Mohit Malik, Archit Arora

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SIX WEEKS INDUSTRIAL TRAININGAT

NATIONAL THERMAL POWER CORPORATION

NEW DELHI

A Training ReportSubmitted in Partial Fulfillment of the

Requirements

For the Award of the Degree of

BACHELOR OF ENGINEERINGIN

ELECTRICAL AND ELECTRONICSTO

GURU GOBIND SINGH INDRAPRASTHA

UNIVERSITYNEW DELHI

BYMOHIT MALIK

(02415004909-Vth SEM)

DEPARTMENT OF ELECTRICAL ENGINEERINGMAHARAJA SURAJMAL INSTITUTE OF TECHNOLOGY


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NEW DELHI-110058November,2011

ACKNOWLEDGMENT

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(DGM,HR) 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-operationand guidance that helped me a lot during the course of training. I have learnt a lotworking under them and I will always be indebted of them for this value addition in me.

I would also like to thank the training in charge of Maharaja Surajmal Institute ofTechnology and all the faculty member of Electrical & Electronics department for theireffort of constant co-operation. Which have been significant factor in theaccomplishment of my industrial training.

[Type text] [Type text]


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CONTENTS

1. Introduction 1-10 NTPC 1 Badarpur Thermal Power Station 4

2. Operation 11-15

3. Electrical Maintenance Division-I 16-24 HT/LT Motors, Turbine & Boilers Side 16 CHP/NCHP 17 HT/LT Switch Gear 21

4. Electrical Maintenance Division-II 25-31 Generator 25 Transformer & Switchyard 29

5. Control & Instrumentation 32-43 Manometry Lab 32 Protection and interlock Lab 33 Automation Lab 34 Furnace Safeguard Supervisory System 42



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Training at BTPS

I was appointed to do six-week training at this esteemed organization from 13th June to

23rd july 2011. In these six 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 six-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 our dailyrequirements of life, is produced.

This report has been made by self-experience at BTPS. The material in this report has

been gathered from my textbooks, senior student report, and trainer manual provided by

training department. The specification & principles are at learned by me from the

employee of each division of BTPS.



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ABOUT NTPCNTPC Limited is the largest thermal power generating company of India. A public sector

company, it was incorporated in the year 1975 to accelerate power development in the

country as a wholly owned company of the Government of India. At present,

Government of India holds 89.5% of the total equity shares of the company and FIIs,Domestic Banks, Public and others hold the balance 10.5%. With in a span of 31 years,

NTPC has emerged as a truly national power company, with power generating facilities

in all the major regions of the country.

POWER GENERATION IN INDIA

NTPCs core business is engineering, construction and operation of power generating

plants. It also provides consultancy in the area of power plant constructions and power

generation to companies in India and abroad. As on date the installed capacity of NTPC

is 27,904 MW through its 15 coal based (22,895 MW), 7 gas based (3,955 MW) and 4

Joint Venture Projects (1,054 MW). NTPC acquired 50% equity of the SAIL PowerSupply Corporation Ltd. (SPSCL). This JV Company operates the captive power plants

of Durgapur (120 MW), Rourkela (120 MW) and Bhilai (74 MW). NTPC also has 28.33%

stake in Ratnagiri Gas & Power Private Limited (RGPPL) a joint venture company

between NTPC, GAIL, Indian Financial Institutions and Maharashtra SEB Co Ltd.



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NTPC has set new benchmarks for the power industry both in the area of power plant

construction and operations. Its providing power at the cheapest average tariff in the

country.

NTPC is committed to the environment, generating power at minimal environmental cost

and preserving the ecology in the vicinity of the plants. NTPC has undertaken massive a

forestation in the vicinity of its plants. Plantations have increased forest area and

reduced barren land. The massive a forestation by NTPC in and around its

Ramagundam Power station (2600 MW) have contributed reducing the temperature in

the areas by about 3c. NTPC has also taken proactive steps forash utilization. In 1991,

it set up Ash Utilization DivisionA "Centre for Power Efficiency and Environment Protection (CENPEEP)" has been

established in NTPC with the assistance of United States Agency for International

Development. (USAID). Cenpeep is efficiency oriented, eco-friendly and eco-nurturing

initiative - a symbol of NTPC's concern towards environmental protection and continued

commitment to sustainable power development in India.

As a responsible corporate citizen, NTPC is making constant efforts to improve the

socio-economic status of the people affected by its projects. Through its Rehabilitation

and Resettlement programmes, the company endeavors to improve the overall socio

economic status Project Affected Persons.

NTPC was among the first Public Sector Enterprises to enter into a Memorandum ofUnderstanding (MOU) with the Government in 1987-88. NTPC has been placed under

the 'Excellent category' every year since the MOU system became operative.

http://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.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.shtmlhttp://www.ntpc.co.in/operations/operations.shtml


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ABOUT BADARPUR THERMAL POWER STATION

MAIN GENERATOR

MAIN TURBINE DATA


Maximum continuous KVA rating 24700KVAMaximum continuous KW 210000KW

Rated 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 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)


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ELECTRICITY FROM COAL

Coal from the coal wagons is unloaded with the help of wagon tipplers in the C.H.P. thiscoal 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 in the

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 sent to pre

heaters while a part goes to the mill for temperature control. Atmospheric air from F.D

fan in the air heaters and sent to the furnace as combustion air.

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

Water from the drum passes through the down comers and goes to the bottom ringheader. 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 water wall tubes. This steam

and water mixture is again taken to the boiler drum where the steam is sent to super

heaters for super heating. The super heaters are located inside the furnace and the

steam is super heated (540 degree Celsius) and finally it goes to the turbine.

Fuel gases from the furnace are extracted from the induced draft fan, which maintains

balance draft in the furnace with F.D fan. These fuel gases heat energy to the various

super heaters and finally through air pre heaters and goes to electrostatic precipitators

where the ash particles are extracted. This ash is mixed with the water to from slurry is

pumped to ash period.

The steam from boiler is conveyed to turbine through the steam pipes and through stop

valve and control valve that automatically regulate the supply of steam to the turbine.

Stop valves and controls valves are located in steam chest and governor driven from

main turbine shaft operates the control valves the amount used.

Steam from controlled valves enter high pressure cylinder of turbines, where it passes


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/hour1. For cooling water temperature (degree Celsius) 24,27,30,331.Reheated steam pressure at inlet of interceptor valvein kg/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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through the ring of blades fixed to the cylinder wall. These act as nozzles and direct the

steam into a second ring of moving blades mounted on the disc secured in the turbine

shaft. The second ring turns the shaft as a result of force of steam. The stationary and

moving blades together.

THERMAL POWER PLANTA Thermal Power Station comprises all of the equipment and a subsystem required to

produce electricity by using a steam generating boiler fired with fossil fuels or befouls to

drive an electrical generator. Some prefer to use the term ENERGY CENTER because

such facilities convert forms of energy, like nuclear 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 the united state; While POWER

STATION prevails in many Commonwealth countries and 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 station

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

8. Intermediate pressure steam turbine9. Steam control valve10. High pressure steam turbine11. Deaerator Feed water heater12. Coal conveyor13. Coal hopper14. Coal pulverizer15. boiler steam drum16. Bottom ash hoper17. Super heater

18. Forced draught(draft) fan19. Reheater20. Combustion air intake21. Economizer22. Air preheater23. Precipitator



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24. Induced draught(draft) fan25. Fuel gas stackThe description of some of the components written above is described as follows:

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

to near the ambivalent web-bulb air temperature. Cooling tower use evaporation of

water to reject heat from processes such as cooling the circulating water used in oil

refineries, Chemical plants, power plants and building cooling, for example. The tower

vary in size from small roof-top units to very large hyperboloid structures that can be up

to 200 meters tall and 100 meters in diameter, or rectangular structure that can be over

40 meters tall and 80 meters long. Smaller towers are normally factory built, while larger

ones are constructed on site.

The primary use of large , industrial cooling tower system is to remove the heat

absorbed in the circulating cooling water systems used in power plants , petroleumrefineries, petrochemical and chemical plants, natural gas processing plants and other

industrial facilities . The absorbed heat is rejected to the atmosphere by the evaporation

of some of the cooling water in mechanical forced-draft or induced draft towers or in

natural draft hyperbolic shaped cooling towers as seen at most nuclear power plants.

2.Three phase transmission lineThree phase electric power is a common method of electric power transmission. It is atype of polyphase system mainly used to power motors and many other devices. A

Three 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 in timeby one-third and two-third of one cycle of the electrical current. This delay betweenphases has the effect of giving constant power transfer over each cycle of the currentand 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 ofelectric currents, one from each electromagnetic coil or winding of the generator. Thecurrent are sinusoidal functions of time, all at the same frequency but offset in time togive 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 that rangesfrom hundreds of volts to 30,000 volts. At the power station, transformers: step-up thisvoltage to one more suitable for transmission.

3.Electrical generatorAn Electrical generator is a device that converts kinetic energy to electrical energy,



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generally using electromagnetic induction. The task of converting the electrical energyinto mechanical energy is accomplished by using a motor. The source of mechanicalenergy may be a reciprocating or turbine steam engine, , water falling through theturbine are made in a variety of sizes ranging from small 1 hp (0.75 kW) units (rare)used as mechanical drives for pumps, compressors and other shaft 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 power stations to drive thegenerators or alternators, which produce electricity. The turbines themselves are drivenby steam generated in Boilers or steam generators as they are sometimes called.Electrical power station use large stem turbines driving electric generators to producemost (about 86%) of the worlds electricity. These centralized stations are of two types:fossil fuel power plants and nuclear power plants. The turbines used for electric powergeneration are most often directly coupled to their-generators .As the generators mustrotate at constant synchronous speeds according to the frequency of the electric powersystem, the most common speeds are 3000 r/min for 50 Hz systems, and 3600 r/min for

60 Hz systems. Most large nuclear 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 into rotational energy as itpasses through the turbine. The turbine normally consists of several stage with eachstages consisting of a stationary blade (or nozzle) and a rotating blade. Stationaryblades convert the potential energy of the steam into kinetic energy into forces, causedby pressure drop, which results in the rotation of the turbine shaft. The turbine shaft isconnected to a generator, which produces the electrical energy.

4.Boiler feed water pump

A Boiler feed water pump is a specific type of pump used to pump water into a steamboiler. The water may be freshly supplied or retuning condensation of the steamproduced by the boiler. These pumps are normally high pressure units that use suctionfrom a condensate return system and can be of the centrifugal pump type or positivedisplacement 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, toforce the water into the boiler; the pump must generate sufficient pressure to overcomethe steam pressure developed by the boiler. This is usually accomplished through theuse of a centrifugal pump.Feed water pumps usually run intermittently and are controlled by a float switch or othersimilar level-sensing device energizing the pump when it detects a lowered liquid levelin the boiler is substantially increased. Some pumps contain a two-stage switch. Asliquid lowers to the trigger point of the first stage, the pump is activated. I f the liquidcontinues to drop (perhaps because the pump has failed, its supply has been cut off orexhausted, or its discharge is blocked); the second stage will be triggered. This stagemay switch off the boiler equipment (preventing the boiler from running dry and



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overheating), trigger an alarm, or both.

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

such as power plants also required feed water pumps. In this situation, though, thepump 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 initial chargeof water into the boiler(before steam power was available to operate the steam-poweredfeed water pump).the pump was often a positive displacement pump that had steamvalves and cylinders at one end and feed water cylinders at the other end; no crankshaftwas required.In thermal plants, the primary purpose of surface condenser is to condense the exhauststeam from a steam turbine to obtain maximum efficiency and also to convert theturbine exhaust steam into pure water so that it may be reused in the steam generatoror boiler as boiler feed water. By condensing the exhaust steam of a turbine at a

pressure below atmospheric pressure, the steam pressure drop between the inlet andexhaust of the turbine is increased, which increases the amount heat available forconversion to mechanical power. Most of the heat liberated due to condensation of theexhaust steam is carried away by the cooling medium (water or air) used by the surfacecondenser.

6. Control valvesControl valves are valves used within industrial plants and elsewhere to controloperating conditions such as temperature,pressure,flow,and liquid Level by fully partially

opening or closing in response to signals received from controllers that compares a setpoint to a process variable whose value is provided by sensors that monitor changesin such conditions. The opening or closing of control valves is done by means ofelectrical, hydraulic or pneumatic systems

7. DeaeratorA Dearator is a device for air removal and used to remove dissolved gases (an alternatewould be the use of water treatment chemicals) from boiler feed water to make it non-corrosive. A dearator typically includes a vertical domed deaeration section as thedeaeration boiler feed water tank. A Steam generating boiler requires that the circulatingsteam, condensate, and feed water should be devoid of dissolved gases, particularlycorrosive ones and dissolved or suspended solids. The gases will give rise to corrosionof the metal. The solids will deposit on the heating surfaces giving rise to localizedheating and tube ruptures due to overheating. Under some conditions it may give tostress corrosion cracking.Deaerator level and pressure must be controlled by adjusting control valves- the levelby regulating condensate flow and the pressure by regulating steam flow. If operatedproperly, most deaerator vendors will guarantee that oxygen in the deaerated water will



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Economizer, or in the UK economizer, are mechanical devices intended to reduceenergy consumption, or to perform another useful function like preheating a fluid. Theterm economizer is used for other purposes as well. Boiler, power plant, and heating,ventilating and air conditioning. In boilers, economizer are heat exchange devices thatheat fluids , usually water, up to but not normally beyond the boiling point of the fluid.

Economizers are so named because they can make use of the enthalpy and improvingthe boilers efficiency. They are a device fitted to a boiler which saves energy by usingthe exhaust gases from the boiler to preheat the cold water used the fill it (the feedwater). Modern day boilers, such as those in cold fired power stations, are still fitted witheconomizer which is decedents of Greens original design. In this context they areturbines before it is pumped to the boilers. A common application of economizer issteam power plants is to capture the waste hit from boiler stack gases (flue gas) andtransfer thus it to the boiler feed water thus lowering the needed energy input , in turnreducing the firing rates to accomplish the rated boiler output . Economizer lower stacktemperatures which may cause condensation of acidic combustion gases and seriousequipment corrosion damage if care is not taken in their design and material selection.

13. Air PreheaterAir 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 air preheateris to recover the heat from the boiler flue gas which increases the thermal efficiency ofthe boiler by reducing the useful heat lost in the fuel gas. As a consequence, the fluegases are also sent to the flue gas stack (or chimney) at a lower temperature allowingsimplified design of the ducting and the flue gas stack. It also allows control over thetemperature of gases leaving the stack.

14. Precipitator

An Electrostatic precipitator (ESP) or electrostatic air cleaner is a particulate device thatremoves particles from a flowing gas (such As air) using the force of an inducedelectrostatic charge. Electrostatic precipitators are highly efficient filtration devices, andcan easily remove fine particulate matter such as dust and smoke from the air steam.ESPs continue to be excellent devices for control of many industrial particulateemissions, including smoke from electricity-generating utilities (coal and oil fired), saltcake collection from black liquor boilers in pump mills, and catalyst collection fromfluidized bed catalytic crackers from several hundred thousand ACFM in the largestcoal-fired boiler application.The original parallel plate-Weighted wire design (described above) has evolved as moreefficient ( and robust) discharge electrode designs were developed, today focusing onrigid discharge electrodes to which many sharpened spikes are attached , maximizingcorona production. Transformer rectifier systems apply voltages of 50-100 Kilovolts atrelatively high current densities. Modern controls minimize sparking and prevent arcing,avoiding damage to the components. Automatic rapping systems and hopperevacuation systems remove the collected particulate matter while on line allowing ESPsto stay in operation for years at a time.

15. Fuel gas stack[Type text] [Type text]


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A Fuel gas stack is a type of chimney, a vertical pipe, channel or similar structurethrough which combustion product gases called fuel gases are exhausted to the outsideair. Fuel gases are produced when coal, oil, natural gas, wood or any other largecombustion device. Fuel gas is usually composed of carbon dioxide (CO2) and watervapor as well as nitrogen and excess oxygen remaining from the intake combustion air.

It also contains a small percentage of pollutants such as particulates matter, carbonmono oxide, nitrogen oxides and sulfur oxides. The flue gas stacks are often quite tall,up to 400 meters (1300 feet) or more, so as to disperse the exhaust pollutants over agreater aria and thereby reduce the concentration of the pollutants to the levels requiredby governmental environmental policies and regulations.When the fuel gases exhausted from stoves, ovens, fireplaces or other small sourceswithin residential abodes, restaurants , hotels or other stacks are referred to aschimneys.

ELECTRICITY GENERATION PROCESS

At NTPC (Badarpur) the mIan two paths are the flue gas or air cycle and steam orcondensate paths.

CAPITAL OVERHAULNTPC has been in news due to extensive load sheds in many areas in delhi and themain cause behind these load sheds was the capital overhaul of one of 210 MW units.Unit IV was under an extensive check , which has caused shut down of the plant andthe plant, was dismantled completely to change the old parts and cleaning up the wholeunit. But capital overhaul has no meaning because such a deep checking of the planthappens once in five to seven years.

HOW ELECTRICITY IS GENERATED?Thermal power station burns fuel and uses the resultant heat to raise steam whichdrives the TURBO GENERATOR. The fuel may be fossil(coal,oil,natural gas) or it maybe fissionable, whichever fuel is used, the objective is same to convert the mechanicalenergy into electricity by rotating a magnet inside a set of winding.

COAL TO STAEMIts other raw materials are air and water. The coal brought to the station by trainsor by other means, travels handling plant by conveyer belts, travels frompulverizing mills, which grind it as fine as the face powder of size upto 20 microns.

The finely produced coal mixed with preheated air is then blown into the boiler by afan called primary air fan where it burns more like a gas than as a solid, in the

conventional domestic or industrial grate, with additional amount of air, calledsecondary air supply, by forced draft fan.As coal is ground so finally the resultant ash is also a fine powder. Some of it bindstogether to form pumps, which falls into ash pits at the bottom of the furnace. Thewater-quenched ash from the bottom is conveyed to pits for subsequent disposal orsale. Most of ash, still in fine partical form is carried out of boilers to the precipitatoras dust, where electrodes charged with high voltage electricity trap it. The dust is



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then conveyed to water to disposal area or to bunker for sale while the clean fluegases are passed on through IP fans to be discharged through chimneys.

The heat released from the coal has been absorbed by the many kilometers tubingwhich line the boiler walls. Inside the tubes the boiler feed water, which istransformed by heat into staemat high temperature and pressure.. The steamsuperheated in further tubes (superheaters) passes to turbine where it is discharged

through the nozzle on the turbine blades. Just as the energy of wind turns the sail ofthe windmill, the energy of steam striking the blade makes the turbine rotate.Coupled to the end of the turbine is the rotor of the generator. The rotor is housedinside the stator having heavy coils of the bars in which electricity is producedthrough the movement of magnetic field created by the rotor. Electricity passesfrom stator windings to step-up transformer which increases its voltage so that itcan be transmited efficiently over lines of grid.

The staem which has given up its heat energy is cahnged back into water in acondenser so that it is ready for re-use. The condenser contains many kilometers oftubing through which cold water is constantly pumped. The staem passing aroundthe tubes looses heat.Thus it is rapidly changed back into water.But, the two lots of water, that is, the boiler feed and cooling water must never mix.

Cooling water is drawn from river- bed, but the boiler feed water must be absolutelypure, far purer than the water we drink(de-mineralized water), otherwise it maydamage the boiler tubes.

TABLES OF CYCLES

COAL CYCLE



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CONDENSATE CYCLE



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FEED WATER CYCLE



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STEAM CYCLE



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EMD IElectrical Maintenance division I

I was assigned to do training in Electrical maintenance division I from 13th Jun 2011 to18th June 2011.

EMD-I is divided as follows :HT/LT switchgearHT/LT Motors, Turbine &Boiler sideCHP/NCHP Electrical

Electrical maintenance division 1It is responsible for maintenance of:

1. Boiler side motors2. Turbine side motors

3. Outside motors4. Switchgear

1. Boiler side motors:

For 1, units 1, 2, 31.1D 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.



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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 whereas the latter

supplies coal to units 4 and V.O.C.H.P. supplies coal to second and third stages in the

advent coal to usable form to (crushed) form its raw form and send it to bunkers, from

where it is send to furnace.

Major Components

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

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

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

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

the conveyor. Estimate of the weight of the conveyor is made through 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 a

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

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

conveyors are double belt, this is done for imp. Conveyors so that if a belt develops any

problem the process is not stalled. The conveyor belt has a switch after every 25-30 mon both sides so stop the belt in case of emergency. The conveyors are 1m wide, 3 cm

thick and made of chemically treated vulcanized rubber. The max angular 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 the belt

and switches off the motor when speed is zero.

4. Metal Separators: - As the belt takes coal to the crusher, No metal pieces should goalong with coal. To achieve this objective, we use metal separators. When coal is

dropped to the crusher hoots, the separator drops metal pieces ahead of coal. It has a

magnet and a belt and the belt is moving, the pieces are thrown away. The capacity of

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



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practically only 300-400 tons coal is transfer

5. 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 oftransfer via conveyor.

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

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

substance like metal impurities easing the load on the magnetic separators.

MILLING SYSTEM

1. RC Bunker: - Raw coal is fed directly to these bunkers. These are 3 in no. per boiler.4 & tons of coal are fed in 1 hr. the depth of bunkers is 10m.

2. RC Feeder: - It transports pre crust coal from raw coal bunker to mill. The quantity ofraw coal fed in mill can be controlled by speed control of aviator drive controlling

damper and aviator change.

3. Ball Mill: - The ball mill crushes the raw coal to a certain height and then allows it tofall down. Due to impact of ball on coal and attraction as per the particles move over

each other as well as over the Armor lines, the coal gets crushed. Large particles are

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

takes place simultaneously inside the mill.

4. Classifier:- It is an equipment which serves separation of fine pulverized coalparticles medium from coarse medium. The pulverized coal along with the carrying

medium strikes the impact plate through the lower part. Large particles are then

transferred to the ball mill.

5. Cyclone Separators: - It separates the pulverized coal from carrying medium. The

mixture of pulverized coal vapour caters the cyclone separators.

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

7. Worm Conveyor: - It is equipment used to distribute the pulverized coal from bunkerof one system to bunker of other system. It can be operated in both directions.



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

(a) ID Fans: - Located between electrostatic precipitator and chimney.Type-radical

Speed-1490 rpm

Rating-300 KW

Voltage-6.6 KV

Lubrication-by oil

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

Type-axial

Speed-990 rpm

Rating-440 KW

Voltage-6.6 KV

(c)Primary Air Fans: - Designed for handling the atmospheric air up to 50 degreesCelsius, 2 in number

And they transfer the powered coal to burners to firing.

Type-Double suction radial

Rating-300 KW

Voltage-6.6 KV

Lubrication-by oil

Type of operation-continuous

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

Motor specification squirrel cage induction motor

Rating-340 KW

Voltage-6600KV

Curreen-41.7A

Speed-980 rpm

Frequency-50 Hz

No-load current-15-16 A



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NCHP

1. Wagon Tippler:-Motor Specification(i) H.P 75 HP

(ii) Voltage 415, 3 phase

(iii) Speed 1480 rpm

(iv) Frequency 50 Hz

(v) Current rating 102 A

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

(ii) Voltage 415V,3 phase

(iii) Speed 1480 rpm

(iv) Frequency 50 Hz

3. Conveyors:-10A, 10B

11A, 11B

12A, 12B

13A, 13B

14A, 14B15A, 15B

16A, 16B

17A, 17B

18A, 18B

4. Transfer Point 6

5. Breaker House

6. Rejection House

7. Reclaim House

8. Transfer Point 7



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9. Crusher House

10. Exit

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

hoppers. If coal is oversized (>400 mm sq) then it is broken manually so that it passes

the hopper mesh. From the hopper mesh it is taken to the transfer point TP6 by

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

size to be 100mm sq. the stones which are not able to pass through the 100mm sq of

hammer are 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 reclaim

hopper, From TP7 coal is taken by conveyors 14A, 14B to crusher house whose

function is to render the size of coal to 20mm sq. now the conveyor labors are present

whose function is to recognize and remove any stones moving in the conveyors . Incrusher before it enters the crusher. After being crushed, if any metal is 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 switched on tono load. Isolation is normally used in various ways for purpose of isolating a certain

portion when required for maintenance.

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

switching. The main application of switching isolation is in connection with transformer

feeders as unit makes it possible to switch out one transformer while other is still on

load.

3. Circuit Breakers: - One which can make or break the circuit on load and even onfaults is referred to as circuit breakers. This equipment is the most important and is

heavy duty equipment mainly utilized for protection of various circuits and operations on

load. Normally circuit breakers installed are accompanied by isolators

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

breakers.



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5. Earth Switches: - Devices which are used normally to earth a particular system, toavoid any accident happening due to induction on account of live adjoining circuits.

These equipments do not handle any appreciable current at all. Apart from this

equipment there are a number of relays etc. which are used in switchgear.

LT SwitchgearIt is classified in following ways:-

1. Main Switch:- Main switch is control equipment which controls or disconnects themain 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 stations extremelyheavy carnets would flow in the fault and the fuse clearing the fault would be required to

withstand extremely heavy stress in process.

It is used for supplying power to auxiliaries with backup fuse protection. 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.L Starting of motors andprotecting the connected motors.

4. Overload Relay: - For overload protection, thermal over relay are best suited for thispurpose. 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. Soin all circuits breakers at large capacity air at high pressure is used which is maximum

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 medium capacity circuit breakers.

HT SWITCH GEAR:-

1. Minimum oil Circuit Breaker: - These use oil as quenching medium. It comprises ofsimple dead tank row pursuing projection from it. The moving contracts are carried on

an iron arm lifted by a long insulating tension rod and are closed simultaneously

pneumatic operating mechanism by means of tensions but throw off spring to be



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provided at mouth of the control 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 pressure around 15 kg per cm^2 is

used for extinction of arc caused by flow of air around the moving circuit . The breaker isclosed by applying pressure at lower opening and opened by applying pressure at

upper opening. When contacts operate, the cold air 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 short and consistent.

iv. Facility for frequent operation since the cooling medium is replaced constantly.

Rated Voltage-6.6 KVCurrent-630 A

Auxiliary current-220 V/DC

3. SF6 Circuit Breaker: - This type of circuit breaker is of construction to dead tankbulk oil to circuit breaker but the principle of current interruption is similar o that of air

blast circuit breaker. It simply employs the arc extinguishing medium namely SF6. the

performance of gas . When it is broken down under an electrical stress. It will quickly

reconstitute itself

Circuit Breakers-HPA

Standard-1 EC 56

Rated Voltage-12 KV

Insulation Level-28/75 KV

Rated Frequency-50 Hz

Breaking Current-40 KA

Rated Current-1600 A



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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

5.Vacuum Circuit Breaker: It works on the principle that vacuum is used to save thepurpose 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 which are

generally used at high pressure. Rated frequency-50 Hz Rated making Current-10 Peak KA Rated Voltage-12 KV Supply Voltage Closing-220 V/DC Rated Current-1250 A Supply Voltage Tripping-220 V/DC Insulation Level-IMP 75 KVP Rated Short Time Current-40 KA (3 SEC) Weight of Breaker-8 KG



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EMD II

Electrical Maintenance division III was assigned to do training in Electrical maintenance division II from 21st June2011 to 25th June 2011.This training in this division was divided as follows. Generator Transformer &switchyard protection Lightning EP

Generator and Auxiliaries Generator and Auxiliaries

Generator Fundamentals FundamentalsThe transformation of mechanical energy into electrical energy is carried out bythe Generator. This Chapter seeks to provide basic understanding about theworking principles and development of Generator.

Working PrincipleThe A.C. Generator or alternator is based upon the principle of electromagneticinduction and consists generally of a stationary part called stator and a rotating

part 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.When the rotor is rotated, the lines of magnetic flux (viz magnetic field) cutthrough the stator windings. This induces an electromagnetic force (e.m.f.) in thestator windings. The magnitude of this e.m.f. is given by the followingexpression.

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 winding

F = 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 hydroturbine drives generators have 14 to 20 poles where as high speed steam turbine



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

Generator component

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

RotorThe 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 ofguaranteeing the dynamic strength and operating stability of such a rotor is complicatedby the fact that a massive non-uniform shaft subjected to a multiplicity of differentialstresses must operate in oil lubricated sleeve bearings supported by a structuremounted on foundations all of which possess complex dynamic be behavior peculiar tothemselves. It is also an electromagnet and to give it the necessary magnetic strength

the windings must carry a fairly high current. The passage of the current through thewindings generates heat but the temperature must not be allowed to become so high,otherwise difficulties will be experienced with insulation. To keep the temperaturedown, the cross section of the conductor could not be increased but this wouldintroduce another problems. In order to make room for the large conductors, body andthis would cause mechanical weakness. The problem is really to get the maximumamount of copper into the windings without reducing the mechanical strength. Withgood design and great care in construction this can be achieved. The rotor is a caststeel ingot, and it is further forged and machined. Very often a hole is bored through thecentre of the rotor axially from one end of the other for inspection. Slots are thenmachined for windings and ventilation.

Rotor windingSilver bearing copper is used for the winding with mica as the insulation betweenconductors. A mechanically strong insulator such as micanite is used for lining the slots.Later designs of windings for large rotor incorporate combination of hollow conductorswith slots or holes arranged to provide for circulation of the cooling gasthrough the actual conductors. When rotating at high speed. Centrifugal force tries to liftthe windings out of the slots and they are contained by wedges. The end rings aresecured to a turned recess in the rotor body, by shrinking or screwing and supported atthe other end by fittings carried by the rotor body. The two ends of windings areconnected to slip rings, usually made of forged steel, and mounted on insulatedsleeves.

Rotor balancingWhen completed the rotor must be tested for mechanical balance, which means that acheck is made to see if it will run up to normal speed without vibration. To do this itwould have to be uniform about its central axis and it is most unlikely that thiswill be so to the degree necessary for perfect balance. Arrangements are thereforemade in all designs to fix adjustable balance weights around the circumference at each



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end.

StatorStator frame: The stator is the heaviest load to be transported. The major part of thisload is the stator core. This comprises an inner frame and outer frame. The outer frame

is a rigid fabricated structure of welded steel plates, within this shell is a fixed cage ofgirder built circular and axial ribs. The ribs divide the yoke in the compartments throughwhich hydrogen flows into radial ducts in the stator core and circulate through the gascoolers housed in the frame. The inner cage is usually fixed in to the yoke by anarrangement of springs to dampen the double frequency vibrations inherent in 2 polegenerators. The end shields of hydrogen cooled generators must be strong enough tocarry shaft seals. In large generators the frame is constructed as two separate parts.The fabricated inner cage is inserted in the outer frame after the stator core has beenconstructed and the winding completed. Stator core: The stator core is built up from alarge number of 'punching" or sections of thin steel plates. The use of cold rolled grain-oriented steel can contribute to reduction in the weight of stator core for two main

reasons:

a) There is an increase in core stacking factor with improvement in lamination coldRolling and in cold buildings techniques.

b) The advantage can be taken of the high magnetic permeance of grain-orientedsteels of work the stator core at comparatively high magnetic saturation withoutfear or excessive iron loss of two heavy a demand for excitation ampere turnsfrom the generator rotor.

Stator Windings

Each stator conductor must be capable of carrying the rated current withoutoverheating. The insulation must be sufficient to prevent leakage currents flowingbetween the phases to earth. Windings for the stator are made up from copper stripswound with insulated tape which is impregnated with varnish, dried under vacuum andhot pressed to form a solid insulation bar. These bars are then place in the stator slotsand held in with wedges to form the complete winding which is connected together ateach end of the core forming the end turns. These end turns are rigidly braced andpacked with blocks of insulation material to withstand the heavy forces which mightresult from a short circuit or other fault conditions. The generator terminals are usuallyarranged below the stator. On recent generators (210 MW) the windings are made upfrom copper tubes instead of strips through which water is circulated for coolingpurposes. The water is fed to the windings through plastic tubes.

Generator Cooling SystemThe 200/210 MW Generator is provided with an efficient cooling system to avoidexcessive heating and consequent wear and tear of its main components duringoperation. This Chapter deals with the rotor-hydrogen cooling system and stator watercooling system along with the shaft sealing and bearing cooling systems.



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Rotor Cooling SystemThe rotor is cooled by means of gap pick-up cooling, wherein the hydrogen gas in theair gap is sucked through the scoops on the rotor wedges and is directed to flow alongthe ventilating canals milled on the sides of the rotor coil, to the bottom of the slot whereit takes a turn and comes out on the similar canal milled on the other side of the rotor

coil to the hot zone of the rotor. Due to the rotation of the rotor, a positive suction aswell as discharge is created due to which a certain quantity of gas flows and cools therotor. This method of cooling gives uniform distribution of temperature. Also, thismethod has an inherent advantage of eliminating the deformation of copper due tovarying temperatures.

Hydrogen Cooling SystemHydrogen is used as a cooling medium in large capacity generator in view of its highheat carrying capacity and low density. But in view of its forming an explosive mixturewith oxygen, proper arrangement for filling, purging and maintaining its purity inside thegenerator have to be made. Also, in order to prevent escape of hydrogen from the

generator casing, shaft sealing system is used to provide oil sealing.The hydrogen cooling system mainly comprises of a gas control stand, a drier, an liquidlevel indicator, hydrogen control panel, gas purity measuring and indicatinginstruments,The system is capable of performing the following functions :

Filling in and purging of hydrogen safely without bringing in contact with air.1. Maintaining the gas pressure inside the machine at the desired value at all the

times.2. Provide indication to the operator about the condition of the gas inside the

machine i.e. its pressure, temperature and purity.

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

remove any water vapour that may be present in it.

4. Indication of liquid level in the generator and alarm in case of high level.

Stator Cooling SystemThe stator winding is cooled by distillate. Which is fed from one end of the machine byTeflon tube and flows through the upper bar and returns back through the lower bar ofanother slot?Turbo generators require water cooling arrangement over and above the usualhydrogen cooling arrangement. The stator winding is cooled in this system by circulatingdemineralised water (DM water) through hollow conductors. The cooling water used for

cooling stator winding calls for the use of very high quality of cooling water. For thispurpose DM water of proper specific resistance is selected. Generator is to be loadedwithin a very short period if the specific resistance of the cooling DM water goes beyondcertain preset values. The system is designed to maintain a constant rate of coolingwater flow to the stator winding at a nominal inlet water temperature of 40 deg.C.

Rating of 95 MW Generator[Type text] [Type text]


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Manufacture by Bharat heavy electrical Limited (BHEL)

Capacity - 117500 KVAVoltage - 10500V

Speed - 3000 rpmHydrogen - 2.5 Kg/cm2Power factor - 0.85 (lagging)Stator current - 6475 AFrequency - 50 HzStator wdg connection - 3 phase

Rating of 210 MW GeneratorCapacity - 247000 KVAVoltage (stator) - 15750 VCurrent (stator) - 9050 A

Voltage (rotor) - 310 VCurrent (rotor) - 2600 VSpeed - 3000 rpmPower factor - 0.85Frequency - 50 HzHydrogen - 3.5 Kg/cm2Stator wdg connection - 3 phase star connectionInsulation class - B

TRANFORMER

A transformer is a device that transfers electrical energy from one circuit to another bymagnetic coupling with out requiring relative motion between its parts. It usuallycomprises two or more coupled windings, and in most cases, a core to concentratemagnetic flux. An alternating voltage applied to one winding creates a time-varyingmagnetic flux in the core, which includes a voltage in the other windings. Varying therelative number of turns between primary and secondary windings determines the ratioof the input and output voltages, thus transformingthe voltage by stepping it up or downbetween circuits. By transforming electrical power to a high-voltage,_low-current formand back again, the transformer greatly reduces energy losses and so enables theeconomic transmission of power over long distances. It has thus shape the electricitysupply industry, permitting generation to be located remotely from point of demand. Allbut a fraction of the worlds electrical power has passed trough a series of transformerby the time it reaches the consumer.

Basic Principles

The principles of the transformer are illustrated byconsideration of a hypothetical ideal transformer consisting oftwo windings of zero resistance around a core of negligible



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reluctance. A voltage applied to the primary winding causes a current, which develops amagneto motive force (MMF) in the core. The current required to create the MMF istermed the magnetizing current; in the ideal transformer it is considered to be negligible,although its presence is still required to drive flux around the magnetic circuit of thecore. An electromotive force (MMF) is induced across each winding, an effect known as

mutual inductance. In accordance with faradays law of induction, the EMFs areproportional to the rate of change of flux. The primary EMF, acting as it does inopposition to the primary voltage, is sometimes termed the back EMF. Energy losses

An ideal transformer would have no energy losses and would have no energy losses,and would therefore be 100% efficient. Despite the transformer being amongst the mostefficient of electrical machines with ex the most efficient of electrical machines withexperimental models using superconducting windings achieving efficiency of 99.85%,energy is dissipated in the windings, core, and surrounding structures. Largertransformers are generally more efficient, and those rated for electricity distributionusually perform better than 95%. A small transformer such as plug-in power brick usedfor low-power consumer electronics may be less than 85% efficient. Transformer losses

are attributable to several causes and may be differentiated between those originated inthe windings, some times termed copper loss, and those arising from the magneticcircuit, sometimes termed iron loss. The losses vary with load current, and mayfurthermore be expressed as no load or full load loss, or at an intermediate loading.Winding resistance dominates load losses contribute to over 99% of the no-load losscan be significant, meaning that even an idle transformer constitutes a drain on anelectrical supply, and lending impetus to development of low-loss transformers. Lossesin the transformer arise from: Winding resistance Current flowing trough the windingscauses resistive heating of the conductors. At higher frequencies, skin effect andproximity effect create additional winding resistance and losses. Hysteresis losses Eachtime the magnetic field is reversed, a small amount of energy is lost due to hysteresis

within the core. For a given core material, the loss is proportional to the frequency, andis a function of the peak flux density to which it is subjected. Eddy currentFerromagnetic materials are also good conductors, and a solid core made from such amaterial also constitutes a single short-circuited turn trough out its entire length. Eddycurrents therefore circulate with in a core in a plane normal to the flux, and areresponsible for resistive heating of the core material. The eddy current loss is a complexfunction of the square of supply frequency and inverse square of the material thickness.Magnetostriction Magnetic flux in a ferromagnetic material, such as the core, causes itto physically expand and contract slightly with each cycle of the magnetic field, an effectknown as magnetostriction. This produces the buzzing sound commonly associatedwith transformers, and in turn causes losses due to frictional heating in susceptiblecores. Mechanical losses In addition to magnetostriction, the alternating magnetic fieldcauses fluctuating electromagnetic field between primary and secondary windings.These incite vibration with in near by metal work, adding to the buzzing noise, andconsuming a small amount of power. Stray losses Leakage inductance is by itself lossless, since energy supplied to its magnetic fields is returned to the supply with the nexthalf-cycle. However, any leakage flux that intercepts nearby conductive material suchas the transformers support structure will give rise to eddy currents and be converted toheat. Cooling system Large power transformers may be equipped with cooling fans, oil



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pumps or water-cooler heat exchangers design to remove heat. Power used to operatethe cooling system is typically considered part of the losses of the transformer

Rating of transformer

Manufactured by Bharat heavy electrical limitedNo load voltage (hv) - 229 KVNo load Voltage (lv) -10.5 KVLine current (hv) - 315.2 ALine current (lv) - 873.2 ATemp rise - 45 CelsiusOil quantity -40180 litWeight of oil -34985 KgTotal weight - 147725 KgCore & winding - 84325 KgPhase - 3

Frequency - 50 Hz



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CONTROL AND INSTRUMENTATION

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

This department is the brain of the plant because from the relays to transmittersfollowed by the electronic computation chipsets and recorders and lastly the controllingcircuitry, all fall under this.I was assigned to do training in control and instrumentation from 27 th June 2011 to 23rdJuly 2011.

Instrumentation can be well defined as a technology of using instruments to measureand control the physical and chemical properties of a material.Control and instrumentation has following labs:

1. Manometry lab2. Protection and interlocks lab3. Automation lab4. Pyrometry5. Water treatment plant6. Furnaces Safety Supervisory System Lab7. Electronics

5.1 MANOMETRY LAB

5.1.1 TRANSMITTERSIt is used for pressure measurements of gases and liquids, its working principle is thatthe 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 apipe or a wall. For liquid or steam measurement transmitters is mounted below mainprocess piping and for gas measurement transmitter is placed above pipe.

5.1.2 MANOMETERIts a tube which is bent, in U shape. It is filled with a liquid. This device corresponds toa difference in pressure across the two limbs.

5.1.3 BOURDEN PRESSURE GAUGEIts an oval section tube. Its one end is fixed. It is provided with a pointer to indicate thepressure on a calibrated scale. It is of 2 types:



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

5.2 PROTECTION AND INTERLOCK LAB

5.2.1 INTERLOCKINGIt is basically interconnecting two or more equipments so that if one equipments failsother one can perform the tasks. This type of interdependence is also created so thatequipments connected together are started and shut down in the specific sequence toavoid damage.For protection of equipments tripping are provided for all the equipments. Tripping canbe considered as the series of instructions connected through OR GATE. When a faultoccurs and any one of the tripping is satisfied a signal is sent to the relay, which tripsthe circuit. The main equipments of this lab are relay and circuit breakers. Some of theinstrument uses for protection are:

1. RELAYIt is a protective device. It can detect wrong condition in electrical circuits by constantlymeasuring the electrical quantities flowing under normal and faulty conditions. Some ofthe electrical quantities are voltage, current, phase angle and velocity.

2. FUSESIt is a short piece of metal inserted in the circuit, which melts when heavy current flowsthrough it and thus breaks the circuit. Usually silver is used as a fuse material because:

a) The coefficient of expansion of silver is very small. As a result no critical fatigueoccurs and thus the continuous full capacity normal current ratings are assured for the

long time.

b) The conductivity of the silver is unimpaired by the surges of the current that producestemperatures 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 specificheat.

5.2.2 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



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- SHORT CIRCUIT TRIP

5.2.3 ROTECTION AND INTERLOCK SYSTEM1. 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 the equipmentto energize it. Because if even a single condition is not true then system will not start.

2. LOW TENSION CONTROL CIRCUITFor low tension system the control circuits are directly excited from the 0.415 KV A.Csupply. The same circuit achieves both excitation and tripping. Hence the tripping coil isprovided for emergency tripping if the interconnection fails.

5.3 Automation Lab

This lab deals in automating the existing equipment and feeding routes. Earlier,the old technology dealt with only (DAS) Data Acquisition System and came to beknown as primary systems. The modern technology or the secondary systems arecoupled with (MIS) Management Information System. But this lab universally applies thepressure measuring instruments as the controlling force. However, the relays are alsoprovided but they are used only for protection and interlocks.

5.4 PYROMETER LAB(1) LIQUID IN GLASS THERMOMETERMercury in the glass thermometer boils at 340 degree Celsius which limits the range oftemperature that can be measured. It is L shaped thermometer which is designed to

reach all inaccessible places.

(2) ULTRA VIOLET CENSORThis device is used in furnace and it measures the intensity of ultra violet rays there andaccording to the wave generated which directly indicates the temperature in the furnace.

(3) THERMOCOUPLESThis device is based on SEEBACK and PELTIER effect. It comprises of two junctions atdifferent temperature. Then the emf 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 the difference is of a resistance. Inthis due to the change in the resistance the temperature difference is measured.In this lab, also the measuring devices can be calibrated in the oil bath or just boilingwater (for low range devices) and in small furnace (for high range devices).



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5.6 FURNACE SAFETY AND SUPERVISORY SYSTEM LABThis 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 the secondand third stage corner firing is employed. Unburnt coal is removed using forced draft orinduced 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 sensor is employed infurnace to measure the intensity of ultra violet rays inside the furnace and according to ita signal in the same order of same mV is generated which directly indicates thetemperature of the furnace.For firing the furnace a 10 KV spark plug is operated for ten seconds over a spray ofdiesel fuel and pre-heater air along each of the feeder-mills. The furnace has six feedermills each separated by warm air pipes fed from forced draft fans. In first stage indirectfiring is employed that is feeder mills are not fed directly from coal but are fed from threefeeders but are fed from pulverized coalbunkers. The furnace can operate on theminimum feed from three feeders but under not circumstances should any one be leftout under operation, to prevent creation of pressure different with in the furnace, which

threatens to blast it.

5.7 ELECTRONICS LABThis lab undertakes the calibration and testing of various cards. It houses various typesof analytical instruments like oscilloscopes, integrated circuits, cards auto analyzers etc.Various processes undertaken in this lab are:1. Transmitter converts mV to mA.2. Auto analyzer purifies the sample before it is sent to electrodes. It extracts themagnetic portion.

AUTOMATION AND CONTROL SYSTEM

AUTOMATION: THE DEFINITIONThe word automation is widely used today in relation to various types of applications,such as office automation, plant or process automation.

This subsection presents the application of a control system for the automation of aprocess / plant, such as a power station. In this last application, the automation activelycontrols the plant during the three main phases of operation: plant start-up, powergeneration in stable or put During plant start-up and shut-down, sequence controllers as

well as long range modulating controllers in or out of operation every piece of the plant,at the correct time and in coordinated modes, taking into account safety as well asoverstressing limits.

During stable generation of power, the modulating portion of the automation systemkeeps the actual generated power value within the limits of the desired load demand.



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During major load changes, the automation system automatically redefines new setpoints and switches ON or OFF process pieces, to automatically bring the individualprocesses in an optimally coordinated way to the new desired load demand. This loadtransfer is executed according to pre- programmed adaptively controlled load gradientsand in a safe way.

AUTOMATION: THE BENEFITSThe main benefits of plant automation are to increase overall plant availability andefficiency. The increase of these two factors is achieved through a series of featuressummarized as follows:

Optimisation of house load consumption during plant start- up, shut-down andoperation, via:Faster plant start-up through elimination of control errors creating delays.Faster sequence of control actions compared to manual ones. Figures 1 shows the

sequence of a rapid restart using automation for a typical coal-fired station. Even a well-trained operator crew would probably not be able to bring the plant to full load in thesame time without considerable risks.Co-ordination of house load to the generated power output.

Ensure and maintain plant operation, even in case of disturbances in the controlsystem, via:Coordinated ON / OFF and modulating control switchover capability from a sub processto a redundant one.Prevent sub-process and process tripping chain reaction following a process componenttrip.

Reduce plant / process shutdown time for repair and maintenance as well as repaircosts, via:Protection of individual process components against overstress (in a stable or unstableplant operation).Bringing processes in a safe stage of operation, where process components areprotected against overstress

PROCESS STRUCTUREAnalysis of processes in Power Stations and Industry advocates the advisability ofdividing the complex overall process into individual sub-processes having distinctlydefined functions. This division of the process in clearly defined groups, termed asFUNCTIONAL GROUPS, results in a hierarchical process structure. While thehierarchical structure is governed in the horizontal direction by the number of drives(motorised valves, fans, dampers, pumps, etc.) in other words the size of the process; inthe vertical direction, there is a distinction made between three fundamental levels,these being the: -

Drive Level



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Function Group Level Unit Level.

To the Drive Level, the lowest level, belong the individual process equipment andassociated electrical drives.

The Function Group is that part of the process that fulfils a particular defined task e.g.,Induced Draft Control, Feed Water Control, Blooming Mill Control, etc. Thus at the timeof planning it is necessary to identify each function group in a clear manner by assigningit to a particular process activity. Each function group contains a combination of itsassociated individual equipment drives. The drive levels are subordinate to this level.The function groups are combined to obtain the overall process control function at theUnit Level.

The above three levels are defined with regard to the process and not from the controlpoint of view.

CONTROL SYSTEM STRUCTUREThe primary requirement to be fulfilled by any control system architecture is that it becapable of being organized and implemented on true process-oriented lines. In otherwords, the control system structure should map on to the hierarchy process structure.BHELs PROCONTROL P, a microprocessor based intelligent remote multiplexing

system, meets this requirement completely.

SYSTEM OVERVIEWThe control and automation system used here is a micro based intelligent multiplexingsystem This system, designed on a modular basis, allows to tighten the scope of controlhardware to the particular control strategy and operating requirements of the process

Regardless of the type and extent of process to control provides system uniformity andintegrity for:Signal conditioning and transmissionModulating controls

CONTROL AND MONITORING MECHANISMSThere are basically two types of Problems faced in a Power PlantMetallurgicalMechanical

Mechanical Problemcan be related to Turbines that is the max speed permissible for a

turbine is 3000 rpm , so speed should be monitored and maintained at that levelMetallurgical Problem can be view as the max Inlet Temperature for Turbile is 1060 oCso temperature should be below the limit.

Monitoring of all the parameters is necessary for the safety of both:EmployeesMachines



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For Switches pressure swithes are used and they can be used for digital means ofmonitoring as swith being ON is referred as high and being OFF is as low.

All the monitored data is converted to either Current or Voltage parameter.The Plant standard for current and voltage are as under

Voltage : 0 10 Volts rangeCurrent : 4 20 milliAmperes

We use 4mA as the lower value so as to check for disturbances and wire breaks.Accuracy of such systems is very high .ACCURACY : + - 0.1 %The whole system used is SCADA baseD.Programmable Logic Circuits ( PLCs) are used in the process as they are the heardt ofInstrumentation .

PressureElectricity

Start Levellow Pressure in line Level High

High level

pump ElectricityStopPressure

ElectricityBASIC PRESSURE CONTROL MECHANISM

TEMPERATURE MONITORINGWe can use Thernocouples or RTDs for temperature monitoringNormally RTDs are used for low temperatures.

Thermocouple selection depends upon two factors:[Type text] [Type text]

HL switch

AN

D

OR


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Temperature Range

Accuracy Required

Normally used Thermocouple is K Type Thermocouple:

Chromel (Nickel-Chromium Alloy) / Alumel (Nickel-Aluminium Alloy)This is the most commonly used general purpose thermocouple. It is inexpensive

and, owing to its popularity, available in a wide variety of probes. They are available inthe 200 C to +1200 C range. Sensitivity is approximately 41 V/C.

RTDs are also used but not in protection systems due to vibrational errors.

We pass a constant curre t through the RTD. So that if R changes then the Voltage alsochanges

RTDs used in Industries are Pt100 and Pt1000

Pt100 : 0 0C 100 ( 1 = 2.5 0C )Pt1000 : 0 0C - 1000Pt1000 is used for higher accuracy

The gauges used for Temperature measurements are mercury filled Temperaturegauges.

For Analog medium thermocouples are usedAnd for Digital medium Switches are used which are basically mercury switches.

FLOW MEASUREMENTFlow measurement does not signify much and is measured just for metering purposesand for monitoring the processes

ROTAMETERS:A Rotameter is a device that measures the flow rate of liquid or gas in a closed tube. Itis occasionally misspelled as 'rotometer'.

It belongs to a class of meters called variable area meters, which measure flow rate byallowing the cross sectional area the fluid travels through to vary, causing somemeasurable effect.

A rotameter consists of a tapered tube, typically made of glass, with a float inside that ispushed up by flow and pulled down by gravity. At a higher flow rate more area (betweenthe float and the tube) is needed to accommodate the flow, so the float rises. Floats are



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made in many different shapes, with spheres and spherical ellipses being the mostcommon. The float is shaped so that it rotates axially as the fluid passes. This allowsyou to tell if the float is stuck since it will only rotate if it is not.

For Digital measurements Flap system is used.

For Analog measurements we can use the following methods :

Flowmeters Venurimeters / Orifice meters Turbines Massflow meters ( oil level ) Ultrasonic Flow meters Magnetic Flowmeter ( water level )

Selection of flow meter depends upon the purpose , accuracy and liquid to be measuredso different types of meters used.

Turbine type are the simplest of all.They work on the principle that on each rotation of the turbine a pulse is generated andthat pulse is counted to get the flow rate.

VENTURIMETERS :



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Referring to the diagram, using Bernoulli's equation in the special case ofincompressible fluids (such as the approximation of a water jet), the theoretical pressuredrop at the constriction would be given by (/2)(v2

2 - v12).

And we know that rate of flow is given by:

Flow = k (D.P)Where DP is Differential Presure or the Pressure Drop.

CONTROL VALVES

A valve is a device that regulates the flow of substances (either gases, fluidizedsolids, slurries, or liquids) by opening, closing, or partially obstructing variouspassageways. Valves are technically pipe fittings, but usually are discussed separately.

Valves are used in a variety of applications including industrial, military, commercial,residential, transportation. Plumbing valves are the most obvious in everyday life, butmany more are used.

Some valves are driven by pressure only, they are mainly used for safety purposes insteam engines and domestic heating or cooking appliances. Others are used in acontrolled way, like in Otto cycle engines driven by a camshaft, where they play a majorrole in engine cycle control.

Many valves are controlled manually with a handle attached to the valve stem. If thehandle is turned a quarter of a full turn (90) between operating positions, the valve is

called a quarter-turn valve. Butterfly valves, ball valves, and plug valves are oftenquarter-turn valves. Valves can also be controlled by devices called actuators attachedto the stem. They can be electromechanical actuators such as an electric motor orsolenoid, pneumatic actuators which are controlled by air pressure, orhydraulicactuators which are controlled by the pressure of a liquid such as oil or water.

So there are basically three types of valves that are used in power industries besidesthe handle valves. They are :

Pneumatic Valves they are air or gas controlled which is compressed to turnor move them

Hydraulic valves they utilize oil in place of Air as oil has better compression Motorised valves these valves are controlled by electric motors

FURNACE SAFEGUARD SUPERVISORY SYSTEMFSSS is also called as Burner Management System (BMS). It is a microprocessorbased programmable logic controller of proven design incorporating all protection



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facilities required for such system. Main objective of FSSS is to ensure safety of theboiler.

The 95 MW boilers are indirect type boilers. Fire takes place in front and in rear side.Thats why its called front and rear type boiler.

The 210 MW boilers are direct type boilers (which means that HSD is in direct contactwith coal) firing takes place from the corner. Thus it is also known as corner type boiler.

IGNITER SYSTEMIgniter system is an automatic system, it takes the charge from 110kv and this spark isbrought in front of the oil guns, which spray aerated HSD on the coal for coalcombustion. There is a 5 minute delay cycle before igniting, this is to evacuate or burnthe HSD. This method is known as PURGING.

PRESSURE SWITCHPressure switches are the devices that make or break a circuit. When pressure isapplied , the switch under the switch gets pressed which is attached to a relay thatmakes or break the circuit.Time delay can also be included in sensing the pressure with the help of pressurevalves.Examples of pressure valves:

1. Manual valves (tap)2. Motorized valves (actuator) works on motor action3. Pneumatic valve (actuator) _ works due to pressure of compressed air

4. Hydraulic valve

Documents

Mohit Malik, Archit Arora