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A

INDUSTRIAL TRAINING REPORT

ON

SURATGARH THERMAL POWER PLANT

(05.06.2012-05.07.2012)

SUBMITED IN PARTIAL FULFILLMENT

FOR THE AWARD OF THE DEGREE OF

BACHELOR OF TECHNOLOGY

(RAJASTHAN TECHNICAL UNIVERSITY,KOTA)

IN

ELECTRICAL ENGINEERING

SESSION (2012-2013)

SUBMITTED TO: SUBMITTED BY:

Ekta Sharma Kamlesh Palsaniya

HOD of Electrical department EE & 7th sem.

G.I.T 09EGJEE028

DEPARTMENT OF ELECTRICAL ENGINEERING

GLOBAL INSTITUTE OF TECHNOLOGY

ITS PARK RIICO SITAPURA, JAIPUR-302022

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ChaptersChapters Page no.Page no.

# ACKNOWLEDGEMENT I

# ABSTRACT II

# MATTER OF TRAINING IIIMATTER OF TRAINING III

LIST OF CONTENTSCONTENTS

1. INTRODUCTION 1

2. SITE SELECTION 2

3. COAL HANDLING PLANT 53.1 Coal Feeders 5

3.1.1 Drag Link coal feeder 6

4. ASH HANDLING PLANT 8

5. DUST EXTRACTION SYSTEM 9

5.1 Electrostatic Preceptors 9

5.2 Description 10

5.3 Electrical System 11

5.4 Interlocking System 11

6. THERMAL POWER GENERATION 126.1Boiler 12

6.2 Electrostatic Precipitator 13

6.3Turbine 13

6.4 Condenser 13

6.5 Deaerater 13

6.6 Boiler feed pump 14

6.7 Generator 14

6.8 HP-LP Bypass System 15

7. REGENERATIVE SYSTEM OF 250 MW UNIT 18

8. TURBO GENERATOR 19

8.1 Stator frame 19

8.2 Stator core 20

8.3 Stator bars 22

8.4 Stator windings 23

8.5 Terminal bushings 24

8.6 Bearings 24

8.7 Ventilation system 24

8.8 Measurement of bearing temperature 26

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9. ROTOR 27

9.1 Rotor windings 28

9.2 Bearings 28

9.3 Slip rings 299.4 Bush gear assembly 29

9.5 Drying of windings 30

10. COOLING SYSTEMS 31

10.1 General 31

10.2 Hydrogen Dryers 32

10.3 Hydrogen filling systems 32

11. EXCITATION SYSTEM 33

11.1 Functions of excitation system 33

11.2 Types of excitation system 33

11.3 Static excitation system 34

11.4 Rectifier transformer 35

11.5 Thyristor converter 35

11.5.1 Automatic voltage controls 35

11.6 field suppression system 36

11.7 Advantages of static excitation system 37

11.8 Operation 37

11.8.1 Synchronizing 37

11.8.2 Machine connected on infinite bus 38

12. TRANSFORMER 3812.1 Station transformer 38

12.2 Unit auxiliary transformer 39

12.3 Unit station transformer 40

12.4 Unit service transformer 40

13 DIFFERENT EQUIPMENTS AND BUS SCHEMES 41

13.1 Bus scheme 41

13.2 Bus system 41

13.3 Sf6 gas C.B. 42

13.4 Isolators 43

13.5 Change over schemes 43

13.6 Bus coupler to main breaker 44

13.7 Synchronization of generator to grid 44

13.8 Current transformers 45

13.9 Lightning arresters 45

13.10 Capacitive voltage transformer 45

13.11 Battery 220V DC 45

13.12 Earth shielding 46

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14. POWER LINE CARIEER COMMUNICATION 47

15. DATA SHEET & SPECIFICATIONS 49

16. ABOUT AVR 51

#References 53

Table List

Tables Page

11.1 Type of cooling for station transformer 38

11.2 Voltage at no load 39

11.1 Specifications of sf6 gas circuit breakers 50

Figure List

Figures Page

Figure 2.1 Plant overview 4

Figure 3.1 Coal handling plant 7

Figure 5.1 Feed water system 16

Figure 5.2 Air & FG system 17

Figure 7.1 Turbine Generator overview 21

Figure 13.1 Overview of PLCC 47

Figure 13.2 block diagram of PLCC 48

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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 am grateful to training incharge Mr. H.K. Tomar, Xen. STPS for giving guidelines to make

the project successful.

I want to give sincere thanks to the Prof. C. M. Arora, Technical Director of Global Technical

Campus and Dr. Renu Joshi, Director of Global Institute of Technology for her valuable

support.

I extend my thanks to Mrs. Ekta Sharma, Head of the Department of Electrical Engineering

for her cooperation and guidance.

Kamlesh Palsaniya

VII Sem.

09GJEE028

CHAPTER 1

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INTRODUCTION

1.1 SURATGARH SUPER THERMAL POWER STATION

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

Ganganagar District. 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.

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 cores on prices prevailing in Sept. 1990. the updated cost of the project is

estimate at Rs. 2300 cores of including IDC

1.2 NEED FOR POWER STATION :-

Rajasthan is the second largest in the country. About 30% Population lives in

village which are local point of development while Rajasthan mineral resources are immense.

But its resources for power station generation not immensurable with the requirement more

over the state government has drawn up a ruler of electrification program with a large demand

on agricultural load with rapid adoption & modern method of agricultural and industrialization

of towns. The mode of living of people in rural and urban areas as changing rapidly with

requirement of more power.

CHAPTER 2

SELECTION OF SITE FOR STEAM POWER PLANTS

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INTRODUCTION:-

This is necessary to choose the location of plant. Generally

almost power plants are located where all requirements should be fulfilled like

as following

2.1. SUPPLY OF WATER:-

A large quantity of water is required in steam power plants. It is required:

(I) It raises the steam in the boiler.

(II) For cooling purposes such as in condensers.

(III) As a carrying medium such as in disposal of ash.

(IV) For drinking purposes.

The efficiency of direct cooled plant is about 0.5% higher than that of the plant in which

cooling towers are used. This means a saving of about Rs. 7.5 lacs per year in fuel cot for a

2000 MW station

2.2 REQUIREMENT OF LAND:-

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.

2.3 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.

2.4 LABOUR SUPPLIES:-

Skilled and unskilled laborers should be available rates near the site the plant.

2.5 ASH DISPOSAL:-Ash is the main waste product of the steam power plant. Hence

some suitable means for disposal of ash should be applied. Ash can be purchased by building

contractors, cement manufacturers or it can be used for brick making near the plant site.

Otherwise wasteland should be available near the plant site for disposal of ash.

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Fig. 2.1 Plant OverviewFig. 2.1 Plant Overview

CHAPTER 3CHAPTER 3

COAL HANDLING PLANTCOAL HANDLING PLANT

Wagon tippler has rated unloading capacity of twelve box wagon per hour, including

shunting and spotting time of haulage equipment.

For vibrating feeders of capacity 350 tons/hr. each have been provided feeding unloads

coal. A steel hopper has been provided in crusher house to receive coal and distribute it through

manually operated rack and pinion gate to three vibrating screens of 675 t/hr. capacity each

coal above 200 mm size passes on granules for crushing and reduction in size. Coal below 20

mm size passes granular and discharged on to crushed coal conveyor belt.

Following permutation and combination of operation are possible with installed system.

To transfer all crushed coal received from crusher house to live storage pipe. To transfer part of

received crushed coal to plant and to balance to storage yard. To deliver the raw coal bunkers

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part and received crushed coal mixed with balanced coal from the live storage pipe. To transfer

the plant crushed coal at 750 T/hr from the reclaim live pile and simultaneously stock and s/

road. the vibrating ones as stated above can be obtained by the use of flap gates which are

installed on various chute and two vibrating feeders, installed on tower. The coal carried on

various conveyers shall be main monitored to ensure proper loading and distributing weightless

and vibrating feeders.

3.1 COAL FEEDERS

Coal 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.

3.1.1 Drag Link Coal Feeders:-

In 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.

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.

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Fig.3.1 Coal Handling Plant

CHAPTER 4CHAPTER 4

DUST EXTRACTION PLANTDUST EXTRACTION PLANT

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In plant the methods used for the removal of dust from gases are ELECTROSTATIC

PRECIPITATOR which uses electrical forces to remove the dust from the gas stream.

4.1 Electrostatic Precipitators

Working Principle:- The principles upon which an electrostatic precipitator operates are thatthe dust laden gases pass into a chamber where the individual particles of dust are given an

electric charge by absorption of free ions from a high voltage d.c. ionizing field. Electric forces

cause a steam of ions to pass from the discharge electrodes to the collecting electrodes and the

particles of dust entrained in the gas are deflected out o the gas steam into the collecting

surfaces where they are retained, either by electrical or molecular attraction. They are removed

by an intermittent blow usually referred to as rapping, this causes the dust particles to drop into

dust hoppers situated below the collecting electrodes.

There are four different steps in the process of precipitation

1. Ionization of gases and charging of dust particles.

2. Migration of the particle to the collector.

3. Deposition of charged particles on the collecting surface.

4. Dislodging of particles from the collecting surface.

Performance Criteria:

The performance of the electrostatic precipitator depends on several factors among which the

prominent are:

Characteristics of dust:

a) Particle size distribution

b) Dust loading

c) Chemical composition

d) Electrical resistively

e) Adhesive/cohesive properties

Characteristics of gases :

a) Temperature.

b) Chemical composition

c) Moisture content

d) Quantity to be handled

e) pressure

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4.2 Description:-

The electrostatic precipitator essentially consists of two sets of electrodes, one in

the from of thin wires called discharge or emitting electrodes and other set called collecting

electrodes in the from of pipes or plates. The emitting electrodes are placed in the centre of pipeor midway between two plates and are connected usually to negative polarity of high voltage

d.c. source if the order if 25-100 kv. The collecting electrodes are connected to the positive

polarity of the source and grounded.

The major fundamental parts of the electrostatic precipitator consist of the following:-

1. Casing

2. Hoppers

3. Has distributor screen

4. Collecting System

5. Emitting system

6. Rapping mechanism for collecting system

7. Rapping mechanism for emitting system

8. Insulator housing

4.3 Electrical System:-

For optimum functional efficiency of the precipitator, the supply voltage cloud

is maintained near the flash over level between the precipitator electrodes. This can be achieved

by an electronic control system which rises the output voltage to flash over level and reduces it

automatically by a small amount in the event of a flash over.

4.4 Interlocking System:

This system is designed for the safety of the personnel and protection of

equipment during the operation and maintenance. This system will not operate unless the

instructions are followed sequentially.

The system consists of rotary switches interlocks and key exchange boxes. The exchange

boxes are located in control room and at prominent places on the precipitator casing.

CHAPTER 5

THERMAL POWER GENERATION

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Steam and water undergo various phases of Carnot Cycle in the Boiler, Turbine and other

equipments during this process.

In Thermal Power Station, fossil coal is used as fuel for steam generation in the Boiler.

Steam so generated is utilised in Steam Turbine to generate mechanical energy for rotating the

Generator for producing electric power.

5.1 BOILER:-

Steam is generated by burning very fine pulverised coal in the Boiler. Initially in the

furnace the coal is burned with the help of oil. But afterwards oil support is withdrawn, when

the furnace temperature reaches to 1150c.

The heat generated by the combustion of coal is absorbed by water (De-mineralised) in the

boiler tubes where it gains sensible heat and latent heat. Air required for combustion of coal

consists of primary air, which transports pulverised coal in the mills to furnace and secondary

air. PA fans supply primary air and SA fans supply secondary air. Flue gases generated in the

process of combustion are removed from the furnace by ID fans and dispersed in the

atmosphere through 220 M high chimney.

Water heated up in the boiler tubes is converted into steam at saturation temperature and

further heated up in the superheater tubes to a temperature of 540 degree C and 149 KG/CM2.

5.2 ELECTROSTATIC PRECIPITATOR:-

Combustion products i.e. flue gases and ash passes through electrostatic precipitator before ID

fans and chimney for separation of ash from flue gases. Electrostatic precipitator has large no

of electrodes charged at voltage of 30 KV. Due to electrostatic force ash particles are attracted

and impinge upon the electrode thus separates ash from flue gases.

5.3 TURBINE:-

The superheated steam when enters the turbine passes through the blades ofturbine creates a couple of force and makes the turbine to rotate. Thus thermal energy is

converted into mechanical energy.

Steam is first entered in HP Turbine; after doing work in HP Turbine,

temperature & pressure of steam gets reduced. This steam is sent to the Boiler for re-

heating in the Re-Heater tubes where the temperature of the steam is raised and it is further

entered in the IP Turbine and LP Turbine. Steam coming out of turbine is at a very low

pressure (vacuum) and temperature (50 degree C).

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5.4 CONDENSER:-

Steam at exhaust of turbine is condensed by its latent heat. Cooling water of

lower temperature is passed through tubes in the condenser. Steam in the condensersurrounding these tubes reject latent heat to cooling water and gets condensed into water

called condensate which is accumulated in the hot well.

5.5 DEAERATER:-

Condensate from hot well is pumped to de aerator by condensate extraction

pump. Functions of de aerator are: -

1. Removal of dissolved air/oxygen in boiler water.

2. Chemical dosing for maintaining quality of boiler water.3. Regenerative heating of feed water for increasing its temperature and efficiency of

plant.

4. Storage of feed water in water/steam cycle.

5.6 BOILER FEED PUMP:-

It is a very important equipment of power station boiler feed pump pumps water from

de aerator to boiler at very high pressure of about 190KG /CM2. In this process feed water is

passed through high pressure heaters where its heating is done by steam taken turbine toincrease the efficiency of plant.

5.7 GENERATOR:-

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 windingwhich 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.

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5.8 HP-LP BYPASS SYSTEM

This bypass system has been provided to allow the steam generator to build up, during

start-up, matching steam parameter with the tribune. The steam generated is dumped into the

condenser, thus avoiding loss of boiler water. This system enables starting of he unit of sliding

parameters and also facilitates hot restarting of the unit. In the event of loss of load on the

turbine, the bypass system disposes the steam produced by; the boiler automatically to he

condenser without affecting the boiler operation.

The bypass system had two sections: HP & LP. The HP-Bypass system diverts the

steam before main steam valve to he cold reheat CRH line. HP Bypass system also reduces the

rated steam parameters of the incoming steam from the superheated to the steam condition

expected in the CRH line (i.e. steam temp. and pressure after HP turbine exhaust).

The LP Bypass diverts the incoming steam from hot reheat line before intercepting

valves to he condenser after reducing the HRH steam parameters to the conditions

approximately to that of LP steam turbine exhaust steam.

HP Bypass station is utilised for the following tasks:

1. To establish flow at the outlet of superheated for raising boiler parameters during starts up.

2. To maintain or controls steam pressure at pre-set value in main steam line during start up.

3. To warm up the steam lines.

4. To control steam temperature down of HP bypass at the reset value

LP Bypass station is utilised for the following tasks:

1. Control of steam pressure after reheater.

Establish flow of steam from reheat lines to condenser by its opening, proportional to the

opening of HP bypass valves.

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Fig. 5.1 Feed Water SystemFig. 5.1 Feed Water System

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Fig.5.2 Air & FG SystemFig.5.2 Air & FG System

CHAPTER 6

Regenerative system of 250 MW units

And Ash handling plant

The regenerative system of the turbine consists of four low-pressure heaters, two gland

coolers, one deaerator and three high-pressure heaters. The condense is drawn by condensate

pumps from the hot well of condenser and is pumped to the deaerator through gland coolers

and low pressure heaters where it is progressively heated up by the steam extracted from seals

and bled points of the turbine. The drain of condensate steam on LP heaters No. 2,3 and 4 flows

in cascade and is ultimately pumped into the main condenasate line after heater No.2 or flows

to condenser. The feed water after being deaerated in the deraerator is drawn buy the boiler

feed pump and pumped to boiler through high pressure heaters where it is heated up by the bled

steam from the turbine. The drain of condensed steam of HP heaters flows in cascade and under

normal load conditions flows to the deaerator.

6.1 ASH HANDLING PLANT6.1 ASH HANDLING PLANT

The 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

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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

CHAPTER 7

TURBO GENERATORTURBO GENERATOR

INTRODUCTION:- Turbo generator manefactured by BHEL in Co-Operate with

most modern design concept and constructional features which ensures reliability, easy and

constructional and operational economicity.

The generator stator is a tight construction, supporting and enclosing the stator wdgs,

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

circulated by fans mounted at either ends of rotor. The Generator is driven by directly cpupiedsteam turbine at a speed of 3000 r.p.m. The generator is designed for continuous operation at

rated O/P.

Temp. detector and other devices installed or connected within the M/c, permit the

measrement of wdgs, teeth core, and hydrogen temp. hydrogen pressure and purity in M/C

under the conditions.

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The Source of excitation to rotor wdgs is thyristorised D.C. supply. The Ausiliary

equipment supplied with M/C superrises and enables the control of hydrogen pressure and

purity, shaft sealing lubricating oils.

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.

7.1 STATOR FRAME :-

The stator frame of welded steel frame construction which gives sufficient

strength and rigidity necessary to minimise the vibrations and to with stand thermal gas

pressure. Heavy end shields enclose the enels of frame and from mountings of generator

bearings and radial shaft seals. The frame is qub divided by ribs and axial members to form

duct from which the cooling gas passes to and from the radial ducts in the core and in

recirculated through internally mounted coolers. All the gas ducts are designed so a s to reduce

balanced distribution of hydrogen to all parts of the core. The stator, constructed in a single

piece, houses the core and wdge. The horizontally mounted water cooled gas cooler being so

arranged that it may be cleaned on the water side without opening the M/c to atmosphere.

All welded joints exposed to hydrogen will be specially prepared to prevent

leakages. The complete frame is subjected to hydroulic test at a pressure of 7 atm.

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Fig. 7.1 Turbo Generator Overview

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7.2 STATOTOR - CORESTATOTOR - CORE

It is built up of special sheet steel laminations and whose assembly is supported by the

guide bass. The mothod of construction insure that the core is firmly supported at a large no ofpoints on its periphery. The laminations of high quality silicon steel which combines high

permeability with low hysteresis and ealdy current losses. After stamping each lamination is

varnished. The laminations are varnished on both sides with two coals.

The segment of insulating material is inserted at frequent interval to provide additional

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

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

ventilation passage. The ventilation elucts are disposed so as to discribute the gas evenly over

the core and in partialarly to give adequate support to teeths. At frequent intervals during

stacking the assembled laminations are passed together in powerful hydrolic press to ensure

tight core which is finally held between heavy clamping plates which are of non magnetic steel.

Use of non-magnetic steel reduces. Consielenably the heating of end iron. Clamping to the

foothed region of the core is provided by pressing figures of non-magnetic steel which are

welded to inner point phery of the clamping plate.

In order to reduce the losses in the end packets special dampers are provided at either

end of core. Mostly dampers are provided to prevent hunting in AC Machines.

7.3 STATOR BARS7.3 STATOR BARS

Stator bars are manufactured as half bars. Each stator half coil is composed of altrnate

strips of double glass covered and bars copper, transposed in straight portion of Robill

method So that each strips occupees every radial portion in the bar. For an equal length along

the bar. They are made in strips to reduce skin effect. The wdgs overhead is in involute shape.

The overhang portion of the bar is divided into four quadrants & insulated. Their arrangement

reduces additions losses due to (self inducing) damping currents which otherwise be present

due to self inducing non-uniform flux distribution in the coil slots. The main insulation for the

bar sinsists of resin rich mica losed thermosating epoxy. This has excellent electrical and

mechanical properties and does not require any impregnation. Its moisture absoption tendency

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is very low and behaviour of mica is far superivor than any other conventional tape insulation

systems.

Semiconductor coating is also applied to a part of overhangs with a straight

overlap of conductive coal in the straight portion, to prevent corona discharge.The strip will be

transposed in side of reduce eddy currents to minimum. Conductor material is electrolytic

copper connections brozed with free flouting silver alloy to obtain joints which are both

mechanically and electrically sound.

7.4 STATOR WINDINGS

Stator wdgs are double star layers. Lap wound co phase short pitch type. The top and

bottom are brazed and insulated at either and to formturn. Several such turns form a phase.

Phases are connected to form a double star wdg. The end wdg formed on involute shaped ends,

is indined towards M/C axis by 20*, thus form a basket wdg. With total induced conical angle

of 40*. Due to this stray load losses in the stator ends to Zero.

The arrangement of complete star wdg. Electrical ckt. is viewed from turbine

end of generator and rotor wdgs. Slot numbering is clock wise from turbine end. The top bar in

slot no 1 is identified by the thick line. End wdgs will be seaered against movement of short

circuit by both axial and pheripherical bracing. The later consist of hardened glass

laminated blocks inserted between adjacent coil sides in coil overhangs, so that with the coils,

they form a continuous rigid ring. Glass cord or top is used for lashing the packing of blocks.

The complete assembly is secured by high tensile brass blots. The wdgs. Is designed to with

stand short circuit stresses. The exposed portion of wdgs are finally given coated. Insulation of

individual bars and stator wdgs at various stages is tested with applied high voltages AC of 50

HZ.

7.5 TERMINAL BUSHING7.5 TERMINAL BUSHING

Six output leads (3 long, 3 short) have been brought out at bottom of casing ont

he exciter side. External connection are to be made to 3 shorten terminals, which are phase

terminals. The large terminals are of neutral and a current x-mar is inserted. The conductor of

generator terminal bushings having hollow copper tube with copper brazed at

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the end to avoid the leakage of hydrogen. Hollow portion enables the bushings to be hydrogen

cooled. Ends of bushings are silver plated. Middle portion of bushing is adequately insulated

and have a circular flang for bolting the stator casing, Gaskets are provided between the flange

of terminal bushings and castings, to make it absolutely gas tight.

7.6 BEARINGS :-

Generator bearings have electrical seats and 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 supplied oil to the turbine, bearings and governer gears. There is a

provision to ensure and measure the rator bearing temp. by inserting a resistance thermometer

in oil pockets.

7.7 VENTILATION SYSTEM :-

The machine is desgned with ventialtion system having 2 atm. Rated hydrogen

pressure circulation on hydrogen is ensured by two axial fans mounted in either side of the

rotor. The stator is designed for radial ventilation by stem. The end stator core packets and core

clampings plates and intensively cooled by hydrogen through special ventilation circuit. Rotor

wdg. Is provided with a direct radial ventilation system.. Design of ventilation system is so as

to ensure almost univorm temp of rotor wdg. And stator core.

Rated load operating temp. are well within the limits corresponding to class B operation.

Continuous Mounting of active parts temp. of hydrogen in generators, embedded resistance

temp. Detectors are provided as:-

(i) RESISTANCE

A resistance temp detector (R.T.D) is a pt. Resistance element operation of R.T.D os based

on the principal of electrical resistance of metallic conductor, varies linearly with temp.

(ii) APPLICATIONS

R.T.D. and its associated equipments are designed for use with generator to determine temp. at

various parts and places. The equipment consists of two parts.

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(iii) The switch board equipments which usually includes a temp. Indicating meter, test

resistors transfer switch and leads. Machine equipments which usually includes the temp.

R.T.D., leads and terminal block with grounding connections, leads from R.T.D. are

brought out to the terminal board by cables through a conduit to protect them from physicaldamage and from contact with high voltage coils.

Such resistance detectors in stator teeth with seven spactors 7 RTDs between

the coil side in the stator slots with 7 spacers and 3 RTD are there in the stator core with 3

spacers.

The location of temp. detectors are in three phases i.e. in the centre of M/C, in each region of

machine and midway between them. The detectors in the stator slots are distributed unitormly

in all three phases. Measurement of temp. in hydrogen cooling water for hydrogen coolers and

metals is as :-

Six R.T.D.s are provided, on at the inlet of each of 6 individual hydrogen

coolers elements for measurement of temp. of hot hydrogen, dimilarly 6 R.T.D.s are provided,

one at outlet of each of six individual cooler elements. One R.T.D. along with one spacer is

provided in the lower part of stator frams for measurement and signalisation of hot hydrogen.. 6

R.T.D.s are provided one at the outlet of six individual cooler elements for measurement of

cooling water at the outlet of hydrogen cooler elements.

7.8 MEASURMENT OF BEARING TEMPERATURE :-

Two resistance detector are provided in the bearings shelves of turbogenerator

for measurement and signatisation of the bearing metal cap.

All the resistance eletectors are provided in bearing shelves of turbogenerator.

Temperature detectors have resistance of 100 at C. The terminals of detectors are brought out

to a common terminal board located on the stator frame.

HYDORGEN COOLERS:-

Three hydrogen coolers, each comprising of two individual units are

horizontally mounted inside the stator frame. The inlet and outlet of cooling water from both

sides of M/C i.e. from the non-driving side as well as turbine side. The clearing of individual

cooler element can be carried out from both ends of generator even during operation. The

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assembly of individual cooler elements in the stator frame is however carried out only from the

non driving side.

CHAPTER 8

ROTOR

INTRODUCTION:-

Rotor shaft conststs of co single piece alloy steel fonging of high mechanical

and magnetic propertics performance test includes :-

(i) Tensile test on specimen piece.

(ii) Surface exmination

(iii) Sulphur print test.

(iv) Magnetic Crack detection.

(v) Visual examination of the bore.

(vi) Ultra sonic examination.

Slots are milled on the rotor forging to receive the rotor ludg. Transverse slots

are machined in the pole taces of the rotor to equalise the moment of inertla in the direct and

quadratelre axis of the rotor with a view of minimising the double frequency vibration of the

rotor. The fully based rotor is dynamically balanced and subjected to 120% over speed test at

the work balancing tunnels so as to ensure reliable operation.

8.1 ROTOR WINDINGS :-

The rotor wdgs. Of direct coil type and consists of parallel strips of very high

conductivily silver bearing copper, bent on edge to form coils.

The coil are placed in statin impregnated glass, laminated short shells, using glass strip

interterm insulation and will be brazed at the ends to form a continuous wdgs.

The complete wdgs. Will be baked at high temp. and pressed to size by heavy steel

damping rings. When the wdgs have cooled, the insulation at the tap of the slot portions will be

seaved by heavy dove tail wedges of non-magnetic materials.

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The cooling medium hydrogen gas will be brought in direct contact with copper by

means of radial slots in embadded portion.

Lateral movement of the coil overhang is provented by treated glass spacess insrted in

between the coils and the solid ring. The formation and description of the spacers is such as to

leave ample space for ventilation.

8.2 BEARINGS:-

The bearing are self-aligned and sonsists of split steel shells linked with spacial bearing

metal having very low co-efficent of friction. The bore is machid to an elliptical shape so as to

increase the mechanical stability of rotor.

The bearings are pressure lubricated from the turbine oil supply. Special precautions are taken

to prevent oil and oil vapor form the shaft seals and bearing along the shaft.

The circulation of shaft current liable the damage. The bearomg surface is

prevented by insulation so placed that the bearings, seals & necessary pipes are indined from

the frame.

8.3 SLIP RINGS :-

The slip rings are made of forged steel. They are located on the either side of the

generetor shift the slip ring towards the exciter side is to be given a the polarity and towards of

retaining side is to be given a - ve polarity Initially. They have helical grooves and skewed hole

in the body for cooling purpose by air.

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

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

supplied to the rotor wdg. Through the slip rings which are connected through semi circuilar

steel excitation leads. The excitation leads are connected to the wdg. On one end and to the

slip rings on the other end with insulated (terminals) studs passing through the radial holes in

the rotor shaft. The terminal studs at both the ends of the excitation leads are fitted gas cat seals

to prevent leakage.

8.4 BUSH GEAR ASSEMBLY:-

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Generator bushes are made from the various compositions of natural graphite and

binding materials. They have a low co-efficient of friction and are self lubricating. The brushes

are provided with a double flexible copper leads or pigtails. A pelical spring is mounted rapidly

over each bush so that pressure is applied on the centre line of bush. A metal cap is rivetted to

the brash bead and is provided with a hole to maintain the position of the spring plug. Several

brush holder, each carrying on brush in radial position are fixed to a silver-plated copper studs

mounted on the collecting arm concentric with each slip rings. The collecting arm is made out

of a Copper (Cu.) Strip.

8.5 DRYING OF WINDINGS :-

Generator stator bars are insulated with mica- insulation which is homogeneousin nature and practically impervious to moisture,and reduces time required to draught.

The insulation resistance of the stator phases wdg. against earth and with

reference to other phases under hot conditions shall not be less than the value of

mathematically obtained.

Rin = U / (S / 100 + 1000) M Ohm.

U - Rated Wdg voltage under test.

Rin - Insulation resistance under hot conditions.

S- Rated output of turbo generator.

The insulation resistance of entire excitation system ckt in hot conditions must not fall below

0.5 M Ohm. The insulation resistance in calculated as per the formula -

Rin = Rv ( U 1 + U 2 / U - 1 )

Rin - Insulation resistence of exciation

Rv - Internal resistance of volt meter

V1 - Voltage measured between the slip ring & shaft /

earth (volts)

V2 - Voltage measured between (-)ive slipring & shaft earth (volts)

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When starting the drying process, the winding. Insulation resistance will usually

decrease when the drying process becomes effective, the insulation resistance will gradually

increase.

CHAPTER 9

COOLING SYSTEM

9.1 INTRODUCTION: -

In S.T.P.S hydrogen cooling system is employed for generator cooling. Hydrogen is

used for cooling medium primarily because of its superior coding properties and its low

density. Thermal conductivity of hydrogen is 7.3 times of air. It has also higher transfer co-

efficient. Its ability to transfer heat through forced convection is about 50% better than air.

Density of hydrogen is approximately 7/14 of the air ata given temp. and pressure. This reduces

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

Increasing the hydrogen pressure within the machine improve its capacity to

absorb and remote heat. Relative cooling properties of air and hydrogen are given below as

shown on the next page.

Elimination of fire risk because hydrogen witllnt support combution.

(i) Corona discharge is not harmful to insulation since oxidation is not possible.

(ii) Smooth operation of machine in view of vertical elimination of windage noise and the

use of heavy gas tight enclousers and hence an elirt proby casing.

At pressure 0.035 atm. Of hydrogen heat carrying capacity is 1. But at 2.0 atm

of hydrogen heat carrying capacity is 2.95.

To over come the serious possibility of hydrogen explosion with in the machine

and to ensure the safety of operation purity of hydrogen on the gen. Casing must be maintained

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as high as possible. The purity of hydrogen should be 98% pr above but should not be less than

98%. In case of hydrogen purity drops below 98%, an alarm is provided.

9.2 HYDROGEN DRYERS :-

Two no. of dryers are provided to absorb the moisture in the hydrogen in the gererator.

Moisture in this gas is absorbed by silica gel in te dryer as the absorbed gas passes through it.

The saturation of silica get is indicated by its change in colour from blue to pink. The silica gel

is reactivated by heating. By suitable change over from drier to the other on uninterrupted

drying is achieved.

9.3 HYDROGEN FILLING SYSTEM :-

The filling operation is carried out in two steps:

(i) Scavanging the air by carbon dioxide and

(ii) Expelling the CO2 with hydrogen.

Before filling the hydrogen at a pressure of 2 atm. In the machine it is necessary

to store :

(a) At least 18 cylinders of 20 kg CO2 each i.e. 360 kg of CO2 and

(b) 48 cylinders of hydrogen.

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CHAPTER 10

EXCITATION SYSTEM

The electric power generators required direct current excited magnets for its

fielf 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 a

fast acting regulators, it is chiefly dependent on exciter.

Exciter supply is given from X-mer and is than rectified.

10.1 FUNCTION OF EXCIATION SYSTEM: -

The main function of exciation 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 control or automatic control so that for all operation & between no load and rated

load. The terminal voltage of the system machine is maintained at its value.

The excitation system makes contribution improving power system stability

limit for transient conditions and also for steady state conditons. The excitation system that are

effective from the stand-point if stability are commonly termed quick response system and have

following principal features.

Exciter of quiet response and high cealing voltages of not less than 1.4 times the

rated field voltage and nominal exciter response of minimum 0.5.

10.2 TYPES OF EXCITATION SYSTEM :-

There have been many developments in excitation system designs. There have been a

continuous reach among the disigns and the use alike from improving the excitation system

performance. The ultimate is to achieve on ideal in value (rate) of response stability in

reliability, accuracy etc.

The modern excitation system adopted presently on B.H.E.L. made turbo-

generators.

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(i) Conventional D.C. Excitation System.

(ii) Brushes Excitation System.

(iii) Stafic Excitation System.

10.3 STATIC EXCITATION SYSTEM:-

In S.T.P.S. static excitation system is provided. If mainly consists of the

following:

(i) Rectifier X-mer

(ii) 6 Nos. of Thyristor converters

(iii) An automatic voltage regulator (AVR)

(iv) Field syppression equipment

(v) Field flashing equipment.

GENERAL ARRANGEMENT :-

In the excitation system the power required for exciation of generation are

tapped from 11 KV bus-ducts through a step down rectifier X-mer. After rectification inthermistor, convertor, the DC power is fed to the generator field wdg through a field breaker.

The AVR controls the O/P from thyristor convortor by adjusting the firing angle depending

upon generation voltages.

The field flashing system facilitates inital built up of the generator voltage from

the static AC or DC supply.

10.4 RECTIFIER X-MER:-This X - mer step down the bus voltage 11 KV to 640 and has a rating of 1360 KVA. It

is dry type, naturally cooled X-mer with resin cast Coils. It is porvided with how-ever current

relays and two temp. sensors.

10.5 THYRISTOR CONVERTOR:-

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The thyristor convertors are housed in thyrert panel and are intended for controlled

rectification of A.C. imput power. 6 Thyristors convertors are comected in parallel each rated

for continuous current O/P of 20% of the rated capacity i.e. 20% of the reserve.

Each thyristor convertor consists of 6 thyristor connected in a 3 - Phase, full

wave, 6 - pulse - dridge from and they are cooled by fans provided with a fuse for protection

against short ckt.

10.5.1 AUTOMATIC VOLTAGE CONTROLS :-

This AVR is a transistorised thyristor controlled equipment with very fast response. The

AVR is also having a provision of Stator and rotor currents limits and load angle limits for

optimum utilization of lagging and leading reactive capacities of generator.

The principal features demanded by modern AVR equipments are as follows :-

a) Maintenance of constant voltage so to permit efficient operation of connected machine

and applications.

b) To control the relative load between a parallel running machine to the best advantager

of the system.

c) To rise the exitation power by the machine as it tends to best advantage of the system,

swing away from the system subsequent to a fault so as to increase the instantaneous

power flowing and there by rise the transient stability limit of the system.

10.6 FIELD SUPRESSION EQUIPMENT :-

The field suppression equipments consists of a field breaker with a discharge

resistors. The field breakers has 4 main breaking contacts and two discharge contacts

which close before main contact break..

10.7 ADVANTAGES OF STATIC EXCITATION SYSTEM :-

1- Very fast response.

2- Extremely reliable in view of static components

3- Low maintenance cost

4- High efficiency

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5- Fast field supression through field and discharge resistance as well as through

thyristor bridge, feeding the generator field.

10.8 OPERATION:-After bringing the speed to operating speed say 3000 r.p.m., the voltage is slowly buit up with

the help of excitation system. This action is taken for synchronising the generator with grid.

10.8 SYNCHRONISING : -

For syncronising the generator to the grid system 5 conditions of equality have to be

satisfied. These are :-

(i) Voltage

(ii) Frequency

(iii) Phase displacement

(iv) Phase sequence

(v) Wave form.

Wave form and phase sequence of the generator are determined at the design

and commissioning stages but voltage, frequency and phase displacement have to be set up

by the operator during each connection of synchronising of the generator.

10.8.2MACHINE CONNECTED ON INFINITE BUS :-

While separating a M/c in parallel with grid we will have two conditions :-

(i) Any increase in the power input of the generator increase its share of electrical loads.

(ii) Any excitation in the excitation of generator increase its share of relative load.

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CHAPTER 11CHAPTER 11

TRANSFORMERSTRANSFORMERS

Transformer is a static device which transfer electric power from one circuit to another circuitTransformer is a static device which transfer electric power from one circuit to another circuit

without changing frequency.without changing frequency.

11.1STATION TRANSFORMERSTATION 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 5 S.Ts in the plant. One for each stage.

Type of cooling ONAN ONAF

MVA rating

H.V.

L.V.

40

26

50

31.05

Current (line)

H.V.

L.V.

105

3351

131

4189

Table 11.1Table 11.1

Voltage (at no load)Voltage (at no load)

H.V. side L.V. side

220 KV 6.9 KV

Table 11.2

Vector group YNyno

Mass of Oil -24400 Kg.

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Untanking mass- 8000Kg.

Volume of oil- 27150 litre.

Frequency -50Hz

11.2 UNIT AUXILIARY TRANSFORMERUNIT AUXILIARY TRANSFORMEREach 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.

11.3 UNIT STATION TRANSFORMER11.3 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.

11.4UNIT SERVICE TRANSFORMER11.4UNIT SERVICE TRANSFORMER

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

to the unit secondary switchgear bus.

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DIFFERENT EQUIPMENTS AND BUS SCHEMESDIFFERENT EQUIPMENTS AND BUS SCHEMES

12.1 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




12.2 BUS SYSTEM:-

There Are Mainly Three Buses

Main Bus-1

Main Bus-2

Transfer Bus

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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.

12.3 SF6 GAS CIRCUIT BREAKERS12.3 SF6 GAS CIRCUIT BREAKERSIn 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 DESIGNATIONTYPE 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.

The common control cubicle (96000), which is installed separately contains all

control devices and most of the monitoring instrumentation with the exception of the

density monitor 98005 mounted on the middle breaker pole. The pressure switches are

installed in the control cubicle. all three poles columns are filled with insulating gas and

interconnected by means of pipe lines. the gas is monitored by a density monitor 98005

( temp. compensated pressure monitor )

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

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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.

12.4 ISOLATORS:-12.4 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.

1. Tightening of the jumper clamps

2. Tightening of electrical connections

3. Cleaning of male female connections

4. Checking of fuses and replacement there F.

5. Checking of operation of isolators

12.5 CHANGE OVER SCHEMES (BUS TIE SYSTEM)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.

Close the isolator e,f, & g of tie Bus.

By using synchronizing trolley close the circuit breaker b1

12.6 BUS COUPLER TO MAIN BREAKER12.6 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

By using synchronizing Troley, close the bus coupler breaker c1

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12.7 SYNCHRONIZATIONOF THE GENERATOR TO THE GRID12.7 SYNCHRONIZATIONOF THE GENERATOR TO THE GRID

(Generator breaker is used)

With The Main Bus1. Close the isolator with the bus selection

2. Close the isolator on both sides of the generator breaker.

3. On Generator control desk panel(GCDP)

a. Put the switch NIT in normal position.

b. Put the synchroscope ON.

c. Measure the voltage and speed matching. Conditions will be included by

checking the synchronizing lamp on GCDP and close the generator breaker.

IMPORTANCE OF THE TRANSFER BUS

Transfer bus is normally free and is used to facilitate repairing job of other breakers by

transferring load on transfer bus.

12.8 CURRENT TRANSFORMERS:-

1. Checking of oil level.

2. Checking of oil and leakage

3. Tightening of jumper clamps

4. Tightening of electrical terminal secondary connection

12.9 LIGHTNING ARRESTERS:-

1. Tightening of jumper connections

2. Tightening of earthing connections

3. Checking of counter reading

4. Checking of porcelain part

5. Checking of grading current

12.10 CAPACITIVE VOLTAGE TRANSFORMER:-

1. Checking of oil level and leakage

2. Tightening of HT jumper clamps.

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3. Tightening of secondary terminal connections

12.11 BATTERY 220V DC:-

1. Cleaning of battery terminals

2. Tightening of battery terminal connections3. Recording of specific gravity and voltage of each cell.

13.12 EARTH SHIELDING :-

It is a mesh of wire upon the tower. Its main purpose is to protect the substation

equipment from direct lightning strokes. Metallic body of each equipment is properly earthed.

The earthing resistance of any switch yard is about 0.2 ohm. Before the building up of the sub

station earthing material of G. I. wire is buried in the ground whose depth depends upon themoisture content of ground. Earthing electrodes are provided at various points. This increases

the number of parallel provided at various points. This increases the number of parallel paths

and hence resistance of earth decreases.

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POWER LINE CARRIER COMMUNICATIONPOWER LINE CARRIER COMMUNICATION

This is a technique in which power lines are used as communication lines by which we

can make contact with other substation

The range of frequency used for communication is 300 KHz to 500 kHz.

Fig.13.1 Overview of PLCC

WORKING

The voice frequency if converted into electrical signal. These signals are super imposed

on a carrier frequency and transmitted on the line through a coupling capacitor. At the receiving

end wave trap does not allow the modulated signal to enter the power circuit where as the

coupling capacitor provides a low resistance path to this signal. This signal is then given to the

line matching unit. In the LMU this frequency is matched and after wards filtration of signal is

done. The signal is demodulated and again converted into the voice signal, which is available at

phone receiver.

SENDING ENDCOUPLING

CAPCITOR

6V

OUTPUT

EARTHED

600 OHMSRECEIVING END

WAVE TRAP

PLCCLMU

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Fig . 13.2 block diagram

MEMEORY

DISPLAY

CONTROLER

123

COMMON

CONTROLER

MICRO

PROCESSOR

8085

DIGIT

EL TO

CONT

ANAL

OG

INPUT

DIGITAL INPUT

DIGITAL

OUTPUT

ANALOG INPUT

ANALOG

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CHAPTER 14

DATA SHEET & SPECIFICATIONS

(Common for Units I, II, III, IV and V)

GENERATOR

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.

BRUSHLESS EXCITER

BHEL

Active Power 1350 kW

Rated Current 3200 Amps.

Voltage 420 Volt

Speed 3000 rpm

PILOT EXCITOR

Apparent Power 35 kVA

Current 105 Amps

Voltage 220+/-22 V

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Speed 3000 rpm

Frequency 400 Hz

RECTIFIER WHEEL

Number of Fuses per Rectifier Wheel =30

Fuse Rating 750V/400 Amp

No. of Wheels 2

SPECIFICATIONS OF SF6 GAS CIRUIT BREAKERS

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 HzRated line charging breaking current 125 A 600 A

Table 14.1Table 14.1


ABOUT AVR

AVR regulates the terminal Voltage of Generator by direct control of the Main Exciter field

current using Thyristor converter.

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AVR is configured as two independent closed loop control systems :

1. Auto

2. Manual

Auto Channel

It controls the generator terminal voltage and is kept normally ON during operation.

To regulate the effect of the Generator reactive current on the Voltage.

To regulate the effect of the Generator active current on the Voltage.

To regulate PF , MVAR of Generator.

To limit V/Hz , max. field current , inductive stator current , capacitive stator current , load

angle , minimum field current .

To dampen active power oscillation.(PSS)

To provide soft start of generator.

Manual Channel

It regulates the Exciter field current.

It serves as backup channel in case of malfunction in Auto channel.

It is basically used for testing and commissioning.

Tracking Feature

Both channels are equipped with tracking feature so that the inactive channel always generates

the same control variable as the active channel under steady state operation. This ensures

smooth switch over Auto to Manual or vice-versa.


REFERENCESREFERENCES

P.S. Bhimbra, electrical machinery pp 238-242, 540-557, 852-868, seventh editionP.S. Bhimbra, electrical machinery pp 238-242, 540-557, 852-868, seventh edition

20042004

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B.R. Gupta,generation of electrical energy pp 80-89, 105-125, 246-260, First EditionB.R. Gupta,generation of electrical energy pp 80-89, 105-125, 246-260, First Edition

19931993

C.L. Wadhwa,electrical power system pp 173-187, 392-407, 500-504 fourth editionC.L. Wadhwa,electrical power system pp 173-187, 392-407, 500-504 fourth edition

20052005

B.L. Theraja, electrical technologypp 1304-1311 volume second twenty third editionB.L. Theraja, electrical technologypp 1304-1311 volume second twenty third edition

20022002

Various html address are:-Various html address are:-

1.1. http://en.wikipedia.org/wiki/thermalhttp://en.wikipedia.org/wiki/thermal power_stationpower_station

2.2. http://www.s-k.com/pr_vac.htm?sitrackingid=664330http://www.s-k.com/pr_vac.htm?sitrackingid=664330

3 http://www.cheresources.som/ejectors.shtmlhttp://www.cheresources.som/ejectors.shtml
http://en.wikipedia.org/wiki/thermalhttp://en.wikipedia.org/wiki/thermalhttp://www.s-k.com/pr_vac.htm?sitrackingid=664330http://www.s-k.com/pr_vac.htm?sitrackingid=664330http://www.cheresources.som/ejectors.shtmlhttp://www.cheresources.som/ejectors.shtmlhttp://en.wikipedia.org/wiki/thermalhttp://www.s-k.com/pr_vac.htm?sitrackingid=664330http://www.cheresources.som/ejectors.shtml

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