Everybody must behaving a thought that a thermal power plant is a place where electricity is
produced. But do you know how it is produced? The chemical energy stored is converted to
heat energy which forms the in put of power plant and electrical energy produced by the
generator is the output .Power is the single most important necessity for the common people
and industrial development of anation. In a convectional power plant the energy is first
converted to a mechanical work and then is converted to electrical energy. Thus the energy
conversions involved are:
The first energy conversion takes in what is called a Boiler or Steam Generator, these cond
in what is called a Turbine and the last conversion takes place in the Generator.
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.
Commercial electric utility power stations are usually constructed on a large scale and
designed for continuous operation. Electric power plants typically use three-phase electrical
generators toproduceal ternating current(ac)electric power at a frequency of50Hz.
1.1 INTRODUCTION OF KaTTP
The site of Kalisindh Thermal Power Project is located in Nimoda ,Undal Motipura,
Singhania and Devri villages of Tehsil Jhalarapatan, Distt. Jhalawar. The proposed
capacity of coal based Thermal Power Project is 1200MW. The project site is about
12km from Jhalawar(Distt.Headquarter)andNH-12.It Is 2km from state highway No.19 and
8 km from proposed RamganjMandi – Bhopal broad gauge railline.
The site selection committee of Central Electricity Authority has visited the Nimodha and
its adjoining villages of Jhalawar Distt. And site was found techno-economical feasible for
setting up of a Power Project.The Govt.of Raj. Have included that project in11th five year
plan.The estimate drevised cost of the project isRs.7723 Crores.M/s.TCE Banglore has
been appointed as the technical consultant for the project.The state irrigation department
has allotted 1200m cft water for the project from proposed Kalisindh dam.The origin of the
Kalisindh river is from northern slop of Vindya Mountains.The river enters from MP to
Rajasthan near village Binda. After flowing 145km in Rajasthan,the Kalisindh river merges
in Chambal river near Nanera village of Distt. Kota. Its catch mentarea is about 7944sq.km
in Jhalawar & Kota Distt. The existing Dam is located at Bhawarasa village, primarily for
P.H.E.D. purpose is being up lifted for providing astorase of 1200mcft water for this power
Fig 1.1 KATPP PLANT PROJECT VIEW AND PRESENT VIEW
The GOR has allotted 842 bigha Government land and acquired 1388 bigha private khatedari
land for the thermal project. Phase-1will be constructed on 1400 bigha land only. Ministry of
coal,Govt.of India has allotted ‘Paras east and Kantabasin‘coal block stock RVUN in
Chhatisgarh state.The RVUN has formed new company under joined venture with
M/s.Adani Enterprises formining of coal block sand new company started the work.
Annual coal requirement for the project is 56 Lacs TPA. GOR also decided to setup two
new units of 2x660 MW in next few years.
1.1.1 ENERGY GENERATED IN KaTPP
= 1200 MW
Total generated Electricity (in one hour)
= 1200 MW x 1
=12.00 Lakh units
Total generated Electricity (in
= 12.00 x 24= 288.0 Lakhs units
Amount of Coal required (per day) in
= 0.5 x 288.0 x 100000 Kg
1.1.2 PLANT OVERVIEW
TABLE 1.1 Details of katpp
Project Kalisindh Super Thermal Power Project Jhalawar
Capacity 1200 MW(2x600 MW)
Village-Undel, Motipura, Nimoda, Singhania & Deveri of
Tehsil Jhalarapatan, Distt. Jhalawar
The project site is about 12 km from NH-12, 2km from state
Project Location highway and 8 km from proposed Ramganj Mandi – Bhopal
broad gauge rail line.
Land Area 2230 Bigha/564 Hq. (1400 bigha/350 Hq. in I stage)
Water source and
Dam on Kalisindh river. 3400 CuM/ Hrs.
Main Fuel- Coal from captive coal blocks (Paras east and
kanta Basin in Chhatisgarh state) Secondary Fuel- FO/HSD.
Quantity of Fuel (at
Coal-56 Lacs TPA FO/HSD-13000-14000 KL/A
99.98 % Capacity
Stack Height 275 Mtr.
1.2 PRINCIPLE OF OPERATION
For each process in a vapour power cycle, it is possible to assume a hypothetical or ideal
process which represents the basis intended operation and do not produce any extraneous
effect like heat loss.
1. For steam boiler, this would be a reversible constant pressure heating process of water
to form steam.
2. For turbine, the ideal process would be a reversible adiabatic expansion of steam.
3. For condenser, it would be a reversible a constant pressure heat rejection as the steam
condenser till it becomes saturated liquid.
4. For pump, the ideal process would be the reversible adiabatic compression of liquid
ending at the initial pressure. When all the above four cycles are combined, the cycle
achieved is called RANKINE CYCLE. Hence the working of a thermal power plant is
based upon Rankine cycle with some modification.
FIG 1.2 SIMPLE LAYOUT OF THERMAL POWER PLANT
1.3 THERMAL PLANT OPERATION PROCEDURE
The basic understanding of the modern thermal power station in terms of major systems
involved can be done under three basic heads viz. generating steam from coal, conversion
of thermal energy to mechanical power and generation & load dispatch of electricpower.
1.3.1 COAL TO STEAM
The coal is burnt at the rate up to 200 tones per hour. From coal stores, the fuel is carried on
conveyor belts to bunkers through coal tipper. It then falls in to coal pulverizing mill, where it is
grounded into powder as fine as flour. Air is drawn in to the boiler house by drought fan and
passed through Preheaters. Some air is passed directly to bunker and rest, through primary air fan,
to pulverizingmill where it is mixed with powdered coal. The mixture is then carried to
bunker of furnace where it mixes with rest of the air and burns to great heat.This heats
circulating water and produces steam, which passes to steam drum at very high pressure.
The steam is then heated further in the Superheater and fed to high pressure
cylinder of steam turbine.The steam is then passed to other cylinders of turbine through
reheater. The spent steam is sent to condenser, where it turns back to water called
condensate. Condensate is sent to lower part of steam drum through feed heater and
economizer. The flue gases leaving boiler are used for heating purpose in feed heater,
economizer and air Preheat The flue gases are then passed to electro-static precipitator
and then, through draught fan, to chimney.
1.3.2 STEAM TO MECHANICAL POWER:
Steam first enters the high pressure cylinder of turbine where it passes over a ring of
stationary/fixed blades which acts as nozzle and directs steam onto a ring of moving
Steam passes to the other cylinders through reheater and the process is repeated again and
again.This rotates the turbine shaft up to 3000 rpm. At each stage, steam expands,
pressure decreases and velocity increases.
1.3.3 MECHANICAL TO ELECTRICAL POWER:
The shaft is connected to an alternator’s armature. Thus the armature is rotated and
electric current is produced in the stator’s windings. The generated electricity is of order
1.3.4 SWITCHING AND TRANSMISSION:
Electricity generated cannot be transmitted as such. It is fed to one side of generator’s
transformer and stepped up to 132000, 220000, or 400000 volts. It is then passed to a
series of three switches an isolator, a circuit-breaker, and another isolator. From circuit-
breaker, current is taken to bus bars and then to another circuit-breaker with it’s
associated isolator before being fed to the main Grid. Each generator has its own
switching and transmission arrangement. Three-phase system is used for power
1.3.5 CONTROL AND INSTRUMENTATION:
Control and Instrumentation (C & I) systems are provided to enable the power station to
be operated in a safe and efficient manner while responding to the demands of the
National grid system. These demands have to be met without violating the safety or
operational constraints of the plants. For example, metallurgical limitations are important
as they set limits on the maximum permissible boiler metal temperature and the chemical
constituents of the Feed water. The control and Instrumentation system provides the
means of the manual and automatic control of plant operating conditions to Maintain an
adequate margin from the safety and operational constraints. Monitor these margins and
the plant conditions, and provide immediate indications and permanent records.Draw the
attention of the operator by an alarm system to any unacceptable reduction in the margin
Shut down the plant if the operating constraints are violated.
COAL HANDLING PLANT
Every thermal power plant is based on steam produced on the expanse of heat energy
produced on combustion of fuel. Fuels used are coal and fuel oil. Coal is more important
as oil is occasionally used. Coal is categorized as follows depending upon fixed carbon,
volatile matter and moisture content:
Anthracite having 86% fixed carbon
Bituminous having 46 to 86% fixed carbon
Lignite having 30% fixed carbon and
Peat having 5 to 10% fixed carbon
Coal from mines is transported to CHP in railway wagons. It is unloaded in track hoppers.
Each project requires transportation of large quantity of coal mines to the power station
site. Each project is established near coal mine which meets the coal requirements for the
span of its entire operational life. For the purpose each plant has Merry Go-Round (MGR)
rail transportation system. The loading operation of the coal rake takes place while it is
moving under the silo at a present speed of 0.8 Km/hr. the loading time for each wagon is
one minute. For unloading of coal from the wagons an underground track hopper is
provided at the power station end.
The term coal handling plant means to store and to handle the coal which is transported
by the train and convey to the bunkers with the help of belt conveyers. Through the
bunkers coal is transferred to the coal mill and drifted to the furnace. The coal handling
plant includes wagon tippler, conveyer belt, crusher house, stacker & reclaimer, bunkers
& coal mill.
2.1.1Coal Supply in KaTPP:-
Ministry of coal, Govt. of India has alloted ‘Paras east and Kanta basin coal blocks to
RVUNin Chhatisgarh state. The RVUN has formed new company under joined venture
with M/s. Adani Enterprises for mining of coal blocks and new company started the
work. Annual coal requirement for the project is 56 Lacs
These are basically coal pulverizing mills. Thermal power stations use pulverized coal
firing system. In this the coal is reduced to fineness such that 70 to 80% passes through a
200 mesh sieve. This fine powdered coal is called pulverized coal and is carried forward
to the burner by air through pipes.
Advantage of pulverized coal firing system:–
1. Efficient utilization of low grade and cheap coal.
2. Flexibility in firing.
3. Ability to meet fluctuating load.
4. Better reaction to automatic control.
5. High efficiency of boiler.
6. Easy complete combustion.
The only disadvantage being its high initial cost.
2.2 STAGES OF COAL HANDLING PLANT:-
2.2.1 WAGON TIPPLER:-
The term Wagon Tippler contains two words WAGON&TIPPLER .Wagon means the
compartment of train which is just like a container which is used to carry the coal from
mines to generating stations & the word Tippler means a machine, which is used to
unload the wagon into the hopper. Hopper is just like a vessel which is made of concrete
& it is covered with a thick iron net on its top. Here big size coal pieces are hammered by
the labors to dispose it into the hopper. Coal is fed into mill through Gravimetric feeder.
When the A.C. supply is switched on the bowl rotate and due to centrifugal force, the coal
moves in the outward direction. As the coal come between grinder and bowl, it gets
pulverized. The unwanted material is removed through scrapers. The pulverized coal is
then carried to burners by primary air through outlet openings. The heavier particles, as
they rise, collide with classifiers and fall back in mill for further grind. Sealing air is
provided through seal air fan to avoid deposition of coal dust in bearings and spring
2.2.2 CONVEY OF COAL TO CRUSHER HOUSE:-
After unloaded the coal wagon into the concrete hopper, the supply of coal is control by
Apron Feeder and Scrapper. Apron feeder is made of iron .After passing through the
scrapper conveyor the coal is fed into the Roll Crusher where the crushing of coal takes
place. In the roll crusher there are two shafts on which metal hammer are mounted, these
two rollers rotates in opposite direction to each other. When the coal comes in between
these two rollers it gets crushed into small pieces and then convey to the separator
through belt conveyor. In Pent house there is a belt weightier which is used to weight the
belt which carry the coal and feed into the separator with the help of Flap Gate.
2.2.3 PRIMARY CRUSHER HOUSE:-
Coal crusher house is a part of coal handling plant where the coal is crushed with the help
of a crusher machines .In crusher machine there is pair of two shafts on which hammer
are fixed. Both shafts rotates in opposite direction due to which when coal comes between
the two shafts crushed into the small pieces and conveyed to the bunkers or open storage
(stacker) according to the requirement through the belt conveyor.
2.2.4 STACKER & RECLAIMER:-
Stacker is a place where the open storage of a coal takes place. Reclaimer means the
unloading of coal from the stacker.
2.2.5 COAL MILL:-
In coal mill, coal is pulverized or crushed properly into the powdered form. Hot air is
mixed with powdered coal to remove the moisture from the coal, which increases the
efficiency of plant. Pulverization is done to increase the surface area of coal. From coal
mill coal is drift to the furnace with the help of air. There are four main equipment of
coal mill, which are as follows:-
Bunkers:-These are basically used to store crushed coil which comes from crusher
Feeders:-These are used to control the supply of crushed coal to the mill depending
upon load condition.
Feeder pipe:- Feeder pipe are used to convey the crushed coal to the Tube mill or Bowl
Tube mill:-Tube mill is used to pulverize the crushed coal. In the tube
Boiler can simply defined as the device where any liquid is boiled or Boiler may be
defined as a device that is used to transfer heat energy being produced by burning of fuel
to liquid, generally water, contended in it to cause its vaporization. Boiler, in simple
terms, can be called “Steam Generator”. The following are factors essential for the
efficient combustion usually referred as “The three T’s”.
A) TIME – It will take a definite time to heat the fuel to its ignition temperature and
having ignited, it will also take time to burn.
B) TEMPERATURE – A fuel will not burn until it reaches its ignition temperature.
C) TURBULENCE – Turbulence is introduced to achieve a rapid relative motion
between the air and fuel particles.
A boiler is an enclosed that provides a means for combustion heat to be transfer into water
until it becomes heated water or steam. Its volume increases 1600 times. The process of
heating a liquid until reaches its gaseous states its called evaporation. The boiler system
a. feed water system
b. steam system
c. Fuel system
3.1.1 Feed Water system:-
It provides water to the boiler and regulate feed according to demand.
3.1.2 Steam system:-
It collects and controls the steam produced in the boiler steam are directed through a
piping system to a point of use. Steam pressure is regulated using valves and checked
with pressure gauges.
3.1.3 Fuel system:-
Fuel system includes all equipments used to provide fuel to generate the necessary heat
for higher boiler efficiency feed water is preheated by economizer using the waste heat in
the flue gases.
3.2 BOILER AUXILIARIES
Efficiency of a system is of most concerned. Thus it is very important to maintain a
system as efficient as possible. Boiler auxiliaries help in improving boiler’s efficiency.
Following are the important auxiliaries used
3.2.1 ECONOMIZER: Its purpose is to preheat feed water before it is introduced into
boiler drum by recovering heat from flue gases leaving the furnace.
3.2.2 SUPER HEATER: It increases the temperature of steam to super-heated region.
3.2.3 REHEATER: It is used for heat addition and increase the temperature of steam
coming from high pressure turbine to 540o.
3.2.4 SOOT BLOWER: It blows off the ash deposited on the water wall surface. It uses
steam for blowing purpose.
3.2.5AIR PREHEATER: It pre-heats the air entering the furnace by recovering heat
from flue gases in order to ease the combustion process.
3.2.6 DRAFT FANS: They handle the supply of air and the pressure of furnace.
3.2.7 OIL GUNS: They are used to spray oil to raise the temperature of furnace to
ignition temperature of fuel.
3.2.8 WIND BOX: It distributes the excess air uniformly throughout furnace.
3.3 BOILER MOUNTINGS
These are used for the safe operation of boiler. Some examples of mountings used are
water level indicator in drum, furnace temperature probe, reheat release valve, pressure
gauges indicating steam pressure et
Turbine is an m/c in which a shaft is rotated steadily by the impact of reaction of steam
of working substance upon blades of a wheel. It converts the potential energy or heat
energy of the working substance into mechanical energy. When working substance is
steam it is called ‘Steam Turbine’
In the steam turbine the pressure of the steam is utilized to overcome external resistance
and the dynamic action of the steam is negligibly small.
Working of the steam turbine depends wholly upon the dynamic action of steam. the
steam is caused to fall with pressure in a passage of nozzle, due to this fall in pressure, a
whole amount of heat energy is converted into mechanical energy & steam is set
moving with the reactor velocity. The rapidly moving particle of steam enter the moving
part of turbine and here suffers a change in the direction of motion which gives rise to
change of momentum and therefore to a force. This constitutes a driving force to a
The passage of the m/c through the moving part of the turbine commonly called the
blade, may take place in such a manner that the pressure at the outlet sides of the blade
is equal to that of the inlet side. Such a turbine is broadly termed as outlet turbine or
Impulse typeOn the other hand, the pressure of the steam at outlet from the moving
blade may be less than that at type inlet side of the blade.
FIG 4.1 PICTURE SHOWING TURBINE
Generator is the main part of thermal power station or any power plant. A generator is a
machine which converts mechanical energy into electrical energy.The generator has gas
cooling construction enclosing the stator winding, core and hydrogen coolers .The
cooling medium hydrogen is contained within the frame and circulation by fans
mounted on either ends of the rotor .The generator is driven by directly coupled steam
turbine at a speed of 3000 rpm.
Provision has been made for circulating the cooling water in order to maintain a
constant temperature of the coolant i.e. H2 as measured at the fan section side which is
in touch with the temperature of the winding, core and other parts as per load.
Each of the 2 units have been provided with 3-phase turbo generator rated output
706MVA, 18.525KA, 22KV, 0.85 lagging p.f. , 984 rpm and 50 cycles/sec .The
generator has closed loop of hydrogen gas system for cooling of the stator and rotor at a
pressure of 4.5kg/sq-cm(g). is filled in a gas tight outer casing of the generator. H2 gas
circulates inside the casing by two single stage rotor mounted fans on either side of the
rotor. The heated H2 is in turn cooled by six surface type water coolers axially mounted
inside the generator casing .The cooling water is supplied to H2 coolers from the BCW
Each generator has terminal led out of its casing and a star point is formed by sorting the
neutral side terminals by a sorting bar. The neutral is grounded by a 1-phase
11000/220V, Neutral grounding transformer, whose secondary coil is laminated by
laminated strip with mechanical ventilating holes, is connected across a 650V, class 0.4
ohm, 50 kW neutral grounding resistors and relays for protection of generator against
stator earth faults and stator in turn faults (rating 1 amp).
The H2 gas inside the generator casing is prevented from leaking in between the rotor
and shields, by a continuous oil film maintained between the rotor and sealing rings
.The shaft sealing system have two independent oil sources associated pumps,
regulators, coolers filters, electrical controls and alarm system. Two independent oil
sources are provided for air side and H2 side sealing rings. The oil circuit of the H2 side
GENERATOR SPECIFICATIONS FOR UNIT I & II:-
TABLE 5.1 GENERATOR SPECIFICATIONS
Make CQ GEARBOX china
Apparent Output 706MVA
Active Output 600 MW
Power factor 0.85 lagging
Rated voltage 22 KV
Rated current 18525 Amp.
Rated speed 3000 rpm
Frequency 50 Hz
Phase connections Double gen. star
Insulation class F(temp limited in B class)
Cooling mode H20-H2-H2
Rated H2 pressure 4.5kg/sq-cm
Excitation type static thyristor excitation
Terminal in generator 6
5.2 DIESEL-GENARATOR SET
It is used to emergency purpose to supply auxiliary system of power plant. 3
Set Diesel generator are use in which 1 is standby. Parameters of generator are
TABLE 5.2 PARAMETERS OF GENERATORS
MAKE BY STAMFORD MAHARASTRA INDIA
RATED CURRENT 2643.37A
RATED TEMP. 40ºC
INSULATION CLASS H
Transformer is made up of following parts:-
3. On load tap changer
6. Auxiliary equipment
7. Insulating Oil
8. Cooling system
In KaTPP there are various transformers for various purposes. They are:-
2.Unit Transformer (UT)
3. Unit Auxiliary Transformer(UAT)
4.Inter Connecting Transformer(ICT)
5.Unit Service Transformer
6.2 GENERATING TRANSFORMER:-
At KaTPP , 3 single phase GT Installed for each phase in single unit.output of generator
has step up up to 400KV by GT.In KaTPP 150/200/250MVA,22.98/22 KV, GT are
TABLE 6.1 SPECIFICATIONS OF GT
MANUFACTURING CROMPTON GREAVES LTD MUMBAI
NOMINAL VOLTAGE(NO LOAD) HV-243.37KV
RATED CURRENT HV-1031.0A
TYPE OF COOLING ONAN ONAF OFAF
RATING (MAV) 150 200 250
TEMP.RISE IN WINDING 50-55 ºC
CONNECTION SYMBOL YND
MASS CORE+WINDING 12.5800kg
OIL MASS 58300/66600kg/ltr.
TOTAL MASS 251800Kg
NO LOAD LOSS 105KW
ON LOAD LOSS 483KW @249KVA
COOLING LOSS 15KW
OLTC (ON LOAD TAP +7.5 %TO -12.5 % IN STEPS OF 1.25%
CHANGER)TAPPING RANG ON HV NEUTRAL SIDE
6.3 UNIT TRANSFORMER:-
Unit Transformer are installed to fed supply to HT switchgear.there are two 80MVA
Transformer installed near GT which are fed throw main bus ducts coming from
generator and fed to the HT switchgear. After step down THIS SUPPLY UP TO 11 KV
HT switchgear used to supply on the major auxiliary of the plant like
BFP,CWP,ID,FD,PA fens etc.The unit transformer is used to HT switchgear and it
supply voltage 22/11KV to UAT and different motors in boiler.UT is rated for
48/64/80MVA,22/11.6/11.6KV, Dyn11yn11 type winding. This permit to voltage down
up to 11KV.it have 2 radiator.
TABLE 6.2 SPECIFICATIONS OF UT
Manufactured BHARAT BIJLEE LTD. MUMBAI
Total no. provided 2
Type of construction CORE
Rated output 48/64/80 MVA
Rated voltage at no load 22/11.6/11.6KV
Phase HV/LV1/LV2 3
Frequency 50 Hz
Oil Temp. Rise 50 ºC
Winding Temp. Rise 50-55 ºC
Connection symbol Dyn11yn11
Insulation level p.f/impulse
H V 50KV(rms)/125KVp
Winding +core mass 47500kg
Mass/volume of oil 23300/27100 kg/ltr.
Total mass 107000kg
6.4 UNIT AUXILLIARY TRANSFORMER:-
There is one more Transformer known as Station Transformer used only for initializing
the start-up of the station (Main Plant).It is very beneficial during emergency situations
such as tripping of Units, shut-down etc.
In KaTPP 2 UAT used for step down voltage 11/3..3KV supply used to switchgear
6.5 INSTRUMENT TRANSFORMER:-
Instrument transformer have wide range in application such as measurement of voltage,
current, power & energy power factor, frequency. It is also used for protection circuit of
the power system for operation of over current, under voltage, earth fault and other type
of relays, the instrument transformer can be classified as
6.5.1 CURRENT TRANSFORMER:-
Current transformer is used for monitoring the current for the purpose of measuring and
protection.The dead tank current transformer accommodate the secondary cores inside
the tank which is at ground potential. CT used current ratio 1000:1 and range is 1A-5A.
6.5.2 POTENTIAL TRANSFORMER:-
The function of P.T. is to step down the voltage so that it can be measured by standard
measurement.Output in pt is 110V.The transformer is generally core type and form Y-Y
group and having the insulation as oil and papers.
Switchyard is considered as the HEART of the Power Plant. Power generation can be
worth only if it is successfully transmitted and received by its consumers. Switchyard
plays a very important role as a buffer between the generation and transmission. It is a
junction, which carries the generated power to its destination (i.e. consumers). Switchyard
is basically a yard or an open area where many different kinds of equipments are located
(isolator, circuit breaker etc…), responsible for connecting & disconnecting the
transmission line as per requirement (e.g. any fault condition). Power transmission is done
at a higher voltage. (Higher transmission voltage reduces transmission losses).
Both units is 22KV in KaTPP. Stepped-up to 400KV by the Generating transformer &
then transmitted to switchyard. Switchyards can be of 400KV, & 200KVIn SSTPS there
are two interconnected switchyards:-
(i) 400KV SWITCHYARD
(ii) 220KV SWITCHYARD
The 400KV & 220KV switch yard have conventional two buses arrangement with a bus
coupled breaker. Both the generator transformer and line feeder taking off from switch
yard can be taken to any of the two buses, similarly two station transformer can be fed
from any two buses. Each of these line feeders has been provided with bypass isolators
connected across line isolators and breaker isolators to facilitate the maintenance of line
breaker. Each 400KV & 220KV lines have provision of local break up protection. In
event of breaker which corresponding to bus bar differential protection scheme and trips
out all the breakers and connected zone bus bars differential protection scheme for bus I
& II. All the breaker of the connected zone and bus coupler, breaker will trip in event of
fault in that zone. Here in KaTPP 4 outgoing line are as below:-
1.400KV TO BTAWDA
2.400KV TO BTAWDA
3.220KV TO JHALAWAR
4.220KV TO JHALAWAR
Each of the two bus bars has one P.T. one for each phase connected to it. Potential
Transformer are make in CROMPTON LTD. Each time line feeders has two nos. Core for
each phase capacitor voltage Transformer. For metering and protection are multicored
single phase, oil filled, nitrogen sealed and are provided at rate of one per phase.
FIG 7.1 SWITCH YARD AREA
7.1 400KV SWITCHYARD:
There are on total 21 bays in this switchyard. (A bay is basically a way for the incoming
power from generator as well as outgoing power for distribution).
3 for unit Generating Transformer.
2 for various distribution lines such as:
BTAWDA LINE 2
For Bus coupler.
2 For TBC.
2 for ICT.
1 for the Bus Section.
There are on total 2 buses in 400KV switchyard.
There are two transfer Buses
Transfer buses are kept spare and remain idle and are used only for emergency purposes.
BUS COUPLER-1 interconnects Bus-1 & Bus-2, respectively. Bus couplers are very
beneficial as they help in load sharing between the different buses.
TBC (TRANSFER BUS COUPLER):
TBC is a bus coupler, which uses transfer bus when there is any defect in the equipments
used (circuit breakers & isolators) in any of the bay. Thus, it offers a closed path through
transfer bus for the flow of power in the respective bus.
A described of electrical equipment at 400KV & 220KV system are as follows: -
Circuit Breaker(VCB& SF6)
Potential Transformers (P.T.)
Capacitor Voltage Transformers (C.V.T.)
Inter connected transformer (ICT)
7.1.1 CIRCUIT BREAKER
It is an automatic controlling switch used in power house, substation & workshop as well as
in power transmission during any unwanted condition (any fault condition-earth fault, over-
current, flashover, single phasing,). During such condition it cuts down the supply
automatically by electromagnetic action or thermal action. It can be used in off-load as well
as on-load condition. When a circuit breaker is operated by sending an impulsethrough
relay, C.B. contact is made or broken accordingly. During this making and breaking, an arc
is produced which has to be quenched; this is done by air, oil, SF6 gas etc…
Depending on the medium being used C.B.s can be categorized into various types.PLANT
for 400 KV/220 KV switchyard only 4 main types are being used:-
ABCB (Air operated circuit breaker):- operated as well as arc quenched through air. Air
operated SF6 circuit breaker:- operated through air but arc quenching done through SF6
MOCB (Minimum oil circuit breaker):-operated through spring action but arc quenching
done through oil (Aerosol fluid oil).
Hydraulic operated SF6 circuit breaker:- operated through hydraulic oil and arc quenching
done through SF6 gas. Hydraulic operated SF6 circuit breaker is the most efficient due to
1. Less maintenance.
2. Arc quenching capability of SF6 gas is more effective than air.
3. Heat transfer capacity is better in this C.B.
Here we use SF6 provided for each stage are SIEMENS made and rated for 420KV/245KV,
3150A Each pole has three interrupters which are oil filled with SF6 gas at 7.5 Kg/sq.
cm.Here in KaTPP 3AP1FI/3AP2FI type CB are used for 400KV &220KV Switchyard.
Interlock Scheme of Circuit Breaker: -
Station Transformer Breaker Line
Bus Coupler Breaker.
PARAMETERS FOR CB
Parameters 400KV yard For 220KV yard
Type 3AP2FI 3AP1FI
Rated voltage 420KV 245KV
Rated Lighting impulse withstand 1425KVp 1050KVp
Rated power Frequency withstand 610KV 460KV
Frequency 50Hz 50Hz
Rated nominal current 3150A 3150A
Rated short circuit breaking current 50KA 40KA
Rated short circuit time duration 3 sec 3 sec
Rated out of phase breaking current 12.5A 10KA
First pole to clear factor 1.3 1.3
Rated Single Capacitorbankbreak 400A 125A
Rated line charging break current 600A 400A
DC component 46% 25%
Rated operation sequence o-.3s-co- 0-.3S-CO-3M-CO
Rated pressure of SF6 at+20deg cel 3min-c0
Weight of SF6 6.0 bar rel 6.0bar rel
Total weight 39kg 22kg
Control voltage 5400kg 3000kg
Operation machnisiom/heating voltage 220V DC 220V DC
240V AC 240V AC
An isolator is also a switching device used to disconnect the line. As the name suggests it
isolate the line from the supply. It is always used in OFF-LOAD condition. Whenever any
fault occurs in the equipments present in the line, in order to remove the fault or replace the
device first of all supply is disconnected. But even after the disconnection of the supply, the
line remains in charged mode so before working on the device (to remove fault) isolator
should be made open. Depending on the structure there are mainly two types of isolators:-
Centre-break isolator (also known as Sequential isolator).
Pentagraph is generally used in buses whereas Centre-break (Sequential) is used in line.
Isolators may be operated in air (pneumatic), electrically or even manually.
TABLE 7.1 PARAMETERS OF ISOLATORS
7.1.3 LIGHTENING ARRESTER:-
It is a protective device, which protects the costly equipments such as overhead lines, poles
or towers, transformer etc. against lightening. As the name suggests it arrests the lightening
of very high voltage (crores of KV) and dump it into the ground.
It works on the principle of easy path for the flow of current. L.A. is connected in parallel
with the line with its lower end connected and the upper end projected above the pole of
Manufacturing by GR-power switchgear ltd Hyderabad
Rated voltage 420/245 KV
Impulse voltage 1050KVp
Total weight 1300/950kg
Short time current 40KA for 3 sec
Control voltage 220V DC
7.1.4 LIGHTENING ARRESTERS:-
It is present at the highest point, at the topmost tower of the switchyard and is connected
together by wires forming a web. The reason for its presence at the topmost point is to grasp
the lightening before it can come, fall and damage the costly equipments present in the
FIG 7.2LIGHTING ARRESTER
SPECIFICATIONS OF LIGHTENING ARRESTER:-
TABLE 7.2 SPECIFICATIONS OF LIGHTENING ARRESTER
Maximum Voltage 245KV
MAX Current 2000A
RELAY Maximum Current 40A
Total weight 215kg
7.1.5 EARTHING ISOLATORS:-
The term ‘Earthing’ means connecting of the non-current carrying parts of the electrical
equipment or the neutral point of the supply system to the general mass of earth in such a
manner that all times an immediate discharge of electrical energy takes place without
danger. An Earthing isolator is a large value of capacitance. This can be charged up to line
voltage. Earthing isolator is used to discharge the line capacitance and work on it.
7.1.6 WAVE TRAPER:-
It is an equipment used to trap the high c arrier frequency of 500 KHz and above and allow the
flow of power frequency (50 Hz). High frequencies also get generated due to capacitance to
earth in long transmission lines. The basic principle of wave trap is that it has low inductance (2
Henry) & negligible resistance, thus it offers high impedance to carrier frequency whereas
very low impedance to power frequency hence allowingit to flow in the station.
FIG 7.3 WAVE TRAPER
7.1.7 CURRENT TRANSFORMER:
FIG 7.4 CURRENT TRANSFORMER
This Transformer is used for basically two major functions: -
Metering which means current measurement.
Protection such as over current protection, overload earth fault protection, Bus-bar
protection, Bus differential protection.
NOTE: - Secondary of the C.T should be kept shorted because (when secondary is kept
open) even the presence of a very small voltage in the primary of C.T will prove to be
harmful as it will start working as a step-up Transformer & will increase the voltage to such
a high value that primary would not be able to bear it & will get burned. CT used current
ratio 1000:1 and range is 1A-5A.CT connected in series while PT in parallel.
TABLE 7.3 SPECIFICATIONS OF CT
In the case of emergency, e.g. total grid failure we take the power from Pipri line for the
initial starting of the station (Main Plant).
Rated voltage 245KV
Current 40KA for 3 sec
Rated primary current 2000A
Continuous current 2400A
Insulation class A
Secondary terminal rating 2A
Oil weight 210kg
Total weight 850 kg
7.1.8 CAPACITOR VOLTAGE TRANSFORMER (CVT)
FIG 7.4 CVT
This Transformer performs mainly two major functions:-
Used for voltage measurement. The high voltage of 400 KV is impossible to measure
directly. Hence a C.V.T is used, (connected in parallel with the line) which step-downs the
voltage of 400 KV to 110 KV, comparatively easy to measure.
The other most important function of C.V.T is that it blocks power frequency of 50Hz and
allows the flow of carrier frequency for communication.Each of the four line feeders provided
with three capacitor volt transformer for metering and synchronizing.
7.1.9 P.T (POTENTIAL TRANSFORMER):
This Transformer is connected in parallel with the line with one end earthed. It is only used
for voltage measurement by stepping-down the voltage to the required measurable value.
7.1.10 INTER CONNECTED TRANSFORMER (ICT)
Purpose of ICT is simply interconnection between 400KV and 220KV Switchyard.
3xM1802-300/D-10.19.300MA2 Type autotransformer is used. Manufacture by
CROMPTON GEARVES TRANSFORMER DIVISION BHOPAL.
TABLE 7.4 PARAMETERS USE IN ICT:
No load HV 400KV
Amperes LV 220KV
ONAN/ONAF/OFAF HV 272.8/363.7/454.6
Rating(MVA) ONAN ONAF ODAF
HV 189 252 315
LV 189 252 315
TV 63 84 109
Guaranted temp. 50 ºC
Connection symbol YNaod11
Core+winding mass 120700kg
Total oil 71600/81800kg/ltr.
Total mass 287000kg
No load & on load 100KW & 600KW,15KW
Impedance tolerance Hv-lv 12.55,hv-tv 45%,tv-lv 30%