ntpc btps electrical project report 2013
TRANSCRIPT
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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
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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