Adani Power Ltd. Training Report

ADANI POWER PLANT

ACKNOWLEDGEMENT

The time I spent here at Adani power Ltd. has been a tremendous learning experience. Not only I have learnt a lot by way of practical application of my theoretical knowledge, I have also gained valuable insights into an exciting industry, its dynamics, and the way a mega project erects.

For this I am grateful to my guide Mr Amitkumar Shah (Sr.Manager, EMD, APL) and Mr Sunil Dave (Senior Engineer, Switchyard, APL) for his valuable time, able guidance, encouragement, feedback, support at every step and his timely inputs.

I would also like to thank all those who helped me in my vocational training.

Mr Rakesh Upadhyaya Mr Kamlesh JogiTraining Department HR Department

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ADANI POWER PLANT

INDEX

SR.NO. TOPICS PAGE NO.

1 OBJECTIVES 32 INTRODUCTION 43 MUDRA THERMAL POWER PLANT

GENERATION CAPACITY6

4 COAL HANDLING PLANT 75 BOILER 106 COAL MILL 127 CLASSIFICATION OF BOILER

CIRCULATION SYSTEM13

8 DESCRIPTION OF PRESSURE PARTS AND ROTARY PARTS

16

9 DM PLANT 2410 COOLING TOWER 2511 SUBCRITICAL BOILER 330 MW 2612 WORKING OF 330 MW 2813 SUPERCRITICAL BOILER 660 MW 3114 OPERATION OF 660 MW 3415 ELECTRICAL SYSTEM OVERVIEW 3716 ELECTRICAL PROCESS IN PLANT 3817 ELEMENTS OF ELECTRICAL

SYSTEM41

18 SWITCHYARD INTRODUCTION 5019 PHASE – 1 SWITCHYARD 5220 PHASE – 2 SWITCHYARD 5521 PHASE – 3 SWITCHYARD 5722 PHASE – 4 SWITCHYARD 5923 HVDC TRANSMISSION 60

OBJECTIVES2

ADANI POWER PLANT

Adani Power Ltd. is one of the upcoming projects of Adani Power, using Super Critical Technology (660 MW Capacity Boiler), which is the second time in India. Proposed Plant Capacity is 4620 MW (5 X 660 MW +4 X 330 MW), which needs an investment of Rs195.00bn.So my basic objectives were:-

To get familiar with the working of a thermal power plant. To understand the current technology that is being used in the erection of a

thermal power plant. To get an overview of the major components of a thermal power plant.

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ADANI POWER PLANT

INTRODUCTION

Adani Power Limited is the power business arm of Indian business conglomerate Adani Group. The company is India's largest thermal private power producer with capacity of 5280 MW and also it is the largest solar power producer of India with capacity 40MW.The company currently operates five supercritical boilers of 660MW each (as per March 2012) at Mundra Gujarat & One 660MW out of 05 units at Tirora, Maharashtra. It also operates a mega solar plant of 40MW at Surendranagar, Gujarat.[2] It is India's first company to achieve the supercritical technology. The plant is the only thermal power plant in India to be certified by UN under CDM.

Mundra Thermal Power Station or Mundra Thermal Power Project is located at Mundra in Kutch district in the Indian state of Gujarat. The power plant is one of the coal-based power plants of Adani Power. The coal for the power plant is imported primarily from Indonesia. Source of water for the power plant is sea water from the Gulf of Kutch. It is the world's fifth-largest single location coal-based thermal power plant as well as India's largest operational power plant as per august,2012 and also in private sector, it is world's largest single location coal-based thermal power plant.

India’s Installed Capacity (132329 MW)

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55%

10%

26%

3% 6%

Coal & Lignite

Gas

Hydro

Nuclear

Other Renewables

PLANT CAPACITY4620 MW

PHASE I PHASE II PHASE III

2 x 330MW 2 x 330MW 2 x 660MW

PHASE IV

3 x 660MW

LargestPower Plant

InINDIA ON SINGLE PLACE

3rd Largest Thermal

Power PlantIn

World

ADANI POWER PLANT

Adani Group’s foray into power sector – The Group’s foray into power sector is natural extension for Adani Group, which has emerged as India’s largest coal importer and second largest power entity in the country.

Adani Power Ltd (APL) is setting up a 4620 MW power project at Mundra based on imported coal. The execution will be done in the following ways as under:-

2*330 Phase I (sub critical) 2 *330 Phase II (sub critical) 2*660 Phase III (super critical) 3*660 Phase IV (super critical)

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Mundra Thermal Power ProjectPower Generation Capacity

ADANI POWER PLANT

COAL HANDLING PLANT (CHP)

The Process of Coal Handling Plant is shown in figure.

Here The Coal is feeded into the coal bunker from Silo to the coal bunker. The process of feeding from silo to the coal bunker is known as coal handling plant. In this process the coal passes from many processes like crushing, vibrating, screening, etc. First the coal is transferred to the stock pile from silo for that process of transferring the coal from silo to the stock pile transferring conveyor belt is used. To stock the coal here we use stacker-reclaimer mechanism. In this stacker-reclaimer mechanism we can put the coal from conveyor belt to stock pile by stacking process and we can also get the coal from stock pile to the conveyor belt by reclaiming process.

The coal used in the plant is transported from Mundra Port to the plant through a Conveyor belt which is 15Km long and runs at a speed of 7 m/sec.

Now from the stock pile the coal is transferred to the crusher house by using flat type conveyor belt. It feeds 2000 tons/hr. So the capacity of the conveyor belt to feed the coal in crusher house from stock pile is 2000 tons/hr. for the safety purpose sprinkler is mounted throughout the conveyor belt. So in case of fire on the coal the sprinkler comes into action and we can control the fire. It is an automated system. The sensor senses the situation and the system takes the action. If the temperature of atmosphere is increased above the critical limit so at that time possibility of coal burning is increased so at that time the sensor senses the temperature of atmosphere and the sprinkler comes into action and we can control the situation and put it in a normal condition. And when the condition comes at a normal condition sprinkler turns off.

Now at a crusher house the coal is crushed by the crusher. Crusher is one type of machine which converts the lump type of coal into small particle by crushing action. To run that crusher we have to use high tension motor which is operated by 6.6 KV and the motor we use H.T. induction type motor.

So now by crushing the lump type coal it now becomes small particle and then We have to transfer that coal to the vibrofeeder via conveyor belt. We use flat type conveyor belt which has capacity of 1200 tons/hr. In vibrofeeder the coal passes through vibrator for screening purpose.

At a screening process the coal passes through the vibrator and if the big particle present in that it will be separated. Small particle is feeded into the belt feeder and

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the big particle is again crushed by secondary crusher and it is converted into small particle and then it is feeded directly into the belt feeder by conveyor belt. Now the conveyor belt using to transfer small particle coal from vibrofeeder to the belt feeder is known as Flat Type Conveyor belt & it feeds 900 tons/hr.

Now the small particle coal is in the belt feeder and it is then passed to the coal bunker via conveyor belt here the coal is stored. There is total four coal bunker for each unit then from coal bunker it then send to the coal mill.

There is one another system for feeding the coal in the crusher house. In this system the coal is directly transferred from the coal wagon to the crusher house. First the wagon is unloaded in the wagon coal hopper which is situated in the tunnel and then it is transferred to the crusher house by Triple Travelling Ride (TTR) belt & then the same process described is followed again.

Here there is possibility of moving of conveyor belt from its normal position so for the safety purpose here we have used 3 Switches

1) Zero Sway Switch2) Pull Coat Switch3) Belt Sway Switch

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ADANI POWER PLANT

1) Zero Sway Switch: - The function of this switch is to give the information about the current situation of the belt. It is assembled at the vibrofeeder side and when the conveyor belt gets breakdown at that time the switch comes into action. There is one sensor which senses whether the conveyor belt is working in normal situation or not & it continuously gives the command to the computer operator’s screen mounted at control room. Any case of breakdown the switch gives the command to the control room and it cuts off the supply to the motor pulley and the rotation of pulley is stopped.

2) Pull Coat Switch: - It is a switch which is mounted throughout the conveyor belt 50 meters away from each other and each switch is connected to each other by one wire if any one sees any abnormal condition anyone pulls that wire then switch is made off and we can maintain that belt. We can manually operate the switch it is not automated system.

3) Belt Sway Switch: - This switch is mounted on both the side of the conveyor belt. Total 3 switches are used & mounted at tail head, top head and at the center. If the belt sways from the pulley at that time the switch comes into action and conveyor belt can be made stopped from running.

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ADANI POWER PLANT

BOILER :

Definition of Boiler;

Boiler a Pressure vessel used for generating (a) steam for power generation, process use or heating purposes and (b) hot water for heating purposes.

However, according to the Indian Boiler Act, 1923, a boiler is a closed pressure vessel with capacity exceeding 22.75 liters used for generating steam under pressure. It includes all the mountings fitted to such vessels, which remain wholly or partly under pressure when steam is shut off.

Various Types of Boilers:

Boiler

Fire tube boiler Water tube boiler

Cornish Boiler Simple vertical boiler, Cochrane boiler, Locomotive Boiler and Scotch Marine Boiler

Fire Tube Boilers:A fire tube boilers, is the boiler wherein the products of combustion pass through inside of the tubes (either one or several) and water which is to be converted in to steam is made to surround outside these tubes. Fire Tube Boilers are used where the steam pressure is normally low and the steam is not generally required to be the superheated. Fire tube boilers are compact and can be easily manufactured in a factory and assembled as a packaged boiler. Fire tube boilers cannot be manufactured in large sizes beyond certain limit due to large size of shell involved.

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Benson boiler waste heat

ADANI POWER PLANT

Fire tube boilers have the advantage of low manufacturing and operating cost.

Water Tube Boilers:In this type of construction of Boilers the fuel is fired in a confined chamber and the water is circulated through divided flow path inside a number of small-bore tubes, which are exposed to the heat generated inside the combustion chamber. InAdani power plant water tube boiler is used Water tube are classified as

Sub critical boiler Super critical boiler

Difference between Sub-Critical and Super-Critical Boilers

SUB-CRITICAL BOILERS SUPER-CRITICAL BOILERS

Operating pressure is below 225.5 bar.

Operating pressure is above 225.5 bar.

Normal circulation: circulation by pump assisted or natural circulation.

Lower load start-up circulation: below 35% NR load.

Power plant efficiency is around 35%.

Power plant efficiency is around 39%.

Pressure : 169 barSH Temp : 538’CRH Temp : 538’C

Pressure : 254 barSH Temp : 571’C RH Temp : 569’C

Base Additional cost to manufacturing and erection of furnace wall.

Vertical water walls. Spirally wounded tilted water walls.Spirally wounded water walls ensures:Uniform heat distribution.Avoid higher thermal stresses in water-walls by reducing the fluid temperature difference in adjacent tubes.

Drum is used Drum is not used

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Coal Mill

Main parts of coal mill are: Gear Plate Motor Gear Box Bottom Housing Grinding track carrier and Scraper Grinding track and nozzle ring Grinding Roller Loading Frame Housing Case Hydraulic Cylinder Rotary Unit Rotary Classifier Oil Lubrication Unit

Description:-

There are 5 running mills and one stand-by mill in phase-I and II each having capacity of around 50 tonnes per hour and there are 6 running mills in phase-III and IV each having capacity of 100 tonnes per hour. There are three rollers mounted on the bowl. Bowl is connected to motor with the help of gear box. Motor rotates at 985 rpm and Gear box ratio is 37.27:1. Rollers are inclined at 15ᵒ. Distance from axis to roller radius is 950 mm. Roller grinds coal from 25 mm to 75 micron. Coal comes from SILO to bunker via conveyor belt and transfer tower. From bunker, coal goes to feeder. There is one center pipe coming in mill from feeder which throws coal on bowl and coal is grinded on bowl with the help of roller. Then through PA fan and centrifugal force, coal will go to the furnace.

If coal is not grinded through roller, it comes down and is rejected by rejection valve. If coal comes to gear box, then it will jamm the gear box. For that purpose, seal air from SA fan is provided under the inlet of PA fan. Pressure of SA fan should be higher than that of PA fan.

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ADANI POWER PLANT

Classification of Boiler Circulation System:

The boiler Circulation can be classified into three different types of systems: Natural circulation system Controlled circulation system Combined circulation system

Natural circulation - well suited for < 145 bar Controlled circulation - optimum solution of reliable high-pressureOnce-through technology - Suitable for sub and supercritical cycles both spiral-wall and vertical-wall arrangements available depending upon capacity and fuel.

Natural Circulation System: -

Water pumped under high pressure, by Boiler Feed Water pumps, enters the boiler at economizer inlet, after getting preheated in the High Pressure Heaters. The temperature of water entering economizer will be well below the saturation level corresponding to the pressure at which it is pumped. The feed water, when it flows through the economizer, gets further heated very close to the saturation temperature by the hot flue gas and gets into the drum.

In a boiler the steam-water drum acts as a storage vessel. Water inside the drum finds its way flowing down the Downcomer pipes and gets distributed by the supply pipes to bottom headers of the water wall. The Downcomer pipes and supply tubes are located outside the boiler-heating zone.

Then the water rises through the water tubes, which are exposed to furnace heat. When the water rises up the water tubes, a portion of the water is converted into vapour and continues to rise upwards as a mixture of steam and water, till it flows back into the drum, through steam water separators.

Inside the drum, the steam, separated from water, enters the Super heater zone, for further increase in the temperature and is sent to the turbine. Remaining water mixes up with the incoming water from the economizer, and the cycle is repeated.

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NATURAL

STEAM DRUM

FURNACE

WALLS

ECON.

CONTROLLED

TO SUPERHEATER

Pump

ADANI POWER PLANT

The circulation, in this case, takes place on the thermo-siphon principle. The Down comer contains relatively cold water, whereas the riser tubes contain a steam water mixture, whose density is comparatively less. This density difference is the driving force, for the mixture. Circulation takes place at such a rate that the driving force and frictional resistance are balanced.

As the pressure increases, the difference in density between water and steam decreases. Thus the hydrostatic head available will not be able to overcome the frictional resistance for a flow corresponding to the minimum requirement of cooling of water wall tubes. Therefore natural circulation is limited to boiler with drum operating pressure around 175 kg/cm2.

Controlled Circulation System

13

Separator

Pump

ECON.

ADANI POWER PLANT

If the Operating pressure is beyond 180 kg/cm2, circulation is to be assisted with mechanical pumps, to overcome frictional losses. To regulate the flow through various tubes, orifice plates are used. This system is applicable in the high sub-critical regions (say 200 kg/cm2).

Combined Circulation System: -

Beyond the critical pressure, phase transformation is absent, and hence a once through system is adopted. However, it has been found that even at supercritical pressures, it is advantageous to re-circulate the water through the furnace tubes at low loads. This protects the furnace wall tubes and simplifies the start-up procedure. A typical operating pressure for such a system is 260 kg/cm2.

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DistributionHeader

ADANI POWER PLANT

DESCRIPTION OF PRESSURE PARTS & ROTARY PARTS

Pressure parts Super heater Economizer Reheater

Super heater: -

The superheater is a heat exchanger in which heat is transferred to the saturated steam to increase its temperature. It raises the overall cycle efficiency. In addition it reduces the moisture content in the last stages of the turbine and thus increases the turbine internal efficiency.In modern utility high pressure boilers, more than 40% of the total heat absorbed in the generation of steam takes place in the super heaters. So, large surface area is required to be provided for superheating of steam.

Superheaters are commonly classified as: Ceiling Superheater: Primary Superheater or the Low Temperature Superheater (LTSH): Convection Superheater: Platen or pendent panel Superheater:

Ceiling Superheater:A panel of small bore tubes interconnecting long header at both ends, forms

the roof of the furnace and the second pass of flue gas path. From here the steam flows through different stages of superheating.

Primary Superheater or the Low Temperature Superheater (LTSH):A panel of small bore tubes formed in “U” shaped coils is connected to long

headers on either ends and located horizontally in second Pass of the flue gas path above the economizer. Superheated steam from Ceiling Superheater enters at inlet and gets heated further, raising the steam temperature. It is located in the low temperature region of flue gas path. The steam just gets superheated and the temperature range to which the steam is heated is very low compared to the final outlet steam temperature and hence called Low Temperature Superheater.

Platen or pendent panel Superheater:Steam from Primary Superheater enters the Platen Superheater. The Platen

Superheater is located just above the combustion zone at the top of the furnace.

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ADANI POWER PLANT

Mainly it receives radiant heat from the furnace and the steam is further superheated. They are hanging panels arranged in rows across the width of the furnace. Each panel is connected with its own small inlet and outlet headers, which are in turn is connected to the big and long common headers, on both inlet and outlet sides.

Convection Superheater:From Platen Superheater the steam enters the next stage of superheating,

which is called Convection Superheater. Convection Superheater is located away from radiant zone of the furnace and the heat transfer takes place by convection process, when the mass of flue gases pass through and across the convection Superheater coils. The steam gets its final heat addition while flowing through the final Superheater stage and flows out through main steam pipes, for the end use.

EconomizerAn economizer is a heat exchanger which raises the temperature of the feed

water leaving the highest pressure feed water heater to about the saturation temperature corresponding to the boiler pressure. This is done by the hot flue gases exiting the last superheater or reheater at a temperature varying from 370`C to 540`C. The throwing away of such high temperature gases involved a great deal of energy loss. By utilizing these gases in heating feed water, higher efficiency and better economy were achieved.

Reheater : The function of Reheater is to reheat the steam coming out from high

pressure turbine. The Reheater is composed of two sections. The front pendant section and rear pendant section.

Rotary parts Air Reheater Draught system

Air reheater

Air preheater are in general divided into two types: Recuperative Regenerative

In Recuperative APH, heat is directly transferred from the hot gases to the air across the heat exchanging surface. They are commonly tubular, although some

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ADANI POWER PLANT

plate types are still in use. Tubular units are essentially counter-flow shell-and-tube heat exchangers in which the hot gases flow inside the vertical straight tubes and air flows outside. Baffles are provided to maximize air contact with the hot tubes.

In ADANI POWER LTD.Regenerative APH are being used.

Regenerative APH are also known as storage type heat exchangers, have an energy storage medium, called the matrix, which is alternately exposed to the hot and cold fluids. When the hot flue gases flow through the matrix in the first half of the cycle, the matrix is heated and the gas is cooled. In the next half of the cycle when air flows through the matrix, air gets heated and the matrix is cooled. The cycle repeats itself.

Air preheater corrugated sheet

Draught system,

Large amount of air is required for combustion of fuel. The gaseous combustion products in huge quantity have also to be removed continuously from the boiler furnace. To produce the required flow of either air or combustion gas, a pressure differential is needed. The term “draught” or “draft” is used to define the static pressure in the furnace, in the various ducts, and the stack.

The function of the draught system is basically two folds:

To supply to the furnace the required quantity of air for complete of fuel. To remove the gaseous products of combustion from the furnace and throw

these through chimney or stack to the atmosphere.

There are two ways of producing draught: Natural draught

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ADANI POWER PLANT

Mechanical draught

Natural Draught:The natural draught is produced by a chimney or a stack. It is caused by the

density difference between the atmospheric air and the hot gas in the stack.

Advantages of Natural Draught: No additional energy is required to produce draught. Low initial investment & very less maintenance cost. Reduces pollution as the flue gas is discharged at sufficient height. The overall life is more.

Disadvantages of Natural Draught:

The maximum furnace draught that can be achieved is just10 to 20 mm of WC due to low-density difference between hot flue gas column and atmospheric cold air column.

To achieve better draught, flue gas is to be discharged at high temperature, which means loss of efficiency.

Due inadequate draught effect, the incoming air velocity will be low as a result of which efficiency of combustion will be affected. Due to low flue gas velocity, heat transfer will not be effective.

Mechanical Draught : Mechanical draught is produced by fans.

Classification of Mechanical Draught System: Artificial system can be again classified into following; Forced Draught System Induced Draught System Balanced Draught System

Induced and Forced Draught Fans:Big fans may be used for sucking and throwing out the flue gas through the

chimney, thereby creating adequate draught inside the furnace. Such Fans are termed as Induced Draught Fans. Forced draught Fans may also be deployed for supply of required quantity of combustion air and maintaining a positive draught inside the furnace. The flue gas will be pushed out the stack with the draught pressure available in the furnace

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ADANI POWER PLANT

FORCED DRAUGHT: -

Air drawn from atmosphere is forced into the furnace, at a pressure higher than the outside atmosphere, by big centrifugal fan or fans to create turbulence and to provide adequate Oxygen for combustion.  Hence the system is known by the name Forced draught system and the fan, used to push through combustion air under pressure, is called Forced Draught Fan. F D fan is normally located at the front or sideways of the furnace.

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ADANI POWER PLANT

INDUCED DRAUGHT: -

Instead of drawing atmospheric air and pushing through furnace, a centrifugal fan can be deployed to draw out the air from the furnace and throw out through the chimney, thereby creating negative pressure in the combustion zone and maintain the negative draught throughout the furnace. The system is called Induced Draught system and the fan deployed for this purpose is known as Induced Draught Fan.

In the Induced Draught system, the fan is fitted at back end of the furnace or near the base of the chimney.  Due to the negative pressure created inside the furnace, by the action of the fan, atmospheric air enters and aids combustion. The entry of air is regulated through air registers and dampers.For similar capacity boilers, the size of an induced draught fan will be more than the size of the forced draught fan required for a forced draught system. This is because the products of combustion is always much higher in volume than the volume of combustion air handled by the forced draught fan. Further the flue gas is hotter and the density is less. Hence the volume is much more. According to Charles Law, when a gas is heated the volume will proportionately increase at constant pressure, with the raise in temperature. According to Boyles Law, if pressure inside a vessel is increased, the volume will proportionately decrease and the vice-versa is also true (P 1/V).

BALANCED DRAUGHT: -20

ADANI POWER PLANT

The system in which combustion air is supplied under pressure through a Fan and a negative draught is created by the suction of another is called Balanced Draught System. It is a combination of the forced and induced draught system. In a balanced draught system, air for combustion is supplied at required pressure by the action of the Forced Draught Fan and the extraction or removal of flue gas is assisted by the Induced Draught Fan, thus a balanced draught is maintained. The control of fuel air ratio in the furnace is accomplished by both forced and induced draught fans, so that draught is regulated and balanced with the amount of supply of combustion air and flue gas generated, so that the draught pressure at the back of the furnace is null and zero.  Starting from the null point the Induced draught fan maintains negative draught and pulls out the gases and throws out to atmosphere.

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ADANI POWER PLANT

Comparison between Forced and Induced Draught Systems :

Forced draught system requires less fan power, since the fan has to handle only cold air, where as in induced draught system, fan has to handle comparatively more volume of hot flue gases.

Forced draught gives better control than induced draught, as air penetrates into the fire-bed or helps in good turbulence and thorough mixing of fuel than in induced draught system and hence rate of burning of fuel is faster and efficient.

With forced draught system, possibility of gas leakage is always outward and hence there is always risk of hot gas blowing out if any peep hole or inspection doors are kept open.

With induced draught, all leakages of air are inward and therefore, heavy air infiltration will occur if refractory and brick work etc. in the flue gas path is not maintained in good condition, resulting in over loading of Induced Draught Fan.

Blades of an Induced Draught Fan get eroded and corroded faster than a forced draught fan, since it has to handle erosive and corrective combustion products. Hence Induced Draught Fans require more maintenance.

Advantages of the Mechanical Draught System over the Natural Chimney Draught System:

Higher evaporative capacity of the boiler since required quantity of air at required pressure can be supplied for combustion.

Easy to burn even low-grade / low calorific value fuels. Better control of combustion is possible and hence burning efficiency can be

improved. Comparatively less emission through Stack. Chimney height required can be less.

Disadvantages of Artificial Draught System :

Initial cost is very high as fans are required Power consumption is more and auxiliary power consumed increases. The overall construction of the plant is complicated. Equipment maintenance cost is high.

In ADANI POWER LTD. Balanced draught is brought into practice.

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ADANI POWER PLANT

D.M. PLANT

The main requirement of Boiler is water and coal for the production of steam. Sea Intake draws water from the sea which is then passed to 20MLD and 7MLD where MLD stands for Million liters per day.20MLD is used for 660 MW units and 7MLD is used for 330 MW units.

This water is then passed to the RO plant (where Reverse Osmosis takes place) for reducing its conductivity and heavy water is removed as waste which is expelled back to sea. The conductivity of water is as high as 75000 W/m^2K which if passed will damage the turbine vanes and will also corrode the blades. Hence it is necessary to reduce the conductivity from 75000 W/m^2K to 1500 W/m^2K which is performed in RO plant. The RO purified water is stored in RO tank which then goes to DM plant for the removal of the many impurities present in water like Na, Cl, Mg, Ca etc.

In DM plant there are many purification systems like anion exchanger, strong acid cation exchanger, degazeretc.There are many Resin plates for removing the positive and negative ions from water.In anion exchanger there are R-H+ resin plates and in cation exchanger there are R-OH- resin plates so that if NaCl is present in water then Na+ and Cl- can be removed by these R-H+ and R-OH- plates.The reaction can be explained as follows: The Na+ ion bonds with R replacing H+ which then bonds with Cl- forming R-Na+ and HCl.

R-H+ + NaCl R-Na+ + HCl

This HCl goes to the strong acid cation exchanger where R-OH- plates are present which results in the formation of H2O and R-Cl.The reaction is expressed as:

R-OH- + HCl R-Cl + H2O

The water thus produced is then stored in DM storage Tank which is then passed to the boiler for the production of the steam. To obtain the original R-H+ and R-OH-, HCl&NaOH are passed through the anion exchanger &cation exchanger respectively .The byproduct of the above process is NaCl which is drained out by other process.

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ADANI POWER PLANT

COOLING TOWER

Cooling tower is used for the purpose of cooling the heated sea water. In electricity generation process steam passes through the H.P, I.P, and L.P. Turbines but there is some heat which is present reduces the efficiency for next cycle. So this heat is transferred to the sea water via use of condenser.

Here the sea water is feeded into the condenser which transfers the heat of steam to the sea water. This sea water is transferred to the cooling tower through the pipes. In cooling tower according to the design it will flow to the upper head of the cooling tower. At the top portion L.T motors are present which fetches the cool air from the atmosphere. The flow of air is from top to ground which cools the water.

Here water free falls on the fins. There is some space for the circulation of natural atmospheric air throughout the cooling tower. By this way water looses its heat and water is now feeded to the circulating water pump through underground water canal system. This water is then feed to the condenser.

In this cycle there is some loss of water. Water should be make up so for that there is a design of sea intake which fetches water from the sea and reduces its conductivity. And it is then feeded to the circulating water pump through different channels.

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ADANI POWER PLANT

Sub critical boiler (330MW)

The boiler which works below critical point called sub-critical boiler.

Furnace:A boiler furnace is that space under or adjacent to a boiler in which fuel is

burned and from which the combustion products pass into the boiler proper. It provides a chamber in which the combustion reaction can be isolated and confined so that the reaction remains a controlled force. In addition it provides support or enclosure for the firing equipment.

Boiler Drum:The function of boiler drum is to separate the water from the steam generated

in the furnace walls and to reduce the dissolved solid contents of the steam to below the prescribed limit of 1 ppm. The drum is located on the upper front of boiler.

Header It is one type of junction.

Water Walls : In modern boilers the combustion chamber is formed by tubes containing

water and configured in such a manner as to form the walls of combustion chamber. Thus, the Combustion Chamber of modern boilers comprises of Water Walls.

Burners:There are total twenty four pulverized coal burners for corner fired boilers

and twelve oil burners provided each in between two pulverized fuel burners. An evident from name itself, these are used for burning pulverized coal or oil.

Igniters:There are twelve igniters per boiler. The atomizing air for igniters is taken

from plant air compressors at 7 kg /cm2 (gauge)

Coal Bunker:Processed coal after crushing from the Coal Handling Plant is stored in silos

(Coal Bunkers). Generally, these bunkers are made up of welded steel plates. These are located on top of the mills so as to aid in gravity feeding of coal.

Coal Feeders:

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Each mill is provided with a drag link chain / rotary / gravimetric feeder to transport raw coal from the bunker to the inlet chute, leading to mill at a desired rate.

MillsThere are six mills (25% capacity each) for every 210 MW units, located

adjacent to the furnace at ‘O’ M level. These Mills pulverize coal to the desired fineness to be fed to the furnace for combustion.

P.A. FanThe primary air fans are designed for handling hot air for conveying the

pulverized coal from mill to the furnace through coal carrying pipes. These fans are located at ‘O’ M level near the boiler. There are two to six fans per boiler.

F.D.Fan: The forced draft fans (2 per unit – 50% capacity each) are designed for

handling secondary air for the boiler. These fans are located at ‘O’ M level near the PA fan.

Chimney : These are tall RCC structures with single / multiple flues chimneys (one flue

per 210 MW units). The height of these chimneys varies depending on the location at considerations; anywhere between 120 m. to 220 m.

Seal Air Fan:These are used mainly for supplying seal air to the mill to prevent ingress of

coal dust into gear box lubrication oil. There are two to six fans per boiler for 210 MW units.

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Working of330 MW: -

1. Anthracite coal from the coal wagons is transported to the coal handling plant.

2. Here coal is crushed in coal crushers. The size of coal is reduced to 1 inch (approx.).

3. This crushed coal with the help of coal conveyers is transported to the coal bunkers.

4. With the help of coal feeders coal from bunkers is made to fall in bowl mill.

5. Coal is grounded to powdery form in bowl mill. This finely grounded coal is known as pulverized coal. Bowl mill consists of a round metallic table and three rollers. Rotating table is made to rotate with the help of a motor. There are three large rollers which are at a spacing of 120”.When there is no coal these rollers does not rotate but when coal is fed to the table it packs between the table and the roller and this forces the rollers to rotate. Coal is crushed by the crushing action between table and rollers.

6. This pulverized coal is taken to the burner in coal pipes with the help of hot and cold air mixture from primary air (PA) fan.

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7. Atmospheric air fed by a forced draught(FD)fan is preheated by the outgoing flue gases ina heat exchanger called air preheater(APH).Air is heated to the desired temperature which varies from 250’C to 400’C depending on the type of coal burnt. This hot secondary air flows into the wind box and getsdistributed to the burners to help combustion. Fuel burns in the furnace with great intensity to some 1350’C or even higher, depending on the quality of coal.

8. Water at 170-260’C (depending on boiler pressure) from the boiler feed pump passesthrough the economizer and reaches the boiler drum. The feedwater leaving economizer is saturated (or a two phase liquid) of low quality. It then enters the boiler drum at midpoint (lengthwise).

9. Water from drum passes through downcomers and goes to bottom ring headers.

10. Water from the down ring header is divided to all the four walls of furnace and act asrisers. Water is partly converted to steam as it rises up in the furnace. The water in the riser tubes receives heat mainly by radiation from the combustion gases and boils.The circulation of water and steam within the boiler circuit may be natural or forced.

11.Steam is separated from the bubbling water in the in the drum and goes to the convectiveor primary superheater (CSH) where heat is absorbed by convective mode.

12.From the convective superheater steam goes to the radiant superheater (RSH) installed at the top of the furnace, where heat is absorbed by radiation.

13. Steam leaving the radiant superheater goes to the desuperheater where water of high purity is sprayed on to the steam to bring down the steam temperature to its desired value, if it exceeds the later.

14. From the desuperheater, steam finally goes to the pendant superheater (PSH) for further superheating before it leaves the main stop valve to the high pressure turbine (HP) turbine.Both RSH and PSH are often termed as secondary superheaters.

15. Steam exiting from the HP turbine goes back to the furnace for being resuperheated to the desired temperature in the reheater.

16. Steam after being reheated flows to the intermediate pressure (IP) turbine for further expansion.

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17. Mixture of water and steam from IP turbine is send to the condenser. Here they exchangeheat with the cold water that is being circulated with the help of circulating water pump.

18. The condensate from the condenser is extracted. In case of presence of air moleculescondensate is passed to the deaerator to get rid of air molecules.

19. The air free condensate is then sent to the condensate polishing tank for further purification.

20. This highly pure condensate is then sent to the boiler drum via economizer with the help of boiler feed pump.

21. The cold water (that was supplied from cooling tower with the help of circulating water Pump to the condenser) becomes hot due to heat exchange with the outlet from IP turbine.

22. This hot water is circulated back to the cooling towers. Here, it exchanges heat with the Atmospheric air which is being drawn with the help of a fan installed at the top of the Tower.

23. The water that is being used in cooling towers is highly pure. Sea water is traced to a reservoir. This highly alkaline sea water is sent to the Demineralization plant (DM) to lower the alkalinity. The alkalinity on PH scale is between 7 and 9. This pure water is then circulated to the cooling towers.

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SUPERCRITICAL BOILER(660MW)

Introduction: -

The thermal efficiency of the power plant can be improved by using the steam at super critical condition. This paper mainly studies the general concept of the super critical boiler and also discuses its merits and demerits. The improvement in overall efficiency of the plant will be at least 2% if the super critical parameters are implemented. The importance of thermal efficiency of the thermodynamic cycle and the methods to improve the thermal efficiency of the cycle are also analyzed.

Therefore, attention is focused on improving the thermal efficiency of the steam power cycle. We can improve the plant efficiency by using the steam at supercritical condition. In this paper, the basic thermodynamic cycles such as Carnot cycle and Rankine cycle are discussed. The supercritical parameters of the plant improve upon the efficiency of the plant compared to sub critical parameters by at least 2% the dry steam state.

DefinitionA Boiler operating at a pressure above critical point is called Supercritical

Boiler. Supercritical Boiler has no drum and heat absorbing surface being, in effect, one continuous tube hence called ‘oncethrough Supercritical Pressure Boilers.The water in boiler is pressurized by Boiler Feed Pump, sensible heat is added in feed heaters, economizer and furnace tubes, until water attains saturation temperature and flashes instantaneously to dry saturated steam and super heating commences.

Figure: Supercritical boiler cycle with SH, RH & Regeneration

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No. 1 HP Heater

BFBP

MD-BFP

CEP

GSC

No.7AB&8ABLP Heater

No.5 LP Heater

DEAERATOR

CONDENSER

LPT LPT IPT HPT

No. 2 HP Heater

No. 3 HP Heater

BRCP

LTRH I/L Header

LTRH

ECO I/L Header

LTSH

ECO

No.6 LP Heater

HP BFWP

CRP

SEPARATOR

SEPARATORDRAIN TANK

ROOF TUBE I/L Header

SH DIV Panel

FSHFRH

VERTICAL WATER WALL

SPIRAL WATER WALL

MSPHRP

HP-BP

LP-BP

WW LOWER Header

GG

TD-BFP

A B

BA

A B C

ADANI POWER PLANT

Features:SupercriticalOnce-through typeSingle furnaceSingle reheatBalanced draughtOutdoor arrangementDried slag dischargeComplete steel structureComplete hanging constructionDouble gas passes

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ABBREVIATIONS USED IN PLANT

BFBP BOILER FEED BOOSTER PUMP

MD BFP MOTOR DRIVEN BOILER FEED PUMP

TD BFP TURBINE DRIVEN BOILER FEED PUMP

BRCP BOILER RECRCULATING PUMP

LTSH LOW TEMPERATURE SUPER HEATER

FSH FINAL SUPER HEATER

LTSH LOW TEMPERATURE REHEATER

FRH FINAL REHEATER

HP HIGH PRESSURE TURBINE

IP INTER MIDATE PRESSURE TURBINE

LP LOW PRESSURE TURBINE

SH DIVPANEL SUPER HEATER DIVISION PANEL

FLOW DIAGRAM OF ADANI SUPER-CRITICAL BOILER

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Operation

Water Circuit:-Feed water is supplied to economizer inlet header via feed regulating station

and check valve. The feed water flow is upward through the economizer coils that are counter flow to the hot flue gases. After feed water is collected by Economizer intermediate header it passes through Economizer hanger tubes to reach top economizer outlet header. The water from economizer outlet header will go tobottom header boiler than it goes in spiral water wall than it goes to out let header of spiral wall it goes in the vertical water wall than out let header of this wall it goes through the down comer to header through arch header to side wall than out let header to separator.

Steam Circuit:- Saturated steam leaves separator the SH radiant roof inlet header

throughconnecting pipes. The path between the roof inlet andoutlet headers forms the front steam cooled roof above the furnace.The steam leaving the roof outlet header enters the rear pass side walls through rear pass side wall inlet header.

Leaving rear side wall inlet header the steam flows down through the rear side wall into a U shaped header at the base of rear pass. This is called rear pass sub outlet header. Fin welded panels connected to feeds the steam to front inlet header via elbow connection.

SH rear pass front inlet header feeds the steam to junction header via rear pass front wall. It also feeds the horizontal pass extended. Side wall through connecting tube on each side. The connection tube between rear pass front inlet header and extended side wall inlet header are called SH hanger tube. The panels from cover the bottom and side portions of extended region and connected to a separate header at top on either sidethe steam from these headers reaches junction header through connecting tubes.

The rear pass junction header supplies steam to rear pass roof tubes. These tubes from the steam cooled rear roof and steam cooled rear wall in the form of tin welded panels ending at the rear pass rear wall outlet header.

Also a portion of steam from on either side enters SHH-8 through elbow connection and goes up to rear wall outlet header.

Leaving the rear pass rear wall outlet header the steam flow upward once again through a series of terminal tubes to the rear horizontal SH inlet header. From the rear horizontal super heater inlet header, steam passes up through horizontal superheater or low temperature super heater. The outlet of the low temperature super heater forms the terminal tubes or hanger tubes and they terminate in rear horizontal super heater outlet header.

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Temperature control feature called (De super heater) are placed in between LTSH outlet header and platen SH inlet header. There are two DESHS. The function of the DESH is to reduce steam temperature when necessary and maintain the SH outlet temperature at the design value during operation. The DESH cool off the steam by spraying feed water when called upon to do so.

After leaving the DESH, the steam now travels on its way to the vertical PSH inlet headerthe inlet header supplies steam to the platen SH coil. After passing through vertical platen SH coil, the steam enters the vertical PSH outlet header

From platen SH outlet header steam enters the final SH inlet header through two connecting pipes. In between these two headers are placed.Will allow the steam to pass through final SH coil to reach final SH outlet header. The main steam line will further carry the steam to HP turbine from either side.

The cold reheat steam flows from the HPT to reheater inlet header. Serving the RH vertical spaced Coils. In these coils steam is reheated up to design value and sent to IPT through hot reheat line from both RH outlet header. An emergency reheater DESH Unit has been provided at the inlet of RH.

SPECIFICATIONS OF 660 MW Super-critical boilers in Adani Power Limited:Technical Specifications:Steam flow : 2115.5 tons/hrSteam temperature : 571’CSteam pressure : 254 barReheat pressure : 43.59 barReheat temperature : 569’CFeed water temperature : 292.6’C

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Advantages of Supercritical Thermal Cycle:1) Improvement in power plant efficiency is more than 2%2) Reduction in coal consumption3) Reduction in Green house gases4) Overall reduction in Auxiliary Power Consumption5) Reduction in requirement of Ash dyke land & Consumptive water.6) Sliding pressure operation due to once through system.7) Uniform distribution of heat due to spiral wall arrangement leading to less

Boiler tube failure, thereby improving system continuity and availability of the station.

8) Low thermal stress in turbine.9) Less start up time of the boiler.

Disadvantages of Supercritical Thermal Cycle:1) Power consumption of Boiler Feed Water Pump is high.2) High Quality feed water is required3) Slight higher capital cost.

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ELECTRICAL SYSTEM OVERVIEW

In Adani Power Plant it consist of 9 units in which unit 1,2,3,4 are subcritical and unit-5, 6, 7, 8, 9 are supercritical plants. The power generated by these units is then transferred to the necessary parts of Gujarat.

For the transmission of this power in Adani Power Plant four switchyard units are placed. In which the first switchyard unit gets the power from Unit-1 & Unity-2 and its capacity is of 220 KV. The second Switchyard unit gets the power from Unit-3 & Unit-4 and its capacity is of 400 KV. The Third Switchyard Unit gets the power from Unit-5 & Unit-6 and its capacity is of 400 KV. The Fourth Switchyard Unit gets the power from Unit-7, Unit-8 & Unit-9 and its capacity is of 400 KV. Here STATION TRANSFORMER units are also used for the input power of Plant in case of failure or breakdown of entire plant power.

This power is supplied by the Government of Gujarat i.e. GEB to the station transformer and it is then distributed in the plant. The power generated by the plant via turbines is the supplied to the Generating transformer and it is then distributed to the switchyard units respectively.

Another small transformers of lower capacity i.e. Unit Auxiliary Transformer UAT’s are then supplied power from the turbo generators and then they are distributed. It consists of two UAT’s which is of 6.6 KV output and is used for running the auxiliaries fitted in the plant.

For the Backup plan the another two systems are made they are

1) Battery Backup Plan2) D.G.SET Backup Plan

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ADANI POWER PLANT

ELECTRICAL PROCESS IN PLANT

ADANI POWER PLANT comprises of 9 unit. It is mainly divided into 4 phase. Phase 1 consists of unit-1 & 2. Phase 2 consists of unit-3 & 4. Phase 3 consists of unit-5 & 6 and phase 4 consists of Unit- 7, 8, & 9. Capacity of plant is 4620 MW. Unit 1 to 4 has a capacity of 330 MW and Unit 5 to 9 has capacity of 660 MW. Generated power is then distributed to the different commercial area as well as industrial and SEZ’s area through the different switchyard and some amount of power is used for the plant to run the plant auxiliaries like motors, control circuits, etc.

In Unit 1 to 4 the mechanical energy generated by the high pressure, intermediate pressure and low pressure turbine is then transferred to the electrical energy by turbo alternator. Here the turbine is used as a prime mover for the turbo alternator. So by use of prime mover the armature winding rotates in the magnetic field which is produced by the field pole and the magnetic field is constant and when the armature winding cuts the magnetic field and induced EMF is generated and we can obtain this EMF via brush. This generated EMF is also called terminal voltage.

TURBO GENERATORTYPE 1255-460 RATED EXCITING

VOLTAGE542 V

RATED OUTPUT 330000 KW

RATED EXCITING CURRENT

2495 A

RATED VOLTAGE 24000 V ROTOR WINDING COOLANT

H2

RATED CURRENT 9339 A STATOR WINDING COOLANT

H20

POWER FACTOR 0.85 ROTOR WINDING INSULATION TYPE

F CLASS

FREQUENCY 50 STATOR WINDING INSULATION TYPE

F CLASS

SPEED 3000 STATOR CORE & ROTOR COOLANT

H2

ABSOLUTE HYDROGEN PRESSURE

0.4 STANDARD IEC

CONNECTION STAR PROTECTION TYPE IP54

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Now the generated voltage is then distributed to the different areas and also some part of power is used for the internal auxiliaries of the plant and for that it passes through different networks and different equipments. The power which is used for distribution is first send to the generating transformer and it is then distributed to the different areas by different networks and different switchyard.

POWER THAT IS USED FOR PLANT AUXILIARIES

In ADANI POWER PLANT there is mainly two type s of auxiliaries which is operated by 6.6. KV and 415V. The auxiliaries operated by 6.6 KV are known as H.T. auxiliaries. The auxiliary which is operated by 415 V is known as L.T. auxiliaries. So to operate these types of auxiliaries we need 6.6 KV and 415 Volt supply. Without these auxiliaries we cannot start up the plant. So first of all take this electric power fromfrom GEB or other power plant in form of 220 KV. In ADANI POWER PLANT for each unit there is one station transformer which is used to stepdown the voltage at 6.6 KV.

Schematic Diagram For this System is shown below: -

Here we can see that the power from the GEB or other sources which passes through the step down station transformer is then feeded to the 6.6 KV bus and we can operate H.T. Auxiliaries using this bus.

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ADANI POWER PLANT

Mainly we use this power at cooling tower auxiliaries’ electrostatic auxiliaries and for the TURBINE MCC and for BOILER MCC & the auxiliaries used for this operates on 415V because it is a low tensile auxiliary.

So there is one more transformer used at the place of cooling tower which step down the power at 415V for ESP there is also one transformer which step down the voltage at 415V & to run boiler side and turbine side auxiliaries we have to stepdown 6.6KV/ 415V. For running these L.T. auxiliaries we took power from 6.6 KV bus and by using stepdown transformer we get 415V.

Hence we can run this type of L.T. auxiliaries. Initially at the startup condition theseare the necessary auxiliaries we have to run so at initial time we have to take electricity from the GEB or from any other power plants. When the plant is started and generating rated voltage is obtained then we can use this power.

The power generated by the plant turbo generator is 330 MW with 24 Kilovolt and rated current is 9339 A with the frequency of 50 Hz. There are two Unit AuxiliariesTransformer’s which stepsdown the 24KV/6.6KV and then we can use L.T. and H.T. auxiliaries. In case of breakdown of the plant there are 2 backup plans.

1) Battery Backup Plan2) D.G. SET Backup Plan

They are explained as below: -

1) Battery Backup Plan: - In battery backup plan there is a large set of D.C. batteries which can give the supply to the plant auxiliaries for 8 to 10 hours. This D.C. batteries are continuously charged when plant is on running condition and gives the power when needed. This D.C supply is also used for the control circuit which uses normally 220 D.C volt supply.

2) D.G. SET Backup Plan: - In this type of backup plan there is one diesel engine which is coupled with the Generator and generates the useful power which is able to operate the plant auxiliaries. Diesel engine uses diesel as a fuel, it burns and generates the mechanical energy and it is supplied to the coupled generator and the armature of the generator rotates in the magnetic field and generates the useful power.

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ADANI POWER PLANT

ELEMENTS OF ELECTRICAL SYSTEM: -

1) Lightning arrestor: -

A lightning arrester is a device used on electrical power systems and telecommunications systems to protect the insulation and conductors of the system from the damaging effects of lightning. The typical lightning arrester has a high-voltage terminal and a ground terminal. When a lightning surge (or switching surge, which is very similar) travels along the power line to the arrester, the current from the surge is diverted through the arrestor, in most cases to earth.

In telegraphy and telephony, a lightning arrestor is placed where wires enter a structure, preventing damage to electronic instruments within and ensuring the safety of individuals near them. Smaller versions of lightning arresters, also called surge protectors, are devices that are connected between each electrical conductor in power and communications systems and the Earth.

These prevent the flow of the normal power or signal currents to ground, but provide a path over which high-voltage lightning current flows, bypassing the connected equipment. Their purpose is to limit the rise in voltage when a communications or power line is struck by lightning or is near to a lightning strike.

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ADANI POWER PLANT

2)Current Voltage Transformer: -

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

The tuning of the divider to the line frequency makes the overall division ratio less sensitive to changes in the burden of the connected metering or protection devices. The device has at least four terminals: a terminal for connection to the high voltage signal, a ground terminal, and two secondary terminals which connect 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 wound primary voltage transformers would be uneconomical. In practice, capacitor C1 is often constructed as a stack of smaller capacitors connected in series. This provides a large voltage drop across C1

and a relatively small voltage drop across C2.

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ADANI POWER PLANT

3) ISOLATORS: -

Adisconnector or isolator switch is used to make sure that an electrical circuit can be completely de-energised for service or maintenance. Such switches are often found in electrical distribution and industrial applications where machinery must have its source of driving power removed for adjustment or repair.

High-voltage isolation switches are used in electrical substations to allow isolation of apparatus such as circuit breakers and transformers, and transmission lines, for maintenance. Often the isolation switch is not intended for normal control of the circuit and is used only for isolation; in such a case, it functions as a second, usually physically distant master switch (wired in series with the primary one) that can independently disable the circuit even if the master switch used in everyday operation is turned on.

There are two types of isolators: -1) Single break type isolator2) Double Side Double Break type isolator

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ADANI POWER PLANT

4) CIRCUIT BREAKER: -

A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to detect a fault condition and, by interrupting continuity, to immediately discontinue electrical flow. Unlike a fuse, which operates once and then must 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.

TYPES OF CIRCUIT BREAKER: -

1) PANEL TYPE CIRCUIT BREAKER

Low voltage (less than 1000 VAC) types are common in domestic, commercial and industrial application, and include:

MCB (Miniature Circuit Breaker)—rated current not more than 100 A. Trip characteristics normally not adjustable. Thermal or thermal-magnetic operation. Breakers illustrated above are in this category.

MCCB (Molded Case Circuit Breaker)—rated current up to 2500 A. Thermal or thermal-magnetic operation. Trip current may be adjustable in larger ratings.

Low voltage power circuit breakers can be mounted in multi-tiers in low-voltage switchboards or switchgear cabinets.

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ADANI POWER PLANT

2) SF6 TYPE CIRCUIT BREAKER: -

A sulfur hexafluoride circuit breaker uses contacts surrounded by sulfur hexafluoride gas to quench the arc. They are most often used for transmission-level voltages and may be incorporated into compact gas-insulated switchgear.

In cold climates, supplemental heating or de-rating of the circuit breakers may be required due to liquefaction of the SF6 gas.

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ADANI POWER PLANT

5) CURRENT TRANSFORMER: -

A current transformer (CT) is used for measurement of electric currents. Current transformers, together with voltage transformers (VT) (potential transformers (PT)), are known as instrument transformers.

When current in a circuit is too high to directly apply to measuring instruments, a current transformer produces a reduced current accurately proportional to the current in the circuit, which can be conveniently connected to measuring and recording instruments.

A current transformer also isolates the measuring instruments from what may be very high voltage in the monitored circuit. Current transformers are commonly used in metering and protective relays in the electrical power industry.

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ADANI POWER PLANT

6) WAVE TRAP:-

Line trap also is known as Wave trap. This is relevant in Power Line Carrier Communication (PLCC) systems for communication among various substations without dependence on the telecom company network. The signals are primarily teleprotection signals and in addition, voice and data communication signals. Line trap also is known as Wave trap. What it does is trapping the high frequency communication signals sent on the line from the remote substation and diverting them to the telecom/teleprotection panel in the substation control room (through coupling capacitor and LMU).

This is relevant in Power Line Carrier Communication (PLCC) systems for communication among various substations without dependence on the telecom company network. The signals are primarily teleprotection signals and in addition, voice and data communication signals.

The Line trap offers high impedance to the high frequency communication signals thus obstructs the flow of these signals in to the substation busbar. If there were not to be there, then signal loss is more and communication will be ineffective/probably impossible.

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ADANI POWER PLANT

7) TRANSFORMER: -

A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field through the secondary winding. This varying magnetic field induces a varying electromotive force (EMF), or "voltage", in the secondary winding. This effect is called inductive coupling.

If a load is connected to the secondary, current will flow in the secondary winding, and electrical energy will be transferred from the primary circuit through the transformer to the load. In an ideal transformer, the induced voltage in the secondary winding (Vs) is in proportion to the primary voltage (Vp) and is given by the ratio of the number of turns in the secondary (Ns) to the number of turns in the primary (Np) as follows:

By appropriate selection of the ratio of turns, a transformer thus enables an alternating current (AC) voltage to be "stepped up" by making Ns greater than Np, or "stepped down" by making Ns less than Np. The windings are coils wound around a ferromagnetic core, air-core transformers being a notable exception.

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ADANI POWER PLANT

8) REACTORS: -

Essentially a reactor is an inductor.  Physically it is a coil of wire that allows a magnetic field to form around the coil when current flowsthrough it. When energized, it is an electric magnet with the strength of the field being proportional to the amperage flowing and the number of turns.

A simple loop of wire is an air core inductor. More loops give a higher inductance rating. Quite often some ferrous material such as iron is added as a core to the winding. This has the effect of concentrating the lines of magnetic flux there by making a more effective inductor.

9) INSULATOR: -

A true insulator is a material that does not respond to an electric field and completely resists the flow of electric charge. In practice, however, perfect insulators do not exist. Therefore, dielectric materials with high dielectric constants are considered insulators. In insulating materials valence electrons are tightly bonded to their atoms. These materials are used in electrical equipment as insulators or insulation. Their function is to support or separate electrical conductors without allowing current through themselves. The term also refers to insulating supports that attach electric power distribution or transmission conductors to utility poles or transmission towers.

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ADANI POWER PLANT

SWITCHYARD INTRODUCTION: -

A Switchyard or Substation, consisting of large breakers and towers, is usually located in an area close to the plant. The substation is used as the distribution centre where:

electrical power is supplied to the plant from the outside, and electrical power is sent from the plant

Often there are at least 2 main Buses. Very high voltages (typically 220,000 or 345,000 volts) are present. Gas and oil circuit breakers are used. The gas (e.g. sulphurhexafluoride) or oil is used to extinguish the arc caused when a breaker is opened, either by a control switch or due to a fault. Manually or motor operated disconnects are provided on either side of the breaker to allow the breaker to be electrically isolated so that maintenance work can be performed. 

Switchyard forms an integral part of any power plant i.e. Industrial CPP, Thermal Power Utilities, Gas Turbines based power plants or Hydel power plants. These power plants have their main plant equipment integral controls (Boiler / Turbine / Gas Turbine / Hydro Turbine) as well as plant DCS System (BoP / Station C & I). While the entire power plant is integrated at the DCS level, true unification is achieved by incorporating / integrating switchyard controls (SCADA) also in the plant DCS.

The Supervisory control and data acquisition system (SCADA) of switchyard consists of Operator Stations, Engineer's Stations, Historical Storage, Computers and associated peripherals and the switchyard bay control systems interconnected through a high speed network .

The system constitutes several operator work stations and engineer's work station with high resolution Color display monitors, touch screen, function key board, mouse, track ball and printers.

The system collects digital and analog information available throughout the plant and presents information in various graphic displays, alarms, logs, reports. 

The operator can perform control via CRT.

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ADANI POWER PLANT

FEATURES OF SWITCHYARD: -

Monitoring of status of switchyard equipment like isolators, breakers, ground switches

Issue of close/open commands to isolators, breakers

Monitoring of system parameters like voltage, current, frequency, MW, MVAR, energy

Time stamping of alarms, events, protective relay operations

Presentation of information useful to operator in different forms

Report generation

Historical storage and retrieval

Remote control and monitoring from Load dispatch centre through fiber optic/PLCC communication

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ADANI POWER PLANT

PHASE 1 SWITCHYARD

Phase 1 Switchyard is known as three bus bar scheme type switchyard. In which there are two main bus (main bus-1 & main bus-2) and third is transfer bus. Unit-1 & unit-2 charges this three buses with the use of different auxiliaries like generator transformer G.T., Current Transformer C.T., Lightning arrestor L.A., Capacitive Voltage Transformer C.V.T., Isolator, Insulators, etc.

In phase-1 generator power of unit-1 &2 are used. First the generator power is supplied to the generating transformer which is delta/star type three phase transformer which has a capacity of 240/320/400 MVA & this transformer is oil natural airforced type transformer. So this transformer converts the input voltage to the 220 KV.

This power charges the buses using many types of equipment. This equipments are used for protection purpose & metering purpose. So power has to pass through the different equipments and at least charge the buses. So first power is supplied to the generating transformer and it supply the power to current transformer by the line. Current transformer is for protection purpose and it consists of 5 secondary cores.

In the CT-1 each have different windings. In between generating transformer and current transformer, the lightning arrestor and the capacitive voltage transformer are parallel connected among of them.

First the L.A is connected which is used for the line protection. When a heavy spark occurs or heavy current flows lightning arrestor ground this faulty current and we can protect the line from heavy faulty current.

Now from CT the line is divided into 2 parts. One is directly connected to the transfer bus through the isolator. Isolator used here are double side double break type isolator which consists of motoring mechanism to isolate the line.

The other part which then charges the main bus-1 & 2 and the power passes first to isolator which has two ground switches on both the ends.

Earth switch are provided for the grounding purpose. In case of maintenance of the line the ground switches of the isolators are used. Then the power passes through the SF6 circuit breaker which is operated manually and automatically.

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Now the power is divided into two paths and it charge BUS-1 & 2 through the isolator. Here both the buses are charged and we can take power from any of the Bus and can feed it to the feeder and supplies it to the station transformer also.

If the buses are charged one time we can use it for distributing the power to the different areas. We can distribute the power by using main bus-1 and main bus-2 or by the use of transfer bus.

If we want to feed the power from the main bus-1 then the isolator of main bus-2 so that transfer bus remains open & main bus-1 isolator remains close. First power passes through the isolator and then it passes through the circuit breaker and it again passes through the current transformer which has 5 core and each core is used for specific protection and metering purpose.

And then it is again flows through the C.T-2 which is mainly used for metering. It has two core if one of them is damaged then we can get the reading from the other core. Now the power flows through the wave trap.

The use of this wave trap is to communicate between two substations and the function is for PLCC operation. Then two CVT’s are parallel connected to the feeder line. One CVT is used for protection and other one is used for tariff metering & one lightning arrestor is parallel connected to the feeder line to protect the line from the heavy faulty current.

At one end of the bus-1 and main bus-2 there is one CVT parallel connected for the protection purpose of the buses. If the bus outgoing voltage and incoming voltage are not same at that time it finds the difference between them and take some necessary operation.

Two station transformers are there in the phase-1 to run the plant auxiliaries in the case of shunt down. We have to take this power from the GEB or other power plants but here the bus-1 is charged so we can take electricity from the main bus-1 or main bus-2.

Station transformer has 3 windings and they are star connected and it step down the voltage from 220 to 6.6 KV and now we can use this power to run the plant auxiliaries of Unit-1 & Unit-2. In both these units plant auxiliaries load are shared on station transformer and unit auxiliary transformer.

In phase-1 switchyard there is one bus coupler and one bus transfer. Bus coupler is used to couple both the main bus-1 & 2. In case of any abnormal situation in which

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we cannot able to charge the second bus then by the use of bus coupler we can charge the second bus by one bus with the use of bus coupler.

There are simple connections between two bus and this connection consists of isolator, CT& SF6 circuit breaker. Second is Bus transfer which is used for couple of transfer bus to the any of the main bus. So with the use of the Bus Transfer we can transfer the power from the transfer bus to the any of the main bus.

MAIN BUS 1 MAIN BUS 2 TRANSFER BUSVOLTAGE (KV) 220 220 220CURRENT (A) 2500 2500 1600

FREQUENCY (Hz) 50 50 50

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PHASE-2 SWITCHYARD

This switchyard is known as interconnecting bus scheme type switchyard. In this switchyard there are two buses which is known as 400 KV main bus- 1& 2. This switchyard gives the feeder the power of unit-3 & 4 and the power of ICT-1 &2. The phase-2 switchyard has very important role because phase-2, 3 &4 buses are of 400 KV but the phase-1 is of 200 KV bus.

So there are two interconnecting transformer which connects the whole phase bus. Interconnecting transformer can convert the power from 220KV to 400 KV and also 400 KV to 220 KV.

Interconnecting transformer is connected with Phase-1 via Bus transfer and bus coupler of Phase-1 because by which the power can be transferred into the whole 3 buses of phase-1. ICT-1 is connected with the Bus Coupler and ICT-2 is connected with the Bus Transfer.

The Bus Coupler and Bus Transfer is connected with ICT-1 &2 with the help of isolator & parallel connected with lightning arrestor. So when there is no use of interconnection the isolator opens and the power interconnection between Phase-1 & 2 Bus will not be held.

The power of Generator flows into the switchyard. In between there is one generating transformer which step ups the voltage to the 400 KV. This power is then feeded to the Circuit Breaker but in between there is one isolator and parallel connected Capacitive Voltage Transformer and Lightning Arrestor.

The Circuit Breaker ends are connected with the two buses with the help of breaker side isolator. When the powers of any bus have to transfer or for charging of bus at that time the isolator becomes close of that side. The Bus isolator is connected with the Circuit Breaker and it is connected with the isolator.

That line connects with the Circuit Breaker with the help of CB side isolator. There are two Current Transformer on both side of the Circuit Breaker for Protection & Metering Purpose.

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By this arrangement two buses are connected with the line and the line power is then feeded to the feeder line but in between them there are some equipments which are isolator, wave trap and parallel connected 2 CVT & 1 Lightning Arrestors.

The same power flow scheme happens between the ICT & the feeder line. The power of ICT is feeded to the feeder via a SF6 Circuit Breaker which is connected to the 2 Buses through the series connected Current Transformer & Isolator to the Bus side Isolator.

The Bus side Isolator is connected to the Current transformer & this CT is connected with the Circuit Breaker & it is connected with isolator and it is connected with the Bus.

Here the channel of ISOLATOR –CB-CT-ISOLATOR is for the protection purpose. So by this both bus connects via Circuit Breaker and it is connected with the line. This line feeds the power to the feeder via Isolator, Wave trap & two parallel connected CVT & one L.A. Here two CVT’s are connected for Protection and Tariff metering purpose.

There are two Bus Sectionalizer to connect the Bus because if there is any fault or any maintenance happens all feeder line does not shut down. So to feed the power to the feeder there are two Bus Sectionalizer. One for main Bus-1 and other for main Bus-2 which connects with the main bus-1 & main bus-2 of phase-3. The Bus Sectionalizer consists two isolator in between there is one Circuit Breaker. So when any faulty current flows in any phase Circuit Breaker opens up and two buses are disconnected.

In this Phase-2 the isolator are Double side Double Break Type Isolator which has two earthing switch. Any type of maintenance occurs both the side of the maintenance location the earthing closes and protection is give to the worker from inductive power.

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PHASE-3 SWITCHYARD

Phase-3 switchyard has a capacity of 440 KV. Here the generating transformer unit-5 & Unit-6 are connected. The power generated by both this units is then supplied to the generating transformer and is then transferred to the switchyard. The transformer used here are three single phase transformer for one unit and same arrangement for the other unit. In Phase-3 Switchyard it consists of one and half Circuit Breaker arrangement.

ONE AND HALF CIRCUIT BREAKER SCHEME: -

In this scheme between two buses i.e. main bus-1 and main bus-2 three circuit breakers are used. Now for the protection purpose across this circuit breaker two isolators are placed. As a result for a single bus it can be protected by one and half circuit breaker placed between the buses. Hence it is named as ONE AND HALF CIRCUIT BREAKER SCHEME. This arrangement is also applied in the Phase-4 Switchyard.

Phase consists of four dia in which the first dia is of generating transformer Unit-5 and the other dia is of the station transformer which is of incoming line for unit-5. The Station Transformer is operated in case of any failure, breakdown or in startup condition.

The Third dia is of the unit-6. The Unit-6 generates 660 MW power and is then transferred to the switchyard via three single phase transformer.

The Fourth dia consists of the 2 reactors at both the end of the Buses. The Reactors are used for the maintaining the amount of the voltage in the line. If the voltage increases then the reactor decreases it to the necessary values then it transfers and vice-versa.

FIRST & SECOND DIA: -

First Dia is of unit-5. The power is transferred from Bus-1 to the Isolator and to the Circuit Breaker. Through this circuit breaker power, input of uni-5 connection appears and gets divided into two paths. The other path has also the same arrangement of the circuit breaker as explained and gets divided into two paths one feeds the feeder and other line charges the bus-2 via circuit breaker and isolator arrangement. The arrangement of Circuit Breaker is known as one & half Circuit Breaker Arrangement.

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Second Dia is of the Station Transformer-5.The power from the GEB is fed to this diaand is then transferred to the ST-5 and gets distributed using the one & half circuit Breaker arrangement.

THIRD & FOURTH DIA: -

Third Dia consists of the generating transformer Unit-6. The power generated by this Unit is then divided into two paths one goes to the Bus-1 and other path goes to the Bus-2 via Circuit Breaker. The first path power comes to the isolator and goes to the circuit breaker and through the isolator charge the Bus-1. For the other path it then feeds to the feeder via SF6 type circuit breaker & is then transferred. For the charging of Bus-2 the power from Bus-1 transfers from SF6 breaker to the isolator and via other breaker it charge the Bus-2.

Fourth dia consists of Reactor Units on both the side of the Bus. The Reactor units are installed and maintain the voltage. The power between both the reactors circulates via one and half circuit breaker arrangement and it then transfers to the Reactor-2 via Circuit Breaker and isolator.

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UNIT-4 SWITCHYARD: -

This Switchyard has a capacity of 400 KV & it consists of unit -7, 8 & 9 and two Station Transformers. The power generated by the Unit-7 is then transferred between two buses.

The one path charges the Bus-1 via Circuit Breaker and Isolator while the other path charges the Bus-2 via two Circuit breakers and four Isolators. The feeder line is also connected after the isolator of second Circuit Breaker. This then feeds to the HVDC terminals and uses its transmission of power.

Same arrangement is used for the Unit-8 & 9 and is the used to feed for HVDC transmission.

Station Transformer-7 & 8 are used for the input of the plant in case of accident or failure the power from the source is then transferred to the ST-7 & ST-8 via one and half Circuit Breaker arrangement and is also used for the charging of the Bus-1 & Bus-2.

This power then can be transferred to the necessary units. Here the station Transformer power comes from phase-1 via underground cable system.

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HVDC TRANSMISSION

High voltage Direct Current transmission is used for the bulk transmission of electrical power. For Long distance transmission HVDC transmission are less expensive and suffer lower electrical losses. For shorter distance high cost of DC Conversion Equipments compared to an AC system may be warranted where other benefits of Direct Current links are useful.

HVDC EQUIPMENTS USED: -

1) Shunt Capacitors

2) Convertors (Silicon Controlled Rectifiers, Converters)

3) Smoothing Reactors

TRANSMISSION MODES: -

1) MONOPOLAR MODE: - The line has one energized conductor with the return path through the Earth.

2) BIPOLAR MODE: - The Bipolar Transmission gives two circuits which are almost independent of each other. Bipolar has one conductor at a positive potential with respect to the ground and a second conductor operating at a negative potential of the same magnitude.

ADVANTAGES OF HVDC TRANSMISSION: -

1) Economic for large distance bulk transmission

2) Greater power per conductor and simpler Line construction.

3) Ground return is possible.

4) No charging current and skin effect.

5) Less voltage regulation problem because only IR drop is involved.

6) Easy reversibility and controllability of power at DC link.

7) DC line is an asynchronous or flexible link it can interconnect two rigid systems

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Operating at different frequencies.

DISADVANTAGES OF HVDC TRANSMISSION: -

1) Installation of complicated convertors and DC switchgear is expensive.

2) Converters require considerable reactive power.

3) Harmonics are generated which requires filter.

4) Convertors do not have overload capacity.

5) Reactive power required by the load is supplied locally as no reactive power can be transmitted over a DC link.

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