REPORT ON BASIC OPERATION OF VINDHYACHAL SUPER THERMAL POWER

STATION

BASED ON SUMMER TRAINING UNDERTAKEN IN

NATIONAL THERMAL POWER CORPORATION LIMITED VINDHYACHAL

DURATION:

MAY 29TH to JUNE 25TH, 2010

SUBMITTED BY:

A. B. M. Omar Maruf

Electrical Engineering

6th Semester

National Institute of Technology, Silchar

Acknowledgement

At the outset I would like to convey my regards towards training department of NTPC, Vindhyachal for giving me such a great opportunity to observe and learn operation of this Superthermal Plant.

My heartfelt thanks goes to Mr. ANIL SHRIVASTAVA, DGM (EMD), NTPC VINDHYACHAL who led the entire team of VSTPS for proper functioning of each department in a modernized and techno-commercial atmosphere to make the project touch such peaking performance. I also express my gratitude towards Mr. S.D.P. PANDEY (Senior Engineer, FES), without his assistance I would not be here. He has provided me the best moral support which I was in need for.

I would give my special thanks to Mr SANJAY SHARMA (HR-EDC), for giving his very kind permission to undergo the training programme under the able guidance of NTPC engineers. I would like to appreciate Mr Pankaj Kumar (Sr. Engineer., EMD DEPT), Mr .Vikas Gupta (Engineer, EMD.) & Mr. Ajit Singh( Engineer, EMD) under whose able guidance I completed the training. All these people were of immense importance regarding the knowledge and supports for the well furnished equipments.

At last I would like to convey my appreciation to all the members of the Electrical and Maintenance Dept. and members of various stages whose valuable guidance and suggestions helped me accomplishing this report.

INTRODUCTION NTPC (National thermal power corporation) is India’s largest power generation company. It was set up in the year 1975 to accelerate power development in India. It has an installed capacity of 37,104 MW and planned to grow up to 75000 MW till year 2017.There are 15 coals based and 7 gas based plant in India located across the country. NTPC is the sixth largest thermal power generator in the world and the second most efficient utility in terms of capacity utilization based on data of 1998.

NTPC HEADQUARTERS:

Sl no Headquarter City1 NCRHQ Noida2 ER-1,HQ Patna3 ER-2,HQ Bhubaneshwa

r4 NER Lucknow5 SR,HQ Hyderabad6 WR,HQ Mumbai

NTPC PLANTS:

Coal based:

Sl no City State Capacity (MW)

1 Singrauli U.P. 20002 Korba Chattisgarh 21003 Ramagundam Andhra Pradesh 26004 Farakka W.B. 16005 Vindhyachal M.P. 32606 Rihand U.P. 20007 Kahalgaon Bihar 23408 NCTPP,Dadri U.P. 13309 Talcher,Kaniha Orissa 300010 Unchahar U.P. 105011 Talcher Thermal Orissa 246012 Simhadri Andhra Pradesh 100013 Tanda U.P. 44014 Badarpur Delhi 70515 Sipat-II Chattisgarh 1000

Total 24885

Gas based:

Sl no City State Capacity(MW)1 Anta Rajasthan 413.22 Kawas Gujarat 645.43 Dadri UP 817.54 Jhanor Gujarat 648.65 Rajiv Gandhi Kerala 350.76 Faridabad Haryana 430

Total 3955Hydel based:

The company has also stepped up its hydel projects implementation. Currently the company is mainly interested in Northeast India wherein the ministry of power in India has projected a hydel power feasibility of 3000 MW.

There are few run of the river hydro projects are under construction on tributary of Ganga. In which three are being made by NTPC limited. These are:

1. Lohariang Pala Hydro Power project(600 MW)2. TapovanVishnugad Hydro power project3. LataTapovan Hydro Power Project4.

As a public sector company, it was incorporated in the year 1975 to accelerate power development in the country as a wholly owned enterprise 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 owned by FIIs, Domestic Banks, public and others. Within a span of 31 years, NTPC has emerged as a truly national power company, with power generating facilities in all the major regions of the country.

NTPC-VINDHYACHAL SUPER THERMAL POWER PROJECT is one of the most prestigious flagships of NTPC striving ahead to bridge the country generation gap especially in the western region. It is the largest power station in India. Vindhyachal super thermal power station was conceived as a pit head coal based super thermal plantfor which land was acquired during stage I of the project. The total land area acquired is 5378 acres of land.

The station is located in Singrauli district in Madhya Pradesh in the north western side of the country. , having a latitude and longitude of 24⁰6’ N and 82⁰40’ E respectively.

It has secured ISO 14001 and ISO 9002 certificate in the field of environment and power generation but also in various other fields. On November 2009, it made glorious achievement by ensuring production up to 3260 MW. By next few months, it adds 1000 MW more to its capacity (i.e. 4260 MW). A proposal has also been made to add another 500 MW in Stage V for which field study is going on.

IMPORTANT DATA

Address- P.O. Vindhyanagar 486 885, SIdhi, Madhyapradesh

Approved Capacity- 3260 MW

Stages:-

Stage1—6×210 =1260 MW

Stage2---2×500=1000 MW

Stage3---2×500=1000MW

Stage4---2×500=1000MW (Under construction)

Stage5---1×500=1000MW (Proposed)

Coal source- Nigahi Hills

Water source- Discharge canal of Singrauli (Shaktinagar) Super Thermal Power Station

Beneficiary States- Madhya Pradesh, Chattisgarh, Maharashtra, Gujarat, Goa, Daman & Diu and Dadar Nagar Haveli.

Units Commissioned

Stage1

Unit 1- 210 MW October 1987

Unit 2- 210 MW July 1988

Unit 3- 210 MW February 1989

Unit 4- 210 MW December 1989

Unit 5- 210 MW March 1990`

Unit 6- 210 MW February 1991

Stage2

Unit 7- 500 MW March 1999

Unit 8-500 MW February 2000

Stage3

Unit 9- 500 MW July 2006

Unit 10- 500 MW March 2007

PRODUCTION OF ELECTRICITY :

Coal Handling

Plant, CHP

Turbines & Generators

BoilerSwitch Gear & Switch

Yard

given b

chimney

Coal to Electricity

The means and steps involved in the production of electricity in a coal-fired power station are described below.

The coal, brought to the station by train or other means, travels from the coal handling plant by conveyer belt to the coal bunkers, from where it is fed to the pulverizing mills which grinds it as fine as face powder. The finely powdered coal mixed with pre-heated air is then blown into the boiler by fan called Primary Air Fan, with additional amount of air called secondary air supplied by Forced Draft Fan. As the coal has been grounded so finely the resultant ash is also a fine powder. Some of this ash binds together to form lumps which fall into the ash pits at the bottom of the furnace. The water quenched ash from the bottom of the furnace is conveyed to pits for subsequent disposal or sale. Most of ash, still in fine particles form is carried out of the boiler to the precipitators as dust, where it is trapped by electrodes charged with high voltage electricity. The dust is th en conveyed by water to disposal areas or to bunkers for sale while the cleaned flue gases pass on through ID Fan to be discharged up the chimney.

Meanwhile the heat released from the coal has been absorbed by the many kilometres of tubing which line the boiler walls. Inside the tubes is the boiler feed water which is transformed by the heat into the steam at high pressure and temperature. The steam super-heated in further tubes (Super Heater) passes to the turbine where it is discharged through the nozzles on the turbine blades. Just the energy of the wind turns the sail of the wind-mill, so the energy of the steam, striking the blades, makes the turbine rotate.

Coupled to the end of the turbine is the rotor of the generator – a large cylindrical magnet, so that when the turbine rotates the rotor turns with it. The rotor is housed inside the stator having heavy coils of copper bars in which electricity is produced through the movement of the magnetic field created by the rotor. The electricity passes from the stator winding to the step-up transformer which increases its voltage so that it can be transmitted efficiently over the power lines of the grid.

The steam which has given up its heat energy is changed back into water in the condenser so that it is ready for re-use. The condenser contains many kilometres of tubing through which the colder is constantly pumped. The steam passing around the

Electrostatic Precipitator,

ESP

Transmission

tubes looses the heat and is rapidly changed back to water. But the two lots of water (i.e. boiler feed water & cooling water) must never mix. The cooling water is drawn from the river, but the boiler feed water must be absolutely pure, so as not to damage the boiler tubes. Chemistry at the power station is largely the chemistry of water.

To condense the large quantities of steam, huge and continuous volume of cooling water is essential. In most of the power stations the same water is to be used over and over again. So the heat which the water extracts from the steam in the condenser is removed by pumping the water out to the cooling towers and then the cooled water is recirculated again through the condenser.

Steps Involved In Power Generation In VSTPS

The conversion of coal into electricity consists of various intermediate stages. This are described below –

1.Coal handling Plant-

CHP is the first stage of any Thermal Power Plant .The coal from the mines is brought to the plant by use of Coal wagons. . Merry-Go-Round rail system of transport is adopted for transportation of coal from the mines to plant site. NTPC has its own MGR system which results in an annual profit of 45 crores. Coals are unloaded by track hoppers. As the coal from mines contain particles of different sizes, so water is sprinkled on the coal so as to stop flow of coal with air and to stop the loss. Coal in the track hopper is then send to crusher house for crushing it to size no less than 20mm. Crushed coal is sent to bunkers through conveyer belt system. Afterwards according to requirement coals are taken into mills through gravimetric feeder to pulverize it to a size of 200 mesh. Primary air mixed with pulverized coal is fed to the centre of boiler burning zone. Pre heated secondary air enters boiler, surrounds the pulverized coal and helps in combustion.

Capacity of each crusher 600MT/HourMaximum coal inlet size 200mmMaximum coal outlet size 20mmMotor Rating 375KWMotor Speed 740 Rpm

Capacity of conveyer belt 1200 T/HourBelt Speed 2.6 m/sBelt width 1.4 mBelt Type Nylon-Nylon Caracus

2.Air Draft System:

Primary air system:

- Ambient air is drawn into the primary air ducting by two 50% duty, motor driven axial reaction fans.

- Air discharging from each fan is divided into two parts, one passes first through a air pre-heater then through a gate into the P.A bus duct. The second

goes to the cold air duct. The mix of both is used to carry the pulverized coal to the boiler.

-Secondary air system:

- Ambient air is drawn into the secondary air system by two 50% duty, motor driven axial reaction forced draft fans with variable pitch control.

- Air discharging from each fan passes first through a air preheater then through a isolating damper into the secondary air bust duct.

- The cross over duct extends around to each side of the boiler furnace to form two secondary air to burner ducts.

- At the sides of the furnace, the ducts split to supply air to two corners. Then split again to supply air to each of nineteen burner/air nozzle elevations in the burner box

-Primary and Secondary air System in the Boiler:

Air Preheater:

Air preheater is heat transfer surface where temperature of air is raised by flue gas. It gives:

-Improved boiler efficiency

- Improved combustion

- Hot primary air for drying coal

Induced draft system:

It sucks flue gas from boiler and releases it to atmosphere through chimney. The flue gas contains fly ash particles, deposited in ESP hoppers and SOx, NOx etc. The flue gas path is shown below

Electrostatic Precipitator (ESP):

It is a device which captures the dust particles from the flue gas thereby reducing the

chimney emission. Precipitators function by electrostatically charging the dust particles in the gas stream. The charged particles are then attracted to and deposited on plates or other collection devices. When enough dust has accumulated, the collectors are shaken to dislodge the dust, causing it to fall with the force of gravity to hoppers below. The dust is then removed by a conveyor system for disposal or recycling.

Theory of Precipitation:

Here six activities typically takes place.

Ionization - Charging of particles.

Migration - Transporting the charged particles to the collecting surfaces.

Collection - Precipitation of the charged particles onto the collecting surfaces.

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1126˚C 1008˚C 744˚C 656˚C 476˚C 362˚C 146˚C

AIR PREHEATER

FD FAN

WIND BOX

MILLS

PA FAN

HOT PA

HOT SA

PA

SECTION

SA

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SECTION

Charge Dissipation - Neutralizing the charged particles on the collecting surfaces.

Particle Dislodging - Removing the particles from the collecting surface to the hopper by rapping mechanism.

Particle Removal - Conveying the particles from the hopper to a disposal point governed by fly ash disposal system.

Major Fans in Boiler Draft System:

• PA Fans

• FD Fans

• ID Fans

PRIMARY AIR FAN: It serves two main purposes:

a) Transportation of coal from mill to furnaceb) Coal moisture removal

• NO OF FANS PER BOILER : TWO

• TYPE : RADIAL

• INDUCTION MOTOR RATING : 1480 KW

• SPEED : 1480 RPM

• CONTROL : INLET VANE CONTROL

FORCED DRAFT FAN: It provides air for combustion.

• NO : TWO

• TYPE : AXIAL REACTION

• MOTOR RATING : 800 KW

• SPEED : 1480 RPM

• CONTROL: BLADE PITCH CONTROL

INDUCED DRAFT FAN: It maintains furnace draft.

• NO OF FANS PER BOILER : TWO

• TYPE : AXIAL IMPULSE

• MOTOR RATING : 1300 KW

• SPEED : 740 RPM

• CONTROL: INLET VANE CONTROL

Steam cycle:-

The demineralised water, which is used to produce steam, passes through various intermediate stages. The DM water passes through a series of water heaters namely LP heaters, Gland Steam Cooler(GSC),HP heaters and afterwards passes through Deaerator, Boiler feed pump, economizer and then goes to boiler drum. In LP heater and HP heater ,heat is transferred from steam (coming from turbine) to water which increases the temperature of the water. The direct mixing of steam with water is not allowed. In Deaerator, steam comes in direct contact of water. Deaerator is used to remove the air of feed water to prevent corrosion of boiler tubes and turbine blades. The presence of air also reduces the efficiency of cycle. The boiler feed pump is used to pump water to boiler drum through economizer. Boiler Economizer are feed-water heaters in which the heat from waste gases is recovered to raise the temperature of feed-water supplied to the boiler. In the midst of HPH and Economizer, a three element feed flow regulating system has been incorporated which regulates the steam flow from the boiler, the feed water flow to the boiler and the water level in the boiler drum.

The boiler drum serves two purposes:-

1. Separating steam from mixture of water and steam

2. It houses all the equipments for purification of steam.

In VSTPS the boiler used is water tube boiler. Here the heat source is outside the tubes and the water to be heated is inside. Most high-pressure and large boilers are of this type. In the water-tube boiler, gases flow over water-filled tubes. These water-filled tubes are in turn connected to boiler drums.

In stage I natural circulation takes place. Natural circulation is the ability of water to circulate continuously, with gravity and changes in temperature being the only driving force known as "thermal head“.

The down comer contain relatively cold water, whereas the riser tube contain steam water mixture ,whose density is comparatively less .this density difference is the driving force ,for the mixture. (thermo-siphon principle).Circulation takes place at such a high rate that the driving force and frictional resistance in water wall are balanced. Natural circulation is limited to boiler with drum operating pressure around 175 Kg/cm2.However, when the pressure in the water-tube boiler is increased, the difference between the densities of the water and saturated steam falls, consequently less circulation occurs. To keep the same level of steam output at higher design pressures, the distance between the Bottom ring header and the steam drum must be increased, or some means of forced circulation must be introduced. Beyond 180 Kg/cm2 of pressure, circulation is to be

assisted with mechanical pumps, to overcome frictional losses. This is known as forced circulation which is employed in stage II and stage III.

The water coming from boiler drum on its passage through down comer and riser tube is converted into a mixture of water and steam and goes back to boiler drum. The steam from boiler drum passes through a series of super heaters like LTSH (Low temperature Super Heater), Platen super heater, convective super heater. Super heater heats the high-pressure steam from its saturation temperature to a higher specified temperature. The steam at super heater outlet gains a temperature of 5400C. It is then passed to HPT (High Pressure turbine) and the temperature of the steam goes down. The steam is sent back to reheater to gain back the temperature. The reheated steam is sent to IPT (Intermediate Pressure Turbine), then from IPT to LPT(Low pressure turbine). The HP, IP, LP turbines and the rotor of the turbo generator are connected on the same shaft. As the high pressurized steam drives the turbine blades, so rotor of the generator also rotates. The steam after losing its pressure begins to condense in condenser by exchanging heat with circulating cooling water. The condensate is then move to hot well. Then from hot well the condensate is pumped by CEP (condensate extraction pump) to LP heater. The cycle continues which is termed as steam cycle.

Steam Turbine:

The steam turbine is a form of heat engine that derives much of its improvement in thermodynamic efficiency from the use of multiple stages in the expansion of the steam. High pressure steam flows through the turbine blades and turns the turbine shaft. Steam turbines extract heat from steam and convert it into mechanical work by expanding the steam from high pressure to low pressure. Steam turbine shaft is connected to a synchronous generator for producing electricity.

Circulating Water System:

Bulk requirement of water is used in thermal plants for the purpose of cooling the steam in condensers. The requirement of water for this purpose is of the order of 1.5-to2.0 cusecs/MW of installation. In VSTPS closed loop cooling system with cooling towers is used for this purpose. The heat which the water extracts from the steam in the condenser is removed by pumping the water out to the cooling towers. The cooling towers are simply concrete shells acting as huge chimneys creating a draught (natural/mechanically assisted by fans) of air. The water is sprayed out at the top of towers and as it falls into the pond beneath it is cooled by the upward draught of air. The cold water in the pond is then circulated by pumps to the condensers. Inevitably, however, some of the water is drawn upwards as vapours by the draught and it is this which forms the familiar white clouds which emerge from the towers seen sometimes.

Water Treatment plant:

Different water qualities are in use in VSTPS. For condenser cooling, ash handling plant and other auxiliaries cooling raw water (clarified and post-chlorinated) is used. Again conditioned Demineralised water is used for boiler feed water and H2 generation plant. For drinking purpose also filtered & post-chlorinated water is provided.

a) Cooling water Management:

In the pre-treatment process, chemicals are added in raw water for bacteria removal and for sedimentation of suspended particles. Then it is pumped through clariflocculators. The clarified water from these clariflocculators flows to the cooling water basin by gravity. A clarified pump is present which pumps the clarified water to the DM plant. The outlets from the cooling water tower basins are connected to the common tunnel which takes the water back to the power house. From this tunnel water is drawn through the following pumps to the various equipments as follows:

1) CW Pumps for circulating cooling water through turbine, condenser and discharging the same to the op of the respective cooling towers.

2) Auxiliary Cooling Water Pumps for supplying cooling water to various auxiliary equipment for their cooling . This water after circulation through various bearings and heat exchangers leads to the CW discharge pipe from the condenser for cooling through the cooling tower.

3) Ash water pumps for supplying water for ash handling.

b) Demineralised water Plant: A demineralising plant is provided for supplying feed water for the heat cycle. . Clarified water is pumped from the clarified water storage pit which passes through pressure filter, activated carbon filter, cation-exchanger, degasser, anion-exchanger and mixed bed exchanger. Adequate facilities are provided for unloading, handling and storage of chemicals. The layout of operation is shown below.

Hydrogen Generation Plant:

This process involves electrolysis of water in an electrochemical cell. The electrolyte used is KOH (30%)+H2O in presence of K2Cr2O7 (1%)catalyst. The water used is D.M. water with temperature kept very low. 60 volts D.C. supply is applied to the electrolyte

ACF: Activated Carbon FilterWAC: Weak Acid CationSAC: Strong Acid CationWBA: Weak Base AnionSBA: Strong Base AnionMB: Mixed BedCST: Condensate Storage Tank

solution. Gas production is directly proportional to Direct Current passing through the solution of caustic potash and D.M. water.

The hydrogen generated is processed in the following way.

(a) Cooling of H2 to regulate gas pressure to vaporise moisture (b) H2, O2 separation

Hydrogen Bottling Plant:

In hydrogen bottling plant the bottle pressure is maintained at 135 kg/cm2. 3 compressors are used to create the required pressure. Bottled H2 is 99.9% pure.

Ash Handling Plant:

Ash is the residue remaining after the coal has been incinerated to constant weight under standard conditions. It is oxidized form of the mineral matters present in coal.

Typical ash composition: SiO2, Al2O3, Fe2O3, CaO, MgO etc.

Ash content of Indian coal used in power station is about 30 to 40 %. A typical 2000 MW station produces around 9000T to 12000T of ash per day. This huge amount of ash needs to be disposed off continuously for avoiding pollution.

(a) Bottom Ash: 20 % Of the ash falls at the bottom of the furnace known as Bottom Ash (BA). BA can form slag and clinker depending on the temperature of the combustion zone and environment inside. Bottom ash is disposed of through bottom ash disposal system.

Bottom ash handling system: Bottom ash can be collected at furnace bottom as Wet or Dry form. Wet bottom ash system consists of i)Trough seal, ii)BA gate, iii)Hopper, iv)Scrapper Conveyer, v)Clinker grinder,vi)BA trench, vii)BA tank, viii)BA pump, ix)BA pond.

Dry bottom ash system consists of i)Trough seal, ii)BA gate, iii)Hopper, iv)Scrapper Conveyer, v)Clinker grinder, vi)Silo.

(b) Fly Ash: 80 % of the ash is carried away with flue gas known as Fly Ash. Fly ash is collected through ESP and disposed through fly ash disposal system.

Fly ash handling system: Fly ash is collected from Air heater hopper, Economiser hopper and ESP hopper either through flushing apparatus or hydrobacter system. In Flushing apparatus system ash is allowed to fall in flushing apparatus under gravitation. Water jet in flushing apparatus carries away the ash to FA trench. High pressure jets

H2 generated Separator Pressurizer Steam heater Heater

Cooler

Drier( Silica Gel- to absorb moisture)

Receiver Tank(20 M3)

(Pressure 10kg/cm2)

Coal Seam

Surge Pile

Pulverize (-150)

Overburden

Fly Ash

Flue Gas Electrostatic Precipitator

Flue Gas Boiler

Fly Ash Bottom Ash

Smoke Stack

Fly Ash Bottom Ash

further carries it to FA sump. Series pumping carries the ash slurry to FA pond. Hydrobacter is a vacuum device to collect ash from the hopper. Water jet ejectors are used for creating vacuum. Dry ash thus collected is sent to silo through belt conveyor. Dry ash is disposed through road transport to a dry ash disposal system. Part of it is sold for commercial purpose.

Ash Utilization:

Major usages of ash are:

• Fly ash bricks / blocks• Concrete and mortar• In manufacture of cement• In manufacture of asbestos products• Road construction• Embankment/back fills/land development• In agriculture• Mine filling• Manufacture of fertilizer• Manufacture of distemper• Floor and wall tiles• Refractory bricks• Manufacture of ceramics• Manufacture of alum• Domestic cleaning powder• In synthetic wood

Fuel oil System:

The purpose of fuel oil is:1) To establish initial boiler light up.2) To support the furnace flame during low load operation.

Fuel oil system consists of fuel oil pumps, oil heaters, filters and steam tracing lines. The objective is to get filtered oil at correct pressure and temperature.

Types of fuel oil:

a) Light diesel oil (LDO)b) High speed diesel oil (HSD)c) Heavy furnace oil (HFO)d) Low sulphur heavy stock (LSHS)

Atomization procedure is used to break the fuel into fine particles that readily mixes with the air for combustion.

Seal and Lube Oil system:

Seals are employed to prevent leakage of hydrogen from the stator at the point of rotor exit. A continuous film between the rotor collar and the seal liner is maintained by means of oil at a pressure which is about 0.5 atmosphere above the casing hydrogen gas pressure. The thrust pad is held against the collar of rotor by means of thrust oil pressure, which is regulated in relation to the hydrogen pressure and provide a positive maintenance of the oil film thickness.

Lube oil system is provided for bearings upon which the generator shaft is mounted.

SPECIFICATION OF MECHANICAL SYSTEMS:

Steam Generator:

The steam generator is a natural circulation pulverized coal fired, radiant furnace, dry bottom, balanced draft type using direct firing system.

The parameters of the steam generator at 100% MCR will be as follows:

For stage I (6×210 MW):

1) Maximum continuous rating 670 T/hr2) Superheater outlet temperature 5400C3) Superheater outlet pressure 140 kg/cm2

4) Cold reheat pressure at boiler inlet 27.5-27.9 kg/cm2

5) Hot reheat outlet temperature 5400C6) Reheat steam flow 590 T/hr7) Feed water temperature at Economiser 2480C

InletFor stage II and stage III (each 2×500 MW):

1) Main steam flow at superheater outlet 1590 T/hr2) Pressure at superheater outlet 179 kg/cm2

3) Temperature at SH outlet 5400C4) RH steam flow 1353 T/hr5) Steam temperature at reheater outlet 5680C

6) Feed water temperature at Economiser 255+-50C Inlet The steam generator is a natural circulation pulverized coal fired, radiant furnace, dry bottom, balanced draft type using direct firing system. The boiler furnace is with a steam drum. The drum supplies water wall system through adequate sized six (6) down comers so as to permit unrestricted circulation.

Each steam generators equipped with three (two working and one standby) of axial type ID fans and two, of centrifuge type FD fans. Six PA fans on the hot air side of air heaters is provided to supply hot air to the mills. There is two regenerative rotary air heaters. There are electrostatic precipitators having an efficiency of 99.5% for collecting fly ash. Each steam generator is provided with six medium speed of direct firing type with provision of one standby.

Main steam from the boiler is supplied to HP turbine (HPT) through two pipes. Cold reheat (HPT exhaust) will be returned to the boiler reheater through two numbers of pipes. Hot reheat steam from boiler will be supplied to IP turbine through four pipes.

The turbine is provided with an automatic governing system and protection devices which ensure turbine operation and tripping under emergency conditions. The governing control system includes speed governor, emergency governor, speed changer, load limiting device, and initial pressure regulator.

Coal for the thermal power station is transported from Nigahi open cast mines. Merry-Go-Round rail system of transport is adopted for transportation of coal from the mines to plant site.

There is an ash handling system of continuous hydro sluicing type.

There is a bottom ash handling system to extract and handle bottom ash.

The fly ash system employs flushing equipments to remove the ash from electrostatic precipitator hoppers and gas ducts low points after regenerative air heater on continuous basis. From the main pump the ash slurry is continuously transported to the disposal area by means of ash slurry pumps and disposal pipes.

For the circulating water scheme a closed circuit cooling system using cooling towers is used. Six numbers induced draft type cooling towers is provided for stage I of the power plant. The C.W. system has C.W. pumps, travelling water screen, butterfly valve and actuator and cooling towers.

There is a water treatment plant which meets up the following requirements.

(i) DM water for boiler make up(ii) Portable water for colony and plant(iii) Clarified water for CW system and auxiliary cooling make up along with other

requirements such as coal dust suppression, water services, ash handling etc. Removal of suspended colloidal matter in the raw water is removed in the pre-treatment plant. The chemical dosing system is there for unloading, handling, solution preparation and dosing of alum, lime and coagulant aid solution.

The demineralising plant consists of four streams of 110 m3/hr capacity each comprises of active carbon filter, weak and strong acidic cation exchanger, degasser system and weak and strong base anion exchangers followed by mixed bed polishing unit.

For fire protection H.P.W. spray system is provided to generating transformer, station transformer, tie transformer, unit aux. transformer, turbine oil storage tanks, oil cooler and seal oil system.

The hydrogen generating plant is provided with two electrolysers, each of nominal capacity of 10 m3/hr for meeting the makeup requirements of the plant. Very high purity for hydrogen (99.9%) is achieved by the electrolysis process.

ELECTRICAL SYSTEMS:

Turbo Generator:

Each turbo generator unit is a 3 phases, 2 pole, and cylindrical rotor type machine directly connected to the steam turbine rotating at 3000rpm.

Generator Parameters:

Cooling System:

The generator cooling system is of hydrogen water type. A closed loop water system is provided for the cooling of the stator winding and thyristor converters of the excitation

Rated Output: 247 MVA

Rated Voltage: 15.75KV

Rated Power Factor: 0.85

Rated Frequency: 50 Hz

Stator current: 9060A

Short Circuit Ratio: 0.48

Rated Efficiency: 98.50%

Rated Hydrogen Pressure: 4 kg/cm2

system. Demineralized water is used for cooling purpose. Hydrogen is provided for cooling rotor winding and active steel of the stator.

Rotor Cooling:

The rotor is cooled by means of gap pick up cooling. The hydrogen gas in the air gap is sucked through the scoops on the rotor wedges and is directed to flow along the ventilating canals milled on the other side of the rotor, a positive suction and discharge is created due to which a certain quantity of the gas flows and cools the rotor. This method of cooling gives uniform distribution of temperature.

Hydrogen Cooling System:

Hydrogen is used as a cooling medium in large capacity generators for its high heat carrying capacity and low density. Proper arrangements are made for filling, purging as it forms explosive mixture if mixed in certain quantities with oxygen. In order to prevent escaping of hydrogen shaft sealing system and generator casing is done.

Hydrogen cooling system mainly comprises of:

a) Gas control standb) Drierc) Liquid level indicatord) Hydrogen control panele) Gas purity measuringf) Indicating instruments and valves

The system is capable of performing the following functions:

a) Filling in and purging of hydrogen safely without bringing in with air contact.b) Maintaining gas pressure inside the machine.c) Provide indication about gas condition i.e. pressure, temperature, purity etcd) Circulation of gas through a drier in order to remove any water vapor.e) Indication of liquid in the generator.

Stator Cooling System:

The stator winding is cooled by distillate, which is fed from one end of the machine by Teflon tube and flows through the upper bar and returns back through the lower bar of another slot. The stator winding is cooled in the system by circulating demineralized water through hollow conductors. DM water of specific resistance is selected for cooling purpose. The system is designed to maintain a constant rate of cooling water flow to stator winding at a nominal inlet water temperature of 40⁰C

As it is a closed loop working, the cooling water is again cooled. The secondary DM cooling water is in turn cooled by clarifies water taken from clarified water header.

Excitation System:

The purpose of excitation system is to provide necessary current in the field coil to produce magnetic flux.The excitation may be of three types:

a) Static Excitation: In static excitation power supply is given through battery at first. After proper voltage build up, an output from generator is taken and step down to required voltage and is given as input to the generator field winding

b) Semi-static Excitation: Here first DC supply is given to the exciter from battery which produces ac. Then using thyristor DC is fed back to exciter. When voltage build up to 70% of generator output voltage then voltage supply is given to generator field winding after rectification process.

c) Brushless Excitation: In brushless excitation there is a pilot exciter and a main exciter. The rotor of the pilot exciter is permanent magnet type. It produces ac in stator winding. This ac is given to stator of main exciter after rectification. All these are mounted on same shaft. As diode rectification is also mounted on shaft so no slip ring brush configuration is required and hence called brushless excitation system.

Excitation System of Stage I:

The turbo generator excitation is provided by a separate excitation system of thyristor type. The turbo generator field winding is fed through the thyristor converters from AC generator exciter mounted on the turbo generator shaft. The auxiliary generator field winding is supplied from the generator stator terminals through rectifier transformer and thyristor convertors.

Under all operating conditions of the turbo generator the voltage across the exciter terminals is maintained automatically at the level corresponding to the turbo generator ceiling excitation voltage. The excitation current control is affected by changing the firing angle of the thyristor of the converters, thus changing the average value of the rectified voltage applied to the turbo generator field winding.

The automatic control of the turbo generator excitation is provided by the automatic voltage regulator acting on the firing control circuits of the thyristor converters. When controlling the turbo generator excitation, the automatic voltage regulator responds to deviations and derivatives of the turbo generator stator terminal voltage and frequency, and also to the rotor current derivative.

To ensure protection of the turbo generator field winding and thyristor converters against possible voltage surges, the multiple action arrestors and resistors are used. In all cases where there is no excitation, the turbo generator field winding is shunted by a resistor. The excitation system makes it possible to connect the turbo generator to the power system both at precise synchronizing and self synchronizing. The system provides for the possibility of change over to a standby exciter without interrupting power supply to the turbo generator field winding.

Excitation system of Stage II & Stage III

Rotor of Mechanical

Rotating Diode Rectifier

Main Exciter

Pilot Exciter

Figure: Brushless Excitation System

The excitation system employed in Stage II and Stage III is brushless excitation system. Here the main shaft of prime mover drives pilot exciter, main exciter and main alternator. Silicon diode rectifiers are also mounted on the main shaft.

Pilot exciter is a permanent magnet alternator with permanent magnet poles on the rotor and three phase armature winding on the stator. Three phase power from pilot exciter is fed to thyristor controlled bridge placed on the floor. After rectification the controlled DC output is supplied to stationary field of main exciter. The three phase power developed in the rotor of the main exciter is fed through hollow shaft to the rotating silicon diode rectifier mounted on the hollow shaft, to the main alternating field without brushes and slip rings.

A signal, picked from alternator terminals through CT and PT controls the firing angle of the thyristor bridge. This enables the control of field current of the main exciter which eventually governs the alternator output voltage.

Ratings:

Excitation voltage- 107 V

Speed- 300 RPM

Insulation Class- F

Excitation ampere- 142 A DC

Coolant- AIR

Volt- 500

Amp- 3780

VINDHYACHAL SWITCHYARD-

The main purpose of Switchyard is to protect the system and transmit power to the consumer premises. The switchyard in VSTPS is of 400/132 KV switchyard and it consists of following equipments. The 400 kV switchyard at VSTPS employs double main and transfer bus switching scheme. The switchyard employs strung bus layout. The 132 kV switchyard shall employ sectionalized main and transfer bus scheme. There are 38 spare bays in switchyard which consists of-

1. 10 generator unit bays

2. 10 transmission lines-(400 KV lines)4 Jabalpur4 Satna2 Korba

3. 3 TBC(Transfer bus coupler)4. 3 BC(Bus Coupler)5. 4 BS (Bus sectionaliser)6. 3 ICT(Inter connecting Transformer)7. 2 HVDC feeders to Vindhyachal-Singrauli Back to Back station

Two 132 KV feeders are also sent to Waidhan.

Bus coupler-It is used to couple two bus bars at the same voltage level. This coupling is required when units of one main bus is to be transferred to the other one.

Bus sectionalizer-It is used to divide a bus into two parts, one carrying current and the other one isolated.

The equipments used in VSTPS power plant are given below--Generator transformers:

The generator is connected to the Generating Transformer by means of isolated bus ducts. This transformer is used to step up the generating voltage of 15.75 KV to bus voltage 4ooKV.This Transformer has elaborate cooling system consisting of number of oil pumps and cooling fans apart from various accessories. The connection is delta on LV side and star with neutral grounded on HV side. There are water pipes to fight in case of fire condition.

Salient features of the generator transformers are as given below:

(i) Power Rating 250 MVA(ii) Voltage ratio 15.75/400 kV(iii) Type of cooling OFAF(iv) Tap changer On load type with ± 10% variation in steps of 1.25%(v) Type of connection yd11

Unit Auxiliary Transformer

The bus-duct leading from the generator to the GT is tapped off conveniently for connection to high voltage side of Unit Auxiliary Transformer used for stepping down the voltage to 6.6kV for supplying power to the unit auxiliary loads of the power station.The rating of UAT is 40 MVA,3 phase,3 windings system(all delta connected).. The Cooling type is: ONAN/ONAF

Each unit auxiliary transformers would be provided with following protections

(i) Transformer differential protection

(ii) Back up over current protection(iii) Back up earth fault protection

In addition each transformer would have a Bucholz relay and winding temperature indication with alarm and trip contacts.

DC System:

Each unit has its own dc system. DC system is there for 400kV switchyard also. DC system is required due to:

a) Meet DC power requirement of unit loads like DC motors, emergency lightingb) Provide power during total AC supply failurec) Feed common DC loads like coal handling, ash handling systems etc

DC system comprises of:

a) Storage battery -This unit contains 115cells each of 2V potenetial. These cells are connected in series resulting in a total voltage of 220 V .

b) Battery Charger -This charger is used to charge the DC battery. It consists of a rectifying unit which converts AC to DC.

Ratings:Input AC- 415V±10%Phase= 3Cycles- 50 HZSpecification- Float cum BoostFloat= 240 V dc Boost= 198-300VFloat= 50 A Boost= 50A

c) Distribution Board

Emergency Power Supply Scheme:

Diesel Generator Set:

It is provided for meeting the power requirements of essential auxiliaries during total failure of AC supply in the power stations. Automatic starting facility is provided for generator set.

Ratings:

Power Output: 600 KVA,3 phase, quick starting type

Rated Output Voltage: 415 Volts

Frequency: 50 Hz

Various essential auxiliaries are:

a) AC Lube Oil Pumpb) Hydrogen Seal Oil Pumpc) Float Charger for DC batteryd) Emergency Lightinge) Barring Gear

Interconnecting Bus Transformer(IBT)

IBT/ICT’s stands for interconnecting BUS/COUPLING transformer.They are autotransformer.They are being utilized for stepping down the 400 kV bus voltage to 132 KV bus voltage for the purpose of supplying the station loads. The specifications of IBT.s are

(i) Rating 200 MVA,400/132KV(ii) Type of cooling ONAF/ONAF/OFAF with 2×50% radiator banks(iii) Tap changers On load type with ± 10% variation in steps of 1.25%

Station Transformer-

This transformer is a step down transformer which transforms 132 KV to 6.6 KV voltage. This transformer is used to intake power from 132 KV bus for running the auxiliary equipments of an unit when the unit is being tripped. The station transformer is a tertiary winding transformer with each winding star connected with neutral grounded. The specification of this transformer is 80 MVA,132/11.5/6.6 KV.

Current Transformer (CT):

A current transformer is a type of instrument transformer designed to provide a current in its secondary winding proportional to the alternating current flowing in its primary. They are single phase oil immersed type. They are commonly used in metering and protective relaying in the electrical power industry where they facilitate the safe measurement of large currents, often in the presence of high voltages.In current transformers different ratios are achieved by secondary taps. Current transformers with five secondary’s (4 for protection and one for metering) are employed. . Current transformers provide satisfactory performance for burdens ranging from 25% to 100% of rated burden over a range of 10% to 100% of rated current in case of metering CTs and up to accuracy limit factor/knee point voltage in case of relaying CTs

Capacitive Voltage Transformer (CVT):

A capacitor voltage transformer (CVT) is a transformer used in power systems to step-down extra high voltage signals and provide low voltage signals either for measurement or to operate a protective relay. In its most basic form the device consists of three parts: two capacitors across which the voltage signal is split, an inductive element used to tune the device to the supply frequency and a transformer used to isolate and further step-down the voltage for the instrumentation or protective relay as shown in figure below:

The device has at least four terminals, a high-voltage terminal for connection to the high voltage signal, a ground terminal and at least one set of secondary terminals for connection to the instrumentation or protective relay. CVTs are typically single-phase devices used for measuring voltages in excess of one hundred kilovolts where the use of voltage transformers would be uneconomical. In practice the first capacitor, C1, is often replaced by a stack of capacitors connected in series. This results in a large voltage drop across the stack of capacitors. This replaced the first capacitor and a comparatively small voltage drop across the second capacitor C2, and hence the secondary terminals.

Circuit Breaker (CB):

A circuit breaker is an automatically-operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Unlike a fuse, which operates once and then has to be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation. Circuit breakers are made in varying sizes, from small devices that protect an individual household appliance up to large switchgear designed to protect high voltage circuits feeding an entire city. There are two mediums used in CB. Quenching medium absorbs or extinguishes the arc produced between the contacts while operating medium is the medium by which the circuit breaks. The circuit breaker can be classified in different ways-

1. On the basis of Quenching medium -Air blast circuit breaker-SF6(sulphur hexa fluoride)circuit breaker

2. On the basis of operating medium -Spring operated circuit breaker-Solenoid operated circuit breaker

-Pressure operated circuit breaker

CB’s on the line are provided with pre-insertion resistors of 400 ohms per pole to limit the switching surges to a value less than 2.5 pu. The tme duration of pre-insertion is less than 8 ms in each pole. Total break time for any current upto rated breaking time is not more than 40 ms and the total closing time is not more than 150 ms.

Local breaker back up protection is provided with each 400 kV breaker from both sides. Each 400 kV breaker would have two sets of trip coils which would be connected to separately fused DC circuits for greater reliability.

Isolators:

An isolator is an electrical device which can break an electrical circuit when the circuit is to be switched on no load.The primary difference between an isolator and a circuit breaker is isolator works only on no load whereas circuit breaker can be made to operate in both loaded and unloaded condition.In VSTPS, 400 kV switchyard pantograph type bus isolators are used which connects the line with the buses.. Other isolators are of horizontal centre break (HCB)type which is a line isolator. An earthing switch is provided with HCB to discharge the residual charges left in the line.

Lightning Protection System-

LA’s are provided at the terminals of the transformer for protection against lightening or any surge development in the system. There is a practice to install lightening arrestor at the incoming terminals of the line. Shielding of the substation from the direct lightening stroke is provided through earth wires located at structures peak. The purpose of the earth wire is to intercept direct lightning strokes which would otherwise strike the phase conductors.All Lightning Arrestor’s of lines & transformers are of gap type. Lightning arrestors are of heavy duty station class type with nominal discharge current of 10kA.Suitable galvanized steel earth wire is installed so that it can withstand two successive lightning strikes of 150 kA. Tension to weight ratio is 20% than the power conductors, shielding angle is 200.

The following equipments are protected against direct stroke of lightning:

a) Main transformer and all other equipments: Lightning mast is used for protectionb) Power station chimney: Using lightning conductor protection is given.c) 400kv switchyard:

1) Lightning mast is used for protection against direct stroke2) For protection against lightning surges coming from transmission lines a set of non linear resistance type surge diverters are used.

d) Buildings, power house and boiler: Using lightning conductor protection is given.

Start Up Power Supply System:

Start up power supply is obtained from 132 kv switchyard. This switchyard gets supply normally from the 400kv switchyard through two 200 MVA, 400/132 kv station transformer.

PLCC:-

It stands for Power Line Carrier communication. It provide high frequency signal to the transmitting side of the main line. It can be used for communicating purpose for even long distance. It is also used for safety purposes. If for any delay in giving command for relay or any delay in the breaker to break the circuit it gives back up command to circuit breaker to break the circuit.

Wave trap:-

It is used to restrict the high frequency signal to the input side (generator side)

Corona:-

Air gets ionised when there is a high voltage flow through the conductor and produces a hissing sound and forms a blue ring which results in corona loss which is maximum at sharp edges.This is reduced by using corona rings.

Shunt reactors:

Shunt reactors are provided at line terminals for the overvoltage control and reactive compensation of 400 kV transmission system. Neutral grounding resistors are used for grounding of the neutral point of shunt reactors in order to minimize the secondary arc current. The parameters are:

(i) Reactive voltage 420 kV(ii) Capacity 50 MVAR & 63 MVAR(iii) Connection star with neutral brought out(iv)Quality factor 250-350 at rated voltage and frequency

Station Grounding System:

Equipment Grounding:

a) Generator neutral is connected to earth only through the potential transformer provided on the neutral side.

b) The 6.6 kV system neutral is unearthed in stage I(Standard Soviet Practice)c) 415V system neutral is solidly grounded.

Safety Grounding:

a) Power house area, switchyard area and other areas of power station have efficient grounding system made of mild steel. All these areas have separate ground grids. The switchyard ground grid is connected to power house ground grid to maintain equipotential area throughout during phase to ground fault.

b) The size of earthing conductor is such as to carry the maximum earth fault current for one second without exceeding specified maximum temperature at joints.

c) The earthing system is designed to keep the touch potential within safe zone. The overall earthing resistance is maintained within 0.5 ohms.

Below towers, a tower footing resistance is used. The tower footing resistance shall be kept below 10 ohms.

Bus bar:

The bus bar arrangements used in VSTPS consists of two main buses and one transfer bus. This is known as TRANSFER BUS scheme. The bus bar supporting structures are generally of steel lattice type. Recent trend is to adopt RCC structure for supporting the buses. These are very economical and are finding wide acceptance in the country. There are two sections of buses-400 KV bus and 132 KV bus. Each 400 kV bus bar section has a separate three phase high speed high stability circulating current type differential protection, along with bus wire supervision and hand reset trip relays

Switchgear:

The drives for auxiliary equipment rated 150kW and above are operated at 6.6kV and drives having a rating below 150kW are operated at 415V, 3-phase, and 4-wire system having a provision for single phase 230V. For starting up of these motors suitable switchgears/starters are provided.

6.6 kV Switchgears: 6.6 kV power received from either Unit Auxiliary Transformer or Reserve Transformer are connected to respectively 6.6kV switchgear bank through suitable breakers for further distribution to motors and to transformers for further step down to 415V.

415 V Switchgear: The 415Vsupply from each 1000kVA transformer are

connected to a suitable 415V bus having its distribution for different motors and starters. Motors capacity above 90kW are controlled by a 415V breaker from respective bus and that of lower capacity by magnetic contractors grouped together in a sheet metal cubicle for a number of motors, termed MCC. Protection and control for individual motors is provided there in Switch Gear System.

Transmission Line equipments:

Transmission lines are required for transmitting power from generating stations to the load centres.

The important components of the transmission lines are—

a) Conductor and accessories -The lines maybe single circuit or double circuit either in vertical or horizontal configurations. A double circuit lines carries double the power than the single circuit line. The conductor used for the transmission lines are of ACSR. These conductors are given animal names on basis of their voltage levels.

66KV – ‘DOG’ ACSR (0.1 sq inch copper equivalent)

132 KV-‘PANTHER’ ACSR (0.2 sq inch copper equivalent)

220 KV-‘ZEBRA’ ACSR (0.4 sq inch copper equivalent)

400KV-‘TWIN MOUSE’ (2×0.5 sq inch copper equivalent)

b) Cables-

132kv Cables: single core, standard aluminium conductors unfilled, cross linked polyethylene, insulated, gas/dry cured, with extruded conductor and insulation shielding, copper tape screened and overall sheathed with extruded PVC

6.6kv Cables: unearthed 6.6kv grade, stranded aluminium conductor, impregnated paper insulated cables

415 V Cables: 1100 V grade, stranded aluminium conductor, PVC, HRPVC/ cross linked polyethylene insulated, PVC sheathed cable

Control Cables: 1100V grade, solid, copper conductor, PVC insulated, PVC sheathed cables.

c) Supporting structures-

The towers are of self supporting lattice steel type designed to carry the line conductors with necessary insulators, earthwire and all fittings under all loaded conditions.

d) Insulator and hardware-High strength toughened glass/brown glazed porcelain disc insulators shall be used. Single suspension strings shall comprise of 23 numbers of discs of 120 KV Electromechanical strength. The maximum voltage across any disc shall not exceed 20 KV. This will reduce ageing and also minimise radio interference.

e) Earthwire and accessories- Earthwire is used to protect the power lines from high lightning strokes.

Protective Relaying:

Generator Transformer System:

The following protections are provided for each unit:

1) Differential Protection for faults between phases of generator stator winding and on terminals

2) Inter-turn fault protection of generator for faults between single phase coils of stator winding

3) Differential protection for faults in transformer bushings.4) Earth fault protection of generator stator winding5) Gas protection for faults inside transformer oil tank6) Back up impedence protection for external symmetrical faults and for redundancy

of unit main protections7) Out of step protection under loss of excitation8) Over voltage protection under idle run condition9) Zero phase sequence protection for external earth faults in 400kv system10)Current protection for rotor overloads11)Maximum current protection for symmetrical overloads.12)Earth fault protection in one point of the rotor.13)Negative phase sequence protection for external asymmetrical faults.14)Pole slipping protection of generator without loss of excitation.

15)Low forward power interlocks.16)Generator transformer over fluxing protection.17)Overall differential protection of generator transformer unit for duplicate of

differential protection of generator and generator transformer.

Generator exciter protection system:

1) 3 phase longitudinal differential protection2) 2 phase maximum current protection3) Protection for forcing drop to avoid prolonged excitation in case the generator

field has not been suppressed incidentally, when the unit is out.4) Protection for generator rotor winding for current 2 times that of the rated value.

Unit and Station Transformer:

1) Differential current protection2) Gas protection of transformer and voltage regulator chamber3) Overload protection for overload of 6.6kv windings4) Overcurrent protection on HV winding side5) Distance protection for back up protection of external faults6) Low oil level protection

6.6KV Switchgear:

Reserve power supply bus bar to 6.6KV section is provided with differential protection to trip an appropriate sectionalizing breaker.

0.415 KV Sections and Diesel Generator Protection:

1) Over Current Protection for external faults

2) Zero phase sequence protection for earth faults in 0.415kv system.

6.6/0.415kv Transformers Protection:

1) Over current protection against external fault

2) Zero phase sequence protection for earth faults

3) Symmetrical overload current protection

4) Current cut-off on 6.6kv side for multi phase faults in the transformer winding and bushings.

Motor Protection:

Each 6.6 kv motor is protected by:

1) Fault current cut off for multi phase faults2) Zero phase sequence protection for earth faults.3) Overload protection due to start-up or starting condition.4) Under voltage protection to trip less important motors with time delay.

Automatic switches with over current device are provided for fault protection of 415 V motors.

CONCLUSION

In this modern era development of a country is measured against its power usage. As India is rising as a global power its need of electricity is escalating day by day due to rapid industrialization and urbanization, which in turn is contributing to India’s rapid economic growth. But to sustain economic growth uninterrupted power supply is must. The major responsibility of meeting this demand will have to be shouldered by NTPC. Its contribution towards the country is acknowledged by bestowing with the title of ‘Bharat Maharatna’. I hope NTPC will continue rendering its reliable service to the people and government of the country. The training undergone was informative and educative. It was the nobility of the employees and working staffs to provide required theoretical background at their continuous job hours. Though the duration was short but I am quite confident that this experience and knowledge gathered in this period will mark its print both in my academic future and professional carrier.