report-N.T.P.C. BADARPUR

8/6/2019 report-N.T.P.C. BADARPUR

1/48


2/48

http://www.final-yearprojects.co.cc / http://troubleshoot4free.com/fyp/

Final Year Project's is One place for all Engineering Projects, Presentation, seminar,summer training report and lot more.

NOTE:-This work is copyright to its Authors. This is only for Educational Purpose.

EP CERTIFICATE

This is to certify that------------------------- student of Batch Electrical & ElectronicsBranch IIIrd Year; Sky line Institute of Engineering & Technology Noida hassuccessfully completed his 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 per the training report submitted by him.

Training InchargeBTPS/NTPCNEW DELHI

Acknowledgement

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

I do extend my heartfelt thanks to Mrs. Rachna Singh for providing me thisopportunity 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 havelearnt a lot working under them and I will always be indebted of them for this valueaddition in me.


3/48




I would also like to thank the training in charge of Skyline Institute of Engineering& Technology Gr. Noida and all the faculty member of Electrical & Electronicsdepartment for their effort of constant co-operation. Which have been significantfactor in the accomplishment of my industrial training.

Training at BTPS

I was appointed to do eight-week training at this esteemed o rganization from 18thJune to 11th august 2007. In these eight weeks I was assigned to visit variousdivision of the plant which were

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

This eight-week training was a very educational adventure for me. It was really

amazing to see the plant by your self and learn how electricity, which is one of ourdaily requirements of life, is produced.

This report has been made by self-experience at BTPS. The material in this reporthas been gathered from my textbooks, senior student report, and trainer manualprovided by training department. The specification & principles are at learned byme from the employee of each division of BTPS.


4/48




ABOUT NTPC

NTPC Limited is the largest thermal power generating company of India. A p ublicsector company, it was incorporated in the year 1975 to accelerate powerdevelopment 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 thecompany 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.

POWER GENERATION IN INDIA

NTPCs core business is engineering, construction and operation of powergenerating plants. It also provides consultancy in the area of power plantconstructions and power generation to companies in India and abroad. As on datethe 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 (1,054 MW). NTPC acquired50% equity of the SAIL Power Supply Corporation Ltd. (SPSCL). This JVCompany operates the captive power plants of Durgapur (120 MW), Rourkela (120MW) and Bhilai (74 MW). NTPC also has 28.33% stake in Ratnagiri Gas & PowerPrivate Limited (RGPPL) a joint venture company between NTPC, GAIL, IndianFinancial Institutions and Maharashtra SEB Co Ltd.NTPC has set new benchmarks for the power industry both in the area of powerplant construction and operations . Its providing power at the cheapest 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. NTPChas undertaken massive a forestation in the vicinity of its plants. Plantations haveincreased forest area and reduced barren land. The massive a forestation by NTPCin and around its Ramagundam Power station (2600 MW) have contributedreducing the temperature in the areas by about 3c. NTPC has also taken proactivesteps for ash utilization . In 1991, it set up Ash Utilization DivisionA "Centre for Power Efficiency and Environment Protection (CENPEEP)" hasbeen established in NTPC with the assistance of United States Agency forInternational Development. (USAID). Cenpeep is efficiency oriented, eco-friendlyand eco-nurturing initiative - a symbol of NTPC's concern towards environmentalprotection and continued commitment to sustainable power development in India.As a responsible corporate citizen, NTPC is making constant efforts to improve the


5/48




socio-economic status of the people affected by its projects. Through itsRehabilitation and Resettlement programmes, the company endeavors to improvethe overall socio economic status Project Affected Persons.NTPC was among the first Public Sector Enterprises to enter into a Memorandumof Understanding (MOU) with the Government in 1987-88. NTPC has been placed

under the 'Excellent category' (the best category) every year since the MOU systembecame operative.

Harmony between man and environment is the essence of healthy life an d growth.Therefore, maintenance of ecological balance and a pristine environment has beenof utmost importance to NTPC. It has been taking various measures discussedbelow for mitigation of environment pollution due to power generation.

Environment Policy & Environment Management SystemDriven by its commitment for sustainable growth of power, NTPC has evolved awell defined environment management policy and sound environment practices forminimizing environmental impact arising out of setting up of power plants andpreserving the natural ecology.

National Environment Policy:At the national level, the Ministry of Environment and Forests had prepared a draftEnvironment Policy (NEP) and the Ministry of Power along with NTPC activelyparticipated in the deliberations 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 a comprehensive documententitled "NTPC Environment Policy and Environment Management System".Amongst the guiding principles adopted in the document are company's proactiveapproach to environment, optimum utilization of equipment, adoption of latesttechnologies and continual environment improvement. The policy also envisagesefficient utilization of resources, thereby minimizing waste, maximizing ashutilization and providing green belt all around the plant for maintaining ecologicalbalance.Environment Management, Occupational Health and Safety Systems:NTPC has actively gone for adoption of best international practices on environment,occupational health and safety areas. The organization has pursued theEnvironmental Management System (EMS) ISO 14001 and the Occupational Healthand Safety Assessment System OHSAS 18001 at its different establishments. As aresult of pursuing these practices, all NTPC power stations have been certified forISO 14001 & OHSAS 18001 by reputed national and international CertifyingAgencies.Pollution Control systems:


6/48




While deciding the appropriate technology for its projects, NTPC integrates manyenvironmental provisions into the plant design. In order to ensure that NTPCcomply with all the stipulated environment norms, various state-of-the-art pollutioncontrol systems / devices as discussed below have been installed to control air andwater pollution.

Electrostatic Precipitators:The ash left behind after combustion of coal is arrested in high efficiencyElectrostatic Precipitators (ESPs) and particulate emission is controlled w ell withinthe stipulated norms. The ash collected in the ESPs is disposed to Ash Ponds inslurry form.Flue Gas Stacks:Tall Flue Gas Stacks have been provided for wide dispersion of the gaseousemissions (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 fired stations, by adopting bestcombustion practices.Neutralisation Pits:Neutralisation pits have been provided in the Water Treatment Plant (WTP) for pHcorrection of the effluents before discharge into Effluent Treatment Plant (ETP) forfurther treatment and use.

Coal Settling Pits / Oil Settling Pits:In these Pits, coal dust and oil are removed from the effluents emanating from theCoal Handling Plant (CHP), coal yard and Fuel Oil Handling areas before dischargeinto ETP.DE & DS Systems:Dust Extraction (DE) and Dust Suppression (DS) systems have been installed in allcoal fired power stations in NTPC to contain and extract the fugitive dust releasedin the Coal Handling Plant (CHP).Cooling Towers:Cooling Towers have been provided for cooling the hot Condenser cooling water inclosed cycle Condenser Cooling Water (CCW) Systems. This helps in reduction inthermal pollution and conservation of fresh water.Ash Dykes & Ash Disposal systems:Ash ponds have been provided at all coal based stations except Dadri where DryAsh Disposal System has been provided. Ash Ponds have been divided into lagoonsand provided with garlanding arrangements for change over of the ash slurry feedpoints for even filling of the pond and for effective settlement of the ash particles.Ash in slurry form is discharged into the lagoons where ash particles get settledfrom the slurry and clear effluent water is discharged from the ash pond. Thedischarged effluents conform to standards specified by CPCB and the same isregularly monitored.


7/48




At its Dadri Power Station, NTPC has set up a unique system for dry ash collectionand disposal facility with Ash Mound formation. This has been envisaged for thefirst time in Asia which has resulted in progressive development of green beltbesides far less requirement of land and less water requirement as compared to thewet ash disposal system.

Ash Water Recycling System:Further, in a number of NTPC stations, as a proactive measure, Ash WaterRecycling System (AWRS) has been provided. In the AWRS, the effluent from ashpond is circulated back to the station for further ash sluicing to the ash pond. Th ishelps in savings of fresh water requirements for transportation of ash from theplant.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 to save 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, Portland pozzolana cement, etc.).DAES has been installed at Unchahar, Dadri, Simhadri, Ramagundam, Singrauli,Kahalgaon, Farakka, Talcher Thermal, Korba, Vindhyachal, Talcher Kaniha andBTPS.

Liquid Waste Treatment Plants & Management System:The objective of industrial liquid effluent treatment plant (ETP) is to dischargelesser and cleaner effluent from the power plants to meet environmental regulations.After primary treatment at the source of their generation, the effluents are sent tothe ETP for further treatment. The composite liquid effluent treatment plant hasbeen designed to treat all liquid effluents which originate within the power statione.g. Water Treatment Plant (WTP), Condensate Polishing Unit (CPU) effluent, CoalHandling Plant (CHP) effluent, floor washings, service water drains etc. The schemeinvolves collection of various effluents and their appropriate treatment centrallyand re-circulation of the treated effluent for various plant uses.NTPC has implemented such systems in a number of its power stations such asRamagundam, 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 fromthe stations.

Sewage Treatment Plants & Facilities:Sewage Treatment Plants (STPs) sewage treatment facilities have been provided atall NTPC stations to take care of Sewage Effluent from Plant and township areas. Ina number of NTPC projects modern type STPs with Clarifloculators, MechanicalAgitators, sludge drying beds, Gas Collection Chambers etc have been provided toimprove the effluent quality. The effluent quality is monitored regularly and treatedeffluent conforming to the prescribed limit is discharged from the station. At severalstations, treated effluents of STPs are being used for horticulture purpose.


8/48




Environmental Institutional Set-up:Realizing the importance of protection of the environment with speedy developmentof the power sector, the company has constituted different groups at project,regional and Corporate Centre level to carry out specific environment related

functions. The Environment Management Group, Ash Utilisation Group and Centrefor Power Efficiency & Environment Protection (CENPEEP) function from theCorporate Centre and initiate measures to mitigate the impact of power projectimplementation on the environment and preserve ecology in the vicinity of theprojects. Environment Management and Ash Utilisation Groups established at eachstation, look after various environmental issues of the individual station.Environment Reviews:To maintain constant vigil on environmental compliance, Environmental Reviewsare carried out at all operating stations and remedial measures have been takenwherever necessary. As a feedback and follow-up of these Environmental Reviews, anumber of retrofit and up-gradation measures have been undertaken at different

stations.Such periodic Environmental Reviews and extensive monitoring of the facilitiescarried out at all stations have helped in compliance with the environmental normsand timely renewal of the Air and Water Consents.

Up gradation & retrofitting of Pollution Control Systems:Waste ManagementVarious types of wastes such as Municipal or domestic wastes, hazardous wastes,Bio-Medical wastes get generated in power plant areas, plant hospital and thetownships of projects. The wastes generated are a number of solid and hazardouswastes like used 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, emptycylinders (refillable), paper, rubber products, canteen (bio-degradable) wastes,buidling material wastes, silica gel, glass wool, fused lamps & tubes, fire resistantfluids etc. These wastes fall 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 (asamended on 06.01.2000 & 20.05.2003). Handling and management of these wastes inNTPC stations have been discussed below.

Advanced / Eco-friendly TechnologiesNTPC has gained expertise in operation and management of 200 MW and 500 MWUnits installed at different Stations all over the country and is looking ahead forhigher capacity Unit sizes with super critical steam parameters for higherefficiencies and for associated environmental gains. At Sipat, higher capacity Unitsof 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 under operation atall gas-based power projects in NTPC. Advanced clean coal technologies such as


9/48


10/48




ELECTRICITY FROM COAL

Coal from the coal wagons is unloaded with the help of wagon tipplers in the C.H.P.this coal is taken to the raw coal bunkers with the help of conveyor belts. Coal is

then transported to bowl mills by coal feeders where it is pulverized and ground inthe powered form.

This crushed coal is taken away to the furnace through coal pipes with the help of hot and cold mixture P.A fan. This fan takes atmospheric air, a part of which is sentto pre heaters while a part goes to the mill for temperature control. Atmospheric airfrom 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 the boilerdrum . Water from the drum passes through the down comers and goes to thebottom ring header. Water from the bottom ring header is divided to all the four

sides of the furnace. Due to heat density difference the water rises up in the waterwall tubes. This steam and water mixture is again taken to the boiler drum wherethe steam is sent to super heaters for super heating. The super heaters are locatedinside the furnace and the steam is super heated (540 degree Celsius) and finally itgoes to the turbine.

Fuel gases from the furnace are extracted from the induced draft fan, whichmaintains balance draft in the furnace with F.D fan. These fuel gases heat energy tothe various super heaters and finally through air pre heaters and goes toelectrostatic precipitators where the ash particles are extracted. This ash is mixedwith the water to from slurry is pumped to ash period.

The steam from boiler is conveyed to turbine through the steam pipes and throughstop valve and control valve that automatically regulate the supply of steam to theturbine. Stop valves and controls valves are located in steam chest and governordriven from main turbine shaft operates the control valves the amount used.

Steam from controlled valves enter high pressure cylinder of turbines, where itpasses through the ring of blades fixed to the cylinder wall. These act as nozzles anddirect the steam into a second ring of moving blades mounted on the disc secured inthe turbine shaft. The second ring turns the shaft as a result of force of steam. Thestationary and moving blades together.

MAIN GENERATOR Maximum continuous KVA rating 24700KVAMaximum continuous KW 210000KWRated terminal voltage 15750V


11/48




MAIN TURBINE DATA

THERMAL POWER PLANT

A Thermal Power Station comprises all of the equipment and a subsystem requiredto produce electricity by using a steam generating boiler fired with fossil fuels orbefouls to drive an electrical generator. Some prefer to use the term ENERGYCENTER because such facilities convert forms of energy, like nuclear energy,gravitational potential energy or heat energy (derived from the combustion of fuel)

Rated Stator current 9050 ARated Power Factor 0.85 lagExcitation current at MCR Condition 2600 ASlip-ring Voltage at MCR Condition 310 VRated Speed 3000 rpm

Rated Frequency 50 HzShort circuit ratio 0.49Efficiency at MCR Condition 98.4%Direction of rotation viewed Anti ClockwisePhase Connection Double Star

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

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 receptor valve 535 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) 24,27,30,331.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


12/48




into electrical energy. However, POWER PLANT is the most common term in theunited state; While POWER STATION prevails in many Commonwealth countriesand especially in the United Kingdom.Such power stations are most usually constructed on a very large scale and designedfor continuous operation.

Typical diagram of a coal fired thermal power station1. Cooling water pump2. Three-phase transmission line3. Step up transformer4. Electrical Generator5. Low pressure steam6. Boiler feed water pump7. Surface condenser8. Intermediate pressure steam turbine9. Steam control valve10. High pressure steam turbine

11. Deaerator Feed water heater12. Coal conveyor13. Coal hopper14. Coal pulverizer15. boiler steam drum16. Bottom ash hoper17. Super heater18. Forced draught(draft) fan19. Reheater20. Combustion air intake21. Economizer22. Air preheater23. Precipitator24. Induced draught(draf t) fan25. Fuel gas stack

The description of some of the components written above is described as follows:

1. Cooling towers

Cooling Towers are evaporative coolers used for cooling water or other workingmedium to near the ambivalent web-bulb air temperature. Cooling tower useevaporation of water to reject heat from processes such as cooling the circulatingwater used in oil refineries, Chemical plants, power plants and building cooling, forexample. The tower vary in size from small roof-top units to very large hyperboloidstructures that can be up to 200 meters tall and 100 meters in diameter, orrectangular structure that can be over 40 meters tall and 80 meters long. Smallertowers are normally factory built, while larger ones are constructed on site.The primary use of large , industrial cooling tower system is to remove the heatabsorbed in the circulating cooling water systems used in power plants , petroleum


13/48




refineries, petrochemical and chemical plants, natural gas processing plants andother industrial facilities . The absorbed heat is rejected to the atmosphere by theevaporation of some of the cooling water in mechanical forced-draft or induceddraft towers or in natural draft hyperbolic shaped cooling towers as seen at mostnuclear power plants.

2.Three phase transmission lineThree phase electric power is a common method of electric power transmission. It isa type of polyphase system mainly used to power motors and many other devices . AThree phase system uses less conductor material to transmit electric power thanequivalent single phase, two phase, or direct current system at the same voltage. In athree phase system, three circuits reach their instantaneous peak values at differenttimes. Taking one conductor as the reference, the other two current are delayed intime by one-third and two-third of one cycle of the electrical current. This delaybetween phases has the effect of giving constant power transfer over each cycle of the current and also makes it possible to produce a rotating magnetic field in an

electric motor.At the power station, an electric generator converts mechanical 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 intime to give different phases. 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 householdvoltage).The power may already have been split into single phase at this point or it may stillbe three phase. Where the step-down is 3 phase, the output of this transformer isusually star connected with the standard mains voltage being the phase-neutralvoltage. Another system commonly seen in North America is to have a deltaconnected secondary with a center tap on one of the windings supplying the groundand neutral. This allows for 240 V three phase as well as three different single phasevoltages( 120 V between two of the phases and neutral , 208 V between the thirdphase ( known as a wild leg) and neutral and 240 V between any two phase) to beavailable from the same supply.3.Electrical generator

An Electrical generator is a device that converts kinetic energy to electrical energy,generally using electromagnetic induction. The task of converting the electricalenergy into mechanical energy is accomplished by using a motor. The source of mechanical energy may be a reciprocating or turbine steam engine, , water fallingthrough the turbine are made in a variety of sizes ranging from small 1 hp (0.75kW) units (rare) used as mechanical drives for pumps, compressors and other shaftdriven equipment , to 2,000,000 hp(1,500,000 kW) turbines used to generateelectricity. There are several classifications for modern steam turbines.


14/48




Steam turbines are used in all of our major coal fired power stations to drive thegenerators or alternators, which produce electricity. The turbines themselves aredriven by steam generated in Boilers or steam generators as they are sometimescalled.Electrical power station use large stem turbines driving electric generators to

produce most (about 86%) of the worlds electricity. These centralized stations areof two types: fossil fuel power plants and nuclear power plants. The turbines usedfor electric power generation are most often directly coupled to their-generators .Asthe generators must rotate at constant synchronous speeds according to thefrequency of the electric power system, the most common speeds are 3000 r/mi n for50 Hz systems, and 3600 r/min for 60 Hz systems. Most large nuclear sets rotate athalf those speeds, and have a 4-pole generator rather than the more common 2-poleone.

Energy in the steam after it leaves the boiler is converted into rotational energy as itpasses through the turbine. The turbine normally consists of several stage with each

stages consisting of a stationary blade (or nozzle) and a rotating blade. Stationaryblades convert the potential energy of the steam into kinetic energy into forces,caused by pressure drop, which results in the rotation of the turbine shaft. Theturbine shaft is connected to a generator, which produces the electrical energy.

4.Boiler feed water pumpA Boiler feed water pump is a specific type of pump used to pump water into asteam boiler. The water may be freshly supplied or retuning condensation of thesteam produced by the boiler. These pumps are normally high pressure units thatuse suction from a condensate return system and can be of the centrifugal pumptype or positive displacement type.

Construction and operationFeed water pumps range in size up to many horsepower and the electric motor isusually separated from the pump body by some form of mechanical coupling. Largeindustrial condensate pumps may also serve as the feed water pump. In either case,to force the water into the boiler; the pump must generate sufficient pressure toovercome the steam pressure developed by the boiler. This is usually accomplishedthrough the use of a centrifugal pump.Feed water pumps usually run intermittently and are controlled by a float switch orother similar level-sensing device energizing the pump when it detects a loweredliquid level in the boiler is substantially increased. Some pumps contain a two-stageswitch. As liquid lowers to the trigger point of the first stage, the pump is activated.I f the liquid continues to drop (perhaps because the pump has failed, its supply hasbeen cut off or exhausted, or its discharge is blocked); the second stage will betriggered. This stage may switch off the boiler equipment (preventing the boilerfrom running dry and overheating), trigger an alarm, or both.5. Steam-powered pumpsSteam locomotives and the steam engines used on ships and stationary applicationssuch as power plants also required feed water pumps. In this situation, though, the


15/48




pump was often powered using a small steam engine that ran using the steamproduced by the boiler. A means had to be provided, of course, to put the initialcharge of water into the boiler(before steam power was available to operate thesteam-powered feed water pump).the pump was often a positive displacement pumpthat 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 is to condense theexhaust steam from a steam turbine to obtain maximum efficiency and also toconvert the turbine exhaust steam into pure water so that it may be reused in t hesteam generator or boiler as boiler feed water. By condensing the exhaust steam of aturbine at a pressure below atmospheric pressure, the steam pressure drop betweenthe inlet and exhaust of the turbine is increased, which increases the amount heatavailable for conversion to mechanical power. Most of the heat liberated due tocondensation of the exhaust steam is carried away by the cooling medium (water orair) used by the surface condenser.

6. Control valvesControl valves are valves used within industrial plants and elsewhere to controloperating conditions such as temperature,pressure,flow,and liquid Level by fullypartially opening or closing in response to signals received from controllers thatcompares a set point to a process variable whose value is provided by sensorsthat monitor changes in such 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 remove dissolved gases (analternate would be the use of water treatment chemicals) from boiler feed water tomake it non-corrosive. A dearator typically includes a vertical domed deaerationsection as the deaeration boiler feed water tank. A Steam generating boiler requiresthat the circulating steam, condensate, and feed water should be devoid of dissolvedgases, particularly corrosive ones and dissolved or suspended solids. The gases willgive rise to corrosion of the metal. The solids will deposit on the heating surfacesgiving rise to localized heating and tube ruptures due to overheating. Under someconditions it may give to stress corrosion cracking.Deaerator level and pressure must be controlled by adjusting control valves- thelevel by regulating condensate flow and the pressure by regulating steam flow. If operated properly, most deaerator vendors will guarantee that oxygen in thedeaerated 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 water delivered toa steam generating boiler. Preheating the feed water reduces the irreversible


16/48




involved in steam generation and therefore improves the thermodynamic efficiencyof the system.[4] This reduces plant operating costs and also helps to avoid thermalshock to the boiler metal when the feed water is introduces back into the steam cycle.In a steam power (usually modeled as a modified Ranking cycle), feed water heatersallow the feed water 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 continuousloop of material- the conveyor Belt that rotates about them. The pulleys arepowered, moving the belt and the material on the belt forward. Conveyor belts ar eextensively used to transport industrial and agricultural material, such as grain,coal, ores etc.

9. Pulverizer

A pulverizer is a device for grinding coal for combustion in a furnace in a fossil fuelpower plant.

10. Boiler Steam Drum

Steam 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 storethe steam generated in the water tubes and act as a phase separator for thesteam/water mixture. The difference in densities between hot and cold water helpsin the accumulation of the hotter-water/and saturated steam into steam drum.Made from high-grade steel (probably stainless) and its working involvestemperatures 390C and pressure well above 350psi (2.4MPa). The separated steamis drawn out from the top section of the drum. Saturated steam is drawn off the topof the drum. The steam will re-enter the furnace in through a super heater, whilethe saturated water at the bottom of steam drum flows down to the mud-drum /feedwater drum by down comer tubes accessories include a safety valve, water levelindicator and fuse plug. A steam drum is used in the company of a mud-drum/feedwater drum which is located at a lower level. So that it acts as a sump for the sludgeor sediments which have a tendency to the bottom.

11. Super Heater

A Super heater is a device in a steam engine that heats the steam generated by theboiler again increasing its thermal energy and decreasing the likelihood that it willcondense inside the engine. Super heaters increase the efficiency of the steam engine,and were widely adopted. Steam which has been superheated is logically known assuperheated 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 powerstations.


17/48




12. EconomizersEconomizer, or in the UK economizer, are mechanical devices intended to reduceenergy consumption, or to perform another useful function like preheating 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 exchangedevices that heat fluids , usually water, up to but not normally beyond the boilingpoint of the fluid. Economizers are so named because they can make use of theenthalpy and improving the boilers efficiency. They are a device fitted to a boile rwhich saves energy by using the exhaust gases from the boiler to preheat the coldwater used the fill it (the feed water). Modern day boilers, such as those in cold firedpower stations, are still fitted with economizer which is decedents of Greensoriginal design. In this context they are turbines before it is pumped to the boilers. Acommon application of economizer is steam power plants is to capture the waste hitfrom boiler stack gases (flue gas) and transfer thus it to the boiler feed water thuslowering the needed energy input , in turn reducing the firing rates to accomplish

the rated boiler output . Economizer lower stack temperatures which may causecondensation of acidic combustion gases and serious equipment corrosion damage if care is not taken in their design and material selection.

13. Air Preheater

Air preheater is a general term to describe any device designed to heat air beforeanother process (for example, combustion in a boiler). The purpose of the airpreheater is to recover the heat from the boiler flue gas which increases the thermalefficiency of the boiler by reducing the useful heat lost in the fuel gas. As aconsequence, the flue gases are also sent to the flue gas stack (or chimney) at a lowertemperature allowing simplified design of the ducting and the flue gas stack. It alsoallows control over the temperature of gases leaving the stack.

14. Precipitator

An Electrostatic precipitator (ESP) or electrostatic air cleaner is a particulate devicethat removes particles from a flowing gas (such As air) using the force of an inducedelectrostatic charge. Electrostatic precipitators are highly efficient filtration devices,and can easily remove fine particulate matter such as dust and smoke from the airsteam.ESPs continue to be excellent devices for control of many industrial particulateemissions, including smoke from electricity-generating utilities (coal and oil fired),salt cake collection from black liquor boilers in pump mills, and catalyst collectionfrom fluidized bed catalytic crackers from several hundred thousand ACFM in thelargest coal-fired boiler application.

The original parallel plate-Weighted wire design (described above) has evolved asmore efficient ( and robust) discharge electrode designs were developed, todayfocusing on rigid discharge electrodes to which many sharpened spikes are attached ,


18/48




maximizing corona production. Transformer rectifier systems apply voltages of 50-100 Kilovolts at relatively high current densities. Modern controls minimizesparking and prevent arcing, avoiding damage to the components. Automaticrapping 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 stack

A Fuel gas stack is a type of chimney, a vertical pipe, channel or similar structure through which combustion product gases called fuel gases are exhausted to theoutside air. Fuel gases are produced when coal, oil, natural gas, wood or any otherlarge combustion device. Fuel gas is usually composed of carbon dioxide (CO2) andwater vapor as well as nitrogen and excess oxygen remaining from the intakecombustion air. It also contains a small percentage of pollutants such as particulatesmatter, carbon mono oxide, nitrogen oxides and sulfur oxides. The flue gas stacksare often quite tall, up to 400 meters (1300 feet) or more, so as to disperse the

exhaust pollutants over a greater aria and thereby reduce the concentration of thepollutants to the levels required by governmental environmental policies andregulations.When the fuel gases exhausted from stoves, ovens, fireplaces or other small sourceswithin residential abodes, restaurants , hotels or other stacks are referred to aschimneys.

C&I

(CONTROL AND INSTRUMENTATION)

I was assigned to do training in control and instrumentation from 25th June 2007 to14th July 2007

CONTROL AND INSTRUMENTATION

This division basically calibrates various instruments and takes care of any faultsoccur in any of the auxiliaries in the plant.

It has following labs:

1. MANOMETRY LAB2. PROTECTION AND INTERLOCK LAB3. AUTOMATION LAB4. WATER TREATEMENT LAB


19/48




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.

5.0 MANOMETRY LAB

5.0.1 TRANSMITTERS It is used for pressure measurements of gases and liquids, its working prin ciple is that the input pressure is converted into electrostatic capacitance and from there it isconditioned 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 devicecorresponds 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 indicatethe 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 LAB5.1.1 INTERLOCKINGIt is basically interconnecting two or more equipments so that if one equipmentsfails other one can perform the tasks. This type of interdependence is also created sothat equipments connected together are started and shut down in the specificsequence to avoid damage.For protection of equipments tripping are provided for all the equipments. Trippingcan be considered as the series of instructions connected through OR GATE. Whena fault occurs and any one of the tripping is satisfied a signal is sent to the relay,which trips the circuit. The main equipments of this lab are relay and circuitbreakers. Some of the instrument uses for protection are:1. RELAY


20/48




It is a protective device. It can detect wrong condition in electrical circuits byconstantly measuring the electrical quantities flowing under normal and faultyconditions. Some of the electrical quantities are voltage, current, phase angle andvelocity.2. FUSES

It is a short piece of metal inserted in the circuit, which melts when heavy currentflows through it and thus breaks the circuit. Usually silver is used as a fuse materialbecause:a) The coefficient of expansion of silver is very small. As a result no critical fat igueoccurs and thus the continuous full capacity normal current ratings are assured forthe long time.b) The conductivity of the silver is unimpaired by the surges of the current thatproduces temperatures just near the melting point.c) Silver fusible elements can be raised from normal operating temperature tovaporization quicker than any other material because 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 other fixed. When a faultoccurs 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. Forstarting the circuit conditions should be in series with the starting coil of theequipment to energize it. 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 from the 0.415 KV


21/48




A.C supply. The same circuit achieves both excitation and tripping. Hence thetripping coil is provided for emergency tripping if the interconnection fails.

5.2 AUTOMATION LABThis lab deals in automating the existing equipment and feeding routes.Earlier, the old technology dealt with only (DAS) Data Acquisition S ystem and cameto be known as primary systems. The modern technology or the secondary systemsare coupled with (MIS) Management Information System. But this lab universally

applies the pressure measuring instruments as the controlling force. However, therelays are also provided but they are used only for protection and interlocks.Once the measured is common i.e. pressure the control circuits can easily bedesigned with single chips having multiple applications. Another point is theuniversality of the supply, the laws of electronic state that it can be any wherebetween 12V and 35V in the plant. All the control instruments are excited by 24Vsupply (4-20mA) because voltage can be mathematically handled with ease thereforeall control systems use voltage system for computation. The latest technology is theuse of ETHERNET for control signals. 5.3 PYROMETER LAB(1) LIQUID IN GLASS THERMOMETER Mercury in the glass thermometer boils at 340 degree Celsius which limits the rangeof temperature that can be measured. It is L shaped thermometer which is designedto reach all inaccessible places.

(2) ULTRA VIOLET CENSOR This device is used in furnace and it measures the intensity of ultra violet rays thereand according to the wave generated which directly indicates the temperature in thefurnace.

(3) THERMOCOUPLESThis device is based on SEEBACK and PELTIER effect. It comprises of two

junctions at different temperature. Then the emf is induced in the circuit due to theflow of electrons. This is an important part in the plant.

(4) RTD (RESISTANCE TEMPERATURE DETECTOR)It performs the function of thermocouple basically but the difference is of aresistance. In this due to the change in the resistance the temperature difference ismeasured.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 range devices).


22/48




5.4 FURNACE SAFETY AND SUPERVISORY SYSTEM LAB This lab has the responsibility of starting fire in the furnace to enable the burning of coal. For first stage coal burners are in the front and rear of the furnace and for thesecond and third stage corner firing is employed. Unburnt coal is removed usingforced draft or induced draft fan. The temperature inside the boiler is 1100 degree

Celsius and its height is 18 to 40 m. It is made up of mild steel. An ultra violet sensoris employed in furnace to measure the intensity of ultra violet rays inside thefurnace and according to it a signal in the same order of same mV is generatedwhich directly indicates the temperature of the furnace.For firing the furnace a 10 KV spark plug is operated for ten seconds over a sp rayof diesel fuel and pre-heater air along each of the feeder-mills. The furnace has sixfeeder mills each separated by warm air pipes fed from forced draft fans. In firststage indirect firing is employed that is feeder mills are not fed directly from coalbut are fed from three feeders but are fed from pulverized coalbunkers. The furnacecan operate on the minimum feed from three feeders but under not circumstancesshould 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 various cards. It houses varioustypes of analytical instruments like oscilloscopes, integrated circuits, cards autoanalyzers etc.Various processes undertaken in this lab are:1. Transmitter converts mV to mA.2. Auto analyzer purifies the sample before it is sent to electrodes. It extracts themagnetic portion.

5.6 ANNUNCIATIN CARDSThey are used to keep any parameter like temperature etc. within limits. It gets asignal if parameter goes beyond limit. It has a switching transistor connected torelay that helps in alerting the UCB.

39. Control and Instrumentation Control and InstrumentationMeasuring Instrumentsments

In any process the philosophy of instrumentation should provide a comprehensiveintelligence feed back on the important parameters viz. Temperature, Pressure,Level and Flow. This Chapter Seeks to provide a basic understanding of theprevalent instruments used for measuring the above parameters.


23/48




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 of temperature in

a substance is due to the resultant increase in molecular activity of the substance onapplication of heat; which increases the internal energy of the material. Thereforethere exists some property of the substance, which changes with its energy content.The change may be observed with substance itself or in a subsidiary system inthermodynamic equilibrium, which is called testing body and the system itself i scalled the hot body.

Expansion Thermometer

Solid Rod Thermometers a temperature sensing - Controlling device may bedesigned incorporating in its construction the principle that some metals expand

more than others for the same temperature range. Such a device is the thermostatused with water heaters (Refer Fig. 69).


24/48




Fig No.-69 Rod Type Thermostat

The mercury will occupy a greater fraction of the volume of the container than itwill at a low temperature.Under normal atmospheric conditions mercury normally boils at a temperature of (347C). To extend the range of mercury in glass thermometer beyond this point thetop end of a thermometer bore opens into a bulb which is many times larger incapacity than the bore. This bulb plus the bore above the mercury, is then filledwith nitrogen or carbon dioxide gas at a sufficiently high pressure to prevent boilingat the highest temperature 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 industrial practices. This fact is obvious by the delicatenature of glass also the position of the measuring element is not always the bestposition to read the result. Types of Hg in Steel Thermometers are:

Bourdon Tube y Most common and simplest type (Refer Fig. 71)

Spiral typey

More sensitive and used where compactness is necessary

Helical Type y Most sensitive and compact. Pointer may be mounted direct on end of helixWhich rotates, thus eliminating backlash and lost motion?Linkages, which only allow the pointer to operate over a selected range of pressureto either side of the normal steam pressure. (Refer Fig No.77)


25/48




Dewrance Critical Pressure Gauge Measurement of Level

Direct Methods

'Sight Glass' is used for local indication on closed or open vessels. A sight glass is atube of toughened glass connected at both ends through packed unions and vessel.The liquid level will be the same as that in the vessel. Valves are provided forisolation and blow down."Float with Gauge Post" is normally used to local indication on closed or openvessels."Float Operated Dial" is used for small tanks and congested areas. The float arm isconnected to a quadrant and pinion which rotates the pointer over a scale.


26/48




Bourden Pressure Gauge a Bourdon pressure gauge calibrated in any fact head isoften connected to a tank at or near the datum level."Mercury Manometer" is used for remote indication of liquid level. The workingprinciple is the same as that of a manometer one limp of a U-tube is connected to thetank, the other being open to atmosphere. The manometer liquid must not mix withthe liquid in the vessel, and where the manometer is at a different level to the vessel,the static head must be allowed in the design of the manometer.'Diaphragm Type' is used for remote level indication in open tanks or docks etc. Apressure change created by the movement of a diaphragm is proportional to achange in liquid level above the diaphragm. This consists of a cylindrical box with arubber or plastic diaphragm across its open end as the level increases .the liquidpressure on the diaphragm increases and the air inside is compressed. This pressureis transmitted via a capillary tube to an indicator or recorder incorporating apressureMeasuring element.

Sealed Capsule Type The application and principle is the same as for the diaphragmbox. In this type, a capsule filled with an inert gas under a slight pressure is exposedto the pressure due to the head of liquid and is connected by a capillary to anindicator. In some cases the capsule is fitted external to the tank and is so arrangedthat it can be removed whilst the tank is still full, a spring loaded valveautomatically shutting off the tapping point.Air Purge System This system provides the simplest means of obtaining anindication of level, or volume, at a reasonable distance and above or below, theliquid being measured. The pressure exerted inside an open ended tube below thesurface of a liquid is proportional to the depth of the liquid


27/48




The Measurement of Flow

Two principle measurements are made by flow m eters viz. quantity of flow and rateof flow. 'Quantity of flow' is the quantity of fluid passing a given point in a giventime, i.e. gallons or pounds. Rate of flow' is the speed of. a fluid passing a givenpoint at a given instant and is proportional to quantity passing at a given instant, i.e.gallons per minute or pounds per hour. There are two groups of measuring devices:-

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

Inferential, which measures the velocity of the flow and the volume passed isinferred, it being equal to the velocity times the cross sectional area of the flow. Theinferential type is the most widely used.

Measurement of Fluid Flow through Pipes:

"The Rotating Impeller Type" is a positive type device which is used for mediumquantity flow measurement i.e., petroleum and other commercial liquids. It consistsof Two fluted rotors mounted in a liquid tight case fluid flow and transmitted to acounter.


28/48




Rotating Oscillating Piston Type This is also a positive type device and is used formeasuring low and medium quantity flows, e.g. domestic water supplies. Thisconsists of a brass meter body into which is fitted a machined brass workingchamber and cover, containing a piston made of ebonite. This piston acts as amoving chamber and transfers a definite volume of fluid from the inlet to the outlet

for each cycle.Helical Vane Type For larger rates of flow, a helical vane is mounted centrally in thebody of the meter. The helix chamber may be vertical or horizontal and is geared toa counter. Usually of pipe sizes 3" to 10" Typical example is the Kent Torrent M eter.Turbine Type this like the helical Vane type is a inference type of device used forlarge flows with the minimum of pressure drop. This consists of a turbine or drumrevolving in upright bearings, retaining at the top by a collar. Water enters thedrumfrom the top and leaves tangentially casings to rotate at a speed dependent upon thequantity of water passed. The cross sectional area of the meter throughout is equalto

the area of the inlet and outlet pipes and is commonly used on direct supply watermains,Combination Meters this is used for widely fluctuating flows. It consists of a largermeter (helical, turbine or fan) in the main with a small rotary meter or suitable typein abypass. Flow is directed into either the main or bypass according to the quantity of flowby an automatic valve. By this means flows of 45 to 40,000 gallons per hour can bemeasured.

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

A formula relates the rate of flow to the height and is dependent upon the design of theVenturi Flumes The head loss caused by the weir flow meter is considerable and itsconstruction is sometimes complicated, therefore the flume is sometimes used. Theprinciple is same as that of venture except that the rate of flow is proportional to thedepth of the liquid in the upstream section. It consists of a local contraction in thecrosssection of flow through a channel in the shape of a venturi. It is only necessary to


29/48




measure the depth of the upstream section which is a measure of the rate of flow.Thismay be done by pressure tapping at the datum point or by a float in an adjacentlevelchamber.

Pressure Difference Flow meters These are the most widely used type of flow metersince they are capable of measuring the flow of all industrial fluids passing throughpipes. They consists of a primary element inserted in the pipeline which generates adifferential pressure, ^he magnitude of which is proportional to the square of the rate of flow and a secondary element 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 quantity of fluid or gas flowingis proportional to the square root of the differential pressure. There are fourprincipal types of primary elements (or restrictions) as enumerate below:Venturi; This is generally used for medium and high quantity fluid flow and itconsists of two hollow truncated cones, the smaller diameters of which areconnected together by a short length of parallel pipe, the smallest diameter of thetube formed by this length of parallel pipe is known as the throat section and thelower of the two pressures, (the throat, or downstream pressure) is measured here.Orifice Plate This is the oldest and most common form of pressure differentialdevice. In its simplest form it consists of a thin metal plate with a central holdclamped between two pipe flanges. In the metering of dirty fluids or fluidscontaining solids the hole is placed so that its lower edge coincides with the insidebottom of the pipe. (Refer Fig.80) It is essential that the leading edge of the hole isabsolutely sharp rounding or burring would have a very marked effect on the flow.


30/48




Fig No.-80 Typical Orifice Plate Pressure Tapping

EMD I

Electri cal Maintenance division I

I was assigned to do training in Electrical maintenance division I from 17th July2007 to 28th July 2007.

This two week of training in this division were divided as follows.


31/48




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 motors4. Switchgear

1. 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 fan s 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


32/48




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 2,3,4,5 and 1 w hereas thelatter supplies coal to units 4 and V.O.C.H.P. supplies coal to second and thirdstages 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, 1480RPM. This motor turns the wagon by 135 degrees and coal falls directly on theconveyor through vibrators. Tippler has raised lower system which enables is toswitch off motor when required till is wagon back to its original position. It is titledby weight balancing principle. The motor lowers the hanging balancing weights,which in turn tilts the conveyor. Estimate of the weight of the conveyor is madethrough hydraulic weighing machine.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 aspeed 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. Fewconveyors are double belt, this is done for imp. Conveyors so that if a belt developsany problem the process is not stalled. The conveyor belt has a switch after every25-30 m on both sides so stop the belt in case of emergency. The conveyors are 1mwide, 3 cm thick and made of chemically treated vulcanized rubber. The maxangular elevation of conveyor is designed 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 themotor is on the motor may burn. So to protect this switch checks the speed of thebelt and switches off the motor when speed is zero.

4. Metal Separators: - As the belt takes coal to the crusher, No metal pieces shouldgo along with coal. To achieve this objective, we use metal separators. When coal isdropped to the crusher hoots, the separator drops metal pieces ahead of coal. It has


33/48




a magnet and a belt and the belt is moving, the pieces are thrown away. Thecapacity 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 transfer5. Crusher: - Both the plants use TATA crushers powered by BHEL. Motors. Thecrusher is of ring type and motor ratings are 400 HP, 606 KV. Crusher is designed

to 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 of 20mm size to go directly to RC bunker, larger particles are sent to crushes. Thisleads to frequent clogging. NCHP uses a technique that crushes the larger of hardersubstance 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. perboiler. 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. Thequantity of raw coal fed in mill can be controlled by speed control of aviator drivecontrolling damper and aviator change.

3. Ball Mill: - The ball mill crushes the raw coal to a certain height and then allowsit to fall down. Due to impact of ball on coal and attraction as per the particles moveover each other as well as over the Armor lines, the coal gets crushed. Largeparticles are broken by impact and full grinding is done by attraction. The Dryingand grinding option takes place simultaneously inside the mill.

4. Classifier:- It is an equipment which serves separation of fine pulverized coalparticles medium from coarse medium. The pulverized coal along with the carryingmedium strikes the impact plate through the lower part. Large particles are thentransferred to the ball 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 frombunker of one system to bunker of other system. It can be operated in bothdirections.

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


34/48




(a) ID Fans: - Located between electrostatic precipitator and chimney.Type-radicalSpeed-1490 rpmRating-300 KWVoltage-6.6 KV

Lubrication-by oil

(b) FD Fans: - Designed to handle secondary air for boiler. 2 in number and provideignition of coal.

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

(c)Primary Air Fans: - Designed for handling the atmospheri c air 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 oilType of operation-continuous

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

Motor specification squirrel cage induction motorRating-340 KWVoltage-6600KVCurreen-41.7ASpeed-980 rpmFrequency-50 HzNo-load current-15-16 A

NCHP

1. Wagon Tippler:-

Motor Specification(i) H.P 75 HP(ii) Voltage 415, 3 phase(iii) Speed 1480 rpm(iv) Frequency 50 Hz


35/48




(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, 11B

12A, 12B13A, 13B14A, 14B15A, 15B16A, 16B17A, 17B18A, 18B

4. Transfer Point 6

5. Breaker House

6. Rejection House

7. Reclaim House

8. Transfer Poi nt 7

9. Crusher House

10. Exit

The coal arrives in wagons via railways and is tippled by the wagon tipplers into thehoppers. If coal is oversized (>400 mm sq) then it is broken manually so that itpasses the hopper mesh. From the hopper mesh it is taken to the transfer point TP6by conveyor 12A ,12B which takes the coal to the breaker house , which renders thecoal size to be 100mm sq. the stones which are not able to pass through the 100mmsq of hammer are rejected via conveyors 18A,18B to the rejection house . Extra coalis to sent to the reclaim hopper via conveyor 16. From breaker house coal is taken tothe TP7 via Conveyor 13A, 13B. Conveyor 17A, 17B also supplies coal from reclaim


36/48




hopper, From TP7 coal is taken by conveyors 14A, 14B to crusher house whosefunction is to render the size of coal to 20mm sq. now the conveyor labors arepresent whose function is to recognize and remove any stones moving in theconveyors . In crusher before it enters the crusher. After being crushed, if any metalis still present it is taken care of by metal detectors 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 sw itched onto no load. Isolation is normally used in various ways for purpose of isolating acertain portion when required for maintenance.

2. Switching Isolation: - It is capable of doing things like interrupting transformermagnetized current, interrupting line charging current and even perform load

transfer switching. The main application of switching isolation is in connection withtransformer feeders as unit makes it possible to switch out one transformer whileother is still on load.

3. Circuit Breakers: - One which can make or break the circuit on load and even onfaults is referred to as circuit breakers. This equipment is the most important and isheavy duty equipment mainly utilized for protection of various circuits andoperations on load. Normally circuit breakers installed are accompanied byisolators

4. Load Break Switches: - These are those interrupting devices which can make orbreak circuits. These are normally on same circuit, which are backed by circuitbreakers.

5. Earth Switches: - Devices which are used normally to earth a particular system,to avoid any accident happening due to induction on account of live adjoiningcircuits. These equipments do not handle any appreciable current at all. Apart fromthis equipment there are a number of relays etc. which are used in switchgear.

LT Switchgear

It is classified in following ways:-

1. Main Switch:- Main switch is control equipment which controls or disconnectsthe 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 power stationsextremely heavy carnets would flow in the fault and the fuse clearing the fault wouldbe required to withstand extremely heavy stress in process.


37/48




It is used for supplying power to auxiliaries with backup fuse protection. Rotaryswitch up to 25A. With fuses, quick break, quick make and double break switchfuses for 63A and 100A, switch fuses for 200A, 400A, 600A, 800A and 1000A areused.

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

4. Overload Relay: - For overload protection, thermal over relay are best suite d forthis purpose. They operate due to the action of heat generated by passage of currentthrough relay element.

5. Air Circuit Breakers: - It is seen that use of oil in circuit breaker may cause a fire.So in all circuits breakers at large capacity air at high pressure is used which ismaximum at the time of quick tripping of contacts. This reduces the possibility of

sparking. The pressure may vary from 50-60 kg/cm^2 for high and mediumcapacity circuit breakers.

HT SWITCH GEAR:-

1. Minimum oil Circuit Breaker: - These use oil as quenching medium. It comprisesof simple dead tank row pursuing projection from it. The moving contracts arecarried on an iron arm lifted by a long insulating tension rod and are closedsimultaneously pneumatic operating mechanism by means of tensions but throw off spring to be provided at mouth of the control the main current within the controlleddevice.

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 pressure around 15 kg per cm^2is used for extinction of arc caused by flow of air around the moving circuit . Thebreaker is closed by applying pressure at lower opening and opened by applyingpressure at upper opening. When contacts operate, the cold air rushes around themovable contacts and blown the arc.


38/48




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 short and consistent.

iv. Facility for frequent operation since the cooling medium is replaced constantly.Rated Voltage-6.6 KVCurrent-630 AAuxiliary current-220 V/DC

3. SF6 Circuit Breaker: - This type of circuit breaker is of construction to dead tank bulk oil to circuit breaker but the principle of current interruption is similar o thatof air blast circuit breaker. It simply employs the arc extinguishing medium namelySF6. the performance of gas . When it is broken down under an electrical stress. Itwill quickly reconstitute 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 that vacuum is used to savethe purpose of insulation and it implies that pr. Of gas at which breakdown voltageindependent of pressure. It regards of insulation and strength, vacuum is superiordielectric medium and is better that all other medium except air and sulphur whichare generally used at high pressure. Rated frequency-50 Hz Rated making Current-10 Peak KA Rated Voltage-12 KV


39/48




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 I I

Electrical Maintenance division II

I was assigned to do training in Electrical maintenance division II from 31st July2007 to 11th August 2007.This two week of training in this division were divided as follows.


40/48




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 AuxiliariesGenerator Fundamentals Fundamentals

The transformation of mechanical energy int o electrical energy is carried out by theGenerator. This Chapter seeks to provide basic understanding about the workingprinciples and development of Generator.

Working Principle

The A.C. Generator or alternator is based upon the principle of electromagneticinduction and consists generally of a stationary part called stator and a rotatingpart called rotor. The stator housed the armature windings. The rotor houses thefield windings. D.C. voltage is applied to the field windings through slip rings. Whenthe rotor is rotated, the lines of magnetic flux (viz magnetic field) cut through thestator windings. 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 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 polesincreases with decrease in speed and vice versa. Therefore, low speed hydro turbinedrives generators have 14 to 20 poles where as high speed steam turbine driven


41/48




generators have generally 2 poles. Pole rotors are used in low speed generators,because the cost advantage as well as easier construction.

Development

The first A.C. Generator concept was enunciated by Michael Faraday in 1831. In1889 Sir Charles A. Parsons developed the first AC turbo-generator. Although slowspeed 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 andimproved 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 theorder of 30 to 50 MW at 3000 rpm.During the war, the development and installation of power plants was delayed andin order to catch up with the delay in plant installation, a large number of 30 MWand 60 MW at 3000 rpm units were constructed during the years immediatelyfollowing the war. The changes in design in this period were relatively small.In any development programme the. Costs of material and labour involved inmanufacturing and erection must be a basic consideration. Coupled very closelywiththese considerations is the restriction is size and weight imposed by transportlimitations.

Development of suitable insulating materials for large turbo-generators is one of themost important tasks and need continues watch as size and ratings of machinesincrease. The present trend is the use only class "B" and higher grade materials andextensive work has gone into compositions of mica; glass and asbestos withappropriate bonding material. An insulation to meet the stresses in generator slotsmustfollow very closely the thermal expansion of the insulated conductor withoutcracking orany plastic deformation. Insulation for rotor is subjected to lower dielectric stressbutmust withstand high dynamic stresses and the newly developed epoxy resins, glassand/or asbestos molded in resin and other synthetic resins are finding wideapplications.

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


42/48




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 per minute. The problem of

guaranteeing the dynamic strength and operating stability of such a rotor iscomplicatedby the fact that a massive non-uniform shaft subjected to a multiplicity of differentialstresses must operate in oil lubricated sleeve bearings supported by a structure mounted on foundations all of which possess complex dynamic be behavior peculiar

Date post:	07-Apr-2018
Category:	Documents
Upload:	kumarshubham3052
View:	225 times
Download:	0 times

report-N.T.P.C. BADARPUR

Documents