ABSTRACT

to meet the power demands of the country, it is required to set up new project,

time to time so that demand and generation gap may be narrowed but most

important is to full utilization of existing capacity .this may be possible only by

increasing the reliability, availability, maintainability of power generation

units and by operating the units at its full capacity.

This vocational training report is concerned with the overall operation of the

plant, water treatment in the plant and thermodynamic cycles used in NTPC,

Auraiya gas power station.

AKNOWLEDGEMENT

A summer project is a golden opportunity for learning and self development . I

consider myself very lucky and honored to have a opportunity provided by

NTPC.

I wish to express my indebted gratitude and special thanks to " MR. M.K.

Sharma sir, MANAGER (HR-EDC) NTPC, auraiya" who in spite of being

extraordinarily busy with his duties, took time to manage the whole summer

training in proper way and allowing me to carry out my industrial training work

at their esteemed organization.

A humble ‘Thank you’ Sir.

It is my glowing feeling to place on record my best regards, deepest sense of

gratitude to all the engineers (associated in NTPC) for their judicious and

precious lectures and guidance about the operation of power plant. which were

extremely valuable for my study both theoretically and practically.

I express my deepest thanks to MR. S.K. Verma sir for their guidance and

support. He supported to us by showing different method of information

collection about the company. He helped all time when we needed and he gave

right direction toward completion of project.

At the last but not least my humble thanks to all who helped me in complearing

my summer training project.

(Gopesh kumar)

Place:- NTPC dibiyapur auraiya

Date:- 22th july 2014

-:CONTENTS:-

INTRODUCTION TO NTPC

TOTAL INSTALLED CAPACITY OF NTPC

INTRODUCTION OF NTPC,AURAIYA GAS POWER STATION

COMBINED CYCLE AND COMBINED CYCLE PLANT

AIR COMPRESSOR AND COMBUSTION CHAMBER

FULES

TURBINES AND GAS TURBINE LAYOUT OF NTPC, AURAIYA

BOILERS AND WASTE HEAT RECOVERY BOILERS

BOILER ECONOMISER AND WASTE HEAT RECOVERY

WATER TREATMENT PLANT,STORAGE AND RESORCES

STEAM TURBINE

VOLTAGE GENERATOR

PASSOUT OR EXTRACTIO TURBINE

CIRCULATING WATER PUMP AND DEAERATOR

COOLING SYSTEM

CONTROLE SYSTEM OF THE PLANT

ELECTRICAL AND SWITCHYARD DEPARTMENT

DEFFFERENT TYPE OF EQUIPMENT USED IN SUB STATIONS

CONCLUSION

REFFERENCE

INTRODUCTION:-

Figure :- image from main plant NTPC auraiya

NTPC Limited (formerly known as National Thermal Power Corporation

Limited) is a Central Public Sector Undertaking (CPSU) under the Ministry

of Power, Government of India. It is the largest power company in India

with an electric power generating capacity of 43,128 MW. Although the

company has approx. 18% of the total national capacity it contributes to

over 27% of total power generation due to its focus on operating its power

plants at higher efficiency levels (approx. 83% against the

national PLF rate of 78%)

It was founded by Government of India in 1975, which held 75% of its

equity shares on 31 March 2013 (after divestment of its stake in 2004,

2010 and 2013).

In May 2010, NTPC was conferred Maharatna status by the Union

Government of India. It is listed in Forbes Global 2000 for 2014 at 424th

rank in the world.

NTPC IN INDIAN POWER SECTOR:-

Presently, NTPC generates power from Coal and Gas. With an installed

capacity of 43,128 MW, NTPC is the lairgest power generating major in the country. It has also diversified into hydro power, coal mining, power equipment

manufacturing, oil & gas exploration, power trading & distribution. With an increasing presence in the power value chain, NTPC is well on its way to

becoming an “Integrated Power Major.”

INSTALLED CAPACITY:-

Present installed capacity of NTPC is 43,128 MW (including 5,974 MW through JVs)

comprising of 38 NTPC Stations (17 Coal based stations, 7 combined cycle gas/liquid

fuel based stations), 7 Joint Venture stations (6 coal based and one gas based) and 7

renewable energy projects.

NO. OF PLANTS CAPACITY (MW)

NTPC Owned

Coal 17 33,015

Gas/Liquid Fuel 7 4,044

Renewable energy projects 7 95

Total 31 37,154

Owned By JVs

Coal & Gas 7 5,974

Total 38 43,128

Regional Spread of Generating Facilities

REGION COAL GAS Renewable TOTAL

Northern 9,015 2,334 20 11,369

Western 10,840 1,313 50 12,203

Southern 4,600 370 15 4,975

Eastern 8,560 - 10 8,570

JVs 4,034 1,967 - 6,001

Total 37,049 5,984 95 43,128

PROJECT PROFILE:-

COAL BASED POWER STATIONS:-

With 17 coal based power stations, NTPC is the largest thermal power generating

company in the country. The company has a coal based installed capacity of 33,015 MW.

COAL BASED(Owned by

NTPC) STATE

COMMISSIONED

CAPACITY(MW)

1. Singrauli Uttar Pradesh 2,000

2. Korba Chhattisgarh 2,600

3. Ramagundam Telangana 2,600

4. Farakka West Bengal 2,100

5. Vindhyachal Madhya Pradesh 4,260

6. Rihand Uttar Pradesh 3,000

7. Kahalgaon Bihar 2,340

8. Dadri Uttar Pradesh 1,820

9. Talcher Kaniha Orissa 3,000

10. Feroze Gandhi, Unchahar Uttar Pradesh 1,050

11. Talcher Thermal Orissa 460

12. Simhadri Andhra Pradesh 2,000

13. Tanda Uttar Pradesh 440

14. Badarpur Delhi 705

15. Sipat Chhattisgarh 2,980

16. Mauda Maharashta 1,000

17. Barh Bihar 660

Total 33,015

Coal Based Joint Ventures:

COAL BASED

(Owned by JVs) STATE

COMMISSIONED

CAPACITY

1. Durgapur West Bengal 120

2. Rourkela Orissa 120

3. Bhilai Chhattisgarh 574

4. Kanti Bihar 220

5. IGSTPP, Jhajjar Haryana 1500

6. Vallur Tamil Nadu 1500

Total 4,034

GAS/LIQUID FUEL BASED POWER STATIONS:-

The details of NTPC gas based power stations is as follows

GAS BASED

(Owned by NTPC) STATE

COMMISSIONED CAPACITY(MW)

1. Anta Rajasthan 419.33

2. Auraiya Uttar Pradesh 663.36

3. Kawas Gujarat 656.20

4. Dadri Uttar Pradesh 829.78

5. Jhanor-Gandhar Gujarat 657.39

6. Rajiv Gandhi CCPP Kayamkulam Kerala 359.58

7. Faridabad Haryana 431.59

Total 4,017.23

GAS BASED JOINT VENTURES:-

COAL BASED

(Owned by JVs) STATE

COMMISSIONED

CAPACITY

1. RGPPL Maharashtra 1967.08

Total 1,967.08

FUTURE PLANNING:-

India’s current capacity of 233,930MW, NTPC accounts for 18.14% with an installed

power generation capacity of 43,128MW. The utility plans to add 14,038MW during the

12th Plan period (2012-17) and has budgeted capital expenditure of Rs.1.5 trillion. It has

set up a target of becoming a 128,000MW power producer by the year 2032.

INTRODUCTION TO GAS POWER STATION

NTPC (AURAIYA):-

Figure :- image from main plant NTPC auraiya

NTPC Auraiya is located at Dibiyapur in Auraiya district in the Indian state

of Uttar Pradesh. The power plant is one of the gas based power plants

of NTPC. The plant has 4 gas turbine(GT) and 2 steam turbine (ST)with 4 waste

heat recovery boiler(WHRB).The gas for the power plant is sourced

from GAIL HBJ Pipeline - South Basin Gas field. Source of water for the power

plant is Auraiya - Etawah Canal. Plant is basically devided in to two module

and each module has 2GTand 1ST and 2WHRB and their capacities are as

follows

MODULE 1:- Gas turbine capacity : 2×111.19 MW

Steam turbine capacity: 109.3 MW Total module1 capacity : 331.68 MW

MODULE 2:- Same as module 1

Total module2 capacity: 3331.68 MW

TOTAL PLANT CAPACITY: 663.36 MW

CAPACITY:-

Stage Unit Number

Installed Capacity (MW)

Date of Commissioning

GT / ST

1st 1 111.19 1989 March GT

1st 2 111.19 1989 July GT

1st 3 111.19 1989 August GT

1st 4 111.19 1989 September GT

1st 5 109.3 1989 December ST

1st 6 109.3 1990 June ST

Total Six 663.36

THE BASIC DIAGRAM OF ARRANGEMENT OF

UNITS IN AURAIYA GAS POWER PLANT:-

STATION CAPACITY

663.36MW

111.19MW 111.19MW 111.19MW 111.19MW

COMBINED CYCLE:-

Combining two or more thermodynamic cycles results in improved overall

efficiency, reducing fuel costs. In stationary power plants, a widely used

combination is a gas turbine (operating by the Brayton cycle) burning natural

gas or synthesis gas from coal, whose hot exhaust powers a steam power

plant (operating by the Rankine cycle). This is called a Combined Cycle Gas

MODULE #1

2×111.19 +109.3 =

331.68MW

MODULE# 2

2×111.19 +109.3 =

331.68MW

ST# 1

109.3 MW

ST# 2

109.3 MW

WHRB #1

WHRB#2 WHRB#3 WHRB#4

GT#1

111.19m

wWW

GT#1

GT#3 GT#4

Turbine (CCGT) plant, and can achieve a thermal efficiency of around 60%, in

contrast to a single cycle steam power plant which is limited to efficiencies of

around 35-42%.

Figure :-combined cycle diagram

COMBINED CYCLE PLANTS:-

The Combined Cycle Power Plant or combined cycle gas turbine, a gas turbine

generator generates electricity and waste heat is used to make steam to generate

additional electricity via a steam turbine. The gas turbine is one of the most

efficient one for the conversion of gas fuels to mechanical power or electricity.

The use of distillate liquid fuels, usually diesel, is also common as alternate

fuels.

More recently, as simple cycle efficiencies have improved and as natural gas

prices have fallen, gas turbines have been more widely adopted for base load

power generation, especially in combined cycle mode, where waste heat is

recovered in waste heat boilers, and the steam used to produce additional

electricity.

This system is known as a Combined Cycle. The basic principle of the

Combined Cycle is simple: burning gas in a gas turbine (GT) produces not only

power – which can be converted to electric power by a coupled generator – but

also fairly hot exhaust gases.

Figure - Combined cycle power plant scheme Routing these gases through a water-cooled heat exchanger produces steam, which can be turned into electric power with a coupled steam turbine and

generator.

COMBINED CYCLE OPERATION AT NTPC

AURAIYA:-

AIR COMPRESSOR:-

in thermal power plant. Compressed air plays the vital role in every gas turbine

plant. Gas turbine is used in power plant to drive the generator, by which we

can produce electricity with other arrangements.

Usually rotary air compressor is used with a gas turbine. Mostly centrifugal

compressors or axial compressors are used.

There are 4 compressor in the plant.4 used in GT and is used in emergency GT.

These are 19 stages series compressor.

Compressor pressor ratio is :- 6.9:1

COMBUSTION CHAMBER:-

Figure:- combustion chamber of gas turbine

The combustion process increases the internal energy of a gas, which translates

into an increase in temperature, pressure, or volume This increase in pressure or

volume can be used to do work

FUELS:-

Mainly two fuel are used in this gas power plant which are listed below

Natural gas

Neptha

Natural gas is supplied by GAIL, dibiyapur and taken directly from the

pipeline which goes from hazira to jagdishpur.

The other fuel is supplied by IOC ,Kanpur and Mathura

STORAGE CAPACITY FOR NEPTHA:- There are two tanks for storarig neptha fuel each having a capacity of 1500KL.

There are three transfer pumps for loading fuel from tankers .the two pumps

works and third is auxiliary. There twelve unloading pipes ,thus twelve truck is

unloading at a time.

If turbine is running at full load then it consumes 20 KL neptha fuel in one

hour

Figure:-GAIL PATA Figure:-IOCL MATHURA

GAS TURBINE:-

A gas turbine, also called a combustion turbine, is a type of internal combustion

engine. It has an upstream rotating compressor coupled to a

downstream turbine, and a combustion chamber in-between.

Figure :-gas turbine

The basic operation of the gas turbine is similar to that of the steam power

plant except that air is used instead of water. Fresh atmospheric air flows

through a compressor that brings it to higher pressure. Energy is then added by

spraying fuel into the air and igniting it so the combustion generates a high-

temperature flow. This high-temperature high-pressure gas enters a turbine,

where it expands down to the exhaust pressure, producing a shaft work output in

the process. The turbine shaft work is used to drive the compressor and other

devices such as an electric generator that may be coupled to the shaft. The

energy that is not used for shaft work comes out in the exhaust gases, so these

have either a high temperature or a high velocity. The purpose of the gas turbine

determines the design so that the most desirable energy form is maximized. Gas

turbines are used to poweraircraft, trains, ships, electrical generators, or

even tanks.

GAS TURBINE LAYOUT OF NTPC ,AURAIYA:-

Gas turbine engines derive their power from burning fuel in a combustion

chamber and using the fast flowing combustion gases to drive a turbine in much

the same way as the high pressure steam drives a steam turbine.

One major difference however is that the gas turbine has a second turbine acting

as an air compressor mounted on the same shaft. The air turbine (compressor)

draws in air, compresses it and feeds it at high pressure into the combustion

chamber increasing the intensity of the burning flame.

It is a positive feedback mechanism. As the gas turbine speeds up, it also causes

the compressor to speed up forcing more air through the combustion chamber

which in turn increases the burn rate of the fuel sending more high pressure hot

gases into the gas turbine increasing its speed even more.

Uncontrolled runaway is prevented by controls on the fuel supply line which

limit the amount of fuel fed to the turbine thus limiting its speed.

The thermodynamic process used by the gas turbine is known as the Brayton

cycle. Analogous to the Carnot cycle in which the efficiency is maximised by

increasing the temperature difference of the working fluid between the input

and output of the machine, the Brayton cycle efficiency is maximised by

increasing the pressure difference across the machine. The gas turbine is

comprised of three main components: a compressor, a combustor, and a turbine.

The working fluid, air, is compressed in the compressor (adiabatic compression

- no heat gain or loss), then mixed with fuel and burned by the combustor under

constant pressure conditions in the combustion chamber (constant pressure heat

addition). The resulting hot gas expands through the turbine to perform work

(adiabatic expansion). Much of the power produced in the turbine is used to run

the compressor and the rest is available to run auxiliary equipment and do

useful work. The system is an open system because the air is not reused so that

the fourth step in the cycle, cooling the working fluid, is omitted.

Figure :-gas turbine

Gas turbines have a very high power to weight ratio and are lighter and smaller

than internal combustion engines of the same power. Though they are

mechanically simpler than reciprocating engines, their characteristics of high

speed and high temperature operation require high precision components and

exotic materials making them more expensive to manufacture.

ELECTRICAL POWER GENERATION:-

In electricity generating applications the turbine is used to drive a synchronous

generator which provides the electrical power output but because the turbine

normally operates at very high rotational speeds of 12,000 r.p.m or more it must

be connected to the generator through a high ratio reduction gear since the

generators run at speeds of 1,000 or 1,200 r.p.m. depending on the AC

frequency of the electricity grid.

TURBINE CONFIGURATIONS:- Gas turbine power generators are used in two basic configurations

Simple Systems consisting of the gas turbine driving an electrical power

generator.

Combined Cycle Systems which are designed for maximum efficiency in which

the hot exhaust gases from the gas turbine are used to raise steam to power a

steam turbine with both turbines being connected to electricity generators.

Turbine Performance

Turbine Power Output

To minimise the size and weight of the turbine for a given output power, the

output per pound of airflow should be maximised. This is obtained by

maximising the air flow through the turbine which in turn depends on

maximising the pressure ratio between the air inlet and exhaust outlet. The main

factor governing this is the pressure ratio across the compressor which can be as

high as 40:1 in modern gas turbines. In simple cycle applications, pressure ratio

increases translate into efficiency gains at a given firing temperature, but there

is a limit since increasing the pressure ratio means that more energy will be

consumed by the compressor.

SYSTEM EFFICIENCY:-

Thermal efficiency is important because it directly affects the fuel consumption

and operating costs.

SIMPLE CYCLE TURBINES:- A gas turbine consumes considerable amounts of power just to drive its

compressor. As with all cyclic heat engines, a higher maximum working

temperature in the machine means greater efficiency (Carnot's Law), but in a

turbine it also means that more energy is lost as waste heat through the hot

exhaust gases whose temperatures are typically well over 1,000°C .

Consequently simple cycle turbine efficiencies are quite low. For heavy plant,

design efficiencies range between 30% and 40%. (The efficiencies of aero

engines are in the range 38% and 42% while low power microturbines

(<100kW) achieve only 18% to 22%). Although increasing the firing

temperature increases the output power at a given pressure ratio, there is also a

sacrifice of efficiency due to the increase in losses due to the cooling air

required to maintain the turbine components at reasonable working

temperatures.

COMBINED CYCLE TURBINES:-

It is however possible to recover energy from the waste heat of simple cycle

systems by using the exhaust gases in a hybrid system to raise steam to drive a

steam turbine electricity generating set . In such cases the exhaust temperature

may be reduced to as low as 140°C enabling efficiencies of up to 60% to be

achieved in combined cycle systems.

In combined-cycle applications, pressure ratio increases have a less pronounced

effect on the efficiency since most of the improvement comes from increases in

the Carnot thermal efficiency resulting from increases in the firing temperature.

Thus simple cycle efficiency is achieved with high pressure ratios. Combined

cycle efficiency is obtained with more modest pressure ratios and greater firing

temperatures.

APPLICATIONS:-

Gas turbines can be used for large scale power generation. Examples are

applications delivering 600 MW or more from a 400 MW gas turbine coupled to

a 200 MW steam turbine in a co-generating installation. Such installations are

not normally used for base load electricity generation, but for bringing power to

remote sites such as oil and gas fields. They do however find use in the major

electricity grids in peak shaving applications to provide emergency peak power.

Low power gas turbine generating sets with capacities up to 5 MW can be

accommodated in transportation containers to provide mobile emergency

electricity supplies which can delivered by truck to the point of need.

BOILER:-

A boiler or steam generator is a device used to create steam by

applying heat energy to water. Although the definitions are somewhat

flexible, it can be said that older steam generators were commonly

termed boilers and worked at low to medium pressure (1–300 psi or

6.895–2,068.427 kPa) but, at pressures above this, it is more usual to speak

of a steam generator.

NTPC auraiya gas power plant has 4 waste haet recovery boiler . all the 4

boiler are non fired and water tube boiler

WASTE HEAT RECOVERY BOILERS (WHRB):-

a WHRB consist of a super heater ,a boiler ,an cconomizer and a stem drum .

waste heat recovery boiler may be horizontal or vertical shell boiler or water

tube boiler. they could be desined to suit indivisual application ranging through

gases from furnaces ,incinerators, gas turbine and die sel exhaust. the prim

requirment is that waste gasse must contain sufficient usable heat to produce

steam or hot water at the condition required.

Figure :-boiler configuration

some boilers may be dealt with my maintaining gas –exit at a pre determined

level to prevent dew point being reached and others by soot blowing. currently,

there is a string interest in small combined heat and power (CHP) stations,

thease will normally incorporate a wsta heat boiler.

WATER TREATMENT PLANT, STORAGE AND

RESORCE:-

Since steam is taken out continuously and returned to the boiler, losses due to

blow downs leakage have to have to be made up for mentaining designed boiler

water quantity by means of the level gauges provided on the boiler drum. For

this continuous make up water is added the boiler water system. Since this make

up requires pure water this quality water is obtained by demineralised

(DM) water treatment plant. For this purpose a storage tank installed from

which continuously DM water is drawn for boiler make up.

Figure :- figure shows the source and path followed by water

The impurities in water input to this plant generally consist calcium and

magnesium salts imparting hardness to the water . these salts have to be

removed from the water. If hardness present in make up water to the boiler, the

salt only from form deposits on the tube surface but also lead to overheating in

tose localities resulting in tube failures. Therefore these have to be compleatly

removed for use as boiler make up., this is done using DMwater treatment plant

which gives us purest form of water.

Figure :-water treatment plant

This is generally consist of CATION,ANION and mixed bed exchangers . the

final water from this process consist generally of hydrogen ion and hydroxide

ions which is the chemical composition of pure water . the DM water being very

pure is highly corrosive , once it absorbs oxygen from the atmosphere because

of its very high affinity for oxygen absorption. The capacity of DM plant is

dictated by the type and quantity of salt in the raw water input.

The storage tank for DM water is made from material not affected by corrosive

water such as PVC . The piping and valves are generally of stainless steel.

STEAM TURBINE:-

A steam turbine is a device that extracts thermal energy from

pressurized steam and uses it to do mechanical work on a rotating output shaft.

Its modern manifestation was invented by Sir Charles Parsons in 1884.

Because the turbine generates rotary motion, it is particularly suited to be used

to drive an electrical generator

Figure :-steam turbine

The first device that may be classified as a reaction steam turbine was little

more than a toy, the classic Aerolipile, described in the 1st century

by Greek mathematician Hero of Alexandria in Roman Egypt. In 1551, Taqi al-

Din in Ottoman Egypt described a steam turbine with the practical application

of rotating a spit. Steam turbines were also described by the Italian Giovanni

Branca (1629) and John Wilkins in England (1648).The devices described by

Taqi al-Din and Wilkins are today known as steam jacks.

The modern steam turbine was invented in 1884 by Sir Charles Parsons, whose

first model was connected to a dynamo that generated 7.5 kW (10 hp) of

electricity. The invention of Parsons' steam turbine made cheap and plentiful

electricity possible and revolutionized marine transport and naval warfare.

recently steam turbine have gained use in power plants and there are a large

number of neuclear plants that generate output in excess of 1000 megawatts by

powering massive steam turbine with high temperature steam generated by a

neuclear reactor .

in order to increase the efficiency of stem turbine , takasago machinery

works,mistubisi heavy industries limeted using 3D design technology to shape

rotor blades , developing and manufacturing larger rotor blades and designing

methods to prevent the loss of steam throughouts .

PASS OUT EXTRACTION TURBINE:-

the steam turbine used in NTPC , AURAIYA are pass out or extraction

turbines . in these types of turbine steam is exhausted at defferent stages and

used in heating the steam water for the boiler processing work .

the high pressure steam from boiler enters HP stage of turbine where it expands

and the pressure is reduced to such a value that is required for processing work

. a part of this low pressure steam leaving the high pressure stage is supplied to

the processing work while the remaining steam expand further in the L.P. stage.

The exhaust steam from the processing plant the low pressure turbine steam is

condensed in the condenser and pumped back to boiler.

GENERATOR HIGH-VOLTAGE SYSTEM:-

The generator voltage for modern utility-connected generators ranges from 11

kV in smaller units to 22 kV in larger units. The generator high-voltage leads

are normally large aluminium channels because of their high current as

compared to the cables used in smaller machines. They are enclosed in well-

grounded aluminium bus ducts and are supported on suitable insulators. The

generator high-voltage leads are connected to step-up transformers for

connecting to a high-voltage electrical substation (usually in the range of 115

kV to 765 kV) for further transmission by the local power grid.

The necessary protection and metering devices are included for the high-

voltage leads. Thus, the steam turbine generator and the transformer form one

unit. Smaller units may share a common generator step-up transformer with

individual circuit breakers to connect the generators to a common bus.

Phase - 3-Ф

Cooling - Hydrogen cooled

Speed - 3000 rpm

Frequency - 50 Hz

Excitation - DC Static excitation

Rated output - 111.19 MW (GTG) & 109.3 MW (STG)

Figure :- generator

CERCULATING WATER PUMP:-

These pumps are used to pump water to the deaerator from where the water

goes to boiler feed Pump.

DEAEREATOR:-

The deaerator are used to deaereator the water before feeding it in to BFP. This

is done because HRB is a water tube boiler and tubes containing water have

very small diameter . there are some gasses like CO2 if present in water they

can create rusting or can choke the tube . so these gasses are removed in the

deareator . there are total 4 deaereator in the NTPC , auraiya each for every

WHRB.

WORKING OF WHRB:-

The feed water enters in to steam drum through boiler economizer from where it

goes in to boiler and converted in to steam. This steam further goes to super

heater and at the output superheated stem at the temperature of 530C is ganed .

this superheated steam is used to drive steam turbine to generated electricity as

in the cycle.

COOLING SYSTEM:-

Why is Cooling Necessary?

power plants boils water to create steam, which then spins turbines to generate

electricity. The heat used to boil water can come from burning of a fuel, from

nuclear reactions, or directly from the sun or geothermal heat sources

underground. Once steam has passed through a turbine, it must be cooled back

into water before it can be reused to produce more electricity. Colder water

cools the steam more effectively and allows more efficient electricity

generation .

TYPES OF COOLING:-

Even though all thermoelectric plants use water to generate steam for electricity

generation, not all plant cooling systems use water. There are three main

methods of cooling:

Once-through systems take water from nearby sources (e.g., rivers, lakes,

aquifers, or the ocean), circulate it through pipes to absorb heat from the steam

in systems called condensers, and discharge the now warmer water to the local

source. Once-through systems were initially the most popular because of their

simplicity, low cost, and the possibility of siting power plants in places with

abundant supplies of cooling water. This type of system is currently widespread

in the eastern U.S. Very few new power plants use once-through cooling,

however, because of the disruptions such systems cause to local ecosystems

from the significant water withdrawals involved and because of the increased

difficulty in siting power plants near available water sources.

Figure:-wet cooling system

WET-RECIRCULATING OR CLOSED-LOOP:-

Power plants built after the 1960s shifted toward cooling systems that reuse

water, known as recirculating systems. systems reuse cooling water in a

second cycle rather than immediately discharging it back to the original water

source. At a recirculating system, water is kept in closed-loop piping so it can

be used repeatedly. Recirculating systems can consist of a cooling tower or a

cooling pond with both using ambient air to draw energy out of the cooling

water that was used to condense the steam. Most commonly, wet-recirculating

systems use cooling towers to expose water to ambient air. Some of the water

evaporates; the rest is then sent back to the condenser in the power plant.

Because wet-recirculating systems only withdraw water to replace any water

that is lost through evaporation in the cooling tower, these systems have much

lower water withdrawals than once-through systems, but tend to have

appreciably higher water consumption.

CONTROLE SYSTEM OF THE PLANT:-

There are three of controlling system available in the plant and they are as

follows :-

LOCAL CONTROLE:-

In this control commands are given to the machine from the place where

machine is located . this system is rarely used .

SWITCHYARD CONTROL :-

In it all controlling commands are given from switch gear room.

REMOTE SYSTEM:-

This system is frequently used . in it all controlling are given from central

computerised controle room ,there are two set of controlling devices . if one set

is shut down for maintenance then commands are given by second set.

ELECTRICAL AND SWITCHYARD DEPARTMENT:-

Electrical energy management system ensures at upply of energy to every

consumer at all times at rated voltage. Frequency and secified waveform at

lowest cost at minimum envoironmental degradation . the switch gear,

protection and network automation are integral part of modern energy

management system and national economy . the modern 3-ph ,50HZ,AC

interconnected system has several conventional and non conventional power

plants , GV transmission network ,substations ,MV and LV distribution system

and connected electrical load. the energy form is supplied to various consumers

located in vast geographical area instantly, automatically and safely with

required quality at all times. the service continuity and high quality of power

supply have become very important .

Figure :-switchyard

for fulfilment the foresaid purpose a state of the art scientifically and

technologically advanced substations is required .substations is the load control

center of the thermal plant where power at the rated voltage ,frequency and

waveform is exported , imported as per requirement

the substation at NTPC ,auraiya has two switch yard one of 220KV and other is

440KV . there are two bus bars and one transfer bus for supplying electricity .

after step up ,the 220KV output from the generator transfer is fed to either of

two bus bars through relays and circuit breakers and these are connected two

various feeders through various equipments.

There are 10 lines going out of NTPC, auraiya for supplying electricity. Their

descriptions are as follows :-

2 lines of 220KV to Agra.

2 lines of 440KV to Agra .

2 lines of 220KV to Maingaon , M.P.

2 lines of 220KV to GAIL , Dibiyapur.

DEFFERENT TYPE OF EQUIPMENTS USED IN SUB-

STATIONS:-

BUS BARS:-

Figurer:- bus bars

When a number of lines operating at the same voltage have to be directly

connected electrically, bus-bars are used as the common electrical component.

Bus-bars are copper or aluminium bars (generally of rectangular x-section) and

operate at constant voltage. The incoming and outgoing lines in a sub-station

are connected to the bus-bars. The most commonly used bus-bar arrangements

in sub-stations are :

Single bus-bar arrangement

Single bus-bar system with sectionalisation

Double bus-bar arrangement

INSULATOR:-

The insulators serve two purposes. They support the conductors (or bus-bars)

and confine the current to the conductors. The most commonly used material for

the manufacture of insulators is porcelain. There are several types of insulators

(e.g. pin type, suspension type, post insulator etc.) and their use in the sub-

station will depend upon the service requirement. For example, post insulator is

used for bus-bars. A post insulator consists of a porcelain body, cast iron cap

and flanged cast iron base. The hole in the cap is threaded so that bus-bars can

be directly bolted to the cap.

Isolating switches:-

Figure :- Isolators in typical sub station

In sub-stations, it is often desired to disconnect a part of the system for general

maintenance and repairs. This is accomplished by an isolating switch or

isolator. An isolator is essentially a knife switch and is designed to open a

circuit under no load. In other words, isolator switches are operated only when

the lines in which they are connected carry no current.

The entire sub-station has been divided into V sections. Each section can be

disconnected with the help of isolators for repair and maintenance.

CIRCUIT BREAKER:-

High voltage circuit breaker

A circuit breaker is an equipment which can open or close a circuit under

normal as well as fault conditions. It is so designed that it can be operated

manually (or by remote control) under normal conditions and automatically

under fault conditions. For the latter operation, a relay circuit is used with a

circuit breaker. Generally, bulk oil circuit breakers are used for voltages upto

66kV while for high (>66 kV) voltages, low oil circuit breakers are used. For

still higher voltages, air-blast, vacuum or SF6 circuit breakers are used.

LIGHTNING ARRESTERS:-

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.

POWER TRANSFORMER:-

A power transformer is used in a sub-station to step-up or step-down the

voltage. Except at the power station, all the subsequent sub-stations use step-

down transformers to gradually reduce the voltage of electric supply and finally

deliver it at utilisation voltage. The modern practice is to use 3-phase

transformers in sub-stations ; although 3 single phase bank of transformers can

also be used. The use of 3-phase transformer (instead of 3 single phase bank of

transformers) permits two advantages. Firstly, only one 3-phase load-tap

changing mechanism can be used. Secondly, its installation is much simpler

than the three single phase transformers. For ratings upto 10 MVA, naturally

cooled, oil immersed transformers are used. For higher ratings, the transformers

are generally air blast cooled.

Instrument Transformer

The lines in sub-stations operate at high voltages and carry current of thousands

of amperes. The measuring instruments and protective devices are designed for

low voltages (generally 110 V) and currents (about 5 A). Therefore, they will

not work satisfactorily if mounted directly on the power lines.

Figure :- transformers

This difficulty is overcome by installing instrument transformers on the power

lines. The function of these instrument transformers is to transfer voltages or

currents in the power lines to values which are convenient for the operation of

measuring instruments and relays. There are two types of instrument

transformers viz.

Current transformer (C.T.)

Potential transformer (P.T.)

CURRENT TRANSFORMER (C.T.):-

A current transformer is essentially a step-up transformer which steps down the

current to a known ratio. The primary of this transformer consists of one or

more turns of thick wire connected in series with the line. The secondary

consists of a large number of turns of fine wire and provides for the measuring

instruments and relays a current which is a constant fraction of the current in the

line. Suppose a current transformer rated at 100/5 A is connected in the line to

measure current. If the current in the line is 100 A, then current in the secondary

will be 5A. Similarly, if current in the line is 50A, then secondary of C.T. will

have a current of 2·5 A. Thus the C.T. under consideration will step down the

line current by a factor of 20.

VOLTAGE TRANSFORMER:-

It is essentially a step down transformer and steps down the voltage to a known

ratio. The primary of this transformer consists of a large number of turns of fine

wire connected across the line. The secondary winding consists of a few turns

and provides for measuring instruments and relays a voltage which is a known

fraction of the line voltage. Suppose a potential transformer rated at 66kV/110V

is connected to a power line. If line voltage is 66kV, then voltage across the

secondary will be 110 V.

METERING AND INDICATING INSTRUMENTS:-

There are several metering and indicating instruments (e.g. ammeters,

voltmeters, energy meters etc.) installed in a sub-station to maintain watch over

the circuit quantities. The instrument transformers are invariably used with them

for satisfactory operation.

MISCELLANEOUS EQUIPMENT:-

In addition to above, there may be following equipment in a sub-station :

fuses

carrier-current equipment

sub-station auxiliary supplies

RELAYS:- In electrical engineering, a protective relay is a device designed to trip a circuit

breaker when a fault is detected. The first protective relays were

electromagnetic devices, relying on coils operating on moving parts to provide

detection of abnormal operating conditions such as over-current, over-voltage,

reverse power flow, over- and under- frequency.

Figure:-Protective relay

CONCLUSION:-

This is the vocational training report deals with over all operation of NTPC

plant in auraiya . also the report has a view of some paert used in plants.

The depleating resources of oil ,gas and coal (the conventional fuels) along with

atmosphere pollution problems have drawn the attentions of the scientists and

engineers all over the world to find out other sources for the generation of

electric power. There sources of energy are going to attain the nerve centre of

the future power plants. Though atomic and nuclear power plants have been

developed on conventional lines, but lot of work yet to be done. Efforts are

being made to atomic and nuclear energy directly into electric power with the

help of magneto hydrodynamic generator and other equipments.

REFFERENCES:-

NTPC, Auraiya

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