Suratgarh Final

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DEPARTMENT OF ELECTRICAL ENGINEERING

A

TRAINING REPORT

ON

SURATGARH SUPER THERMAL POWERSTATION

(For Fulfillment of The Requirement of Bachelor of Engineering)

15th June to 14th July

2009Department of Electrical Engineering

College of Technology & Engineering

Maharana Pratap University of Agriculture & Technology

Udaipur, Rajasthan.

Submitted By:

RISHABH LOHIYA

B.E.- II YEAR

ELECTRICAL ENGG




ACKNOWLEDGEMENT

I wish to acknowledge the encouragement and support received from Dr. R.R. JOSHI

(HOD, Electrical department, C.T.A.E., Udaipur) & Mr. VINOD YADAV (Training

incharge) for initiating my interest in training.

Their mastery & work helped me in covering out this work smoothly. I am also

grateful of all the workers of various departments who have helped me to improvemy thinking as well as the practical knowledge.

I am thankful and grateful to Mr. R.S. Mathur, SUPTDG Engineer(TM &

TRG.) for giving me chance of training at their prestigious industry, which will be

helpful in my progress toward bright future.

I am also thankful to the executive staff, technical and non-technical staff of

S.T.P.S. for extending their kind support, information and practical knowledge duringmy four-week practical training at their units in S.T.P.S, Suratgarh.

RISHABH LOHIYA




PREFACE

Practical training is a way to implement theoretical knowledge to practical use to

become a successful engineer it is necessary to have a sound practical knowledge

because it is only way by which one can acquire proficiency & skill to work

successfully different industries.

It is proven fact that bookish knowledge is not sufficient because things are not as

ideal in practical field as they should be.

SURATGARH THERMAL SUPER POWER PLANT is one of the best examples to

understand the generation process of Electricity.

This report is an attempt made to study the overall generation system & related action

of Power Plant. It is engaged in production of electricity using the Bituminous coal

as the primary fuel & other byproducts like ash produced is used in Cement plant.

RISHABH LOHIYA




CONTENTS

1. INTRODUCTION...............................................................3.

2. SWITCHYARD....................................................................5.

3. TRANSFORMER.................................................................9.

4. TURBO GENERATOR.......................................................13.

5. BOILER................................................................................20.

6. STEAM TURBINE...............................................................30.

7. E.S.P......................................................................................32.

8. COAL HANDLING..............................................................33.

9. ASH HANDLING................................................................34.

10. COMMON AUXILARIES...................................................35.

11. PROTECTION......................................................................36.

12. SALIENT FEATURES OF UNIT AUXILARIES................37.

13.

CONCLUSION......................................................................41.




1. INTRODUCTION

Suratgarh Super Thermal Power Station

Suratgarh Thermal Power Station is the First Super Thermal Power Station of

Rajasthan with a total planned installed capacity of 1500 MW Presently the operational

installed capacity of STPS is 1250(5x250) and one more unit of 250MW is slated for

commissioning in March 2009.

There are Units (6*250 MW) in 4 stages

Stage Unit No. Capacity (MW) SynchronizingDate

Cost(Rs. Crore)‟

I 1 250 10.05.1998 2220

2 250 28.03.2000

II 3 250 27.10.2001 1900

4 250 24.03.2002

III 5 250 30.06.2003 753

IV 6 250 31.03.2009 1117

Location:-

STPS is situated near village thukrana about 27km South East of Suratgarh town is

Shri Ganganagar Distt. Suratgarh was considered an ideal location for setting up a thermal

power station in the state having regards to the availability of land, water, transmission

network proximity to broad gauge railway and being an important load centre for North

West Rajasthan.

Coal:-

Thermal power station is based on coal. Coal is bitumen “d” grade coal. Coal from

M.P., Bihar, Jharkhand coal mines by railway transportation with 3900 to 4200 kcal/kg.

Awards:-

1. Cash award of 3.75 lacks (for productivity) and Rs. 6.19 lacks for specific oil

consumption

2. Golden Shield award from Union Ministry of power




Operational Performance of Plant

The performance of Suratgarh Thermal Power Station has been exemplary right from the

beginning since commissioning of Unit-I

Particulars 2004-05 2005-06 2006-07 2007-08 2008-09

Gross Generation(MU) 9362.32 9951.22 10205.59 10222.5 9740.61

Plant Load Factor (%) 85.5 90.88 93.2 93.1 88.96

Aux. Power Consumption

(%) 9.3 9.15 9.16 9.12 9.19

Sp. Oil

Consumption(ml/kwh) 0.83 0.64 0.53 0.59 0.77

Environmental Profile

Adequate measures have been taken to control pollution and ensure atmospheric

emission within the prescribed limits of Environment (Protection) Act1986.

220 meter high stack have been provided to release flue gases into the atmosphere

Adequate water spraying arrangements have been provided at coal unloading,

transfer and conveying system to arrest and restrict Fugitive Emission.

About 2.5 lacks plants of various species have been planted in STPS and ash dyke.

Mobile laboratory vans are also available for regular monitoring of stack Emission,

Ambient Air Quality and Trade Effluent.

Regular monitoring of Stack Emission, Ambient Air Quality and Trade Effluent is

carried out.

Extension Unit # 7&8( 2 x 660 MW)

Two more Units of 660 MW each have been planned to add at STPS. These Units are

expected to be synchronized by March 2013 and Sept. 2013 respectively.




2. SWITCHYARD 220 KV & 400 KV SWITCHYARD AND DIFFERENT EQUIPMENTS

INSTALLED AND BUS SCHEMES

BUS SCHEME

Main Function Of The Stations Is To Receive The Energy And Transmit It At The Required

Voltage Level With The Facility Of Switching.

At STPS Following Are The Bays:-

Bus Coupler – 1

Sog -1

Sog -2

Generator Transformer -1

Ratangarh -1

Station Transformer -1

Bus Sectionalizer Ratangarh – 2

Bus Tie

Generator Transformer-2

Interlinking-1

Station Transformer-2

Interlinking -2







BUS SYSTEM There Are Mainly Three Buses

Main Bus-1

Main Bus-2

Transfer Bus

Material of bus bar- Tarantull Al conductor with a capacity of 2400 amperes. Bus

coupler-1 can be used as GT breaker for unit 1, 2 and 3. Only one bus coupler can be used

as a GT breaker at a time.

CIRCUIT BREAKERS

SF6 GAS CIRCUIT BREAKERS

In this type of breaker quenching of arc is done by SF6 gas. The opening and

closing of the circuit breaker is done by air.

TYPE DESIGNATION

E : S F 6 Gas Insulation

L : Generation

F : Out Door Design

SL: Breaker Construction

4 : Code BIL Rated Voltage 4 – 245 / 460 / 1050 kv

1 : No. of chamber

The high voltage circuit breaker type ELF SL 4-1 comprises 3 breaker poles , a common

control cubicle and a pneumatic unit ( compressed air plant)

a breaker pole consists of :-

- SUPPORT (FRAME) - 40000

- POLE COLUMN - 41309 N

- PNEUMATIC ACTUATOR (PKA) - 90200




The actuator is operated with compressed air.

A pneumatic unit (97200), an air receiver and a unit compressor is installed to supply the

compressed air. The compressed air stored in the air receiver is distributor to the three

actuator via pipe line.

If all the poles of the circuit breaker do not close simultaneously then the pole discrepancy

relay will operate and trip the breaker. Also at the time of tripping, if all the breakers do not

trip simultaneously, then again the tripping command through the pole discrepancy relay

will initiate to trip the breaker and annunciation will appear in the sub station control room

and the UCB.

ISOLATORS

Isolators are used to make or break the circuit on no load. They should never be

operated on load. The isolators installed in the sub station have a capacity of 1250 amperes.

They are double end break type motor operated and can be operated from local as well as

remote.

CURRENT AND CAPACTIVE VOLTAGE TRANSFORMERS

These are used for metering and protection. It should always be kept in mind that a

CT should never be open circuited and a PT should never be short-circuited.




LIGHTINING ARRESTOR AND ARC HORNS

Lightning arrester is a device used on electrical power

systems to protect the insulation on the system from the

damaging effect of lightning. The typical lightning arrester

also known as surge arrester has a high voltage terminal and

a ground terminal. When a lightning surge or switching

surge travels down the power system to the arrester, the

current from the surge is diverted around the protectedinsulation in most cases to earth.

Arcing horns are projecting conductors used to protect insulators on high voltage

electric power transmission systems from damage during flashover. The horns encourage

flashover between themselves rather than across of the surface of the insulator they serve to

protect. Horns are normally paired on either side of the insulator, one connected to the high

voltage part and the other to ground. They are frequently to be seen on insulator strings on

overhead lines, or protecting transformer bushings.

http://en.wikipedia.org/wiki/Power_systems


http://en.wikipedia.org/wiki/Lightning

http://en.wikipedia.org/wiki/Conductor_(material)

http://en.wikipedia.org/wiki/Electrical_insulation

http://en.wikipedia.org/wiki/Electric_power_transmission

http://en.wikipedia.org/wiki/Electric_arc

http://en.wikipedia.org/wiki/Ground_(electricity)

http://en.wikipedia.org/wiki/Insulator_string

http://en.wikipedia.org/wiki/Transformer

http://en.wikipedia.org/wiki/Bushing_(electrical)

http://en.wikipedia.org/wiki/Bushing_(electrical)

http://en.wikipedia.org/wiki/Transformer

http://en.wikipedia.org/wiki/Insulator_string

http://en.wikipedia.org/wiki/Ground_(electricity)

http://en.wikipedia.org/wiki/Electric_arc

http://en.wikipedia.org/wiki/Electric_power_transmission

http://en.wikipedia.org/wiki/Electrical_insulation

http://en.wikipedia.org/wiki/Conductor_(material)

http://en.wikipedia.org/wiki/Lightning






4. TRANSFORMER

Transformer is made up of the following Parts:

1. Core

2. Winding

3. On Load Tap Changer

4. Tank

5. Bushing

6. Auxiliary Equipments

7. Insulating Oil

8.

Cooling System

In sstps there are various transformer are used for various purpose. They are:

a) Generating Transformer

b) Unit Auxiliary Transformer

c) Station Transformer

d) Instrument Transformer

(A). Potential Transformer

(B). Current Transformer

STATION TRANSFORMER

When the unit is to be started, power supplied to the auxiliaries is taken from the

station transformer. The rating of the station transformer is 50 MVA. It takes power from

the grid at 220 kV and steps it down to 6.6 kV. At the time of starting all the auxiliaries are

supplied from the station transformer. When the generator is synchronized and starts

producing power, about 80% of the load is shifted on to the unit auxiliary transformer. The

load that requires uninterrupted supply is left connected on the station transformer.

There are 6 S.T‟s in the plant. One for each stage.




Technical Data Of Transformer

HV LV

KVA 40000/50000 40000/50000

Volts (No Load) 220000 6900

Amp (Line Voltage) 105/131 3351/4189

UNIT AUXILIARY TRANSFORMER

Each unit has two unit auxiliary transformers. When the unit starts generating

electricity these transformers are energized and then supplies power to the auxiliaries.

Before starting of the unit, UAT bus is connected to the station bus. Auxiliaries of one unit

takes about 20MW of power. UAT is connected between the generator and the GT. A

tapping is taken from the power coming from the generator to the GT. UAT relieves GT

from extra load of about 20 MW which is to be supplied to the auxiliaries via GT and ST

thus increasing the efficiency. It is a step down transformer, which steps down the voltage

from 16.5 kV to 6.9kV. The rating of UAT is 20 MVA. UAT bus supplies only those

auxiliaries, which are not necessary to be energized in case of sudden tripping of generator.

NO. Of Phase & Frequency 3, 50 Hz

Types Of Coolant ONAN / ONAF

Connection Symbol YNyno

Mass Of Care And WDG 44470 Kg

Mass Of Oil 22780 Kg

Total Mass 86210 Kg

Volume Of Oil 25600 Litre

Air Circulation 10×80 M3 /min




UNIT STATION TRANSFORMER

It is a step down transformer, which is connected to the station bus. It steps down the

voltage from 6.6 kV to 0.433 kV it is used to supply the low voltage auxiliaries.

UNIT SERVICE TRANSFORMER

It is also a 66 kV/ 415 V transformer which is used to supply the auxiliaries

connected to the unit secondary switchgear bus.

INSTRUMENT TRANSFORMER

Instrument transformer has very wide range in application such as measurement of

voltage, current, power and energy, power factor, frequency. It is also used for protection

circuit of the power system for operation of over current, under voltage, earth fault and other

type of relay.

According to measuring purpose, instrument transformer can be classified as:

A. Current Transformer

B. Potential Transformer

A. CURRENT TRANSFORMER

Current transformer is used for monitoring the current for the purpose of measuringand protection. They can be classified as Dead Tank and inverter type. The dead tank

current transformer accommodates the secondary cores inside the tank which is at the

ground potential. The insulated primary passes through the porcelain and the tank and the

terminals into the top chamber. The primary used in such type of constructions of „u‟ type.

The inserted secondary cores are insulated to the system voltage and hence inside the

top chamber which is at the line potential. Before commissioning of the current transformer,




the earthing of the power terminal and base is essential, otherwise excessive high voltage

appears at the power factor terminals and leads to heavy spark. The secondary terminal of

the core should be short circuited and earthed which are not in use otherwise excessive high

voltage will be develop across the current transformer secondary. The current transformer

should always be in vertical position so that gas forming at the top does not enter the

insulated parts.

B. POTENTIAL TRANSFORMER

The function of potential transformer is to step down the voltage so that it can be

measured by standard measurement. The outlook of current and potential transformer is

almost same except there is a ground terminal. They are either of 1-Фor 3-Ф.in the 3-Ф

P.T. there are again three limbs and five limb core construction. The P.T. may be dry or oil

field. The P.T. above 66 KV are essentially sealed with inert gas cushion provided in the

top chamber to take care of expansion and construction. The transformer generally core

type and form Y-Y group having the insulation as oil & paper. Every P.T. is connected to

phase hence there may be three P.T.s and connected to the same bus bar coming to same

meter mounted on the panel through a selector switch which can be used to measure

different line voltages. As the voltage of the feeders connected to same bus bar and the

same voltage and we don‟t use separate P.T. for each feeder.




3. TURBO GENERATOR

TURBO GENERATOR manufactured by B.H.E.L. and incorporated with

most modern design concepts and constructional features, which ensures reliability, with

constructional & operational economy.

4.1. STATOR

The generator stator is a tight construction, supporting & enclosing the stator windings,

core and hydrogen coolers. Cooling medium hydrogen is contained within frame &

circulated by fans mounted at either ends of rotor. The generator is driven by directly

coupled steam turbine at a speed of 3000 r.p.m. the Generator is designed for continuous

operation at the rated output. Temperature detectors and other devices installed or

connected within then machine, permit the windings, teeth core & hydrogen temperature,

pressure & purity in machine under the conditions. There is a provision for cooling water in

order to maintain a constant temperature of coolant (hydrogen) which controls the

temperature of windings.

4.1.1 STATOR FRAME: The stator frame of welded steel frame construction, which gives

sufficient & necessary rigidity to minimize the vibrations and to withstand the thermal gas

pressure. Heavy end shields enclose the ends of frame and form mounting of generator

bearings and radial shaft seals. Ribs subdivide the frame and axial members to form duct

from which the cooling gas to & fro radial ducts in the core and is re-circulated through

internally mounted coolers. The horizontally mounted water cooled gas coolers being so

arranged that it may be cleaned on the water side without opening the machine to

atmosphere

4.1.2 STATOR CORE: It is built up of special sheet laminations and whose assembly is

supported by a special guide bass. The method of construction ensures that the core is

firmly supported at a large number of points on its periphery. The laminations of high

quality silicon steel which combines high permeability with low hysteresis and eddy current




losses. After stamping each lamination is varnished on both sides with two coats. The

segment of insulating material is inserted at frequent intervals to provide additional

insulation. The laminations are stamped out with accurately fine combination of ties.

Laminations are assembled on guide bass of group separated by radial ducts to provide

ventilation passage. The ventilation ducts are disposed so as to distribute the gas evenly

over the core & in particularly to give adequate supports to the teeth.

4.1.3 STATOR BARS: Stator bars are manufactured as half bars. Each stator half coil is

composed of double glass cover and bars of copper transposed in straight portion of “ Robill

Method” so that each strip occupies every radial portion in the bar. For an equal length

along the bar. They are made in strips to reduce skin effect. The winding overhead is in

volute shape. The overhung portion of the bar is divided into four quadrants & insulated

4.1.4 STATOR WINDINGS: Stator windings are double star layers, lap wound, three phase

and short pitch type. The top & bottom are brazed and insulated at either end to form turns.

Several such turns form a phase. Phases are connected to form a double star winding. The

end of winding form involute shape ends, inclined towards machine axis by 20o

, thus form a

basket winding with total induced conical angle of 400

End windings will be sealed against

movement of short circuit by both axial & peripheral bracing. The exposed portions of

windings are finally coated. Insulation of individual bars & stator windings at various

stresses is tested with applied high voltages of AC of Hz.

4.1.5 TERMINAL BUSHINGS: Six output leads (3 long, 3 short) have been brought out of

the coming on the exciter side. External connections are to be made to the three shorter

terminals, which are phase terminals. The large terminals are of neutral & current

transformer is inserted. The conductor of Generator terminal bushing having hollow copper

tubes with Copper brazed at the ends to avoid leakage of hydrogen. Hollow portions enable

bushings to be hydrogen cooled. Ends of bushings are Silver-plated: middle portion of the

bushing is adequately insulated & has a circular flange for bolting the stator casing. Gaskets

are provided between the Flange of terminal bushings and castings to make it absolutely

gas tight.




4.1.6 BEARINGS: Generator bearings have electrical seats of consists of steel bodies with

removable steel pads. The bearings are formed for forced lubrication of oil at a pressure of

2-3 ATM/ from the same pump that supplies oils to the turbine, bearings & governing gears.

There is a provision to ensure & measure the rotor bearing temperature by inserting a

resistance thermometer in the oil pockets.

4.1.7 VENTILATION SYSTEM: The machine is designed with ventilation system having 2

ATM rated hydrogen pressure. Two axial fans mounted on either side of the rotor to ensure

circulation of hydrogen. The stator is designed for radial ventilation by stem. The end stator

core packets & core clamping & plates are intensively cooled by Hydrogen through special

ventilation system. Design of special ventilation is so as to ensure almost uniform

temperature of rotor windings and stator core. Rated load operating temperature is well

within the limits corresponding to the Class B operation. Embedded Resistance

Temperature Detectors do continuous monitoring of Hydrogen temperature at active parts of

Generator.

4.2. ROTOR

4.2.1 ROTOR SHAFT: Rotor shaft consists of single piece alloy steel forging of high

mechanical and magnetic properties performance test includes:-

1. Tensile test on specimen piece.

2. Surface examination.

3. Sulfur prist tests.

4. Magnetic crack detection.

5. Visual examination of bore.

6. Ultrasonic examination.

Slots are milled on the rotor gorging to receive the rotor winding. Transverse slots

machined in the pole faces of the rotor to equalize the moment of inertia in direct and

quadrilateral axis of rotor with a view minimizing the double frequency.




4.2.2 ROTOR WINDINGS: rotor winding is of direct coil type and consists of parallel strips

of very high conductivity Silver Bearing Copper, bent on edge to form coil. The coils are

placed in impregnated glass, laminated short shells; using glass strips inter turn insulation

and will be brazed at the end to form continuous winding. The complete winging will be

packed at high temperature and pressed to size by heavy steel damping rings. When the

windings have cooled, heavy dove tail wedges of non-magnetic materials will seal the

insulation at the top of slot portion. The cooling medium hydrogen gas will be brought in

direct contact with copper by means of radial slots in embedded portion. Treated glass

spacers inserted between the coils and solid ring prevent lateral movement of coil overhang.

The formation and description of glass spacer is such as to leave ample space for

ventilation.

4.2.3 RETAINING RING: The centrifugal force of the rotor end windings are contained by

single-phase rotor retaining rings. The retaining rings are made of non magnetic high-

strength steel in order to reduce stray losses. Each retaining ring with its shrink fitted ring is

shrunk onto the rotor body in an overhung position . the retaining ring is secures in the axial

position by a snap ring.

4.2.4 FIELD CONNECTION: The field current is supplied to the rotor winding through

radial terminal bolts and two semicircular conductors located in the hollow bores of the

exciter and rotor shafts. The field current leads are connected to the exciter leads at the

exciter coupling with Multikontakt plug-in contacts which allow for unobstructed thermal

expansion of the field current leads.

4.3 BEARINGS: The bearings are self-aligned & consist of slip steel shells linked with

special bearing metal having very low coefficient of friction. The bore is machined on an

elliptical shape so as to increase the mechanical stability of the rotor. The bearing are

pressure lubricated from the turbine oil supply. Special precautions are taken to prevent oil

& oil vapor from shaft seals and bearing along the shaft. The circulation of shaft current is

liable to damage. The bearing surface is protected by insulation so placed that the bearings,

seals & necessary pipes are inclined from the frame.




4.4 SLIP RINGS : The slip rings are made of forged steel. They are located at either side

of Generator Shaft. The slip ring towards the exciter side is given +ive polarity initially.

They have helical grooves and skewed holes in the body for cooling purpose by air.

Calibrated mica is first built up to required thickness on the shaft where slip rings are

located. The slip rings are insulated from the rotor shaft. Excitation current is supplied to

the rotor winding. Through the slip rings which are connected to the winding. On one end

and to the slip ring on the other end with insulated (terminal) studs passing „though‟ the

radial holes in the rotor shaft. The terminal studs at both the ends of excitation leads are

fitted gas cat seals to prevent leakage.

4.5 BUSH GEAR ASEMBLY: Generator bushes are made from the various compositions

of natural graphite and binding material. They have a low coefficient of friction and are self

lubricating. The brushes are provided with a double flexible copper or pigtails. A helical

spring is mounted rapidly over each bush so that pressure is applied on the centerline of

bush. A metal cap is riveted to the brass bead and is provided with a hole to maintain the

position of the spring plug. Several brush holders, each carrying on brush in radial position

are fixed to silver plated copper studs mounted on the collecting arm concentric with each

slip rings. The collecting arm is made out of a copper strip.

4.6 COOLING SYSTEM: In SSTPS hydrogen cooling system is employed for generator

cooling. Hydrogen is used for cooling medium primarily because of its superior cooling

properties & low density.

Thermal conductivity of hydrogen 7.3 times of air.

It also has higher transfer co-efficient.

Its ability to transfer heat through forced convection is about 75% better than air.

Density of hydrogen is approx. 7/14 of the air at a given temperature and pressure.

This reduces the windage losses in high speed machine like turbo-generator.

Increasing the hydrogen pressure the machines improve its capacity to absorb & remote

heat.




Relative cooling properties of air and hydrogen are given below:-

1) Elimination of fire risk because hydrogen will not support combustion.

2) Corona discharge is not harmful to insula ? since oxidation is not possible.

3) Smooth operation of machine in view of vertical elimination of wind age noise & the

use of heavy gas light enclosure and dirty proby casing.

GENERATOR SPECIFICATION

KVA : 294100P.F : 0.85

Stator

Volts : 16500 V

Amps : 10290 A

Rotor

Volts : 319 V

Amps : 238 A

RPM : 3000

Frequency : 50 Hz

Coolant : HYDEOGEN 3 bar Gas Pressure

EXCITATION SYSTEM The electric power Generators require direct current excited

magnets for its field system. The excitation system must be reliable, stable in operation and

must response quickly to excitation current requirements. When excitation system response

is controlled by fast acting regulators, it is chiefly dependent on exciter. Exciter supply is

given from transformer and then rectified.

(A) Function of excitation system: The main function of excitation system is to supply

required excitation current at rated load condition of turbo Generator. It should be




able to adjust the field current of the Generator, either by normal controller automatic

control so that for

(B) All operation & between no load and rated load. The terminal voltage of the system

machine

(C) Maintained at its value. The excitation system makes contribution improving power

system stability steady state condition. The excitation system that are commonly

termed quick response system and have following principal feature :- Exciter of

quick response & high voltage of not less than 1.4 times the rated filed voltage and

nominal exciter response of minimum 0.5.

Type of excitation system: There have been many developments in excitation system

design. There has been continuing reach among the design and the use alike from improving

the excitation system performance. The ultimate is to achieve stability; accuracy etc. the

modern excitation system adopted presently on BHEL make turbo-generator.

I. Conventional DC excitation system

II. Brushes excitation system.




5. BOILER

It consist three different units.

5.1 Boiler Unit

5.2 Mills

5.3 Fans

5.1 Boiler Unit

The Boiler Unit comprise the following elements:-

Boiler

Super heater

Reheater

Economizer

Airpreheater

Furnace

5.1.1 Boiler

The boiler installed in S.T.P.S. is made by M/s BHEL. Each of the boilers are

single drum, tangential fired water tube naturally circulated over hanged, balanced draft, dry

bottom reheat type and is designed for pulverizing coal firing with a max. Continuous steam

output of 375 tons/hour at 138 kg/cm2

pressure and 5400C temperature.

The thermal efficiency of each boiler at MCR is 86.8 %. Four no. of bowl mills have

been installed for each boiler. Oil burners are provided for initial start up and stabilization of

low load.

Two E.S.P.(one for each boiler) is arranged to handle flue gases from the respective

boilers. The gases from E.S.P. are discharged through 180 meters high chimney. I.D. fan

and a motor is provided with a balanced draft consisting of two forced draft fans and two

induced draft fans. Flue gases are utilized to heat the secondary air for combustion in the

tubular type air heaters installed in the boilers. Since the boiler furnace is maintained at a

negative pressure, to avoid atmospheric air entering the furnace a hydraulic pressure is

maintained at the furnace bottom.






Connecting pipe and safety components like safety valve non return valve isolating

valve steam temp. regulating equipment etc. A reheater is composed of two sections viz.

front pendent vertical spaced, rear pendent vertical spaced. The front pendent vertical

section is located between the rear water wall hanger tubes and the super heater plates

section. The rear pendent vertical spaced section is located above the furnace arch between

the water-cooled system wall tubes and heat wall hanger tubes.

5.1.4 Economizer

The function of an economizer in a steam-generating unit is to absorb heat from the

flue gases and add this as sensible heat to fed water before the water enters the evaporating

ckt. Of the boilers. The coils of the economizer are designed for horizontal placement which

facilitates the draining of the coil and favours the arrangement in second path of boiler.

Water flows bottom to the top so that steam in any from during the heat transfer can move

along with water and prevent the lock up steam which will cause over heating and failure of

economizer.

5.1.5 Airpreheater

Air preheater is a heat exchanger in which air temp. is raised by transferring heat

from other fluids such as flue gas. Since air heater can be successfully employed to reclaim

heat from flue gas at lower temp. level, then it is possible with economizer the heat ejected

to chimney can be reduced to a great extent thus increasing the efficiency of a boiler.

5.1.6 Furnace

Furnace is the primary element part of the boiler where the chemical is obtained by

combustion. Furnace is designed for maximum heat release from the face with in the

combustion chamber. In water cooled chamber furnace the whole combustion region is

surrounded by tubes through which water flows. These are baked by refractory walls.




MILLING PLANT

5.2.1 Pulverized coal Systems

5.2.2 Direct Firing System

5.2.3 Drum/Tube mills

5.2.1 PULVERIZED COAL SYSTEMS

For steam generation, there is basically system of pulverization normally in STPS plant used

is Direct Firing System

DIRECT FIRING SYSTEM

Hot Primary System :

In this system the fan is located before the pulverized and handles complete primary

air required for drying a transporting the coal. Disadvantages are that the fan is required to

handle high temperature air resulting in high a fan power. Separate sealing air fans are

required to seal the mill and Journal bearings.

Cold Primary Air System :

The primary air fan handles clean cold air either from FD fan discharge or taking

suction from atmosphere. The advantages are saving in fan power and maintenance. The

only disadvantage. Is the cost increase due to additional duct work and air heater.

Suction System :

In this system the mill operates under negative pressure. Suction being created by an

exhauster placed after the mill. The exhauster handles all the coal air mixture and forces it

into the burners. The advantage of suction system is that the plant can be maintained clean.

The disadvantage of this system id that he high speed exhauster has to handle coal air

mixture and tends to wear more as the pulverized size increase.




Pressurized Exhauster system :

In this system the mills operate under positive pressure. With exhauster provided at hr exit

of pulverize to boost the pulverized coal into the pressurized furnace. Since the pulverized

operates with lesser pressure than forced draft fan pressure.

In plant TUBE type o pulverized mill is used.

5.2.3 DRUM / TUBE MILLS

This type mills is slow speed type. They operate at a speed of 17-20 rev/min and

formerly were designed as suction mills.

The mill drum carrying the ball charge rotates in the antifriction bearings. Raw-coal

is fed to the drum through the inlet elbow and gets crushed to powder inside the mill drum.

The ball charge and the coal are carried to certain height inside the drum and slowed to fall

down. Due to the impact of the balls on cola particle sand due to attrition as the particles

slide over each other and also over the liners, the coal gets crushed. Hot flue gases are used

for drying and transporting the pulverized coal from the mill to the classifier.

Advantage :

High output possible, up to 50 tones per hour.

No maintenance over long periods

High availability

Because of high availability no stand by capacity is required

No mill rejects, no problems with „tramp‟ iron

Reserve of fuel within mill makes output more stable.

Disadvantage :

High power consumption

Some problems with control of coal level within the mill.

Virtually constant power consumption at all loads; low load operation of therefore not

economical.

With high moisture content fuels a high primary air temperature is required because of the

low air/fuel ratio




Unplanned stops leave the mill full of coal which, under unfavorable conditions, can ignite.

This coal has to be quenched and even dug out otherwise the mill cannot be restarted.

Heat Transfer in Boiler :

In boiler heat energy is released from the combustion of fossil fuels and the heat is

transferred to different fluids in the system and a part of it is lost or left out as unutilized.

There are three modes of heat transfer:

Conduction

Convection

Radiation

Heat energy is transferred from a heat source to a heat receiver by one or more of

these modes for which heat source should be at a higher temperature than the receive.

In superheater tube with high temperature region but does not directly view the flam.

Here the heat is transferred from flue gas to superheater tube metal by convection and by

non-luminous radiation and in the tube metal by conduction and to the steam by forced

convection.

The power plant boilers are large capacity steam generators used purely for the

electrical power generation.




5.3 FANS

5.3.1 F.D. FAN (Forced fan)

5.3.2 I.D. FAN (Induced fan)

5.3.3 P.A. FAN (Primary fan)

5.3.1 FORCED DRAFT FAN

In the Axial Reaction Fans (Type AP), the major part of (about 80%) energy

transferred is converted into static pressure in the impeller itself. The rest of the energy is

converted into static pressure in the diffuser. These fans are generally driven at constant

speed. Varying the angle of incidence of impeller blades controls the flow.

Technical Data:

Application : Forced Draft Fan

No. off : 2

Medium handled : Atmospheric Air

Orientation : Vertical Suction and Horizontal Delivery

Capacity : 105.2 m3 /Sec

Temp. Of medium : 450C

Speed : 1480 rpm

Coupling : Rigiflex coupling

Drive motor

Rating : 700 KWSpeed : 1480 rpm

Fan Weight : 8 Tones

Type of fan regulation : Blade Pitch Control




When looking in flow direction, the fan consists of the following Components :

Suction chamber

Fan Housing

Rotor Consisting go shaft, on impeller with adjustable blades with pitch control

mechanism.

Main bearings (Antifriction bearings)

Outlet Guide Vane housing with guide vanes

Diffuser

5.3.2 INDUCED DRAFT FAN

Radial fans manufactured are single stage, single/ double suction, simply

supported/overhung centrifugal machine which can be used to handle fresh air as will as hot

gases in power plant application. These fans are generally driven by constant speed motors.

The output of the fan is usually controlled by inlet dampers or inlet guide vanes or by

varying the speed of the fan by suitable speed control device.

Technical data:

Application : Induced Draft Fan

No. off : 3

Type : NDZV 33 S

Medium handled : Flue Gas

Orientation : 450

Top incl. Suction

Bottom Horizontal, DeliveryCapacity : 250.5 m

3 /Sec

Temp. of medium : 1540C

Speed : 740 rpm

Coupling : Hydraulic Coupling

Motor Rating : 1750 KW

Speed : 740 rpm

Fan Weight : 52.7 Tones




The major sub-assemblies of the fan are as follows :

Impeller with shaft assembly

Bearings and thermometers

Suction chamber and spiral casing

Flow regulation devices

Shaft seals

Couplings

The fan is drive by an electric motor.

The fan bearings are lubricated by means of oil lubrication. The oil must not foam during

operation. Foam removing agents containing silicon must not be utilized. The oil must have

good anti-corrosion properties.

5.3.3 PRIMARY AIR FAN

PA Fan is same as forced draft fan. Only the differences is that in this fan there are

two stages AP fan (Axial Profiles fan), the two impellers are connected by means of a link

rod, with this we can operate both the impeller blades synchronously.

Technical data:

Application : Primary Air Fan

No. off : 3

Type : Ap2 17/12

Medium Handled : Atmospheric Air

Speed : 1480 rpm

Rating : 1400 KW

Fan wt. : 10.8 tones




6. STEAM TURBINE

6.1 Introduction :-Turbine is a machine in which a shaft is rotated steadily by impact or reaction of

current or stream of working substance (steam, air, water, gases etc) upon blades of a wheel.

It converts the potential or kinetic energy of the working substance into mechanical power

by virtue of dynamic action of working substance. When the working substance is steam it

is called the steam turbine.

The steam turbines and their auxiliaries installed have been manufactured by M/s BHEL.

The turbines are three cylinders, compound 3000 rpm, double flow exhaust type reheat units

with initial parameters of 13 kg/cm2

and 5 low pressure heaters are fed. The high pressure

cylinder comprises of two curt is wheels as a regulation stage Intermediate pressure

cylinders comprise of twelve stages and each of the double flow section of the L.P. cylinder

consists of four stages.

6.2 Operation :-

There are two live steam lines connecting the boiler to the turbine. The superheated

steam enters the H.P. turbine and strikes its blades hence heat energy of steam is converted

into mechanical energy. The steam from H.P. turbine is reheated in reheater and reheated

steam is sent to I.P. turbine through hot steam lines. Here second stage of energy conversion

is takes place. Then steam is sent to L.P. turbine from where it is ejected by vacuum ejectors

and condensed. Here are two cold reheat and two hot reheat lines connecting the reheater

and turbine. In each of the two live steam lines one electrically operated isolation valve, one

water separator and one quick closing stop valve are mounted. The direction of revolution of

turbine is clock wise when looking at turbine from front bearing pedestal. For the oil

lubrication of bearings and for governing, the main oil pump driven shaft is assembled into

the front bearing pedestal of turbine itself.




6.3 Description of Steam Turbine

6.3.1 Steam flow:

Steam turbine is a tandem compound machine with HP, IP & LP parts. The HP part

is single flow cylinder and HP & LP parts are double flow cylinders. The individual turbine

rotors and generator rotor are rigidly coupled. The HP cylinder has a throttle control. Main

steam is admitted before blending by two combined main stop and control valves.

The HP

turbine exhaust (CRH) leading to reheated have tow swing check valves that prevent back

flow of hot steam from reheated, into HP turbine. The steam coming from reheated called

HRH is passed to turbine via two combined stop and control valves. The IP turbine

exhausts directly goes to LP turbine by cross ground pipes.

6.3.2 HP Turbine:

The HP casing is a barrel type casing without axial joint. Because of its rotation

symmetry the barrel type casing remain constant in shape and leak proof during quick

change in temperature. The inner casing too is cylinder in shape as horizontal joint flange

are relieved by higher pressure arising outside and this can kept small. Due to this reason

barrel type casing are especially suitable for quick start up and loading.

The HP turbine consists of 25 reaction stages. The moving and stationary blades are

inserted into appropriately shapes into inner casing and the shaft to reduce leakage losses at

blade tips.




6.3.3 IP Turbine:

The IP part of turbine is of double flow construction. The casing of IP turbine is

split horizontally and is of double shell construction. The double flow inner casing is

supported kinematic ally in the outer casing. The steam from HP turbine after reheating

enters the inner casing from above and below through two inlet nozzles. The centre flows

compensate the axial thrust and prevent steam inlet temperature affecting brackets, bearing

etc. The arrangements of inner casing confines high steam inlet condition to admission

branch of casing, while the joints of outer casing is subjected only to lower pressure and

temperature at the exhaust of inner casing. The pressure in outer casing relieves the joint of

inner casing so that this joint is to be sealed only against resulting differential pressure.

The IP turbine consists of 20 reaction stages per flow. The moving and stationary

blades are inserted in appropriately shaped grooves in shaft and inner casing.

6.3.4 LP Turbine:

The casing of double flow type LP turbine is of three shell design. The shells are

axially split and have rigidly welded construction. The outer casing consist of the front and

rear walls, the lateral longitudinal support bearing and upper part.




7. E.S.P.

7.1 E.S.P THEORY :-

An electrostatic precipitator (ESP), or electrostatic air cleaner is a particulate

collection device that removes particles from a flowing gas (such as air) using the force of

an induced electrostatic charge. Electrostatic precipitators are highly efficient filtration

devices that minimally impede the flow of gases through the device, and can easily remove

fine particulate matter such as dust and smoke from the air stream.

7.2 WORKING PRINCIPLE :-

E.S.P. can handle large volume of gases from which solid particles are to be removed

Advantages of E.S.P. are:- High collection efficiency Low resistance path for gas flow

Treatment of large volumes at high temp. Ability of cope with corrosive atm. An E.S.P. can

be defined as a device which utilized electric forces to separate suspended particles from

flue gases.

7.3 WORKING STEPS :-

Ionization of gases and charging of dust particles Migration of dust particles.

Deposition of charge particles on collector surface. Removal of pa E.S.P. consist of two sets

of electrodes, one in the form of thin wire, called discharge or emitting electrode in the form

of plates. The emitting electrodes are placed in the center or midway between two plates and

are connected to -ve polarity of H.V. D.C. source of order of 37 KV collecting electrodes

are connected to + ve polarity. The voltage gradient between electrodes creates “CORONA

DISCHARGE”, ionizing the gas molecules. The dust particles present in flue gases acquire

– ve charge and deposited on collecting electrodes. The deposited particles are removed by

knocking the electrode by process called “RAPPING‟ DONE BY “RAPPING MOTORS”.

http://en.wikipedia.org/wiki/Particulate

http://en.wikipedia.org/wiki/Electrostatic_charge

http://en.wikipedia.org/wiki/Filtration

http://en.wikipedia.org/wiki/Filtration

http://en.wikipedia.org/wiki/Electrostatic_charge

http://en.wikipedia.org/wiki/Particulate




8. COAL HANDLING PLANT

Coal transferred by Railway system. One rail (Rack) consist 58-59 boxes with 60 Tons coal

loaded in each box. The main equipment of coal handling plant is as-

8.1 Wagon Tripler: Tripler is equipment which the coal is unloaded from box by lifting

& tilting the box. Wagon tippler has rated unloading capacity of twelve-box wagon per

hour, including shunting and spotting time of haulage equipment.

8.2 Side Arm Charger: Box is placed on tripler platform and push or carries the loaded

empty boxes.8.3 Crusher: Coal is crushed in desired size by crusher.

8.4 Conveyor: A different sizes and different capacity conveyors are installed for

transporting feed the coal from wagon Tripler to Bunkers.

8.5 Stacker/Reclaimer: The crushed coals are stack or reclaim the stacked coal by

stacker/reclaimer.

8.6 Bunkers: Crushed coal stored in the canonical shape bunkers.




9. ASH HANDLING PLANT

The ash handling system provide for continuous collection of bottom ash from thefurnace hearth and its intermittent removal by hydro ejectors to a common slurry

sump.

It also provides for removal of fly ash to the common slurry sump.

Each boiler is provided with ash precipitator for collecting the fly ash from the flue

gases with high efficiency of collection to minimize the dust mains and to reduce the

wear of induced draft fan. The fly ash separated from flue gases in the ash

precipitator is collected in hoppers at the bottom from where it is mixed with water to

form slurry and disposed off to pumping area by means of hydro ash pumps. Bottom

ash from the boiler furnace is passed through slag crushers and then slurred to the

chamber at the suction of the ash disposal pumps. These are high pressure and low

pressure pumps for this purpose.

At a time one pump is working and other two are stand by from the ash disposal

pump house ash slurry is pumped through pipe lines to the ash dump area within

about 1.5 km away from the ash disposal pump house.

Too separate discharge lines are provided one for each unit but only one line is used.

The ash slurry from the two units is taken in one discharge line through electrically

operated valves.




10. COMMON AUXILIARY

Common Auxiliaries

Cooling Water Pump

Auxiliaries Cooling Water Pump

Compressor

Common auxiliaries: Common auxiliaries supply the support to run the power plant. In this

cooling water and air are mainly supply.

Cooling Tower: Both CW and ACW water cooled in cooling tower by spraying and

exhausting the hot air from the water.

Cooling Water Pump: This is cooling feed to condenser for condensate the exhaust

steam from LP Turbine in condenser then hot well.

Auxiliaries Cooling Water Pump: By name it is supply auxiliaries cooling water to

rotating equipment lub oil cooling.

Compressor: It is mainly two type .

Service air

Instrument air

Service air: The service air are used for boiler operation

Instrument air: The instrument air are used for generally for operation of the control

valve, etc.




11. PROTECTION

A. Field Protection.

B. Pole Slipping.

C. Plane Overload Protection.

D. Inter-turn Fault

E. Negative Phase Sequence Protection.

F. Reverse Power Protection.

G. Forward Power Protection.

H. Under Frequency & Over Frequency Protection.

I. Generator Voltage Protection.

J. Rotor Earth Fault Protection.

General Protection:

It is most important electrical equipment of many generating station. Tripping of even a

generating unit may cause overloading of associated machines and even to system un-

stability. The basis function of protection applied to generator is to reduce voltage to

minimum by rapid discrimination clearance of faults. Unlike other apparatus the opening of

C.B. to isolate faulty generator is not sufficient to prevent future damage. Since generator

would continue to supply power to stator winding fault , until its excitation is suppressed. It

is, therefore, necessary to open field stop fuel supply to prime mover & in some casebreaking also.




12. SALIENT FEATURES OF UNIT AUXILIARIES

A. BOILER AREA

I. ID FAN : - 3Φ,6.6 KV, 1750 KW

Rated Current : - 192.1 A

RPM : - 745

Discharge : - 720.98 T/hour

II. FD FAN : - 3Φ,6.6 KV, 700 KW Rated Current : - 73.6 A

RPM : - 1491


III. PA FAN : - 3Φ,6.6 KV, 1400 KW


RPM : - 1400Discharge : - 323.4 T/hour

IV. MAIN MILL MOTOR : - 3Φ,6.6 KV, 2400 KW Rated Current : - 266.2 A

RPM : - 1488

V. AUX. MOTOR OF MILL : - 3Φ,415 KV, 30 KW

Rated Current : - 52 A

RPM : - 1470

VI. SEAL AIR FAN OF MILL : - 3Φ,415 V, 120 KW

Rated Current : - 198A

RPM : - 3000

VII. AIR HEATER MOTOR : - 3Φ,415V, 11 KW

Rated Current : - 52A

RPM : - 1450




B. TURBINE AREA

I. BFP : - 3Φ, 6.6 KV, 4600 KW

Rated current : - 469 A

RPM : - 1485Discharge : - 720.98 T/hour

II. CEP : - 3Φ, 6.6 KV, 325 KW

Rated current : - 35.4 ARPM : - 1466


III. CVP : - 3Φ, 415 V, 100 KW


RPM : - 588

IV. AOP : - 3Φ, 415 V, 100 KW


RPM : - 2980

V. JOP (AC) : - 3Φ, 415 V, 45 KW


RPM : - 2960

VI. JOP (DC) : - DC 45 KWRated Current : - 250 A

RPM : - 2900

VII. EOP (AC) : - 3Φ, 415 V, 15 KW


RPM : - 1450

VIII. EOP (DC) : - DC 13 KW


RPM : - 1420




C. ELECTRICAL & CA AREA

I. GENERATOR : - 3Φ, 294.1MVA, 16.5 KV

Rated current : - 10290A

P.F : - 0.85 (lag)

II. GENERATOR TRANSFORMER : - 3Φ, 315 MVA

HV voltage : - 235 KV

LV voltage : - 16.5 KVHV current : - 773.9 A

LV current : - 11022.1 A

III. STATION TRANSFORMER : - 3Φ, 40/50 MVA

Voltage : - 220/6.9 KV

HV current : - 105/131 ALV current : - 3351/41898 A

IV. CW PUMP (Stage 1) : - 3Φ, 6.6 KV, 1485 KW


Discharge : - 17000 M3 /hour

V. CW PUMP (Stage 2) : - 3Φ, 6.6 KV, 1850 KW


VI. ACW PUMP (Stage 1) : - 3Φ, 6.6 KV, 525 KW Rated current : - 60 A


VII. ACW PUMP (Stage 2) : - 3Φ, 6.6 KV, 500 KW

Rated current : - 57A

VIII. ASH SLURY PUMP #1 : - 3Φ, 6.6 KV, 175 KW Rated current : - 21 A

RPM : - 988


IX. ASH SLURRY PUMP #2 : - 3Φ, 6.6 KV, 280 KW


RPM : - 1480


X. HP PUMP : - 3Φ, 6.6 KV, 710 KW


RPM : - 1486


XI. LP PUMP : - 3Φ, 415 V, 75 KW





RPM : - 1483Discharge : - 300 M

3 /hour

XII.

INTAKE PUMP : - 3Φ, 415V, 90 KW Rated current : - 159 A

RPM : - 985


XIII. RAW WATER PUMP : - 3Φ, 415 V, 135 KW

Rated current : - 236 ADischarge : - 1600 M

3 /hour

XIV. COOLING TOWER FAN : - 3Φ, 415 V, 37 KW


XV. DMCCW PUMP : - 3Φ, 415 V, 140 KW


XVI. JOCKEY PUMP : - 3Φ, 415 V, 30 KW



XVII. ASH WATER PUMP : - 3Φ, 415 V, 90 KW

Rated current : - 159 ADischarge : - 700 M

3 /hour

XVIII. DUST SUPPRESSION PUMP : - 3Φ, 415 V, 37 KW



XIX. HP SPRAY : - 3Φ, 415 V, 180 KW



XX. AIR COMPRESSOR : - 3Φ, 415 V, 135 KWRated current : - 225 A

RPM : - 1484




13. CONCLUSION

The first phase of practical training has proved to be quiet fruitful. It

provided an opportunity for encounter with such huge machines like wagon tippler,110 MW

& 210 MW turbines and generators.

The architecture of the power plant the way various

units are linked and the way working of whole plant is controlled make the student realize

that engineering is not just learning the structured description and working of various

machines, but the greater part is of planning proper management.

It also provides an opportunities to lean low technology used at proper place and time cancave a lot of labour e.g. wagon tippler (CHP).

But there are few factors that require special

mention. Training is not carried out into its tree sprit. It is recommended that there should

be some project specially meant for students where presence of authorities should be

ensured. There should be strict monitoring of the performance of students and system of

grading be improved on the basis of work done.

However training has proved to be quite fruitful. It has allowed an opportunity to get an

exposure of the practical implementation to theoretical fundamentals.



PROPERTIES OF POWER STATION COAL FROM THE IMPORTANT

COAL FIELDS OF INDIA

NAME OF COAL FIELD/

COLLIERY G.C.V OF

COAL

KCAL/KG PROXIMITE ANALYSIS

H G I

SULP

HUR

TOTA

L %

G.C.V

ON

D.M.F

BASIS

KCAL/K

G MOIST

URE

% ASH

% VOLATI

LES % RANIGANJ 4900-5300 4--9 10--25 30--40 40--50 <1 8200 WARDHA VALLY-KAMPTEE 4600-5000 7--10 25--35 23--30 60-70 <1 8000 NORTH KARANPURA 5800-6200 4--6 15--22 25--35 50-60 <1 8100 TALCHER 4600-4900 7--9 28--31 27--31 60-66 <1 8100 SINGRAULI-JINGUDA SEAM(U.P) 4450-4800 9--10 21--24 28--29 50-65 <1 8100 SINGARENI -ANDHRA PRADESH 4000-4400 7--10 25--35 25--35 44-60 <1 8000 CENTRAL IDIA-PENCH 4800-6200 2--9 16--32 17--33 46-69 <1 8000 CENTRA INDIA-BISRAMPUR 5600-6000 9--11 10--17 25--35 60-70 <1 8000 NEYVELI-LIGNITE 2900-3300 30--60 2--15 20--26 HIGH <1 7900

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