btps project report elec engg

7/27/2019 Btps Project Report Elec Engg

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DEPARTMENT OF APPLIED PHYSICS (BTech ELECTRICAL ENGINEERING)

UNIVERSITY COLLEGE OF SCIENCE AND TECHNOLOGY

UNIVERSITY OF CALCUTTA

VOCATIONAL TRAINING REPORT ON

BANDEL THERMAL

POWER STATION(WBPDCL)

SUVADIP ROY


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Department of Applied Physics (EE), University of Calcutta

ACKNOWLEDGEMENT

As a student of The Department of Applied Physics (B.Tech. in Electrical Engineering), University

College of Science and Technology, University of Calcutta,I am thankful to all the respected

employees of various departments where we undergo this training session. It is not easy to know

the full system of BTPS but they always try to answer our curiosity.

The experience of this training as an electrical engineering student is excellent.

PREFACE

Practical knowledge means the visualization of the knowledge which we read in the books. For this

we perform experiments and get observations. Practical knowledge is very important in every field.

One must be familiar with the problems related to the field so that he may solve them and become a

successful person.

After achieving the proper goal of life, an engineer has to enter in professional life. According to this

field he has to serve an industry, may be public or private sector or self-own. For efficient work in

the field he must be aware of practical knowledge as well as theoretical knowledge.

To be a good engineer, one must be aware of the industrial environment and must know about

management working in industry, labour problems etc., so he can tackle them successfully.

Due to all the above reasons and to bridge a gap between theory and practical, our engineering

curriculum provides a practical training course of 20 days. During this period a student in industry

gets all type of experience and knowledge about the working and maintenance of various types of

machinery.

I have undergone by 20 days of training at BANDEL THERMAL POWER STATION. This report have

been prepared on the basis of the knowledge which I have acquired during my 20 days

(17/06/2013 to 09/07/2013) training in the plant.

SUVADIP ROY


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CONTENTS

BTPS AT A GLANCE ................................................................................................................................................................4

SCHEMATIC REPRESENTATION OF A THERMAL POWER PLANT.................................................................5

COAL HANDLING PLANT.....................................................................................................................................................6

COMBUSTION AND FUEL EFFICIENCY......................................................................................................................10

MECHANICAL OPERATIONS ...........................................................................................................................................11

INSTRUMENTATION & PROCESS CONTROL, CONTROL & INSTRUMENTATION ...............................20

OPH .............................................................................................................................................................................................23

RELAY AND INSTRUMENTS............................................................................................................................................28

IPH ...............................................................................................................................................................................................33

MAJOR CONSTRAINTS AT BTPS

CONCLUSION.


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BTPS AT A GLANCE

Situated on the western bank of Bhagirathi River, Bandel Thermal Power Station is just 1 Km from

the Assam Road and connected with a heavy duty metal lead road 3 km off the Grand trunk Road,

NH2. Bandel Thermal Power Stations nearest rail head is Tribeni on the Bandel- Katwa- Azimgunj

Line under Eastern Railways. Successfully meeting the power sector demand for the State for more

than four decades, Ban del Thermal Power Station still remains a prominent player in the states

power supply chain. Bandel Thermal Power Stations fifth unit with a capacity of 210 MW installed

in 1982, was first of its kind in Eastern India & fifth in India. Today, with five operational units the

total installed capacity of the station stands at 450 MW .

Total area of land acquired by WBPDCL for BTPS is as under:

BTPS Township: 350 acres

BTPS Plant: 800 acres

Ash Plant: 100 acres

The various units at BTPS and their commissioning dates are as under:

Unit Date of Commissioning Capacity (MW) Status1 01.01.1974 120 Shut Down

2 16.07.1975 120 Shut Down

3 06.12.1978 120 Shut Down

4 03.03.1981 120 Shut Down

5 07.04.2009 250 Operational

6 30.06.2011 250 Operational

BTPS has achieved the meritorious award from electricity authority from 1992 1993 on the

following:

1. Maximum Generation2. Minimum Auxiliary Consumption3. Minimum Specific Fuel Consumption


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A SCHEMATIC REPRESENTATION OF A THERMAL POWER PLANT

1. Cooling tower 10. Steam Control valve 19. Superheater

2. Cooling water pump 11. High pressure turbine 20. Forced draught (draft) fan

3. Transmission line 12. Deaerator 21. Reheater

4. Step-up transformer 13. Feedwater heater 22. Combustion air intake

5. Electrical generator 14. Coal conveyor 23. Economizer

6. Low pressure turbine 15. Coal hopper 24. Air preheater

7. Condensate pump 16. Coal pulverizer 25. Precipitator

8. Surface condenser 17. Boiler steam drum 26. Induced draught fan

9. IPT 18. Bottom ash hopper 27. Chimney


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Coal Handling Plant

Brief Descriptions:

Equipments of CHP

o Two nos. chain driven wagon tipplers U1 and U2 , each of capacity 100 T &one no.rope driven wagon tippler U3 of 90 T capacity.

o Sixteen (16) nos. vibrating feeders (two nos. unbalanced motor type and six nos.originally EM type feeder for each wagon tippler) U1 & U2.

o Three(3) nos. unbalanced motor type vibrating feeders for wagon tippler U3.o Reversible belt feeders U1 & U2, conveyors 1A & 1B ,conveyors 2A 2B,conveyor 3A

& 3B, conveyor 6A/6B, conveyor 7A/7B, conveyor 8A/8B, conveyor 11A/11B,

conveyor 12A/12B.

o Underground conveyor 9A /9B , conveyor 10A / 10B & conveyor 4A &4B.o Six nos. reciprocating vibrating feeders below Reclaim hoppers for feeding to

conveyors 9A /9B and six nos. EM vibrating feeders below Reclaim hoppers for

feeding to conveyors 4A/4B .

o Two nos. Rotary(Two Rolls) Crushers house -1 for stacking route.o Vibrating Screens 1 and 2.o Ring Granulator type Crushers 1 and 2 in Crusherhouse-2 for direct bunker feeding.o Stacker 1 & stacker2 (Boom stacker:both swing and hoisting mechanism are in

running condition).

o Inline magnetic separators on conveyors 1A/1B , 6A/6B &9A/9B.o Two nos. Cross belt Magnetic separators on conveyor 11A/11B .

Route Description

a) Wagon tippler to crusher

From Wagon tippler -1/2, coal is fed to respective reversible belt feeder U1/U2through vibrating feeders. From either of the reversible belt feeder U1 & U2 coal


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flows to any of the conveyors 1A/1B or 6A/6B. conveyor 1A/1B feeds coal to two

rotary crushers for stacking.

From Wagon tippler U3 ,coal is fed to the conveyors 6A/6B only. Conveyor 6A/6Bfeeds coal to either of the two conveyor 7A/7B.

Subsequently from conveyor 7A/7B, coal is fed to either of the two screen 1/2.Smaller size coal i.e. below 24 mm flows to either of the two conveyors 8A/8B

bypassing the crushers. Bigger size coal from screen -1 goes to Ring Granulator type

crusher-1and coal from screen -2 fed to Ring Granulator type Crusher-2.

At the head ends of conveyors 1A /1B & 6A /6B, In line magnetic separators (ILMS)have been provided.

b) Crusher to stack yard

Crushed coal from Rotary Crusher of size below 24 mm is fed to either of theconveyors 2A &2B. From conveyor 3A, coal is fed to yard conveyor 3A for stacking

and from conveyor 3B , coal is fed to yard 3B for stacking purpose.Stacker-1 and

stacker -2 run along with yard conveyor 3A & 3B respectively and are standing in

fixed position in the existing coal stack yard.

The crusher coal from Ring Granulator type crushers flows to either of theconveyors 8A &8B.

For stacking, coal from conveyor 8A/8B is fed to either of the conveyor2A/2B. Coal fromconveyor 2A is fed to 3A and subsequently stacked in stack yard through static stacker-

1 . Coal from conveyor 2B is fed to conveyor 3B and subsequently stacked in the stack

yard through static stacker-2.

c) Crusher to Boiler bunker

For direct feeding to bunker of Unit #5, coal is fed to conveyor 11A/11B from 8A/8Band then from conv. 11A/11Bfed to conv. 12A/12B .

For direct feeding to bunker to Unit#(1-4) coal bunker ,coal from conv. 12B is fed toconv. via conv. 13 &14.

There are three stacking zones via stack yards 1,2 &3 in CHP of BTPS as indicated inlayout Drawing ,dimension of each stock pile is 300m x 61m.

1. Stacker -1 can discharge coal to stack yard 1 and stack yard 22. Stacker -2can discharge coal to stack yard 3 and stack yard 2


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In each zone, there are four reclaim hoppers, two for feeding conveyor 9A/9B ,two

for feeding coal to conveyor 4A/4B.

The coal stacks are leveled with the help of bulldozers


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d)Stack yard to Unit #(1-4)

For bunker feeding of unit #(1-4) from stack yard,coal is fed to six nos. reclaim hoppers by

bulldozing. Vibrating feeders under the reclaim hoppers are feeding coal to conveyors 4A/4B. From

conveyor 4A/4B coal flows to bunker through mobile tippler on conveyor 5.

e)Stack yard to Unit #5

Coal is fed to six nos. reciprocating feeders under six nos. reclaim hoppers by bulldozer.

These reciprocating feeders feed coal to conveyor 9A/9B which subsequently feed to conveyor

10A/10B.From either of the conveyor 10A/10B,coal is fed conveyor 11A/11B. From either of the

conveyor 11A/11B,coal is fed conveyor 12A/12B.

At the head ends of conveyors 9A &9B, Inline magnetic separators have been provided. In

addition, on conveyor 9A/9B , metal detectors have been provided for acting ILMS if any metal is

detected on flowing coal.

Two nos. cross belt magnetic separators each on conveyor 11A &11B are in service.

Technical Details:

Sl

No

Conveyor

No.

Capacity

(TPH)

Belt width

(mm)

Speed

(M/s)

Motor HP Power supply MCC Length

(M)

1 U1/U2 400 1000 1.67 15 9A/10A(380V) 20

2 U3 500 1000 2.0 15 R25(415V) 183 1A/1B 400 900 1.67 50/50 9A/10A(380V) 125

4 2A 400 900 1.67 20 9A(380V) 95

5 2B 400 900 1.67 30 10A(380V) 155

6 3A/3B 500 900 1.67 40/40 9A/10A(380V) 280

7 4A/4B 400 900 1.67 100/100 11A(380V) 283

8 5 400 900 1.67 30 11A(380V) 120

9 6A/6B 500 1000 2.0 75/75 R24/R25(415V) 110

10 7A/7B 500 1000 2.0 60/60 R24/R25(415V) 91

11 8A/8B 500 1000 2.0 50/50 R24/R25(415V) 64

12 9A/9B 500 1000 2.0 50/50 R24(415V) 136

13 10A/10B 500 1000 2.0 50/50 R24/R25(415V) 118

14 11A/11B 500 1000 2.0 125/125 R31(415V) 177

15 12A/12B 500 1000 2.0 45/45 R31(415V) 68

16 13 500 1000 1.67 30 R31(415V) 13

17 14 400 1000 1.67 30 R31(415V) 22


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Recent Development

New approach for breaking of coal lump & removal of stones at CHP

A most effective approach has been taken for breaking of coal lump and removal of stonesfrom coal on net of Wagon tippler-3 by using Hydraulic Excavator at very faster rate which

will facilitate us to reduce demurrage charge for detention of rakes beyond free time.

Hydraulic Excavator

New Shade Over Wagon Tippler-1&2 (Erection in 2012)

To facilitate O&M job


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4.3 Bottlenecks in CHP

BTPS does not have any Stacker cum Reclaimer. So coal from different grade cannot beblend which is bare necessity in present scenario to get optimum fuel efficiency.

BTPS does not have Track Hopper facility so unloading of wagons through conventionalwagon tippler system delays whole coal unloading activity & this leads to

huge demurrage inadequate coal feed rate to the system depleted stock.


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COMBUSTION & FUEL EFFICIENCY

Its a techno-commercial department which checks the quality of fuel & coal from BCCL, ECL &

provides it to CHP. The department quantifies the coal by Weigh Bridge (Load cell) & fuel by fuel

meter & randomly checks the quality of coal and fuel. Based on the ash content, gross calorific value

and useful heat value; Indian coal is classified in six categories as given in Table below:

CLASSIFICATION OF INDIAN COAL:

Grade (Ash + Moisture %) Approx.

(UHV) (Kcal/kg)

Useful heat value

(UHV)

A 19.5 or less Above 6200

B 24.0 - 19.5 5600-6200

C 28.7 24.0 4940-5600

D 34.0 - 28.7 4200-4940

E 40.0 34.0 3360-4200

F 47.0 40.0 2400-3360

G 55.0 47.0 1300-2400

GRADING OF INDIAN COAL:

Serial No. Grading of Coal Criteria

1 Superior grade Grade (A+B+C) (5800

Kcal/kg)

2 Intermediate grade Grade (D) (5800 Kcal/kg)

3 Inferior grade Grade (E+F+G) (4000Kcal/kg)

High ash content in the coal supplied to the power plants not only possess environmental problems

but also results in poor plant performance and high cost for Operation & Maintenance and ash

disposal.


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MECHANICAL OPERATIONS

Overview:

In a Thermal Power Station, Chemical Energy of fuel, which is either Coal or Oil, is converted to

Electrical Energy. This energy conversion takes place in different stages.

First, in the Boiler, the chemical energy in fuel (Coal /Oil) is converted into heat energy. Duringthe process of combustion heat is absorbed by the water from water-walls of the furnace and

generates steam (heat energy).

Secondly, in the Turbine, this heat energy, in the form of steam, is converted into mechanicalenergy.

And finally, in the Generator, directly coupled to the turbine, this mechanical energy isconverted into electrical energy.

In a modern boiler of a Thermal Power Station, combustion process is very fast due to high

steaming rate with increased unit capacity. Moreover, to reduce cost, the present boilers are

operated at maximum permissible temperature limit of its metal.

Further, due to small capacity of the Drum and high steam output to water storage ratio, the

modern boiler demands continuous water feeding and a constant drum water level. This is essentialto prevent starvation of the boiler.

To prevent boiler explosions and flame failure, the furnace draft (pressure) is to be maintained

constant.

All the above things indicate that the steam pressure & temperature, drum water level, furnace

drafts etc are to be maintained constant.

The entire mechanical functioning of any Thermal Power Plant can be classified into various cycles

which have been briefly described in the following pages through block diagrams and descriptions

on the equipments and machines required with specifications of the ones used at BTPS.


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THE BASIC THERMODYNAMIC CYCLE:

The basic thermodynamic cycle employed in a thermal power plant is Rankine Cycle. The diagram

shown below is a schematic representation of how Rankine Cycle is maintained in a thermal power

plant.

Heat is being given to the DM water at the boiler drum which produces steam to cause the turbine

to rotate and do work. The weak steam coming out of the turbine is being condensed at the

Condenser extracting heat from the steam. The temperature at the boiler drum and the condensate

is given by T1 and T2 respectively. The efficiency of Rankine cycle (T1 T2).

Thus to obtain an efficient Rankine cycle temperature of the boiler drum should be increased

enormously as well as temperature T2 should be decreased. This however isnt practically suitable

as enormous rise in temperature at the boiler drum results in development of stress inside the

material, which may cause the drum to buckle up.

To avoid the above mishaps regenerative heating and reheating is done. Regenerative heating

involves tapping of the steam coming out of the boiler drum and directing it to different water paths

causing heat to be added to the water before entering the boiler drum.

Two turbines instead of one turbine is used. Steam extracted from the boiler drum is made to pass

through the High Pressure Turbine (HPT) first and is made to pass through a reheater and then to a

Weak steam

Condenser

BFP

Boiler Drum

Turbine

Heat

provided

Heat extracted

Work done


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Low Pressure Turbine (LPT), thus enhancing the efficiency of the system. This also prevents the

expanded steam from condensing, which would have caused erosion to the turbine blades. The

above process is called Reheating.

TURBINES:

The turbine is a tandem compound machine with separate HP, IP and LP sections, the HP and IP

sections being single-flow cylinders and LP sections double-flow cylinders. The turbine rotors and

the generator rotor are connected by rigid couplings. The HP turbine is nozzle controlled. The initial

steam is admitted before the blading by four combined main stop and control valves. The line

leading from the HP exhaust going to the reheater is provided with swing check valve which

prevent hot steam from the reheater flowing back into the HP turbine. The steam coming from the

Reheater is passed to the IP turbine via two reheat stop and control valve combinations. Cross

around pipes connect the IP and LP cylinders. Bleeds are arranged at several points of the turbine.

HP TURBINE:

The outer casing of the HP turbine is of the barrel type and has neither an axial nor a radial flange.

This prevents mass concentration which would have caused high thermal stresses. The almost

perfect asymmetric design of the casing permits moderate and nearly uniform wall thickness at all

sections. The inner casing is axially split and supported so as to be free to move in response to

thermal expansion. As only slight pressure differences are effective, the horizontal flange and jointbolts of the inner casing can be kept small. The barrel type casing permits flexibility of operation in

the form of short start-up times and a high rate of change of load even at high initial steam

conditions.

IP TURBINE:

The IP turbine section is of single flow construction with horizontally split casings. Allowance is

made for thermal movement of the inner casing within the outer casing. The inner casing carries

the stationary blading. The reheated steam enters the inner casing from top and bottom. The

provision of an inner casing confines high steam inlet conditions to the admission section of this

casing, while the joint

flange of the outer casing is subjected only to the lower pressure and temperature effective at

the exhaust from the inner casing.


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LP TURBINE:

The casing of the double-flow LP cylinder is of three-shell design. The shells are horizontally split

and are of rigid welded construction. The innermost shell, which carries the first rows of stationary

blades, is supported so as to allow thermal expansion within the intermediate shell. The

intermediate shell rests at four points on longitudinal girders, independent of the outer shell. Guide

blade carriers, carrying the last stationary blade rows are also attached to the intermediate shell.

TURBINE GENERATOR SET AT BTPS


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AIR CYCLE:

80C

PA Fan Primary Air Fan

FD Fan Forced Draft or Secondary Air Fan

The air pressure coming out of the PA Fan is much higher than the one coming out of the FD Fan

due to their different modes of operation. The PA Fan mainly provides air which is used to blow the

pulverized coal from the mill into the furnace. Hence requires a higher pressure. Whereas the FD

Fan is used only to provide the excess air required for proper combustion of coal inside the furnace.

PA

Fan

FD

Fan

Regener

ative Air

Heater

Mill

Furnace

Cold PA Dam er

Hot PA Damper


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FEED WATER CYCLE:

CEP Condensate Extraction Pump

BFP Boiler Feed Pump

HPH High Pressure Heater

LPH Low Pressure Heater

The regenerative cycle or the feed water cycle is actually the loop through which the feed water

entering the boiler drum passes through the regenerative heating phase from the condenser so as

to have its enthalpy raised. In the condenser the weak steam loses its energy and water

(condensate) is obtained and is collected in the hot well. The condensate extraction pump (CEP)

then extracts the condensate from the condenser and pumps it towards the deaerator.

The Low Pressure Heater(LPH) heats up the condensate extracted by the CEP, which is done by

steam extract from various parts of the steam cycle. There are 3 LPHs from LPH1 to LPH3. The

Deaerator

Economizer

Boiler Drum

BFP CEP

Steam

Drain Valves

Condensate

HPH6 HPH5

LPH3

LPH2

LPH1


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condensate on emerging out of LPH3 has certain amount of heat in it which it has gained

progressively while passing through different the different LPHs. The CEP output pressure raises

the heated up water up into the deaerator.

The condensate on reaching the deaerator is called the feed water. At the deaerator steam isapplied to the feed water. The steam on emerging out of the feed water forms bubbles which on

going up increases in size and thus increases in surface area, causing heat transfer to occur from the

steam to the feed water. Here the feed water also gets free from the entrapped air.

The Boiler Feed pump pumps the feed water into the boiler drum after passing through High

Pressure Heaters (HPH) and finally the economizer. This is a pump that must be reliable and rugged

to withstand not only continuous high-pressure pumping operation but also transient system upset

conditions and possible frequent loading variations to match the plants load output requirements.

The Economizer adds the final heat to the feed water before entering the drum.

FLUE GAS CYCLE:

The combustion of coal inside the furnace forms Flue gas that leaves the plant through the chimney

after passing through various heat exchanging ducts. This path is called the flue gas cycle.

FURNACE

ECONOMISER

PRIMARY

SUPER HEATER

REHEATER PLATEN SUPER

HEATER

FINAL SUPER

HEATER

REGENERATIVE

A/H

ID FAN ESPSTACK

(CHIMNEY)


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FURNACE:

The rectangular furnace is about 50 feet (15 m) on a side and 130 feet (40 m) tall. Its walls are

made of a web of high pressure steel tubes about 2.3 inches (58 mm) in diameter. Pulverized coal is

air-blown into the furnace from fuel nozzles at the four corners and it rapidly burns, forming a largefireball at the center. The thermal radiation of the fireball heats the water that circulates through

the boiler tubes near the boiler perimeter. The water circulation rate in the boiler is three to four

times the throughput and is typically driven by pumps. As the water in the boiler circulates it

absorbs heat and changes into steam at 700 F (371 C) and 3,200 psi.

The pressure inside the furnace is maintained at a negative value, firstly so that the hot air inside

doesnt escape out in case of any leakage. Secondly the pressure is negative so as to allow the flame

to be observed through a peep hole (Judas Window) to check for proper combustion.

REHEATER:

The steam flows through the reheater of three horizontal banks, bottom intermediate, and top

placed in parallel with the horizontal primary super heater, pendent intermediate bank, reheater

horizontal two sides of unit before the safety valves on the reheater inlet piping. The function of

reheaters is to re superheat the partly expanded steam from the turbine. This is done so that the

steam remains dry as far as possible through the last stage of the turbine.

SUPERHEATERS:

Fossil fuel power plants can have a superheater section in the steam generating furnace. In a fossil

fuel plant, after the steam is conditioned by the drying equipment inside the steam drum, it is piped

from the upper drum area into tubes inside an area of the furnace known as the superheater, which

has an elaborate set up of tubing where the steam vapor picks up more energy from hot flue gases

outside the tubing and its temperature is now superheated above the saturation temperature. The

superheated steam is then piped through the main steam lines to the valves before the high

pressure turbine.

Primary Superheater - This is a single steam pass arranged in counter flow with respect tothe gas flow.


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Platen Superheater - Steam passes from the primary superheater outlet box to the platensuperheater inlet box. This is a single steam pass in parallel flow with the gas.

Secondary Superheater - This is also a single steam pass arrangement parallel flow with thegas.

ECONOMIZER:

It is the device which heats the feed water on its way to bowl by driving heat from the fuel gas. The

result is rising boiler efficiency, saving fuel & reduce stresses the boiler due to higher temperature

of feed water. An Economizer consists of a large number of closely spaced parallel steel tubes

connected by headers o f drum. The feed water flows through these tubes and the flue gas flows

outside. A part of heat of flue gas is transferred to feed water, thus rising the temperature of the

latter.

ID FAN:

The ID fan maintains a differential pressure between the furnace and the stack (or chimney), so as

to force the flue gas to pass through the chimney via different heat exchanging ducts.

Type: BAB 65 AEROFOIL BLADE Double Inlet

No. per boiler: 2, Coupling: Hydraulic Type

Bearing Type: High Speed spherical reheated ring lubricated water cooled.

Motor HP: 900, Motor RPM: 740

CHIMNEY (STACK):

The chimney is a structure for venting hot flue gases from the furnace to the outside atmosphere.

Chimneys are typically vertical, or as near as possible to vertical, to ensure that the gases flow

smoothly, drawing air into the combustion in what is known as the stack, or chimney, effect. Theheight of chimneys plays role in their ability to transfer flue gases using stack effect, the dispersion

of pollutants at higher altitude helps to ease down its influence on surroundings. The dispersion of

pollutants over greater area reduces their concentrations in compliance with regulatory limits. The

two chimneys at BTPS are each 220 meters high.


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PRESSURE MEASUREMENT:

In a Thermal Power Plant measurement of control of pressure of liquid and gases is very important

e.g. in furnace the pressure must be maintained -3 to -4 mmHg. Otherwise malfunction may arise.

For local indication Bourdon Gauge must be used.

1. Pressure gauge: Here mechanical deformation of an elastic material is done due to themeasuring pressure. Measuring the deformation pressure is measured.

2. Pressure transmitter: It converts the mechanical output from sensors to mechanicalequivalent. It consists of three elements pressure sensing element (e.g. diaphragm,

bourdon tube), primary conversion element, secondary conversion element.

FLOW MEASUREMENT:

In a Thermal Power Plant measurement of flow rate of air, water, and steam is very important.

Instruments for flow measurements are given below:

Venturi Tube: It follows Bernoullis theorem. It is used where permanent pressure loss is of prime

importance and maximum accuracy is desired for high viscous fluids.

Orifice Plate: Its the simplest and cheapest flow measuring instrument. Here pressure loss is

maximum.

Rota meter: Here flow rate is proportional to area. Here linear scale is used. A float moves up and

down the tube as indicator.

LEVEL MEASUREMENT:

In a Thermal Power Plant, measurement of level is essential for the purpose of safe and efficient

operation of the plant. For the purpose of co-ordination and control, level measurement is also

required. In a Thermal Power Station, measurement of level is carried out for liquid and solid. The

coal level in the coal bunkers is measured, which is an example of measurement of the level of

solids. Measurement of Boiler drum water level, De-aerator water level, Condenser Hot well level,

etc are examples of measurement of level of a liquid.

In some cases, level is measured for remote indication and for control. For this type of level

measurement differential pressure transmitters (DP transmitter) are normally used. The DP


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transmitter may be of the LVDT, Reluctance, or Capacitance type.

Areas of application: Drum level control (three element control), De-aerator level control, HP

heaters level control, LP heaters level control, Hotwell level control.

ANALYTICAL INSTRUMENTS:

Depending on the paramagnetic effect, chemical heating etc. some instruments are used to analyze

various samples. Various application fields are:

Oxygen in flue gas: Excess oxygen indicates inefficiency & less oxygen indicates incomplete

combustion. So for efficient operation this measurement is important.

Dissolved oxygen in feed water: Dissolved oxygen in feed water may react with metal parts of boiler

& turbine & result in corrosion. So measurements are to be made to check removal of oxygen from

the feed water.

Conductivity of feed water: If water is acidic or alkaline, it may affect the boiler. So pH measurement

is necessary.

Hydrogen purity: Hydrogen is used for cooling of stator & rotor of alternator. Heating of generator

causes reduction of load. So purity measurement of hydrogen is important.

Opacity of flue gas: Opacity/dust particles in flue gas are monitored by opacity monitor.

PNEUMATIC ACTUATOR:

Actuator causes movement of valve stem according to applied signal. Actuator is opened, closed or

positioned by air, hydraulics or manually. In spring-diaphragm actuator variable air pressure is

applied to flexible diaphragm to oppose spring. This force is used to balance fluid force on valve.

Both spring-diaphragm and piston type actuator produce linear motion to move the valve.


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OPH

SWITCH YARD:

BUS BAR ARRANGEMENT:

At the 132 KV switch yard in the Bandel thermal power station main bus with transferbus scheme

has been used. It ensures continuity of supply in case of bus fault with the disadvantage of

additional cost.

SWITCH YARD EQUIPMENTS:

FEEDERS:

1. 132 KV Dharampur#12. 132 KV Dharampur#23. 132 KV Dharampur#34. 132 KV Bighati#15. 132 KV Bighati#26. 132 KV Adisaptagram#17. 132 KV Adisaptagram#28. 132 KV Khanyan9. 132 KV Satgachiya10.132 KV Chanditala11.132 KV Liluah12.132 KV Kalyani

CIRCUIT BREAKER: Circuit breakers are designed to operate in faulty conditions of a circuit and

have rated breaking and making capacities in MVA. Making capacity is decided by consideration of

asymmetrical making current during closing of circuit breaker in an already short circuited line.

Hence calculation of Fault MVA by network analysis is essential for selection of circuit breakers to

be of the adequate capacity.

Some of the circuit breakers at BTPS are SF6 circuit breakers. As SF6 is a strong electro negative

gas, it is de ionized and recovers breakdown voltage very rapidly and the arc extinguishes at

natural current zero. Zero current interruption is an excellent feature which makes it free from any

form of current chopping, high TRV and restriking. Therefore no damping resistance is required to


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control the TRV. Pre-Closing circuit breakers are used when such breakers are employed in long

transmission lines of comparatively high voltage to control voltage surge during closing of breakers.

On the contrary MOCB has inherent problems of current chopping and requires damping resistance.

BULK OIL CIRCUIT BREAKER: In this circuit breaker the current interruption take place insidethe interrupter. The enclose of interrupter is made of insulating material link porcelain. Hence the

clearance between the live parts and the enclosure can be reduced and lesser quantity of oil

requires for internal operation.

SPACIFICATIONS:-

132 KV BOCB at BANDEL THERMAL POWER STATION SWITCHYARD

CONDUCTORS: The Conductors used at the BTPS switch yard is of the ACSR type. Aluminum

conductor steel reinforced (or ACSR) cable is a specific type of high-capacity, high-strength

stranded cable typically used in overhead power lines. The outer strands are aluminum, chosen forits excellent conductivity, low weight and low cost. The center strand is of steel for the strength

required to support the weight without stretching the aluminum due to its ductility. This gives the

cable an overall high tensile strength. Each conductor can carry currents up to 900 A. The strands

are in the sequence of 12, 18 and 24.

Name SF6 OCB ACB

Voltage level 138 KV 145 KV 145 KV

Current level 1600 A 1600 A 1600 A

Fault level 10000MVA 7000MVA 7000MVA

Medium used SF6 Oil Air


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LIGHTNING ARRESTOR: Over voltages may occur in substation by incident on travelling wave from

transmission line due to lightning impulse with steep waveform in the range of 1/50 micro sec.

temporary over voltages (TOV) may be caused by a number of systems, events such as line to

ground fault, circuit back feeding, load rejection, Ferro resonance, etc. there may be also be other

internal surges known to be switching surges due to current chopping, successive restrike by

interruption of capacitive current, etc.

A lightning arrestor resembling a safety valve of the system diverts this over voltages to ground by

lowering its resistance and also interrupts power frequency follow up current by developing its

own resistance to high value as soon as the voltage comes to a normal value.

ISOLATORS: Isolators are used for no load opening and closing of circuits. They can be operated

from remote by motorized, hydraulic, or pneumatic mechanisms. Three poles are either

mechanically or electrically ganged and may be provided with earth switching having either

electrical or mechanical interlock or both for safe operation only during de energized condition.

The isolators are interlocked with circuit breakers for their operation while breaker status is OFF

only. This electrical interlock is achieved by isolation of DC control power of isolator at ON

position of breaker.


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CURRENT TRANSFORMER (CT): A basic element of relaying and metering, CT is a series connected

transformer having single bar primary, several protection cores and one metering core of

respective accuracy class and secondary. Transient saturation, DC offset is the ruling factor in the

design and deciding accuracy of CT, and pose problem where the relaying scheme operates on

current balance principle. The performance characteristics of distance relaying are also affected by

these factors. The entire transformer element is kept in porcelain case with transformer oil insealed condition and in pressurized by nitrogen for reducing corona. The salient particulars of a

protection class current transformer are current ratings, VA burden, accuracy class (viz 5P, 10P,

15P). Accuracy limit factors (ALF viz 5, 10, 15, 20, 30), short time factor, knee point voltage. The

cables from CT are taken to a nearby CTJB (Junction Box) where shorting links and earth

connections are provided and then to control room panels.

VOLTAGE TRANSFORMER (VT): Electromagnetic voltage transformer (EMVT) is common up to 220

KV and its insulation is economically designed by cascade connection of several VTs in which there

primaries are in series. Coupling windings alongside the primary windings equalize the voltage.

Secondary connections from VT are taken through fuses.

WAVE TRAP: A wave trap traps the high frequency communication signals sent on the line from the

remote substation and diverting them to the telecom/teleprotection panel in the substation control

room (through coupling capacitor and LMU).


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This is relevant in Power Line Carrier Communication (PLCC) systems for communication among

various substations without dependence on the telecom company network. The signals are

primarily teleprotection signals and in addition, voice and data communication signals. The Line

trap offers high impedance to the high frequency communication signals thus obstructs the flow of

these signals in to the substation busbars. If there were not to be there, then signal loss is more and

communication will be ineffective/probably impossible.

CAPACITOR VOLTAGE TRANSFORMER: A capacitor voltage transformer (CVT), or capacitancecoupled voltage transformer (CCVT) is a transformer used in power systems to step down extra

high voltage signals and provide a low voltage signal, for measurement or to operate a protective

relay. In its most basic form the device consists of three parts: two capacitors across which the

transmission line signal is split, an inductive element to tune the device to the line frequency, and a

transformer to isolate and further step down the voltage for the instrumentation or protective

relay. The CVT is also useful in communication systems. CVTs in combination with wave traps are

used for filtering high frequency communication signals from power frequency. This forms a carrier

communication network throughout the transmission network.


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SWITCHYARD AT BTPS

GENERATOR TRANSFORMER:

The generator transformer is the one connected directly after the generator. Each operational unit

at BTPS has one generator transformer each with H.V side: 132 KV and L.V side: 13.8 KV.

GENERATOR TRANSFORMER UNIT5, BTPS


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STATION TRANSFORMER:

These transformers are used when there is no generation at a unit, and to supply auxiliary power to

the units.

AUXILIARY TRANSFORMER:

When the units are in operation, unit transformers are used to provide auxiliary power to them.

Each operational unit at BTPS (1,2,3&4) have one auxiliary transformers each. All are of 13.8/3 KV.

The 5th unit has two auxiliary transformers of 15.75/6.6 KV.


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RELAY AND INSTRUMENTS

GENERATOR PROTECTION:

1. Low Forward Power Protection: The generator will not develop output power when turbineinput is less than the no load losses and motoring action develops on the turbine. The

generator is able to generate power, usually 55 to 10% of generator capacity, within pre-

determined time after closing of breaker.

2. Reverse Power Protection: The reverse-power relay senses real power flow into thegenerator, which will occur if the generator loses its prime-mover input. Since the generator

is not faulted, CTs on either side of the generator would provide the same measured

current. In a steam-turbine, the low pressure blades will overheat with the lack of steam

flow. Therefore, anti-motoring protection is recommended whenever the unit may be

connected to a source of motoring power.

3. Differential Protection: In this type of protection the relay picks up when the vectordifference of two same electrical entities reaches above a particular set value. This is

applicable to generators, motors, transformers, as well as bus bars.

4. Loss of Excitation Protection: When the synchronous machine with excitation, is connectedto the grid, it generates reactive power along with active power to the grid and the rotor

speed is same as that of grid frequency. Loss of field or loss of excitation results in loss of

synchronism between rotor flux & stator flux. The synchronous machine operates as an

induction machine at higher speed and draws reactive power from the grid. This will result

in the flow of slip frequency currents in the rotor body as well as severe torque oscillations

in the rotor shaft. As the rotor is not designed to sustain such currents or to withstand the

high alternating torques which results in rotor overheating, coupling slippage and even

rotor failure. A loss of excitation normally indicates a problem with the excitation system.

Sometimes it may be due to inadvertent tripping of filed breaker, open or short circuit of

field winding or loss of source to the exciter.

5. Over Excitation Protection: Over excitation can occur due to higher than rated voltage, orrated or lower voltage at less than rated frequency. For a given flux level, the voltage output

of a machine will be proportional to frequency. Since maximum flux level is designed for

normal frequency and voltage, when a machine is at reduced speed, maximum voltage is

proportionately reduced. . IEEE C50.13 specifies that a generator should continuously


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withstand 105% of rated excitation at full load. With the unit off line, and with voltage-

regulator control at reduced frequency, the generator can be overexcited if the regulator

does not include an over excitation limiter.

6. Under Voltage Protection: When two or more generators are working in parallel and one ofthem suddenly trips then the other generators may experience overload condition and in

this time the load current will increase with the gradual decrease in terminal voltage. The

under voltage protection restricts the fall of terminal voltage up to a specified value.

7. Over Voltage Protection: The protection used is an AC over voltage relay which has a pickup value of 110% of the normal value and operates instantaneously at about 130% to 150%

of the rated voltage. The operation of the relay introduces resistance in the generator or

exciter field circuit and if the over voltage still persists the main generator breaker and the

generator or exciter field breaker trips.

8. Over Frequency Protection: Over frequency results from the excess generation and it caneasily be corrected by reducing its power output with the help of the governor or manual

control.

9. Under Frequency Protection: Under frequency occurs when the generator undergoesthrough over load condition. The power system survives only when we drop the excess

load. The rate at which frequency drops depend on the time, amount of overload and also on

the load and generator variations as the frequency changes. The scheme drops the load in

steps as the frequency decreases. Generally load shedding drops 20 to 50 % of load in four

to six frequency steps. Load shedding scheme works by tripping the substation feeders to

decrease the system load.

10.Back Up Impedance Protection: As in name implies, it is used to protect the generator fromsupplying an over loaded or faulty system. It is the backup protection of the generator over

current protection. It measures ratio of the voltage and current supplied by the generator

and initiates trip signal when the measured impedance is less than the preset value.

11.Out of Step or Pole Slipping Protection: When a generator pulls out of synchronism with thesystem, current will rise relatively slowly compared to the instantaneous change in current

associated with a fault. The out-of-step relay uses impedance techniques to sense this

condition. The relay will see an apparent load impedance swing as impedance moves from

Zone 1 to Zone 2. The time it takes for the load impedance to traverse from Zone 1 to Zone 2

is used to decide if an out of step condition is occurring. Moving impedance is identified as a

swing rather than a fault, so appropriate fault detection relaying may be blocked.


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12.Turbine Over Speed Protection: The speed goes up whenever there is sudden loss of load,i.e. there is sudden loss in the o/p of the generator. This reduction in the o/p can be

detected by using a watt metric relay at the generator terminals which operates

instantaneously to close its contacts.

13.Negative Sequence Protection: In negative sequence protection, a current segregatingnetwork is used. The output of which is proportional to the generator negative sequence

current and is fed to a relay with an inverse square law characteristic. i.e. I2t = k. The pickup

and time delay adjustments are provided such that the relay characteristic can be chosen to

match closely any machine characteristic. It is normally an IDMT relay.

14.Earth Fault Protection: It is similar to generator differential protection in working. Itprotects the high voltage winding of 11/220 KV power transformer against internal faults.

One set current transformers of the power transformer on neutral and phase side, is

exclusively used for this protection. The protection cannot detect turn-to-turn fault within

one winding. Upon the detection of a phase-to-phase or phase-to-ground fault in the

winding, the unit will be tripped without time delay. Once the restricted earth fault

protection is operated, the unit cannot be taken into service unless the transformer winding

is thoroughly examined by the maintenance staff for any internals faults.

15.Over Current Protection: Normally generators are designed to operate continuously at ratedMVA, frequency and power factor over a range of 95 to 105% rated voltage. Operating the

generator at rated MVA with 95% voltage, 105% stator current is permissible. Operating of

the generator beyond rated MVA may result in harmful stator over current. A consequence

of over current in winding is stator core overheating and leads to failure of insulation.

TRANSFORMER PROTECTION:

1. Over Flux Protection: Transformer over fluxing can be a result of: Overvoltage

Low system frequency

A transformer is designed to operate at or below a maximum magnetic flux density in the

transformer core. Above this design limit the eddy currents in the core and nearby

conductive components cause overheating which within a very short time may cause severe

damage. The magnetic flux in the core is proportional to the voltage applied to the winding

divided by the impedance of the winding. The flux in the core increases with either

increasing voltage or decreasing frequency. During startup or shutdown of generator-


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connected transformers, or following a load rejection, the transformer may experience an

excessive ratio of volts to hertz, that is, become overexcited. When a transformer core is

overexcited, the core is operating in a non-linear magnetic region, and creates harmonic

components in the exciting current. A significant amount of current at the 5th harmonic is

characteristic of over excitation.

2. Earth Fault Protection: The restricted ground fault function can be used to providedifferential protection for such ground faults, down to faults at 5% of the transformer

winding. Restricted ground fault protection can be a low impedance differential function or

a high impedance differential function. The low impedance function has the advantage to

being able to precisely set the sensitivity to meet the application requirement. This sensitive

protection limits the damage to the transformer to allow quicker repair. The restricted

ground fault element uses adaptive restraint based on symmetrical components to provide

security during external phase faults with significant CT error. This permits the function to

maximize sensitivity without any time delay.

3. Over Current ProtectionMOTOR PROTECTION:

1. Thermal Overload Protection: Stator over heating is caused due to the overloads and failurein cooling system. It is very difficult to detect the overheating due to the short circuiting of

the lamination before any serious damage is caused. Temperature rise depend upon I2Rt

and also on the cooling. Over current relays cannot detect the winding temperature because

electrical protection cannot detect the failure of the cooling System. So to protect the stator

against overheating, embed resistance temperature detector or thermocouples are used in

the slots below the stator coils. These detectors are located on the different places in the

windings so that to detect the temperature throughout the stator.

2. Earth Fault Protection (Derived and Sensitive)3. Negative Sequence Protection4. Short Circuit Protection5. Stalling Protection: The stall protection is only inactive during the starting procedure of the

motor. When the motor is running and then all of a sudden a stall situation happens, then

the motor will be tripped at once, when the parameterized stall current (e.g. 400%) is

reached.


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FEEDER PROTECTION:

1. Over Current Protection: The over current protection is the simplest and cheapest form ofprotection. It is the most difficult to apply and needs readjustments whenever a change

occurs in the circuit. The other advantages of o/c protection are that in case of nondirectional o/c relays no a.c voltage is required. O/C protection is also used for phase and

ground faults where distance protection is costly. Over current protection is mainly used as

back up protection where the primary protection is provided with distance schemes.

2. Distance Protection: Whenever over current relaying is found slow or is not selective,distance protection should be used. Since the fault currents depend upon the generating

capacity and system configuration, the distance relays are preferred to o/c relays.

3. Power Line Carrier Communication ProtectionBUS BAR PROTECTION:

1. Breaker Protection2. Local Breaker Back Up Protection: This protection is initiated only when the confirmation of

the tripping of the main breaker is not received within a specified amount of time. This may

have happened due to the mechanical failures in the main breaker.

3. Bus Differential Protection: This protection is provided between two main buses coupledwith a bus coupler breaker; so that in case of a fault in one main bus, the excess fault current

in that bus trips the particular relay which opens the bus coupler breaker contacts. Thisisolates the faulty bus from the system and hence isolates the fault.


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IPH

The IPH comprises of two 6.6 KV UNIT SWBD (5SA & 5SB) and two 6.6 KV STATION SWBD (OSA &

OSB).

From each unit Bus the power is supplied to:

1. ELECTRO STATIC PRECIPITATOR (ESP) PMCC (5DB & 5DC) to ESP cum AHP (ASHHANDLING PLANT) control bldg & Vent MCC

2. MLDB3. Unit PCC (5DA) to

(i) Turbine Auxiliary(5KA) MCC and Turbine V/V ACDB(5KB)(ii) Boiler Auxiliary MCC (5HA), SOOT Blower MCC (5HC) & Boiler V/V ACDB(iii) Emergency MCC(5EA) & 415 V EMER DG PCC

4. From Emergency MCC (5EA) to ACELDB 1 & 2 through 100 KVA Dy11 415/433 VTransformer

For SWBD # 5SA the above is done by transformers 5DAT01, 5DBT01 and 5DCT01 each of 2 MVA

capacity and rating 6.6 KV/415 V.

And for SWBD # 5SB the transformers used are 5DCT02, 5DBT02 and 5DAT02 each of capacity 2MVA and rating 6.6 KV/415 V.

From each station SWBD (OSA & OSB) the power is supplied to:

1. Ash Handling Switch Gear(i) Ash Handling PMCC to Ash Handling MCC and Silo Area MCC through 1.6 MVA

ODFT01 & 02 transformer

(ii) Fly Ash PMCC to Fly Ash Conveyer Blower BLDG MCC and Ash Water RecoveryPMCC

(iii) Raw Water PMCC to Clarified Water P/H MCC and Chemical House MCC and DMPlant MCC

(iv) CW Area PMCC to Fire Water MCC and Chlorination PLANT MCC(v) Station PCC to

(a)Vent MCC TG Hall MCC to UPS


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(b)Power House AC MCC(c) Power House ACDB

The Breakers used in the 6.6 KV system are Vacuum Circuit Breakers and the ones used in the 415 V

system are Air Circuit Breakers.

When the unit is not working or is about to start, the station transformer will supply the required

power to the unit bus trough the Bus Coupler breaker.

STATION BATTERY AND BATTERY CHARGER:

One 240 V battery ad one battery charger of adequate capacity are provided. The system supplies

DC power to the turbo generator for emergency lubrication purpose as well as to the seal oil pumps.

It also supplies power to the emergency lighting systems and to the tripping circuit of the circuit

breakers.

BRUSHLESS GENERATOR EXCITER:

With the advent of mechanically robust silicone diode capable of converting A.C. to D.C. at a high

power levels, brushless excitation system has become popular and being employed. The basic

arrangement of a typical brushless excitation system presently is used in BHEL machines. This

system consists of main components as listed below:

1. Three phase pilot exciter2. Three phase main exciter3. Rotating rectifier wheels4. Cooler5. Metering and supervisory system.

THREE PHASE PILOT EXCITER:

Three phase pilot exciter has a revolving field with permanent magnet poles. The controlled

rectified d.c. is fed to the main exciter field. The induced Three Phase a.c voltage is rectified in the

rotating rectifier bridge and is fed to the generator rotor winding through the d.c leads in the shaft.

The pilot exciter has 16 poles. The output is 220 V (+ - 10%), 400 Hz. Ten magnets are housed

together in a non magnetic enclosure and this make one pole. These magnets are braced between

the hub and external pole shoe with bolts.


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THREE PHASE MAIN EXCITER:

The three phase main exciter is a six pole rotating armature unit. The field poles with the damper

windings are arranged in the stator frame. Laminated magnetic poles are arranged to form the field

winding. To measure the exciter current a quadrature axis coil is fitted between two poles.

The winding conductors are transposed within the core length, and the end turns of the rotor

windings are secured with steel bands. The connections are made at rectifier wheel end. A ring bus

formed at the winding end and leads to rotating rectifier wheel are also connected to the same. The

complete rotor is shrunk fit on the shaft. The rotor is supported on a journal bearing positioned

between the main and the pilot exciters. Lubrication of the bearing is formed from the turbine oil

system.

ROTATING RECTIFIER WHEELS:

The silicon diodes are arranged on the rectifier wheels in three configurations. The diodes are so

made that the contact pressure increases during rotation due to the centrifugal force. There are two

diodes.

COOLERS:

Because of these properties, hydrogen will extract more heat per unit volume/min. Thus for a given

rise of temperature, machine capacity can be increased. It has been estimated that by use of

Hydrogen 20% reduction in active construction materials can be affected. At 0.035 kg/cm of

hydrogen, machine rating is increased by 22-25% and at 2.109 kg/cm the rating increase is 35%.


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Major Constraints at BTPS

Major Constraints

a) Technology being vintage most of the drives of the system has to be runmanually. This has to lead to higher MAN/ MW Ratio in comparison to Modern PowerStation.

b) All Boilers of BTPS having Front Fuel Firing System which cater toward good combustion, only

with good quality of coal. But with the dwindling supply of good quality of coal and with the

compulsion to use inferior quality of coal in power plants, all boiler technology has shifted to

Corner Fuel Firing System leading to better combustion with inferior quality of coal. So in

present worst coal scenario with low GCV & high ash content, Front Fired Boiler has become a

major concern at BTPS.

Constraints in Power evacuationBTPS Switch Yard faces constraints in power evacuation due to following reasons:

Single 132 KV main bus system. Space constraints

During peak hours excessive VARs are catered by BTPS generating units almost bordering on its

capability limit.

Constraints in CHPNo provision of Stacker cum Reclaimer & Track Hopper

Further to that BTPS is really handicapped with huge amount of stones that comes with

coal which further increases demurrage and unwarranted damage of the equipment.


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Conclusion

In the present scenario of Indian Power Sector, Bandel Thermal Power Station which has

very small capacity, 450 MW only, consisting very old technology like pneumatic control in

instrumentation system, electro-magnetic relays in most of the electrical systems etc. plays avital role in west Bengal due to its location and heritage of power stations. At the Plant level,

there are so many attempts done to improve systems at BTPS. After imposing Electricity Act,

2003 it is better to generate power in efficient way by using the optimization of assets. So the

Ministry of Power, West Bengal already gives encouragements to do the R&M works for all units

in BTPS. The EER&M of Unit 5, BTPS will be started on 2013.The effect of power blackout on

31.07.12 has been depicted to search the root cause and to analysis the parameters at

generating stations under WBPDCL, eastern grid etc. during the grid collapse.

btps project report elec engg

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