A

Practical Training

Taken

At

“ Suratgarh Super Thermal Power Station”

Submitted to

Rajasthan Technical University, Kota

In Partial Fulfillment For The Award of

Degree Of

Bachelor Of Technology(B.Tech.)In

Electrical Engineering

Submitted To:- Submitted By:-

Mr. Hemant Kaushik Sarita Sharma

(Reader) B. Tech.(final year)

Electrical Department Roll No. – 11EMEEE213

Department of Electrical Engineering

Marudhar Engineering College, NH-11 Raiser, Bikaner(Raj.)

Acknowledgement

This is opportunity to express my heartfelt words for the people who were part of

this training in numerous ways, people who gave me unending support right from

beginning of the training.

I place on record my sense of gratitude to Mr. B.P.Chakraborty(X.E.N. STPS)

for enabling me to carry out my training at STPS.

I wish to express my sincere gratitude to Mr. H.K. Tomar(A.E.N. STPS),Mr.

Neeraj Gahlot(J.E.N. STPS) and Mr. Ramdutt(Operator) for providing me the

valuable knowledge that I gained at STPS.

I am equally obliged to all other Engineers and Technical personnel and operators

at STPS who gave me their valuable time and rendered practical knowledge in my

training period.

I am grateful to Training In charge Mr. Hemant Kaushik for giving guidelines

to make my training a success.

I want to give sincere thanks to the Principal, Dr. R.P.S. Jakhar for his valuable

support.

I extend my thanks to Dr. Javed Khan Bhutto Head of the Department for his

cooperation and guidance.

At last I would like to express my sincere thanks to one and all who, directly or

indirectly, have lent their helping hand in this venture.

Yours Sincerely,

Sarita Sharma.

(II)

ABSTRACT

Suratgarh thermal power station is the first super thermal plant of Rajasthan. Suratgarh Super

Thermal Power Station is owned by Rajasthan Rajya Vidhyut Utpadan Nigam Ltd. and is

situated near village Raiyanwali about 25 kms from Suratgarh town, 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.

The techno-economic clearance for the prefect was issued by CEA in June 1991 –the planning

commission accorded investment sanction for the project in Nov. 91 for a total estimated cost

of Rs. 1253.31 crores on prices prevailing in Sept. 1990. The updated cost of the project is

estimate at Rs. 2300 crores of including IDC. It has generation capacity of 1500 MW and

installed with six Units of 250 MW each. It is a coal base thermal station. Water and coal

required in a large amount. Coal is received here from coal-fields of MP which are state owned

through railways and water is received from INDIRA GANDHI CANAL. The supply of coal is

from MP, Jarkhand by rail. About 18000 tonne coal required per day for whole unit and each

unit consumes 150 tonnes coal per day. About 2x3 km2 area covered by plant and

approximately 1800 employees works in a plant including chief engineer to labour. The supply

electricity to the northern Rajasthan, Ratangarh, Bikaner, Ganganagar

.It has been decided to set up 2 X 660 MW super critical units (Unit # 7 & 8) at SSTPS. For this

purpose about 446 Hectare land has been identified adjacent to the existing 6 X 250 MW plant.

This land is under process of acquisition. M/s TEC have been appointed consulting engineers

for this project. The state Govt. has also accorded its inpriciple approval for setting up in future,

two additional units of 2 X 660 MW (UNIT # 9& 10) also based on super critical technology.

(III)

Index Of ContentsSerial No. Particulars Page No.

1. Basic operation of thermal power station 1

2. Classification of thermal power plant 2

3. Selection of site for thermal power plant 8

5. Plant familiarization 9

6. Coal handling plant 10

7. Milling plant 12

8. Water treatment plant 14

9. Boiler 15

10 Turbine 21

11. Generator 25

12. Condenser 29

13. Cooling towers 31

14. Deaerator 32

15. Pumps 33

16. E.S.P. 3617. Ash handling plant 3718. 220 kv & 400 kv switchyard and

different equipments installed and bus

schemes

39

19. Maintenance jobs to be done on 220 kv

& 400 kv switch yard

43

20. Conclusion 49

21. References 50

(IV)

List Of Figures

Fig. No. Description Page no.

Fig.1 General layout of thermal power plant 3

Fig.2 Introduction to STPS 4

Fig.3 Plant overview 7

Fig.4 Coal handling 11

Fig.5 Coal crusher 13

Fig.6 Tube mill 13

Fig.7 Clarifloculator bridge 15

Fig.8 Water treatment plant 15

Fig.9 Boiler drum 16

Fig.10 Air pre heater 18

Fig.11 Economizer 19

Fig.12 Turbine 23

Fig.13 Turbine governor 24

Fig.14 Generator after the removal of end shields 26

Fig.15 Surface condenser 30

Fig.16 Cooling towers 31

Fig.17 Deaerator 32

Fig.18 E.S.P. 36

Fig.19 Ash handling 37

Fig.20 400 KV layout of STPS 38

(V)

List Of Tables

Table No. Description Page No.

Table 1 Installed capacity 5

Table 2 Sanction of schemes 5

Table 3 Commissioning targets and

achievements

6

Table 4 Generator transformer data 28

Table 5 Technical data of SF6 circuit breaker for 220 and 400 KV

41

(VI)

BASIC OPERATION OF THERMAL POWER STATION

Coal is used as fuel for the generation of heat energy. As the water in the boiler evaporated due to the intense heat, it becomes high pressure steam.

And the steam passes through a conduit (there is a turbine at the other end of the tunnel), it forces its way through the turbine, thus rotating the turbine. As the steam is high pressurized, the turbine rotates very fast.

The turbine is connected to a generator via a coupler. As the turbine is rotating from the force of the steam, electrical energy is being produced.

After the steam have passed through the turbine, it enters a condenser. The condenser has got a cooling agent (namely sea water) and the steam will go through the cooling agent via a pipe. The steam thus changes back to its liquid form and returns to the boiler.

And the whole process repeats.

1

CLASSIFICATION OF THERMAL POWER PLANTS

Thermal power plants are classified by the type of fuel and the type of prime mover installed.

1. BY FUEL-

Fossil Fueled power plants may also use a steam turbine generator or in the case of natural gas fired plants may use a combustion turbine. A coal fired power stations produces electricity by burning coal to generate steam and has the side effect of producing a large amount of carbon dioxide, which is released from burning coal and contributes to global warming.

2. BY PRIME MOVER-

Steam turbine plants use the dynamic pressure generated by expanding steam to turn the blades of a turbine. Almost all large non hydro plants use this system. About 80% of all electric power produced in the work is by use of steam turbines.Gas turbine plants use the dynamic pressure from flowing gases (air and combustion products) to directly operate the turbine. Natural gas fuelled (and oil fuelled) and so are used to supply “peak” energy during periods of high demand, though at higher cost than base-loaded plants.

2GENERAL LAYOUT OF THERMAL POWER PLANT

3

INTRODUCTION TO SURATGARH SUPER THERMAL POWER

STATION

Fig.1. general layout of thermal power plant

4

Table 1. Installed capacityStage Unit No. Installed

Capacity(MW)

Date of

Commissioning

Status

Fig.2. introduction to

Stage I 1 250 May, 1998 Running

Stage I 2 250 March, 2000 Running

Stage II 3 250 October, 2001 Running

Stage II 4 250 March, 2002 Running

Stage III 5 250 June, 2003 Running

Stage IV 6 250 May,2010 Running

Table 2. Sanction of scheme (Stage-I to IV)Stage Unit No. Capacity(MW) Cost(Rs.Crore)

I I & II 2x250 2300

II III & IV 2X250 2057

III V 1X250 753

IV VI 1X250 1117

TOTAL 5127

 

5

Table 3. Commissioning targets and achievements

UNITSZERO

DATETARGET

ACTUAL

DATE

DATE OF

COAL

FIRING

DATE OF

COMMERCIAL

OPERATION

Remarks

UNIT-1 Jun-91 MAR-199710-MAY-

1998

04-OCT-

199801-FEB-1999

UNIT-2 Jun-91 SEP-200028-MAR-

2000

07-JUN-

200001-OCT-2000

COMMISSIONED 6

MONTH AHEAD OF

SCHEDULE

UNIT-323-Jun-

99MAR-2002

29-OCT-

2001

08-DEC-

200115-JAN-2002

COMMISSIONED 6

MONTH AHEAD OF

SCHEDULE

UNIT-423-Jun-

99SEP-2002

25-MAR-

2002

17-JUN-

200231-JUL-2002

COMMISSIONED 6

MONTH AHEAD OF

SCHEDULE

UNIT-51-Feb-

01JUN-2003

30-JUN-

2003

30-JUN-

200319-AUG-2003

COMMISSIONED IN

RECORD TIME OF

29 MONTH

UNIT-615-Jun-

06OCT-2008

31-MAR-

2009

24-AUG-

200930-DEC-2009

COMMISSIONED IN

RECORD TIME OF

29 MONTH

5

PLANT OVERVIEW

7

SELECTION OF SITE FOR STEAM POWER PLANTS

1- SUPPLY OF WATER:A large quantity of water is required in steam power plants.a- It raise the steam in the boiler .b- For cooling purposes such as in condensers.

2- REQUIREMENT OF LAND:

Fig.3. plant overview

The land is required not only for setting up of the plant but also for other purposes such as staff colonies, coal storage, ash disposal, etc. cost of land adds to the final cost of the plant. So it should be available at a reasonable cost. Land should be of good bearing capacity since it has to withstand about 7 kg.per.sq.cm. Moreover, land should be reasonably level. It should not be low lying.

3- TRANSPORTATION FACILITY:The land and rail connections should be proper and capable of taking heavy and over dimensioned loads of machines etc. To carry coal, oil, etc. which are daily requirements, we need these transport linkages.

4- LABOUR SUPPLIES:Skilled and unskilled laborers should be available rates near the site of the plant.

5- ASH DISPOSAL:Ash is the main waste product of the steam power plant. Hence some suitable means for disposal of ash should be applied.

8

PLANT FAMILIARIZATION Main parts of plant are:

Coal Handling Plant

Water treatment plant

Boiler

o Super heater

o Re heater

o Economizer

o Air pre heater

Forced draft fan

Induced draft fan

Primary air fan

Turbine

Generator

o Transformer

Condenser

Cooling towers

Deaerator

BFP(Boiler feed pump)

E.S.P.

Ash handling plant

9

COAL HANDLING PLANT

1. INTRODUCTION

It can be called the heart of thermal power plant because it provided the fuel for combustion in boiler. The coal is brought to the S.T.P.S through rails; there are eight tracks in all for transportation of coal through rails.The coal handling plant can be broadly divided into three sections –

1- WAGON UNLOADING SYSTEM2- CRUSHING SYSTEM3- CONVEYING SYSTEM

CHP is a plant which handles the coal from its receipt to transporting it to boiler and store in bunkers. It also processes the raw coal to make it suitable for boiler operation.In brief we can say that receipt of coal mines, weighing of coal, crushing it to required size and transferring the quanta of coal to various coal mill bunkers. This is the responsibility and duty of the CHP and its staff.RECEIPT OF COAL:Normally thermal power station receives the coal by 3 modes of transportation:

1- By railway (80-90% of the requirement is fulfilled by this way)2- By road ( if required 5-10% of the requirement is fulfilled)3- By Arial ropeways.

2. MAJOR EQUIPMENTS OF CHP

1- WAGON TIPPLERS

2- VIBRATING FEEDERS3- CONVEYOR BELTS4- COAL CRUSHERS5- ELECTROMAGNETIC SEPARATORS6- DUST EXTRACTION SYSTEMS7- GAS EXTRACTOR8- TRIPPER

3. OPERATIONAL CYCLES

1. NORMAL BUNKERING CYCLE- Shifting of coal received from coal wagons directly to coal bunkers is normal bunkering cycle.

102. RECLAIMING CYCLE- When coal wagons are not available the requirement of coal

bunkers reclaiming cycle.

3. WEIGHING OF COAL

Weighing of coal is carried out at wagon tipplers. Weight of loaded wagon is taken after unloading the coal, weight of empty wagon is taken the difference of the two mill give the weight of the coal( NORMALLY 55-60 METRIC TONS OF COAL COME IN EACH WAGON).

4. CHEMICAL ANALYSIS OF COAL

Sample of coal is randomly collected from each rake by concerned, thermal staff and detailed chemical analysis, calculation of calorific value is carried out and is confirmed whether it is as per agreement with the coal mines or not.

11

MILLING PLANT1. PULVERIZED COAL SYSTEMS

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

used is Direct Firing System.

1.1 Direct Firing System

1.1.1 Hot Primary SystemIn 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.

1.1.2 Cold Primary Air System

Fig.4. Coal handling

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.

1.1.3 Suction SystemIn 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.

1.2 Pressurized Exhauster systemIn 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.

2. DRUM/TUBE MILLSIn plant TUBE type of pulverized mill is used. This type mills is slow speed type.

They operate at a speed of 17-20 rev/min and formerly were designed as suction mills.

11

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 coal particles and 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. As a result of this high availability in a tube- ball mill installation, it is not

normal to provide standby milling capacity; this helps to reduce the overall capital cost

of the plant. Power requirements have also been reduced, but they are still much

greater than those for medium speed mills.

3. COAL FEEDERSCoal feeders deliver the cola from the bunkers to the mill. Since the amount of coal

delivered determines the output of the mill, if follows that the cola flow, through the

feeder has to be controlled. This is normally achieved either by control of feeder speed

or by control of the position of a scraper knife or plough.In plant Drag Link Coal

Feeders type of Coal Feeder is used.

3.1 Drag Link Coal FeedersIn this type of cola feeder, the coal leaves the bottom of the bunker through a large outlet

hopper which is connected directly to the feeder casing. The cola falls on the feeder top plate

and is dragged along by the conveyor chain to the point where the top plate ends. The depth of

the cola bed is controlled by the height regulating gate. At the end of the top plate the cola falls

down between the stands of the chains to the Point of discharge at the mill inlet coal delivery

chute. The rate of coal feeds controlled by variable speed motor drive.

12

Fig.5. coal

13

WATER TREATMENT PLANT1. INTRODUCTION

The natural water contains solid, liquid and gaseous impurities and therefore, this water cannot

be used for the generation of steam in the boilers. The impurities present in the water should be

removed before its use in steam generation. The necessity for reducing the corrosive nature &

quantity of dissolved and suspended solids in feed water has become increasingly important

with the advent for high pressure, critical & supercritical boilers.

2. IMPURITIES IN WATER

Fig.6. tube mill

The impurities present in the feed water are classified as given below –

1. Undissolved and suspended solid materials

Turbidity and Sediment

Sodium and Potassium Salts

Chlorides

2. Dissolved Salts and Minerals

Calcium and Magnesium Slats

3. Dissolved Gases

Oxygen

Carbon Dioxide

3. REMOVAL OF IMPURITIES

Our major concern is industrial water treatment, whereby, water used directly or indirectly in

an industrial process is made suitable for that particular application. The use of water in boilers

fro steam generation is an obvious industrial use. Depending on the process, varying degrees of

purity of treated water are required. For example, a textile processing unit will require soft and

clear water for process use: a chemical plant or electronic components manufacturing unit will

require ultra-pure water containing total dissolved impurities not exceeding 0.5mg/litre or less.

14

Fig.7. clarifloculator bridge

BOILER1. INTRODUCTION

The boiler is the main part of any thermal power plant. It converts the fuel energy into steam

energy. The fuel may be furnace oil, diesel oil, natural gas or coal. The boilers may be fired

from the multiple fuels. The boiler installed in S.T.P.S. are 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.

15

Continuous steam output of 375 tons/hour at 138 kg/cm2 pressure and 540 degree cent. Temp.

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 near the chimney to induce the flue gases.

Fig.8. water treatment plant

1- CIRCULATION SYSTEMIt is essential to provide an adequate flow of water and/or of water-steam mixture for an

efficient transfer of heat from furnace to the working fluid and to prevent ‘burn-outs’. This is

irrespective of the mode of circulation being used. In STPS natural type of circulation system

are used.

1.1 Natural CirculationIn this type, no external pumping device is used for the movement of the fluid. The difference

in densities in contents of fluids in down comers from the drum and risers in the furnaces is

used to effect the movement of fluids. This type of circulation is employed in most of the utility

boiler.

16

One of the characteristics of natural circulation is its tendency to provide the highest flow in the

tubes with the greatest heat absorption.

2. HEAT TRANSFER IN BOILERIn 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 :

Fig.9. boiler drum

Conduction

Convection

Radiation

3. BOILER OPERATIONPulverized coal is air blown into the furnace from fuel nozzles at the four corners and it rapidly burns, forming a large fireball at the centre. The thermal radiation of the fireball heats the water that circulates through the boiler tubes near the boiler perimeter. The water circulation rate in the boiler is three to four times the throughput and is typically driven by pumps. As the water in the boiler circulates it absorbs heat and changes into steam at 700 degree F and 3200 psi. It is separated from the water inside a drum at the top of the furnace. The saturated steam is introduced into superheat pendant tubes that hang in the hottest part of the combustion gases as they exit the furnace. Here the steam is superheated to 1000 degree F to prepare it for the turbine. Plants designed for lignite (brown coal). Lignite is a much younger form of coal than black coal. It has a lower energy density than black coal and requires a much larger furnace for equivalent heat output. Such coals may contain up to 70% water and ash, yielding lower furnace temperatures and requiring larger induced draft fans. The firing systems also differ from black coal and typically draw hot gas from the furnace exit level and mix it with the incoming coal in fan type mills that inject the pulverized coal and hot gas mixture into the boiler.

4. BOILER PARTS4.1. Super heater

Fossil fuel power plants can have a super heater or re-heater section in the steam generating furnace. it is piped from the upper drum area into tubes inside an area of the furnace known as the super heater, which has an elaborate set-up of tubing where the steam vapour picks up more energy from hot flue gases outside the tubing and its temperature is now super heated above the saturation temperature heaters in an attempt to improve overall plant operating cost.

17

4.2. ReheaterReheater are provided to raise the temperature of the steam from which part of energy

already been extracted by HP turbine. The reheater is composed of two stages or

section, the front pendant vertical spaced platen section and the rea5r pendant vertical

spaced platen section. The rear pendant vertical spaced section is located above the

furnace arch between the water- cooled screen tubes and rear water wall hanger tubes.

The front pendant vertical spaced plated section is located between the rear waterwall

hanger tubes and the superheated platen section. All reheater drains and vents are

opened before lighting off. The vents and drains to the atmosphere must be closed prior

to raising a vacuum in the condenser. Drains connecting with the condenser may be lift

open until the boiler is under light load.

4.3. EconomizerEconomiser is a feed water heater.It uses the heat produced by the flue gases for this

purpose.The feed water is passed through the economiser before supplying it to the boiler

18

Fig.10. air preheater

Fig.11.economi

4.4. Air preheatersAir 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. In STPS, there are three fans:

1. F.D.FAN (Forced fan)

2. I.D.FAN (Induced fan)

3. P.A.FAN (Primary fan)

4.4.1. 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. The flow is

controlled by varying the angle of incidence of impeller blades. It therefore becomes possible

by this process to achieve high efficiencies even during part load operation. The blade pitching

operation is performed by mechanical linkages connected to a hydraulic servomotor which is

flanged to the impeller.

19

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 KW

Speed : 1480 rpm

Fan Weight : 8 Tones

Type of fan regulation : Blade Pitch Control

4.4.2. 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.

Technical data:

Application : Induced Draft Fan

No. off : 3

Type : NDZV 33 S

Medium handled : Flue Gas

Orientation : 450 Top incl. Suction Bottom Horizontal,

Delivery

Capacity : 250.5 m3/Sec

Temp. of medium : 1540C

Speed : 740 rpm

Coupling : Hydraulic Coupling

20

Rating : 1750 KW

Speed : 740 rpm

Fan Weight : 52.7 Tones

4.4.3. 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 : AP 2 17/12

Medium Handled : Atmospheric Air

Speed : 1480 rpm

Rating : 1400 KW

Fan wt. : 10.8 tones

STEAM TURBINE

1. INTRODUCTIONSteam turbine is a rotating machine which CONVERTS HEAT ENERGY OF

STEAM TO MECHANICAL ENERGY.

In India, steam turbines of different capacities, varying from 15 MW to 500

MW, are employed in the field of thermal power generation.

2. BASIC PRINCIPLESThe Thermal Power Plants with steam turbine uses Rankine cycle. Rankine cycle is a vapour

power cycle having two basic characteristics:

21

1. the working fluid is a condensable vapour which is in liquid phase during part

of the cycle and

2. The cycle consists of a succession of steady flow processes, with each

processes carried out in a separate component specially designed for the

purpose. Each constitute an open system, and all the components are

connected in series so that as the fluid circulates through the power plant each

fluid element passes through a cycle of mechanical and thermodynamic

stages.

The turbine is of tandem compound design with separate HP, IP and LP cylinder.

The HP & IP turbines are of single flow type while LP turbine is of double flow type;

the turbine is condensing type with single reheat. It is basically engineered on

reaction principle with throttle governing. The stages are arranged in HP, IP and LP

turbines, driving alternating current full capacity Turbo generators.

3. SPECIFICATIONType - tandem compound condensing Reaction

Rated output of turbine - 250 KW

Rated speed - 3000 RPM

Main steam temperature - 537 C

Rated pressure - 150 kg/cm

22

4. TURBINE COMPONENTS

4.1 Casing or Cylinders:A casing is essentially a pressure vessel which must be

capable of withstanding the maximum working pressure and temperature that can be

produced within it. The working pressure aspects demand thicker and thicker casing and

the temperature aspects demand thinner and thinner casings.

4.1.1 H.P Turbine Casing: The principal parts of the HP turbine casing are and

axially split inner shell, enclosing the rotor and outer shell of a barrel-type

construction. The barrel type of cylinder construction ensures symmetry of the

wall thickness around the axis of rotation and hence the wall thickness itself is

relatively less than that used in other type of construction.

4.1.2 I.P. Turbine Casing: The IP turbine is split axially and is of single shell

design. The outer casing accommodates a double flow inner casing. which are

symmetrically arranged in the top and bottom halves of the outer casing

23

Fig.12.turbine

4.1.3 L.P Turbine Casing: The LP turbine is of double flow type. The casing is of

triple shell, fabricated construction. The outer casing consists of the front and

rear end walls, two longitudinal girders and a top cover. The inner shell of the

inner casing acts as the guide blade carriers for the initial stages of the turbine.

The guide blade carriers of the LP stage groups are so designed that, together

with the inner casing, they form annular ducts which are used for extractions.

5. TURBINE GOVERNING SYSTEM The main purpose of governor is to maintain this desired speed of turbine during fluctuations of

load on the generator by varying steam input to the turbine. The governing system in addition

to ensuring the falling load-speed characteristics of the turbine also ensures the following

functions:

1. The run up the turbine from rest to rated speed and

synchronizing with the grid.

2. Meeting the system load variations in a predetermined manner, when running in

parallel with other machines.

3. Protecting the machine by reducing the load or shutting off completely in

abnormal and emergency situations.

The governing system also includes other devices to protect the turbine from

abnormal condition that may arise during operation.

Fig.13.turbine governor

24

GENERATOR2. INTRODUCTION

Mechanical energy is converted into electric power the stator windings of generator by the

interaction of rotating magnetic field. Rotating magnetic field is created by field windings

mounted on rotor shaft with the help of excitation system. When the shaft is rotated at 3000

RPM by the coupled turbine electric power is generated at a voltage 16.5 KV and 50 HZ

frequency. Generator is filled with hydrogen gas for cooling its winding which in turn is cooled

by circulating water. The voltage of such generated electricity is step up to 220kv or 400kv

through transformer and power transmitted to Ratangarh GSS for Northern Grid, and different

areas of Rajasthan. 6.0 million units energy is generated in 250 MW unit in a single day, out of

this about ten percent is consumed in unit itself for running its auxiliary equipments like

pumps, fans etc. about 3300 metric tons of coal is consumed in one 250 MW unit in one day.

Turbo generator manufactured by BHEL in Co-Operate with most modern design concept and

constructional features which ensures reliability, easy and constructional and operational

economicity. There is a provision for cooling water in order to maintain a constant temp. of

coolant (hydrogen) which controls the temp. of wdg., core etc as per loads.

Technical Data:

Apparent power - 294MVA

Active Power - 250 MW

Current - 10290 Amps.

Voltage - 16.5 kV+/- 825V

Speed - 3000 rpm

Power Factor - 0.85

Hydrogen Pr. - 3.0 bar

Rated Field Current - 2386 Amps

25 3. GENERATOR COOLINGHydrogen gas cooling, in an oil-sealed casing, is used because it has the highest known heat transfer coefficient of any gas and for its low viscosity which reduces special handling during start-up, with air in the generator enclosure first displaced by carbon dioxide before filling with hydrogen. This ensures that the highly flammable hydrogen does not mix with oxygen in the air.The hydrogen pressure inside the casing is maintained slightly higher than atmospheric pressure to avoid outside air ingress. The hydrogen must be sealed against outward leakage where the shaft emerges from the casing. The generator also uses water cooling.

TRANSFORMERS

1. 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.

Fig.14. generator after removal of end shield

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2. UNIT AUXILIARY TRANSFORMER

Each unit has two unit auxiliary transformers. Before starting of the unit, UAT bus is connected to the station bus. UAT is connected between the generator and 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 6.9 KV. 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.

3. UNIT STATION TRANSFORMER

It is a step down transformer, which is connected to the station bus. It steps down the voltage 6.6 KV to 0.433 KV. It is used to supply the low voltage auxiliaries.

4. 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.

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Table 4. Generator transformer data

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CONDENSER1. FUNCTIONS

To provide lowest economic heat rejection temperature from the steam. Thus saving on

steam required per unit of electricity.

To convert exhaust steams to water for reuse this saving on feed water requirement.

Deaeration of make-up water introduced in the condenser.

To form a convenient point for introducing makes up water.

2. DESCRIPTION OF CONDENSER

The condenser group consists of two condensers, each connected with exhaust part of low

pressure casing. A by-pass branch pipe has interconnected these woe condensers. The

condenser has been designed to create vacuum at the exhaust of steam turbine and to provide

pure condensate for reusing as feed water for the boilers. The tube layout of condenser has been

arranged to ensure efficient heat transfer from steam to cooking water passing through the

tubes, and at the same time the resistance to flow of steam has been reduced to the barest

minimum. 350% capacity condensate pumping sets are installed for pumping the condensate

from condenser to the deaerator4 through low-pressure heaters. Two pumps are for normal

operation and one works as stand by pump.

IN STPS RVUN SURFACE CONDESER is used.

2.1 Surface condenser:

This type is generally used for modern steam turbine installations. Condensation of exhaust

steam takes place on the outer surface of the tubes, which are cooled by water flowing inside

them. The condenser essentially consists of a shell, which encloses the steam space. Tubes

carrying cooling water pass through the steam space. Instead of one inlet and one outlet water

boxes, the may be two or more pair of separate inlet-outlet water boxes, each supplying cooling

water to a separate bundle of tubes.

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COOLING TOWERS

1. INTRODUCTIONCooling towers are heat removal devices used to transfer process waste heat to the atmosphere.

Cooling towers may either use the evaporation of water to remove process heat and cool the

working fluid to near the wet-bulb air temperature or rely solely on air to cool the working fluid

to near the dry-bulb air temperature. Common applications include cooling the circulating

water used in oil refineries, chemical plants, power stations.

1.1. CW Pump

Type is single stage double suction centrifugal pump

Type : 1400S25-1

Capacity : 16000m3/H

Speed : 370rpm

Power : 1600KW

Weight : 35000kg

Fig.15. surface condenser

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1.2. Cooling Water Pump Motor Specifications

The motor of the CWP has following specification;

Type : Y1600-16/2150

Out Put Power : 1600KW

Stator Voltage : 6.6KV

Speed : 372rpm

Frequency : 50Hz

Stator Rated Current : 182A

Stator Connection : 2Y

Ambient Temperature : 50C

Insulation : Class B

Weight : 17500Kg

Fig.16. cooling

towers

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DEAERATER FUNCTIONS

Removal of dissolved air/oxygen in boiler water.

Chemical dosing for maintaining quality of boiler water.

Regenerative heating of feed water for increasing its temperature and efficiency

of plant.

Storage of feed water in water/steam cycle.

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PUMPS1. BOOSTER PUMP

1.1. Working50 % tandem boiler feed pump sets are supplied to this contact, three pump sets for each boiler.

Two sets are run in parallel, supplying each boiler, with one pump set being on stand-by.

Each pump set consists of a “FA1856” booster pump, directly driven form one end of the shaft

of an electric driving motor, and a “FK6D30’ boiler feed pump driven from the opposite end of

the motor shaft through a variable speed turbo-coupling. The

drive is transmitted, in each case through a spacer type flexible coupling. The bearings in the

booster pump and pressure stage pump and in the motor are lubricated from a forced

lubricating oil system incorporated in the turbo coupling. The booster pump is a single stage,

horizontal, axial split casing type, having the suction and discharge branches on the casing

bottom half, thus allowing the pump internals to be removed without disturbing the suction and

discharge pipe work of the alignment between the pump and the motor. The pump shaft is

sealed at the drive end and the non-drive end by mechanical seals which are flushed by a

supply of clarified water.

1.2. Technical specifications

Pump type : FA1856

Direction of rotation : Anti - clockwise

(Viewed from drive end)

Liquid pumped : Boiler Feed Water

Suction temp. : 161.10C

Flow rate : 490 m3/hr.

Efficiency : 81 %

Input power : 151 KW

Speed of pump : 1485 rpm

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2 BOILER FEED PUMP

1.3. Working

The FK6D30 type Boiler Feed Pump is a six stage, horizontal centrifugal pump of barrel casing

design.The pump internals are designed as cartridge which can be easily removed for

maintenance without disturbing the suction and discharge piping work or the alignment of the

pump and the turbo coupling. The pump shaft is sealed at the drive end and non-drive end by

mechanical seals, each seal being flushed by water in a closed circuit and

which is circulated by the action is cooled by, [assign through a seal cooler, one per pump,

which is circulated with clarified cooling water. The rotating assembly is supported by plain

white metal lined journal bearings and axially located by a Glacier double tilting pad thrust

bearing.

2.2 Technical data:

Pump type : FK6D30

No. of stages : 6

Direction of rotation : Anti – clockwise

(Viewed form drive end)

Suction temp. : 161.10C

Design flow : 490 m3/hr.

Efficiency : 81 %

Speed : 5310 rpm

Input power : 3322 KW

Drive Motor

Manufacturer : B.H.E.L., Haridwar

Rating : 3550 KW

Speed : 1492 rpm

Electrical supply : 6.6 kv, 3-ph, 50 Hz

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2. CONDENSATE EXTRACTION PUMP

2.1. Working

The condensate Extraction Pumps are of the vertical, eight stage, Centrifugal

canister type, with the driving motor supported on a fabricated head piece and the

eight inter connected pump stage are suspended below the head piece. The pump

discharge branch and suction branch are formed on the head piece above floor level.

The eight pump stages are contained within a fabricated canister, and each stage

casing is located by spigot and secured together with bolts, nuts and lock washer.

The canister is suspended and secure to a foundation ring with screws. The head

piece is also secure to the canister with screws.

Each pump directly driven through a flexible coupling by a 325 KW electric motor.

2.2. Technical Specifications

Type : EN 8 H 32

Direction of rotation viewed : Clock-wise

Suction temp. : 46.10C

Sp. Gravity : 0.9901

Speed : 1485

Power absorbed : 266 KW

Efficiency : 78 %

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ELECTROSTATIC PRECIPITATORS1. THEORYE.S.P. is a highly efficient device for extraction of suspended particles and fly ash from the

industrial flue gases. 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 .

3. WORKING

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

charge particles on collector surface. Removal of particles. 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 a process called “RAPPING’ DONE BY “ RAPPING MOTORS”.

Fig.18. E.S.P.

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ASH HANDLING PLANTThe ash handling system provide for continuous collection of bottom ash from the furnace

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 slurry 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.

Fig.19. ash handling

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Fig.20. 400 KV layout of

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220 KV & 400 KV SWITCHYARD AND DIFFERENT

EQUIPMENTS INSTALLED AND BUS SCHEMES1. 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

Station transformer-3

Station transformer-4

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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.

3. 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.

3.1. 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

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3.2. Specifications of SF6 gas ciruit breakers

Table 5. Technical data of SF6 circuit breaker for 220 and 400 KV

CIRUIT BREAKERS FOR 220 KV 400KV

Rated lightning impulse with stand voltage 1050 kvp 1425 kvp

Rated short circuit breaking current 17 ka 17 ka

Rated operating pressure of air 15 kg / cm 2 15.5 kg / cm2

First pole to clear factor 1.5 1.3

Rated voltage 245 kv 420kv

Rated current 200A 200A

Rated closing circuit voltage 220 V DC 220 V DC

Rated opening circuit voltage 220 V DC 220 V DC

Rated voltage, frequency 415 V AC 50 Hz 415 V AC 50 Hz

Rated line charging breaking current 125 A 600 A

4. 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.

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5. 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.

6. LIGHTINING ARRESTOR AND ARC HORNS

Protection against lighting

7. BUS COUPLER TO MAIN BREAKER

Close the isolator 1 & 3 of GT.

Close the breaker a 1 of GT

Close the isolator 5,7 & breaker b 1

After this work close the isolator 9, 10

8. CHANGE OVER SCHEMES (BUS TIE SYSTEM)When main breaker is in service (on load change over):

Ensure Transfer bus is free (check any temporary earthing)

Charge the transfer by closing bus coupler isolator and circuit breaker.

Put the switches provided on bus coupler on generator control cum desk panel.

Charge the transfer bus by closing isolator d of GT.

Check the isolator of GT through which it has been already connected to the bus.

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MAINTENANCE JOBS TO BE DONE ON 220 KV & 400

KV SWITCH YARD

1. DAILY JOB

Visual checking for any hot spot

Checking of air leakage from the breaker

Checking for any gas leakage from the breaker

Checking of air pressure of breaker

Checking of gas pressure of breaker

Checking of oil leakage form CT and CVT

Checking of oil level from CT and CVT

Checking of lubricating oil level in compressors

Checking healthiness of trip circuit for all breakers.

2. MONTHLY JOB

Thermo vision scanning of conductor joints and attending to the hot

spot on available opportunity

Breaker operation checking from local and remote

Isolators operation from remote and local.

Measurement of specific gravity and voltage of 220 V D. C> Battery

cells.

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3. QUARTERLY JOB

3.1. Breakers

Tightening of breaker clamps

Cleaning of breaker cubicles

Checking of oil level of compressors of SF6 breakers.

Lubrication of rollers, mechanism shafts, anti pumping pin and c clips.

Checking operation of breakers through trip coil 1, trip coil 2, both the coils, anti

pumping operation and pole discrepancy operation

Checking of pressure of gas and air pressure of breakers.

3.2. Isolators

Tightening of the jumper clamps

Tightening of electrical connections

Cleaning of male female connections

Checking of fuses and replacement there F.

Checking of operation of isolators

3.3. Current transformers

Checking of oil level.

Checking of oil and leakage

Tightening of jumper clamps

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3.4. Lightning Arrestors

Tightening of jumper connections

Tightening of earthing connections

Checking of counter reading

Checking of porcelain part

Checking of grading current

3.5. Capacitive Voltage Transformer

Checking of oil level and leakage

Tightening of HT jumper clamps.

Tightening of secondary terminal connections

3.6 Battery 220 V D.C.

Cleaning of battery terminals

Tightening of battery terminal connections

Recording of specific gravity and voltage of each cell.

4. DURING ANNUAL SHUT DOWN OF UNITS

4.1. Breaker

Checking and cleaning of porcelain part of the breaker.

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Cleaning of breaker cubical

Tightening of all the terminal connection

Lubrication of I) C and D Roller (II) Locking pins (III) Anti Pumping pins (IV)

Mechanism Shafts

Recording of closing and tripping of each phase

Recording of insulation resistance value of breaker

Checking of annunciator and inter locks.

Checking of tripping through

Trip Coil I

Trip Coil II

Measurement of resistance of trip cells and closing coils

Checking of air leakage and its stoppage

Checking the gas leakage

Replacing the oil of compressors

Checking of auto operation of compressors

Complete maintenance of compressors

4.2. Isolators

Cleaning of male female connections

Tightening of all the jumper clamps

Lubrication of control rotary post insulator with grease

Checking of proper operation of the isolator

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Cleaning the motor cubical

Tightening of all the terminal connections

Greasing the gear box of motor

Checking of all the fuses

Checking of operation of isolator from local/remote

4.3. Current Transformers

Checking / cleaning of porcelain part of CT

Checking of oil and level and stopping it if low

Checking of oil leakage and its stoppage

Checking of N2 pressure and maintaining it at 0.2 kg/cm2

Tightening of earthing connection

Checking of BDV value of CT oil

Tightening of all the secondary terminal connections

Cleaning of marshalling box and tightening of terminal connections

Recording of IR values of primary and secondary side of CT

Tightening of bushing clamps.

4.4. Capacitive Voltage Transformers

Checking of oil level and topping thereof

Checking of N2 pressure and maintaining it at 0.2 kg/cm2

tightening of jumper clamps.

Tightening of secondary connection

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4.5. Lightning Arrestors

Cleaning of porcelain part and checking

Tightening of earthing connection

Tightening of jumper connection

Recording of IR values

Checking of counter readings

Checking of grading current

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CONCLUSION

The first phase of practical training has proved to be quite 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 learn low technology used at proper place and time can have a lot of labour eg. Wagon tippler (CHP). But there are few factors that require special mention. Training is not carried out into its free 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.

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REFERENCES

1. http://en.wikipedia.org/wiki/Thermal_power_station

2. http://en.wikipedia.org/wiki/Deaerator

3. http://en.wikipedia.org/wiki/Economiser

4. http://en.wikipedia.org/wiki/Regenerative_heat_exchanger

5. http://www.tva.gov/power/coalart.htm

6. http://www.google.co.in/images

7. http://wapedia.mobi

8. http://images.google.co.in/images

9. http://www.rerc.gov.in

10. http://www.rvunl.com

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