NATIONAL THERMAL
POWER CORPORATION
INDUSTRIAL TRAINING
HIMANSHU PANDEY
B.TECH 4th YEAR (ELECTRICAL AND ELECTRONICS ENGINEE...
CONTENTS
INTRODUCTION
NTPC Limited is the largest thermal power generating company
of India. A public sector company, it was incorp...
BACKGROUND
Feroze Gandhi Unchahar Thermal Power Project
conceived as a load center station by the U.P. government for
the ...
UNIT OVERVIEW
Unit 1 -21 NOV 1988
Unit 2 -22 MARCH 1989
Unit 3 -27 JAN 1999
Unit 4 -22 OCT 1999
ABOUT STPP UNCHAHAR
Foundation stone was laid by Late Prime Minister Mrs.
Indira Gandhi in June 1981.
First two units of 2...
PRINCIPLE OF STEAM POWER PLANT
GENERATION
The working principle of a steam plant is based upon the
Rankine cycle. Generall...
Plant Flow Diagram(Modified Rankine
Cycle)
AB- Heating of feed water (i.e. sensible heat addition)
BC- Evaporation of wate...
VARIOUS PATH IN POWER PLANT
1. Coal Cycle:
Railway wagon  power house wagon tipplercoal
hopper CHP  conveyor belt  c...
Contd……………
1. Steam cycle :
Boiler drum  LT SH  platen SH  final SH  HP turbine
 reheater IP turbine  LP turbine  ...
PLANT LAYOUT AT UNCHAHAR
COAL HANLING
The fuel used in the thermal power plants in the boiler
furnace is coal. Coal undergoes various processes lik...
DEMINERALIZE WATER PLANT
Water is required in plant for many purposes like for formation
of steam, for removal of ash, for...
1. Strong base anion exchanger-: After passing though the
two chambers of strong acid cation exchanger water is sent
to th...
COAL CYCLE
 → → → →




STEAM CYCLE
Boiler drums → Ring Header → Boiler Drum (Steam
chamber) → Super Heater → H.P. Turbine → Reheater → I.
P. Turb...
Contd………..
TURBINE:-
Steam turbine converts the heat energy in to mechanical
energy and drives on initial and final heat c...
STEAM PRODUCTION


DIAGRAM OF WATER TUBE BOILER
Furnace is placed at the bottom of the most important part
of the thermal plant where steam is generated. The boiler used
...
Soot blowers are basically pipe like structures that go
inside the furnace and the boiler for efficient cleaning. Cleaning...
TURBINE
The superheated steam after coming out of the superheater
goes to the turbine. A turbine is a form of an engine ru...
View Of Steam Turbine
The steam flow in the turbine takes place as follows; the
steam from the superheater first goes to t...
ASH HANDLING PLANT





ELECTROSTATIC PRECIPITATORS



STEPS-
1. Ionisation of gases and charging of particles.
2. Migration of particles to respective electrodes.
3. Deposition...
Mechanism
The following mechanism takes place electrically:
Emitter electrode (E) creates a strong electric field near the...
ELECTRICAL MAINTENANCE DEPARTMENT – I (EMD-I)
It includes:
 Motors
 High Tension/Low Tension Switchgear
 Coal handling ...
MOTORS
AC MOTORS
 Squirrel cage motor
 Wound motor
 Slip ring induction motor
In modern thermal power plant three phase...
BEARINGS AND LUBRICATIONS
A good bearing is needed for trouble free operation of motor. Since it is very costly part
of th...
SWITCH GEAR
 Switchgear is one that makes or breaks the electrical circuit.
 It is a switching device that opens & close...
THE EQUIPMENTS THAT NORMALLY FALL IN THIS
CATEGORY ARE:-
ISOLATOR
 Isolator cannot operate unless breaker is open
 Bus 1...
Low Tension SWITCHGEAR
MAIN SWITCH
 Main switch is control equipment which controls or disconnects the main supply. The m...
Contactors used in ntpc
Thermal overload relay
HT SWITCHGEAR
MINIMUM OIL CIRCUIT BREAKER
 These use oil as quenching medium.
AIR CIRCUIT BREAKER
 In this the compresse...
OIL CIRCUIT
BREAKERS
AIR CIRCUIT
BREAKERS
SF6 CIRCUIT
BREAKERS
ELECTRICAL MAINTENANCE DEPARTMENT –II
(EMD-II)
It includes:
 Generators
 Transformers
 Switch yard
GENERATORS
 The generator works on the principle of
electromagnetic induction. There are two
components stator and rotor....
RATINGS OF THE GENERATORS USED
 Turbo generator 100MW
 TURBO GENERATOR 210 MW
 The 100 MW generator generates 10.75 KV ...
TURBO GENERATOR 210MW
MAKE BHEL, Haridwar
CAPACITY 247,000 KVA
POWER 210,000 KW
STATOR VOLTAGE 15,750 V
STATOR CURRENT 905...
TRANSFORMERS
It is a static machine which increases or
decreases the AC voltage without changing
the frequency of the supp...
COOLING OF TRANSFORMERS
OF LARGE MVA
As size of transformer becomes large, the rate of the oil circulating becomes insuffi...
MAIN PARTS OF TRANSFORMER
1. Secondary Winding
2. Primary Winding.
3. Oil Level
4. Conservator
5. Breather
6. Drain Cock
7...
GENERATOR TRANSFORMER
(125MVA UNIT-I & UNIT-III)
 RATING 125MVA
 TYPE OF COOLING OFB
 TEMP OF OIL 45^C
 TEMP WINDING 6...
GENERATOR TRANSFORMER
(166 MVA UNIT-IV)
 RATING 240MVA
 TYPE OF COOLING ON/OB/OFB
 TEMP OF OIL 45C
 TEMP WINDING 60C...
UNIT AUXILIARY TRANSFORMER (UAT)
Unit I & V- 12.5 MVA
The UAT draws its input from the main bus-ducts. The total KVA
capac...
SWITCH YARD
As we know that electrical energy can’t be stored like cells, so what we generate should be consumed
instantan...
EARTHING ROD
Normally un-galvanized mild steel flats are used for earthling. Separate earthing electrodes
are provided to ...
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National thermal power corporation

  1. 1. NATIONAL THERMAL POWER CORPORATION INDUSTRIAL TRAINING HIMANSHU PANDEY B.TECH 4th YEAR (ELECTRICAL AND ELECTRONICS ENGINEERING),G.L.A.I.T.M
  2. 2. CONTENTS
  3. 3. INTRODUCTION NTPC Limited is the largest thermal power generating company of India. A public sector company, it was incorporated in the year 1975 to accelerate power development in the country as a wholly owned company of the Government of India. At present, Government of India holds 89.5% of the total equity shares of the company and the balance 10.5% is held by FIIs, Domestic Banks, Public and other. Within a span of 32 years, NTPC has emerged as a truly national power company, with power generating facilities in all the major regions of the country.
  4. 4. BACKGROUND Feroze Gandhi Unchahar Thermal Power Project conceived as a load center station by the U.P. government for the benefit of the stage and is stated to have the ultimate capacity of 1050 MW (5*210 MW) stages of the project consisting of two units of 210 MW each was implemented by state government.
  5. 5. UNIT OVERVIEW Unit 1 -21 NOV 1988 Unit 2 -22 MARCH 1989 Unit 3 -27 JAN 1999 Unit 4 -22 OCT 1999
  6. 6. ABOUT STPP UNCHAHAR Foundation stone was laid by Late Prime Minister Mrs. Indira Gandhi in June 1981. First two units of 210 MW were commissioned on 21st November, 1988 and 22nd March, 1989 by U.P. Rajya Vidyut Utpadan Nigam. FGUTPP was handed over by U.P. Rajya Vidyut Utpadan Nigam to NTPC in 13th February, 1992. After take over of FGUTPP from UPRVUN to NTPC, unit- 3, unit-4 and unit-5 were commissioned on 27th January1999, 22nd October 1999 and 2006 respectively. NTPC has been ranked first as per total income in the power generation, transmission, distribution sector among India’s top 500 companies for the year 2006 by Dun and Bradstreet.
  7. 7. PRINCIPLE OF STEAM POWER PLANT GENERATION The working principle of a steam plant is based upon the Rankine cycle. Generally steam is taken as the working medium due to its ability to be stable and that it’s readily stable. The flow of steam in the plant can be very easily be understood by the flow diagram of the plant. A graph plotted between the temperature and the entropy would indicate the technical details of the working by the Rankine cycle.
  8. 8. Plant Flow Diagram(Modified Rankine Cycle) AB- Heating of feed water (i.e. sensible heat addition) BC- Evaporation of water in boiler (i.e. latent heat addition) CD- Superheating of steam (i.e. heat addition) DE- Isentropic expansion of steam in HP turbine EF- Reheating of steam in Reheaters FH- Isentropic expansion of steam in IP and LP turbine
  9. 9. VARIOUS PATH IN POWER PLANT 1. Coal Cycle: Railway wagon  power house wagon tipplercoal hopper CHP  conveyor belt  crusher house conveyor belt coal stockyard or RC bunker RC feeder pulverised mill  furnace 2. Feed water cycle : Deaerator  boiler feed pump  Hp heatereconomiser  boiler drum Condensate water cycle : Condenser  hot well  condensate extraction pump  gland steam cooler  LP heater  deaerator
  10. 10. Contd…………… 1. Steam cycle : Boiler drum  LT SH  platen SH  final SH  HP turbine  reheater IP turbine  LP turbine  condenser 1. Air Path : P.A. fan  air heater & cold P.A. fan  mill  furnace F.D. fan 1. Flue gas path : Furnace  reheater  economiser  air preheater E.S.P.  I.D. fan  chimney  atmosphere
  11. 11. PLANT LAYOUT AT UNCHAHAR
  12. 12. COAL HANLING The fuel used in the thermal power plants in the boiler furnace is coal. Coal undergoes various processes like separation, crushing, etc and is then finally moved to the furnace in the form of pulverised coal. Coal: It is a mixture of organic chemicals and mineral materials produced by natural process of growth and decay. The chemical properties of any coal depend upon the proportions of different chemicals components present in it. There are four types of coal: 1. Peat 2. Lignite 3. Bituminous Coal 4. Anthracite
  13. 13. DEMINERALIZE WATER PLANT Water is required in plant for many purposes like for formation of steam, for removal of ash, for safety during fire etc. But the water required for formation of steam should be perfectly devoid of minerals because if it would be present with the steam then it will strike the blades of turbine and due to being in high pressure it produces scars or holes on the turbine blades. Water is purified in DM plant through a chain of processes as under:- 1. Carbon filter -: Water taken from river is first sent to the carbon filter for the removal of carbon content in the water. 2. Strong acid cation exchanger-: After passing through the carbon filter water is sent to the strong acid cation exchanger which is filled with the concentrated HCL. The acid produces anions which get combined with the cations present in the water.
  14. 14. 1. Strong base anion exchanger-: After passing though the two chambers of strong acid cation exchanger water is sent to the stron base anion exchanger which is filled with the concentrated NaOH. The base produces cations which get combined with the anions present in the water. 2. Mixed bed exchanger -: At last water is sent to the chamber of mixed bed exchanger where the remaining ions are removed.
  15. 15. COAL CYCLE  → → → →    
  16. 16. STEAM CYCLE Boiler drums → Ring Header → Boiler Drum (Steam chamber) → Super Heater → H.P. Turbine → Reheater → I. P. Turbine → L.P. Turbine. BOILER DRUM:- Boiler drum consist two chamber water chambers, steam chamber. Before entering in super heater the steam is going in to boiler drum, where the boiler drum filtered the moisture and stored in to water chamber. SUPER HEATER:- The function of super heater is to remove the last traces of moisture from the saturated steam leaving the water tube boiler. The temperature is approx 5300 c.
  17. 17. Contd……….. TURBINE:- Steam turbine converts the heat energy in to mechanical energy and drives on initial and final heat content of the steam. Turbine having number of stage in WHICH the pressure drops takes place.
  18. 18. STEAM PRODUCTION  
  19. 19. DIAGRAM OF WATER TUBE BOILER
  20. 20. Furnace is placed at the bottom of the most important part of the thermal plant where steam is generated. The boiler used at FGUTPP is the water tube boiler type in which, water circulates in tubes surrounded by fire. Hence it takes up heat and gets converted into steam. The steam then rises up and gets collected inside the boiler drum. The boiler is made up of carbon steel. The temperature of steam that comes out of the boiler is around 5300 Celsius and its pressure is 120kg/cm2 . The type of boiler can be further elaborated as natural circulation, dry bottom, and tangential fired, radiant heat type with direct fired pulverised coal system. Once the steam is produced in the boiler, it gets collected inside the boiler drum. Boiler drum is a special type of cylindrical drum like structure which contains a mixture of water and steam. Steam being lighter gets collected at the top portion and beneath it we have the water. It is very important to maintain a safe level of water in the drum since we have two main types of constraints in this regard. If the steam produced and collected is more then it can lead to a blast in the boiler drum else tiny droplets of water can enter the turbine. Hence in order to keep a check we measure the level by hydrastep. Hydrastep is based on the difference in the conductivities of water and steam.
  21. 21. Soot blowers are basically pipe like structures that go inside the furnace and the boiler for efficient cleaning. Cleaning is done by the superheated steam which is tapped from the superheater for the purpose of soot blowing. The pressure is reduced to 31kg/cm2 at 330 deg Celsius by means of reducing valve. We mainly have three types of soot blowers: 1. long retraceable soot blower 2. wall blower 3. air reheater Before sending this steam to the turbine, the steam is again superheated and then its temperature is around 5800 Celsius. This increases the efficiency since the temperature is the measure of energy hence higher temperature higher is the energy. Hence, during the phenomenon of superheating the steam which is dry and saturated, is being heated and hence the temperature of steam again rises. First the steam from boiler drum enters the low temperature super heater (LTSH). After LTSH steam enters the platen superheater and then finally to a high temperature superheater. The steam which is now produced goes to the HP turbine.
  22. 22. TURBINE The superheated steam after coming out of the superheater goes to the turbine. A turbine is a form of an engine running on steam, which requires a source of high grade energy and a source of low grade energy. When the fluid flows through the turbine a part of the energy content is continuously extracted and continuously converted into useful mechanical work.The main advantage of using a steam turbine rather than a prime mover is that the steam in a turbine can be expanded down to a lower back pressure, thereby making available a greater heat drop and a larger amount of this heat drop can be converted into useful mechanical work due to higher efficiency of the turbine. Therefore a turbine is suitable for driving a generator. Turbines are of two types: 1. Impulse Turbine 2. Reaction Turbine However another form called impulse-reaction turbine is also used which provide benefits of both types. The impulse- reaction turbine is used here at FGUTPP. Here three stages of turbine are used: HP turbine (high pressure) IP turbine (intermediate pressure) LP turbine (low pressure)
  23. 23. View Of Steam Turbine The steam flow in the turbine takes place as follows; the steam from the superheater first goes to the HP turbine where it does work and loses its temperature. The steam from HP turbine is the fed to the reheater where its temperature is increased pressure remains the same as that from the outlet from HP turbine. The steam from the reheater is then fed to the IP turbine and then finally to the LP turbine. The LP turbine is connected to the generator and the mechanical output from the turbine is used to drive it.
  24. 24. ASH HANDLING PLANT     
  25. 25. ELECTROSTATIC PRECIPITATORS   
  26. 26. STEPS- 1. Ionisation of gases and charging of particles. 2. Migration of particles to respective electrodes. 3. Deposition of particles on the electrodes. 4. Dislodging of particles from the electrodes. Description: The ESP consist of two sets of electrodes, one in the form of helical thin wires called emitting electrode which is connected to -70KV DC and the collecting electrode in grounded.
  27. 27. Mechanism The following mechanism takes place electrically: Emitter electrode (E) creates a strong electric field near the surface and corona discharge takes place. Positive and negative ions are formed by this discharge. The positive ions move towards anti positive charge line electrodes called emitting electrodes and the negative ions towards collecting electrodes. During this passage ions collide with ash particles and adhere to them. These charged particles stick on the collector curtain which is the dislodged by the rapping motors which is collected by the hoppers. For optimum functional efficiency of the precipitator the supply voltage should be maintained near above the flash over level between electrodes. This is achieved by the electronic control. The efficiency of ESP is about 99.95%.
  28. 28. ELECTRICAL MAINTENANCE DEPARTMENT – I (EMD-I) It includes:  Motors  High Tension/Low Tension Switchgear  Coal handling plant
  29. 29. MOTORS AC MOTORS  Squirrel cage motor  Wound motor  Slip ring induction motor In modern thermal power plant three phase squirrel cage induction motors are used but sometime double wound motor is used when we need high starting torque e.g. in ball mill. THREE PHASE INDUCTION MOTOR  Ns (speed) =120f/p  Stator can handle concentrated single layer winding, with each coil occupying one stator slot  The most common type of winding are:  DISTRIBUTED WINDING : This type of winding is distributed over a number of slots.  DOUBLE LAYER WINDING : Each stator slot contains sides of two different coils. SQUIRREL CAGE INDUCTION MOTOR  Squirrel cage and wound cage have same mode of operation. Rotor conductors cut the rotating stator magnetic field. an emf is induced across the rotor winding, current flows, a rotor magnetic field is produced which interacts with the stator field causing a turning motion. The rotor does not rotate at synchronous speed, its speed varies with applied load. The slip speed being just enough to enable sufficient induced rotor current to produce the power dissipated by the motor load and motor losses.
  30. 30. BEARINGS AND LUBRICATIONS A good bearing is needed for trouble free operation of motor. Since it is very costly part of the motor, due care has to be taken by checking it at regular intervals. So lubricating plays an important role. Two types of lubricating are widely used  Oil lubrication  Grease lubrication  Insulation INSULATION Winding is an essential part so it should be insulated. Following types of insulation are widely used INSTRUMENTS SEEN MICROMETER This instrument is used for measuring inside as well as outside diameter of bearing. MEGGAR This instrument is used for measuring insulation resistance. VIBRATION TESTER It measures the vibration of the motor. It is measured in three dimensions-axial, vertical and horizontal.
  31. 31. SWITCH GEAR  Switchgear is one that makes or breaks the electrical circuit.  It is a switching device that opens & closes a circuit that defined as apparatus used for switching, Lon rolling & protecting the electrical circuit & equipments.  The switchgear equipment is essentially concerned with switching & interrupting currents either under normal or abnormal operating conditions.  The tubular switch with ordinary fuse is simplest form of switchgear & is used to control & protect& other equipments in homes, offices etc.  For circuits of higher ratings, a High Rupturing Capacity (H.R.C) fuse in condition with a switch may serve the purpose of controlling & protecting the circuit.  However such switchgear cannot be used profitably on high voltage system (3.3 KV) for 2 reasons.  Firstly, when a fuse blows, it takes some time to replace it & consequently there is interruption of service to customer.  Secondly, the fuse cannot successfully interrupt large currents that result from the High Voltage System.  In order to interrupt heavy fault currents, automatic circuit breakers are used.  There are very few types of circuit breakers in B.P.T.S they are VCB, OCB, and SF6 gas circuit breaker.  The most expensive circuit breaker is the SF6 type due to gas.  There are various companies which manufacture these circuit breakers: VOLTAS, JYOTI, and KIRLOSKAR.  Switchgear includes switches, fuses, circuit breakers, relays & other equipments.  In low tension switch gear thermal over load relays are used whereas in high tension 5 different types of relays are used.
  32. 32. THE EQUIPMENTS THAT NORMALLY FALL IN THIS CATEGORY ARE:- ISOLATOR  Isolator cannot operate unless breaker is open  Bus 1 and bus 2 isolators cannot be closed simultaneously  The interlock can be bypass in the event of closing of bus coupler breaker.  No isolator can operate when the corresponding earth switch is on SWITCHING ISOLATOR  Switching isolator is capable of:  Interrupting charging current  Interrupting transformer magnetizing current  Load transformer switching. Its main application is in connection with the transformer feeder as the unit makes it possible to switch gear one transformer while the other is still on load. CIRCUIT BREAKER  One which can make or break the circuit on load and even on faults is referred to as circuit breakers. This equipment is the most important and is heavy duty equipment mainly utilized for protection of various circuits and operations on load. Normally circuit breakers installed are accompanied by isolators. LOAD BREAK SWITCHES  These are those interrupting devices which can make or break circuits. These are normally on same circuit, which are backed by circuit breakers EARTH SWITCHES  Devices which are used normally to earth a particular system, to avoid any accident happening due to induction on account of live adjoining circuits. These equipments do not handle any appreciable current at all. Apart from this equipment there are a number of relays etc. which are used in switchgear.
  33. 33. Low Tension SWITCHGEAR MAIN SWITCH  Main switch is control equipment which controls or disconnects the main supply. The main switch for 3 phase supply is available for the range 32A, 63A, 100A, 200Q, 300A at 500V grade. FUSES  With Avery high generating capacity of the modern power stations extremely heavy carnets would flow in the fault and the fuse clearing the fault would be required to withstand extremely heavy stress in process. It is used for supplying power to auxiliaries with backup fuse protection. With fuses, quick break, quick make and double break switch fuses for 63A and 100A, switch fuses for 200A,400A, 600A, 800A and 1000A are used. CONTACTORS  AC Contractors are 3 poles suitable for D.O.L Starting of motors and protecting the connected motors. OVERLOAD RELAY  For overload protection, thermal overload relay are best suited for this purpose. They operate due to the action of heat generated by passage of current through relay element. AIR CIRCUIT BREAKERS  It is seen that use of oil in circuit breaker may cause a fire. So in all circuits breakers at large capacity air at high pressure is used which is maximum at the time of quick tripping of contacts. This reduces the possibility of sparking. The pressure may vary from 50-60kg/cm^2 for high and medium capacity circuit breakers.
  34. 34. Contactors used in ntpc Thermal overload relay
  35. 35. HT SWITCHGEAR MINIMUM OIL CIRCUIT BREAKER  These use oil as quenching medium. AIR CIRCUIT BREAKER  In this the compressed air pressure around 15 kg per cm^2 is used for extinction of arc caused by flow of air around the moving circuit . The breaker is closed by applying pressure at lower opening and opened by applying pressure at upper opening. When contacts operate, the cold air rushes around the movable contacts and blown the arc SF6 CIRCUIT BREAKER  The principle of current interruption is similar to that of air blast circuit breaker. It simply employs the arc extinguishing medium namely SF6. When it is broken down under an electrical stress, it will quickly reconstitute itself. VACUUM CIRCUIT BREAKER  It works on the principle that vacuum is used to save the purpose of insulation and. In regards of insulation and strength, vacuum is superior dielectric medium and is better that all other medium except air and sulphur which are generally used at high pressure.
  36. 36. OIL CIRCUIT BREAKERS AIR CIRCUIT BREAKERS SF6 CIRCUIT BREAKERS
  37. 37. ELECTRICAL MAINTENANCE DEPARTMENT –II (EMD-II) It includes:  Generators  Transformers  Switch yard
  38. 38. GENERATORS  The generator works on the principle of electromagnetic induction. There are two components stator and rotor. The rotor is the moving part and the stator is the stationary part. The rotor, which has a field winding, is given a excitation through a set of 3000rpm to give the required frequency of HZ. The rotor is cooled by Hydrogen gas, which is locally manufactured by the plant and has high heat carrying capacity of low density. If oxygen and hydrogen get mixed then they will form very high explosive and to prevent their combining in any way there is seal oil system. The stator cooling is done by de-mineralized (DM) water through hollow conductors. Water is fed by one end by Teflon tube. A boiler and a turbine are coupled to electric generators. Steam from the boiler is fed to the turbine through the connecting pipe. Steam drives the turbine rotor. The turbine rotor drives the generator rotor which turns the electromagnet within the coil of wire conductors.  Carbon dioxide is provided from the top and oil is provided from bottom to the generator. With the help of carbon dioxide the oil is drained out to the oil tank.
  39. 39. RATINGS OF THE GENERATORS USED  Turbo generator 100MW  TURBO GENERATOR 210 MW  The 100 MW generator generates 10.75 KV and 210 MW generates 15.75 KV. The voltage is stepped up to 220 KV with the help of generator transformer and is connected to the grid.  The voltage is stepped down to 6.6 KV with the help of UNIT AUXILLARY TRANSFORMER (UAT) and this voltage is used to drive the HT motors. The voltage is further stepped down to 415 V and then to 220 V and this voltage is used to drive Lt Motors.
  40. 40. TURBO GENERATOR 210MW MAKE BHEL, Haridwar CAPACITY 247,000 KVA POWER 210,000 KW STATOR VOLTAGE 15,750 V STATOR CURRENT 9050 A SPEED 5000 rpm POWER FACTOR 0.85 FREQUENCY 50 HZ EXCITATION 310 V GAS PRESSURE 3.5 kg/cm
  41. 41. TRANSFORMERS It is a static machine which increases or decreases the AC voltage without changing the frequency of the supply. It is a device that:  Transfer electric power from one circuit to another.  It accomplishes this by electromagnetic induction.  In this the two electric circuits are in mutual inductive influence of each other.  WORKING PRINCIPLE: It works on FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION (self or mutual induction depending on the type of transformer).
  42. 42. COOLING OF TRANSFORMERS OF LARGE MVA As size of transformer becomes large, the rate of the oil circulating becomes insufficient to dissipate all the heat produced & artificial means of increasing the circulation by electric pumps. In very large transformers, special coolers with water circulation may have to be employed. TYPES OF COOLING: Air cooling Air Natural (AN) Air Forced (AF) Oil immersed cooling Oil Natural Air Natural (ONAN) Oil Natural Air Forced (ONAF) Oil Forced Air Natural (OFAN) Oil Forced Air Forced (OFAF) Oil immersed Water cooling Oil Natural Water Forced (ONWF) Oil Forced Water Forced (OFWF)
  43. 43. MAIN PARTS OF TRANSFORMER 1. Secondary Winding 2. Primary Winding. 3. Oil Level 4. Conservator 5. Breather 6. Drain Cock 7. Cooling Tubes. 8. Transformer Oil. 9. Earth Point 10. Explosion Vent 11. Temperature Gauge. 12. Buchholz Relay 13. Secondary Terminal 14. Primary Terminal
  44. 44. GENERATOR TRANSFORMER (125MVA UNIT-I & UNIT-III)  RATING 125MVA  TYPE OF COOLING OFB  TEMP OF OIL 45^C  TEMP WINDING 60^C  KV (no load) HV-233 KVA LV-10.5 KVA  LINE AMPERES HV-310 A LV-6880  PHASE THREE  FREQUENCY 50 HZ  IMPEDANCE VOLTAGE 15%  VECTOR GROUP Y DELTA  INSULATION LEVEL HV-900 KV LV-Neutral-38  CORE AND WINDING WEIGHT 110500 Kg  WEIGHT OF OIL 37200 Kg  TOTAL WEIGHT 188500 Kg  OIL QUANTITY 43900 lit
  45. 45. GENERATOR TRANSFORMER (166 MVA UNIT-IV)  RATING 240MVA  TYPE OF COOLING ON/OB/OFB  TEMP OF OIL 45C  TEMP WINDING 60C  VOLTS AT NO LOAD HV-236000 LV-A5750  LINE AMPERES HV-587 A LV-8798  PHASE THREE  FREQUENCY 50 HZ  IMPEDANCE VOLTAGE 15.55%  VECTOR GROUP Y DELTA  CORE AND WINDING WEIGHT 138800 Kg  WEIGHT OF OIL 37850 Kg  TOTAL WEIGHT 234000 Kg  OIL QUANTITY 42500 lit  GUARANTEED MAX TEMP 45C  DIVISION KERELA  YEAR 1977
  46. 46. UNIT AUXILIARY TRANSFORMER (UAT) Unit I & V- 12.5 MVA The UAT draws its input from the main bus-ducts. The total KVA capacity of UAT required can be determined by assuming 0.85 power factor & 90% efficiency for total auxiliary motor load. It is safe & desirable to provide about 20% excess capacity then circulated to provide for miscellaneous auxiliaries & possible increase in auxiliary. STATION TRANSFORMER It is required to feed power to the auxiliaries during startups. This transformer is normally rated for initial auxiliary load requirements of the unit in typical cases; this load is of the order of 60% of the load at full generating capacity. It is provided with on load tap change to cater to the fluctuating voltage of the grid. NEUTRAL GROUNDED TRANSFORMER This transformer is connected with supply coming out of UAT in stage-2. This is used to ground the excess voltage if occurs in the secondary of UAT in spite of rated voltage.
  47. 47. SWITCH YARD As we know that electrical energy can’t be stored like cells, so what we generate should be consumed instantaneously. But as the load is not constants therefore we generate electricity according to need i.e. the generation depends upon load. The yard is the places from where the electricity is send outside. It has both outdoor and indoor equipments. OUTDOOR EQUIPMENTS  BUS BAR.  LIGHTENING ARRESTER  WAVE TRAP  BREAKER  CAPACITATIVE VOLTAGE TRANSFORMER  EARTHING ROD  CURRENT TRANSFORMER.  POTENTIAL TRANSFORMER  LIGHTENING MASK INDOOR EQUIPMENTS  RELAYS.  CONTROL PANELS  CIRCUIT BREAKERS
  48. 48. EARTHING ROD Normally un-galvanized mild steel flats are used for earthling. Separate earthing electrodes are provided to earth the lightening arrestor whereas the other equipments are earthed by connecting their earth leads to the rid/ser of the ground mar. CURRENT TRANSFORMER It is essentially a step up transformer which step down the current to a known ratio. It is a type of instrument transformer designed to provide a current in its secondary winding proportional to the alternating current flowing in its primary. POTENTIAL TRANSFORMER It is essentially a step down transformer and it step downs the voltage to a known ratio. RELAYS Relay is a sensing device that makes your circuit ON or OFF. They detect the abnormal conditions in the electrical circuits by continuously measuring the electrical quantities, which are different under normal and faulty conditions, like current, voltage frequency. Having detected the fault the relay operates to complete the trip circuit, which results in the opening of the circuit breakers and disconnect the faulty circuit. There are different types of relays: Current relay Potential relay Electromagnetic relay Numerical relay etc. AIR BREAK EARTHING SWITCH The work of this equipment comes into picture when we want to shut down the supply for maintenance purpose. This help to neutralize the system from induced voltage from extra high voltage. This induced power is up to 2KV in case of 400 KV lines.
  49. 49. THANK YOU
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