The document provides details about Gourab Sarkar's 3-week vocational training at the Bandel Thermal Power Station (BTPS) in West Bengal, India. BTPS has a total installed capacity of 2340 MW from units ranging from 210 MW to 60 MW. It uses coal and water from the Hooghly River. The training covered the mechanical and electrical operations of the thermal power plant, including the coal handling process, boiler and turbine systems, generators, transformers, switchyard, and other components.
A nuclear power plant or nuclear power station is a thermal power station in which the heat source is a nuclear reactor. As is typical in all conventional thermal power stations the heat is used to generate steam which drives a steam turbine connected to an electric generator which produces electricity.
A thermal power station is a power station in which heat energy is converted to electric power. In most of the places in the world the turbine is steam-driven. Water is heated, turns into steam and spins a steam turbine which drives an electrical generator.
A nuclear power plant or nuclear power station is a thermal power station in which the heat source is a nuclear reactor. As is typical in all conventional thermal power stations the heat is used to generate steam which drives a steam turbine connected to an electric generator which produces electricity.
A thermal power station is a power station in which heat energy is converted to electric power. In most of the places in the world the turbine is steam-driven. Water is heated, turns into steam and spins a steam turbine which drives an electrical generator.
Thermal Power Plant - Full Detail About Plant and Parts (Also Contain Animate...Shubham Thakur
A thermal power station is a power plant in which the prime mover is steam driven. Water is heated, turns into steam and spins a steam turbine which drives an electrical generator. After it passes through the turbine, the steam is condensed in a condenser and recycled to where it was heated; this is known as a Rankine cycle. The greatest variation in the design of thermal power stations is due to the different fossil fuel resources generally used to heat the water. Some prefer to use the term energy center because such facilities convert forms of heat energy into electrical energy.[1] Certain thermal power plants also are designed to produce heat energy for industrial purposes of district heating, or desalination of water, in addition to generating electrical power. Globally, fossil fueled thermal power plants produce a large part of man-made CO2 emissions to the atmosphere, and efforts to reduce these are varied and widespread.
For Video on Themal Power Plant (Animated Working Video) :- https://www.youtube.com/watch?v=ouWOhk1INjo
Subscribe To Our Youtube Channel For More Videos:-
https://www.youtube.com/TheEngineeringScienc
Click Here To Subscribe:-
http://www.youtube.com/user/TheEngineeringScienc?sub_confirmation=1
Thermal Power Plant - Full Detail About Plant and Parts (Also Contain Animate...Shubham Thakur
A thermal power station is a power plant in which the prime mover is steam driven. Water is heated, turns into steam and spins a steam turbine which drives an electrical generator. After it passes through the turbine, the steam is condensed in a condenser and recycled to where it was heated; this is known as a Rankine cycle. The greatest variation in the design of thermal power stations is due to the different fossil fuel resources generally used to heat the water. Some prefer to use the term energy center because such facilities convert forms of heat energy into electrical energy.[1] Certain thermal power plants also are designed to produce heat energy for industrial purposes of district heating, or desalination of water, in addition to generating electrical power. Globally, fossil fueled thermal power plants produce a large part of man-made CO2 emissions to the atmosphere, and efforts to reduce these are varied and widespread.
For Video on Themal Power Plant (Animated Working Video) :- https://www.youtube.com/watch?v=ouWOhk1INjo
Subscribe To Our Youtube Channel For More Videos:-
https://www.youtube.com/TheEngineeringScienc
Click Here To Subscribe:-
http://www.youtube.com/user/TheEngineeringScienc?sub_confirmation=1
La impugnabilidad de la resolución de secuestro en la jurisdicción marítima, ...Nelson Carreyó Collazos
Las medidas cautelares como mecanismos de coerción en algunas ocasiones puede representar injusticias; de allí que el legislador se haya preocupado en estructurar instrumentos procedimentales idóneos para el ejercicio del derecho de defensa los cuales pueden ser utilizados en la misma instancia, en apelación o como recurso extraordinario.
En este trabajo nos proponemos analizar esos métodos de impugnación y en especial dilucidar si puede considerarse (como en la práctica lo ha hecho la jurisdicción marítima en algunos fallos) que el fenómeno jurídico de la prescripción de la acción extingue los créditos marítimos privilegiados para efectos de estimar o desestimar la principal de esas medidas como es el Apremio.
training report on Mejia Thermal Power Stationsagnikchoudhury
Mejia Thermal Power Station is located at Durlovpur, Bankura, 35 km from Durgapur city in West Bengal. The power plant is one of the coal based power plants of DVC
MSEB was set up in 1960 to generate, transmit and distribute power to all consumers in
Maharashtra excluding Mumbai. MSEB was the largest SEB in the country. The generation
capacity of MSEB has grown from 760 MW in 1960-61 to 9771 MW in 2001-02. The customer
base has grown from 1,07,833 in 1960-61 to 1,40,09,089 in 2001-02.
C.S.T.P.S in contribution much in field of production of electricity. It is not only number
one thermal power station in Asia but also has occupied specific position on the international
map.
The first set was commission on August 1983 & was dedicated to nation by then PM
(late) Mrs. Indira Gandhi & second set commission on July 1984. The third & fourth units of
CSTPS under stage 2 were commissioned on the 3rd May 1985 & 8th March 1986 respectively.
The units 5 & 6 were commissioned on the 22nd March 1991 & 11th March 1992 respectively one
more units of 500MW was added to the CSTPS on making its generation to 2340 MW &
making “C.S.T.P.S.” as the giant in Power Generation of CSTPS.
Abhinav Kumar Mechanical Engineering Vocational Training NTPC Ltd UnchaharABHINAV KUMAR
This is the vocational training report needed to be submitted with the EDC HR Dept in order to acquire the certificate of completion. And additional copy is submitted with the Mechanical Department of my respective college.
it is the very important notes on :
1. Turbine
2. turbine component
3. princple of turbine
4.contruction of turbine
5.production process with hydroelectric and chp
Installation & Working of Coal Fired Thermal Power PlantMuhammad Awais
Statement of Submission:
It is certified that the following students of PRESTON University Islamabad (Mechanical Department) have successfully completed the project named Installation & Working of Coal Fired Thermal Power Plant. This project fulfills the complete requirement of the topic given by the project adviser.
PREFACE
This thesis ″Installation & Working of Coal Fired Thermal Power Plant ″ is made on a final semester project of B-Tech (Hons) Mechanical.
This thesis includes the basic concept of Coal Fired Thermal Power Plant, there principles, factors, types of Boilers, Coal, Turbines, calculation and basic design of C.F.T.P.P system for energy.
This thesis has been written according to rules and standards of ASME (American Society of Mechanical Engineers).
All the concepts, factors, calculations, design fulfills the proper rules of Coal Fired Thermal Power Plant according to ASME.
In this book the chapters contains the following
Introduction to Thermal coal fired power plant.
Introduction to Thermal coal fired power plant System
Coal
Boiler
Turbine
Generator
Transmission Line
Best Regards,
C.F.T.P.P Project Group
The whole world is suffering from energy crisis and the pollution is
manifesting itself in the spiralling cost of energy. The economic, both micro and macro, growth of any nation depends on
the power sector, because if that fails, slowly from minor to perhaps
complete breakdown of the system can occur. Energy is created by the following plants: 1. Thermal 2. Nuclear 3. Hydel 4. Hydraulic 5. Gas 6. GeoThermal
Alongwith cheap energy, control of the waste generation and pollution
needs to be done, which is a bigger devil on the long run. A pioneer in such an enterprise is Mejia Thermal Power Station, Durlabhpur, Bankura. We undertook Vocational Training in this
institution, and learned about the process of power generation and it’s
by-products. The Power station has a total of 8 units, final two units inducted in
2012 and 2013, and thus being extremely advanced, with newest
thermodynamic designs, and fast, digital and reliable controls. It
employs Tilting Corner Fired Combustion Burner, and KWU West
Germany Design Reaction Turbine, both manufactured by BHEL, India. MTPS units have many special features including Turbo mill, DIPC
(Direct Ignition of Pulverised Coal) system, HPLP bypass system, Automatic Turbine run up system , and Furnace Safeguard Supervisory
System.
1. A REPORT OF THE VOCATIONAL
TRAINING
FOR THE PERIOD OF THREE WEEKS FROM
01.07.16 TO 20.07.16
at
Bandel THERMAL POWER STATION
P.O. Bandel, DIST. HOOGHLY
WEST BENGAL
OF
West Bengal power Development
Corporation
(W.B.P.D.C.L.)
by
GOURAB SARKAR
MCKV INSTITUTE OF TECHNOLOGY
1
2. PREFACE
Economic growth in India, being dependent on the power sector, has necessiated an
enormous growth in electricity demand over the last two decades. Electricity in bulk
quantities is produced in power plants, which can be of the following types: (a)
Thermal (b) Nuclear (c) Hydraulic, (d) Gas turbine and (e) Geothermal.
I have done my vocational training in Bandel THERMAL POWER STATION under
West Bengal power Development Corporation (W.B.P.D.C.L.) comprising 1 units of
210 MW each, 4 units of 60 MW each . It is a modern thermal power station having
tilting burner corner fired combustion engineering USA design boiler and KWU West
Germany Design Reaction Turbine. Both these main equipments have been designed,
manufactured and supplied by Bharat Heavy Electricals Limited, India. BTPS units
have many special features such as Turbo mill, DIPC (Direct Ignition of Pulverised
Coal) system, HPLP bypass system, Automatic Turbine Run up system, and Furnace
Safeguard Supervisory System.
2
3. ACKNOWLEDGEMENT
The dissertation has been prepared based on the vocational training
undergone in a highly esteemed organisation of Eastern region, a pioneer in
Generation Transmission & Distribution of power, one of the most technically
advanced & largest thermal power stations in West Bengal, the Bandel
Thermal Power Station (W.B.P.D.C.L.), under WBPDCL.
I would like to express my heartfelt gratitude to the authorities of Bandel
Thermal Power Station and for providing me such an opportunity to
undergo training in the thermal power plant of WBPDCL, BTPS. I would
also like to thank the Engineers, highly experienced without whom such
type of concept building in respect of thermal power plant would not have
been possible.
3
4. CONTENTS
Page No
1. Introduction..................................................................................................................................5
2.Technical Specification of Bandel thermal power plant........................................ 6
3.Overview of a Thermal power plant................................................................................. 7
4.Mechanical operation
a.Coal handling Plant................................................................................................................ 8
b.Water Treatment Plant.......................................................................................................... 9
c.Water De-mineralization Plant.........................................................................................9
d.Boiler System............................................................................................................................ 10
e.Ash handling plant................................................................................................................... 13
f.ESP.................................................................................................................................................... 13
g.Boiler auxilliaries......................................................................................................................15
h.Steam Turbine..............................................................................................................................17
i.Cooling tower................................................................................................................................19
j.Chimney...........................................................................................................................................19
5.Electrical operation
a.Generator..........................................................................................................................................20
b.transformers................................................................................................................................... 22
c.control room................................................................................................................................... 26
d.Excitation system........................................................................................................................ 27
e.Switchyard Section & its Components............................................................................27
f.Switchgear.......................................................................................................................................32
g.Switching Schemes.................................................................................................................... 33
h.Protection...................................................................................................................35
i.Motors for thermal power plant............................................................................................ 38
j.Battery bank................................................................................................................................... 38
6.Conclusion........................................................................................................................................ 39
7.Bibliography.................................................................................................................................... 40
4
5. INTRODUCTION
West Bengal power Development Corporation was established on 7th July 1948.It is the
most reputed company in the eastern zone of India. WBPDCL in established on the
Hooghly River. The BTPS under the WBPDCL is the second largest thermal plant in West
Bengal. It has the capacity of 450MW .With the introduction of another two units of 60
MW that is in construction it will be the largest in West Bengal. Bandel Thermal Power
Station also known as BTPS is located in the outskirts of Raniganj in HOOGHLY District. It
is one of the 5 Thermal Power Stations of West Bengal power Development Corporation in
the state of West Bengal. The total power plant campus area is surrounded by boundary
walls and is basically divided into two major parts, first the Power Plant area itself and the
second is the Colony area for the residence and other facilities for BTPSsemployees.
5
6. TECHNICAL SPECIFICATION OF BTPS :
INSTALLED CAPACITY: -
1) Total number of Units : - 1X 210 MW ,4*60 MW
2) Total Energy Generation: - 2340 MW
3) Source of Water: - Hooghly River
4) Sources of Coal: - B.C.C.L and E.C.L, also imported from Indonesia
In a Thermal Power generating unit, combustion of fossil fuel (coal, oil or natural
gas) in Boiler or fissile element (uranium,plutonium) in Nuclear Reactor generates
heat energy. This heat energy transforms water into steam at high pressure and
temperature. This steam is utilised to generate mechanical energy in a Turbine. This
mechanical energy, in turn is converted into electrical energy with thehelp of an
Alternator coupled with the Turbine. The production of electric energy utilising heat
energy is known as thermal power generation.
The heat energy changes into mechanical energy following the principle of Rankine
reheat-regenerative cycle and this mechanical energy transforms into electrical
energy based on Faraday’s laws of electromagnetic induction. The generated output
of Alternator is electrical power of three-phase alternating current (A.C.) . A.C.
supply has several advantages over direct current (D.C.) system and hence , it is
preferred in modern days. The voltage generated is of low magnitude (14 to 21 KV
for different generator rating) and is stepped up
suitably with the help of transformer for efficient and economical transmission
of electric power from generating stations to different load centres at distant
locations.
6
7. OVERVIEW OF A THERMAL POWER PLANT
A thermal power plant continuously converts the energy stored in the fossil
fuels(coal, oil, natural gas) into shaft work and ultimately into electricity. The
working fluid is water which is sometimes in liquid phase and sometimes in vapour
phase during its cycle of operation. Energy released by the burning of fuel is
transferred to water in the boiler to generate steam at high pressure and temperature,
which then expands in the turbine to a low pressure to produce shaft work. The
steam leaving the turbine is condensed into water in the condenser where cooling
water from a river or sea circulates carrying away the heat released during
condensation. The water is then fed back to the boiler by the pump and the cycle
continues. The figure below illustrates the basic components of a thermal power
plant where mechanical power of the turbine is utilised by the electric generator to
produce electricity and ultimately transmitted via the transmission lines.
1. Cooling tower. 2. Cooling water pump. 3. Transmission line (3-phase). 4. Unit transformer (3-
phase). 5. Electric generator (3-phase). 6. Low pressure turbine. 7. Condensate extraction pump.
8. Condenser. 9. Intermediate pressure turbine. 10. Steam governor valve. 11. High pressure
turbine. 12. De-aerator. 13. Feed heater. 14. Coal conveyor. 15. Coal hopper. 16. Pulverised fuel
mill. 17. Boiler drums. 18. Ash hopper. 19. Super heater. 20. Forced draught fan. 21. Re-heater.
22. Air intake. 23. Economiser. 24. Air pre heater. 25. Precipitator. 26. Induced draught fan. 27.
Chimney Stack.
7
8. MECHANICAL OPERATION
COAL HANDLING PLANT
Generally most of the thermal power plants uses low grades bituminous coal. The
conveyer belt system transports the coal from the coal storage area to the coal mill.
Now the FHP(Fuel Handling Plant) department is responsible for converting the coal
converting it into fine granular dust by grinding process. The coal from the coal
bunkers.Coal is the principal energy source because of its large deposits and
availability. Coal can be recovered from different mining techniques like
• shallow seams by removing the over burnt expose the coal seam
• underground mining.
The coal handling plant is used to store, transport and distribute coal which comes
from the mine. The coal is delivered either through a conveyor belt system or by rail
or road transport. The bulk storage of coal at the power station is important for the
continues supply of fuel. Usually the stockpiles are divided into three main categories.
• live storage
• emergency storage
• long term compacted stockpile.
The figure below shows the schematic representation of the coal handling plant.
Firstly the coal gets deposited into the track hopper from the wagon and then via the
paddle feeder it goes to the conveyer belt#1A. Secondly via the transfer port the
coal goes to another conveyer belt#2B and then to the crusher house. The coal after
being crushed goes to the stacker via the conveyer belt#3 for being stacked or
reclaimed and finally to the desired unit. ILMS is the inline magnetic separator
where all the magnetic particles associated with coal get separated.
COAL HANDLING PLANT PROCEDURE
8
9. WATER TREATMENT PLANT
Raw water supply:
Raw water received at the thermal power plant is passed through Water Treatment Plant to
separate suspended impurities and dissolved gases including organic substance and then
through De-mineralised Plant to separate soluble impurities.
Deaeration:
In this process, the raw water is
sprayed over cascade aerator in
which water flows downwards
over many steps in the form of
thin waterfalls. Cascading
increases surface area of water
to facilitate easy separation of
dissolved undesirable gases
(like hydrogen sulphide,
ammonia,
volatile organic compound etc.) or to help in oxygenation of mainly ferrous ions in presence
of atmospheri oxygen to ferric ions. These ferric ions promote to some extent in coagulation
process.
Coagulation:
Coagulation takes place in clariflocculator. Coagulant destabilises suspended solids
and agglomerates them into heavier floc, which is separated out through
sedimentation. Prime chemicals used for coagulation are alum, poly-aluminium chloride
(PAC).
Filtration:
Filters remove coarse suspended matter and remaining floc or sludge after
coagulation and also reduce the chlorine demand of the water. Filter beds are developed by
placing gravel or coarse anthracite and sand in layers. These filter beds are regenerated by
backwashing and air blowing through it.
Chlorination:
Neutral organic matter is very heterogeneous i.e. it contains many classes of high molecular
weight organic compounds. Humic substances constitute a major portion of the dissolved
organic carbon from surface waters. They are complex mixtures of organic
compounds with relatively unknown structures and chemical composition.
DM (Demineralised Water) Plant
In De-mineralised Plant, the filter water of Water Treatment Plant is passed
through the pressure sand filter (PSF) to reduce turbidity and then through
activated charcoal filter (ACF) to adsorb the residual chlorine and iron in filter water.
9
10. BOILER SYSTEM
BOILER:
Working principle of Boiler (Steam Generator):
In Boiler, steam is generated from de-
mineralized water by the addition of heat. The
heat added has two parts: sensible heat and
latent heat. The sensible heat raises the
temperature and pressure of water as well as
steam. The latent heat converts water into steam
(phase change). This conversion is also known
as boiling of water, which is dependent on
pressure and corresponding temperature.
Thermodynamically, boiling is a process of heat
addition to water at constant pressure &
temperature.
The quantity of latent heat decreases with
increase in pressure of water and it becomes
zero at 221.06 bars. This pressure is termed
as critical pressure. The steam generators are
designated as sub-critical or super critical
based on its working pressure as below critical
or above critical pressure. The steam, thus
formed is dry & saturated. Further, addition
of heat raises the temperature and pressure of
steam, which is known as superheated steam.
The differential specific weight between
steam and water provides the driving force
for natural circulation during the steam generation process. This driving force
considerably reduces at pressure around 175 Kg/cm2 and is not able to overcome the
frictional resistance of its flow path. For this, forced or assisted circulation is
employed at higher sub-critical pressure range due to the reason of economy. But, at
supercritical pressures and above, circulation is forced one (such boiler is called once
through boiler).
Important parts of Boiler & their functions:
Economizer:
Feed water enters into the boiler through economizer. Its function is to recover
residual heat of flue gas before leaving boiler to preheat feed water prior to its entry
into boiler drum. The drum water is passed through down-comers for circulation
through the water wall for absorbing heat from furnace. The economizer
10
11. recirculation line connects down-comer with the economizer inlet header through
an isolating valve and a non-return valve to protect economizer tubes from
overheating caused by steam entrapment and starvation. This is done to ensure
circulation of water through the tubes during initial lighting up of boiler, when there
is no feed water flow through economizer.
Drum:
Boiler drum is located outside the furnace region or flue gas path. This stores certain
amount of water and separates steam from steam-water mixture. The minimum drum
water level is always maintained so as to prevent formation of vortex and to protect
water wall tubes (especially its corner tubes) from steam entrapment / starvation due
to higher circulation ratio of boiler.
The secondary stage consists of two opposite bank of closely spaced thin
corrugated sheets which direct the steam through a tortuous path and force the
remaining entrained water against the corrugated plates. Since, the velocity is
relatively low, this water does not get picked up again but runs down the plates and
off the second stage lips at the two steam outlets.
From the secondary separators, steam flows uniformly and with relatively low
velocity upward to the series of screen dryers (scrubbers), extending in layers across
the length of the drum. These screens perform the final stage of separation.
Superheater:
Superheaters (SH) are meant for elevating the steam temperature above the saturation
temperature in phases; so that maximum work can be extracted from high energy
(enthalpy) steam and after expansion in Turbine, the dryness fraction does not reach
below 80%, for avoiding Turbine blade erosion/damage and attaining maximum
Turbine internal efficiency. Steam from Boiler Drum passes through primary
superheater placed in the convective zone of the furnace, then through platen
superheater placed in the radiant zone of furnace and thereafter, through final
superheater placed in the convective zone. The superheated steam at requisite
pressure and temperature is taken out of boiler to rotate turbo-generator.
Reheater:
In order to improve the cycle efficiency, HP turbine exhaust steam is taken back to
boiler to increase temperature by reheating process. The steam is passed through
Reheater, placed in between final superheater bank of tubes & platen SH and finally
taken out of boiler to extract work out of it in the IP and LP turbine.
De-superheater (Attemperator):
Though superheaters are designed to maintain requisite steam temperature, it is
necessary to use de-superheater to control steam temperature. Feed water, generally
taken before feed water control station, is used for de-superheating steam to control
its temperature at desired level.
Drain & Vent:
Major drains and vents of boiler are (i) Boiler bottom ring header drains, (ii)
11
12. Boiler drum drains & vents , (iii) Superheater & Reheater headers drains & vents,
(iv) Desuperheater header drains & vents etc. Drains facilitate draining or hot
blow down
of boiler, as and when required; while vents ensure blowing out of air from boiler
during initial lighting up as well as facilitate depressurizing of boiler. The continuous
blow down (CBD) valve facilitates reduction in contaminant concentration in drum
water and also complete draining of drum water. The intermittent blow down (IBD) /
emergency blow down (EBD) valve helps to normalize the excess drum water level
during emergency situation.
Technical data of the Boiler
Type Radiant, Reheat, Natural circulation, Single
Drum, Balanced drift, Dry bottom, Tilting
tangential, Coal and oil fired with DIPC (Direct
Ignition of Pulverized Coal) system.
Furnace
Width 13868 mm.
Depth 10592 mm.
Volume 5240 m3
Fuel heat input per hour 106 kcal
Designed pressure 175.8 kg/cm2
Superheater Outlet pressure 155 kg/cm2
Low temperature SH (horizontally spaced) 2849 m2
(total heating surface area)
Platen SH (Pendant platen) 1097 m2
(total heating surface area)
Final superheater (vertically spaced) 1543 m2
(total heating surface area)
Attemperator
Type Spray
No. of stages One
Spray medium Feed water from boiler feed pump (BFP)
Reheater
Type Vertical spaced
Total H.S. area 2819 m2
Control Burner tilt & excess air
Economiser
Type Plain tube
Total H.S. area 6152 m2
12
13. ASH HANDLING PLANT
A large quantity of ash is, produced in steam power plants using coal.
Ash produced in about 10 to 20% of the total coal burnt in the furnace. Handling of
ash is a problem because ash coming out of the furnace is too hot, it is dusty and
irritating to handle and is accompanied by some poisonous gases. It is desirable to
quench the ash before handling due to following reasons:
1. Quenching reduces the temperature of ash.
2. It reduces the corrosive action of ash.
3. Ash forms clinkers by fusing in large lumps and by quenching clinkers
will disintegrate.
4. Quenching reduces the dust accompanying the ash.
Flyash is collected with an electrostatic precipitator(ESP)
ELECTROSTAIC PRECIPITATOR
The principal components of an ESP are 2 sets of electrodes insulated from each
other. First set of rows are electrically grounded vertical plates called collecting
electrodes while the second set consists of wires called discharge electrodes.
The above figure shows the operation of an ESP. the negatively charged fly ash
particles are driven towards the collecting plate and the positive ions travel to the
negatively charged wire electrodes. Collected particulate matter is removed from
the collecting plates by a mechanical hammer scrapping system.
Technical data of the ESP (Electrostatic Precipitator)
Gas flow rate 339 m3
/s
Temperature 142°C
Dust concentration 62.95 gms/N-cubic meter
Collecting electrodes
No. of rows of collecting electrode per field 49
13
14. No. of collecting electrode plate 294
Total no. of collecting plates per boiler 3528
Nominal height of collecting plate 13.5 m.
Nominal length of collecting electrodes per field 4.5 m.
in the direction of gas field
Nominal width of collecting plate 750 mm.
Specific collecting area 206.4 m2
/cubic meter. sec-1
Emitting electrodes
Type Spiral with hooks
Size Diameter—2.7 mm.
No. of electrodes in the frame forming one row 54 fields
No. of electrodes in the field 2592
Total no. of electrodes per boiler 31104
Total length of electrodes per field 14541 m.
Plate/wire spacing 150 mm.
Electrical items
Rectifier Rating 70 kV (peak), 80 mA (mean)
Number 24
Type Silicon diode full wave bridge
connection
located Mounted on the top of the
precipitator
Rectifier control Type of control SCR (Silicon Controlled
panel Rectifier)
Number 24
Location In the control room at ground
level
Auxiliary control Number 2
panel Equipment controlled Geared motors of rapping
mechanism of collecting &
emitting electrodes.
Location In the control room at the ground
level.
Motors Quantity 24
Rating Geared motor 0.33 HP, 3 phase,
415 V, 50 Hz.
Location On root panels of the casing
14
15. BOILER AUXILIARIES
Induced draft fan (ID fan):
Induced draft represents the system where air or products of combustion are
driven out after combustion at boiler furnace by maintaining them at a progressively increasing sub
atmospheric pressure. This is achieved with the help of induced draft fan and stack. Induced draft
fan is forward curved centrifugal (radial) fan and sucks the fly-ash laden
gas of temperature around 125°C out of the furnace to throw it into stack (chimney). The fan
is connected with driving motor through hydro-coupling or with variable frequency drive
(VFD) motor to keep desired fan speed.
Technical data of the I.D.Fan (Induced Draught Fan) at Unit #1
No. of boiler 3
Type Radial, NDZV 31 Sidor
Medium handled Flue gas
Location Ground floor
Orientation Suction—Vertical/45 degree to Horizontal
Delivery—Bottom Horizontal.
Forced draft fan (FD fan):
Forced draft represents flow of air or products of combustion at a pressure above
atmosphere. The air for combustion is carried under forced draft conditions and the fan
used for this purpose is called Forced Draft (FD) fan. It is axial type fan and
is used to take air from atmosphere at ambient temperature to supply air for combustion,
which takes entry to boiler through wind box. In all units except Durgapur TPS Unit #4,
this fan also supplies hot /cold air to the coal mills. The output of fan is controlled by
inlet vane / blade pitch control system.
Technical data of the F.D.Fan (Forced Draught Fan) at Unit #1
No. of boiler 2
Type Radial, NDZV 28/Sidor
Medium handled Clean air
Location Ground floor
Orientation 45° horizontal, delivery-bottom horizontal.
Primary air fan (PA fan) or Exhauster fan:
The function of primary air is to transport pulverized coal from coal mill to the furnace,
to dry coal in coal mill and also to attain requisite pulverized coal temperature for
ready combustion at furnace. In some units like Chandrapura TPS
unit 1, 2 & 3, the exhauster fan sucks pulverized coal and air mixture from coal mill and
sends it to the furnace.
Technical data of the P.A.Fan (Primary Air Fan) at Unit #1
No. of boilers 3
Type Radial, NDZV 20 Herakles
Medium handled Hot air
Location Ground floor
Orientation Suction—Vertical/45 degrees to Horizontal Delivery—Bottom Horizontal.
15
16. Coal mill or pulveriser:
Most efficient way of utilizing coal for steam generation is to burn it in pulverised form.
The coal is pulverized in coal mill or pulveriser to fineness such that 70-80%
passes through a 200 mesh sieve. The factors that affect the operation of the mill
or reduce the mill output are:
Grindability of coal: Harder coal (i.e. coal having lower hard-grove index (H.G.I.))
reduces mill output and vice versa.
Moisture content of coal: More the moisture content in coal, lesser will be the mill
output & vice versa.
Fineness of output: Higher fineness of coal output reduces mill capacity.
Size of coal input: Larger size of raw coal fed to the mill reduces mill output.
Wear of grinding elements: More wear and tear of grinding elements reduces
the output from mill.
Fuel oil system:
In a coal fired boiler, oil firing is adopted for the purpose of warming up of the boiler or
assisting initial ignition of coal during introduction of coal mill or imparting stability to
the coal flame during low boiler load condition. Efficient or complete
combustion of the fuel oil is best achieved by atomizing oil by compressed air for
light oi l (LDO) or by steam for heavy oil (HFO) in order to have proper turbulent
mixing of oil with combustion air. Use of HFO is beneficial with respect to LDO in
view of its lower cost and saving in foreign exchange.
The oil burners and igniters are the basic elements of oil system. Oil is supplied by light
oil pump or by heavy oil pump through oil heater. Steam heater reduces the viscosity of
heavy oil and aids flow ability as well as better atomization. The oil burners are located
in the compartmented corner of wind boxes, in the different
elevation of auxiliary air compartments, sandwiched between the coal burner nozzles. Each oil
burner is associated with an igniter, arranged at the side.
16
17. STEAM TURBINE
A steam turbine is a prime mover which continuously converts the energy of
high pressure, high temperature steam supplied by the boiler into shaft work with
low pressure, low temperature steam exhausted to a condenser.
17
18. 500 MW(KWU) Steam turbine (Bandel )
Maker Bharat Heavy Electricals Limited
Type Reaction turbine
Type of governing Throttling
Number of cylinders 3
Speed (RPM) 3000
Rated output (kW) 210000(for unit1,2,3,4)
250000(for unit 5 & 6)
Steam pressure before emergency stop valve 150 kg/cm2
(abs)
Steam temperature before emergency stop valve 535°C (for unit1,2,3,4)
537°C (for unit 5 & 6)
Reheat temperature 535°C (for unit 1,2,3 &4)
537°C (for unit 5 & 6)
18
19. Cooling tower
Cooling towers cool the warm water discharged from the condenser and feed the cooled water
back to the condenser. They thus reduce the cooling water demand in the power plants. Wet
cooling towers could be mechanically draught or natural draught. In W.B.P.D.C.L. the cooling
towers are I.D. type for units 1-6 and natural draught for units 7&8.
Cooling towers
for units 7 and 8 natural draught
CHIMNEY
A chimney may be considered as a cylindrical hollow tower made of bricks or steel. In BTPS the
chimneys of eight units are made of bricks. Chimneys are used to release the exhaust
gases(coming from the furnace of the boiler)high up in the atmosphere. So, the height of the
chimneys are made high.
19
20. ELECTRICAL OPERATION
The electrical operation of a power plant comprises of generation, transmission and
distribution of electrical energy. In a power station both distribution and
transmission operation can take place. When power is sent from power station to all
other power station in the grid, it is known as distribution of power. When power
plant is driving power from other power station it is known as transmission of
power/electrical energy.
ELECTRIC GENERATOR
In W.B.P.D.C.L.. there are 6 electric generators for units 1 to 6. These are 3 phase
turbo generators, 2 pole cylindrical rotor type synchronous machines which are
directly coupled to the steam turbine. The generator consist of 2 parts mainly the
stator and the rotor.
Stator: The stator body is designed to withstand internal pressure of hydrogen-air
mixture without any residual deformation. The stator core is built up of segmental
punching of high permeability, low loss CRGOS steel and are in interleaved manner
on spring core bars to reduce heating and eddy current loss. The stator winding has
3 phase double layer short corded bar type lap winding having 2 parallel paths. The
winding bars are insulated with mica thermosetting insulation tape which consists of
flexible mica foil, fully saturated with a synthetic resin having excellent electrical
properties. Water cooled terminal bushings are housed in the lower part of the stator
on the slip ring side.
Rotor : Rotor is of cylindrical type shaft and body forged in one piece from chromium
nickel molybdenum and vanadium steel. Slots are machined on the outer surface to
incorporate windings. Winding consists of coil made from hand drawn silver copper
with bonded insulation. Generator casing is filled up with H2 gas with required pressure,
purity of gas is always maintained>97%. Propeller type fans are mounted on either side
of the rotor shaft for circulating the cooling gas inside the generators.
Turbogenerator
20
21. Technical Data of Turbogenerator
Main parameters
Rated kW capacity 210000 kW
Rated kVA capacity 247000 kVA
Rated terminal voltage 15750 V
Rated power factor 0.85 lag
Rated stator current 9050 amps
Rated speed 3000 RPM
Rated frequency 50 Hz
Efficiency at rated power output & power factor 98.55%
Power factor short circuit ratio 0.49
Temperature rating
Class of insulation of generator windings Class 'B'
Temperature of cooling water (maximum) 37°C
Temperature of cooling Hydrogen (maximum) 44°C
Temperature of cooling distilate (maximum) 45°C
Maximum temperature of stator core 105°C
Maximum temperature of stator winding 75°C
Maximum temperature of rotor winding 115°C
Other particulars
Critical speed of rotor (calculated) 1370/3400 RPM
Fly wheel moment of rotor 21.1 T-M
Ratio of short circuit torque to full load torque 8
Quantity of oil required for cooling per bearing 300 litre/min.
Oil pressure for lubrication of bearings 0.3-0.5 kg/cm2
Quantity of oil required for both the shaft seals 7.7 litres/min.
Rated pressure of the shaft seal oil (gauge) 5 kg/cm2
Quantity of water required for gas coolers 350 m3
/hr.
Maximum allowable water pressure in gas 3 kg/cm2
coolers
Quantity of distillate for cooling stator winding 27 m3
/hr.
Max. distillate pressure at inlet to stator winding 3.3 kg/cm2
Average qty of Hydrogen required for makeup 15 m3
per day
% Purity of Hydrogen inside the machine 97% min
Max allowable moisture content inside the body 1.5 g/m3
21
22. Weights of different parts
Heaviest weight (weight of stator) (kg.) 170000
Bearing with brush rocker & foundation plate 9300
(kg)
Rotor (kg.) 42000
Gas cooler (kg.) 1415
Terminal bushing (kg.) 85
Total weight of generator (kg.) 239000
TRANSFORMERS
The electricity thus produced by the
generator then goes to the generating
transformer where the voltage is
increased for transmission of electricity
with minimized copper losses.
In general a transformer consists of
primary and secondary windings which
are insulated from each other by varnish.
In W.B.P.D.C.L.. all are either oil cooled
or air cooled. Some of the transformer
accessories are: 1. Conservator tank 2.
Buccholz relay 3. Fans for cooling 4.
Lightning arrestors 5. Transformer
bushings 6. Breather and silica gel.
Generating transformer #1, 2,
3,4
MVA: 150/200/250 (H.V.) MVA: 150/200/250 (L.V.)
Volts at no load: 240000 (H.V.) Volts at no load: 15750 (L.V.)
Ampere line value: 361/482/602 (H.V.)
Ampere line value: 5505/7340/9175 (L.V.)
Phase-3 frequency: 50 Hz.
Mass of core and windings: 139000 kg.
Mass of oil: 38070 kg. Mass of heaviest package: 164000 kg.
Connection: YNd1 connection.
Generating transformer#5 and 6
MVA: 189/252/315 (H.V.) MVA: 189/252/315 (L.V.)
Volts at no load: 16.5kV (L.V.) Volts at no load: 240kV (H.V.)
Ampere line value: 757.57 (H.V.)
Ampere line value: 11022.14 (L.V.)
Phase-3 frequency: 50 Hz.
Mass of core and windings: 155000 kg.
Mass of oil: 53070 kg. Mass of heaviest package: 18000 kg.
Connection: YNd1 connection.
22
23. Specifications of Generator Transformer (GT) at Unit #7
Type of cooling ONAN/ONAF/OFAF
Rating HV (MVA) 120/160/200
Rating LV (MVA) 120/160/200
No load voltage HV (kV) 242.494
No load voltage LV (kV) 21
Line current HV (amps) 824.79
Line current LV (amps) 9523.8
Temperature rise oil (°C) 40 (Over ambient of 50°C)
Temperature rise winding (°C) 45 (Over ambient of 50°C)
Phase 3
Frequency (Hz) 50
Connection symbol YNd11
Impedance volt at 200 MVA Base
HV Position on 5/LV (nor tap) – 12% to 15%
HV Position on 1/LV (max tap) – 12% to 15%
HV Position on 9/LV (min tap) – 12% to 15%
Insulation level (HV) SL 1050 LI 1300 – AC 38
Insulation level (LV) LI 125 – AC 50
Core & Winding (kg) 153530
Weight of oil (kg) 48910
Total weight (kg) 257500
Oil quantity (litre) 56220
Transport weight (kg) 174900
Untanking weight (kg) 13790
Vector Diagram
AUXILIARY TRANSFORMRERS
Station Service Transformers
Normal source to the station auxiliaries and standby source to the unit auxiliaries during start up
and after tripping of the unit is station auxiliary transformer. Quantity of station service
transformers and their capacity depends upon the unit sizes and nos. Each station supply
transformer shall be one hundred percent standby of the other. Station service transformers shall
cater to the simultaneous load demand due to start up power requirements for the largest unit,
power requirement for the station auxiliaries required for running the station and power
23
24. requirement for the unit auxiliaries of a running unit in the event of outage of the unit source of
supply. The no. and approximate capacity of the SST depending upon the no. and MW rating
of the TG sets are indicated below.
Specifications of Station Service Transformer (SST) at Unit 7 and 8
Type of cooling ONAF/ONAN
Rating HV (MVA) 16/12.50
Rating LV (MVA) 16/12.50
No load voltage HV (kV) 11
No load voltage LV (kV) 3.45
Line current HV (amps) 839.78/656.08
Line current LV (amps) 2677.57/2091.85
Temperature rise oil (°C) 40
Temperature rise winding (°C) 45
Phase 3
Frequency (Hz) 50
Connection symbol Dyn1
Impedance volts % HV-LV 25%
Unit Auxiliary Transformer
The normal source of HV Power to unit auxiliaries is unit auxiliary transformer. The sizing of the
UAT is usually based on the total connected capacity of running unit auxiliaries i.e., excluding the
stand by drives. It is safe anddesirable to provide about 20% excess capacity than calculated. The
no. and recommended MVA rating of unit auxiliary transformers are as shown in the above table:
The UATs shall have Ddo(ungrounded system) or Dy1 (for grounded system) connection with on
load tap changer to provide +10 % variation in steps of 1.25 %. Usual cooling arrangement to unit
auxiliary transformers are ONAN. Radiators are usually divided in two equal halves.
Specification
Unit auxiliary transformer #1,2,3
MVA: 12.5/16 Manufacturer: Atlanta Electricals
Volts at no load: 15750 (H.V.) Volts at no load: 6900 (L.V.)
Ampere line value: 458.2/586.5 (H.V.)
Ampere line value: 1045.9/1338.8 (L.V.)
Phase-3 frequency: 50 Hz.
Mass of core and windings: 14300kg.
Mass of oil: 8600kg. Mass of heaviest package: 25000kg.
Total weight: 30,500 kg.
24
25. Unit auxiliary transformer #5 & 6
Type of cooling: ONAN/ONAF (oil natural/ oil natural air force)
Rating (H.V.): 20/16 MVA Rating (L.V.): 20/16 MVA
No load voltage: 13.5 kV (H.V.) No load voltage: 6.9 kV (L.V.)
Line current: 1673.479/1336.783 amp.
Temperature rise of winding: 55*C
Insulation level: 931 KVI 38kV r.m.s (H.V.) 60kVI 20kV r.m.s (L.V.)
Specifications of Unit Auxiliary Transformer (UAT) at Unit #7
Type of cooling ONAN/ONAF
Rating HV (MVA) 45/36
Rating LV (MVA) 45/36
No load voltage HV (kV) 21
No load voltage LV (kV) 11.5
Line current HV (amps) 1238.64
Line current LV (amps) 2261.87
Temperature rise oil (°C) 40 (Over ambient of 50°C)
Temperature rise winding (°C) 45 (Over ambient of 50°C)
Phase 3
Frequency (Hz) 50
Connection symbol Dyn1
Impedance volt at 45 MVA Base
HV Position on 7/LV (nor tap) – 11.5%
HV Position on 1/LV (max tap) – 10% to 13%
HV Position on 17/LV (min tap) – 10% to 13%
Insulation level (high voltage) L1 125 – AC 50
Insulation level (low voltage) L1 75 – AC 28
Core & winding (kg) 40065
Weight of Oil (kg) 25765
Total weight (kg) 85265
Transport weight (kg) 50000
Untanking weight (kg) 41000
25
26. CONTROL ROOM UNI T:
The above figure shows the power line diagram in the control room. It clearly shows how the electric
power generated by the generator is transmitted through the generating transformers into the
bus and the distribution of power by the unit auxiliary transformers.
EXCITATION SYSTEM
The purpose of excitation system is to continuously provide the appropriate amount of D.C. field
current to the generator field winding. The excitation system is required to function reliably under
the following conditions of the generator and the system to which it is connected.
Functional components of an excitation system :
A good excitation system consists of properly co-ordinated functional components
which are
a) Excitation Power source
b) Semiconductor Rectifier
c) Voltage controller
d) Protective, limiting and switching equipments
e) Monitoring, Metering and indicating equipments and
f) Cooling system
Types of Excitation System :
In earlier days DC excitation system was in use. Increase in generator capacity in turn
raised the demand of excitation power which was notachievable by the DC exciters.
This led to the accelerated development of AC excitation system in pace with
generator capacity. With the maturing of solid state semiconductor technology AC
26
27. excitation system found to be superior technically as well as economically.
Excitation system can be categorized and subdividedinto the following : a)
D.C. excitation system
i) Pilot Main Exciter excitation system
ii) Rotating Amplifier excitation system.
b) A.C. excitation system
i) Rotating High Frequency excitation system
ii) Static excitation system
iii) Brushless excitation system
SWITCHYARD SECTION
A switchyard is essentially a hub for electrical power sources. For instance, a switchyard
will exist at a generating station to coordinate the exchange of power between the generators and
the transmission lines in the area. A switchyard will also exist when high voltage lines need to be
converted to lower voltage for distribution to consumers. Here in BTPS there is a big switch yard
section for the units one to six, and also for seven & eight there also a switch yard. Some of the
operation of the components of the switch yard is sometimes done from the control rooms of
respective units. That is the switch yard under each unit is sometimes control from the control
rooms of each unit respectively
.
Circuit Diagram: 220kV switchyard of W.B.P.D.C.L.
A switchyard may be considered as a junction point where electrical power is comingin
from one or more sources and is going out through one or more circuits. Thisjunction point is in
the form of a high capacity conductor spread from one end to theother end of the yard. As the
switchyard handles large amount of power, it is necessarythat it remains secure and serviceable to
supply the outgoing transmission feederseven under conditions of major equipment or bus failure.
There are differentschemes available for bus bar and associated equipment connection to facilitate
switching operation. The important points which dictate the choice of bus switching
scheme are –
a. Operational flexibility, b. Ease of maintenance,
c. System security, d. Ease of sectionalizing,
e. Simplicity of protection scheme, f. Installation cost and land requirement.
g. Ease of extension in future.
27
29. The basic components of a switchyard are as follows:
1.Circuit breaker: A circuit breaker is an equipment that breaks a circuit either manually or
automatically under all conditions at no load, full load or short circuit. Oil circuit breakers, vacuum
circuit breakers and SF6 circuit breakers are a few types of circuit breakers.
2.Isolator: Isolators are switches which isolate the circuit at times and thus serve the purpose of
protection during off load operation.
3.Current Transformer: These transformers used serve the
purpose of protection and metering. Generallythe same transformer
can be used as a current or potential transformer depending on the
type of connection with the main circuit that is series or parallel
respectively.
In electrical system it is necessary to
a) Read current and power factor
b) Meter power consumption.
c) Detect abnormalities and feed impulse to protectivedevices.
4.Potential transformers :
In any electrical power system it is
Fig. C.T.necessary to -
a) Monitor voltage and power factor,
b) Meter power consumption,
c) Feed power to control and indication circuit and
d) Detect abnormalities (i.e. under/over voltage, direction of
power flow etc) and feed impulse to protective device/alarm circuit.
Standard relay and metering equipments does not permit them to be
connected directly to the high voltage system.Potential
transformers therefore play a key role by performing the following
functions.
a) Electrically isolating the instruments and relays from HV side.
b) By transferring voltage from higher values to proportional standardized lower values.
5.POWER TRANSFORMER:
The use of power transformer in
a switchyard is to change the
voltage level. At the sending and
usually step up transformers are
used to evacuate power at
transmission voltage level. On
the other hand at the receiving
end step down transformers are
installed to match the voltage to
sub transmission or distribution
level. In many switchyards
autotransformers are used widely
for interconnecting two
switchyards with different
voltage level (such as 132 and
220 KV)
33/11 KV Power Transformer in a switchyard
29
30. ( 1-Main tank 2-Radiator 3-Reservoir tank 4-Bushing 5-WTI & OTI Index 6-Breather 7-Buccholz relay)
6.Insulator :
The live equipments are mounted over the steel structures or suspended from gantries with
sufficient insulation in between them. In outdoor use electrical porcelain insulators are most
widely used. Following two types of insulators are used in switchyard.
a. Pedestal type b. Disc type
Pedestal type insulators are used on steel structures for rigid supporting of the pipe bus bars,
for holding the blade and the fixed contacts of theisolators.
The above figure shows a complete bay for 220kV switchyard.
Electric power is generated by the generator which is circulated to the main bus 1
or 2 and accordingly the respective isolator is closed. In case of any fault in the
circuit breaker the power from the generator goes via the transfer bus into the main
bus by means of the bus coupler. A bus tie represents the connection between the
two main buses. Two 80MVA transformers draw power from the main buses and
transfer the voltage to 33kV and the power goes to 33kV switchyard. A station
service transformer supplies power to the auxiliary load.
30
31. The above figure shows the power flow diagram of 33kV switchyard.
The electric power after voltage transformation to 33kV by 80MVA transformers goes to the main bus
of the 33kV switchyard from where power is fed to various industries and other nearbystations. There
are two earthing transformers in the yard. From the bus the power is fed to two 5MVA transformers
which step down the voltage level to 11kV and is thus distributed to the locality.
THE TYPE OF RELAYS USED IN BTPS FOR PROTECTION OF POWER
SYSTEM COMPONENTS
• Auxiliary relay for isolations
• Fail accept relay
• Directional over current relay
• Master trip relay
• Multi relay for generator function
• Supervision relay
• Instantaneous relay
• Bus bar trip relay
• Lock out relay
• Numerical LBB protection relay
• Transformer differential protection relay
• Circulating differential protection relay
• Contact multi-relay
• Auxiliary relay
• Trip circuit R-Phase relay
• EUS section relay
• DC fail accept relay
• Trip circuit R-phase super relay Y-phase B-phase
• LBB protection relay.
31
32. SOME PUMP & MOTOR IS USED IN BTPS
PUMP :-
• Service water pump -360Kw
• Primary air fan(PA fan) -800Kw
• Coal mill motor -2250Kw
• Condense extraction pump -500Kw
MOTOR :-
Boiler feed pump motor -3500Kw
ID fan motor -1500Kw
FD fan motor -1000Kw
CW pump motor -1200Kw
SWITCHGEAR
HV Switchgears:
Indoor metal clad draw out type
switchgears with associated protective
and control equipments are employed
(fig. 2). Air break, Air Blast circuit
breakers and Minimum Oil circuit
breakers could still be found in some
very old stations. Present trend is to use
SF6or vacuum circuit breakers. SF6 and
vacuum circuit breakers requires smaller
size panels and thereby
reasonable amount of space is saved. Fig. 2: General arrangement of 6.6 KV
switchgearpanels The main bus bars of the switchgears are most commonly made up of
high conductivity aluminium or aluminium alloy with rectangular cross section mounted in
side the switchgear cubicle supported by moulded epoxy, fibre glass or porcelain insulators.
For higher current rating copper bus bars are sometimes used in switchgears.
32
33. LV Switchgears:
LV switchgears feed power supply to motors above 110 KW and upto160
KW rating and to Motor Control Centers (M.C.C). LV system is also a grounded system
where the neutral of transformers are solidly connected to ground. The duty involves
momentary loading, total load throw off, direct on line starting of motors and under certain
emergency condition automatic transfer of loads from one source of supply to the other.
The switchgear consists of metal clad continuous line up of multi tier draw out type
cubicles of simple and robust construction.
Each feeder is provided with an individual
front access door. The main bus bars and
connections shall be of high grade
aluminium or aluminium alloy sized for
the specified current rating. The circuit
breakers used in the LV switchgear shall
be air break 3 pole with stored energy,
trip free shunt trip mechanism. These are draw out type with three distinct position namely,
Service, Test and Isolated. Each position shall have mechanical as well as electrical
indication. Provision shall be there for local and remote electrical operation of the breakers.
Mechanical trip push button shall be provided to trip manually in the event of failure of
electrical trip circuit. Safety interlocks shall be provided to prevent insertion and removal of
closed breaker from Service position to Test position and vice versa.
SWITCHING SCHEMES
One Main Bus and Transfer Bus scheme
This scheme is used in switchyards up to 132 KV. Under normal condition all feeders arefed
through their respective circuit breakers from the main bus bar. During shutdown or outage of
any feeder breaker, that feeder can be transferred to transfer bus and diverted through bus
coupler breaker. In that case the protection shall be transferred to the bus coupler circuit breaker
by changing the position of the trip transfer switch located at the switchyard control panel. This
diversion of the feeder from its own circuit breaker to bus coupler circuit breaker and the vice
versa is possible even in live condition without any interruption of supply to that feeder. In case
of any main bus fault the entire switchyard will collapse. To avoid such total collapse of the
switchyard a bus section circuit breaker is provided in the middle
33
34. position of the main bus.
Two Main Bus and One transfer Bus scheme
In this scheme there is an arrangement for a duplicate main bus (MB).
All the feeders in the yard may be connected to either MB # 1 or MB # 2 or may be divided
in two groups and distributed in two buses. In case of outage of any circuit breaker that
feeder can be diverted through bus coupler breaker. Bus tie breaker is used to tie up MB #1
& MB # 2.
34
35. One and Half Breaker Scheme
In one and half breaker scheme (Fig. 4) under normal condition all the circuit breakers will remain
closed. At the time of maintenance of feeder breaker, only that breaker would be kept open and
isolated. During maintenance of bus, all the breakers connected to that bus would remain open to
isolate the bus. At that time, the power supply may be maintained through other bus. All
equipments in the switchyard except the line side isolators can be maintained without taking shut
down of any feeder. This scheme has gained popularity in many 400 KV switchyards in our country.
GENERATOR PROTECTION
The purpose of generator protection is to provide protectionagainst abnormal operating
condition and during fault condition. In the first case the machine and the associated circuit
may be in order but the operating parameters (load, frequency, temperature) and beyond the
specified limits. Such abnormal running condition would result in gradual deterioration and
ultimately lead to failure of the generator.
Protection under abnormal running conditions
a) Over current protection: The over current protection is used in generator
protection against external faults as back up protection. Normally external short
circuits are cleared by protection of the faulty section and are not dangerous to the
generator. If this protection fails the short circuit current contributed by the
generator is normally higher than the rated currentof the generator and cause over
heating of the stator, hence generators are provided with back up over current
protection which is usually definite time lag over current relay.
35
36. b) Over load protection: Persistent over load in rotor and stator circuit cause
heating of winding and temperature rise of the machine. Permissible duration of
the stator and rotor overload depends upon the class of insulation, thermal time
constant, cooling of the machine and is usually recommended by the
manufacturer. Beyond these limits the running of the machine is not
recommended and overload protection thermal relays fed by current transformer
or thermal sensors are provided.
c) Over voltage protection: The over voltage at the generator terminals may b e caused
by sudden drop of load and AVR malfunctioning. High voltage surges in the system
(switching surges or lightning) may also cause over voltage at the generator terminals.
Modern high speed voltage regulators adjust the excitation current to take care against the
high voltage due to load rejection. Lightning arresters connected across the generator
transformer terminals take care of the sudden high voltages due to external surges. As such
no special protection against generator high voltage may be needed. Further protection
provided against high magnetic flux takes care of dangerous increase of voltage.
e) Unbalance loading protection: Unbalance loading is caused by single phase
short circuit outside the generator, opening of oneof the contacts of the generator
circuit breaker, snapping of conductors in the switchyard or excessive single phase
load. Unbalance load produces –ve phase sequence current which cause overheating
of the rotor surface and mechanical vibration. Normally 10% of unbalance is
permitted provided phase currents do not exceed the rated values. For –ve phase
sequence currents above 5-10% of rated value dangerous over heating of rotor is
caused and protection against this is an essential requirement.
g) Loss of prime mover protection: In the event of loss of prime mover the
generator operates as a motor and drives the prime mover itself. In some cases
this condition could be very harmful as in the case of steam turbine sets where steam
acts as coolant, maintaining the turbine blades at a constant temperature and the
failure of steam results in overheating due to friction and windage loss with
subsequent distortion of the turbine blade. This can be sensed by a power relay
with a directional characteristic and the machine can be taken out of bar under
this condition. Because of the same reason a continuousvery low level of output
from thermal sets are not permissible.
36
37. Protection under fault condition
a) Differential protection: The protection is used for detection of internal faults in
a specified zone defined by the CTs supplying the differential relay. For an unit
connected system separate differential relays are provided for generator, generator
transformer and unit auxiliary transformer in addition to the overall differential
protection. In order to restrict damage very high differential relay sensitivity is
demanded but sensitivity is limited by C.T errors, high inrush current during external
fault and transformer tap changer variations.
b) Back up impedance protection:This protection is basically designed as back up
protection for the part of the installation situated between the generator and the
associated generator and unit auxiliary transformers. A back up protection in the
form of minimum impedance measurement is used, in which the current windings
are connected to the CTs in the neutral connection of the generator and its voltage
windings through a P.T to the phase to phase terminal voltage. The pick up
impedance is set to such a value that it is only energized by short circuits in the
zone specified above and does not respond to faultsbeyond the transformers.
c) Stator earth fault protection: The earth fault protection is the protection of the
generator against damages caused by the failure of insulation to earth. Present
practice of grounding the generator neutral is so designed that the earth fault current
is limited within 5 and 10 Amp. Fault current beyond this limit may cause serious
damage to the core laminations. This leadsto very high eddy current loss with
resultant heating and melting of the core.
d) 95% stator earth fault protection: Inverse time voltage relay connected across
the secondary of the high impedance neutral grounding transformer relay is used for
protection of around 95% of the stator winding against earth fault.
e) 100% stator earth fault protection: Earth fault in the entire stator circuits are
detected by a selective earth fault protection covering 100% of the stator windings.
This 100% E/f relay monitors the whole stator winding by means of a coded signal
current continuously injected in the generator winding through a coupling. Under
normal running condition the signal current flows only in the stray capacitances of
the directly connected system circuit. .
37
38. f) Rotor earth fault protection: Normally a single rotor earth fault is not so dangerous as
the rotor circuit is unearthed and current at fault point is zero. So only alarm is
provided on occurrence of 1st
rotor earth fault. On occurrence of the 2nd rotor earth fault
between the points of fault the field winding gets short circuited. The current in field
circuit increases, resulting in heating of the field circuit and the exciter. But the
more dangerous is disturbed symmetry of magnetic circuit due to partial short
circuited coils leading to mechanical unbalance.
MOTORS FOR THERMAL POWER PLANT
All the motors in Thermal Power Stations shall be of the 3-ph. A.C. squirrel cage type
except for some auxiliaries, which are emergent in nature,for which DC motors shall
be used. For some small valves, single phase motors may be used. All A.C. motors
shall be suitable for direct on line starting.
Battery Bank
Normally D.C. power is supplied by the float charger and the batteries are kept in float
condition at 2.15 V per cell to avoid discharging. The charger consists of silicon diode
or thyristor rectifiers preferably working on 3 ph.
415 V supply in conjunction with an automatic
voltage regulator. When there is a failure in the
A.C. supply the batteries will
come into operation and in this process the
batteries run down within few hours. After
normalization of A.C. power the batteries are
charged quickly by using the boost charger at 2.75
V per cell. During this time the float chargeris
isolated and load is connected through the tap off
point. After normalization of battery voltage these
are again put back into the float charging mode.
The output from the battery as well as the charger is connected to the D.C. distribution
board. From D.C. distribution board power supply is distributed to different circuits. D.C.
system being at the core of the protection and control mechanism very often two 100%
capacity boards with individual chargers and battery sets are used from the consideration
of the reliability and maintenance facility. These two boards are interconnected by
suitable tie lines.
38
39. CONCLUSION
The practical experience that I have gathered during the overview training of
large thermal power plant having a large capacity of 450 MW in three weeks
will be very useful as a stepping stone in building bright professional career
in future life. It gave me large spectrum to utilize the theoretical knowledge
and to put it into practice. The trouble shooting activities in operation and
decision making in case of crisis made me more confident to work in the
industrial atmosphere.
Moreover, this overview training has also given a self realization & hands-on
experience in developing the personality, interpersonal relationship with the
professional executives, staffs and to develop the leadership ability in
industry dealing with workers of all categories.
I would like to thank everybody who has been a part of this project, without
whom this project would never be completed with such ease.
39
40. BIBLIOGRAPHY
➢ THERMAL POWER ENGINEERING by R.K.RAJPUT.
➢ THEORY & PERFORMANCE of ELECTRICAL MACHINE by J.B.GUPTA
➢ AC & DC MACHINE by B.L.THERAJA & A.K.THERAJA.
➢ A COURSE IN ELECRICAL POWER by J.B.GUPTA.
40