Ntpc Btps Electrical Project Report 2013

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BADARPUR THERMAL

POWER STATION

SUMMER TRAINING REPORT(03

RDJUNE 201306

THJULY 2013)

BY:

Pratinav Kanth (VT1095)

B.Tech EEE 2nd

year

DTU (Delhi Technological University) formerly DCE
http://www.google.co.in/url?sa=i&rct=j&q=ntpc+logo&source=images&cd=&cad=rja&docid=4NcK0XW6v5ghJM&tbnid=FXEuEeuMIsnzJM:&ved=0CAUQjRw&url=http://www.cpjimt.com/RecruitComp.htm&ei=6GjRUYmkC8zqrQeu3YGoAQ&bvm=bv.48572450,d.bmk&psig=AFQjCNEk6A8x7KGtasa1TXPlltZOGAap9Q&ust=1372764724529926http://answers.ind.in/f/4266-logo-dtu.htmlhttp://www.google.co.in/url?sa=i&rct=j&q=ntpc+logo&source=images&cd=&cad=rja&docid=4NcK0XW6v5ghJM&tbnid=FXEuEeuMIsnzJM:&ved=0CAUQjRw&url=http://www.cpjimt.com/RecruitComp.htm&ei=6GjRUYmkC8zqrQeu3YGoAQ&bvm=bv.48572450,d.bmk&psig=AFQjCNEk6A8x7KGtasa1TXPlltZOGAap9Q&ust=1372764724529926http://answers.ind.in/f/4266-logo-dtu.html


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This is to certify that PRATINAV KANTH (2K11/EL/052), student of

2011-2015 batch of EEE (Electrical and Electronics Engineering) in 2nd

year of Delhi Technological University (formerly DCE) has successfully

completed his summer training at BTPS (Badarpur Thermal Power

Station) NTPC limited, New Delhi for 5 weeks from 03rd

June to 06th

July 2013.

Training In-Charge,

Badarpur Thermal Power Station,

NTPC limited,

Badarpur, New Delhi


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ACKNOWLEDGEMENT

With profound respect and gratitude, I take the opportunity to convey my

thanks to all those at my University who made this training possible.

Here at National Thermal Power Corporation Limited, Badarpur Thermal

Power Station, Badarpur, New Delhi I do extend my heartfelt thanks to

Ms. Rachana Singh Bhal for providing me this opportunity to be a part of

this esteemed organization. I am extremely grateful to Mr. G. D. Sharma,

Superintendent of In-Plant Training at BTPS-NTPC, Badarpur for hisguidance during the whole training period. I am extremely grateful to all

the technical staff of BTPS-NTPC for their help, co-operation and

guidance that helped me a lot during the course of training. I have learnt a

lot working with and under them and I will always be indebted of them for

this value addition in me.

Finally, I am indebted to all whosoever have contributed in this report

work and friendly stay at Badarpur Thermal Power Station,NTPC, Badarpur, New Delhi.


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CONTENTS

NTPCABOUT THE COMPANY

BTPS (Badarpur Thermal Power Station), BADARPUR

EMD-I (Electrical Maintenance DepartmentI)

EMD-II (Electrical Maintenance DepartmentII)

C & I (Control and Instrumentation)


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NTPC (NATIONAL THERMAL

POWER CORPORATION)

LIMITED

ABOUT THE COMPANY

Indias largest power company, NTPC was set up in 1975 to acceleratepower development in India. NTPC is emerging as a diversified power

major with presence in the entire value chain of the power generation

business. Apart from power generation, which is the mainstay of the

company, NTPC has already ventured into consultancy, power trading, ash

utilisation and coal mining. NTPC ranked 341stin the 2010, Forbes

Global 2000 ranking ofthe Worlds biggest companies.NTPC became a

Maharatna company in May 2010, one of the only four companies to be

awarded this status.

The total installed capacity of the company is 39,174 MW (including JVs)

with 16 coal based and 7 gas based stations, located across the country. In

addition under JVs, 7 stations are coal based & another station uses

naphtha/LNG as fuel. The company has set a target to have an installed

power generating capacity of 128,000 MW by the year 2032. The capacity

will have a diversified fuel mix comprising 56% coal, 16% Gas, 11%

Nuclear and 17% Renewable Energy Sources(RES) including hydro. By

2032, non fossil fuel based generation capacity shall make up nearly 28%

of NTPCs portfolio.

NTPC has been operating its plants at high efficiency levels. Although the

company has 17.75% of the total national capacity, it contributes 27.40%

of total power generation due to its focus on high efficiency.


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In October 2004, NTPC launched its Initial Public Offering (IPO)

consisting of 5.25% as fresh issue and 5.25% as offer for sale by

Government of India. NTPC thus became a listed company in November

2004 with the Government holding 89.5% of the equity share capital. In

February 2010, the Shareholding of Government of India was reduced

from 89.5% to 84.5% through Further Public Offer. The rest is held by

Institutional Investors and the Public.


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At NTPC,People before Plant Load Factoris the mantra that guides all

HR related policies. NTPC has been awarded No.1, Best Workplace in

India among large organisations and the best PSU for the year 2010, by the

Great Places to Work Institute, India Chapter in collaboration with The

Economic Times.

The concept of Corporate Social Responsibility is deeply ingrained in

NTPC's culture. Through its expansive CSR initiatives, NTPC strives to

develop mutual trust with the communities that surround its power

stations.

VISION AND MISSION

VISION

To be the worlds largest and best power producer, powering Indias growth.

MISSIONDevelop and provide reliable power, related products and services at

competitive prices, integrating multiple energy sources with innovative and eco-

friendly technologies and contribute to society.

CORE VALUESBE COMMITTED

B Business Ethics

E Environmentally & Economically Sustainable

C Customer Focus

O Organisational & Professional PrideM Mutual Respect & Trust

M Motivating Self & others

I Innovation & Speed

T Total Quality for Excellence

T Transparent & Respected Organisation

E Enterprising

D Devoted


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STRATEGIES

TECHNOLOGICAL INITIATIVE

Introduction of steam generators (boilers) of the size of 800 MW.

Integrated Gasification Combined Cycle (IGCC) Technology.

Launch of Energy Technology Centre -A new initiative for developmentof technologies with focus on fundamental R&D.

The company sets aside up to 0.5% of the profits for R&D.

Roadmap developed for adopting Clean Development

Mechanism to help get / earn Certified Emission Reduction


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CORPORATE SOCIAL RESPONSIBILITY

As a responsible corporate citizen NTPC has taken up number of CSRinitiatives.

NTPC Foundation formed to address Social issues at national level.

NTPC has framed Corporate Social Responsibility Guidelines committingup to 0.5% of net profit annually for Community Welfare Measures on

perennial basis.

The welfare of project affected persons and the local population around

NTPC projects are taken care of through well drawn Rehabilitation andResettlement policies.

The company has also taken up distributed generation for remote ruralareas.

PARTNERING GOVERNMENT IN VARIOUS INITIATIVES

Consultant role to modernize and improvise several plants across thecountry.

Disseminate technologies to other players in the sector.

Consultant role partnership in excellence programme for improvementof PLF of 15 power stations of SEBs.

Rural Electrification work under Rajiv Gandhi Gramin Vidyutikaran.


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ENVIRONMENT POLICIES

ENVIRONMENT POLICY & ENVIRONMENT MANAGEMENT

SYSTEM

For NTPC, the journey extends much beyond generating power. Right from its

inception, the company had a well defined environment policy. More than just

generating power, it is committed to sustainable growth of power.

NTPC has evolved sound environment practices.

NATIONAL ENVIRONMENT POLICY

The Ministry of Environment and Forests and the Ministry of Power and NTPC

were involved in preparing the draft Environment Policy (NEP) which was later

approved by the Union Cabinet in May 2006.

NTPC ENVIRONMENT POLICY


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Since its inception NTPC has been at the forefront of Environment

management. In November 1995, NTPC brought out a comprehensive document

entitled NTPC Environment Policy and Environment Management System.

Amongst the guiding principles adopted in the document are the company's pro-

active approach to environment, optimum utilisation of equipment, adoption olatest technologies and continual environment improvement. The policy also

envisages efficient utilisation of resources, thereby minimising waste,

maximising ash utilisation and ensuring a green belt all around the plant for

maintaining ecological balance.

ENVIRONMENT MANAGEMENT, OCCUPATIONAL HEALTH AND

SAFETY SYSTEMS

NTPC has actively gone for adoption of the best international practices on

environment, occupational health and safety areas. The organisation has pursued

the Environmental Management System (EMS) ISO 14001 and the

Occupational Health and Safety Assessment System OHSAS 18001 at its

different establishments. As a result of pursuing these practices, all NTPC

power stations have been certified for ISO 14001 & OHSAS 18001 by reputed

national and international certifying agencies.

POLLUTION CONTROL SYSTEMS

While deciding the appropriate technology for its projects, NTPC integrates

many environmental provisions into the plant design. In order to ensure that

NTPC complies with all the stipulated environment norms, following state-of-

the-art pollution control systems / devices have been installed to control air and

water pollution:

Electrostatic Precipitators

Flue Gas Stacks

Low-NOX Burners

Neutralisation Pits

Coal Settling Pits / Oil Settling Pits

DE & DS Systems Cooling Tower

Ash Dykes & Ash Disposal Systems

Ash Water Recycling System

Dry Ash Extraction System (DAES)


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Liquid Waste Treatment Plants & Management System

Sewage Treatment Plants & Facilities

Environmental Institutional Set-up

Following are the additional measures taken by NTPC in the area ofEnvironment Management:

Environment Management During Operation Phase

Monitoring of Environmental Parameters

On-Line Data Base Management

Environment Review

Up gradation & Retrofitting of Pollution Control Systems

Resources Conservation Waste Management

Municipal Waste Management

Hazardous Waste Management

Bio-Medical Waste Management

Land Use / Bio-diversity

Reclamation of Abandoned Ash ponds

Green Belts, Afforestation & Energy Plantations

EVOLUTION

NTPC was set up in 1975 in 100% by the ownership ofGovernment of India. In the last 30 years NTPC has grown into

the largest power utility in India.

In 1997, Government of India granted NTPC status of

Navratna being one of the nine jewels of India, enhancing the

powers to the Board of directors.

1975

1997


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NTPC HEADQUARTERS

NTPC Limited is divided in 8 Headquarters

Sr No. Headquarter City

1 NCRHQ Delhi

2 ER-I, HQ Patna

3 ER-II, HQ Bhubaneshwar

4 NRHQ Lucknow

5 SR HQ Hyderabad

6 WR-I HQ Mumbai

7 Hydro HQ Delhi

8 WR-II HQ Raipur

NTPC PLANTS

1. THERMAL COAL BASED

Sr No. City State Installed Capacity

1 Singrauli Uttar Pradesh 2,000

2 Korba Chhattisgarh 2,600

3 Ramagundam Andhra Pradesh 2,600

4 Farakka West Bengal 2,100

5 Vindhyachal Madhya Pradesh 3,260

6 Rihand Uttar Pradesh 2,500

7 Kahalgaon Bihar 2,340

8 Dadri Uttar Pradesh 1,820


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9 Talcher Orissa 3,000

10 Unchahar Uttar Pradesh 1,050

11 Talcher Orissa 460

12 Simhadri Andhra Pradesh 1,500

13 Tanda Uttar Pradesh 440

14 Badarpur Delhi 705

15 Sipat Chhattisgarh 2320

16 Sipat Chhattisgarh 1980

17 Bongaigaon Assam 750

18 Mouda Maharashtra 1000 (2x500 MW)

19 Rihand Uttar Pradesh 2*500 MW

20 Barh Bihar 3300 (5x660 MW)

Total 31,495MW

2. COAL BASED (Owned by JVs)

Sr. No. Name of the JV City State Installed Capacity

1 NSPCL Durgapur West Bengal 120

2 NSPCL Rourkela Orissa 120

3 NSPCL Bhilai Chhattisgarh 574

4 NPGC Aurangabad Bihar 1980

5 M.T.P.S Kanti Bihar 110

6 BRBCL Nabinagar Bihar 1000

Total 3904MW


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3. GAS BASED

Sr. No. City State Installed Capacity

1 Anta Rajasthan 419

2 Auraiya Uttar Pradesh 652

3 Kawas Gujarat 645

4 Dadri Uttar Pradesh 817

5 Jhanor Gujarat 648

6 Kayamkulam Kerala 350

7 Faridabad Haryana 430

Total 3995MW

OVERALL POWER GENERATION

Unit 1997-98 2006-07 % of increase

Installed Capacity MW 16,847 26,350 56.40

Generation MUs 97,609 1, 88,674 93.29

No. of employees No. 23,585 24,375 3.34

Generation/employee MUs 4.14 7.74 86.95

The table below shows the detailed operational performance of coal based stations over the years.

OPERATIONAL PERFORMANCE OF COAL BASED NTPC STATIONS

Unit: 97-98 98-99 99-00 00-01 01-02 02-03 03-04 04-05 05-06 06-07

Generation BU: 106.2 109.5 118.7 130.1 133.2 140.86 149.16 159.11 170.88 188.67

PL %: 75.20 76.60 80.39 81.8 81.1 83.6 84.4 87.51 87.54 89.43

Availability Factor: 85.03 89.36 90.06 88.54 81.8 88.7 88.8 91.20 89.91 90.09


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POWER BURDEN

India, as a developing country is characterized by increase in demand for

electricity and as of moment the power plants are able to meet only about 60

75% of this demand on an yearly average. The only way to meet therequirement completely is to achieve a rate of power capacity addition

(implementing power projects) higher than the rate of demand addition. NTPC

strives to achieve this and undoubtedly leads in sharing this burden on the

country.


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In 1978 the management of the plant was transferred to NTPC, from CEA. The

performance of the plant increased significantly and steadily after take over by

NTPC till 2006, but now the plant is facing various issues.

Being an old plant, Badarpur Thermal Power Station (BTPS) has little

automation. Its performance is deteriorating due to various reasons, like aging,

poor quantity and quality of cooling water etc. It receives cooling water fromAgra Canal, which is an irrigation canal from Yamuna river. Due to rising water

pollution, the water of Yamuna is highly polluted. This polluted water when

goes into condenser, adversely affect life of condenser tubes, resulting in

frequent tube leakages. This dirty water from tube leakage gets mixed into feed

water cycle causes numerous problems, like frequent boiler tube leakages, and

silica deposition on turbine blades.

Apart from poor quality, the quantity of water supply is also erratic due to lackof co-ordination between NTPC and UP irrigation which manages Agra Canal.

The quality of the coal supplied has degraded considerably. At worst times,

there were many units tripping owing to poor quality. The poor coal quality also

put burdens on equipment, like mills and their performance also goes down. The

coal for the plant is fetched from far away, that makes the total fuel cost double

of coal cost at coalmine. This factor, coupled with low efficiency due to aging

and old design makes electricity of the plant costlier. With new splurge in no of


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power plant, the distribution company does not purchase full power from it.

Presently the management is headed by Mr. N. K. Kothari, General manager.

INSTALLED CAPACITY

Stage Unit Number Installed Capacity (MW) Date of Commissioning Status

First 1 95 July, 1973 Running

First 2 95 August, 1974 Running

First 3 95 March, 1975 Running

Second 4 210 December, 1978 Running

Second t 5 210 December, 1981Running

INTRODUCTION

A thermal power station is a power plant in which the prime-

moveris steam driven. Water is heated, turns into steam and spins a steam

turbine which drives an electrical generator. After it passes through the turbine,

the steam is condensed in a condenserand recycled to where it was heated; this

is known as a Rankine cycle. The greatest variation in the design of thermal

power stations is due to the different fuel source. Almost

all coal, nuclear, geothermal, solar thermal electric, and waste incineration

plants, as well as many natural gas power plants are thermal. Natural gas is

frequently combusted in gas turbines as well as boilers. The waste heat from a

gas turbine can be used to raise steam, in a combined cycleplant that improves

overall efficiency. Power plants burning coal, fuel oil, or natural gas are often

calledfossil-fuel power plants. Some biomass-fuel thermal power plants have

appeared also. Non-nuclear thermal power plants, particularly fossil-fuel plants,

which do not use co-generation, are sometimes referred to as conventional

ower plants.
http://en.wikipedia.org/wiki/Watt#Megawatthttp://en.wikipedia.org/wiki/Power_planthttp://en.wiktionary.org/wiki/prime_moverhttp://en.wiktionary.org/wiki/prime_moverhttp://en.wikipedia.org/wiki/Steamhttp://en.wikipedia.org/wiki/Steam_turbinehttp://en.wikipedia.org/wiki/Steam_turbinehttp://en.wikipedia.org/wiki/Electrical_generatorhttp://en.wikipedia.org/wiki/Condensationhttp://en.wikipedia.org/wiki/Surface_condenserhttp://en.wikipedia.org/wiki/Rankine_cyclehttp://en.wikipedia.org/wiki/Coalhttp://en.wikipedia.org/wiki/Nuclear_powerhttp://en.wikipedia.org/wiki/Geothermal_powerhttp://en.wikipedia.org/wiki/Solar_thermal_electrichttp://en.wikipedia.org/wiki/Incinerationhttp://en.wikipedia.org/wiki/Incinerationhttp://en.wikipedia.org/wiki/Natural_gashttp://en.wikipedia.org/wiki/Flue-gas_emissions_from_fossil-fuel_combustionhttp://en.wikipedia.org/wiki/Gas_turbinehttp://en.wikipedia.org/wiki/Boilerhttp://en.wikipedia.org/wiki/Waste_heathttp://en.wikipedia.org/wiki/Combined_cyclehttp://en.wikipedia.org/wiki/Fuel_oilhttp://en.wikipedia.org/wiki/Fossil-fuel_power_planthttp://en.wikipedia.org/wiki/Fossil-fuel_power_planthttp://en.wikipedia.org/wiki/Fossil-fuel_power_planthttp://en.wikipedia.org/wiki/Biomasshttp://en.wikipedia.org/wiki/Co-generationhttp://en.wikipedia.org/wiki/Co-generationhttp://en.wikipedia.org/wiki/Biomasshttp://en.wikipedia.org/wiki/Fossil-fuel_power_planthttp://en.wikipedia.org/wiki/Fuel_oilhttp://en.wikipedia.org/wiki/Combined_cyclehttp://en.wikipedia.org/wiki/Waste_heathttp://en.wikipedia.org/wiki/Boilerhttp://en.wikipedia.org/wiki/Gas_turbinehttp://en.wikipedia.org/wiki/Flue-gas_emissions_from_fossil-fuel_combustionhttp://en.wikipedia.org/wiki/Natural_gashttp://en.wikipedia.org/wiki/Incinerationhttp://en.wikipedia.org/wiki/Incinerationhttp://en.wikipedia.org/wiki/Solar_thermal_electrichttp://en.wikipedia.org/wiki/Geothermal_powerhttp://en.wikipedia.org/wiki/Nuclear_powerhttp://en.wikipedia.org/wiki/Coalhttp://en.wikipedia.org/wiki/Rankine_cyclehttp://en.wikipedia.org/wiki/Surface_condenserhttp://en.wikipedia.org/wiki/Condensationhttp://en.wikipedia.org/wiki/Electrical_generatorhttp://en.wikipedia.org/wiki/Steam_turbinehttp://en.wikipedia.org/wiki/Steam_turbinehttp://en.wikipedia.org/wiki/Steamhttp://en.wiktionary.org/wiki/prime_moverhttp://en.wiktionary.org/wiki/prime_moverhttp://en.wikipedia.org/wiki/Power_planthttp://en.wikipedia.org/wiki/Watt#Megawatt


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Commercial electric utilitypower stations are usually constructed on a large

scale and designed for continuous operation. Electric power plants typically

use three-phase electrical generators to produce alternating current (AC) electric

power at a frequency of 50 Hz or 60 Hz. Large companies or institutions may

have their own power plants to supply heating or electricity to their facilities.

BASIC PRINCIPLE AND STEPS OF OPERATION OF THERMAL

POWER PLANT

The Rankine cycle is a cycle that converts heat into work. The heat is supplied

externally to a closed loop, which usually uses water. This cycle generates about

90% of all electric power used throughout the world. The Rankine cycle is thefundamental thermodynamic underpinning of the steam engine

The Rankine cycle most closely describes the process by which steam-

operated heat engines most commonly found in power generation

plants generate power.
http://en.wikipedia.org/wiki/Electric_utilityhttp://en.wikipedia.org/wiki/Three-phasehttp://en.wikipedia.org/wiki/Electrical_generatorhttp://en.wikipedia.org/w/index.php?title=Utilty_frequency&action=edit&redlink=1http://en.wikipedia.org/wiki/Hertzhttp://en.wikipedia.org/wiki/Heatinghttp://en.wikipedia.org/wiki/Steam_enginehttp://en.wikipedia.org/wiki/Heat_enginehttp://en.wikipedia.org/wiki/Power_stationhttp://en.wikipedia.org/wiki/Power_stationhttp://en.wikipedia.org/wiki/Power_stationhttp://en.wikipedia.org/wiki/Power_stationhttp://en.wikipedia.org/wiki/Heat_enginehttp://en.wikipedia.org/wiki/Steam_enginehttp://en.wikipedia.org/wiki/Heatinghttp://en.wikipedia.org/wiki/Hertzhttp://en.wikipedia.org/w/index.php?title=Utilty_frequency&action=edit&redlink=1http://en.wikipedia.org/wiki/Electrical_generatorhttp://en.wikipedia.org/wiki/Three-phasehttp://en.wikipedia.org/wiki/Electric_utility


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The efficiency of a Rankine cycle is usually limited by the working fluid.

Without the pressure reaching super critical levels for the working fluid, the

temperature range the cycle can operate over is quite small: turbine entry

temperatures are typically 565C (the creep limit of stainless steel) and

condenser temperatures are around 30C. This gives a theoretical Carnot

efficiency of about 63% compared with an actual efficiency of 42% for a

modern coal-fired power station. This low turbine entry temperature (compared

with a gas turbine) is why the Rankine cycle is often used as a bottoming cyclein combined-cycle gas turbinepower stations.

.

One of the principal advantages the Rankine cycle holds over others is that

during the compression stage relatively little work is required to drive the pump,

the working fluid being in its liquid phase at this point. By condensing the fluid,

the work required by the pump consumes only 1% to 3% of the turbine power

and contributes to a much higher efficiency for a real cycle. The benefit of this

is lost somewhat due to the lower heat addition temperature. Gas turbines, forinstance, have turbine entry temperatures approaching 1500C. Nonetheless, the

efficiencies of actual large steam cycles and large modern gas turbines are fairly

well matched.
http://en.wikipedia.org/wiki/Critical_point_(thermodynamics)http://en.wikipedia.org/wiki/Creep_(deformation)http://en.wikipedia.org/wiki/Carnot_efficiencyhttp://en.wikipedia.org/wiki/Carnot_efficiencyhttp://en.wikipedia.org/wiki/Gas_turbinehttp://en.wikipedia.org/wiki/Combined_cyclehttp://en.wikipedia.org/wiki/Gas_turbinehttp://en.wikipedia.org/wiki/Gas_turbinehttp://en.wikipedia.org/wiki/Combined_cyclehttp://en.wikipedia.org/wiki/Gas_turbinehttp://en.wikipedia.org/wiki/Carnot_efficiencyhttp://en.wikipedia.org/wiki/Carnot_efficiencyhttp://en.wikipedia.org/wiki/Creep_(deformation)http://en.wikipedia.org/wiki/Critical_point_(thermodynamics)


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FOUR PROCESS OF RANKINE CYCLE

Process 1-2: The working fluid is pumped from low to high pressure. As the

fluid is a liquid at this stage the pump requires little input energy.

Process 2-3: The high pressure liquid enters a boiler where it is heated at

constant pressure by an external heat source to become a dry saturated

vapour. The input energy required can be easily calculated using mollier

diagram orh-s chart orenthalpy-entropy chart also known as steam tables.

Process 3-4: The dry saturated vapour expands through a turbine, generating

power. This decreases the temperature and pressure of the vapour, and some

condensation may occur. The output in this process can be easily calculated

using the Enthalpy-entropy chart or the steam tables.

Process 4-1: The wet vapour then enters a condenserwhere it is condensed at

a constant temperature to become a saturated liquid.

EQUATIONS OF RANKINE CYCLE

In general, the efficiency of a simple Rankine cycle can be defined as:

Each of the next four equations is easily derived from the energy and mass

balance for a control volume. Defines the thermodynamic efficiency of

the cycle as the ratio of net power output to heat input. As the work required by

the pump is often around 1% of the turbine work output, it can be simplified.
http://en.wikipedia.org/wiki/Mollier_diagramhttp://en.wikipedia.org/wiki/Mollier_diagramhttp://en.wikipedia.org/wiki/H-s_charthttp://en.wikipedia.org/wiki/Enthalpy-entropy_charthttp://en.wikipedia.org/wiki/Steam_tablehttp://en.wikipedia.org/wiki/Turbinehttp://en.wikipedia.org/wiki/Enthalpy-entropy_charthttp://en.wikipedia.org/wiki/Surface_condenserhttp://en.wikipedia.org/wiki/Boiling_pointhttp://en.wikipedia.org/wiki/Energyhttp://en.wikipedia.org/wiki/Mass_balancehttp://en.wikipedia.org/wiki/Mass_balancehttp://en.wikipedia.org/wiki/Thermodynamic_efficiencyhttp://en.wikipedia.org/wiki/Thermodynamic_efficiencyhttp://en.wikipedia.org/wiki/Mass_balancehttp://en.wikipedia.org/wiki/Mass_balancehttp://en.wikipedia.org/wiki/Energyhttp://en.wikipedia.org/wiki/Boiling_pointhttp://en.wikipedia.org/wiki/Surface_condenserhttp://en.wikipedia.org/wiki/Enthalpy-entropy_charthttp://en.wikipedia.org/wiki/Turbinehttp://en.wikipedia.org/wiki/Steam_tablehttp://en.wikipedia.org/wiki/Enthalpy-entropy_charthttp://en.wikipedia.org/wiki/H-s_charthttp://en.wikipedia.org/wiki/Mollier_diagramhttp://en.wikipedia.org/wiki/Mollier_diagram


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STEPS OF OPERATION

1. COAL SUPPLYafter haulers drop off the coal, a set of crushers and

conveyors prepare and deliver the coal to the power plant. When the plant

needs coal, coal hoppers crush coal to a few inches in size and conveyor

belts bring the coal inside.

2. COAL PULVERISERthe belts dump coal into a huge bin (pulveriser),

which reduces the coal to a fine powder. Hot air from nearby fans blows the

powdered coal into huge furnaces (boilers).

3. BOILERthe boiler walls are lined with many kilometres of pipe filled

with water. As soon as the coal enters the boiler, it instantly catches fire and

burns with high intensity (the temperatures inside the furnace may climb to

1,300 C). This heat quickly boils the water inside the pipes, changing it into

steam.

4. PRECIPITATORS AND STACKas the coal burns, it produces

emissions (carbon dioxide, sulphur dioxide and nitrogen oxides) and ash. Thegases, together with the lighter ash (fly ash), are vented from the boiler up

the stack. Huge air filters called electrostatic precipitators remove nearly all

the fly ash before it is released into the atmosphere. The heavier ash (bottom

ash) collects in the bottom of the boilers and is removed.

5. TURBINE AND GENERATORmeanwhile, steam moves at high speed

to the turbines, massive drums with hundreds of blades turned at an angle,

like the blades of a fan. As jets of high-pressure steam emerge from the

pipes, they propel the blades, causing the turbine to spin rapidly. A metal


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shaft connects the turbine to a generator. As the turbine turns, it causes an

electro-magnet to turn inside coils of wire in the generator. The spinning

magnet puts electrons in motion inside the wires, creating electricity.

6. CONDENSORS AND COOLING WATER SYSTEMNext, the steamexits the turbines and passes over cool tubes in the condenser. The

condensers capture the used steam and transform it back to water. The cooled

water is then pumped back to the boiler to repeat the heating process. At the

same time, water is piped from a reservoir or river to keep the condensers

constantly cool. This cooling water, now warm from the heat exchange in the

condensers, is released from the plant.

7. WATER PURIFICATIONto reduce corrosion, plants purify water foruse in the boiler tubes. Wastewater is also treated and pumped out to holding

ponds.

8. ASH SYSTEMSAsh is removed from the plant and hauled to disposal

sites or ash lagoons. Ash is also sold for use in manufacturing cement.

9. TRANSFORMER AND TRANSMISSION LINEStransformers

increase the voltage of the electricity generated. Transmission lines then

carry the electricity at high voltages from the plant to substations in cities and

towns.

ESSENTIALS OF STEAM POWER PLANT EQUIPMENT

Steam is an important medium of producing mechanical energy. Steam has the

advantage that, it can be raised from water which is available in abundance it

does not react much with the materials of the equipment of power plant and is

stable at the temperature required in the plant Steam is used to drive steam

engines, steam turbines etc. Steam power station is most suitable where coal is

available in abundance. Thermal electrical power generation is one of the major

methods. Out of total power developed in India about 60% is thermal. For a

thermal power plant the range of pressure may vary from 10 kg/cm2 to super

critical pressures and the range of temperature may be from 250C to650C.The average all India Plant load factor (P.L.F.) of thermal power plants


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in 1987-88 has be worked out to be 56.4% which is the highest P.L.F. recorded

by thermal sector so far.

Coal Handling

Coal delivery equipment is one of the major components of plant cost. The

various steps involved

in coal handling are as follows :

(i) Coal delivery(ii) Unloading(iii) Preparation(iv) Transfer(v) Outdoor storage(vi) Covered storage(vii) In plant handling(viii) Weighing and measuring(ix) Feeding the coal into furnace.(i) COAL DELIVERY: The coal from supply points is delivered by

ships or boats to power stations situated near to sea or river whereas

coal is supplied by rail or trucks to the power stations which are

situated away from sea or river. The transportation of coal by trucks is

used if the railway facilities are not available.

(ii) UNLOADING: The type of equipment to be used for unloading thecoal received at the power station depends on how coal is received at


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the power station. If coal is delivered by trucks, there is no need of

unloading device as the trucks may dump the coal to the outdoor

storage. Coal is easily handled if the lift trucks with scoop are used. In

case the coal is brought by railway wagons, ships or boats, the

unloading may be done by car shakes, rotary car dumpers, cranes, grabbuckets and coal accelerators. Rotary car dumpers although costly are

quite efficient for unloading closed wagons.

(iii) PREPARATION: When the coal delivered is in the form of big lumpsand it is not of proper size, the preparation (sizing) of coal can be

achieved by crushers, breakers, sizers driers and magnetic separators.

(iv) TRANSFER: After preparation coal is transferred to the dead storageby means of the following system :

BELT CONVEYOR: It consists of an endless belt moving over a pair of end

drums (rollers). At some distance a supporting roller is provided at the centre.

The belt is made, up of rubber or canvas. Belt conveyor is suitable for the

transfer of coal over long distances. It is used in medium and large power plants.

The initial cost of the system is not high and power consumption is also low.

The inclination at which coal can be successfully elevated by belt conveyor is

about 20. Average speed of belt conveyors varies between 200-300 r.p.m. This

conveyor is preferred than other types.

ADVANTAGES OF BELT CONVEYOR

1. Its operation is smooth and clean.

2. It requires less power as compared to other types of systems.

3. Large quantities of coal can be discharged quickly and continuously.

4. Material can be transported on moderates inclines.


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COAL STORAGE

The coal is stored by the following methods :

(i) STOCKING THE COAL IN HEAT: The coal is piled on the ground up to

10-12 m height. The pile top should be given a slope in the direction in which

the rain may be drained off.

The sealing of stored pile is desirable in order to avoid the oxidation of coal

after packing an air tight layer of coal. Asphalt, fine coal dust and bituminous

coating are the materials commonly used for this purpose.

(ii) UNDER WATER STORAGE: The possibility of slow oxidation and

spontaneous combustion can be completely eliminated by storing the coalunder water.

Coal should be stored at a site located on solid ground, well drained, free

Of standing water preferably on high ground not subjected to flooding.

(iii) IN PLANT HANDLING: From the dead storage the coal is brought to

covered storage (Live storage) (bins or bunkers). In plant handling may include

the equipment such as belt conveyors, screw conveyors, bucket elevators etc. to

transfer the coal.


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STEAM GENERATOR/BOILER

The boiler is a rectangular furnace about 50 ft (15 m) on a side and 130 ft (40

m) tall. Its walls are made of a web of high pressure steel tubes about 2.3 inches

(60 mm) in diameter. Pulverized coal is air-blown into the furnace from fuelnozzles at the four corners and it rapidly burns, forming a large fireball at the

centre.

That circulates through the boiler tubes near the boiler perimeter. The water

circulation rate in the boiler is three to four times the throughput and is typically

driven by pumps. As the water in the boiler circulates it absorbs heat and

changes into steam at 700 F (370 C) and 3,200 psi (22.1MPa). It is separated

from the water inside a drum at the top of the furnace. The saturated steam isintroduced into superheat pendant tubes that hang in the hottest part of the

combustion gases as they exit the furnace. Here the steam is superheated to

1,000 F (540 C) to prepare it for the turbine.

The steam generating boiler has to produce steam at the high purity, pressure

and temperature required for the steam turbine that drives the electrical

generator. The generator includes the economizer, the steam drum, the chemical

dosing equipment, and the furnace with its steam generating tubes and thesuperheater coils. Necessary safety valves are located at suitable points to avoid

excessive boiler pressure. The air and flue gas path equipment include: forced

draft (FD) fan, air preheater (APH), boiler furnace, induced draft (ID) fan, fly

ash collectors (electrostatic precipitator or baghouse) and the flue gas stack.

For units over about 210 MW capacities, redundancy of key components is

provided by installing duplicates of the FD fan, APH, fly ash collectors and ID

fan with isolating dampers. On some units of about 60 MW, two boilers per unit

may instead be provided.


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BOILER FURNACE AND STEAM DRUM

Once water inside the boiler or steam generator, the process of adding the latent

heat of vaporization or enthalpy is underway. The boiler transfers energy to the

water by the chemical reaction of burning some type of fuel.

The water enters the boiler through a section in the convection pass called the

economizer. From the economizer it passes to the steam drum. Once the water

enters the steam drum it goes down the down comers to the lower inlet water

wall headers. From the inlet headers the water rises through the water walls and

is eventually turned into steam due to the heat being generated by

The burners located on the front and rear water walls (typically). As the water isturned into steam/vapour in the water walls, the steam/vapour once again enters

the steam drum.

The steam/vapour is passed through a series of steam and water separators and

then dryers inside the steam drum. The steam separators and dryers remove the

water droplets from the steam and the cycle through the water walls is repeated.


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This process is known as natural circulation. The boiler furnace auxiliary

equipment includes coal feed nozzles and igniter guns, soot blowers, water

lancing and observation ports (in the furnace walls) for observation of the

furnace interior. Furnace explosions due to any accumulation of combustiblegases after a tripout are avoided by flushing out such gases from the combustion

zone before igniting the coal. The steam drum (as well as the superheater coils

and headers) have air vents and drains needed for initial start-up. The steam

drum has an internal device that removes moisture from the wet steam entering

the drum from the steam generating tubes. The dry steam then flows into the

superheater coils. Geothermal plants need no boiler since they use naturally

occurring steam sources. Heat exchangers may be used where the geothermal

steam is very corrosive or contains excessive suspended solids. Nuclear plantsalso boil water to raise steam, either directly passing the working steam through

the reactor or else using an intermediate heat exchanger.

FUEL PREPARATION SYSTEM

In coal-fired power stations, the raw feed coal from the coal storage area is first

crushed into small pieces and then conveyed to the coal feed hoppers at theboilers. The coal is next pulverized into a very fine powder. The pulverisers may

be ball mills, rotating drum grinders, or other types of grinders. Some power

stations burn fuel oil rather than coal. The oil must kept warm (above its pour

point) in the fuel oil storage tanks to prevent the oil from congealing and

becoming unpumpable. The oil is usually heated to about 100C before being

pumped through the furnace fuel oil spray nozzles.

Boilers in some power stations use processed natural gas as their main fuel.

Other power stations may use processed natural gas as auxiliary fuel in the event

that their main fuel supply (coal or oil) is interrupted. In such cases, separate gas

burners are provided on the boiler furnaces.


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FUEL FIRING AND IGNITE SYSTEM

From the pulverized coal bin, coal is blown by hot air through the furnace coal

burners at an angle which imparts a swirling motion to the powdered coal to

enhance mixing of the coal powder with the incoming preheated combustion airand thus to enhance the combustion. To provide sufficient combustion

temperature in the furnace before igniting the powdered coal, the furnace

temperature is raised by first burning some light fuel oil or processed natural gas

(by using auxiliary burners and igniters provide for that purpose).

AIR PATH

External fans are provided to give sufficient air for combustion. The forced draft

fan takes air from the atmosphere and, first warming it in the air preheater for

better combustion, injects it via the air nozzles on the furnace wall. The induced

draft fan assists the FD fan by drawing out combustible gases from the furnace,

maintaining a slightly negative pressure in the furnace to avoid backfiring

through any opening. At the furnace outlet and before the furnace gases are

handled by the ID fan, fine dust carried by the outlet gases is removed to avoidatmospheric pollution. This is an environmental limitation prescribed by law,

and additionally minimizes erosion of the ID fan.


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AUXILIARY SYSTEMS

FLY ASH COLLECTION

Fly ash is captured and removed from the flue gas by electrostatic precipitators

or fabric bag filters (or sometimes both) located at the outlet of the furnace and

before the induced draft fan. The fly ash is periodically removed from the

collection hoppers below the precipitators or bag filters. Generally, the fly ash is

pneumatically transported to storage silos for subsequent transport by trucks or

railroad cars.

BOTTOM ASH COLLECTION AND DISPOSAL

At the bottom of every boiler, a hopper has been provided for collection of the

bottom ash from the bottom of the furnace. This hopper is always filled with

water to quench the ash and clinkers falling down from the furnace. Some

arrangement is included to crush the clinkers and for conveying the crushed

clinkers and bottom ash to a storage site.

BOILER MAKE-UP WATER TREATMENT PLANT AND STORAGE

Since there is continuous withdrawal of steam and continuous return of

condensate to the boiler, losses due to blow-down and leakages have to be made

up for so as to maintain the desired water level in the boiler steam drum. For

this, continuous make-up water is added to the boiler water system. The

impurities in the raw water input to the plant generally consist of calcium and

magnesium salts which impart hardness to the water. Hardness in the make-up

water to the boiler will form deposits on the tube water surfaces which will leadto overheating and failure of the tubes. Thus, the salts have to be removed from

the water and that is done by a WTP plant. That we will discuss later.


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WATER DEMINERALISING TREATMENT PLANT (DM)

A DM plant generally consists of cation, anion and mixed bed exchangers. The

final water from this process consists essentially of hydrogen ions andhydroxide ions which is the chemical composition of pure water. The DM

water, being very pure, becomes highly corrosive once it absorbs oxygen from

the atmosphere because of its very high affinity for oxygen absorption. The

capacity of the DM plant is dictated by the type and quantity of salts in the raw

water input. However, some storage is essential as the DM plant may be down

for maintenance.

For this purpose, a storage tank is installed from which DM water iscontinuously withdrawn for boiler make-up. The storage tank for DM water is

made from materials not affected by corrosive water, such as PVC. The piping

and valves are generally of stainless steel. Sometimes, a steam blanketing

arrangement or stainless steel doughnut float is provided on top of the water in

the tank to avoid contact with atmospheric air. DM water make-up is generally

added at the steam space of the surface condenser (i.e., the vacuum side). This

arrangement not only sprays the water but also DM water gets deaerated, with

the dissolved gases being removed by the ejector of the condenser itself.


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ELECTRIC GENERATOR

The steam turbine-driven generators have auxiliary systems enabling them to

work satisfactorily and safely. The steam turbine generator being rotating

equipment generally has a heavy, large diameter shaft. The shaft thereforerequires not only supports but also has to be kept in position while running. To

minimize the frictional resistance to the rotation, the shaft has a number of

bearings. The bearing shells, in which the shaft rotates, are lined with a low

friction material like Babbitt metal. Oil lubrication is provided to further reduce

the friction between shaft and bearing surface and to limit the heat generated.

BARRING GEAR OR TURNING GEAR

Barring gear is the term used for the mechanism provided for rotation of the

turbine generator shaft at a very low speed (about one revolution per minute)

after unit stoppages for any reason. Once the unit is "tripped" (i.e., the turbine

steam inlet valve is closed), the turbine starts slowing or "coasting down". When

it stops completely, there is a tendency for the turbine shaft to deflect or bend if

allowed to remain in one position too long. This deflection is because the heat


37/98

inside the turbine casing tends to concentrate in the top half of the casing, thus

making the top half portion of the shaft hotter than the bottom half. The shaft

therefore warps or bends by millionths of inches, only detectable by monitoring

eccentricity meters. But this small amount of shaft deflection would be enoughto cause vibrations and damage the entire steam turbine generator unit when it is

restarted. Therefore, the shaft is not permitted to come to a complete stop by a

mechanism known as "turning gear" or "barring gear" that automatically takes

over to rotate the unit at a preset low speed. If the unit is shut down for major

maintenance, then the barring gear must be kept in service until the temperatures

of the casings and bearings are sufficiently low.

CONDENSER

The surface condenser is a shell and tube heat exchanger in which cooling water

is circulated through the tubes. The exhaust steam from the low pressure turbine

enters the shell where it is cooled and converted to condensate (water) by

flowing over the tubes as shown in the adjacent diagram. Such condensers use

steam ejectors or rotary motor-driven exhausters for continuous removal of air

and gases from the steam side to maintain vacuum.For best efficiency, thetemperature in the condenser must be kept as low as practical in order to achieve

the lowest possible pressure in the condensing steam. Since the condenser

temperature can almost always be kept significantly below 100

C where the

vapour pressure of water is much less than atmospheric pressure, the condenser

generally works under vacuum. Plants operating in hot climates may have to

reduce output if their source of condenser cooling water becomes warmer;

unfortunately this usually coincides with periods of high electrical demand forair conditioning. The condenser generally uses either circulating cooling water

from a cooling tower to reject waste heat to the atmosphere, or once-through

water from a river, lake or ocean.


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FEEDWATER HEATER

A Rankine cycle with a two-stage steam turbine and a single feedwater heater.

In the case of a conventional steam-electric power plant utilizing a drum boiler,

the surface condenser removes the latent heat of vaporization from the steam as

it changes states from vapour to liquid. The heat content (btu) in the steam is

referred to as Enthalpy. The condensate pump then pumps the condensate waterthrough a feedwater heater. The feedwater heating equipment then raises the

temperature of the water by utilizing extraction steam from various stages of the

turbine. Preheating the feedwater reduces the irreversibilitys involved in steam

generation and therefore improves the thermodynamic efficiency of the system.

This reduces plant operating costs and also helps to avoid thermal shock to the

boiler metal when the feedwater is introduced back into the steam cycle.


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SUPERHEATER

As the steam is conditioned by the drying equipment inside the drum, it is piped

from the upper drum area into an elaborate set up of tubing in different areas of

the boiler. The areas known as superheater and reheater. The steam vapour picks

up energy and its temperature is now superheated above the saturationtemperature. The superheated steam is then piped through the main steam lines

to the valves of the high pressure turbine.

DEAERATOR

A steam generating boiler requires that the boiler feed water should be devoid of

air and other dissolved gases, particularly corrosive ones, in order to avoidcorrosion of the metal. Generally, power stations use a deaerator to provide for

the removal of air and other dissolved gases from the boiler feedwater. A

deaerator typically includes a vertical, domed deaeration section mounted on top

of a horizontal cylindrical vessel which serves as the deaerated boiler feedwater

storage tank.


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There are many different designs for a deaerator and the designs will vary from

one manufacturer to another. The adjacent diagram depicts a typical

conventional trayed deaerator. If operated properly, most deaerator

manufacturers will guarantee that oxygen in the deaerated water will not exceed

7 ppb by weight (0.005 cm3/L).

AUXILIARY SYSTEMS IN ELETRIC GENERATOR

OIL SYSTEM

An auxiliary oil system pump is used to supply oil at the start-up of the steam

turbine generator. It supplies the hydraulic oil system required for steam

turbines main inlet steam stop valve, the governing control valves, the bearing

and seal oil systems, the relevant hydraulic relays and other mechanisms. At a

preset speed of the turbine during start-ups, a pump driven by the turbine main

shaft takes over the functions of the auxiliary system.


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GENERATOR HEAT DISSIPATION

The electricity generator requires cooling to dissipate the heat that it generates.

While small units may be cooled by air drawn through filters at the inlet, larger

units generally require special cooling arrangements. Hydrogen gas cooling, inan oil-sealed casing, is used because it has the highest known heat transfer

coefficient of any gas and for its low viscosity which reduces windage losses.

This system requires special handling during start-up, with air in the chamber

first displaced by carbon dioxide before filling with hydrogen. This ensures that

the highly flammable hydrogen does not mix with oxygen in the air. The

hydrogen pressure inside the casing is maintained slightly higher than

atmospheric pressure to avoid outside air ingress. The hydrogen must be sealedagainst outward leakage where the shaft emerges from the casing. Mechanical

seals around the shaft are installed with a very small annular gap to avoid

rubbing between the shaft and the seals. Seal oil is used to prevent the hydrogen

gas leakage to atmosphere. The generator also uses water cooling. Since the

generator coils are at a potential of about 15.75kV and water is conductive, an

insulating barrier such as Teflon is used to interconnect the water line and the

generator high voltage windings. Demineralised water of low conductivity is

used.

GENERATOR HIGH VOLTAGE SYSTEM

The generator voltage ranges from 10.5 kV in smaller units to 15.75 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 channels are

connected to step-up transformers for connecting to a high voltage electrical

substation (of the order of 220 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. In smaller units, generating at 10.5kV, a breaker is provided to connect it

to a common 10.5 kV bus system.


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OTHER SYSTEMS

MONITORING AND ALARM SYSTEM

Most of the power plants operational controls are automatic. However, at times,

manual intervention may be required. Thus, the plant is provided with monitors

and alarm systems that alert the plant operators when certain operating

parameters are seriously deviating from their normal range.

BATTERY SUPPLIED EMERGENCY LIGHTING &COMMUNICATION

A central battery system consisting of lead acid cell units is provided to supply

emergency electric power, when needed, to essential items such as the power

plant's control systems, communication systems, turbine lube oil pumps, and

emergency lighting. This is essential for safe, damage-free shutdown of the units

in an emergency situation.


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EMD-I(Electrical Maintenance

Division I)

It is responsible for the maintenance of:

1. HT/LT MOTORS TURBINE & BOILER SIDE

Boiler Side Motors:

For units 1, 2, 3

1. ID Fans 2 in no.

2. FD Fans 2 in no.

3. PA Fans 2 in no.

4. Mill Fans 3 in no.

5. Ball mill fans 3 in no.

6. RC feeders 3 in no.

7. Slag Crushers 5 in no.

8. DM Make up Pump 2 in no.

9. PC Feeders 4 in no.

10. Worm Conveyor 1 in no.

11. Furnikets 4 in no.


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For stage units 1, 2, 3

1. I.D Fans 2 in no.

2. F.D Fans 2 in no.3. P.A Fans 2 in no.

4. Bowl Mills 6 in no.

5. R.C Feeders 6 in no.

6. Clinker Grinder 2 in no.

7. Scrapper 2 in no.

8. Seal Air Fans 2 in no.

9. Hydrazine & Phosphorous Dozing 2 in no.

2. COAL HANDLING PLANT (C.H.P)

The old coal handling plant caters to the need of units 2,3,4,5 and 1 whereas the

latter supplies coal to units 4 and V.O.C.H.P. supplies coal to second and third

stages in the advent coal to usable form to (crushed) form its raw form and send

it to bunkers, from where it is send to furnace.

MAJOR COMPONENTS

1. WAGON TIPPLER: Wagons from the coal yard come to the tippler and are

emptied here. The process is performed by a slip ring motor of rating: 55 KW,

415V, 1480 RPM. This motor turns the wagon by 135 degrees and coal falls

directly on the conveyor through vibrators. Tippler has raised lower system

which enables is to switch off motor when required till is wagon back to its

original position. It is titled by weight balancing principle. The motor lowers the

hanging balancing weights, which in turn tilts the conveyor. Estimate of theweight of the conveyor is made through hydraulic weighing machine.


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2. CONVEYOR: There are 14 conveyors in the plant. They are numbered so

that their function can be easily demarcated. Conveyors are made of rubber and

more with a speed of 250-300m/min. Motors employed for conveyors has a

capacity of 150 HP. Conveyors have a capacity of carrying coal at the rate o400 tons per hour. Few conveyors are double belt, this is done for imp.

Conveyors so that if a belt develops any problem the process is not stalled. The

conveyor belt has a switch after every 25-30 m on both sides so stop the belt in

case of emergency. The conveyors are 1m wide, 3 cm thick and made of

chemically treated vulcanized rubber. The max angular elevation of conveyor is

designed such as never to exceed half of the angle of response and comes out to

be around 20 degrees.

3. ZERO SPEED SWITCH: It is safety device for motors, i.e., if belt is not

moving and the motor is on the motor may burn. So to protect this switch

checks the speed of the belt and switches off the motor when speed is zero.

4. METAL SEPARATOR: As the belt takes coal to the crusher, No metal

pieces should go along with coal. To achieve this objective, we use metal

separators. When coal is dropped to the crusher hoots, the separator drops metal

pieces ahead of coal. It has a magnet and a belt and the belt is moving, thepieces are thrown away. The capacity of this device is around 50 kg. .The CHP

is supposed to transfer 600 tons of coal/hr, but practically only 300-400 tons

coal is transfer

5. CRUSHER: Both the plants use TATA crushers powered by BHEL. Motors.

The crusher is of ring type and motor ratings are 400 HP, 606 KV. Crusher is

designed to crush the pieces to 20 mm size i.e. practically considered as the

optimum size of transfer via conveyor.

6. ROTATORY BREAKER: OCHP employs mesh type of filters and allows

particles of 20mm size to go directly to RC bunker, larger particles are sent to

crushes. This leads to frequent clogging. NCHP uses a technique that crushes

the larger of harder substance like metal impurities easing the load on the

magnetic separators.


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3. MILLING SYSTEM

1. RC BUNKER: Raw coal is fed directly to these bunkers. These are 3 in no.

per boiler. 4 & tons of coal are fed in 1 hr. the depth of bunkers is 10m.

2. RC FEEDER: It transports pre crust coal from raw coal bunker to mill. The

quantity of raw coal fed in mill can be controlled by speed control of aviator

drive controlling damper and aviator change.

3. BALL MILL: The ball mill crushes the raw coal to a certain height and then

allows it to fall down. Due to impact of ball on coal and attraction as per the

particles move over each other as well as over the Armor lines, the coal gets

crushed. Large particles are broken by impact and full grinding is done byattraction. The Drying and grinding option takes place simultaneously inside the

mill.

4. CLASSIFIER: It is equipment which serves separation of fine pulverized

coal particles medium from coarse medium. The pulverized coal along with the

carrying medium strikes the impact plate through the lower part. Large particles

are then transferred to the ball mill.

5. CYCLONE SEPARATORS: It separates the pulverized coal from carrying

medium. The mixture of pulverized coal vapour caters the cyclone separators.

6. THE TURNIKET: It serves to transport pulverized coal from cyclone

separators to pulverized coal bunker or to worm conveyors. There are 4

turnikets per boiler.

7. WORM CONVEYOR: It is equipment used to distribute the pulverized coal

from bunker of one system to bunker of other system. It can be operated in bothdirections.

8. MILL FANS: They are of 3 types:

Six in all and are running condition all the time.

(a) ID Fans: Located between electrostatic precipitator and chimney.

Type-radical

Speed-1490 rpm


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Rating-300 KW

Voltage-6.6 KV

Lubrication-by oil(b) FD Fans: Designed to handle secondary air for boiler. 2 in number and

provide ignition of coal.

Type-axial

Speed-990 rpm

Rating-440 KW

Voltage-6.6 KV

(c) Primary Air Fans: Designed for handling the atmospheric air up to 50

degrees Celsius, 2 in number

And they transfer the powered coal to burners to firing.

Type-Double suction radial

Rating-300 KW

Voltage-6.6 KV

Lubrication-by oil

Type of operation-continuous

9. BOWL MILL: One of the most advanced designs of coal pulverizes

presently manufactured.

Motor Specification

Squirrel cage induction motor

Rating-340 KW

Voltage-6600KV

Curreen-41.7A


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Speed-980 rpm

Frequency-50 Hz

No-load current-15-16 A

4. NEW COAL HANDLING PLANT

1. WAGON TIPPLER:

Motor Specification

(i) H.P 75 HP

(ii) Voltage 415, 3 phase

(iii) Speed 1480 rpm

(iv) Frequency 50 Hz

(v) Current rating 102 A

2. COAL FEED TO PLANT:

Feeder motor specification

(i) Horse power 15 HP

(ii) Voltage 415V,3 phase

(iii) Speed 1480 rpm

(iv) Frequency 50 Hz

3. CONVEYORS:

10A, 10B

11A, 11B

12A, 12B


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13A, 13B

14A, 14B

15A, 15B16A, 16B

17A, 17B

18A, 18B

4. TRANSFER POINT 6

5. BREAKER HOUSE

6. REJECTION HOUSE

7. RECLAIM HOUSE

8. TRANSFER POINT 7

9. CRUSHER HOUSE

The coal arrives in wagons via railways and is tippled by the wagon tipplers intothe hoppers. If coal is oversized (>400 mm sq) then it is broken manually so that

it passes the hopper mesh. From the hopper mesh it is taken to the transfer point

TP6 by conveyor 12A ,12B which takes the coal to the breaker house , which

renders the coal size to be 100mm sq. the stones which are not able to pass

through the 100mm sq of hammer are rejected via conveyors 18A,18B to the

rejection house . Extra coal is too sent to the reclaim hopper via conveyor 16.

From breaker house coal is taken to the TP7 via Conveyor 13A, 13B. Conveyor

17A, 17B also supplies coal from reclaim hopper, From TP7 coal is taken by

conveyors 14A, 14B to crusher house whose function is to render the size o

coal to 20mm sq. now the conveyor labourers are present whose function is to

recognize and remove any stones moving in the conveyors . In crusher before it

enters the crusher. After being crushed, if any metal is still present it is taken

care of by metal detectors employed in conveyor 10.


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5. SWITCH GEAR

It makes or breaks an electrical circuit.

1. ISOLATION: A device which breaks an electrical circuit when circuit isswitched on to no load. Isolation is normally used in various ways for purpose

of isolating a certain portion when required for maintenance.

2. SWITCHING ISOLATION: It is capable of doing things like interrupting

transformer magnetized current, interrupting line charging current and even

perform load transfer switching. The main application of switching isolation is

in connection with transformer feeders as unit makes it possible to switch out

one transformer while other is still on load.3. CIRCUIT BREAKERS: One which can make or break the circuit on load

and even on faults is referred to as circuit breakers. This equipment is the most

important and is heavy duty equipment mainly utilized for protection of various

circuits and operations on load. Normally circuit breakers installed are

accompanied by isolators

4. LOAD BREAK SWITCHES: These are those interrupting devices which

can make or break circuits. These are normally on same circuit, which are

backed by circuit breakers.

5. EARTH SWITCHES: Devices which are used normally to earth a particular

system, to avoid any accident happening due to induction on account of live

adjoining circuits. These equipments do not handle any appreciable current at

all. Apart from this equipment there are a number of relays etc. which are used

in switchgear.

LT SWITCHGEAR

It is classified in following ways:-

1. MAIN SWITCH: Main switch is control equipment which controls or

disconnects the main supply. The main switch for 3 phase supply is available for

the range 32A, 63A, 100A, 200Q, 300A at 500V grade.


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2. FUSES: With Avery high generating capacity of the modern power stations

extremely heavy carnets would flow in the fault and the fuse clearing the fault

would be required to withstand extremely heavy stress in process.

It is used for supplying power to auxiliaries with backup fuse protection. Rotaryswitch up to 25A. With fuses, quick break, quick make and double break switch

fuses for 63A and 100A, switch fuses for 200A, 400A, 600A, 800A and 1000A

are used.

3. CONTRACTORS: AC Contractors are 3 poles suitable for D.O.L Starting

of motors and protecting the connected motors.

4. OVERLOAD RELAY: For overload protection, thermal over relay are bestsuited for this purpose. They operate due to the action of heat generated by

passage of current through relay element.

5. AIR CIRCUIT BREAKERS: It is seen that use of oil in circuit breaker may

cause a fire. So in all circuits breakers at large capacity, air at high pressure is

used, which is maximum at the time of quick tripping of contacts. This reduces

the possibility of sparking. The pressure may vary from 50-60 kg/cm^2 for high

and medium capacity circuit breakers.

HT Switch Gear

1. MINIMUM OIL CIRCUIT BREAKER: These use oil as quenching

medium. It comprises of simple dead tank row pursuing projection from it. The

moving contracts are carried on an iron arm lifted by a long insulating tension

rod and are closed simultaneously pneumatic operating mechanism by means oftensions but throw off spring to be provided at mouth of the control the main

current within the controlled device.

Type-HKH 12/1000c

Rated Voltage-66 KV

Normal Current-1250A

Frequency-5Hz


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Breaking Capacity-3.4+KA Symmetrical

3.4+KA Asymmetrical

360 MVA Symmetrical Operating Coils-CC 220 V/DC

FC 220V/DC

Motor Voltage-220 V/DC

2. AIR CIRCUIT BREAKER: In this the compressed air pressure around 15kg per cm^2 is used for extinction of arc caused by flow of air around the

moving circuit. The breaker is closed by applying pressure at lower opening and

opened by applying pressure at upper opening. When contacts operate, the cold

air rushes around the movable contacts and blown the arc.

It has the following advantages over OCB:-

i. Fire hazard due to oil are eliminated.

ii. Operation takes place quickly.

iii. There is less burning of contacts since the duration is short and consistent.

iv. Facility for frequent operation since the cooling medium is replaced

constantly.

Rated Voltage-6.6 KV

Current-630 A

Auxiliary current-220 V/DC

3. SF6 CIRCUIT BREAKER: This type of circuit breaker is of construction to

dead tank bulk oil to circuit breaker but the principle of current interruption is

similar o that of air blast circuit breaker. It simply employs the arc extinguishing

medium namely SF6. The performance of gas. When it is broken down under an


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electrical stress. It will quickly reconstitute itself

Circuit Breakers-HPA

Standard-1 EC 56 Rated Voltage-12 KV

Insulation Level-28/75 KV

Rated Frequency-50 Hz

Breaking Current-40 KA

Rated Current-1600 A

Making Capacity-110 KA

Rated Short Time Current 1/3s -40 A

Mass Approximation-185 KG

Auxiliary Voltage

Closing Coil-220 V/DC

Opening Coil-220 V/DC

Motor-220 V/DC

SF6 Pressure at 20 Degree Celsius-0.25 KG

SF6 Gas Per pole-0.25 KG

4. VACUUM CIRCUIT BREAKER: It works on the principle that vacuum is

used to save the purpose of insulation and it implies that pr. Of gas at which

breakdown voltage independent of pressure. It regards of insulation and

strength, vacuum is superior dielectric medium and is better that all other

medium except air and sulphur which are generally used at high pressure.

Rated frequency-50 Hz

Rated making Current-10 Peak KA


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Rated Voltage-12 KV

Supply Voltage Closing-220 V/DC

Rated Current-1250 A Supply Voltage Tripping-220 V/DC

Insulation Level-IMP 75 KVP

Rated Short Time Current-40 KA (3 SEC)

Weight of Breaker-8 KG


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EMD-II(Electrical Maintenance

Division II)

This division is divided as follows:

GENERATOR AND AUXILIARIES

GENERATOR FUNDAMENTALS

The transformation of mechanical energy into electrical energy is carried out by

the Generator. This Chapter seeks to provide basic understanding about the

working principles and development of Generator.

WORKING PRINCIPLE

The A.C. Generator or alternator is based upon the principle of electromagnetic

induction and consists generally of a stationary part called stator and a rotating

part called rotor. The stator housed the armature windings. The rotor houses the

field windings. D.C. voltage is applied to the field windings through slip rings.

When the rotor is rotated, the lines of magnetic flux (viz magnetic field) cut

through the stator windings. This induces an electromagnetic force (e.m.f.) in

the stator windings. The magnitude of this e.m.f. is given by the followingexpression.

E = 4.44 /O FN volts

0 = Strength of magnetic field in Webers.

F = Frequency in cycles per second or Hertz.

N = Number of turns in a coil of stator winding

F = Frequency = Pn/120


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Where P = Number of poles

n = revolutions per second of rotor.

From the expression it is clear that for the same frequency, number of polesincreases with decrease in speed and vice versa. Therefore, low speed hydro

turbine drives generators have 14 to 20 poles were as high speed steam turbine

driven generators have generally 2 poles.

GENERATOR COMPONENT

This deals with the two main components of the Generator viz. Rotor, its

winding & balancing and stator, its frame, core & windings.

ROTOR

The electrical rotor is the most difficult part of the generator to design. It

revolves in most modern generators at a speed of 3,000 revolutions per minute.

The problem of guaranteeing the dynamic strength and operating stability o

such a rotor is complicated by the fact that a massive non-uniform shaft

subjected to a multiplicity of differential stresses must operate in oil lubricated

sleeve bearings supported by a structure mounted on foundations all of which

possess complex dynamic be behaviour peculiar to them. It is also an

electromagnet and to give it the necessary magnetic strength

The windings must carry a fairly high current. The passage of the current

through the windings generates heat but the temperature must not be allowed to

become so high, otherwise difficulties will be experienced with insulation. To

keep the temperature down, the cross section of the conductor could not be

increased but this would introduce another problems. In order to make room for

the large conductors, body and this would cause mechanical weakness. The

problem is really to get the maximum amount of copper into the windings

without reducing the mechanical strength. With good design

And great care in construction this can be achieved. The rotor is a cast steel

ingot, and it is further forged and machined. Very often a hole is bored through

the centre of the rotor axially from one end of the other for inspection. Slots are


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then machined for windings and ventilation.

ROTOR WINDING: Silver bearing copper is used for the winding with mica

as the insulation between conductors. A mechanically strong insulator such as

micanite is used for lining the slots. Later designs of windings for large rotorincorporate combination of hollow conductors with slots or holes arranged to

provide for circulation of the cooling gas through the actual conductors. When

rotating at high speed. Centrifugal force tries to lift the windings out of the slots

and they are contained by wedges. The end rings are

Secured to a turned recess in the rotor body, by shrinking or screwing and

supported at the other end by fittings carried by the rotor body. The two ends o

windings are connected to slip rings, usually made of forged steel, and mountedon insulated sleeves.

ROTOR BALANCING: When completed the rotor must be tested for

mechanical balance, which means that a check is made to see if it will run up to

normal speed without vibration. To do this it would have to be uniform about its

central axis and it is most unlikely that this will be so to the degree necessary for

perfect balance. Arrangements are therefore made in all designs to fix adjustable

balance weights around the circumference at each end.

STATOR

STATOR FRAME: The stator is the heaviest load to be transported. The major

part of this load is the stator core. This comprises an inner frame and outer

frame. The outer frame is a rigid fabricated structure of welded steel plates,

within this shell is a fixed cage of girder built circular and axial ribs. The ribs

divide the yoke in the compartments through which hydrogen flows into radial

ducts in the stator core and circulate through the gas coolers housed in the

frame. The inner cage is usually fixed in to the yoke by an arrangement of

springs to dampen the double frequency vibrations inherent in 2 pole generators.

The end shields of hydrogen cooled generators must be strong enough to carry

shaft seals. In large generators the frame is constructed as two separate parts.

The fabricated inner cage is inserted in the outer frame after the stator core hasbeen constructed and the winding completed.


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STATOR CORE: The stator core is built up from a large number of 'punching"

or sections of thin steel plates. The use of cold rolled grain-oriented steel can

contribute to reduction in the weight of stator core for two main reasons:

a) There is an increase in core stacking factor with improvement in laminationcold Rolling and in cold buildings techniques.

b) The advantage can be taken of the high magnetic permeance of grain-oriented

steels of work the stator core at comparatively high magnetic saturation without

fear or excessive iron loss of two heavy a demand for excitation ampere turns

from the generator rotor.

STATOR WINDINGS: Each stator conductor must be capable of carrying therated current without overheating. The insulation must be sufficient to prevent

leakage currents flowing between the phases to earth. Windings for the stator

are made up from copper strips wound with insulated tape which is impregnated

with varnish, dried under vacuum and hot pressed to form a solid insulation bar.

These bars are then place in the stator slots and held in with wedges to form the

complete winding which is connected together at each end of the core forming

the end turns. These end turns are rigidly braced and packed with blocks o

insulation material to withstand the heavy forces which might result from ashort circuit or other fault conditions. The generator terminals are usually

arranged below the stator. On recent generators (210 MW) the windings are

made up from copper tubes instead of strips through which water is circulated

for cooling purposes. The water is fed to the windings through plastic tubes.

GENERATOR COOLING SYSTEM

The 200/210 MW Generator is provided with an efficient cooling system to

avoid excessive heating and consequent wear and tear of its main components

during operation. This Chapter deals with the rotor-hydrogen cooling system

and stator water cooling system along with the shaft sealing and bearing cooling

systems.


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ROTOR COOLING SYSTEM

The rotor is cooled by means of gap pick-up cooling, wherein the hydrogen gas

in the air gap is sucked through the scoops on the rotor wedges and is directed to

flow along the ventilating canals milled on the sides of the rotor coil, to thebottom of the slot where it takes a turn and comes out on the similar canal

milled on the other side of the rotor coil to the hot zone of the rotor. Due to the

rotation of the rotor, a positive suction as well as discharge is created due to

which a certain quantity of gas flows and cools the rotor. This method of

cooling gives uniform distribution of temperature. Also, this method has an

inherent advantage of eliminating the deformation of copper due to varying

temperatures.

HYDROGEN COOLING SYSTEM

Hydrogen is used as a cooling medium in large capacity generator in view of its

high heat carrying capacity and low density. But in view of its forming an

explosive mixture with oxygen, proper arrangement for filling, purging and

maintaining its purity inside the generator have to be made. Also, in order toprevent escape of hydrogen from the generator casing, shaft sealing system is

used to provide oil sealing. The hydrogen cooling system mainly comprises of a

gas control stand, a drier, an liquid level indicator, hydrogen control panel, gas

purity measuring and indicating instruments,

The system is capable of performing the following functions :

I. Filling in and purging of hydrogen safely without bringing in contact with

air.

II. Maintaining the gas pressure inside the machine at the desired value at all

the times.

III. Provide indication to the operator about the condition of the gas inside the

machine i.e. its pressure, temperature and purity.

V. Continuous circulation of gas inside the machine through a drier in order

to remove any water vapour that may be present in it.

V. Indication of liquid level in the generator and alarm in case of high level.


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STATOR COOLING SYSTEM

The stator winding is cooled by distillate.Turbo generators require water cooling arrangement over and above the usual

hydrogen cooling arrangement. The stator winding is cooled in this system by

circulating demineralised water (DM water) through hollow conductors. The

cooling water used for cooling stator winding calls for the use of very high

quality of cooling water. For this purpose DM water of proper specific

resistance is selected. Generator is to be loaded within a very short period if the

specific resistance of the cooling DM water goes beyond certain preset values.The system is designed to maintain a constant rate of cooling water flow to the

stator winding at a nominal inlet water temperature of 40 degrees Celsius.

Rating of 95 MW Generator-

Manufacture by Bharat heavy electrical Limited (BHEL)

Capacity - 117500 KVA

Voltage - 10500V

Speed - 3000 rpm

Hydrogen - 2.5 Kg/cm2

Power factor - 0.85 (lagging)

Stator current - 6475 A

Frequency - 50 Hz

Stator winding connection - 3 phase

Rating of 210 MW Generator-

Manufacture by Bharat heavy electrical Limited (BHEL)


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Capacity - 247000 KVA

Voltage (stator) - 15750 V

Current (stator) - 9050 AVoltage (rotor) - 310 V

Current (rotor) - 2600 V

Speed - 3000 rpm

Power factor - 0.85

Frequency - 50 Hz

Hydrogen - 3.5 Kg/cm2

Stator winding connection - 3 phase star connection

Insulation class - B

TRANSFORMER

A transformer is a device that transfers electrical energy from one circuit to

another by magnetic coupling without requiring relative motion between its

parts. It usually comprises two or more coupled windings, and in most cases, a

core to concentrate magnetic flux. An alternating voltage applied to one winding

creates a time-varying magnetic flux in the core, which includes a voltage in the

other windings. Varying the relative number of turns between primary and

secondary windings determines the ratio of the input and output voltages, thustransforming the voltage by stepping it up or down between circuits. By

transforming electrical power to a high-voltage, _low-current form and back

again, the transformer greatly reduces energy losses and so enables the

economic transmission of power over long distances. It has thus shape the

electricity supply industry, permitting generation to be located remotely from

point of demand. All but a fraction of the worlds electrical power has passed

through a series of transformer by the time it reaches the consumer.


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BASIC PRINCIPLES

The principles of the transformer are illustrated by consideration of a

hypothetical ideal transformer consisting of two windings of zero resistance

around a core of negligible reluctance. A voltage applied to the primary windingcauses a current, which develops a magneto motive force (MMF) in the core.

The current required to create the MMF is termed the magnetizing current; in

the ideal transformer it is considered to be negligible, although its presence is

still required to drive flux around the magnetic circuit of the core. An

electromotive force (MMF) is induced across each winding, an effect known as

mutual inductance. In accordance with faradays law of induction, the EMFs are

proportional to the rate of change of flux. The primary EMF, acting as it does inopposition to the primary voltage, is sometimes termed the back EMF. Energy

losses An ideal transformer would have no energy losses and would have no

energy losses, and would therefore be 100% efficient. Despite the transformer

being amongst the most efficient of electrical machines with ex the most

efficient of electrical machines with experimental models using superconducting

windings achieving efficiency of 99.85%, energy is dissipated in the windings,

core, and surrounding structures. Larger transformers are generally more

efficient, and those rated for electricity distribution usually perform better than95%. A small transformer such as plug-in power brick used for low-power

consumer electronics may be less than 85% efficient. Transformer losses are

attributable to several causes and may be differentiated between those originated

in the windings, sometimes termed copper loss, and those arising from the

magnetic circuit, sometimes termed iron loss. The losses vary with load current,

and may furthermore be expressed as no load or full load loss, or at an

intermediate loading. Winding resistance dominates load losses contribute toover 99% of the no-load loss can be significant, meaning that even an idle

transformer constitutes a drain on an electrical supply, and lending impetus to

development of low-loss transformers. Losses in the transformer arise from:

Winding resistance current flowing through the windings causes resistive

heating of the conductors. At higher frequencies, skin effect and proximity

effect create additional winding resistance and losses. Hysteresis losses each

time the magnetic field is reversed, a small amount of energy is lost due to

hysteresis within the core. For a given core material, the loss is proportional to


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the frequency, and is a function of the peak flux density to which it is subjected.

Eddy current Ferromagnetic materials are also good conductors, and a solid core

made from such a material also constitutes a single short-circuited turn trough

out its entire length. Eddy currents therefore circulate with in a core in a planenormal to the flux, and are responsible for resistive heating of the core material.

The eddy current loss is a complex function of the square of supply frequency

and inverse square of the material thickness. Magnetostriction Magnetic flux in

a ferromagnetic material, such as the core, causes it to physically expand and

contract slightly with each cycle of the magnetic field, an effect known as

magnetostriction. This produces the buzzing sound commonly associated with

transformers, and in turn causes losses due to frictional heating in susceptible

cores. Mechanical losses In addition to magnetostriction, the alternatingmagnetic field causes fluctuating electromagnetic field between primary and

secondary windings. These incite vibration within nearby metal work, adding to

the buzzing noise, and consuming a small amount of power. Stray losses

Leakage inductance is by itself loss less, since energy supplied to its magnetic

fields is returned to the supply with the next half-cycle. However, any leakage

flux that intercepts nearby conductive material such as the transformers support

structure will give rise to eddy currents and be converted to heat. Coolingsystem Large power transform

Ntpc Btps Electrical Project Report 2013

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