BADARPUR THERMAL POWER STATIONSUMMER TRAINING REPORT 2012 NTPC LIMITED
Training at BTPSI was appointed to do 6 week training at this esteemedorganization from 11th June to 21st July, 2012. I was assigned to visitvarious 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. Itwas really amazing to see the plant by yourself and learn howelectricity, which is one of our daily requirements of life, isproduced. This report has been made by my experience at BTPS.The material in this report has been gathered from mytextbook, senior student reports and trainers manuals and powerjournals provided by training department. The specification andprinciples are as learned by me from the employees of eachdivision of BTPS.Anubhav Ghosh
INDEX1) ABOUT NTPC2) STRATEGIES3) JOURNEY OF NTPC4) ABOUT BTPS5) OPERATION OF POWER PLANT6) PARTS OF A POWER PLANT7) VARIOUS CYCLES AT POWER STATION8) ELECTRICAL MAINTENANCE DEPARTMENT-9) ELECTRICAL MAINETNANCE DEPARTMENT-II10) 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.
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. Mehrauli 2. Okhla 3. Ballabgarh 4. Indraprastha 5. UP (Noida) 6. Jaipur
Given below are the details of unit with the year they’re installed
OPERATION OF A POWER PLANTBasic 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 Thebasic 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 PLANT 1. Cooling tower 2. Cooling water pump 3. Transmission line (3-phase) 4. Unit transformer (3-phase) 5. Electric generator (3-phase) 6. Low pressure turbine 7. Condensate extraction pump 8. Condenser 9. Intermediate pressure turbine 10. Steam governor valve 11. High pressure turbine 12. Deaerator 13. Feed heater 14. Coal conveyor 15. Coal hopper 16. Pulverised fuel mill 17. Boiler drum 18. Ash hopper 19. Super heater 20. Forced draught fan 21. Reheater 22. Air intake 23. Economiser 24. Air preheater 25. Precipitator 26. Induced draught fan 27. 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 motorIn modern thermal power plant three phase squirrel cage induction motors are used but sometimedouble 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 LUBRICATIONSA good bearing is needed for trouble free operation of motor. Since it is very costly partof the motor, due care has to be taken by checking it at regular intervals. So lubricatingplays an important role. Two types of lubricating are widely used Oil lubrication Grease lubrication InsulationINSULATIONWinding is an essential part so it should be insulated. Following types of insulation arewidely usedINSTRUMENTS SEENMICROMETERThis instrument is used for measuring inside as well as outside diameter of bearing. MEGGARThis instrument is used for measuring insulation resistance. VIBRATION TESTERIt measures the vibration of the motor. It is measured in three dimensions-axial, verticaland 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 THISCATEGORY 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 onSWITCHING 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 breakersEARTH 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 SWITCHGEARMAIN 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 ntpc Thermal overload relay
HT SWITCHGEARMINIMUM 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 arcSF6 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.
AIR CIRCUIT BREAKERSOIL 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) TheOCHP 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.
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 SWITCH It 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.
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.
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 100MWMAKE BHEL, HaridwarCAPACITY 117,500 KVAPOWER 100,000 KWSTATOR VOLTAGE 10,500 VSTATOR CURRENT 6475 ASPEED 5000rpmPOWER FACTOR 0.85FREQUENCY 50 HZEXCITATION 280 V
TRANSFORMERSIt is a static machine which increases ordecreases the AC voltage without changingthe 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 MVAAs size of transformer becomes large, the rate of the oil circulating becomes insufficient todissipate all the heat produced & artificial means of increasing the circulation by electricpumps. In very large transformers, special coolers with water circulation may have to beemployed.TYPES OF COOLING:Air coolingAir Natural (AN)Air Forced (AF)Oil immersed coolingOil Natural Air Natural (ONAN)Oil Natural Air Forced (ONAF)Oil Forced Air Natural (OFAN)Oil Forced Air Forced (OFAF)Oil immersed Water coolingOil Natural Water Forced (ONWF)Oil Forced Water Forced (OFWF)
MAIN PARTS OF TRANSFORMER1. Secondary Winding2. Primary Winding.3. Oil Level4. Conservator5. Breather6. Drain Cock7. Cooling Tubes.8. Transformer Oil.9. Earth Point10. Explosion Vent11. 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 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.
SWITCH YARD As we know that electrical energy can’t be stored like cells, so what we generate should be consumedinstantaneously. 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. Ithas both outdoor and indoor equipments.OUTDOOR EQUIPMENTS BUS BAR. LIGHTENING ARRESTER WAVE TRAP BREAKER CAPACITATIVE VOLTAGE TRANSFORMER EARTHING ROD CURRENT TRANSFORMER. POTENTIAL TRANSFORMER LIGHTENING MASKINDOOR EQUIPMENTS RELAYS. CONTROL PANELS CIRCUIT BREAKERS
BUS BARBus bars generally are of high conductive aluminum conforming to IS-5082 or copperof adequate cross section. Bus bar located in air insulated enclosures & segregated from allother 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. Whenany operation bus has fault, this bus is brought into circuit and then faulty line is removed thereby restoring healthy power line.LIGHTENING ARRESTORIt saves the transformer and reactor from over voltage and over currents. It grounds theoverload 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 highfrequency carrier waves (24 KHz to 500 KHz) and let power waves (50 Hz - 60 Hz) to pass-through.BREAKERCircuit breaker is an arrangement by which we can break the circuit or flow of current. Acircuit breaker in station serves the same purpose as switch but it has many added andcomplex features. The basic construction of any circuit breaker requires the separation ofcontact 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 electrodesare provided to earth the lightening arrestor whereas the other equipments are earthed byconnecting their earth leads to the rid/ser of the ground mar.CURRENT TRANSFORMERIt is essentially a step up transformer which step down the current to a known ratio. It is a typeof instrument transformer designed to provide a current in its secondary winding proportionalto the alternating current flowing in its primary.POTENTIAL TRANSFORMERIt 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 abnormalconditions in the electrical circuits by continuously measuring the electrical quantities, whichare different under normal and faulty conditions, like current, voltage frequency. Havingdetected the fault the relay operates to complete the trip circuit, which results in the openingof 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 formaintenance purpose. This help to neutralize the system from induced voltage from extra highvoltage. 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 takescare of any faults occur in any of the auxiliaries in the plant.“Instrumentation can be well defined as a technology ofusing instruments to measure and control the physical andchemical 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