Project Report ( n.t.p.c. b

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Ashutosh Kumar welcome you

PROJECT REPORT ( N.T.P.C. BADARPUR, NEW DELHI )

INDUSTRIAL TRAINING REPORT

(SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIRMENT OF THE COURSE OF B.TECH.)

UNDERTAKEN AT

N.T.P.C. BADARPUR, NEW DELHI FROM: 18th JUNE to 11th August, 2007

SUBMITTED TO: SUBMITTED BY:

Mrs. RACHNA SINGH Ashutosh Kumar N.T.P.C. Badarpur B.Tech 3rd Year

Electrical Engineering

JSS ACADEMY OF TECHNICAL EDUCATION (NOIDA)

TABLE OF CONTENT

Certificate Acknowledgement

Training at BTPS

1. Introduction

¨ NTPC

¨ Badarpur Thermal Power Station

2. Operation3. Control & Instrumentation

¨ Manometry Lab

¨ Protection and interlock Lab¨ Automation Lab

¨ Water Treatment Plant

¨ Furnace Safeguard Supervisory System

¨ Electronic Test Lab

4. Electrical Maintenance Division-I

¨ HT/LT Switch Gear

¨ HT/LT Motors, Turbine & Boilers Side

¨ CHP/NCHP

5. Electrical Maintenance Division-II

¨ Generator

¨ Transformer & Switchyard

¨ Protection

¨ Lighting

¨ EP CERTIFICATE

This is to certify that------------------------- student of Batch Electrical & Electronics Branch IIIrd Year; Sky line

ECT REPORT ( N.T.P.C. BADARPUR, NEW DELHI ) - Ashutosh... http://ashutosh.wetpaint.com/page/PROJECT+REPORT+(+N.T

8 5/18/2011



Institute of Engineering & Technology Noida has successfully completed his industrial training at

Badarpur Thermal power station New Delhi for eight week from 18th June to 11th august 2007

He has completed the whole training as per the training report submitted by him.

Training Incharge

BTPS/NTPC

NEW DELHI

Acknowledgement

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

training here.

I do extend my heartfelt thanks to Mrs. Rachna Singh for providing me this opportunity to be a part of

this esteemed organization.

I am extremely grateful to all the technical staff of BTPS/NTPC for their co-operation and guidance that

helped me a lot during the course of training. I have learnt a lot working under them and I will always be

indebted of them for this value addition in me.

I would also like to thank the training in charge of Skyline Institute of Engineering & Technology Gr. Noida

and all the faculty member of Electrical & Electronics department for their effort of constant

co-operation. Which have been significant factor in the accomplishment of my industrial training.

Training at BTPS

I was appointed to do eight-week training at this esteemed organization from 18th June to 11th august

2007. In these eight weeks I was assigned to v isit various division of the plant which were

Operation1.

Control and instrumentation (C&I)2.

Electrical maintenance division I (EMD-I)3.


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Electrical maintenance division II (EMD-II)4.

This eight-week training was a very educational adventure for me. It was really amazing to see the plant

by your self and learn how electricity, which is one of our daily requirements of life, is produced.

This report has been made by self-experience at BTPS. The material in this report has been gathered

from my textbooks, senior student report, and trainer manual provided by training department. The

specification & principles are at learned by me from the employee of each division of BTPS.

ABOUT NTPC

NTPC Limited is the largest thermal power generating company of India. A public sector company, it was

incorporated in the year 1975 to accelerate power development in the country as a wholly owned

company of the Government of India. At present, Government of India holds 89.5% of the total equity

shares of the company and FIIs, Domestic Banks, Public and others hold the balance 10.5%. With in a

span of 31 years, NTPC has emerged as a truly national power company, with power generating facilities

in all the major regions of the country.


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POWER GENERATION IN INDIA

NTPC’s core business is engineering, construction and operation of power generating plants. It also

provides consultancy in the area of power plant constructions and power generation to companies in

India and abroad. As on date the installed capacity of NTPC is 27,904 MW through its 15 coal based(22,895 MW), 7 gas based (3,955 MW) and 4 Joint Venture Projects (1,054 MW). NTPC acquired 50%

equity of the SAIL Power Supply Corporation Ltd. (SPSCL). This JV Company operates the captive power

plants of Durgapur (120 MW), Rourkela (120 MW) and Bhilai (74 MW). NTPC also has 28.33% stake in

Ratnagiri Gas & Power Private Limited (RGPPL) a joint venture company between NTPC, GAIL, Indian

Financial Institutions and Maharashtra SEB Co Ltd.

NTPC has set new benchmarks for the power industry both in the area of power plant construction and

operations. Its providing power at the cheapest average tariff in the country..

NTPC is committed to the environment, generating power at minimal environmental cost and preserving

the ecology in the vicinity of the plants. NTPC has undertaken massive a forestation in the vicinity of its

plants. Plantations have increased forest area and reduced barren land. The massive a forestation by

NTPC in and around its Ramagundam Power station (2600 MW) have contributed reducing the

temperature in the areas by about 3°c. NTPC has also taken proactive steps for ash utilization. In 1991, itset up Ash Utilization Division

A "Centre for Power Efficiency and Environment Protection (CENPEEP)" has been established in NTPC

with the assistance of United States Agency for International Development. (USAID). Cenpeep is

efficiency oriented, eco-friendly and eco-nurturing initiative - a symbol of NTPC's concern towards

environmental protection and continued commitment to sustainable power development in India.

As a responsible corporate citizen, NTPC is making constant efforts to improve the socio-economic

status of the people affected by its projects. Through its Rehabilitation and Resettlement programmes,

the company endeavors to improve the overall socio economic status Project Affected Persons.

NTPC was among the first Public Sector Enterprises to enter into a Memorandum of Understanding

(MOU) with the Government in 1987-88. NTPC has been placed under the 'Excellent category' (the best

category) every year since the MOU system became operative.

Harmony between man and environment is the essence of healthy life and growth. Therefore,

maintenance of ecological balance and a pristine environment has been of utmost importance to NTPC.

It has been taking various measures discussed below for mitigation of environment pollution due to

power generation.

Environment Policy & Environment Management System

Driven by its commitment for sustainable growth of power, NTPC has evolved a well defined

environment management policy and sound environment practices for minimizing environmental impact


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arising out of setting up of power plants and preserving the natural ecology.

National Environment Policy:

At the national level, the Ministry of Environment and Forests had prepared a draft Environment Policy

(NEP) and the Ministry of Power along with NTPC actively participated in the deliberations of the draft

NEP. The NEP 2006 has since been approved by the Union Cabinet in May 2006.

NTPC Environment Policy:

As early as in November 1995, NTPC brought out a comprehensive document entitled "NTPC

Environment Policy and Environment Management System". Amongst the guiding principles adopted inthe document are company's proactive approach to environment, optimum utilization of equipment,

adoption of latest technologies and continual environment improvement. The policy also envisages

efficient utilization of resources, thereby minimizing waste, maximizing ash utilization and providing

green belt all around the plant for maintaining ecological balance.

Environment Management, Occupational Health and Safety Systems:

NTPC has actively gone for adoption of best international practices on environment, occupational health

and safety areas. The organization has pursued the Environmental Management System (EMS) ISO14001 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 environmentalprovisions into the plant design. In order to ensure that NTPC comply with all the stipulated environment

norms, various state-of-the-art pollution control systems / devices as discussed below have been

installed to control air and water pollution.

Electrostatic Precipitators:

The ash left behind after combustion of coal is arrested in high efficiency Electrostatic Precipitators

(ESP’s) and particulate emission is controlled well within the stipulated norms. The ash collected in the

ESP’s is disposed to Ash Ponds in slurry form.

Flue Gas Stacks:

Tall Flue Gas Stacks have been provided for wide dispersion of the gaseous emissions (SOX, NOX etc)into the atmosphere.

Low-NOXBurners:

In gas based NTPC power stations, NOx emissions are controlled by provision of Low-NOx Burners (dry

or wet type) and in coal fired stations, by adopting best combustion practices.

Neutralisation Pits:

Neutralisation pits have been provided in the Water Treatment Plant (WTP) for pH correction of the

effluents before discharge into Effluent Treatment Plant (ETP) for further treatment and use.

Coal Settling Pits / Oil Settling Pits:

In these Pits, coal dust and oil are removed from the effluents emanating from the Coal Handling Plant

(CHP), coal yard and Fuel Oil Handling areas before discharge into ETP.

DE & DS Systems:

Dust Extraction (DE) and Dust Suppression (DS) systems have been installed in all coal fired power

stations in NTPC to contain and extract the fugitive dust released in the Coal Handling Plant (CHP).

Cooling Towers:

Cooling Towers have been provided for cooling the hot Condenser cooling water in closed cycle

Condenser Cooling Water (CCW) Systems. This helps in reduction in thermal pollution and conservation

of fresh water.

Ash Dykes & Ash Disposal systems:

Ash ponds have been provided at all coal based stations except Dadri where Dry Ash Disposal System

has been provided. Ash Ponds have been divided into lagoons and provided with garlanding

arrangements for change over of the ash slurry feed points for even filling of the pond and for effective

settlement of the ash particles.


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Ash in slurry form is discharged into the lagoons where ash particles get settled from the slurry and

clear effluent water is discharged from the ash pond. The discharged effluents conform to standards

specified by CPCB and the same is regularly monitored.

At its Dadri Power Station, NTPC has set up a unique system for dry ash collection and disposal facility

with Ash Mound formation. This has been envisaged for the first time in Asia which has resulted in

progressive development of green belt besides far less requirement of land and less water requirement

as compared to the wet ash disposal system.

Ash Water Recycling System:

Further, in a number of NTPC stations, as a proactive measure, Ash Water Recycling System (AWRS)

has been provided. In the AWRS, the effluent from ash pond is circulated back to the station for further ash sluicing to the ash pond. This helps in savings of fresh water requirements for transportation of ash

from the plant.

The ash water recycling system has already been installed and is in operation at Ramagundam,

Simhadri, Rihand, Talcher Kaniha, Talcher Thermal, Kahalgaon, Korba and Vindhyachal. The scheme has

helped stations to save huge quantity of fresh water required as make-up water for disposal of ash.

Dry Ash Extraction System (DAES):

Dry ash has much higher utilization potential in ash-based products (such as bricks, aerated autoclavedconcrete blocks, concrete, Portland pozzolana cement, etc.). DAES has been installed at Unchahar,

Dadri, Simhadri, Ramagundam, Singrauli, Kahalgaon, Farakka, Talcher Thermal, Korba, Vindhyachal,

Talcher Kaniha and BTPS.

Liquid Waste Treatment Plants & Management System:The objective of industrial liquid effluent treatment plant (ETP) is to discharge lesser and cleaner effluent

from the power plants to meet environmental regulations. After primary treatment at the source of their

generation, the effluents are sent to the ETP for further treatment. The composite liquid effluent

treatment plant has been designed to treat all liquid effluents which originate within the power station

e.g. Water Treatment Plant (WTP), Condensate Polishing Unit (CPU) effluent, Coal Handling Plant (CHP)

effluent, floor washings, service water drains etc. The scheme involves collection of various effluents

and their appropriate treatment centrally and re-circulation of the treated effluent for various plant uses.

NTPC has implemented such systems in a number of its power stations such as Ramagundam,

Simhadri, Kayamkulam, Singrauli, Rihand, Vindhyachal, Korba, Jhanor Gandhar, Faridabad, Farakka,

Kahalgaon and Talcher Kaniha. These plants have helped to control quality and quantity of the effluents

discharged from the stations.

Sewage Treatment Plants & Facilities:

Sewage Treatment Plants (STPs) sewage treatment facilities have been provided at all NTPC stations to

take care of Sewage Effluent from Plant and township areas. In a number of NTPC projects modern type

STPs with Clarifloculators, Mechanical Agitators, sludge drying beds, Gas Collection Chambers etc have

been provided to improve the effluent quality. The effluent quality is monitored regularly and treated

effluent conforming to the prescribed limit is discharged from the station. At several stations, treated

effluents of STPs are being used for horticulture purpose.

Environmental Institutional Set-up:

Realizing the importance of protection of the environment with speedy development of the power sector,

the company has constituted different groups at project, regional and Corporate Centre level to carry

out specific environment related functions. The Environment Management Group, Ash Utilisation Group

and Centre for Power Efficiency & Environment Protection (CENPEEP) function from the Corporate

Centre and initiate measures to mitigate the impact of power project implementation on the environment

and preserve ecology in the vicinity of the projects. Environment Management and Ash Utilisation

Groups established at each station, look after various environmental issues of the individual station.

Environment Reviews:

To maintain constant vigil on environmental compliance, Environmental Reviews are carried out at all

operating stations and remedial measures have been taken wherever necessary. As a feedback and

follow-up of these Environmental Reviews, a number of retrofit and up-gradation measures have been

undertaken at different stations.

Such periodic Environmental Reviews and extensive monitoring of the facilities carried out at all stations

have helped in compliance with the environmental norms and timely renewal of the Air and Water


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Unit 1997-98 2006-07 % of increase

Installed Capacity MW 16,847 26,350 56.40

Consents.

Up gradation & retrofitting of Pollution Control Systems:

Waste Management

Various types of wastes such as Municipal or domestic wastes, hazardous wastes, Bio-Medical wastes

get generated in power plant areas, plant hospital and the townships of projects. The wastes generated

are a number of solid and hazardous wastes like used oils & waste oils, grease, lead acid batteries, other

lead bearing wastes (such as garkets etc.), oil & clarifier sludge, used resin, used photo-chemicals,

asbestos packing, e-waste, metal scrap, C&I wastes, electricial scrap, empty cylinders (refillable), paper,

rubber products, canteen (bio-degradable) wastes, buidling material wastes, silica gel, glass wool, fusedlamps & tubes, fire resistant fluids etc. These wastes fall either under hazardous wastes category or

non-hazardous wastes category as per classification given in Government of India’s notification on

Hazardous Wastes (Management and Handling) Rules 1989 (as amended on 06.01.2000 & 20.05.2003).

Handling and management of these wastes in NTPC stations have been discussed below.

Advanced / Eco-friendly Technologies

NTPC has gained expertise in operation and management of 200 MW and 500 MW Units installed atdifferent Stations all over the country and is looking ahead for higher capacity Unit sizes with super

critical steam parameters for higher efficiencies and for associated environmental gains. At Sipat, higher

capacity Units of size of 660 MW and advanced Steam Generators employing super critical steam

parameters have already been implemented as a green field project.

Higher efficiency Combined Cycle Gas Power Plants are already under operation at all gas-based power projects in NTPC. Advanced clean coal technologies such as Integrated Gasification Combined Cycle

(IGCC) have higher efficiencies of the order of 45% as compared to about 38% for conventional plants.

NTPC has initiated a techno-economic study under USDOE / USAID for setting up a commercial scale

demonstration power plant by using IGCC technology. These plants can use low-grade coals and have

higher efficiency as compared to conventional plants.

With the massive expansion of power generation, there is also growing awareness among all concerned

to keep the pollution under control and preserve the health and quality of the natural environment in the

vicinity of the power stations. NTPC is committed to provide affordable and sustainable power in

increasingly larger quantity. NTPC is conscious of its role in the national endeavour of mitigating energy

poverty, heralding economic prosperity and thereby contributing towards India’s emergence as a major

global economy.

Lay out of Employee’s

Overall Power Generation


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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

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 06-07Generation BU 106.2 109.5 118.7 130.1 133.2 140.86 149.16 159.11 170.88 188.67

PLF % 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

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

The energy conservation parameters like specific oil consumption and auxiliary power consumption

have also shown considerable improvement over the years.

ABOUT BADARPUR THERMAL POWER STATION


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Maximum continuous KVA rating 24700KVA

Maximum continuous KW 210000KW

I was assigned to do training in operation division from 18th June 2007 to 23rd June 2007

ELECTRICITY FROM COAL

Coal from the coal wagons is unloaded with the help of wagon tipplers in the C.H.P. this coal is taken to

the raw coal bunkers with the help of conveyor belts. Coal is then transported to bowl mills by coalfeeders where it is pulverized and ground in the powered form.

This crushed coal is taken away to the furnace through coal pipes with the help of hot and cold mixture

P.A fan. This fan takes atmospheric air, a part of which is sent to pre heaters while a part goes to the mill

for temperature control. Atmospheric air from F.D fan in the air heaters and sent to the furnace as

combustion air.

Water from boiler feed pump passes through economizer and reaches the boiler drum . Water from the

drum passes through the down comers and goes to the bottom ring header. Water from the bottom ring

header is divided to all the four sides of the furnace. Due to heat density difference the water rises up in

the water wall tubes. This steam and water mixture is again taken to the boiler drum where the steam is

sent to super heaters for super heating. The super heaters are located inside the furnace and the steamis super heated (540 degree Celsius) and finally it goes to the turbine.

Fuel gases from the furnace are extracted from the induced draft fan, which maintains balance draft in

the furnace with F.D fan. These fuel gases heat energy to the various super heaters and finally through

air pre heaters and goes to electrostatic precipitators where the ash particles are extracted. This ash is

mixed with the water to from slurry is pumped to ash period.

The steam from boiler is conveyed to turbine through the steam pipes and through stop valve and

control valve that automatically regulate the supply of steam to the turbine. Stop valves and controls

valves are located in steam chest and governor driven from main turbine shaft operates the control

valves the amount used.

Steam from controlled valves enter high pressure cylinder of turbines, where it passes through the ring

of blades fixed to the cylinder wall. These act as nozzles and direct the steam into a second ring of

moving blades mounted on the disc secured in the turbine shaft. The second ring turns the shaft as a

result of force of steam. The stationary and moving blades together.

MAIN GENERATOR


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Rated terminal voltage 15750V

Rated Stator current 9050 A

Rated Power Factor 0.85 lag

Excitation current at MCR Condition 2600 A

Slip-ring Voltage at MCR Condition 310 V

Rated Speed 3000 rpm

Rated Frequency 50 Hz

Short circuit ratio 0.49

Efficiency at MCR Condition 98.4%

Direction of rotation viewed Anti ClockwisePhase Connection Double Star

Number of terminals brought out 9( 6 neutral and 3 phase)

Rated output of Turbine 210 MW

Rated speed of turbine 3000 rpm

Rated pressure of steam before emergency 130 kg/cm^2

Stop valve rated live steam temperature 535 degree Celsius

Rated steam temperature after reheat at inlet to receptor

valve

535 degree Celsius

Steam flow at valve wide open condition 670 tons/hour

Rated quantity of circulating water through condenser 27000 cm/hour

1. For cooling water temperature (degree Celsius) 24,27,30,33

1.Reheated steam pressure at inlet of interceptor valve in

kg/cm^2 ABS

23,99,24,21,24,49,24.82

2.Steam flow required for 210 MW in ton/hour 68,645,652,662

3.Rated pressure at exhaust of LP turbine in mm of Hg 19.9,55.5,65.4,67.7

MAIN TURBINE DATA


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THERMAL POWER PLANT

A Thermal Power Station comprises all of the equipment and a subsystem required to produce electricity

by using a steam generating boiler fired with fossil fuels or befouls to drive an electrical generator. Some

prefer to use the term ENERGY CENTER because such facilities convert forms of energy, like nuclear

energy, gravitational potential energy or heat energy (derived from the combustion of fuel) into electrical

energy. However, POWER PLANT is the most common term in the united state; While POWER STATIONprevails in many Commonwealth countries and especially in the United Kingdom.

Such power stations are most usually constructed on a very large scale and designed for continuous

operation.

Typical diagram of a coal fired thermal power station

1. Cooling water pump

2. Three-phase transmission line

3. Step up transformer 4. Electrical Generator

5. Low pressure steam

6. Boiler feed water pump

7. Surface condenser

8. Intermediate pressure steam turbine9. Steam control valve

10. High pressure steam turbine

11. Deaerator Feed water heater

12. Coal conveyor

13. Coal hopper

14. Coal pulverizer

15. boiler steam drum

16. Bottom ash hoper

17. Super heater

18. Forced draught(draft) fan

19. Reheater

20. Combustion air intake21. Economizer

22. Air preheater

23. Precipitator

24. Induced draught(draft) fan

25. Fuel gas stack

The description of some of the components written above is described as follows:

1. Cooling towers

Cooling Towers are evaporative coolers used for cooling water or other working medium to near the

ambivalent web-bulb air temperature. Cooling tower use evaporation of water to reject heat from

processes such as cooling the circulating water used in oil refineries, Chemical plants, power plants and

building cooling, for example. The tower vary in size from small roof-top units to very large hyperboloid

structures that can be up to 200 meters tall and 100 meters in diameter, or rectangular structure that can

be over 40 meters tall and 80 meters long. Smaller towers are normally factory built, while larger ones are

constructed on site.

The primary use of large , industrial cooling tower system is to remove the heat absorbed in the

circulating cooling water systems used in power plants , petroleum refineries, petrochemical and

chemical plants, natural gas processing plants and other industrial facilities . The absorbed heat is

rejected to the atmosphere by the evaporation of some of the cooling water in mechanical forced-draft

or induced draft towers or in natural draft hyperbolic shaped cooling towers as seen at most nuclear

power plants.


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2.Three phase transmission line

Three phase electric power is a common method of electric power transmission. It is a type of polyphase

system mainly used to power motors and many other devices. A Three phase system uses less

conductor material to transmit electric power than equivalent single phase, two phase, or direct current

system at the same voltage. In a three phase system, three circuits reach their instantaneous peak

values at different times. Taking one conductor as the reference, the other two current are delayed in

time by one-third and two-third of one cycle of the electrical current. This delay between “phases” has

the effect of giving constant power transfer over each cycle of the current and also makes it possible to

produce a rotating magnetic field in an electric motor.At the power station, an electric generator converts mechanical power into a set of electric currents, one

from each electromagnetic coil or winding of the generator. The current are sinusoidal functions of time,

all at the same frequency but offset in time to give different phases. In a three phase system the phases

are spaced equally, giving a phase separation of one-third one cycle. Generators output at a voltage that

ranges from hundreds of volts to 30,000 volts. At the power station, transformers: step-up” this voltage

to one more suitable for transmission.

After numerous further conversions in the transmission and distribution network the power is finallytransformed to the standard mains voltage (i.e. the “household” voltage).

The power may already have been split into single phase at this point or it may still be three phase.

Where the step-down is 3 phase, the output of this transformer is usually star connected with the

standard mains voltage being the phase-neutral voltage. Another system commonly seen in North

America is to have a delta connected secondary with a center tap on one of the windings supplying theground and neutral. This allows for 240 V three phase as well as three different single phase voltages(

120 V between two of the phases and neutral , 208 V between the third phase ( known as a wild leg) and

neutral and 240 V between any two phase) to be available from the same supply.

3.Electrical generator

An Electrical generator is a device that converts kinetic energy to electrical energy, generally using

electromagnetic induction. The task of converting the electrical energy into mechanical energy is

accomplished by using a motor. The source of mechanical energy may be a reciprocating or turbine

steam engine, , water falling through the turbine are made in a variety of sizes ranging from small 1 hp

(0.75 kW) units (rare) used as mechanical drives for pumps, compressors and other shaft driven

equipment , to 2,000,000 hp(1,500,000 kW) turbines used to generate electricity. There are several

classifications for modern steam turbines.Steam turbines are used in all of our major coal fired power stations to drive the generators or

alternators, which produce electricity. The turbines themselves are driven by steam generated in

‘Boilers’ or ‘steam generators’ as they are sometimes called.

Electrical power station use large stem turbines driving electric generators to produce most (about 86%)

of the world’s electricity. These centralized stations are of two types: fossil fuel power plants and nuclear

power plants. The turbines used for electric power generation are most often directly coupled to their-

generators .As the generators must rotate at constant synchronous speeds according to the frequency

of the electric power system, the most common speeds are 3000 r/min for 50 Hz systems, and 3600

r/min for 60 Hz systems. Most large nuclear sets rotate at half those speeds, and have a 4-pole

generator rather than the more common 2-pole one.

Energy in the steam after it leaves the boiler is converted into rotational energy as it passes through the

turbine. The turbine normally consists of several stage with each stages consisting of a stationary blade

(or nozzle) and a rotating blade. Stationary blades convert the potential energy of the steam into kinetic

energy into forces, caused by pressure drop, which results in the rotation of the turbine shaft. The

turbine shaft is connected to a generator, which produces the electrical energy.

4.Boiler feed water pump

A Boiler feed water pump is a specific type of pump used to pump water into a steam boiler. The water

may be freshly supplied or retuning condensation of the steam produced by the boiler. These pumps are

normally high pressure units that use suction from a condensate return system and can be of the

centrifugal pump type or positive displacement type.


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Construction and operation

Feed water pumps range in size up to many horsepower and the electric motor is usually separated from

the pump body by some form of mechanical coupling. Large industrial condensate pumps may also

serve as the feed water pump. In either case, to force the water into the boiler; the pump must generate

sufficient pressure to overcome the steam pressure developed by the boiler. This is usually

accomplished through the use of a centrifugal pump.

Feed water pumps usually run intermittently and are controlled by a float switch or other similar level-

sensing device energizing the pump when it detects a lowered liquid level in the boiler is substantially

increased. Some pumps contain a two-stage switch. As liquid lowers to the trigger point of the first

stage, the pump is activated. I f the liquid continues to drop (perhaps because the pump has failed, itssupply has been cut off or exhausted, or its discharge is blocked); the second stage will be triggered.

This stage may switch off the boiler equipment (preventing the boiler from running dry and overheating),

trigger an alarm, or both.

5. Steam-powered pumps

Steam locomotives and the steam engines used on ships and stationary applications such as power

plants also required feed water pumps. In this situation, though, the pump was often powered using a

small steam engine that ran using the steam produced by the boiler. A means had to be provided, of course, to put the initial charge of water into the boiler(before steam power was available to operate the

steam-powered feed water pump).the pump was often a positive displacement pump that had steam

valves and cylinders at one end and feed water cylinders at the other end; no crankshaft was required.

In thermal plants, the primary purpose of surface condenser is to condense the exhaust steam from asteam turbine to obtain maximum efficiency and also to convert the turbine exhaust steam into pure

water so that it may be reused in the steam generator or boiler as boiler feed water. By condensing the

exhaust steam of a turbine at a pressure below atmospheric pressure, the steam pressure drop between

the inlet and exhaust of the turbine is increased, which increases the amount heat available for

conversion to mechanical power. Most of the heat liberated due to condensation of the exhaust steam is

carried away by the cooling medium (water or air) used by the surface condenser.

6. Control valves

Control valves are valves used within industrial plants and elsewhere to control operating conditions

such as temperature,pressure,flow,and liquid Level by fully partially opening or closing in response to

signals received from controllers that compares a “set point” to a “process variable” whose value isprovided by sensors that monitor changes in such conditions. The opening or closing of control valves

is done by means of electrical, hydraulic or pneumatic systems

7. Deaerator

A Dearator is a device for air removal and used to remove dissolved gases (an alternate would be the

use of water treatment chemicals) from boiler feed water to make it non-corrosive. A dearator typically

includes a vertical domed deaeration section as the deaeration boiler feed water tank. A Steam

generating boiler requires that the circulating steam, condensate, and feed water should be devoid of

dissolved gases, particularly corrosive ones and dissolved or suspended solids. The gases will give rise

to corrosion of the metal. The solids will deposit on the heating surfaces giving rise to localized heating

and tube ruptures due to overheating. Under some conditions it may give to stress corrosion cracking.

Deaerator level and pressure must be controlled by adjusting control valves- the level by regulating

condensate flow and the pressure by regulating steam flow. If operated properly, most deaerator

vendors will guarantee that oxygen in the deaerated water will not exceed 7 ppb by weight (0.005 cm3/L)

8. Feed water heater

A Feed water heater is a power plant component used to pre-heat water delivered to a steam generating

boiler. Preheating the feed water reduces the irreversible involved in steam generation and therefore

improves the thermodynamic efficiency of the system.[4] This reduces plant operating costs and also

helps to avoid thermal shock to the boiler metal when the feed water is introduces back into the steam

cycle.


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In a steam power (usually modeled as a modified Ranking cycle), feed water heaters allow the feed water

to be brought up to the saturation temperature very gradually. This minimizes the inevitable

irreversibility’s associated with heat transfer to the working fluid (water). A belt conveyor consists of two

pulleys, with a continuous loop of material- the conveyor Belt – that rotates about them. The pulleys are

powered, moving the belt and the material on the belt forward. Conveyor belts are extensively used to

transport industrial and agricultural material, such as grain, coal, ores etc.

9. Pulverizer

A pulverizer is a device for grinding coal for combustion in a furnace in a fossil fuel power plant.

10. Boiler Steam Drum

Steam Drums are a regular feature of water tube boilers. It is reservoir of water/steam at the top end of

the water tubes in the water-tube boiler. They store the steam generated in the water tubes and act as aphase separator for the steam/water mixture. The difference in densities between hot and cold water

helps in the accumulation of the “hotter”-water/and saturated –steam into steam drum. Made from

high-grade steel (probably stainless) and its working involves temperatures 390’C and pressure well

above 350psi (2.4MPa). The separated steam is drawn out from the top section of the drum. Saturated

steam is drawn off the top of the drum. The steam will re-enter the furnace in through a super heater,while the saturated water at the bottom of steam drum flows down to the mud-drum /feed water drum by

down comer tubes accessories include a safety valve, water level indicator and fuse plug. A steam drum

is used in the company of a mud-drum/feed water drum which is located at a lower level. So that it acts

as a sump for the sludge or sediments which have a tendency to the bottom.

11. Super Heater

A Super heater is a device in a steam engine that heats the steam generated by the boiler again

increasing its thermal energy and decreasing the likelihood that it will condense inside the engine. Super

heaters increase the efficiency of the steam engine, and were widely adopted. Steam which has been

superheated is logically known as superheated steam; non-superheated steam is called saturated steam

or wet steam; Super heaters were applied to steam locomotives in quantity from the early 20th century,to most steam vehicles, and so stationary steam engines including power stations.

12. Economizers

Economizer, or in the UK economizer, are mechanical devices intended to reduce energy consumption,

or to perform another useful function like preheating a fluid. The term economizer is used for other

purposes as well. Boiler, power plant, and heating, ventilating and air conditioning. In boilers,

economizer are heat exchange devices that heat fluids , usually water, up to but not normally beyond the

boiling point of the fluid. Economizers are so named because they can make use of the enthalpy and

improving the boiler’s efficiency. They are a device fitted to a boiler which saves energy by using the

exhaust gases from the boiler to preheat the cold water used the fill it (the feed water). Modern day

boilers, such as those in cold fired power stations, are still fitted with economizer which is decedents of

Green’s original design. In this context they are turbines before it is pumped to the boilers. A common

application of economizer is steam power plants is to capture the waste hit from boiler stack gases (flue

gas) and transfer thus it to the boiler feed water thus lowering the needed energy input , in turn reducing

the firing rates to accomplish the rated boiler output . Economizer lower stack temperatures which may

cause condensation of acidic combustion gases and serious equipment corrosion damage if care is not

taken in their design and material selection.

13. Air Preheater

Air preheater is a general term to describe any device designed to heat air before another process (for

example, combustion in a boiler). The purpose of the air preheater is to recover the heat from the boiler

flue gas which increases the thermal efficiency of the boiler by reducing the useful heat lost in the fuel


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gas. As a consequence, the flue gases are also sent to the flue gas stack (or chimney) at a lower

temperature allowing simplified design of the ducting and the flue gas stack. It also allows control over

the temperature of gases leaving the stack.

14. Precipitator

An Electrostatic precipitator (ESP) or electrostatic air cleaner is a particulate device that removes

particles from a flowing gas (such As air) using the force of an induced electrostatic charge.

Electrostatic precipitators are highly efficient filtration devices, and can easily remove fine particulate

matter such as dust and smoke from the air steam.ESP’s continue to be excellent devices for control of many industrial particulate emissions, including

smoke from electricity-generating utilities (coal and oil fired), salt cake collection from black liquor

boilers in pump mills, and catalyst collection from fluidized bed catalytic crackers from several hundred

thousand ACFM in the largest coal-fired boiler application.

The original parallel plate-Weighted wire design (described above) has evolved as more efficient ( and

robust) discharge electrode designs were developed, today focusing on rigid discharge electrodes towhich many sharpened spikes are attached , maximizing corona production. Transformer –rectifier

systems apply voltages of 50-100 Kilovolts at relatively high current densities. Modern controls minimize

sparking and prevent arcing, avoiding damage to the components. Automatic rapping systems and

hopper evacuation systems remove the collected particulate matter while on line allowing ESP’s to stay

in operation for years at a time.

15. Fuel gas stack

A Fuel gas stack is a type of chimney, a vertical pipe, channel or similar structure through which

combustion product gases called fuel gases are exhausted to the outside air. Fuel gases are produced

when coal, oil, natural gas, wood or any other large combustion device. Fuel gas is usually composed of

carbon dioxide (CO2) and water vapor as well as nitrogen and excess oxygen remaining from the intake

combustion air. It also contains a small percentage of pollutants such as particulates matter, carbon

mono oxide, nitrogen oxides and sulfur oxides. The flue gas stacks are often quite tall, up to 400 meters

(1300 feet) or more, so as to disperse the exhaust pollutants over a greater aria and thereby reduce the

concentration of the pollutants to the levels required by governmental environmental policies and

regulations.When the fuel gases exhausted from stoves, ovens, fireplaces or other small sources within residential

abodes, restaurants , hotels or other stacks are referred to as chimneys.


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C&I

(CONTROL AND INSTRUMENTATION)

I was assigned to do training in control and instrumentation from 25th June 2007 to 14th July 2007

CONTROL AND INSTRUMENTATION

This division basically calibrates various instruments and takes care of any faults occur in any of the

auxiliaries in the plant.

It has following labs:

MANOMETRY LAB1.

PROTECTION AND INTERLOCK LAB2.

AUTOMATION LAB3.

WATER TREATEMENT LAB4.

FURNACE SAFETY SUPERVISORY SYSTEM(FSSS)5.ELECTRONICS TEST LAB6.

This department is the brain of the plant because from the relays to transmitters followed by the

electronic computation chipsets and recorders and lastly the controlling circuitry, all fall under this.

5.0 MANOMETRY LAB

5.0.1 TRANSMITTERS

It is used for pressure measurements of gases and liquids, its working principle is that the input

pressure is converted into electrostatic capacitance and from there it is conditioned and amplified. It

gives an output of 4-20 ma DC. It can be mounted on a pipe or a wall. For liquid or steam measurement

transmitters is mounted below main process piping and for gas measurement transmitter is placed

above pipe.

5.0.2 MANOMETER

It’s a tube which is bent, in U shape. It is filled with a liquid. This dev ice corresponds to a difference in

pressure across the two limbs.

5.0.3 BOURDEN PRESSURE GAUGEIt’s an oval section tube. Its one end is fixed. It is provided with a pointer to indicate the pressure on a

calibrated scale. It is of 2 types:

(a) Spiral type: for Low pressure measurement.

(b) Helical Type: for High pressure measurement.

5.1 PROTECTION AND INTERLOCK LAB

5.1.1 INTERLOCKING

It is basically interconnecting two or more equipments so that if one equipments fails other one canperform the tasks. This type of interdependence is also created so that equipments connected together


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are started and shut down in the specific sequence to avoid damage.

For protection of equipments tripping are provided for all the equipments. Tripping can be considered as

the series of instructions connected through OR GATE. When a fault occurs and any one of the tripping

is satisfied a signal is sent to the relay, which trips the circuit. The main equipments of this lab are relay

and circuit breakers. Some of the instrument uses for protection are:

1. RELAY

It is a protective device. It can detect wrong condition in electrical circuits by constantly measuring the

electrical quantities flowing under normal and faulty conditions. Some of the electrical quantities are

voltage, current, phase angle and velocity.2. FUSES

It is a short piece of metal inserted in the circuit, which melts when heavy current flows through it and

thus breaks the circuit. Usually silver is used as a fuse material because:

a) The coefficient of expansion of silver is very small. As a result no critical fatigue occurs and thus the

continuous full capacity normal current ratings are assured for the long time.

b) The conductivity of the silver is unimpaired by the surges of the current that produces temperatures just near the melting point.

c) Silver fusible elements can be raised from normal operating temperature to vaporization quicker than

any other material because of its comparatively low specific heat.

5.1.2 MINIATURE CIRCUIT BREAKER

They are used with combination of the control circuits to.

a) Enable the staring of plant and distributors.

b) Protect the circuit in case of a fault.

In consists of current carrying contacts, one movable and other fixed. When a fault occurs the contacts

separate and are is stuck between them. There are three types of

- MANUAL TRIP

- THERMAL TRIP- SHORT CIRCUIT TRIP

5.1.3 ROTECTION AND INTERLOCK SYSTEM

1. HIGH TENSION CONTROL CIRCUIT

For high tension system the control system are excited by separate D.C supply. For starting the circuit

conditions should be in series with the starting coil of the equipment to energize it. Because if even a

single condition is not true then system will not start.

2. LOW TENSION CONTROL CIRCUIT

For low tension system the control circuits are directly excited from the 0.415 KV A.C supply. The same

circuit achieves both excitation and tripping. Hence the tripping coil is provided for emergency tripping if

the interconnection fails.


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5.2 AUTOMATION LAB

This lab deals in automating the existing equipment and feeding routes.

Earlier, the old technology dealt with only (DAS) Data Acquisition System and came to be known as

primary systems. The modern technology or the secondary systems are coupled with (MIS) Management

Information System. But this lab universally applies the pressure measuring instruments as the

controlling force. However, the relays are also provided but they are used only for protection and

interlocks.

Once the measured is common i.e. pressure the control circuits can easily be designed with single chipshaving multiple applications. Another point is the universality of the supply, the laws of electronic state

that it can be any where between 12V and 35V in the plant. All the control instruments are excited by 24V

supply (4-20mA) because voltage can be mathematically handled with ease therefore all control systems

use voltage system for computation. The latest technology is the use of ‘ETHERNET’ for control signals.

5.3 PYROMETER LAB

(1) LIQUID IN GLASS THERMOMETER

Mercury in the glass thermometer boils at 340 degree Celsius which limits the range of temperature thatcan be measured. It is L shaped thermometer which is designed to reach all inaccessible places.

(2) ULTRA VIOLET CENSOR

This device is used in furnace and it measures the intensity of ultra violet rays there and according to

the wave generated which directly indicates the temperature in the furnace.

(3) THERMOCOUPLES

This device is based on SEEBACK and PELTIER effect. It comprises of two junctions at different

temperature. Then the emf is induced in the circuit due to the flow of electrons. This is an important part

in the plant.

(4) RTD (RESISTANCE TEMPERATURE DETECTOR)

It performs the function of thermocouple basically but the difference is of a resistance. In this due to the

change in the resistance the temperature difference is measured.

In this lab, also the measuring devices can be calibrated in the oil bath or just boiling water (for low

range devices) and in small furnace (for high range devices). 5.4 FURNACE SAFETY AND SUPERVISORY

SYSTEM LABThis lab has the responsibility of starting fire in the furnace to enable the burning of coal. For first stage

coal burners are in the front and rear of the furnace and for the second and third stage corner firing is

employed. Unburnt coal is removed using forced draft or induced draft fan. The temperature inside the

boiler is 1100 degree Celsius and its height is 18 to 40 m. It is made up of mild steel. An ultra violet

sensor is employed in furnace to measure the intensity of ultra violet rays inside the furnace and

according to it a signal in the same order of same mV is generated which directly indicates the

temperature of the furnace.

For firing the furnace a 10 KV spark plug is operated for ten seconds over a spray of diesel fuel and

pre-heater air along each of the feeder-mills. The furnace has six feeder mills each separated by warm

air pipes fed from forced draft fans. In first stage indirect firing is employed that is feeder mills are not

fed directly from coal but are fed from three feeders but are fed from pulverized coalbunkers. The

furnace can operate on the minimum feed from three feeders but under not circumstances should any

one be left out under operation, to prevent creation of pressure different with in the furnace, which

threatens to blast it.

5.5 ELECTRONICS LAB

This lab undertakes the calibration and testing of various cards. It houses various types of analytical

instruments like oscilloscopes, integrated circuits, cards auto analyzers etc.

Various processes undertaken in this lab are:

1. Transmitter converts mV to mA.

2. Auto analyzer purifies the sample before it is sent to electrodes. It extracts the magnetic portion.


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5.6 ANNUNCIATIN CARDS

They are used to keep any parameter like temperature etc. within limits. It gets a signal if parameter goes

beyond limit. It has a switching transistor connected to relay that helps in alerting the UCB.

39. Control and Instrumentation Control and Instrumentation

Measuring Instrumentsments

In any process the philosophy of instrumentation should provide a comprehensive intelligence feed

back on the important parameters viz. Temperature, Pressure, Level and Flow. This Chapter Seeks to

provide a basic understanding of the prevalent instruments used for measuring the above parameters.

Temperature Measurement

The most important parameter in thermal power plant is temperature and its measurement plays a vital

role in safe operation of the plant. Rise of temperature in a substance is due to the resultant increase in

molecular activity of the substance on application of heat; which increases the internal energy of thematerial. Therefore there exists some property of the substance, which changes with its energy content.

The change may be observed with substance itself or in a subsidiary system in thermodynamic

equilibrium, which is called testing body and the system itself is called the hot body.

Expansion Thermometer

Solid Rod Thermometers a temperature sensing - Controlling device may be designed incorporating in

its construction the principle that some metals expand more than others for the same temperature

range. Such a device is the thermostat used with water heaters (Refer Fig. 69).


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Fig No.-69 Rod Type Thermostat

The mercury will occupy a greater fraction of the volume of the container than it will at a low temperature.

Under normal atmospheric conditions mercury normally boils at a temperature of (347°C). To extend the

range of mercury in glass thermometer beyond this point the top end of a thermometer bore opens into

a bulb which is many times larger in capacity than the bore. This bulb plus the bore above the mercury,

is then filled with nitrogen or carbon dioxide gas at a sufficiently high pressure to prevent boiling at the

highest temperature to which the thermometer may be used.

Mercury in Steel the range of liquid in glass thermometers although quite large, does not lend itself to all

industrial practices. This fact is obvious by the delicate nature of glass also the position of the

measuring element is not always the best position to read the result. Types of Hg in Steel Thermometers

are:

Bourdon Tube

Most common and simplest type (Refer Fig. 71)

Spiral type

More sensitive and used where compactness is necessary

Helical Type

Most sensitive and compact. Pointer may be mounted direct on end of helix

Which rotates, thus eliminating backlash and lost motion?

Linkages, which only allow the pointer to operate over a selected range of pressure to either side of the

normal steam pressure. (Refer Fig No.77)

Dewrance Critical Pressure Gauge Measurement of Level

Direct Methods

'Sight Glass' is used for local indication on closed or open vessels. A sight glass is a tube of toughened

glass connected at both ends through packed unions and vessel. The liquid level will be the same as

that in the vessel. Valves are provided for isolation and blow down.

"Float with Gauge Post" is normally used to local indication on closed or open vessels.

"Float Operated Dial" is used for small tanks and congested areas. The float arm is connected to a

quadrant and pinion which rotates the pointer over a scale.


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Bourden Pressure Gauge a Bourdon pressure gauge calibrated in any fact head is often connected to a

tank at or near the datum level.

"Mercury Manometer" is used for remote indication of liquid level. The working principle is the same as

that of a manometer one limp of a U-tube is connected to the tank, the other being open to atmosphere.

The manometer liquid must not mix with the liquid in the vessel, and where the manometer is at a

different level to the vessel, the static head must be allowed in the design of the manometer.

'Diaphragm Type' is used for remote level indication in open tanks or docks etc. A pressure change

created by the movement of a diaphragm is proportional to a change in liquid level above the

diaphragm. This consists of a cylindrical box with a rubber or plastic diaphragm across its open end as

the level increases .the liquid pressure on the diaphragm increases and the air inside is compressed.

This pressure is transmitted via a capillary tube to an indicator or recorder incorporating a pressure

Measuring element.

Sealed Capsule Type The application and principle is the same as for the diaphragm box. In this type, a

capsule filled with an inert gas under a slight pressure is exposed to the pressure due to the head of


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liquid and is connected by a capillary to an indicator. In some cases the capsule is fitted external to the

tank and is so arranged that it can be removed whilst the tank is still full, a spring loaded valve

automatically shutting off the tapping point.

Air Purge System This system provides the simplest means of obtaining an indication of level, or

volume, at a reasonable distance and above or below, the liquid being measured. The pressure exerted

inside an open ended tube below the surface of a liquid is proportional to the depth of the liquid

The Measurement of Flow

Two principle measurements are made by flow meters viz. quantity of flow and rate of flow. 'Quantity of

flow' is the quantity of fluid passing a given point in a given time, i.e. gallons or pounds. ‘Rate of flow' is

the speed of. a fluid passing a given point at a given instant and is proportional to quantity passing at a

given instant, i.e. gallons per minute or pounds per hour. There are two groups of measuring devices: -

Positive, or volumetric, which measure flow by transferring a measured quantity of fluid from the inlet to

the outlet.

Inferential, which measures the velocity of the flow and the volume passed is inferred, it being equal to

the velocity times the cross sectional area of the flow. The inferential type is the most widely used.

Measurement of Fluid Flow through Pipes:

"The Rotating Impeller Type" is a positive type device which is used for medium quantity flow

measurement i.e., petroleum and other commercial liquids. It consists of


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Two fluted rotors mounted in a liquid tight case fluid flow and transmitted to a counter.

Rotating Oscillating Piston Type This is also a positive type device and is used for measuring low and

medium quantity flows, e.g. domestic water supplies. This consists of a brass meter body into which is

fitted a machined brass working chamber and cover, containing a piston made of ebonite. This piston

acts as a moving chamber and transfers a definite volume of fluid from the inlet to the outlet for each

cycle.

Helical Vane Type For larger rates of flow, a helical vane is mounted centrally in the body of the meter.

The helix chamber may be vertical or horizontal and is geared to a counter. Usually of pipe sizes 3" to

10" Typical example is the Kent Torrent Meter.

Turbine Type this like the helical Vane type is a inference type of device used for large flows with the minimum of pressure drop. This consists of a turbine or drum

revolving in upright bearings, retaining at the top by a collar. Water enters the drum

from the top and leaves tangentially casings to rotate at a speed dependent upon the

quantity of water passed. The cross sectional area of the meter throughout is equal to

the area of the inlet and outlet pipes and is commonly used on direct supply water

mains,

Combination Meters this is used for widely fluctuating flows. It consists of a larger meter (helical, turbine or fan) in the main with a small rotary meter or suitable type in a

bypass. Flow is directed into either the main or bypass according to the quantity of flow

by an automatic valve. By this means flows of 45 to 40,000 gallons per hour can be

measured.

Measurement of Fluid Flow through Open Channels:

The Weir If a fluid is allowed to flow over a square weir of notch, The height of the liquid above the still of

the weir, or the bottom of the notch will be a measure of the rate of flow.

A formula relates the rate of flow to the height and is dependent upon the design of theVenturi Flumes The head loss caused by the weir flow meter is considerable and its

construction is sometimes complicated, therefore the flume is sometimes used. The

principle is same as that of venture except that the rate of flow is proportional to the

depth of the liquid in the upstream section. It consists of a local contraction in the cross

section of flow through a channel in the shape of a venturi. It is only necessary to

measure the depth of the upstream section which is a measure of the rate of flow. This

may be done by pressure tapping at the datum point or by a float in an adjacent level

chamber.

Pressure Difference Flow meters These are the most widely used type of flow meter since they are

capable of measuring the flow of all industrial fluids passing through pipes. They consists of a primary

element inserted in the pipeline which generates a differential pressure, ^he magnitude of which is

proportional to the square of the rate of flow and a secondary element which measures this differential

pressure and translates it into terms of flow. (Refer fig. 79).


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Fig. No-79 Pressure Differential Flow meters

Primary elements Bernoulli's theorem states that the quantity of fluid or gas flowing is proportional to the

square root of the differential pressure. There are four principal types of primary elements (or

restrictions) as enumerate below:

Venturi; This is generally used for medium and high quantity fluid flow and it consists of two hollow

truncated cones, the smaller diameters of which are connected together by a short length of parallel

pipe, the smallest diameter of the tube formed by this length of parallel pipe is known as the throatsection and the lower of the two pressures, (the throat, or downstream pressure) is measured here.

Orifice Plate This is the oldest and most common form of pressure differential device. In its simplest

form it consists of a thin metal plate with a central hold clamped between two pipe flanges. In the

metering of dirty fluids or fluids containing solids the hole is placed so that its lower edge coincides with

the inside bottom of the pipe. (Refer Fig.80) It is essential that the leading edge of the hole is absolutelysharp rounding or burring would have a very marked effect on the flow.

Fig No.-80 Typical Orifice Plate Pressure Tapping

EMD I


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Electrical Maintenance division I

I was assigned to do training in Electrical maintenance division I from 17th July 2007 to 28th July 2007.

This two week of training in this division were divided as follows.

17th to 19th July 2007- HT/LT switchgear

21st to 24th July 2007 - HT/LT Motors, Turbine &Boiler side

26th to 28th July 2007- CHP/NCHP Electrical

Electrical maintenance division 1

It is responsible for maintenance of:

1. Boiler side motors

2. Turbine side motors

3. Outside motors

4. Switchgear

1. Boiler side motors:

For 1, units 1, 2, 3

1.1D Fans 2 in no.

2.F.D Fans 2 in no.

3.P.A.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.

For stage units 1, 2, 3


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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 and Phosphorous Dozing 2 in no.2/3 in no.

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

2. NEW COAL HANDLING PLANT (N.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 135degrees 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 the weight of the conveyor is made through hydraulic weighing machine.

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

of 400 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 Separators: - 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, the

pieces 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.

MILLING SYSTEM

1. RC Bunker: - Raw coal is fed directly to these bunkers. These are 3 in no. per boiler. 4 & ½ tons of coal

are fed in 1 hr. the depth of bunkers is 10m.


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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 by attraction.

The Drying and grinding option takes place simultaneously inside the mill.

4. Classifier:- It is an 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 thelower 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 Tturniket: - 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 both directions.

8. Mills Fans: - It is 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

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

Speed-980 rpm

Frequency-50 Hz


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No-load current-15-16 A

NCHP

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

13A, 13B

14A, 14B

15A, 15B

16A, 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

10. Exit

The coal arrives in wagons via railways and is tippled by the wagon tipplers into the 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 to 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 of coal to 20mm sq. now the conveyor


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labors 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.

SWITCH GEAR-

It makes or breaks an electrical circuit.

1. Isolation: - A device which breaks an electrical circuit when circuit is switched 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 tha range 32A, 63A, 100A, 200Q, 300A at 500V grade.

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. Rotary switch 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 best suited 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.


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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 of

tensions 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

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 15 kg 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 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


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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 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

EMD II

Electrical Maintenance division II

I was assigned to do training in Electrical maintenance division II from 31st July 2007 to 11th August

2007.

This two week of training in this division were divided as follows.


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31st to 2nd August 2007- Generator

4th August 2007 - Transformer &switchyard

7th August 2007 - protection

9th August2007 - Lightning

11th August 2007 - EP

Generator and Auxiliaries Generator and Auxiliaries

Generator Fundamentals Fundamentals

The transformation of mechanical energy into electrical energy is carried out by the Generator. ThisChapter 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 following expression.

E = 4.44 /O FN volts

0 = Strength of magnetic field in Weber’s.

F = Frequency in cycles per second or Hertz.

N = Number of turns in a coil of stator winding

F = Frequency = Pn/120

Where P = Number of poles

n = revolutions per second of rotor.

From the expression it is clear that for the same frequency, number of poles increases with decrease in

speed and vice versa. Therefore, low speed hydro turbine drives generators have 14 to 20 poles where

as high speed steam turbine driven generators have generally 2 poles. Pole rotors are used in low speed

generators, because the cost advantage as well as easier construction.

Development

The first A.C. Generator concept was enunciated by Michael Faraday in 1831. In 1889 Sir Charles A.

Parsons developed the first AC turbo-generator. Although slow speed AC generators have been built for

some time, it was not long before that the high-speed generators made its impact.


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Development contained until, in 1922, the increased use of solid forgings and improved techniques

permitted an increase in generator rating to 20MW at 300rpm. Up to the out break of second world war,

in 1939, most large generator;- were of the order of 30 to 50 MW at 3000 rpm.

During the war, the development and installation of power plants was delayed and in order to catch up

with the delay in plant installation, a large number of 30 MW and 60 MW at 3000 rpm units were

constructed during the years immediately following the war. The changes in design in this period were

relatively small.

In any development programme the. Costs of material and labour involved in manufacturing and

erection must be a basic consideration. Coupled very closely with

these considerations is the restriction is size and weight imposed by transport limitations.

Development of suitable insulating materials for large turbo-generators is one of the

most important tasks and need continues watch as size and ratings of machines

increase. The present trend is the use only class "B" and higher grade materials and

extensive work has gone into compositions of mica; glass and asbestos with

appropriate bonding material. An insulation to meet the stresses in generator slots must

follow very closely the thermal expansion of the insulated conductor without cracking or any plastic deformation. Insulation for rotor is subjected to lower dielectric stress but

must withstand high dynamic stresses and the newly developed epoxy resins, glass

and/or asbestos molded in resin and other synthetic resins are finding wide

applications.

Generator component

This Chapter 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 of 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 structuremounted on foundations all of which possess complex dynamic be behavior peculiar to

themselves. 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 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 rotor incorporate 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


38 5/18/2011



the other end by fittings carried by the rotor body. The two ends of windings are

connected to slip rings, usually made of forged steel, and mounted on 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 itwould 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 byan 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 has been constructed and the winding completed. 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 lamination cold

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 withoutfear 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 the rated 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 of

insulation material to withstand the heavy forces which might result from a short 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


38 5/18/2011



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.

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 the bottom 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, inorder to prevent 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 :

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

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

times.

Provide indication to the operator about the condition of the gas inside themachine i.e. its pressure, temperature and purity.

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

remove any water vapour that may be present in it.

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

Stator Cooling System

The stator winding is cooled by distillate. Which is fed from one end of the machine by Teflon tube and

flows through the upper bar and returns back through the lower bar of another slot?

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 deg.C.

Rating of 95 MW Generator


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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 AFrequency - 50 Hz

Stator wdg connection - 3 phase

Rating of 210 MW Generator

Capacity - 247000 KVA

Voltage (stator) - 15750 VCurrent (stator) - 9050 A

Voltage (rotor) - 310 V

Current (rotor) - 2600 V

Speed - 3000 rpm

Power factor - 0.85Frequency - 50 Hz

Hydrogen - 3.5 Kg/cm2

Stator wdg connection - 3 phase star connection

Insulation class - B

TRANFORMER

A transformer is a device that transfers electrical energy from one circuit to another by magneticcoupling with out 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, thus transforming 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 world’s electrical power has passed trough a series of transformer by

the time it reaches the consumer.

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 winding causes 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 faraday’s law of induction, the EMFs are

proportional to the rate of change of flux. The primary EMF, acting as it does in opposition to the primary

voltage, is sometimes termed the back EMF”. Energy losses An ideal transformer would have no energy


38 5/18/2011



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 than 95%. 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, some times 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 lossescontribute to over 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 trough 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 the frequency, and is a function of the peak flux density to which it issubjected. 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 plane normal 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 alternating magnetic field causes fluctuating electromagnetic field

between primary and secondary windings. These incite vibration with in near by 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. Cooling system Large power

transformers may be equipped with cooling fans, oil pumps or water-cooler heat exchangers design to

remove heat. Power used to operate the cooling system is typically considered part of the losses of the

transformer

Rating of transformer

Manufactured by Bharat heavy electrical limited

No load voltage (hv) - 229 KV

No load Voltage (lv) -10.5 KV

Line current (hv) - 315.2 A

Line current (lv) - 873.2 A

Temp rise - 45 Celsius

Oil quantity -40180 lit

Weight of oil -34985 Kg

Total weight - 147725 Kg

Core & winding - 84325 Kg

Phase - 3

Frequency - 50 Hz


38 5/18/2011



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