NTPC LIMITED

We were appointed to do 24 week training at this esteemed organization. We were assigned to visit various division of the plant.

These 24 weeks training was a very educational adventure for us. It was really amazing to see the plant by our self and learn how electricity, which is one of our daily requirements of life, is produced. This report has been made by our experience at NTPC Badarpur and Faridabad. The material in this report has been gathered from senior student reports, trainers manuals and power journals provided by training department. The specification and principles are as learned by us from the employees of each division of respective units.

1) ABOUT NTPC2) STRATEGIES 3) JOURNEY OF NTPC 4) ABOUT BTPS 5) OPERATION OF POWER PLANT6) BASIC STEPS OF ELECTRICITY GENERATION7) PARTS OF A POWER PLANT8) VARIOUS CYCLES AT POWER STATION 9) MOTORS10) COAL HANDLING PLANT (CHP)11) ABOUT FARIDABAD THERMAL POWER STATION12) POWER GENERATION PROCESS13) SWITCHYARD14) LT/HT SWITCHGEAR15) TRANSFORMER16) MAIN PARTS OF TRANSFORMER

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.

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

Basic PrincipleAs 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.

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

1. 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

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

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. 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.

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.

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 SWITCHThese 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.

Est. 1997, this state of the art power plant has a production capacity of up to 430 MW.

It is the only power plant in this country to supply its entire power to a state i.e. Haryana rather than to the national grid.

It consist of 2 Gas Turbines and 1 Steam Turbine.

The source of fuel is Natural Gas through HBJ pipeline.

The water source canal is Gurgaon Canal.

The Gas/Naphtha from pipeline is taken and supplied to GT Combustion Chamber where it is burnt as fuel along with air drawn from atmosphere. This heat is then converted into mechanical energy in the Gas Turbine. Gas turbine through a common shaft rotates a Generator, which produces electric power. Flue gas from the turbine exhaust is used to convert water into steam in the Waste Heat Recovery Boiler (WHRB). Water required for steam generation is circulated through the tubes in the boiler, where heat exchange takes place and water gets converted into steam. The steam generated from WHRBs is used to run a steam turbo generator and produce electric power. This power is supplied to customer through 220KV lines.

Line Diagram of Gas Turbine cycle

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. 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.

ISOLATOR 

SWITCHING ISOLATOR 

CIRCUIT BREAKER 

LOAD BREAK SWITCHES

EARTH SWITCHES

MAIN SWITCHMain 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. FUSESWith 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.  CONTACTORSAC 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

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

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).

CONSERVATOR It is used generally to conserve the insulating property of the oil from deterioration&

protect the transformer against failure on account of bad quality of oil.

SILICAGEL DEHYDRATING BREATHER It is used to prevent entry of moisture inside the transformer tank. The breather

consists of silica gel.

GAS OPERATED RELAY (BUCHHOLZ RELAY) It is a gas actuated relay used for protecting oil immersed transformer against all types

of faults. It indicates presence of gases in case of some minor fault & take out the transformer out of circuit in case of serious fault.

OIL GUAGE Every transformer with an oil guage to indicate the oil level. The oil guage may be

provided with the alarm contacts which gave an alarm the oil level has dropped beyond permissible height due to oil leak etc.

BUSHINGS It is made from highly insulating material to insulate & to bring out the

terminals of the transformer from the container. The bushings are of 3 types:

a. Porcelain bushings used for low voltage transformer b. b. Oil filled bushings used for voltage up to 33KV. c. c. Condensed type bushings used for voltage above 33KV.

TAPPINGS The transformer are usually provided with few tappings on secondary side

so that output voltage can be varied for constant input voltage.

RADIATORS It increases the surface area of the tank & more heat is thus radiated in less

time.

WINDINGS TEMPERATURE INDICATOR (OIL GUAGE) Device which indicates the temperature of winding of transformer &

possible damage to the transformer due too overload can be prevented.