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PROJECT REPORT ( N.T.P.C. BADARPUR, NEWDELHI )

INDUSTRIAL TRAINING REPORT

(SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIRMENT OFTHE COURSE OF B.TECH.)

UNDERTAKEN AT

N.T.P.C. BADARPUR, NEW DELHI FROM: 18th JUNE to 11thAugust, 2007

SUBMITTED TO: SUBMITTED BY:Mrs. RACHNA SINGH Ashutosh KumarN.T.P.C. Badarpur B.Tech 3rd YearElectrical EngineeringJSS ACADEMY OF TECHNICAL EDUCATION (NOIDA)TABLE OF CONTENT

Certificate Acknowledgement

Training at BTPS

1. Introduction NTPC Badarpur Thermal Power Station2. Operation3. Control & Instrumentation Manometry Lab Protection and interlock Lab Automation Lab

Water Treatment Plant Furnace Safeguard Supervisory System Electronic Test Lab

4. Electrical Maintenance Division-I HT/LT Switch Gear HT/LT Motors, Turbine & Boilers Side


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CHP/NCHP

5. Electrical Maintenance Division-II Generator Transformer & Switchyard

Protection Lighting EP CERTIFICATE

This is to certify that------------------------- student of BatchElectrical & Electronics Branch IIIrd Year; Sky line Institute ofEngineering & Technology Noida has successfully completedhis industrial training at Badarpur Thermal power station New

Delhi for eight week from 18th June to 11th august 2007He has completed the whole training as perthe training report submitted by him.

Training InchargeBTPS/NTPCNEW DELHI

Acknowledgement


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With profound respect and gratitude, I take the opportunity toconvey my thanks to complete the training here.

I do extend my heartfelt thanks to Mrs. Rachna Singh for

providing me this opportunity to be a part of this esteemedorganization.

I am extremely grateful to all the technical staff of BTPS/NTPCfor their co-operation and guidance that helped me a lot duringthe course oftraining . I have learnt a lot working under themand I will always be indebted of them for this value addition inme.

I would also like to thank the training in charge of Skyline

Institute of Engineering & Technology Gr. Noida and all thefaculty member of Electrical & Electronics department for theireffort of constant co-operation. Which have been significantfactor in the accomplishment of my industrial training .

Training at BTPS

I was appointed to do eight-weektraining at this esteemedorganization from 18th June to 11th august 2007. In theseeight weeks I was assigned to visit various division of the plantwhich were

1. Operation2. Control and instrumentation (C&I)3. Electrical maintenance division I (EMD-I)4. Electrical maintenance division II (EMD-II)

This eight-weektraining was a very educational adventure forme. It was really amazing to see the plant by your self and


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learn how electricity, which is one of our daily requirements oflife, is produced.

This report has been made by self-experience at BTPS. Thematerial in this report has been gathered from my textbooks,

senior student report , and trainer manual providedby training department. The specification & principles are atlearned by me from the employee of each division of BTPS.


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ABOUT NTPC

NTPC Limited is the largest thermal power generating companyof India. A public sector company, it was incorporated in theyear 1975 to accelerate power development in the country as awholly owned company of the Government of India. At present,Government of India holds 89.5% of the total equity shares ofthe company and FIIs, Domestic Banks, Public and others holdthe balance 10.5%. With in a span of 31 years, NTPC has

emerged as a truly national power company, with powergenerating facilities in all the major regions of the country.

POWER GENERATION IN INDIA

NTPCs core business is engineering, construction andoperation of power generating plants. It also providesconsultancy in the area of power plant constructions andpower generation to companies in India and abroad. As on datethe installed capacity of NTPC is 27,904 MW through its 15 coalbased (22,895 MW), 7 gas based (3,955 MW) and 4 Joint


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Venture Projects (1,054 MW). NTPC acquired 50% equity of theSAIL Power Supply Corporation Ltd. (SPSCL). This JV Companyoperates 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

venture company between NTPC, GAIL, Indian FinancialInstitutions and Maharashtra SEB Co Ltd.NTPC has set new benchmarks for the power industry both inthe area of power plant construction and operations. Itsproviding power at the cheapest average tariff in the country..NTPC is committed to the environment, generating power atminimal environmental cost and preserving the ecology in thevicinity of the plants. NTPC has undertaken massive aforestation in the vicinity of its plants. Plantations haveincreased forest area and reduced barren land. The massive a

forestation by NTPC in and around its Ramagundam Powerstation (2600 MW) have contributed reducing the temperaturein the areas by about 3c. NTPC has also taken proactive stepsfor ash utilization. In 1991, it set up Ash Utilization DivisionA "Centre for Power Efficiency and EnvironmentProtection (CENPEEP)" has been established in NTPC with theassistance of United States Agency for InternationalDevelopment. (USAID). Cenpeep is efficiency oriented, eco-friendly and eco-nurturing initiative - a symbol of NTPC'sconcern towards environmental protection and continued

commitment to sustainable power development in India.As a responsible corporate citizen, NTPC is making constantefforts to improve the socio-economic status of the peopleaffected by its projects. Through its Rehabilitation andResettlement programmes, the company endeavors to improvethe overall socio economic status Project Affected Persons.NTPC was among the first Public Sector Enterprises to enterinto a Memorandum of Understanding (MOU) with theGovernment in 1987-88. NTPC has been placed under the'Excellent category' (the best category) every year since the

MOU system became operative.

Harmony between man and environment is the essence ofhealthy life and growth. Therefore, maintenance of ecological
http://www.ntpc.co.in/operations/operations.shtmlhttp://www.ntpc.co.in/operations/operations.shtmlhttp://www.ntpc.co.in/infocus/environment.shtmlhttp://www.ntpc.co.in/infocus/environment.shtmlhttp://www.ntpc.co.in/infocus/ashutilisation.shtmlhttp://www.ntpc.co.in/infocus/ashutilisation.shtmlhttp://www.ntpc.co.in/otherlinks/cenpeep.shtmlhttp://www.ntpc.co.in/otherlinks/cenpeep.shtmlhttp://www.ntpc.co.in/infocus/socialcomm.shtmlhttp://www.ntpc.co.in/infocus/socialcomm.shtmlhttp://www.ntpc.co.in/infocus/socialcomm.shtmlhttp://www.ntpc.co.in/operations/operations.shtmlhttp://www.ntpc.co.in/infocus/environment.shtmlhttp://www.ntpc.co.in/infocus/ashutilisation.shtmlhttp://www.ntpc.co.in/otherlinks/cenpeep.shtmlhttp://www.ntpc.co.in/infocus/socialcomm.shtmlhttp://www.ntpc.co.in/infocus/socialcomm.shtml


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balance and a pristine environment has been of utmostimportance to NTPC. It has been taking various measuresdiscussed below for mitigation of environment pollution due topower generation.

Environment Policy & Environment Management SystemDriven 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 plantsand preserving the natural ecology.

National Environment Policy:At the national level, the Ministry of Environment and Forests

had prepared a draft Environment Policy (NEP) and theMinistry of Power along with NTPC actively participated in thedeliberations of the draft NEP. The NEP 2006 has since beenapproved by the Union Cabinet in May 2006.NTPC Environment Policy:As early as in November 1995, NTPC brought out acomprehensive document entitled "NTPC Environment Policyand Environment Management System". Amongst the guidingprinciples adopted in the document are company's proactiveapproach to environment, optimum utilization of equipment,

adoption of latest technologies and continual environmentimprovement. The policy also envisages efficient utilization ofresources, thereby minimizing waste, maximizing ashutilization and providing green belt all around the plant formaintaining ecological balance.Environment Management, Occupational Health and SafetySystems:NTPC has actively gone for adoption of best internationalpractices on environment, occupational health and safetyareas. The organization has pursued the Environmental

Management System (EMS) ISO 14001 and the OccupationalHealth and Safety Assessment System OHSAS 18001 at itsdifferent establishments. As a result of pursuing thesepractices, all NTPC power stations have been certified for ISO14001 & OHSAS 18001 by reputed national and internationalCertifying Agencies.Pollution Control systems:


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While deciding the appropriate technology for its projects,NTPC integrates many environmental provisions into the plantdesign. In order to ensure that NTPC comply with all thestipulated environment norms, various state-of-the-artpollution control systems / devices as discussed below have

been installed to control air and water pollution.

Electrostatic Precipitators:The ash left behind after combustion of coal is arrested in highefficiency Electrostatic Precipitators (ESPs) and particulateemission is controlled well within the stipulated norms. Theash collected in the ESPs is disposed to Ash Ponds in slurryform.

Flue Gas Stacks:Tall Flue Gas Stacks have been provided for wide dispersion ofthe gaseous emissions (SOX, NOX etc) into the atmosphere.Low-NOXBurners:In gas based NTPC power stations, NOx emissions arecontrolled by provision of Low-NOx Burners (dry or wet type)and in coal fired stations, by adopting best combustionpractices.Neutralisation Pits:Neutralisation pits have been provided in the Water Treatment

Plant (WTP) for pH correction of the effluents before dischargeinto Effluent Treatment Plant (ETP) for further treatment anduse.

Coal Settling Pits / Oil Settling Pits:In these Pits, coal dust and oil are removed from the effluentsemanating from the Coal Handling Plant (CHP), coal yard andFuel Oil Handling 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 tocontain and extract the fugitive dust released in the CoalHandling Plant (CHP).Cooling Towers:Cooling Towers have been provided for cooling the hotCondenser cooling water in closed cycle Condenser CoolingWater (CCW) Systems. This helps in reduction in thermal


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pollution and conservation of fresh water.Ash Dykes & Ash Disposal systems:Ash ponds have been provided at all coal based stationsexcept Dadri where Dry Ash Disposal System has beenprovided. Ash Ponds have been divided into lagoons and

provided with garlanding arrangements for change over of theash slurry feed points for even filling of the pond and foreffective settlement of the ash particles.Ash in slurry form is discharged into the lagoons where ashparticles get settled from the slurry and clear effluent water isdischarged from the ash pond. The discharged effluentsconform to standards specified by CPCB and the same isregularly monitored.At its Dadri Power Station, NTPC has set up a unique systemfor dry ash collection and disposal facility with Ash Mound

formation. This has been envisaged for the first time in Asiawhich has resulted in progressive development of green beltbesides far less requirement of land and less waterrequirement as compared to 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 theAWRS, the effluent from ash pond is circulated back to thestation for further ash sluicing to the ash pond. This helps insavings of fresh water requirements for transportation of ash

from the plant.The ash water recycling system has already been installed andis in operation at Ramagundam, Simhadri, Rihand, TalcherKaniha, Talcher Thermal, Kahalgaon, Korba and Vindhyachal.The scheme has helped stations to save huge quantity of freshwater required as make-up water for disposal of ash.Dry Ash Extraction System (DAES):Dry ash has much higher utilization potential in ash-basedproducts (such as bricks, aerated autoclaved concrete blocks,concrete, Portland pozzolana cement, etc.). DAES has been

installed at Unchahar, Dadri, Simhadri, Ramagundam,Singrauli, Kahalgaon, Farakka, Talcher Thermal, Korba,Vindhyachal, Talcher Kaniha and BTPS.

Liquid Waste Treatment Plants & Management System:The objective of industrial liquid effluent treatment plant (ETP)is to discharge lesser and cleaner effluent from the power


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plants to meet environmental regulations. After primarytreatment at the source of their generation, the effluents aresent to the ETP for further treatment. The composite liquideffluent treatment plant has been designed to treat all liquideffluents which originate within the power station 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 ofvarious effluents and their appropriate treatment centrally andre-circulation of the treated effluent for various plant uses.NTPC has implemented such systems in a number of its powerstations such as Ramagundam, Simhadri, Kayamkulam,Singrauli, Rihand, Vindhyachal, Korba, Jhanor Gandhar,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 facilitieshave been provided at all NTPC stations to take care ofSewage Effluent from Plant and township areas. In a number ofNTPC projects modern type STPs with Clarifloculators,Mechanical Agitators, sludge drying beds, Gas CollectionChambers etc have been provided to improve the effluentquality. The effluent quality is monitored regularly and treated

effluent conforming to the prescribed limit is discharged fromthe station. At several stations, treated effluents of STPs arebeing used for horticulture purpose.

Environmental Institutional Set-up:Realizing the importance of protection of the environment withspeedy development of the power sector, the company hasconstituted different groups at project, regional and CorporateCentre level to carry out specific environment relatedfunctions. The Environment Management Group, Ash

Utilisation Group and Centre for Power Efficiency &Environment Protection (CENPEEP) function from theCorporate Centre and initiate measures to mitigate the impactof power project implementation on the environment andpreserve ecology in the vicinity of the projects. EnvironmentManagement and Ash Utilisation Groups established at eachstation, look after various environmental issues of the


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individual station.Environment Reviews:To maintain constant vigil on environmental compliance,Environmental Reviews are carried out at all operating stationsand remedial measures have been taken wherever necessary.

As a feedback and follow-up of these Environmental Reviews, anumber of retrofit and up-gradation measures have beenundertaken at different stations.Such periodic Environmental Reviews and extensivemonitoring of the facilities carried out at all stations havehelped in compliance with the environmental norms and timelyrenewal of the Air and Water Consents.

Up gradation & retrofitting of Pollution Control Systems:Waste Management

Various types of wastes such as Municipal or domestic wastes,hazardous wastes, Bio-Medical wastes get generated in powerplant areas, plant hospital and the townships of projects. Thewastes generated are a number of solid and hazardous wasteslike used oils & waste oils, grease, lead acid batteries, otherlead bearing wastes (such as garkets etc.), oil & clarifiersludge, used resin, used photo-chemicals, asbestos packing, e-waste, metal scrap, C&I wastes, electricial scrap, emptycylinders (refillable), paper, rubber products, canteen (bio-degradable) wastes, buidling material wastes, silica gel, glass

wool, fused lamps & tubes, fire resistant fluids etc. Thesewastes fall either under hazardous wastes category or non-hazardous wastes category as per classification given inGovernment of Indias notification on Hazardous Wastes(Management and Handling) Rules 1989 (as amended on06.01.2000 & 20.05.2003). Handling and management of thesewastes in NTPC stations have been discussed below.

Advanced / Eco-friendly TechnologiesNTPC has gained expertise in operation and management of

200 MW and 500 MW Units installed at different Stations allover the country and is looking ahead for higher capacity Unitsizes with super critical steam parameters for higherefficiencies and for associated environmental gains. At Sipat,higher capacity Units of size of 660 MW and advanced SteamGenerators employing super critical steam parameters havealready been implemented as a green field project.


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Higher efficiency Combined Cycle Gas Power Plants are alreadyunder operation at all gas-based power projects in NTPC.Advanced clean coal technologies such as IntegratedGasification Combined Cycle (IGCC) have higher efficiencies ofthe order of 45% as compared to about 38% for conventional

plants. NTPC has initiated a techno-economic study underUSDOE / USAID for setting up a commercial scaledemonstration power plant by using IGCC technology. Theseplants can use low-grade coals and have higher efficiency ascompared to conventional plants.With the massive expansion of power generation, there is alsogrowing awareness among all concerned to keep the pollutionunder control and preserve the health and quality of thenatural environment in the vicinity of the power stations. NTPCis committed to provide affordable and sustainable power in

increasingly larger quantity. NTPC is conscious of its role in thenational endeavour of mitigating energy poverty, heraldingeconomic prosperity and thereby contributing towards Indiasemergence as a major global economy.Lay out of Employees

Overall Power Generation


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The table below shows the detailed operational performance ofcoal based stations over the years.

The energy conservation parameters like specific oilconsumption and auxiliary power consumption have alsoshown considerable improvement over the years.

ABOUT BADARPUR THERMAL POWER STATION

Unit 1997-98 2006-07 % of increaseInstalled Capacity MW 16,847 26,350 56.40Generation MUs 97,609 1,88,674 93.29No. of employees No. 23,585 24,375 3.34Generation/employee MUs 4.14 7.74 86.95

OPERATIONAL PERFORMANCE OF COAL BASED NTPC STATIONSUnit 97-98 98-99 99-00 00-01 01-02 02-03 03-04 04-05 05-06 06-07

Generation BU 106.2 109.5 118.7 130.1 133.2 140.86 149.16 159.11 170.88 188.67PLF % 75.20 76.60 80.39 81.8 81.1 83.6 84.4 87.51 87.54 89.43AvailabilityFactor

% 85.03 89.36 90.06 88.54 81.8 88.7 88.8 91.20 89.91 90.09


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I was assigned to do training in operation division from 18th

June 2007 to 23rd June 2007

ELECTRICITY FROM COAL

Coal from the coal wagons is unloaded with the help of wagontipplers in the C.H.P. this coal is taken to the raw coal bunkerswith the help of conveyor belts. Coal is then transported tobowl mills by coal feeders where it is pulverized and ground inthe powered form.

This crushed coal is taken away to the furnace through coalpipes with the help of hot and cold mixture P.A fan. This fantakes atmospheric air, a part of which is sent to pre heaterswhile a part goes to the mill for temperature control.Atmospheric air from F.D fan in the air heaters and sent to thefurnace as combustion air.

Water from boiler feed pump passes through economizer andreaches the boiler drum . Water from the drum passes throughthe down comers and goes to the bottom ring header. Water

from the bottom ring header is divided to all the four sides ofthe furnace. Due to heat density difference the water rises upin the water wall tubes. This steam and water mixture is againtaken to the boiler drum where the steam is sent to superheaters for super heating. The super heaters are located insidethe furnace and the steam is super heated (540 degreeCelsius) and finally it goes to the turbine.

Fuel gases from the furnace are extracted from the induceddraft fan, which maintains balance draft in the furnace with

F.D fan. These fuel gases heat energy to the various superheaters and finally through air pre heaters and goes toelectrostatic precipitators where the ash particles areextracted. This ash is mixed with the water to from slurry ispumped to ash period.

The steam from boiler is conveyed to turbine through the


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steam pipes and through stop valve and control valve thatautomatically regulate the supply of steam to the turbine. Stopvalves and controls valves are located in steam chest andgovernor driven from main turbine shaft operates the controlvalves the amount used.

Steam from controlled valves enter high pressure cylinder ofturbines, where it passes through the ring of blades fixed tothe cylinder wall. These act as nozzles and direct the steaminto a second ring of moving blades mounted on the discsecured in the turbine shaft. The second ring turns the shaft asa result of force of steam. The stationary and moving bladestogether.

MAIN GENERATOR

Maximum continuous KVA rating 24700KVAMaximum continuous KW 210000KWRated terminal voltage 15750VRated Stator current 9050 ARated Power Factor 0.85 lagExcitation current at MCR Condition 2600 ASlip-ring Voltage at MCR Condition 310 VRated Speed 3000 rpmRated Frequency 50 Hz

Short circuit ratio 0.49Efficiency at MCR Condition 98.4%Direction of rotation viewed Anti ClockwisePhase Connection Double StarNumber of terminals brought out 9( 6 neutral and 3 phase)


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MAIN TURBINE DATA

Rated output of Turbine 210 MWRated speed of turbine 3000 rpmRated pressure of steam before emergency 130 kg/cm^2Stop valve rated live steam temperature 535 degree CelsiusRated steam temperature after reheat at inlet to receptorvalve

535 degree Celsius

Steam flow at valve wide open condition 670 tons/hourRated quantity of circulating water through condenser 27000 cm/hour1. For cooling water temperature (degree Celsius) 24,27,30,331.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 68,645,652,6623.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 asubsystem required to produce electricity by using a steamgenerating boiler fired with fossil fuels or befouls to drive anelectrical generator. Some prefer to use the term ENERGY

CENTER because such facilities convert forms of energy, likenuclear energy, gravitational potential energy or heat energy(derived from the combustion of fuel) into electrical energy.However, POWER PLANT is the most common term in theunited state; While POWER STATION prevails in manyCommonwealth countries and especially in the UnitedKingdom.Such power stations are most usually constructed on a verylarge scale and designed for continuous operation.Typical diagram of a coal fired thermal power station

1. Cooling water pump2. Three-phase transmission line3. Step up transformer4. Electrical Generator5. Low pressure steam6. Boiler feed water pump7. Surface condenser


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8. Intermediate pressure steam turbine9. Steam control valve10. High pressure steam turbine11. Deaerator Feed water heater12. Coal conveyor

13. Coal hopper14. Coal pulverizer15. boiler steam drum16. Bottom ash hoper17. Super heater18. Forced draught(draft) fan19. Reheater20. Combustion air intake21. Economizer22. Air preheater

23. Precipitator24. Induced draught(draft) fan25. Fuel gas stack

The description of some of the components written above isdescribed as follows:

1. Cooling towers

Cooling Towers are evaporative coolers used for cooling water

or other working medium to near the ambivalent web-bulb airtemperature. Cooling tower use evaporation of water to rejectheat from processes such as cooling the circulating water usedin oil refineries, Chemical plants, power plants and buildingcooling, for example. The tower vary in size from small roof-top units to very large hyperboloid structures that can be up to200 meters tall and 100 meters in diameter, or rectangularstructure that can be over 40 meters tall and 80 meters long.Smaller towers are normally factory built, while larger ones areconstructed on site.

The primary use of large , industrial cooling tower system is toremove the heat absorbed in the circulating cooling watersystems used in power plants , petroleum refineries,petrochemical and chemical plants, natural gas processingplants and other industrial facilities . The absorbed heat isrejected to the atmosphere by the evaporation of some of thecooling water in mechanical forced-draft or induced draft


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towers or in natural draft hyperbolic shaped cooling towers asseen 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 mainlyused to power motors and many other devices. A Three phasesystem uses less conductor material to transmit electric powerthan equivalent single phase, two phase, or direct currentsystem at the same voltage. In a three phase system, threecircuits reach their instantaneous peak values at differenttimes. Taking one conductor as the reference, the other twocurrent are delayed in time by one-third and two-third of onecycle of the electrical current. This delay between phaseshas the effect of giving constant power transfer over each

cycle of the current and also makes it possible to produce arotating magnetic field in an electric motor.At the power station, an electric generator convertsmechanical power into a set of electric currents, one from eachelectromagnetic coil or winding of the generator. The currentare sinusoidal functions of time, all at the same frequency butoffset in time to give different phases. In a three phase systemthe phases are spaced equally, giving a phase separation ofone-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 moresuitable for transmission.After numerous further conversions in the transmission anddistribution network the power is finally transformed to thestandard mains voltage (i.e. the household voltage).The power may already have been split into single phase atthis point or it may still be three phase. Where the step-downis 3 phase, the output of this transformer is usually starconnected with the standard mains voltage being the phase-neutral voltage. Another system commonly seen in North

America is to have a delta connected secondary with a centertap on one of the windings supplying the ground and neutral.This allows for 240 V three phase as well as three differentsingle phase voltages( 120 V between two of the phases andneutral , 208 V between the third phase ( known as a wild leg)and neutral and 240 V between any two phase) to be availablefrom the same supply.


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3.Electrical generator

An Electrical generator is a device that converts kinetic energyto electrical energy, generally using electromagneticinduction. The task of converting the electrical energy into

mechanical energy is accomplished by using a motor. Thesource of mechanical energy may be a reciprocating or turbinesteam engine, , water falling through the turbine are made in avariety of sizes ranging from small 1 hp (0.75 kW) units (rare)used as mechanical drives for pumps, compressors and othershaft driven equipment , to 2,000,000 hp(1,500,000 kW)turbines used to generate electricity. There are severalclassifications for modern steam turbines.Steam turbines are used in all of our major coal fired powerstations to drive the generators or alternators, which produce

electricity. The turbines themselves are driven by steamgenerated in Boilers or steam generators as they aresometimes called.Electrical power station use large stem turbines drivingelectric generators to produce most (about 86%) of the worldselectricity. These centralized stations are of two types: fossilfuel power plants and nuclear power plants. The turbines usedfor electric power generation are most often directly coupledto 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 50Hz systems, and 3600 r/min for 60 Hz systems. Most largenuclear sets rotate at half those speeds, and have a 4-polegenerator rather than the more common 2-pole one.

Energy in the steam after it leaves the boiler is converted intorotational energy as it passes through the turbine. The turbinenormally consists of several stage with each stages consistingof a stationary blade (or nozzle) and a rotating blade.Stationary blades convert the potential energy of the steam

into kinetic energy into forces, caused by pressure drop, whichresults in the rotation of the turbine shaft. The turbine shaft isconnected to a generator, which produces the electricalenergy.

4.Boiler feed water pumpA Boiler feed water pump is a specific type of pump used to


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pump water into a steam boiler. The water may be freshlysupplied or retuning condensation of the steam produced bythe boiler. These pumps are normally high pressure units thatuse suction from a condensate return system and can be of thecentrifugal pump type or positive displacement type.

Construction and operationFeed water pumps range in size up to many horsepower andthe electric motor is usually separated from the pump body bysome form of mechanical coupling. Large industrial condensatepumps may also serve as the feed water pump. In either case,to force the water into the boiler; the pump must generatesufficient pressure to overcome the steam pressure developedby the boiler. This is usually accomplished through the use of acentrifugal pump.

Feed water pumps usually run intermittently and arecontrolled by a float switch or other similar level-sensingdevice energizing the pump when it detects a lowered liquidlevel in the boiler is substantially increased. Some pumpscontain a two-stage switch. As liquid lowers to the triggerpoint of the first stage, the pump is activated. I f the liquidcontinues to drop (perhaps because the pump has failed, itssupply has been cut off or exhausted, or its discharge isblocked); the second stage will be triggered. This stage mayswitch off the boiler equipment (preventing the boiler from

running dry and overheating), trigger an alarm, or both.5. Steam-powered pumpsSteam locomotives and the steam engines used on ships andstationary applications such as power plants also required feedwater pumps. In this situation, though, the pump was oftenpowered using a small steam engine that ran using the steamproduced by the boiler. A means had to be provided, of course,to put the initial charge of water into the boiler(before steampower was available to operate the steam-powered feed waterpump).the pump was often a positive displacement pump that

had steam valves and cylinders at one end and feed watercylinders 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 obtainmaximum efficiency and also to convert the turbine exhauststeam into pure water so that it may be reused in the steam


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generator or boiler as boiler feed water. By condensing theexhaust steam of a turbine at a pressure below atmosphericpressure, the steam pressure drop between the inlet andexhaust of the turbine is increased, which increases theamount heat available for conversion to mechanical power.

Most of the heat liberated due to condensation of the exhauststeam is carried away by the cooling medium (water or air)used by the surface condenser.

6. Control valvesControl valves are valves used within industrial plants andelsewhere to control operating conditions such astemperature,pressure,flow,and liquid Level by fully partiallyopening or closing in response to signals received from

controllers that compares a set point to a process variablewhose value is provided by sensors that monitor changes insuch conditions. The opening or closing of control valves isdone by means of electrical, hydraulic or pneumatic systems

7. Deaerator

A Dearator is a device for air removal and used to removedissolved gases (an alternate would be the use of watertreatment chemicals) from boiler feed water to make it non-

corrosive. A dearator typically includes a vertical domeddeaeration section as the deaeration boiler feed water tank. ASteam generating boiler requires that the circulating steam,condensate, and feed water should be devoid of dissolvedgases, particularly corrosive ones and dissolved or suspendedsolids. The gases will give rise to corrosion of the metal. Thesolids will deposit on the heating surfaces giving rise tolocalized heating and tube ruptures due to overheating. Undersome conditions it may give to stress corrosion cracking.Deaerator level and pressure must be controlled by adjusting

control valves- the level by regulating condensate flow and thepressure by regulating steam flow. If operated properly, mostdeaerator vendors will guarantee that oxygen in the deaeratedwater will not exceed 7 ppb by weight (0.005 cm3/L)

8. Feed water heater


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A Feed water heater is a power plant component used to pre-heat water delivered to a steam generating boiler. Preheatingthe feed water reduces the irreversible involved in steamgeneration and therefore improves the thermodynamicefficiency of the system.[4] This reduces plant operating costs

and also helps to avoid thermal shock to the boiler metal whenthe feed water is introduces back into the steam cycle.In a steam power (usually modeled as a modified Rankingcycle), feed water heaters allow the feed water to be broughtup to the saturation temperature very gradually. Thisminimizes the inevitable irreversibilitys associated with heattransfer to the working fluid (water). A belt conveyor consistsof two pulleys, with a continuous loop of material- theconveyor Belt that rotates about them. The pulleys arepowered, moving the belt and the material on the belt forward.

Conveyor belts are extensively used to transport industrial andagricultural material, such as grain, coal, ores etc.

9. Pulverizer

A pulverizer is a device for grinding coal for combustion in afurnace in a fossil fuel power plant.

10. Boiler Steam Drum

Steam Drums are a regular feature of water tube boilers. It isreservoir of water/steam at the top end of the water tubes inthe water-tube boiler. They store the steam generated in thewater tubes and act as a phase separator for the steam/watermixture. The difference in densities between hot and coldwater helps in the accumulation of the hotter-water/andsaturated 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 separatedsteam is drawn out from the top section of the drum.Saturated steam is drawn off the top of the drum. The steamwill re-enter the furnace in through a super heater, while thesaturated water at the bottom of steam drum flows down tothe mud-drum /feed water drum by down comer tubesaccessories include a safety valve, water level indicator and


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fuse plug. A steam drum is used in the company of a mud-drum/feed water drum which is located at a lower level. Sothat it acts as a sump for the sludge or sediments which have atendency to the bottom.

11. Super Heater

A Super heater is a device in a steam engine that heats thesteam generated by the boiler again increasing its thermalenergy and decreasing the likelihood that it will condenseinside the engine. Super heaters increase the efficiency of thesteam engine, and were widely adopted. Steam which hasbeen superheated is logically known as superheatedsteam; non-superheated steam is called saturated steam orwet steam; Super heaters were applied to steam locomotives

in quantity from the early 20th century, to most steamvehicles, and so stationary steam engines including powerstations.

12. EconomizersEconomizer, or in the UK economizer, are mechanical devicesintended to reduce energy consumption, or to perform anotheruseful function like preheating a fluid. The term economizer isused for other purposes as well. Boiler, power plant, andheating, ventilating and air conditioning. In boilers,

economizer are heat exchange devices that heat fluids ,usually water, up to but not normally beyond the boiling pointof the fluid. Economizers are so named because they can makeuse of the enthalpy and improving the boilers efficiency. Theyare a device fitted to a boiler which saves energy by using theexhaust gases from the boiler to preheat the cold water usedthe fill it (the feed water). Modern day boilers, such as those incold fired power stations, are still fitted with economizer whichis decedents of Greens original design. In this context theyare turbines before it is pumped to the boilers. A common

application of economizer is steam power plants is to capturethe waste hit from boiler stack gases (flue gas) and transferthus it to the boiler feed water thus lowering the neededenergy input , in turn reducing the firing rates to accomplishthe rated boiler output . Economizer lower stack temperatureswhich may cause condensation of acidic combustion gases andserious equipment corrosion damage if care is not taken in


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their design and material selection.

13. Air Preheater

Air preheater is a general term to describe any device

designed to heat air before another process (for example,combustion in a boiler). The purpose of the air preheater is torecover the heat from the boiler flue gas which increases thethermal efficiency of the boiler by reducing the useful heat lostin the fuel gas. As a consequence, the flue gases are also sentto the flue gas stack (or chimney) at a lower temperatureallowing simplified design of the ducting and the flue gasstack. It also allows control over the temperature of gasesleaving the stack.

14. Precipitator

An Electrostatic precipitator (ESP) or electrostatic air cleaneris a particulate device that removes particles from a flowinggas (such As air) using the force of an induced electrostaticcharge. Electrostatic precipitators are highly efficient filtrationdevices, and can easily remove fine particulate matter such asdust and smoke from the air steam.ESPs continue to be excellent devices for control of manyindustrial particulate emissions, including smoke from

electricity-generating utilities (coal and oil fired), salt cakecollection from black liquor boilers in pump mills, and catalystcollection from fluidized bed catalytic crackers from severalhundred thousand ACFM in the largest coal-fired boilerapplication.

The original parallel plate-Weighted wire design (describedabove) has evolved as more efficient ( and robust) dischargeelectrode designs were developed, today focusing on rigiddischarge electrodes to which many sharpened spikes are

attached , maximizing corona production. Transformer rectifier systems apply voltages of 50-100 Kilovolts atrelatively high current densities. Modern controls minimizesparking and prevent arcing, avoiding damage to thecomponents. Automatic rapping systems and hopperevacuation systems remove the collected particulate matterwhile on line allowing ESPs to stay in operation for years at a


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time.

15. Fuel gas stack

A Fuel gas stack is a type of chimney, a vertical pipe, channel

or similar structure through which combustion product gasescalled fuel gases are exhausted to the outside air. Fuel gasesare produced when coal, oil, natural gas, wood or any otherlarge combustion device. Fuel gas is usually composed ofcarbon dioxide (CO2) and water vapor as well as nitrogen andexcess oxygen remaining from the intake combustion air. Italso contains a small percentage of pollutants such asparticulates matter, carbon mono oxide, nitrogen oxides andsulfur oxides. The flue gas stacks are often quite tall, up to400 meters (1300 feet) or more, so as to disperse the exhaust

pollutants over a greater aria and thereby reduce theconcentration of the pollutants to the levels required bygovernmental environmental policies and regulations.When the fuel gases exhausted from stoves, ovens, fireplacesor other small sources within residential abodes, restaurants ,hotels or other stacks are referred to as chimneys.


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C&I

(CONTROL AND INSTRUMENTATION)

I was assigned to do training in control and instrumentationfrom 25th June 2007 to 14th July 2007

CONTROL AND INSTRUMENTATION

This 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 LAB2. PROTECTION AND INTERLOCK LAB3. AUTOMATION LAB4. WATER TREATEMENT LAB5. FURNACE SAFETY SUPERVISORY SYSTEM(FSSS)6. ELECTRONICS TEST LAB

This department is the brain of the plant because from therelays to transmitters followed by the electronic computationchipsets and recorders and lastly the controlling circuitry, allfall under this.

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 intoelectrostatic capacitance and from there it is conditioned andamplified. It gives an output of 4-20 ma DC. It can be mountedon a pipe or a wall. For liquid or steam measurementtransmitters is mounted below main process piping and for gasmeasurement transmitter is placed above pipe.


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5.0.2 MANOMETERIts a tube which is bent, in U shape. It is filled with a liquid.This device corresponds to a difference in pressure across thetwo limbs.

5.0.3 BOURDEN PRESSURE GAUGEIts an oval section tube. Its one end is fixed. It is providedwith a pointer to indicate the pressure on a calibrated scale. Itis of 2 types:

(a) Spiral type: for Low pressure measurement.(b) Helical Type: for High pressure measurement.

5.1 PROTECTION AND INTERLOCK LAB5.1.1 INTERLOCKINGIt is basically interconnecting two or more equipments so thatif one equipments fails other one can perform the tasks. Thistype of interdependence is also created so that equipmentsconnected together are started and shut down in the specificsequence to avoid damage.

For protection of equipments tripping are provided for all theequipments. Tripping can be considered as the series ofinstructions connected through OR GATE. When a fault occursand any one of the tripping is satisfied a signal is sent to therelay, which trips the circuit. The main equipments of this labare relay and circuit breakers. Some of the instrument uses forprotection are:1. RELAY

It is a protective device. It can detect wrong condition in

electrical circuits by constantly measuring the electricalquantities flowing under normal and faulty conditions. Some ofthe electrical quantities are voltage, current, phase angle andvelocity.2. FUSES

It is a short piece of metal inserted in the circuit, which melts


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when heavy current flows through it and thus breaks thecircuit. Usually silver is used as a fuse material because:a) The coefficient of expansion of silver is very small. As aresult no critical fatigue occurs and thus the continuous fullcapacity normal current ratings are assured for the long time.

b) The conductivity of the silver is unimpaired by the surges ofthe current that produces temperatures just near the meltingpoint.c) Silver fusible elements can be raised from normal operatingtemperature to vaporization quicker than any other materialbecause of its comparatively low specific heat.

5.1.2 MINIATURE CIRCUIT BREAKER

They 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 otherfixed. When a fault occurs the contacts separate and are isstuck 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 byseparate D.C supply. For starting the circuit conditions should

be in series with the starting coil of the equipment to energizeit. Because if even a single condition is not true then systemwill not start.

2. LOW TENSION CONTROL CIRCUIT

For low tension system the control circuits are directly excited


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from the 0.415 KV A.C supply. The same circuit achieves bothexcitation and tripping. Hence the tripping coil is provided foremergency tripping if the interconnection fails.

5.2 AUTOMATION LABThis lab deals in automating the existing equipment andfeeding routes.

Earlier, the old technology dealt with only (DAS) DataAcquisition System and came to be known as primary systems.The modern technology or the secondary systems are coupledwith (MIS) Management Information System. But this labuniversally applies the pressure measuring instruments as thecontrolling force. However, the relays are also provided butthey are used only for protection and interlocks.Once the measured is common i.e. pressure the control circuitscan easily be designed with single chips having multipleapplications. Another point is the universality of the supply,

the laws of electronic state that it can be any where between12V and 35V in the plant. All the control instruments areexcited by 24V supply (4-20mA) because voltage can bemathematically handled with ease therefore all controlsystems use voltage system for computation. The latesttechnology is the use of ETHERNET for control signals. 5.3PYROMETER LAB(1) LIQUID IN GLASS THERMOMETERMercury in the glass thermometer boils at 340 degree Celsiuswhich limits the range of temperature that can be measured. It

is L shaped thermometer which is designed to reach allinaccessible places.

(2) ULTRA VIOLET CENSORThis device is used in furnace and it measures the intensity ofultra violet rays there and according to the wave generatedwhich directly indicates the temperature in the furnace.


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(3) THERMOCOUPLESThis device is based on SEEBACK and PELTIER effect. Itcomprises of two junctions at different temperature. Then theemf is induced in the circuit due to the flow of electrons. This

is an important part in the plant.

(4) RTD (RESISTANCE TEMPERATURE DETECTOR)It performs the function of thermocouple basically but thedifference is of a resistance. In this due to the change in theresistance the temperature difference is measured.In this lab, also the measuring devices can be calibrated in theoil bath or just boiling water (for low range devices) and insmall furnace (for high range devices). 5.4 FURNACE SAFETY

AND SUPERVISORY SYSTEM LAB

This lab has the responsibility of starting fire in the furnace toenable the burning of coal. For first stage coal burners are inthe front and rear of the furnace and for the second and thirdstage corner firing is employed. Unburnt coal is removed usingforced draft or induced draft fan. The temperature inside theboiler is 1100 degree Celsius and its height is 18 to 40 m. It ismade up of mild steel. An ultra violet sensor is employed infurnace to measure the intensity of ultra violet rays inside thefurnace and according to it a signal in the same order of samemV is generated which directly indicates the temperature of

the furnace.For firing the furnace a 10 KV spark plug is operated for tenseconds over a spray of diesel fuel and pre-heater air alongeach of the feeder-mills. The furnace has six feeder mills eachseparated by warm air pipes fed from forced draft fans. In firststage indirect firing is employed that is feeder mills are notfed directly from coal but are fed from three feeders but arefed from pulverized coalbunkers. The furnace can operate onthe minimum feed from three feeders but under notcircumstances should any one be left out under operation, to

prevent creation of pressure different with in the furnace,which threatens to blast it.

5.5 ELECTRONICS LAB

This lab undertakes the calibration and testing of variouscards. It houses various types of analytical instruments like


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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 it is sent toelectrodes. It extracts the magnetic portion.

5.6 ANNUNCIATIN CARDSThey are used to keep any parameter like temperature etc.within limits. It gets a signal if parameter goes beyond limit. Ithas a switching transistor connected to relay that helps inalerting the UCB.

39. Control and Instrumentation Control and InstrumentationMeasuring Instrumentsments

In any process the philosophy of instrumentation shouldprovide a comprehensive intelligence feed back on theimportant parameters viz. Temperature, Pressure, Level andFlow. This Chapter Seeks to provide a basic understanding of

the prevalent instruments used for measuring the aboveparameters.

Temperature Measurement

The most important parameter in thermal power plant istemperature and its measurement plays a vital role in safeoperation of the plant. Rise of temperature in a substance isdue to the resultant increase in molecular activity of thesubstance on application of heat; which increases the internal

energy of the material. Therefore there exists some propertyof the substance, which changes with its energy content. Thechange may be observed with substance itself or in asubsidiary system in thermodynamic equilibrium, which iscalled testing body and the system itself is called the hotbody.


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Expansion Thermometer

Solid Rod Thermometers a temperature sensing - Controllingdevice may be designed incorporating in its construction theprinciple that some metals expand more than others for the

same temperature range. Such a device is the thermostat usedwith water heaters (Refer Fig. 69).


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Fig No.-69 Rod Type Thermostat

The mercury will occupy a greater fraction of the volume of the

container than it will at a low temperature.Under normal atmospheric conditions mercury normally boilsat a temperature of (347C). To extend the range of mercury inglass thermometer beyond this point the top end of athermometer bore opens into a bulb which is many timeslarger in capacity than the bore. This bulb plus the bore abovethe mercury, is then filled with nitrogen or carbon dioxide gasat a sufficiently high pressure to prevent boiling at the highesttemperature to which the thermometer may be used.Mercury in Steel the range of liquid in glass thermometers

although quite large, does not lend itself to all industrialpractices. This fact is obvious by the delicate nature of glassalso the position of the measuring element is not always thebest position to read the result. Types of Hg in SteelThermometers are:

Bourdon TubeMost common and simplest type (Refer Fig. 71)

Spiral type

More sensitive and used where compactness is necessary

Helical TypeMost sensitive and compact. Pointer may be mounted direct onend of helixWhich rotates, thus eliminating backlash and lost motion?Linkages, which only allow the pointer to operate over a


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selected range of pressure to either side of the normal steampressure. (Refer Fig No.77)

Dewrance Critical Pressure Gauge Measurement of Level

Direct Methods

'Sight Glass' is used for local indication on closed or openvessels. A sight glass is a tube of toughened glass connectedat both ends through packed unions and vessel. The liquidlevel will be the same as that in the vessel. Valves areprovided for isolation and blow down."Float with Gauge Post" is normally used to local indication onclosed or open vessels."Float Operated Dial" is used for small tanks and congested

areas. The float arm is connected to a quadrant and pinionwhich rotates the pointer over a scale.


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Bourden Pressure Gauge a Bourdon pressure gauge calibratedin any fact head is often connected to a tank at or near thedatum level."Mercury Manometer" is used for remote indication of liquidlevel. The working principle is the same as that of amanometer one limp of a U-tube is connected to the tank, theother being open to atmosphere. The manometer liquid mustnot mix with the liquid in the vessel, and where the

manometer is at a different level to the vessel, the static headmust be allowed in the design of the manometer.'Diaphragm Type' is used for remote level indication in opentanks or docks etc. A pressure change created by themovement of a diaphragm is proportional to a change in liquidlevel above the diaphragm. This consists of a cylindrical boxwith a rubber or plastic diaphragm across its open end as thelevel increases .the liquid pressure on the diaphragm increasesand the air inside is compressed. This pressure is transmittedvia a capillary tube to an indicator or recorder incorporating a

pressureMeasuring element.

Sealed Capsule Type The application and principle is the sameas for the diaphragm box. In this type, a capsule filled with aninert gas under a slight pressure is exposed to the pressuredue to the head of liquid and is connected by a capillary to anindicator. In some cases the capsule is fitted external to the


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tank and is so arranged that it can be removed whilst the tankis still full, a spring loaded valve automatically shutting off thetapping point.Air Purge System This system provides the simplest means ofobtaining an indication of level, or volume, at a reasonable

distance and above or below, the liquid being measured. Thepressure exerted inside an open ended tube below the surfaceof a liquid is proportional to the depth of the liquid

The Measurement of Flow

Two principle measurements are made by flow meters viz.quantity of flow and rate of flow. 'Quantity of flow' is thequantity of fluid passing a given point in a given time, i.e.gallons or pounds. Rate of flow' is the speed of. a fluidpassing a given point at a given instant and is proportional to


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quantity passing at a given instant, i.e. gallons per minute orpounds per hour. There are two groups of measuring devices: -

Positive, or volumetric, which measure flow by transferring ameasured quantity of fluid from the inlet to the outlet.

Inferential, which measures the velocity of the flow and thevolume passed is inferred, it being equal to the velocity timesthe cross sectional area of the flow. The inferential type is themost widely used.

Measurement of Fluid Flow through Pipes:

"The Rotating Impeller Type" is a positive type device which isused for medium quantity flow measurement i.e., petroleumand other commercial liquids. It consists ofTwo fluted rotors mounted in a liquid tight case fluid flow andtransmitted to a counter.Rotating Oscillating Piston Type This is also a positive type

device and is used for measuring low and medium quantityflows, e.g. domestic water supplies. This consists of a brassmeter body into which is fitted a machined brass workingchamber and cover, containing a piston made of ebonite. Thispiston acts as a moving chamber and transfers a definitevolume of fluid from the inlet to the outlet for each cycle.Helical Vane Type For larger rates of flow, a helical vane ismounted centrally in the body of the meter. The helix chambermay be vertical or horizontal and is geared to a counter.Usually of pipe sizes 3" to 10" Typical example is the Kent

Torrent Meter.Turbine Type this like the helical Vane type is a inference typeof device used forlarge flows with the minimum of pressure drop. This consistsof a turbine or drumrevolving in upright bearings, retaining at the top by a collar.Water enters the drum


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from the top and leaves tangentially casings to rotate at aspeed dependent upon thequantity of water passed. The cross sectional area of the meterthroughout is equal tothe area of the inlet and outlet pipes and is commonly used on

direct supply watermains,Combination Meters this is used for widely fluctuating flows. Itconsists of a largermeter (helical, turbine or fan) in the main with a small rotarymeter or suitable type in abypass. Flow is directed into either the main or bypassaccording to the quantity of flowby an automatic valve. By this means flows of 45 to 40,000gallons per hour can be

measured.

Measurement of Fluid Flow through Open Channels:The Weir If a fluid is allowed to flow over a square weir ofnotch, The height of the liquid above the still of the weir, orthe bottom of the notch will be a measure of the rate of flow.

A formula relates the rate of flow to the height and isdependent upon the design of theVenturi Flumes The head loss caused by the weir flow meter isconsiderable and itsconstruction is sometimes complicated, therefore the flume issometimes used. The

principle is same as that of venture except that the rate offlow is proportional to thedepth of the liquid in the upstream section. It consists of alocal contraction in the crosssection of flow through a channel in the shape of a venturi. Itis only necessary tomeasure the depth of the upstream section which is a measureof the rate of flow. This


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may be done by pressure tapping at the datum point or by afloat in an adjacent levelchamber.Pressure Difference Flow meters These are the most widelyused type of flow meter since they are capable of measuring

the flow of all industrial fluids passing through pipes. Theyconsists of a primary element inserted in the pipeline whichgenerates a differential pressure, ^he magnitude of which isproportional to the square of the rate of flow and a secondaryelement which measures this differential pressure andtranslates it into terms of flow. (Refer fig. 79).

Fig. No-79 Pressure Differential Flow meters

Primary elements Bernoulli's theorem states that the quantityof fluid or gas flowing is proportional to the square root of thedifferential pressure. There are four principal types of primary

elements (or restrictions) as enumerate below:Venturi; This is generally used for medium and high quantityfluid flow and it consists of two hollow truncated cones, thesmaller diameters of which are connected together by a shortlength of parallel pipe, the smallest diameter of the tubeformed by this length of parallel pipe is known as the throatsection and the lower of the two pressures, (the throat, or


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downstream pressure) is measured here.Orifice Plate This is the oldest and most common form ofpressure differential device. In its simplest form it consists of athin metal plate with a central hold clamped between two pipeflanges. In the metering of dirty fluids or fluids containing

solids the hole is placed so that its lower edge coincides withthe inside bottom of the pipe. (Refer Fig.80) It is essential thatthe leading edge of the hole is absolutely sharp rounding orburring would have a very marked effect on the flow.

Fig No.-80 Typical Orifice Plate Pressure Tapping

EMD I


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Electrical Maintenance division I

I was assigned to do training in Electrical maintenance divisionI from 17th July 2007 to 28th July 2007.

This two week of training in this division were divided asfollows.

17th to 19th July 2007- HT/LT switchgear

21st to 24th July 2007 - HT/LT Motors, Turbine &Boiler side 26th to 28th July 2007- CHP/NCHP Electrical

Electrical maintenance division 1

It is responsible for maintenance of:

1. Boiler side motors2. Turbine side motors3. Outside motors

4. Switchgear

1. Boiler side motors:

For 1, units 1, 2, 3


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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.

1. COAL HANDLING PLANT (C.H.P)

2. NEW COAL HANDLING PLANT (N.C.H.P)The old coal handling plant caters to the need of units 2,3,4,5and 1 whereas the latter supplies coal to units 4 andV.O.C.H.P. supplies coal to second and third stages in theadvent coal to usable form to (crushed) form its raw form andsend 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 emptied here. The process is performed by aslip ring motor of rating: 55 KW, 415V, 1480 RPM. This motorturns the wagon by 135 degrees and coal falls directly on theconveyor through vibrators. Tippler has raised lower systemwhich enables is to switch off motor when required till iswagon back to its original position. It is titled by weightbalancing principle. The motor lowers the hanging balancing


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weights, which in turn tilts the conveyor. Estimate of theweight of the conveyor is made through hydraulic weighingmachine.2. Conveyor: - There are 14 conveyors in the plant. They arenumbered so that their function can be easily demarcated.

Conveyors are made of rubber and more with a speed of 250-300m/min. Motors employed for conveyors has a capacity of150 HP. Conveyors have a capacity of carrying coal at the rateof 400 tons per hour. Few conveyors are double belt, this isdone for imp. Conveyors so that if a belt develops any problemthe process is not stalled. The conveyor belt has a switch afterevery 25-30 m on both sides so stop the belt in case ofemergency. The conveyors are 1m wide, 3 cm thick and madeof chemically treated vulcanized rubber. The max angularelevation of conveyor is designed such as never to exceed half

of the angle of response and comes out to be around 20degrees.

3. Zero Speed Switch:-It is safety device for motors, i.e., if beltis not moving and the motor is on the motor may burn. So toprotect this switch checks the speed of the belt and switchesoff the motor when speed is zero.

4. Metal Separators: - As the belt takes coal to the crusher, Nometal pieces should go along with coal. To achieve this

objective, we use metal separators. When coal is dropped tothe crusher hoots, the separator drops metal pieces ahead ofcoal. It has a magnet and a belt and the belt is moving, thepieces are thrown away. The capacity of this device is around50 kg. .The CHP is supposed to transfer 600 tons of coal/hr,but practically only 300-400 tons coal is transfer5. Crusher: - Both the plants use TATA crushers powered byBHEL. Motors. The crusher is of ring type and motor ratings are400 HP, 606 KV. Crusher is designed to crush the pieces to 20mm size i.e. practically considered as the optimum size of

transfer via conveyor.

6. Rotatory Breaker: - OCHP employs mesh type of filters andallows particles of 20mm size to go directly to RC bunker,larger particles are sent to crushes. This leads to frequentclogging. NCHP uses a technique that crushes the larger ofharder substance like metal impurities easing the load on the


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magnetic separators.MILLING SYSTEM

1. RC Bunker: - Raw coal is fed directly to these bunkers. Theseare 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 coalbunker to mill. The quantity of raw coal fed in mill can becontrolled by speed control of aviator drive controlling damperand aviator change.

3. Ball Mill: - The ball mill crushes the raw coal to a certainheight and then allows it to fall down. Due to impact of ball oncoal and attraction as per the particles move over each other

as well as over the Armor lines, the coal gets crushed. Largeparticles are broken by impact and full grinding is done byattraction. The Drying and grinding option takes placesimultaneously inside the mill.

4. Classifier:- It is an equipment which serves separation offine pulverized coal particles medium from coarse medium. Thepulverized coal along with the carrying medium strikes theimpact plate through the lower part. Large particles are thentransferred to the ball mill.

5. Cyclone Separators: - It separates the pulverized coal fromcarrying medium. The mixture of pulverized coal vapour catersthe cyclone separators.

6. The Tturniket: - It serves to transport pulverized coal fromcyclone separators to pulverized coal bunker or to wormconveyors. 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 othersystem. 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.


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(a) ID Fans: - Located between electrostatic precipitator andchimney.Type-radicalSpeed-1490 rpmRating-300 KW

Voltage-6.6 KVLubrication-by oil

(b) FD Fans: - Designed to handle secondary air for boiler. 2 innumber and provide ignition of coal.

Type-axialSpeed-990 rpmRating-440 KWVoltage-6.6 KV

(c)Primary Air Fans: - Designed for handling the atmosphericair up to 50 degrees Celsius, 2 in number

And they transfer the powered coal to burners to firing.

Type-Double suction radialRating-300 KWVoltage-6.6 KVLubrication-by oil

Type of operation-continuous

9. Bowl Mill: - One of the most advanced designs of coalpulverizes presently manufactured.

Motor specification squirrel cage induction motorRating-340 KWVoltage-6600KVCurreen-41.7ASpeed-980 rpm

Frequency-50 HzNo-load current-15-16 A

NCHP

1. Wagon Tippler:-


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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, 10B11A, 11B12A, 12B13A, 13B14A, 14B15A, 15B

16A, 16B17A, 17B18A, 18B

4. Transfer Point 6

5. Breaker House

6. Rejection House

7. Reclaim House

8. Transfer Point 7

9. Crusher House

10. Exit


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The coal arrives in wagons via railways and is tippled by thewagon tipplers into the hoppers. If coal is oversized (>400 mmsq) then it is broken manually so that it passes the hoppermesh. From the hopper mesh it is taken to the transfer point

TP6 by conveyor 12A ,12B which takes the coal to the breakerhouse , which renders the coal size to be 100mm sq. the stoneswhich are not able to pass through the 100mm sq of hammerare rejected 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 reclaimhopper, From TP7 coal is taken by conveyors 14A, 14B tocrusher house whose function is to render the size of coal to20mm sq. now the conveyor labors are present whose function

is to recognize and remove any stones moving in theconveyors . In crusher before it enters the crusher. After beingcrushed, if any metal is still present it is taken care of by metaldetectors employed in conveyor 10.

SWITCH GEAR-

It makes or breaks an electrical circuit.

1. Isolation: - A device which breaks an electrical circuit when

circuit is switched on to no load. Isolation is normally used invarious ways for purpose of isolating a certain portion whenrequired for maintenance.

2. Switching Isolation: - It is capable of doing things likeinterrupting transformer magnetized current, interrupting linecharging current and even perform load transfer switching.The main application of switching isolation is in connectionwith transformer feeders as unit makes it possible to switchout one transformer while other is still on load.

3. Circuit Breakers: - One which can make or break the circuiton load and even on faults is referred to as circuit breakers.This equipment is the most important and is heavy dutyequipment mainly utilized for protection of various circuits andoperations on load. Normally circuit breakers installed areaccompanied by isolators


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4. Load Break Switches: - These are those interrupting deviceswhich can make or break circuits. These are normally on samecircuit, which are backed by circuit breakers.

5. Earth Switches: - Devices which are used normally to earth aparticular system, to avoid any accident happening due toinduction on account of live adjoining circuits. Theseequipments do not handle any appreciable current at all. Apartfrom this equipment there are a number of relays etc. whichare used in switchgear.

LT Switchgear

It is classified in following ways:-

1. Main Switch:- Main switch is control equipment whichcontrols or disconnects the main supply. The main switch for 3phase supply is available for tha range 32A, 63A, 100A, 200Q,300A at 500V grade.

2. Fuses: - With Avery high generating capacity of the modernpower stations extremely heavy carnets would flow in the faultand the fuse clearing the fault would be required to withstandextremely heavy stress in process.

It is used for supplying power to auxiliaries with backup fuseprotection. Rotary switch up to 25A. With fuses, quick break,quick make and double break switch fuses for 63A and 100A,switch fuses for 200A, 400A, 600A, 800A and 1000A are used.

3. Contractors: - AC Contractors are 3 poles suitable for D.O.LStarting of motors and protecting the connected motors.

4. Overload Relay: - For overload protection, thermal over

relay are best suited for this purpose. They operate due to theaction of heat generated by passage of current through relayelement.

5. Air Circuit Breakers: - It is seen that use of oil in circuitbreaker may cause a fire. So in all circuits breakers at largecapacity air at high pressure is used which is maximum at the


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time of quick tripping of contacts. This reduces the possibilityof sparking. The pressure may vary from 50-60 kg/cm^2 forhigh and medium capacity circuit breakers.

HT SWITCH GEAR:-

1. Minimum oil Circuit Breaker: - These use oil as quenchingmedium. It comprises of simple dead tank row pursuingprojection from it. The moving contracts are carried on an ironarm lifted by a long insulating tension rod and are closedsimultaneously pneumatic operating mechanism by means oftensions but throw off spring to be provided at mouth of thecontrol the main current within the controlled device.

Type-HKH 12/1000c Rated Voltage-66 KV Normal Current-1250A Frequency-5Hz Breaking Capacity-3.4+KA Symmetrical 3.4+KA Asymmetrical 360 MVA Symmetrical Operating Coils-CC 220 V/DC FC 220V/DC Motor Voltage-220 V/DC

2. Air Circuit Breaker: - In this the compressed air pressurearound 15 kg per cm^2 is used for extinction of arc caused byflow of air around the moving circuit . The breaker is closed byapplying pressure at lower opening and opened by applyingpressure at upper opening. When contacts operate, the coldair rushes around the movable contacts and blown the arc.

It has the following advantages over OCB:-

i. Fire hazard due to oil are eliminated.ii. Operation takes place quickly.iii. There is less burning of contacts since the duration is shortand consistent.iv. Facility for frequent operation since the cooling medium isreplaced constantly.Rated Voltage-6.6 KV


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Current-630 AAuxiliary current-220 V/DC

3. SF6 Circuit Breaker: - This type of circuit breaker is ofconstruction to dead tank bulk oil to circuit breaker but the

principle of current interruption is similar o that of air blastcircuit breaker. It simply employs the arc extinguishingmedium namely SF6. the performance of gas . When it isbroken down under an electrical stress. It will quicklyreconstitute itself

Circuit Breakers-HPA Standard-1 EC 56 Rated Voltage-12 KV Insulation Level-28/75 KV

Rated Frequency-50 Hz Breaking Current-40 KA Rated Current-1600 A Making Capacity-110 KA Rated Short Time Current 1/3s -40 A Mass Approximation-185 KG Auxiliary Voltage Closing Coil-220 V/DC Opening Coil-220 V/DC Motor-220 V/DC

SF6 Pressure at 20 Degree Celsius-0.25 KG SF6 Gas Per pole-0.25 KG

4. Vacuum Circuit Breaker: - It works on the principle thatvacuum is used to save the purpose of insulation and it implies

that pr. Of gas at which breakdown voltage independent ofpressure. It regards of insulation and strength, vacuum issuperior dielectric medium and is better that all other mediumexcept air and sulphur which are generally used at highpressure. Rated frequency-50 Hz Rated making Current-10 Peak KA


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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 Time Current-40 KA (3 SEC) Weight of Breaker-8 KG

EMD II

Electrical Maintenance division II


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I was assigned to do training in Electrical maintenance divisionII from 31st July 2007 to 11th August 2007.This two week of training in this division were divided asfollows.

31st to 2nd August 2007- Generator 4th August 2007 - Transformer &switchyard 7th August 2007 - protection 9th August2007 - Lightning 11th August 2007 - EP

Generator and Auxiliaries Generator and Auxiliaries

Generator Fundamentals Fundamentals

The transformation of mechanical energy into electrical energyis carried out by the Generator. This Chapter seeks to providebasic understanding about the working principles anddevelopment of Generator.

Working Principle

The A.C. Generator or alternator is based upon the principle of

electromagnetic induction and consists generally of astationary part called stator and a rotating part called rotor.The stator housed the armature windings. The rotor housesthe field windings. D.C. voltage is applied to the field windingsthrough slip rings. When the rotor is rotated, the lines ofmagnetic flux (viz magnetic field) cut through the statorwindings. This induces an electromagnetic force (e.m.f.) in the


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stator windings. The magnitude of this e.m.f. is given by thefollowing expression.

E = 4.44 /O FN volts0 = Strength of magnetic field in Webers.

F = Frequency in cycles per second or Hertz.N = Number of turns in a coil of stator windingF = Frequency = Pn/120Where P = Number of polesn = revolutions per second of rotor.

From the expression it is clear that for the same frequency,number of poles increases with decrease in speed and viceversa. Therefore, low speed hydro turbine drives generatorshave 14 to 20 poles where as high speed steam turbine driven

generators have generally 2 poles. Pole rotors are used in lowspeed generators, because the cost advantage as well aseasier construction.

Development

The first A.C. Generator concept was enunciated by MichaelFaraday in 1831. In 1889 Sir Charles A. Parsons developed thefirst AC turbo-generator. Although slow speed AC generatorshave 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 ofsolid forgings and improved techniques permitted an increasein generator rating to 20MW at 300rpm. Up to the out break ofsecond 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 powerplants was delayed and in order to catch up with the delay inplant installation, a large number of 30 MW and 60 MW at 3000rpm units were constructed during the years immediatelyfollowing the war. The changes in design in this period wererelatively small.


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In any development programme the. Costs of material andlabour involved in manufacturing and erection must be a basicconsideration. Coupled very closely withthese considerations is the restriction is size and weightimposed by transport limitations.

Development of suitable insulating materials for large turbo-generators is one of themost important tasks and need continues watch as size andratings of machinesincrease. The present trend is the use only class "B" andhigher grade materials andextensive work has gone into compositions of mica; glass andasbestos withappropriate bonding material. An insulation to meet the

stresses in generator slots mustfollow very closely the thermal expansion of the insulatedconductor without cracking orany plastic deformation. Insulation for rotor is subjected tolower dielectric stress butmust withstand high dynamic stresses and the newlydeveloped epoxy resins, glassand/or asbestos molded in resin and other synthetic resins arefinding wideapplications.

Generator componentThis Chapter deals with the two main components of theGenerator viz. Rotor, its winding & balancing and stator, itsframe, core & windings.

Rotor

The electrical rotor is the most difficult part of the generator

to design. It revolves inmost modern generators at a speed of 3,000 revolutions perminute. The problem ofguaranteeing the dynamic strength and operating stability ofsuch a rotor is complicatedby the fact that a massive non-uniform shaft subjected to amultiplicity of differential


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stresses must operate in oil lubricated sleeve bearingssupported by a structuremounted on foundations all of which possess complex dynamicbe behavior peculiar tothemselves. It is also an electromagnet and to give it the

necessary magnetic strengththe windings must carry a fairly high current. The passage ofthe current through thewindings generates heat but the temperature must not beallowed to become so high,otherwise difficulties will be experienced with insulation. Tokeep the temperature down,the cross section of the conductor could not be increased butthis would introduceanother problems. In order to make room for the large

conductors, body and this wouldcause mechanical weakness. The problem is really to get themaximum amount ofcopper into the windings without reducing the mechanicalstrength. With good designand great care in construction this can be achieved. The rotoris a cast steel ingot, andit is further forged and machined. Very often a hole is boredthrough the centre of therotor axially from one end of the other for inspection. Slots are

then machined forwindings and ventilation.

Rotor winding

Silver bearing copper is used for the winding with mica as theinsulation between conductors. A mechanically stronginsulator such as micanite is used for lining the slots. Laterdesigns of windings for large rotor incorporate combination ofhollow 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 bywedges. The end rings aresecured to a turned recess in the rotor body, by shrinking orscrewing and supported at


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the other end by fittings carried by the rotor body. The twoe

ntpc dadri 2

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