic Environmental Reviews and extensivemonitoring of the facilities carried out at all stations have helped incompliance with the environmental norms and timely renewal of the

Air and Water Consents.

Up gradation & retrofitting of Pollution ControlSystems:

Waste Management Various types of wastes such as Municipal ordomestic wastes, hazardous wastes, Bio-Medical wastes get generatedin power plant areas, plant hospital and the townships of projects. The

wastes generated are a number of solid and hazardous wastes likeused oils & waste oils, grease, lead acid batteries, other lead bearingwastes (such as garkets etc.), oil & clarifier sludge, used resin, used

photo-chemicals, asbestos packing, e-waste, metal scrap, C&I wastes,electricial scrap, empty cylinders (refillable), paper, rubber products,canteen (bio-degradable) wastes, buidling material wastes, silica gel,

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glass wool, fused lamps & tubes, fire resistant fluids etc. These wastesfall either under hazardous wastes category or non-hazardous wastes

category as per classification given in Government of Indiasnotification on Hazardous Wastes (Management and Handling) Rules

1989 (as amended on 06.01.2000 & 20.05.2003). Handling and

management of these wastes in NTPC stations have been discussedbelow.

Advanced / Eco-friendly TechnologiesNTPC has gained expertise in operation and management of 200 MWand 500 MW Units installed at different Stations all over the countryand is looking ahead for higher capacity Unit sizes with super critical

steam parameters for higher efficiencies and for associatedenvironmental gains. At Sipat, higher capacity Units of size of 660 MW

and advanced Steam Generators employing super critical steamparameters have already been implemented as a green field project.

Higher efficiency Combined Cycle Gas Power Plants are already underoperation at all gas-based power projects in NTPC. Advanced clean coal

technologies such as Integrated Gasification Combined Cycle (IGCC)have higher efficiencies of the order of 45% as compared to about 38%

for conventional plants. NTPC has initiated a techno-economic studyunder USDOE / USAID for setting up a commercial scale demonstrationpower plant by using IGCC technology. These plants can use low-gradecoals and have higher efficiency as compared to conventional plants.

With the massive expansion of power generation, there is also growingawareness among all concerned to keep the pollution under control

and preserve the health and quality of the natural environment in the

vicinity of the power stations. NTPC is committed to provide affordableand sustainable power in increasingly larger quantity.

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NTPC GROUP

NTPC Limited

Subsidiaries

13

NTPC Vidyut

VyaparNigam Limited

100%

NTPC Electric

SupplyCo. Limited

100%

Pipavav Power

Development Co.Ltd

100%

NTPC Hydr

Limited100%


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Joint

Ventures

14

Utility

Powertech

Limited

50%

NTPC AlstomPower

Services Pvt.

Limited50%

Bhilai ElectricSupply Co. Pvt.

Limited

50%

NTPC-SAIL Power

Company Pvt.

Limited50%

NTPC-SAIL Power

Company Pvt.Limited

50

Ratnagiri Gas &

Power PrivateLtd

28.33%

PTC India

Limited

8%

NTPC Tamilnadu

Energy Co.Limited

50%


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INSTALLED CAPACITY

AN OVERVIEW

Projects No. of Projects

Commissioned

Capacity

(MW)

NTPC OWNED

COAL 15 22,895

GAS/LIQ. FUEL 07 3,955TOTAL 22 26,850

OWNED BY JVCs

Coal 3 314*

Gas/LIQ. FUEL 1 740**

GRAND TOTAL 26 27,904

* Captive Power Plant under JVs with SAIL

** Power Plant under JV with GAIL, FIs & MSEB

PROJECT PROFILE

Coal Based Power Stations

Coal based State

Commissioned

Capacity

(MW)

1. Singrauli Uttar Pradesh 2,000

2. Korba Chattisgarh 2,100

3. Ramagundam Andhra Pradesh 2,600

4. Farakka West Bengal 1,600

5. Vindhyachal Madhya Pradesh 3,260

6. Rihand Uttar Pradesh 2,000

7. Kahalgaon Bihar 1,340

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ABOUT BADARPUR THERMAL POWER

STATION

ELECTRICITY FROM COAL Coal from the coal wagons is unloaded with thehelp of wagon tipplers in the C.H.P. this coal is taken to the raw coal bunkerswith the help of conveyor belts. Coal is then transported to bowl mills by coalfeeders where it is pulverized and ground in the powered form. This crushedcoal is taken away to the furnace through coal pipes with the help of hot andcold mixture P.A fan. This fan takes atmospheric air, a part of which is sent topre heaters while a part goes to the mill for temperature control. Atmosphericair from F.D fan in the air heaters and sent to the furnace as combustion air.

Water from boiler feed pump passes through economizer and reaches theboiler drum . Water from the drum passes through the down comers and

goes to the bottom ring header. Water from the bottom ring header is divided

to all the four sides of the furnace. Due to heat density difference the waterrises up in the water wall tubes. This steam and water mixture is again takento the boiler drum where the steam is sent to super heaters for super

heating. The super heaters are located inside the furnace and the steam issuper heated (540 degree Celsius) and finally it goes to the turbine. Fuelgases from the furnace are extracted from the induced draft fan, which

maintains balance draft in the furnace with F.D fan. These fuel gases heatenergy to the various super heaters and finally through air pre heaters and

goes to electrostatic precipitators where the ash particles are extracted. Thisash is mixed with the water to from slurry is pumped to ash period. Thesteam from boiler is conveyed to turbine through the steam pipes and

through stop valve and control valve that automatically regulate the supply

of steam to the turbine. Stop valves and controls valves are located in steamchest and governor driven from main turbine shaft operates the control

valves the amount used. Steam from controlled valves enter high pressurecylinder of turbines, where it passes through the ring of blades fixed to the

cylinder wall. These act as nozzles and direct the steam into a second ring ofmoving blades mounted on the disc secured in the turbine shaft. The secondring turns the shaft as a result of force of steam. The stationary and moving

blades together.

MAIN GENERATOR

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MAIN TURBINE DATA

Nurturing

Human

Resource

TechnoloFurther

Maintain

sectorLeadership

position

through

expansion

Sustainable

Development

STRATEGI

ES - NTPC

Maximum continuous KVA rating 24700KVA

Maximum continuous KW 210000KW

Rated terminal voltage 15750V

Rated Stator current 9050 A

Rated Power Factor 0.85 lag

Excitation current at MCR Condition 2600 A

Slip-ring Voltage at MCR Condition 310 V

Rated Speed 3000 rpm

Rated Frequency 50 Hz

Short circuit ratio 0.49

Efficiency at MCR Condition 98.4%

Direction of rotation viewed Anti Clockwise

Phase Connection Double Star

Number of terminals brought out 9( 6 neutral and 3 phase)

Rated output of Turbine 210 MW

Rated speed of turbine 3000 rpm

Rated pressure of steam before emergency 130 kg/cm^2

Stop valve rated live steam temperature 535 degree Celsius

Rated steam temperature after reheat at inlet to receptor

valve535 degree Celsius

Steam flow at valve wide open condition 670 tons/hour

Rated quantity of circulating water through condenser 27000 cm/hour

1. For cooling water temperature (degree Celsius) 24,27,30,33

1.Reheated steam pressure at inlet of interceptor valve inkg/cm^2 ABS

23,99,24,21,24,49,24.82

2.Steam flow required for 210 MW in ton/hour 68,645,652,662

3.Rated pressure at exhaust of LP turbine in mm of Hg 19.9,55.5,65.4,67.7

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THERMAL POWER PLANT

A Thermal Power Station comprises all of the equipment and a subsystemrequired to produce electricity by using a steam generating boiler fired withfossil fuels or befouls to drive an electrical generator. Some prefer to use theterm ENERGY CENTER because such facilities convert forms of energy, likenuclear energy, gravitational potential energy or heat energy (derived fromthe combustion of fuel) into electrical energy. However, POWER PLANT is the

most common term in the united state; While POWER STATION prevails inmany Commonwealth countries and especially in the United Kingdom. Such

power stations are most usually constructed on a very large scale anddesigned for continuous operation. Typical diagram of a coal fired thermalpower station 1. Cooling water pump 2. Three-phase transmission line 3.

Step up transformer 4. Electrical Generator 5. Low pressure steam 6. Boilerfeed water pump 7. Surface condenser 8. Intermediate pressure steam

turbine 9. Steam control valve 10. High pressure steam turbine 11.Deaerator Feed water heater 12. Coal conveyor 13. Coal hopper 14. Coalpulverizer 15. boiler steam drum 16. Bottom ash hoper 17. Super heater18. Forced draught(draft) fan 19. Reheater 20. Combustion air intake 21.Economizer 22. Air preheater 23. Precipitator 24. Induced draught(draft)fan 25. Fuel gas stack The description of some of the components written

above is described as follows:

1. Cooling towersCooling Towers are evaporative coolers used for cooling water or other

working medium to near the ambivalent web-bulb air temperature. Coolingtower use evaporation of water to reject heat from processes such as coolingthe circulating water used in oil refineries, Chemical plants, power plants andbuilding cooling, for example. The tower vary in size from small roof-top units

to very large hyperboloid structures that can be up to 200 meters tall and100 meters in diameter, or rectangular structure that can be over 40 meters

tall and 80 meters long. Smaller towers are normally factory built, whilelarger ones are constructed on site. The primary use of large , industrialcooling tower system is to remove the heat absorbed in the circulating

cooling water systems used in power plants , petroleum refineries,petrochemical and chemical plants, natural gas processing plants and otherindustrial facilities . The absorbed heat is rejected to the atmosphere by the

evaporation of some of the cooling water in mechanical forced-draft orinduced draft towers or in natural draft hyperbolic shaped cooling towers as

seen at most nuclear power plants.

2.Three phase transmission lineThree phase electric power is a common method of electric power

transmission. It is a type of polyphase system mainly used to power motorsand many other devices. A Three phase system uses less conductor materialto transmit electric power than equivalent single phase, two phase, or directcurrent system at the same voltage. In a three phase system, three circuits

reach their instantaneous peak values at different times. Taking oneconductor as the reference, the other two current are delayed in time by one-

Exploit new

business

opportunities

ue secur y

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third and two-third of one cycle of the electrical current. This delay betweenphases has the effect of giving constant power transfer over each cycle ofthe current and also makes it possible to produce a rotating magnetic field in

an electric motor. At the power station, an electric generator convertsmechanical power into a set of electric currents, one from each

electromagnetic coil or winding of the generator. The current are sinusoidal

functions of time, all at the same frequency but offset in time to give differentphases. In a three phase system the phases are spaced equally, giving a

phase separation of one-third one cycle. Generators output at a voltage thatranges from hundreds of volts to 30,000 volts. At the power station,

transformers: step-up this voltage to one more suitable for transmission.After numerous further conversions in the transmission and distribution

network the power is finally transformed to the standard mains voltage (i.e.the household voltage). The power may already have been split into singlephase at this point or it may still be three phase. Where the step-down is 3

phase, the output of this transformer is usually star connected with thestandard mains voltage being the phase-neutral voltage. Another system

commonly seen in North America is to have a delta connected secondary with

a center tap on one of the windings supplying the ground and neutral. Thisallows for 240 V three phase as well as three different single phase

voltages( 120 V between two of the phases and neutral , 208 V between thethird phase ( known as a wild leg) and neutral and 240 V between any two

phase) to be available from the same supply.

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3.Electrical generator

An Electrical generator is a device that converts kinetic energy to electricalenergy, generally using electromagnetic induction. The task of converting theelectrical energy into mechanical energy is accomplished by using a motor.

The source of mechanical energy may be a reciprocating or turbine steamengine, , water falling through the turbine are made in a variety of sizesranging from small 1 hp (0.75 kW) units (rare) used as mechanical drives for

pumps, compressors and other shaft driven equipment , to 2,000,000hp(1,500,000 kW) turbines used to generate electricity. There are several

classifications for modern steam turbines. Steam turbines are used in all ofour major coal fired power stations to drive the generators or alternators,which produce electricity. The turbines themselves are driven by steam

generated in Boilers or steam generators as they are sometimes called.Electrical power station use large stem turbines driving electric generators to

produce most (about 86%) of the worlds electricity. These centralizedstations are of two types: fossil fuel power plants and nuclear power plants.

The turbines used for electric power generation are most often directlycoupled to their-generators .As the generators must rotate at constantsynchronous speeds according to the frequency of the electric power system,the most common speeds are 3000 r/min for 50 Hz systems, and 3600 r/minfor 60 Hz systems. Most large nuclear sets rotate at half those speeds, and

have a 4-pole generator rather than the more common 2-pole one. Energy inthe steam after it leaves the boiler is converted into rotational energy as itpasses through the turbine. The turbine normally consists of several stagewith each stages consisting of a stationary blade (or nozzle) and a rotating

blade. Stationary blades convert the potential energy of the steam intokinetic energy into forces, caused by pressure drop, which results in the

rotation of the turbine shaft. The turbine shaft is connected to a generator,

which produces the electrical energy.

4.Boiler feed water pump

A Boiler feed water pump is a specific type of pump used to pump water intoa steam boiler. The water may be freshly supplied or retuning condensation

of the steam produced by the boiler. These pumps are normally high pressureunits that use suction from a condensate return system and can be of thecentrifugal pump type or positive displacement type. Construction and

operation Feed water pumps range in size up to many horsepower and theelectric motor is usually separated from the pump body by some form of

mechanical coupling. Large industrial condensate pumps may also serve as

the feed water pump. In either case, to force the water into the boiler; thepump must generate sufficient pressure to overcome the steam pressuredeveloped by the boiler. This is usually accomplished through the use of a

centrifugal pump. Feed water pumps usually run intermittently and arecontrolled by a float switch or other similar level-sensing device energizingthe pump when it detects a lowered liquid level in the boiler is substantiallyincreased. Some pumps contain a two-stage switch. As liquid lowers to the

trigger point of the first stage, the pump is activated. I f the liquid continues

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to drop (perhaps because the pump has failed, its supply has been cut off orexhausted, or its discharge is blocked); the second stage will be triggered.

This stage may switch off the boiler equipment (preventing the boiler fromrunning dry and overheating), trigger an alarm, or both.

Steam-powered pumpsSteam locomotives and the steam engines used on ships and stationary

applications such as power plants also required feed water pumps. In thissituation, though, the pump was often powered using a small steam engine

that ran using the steam produced by the boiler. A means had to be provided,of course, to put the initial charge of water into the boiler(before steam

power was available to operate the steam-powered feed water pump).thepump was often a positive displacement pump that had steam valves and

cylinders at one end and feed water cylinders at the other end; no crankshaft

was required. In thermal plants, the primary purpose of surface condenser isto condense the exhaust steam from a steam turbine to obtain maximumefficiency and also to convert the turbine exhaust steam into pure water sothat it may be reused in the steam generator or boiler as boiler feed water.

By condensing the exhaust steam of a turbine at a pressure belowatmospheric pressure, the steam pressure drop between the inlet andexhaust of the turbine is increased, which increases the amount heat

available for conversion to mechanical power. Most of the heat liberated dueto condensation of the exhaust steam is carried away by the cooling medium

(water or air) used by the surface condenser.

Control valvesControl valves are valves used within industrial plants and elsewhere to

control operating conditions such as temperature,pressure,flow,and liquidLevel by fully partially opening or closing in response to signals received fromcontrollers that compares a set point to a process variable whose value isprovided by sensors that monitor changes in such conditions. The opening or

closing of control valves is done by means of electrical, hydraulic orpneumatic systems

7. DeaeratorA Dearator is a device for air removal and used to remove dissolved gases(an alternate would be the use of water treatment chemicals) from boiler

feed water to make it non-corrosive. A dearator typically includes a verticaldomed deaeration section as the deaeration boiler feed water tank. A Steamgenerating boiler requires that the circulating steam, condensate, and feedwater should be devoid of dissolved gases, particularly corrosive ones anddissolved or suspended solids. The gases will give rise to corrosion of the

metal. The solids will deposit on the heating surfaces giving rise to localizedheating and tube ruptures due to overheating. Under some conditions it may

give to stress corrosion cracking. Deaerator level and pressure must becontrolled by adjusting control valves- the level by regulating condensate

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flow and the pressure by regulating steam flow. If operated properly, mostdeaerator vendors will guarantee that oxygen in the deaerated water will not

exceed 7 ppb by weight (0.005 cm3/L)

8. Feed water heater

A Feed water heater is a power plant component used to pre-heat waterdelivered to a steam generating boiler. Preheating the feed water reducesthe irreversible involved in steam generation and therefore improves thethermodynamic efficiency of the system.[4] This reduces plant operating

costs and also helps to avoid thermal shock to the boiler metal when the feedwater is introduces back into the steam cycle. In a steam power (usuallymodeled as a modified Ranking cycle), feed water heaters allow the feedwater to be brought up to the saturation temperature very gradually. This

minimizes the inevitable irreversibilitys associated with heat transfer to theworking fluid (water). A belt conveyor consists of two pulleys, with a

continuous loop of material- the conveyor Belt that rotates about them. The

pulleys are powered, moving the belt and the material on the belt forward.Conveyor belts are extensively used to transport industrial and agriculturalmaterial, such as grain, coal, ores etc.

9. PulverizerA pulverizer is a device for grinding coal for combustion in a furnace in a

fossil fuel power plant.

10. Boiler Steam DrumSteam Drums are a regular feature of water tube boilers. It is reservoir of

water/steam at the top end of the water tubes in the water-tube boiler. They

store the steam generated in the water tubes and act as a phase separatorfor the steam/water mixture. The difference in densities between hot and

cold water helps in the accumulation of the hotter-water/and saturated steam into steam drum. Made from high-grade steel (probably stainless) and

its working involves temperatures 390C and pressure well above 350psi(2.4MPa). The separated steam is drawn out from the top section of the

drum. Saturated steam is drawn off the top of the drum. The steam will re-enter the furnace in through a super heater, while the saturated water at the

bottom of steam drum flows down to the mud-drum /feed water drum bydown comer tubes accessories include a safety valve, water level indicatorand fuse plug. A steam drum is used in the company of a mud-drum/feed

water drum which is located at a lower level. So that it acts as a sump for the

sludge or sediments which have a tendency to the bottom.

11. Super HeaterA Super heater is a device in a steam engine that heats the steam generated

by the boiler again increasing its thermal energy and decreasing thelikelihood that it will condense inside the engine. Super heaters increase theefficiency of the steam engine, and were widely adopted. Steam which has

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been superheated is logically known as superheated steam; non-superheated steam is called saturated steam or wet steam; Super

heaters were applied to steam locomotives in quantity from the early 20thcentury, to most steam vehicles, and so stationary steam engines including

power stations.

12. EconomizersEconomizer, or in the UK economizer, are mechanical devices intended to

reduce energy consumption, or to perform another useful function likepreheating a fluid. The term economizer is used for other purposes as well.Boiler, power plant, and heating, ventilating and air conditioning. In boilers,economizer are heat exchange devices that heat fluids , usually water, up to

but not normally beyond the boiling point of the fluid. Economizers are sonamed because they can make use of the enthalpy and improving the

boilers efficiency. They are a device fitted to a boiler which saves energy byusing the exhaust gases from the boiler to preheat the cold water used the fill

it (the feed water). Modern day boilers, such as those in cold fired power

stations, are still fitted with economizer which is decedents of Greensoriginal design. In this context they are turbines before it is pumped to theboilers. A common application of economizer is steam power plants is to

capture the waste hit from boiler stack gases (flue gas) and transfer thus it tothe boiler feed water thus lowering the needed energy input , in turn

reducing the firing rates to accomplish the rated boiler output . Economizerlower stack temperatures which may cause condensation of acidic

combustion gases and serious equipment corrosion damage if care is nottaken in their design and material selection.

13. Air Preheater

Air preheater is a general term to describe any device designed to heat airbefore another process (for example, combustion in a boiler). The purpose ofthe air preheater is to recover the heat from the boiler flue gas which

increases the thermal efficiency of the boiler by reducing the useful heat lostin the fuel gas. As a consequence, the flue gases are also sent to the flue gasstack (or chimney) at a lower temperature allowing simplified design of the

ducting and the flue gas stack. It also allows control over the temperature ofgases leaving the stack.

14. PrecipitatorAn Electrostatic precipitator (ESP) or electrostatic air cleaner is a particulate

device that removes particles from a flowing gas (such As air) using the force

of an induced electrostatic charge. Electrostatic precipitators are highlyefficient filtration devices, and can easily remove fine particulate matter suchas dust and smoke from the air steam. ESPs continue to be excellent devices

for control of many industrial particulate emissions, including smoke fromelectricity-generating utilities (coal and oil fired), salt cake collection from

black liquor boilers in pump mills, and catalyst collection from fluidized bedcatalytic crackers from several hundred thousand ACFM in the largest coal-

fired boiler application. The original parallel plate-Weighted wire design

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(described above) has evolved as more efficient ( and robust) dischargeelectrode designs were developed, today focusing on rigid discharge

electrodes to which many sharpened spikes are attached , maximizing coronaproduction. Transformer rectifier systems apply voltages of 50-100 Kilovoltsat relatively high current densities. Modern controls minimize sparking and

prevent arcing, avoiding damage to the components. Automatic rapping

systems and hopper evacuation systems remove the collected particulatematter while on line allowing ESPs to stay in operation for years at a time.

15. Fuel gas stackA Fuel gas stack is a type of chimney, a vertical pipe, channel or similarstructure through which combustion product gases called fuel gases are

exhausted to the outside air. Fuel gases are produced when coal, oil, naturalgas, wood or any other large combustion device. Fuel gas is usually

composed of carbon dioxide (CO2) and water vapor as well as nitrogen andexcess oxygen remaining from the intake combustion air. It also contains asmall percentage of pollutants such as particulates matter, carbon mono

oxide, nitrogen oxides and sulfur oxides. The flue gas stacks are often quitetall, up to 400 meters (1300 feet) or more, so as to disperse the exhaustpollutants over a greater aria and thereby reduce the concentration of the

pollutants to the levels required by governmental environmental policies andregulations.

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Electrical Maintenance division II was assigned to do training in Electrical maintenance division I from

01st June 2010 to 14th June 2010. These weeks of training in this

division were divided as follows.

HT/LT switchgear

HT/LT Motors

Turbine &Boiler side

CHP/NCHP Electrical

Electrical maintenance division 1 It is responsible for maintenance of: 1.

Boiler side motors 2. Turbine side motors 3. Outside motors 4. Switchgear

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Boiler side motors:For 1, units 1, 2, 3

1.1D Fans 2 in no.

2.F.D Fans 2 in no.

3.P.A.Fans 2 in no.

4.Mill Fans 3 in no.

5.Ball mill fans 3 in no.6.RC feeders 3 in no.

7.Slag Crushers 5 in no.

8.DM Make up Pump 2 in no.

9.PC Feeders 4 in no.

10.Worm Conveyor 1 in no.

11.Furnikets 4 in no.

For stage units 1, 2, 3

1.I.D Fans 2 in no.

2.F.D Fans 2 in no.

3.P.A Fans 2 in no.

4.Bowl Mills 6 in no.

5.R.C Feeders 6 in no.

6.Clinker Grinder 2 in no.

7.Scrapper 2 in no.

8.Seal Air Fans 2 in no.

9.Hydrazine and Phosphorous Dozing 2 in no.

2/3 in no.

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COAL HANDLING PLANT (C.H.P)

The old coal handling plant caters to the need of units 2,3,4,5 and 1 whereas

the latter supplies coal to units 4 and V.O.C.H.P. supplies coal to second and

third stages in the advent coal to usable form to (crushed) form its raw form

and send it to bunkers, from where it is send to furnace.

Major Components

1. Wagon Tippler: - Wagons from the coal yard come to the tippler and are emptiedhere. The process is performed by a slip ring motor of rating: 55 KW, 415V, 1480 RPM.

This motor turns the wagon by 135 degrees and coal falls directly on the conveyor

through vibrators. Tippler has raised lower system which enables is to switch off motor

when required till is wagon back to its original position. It is titled by weight balancingprinciple. The motor lowers the hanging balancing weights, which in turn tilts the

conveyor. Estimate of the weight of the conveyor is made through hydraulic weighingmachine.

2. Conveyor: - There are 14 conveyors in the plant. They are numbered so that theirfunction can be easily demarcated. Conveyors are made of rubber and more with a speed

of 250-300m/min. Motors employed for conveyors has a capacity of 150 HP. Conveyors

have a capacity of carrying coal at the rate of 400 tons per hour. Few conveyors are

double belt, this is done for imp. Conveyors so that if a belt develops any problem theprocess is not stalled. The conveyor belt has a switch after every 25-30 m on both sides

so stop the belt in case of emergency. The conveyors are 1m wide, 3 cm thick and madeof chemically treated vulcanized rubber. The max angular elevation of conveyor isdesigned such as never to exceed half of the angle of response and comes out to be

around 20 degrees.

3. Zero Speed Switch:-It is safety device for motors, i.e., if belt is not moving and the

motor is on the motor may burn. So to protect this switch checks the speed of the belt and

switches off the motor when speed is zero.

4. Metal Separators: - As the belt takes coal to the crusher, No metal pieces should go

along with coal. To achieve this objective, we use metal separators. When coal is dropped

to the crusher hoots, the separator drops metal pieces ahead of coal. It has a magnet and abelt and the belt is moving, the pieces are thrown away. The capacity of this device is

around 50 kg. .The CHP is supposed to transfer 600 tons of coal/hr, but practically only

300-400 tons coal is transfer

5. Crusher: - Both the plants use TATA crushers powered by BHEL. Motors. The

crusher is of ring type and motor ratings are 400 HP, 606 KV. Crusher is designed to

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crush the pieces to 20 mm size i.e. practically considered as the optimum size of transfer

via conveyor.

6. Rotatory Breaker: - OCHP employs mesh type of filters and allows particles of20mm size to go directly to RC bunker, larger particles are sent to crushes. This leads to

frequent clogging. NCHP uses a technique that crushes the larger of harder substance like

metal impurities easing the load on the magnetic separators.

MILLING SYSTEM

1. RC Bunker: - Raw coal is fed directly to these bunkers. These are 3 in no. per boiler.

4 & tons of coal are fed in 1 hr. the depth of bunkers is 10m.

2. RC Feeder: - It transports pre crust coal from raw coal bunker to mill. The quantity of

raw coal fed in mill can be controlled by speed control of aviator drive controlling

damper and aviator change.

3. Ball Mill: - The ball mill crushes the raw coal to a certain height and then allows it to

fall down. Due to impact of ball on coal and attraction as per the particles move over eachother as well as over the Armor lines, the coal gets crushed. Large particles are broken by

impact and full grinding is done by attraction. The Drying and grinding option takes

place simultaneously inside the mill.

4. Classifier:- It is an equipment which serves separation of fine pulverized coal particles

medium from coarse medium. The pulverized coal along with the carrying medium

strikes the impact plate through the lower part. Large particles are then transferred to theball mill.

5. Cyclone Separators: - It separates the pulverized coal from carrying medium. Themixture of pulverized coal vapour caters the cyclone separators.

6. The Tturniket: - It serves to transport pulverized coal from cyclone separators topulverized coal bunker or to worm conveyors. There are 4 turnikets per boiler.

7. Worm Conveyor: - It is equipment used to distribute the pulverized coal from bunker

of one system to bunker of other system. It can be operated in both directions.

8. Mills Fans: - It is of 3 types: Six in all and are running condition all the time. (a) ID

Fans: - Located between electrostatic precipitator and chimney. Type-radical Speed-1490rpm Rating-300 KW Voltage-6.6 KV Lubrication-by oil (b) FD Fans: - Designed to

handle secondary air for boiler. 2 in number and provide ignition of coal. Type-axial

Speed-990 rpm Rating-440 KW Voltage-6.6 KV (c)Primary Air Fans: - Designed forhandling the atmospheric air up to 50 degrees Celsius, 2 in number And they transfer the

powered coal to burners to firing. Type-Double suction radial Rating-300 KW Voltage-

6.6 KV Lubrication-by oil Type of operation-continuous

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9. Bowl Mill: - One of the most advanced designs of coal pulverizes presently

manufactured. Motor specification squirrel cage induction motor Rating-340 KW

Voltage-6600KV Curreen-41.7A Speed-980 rpm Frequency-50 Hz No-load current-15-16 A

NEW COAL HANDLING PLANT (N.C.H.P)

1. Wagon Tippler:- Motor Specification (i) H.P 75 HP (ii) Voltage 415, 3 phase (iii)

Speed 1480 rpm (iv) Frequency 50 Hz (v) Current rating 102 A

2. Coal feed to plant:- Feeder motor specification (i) Horse power 15 HP (ii) Voltage

415V,3 phase (iii) Speed 1480 rpm (iv) Frequency 50 Hz

3. Conveyors:- 10A, 10B 11A, 11B 12A, 12B 13A, 13B 14A, 14B 15A, 15B 16A, 16B

17A, 17B 18A, 18B

4. Transfer Point 6

5. Breaker House

6. Rejection House

7. Reclaim House

8. Transfer Point 7

9. Crusher House

10. Exit The coal arrives in wagons via railways and is tippled by the wagon tipplers into

the hoppers. If coal is oversized (>400 mm sq) then it is broken manually so that it passesthe hopper mesh. From the hopper mesh it is taken to the transfer point TP6 by conveyor

12A ,12B which takes the coal to the breaker house , which renders the coal size to be

100mm sq. the stones which are not able to pass through the 100mm sq of hammer arerejected via conveyors 18A,18B to the rejection house . Extra coal is to sent to the

reclaim hopper via conveyor 16. From breaker house coal is taken to the TP7 via

Conveyor 13A, 13B. Conveyor 17A, 17B also supplies coal from reclaim hopper, From

TP7 coal is taken by conveyors 14A, 14B to crusher house whose function is to renderthe size of coal to 20mm sq. now the conveyor labors are present whose function is to

recognize and remove any stones moving in the conveyors . In crusher before it enters the

crusher. After being crushed, if any metal is still present it is taken care of by metaldetectors employed in conveyor 10.

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SWITCH GEAR-

It makes or breaks an electrical circuit.

1. Isolation: - A device which breaks an electrical circuit when circuit isswitched on to no load. Isolation is normally used in various ways for purpose

of isolating a certain portion when required for maintenance.

2. Switching Isolation: - It is capable of doing things like interruptingtransformer magnetized current, interrupting line charging current and evenperform load transfer switching. The main application of switching isolation isin connection with transformer feeders as unit makes it possible to switch out

one transformer while other is still on load.

3. Circuit Breakers: - One which can make or break the circuit on load andeven on faults is referred to as circuit breakers. This equipment is the mostimportant and is heavy duty equipment mainly utilized for protection of

various circuits and operations on load. Normally circuit breakers installed areaccompanied by isolators

4. Load Break Switches: - These are those interrupting devices which canmake or break circuits. These are normally on same circuit, which are backed

by circuit breakers.

5. Earth Switches: - Devices which are used normally to earth a particularsystem, to avoid any accident happening due to induction on account of live

adjoining circuits. These equipments do not handle any appreciable currentat all. Apart from this equipment there are a number of relays etc. which areused in switchgear.

LT Switchgear

It is classified in following ways:-

1. Main Switch:- Main switch is control equipment which controls ordisconnects the main supply. The main switch for 3 phase supply is available

for tha range 32A, 63A, 100A, 200Q, 300A at 500V grade.

2. Fuses: - With Avery high generating capacity of the modern powerstations extremely heavy carnets would flow in the fault and the fuse clearingthe fault would be required to withstand extremely heavy stress in process. Itis used for supplying power to auxiliaries with backup fuse protection. Rotary

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switch up to 25A. With fuses, quick break, quick make and double breakswitch fuses for 63A and 100A, switch fuses for 200A, 400A, 600A, 800A and

1000A are used.

3. Contractors: - AC Contractors are 3 poles suitable for D.O.L Starting ofmotors and protecting the connected motors.

4. Overload Relay: - For overload protection, thermal over relay are bestsuited for this purpose. They operate due to the action of heat generated by

passage of current through relay element.

5. Air Circuit Breakers: - It is seen that use of oil in circuit breaker maycause a fire. So in all circuits breakers at large capacity air at highpressure is used which is maximum at the time of quick tripping ofcontacts. This reduces the possibility of sparking. The pressure may

vary from 50-60 kg/cm^2 for high and medium capacity circuitbreakers.

6.

7. HT SWITCH GEAR:-

1. Minimum oil Circuit Breaker: - These use oil as quenching medium. Itcomprises of simple dead tank row pursuing projection from it. The movingcontracts are carried on an iron arm lifted by a long insulating tension rod

and are closed simultaneously pneumatic operating mechanism by means oftensions but throw off spring to be provided at mouth of the control the maincurrent within the controlled device. Type-HKH 12/1000c Rated Voltage-66

KV Normal Current-1250A Frequency-5Hz Breaking Capacity-3.4+KASymmetrical 3.4+KA Asymmetrical 360 MVA Symmetrical Operating

Coils-CC 220 V/DC FC 220V/DC Motor Voltage-220 V/DC

2. Air Circuit Breaker: - In this the compressed air pressure around 15 kg percm^2 is used for extinction of arc caused by flow of air around the movingcircuit . The breaker is closed by applying pressure at lower opening and

opened by applying pressure at upper opening. When contacts operate, thecold air rushes around the movable contacts and blown the arc. It has thefollowing advantages over OCB:- i. Fire hazard due to oil are eliminated. ii.

Operation takes place quickly. iii. There is less burning of contacts since theduration is short and consistent. iv. Facility for frequent operation since thecooling medium is replaced constantly. Rated Voltage-6.6 KV Current-630 A

Auxiliary current-220 V/DC

3. SF6 Circuit Breaker: - This type of circuit breaker is of construction to deadtank bulk oil to circuit breaker but the principle of current interruption is

similar o that of air blast circuit breaker. It simply employs the arcextinguishing medium namely SF6. the performance of gas . When it is

broken down under an electrical stress. It will quickly reconstitute itself Circuit Breakers-HPA Standard-1 EC 56 Rated Voltage-12 KV InsulationLevel-28/75 KV Rated Frequency-50 Hz Breaking Current-40 KA Rated

Current-1600 A Making Capacity-110 KA Rated Short Time Current 1/3s -40

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A Mass Approximation-185 KG Auxiliary Voltage Closing Coil-220 V/DC Opening Coil-220 V/DC Motor-220 V/DC SF6 Pressure at 20 Degree Celsius-

0.25 KG SF6 Gas Per pole-0.25 KG4. Vacuum Circuit Breaker: - It works on the principle that vacuum is used to

save the purpose of insulation and it implies that pr. Of gas at whichbreakdown voltage independent of pressure. It regards of insulation and

strength, vacuum is superior dielectric medium and is better that all othermedium except air and sulphur which are generally used at high pressure. Rated frequency-50 Hz Rated making Current-10 Peak KA Rated Voltage-12 KV Supply Voltage Closing-220 V/DC Rated Current-1250 A Supply

Voltage Tripping-220 V/DC Insulation Level-IMP 75 KVP Rated Short TimeCurrent-40 KA (3 SEC) Weight of Breaker-8 KG

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EMD II

Electrical Maintenance division II- I was assigned to do training in Electrical

maintenance division II from 14th June 2010 to 28th June 2010.

This week of training in this division was divided as follows.

- Generator ,ESP,lighting.

-Excitation,Protection.

-Testing,Transformer.

-Switchyard.

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Generator and Auxiliaries Generator and Auxiliaries

Fundamentals The transformation of mechanical energy into electrical energy iscarried out by the Generator. This Chapter seeks to provide basic understanding about the

working principles and development of Generator.

Working PrincipleThe A.C. Generator or alternator is based upon the principle ofelectromagnetic induction and consists generally of a stationary part called stator and arotating part called rotor. The stator housed the armature windings. The rotor houses the

field windings. D.C. voltage is applied to the field windings through slip rings. When the

rotor is rotated, the lines of magnetic flux (viz magnetic field) cut through the statorwindings. This induces an electromagnetic force (e.m.f.) in the stator windings. The

magnitude of this e.m.f. is given by the following expression. E = 4.44 /O FN volts 0 =

Strength of magnetic field in Webers. F = Frequency in cycles per second or Hertz. N =

Number of turns in a coil of stator winding F = Frequency = Pn/120 Where P = Number

of poles n = revolutions per second of rotor. From the expression it is clear that for thesame frequency, number of poles increases with decrease in speed and vice versa.

Development The first A.C. Generator concept was enunciated by Michael Faraday in1831. In 1889 Sir Charles A. Parsons developed the first AC turbo-generator. Although

slow speed AC generators have been built for some time, it was not long before that thehigh-speed generators made its impact. Development contained until, in 1922, the

increased use of solid forgings and improved techniques permitted an increase in

generator rating to 20MW at 300rpm. Up to the out break of second world war, in 1939,most large generator;- were of the order of 30 to 50 MW at 3000 rpm. During the war, the

development and installation of power plants was delayed and in order to catch up with

the delay in plant installation, a large number of 30 MW and 60 MW at 3000 rpm unitswere constructed during the years immediately following the war. The changes in design

in this period were relatively small. In any development programme the. Costs of

material and labour involved in manufacturing and erection must be a basic

consideration.

Generator componentsThis Chapter deals with the two main components of the Generator viz. Rotor, its

winding & balancing and stator, its frame, core & windings.

RotorThe electrical rotor is the most difficult part of the generator to design. Itrevolves inmost modern generators at a speed of 3,000 revolutions per minute. Theproblem ofguaranteeing the dynamic strength and operating stability of such a rotor iscomplicated

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by the fact that a massive non-uniform shaft subjected to a multiplicity ofdifferentialstresses must operate in oil lubricated sleeve bearings supported by astructuremounted on foundations all of which possess complex dynamic be behaviorpeculiar to

themselves. It is also an electromagnet and to give it the necessary magneticstrengththe windings must carry a fairly high current. The passage of the currentthrough thewindings generates heat but the temperature must not be allowed to becomeso high,otherwise difficulties will be experienced with insulation. To keep thetemperature down,the cross section of the conductor could not be increased but this wouldintroduceanother problems. In order to make room for the large conductors, body andthis would

cause mechanical weakness. The problem is really to get the maximumamount ofcopper into the windings without reducing the mechanical strength. Withgood designand great care in construction this can be achieved. The rotor is a cast steelingot, andit is further forged and machined. Very often a hole is bored through thecentre of therotor axially from one end of the other for inspection. Slots are thenmachined forwindings and ventilation.

Rotor winding

Silver bearing copper is used for the winding with mica as the insulationbetween conductors. A mechanically strong insulator such as micanite is used

for lining the slots. Later designs of windings for large rotor incorporatecombination of hollow conductors with slots or holes arranged to provide for

circulation of the cooling gasthrough the actual conductors. When rotating at high speed. Centrifugal force

tries to liftthe windings out of the slots and they are contained by wedges. The end

rings aresecured to a turned recess in the rotor body, by shrinking or screwing and

supported atthe other end by fittings carried by the rotor body. The two ends of windings

areconnected to slip rings, usually made of forged steel, and mounted on

insulatedsleeves.

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Rotor balancing

When completed the rotor must be tested for mechanical balance, whichmeans that a

check is made to see if it will run up to normal speed without vibration. To dothis it

would have to be uniform about its central axis and it is most unlikely thatthis

will be so to the degree necessary for perfect balance. Arrangements aretherefore

made in all designs to fix adjustable balance weights around thecircumference at each

end.

StatorStator frame: The stator is the heaviest load to be transported. The

major part of this load is the stator core. This comprises an inner frame andouter frame. The outer frame is a rigid fabricated structure of welded steelplates, within this shell is a fixed cage of girder built circular and axial ribs.

The ribs divide the yoke in the compartments through which hydrogen flowsinto radial ducts in the stator core and circulate through the gas coolershoused in the frame. The inner cage is usually fixed in to the yoke by an

arrangement of springs to dampen the double frequency vibrations inherentin 2 pole generators. The end shields of hydrogen cooled generators must be

strong enough to carry shaft seals. In large generators the frame is

constructed as two separate parts. The fabricated inner cage is inserted inthe outer frame after the stator core has been constructed and the winding

completed.

Stator core:

The stator core is built up from a large number of 'punching" or sections ofthin steel plates. The use of cold rolled grain-oriented steel can contribute to

reduction in the weight of stator core for two main reasons: a) There is anincrease in core stacking factor with improvement in lamination cold Rollingand in cold buildings techniques. b) The advantage can be taken of the high

magnetic permeance of grain-orientedsteels of work the stator core at comparatively high magnetic saturation

withoutfear or excessive iron loss of two heavy a demand for excitation ampere turns

from the generator rotor.

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Stator Windings

Each stator conductor must be capable of carrying the rated current withoutoverheating. The insulation must be sufficient to prevent leakage currentsflowing between the phases to earth. Windings for the stator are made up

from copper strips wound with insulated tape which is impregnated withvarnish, dried under vacuum and hot pressed to form a solid insulation bar.These bars are then place in the stator slots and held in with wedges to form

the complete winding which is connected together at each end of the coreforming the end turns. These end turns are rigidly braced and packed with

blocks of insulation material to withstand the heavy forces which might resultfrom a short circuit or other fault conditions. The generator terminals are

usually arranged below the stator. On recent generators (210 MW) thewindings are made up from copper tubes instead of strips through whichwater is circulated for cooling purposes. The water is fed to the windings

through plastic tubes.

Generator Cooling System

The 200/210 MW Generator is provided with an efficient cooling system to avoid

excessive heating and consequent wear and tear of its main components during

operation. This Chapter deals with the rotor-hydrogen cooling system and stator

water cooling system along with the shaft sealing and bearing cooling systems.

Rotor Cooling SystemThe rotor is cooled by means of gap pick-up cooling, wherein the hydrogen gas in theair

gap is sucked through the scoops on the rotor wedges and is directed to flow along theventilating canals milled on the sides of the rotor coil, to the bottom of the slot where it

takes a turn and comes out on the similar canal milled on the other side of the rotor coil to

the hot zone of the rotor. Due to the rotation of the rotor, a positive suction as well as

discharge is created due to which a certain quantity of gas flows and cools the rotor. Thismethod of cooling gives uniform distribution of temperature. Also, this method has an

inherent advantage of eliminating the deformation of copper due to varying temperatures.

Hydrogen Cooling SystemHydrogen is used as a cooling medium in large capacity generator in view of its high heat

carrying capacity and low density. But in view of its forming an explosive mixture withoxygen, proper arrangement for filling, purging and maintaining its purity inside the

generator have to be made. Also, in order to prevent escape of hydrogen from the

generator casing, shaft sealing system is used to provide oil sealing. The hydrogencooling system mainly comprises of a gas control stand, a drier, an liquid level indicator,

hydrogen control panel, gas purity measuring and indicating instruments, The system is

capable of performing the following functions : Filling in and purging of hydrogen

safely without bringing in contact with air. Maintaining the gas pressure inside the

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machine at the desired value at all the times. Provide indication to the operator about

the condition of the gas inside the machine i.e. its pressure, temperature and purity.

Continuous circulation of gas inside the machine through a drier in order to

remove any water vapour that may be present in it. Indication of liquid level in the generator and alarm in case of high level.

Stator Cooling SystemThe stator winding is cooled by distillate. Which is fed from one end of the machine byTeflon tube and flows through the upper bar and returns back through the lower bar of

another slot? Turbo generators require water cooling arrangement over and above the

usual hydrogen cooling arrangement. The stator winding is cooled in this system by

circulating demineralised water (DM water) through hollow conductors. The coolingwater used for cooling stator winding calls for the use of very high quality of cooling

water. For this purpose DM water of proper specific resistance is selected. Generator is to

be loaded within a very short period if the specific resistance of the cooling DM watergoes beyond certain preset values. The system is designed to maintain a constant rate of

cooling water flow to the stator winding at a nominal inlet water temperature of 40 deg.C.

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Rating of 95 MW Generator

Manufacture by Bharat heavy electrical Limited (BHEL)

Capacity - 117500 KVA

Voltage - 10500V

Speed - 3000 rpm

Hydrogen - 2.5 Kg/cm2

Power factor - 0.85 (lagging)

Stator current - 6475 A

Frequency - 50 Hz

Stator wdg connection - 3 phase

Rating of 210 MW Generator

Capacity - 247000 KVA

Voltage (stator) - 15750 V

Current (stator) - 9050 A

Voltage (rotor) - 310 V

Current (rotor) - 2600 V

Speed - 3000 rpm

Power factor - 0.85

Frequency - 50 Hz

Hydrogen - 3.5 Kg/cm2

Stator wdg connection - 3 phase star connection

Insulation class B

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TRANFORMER

A transformer is a device that transfers electrical energy from one circuit to another by

magnetic coupling with out requiring relative motion between its parts. It usually

comprises two or more coupled windings, and in most cases, a core to concentrate

magnetic flux. An alternating voltage applied to one winding creates a time-varying

magnetic flux in the core, which includes a voltage in the other windings. Varying the

relative number of turns between primary and secondary windings determines the ratio of

the input and output voltages, thus transformingthe voltage by stepping it up or down

between circuits. By transforming electrical power to a high-voltage,_low-current form

and back again, the transformer greatly reduces energy losses and so enables the

economic transmission of power over long distances. It has thus shape the electricity

supply industry, permitting generation to be located remotely from point of demand. All

but a fraction of the worlds electrical power has passed trough a series of transformer by

the time it reaches the consumer

Basic principles

The principles of the transformer are illustrated by consideration of a hypothetical ideal

transformer consisting of two windings of zero resistance around a core of negligible

reluctance. A voltage applied to the primary winding causes a current, which develops a

magneto motive force (MMF) in the core. The current required to create the MMF is

termed the magnetizing current; in the ideal transformer it is considered to be negligible,

although its presence is still required to drive flux around the magnetic circuit of the core.

An electromotive force (MMF) is induced across each winding, an effect known as

mutual inductance. In accordance with faradays law of induction, the EMFs are

proportional to the rate of change of flux. The primary EMF, acting as it does in

opposition to the primary voltage, is sometimes termed the back EMF. Energy losses An

ideal transformer would have no energy losses and would have no energy losses, and

would therefore be 100% efficient. Despite the transformer being amongst the most

efficient of electrical machines with ex the most efficient of electrical machines with

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experimental models using superconducting windings achieving efficiency of 99.85%,

energy is dissipated in the windings, core, and surrounding structures. Larger

transformers are generally more efficient, and those rated for electricity distribution

usually perform better than 95%. A small transformer such as plug-in power brick used

for low-power consumer electronics may be less than 85% efficient. Transformer losses

are attributable to several causes and may be differentiated between those originated in

the windings, some times termed copper loss, and those arising from the magnetic circuit,

sometimes termed iron loss. The losses vary with load current, and may furthermore be

expressed as no load or full load loss, or at an intermediate loading. Winding

resistance dominates load losses contribute to over 99% of the no-load loss can be

significant, meaning that even an idle transformer constitutes a drain on an electrical

supply, and lending impetus to development of low-loss transformers.

Losses in the transformer arise from:

Winding resistance Current flowing trough the windings causes resistive heating of

the conductors. At higher frequencies, skin effect and proximity effect create additional

winding resistance and losses.

Hysteresis lossesEach time the magnetic field is reversed, a small amount of energy is

lost due to hysteresis within the core. For a given core material, the loss is proportional to

the frequency, and is a function of the peak flux density to which it is subjected.

Eddy currentFerromagnetic materials are also good conductors, and a solid core made

from such a material also constitutes a single short-circuited turn trough out its entire

length. Eddy currents therefore circulate with in a core in a plane normal to the flux, and

are responsible for resistive heating of the core material. The eddy current loss is a

complex function of the square of supply frequency and inverse square of the material

thickness

. MagnetostrictionMagnetic flux in a ferromagnetic material, such as the core, causes

it to physically expand and contract slightly with each cycle of the magnetic field, an

effect known as magnetostriction. This produces the buzzing sound commonly associated

with transformers, and in turn causes losses due to frictional heating in susceptible cores.

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Mechanical lossesIn addition to magnetostriction, the alternating magnetic field

causes fluctuating electromagnetic field between primary and secondary windings. These

incite vibration with in near by metal work, adding to the buzzing noise, and consuming a

small amount of power.

Stray lossesLeakage inductance is by itself loss less, since energy supplied to its

magnetic fields is returned to the supply with the next half-cycle. However, any leakage

flux that intercepts nearby conductive material such as the transformers support structure

will give rise to eddy currents and be converted to heat.

Cooling system

Large power transformers may be equipped with cooling fans, oil pumps or water-cooler

heat exchangers design to remove heat. Power used to operate the cooling system istypically considered part of the losses of the transformer.

Rating of transformer

Manufactured by Bharat heavy electrical limited

No load voltage (hv) - 229 KV

No load Voltage (lv) -10.5 KV

Line current (hv) - 315.2 A

Line current (lv) - 873.2 A

Temp rise - 45 Celsius

Oil quantity -40180 lit

Weight of oil -34985 Kg

Total weight - 147725 Kg

Core & winding - 84325 Kg

Phase 3

Frequency - 50 Hz

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C&I (CONTROL AND INSTRUMENTATION)

I was assigned to do training in control and instrumentation department from

28th June 2010 to 10th July 2010.

CONTROL AND INSTRUMENTATIONThis division

basically calibrates various instruments and takes care of any faults

occur in any of the auxiliaries in the plant. It has following labs:

1. MANOMETRY LAB

2. PROTECTION AND INTERLOCK LAB

3. AUTOMATION LAB

4. WATER TREATEMENT LAB

5. FURNACE SAFETY SUPERVISORY SYSTEM(FSSS)

6. ELECTRONICS TEST LAB

This department is the brain of the plant because from the relays

to transmitters followed by the electronic computation chipsets

and recorders and lastly the controlling circuitry, all fall under

this.

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5.0 MANOMETRY LAB

5.0.1 TRANSMITTERSIt is used for pressure measurements of gases and

liquids, its working principle is that the input pressure is converted into

electrostatic capacitance and from there it is conditioned and amplified. It

gives an output of 4-20 ma DC. It can be mounted on a pipe or a wall. For

liquid or steam measurement transmitters is mounted below main process

piping and for gas measurement transmitter is placed above pipe.

5.0.2 MANOMETER Its a tube which is bent, in U shape. It is filled with a

liquid. This device corresponds to a difference in pressure across the two

limbs

5.0.3 BOURDEN PRESSURE GAUGEIts an oval section tube. Its one

end is fixed. It is provided with a pointer to indicate the pressure on a

calibrated scale. It is of 2 types: (a)Spiral type: for Low pressure

measurement. (b)Helical Type: for High pressure measurement.

5.1 PROTECTION AND INTERLOCK LAB

5.1.1 INTERLOCKING It is basically interconnecting two or more equipments so that

if one equipments fails other one can perform the tasks. This type of interdependence is

also created so that equipments connected together are started and shut down in the

specific sequence to avoid damage. For protection of equipments tripping are provided

for all the equipments. Tripping can be considered as the series of instructions connected

through OR GATE. When a fault occurs and any one of the tripping is satisfied a signal is

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sent to the relay, which trips the circuit. The main equipments of this lab are relay and

circuit breakers. Some of the instrument used for protection are: 1. RELAY It is a

protective device. It can detect wrong condition in electrical circuits by constantly

measuring the electrical quantities flowing under normal and faulty conditions. Some of

the electrical quantities are voltage, current, phase angle and velocity. 2. FUSES It is a

short piece of metal inserted in the circuit, which melts when heavy current flows through

it and thus breaks the circuit.

5.1.2 MINIATURE CIRCUIT BREAKERThey are used with combination of the

control circuits to. a) Enable the staring of plant and distributors. b) Protect the circuit in

case of a fault. In consists of current carrying contacts, one movable and other fixed.

When a fault occurs the contacts separate and are is stuck between them. There are three

types of - MANUAL TRIP - THERMAL TRIP - SHORT CIRCUIT TRIP

5.1.3 ROTECTION AND INTERLOCK SYSTEM

1. HIGH TENSION CONTROL CIRCUIT For high tension system the control system

are excited by separate D.C supply. For starting the circuit conditions should be in series

with the starting coil of the equipment to energize it. Because if even a single condition is

not true then system will not start.

2. LOW TENSION CONTROL CIRCUIT For low tension system the control circuits

are directly excited from the 0.415 KV A.C supply. The same circuit achieves both

excitation and tripping. Hence the tripping coil is provided for emergency tripping if the

interconnection fails.

5.2 AUTOMATION LAB

This lab deals in automating the existing equipment and feeding routes.Earlier, the old technology dealt with only (DAS) Data Acquisition System andcame to be known as primary systems. The modern technology or thesecondary systems are coupled with (MIS) Management Information System.But this lab universally applies the pressure measuring instruments as thecontrolling force. Another point is the universality of the supply, the laws ofelectronic state that it can be any where between 12V and 35V in the plant.All the control instruments are excited by 24V supply (4-20mA) because

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voltage can be mathematically handled with ease therefore all controlsystems use voltage system for computation. The latest technology is the useof ETHERNET for control signals.

5.3 PYROMETER LAB

(1) LIQUID IN GLASS THERMOMETER Mercury in the glass thermometerboils at 340 degree Celsius which limits the range of temperature that can bemeasured. It is L shaped thermometer which is designed to reach allinaccessible places.(2) ULTRA VIOLET CENSORThis device is used in furnace and it measuresthe intensity of ultra violet rays there and according to the wave generatedwhich directly indicates the temperature in the furnace.(3) THERMOCOUPLES This device is based on SEEBACK and PELTIER effect.It comprises of two junctions at different temperature. Then the emf isinduced in the circuit due to the flow of electrons. This is an important part inthe plant.

(4) RTD (RESISTANCE TEMPERATURE DETECTOR) It performs thefunction of thermocouple basically but the difference is of a resistance. In thisdue to the change in the resistance the temperature difference is measured.In this lab, also the measuring devices can be calibrated in the oil bath or justboiling water (for low range devices) and in small furnace (for high rangedevices).

5.4 FURNACE SAFETY AND SUPERVISORYSYSTEM LAB

This lab has the responsibility of starting fire in the furnace to enable theburning of coal. For first stage coal burners are in the front and rear of thefurnace and for the second and third stage corner firing is employed. Unburntcoal is removed using forced draft or induced draft fan. The temperatureinside the boiler is 1100 degree Celsius and its height is 18 to 40 m. For firingthe furnace a 10 KV spark plug is operated for ten seconds over a spray ofdiesel fuel and pre-heater air along each of the feeder-mills. The furnace hassix feeder mills each separated by warm air pipes fed from forced draft fans.In first stage indirect firing is employed that is feeder mills are not feddirectly from coal but are fed from three feeders but are fed from pulverizedcoalbunkers. The furnace can operate on the minimum feed from threefeeders but under not circumstances should any one be left out underoperation, to prevent creation of pressure different with in the furnace, whichthreatens to blast it.

5.5 ELECTRONICS LAB

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This lab undertakes the calibration and testing of various cards. It housesvarious types of analytical instruments like oscilloscopes, integrated circuits,cards auto analyzers etc. Various processes undertaken in this lab are: 1.

Transmitter converts mV to mA. 2. Auto analyzer purifies the sample before itis sent to electrodes. It extracts the magnetic portion.

5.6 ANNUNCIATIN CARDS

They are used to keep any parameter like temperature etc. within limits. Itgets a signal if parameter goes beyond limit. It has a switching transistorconnected to relay that helps in alerting the UCB.

Measuring Instrumentsments

In any process the philosophy of instrumentation should provide acomprehensive intelligence feed back on the important parameters viz.

Temperature, Pressure, Level and Flow. This Chapter Seeks to provide a basicunderstanding of the prevalent instruments used for measuring the aboveparameters.

Temperature Measurement

The most important parameter in thermal power plant is temperature and itsmeasurement plays a vital role in safe operation of the plant. Rise oftemperature in a substance is due to the resultant increase in molecularactivity of the substance on application of heat; which increases the internalenergy of the material. Therefore there exists some property of thesubstance, which changes with its energy content. The change may beobserved with substance itself or in a subsidiary system in thermodynamicequilibrium, which is called testing body and the system itself is called thehot body.

Expansion Thermometer

Solid Rod Thermometers a temperature sensing - Controlling device may bedesigned incorporating in its construction the principle that some metalsexpand more than others for the same temperature range. Such a device isthe thermostat used with water heaters .

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The mercury will occupy a greater fraction of the volume of the containerthan it will at a low temperature. Under normal atmospheric conditionsmercury normally boils at a temperature of (347C). To

kanika nn12 ntpc

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