ntpc report

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2011

Report on Vocational Summer

Training at NTPC Tanda Electrical Energy Generation

SACHIN VERMA

Electrical & Electronics Engineering

AEC AGRA

Roll No. 0800121079

Mail : [email protected]

Blog:https://way2sac.wordpress.com

ACKNOWLEDGEMENT

We hereby take this opportunity to thank NTPC Tanda for giving us this opportunity to conduct our vocational training in NTPC Tanda. We are grateful to Mr.V. P.Dubey (DGM EMD) & Mr. Pankaj Goel (Officer HR) for allowing us to conduct our training in the Electrical Maintenance Department .We are heartily indebted to our project guide Mr. S.C. Dwivedi (Sr.Supdt EMD) for providing us with detailed in depth knowledge and very useful information about the process and system used in the plant. His support was instrumental in our training being fruitful. We are also thankful to the entire officer and staff of NTPC Tanda for extending a helping hand whenever we need it.

MR. SACHIN VERMA

EN Department

Roll No. 0800121079

AEC KEETHAM AGRA



Table of contents 1.0 Introduction 2.0 Brief description of Tanda thermal power plant

2.1 Geographical location 2.2 Features

3.0 Working of power plant 3.1 Rankine cycle 3.2 Regenerative Rankine cycle

4.0 Plant load factor 5.0 Production of electricity

5.1 Coal handling plant (CHP) 5.2 Way of producing steam by boiler 5.3 Steams to mechanical power 5.4 Mechanical power to electrical power

6.0 Explanation of power plant cycles 6.1 Steam cycle 6.2 Feed water cycle 6.3 Condensate water cycle

7.0 Boiler 7.1 Economiser 7.2 Boiler drum



7.3 Boiler drum level control 7.4 Down comers 7.5 Water wall

7.5.1 advantages 8.0 Introduction to steam turbine

8.1 Classification of steam turbine 8.2 Parts of steam turbine

8.2.1 Blades 8.3 Rotors 8.4 Bearings 8.5 Coupling

8.6 Bearing pedestal 8.7 Balancing hole

9.0 Fundamental of steam turbine system 10.0 Electrical equipment

10.1 Generator 10.2 Generator transformer 10.3 Unit transformer 10.4 Start cum reserve transformer 10.5 LT Auxiliary transformer



10.6 DC supply system 10.7 Switch gear 10.8 Switch yard

11.0 Auxiliary system 11.1 Coal handling process 11.2 Fuel oil system 11.3 Ash handling system 11.4 Cooling water management 11.5 Water treatment plant

12.0 Future prospects of NTPC Tanda



1. INTRODUCTION NTPC is the largest power generation company in India, with comprehensive in-house capabilities in building and operating power projects. It is producing 28,644MW. Its family consists of 18 coal based power plant producing (23209 MW) and 8 gas based power plant having a capacity of (5435 mw). It is also setting up a hydro based power plants having capacity of 2471MW. It is one of the largest Indian companies with a market cap of more than US$50 BILLION and has total assets of around US$ 20 BILLION. In this firm government has 89.5% stake and 10.5% with public. NTPC is ranked 463rd biggest company in the world, 5th biggest Indian company and 2nd largest Asian power generator. It produces 26350MW which is 20.18% of the total 130,539MW of all India consumption. More than one-fourth of India’s generation with one-fifth capacity. The next largest power

utility owns 7.9% of market share in terms of capacity and 8.12% of share in terms of units generated. NTPC’s vision is to become world class integrated power major, powering India’s growth, with increasing global presence. It also develops and provides reliable power, related products and services at competitive prices, integrating multiple energy sources with innovative and eco-friendly technologies and contributes to society. NTPC stations are regular recipients of CEA’s meritorious performance awards. This firm is also well concern about the environmental factors.

It uses world’s largest ESP’s and also gives emphasis on environmental monitoring along with efforts to increase energy efficiency.



2. BRIEF DESCRIPTION OF TANDA THERMAL PROJECT

2.1 Geographical location:-

The Tanda Thermal Power Project is located about 185kms from Lucknow. It is nearly 55kms from Faizabad. The nearest rail ahead is Akbarpur (now called as Ambedkarnagar). The project lies in the Ambedkarnagar district and is about 22kms from the nearest railway station.

The complete project is situated on the bank of Saryu River. The climate conditions are quite favourable with greenery all around.

2.2 Features:-

The installed capacity is 4 X 110 MW The water requirement of the station is met from the Saryu River through Mehripur pumping Station constructed for feeding Mehripur Pump Canal. The coal linkages for the station have been provided from

North Karnpura & BCCL. The power generation is evacuated through 220kV feeders connected to Sultanpur (2 feeders), Basti & Gorakhpur (1 each) 220kV substations.

The total area of the power house including colony is 235 hectares and the land for ash disposal is 170 hectares.

ü The main plant equipment like boiler, turbine and generator have been supplied by M/s BHEL ü Generator-transformer has been supplied M/s NGEF



ü CHP(Coal Handling Plant) has been supplied by M/s TRF ü Cooling Towers by Paharapur Cooling Towers ü C&I(Control & Instrumentation sets) have been supplied by M/s Instrumentation limited kota. ü DM(De-mineralized) plant has been set up by M/s. WATCO, Hyderabad The designed boiler efficiency, turbine heat rate and unit heat rate are 84.7% and 2172.8kcal/kWh & 2565.3kcal/kWh respectively.

The designed HHV of coal is 3850kcal/kg and the boiler is designed to work at worst quality of coal having HHV of 3400kcal/kg.

3. WORKING OF POWER PLANT The working of power plant is based on regenerative rankine cycle explained as below:

3.1 Rankine cycle

The Rankine cycle is a cycle which converts heat into work. The heat is supplied externally to a closed loop, which usually uses water. This cycle generates about 80% of all electric power used throughout the world, including virtually all solar thermal, biomass, coal and nuclear power plants. It is named after William John Macquorn Rankine, a Scottish polymath.

Physical layout of the four main devices used in the Rankine cycle is shown on next page.



Description

A Rankine cycle describes a model of steam operated heat engine most commonly found in power generation plants.

Common heat sources for power plants using the Rankine cycle are the combustion of coal, natural gas and oil, and nuclear fission.

The efficiency of a Rankine cycle is usually limited by the working fluid. Without the pressure reaching super critical levels for the working fluid, the temperature range the cycle can operate over is quite small: turbine entry temperatures are typically 565°C (the creep limit of stainless steel) and condenser temperatures are around 30°C.



This gives a theoretical Carnot efficiency of about 63% compared with an actual efficiency of 42% for a modern coal-fired power station. This low turbine entry temperature (compared with a gas turbine) is why the Rankine cycle is often used as a bottoming cycle in combined cycle gas turbine power stations.

Processes of the Rankine cycle

TS diagram of a typical Rankine cycle operating between pressures of 0.06bar and 50bar

There are four processes in the Rankine cycle; these states are identified by number in the diagram to the right.

• Process 1-2: The working fluid is pumped from low to high pressure, as the fluid is a liquid at this stage the pump requires little input energy.

• Process 2-3: The high pressure liquid enters a boiler where it is heated at constant pressure by an external heat source to become a dry saturated vapor.

• • • Process 3-4: The dry saturated vapor expands

through a turbine, generating power. This decreases the temperature and pressure of the vapor, and some condensation may occur.

• Process 4-1: The wet vapor then enters a condenser where it is condensed at a constant pressure to become a saturated liquid.



In an ideal Rankine cycle the pump and turbine would be isentropic, i.e., the pump and turbine would generate no

entropy and hence maximize the net work output. Processes 1-2 and 3-4 would be represented by vertical lines on the T-S diagram and more closely resemble that of the Carnot cycle.

The Rankine cycle shown here prevents the vapor ending up in the superheat region after the expansion in the turbine,[1]

which reduces the energy removed by the condensers

3.2 Regenerative Rankine cycle

The regenerative Rankine cycle is so named because after emerging from the condenser (possibly as a sub cooled liquid) the working fluid is heated by

steam tapped from the hot portion of the cycle. On the diagram shown, the fluid at 2 is mixed with the fluid at 4 (both at the same pressure) to end up with the saturated liquid at 7. This is called "direct contact heating". The Regenerative Rankine cycle (with minor variants) is commonly used in real power stations.

Another variation is where 'bleed steam' from between turbine stages is sent to feed water heaters to preheat the water on its way from the condenser to the boiler. These heaters do not mix the input steam and condensate, function as an ordinary tubular heat exchanger, and are named "closed feed water heaters".

The regenerative features here effectively raise the nominal cycle heat input temperature, by reducing the addition of heat from the boiler/fuel source at the relatively low feed water temperatures that would exist without regenerative feed water heating. This improves the efficiency of the cycle, as more of the heat flow into the cycle occurs at higher temperature.



Tanda plant PLF:-

A plant load factor is a measure of average capacity utilization. It is a measure of the output of a power plant compared to the maximum output it could produce.

The two commonest definitions are:

Ø Ratio of average load to capacity. Ø Ratio of average load to peak load in a period.

2000 2006 2008



5.0 PRODUCTION OF ELECTRICITY

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

Ø Ø Ø Ø

Coal Handling Plant, CHP

BoilTurbines & Generators

Switch Gear & Switch Yard

Electrostatic Precipitator,

ESP



Ø 5.1 Coal handling plant: The coal, brought to the station by train or other means, we use wagon tripler for putting the coal on the conveying belt which consists of mechanical equipment and motor to drive it. Coal travels from the coal handling plant by conveyer belt to the coal bunkers. There are magnetic separator and magnet detecting device placed at conveyer to remove the magnetic element coming with coal and to indicate magnetic element by the two devices respectively. Now the coal is collected certain place which is called stacking, 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 where it burns, more like a gas than as a solid in convectional domestic or industrial grate, 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 then 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.

Coal GrinderTo the boiler

through conveyer belt



Ø 5.2 Way of producing steam by the boiler: Initially we maintain a certain temperature inside the boiler. We pass mixture of oil and air which is ignited by igniter placed at the corner of the boiler. Oil used in this purpose may be HSD, HFO and LSHS. After reaching a certain temperature we pass powdered coal inside the boiler. This produces lots of heat which helps in producing steam. The steam super-heated in further tubes (Super Heater) and reaches a temperature about 540 degree centigrade and about 135 kg per square centimetre pressure and then it passes to the turbine where it is discharged through the nozzles on the turbine blades.



As the steam strikes on the turbine blades, shaft of the turbine gets movement due to so it starts rotation and reaches a speed about 3000 rpm. Then we control the speed of shaft by controlling the passes of powdered coal to the boiler. The shaft of turbine is mechanically coupled with the shaft of the generator due to so generator’s shaft also rotates with a speed about 3000 rpm. 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 movement of shaft i.e. 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 tubes loses 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, far purer than the water we drink, if it is not to damage the boiler tubes. 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. 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.



Why bother to change steam from the turbine back into water if it has to be heated up again immediately? The answer lies in heat law of physics which states that the boiling point of water is related to pressure. The lower the pressure, the lower the temperature at which water boils. The turbine designer want as low boiling point of water as possible because he can only utilize the energy of the steam – when the steam changes back into water he can get NO more work out of it. So a condenser is built, which by rapidly changing the steam back into water creates a vacuum. This vacuum results in a much lower boiling point which, in turns, means he can continue getting work out of the stem well below 100 degree Celsius at which it would normally change into water.

1. COAL TO STEAM

Coal from the coal wagons is unloaded in the coal handling plant. This coal is transported up to the raw coal bunkers with the help of belt conveyors. Coal is transported to mills by coal feeder. The coal is pulverized into powder form.

This crushed coal is taken away to the furnace through coal pipes with the help of hot and cold air mixture from P.A. fans. P.A. fans taken atmospheric air, a part of which is sent to atmosphere for heating while a part goes directly to the mill for temperature control. Atmospheric air F.D. fan is heated in the air heaters and sent to the furnace as combustion air.

Water from the boiler fed pump passes through economizer and reaches the boiler drum. Water from the drum passes through down comers and goes to bottom ring header. Water from the bottom ring header is divided to all the four sides of the furnace. Due to heat and the density difference the water rises up in the water well tubes “Water is partly converted to steam as it rises up in the furnace. This steam and water mixture is again taken to boiler drum where the steam is separated from



water. Water follows the same path while the steam is sent to super heater for superheating. The super heaters are located inside the furnace and the steam is superheated (540”C) and finally it goes to turbine .

5.3 STEAMS TO MECHANICAL POWER

From the boiler saturated superheated steam enters the high pressure turbine where it passes through its various stages. The steam leaving the high pressure turbine goes back to the boiler for reheating and returns by a further pipe to the intermediate pressure turbine. Here it passes through another series of blades.

Finally the steam is taken to the low pressure turbines, each of which it enters at the center flowing outwards in opposite directions through the rows of turbine blades. As the steam gives up its heat energy to drive the turbine, its temperature and pressure fall and it expands. Because of this expansion the blades are much larger and longer towards low pressure ends of turbine.

When as much energy as possible is extracted from the steam it is exhausted directly to the condenser and further condensate cycle and feed water cycle take place. It is passed through further boiler for reconversion into steam.

5.4 MECHANICAL POWER TO ELECTRICAL POWER

LP turbine end is connected to generator. Generator converts mechanical energy to electrical energy.Turbine shaft usually rotates at 3,000 rpm. This speed determined by the frequency of the electrical system used in this country and is the speed at which a 2-pole generator must be driven to generate alternating current frequency of 50 cycles per second.



6. EXPALANATION OF POWER PLANT CYCLES

6.1 STEAM CYCLE:

Steam coming out from super heater at 540degree C and 139kg per square cm. Three cylinders of 2 set of main stop and governing valve arrangement on either side of HP casing and each set consist of one stop valve and 2 governing valve assembling series. The steam from the boiler is admitted the reheater where it heated at original temp. The reheated steam is taken to IP casing through combined stop and interceptor valve arrangement at either of IP casing. The exhaust from the IP casing has taken directly the LP casing. The steam expanded in the LP turbine to a very low blade pressure which is maintained by the condenser below atmospheric pressure about 3% of makeup water is required to condensate the losses of cooling water due to evaporation in cooling tower. Finally steam exhausted by LP turbine is condensed in the surface type condenser type cooling water following through a large no. of tubes. The HP, IP &LP turbine coupled in series and mechanical power generated from steam transmitted to generator.



HP

From Final S/H

MP

LP

TURBINE GENERATOR

R/H

32 Ksc,535 `C

MAIN STEAM

130Ksc

535 `C

34 Ksc,370 `C

condenser

Hot well

STEAM CYCLE

Hp

By-pass



6.2 Feed water cycle:-

This cycle deals with the flow of water to boiler feed pump from feed storage tank ,which is later fed to the boiler drum passing through high pressure heater and economizer This system plays an important role in the supply of feed water to the boiler at requisite pressure and steam/water ratio. This system starts from boiler feed pump to feed regulating station via HP heaters.

Boiler feed pump: this pump is horizontal and barrel design driven by an electric motor through a hydraulic coupling. all the bearings of the pump and motor are forced lubricated by oil lubricating system.

The feed pump consists of pump barrel into which is mounted the inside starter, together with rotor. Water cooling and oil lubricating are provided with their accessories. The brackets of the radial bearing of the suction side and the radial and thrust bearing of the discharged side are fixed to low pressure cover.

High pressure heater: these are regenerative feed water heater operating at high pressure and located by the side of turbine. It is connected in series on feed water side and by such arrangement the feed water after feed pump enters the hp heater. The steam supply to these heaters from the bleed point of the turbine through motor operated valves.



.



6.3 Condensate water cycle: It deals with the water flowing through the condenser which plays an important role in increasing the efficiency of the plant. It consists of a feedback path from main ejector to hot well. The steam after condensing in the condenser known as condensate is extracted out of the condenser hot well by condensate pump and taken to the de-aerator through ejectors, gland steam cooler and series of LP heaters.

HOT WELL 40

°C

LPM/E

LPH3

LPH4

LPH5

D/A

3 CE PUMP

150°C

HEIGHT 42M

FEEDBACK PATH

45



.



7. BOILER

A STEAM GENERATOR IS A COMPLEX INTEGRATION OF THE FOLLOWING ACCESSORIES:

1. ECONOMISER 7. DIV PANEL 2. BOILER DRUM 8. PLATEN SH 3. DOWN COMERS 9. REHEATER 4. CCW PUMPS 10. BURNERS 5. BOTTOM RING HEADER 11. APHs 6. WATER WALLS


7.1 ECONOMISER

Ø Boiler Economizers are feed-water heaters in which the heat from waste gases is recovered to raise the temperature of feed-water supplied to the boiler.

Ø It preheats the feed water by utilizing the residual heat of the flue gas. Ø It reduces the exhaust gas temperature and saves the fuel.

7.2 BOILER DRUM

• It is an enclosed Pressure Vessel • Heat generated by Combustion of Fuel is transferred to water to become steam Ø Serves two main functions. Ø Separating heat from the mixture of water and steam. Ø It consists of all equipment used for purification of the steam after being separated from water.

7.3 BOILER DRUM LEVEL CONTROL

Ø Important for both plant protection and equipment safety. Ø Maintain drum up to level at boiler start-up and maintain the level at constant steam load. Ø Decrease in this level will uncover boiler tubes and get overheated and damaged. Ø Increase in this level will make separation between steam and moisture difficult within drum. Ø Controlled circulation is required to maintain the difference in the density between water and steam with increase in

pressure.



7.4 DOWN COMERS

Ø It carries water from boiler drum to the ring header. Ø They are installed from outside the furnace to keep density difference for natural circulation of water & steam. Ø Heating and evaporating the feed water supplied to the boiler from the economizer.

7.5 WATER WALLS

• These are membrane walls, no. of tubes are joined. • Vertical tubes connected at the top and bottom of the Headers. • Receives water from the boiler drum by down –comers.

7.5.1 ADVANTAGES

• Increase in efficiency • Better load response simpler combustion control. • Quicker starting and stopping • Increased availability of boiler. • Heat transfer is better • Weight is saved in refractory and structure • Erection is made easy and quick


8. INTRODUCTION TO STEAM TURBINE

The steam turbine is the prime mover in which the pressure energy of the steam is transformed into the kinetic energy of the rotor and later it is converted into electrical energy.

8.1 CLASSIFICATION OF STEAM TURBINE

1. According to the no. of pressure stages:

a) Single stage turbine,

b) Multistage turbine.

2. According to the direction of steam flow:

a) Axial turbine,

b) Radial turbine.

3. According to the no. of cylinder:

a) Single cylinder turbine,

b) Double cylinder turbine,

c) Three cylinder turbine,

d) Four cylinder turbine.

4. According to the method of governing:

a) Throttle with turbine,

b) Turbine with nozzle governing.

5. According to steam condition at inlet to turbine:

a) Low Pressure Turbine: Using steam at a pressure below 5 atm.

b) Medium Pressure Turbine: Using steam at a pressure between 5 atm. to 40 atm.

c) High Pressure Turbine: Using steam above 40 atm.

6. According to action of turbine:

a) Impulse turbine,

b) Reaction turbine.


8.2 PARTS OF STEAM TURBINE BLADE:

8.2.1 BLADE: Blades of turbine are classified in following manner:

8.2.1. 0 According to steam action:

a) Impulse turbine,

b) Reaction turbine.

In case of Impulse turbine blade, pressure drop does not take place in moving blades.

While in case of Reaction blade, pressure drop takes place in moving blades.

8.2.1.2 According to Position:

a) Fixed Blade

b) Moving Blade.

8.2.1.3 According to construction:

a) Free standing blade: This type of blade is not covered by anything and freely stands on the shaft of turbine.

b) Shroud blade: This type of blade is covered by a plate of iron on the tip of the blade.

c) Laeed wined blade: When the blade is tightened by thick wire, it is called Laeed wined blade. It is also called

ribbon wined or Damping wined or Laeing wined blade.

8.3 ROTORS:

The three rotors of turbine are supported on only five bearings, the thrust cum journal bearing being common to HP and MP rotates. It is the rotating part of turbine. It is also termed as Shaft. It has following classification:

a) Flexible Shaft: The working speed of such type of rotor is below their critical speed.

b) Rigid Shaft: The working speed of such type of rotor is more than their critical speed.



8.4 BEARING: Bearings are classified in following manner:

a) Friction Bearing: In such type of bearings there is a line of contact between contacting surfaces.

b) Antifriction Bearing: In such type of bearing there is a point contact between contacting surfaces.

In NTPC Tanda, journal bearing which a type of friction is earing is used to support parts. There are 7 journal bearings among which second one is thrust cum journal bearing

8.5 COUPLING :

Rigid type of coupling is used in NTPC Tanda to connect the shaft of turbine.

8.6 BEARING PEDESTAL:

Two bearing pedestals, front and rear. The front bearing pedestal carries all the governing system components, MOP

and front HP bearings. The rear bearing pedestal carries the thrust bearing and its protection equipment.

8.7 BALANCING HOLE:

Balancing hole is provided in blade for the passage of steam. In NTPC Tanda, it exits in HP&IP turbine.



9. Fundamentals of steam turbine systems Principles of operation - The motive power in a steam turbine is obtained by the rate of change in momentum of a high velocity jet of steam impinging on a

curved blade which is free to rotate. - The steam from the boiler is expanded in a nozzle, resulting in the emission of a high velocity jet. This jet of steam impinges on

the moving vanes or blades, mounted on a shaft. Here it undergoes a change of direction of motion which gives rise to a change in momentum and therefore a force.

- Principle of operation is shown below: - The relationship between work, force and blade velocity can be expressed in the other graph. - Steam turbines are mostly 'axial flow' types; the steam flows over the blades in a direction parallel to the axis of the wheel.

'Radial flow' types are rarely used.

STAGE: Pair of moving and fixed wheel is called a stage.

No. of stages in each turbine:

HP: 8 stages

IP: 12 stages

LP: 2x4 stages



10. Electrical Equipment’s

10.1 Generator:- The generator is directly coupled with its respective turbine normally rated for 110 MW at 0.88 power factor (i.e. 125 MVA), 11kV, 3 phases, 50Hz. The hydrogen cooling mechanism is used for the generator. The neutral point of the generator is earthed through a single phase Distribution Transformer, the secondary of which is shunted through a suitable resistance.

The excitation system consists of high frequency AC mains and pilot exciters directly driven from the main shaft, silicon rectifying unit and associated control gears.



10.1 Generator Transformer:- The generation voltage of 11kV is stepped up to 220kV by generator-transformer (in short GT) whose low voltages side is directly connected with the generator through an isolated phase bus duct. The rating of generator-transformer is 125MVA, 11/220kV, 3 phase, 50 Hz having an ON/OFF cooling. The high voltage side of the transformer is connected to the 220kV system in 220kV switchyard.

10.2 Unit 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 the UAT is 15MVA, 11/6.6kV, 3-phase, 50 Hz.

10.3 Start-up cum Reserve Transformer:- Each of the four units draw its start-up power from the 220kV system through two/three windings common start-up cum reserve transformer rated for 30/10/20 MVA, 220/33/6.6 kV, 3 phase, 50Hz. The transformer supplies the 33kV load requirements. This transformer also meets the requirement of station loads like coal & ash handling, compressed air and water treatment plant, station lightening and other common services as well as act as a standby source of power to unit auxiliaries.



10.5 L.T Auxiliary Transformer:-

For further step down of 6.6kV power from the reserve system for utilization at medium voltage 16 nos. 1000kVA, 6.6kV/415V, 3-phase, 50Hz transformers have been envisaged. The actual requirement is assessed after detail design of the system.

Power for station illumination, unit wise is provided by five 300kVA, 6.6kV/415V, 3-phase, 4 wire transformers.

10.6 DC Supply System:- Charger and control &

distribution system is installed as required for supply to all loads either for normal operation A station battery unit, complete with battery or during any emergency conditions.

Exact rating is however determined after the detail study of all loads and their durations.

10.7 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.

1. 6.6 kV Switchgearsà 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.

2. 415 V Switchgearà The 415V supply 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.

10.8 220kV Switch Yard: Generator Transformer

step-up the 11 kV voltage generated by the Generator to 220 kV. This voltage is used to charge the three buses in the Switch yard which follows Double Bus Bar with Transfer Bus Scheme.

Switch yard provides protection between generator transformer and transmission lines.



Major components of 220 kV Switch yard is:

• Buses (Bus #1, Bus #2 & Transfer Bus). • Isolators. • Circuit breaker.(Air Blast Circuit Breaker) • Current Transformer (CT). • Capacitor Voltage Transformer (CVT). • Wave Tape. • Potential Transformer (PT). • Bays(4-Transmission line , 4-GT , 2-Station transformer ,

1-Bus coupler , 1- Transfer Bus)

Switch yard at NTPC tanda


11. Auxiliary systems:

The following auxiliary systems for the 4X110 MW as envisaged is described below:-

11.1 Coal Handling System:- Railway is only the means of transport of coal to this power station. Annual coal requirement for 4X110 MW units is estimated to be approximately 13.70 lakhs mega tonnes. The coal yard in the layout is adequate for about 30 days storage with two coal stock piles and considering 3800 MT of coal requirement daily.

Considering inadequate & irregular coal movement by railways it is adequate to have a marshalling yard capable of handling two rakes a day normally & three rakes occasionally. Railway siding and marshalling yard is capable of meeting this requirement.

The coal handling system consists of two wagon tipplers with integral weight bridge and marshalling equipment for unloading coal into hoppers. Duplicate belt conveyor system each rated 600 tons/hr feeds coal from the tippler hoppers to Crusher House. There are two crushers, each rated

600tons/hr. Crushed coal is either stacked in crusher coal yard or conveyed straight to power house. Duplicate conveyor system carries coal to the top of boiler bunkers. To stackers/re-claimers are there for stacking and re-claiming of coal each rated 600 tons/hr.

CHP system with wagon



In the power house, over the bunkers, duplicate belt conveyors run, each provided with a travelling tippler. Suitable arrangements are made for magnetic separation of iron particles from coal at the inlet to the crusher house. An automatic belt weighing system is provided at the power house entry point to register the amount of coal fed into the bunkers.

For emergency, manual arrangements are made for unloading the coal from wagons and conveying the same to the crusher house.

Necessary dust suppressing equipment and ventilation equipment is provided as a part of the coal conveying system. The operation of the entire system is controlled and supervised from control room. The system also has necessary interlock & safety features. For the purpose of shunting, it has three diesel locomotives.

11.2 Fuel Oil System:-

The fuel oil is made available to the power station in tank wagon. The lighter grade oil such as light diesel oil is made available for starting of boiler from cold condition & furnace oil is made available for flame stabilisation purpose during low load operation and during any other period when flame stability is not satisfactory. The oil received from the tank wagon is pumped into the storage tank. The railway siding facilities provided is able to accommodate on the rake of tank wagons. Two storage tanks for heavy oil and one for light oil is provided. Provision is made for heating the tanks, steam tracing the piping and supply of heating steam to tank wagons.

Oil from storage tank is pumped into day oil tanks. The day oil tank is located near the boiler. Pumps and heaters sets of suitable design then pump the oil from day storage to the burner. Return oil is fed back into the day tank. Similar installation is provided for the light oil but the day tank is not present.



11.3 Ash Handling System:- The ash disposal area is within the distance of 4~5kms from the power station and this is a low lying area. The ash from the boiler hoppers is conveyed to the ash disposal area either by direct sluicing or hydro-pneumatic system. Boilers manufactured by M/s. BHEL or AVB are so designed that it was possible to adopt either of the system for both fly as well as bottom ash.

The ash disposal area has adequate capacity for storage of ash for a 640 MW station for over 15 yrs without reclamation. This area is now being used by Jaypee cement factory for production of cement and ash bricks. However this area may also be used for agriculture purposes by covering it with a layer of silt brought from the raw water reservoir in future.

11.4 Cooling Water Management:- The general arrangement & the system have been discussed earlier in the report. Only the equipment’s involved in the mechanical system are described below:-

Water cooling plant



Water from the raw water reservoir is pumped through clariflocculators. The clarified water from these clarifloccolator flows to the cooling water basin by gravity. A clarified pump is present which pumps the clarified water to the DM plant. For this, three pumps are involved. 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 equipment’s as follows:-

1. ) CW Pumps for circulating cooling water through turbine, condenser and discharging the same to the op of the respective cooling towers. Two CW Pumps each rated 50% capacity is installed.

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. The number of pumps in this case is also two, each of 50% capacity.

3. ) Ash Water Pumps for supplying water for ash handling. There are two pumps per unit. Ash water is discharged to

the ash disposal area but this continues the part of cooling water blow-down as well and therefore forms the part of total make-up water of the cooling tower.

11.5 Water Treatment Plant:-

A demineralising plant is provided for supplying make-up water for the heat cycle. Clarified water is pumped from the clarified water storage pit which passes through pressure filter, activated carbon filter, caution exchanger, degassifier, anion exchanger and mixed bed exchanger. There are four streams each rated 30m3/hr. Adequate facilities are provided for unloading, handling and storage of chemicals. Waste effluent is neutralised before it is discharged to outside drain.



Water treatment tankers

12. FUTURE PROSPECTS OF NTPC TANDA

NTPC Tanda is providing electricity to 3 different cities (Gorakhpur, Basti & Sultanpur).At present time, plant is delivering electricity up to PLF 102% i.e. generating power more than specified. In near future, generating capacity of plant is going to be increased by two units of 660MW each. So NTPC is playing a major role in development of INDIA.



Thnakfull doer who co-operated in learning Mr. Maurya (Supdt. Chemistry)

Mr.Vinay Tiwari (Er. Operation Department)

Mr. Pankaj Goel (Sr. officer HR)

Mr. Sushil kumar (Er. EM Department)



THNAK

YOU

ntpc report

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