1. 1. INTRODUCTION
1.1GENERAL OVERVIEW
For the power generation with 2x110 MW, 3x210 MW, 2x195MW, K.S.T.P.S. authorities are
required to have full control over all the auxiliaries which are basically operated on L.T. System
i.e. 415 V 3-Ø power supply is made available to the system after providing the station
transformer of 3x50 MVA capacity with different service transformers of capacity 1.0 MVA, 1.5
MVA, 2.0 MVA, which are located near the load centre as the transformer having the voltage of
6.6 KV /415 V. The 6.6 KV power is distributed through 6.6 KV interconnected Bus System for
all the SEVEN units with a control through DC of 220 V.
The 415 V power supply is done through a L.T. SWGR (Switchgear) which are located
nearby the distribution transformer as well as the load centers. The 6.6 KV power supply which
are either MOCB (Minimum Oil Circuit Breaker) or Air Circuit Breakers.
The 6.6 KV power is supplied to various draining equipments is made through breakers
which are either MOCB or air circuit breaker which are either of voltage makers as well as SF 6
of NGEF make. The LT supply is also controlled through air break circuit breakers. The various
H.T. motors are switched on through Direct ON line (DOL) in order to increase the availability
of equipment at full efficiency without time gap.
Further, the 6.6 KV system which is normally in delta configuration and termed as an
unearthed system. Earthing is detected by a protection system with alarm facility to take
remedial measures immediately and at the same time to maintain the generation level in the same
condition, prior to occurring the earth fault the single phase earth fault is detected in due course
till the motor is not earthed to any phase. “PUBLIC ADDRESS SYSTEM” is available through
in area of each unit which helps in fast communication for prompt remedial measure.
Soot Blowers are there in the boiler area on the furnace side or Zone which helps in
blowing the soot / ash deposition regularly of the furnace wall / economizer tubes to keep heat
transfer at the required parameter.
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2. In April 1973, Central Electricity Authority prepared a Project Report for power station
comprising of the two units of each of capacity 110 MW for RSEB. Subsequently in September
1975 this was revised by the Consultant Thermal Design Organization, Central Electricity
Authority for invention of 2x110 MW units being manufactured by BHEL, Hyderabad in 1 st
Stage. The planning commission cleared the project report in Sept, 1976 for installation of two
units each of 110 MW in first estimated cost of Rs. 143 Crores.
*The total power generated in KSTPS is 1240 MW.
1.1.1 Designed Stages
 STAGE I - 2x110 MW
 STAGE II - 2X210 MW
 STAGE III - 1X210 MW
 STAGE IV - 1X195 MW
 STAGE V - 1X195 MW
1.1.2 Location
The Kota Thermal Power Station is ideally on the left bank of Chambal River at Up Stream of
Kota Barrage. The large expanse of water reached by the barrage provides an efficient direct
circulation of cooling system for the power station. The 220 KV GSS is within ½ Kms. from the
power station.
1.1.3 Land
Land measuring approx. 250 hectares was required for the project in 1976. Ash tank is
constructed very near to the plant for the ease of disposal of ash and slurry.
1.1.4 Coal
Coal India limited owns and operates all the major coal fields in India through its coal producing
subsidiary companies viz. Eastern Coal Fields Limited, Western Coal Fields Limited. Coal India
limited supplies coal from its coal mines of coal producing subsidiaries BCCL, SECL & ECL to
Kota Thermal Power Station through railway wagons. The average distances of SECL, ECL &
BCCL are 800, 950 and 1350 Kms. respectively.
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3. 1.1.5 Water
The source of water for power station is reservoir formed by Kota Barrage on the Chambal
River. In case of large capacity plants huge quantities of coal and water is required. The cost of
transporting coal and water is particularly high. Therefore, as far as possible, the plant must be
located near the pit rather than at load centre for load above 200 MW and 375 MW. The
transportation of electrical energy is more economical as compared to the transportation of coal.
1.1.6 Design Features
The satisfactory design consists of the following steps.
Estimation of cost.
Selection of site.
Capacity of Power Station.
Selection of Boiler & Turbine.
Selection of Condensing Unit.
Selection of Electrical Generator.
Selection of Cooling System.
Design of Control and instrumentation system.
The design of steam power station requires wide experience as the subsequent operation and
maintenance are greatly affected by its design. The most efficient design consists of properly
sized component designed to operate safely and conveniently along with its auxiliaries and
installation.
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4. 2.GENERAL LAYOUT AND BASIC IDEA
A control system of station basically works on Rankin Cycle. Steam is produced in Boiler is
exported in prime mover and is condensed in condenser to be fed into the boiler again.
FIG.1
The Kota Thermal Power Station is divided in four main circuits:
 Fuel and Ash Circuit.
 Air and Gas Circuit.
 Feed water and Steam Circuit.
 Cooling Water Circuit.
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5. 2.1 FUEL & ASH CIRCUIT
Fuel from the storage is fed to the boiler through fuel handling device. The fuel used in KSTPS
is coal, which on combustion in the boiler produces the ash. The quantity of ash produced is
approximately 35-40% of coal used. This ash is collected at the back of the boiler and removed
to ash storage tank through ash disposal equipment.
2.2 AIR AND GAS CIRCUIT
Air from the atmosphere is supplied to the combustion chamber of Boiler through the action of
forced draft fan and induced draft fan. The flue gases first pass around the boiler tubes and
superheated tubes in the furnace, next through dust collector (ESP) & then economizer. Finally,
they are exhausted to the atmosphere through fans.
2.3 FEED WATER AND STEAM CIRCUIT
The condensate leaving the condenser is first heated in LP heaters through extracted steam from
the lower pressure extraction of the turbine. Then it goes to de-aerator where extra air and non-
condensable gases are removed from the hot water to avoid pitting/oxidation. From de-aerator it
goes to BFP (boiler feed pump) which increases the pressure of the water, then passes through
the HP heater and enters into the boiler drum through economizer. This wet steam passes through
superheater. From superheater it goes into the HP turbine then to IP turbine and finally to the LP
turbine and then exhausted through the condenser into hot well.
2.4COOLING WATER CIRCUIT
A large quantity of cooling water is required to condense the steam in condenser and marinating
low pressure in it. The water is drawn from reservoir and after use it is drained back into the
river.
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6. 3.PROCESSING OVERVIEW
3.1COAL HANDLING PLANT
It can be called the heart of thermal power plant because it provides the fuel for combustion in
boiler. The coal is brought to the KSTPS through rails via 16 railway tracks. The main coal
sources for KSTPS are SECL (South Eastern Coalfields Limited), ECL (Eastern Coalfield
Limited) and BCCL (Bharat Coking Coal Limited). Everyday 6 to 7 trains of coal are unloaded
at KSTPS. Each train consists of 58 wagons and each wagon consists of 60 tonnes tonnes of
coal. The approximate consumption at KSTPS is about 20,000 per day. It costs approximate 2
crores of rupees per day including transportation expenses.
The coal is firstly unloaded from wagon by wagon tipplers, then crushed by crushers and
magnetic pulley and pulverized to be transformed to the boiler. The whole transportation of coal
is through conveyor belt operated by 3-Ø Induction motor.
The coal handling plant can broadly be divided into three sections:
1) Wagon Unloading System
2) Crushing System
3) Conveying System
3.1.1 WAGON UNLOADING SYSTEM
Wagon Tippler unloads the coal from wagon to hopper which is made of Iron, in the form of net
so that coal pieces of only equal to and less than 200 mm size pass through it. The bigger ones
are broken by the workers with the help of hammers. From the hopper coal pieces fall on the
vibrator. It is a mechanical system having two rollers each at its ends. The rollers roll with the
help of a rope moving on pulley operated by a slip ring induction motor.
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7. FIG 2.
The four rollers place themselves respectively behind the first and the last pair of wheels of
the wagon. When the motor operates the rollers roll in forward direction moving the wagon
towards the “Wagon Table”. On the Wagon table a limit is specified in which wagon has to be
kept otherwise the triple would not be achieved.
3.1.2 CRUSHING SYSTEM
It consists of crushers which are used to crush the coal to 20 mm size. There are mainly two
types of crushers working in KSTPS:-
Primary Crushers i.e. 1) Rail crushers or 2) Rotary breaker.
Secondary Crushers i.e. Ring granulators.
3.1.2.1 Primary Crushers:- These are provided in only CHP stage 3. These are:
1) Rail crushers, 2) Rotary breaker
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8. 3.1.2.2 Secondary Crusher:- In this, there are following ways to reduce material size:
1) Impact attrition, 2) Shearing, 3) Compression.
Most of the crushers employ a combination of three crushing methods.
3.1.3 CONVEYING SYSTEM
The stacker/re-claimer unit stacks the material on to the pipe and feeds on to the main line
conveyor. Simultaneously vibrating feeder on the intermediate conveyor feeds the boom
conveyor of the stacker/reclaimer. Feeder is erected to serve the purpose of storage.
Underground machines known as plow feeder collect the coal from conveyor and drop it to other
side from other conveyor, with the help of jaws and this coal is taken to huge erected structure
from where the coal falls to the ground.
Figure 3.2
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9. 3.2.ASH HANDLING PLANT
This plant can be divided into 3 sub plants as follows:-
1) Fuel and Ash Plant
2) Air and Gas Plant
3) Ash Disposal & Dust Collection Plant
3.2.1 FUEL AND ASH PLANT
Coal is used as combustion material in KSTPS. The Pulverization also increases the overall
efficiency and flexibility of boilers. However, for light up and withstand static load, oil burners
are also used. Ash produced as the result of combustion of coal is connected and removed by ash
handling plant which consists of specially designed bottom ash and fly ash in electro static
precipitator economizer.
3.2.2 AIR & GAS PLANT
Air from atmosphere is supplied to combustion chamber of boiler through the action of forced
draft fan. In KTPS there are 2 FD fans and 3 ID fans available for draft system per unit.
Additional amount of air used called secondary air is supplied by Forced Draft (FD) Fan. The air,
before being supplied to the boiler, passes through pre-heater where the flue gases formed due to
combustion of coal heat it. In economizer the heat of flue gases raises the temperature of feed
water. Finally the flue gases after passing through the Electro-Static Precipitator is exhausted
through chimney.
3.2.3 ASH DISPOSAL & DUST COLLECTION PLANT
KSTPS has dry bottom furnace. Bottom ash hopper receives the bottom ash from the furnace
from where it is stored and discharged through the clinker grinder. Two slurry pumps are
provided which are common to both units & used to make slurry and further transportation to ash
dyke thro independent fly ash system. The ash removed from fly ash hoppers is in dry state &
carried to the collecting equipment where it is mixed with water and resulting slurry sump is
discharged.
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10. ugh pipe line. Dry free fly ash is collected in 31 fly ash hoppers, handled by two independent fly
ash system. The ash removed from fly ash hoppers is in dry state & carried to the collecting
equipment where it is mixed with water and resulting slurry sump is discharged.
3.3 ELECTRO-STATIC PRECIPITATOR
3.3.1 SCOPE & PRINCIPLE OF OPERATION
As far as air pollution is concerned, various flue gases filter are available. The choice depends
on the size of suspended particle matter. These filters are E.S.P. Fabric filter, High efficiency
cyclone separators etc. For fly ash, the particle sizes vary from 0.75 microns to 100 micron. In an
ESP the dust lidded gas is passed through an intense electric field, which causes ionization of the
gases & they changed into ion. While travelling towards opposite charged electrode, ions get
deposited as particles and thus dust is electrically deposited an electrode.
Figure 3.3
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11. 3.3.2 E.S.P. FIELD WORKING
The field consists of emitting and collecting electrodes structure which are totally isolated from
each other and hanging with the top roof of field. The emitting electrodes are also isolated from
the roof through the support insulators which also feed the supply to these electrodes. The
collecting electrodes are of the shape of flat plates. Emitting electrodes are of the shape of
spring..
4.BOILER
A boiler (or steam generator), one of the major components of the thermal plant is a closed
vessel in which water, under pressure is converted into steam. It is always designed to absorb
maximum amount of heat released in process of combustion, which is transferred to the boiler by
all the three modes of heat transfer i.e. conduction, convection and radiation.
4.1CLASSIFICATION OF BOILERS
4.1.1FIRE TUBE BOILER
In this type the products of combustion pass through the tubes which are surrounded by water.
These are economical for low pressure only.
4.1.2WATER TUBE BOILER
In this type of boiler water flows inside the tubes and hot gases flow outside the tubes. These
tubes are interconnected to common water channels and to steam outlet.
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12. 4.2 FEATURES
High evaporation capacity due to availability of large heating surface.
Better heat transfer to the mass of water.
Better efficiency of plant owing to rapid and uniform circulation of water in tubes.
Better overall control.
Easy removal of scale from inside the tubes.
In KSTPS, Natural circulation, tangentially fired, over hanged type, Water tube boilers are used.
Oil burners are provided between coal burners for initial start up and flame stabilization. Firstly,
light oil (diesel oil) is sprayed for initialization then heavy oil (high speed diesel oil) is used for
stabilization of flame. Pulverized coal is directly fed from the coal mills to the burners at the
four corners of the furnace through coal pipes with the help of heated air coming from PA fan.
The pressure inside boiler is negative so as to minimize the pollution and losses & to prevent the
accidents outside the boiler.
This equipment systematically feed fuel to furnace as per load requirement. The UV
flame scanners installed in each of the four corners of the furnace, scan the flame conditions and
in case of unsafe working conditions, trip the boiler and consequently the turbine.
4.3FURNACE
Furnace is primary part of the boiler where the
chemical energy available in the fuel is converted
into thermal energy by combustion. Major factors
that assist for efficient combustion are the
temperature inside the furnace and turbulence,
which causes rapid mixing of fuel and air. In
modern boilers, water-cooled furnaces are used.
Figure 5
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13. 4.4PULVERISED FUEL SYSTEM
The boiler fuel firing system is tangentially firing system in which the fuel is introduced from
wind nozzle located in the four corners inside the boiler.
The crushed coal from the coal crusher is transferred
into the unit coalbunkers where the coal is stored for feeding
into pulverizing mill through rotary feeder. Then coal burners
are employed to fire the pulverized coal along with primary air
into furnace. These burners are placed in the corners of the
furnace and they send horizontal streams of air and fuel tangent
to an imaginary circle in the center of the furnace.
4.4.1 FUEL OIL SYSTEM Figure 6
The functional requirement of the fuel burning system is to supply a controllable and
uninterrupted flammable furnace input of fuel and air and to continuously ignite and burn the
fuel as rapidly as it is introduced into the furnace. This system provides efficient conversion of
chemical energy of fuel into heat energy. The fuel burning system should function such that fuel
and air input is ignited continuously and immediately upon its entry into furnace.
Ignition takes place when the flammable furnace input is heated above the ignition
temperature. Ignition energy is usually supplied in the form of heat, provided by oil guns and by
igniters.
4.5 BOILER DRUM
The drum is a pressure vessel. Its function is to separate water and steam from the mixture
(steam & water) generated in the furnace walls. It provides water storage for preventing the
saturation of tubes. It also houses the equipment needed for purification of steam. The drum
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14. internals reduce the dissolved solids content of the steam to below the acceptable limit. Drum is
made up of two halves of carbon steel plates having thickness of 133 mm.
Figure 7
Boiler drum is located at a height of 53m from ground. The drum form the part of boiler
circulating system i.e. movement of fluid from the drum to the combustion zone and back to
boiler drum. Feed water is supplied to the drum from the economizer through feed nozzles.
Water from the drum goes to water walls through six down comers.
Main parts of boiler drum are:-
Feed pipe
Riser tube
Down comer
Baffle plate
Chemical dosing pipe
Turbo separation
Screen dryer
Drum level gauge
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15. 4.6DRAFT SYSTEM
The combustion process in a furnace can take place only when it receives a steady flow of air
and has the combustion gases continuously removed. Theoretically balanced draft means keeping
furnace pressure equal to atmospheric pressure, but in practice the furnace is kept slightly below
atmospheric pressure.
4.6.1DRAUGHT FANS
A fan can be defined as volumetric machine which moves quantities of air or gas from one place
to another. In doing this, it overcomes resistance to flow by supplying the fluid with the energy
necessary for contained motion. The following fans are used in boiler house:
4.6.1.1 Primary air fan (P.A. fan) or Exhauster fan
Pulverized coal is directly fed from coal mills to the burners at the four corners of the furnace
through coal pipes with the help of heated air coming from PA fan. Secondly, this fan also dries
the coal.
4.6.1.2 Forced draught fan (F.D. fan)
The combustion process in the furnace can take place only when it receives a steady flow of air.
This air is supplied by FD fan. Thus FD fan takes air from atmosphere at ambient temperature &
so provides additional draught. Its speed is 1500 RPM
4.6.1.3 Induced draught fan (I.D. fan)
Figure 8
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16. The flue gases coming out of the boiler are passed to the ESP & then dust free gases are
discharged up by the chimney to the atmosphere through the ID fan. Its speed is 745 RPM.
4.6.2 IGNITER AIR FAN
It is used to provide necessary combustion air to igniter. Two fans are usually provided. One will
run and 2nd will remain as stand by. A control damper is provided on the discharge which
modules to maintain a constant differential pressure across igniter when any igniter is in service.
Typical speed is 1460 RPM.
4.6.3 SCANNER AIR FAN
Used to provide necessary cooling air to the flame scanners. Two air fans are usually provided.
One will run and other will remain as stand by. When F.D. fans trip, the scanner air fan will draw
air from atmosphere through emergency damper. Typical speed 3000 RPM.
4.7ECONOMIZER
. FIG.9
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17. The flue gases coming out of the boiler carry lot of heat. An economizer extracts a part of this
heat from the flue gases and uses it for heating the feed water before it enters into the steam
drum. The use of economizer results in saving fuel consumption and higher boiler efficiency but
needs extra investment. In an economizer, a large number of small diameter thin walled tubes are
placed between two headers. Feed water enters the tubes through the other. The flue gases flow
outside the tubes.
4.8. HEATERS
4.8.1 AIR PRE-HEATERS
Figure 10
Air pre-heaters are employed to recover the heat from the flue gases leaving the economizer and
are used to heat the incoming air for combustion. This raises the temperature of the furnace
gases, improves combustion rates and efficiency and lowers the stack (chimney) temperature,
thus improving the overall efficiency of the boiler. Cooling of flue gases by 20% raises the plant
efficiency by 1%.
4.8.2 SUPER-HEATER
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18. Superheated steam is that steam, which contains more heat than the saturated steam at the same
pressure. This additional heat provides more energy to the turbine and thus the electrical power
output is more.
A super-heater is a device which removes the last traces of moisture from the saturated
steam leaving the boiler tubes and also increases its temperature above the saturation
temperature.
4.8.3 RE-HEATER
Re-heaters are provided to raise the temperature of the steam from which part of energy has
already been extracted by HP turbine. This is done so that the steam remains dry as far as
possible through the last stage of the turbine. A re-heater can also be convection, radiation or
combination of both.
4.9. CIRCULATION SYSTEM
In natural circulation system, water delivered to steam generator from header, which are at a
temperature well below the saturation value corresponding to that pressure. After header, it is
delivered to economizer, which heats it to above the saturation temperature. From economizer
the water enters the drum and thus joins the circulation system through down covering water
wall tubes. In water wall tubes a part of the water is converted to steam due to boiler and the
mixture flows back to the drum. In the drum, the steam is separated out through the steam
separators and passed to the super heater. After the super heater when the steam temperature
becomes high and pressure up to 150 Kg/cm3 steam is allowed to enter the turbine to convert
potential energy to kinetic energy.
4.10. SOOT BLOWER
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19. The boiler tubes are cleaned with the help of steam by the process called soot blowing. We are
well known that a greater no. of tubes are presented inside the boiler. Slowly and slowly the fine
ash particles are collected on the tube surface and from a layer this is called soot. Soot is a
thermal insulating material.
There are mainly three types of soot blower are used in KSTPS: -
Water wall soot blower
Super heater soot blower
Air pre heater soot blower
4.11. FUEL SPECIFICATIONS
a) COAL
Type : Slack Coal
Quantity consumed : 20000 tonnes per day
Type of handling : Conveyor
Ash disposal : Wet system
b) OIL
Type : HSD and fuel oil
No. of chimney : 4
Height of Chimney : 180 Meters
Volume of flue Gas : 198 M3/ Sec Air emitted
Temp. of flue gases : 140oC
ESP : One for each unit
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20. 4.12. GENERAL DESCRIPTION
Boilers are tangentially fired; balance draft, natural circulation, radiant type and dry bottom with
direct fired pulverized coal from bowl/ball mills. They are designed for burning low grade coal
with high ash content. Oil burners are located between coal burners for flame stabilization.
Pulverized coal is directly fed from the coal mills to the burners at the four corners of the furnace
through coal pipes. The pulverized fuel pipes from the mills to the bunkers are provided with
basalt lined bends to reduce erosion and to improve the life of these pipes owing to poor grade of
coal, there is a high percentage of mill rejects. The mill rejects are conveyed in a sluice way to
an under-ground tank. From this tank the mixture is taken to an overhead hydro-bin where water
is decanted and the mill reject are disposed off by trucking.
The air required for combustion is supplied by two FD fans.
Three ID fans each of 60% capacity have been provided one ID fan to serve as standby.
Facilities have been provided to simultaneously unload and transfer 10 light oil and 40 heavy
oil tankers to the designated tanks. Oil preheating arrangement is provided on the tanks floors
for the heavy oil tanks.
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21. 5.STEAM TURBINE & GENERATION
5.1INTRODUCTION
Turbine is a machine in which a shaft is rotated steadily by impact or reaction of current or
stream of working substance (steam, air, water, gases etc.) upon blades of a wheel. It converts
the potential or kinetic energy of the working substance into mechanical power by virtue of
dynamic action of working substance. When the working substance is steam it is called the
steam turbine.
FIG.
5.2WORKING PRINCIPLE
Working of the steam turbine depends wholly upon the dynamic action of Steam. The steam is
caused to fall in pressure in a passage of nozzle, due to this fall in pressure a certain amount of
heat energy is converted into mechanical kinetic energy and the steam is set to move with a
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22. greater velocity. The rapidly moving particles of steam enter the moving part of the turbine and
here suffer a change in direction of motion. It gives rise to change of momentum and therefore
constitutes the driving force of the machine. The procedure of expansion and direction changing
may occur once or a number of times in succession.
The majority of the steam turbine have, therefore two important elements. These are-
1. The nozzle in which the system expands from high pressure end is comparatively in rapid
motion to that of lower pressure end.
2. The blades attached to the rotating elements, in which the steam particles changes its
directions and hence its momentum, are attached to the stationary part of the turbine i.e. stator,
casing or cylinder.
Although the fundamental principles of all steam turbine are same, yet the methods vary and
thus certain types of turbines have come into existence.
5.3DESCRIPTION
5.3.1 STEAM FLOW
210 MW steam turbine is a compound machine with HP, IP & LP parts. The HP part is single
flow cylinder and IP & LP parts are double flow cylinders. The individual turbine rotors and
generator rotor are rigidly coupled. The HP cylinder has a throttle control. Main steam is
admitted before blending by two combined main stop and control valves. The IP turbine exhausts
directly goes to LP turbine by cross ground pipes.
5. 3.2 HP TURBINE
The HP casing is a barrel type casing without axial joint. Because of its rotation symmetry the
barrel type casing remain constant in shape and leak proof during quick change in temperature.
The inner casing too is cylinder in shape. This is suitable for quick start up and loading. The HP
turbine consists of 25 reaction stages. The moving and stationary blades are inserted into
appropriately shaped inner casing and the shaft to reduce leakage losses at blade tips.
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23. 5.3.3 IP TURBINE
The IP turbine is of double flow construction (double shell construction). The double flow inner
casing is supported kinematically in the outer casing. The steam from HP turbine after reheating
enters the inner casing from above and below through two inlet nozzles. The arrangements of
inner casing confines high steam inlet condition, while the joints of outer casing is subjected only
to lower pressure and temperature at the exhaust of inner casing. The pressure in outer casing
relieves the joint of inner casing so that this joint is to be sealed only against resulting differential
pressure. The IP turbine consists of 20 reaction stages per flow. The moving and stationary
blades are inserted in appropriately shaped grooves in shaft and inner casing.
5.3.4 LP TURBINE
The casing of double flow type LP turbine is of three shell design. The shells have rigidly welded
construction. The outer casing is supported by the ends of longitudinal beams on the base plates
of foundation. The double flow inner casing consists of outer shell and inner shell. The inner
shell is attached to outer shell with provision of free thermal movement. Steam admitted to LP
turbine from IP turbine flows into the inner casing from both sides through steam inlet nozzles.
5.4.ELECTRICITY GENERATION
Thermal power station burns the fuel and use the resultant heat to raise the steam temperature
which drives the turbo-generator. The fuel may be “Fossil” (Coal, Oil and Natural Gas) but the
object is same to convert the heat into mechanical energy and further to electrical energy by
rotating a magnet inside the set of winding. In a coal fired thermal power station other raw
materials are air and water.
Meanwhile the heat reloaded from the coal has been absorbed by a long tube which lies
in boiler walls. Inside the tubes “Boiler Feed Water” is transferred into turbine blades and makes
them rotate. To the end of the turbine rotor of generator is coupled, so that when turbine rotates
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24. the rotor turns with it. The rotor is housed inside the stator having coil of copper bars in which
electricity is produced through the movement of magnetic field created by rotor. The electricity
passes from the stator winding to the transformer which steps up the voltage so that it can be
transmitted effectively over the power line of grid.
The steam which has given up its heat energy in changed back into a condensate so that it
is ready for reuse. The cold water is continuously pumped in condenser. The steam passing
around the tubes loose heat and rapidly change into water. The cooling water is drawn from the
river but the Boiler Feed Water must be pure than potable water (DM Water).
*The rated speed of turbine is 3000rpm.
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25. 6.WATER TREATMENT PLANT
The principle problem in high pressure boiler is to control corrosion and steam quality. Internal
corrosion costs crores of rupees in repair. Without strict control, impurities in steam also form
deposit over turbine blades and nozzles. The impurities present in water are as follows:-
 Un-dissolved and suspended solid materials.
 Dissolved slats and minerals.
 Dissolved gases.
 Other minerals (oil, acid etc.).
 Turbidity & Sediment.
 Silica.
 Micro Biological.
 Sodium & Potassium Salt.
 Dissolved Sales Minerals.
 O2gas.
 CO2 gas.
Thus to make water pure for feeding in B.F.P. and to have protection against corrosion and other
above mentioned problems de-mineralisation is needed. The procedure is explained as-
6.1 D.M. PLANT
In this plant process, impure water is fed. This plant consists of two streams, each stream passes
through activated carbon filter, weak acid, cation exchanger and mixed bed exchanger. The
impure water is fed to DM plant through 250 dia. header from it is taken to softening plant. Two
filtered water booster pumps are provided on filtered water line for meeting the pressure
requirement in DM Plant.
Sodium Sulphate solution of required strength is dosed into different filtered water streams
by means of dosing pump to neutralize chlorine prior to activated carbon filter. Water passes
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26. through an activated carbon filter to remove residual chlorine from water. Water then goes to
weak base anion exchanger unit & enters de-gasified unit where free CO2 is scrubbed out of
water by upward counter flow of low pressure air flow. This de-gasified water is pumped to
strong base exchanger (anion exchanger).
6.2C.W. PLANT
Circulating water pump house has pumps for condensing the steam for condenser. After
condensing the water is discharged back into the river. Each of the 5 pumps for 1st and 2nd unit
has capacity of 8275 M3/Hr, and develop pressure about 1.94 kg. /Cm2. 3 seal water pumps are
used for sealing circulating water pump shaft at pr. 4.5 kg. /cm2. One pump is taken standby at a
time.
From main line water passes through filter bed to filter the water. Chlorified water is
pumped to 42 m elevation where water is stored in tank and used for cooling the oil coolers and
returns back to river.
6.3B.C.W. PUMP HOUSE
Filtered water after demineralization is used for Bearing Cooling from BCW pump house. Water
enters at 30-32oC and leave exchanger at 38oC. The raw water used in ash handling plant and
remaining quantity is stored in BCW Pump House. From here the water is pumped to CW
pumps. BCW here stand for water used for cooling oil used for cooling the bearing. In CW
pump house water is discharged from nozzle and impinged for travelling water screens for
cleaning it.
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27. 7.SWITCH YARD
7.1 220 KV SYSTEM
Two 220 KV bus bars have been provided in switch yard and are inter-connected through a bus
coupler. Each of the generators is connected to this system through a step up of 125 MVA 240 /
11 KV yard generator transformers. There are two step down transformer each feeding 6.6 KV.
Each station transformer has two windings one secondary side and one primary side. Four
feeders take off from 220 switch yard, 2 to SKATPURA GSS and other 2 to HEERAPURA,
Jaipur GSS. Each of the four feeders is provided with bypass isolators which are connected
across line breaker and breaker isolator. A brief description of equipments of 220 KV system is
as follows-
7.1.1 CIRCUIT BREAKERS
Each of generator transformer, station transformer, line feeder and bus coupler is provided with
minimum oil circuit breaker of BHEL make. It is used to break the circuit either in load
condition or in no load condition.
7.1.2 ISOLATORS
All the isolators are provided in 220KV switchyard and are motor operated. Triple pole double
breaker type and power switch yard L&T make these and are rates for 245 KV and 1250 A. The
four isolators are provided with earth switch.
7.1.3 CIRCUIT TRANSFORMER
All the 220 KV current transformers are provided for measuring and protection. They are BHEL
make, single phase, oil filled nitrogen sealed outdoor type.
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28. 7.1.4 POTENTIAL TRANSFORMER
Each of 220 KV buses is provided with three P.T.’S for each phase of BHEL make. There are
single phase, oil filled outdoor. N2 sealed magnetic type. Potential Transformer has two
secondary windings on secondary side.
7.1.5 LIGHTENING ARRESTOR
For protection against lightening, each of line feeders, generator transformer and station
transformer has been provided with three L.A. (one for each phase). All the L.A. are 2 Ø
outdoor types and are rated for 198 KV. The L.A. of generator transformer and station
transformer are located nearby. If we have to do some work on line, firstly line through earthing
isolator is earthed for discharging the line capacitance and then work is proceeded.
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29. 8.PROTECTION AND MISCELLANEOUS
8.1GENERAL PROTECTION
Generator is the most important electrical equipment of many generating station. Tripping of
even a generating unit may cause overloading of associated machines and even to system un-
stability. The basic function of protection applied to generator is to reduce voltage to minimum
by rapid discrimination clearance of faults. Unlike other apparatus the opening of C.B. to isolate
faulty generator is not sufficient to prevent future damage.
8.1.1SPECIFIC PROTECTION
Following are the protection purposes for the plant-
1. Field Protection.
2. Pole Slipping.
3. Plane Overload Protection.
4. Inter-turn Fault.
5. Negative Phase Sequence Protection.
6. Reverse Power Protection.
7. Forward Power Protection.
8. Under Frequency & Over Frequency Protection.
9. Generator Voltage Protection.
10. Rotor Earth Fault Protection.
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