SUMMER TRAINING REPORT

2012

NTPC LIMITED

BADARPUR THERMAL POWER

STATION

Training at BTPS

I was appointed to do 6 week training at this esteemed organization from 11th June to 21st July, 2012. I was assigned to visit various division of the plant, which were:

Electrical Maintenance Department I (EMD-I) Electrical Maintenance Department II (EMD-II) Control and Instrumentation Department (C&I)

These 6 weeks training was a very educational adventure for me. It was really amazing to see the plant by yourself and learn how electricity, which is one of our daily requirements of life, is produced. This report has been made by my experience at BTPS. The material in this report has been gathered from my textbook, senior student reports and trainers manuals and power journals provided by training department. The specification and principles are as learned by me from the employees of each division of BTPS.

Anubhav Ghosh

INDEX

1) ABOUT NTPC2) STRATEGIES 3) JOURNEY OF NTPC 4) ABOUT BTPS 5) OPERATION OF POWER PLANT6) PARTS OF A POWER PLANT7) VARIOUS CYCLES AT POWER STATION 8) ELECTRICAL MAINTENANCE DEPARTMENT-9) ELECTRICAL MAINETNANCE DEPARTMENT-II 10) CONTROL AND INSTRUMENTATION

ABOUT NTPC India’s largest power company, NTPC was set up in

1975 to accelerate power development in India. NTPC became a Maharatna company in May, 2010,

one of the only four companies to be awarded this status. 

The total installed capacity of the company is 39,174 MW (including JVs) with 16 coal based and 7 gas based stations, located across the country.

In addition under JVs, 7 stations are coal based & another station uses naptha/LNG as fuel. 

The company has set a target to have an installed power generating capacity of 1,28,000 MW by the year 2032.

Strategies of NTPC

JOURNEY OF NTPC

About BTPS BADARPUR THERMAL POWER STATION was established on 1973 and it was

the part of Central Government. On 01/04/1978 is was given to NTPC. Since then operating performance of NTPC has been considerably above the

national average.   Badarpur thermal power station started with a single 95 mw unit. There were 2 more units (95 MW each) installed in next 2 consecutive years. Now it has total five units with total capacity of 720 MW. Ownership of BTPS

was transferred to NTPC with effect from 01.06.2006  The power is supplied to a 220 KV network that is a part of the northern

grid. The ten circuits through which the power is evacuated from the plant are:

1. Mehrauli2. Okhla3. Ballabgarh4. Indraprastha5. UP (Noida)6. Jaipur

Given below are the details of unit with the year they’re installed

OPERATION OF A POWER PLANT

Basic Principle As per FARADAY’s Law-“Whenever the amount of magnetic flux linked with a

circuit changes, an EMF is produced in the circuit. Generator works on the principle of producing electricity. To change the flux in the generator turbine is moved in a great speed with steam.” 

To produce steam, water is heated in the boilers by burning the coal. In a Badarpur Thermal Power Station, steam is produced and used to spin a

turbine that operates a generator. Water is heated, turns into steam and spins a steam turbine which drives an

electrical generator. After it passes through the turbine, the steam is condensed in a condenser. The electricity generated at the plant is sent to consumers through high-

voltage power lines The Badarpur Thermal Power Plant has Steam Turbine-Driven Generators

which has a collective capacity of 705MW.  The fuel being used is Coal which is supplied from the Jharia Coal Field in

Jharkhand. Water supply is given from the Agra Canal.

Basic Steps of Electricity Generation

The basic steps in the generation of electricity from coal involves following steps: Coal to steam Steam to mechanical power  Mechanical power to electrical power

PARTS OF A POWER PLANT1. Cooling tower 2. Cooling water pump3. Transmission line (3-phase)4. Unit transformer (3-phase)5. Electric generator (3-phase)6. Low pressure turbine7. Condensate extraction pump8. Condenser9. Intermediate pressure turbine10. Steam governor valve11. High pressure turbine12. Deaerator13. Feed heater14. Coal conveyor15. Coal hopper16. Pulverised fuel mill17. Boiler drum18. Ash hopper19. Super heater20. Forced draught fan21. Reheater22. Air intake23. Economiser24. Air preheater25. Precipitator26. Induced draught fan27. Flue Gas

VARIOUS CYCLES AT POWER STATION

PRIMARY AIR CYCLE SECONDARY AIR CYCLE COAL CYLCE ELECTRICITY CYCLE FLUE GAS CYCLE CONDENSATE CYCLE FEED WATER CYCLE STEAM CYCLE

ELECTRICAL MAINTENANCE DEPARTMENT – I (EMD-I)

It includes: Motors High Tension/Low Tension Switchgear Coal handling plant

MOTORSAC 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.

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.

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.

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.

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.

Contactors used in ntpcThermal overload relay

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.

OIL CIRCUIT BREAKERS

AIR CIRCUIT BREAKERS

SF6 CIRCUIT BREAKERS

COAL HANDLING PLANT (CHP)

The coal handling plant consists of two plants:

Old Coal Handling Plant (OCHP) New Coal Handling Plant (NCHP)

The OCHP supplies coal to Unit- I, II, III & NCHP supplies coal to Unit- IV and V. COAL SUPPLIED AT BTPSCoal is supplied to BTPS by Jharia coal mines.

COAL CYCLE

The main constituents of CHP plant are:-  WAGON TIPPLER 

Wagon from coal yard come to the tippler and emptied here. There are 2 wagon tipplers in the OCHP.

CONVEYER Conveyer belts are used in the OCHP to transfer coal from one place to other as required in a convenient & safe way.

ZERO SPEED SWITCHIt is used as a safety device for the motor i.e. if the belt is not moving & the motor is ON, then it burns to save the motor. This switch checks the speed of the belt & switches off the motor when speed is zero.

METAL DETECTOR As the conveyer belt take coal from wagon to crusher house, no metal piece should go along with coal. To achieve this objective, metal detectors & separators are used.

CRUSHER HOUSE Both the plants i.e. OCHP & NCHP use TATA crusher powered by BHEL motor. Crusher is designed to crush the pieces to 20 mm size i.e. practically considered as the optimum size for transfer via conveyer.

ROTARY BREAKER If any large piece of metal of any hard substances like metal impurities comes in the conveyer belt which cause load on the metal separator, then the rotary breaker rejects them reducing the load on the metal detector.

PULL GUARD SWITCH These are the switches which are installed at every 10m gap in a conveyer belt to ensure

the safety of motors running the conveyer belts. If at any time some accident happens or coal jumps from belt and starts collecting at a place, then the switch can be used.

SEQUENTIAL OPERATION OF OCHP

Unloading the coal Crushing & storage. Conveying to boiler bunkers.

Coal arrives to plant via road, rail, sea, and river or canal route from collieries. Most of it arrives by rail route only in railway wagons. Coal requirement by this plant is approximately 10,500 metric ton/day.

This coal is tippled into hoppers. If the coal is oversized (400 mm sq), then it is broken manually so that it passes the hopper mesh where through elliptic feeder it is put into vibrators & then to conveyor belt 1A & 1B.

The coal through conveyor belts 1A & 1B goes to the crusher house. Also the extra coal is sent to stockyard through these belts.

In the crusher house the small size coal pieces goes directly to the belt 2A & 2B whereas the big size coal pieces are crushed in the crusher & then given to the belts 2A & 2B.

The crushed coal is taken to the bunker house via the conveyor belts 3A & 3B where it can be used for further operations.

OCHP

SEQUENTIAL OPERATION OF NCHP

Coal arrives in wagons and tipples into hoppers. if the coal is oversized (400mm sq), then it is broken manually

so that it passes through the hopper mesh. From hopper it is taken to TP-6 12A & 12B. Conveyors 12A & 12B take the coal to the breaker house

which renders the coal size to be 100 mm sq. Metal separator & metal detector are installed in conveyor

belts 14A/B & 15A/B respectively to remove the metal impurities

Stones which are not able to pass through the 100mm sq mesh of hammer are rejected via 18A & 18B to the rejection house.

Extra coal is sent to the reclaim hopper via conveyor 16A & 16B.

From TP-7, coal is taken by conveyor 14A & 14B to the crusher house whose function is to render size of the coal to 20mm sq. 

NCHP

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. 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.

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.

 

TURBO GENERATOR 100MW

MAKE  BHEL, HaridwarCAPACITY  117,500 KVAPOWER  100,000 KWSTATOR VOLTAGE  10,500 VSTATOR CURRENT 6475 ASPEED 5000rpmPOWER FACTOR 0.85FREQUENCY  50 HZEXCITATION  280 V

TURBO GENERATOR 210MW

  MAKE  BHEL, HaridwarCAPACITY  247,000 KVAPOWER  210,000 KWSTATOR VOLTAGE  15,750 VSTATOR CURRENT 9050 ASPEED  5000 rpmPOWER FACTOR 0.85FREQUENCY  50 HZEXCITATION 310 VGAS PRESSURE 3.5 kg/cm

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).

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 coolingAir 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)

MAIN PARTS OF TRANSFORMER 1. Secondary Winding2. Primary Winding.3. Oil Level4. Conservator5. Breather6. Drain Cock7. Cooling Tubes.8. Transformer Oil.9. Earth Point10. Explosion Vent 11. Temperature Gauge.12. Buchholz Relay13. Secondary Terminal14. Primary Terminal

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 

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

UNIT AUXILIARY TRANSFORMER (UAT) 

Unit I & V- 12.5 MVAThe 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 TRANSFORMERIt 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.

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

BUS BAR Bus bars generally are of high conductive aluminum conforming to IS-5082 or copper of adequate cross section. Bus bar located in air insulated enclosures & segregated from all other components .Bus bar is preferably cover with polyurethane. BY PASS BUSThis bus is a backup bus which comes handy when any of the buses become faulty. When any operation bus has fault, this bus is brought into circuit and then faulty line is removed there by restoring healthy power line.

LIGHTENING ARRESTOR It saves the transformer and reactor from over voltage and over currents. It grounds the overload if there is fault on the line and it prevents the generator transformer. WAVE TRAPWAVETRAP is connected in series with the power (transmission) line. It blocks the high frequency carrier waves (24 KHz to 500 KHz) and let power waves (50 Hz - 60 Hz) to pass-through.

BREAKER Circuit breaker is an arrangement by which we can break the circuit or flow of current. A circuit breaker in station serves the same purpose as switch but it has many added and complex features. The basic construction of any circuit breaker requires the separation of contact in an insulating fluid that servers two functions:  extinguishes the arc drawn between the contacts when circuit breaker opens. It provides adequate insulation between the contacts and from each contact to earth.

EARTHING RODNormally 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. RELAYSRelay 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 relayPotential relayElectromagnetic relayNumerical relay etc. AIR BREAK EARTHING SWITCHThe 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.

CONTROL & INSTRUMENTATION

INTRODUCTION C&I LABS CONTROL & MONITORING MECHENISM PRESSURE MONITORING TEMPERATURE MONITORING FLOW MEASUREMENT CONTROL VALVES

INTRODUCTIONThis division basically calibrates various instruments and takes care of any faults occur in any of the auxiliaries in the plant.“Instrumentation can be well defined as a technology of using instruments to measure and control the physical and chemical properties of a material.”

C&I LABSControl and Instrumentation Department has following labs: 

Manometry Lab. Protection and Interlocks Lab. Automation Lab. Electronics Lab. Water Treatment Plant. Furnaces Safety Supervisory System Lab

THANKU