The document is a summer training report submitted to Thapar University describing a 6-week internship at the Dongamahua Captive Power Plant owned by Jindal Steel and Power Limited. It provides an overview of the power plant, including its location and capacity. It then describes the working of the thermal power plant, from coal handling, combustion in the boiler to generate steam, steam passing through turbines to the generator to produce electricity, and the condensing and feeding processes to close the Rankine cycle.

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A
SUMMER TRAINING REPORT
ON
JINDAL STEEL AND POWER LIMITED
(DONGAMAHUA CAPTIVE POWER PLANT)
B.E. [Electrical Engineering] of
THAPAR UNIVERSITY,PATIALA
Submitted To: Submitted By:
Mr. Nitin Narang Amit Bansal
(Assistance Prof. EIED) 5th
Sem.(UEE591)
101204012
DEPARTMENT OF ELECTRICAL AND INSTRUMENTATION ENGINEERING
THAPAR UNIVERSITY
(Deemed University)
P.O. Box -32, Patiala-147004

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ACKNOWLEDGEMENT
I would like to extend my heartfelt gratitude to all those who have contributed
towards the successful completion of my project and converge my thanks to HOD
of power plant Mr. A.N. Sar. I would be failing in my duty, if I do not express my
gratitude to training head Mr. Gautam Mazumdar for his helpfulness generously
extended support and by sparing his valuable time to guide and suggest me towards
the completion of my project also thanks to Mr. Dilip Kumar Pathak head of
electrical department in power plant who guide me to understand the most
important things of power plant.
I attribute heartiest thanks to all the engineers of electrical department of especially
to Mr. Amit Sir who helped me out in every step of my training schedule and I
would even like to thank Mr. Vikas Kr. Gupta and Mr. Pankaj Panda for their
guidance.
I do owe a great sense of gratitude to all my friends and all those who stood with
me and for their continuous support and co-operation during the project.
Thank you

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PREFACE
With immense pleasure and deep sense of sincerity, I have completed my 6 weeks
Industrial Training. It is an essential requirement for each and every student to
have some practical exposure towards real world situations. A systematized
practical experience is essential to inculcate self confidence in a student, so that
they can mentally prepare themselves for this competitive environment.
The purpose of this training is:-
1. Developing intellectual ability
2. Bring confidence
3. Developing skills
4. Modify attitude
5. Understand work culture

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 Introduction of JSPL
 Power Plant overview
 Thermal power plant
 Rankine cycle
 Classification of Thermal Power plant
 By fuel
 By prime mover
 Typical view of a thermal power plant
 Site selection
 Working of DCPP
 Generator
 Switchyard
 Busbar
 Lightening arrester
 SF6 Circuit breaker
 Isolator
 Current transformer
 Potential transformer
 power transformer
 transformer oil
 insulation resistance test
 protection of transformer
 breather
 radiator
 conservator tank
 buchholz relay
 transformer noise
 safety measures
 conclusion
 reference
CONTENTS

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ABOUT JSPL
Jindal Steel and Power Limited (JSPL) is an Indian steel and energy company
based in New Delhi, India and founded in 1969. with turnover of approx. US$ 3.56
billion, JSPL is a part of about US$ 17 billion diversified Jindal group
conglomerate. JSPL is a leading player in steel, oil, power, mining and gas and
infrastructure in India. The company produces steel and power through backward
integration from its own captive coal and iron-ore mines. In terms of tonnage, it is
the third largest producer of steel in India. Shri Naveen Jindal, youngest son of
legendary Shri O.P Jindal, spearheads of J.S.P.L and its group companies. The
company produces Blooms/Slabs, Billets, Beam Blanks, TMT bars, Round wires,
Rod, Beams, Angle etc. JSPL is the 11th
fastest growing company in India. Forbes
also listed JSPL in top 50 companies in India. Company has around 15,000
employees. Company also won several awards in quality, energy and environment.
J.S.P.L. endeavors to strengthen India’s industrial base by aiding infrastructural
development, through sustainable development approaches and inclusive growth.
The company deploys its resources to improve infrastructure, education, health,
water, sanitation, environment, etc.

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POWER PLANT OVERVIEW
Power plant in Dongamahua is a captive power plant in Raigarh district of
Chattisgarh. DCPP consist of 4 units of 135 MW each with total capacity to
generate 540 MW of electricity. The main purpose of this power plant is to provide
electricity to the Jindal steel located in Raigarh, Chattisgarh. In plant there are two
transmission lines, line one is going to Jindal Steel and Power Limited (JSPL) and
second line is going to Jindal Power Plant (JPL). Coal used in plant is of low
grade. In plant there are 4 Generating transformers (GT) of 180 MVA each, 3
Substation transformers (ST) of 40 MVA each, 2 Mines Station transformers
(MST) of 50 MVA each, 4 Unit Auxiliary Transformers (UAT) of 25 MVA each.
Generator used is of rating 135 MW. There are total 16 bays in the switchyard.
There are total 6 voltage levels in the plant- 220 KV, 33 KV, 13.8 KV, 6.6 KV,
440 V and 110 V.

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THERMAL POWER PLANT
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 stream
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 rankine cycle.

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RANKINE CYCLE
The rankine cycle is an idealized thermodynamic cycle of a heat engine that
converts heat into mechanical work. The heat is supplied externally to a close loop,
which usually uses water as the working fluid.

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Process 1-2: The working fluid is pumped from low to high pressure. As the
fluid is a liquid at this stage, the pump requires little input energy.
Process 2-3: The high pressure liquid enters a boiler where it is heated at
constant pressure by an external heat source to become a dry saturated vapour. The
input energy required can be easily calculated using mollier diagram or h-s chart or
enthalpy-entropy chart also known as steam tables.
Process 3-3’
: superheating of steam because compression by the pump and
expansion in the turbine is not isentropic. So as the water condenses, water droplets
hit the turbine blades causing pitting and erosion of the turbine, so by superheating
we make the steam dry.
Process 3’
-4’
: The dry saturated vapour expands through a turbine, generating
power. This decreases the temperature and pressure of the vapour, and some
condensation may occur. The output in this process can be easily calculated using
the Enthalpy-entropy chart or the steam tables.
Process 4’
-1: The wet vapour then enters a condenser where it is condensed at a
constant pressure to become a saturated liquid.

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CLASSIFICATION OF THERMAL POWER PLANTS
Thermal power plants are classified by the type of fuel and the type
of prime mover installed.
1) By Fuel
 Nuclear power plants use nuclear heat to operate a steam
turbine generator.
 Fossil fuelled power plants may also use a steam turbine generator or
in the case of natural gas fired plants may use a combustion turbine.
 Geothermal power plants use steam extracted from hot underground
rocks.
 Renewable energy plants may be fuelled by waste from sugar
cane, municipal solid waste, landfill methane, or other forms of biomass.
 In integrated steel mills, blast furnace exhaust gas is a low-cost, although
low-energy-density, fuel.
 Waste heat from industrial processes is occasionally concentrated
enough to use for power generation, usually in a steam boiler and turbine.
 Solar thermal electric plants use sunlight to boil water, which turns the
generator.

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2) By Prime Mover
 Steam turbine plants use the dynamic pressure generated by expanding
steam to turn the blades of a turbine. Almost all large non-hydro plants use
this system.
 Gas turbine plants use the dynamic pressure from flowing gases to
directly operate the turbine. Natural-gas fuelled turbine plants can start
rapidly and so are used to supply "peak" energy during periods of high
demand, though at higher cost than base-loaded plants. These may be
comparatively small units, and sometimes completely unmanned, being
remotely operated. This type was pioneered by the UK, Prince town being
the world's first, commissioned in 1959.
 Combined cycle plants have both a gas turbine fired by natural gas, and a
steam boiler and steam turbine which use the exhaust gas from the gas
turbine to produce electricity. This greatly increases the overall efficiency of
the plant, and many new base load power plants are combined cycle plants
fired by natural gas.
 Internal combustion Reciprocating engines are used to provide power for
isolated communities and are frequently used for small cogeneration plants.
Hospitals, office buildings, industrial plants, and other critical facilities also
use them to provide backup power in case of a power outage. These are
usually fuelled by diesel oil, heavy oil, natural gas and landfill gas.

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TYPICAL VIEW OF A COAL FIRED THERMAL
POWER PLANT

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1. Cooling tower 2. Cooling water Pump
3. Transmission line (3-phase) 4. Step-up transformer (3-phase)
5. Electrical generator (3-phase) 6. Low pressure steam turbine
7. Condensate pumps 8. Surface condenser
9. Intermediate pressure steam turbine
10. Steam Control valve
11. High pressure steam turbine 12. Deaerator
13. Feed water heater 14. Coal conveyor
15. Coal hopper 16. Coal pulverizer
17. Boiler steam drums 18. Bottom ash hopper
19. Super heater 20. Forced draught (draft) fan
21. Re heater 22. Combustion air intake
23. Economizer 24. Air pre heater
25. Precipitator 26. Induced draught (draft) fan
27. Flue gas stack

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SITE SELECTION OF THERMAL POWER PLANT
In general, both the construction and operation of a power plant requires the
existence of some conditions such as water resources and stable soil type.
Still there are other criteria that although not required for the power plant,
yet should be considered because they will be affected by either the
construction or operation of the plants such as population centers and
protected areas. The following list corresponds most of the factors that was
studied and considered in selection of proper site for Dongamahua power
plant construction:
 Transportation Network: Easy and enough access to transportation network is
required in both power plant construction and operation periods.
 Power Transmission Network: To transfer the generated electricity to the
consumers, the plant should be connected to electrical transmission system.
Therefore the nearness to the electric network can play a roll.
 Geology and Soil Type: The power plant should be built in an area with soil and
rock layers that could stand the weight and vibrations of the power plant.
 Earthquake and Geological Faults: Even weak and small earthquakes can damage
many parts of a power plant intensively. Therefore the site should be away
enough from the faults and previous earthquake areas.
 Topography: It is proved that high elevation has a negative effect on
production efficiency of gas turbines. In addition, changing of a sloping area

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into a flat site for the construction of the power plant needs extra budget.
Therefore, the parameters of elevation and slope should be considered.
 Rivers and Floodways: obviously, the power plant should have a reasonable
distance from permanent and seasonal rivers and floodways.
 Water Resources: For the construction and operating of power plant different
volumes of water are required. This could be supplied from either rivers or
underground water resources. Therefore to meet the requirement of water
supply a 18m high dam is constructed over kurket river.
 Environmental Resources: Operation of a power plant has important impacts on
environment. Therefore, priority will be given to the locations that are far
enough from national parks, wildlife, protected areas, etc.
 Population Centers: For the same reasons as above, the site should have an
enough distance from population centers.
 Need for Power: In general, the site should be near the areas that there is more
need for generation capacity, to decrease the amount of power loss and
transmission expenses.
 Climate: Parameters such as temperature, humidity, wind direction and speed
affect the productivity of a power plant and always should be taken into
account.
 Land Cover: Some land cover types such as forests, orchard, agricultural land,
pasture are sensitive to the pollutions caused by a power plant. The effect of
the power plant on such land cover types surrounding it should be counted
for.

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 Area Size: Before any other consideration, the minimum area size required for
the construction of power plant should be defined.
 Distance from Airports: Usually, a power plant has high towers and chimneys
and large volumes of gas. Consequently for security reasons, they should be
away from airports.
 Archeological and Historical sites: Usually historical building are fragile and at
same time very valuable. Therefore the vibration caused by power plant can
damage them, and a defined distance should be considered.

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WORKING OF DONGAMAHUA CAPTIVE POWER
PLANT
1) Coal is conveyed with the help of truks from the nearby dongamahua
captive coal mines to the coal handling plant.
2) In coal handling plant (CHP) coal is separated as high grade coal and low
grade coal. High grade coal is conveyed to JPL and low grade coal is
conveyed to DCPP. Pulverization of coal is also takes place in CHP.
3) From CHP coal is transported to boiler there it is mixed with preheated
air driven by the Forced draught fan.
4) The hot air-fuel mixture is forced at high pressure into the Boiler where it
rapidly ignites.
5) Water of a high purity flows vertically up the tube-lined walls of the
boiler, where it turns into steam, and is passed to the boiler drum, where
steam is separated from any remaining water.
6) Water is supplied from de-mineralized plant (DM) plant.
7) The steam passes through a manifold in the roof of the drum into the
pendant Super heater where its temperature and pressure increase rapidly
to around 136 bar and 535°C, sufficient to make the tube walls glow a
dull red.
8) The steam is piped to the high-pressure turbine, the first of a three-stage
turbine process.
9) A Steam governor valve allows for both manual control of the turbine
and automatic set point following.
10) The steam is exhausted from the high-pressure turbine, and reduced in
both pressure and temperature, is returned to the boiler reheater.

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11) The reheated steam is then passed to the Intermediate pressure
turbine, and from there passed directly to the low pressure turbine set.
12) The exiting steam, now a little above its boiling point, is brought into
thermal contact with cold water (pumped in from the cooling tower) in
the Condenser, where it condenses rapidly back into water, creating near
vacuum-like conditions inside the condenser chest.
13) The condensed water is then passed by a feed pump through a
deaerator (device that is widely used for the removal of oxygen and other
dissolved gases from the feed water to steam-generating boilers) and pre
warmed, first in a feed heater powered by steam drawn from the high
pressure set, and then in the Economizer, before being returned to the
boiler drum.
14) The cooling water from the condenser is sprayed inside a Cooling
tower, creating a highly visible plume of water vapor, before being
pumped back to the Condenser in cooling water cycle.
15) The three turbine sets are coupled on the same shaft as the three-phase
electrical Generator of 135 MW which generates an intermediate level
voltage (typically 13-15 kV).
16) This is stepped up by the generating transformer of 180 MVA to a
voltage more suitable for transmission (typically 220-250 kV) and is sent
out onto the three-phase transmission system.
17) Exhaust gas from the boiler is drawn by the induced draft fan through
an Electrostatic Precipitator (ESP) and is then vented through the
Chimney stack.

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18) ESP is a device which removes dust or other finely divided particles
from flue gases by charging the particles inductively with an electric
field, then attracting them to highly charged collector plates also known
as precipitator. The process depends on two steps. In the first step the
suspension passes through an electric discharge area where ionization of
the gas occurs. The charged particles drift toward an electrode of
opposite sign and are deposited on the electrode where their electric
charge is neutralized. Among the advantages of the ESP is its ability to
handle large volumes of gases, at elevated temperatures if necessary, with
a reasonably small pressure drop, and the removal of particles in the
micrometer range
19) Fly ash is captured and removed from the flue gas by ESP located at
the outlet of the furnace and before the induced draft fan. The fly ash is
periodically removed from the collection hoppers below the precipitators.
Generally, the fly ash is pneumatically transported to storage silos for
subsequent transport by trucks.
20) Flue gases coming out of the boiler carry lot of heat. Function of
economizer is to recover some of the heat from the heat carried away in
the flue gases up the chimney and utilize for heating the feed water to the
boiler. It is placed in the passage of flue gases in between the exit from
the boiler and the entry to the chimney. The use of economizer results in
saving in coal consumption, increase in steaming rate and high boiler
efficiency but needs extra investment and increase in maintenance costs
and floor area required for the plant.
21) The remaining heat of flue gases is utilized by air preheater. It is a
device used in steam boilers to transfer heat from the flue gases to the
combustion air before the air enters the furnace. Also known as air
heater; air-heating system. It is kept at a place nearby where the air enters
in to the boiler. The purpose of the air preheater is to recover the heat
from the flue gas from the boiler to improve boiler efficiency by burning
warm air which increases combustion efficiency, and reducing useful
heat lost from the flue. After extracting heat flue gases are passed to ESP.

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GENERATOR
In DCPP, there are four synchronous generators of rating 135 MW are used.
It is a 3-phase,two pole synchronous generator. It also has brushless
excitation system. Its rated current is 7060 A and rated power factor is 0.8
lagging. Its efficiency is about 98.65% at full load. Its r.p.m. is 3000.
Generators are used to convert mechanical energy to electrical energy. It
works on the principle of Faraday’s law of induction. It contains a stationary
stator and a spinning rotor. Each generator is mechanically coupled with
turbine through a shaft. Shaft is further connected to a coil of a copper wire
known as armature. On either side of the armature, on the casing of the
generator, we have two polar field magnets that create a magnetic field
inside the space within the generator. As the rotor, shaft and armature
rotates, they move within the magnetic field created by the magnets.

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SWITCHYARD
Switchyard forms an integral part of any power plant. Switchyard provides
the facility of switching, control and protection of electric power. Here
voltage is transformed from low (13.6 KV) to high (220 KV). In DCPP
switchyard there are total 16 bays. All switchyard equipments are grounded
by two earthing connections.
It consists of following equipments:
 BUSBAR
 LIGHTENING ARRESTER
 SF6 CIRCUIT BREAKER
 ISOLATOR
 CURRENT TRANSFORMER
 POWER TRANSFORMER
 POTENTIAL TRANSFORMER
A VIEW OF DCPP SWITCHYARD

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BUSBAR
In electrical power distribution, a busbar is a strip or bar of copper, brass or
aluminum that conducts electricity within a switchboard, distribution board,
substation, battery bank or other electrical apparatus. Its main purpose is to
conduct a substantial current of electricity.
The cross-sectional size of the busbar determines the maximum amount of current
that can be safely carried. Busbars can have a cross-sectional area of as little as 10
mm2
but electrical substations may use metal pipes of 50 mm in diameter (20 cm2
)
or more as busbars.

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LIGHTENING ARRESTER
A surge arrester is a product installed near the end of any conductor which is long
enough before the conductor lands on its intended electrical component. The
purpose is to divert damaging lightning-induced transients safely to ground. This
equipment is always placed before the costliest equipments to provide better
safety.
When an electrically charged cloud comes nearby an electrical transmission line,
the cloud induces an electric charge in the line. When the charge cloud is suddenly
discharged through lightening the induced charge is no longer static. It starts
travelling and originate dynamic transient over voltage. The transient over voltage
travel towards both load and source side on transmission line because of
distributed line inductance and stray capacitance. This surge voltage travels with
speed of light. At the end of transmission line as the surge impedance changes
surge voltage wave reflected back. This forward and backward travelling of surge
voltage wave continues until the energy of impulse is attenuated by line resistance.
This causes stress on transmission line. So, to prevent equipments we use
lightening arrester.

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SF6 CIRCUIT BREAKER
A circuit breaker is an automatically operated electrical switch designed to protect
an electrical circuit from damage caused by overload or short circuit. Its basic
function is to detect a fault condition and interrupt current flow. A circuit breaker,
in which the current carrying contacts operate in SF6 gas.
SF6 has excellent insulating property and has high electronegativity that means it
has high affinity of absorbing free electron whenever a free electron collides with
SF6 gas molecule it is absorbed by that gas molecule and forms a negative ion.
SF6 + e-
SF6
-
SF6 + e-
SF5
-
+ F
These negative ion obviously much heavier than free e-
and therefore over all
mobility of the charged particle in the SF6 gas is much less as compared to other
gas. We know that mobility of charged particle is majorly responsible for
conducting current through a gas.
Hence, for heavier and less mobile charged particle in SF6 gas, it acquires very
high dielectric strength. Gas also has very good heat transfer property due to its
low gaseous viscosity.
Working of SF6 Circuit Breaker
The working of SF6 CB of first generation was quite simple it is some extent
similar to air blast circuit breaker. Here SF6 gas was compressed and stored in high
pressure reservoir. During operation of SF6 circuit breaker this highly
compressed gas is released through the arc in breaker and collected to relatively
low pressure reservoir and then it pumped back to the high pressure reservoir for re
utilize.
The working of SF6 circuit breaker is little bit different in modern time.
Innovation of puffer type design makes operation of SF6 CB much easier. In buffer
type design, the arc energy is utilized to develop pressure in the arcing chamber for
arc.

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Here the breaker is filled with SF6 gas at rated pressure. There are two fixed

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contact fitted with a specific contact gap. A sliding cylinder bridges these to fixed
contacts. The cylinder can axially slide upward and downward along the contacts.
There is one stationary piston inside the cylinder which is fixed with other
stationary parts of the SF6 circuit breaker, in such a way that it can not change its
position during the movement of the cylinder. As the piston is fixed and cylinder is
movable or sliding, the internal volume of the cylinder changes when the cylinder
slides.
During opening of the breaker the cylinder moves downwards against position of
the fixed piston hence the volume inside the cylinder is reduced which produces
compressed SF6 gas inside the cylinder. The cylinder has numbers of side vents
which were blocked by upper fixed contact body during closed position. As the
cylinder move further downwards, these vent openings cross the upper fixed
contact, and become unblocked and then compressed SF6 gas inside the cylinder
will come out through this vents in high speed towards the arc and passes through
the axial hole of the both fixed contacts. The arc is quenched during this flow of
SF6 gas.
During closing of the circuit breaker, the sliding cylinder moves upwards and as
the position of piston remains at fixed height, the volume of the cylinder increases
which introduces low pressure inside the cylinder compared to the surrounding.
Due to this pressure difference SF6 gas from surrounding will try to enter in the
cylinder. The higher pressure gas will come through the axial hole of both fixed
contact and enters into cylinder via vent and during this flow; the gas will quench
the arc.

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ISOLATOR
Circuit breaker always trip the circuit but open contacts of breaker cannot be
visible physically from outside of the breaker and that is why it is recommended
not to touch any electrical circuit just by switching off the circuit breaker. So for
better safety there must be some arrangement so that one can see open condition of
the section of the circuit before touching it. Isolator is a mechanical switch which
isolates a part of circuit from system as when required. Electrical isolators separate
a part of the system from rest for safe maintenance works.
So definition of isolator can be rewritten as Isolator is a manually operated
mechanical switch which separates a part of the electrical power system normally
at off load condition.
Operation
As no arc quenching technique is provided in isolator it must be operated when
there is no chance current flowing through the circuit. No live circuit should be
closed or open by isolator operation. A complete live closed circuit must not be
opened by isolator operation and also a live circuit must not be closed and
completed by isolator operation to avoid huge arcing in between isolator contacts.
That is why isolators must be open after circuit breaker is open and these must be
closed before circuit breaker is closed. Isolator can be operated by hand locally as
well as by motorized mechanism from remote position. Motorized operation
arrangement costs more compared to hand operation; hence decision must be taken
before choosing an isolator for system whether hand operated or motor operated
economically optimum for the system. For voltages up to 145KV system hand
operated isolators are used whereas for higher voltage systems like 245 KV or 420
KV and above motorized isolators are used.

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CURRENT TRANSFORMER
A CT is an instrument transformer in which the secondary current is substantially
proportional to primary current and differs in phase from it by ideally zero degree.
It is used in electrical power system for stepping down currents of the system for
metering and protection purpose. Actually relays and meters used for protection
and metering, are not designed for high currents and voltages. High currents or
voltages of electrical power system cannot be directly fed to relays and meters. CT
steps down rated system current to 1 Amp or 5 Amp. The relays and meters are
generally designed for 1 Amp and 5 Amp. Turns ratio of current transformer is
2000/1.
A CT functions with the same basic working principle of electrical power
transformer, but here is some difference. In an electrical power transformer or
other general purpose transformer, primary current varies with load or secondary
current. In case of CT, primary current is the system current and this primary
current or system current transforms to the CT secondary, hence secondary current
depends upon primary current of the current transformer.

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POTENTIAL TRANSFORMER
Potential transformer or voltage transformer gets used in electrical power system
for stepping down the system voltage to a safe value which can be fed to low
ratings meters and relays. Commercially available relays and meters used for
protection and metering, are designed for low voltage. Primary of this transformer
is connected across the phase and ground. Just like the transformer used for
stepping down purpose, potential transformer i.e. PT has lower turns winding at its
secondary. The system voltage is applied across the terminals of primary winding
of that transformer, and then proportionate secondary voltage appears across the
secondary terminals of the PT. The secondary voltage of the PT is generally 110 V.

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POWER TRANSFORMER
A transformer is a static machine used for transforming power from one circuit to
another without changing frequency. This is a very basic definition of transformer.
Generation of electrical power in low voltage level is very much cost effective.
Hence electrical power is generated in low voltage level. Theoretically, this low
voltage level power can be transmitted to the receiving end. But if the voltage level
of a power is increased, the electric current of the power is reduced which causes
reduction in ohmic or I2
R losses in the system, reduction in cross sectional area of
the conductor i.e. reduction in capital cost of the system and it also improves the
voltage regulation of the system. Because of these, low level power must be
stepped up for efficient electrical power transmission. This is done by step up
transformer at the sending side of the power system network. As this high voltage
power may not be distributed to the consumers directly, this must be stepped down
to the desired level at the receiving end with the help of step down transformer.
These are the uses of electrical power transformer in the electrical power system.
In DCPP there are basically 4 different ratings of transformers are used:
1. GENERATING TRANSFORMER (GT)
2. SUBSTATION TRANSFORMER (ST)
3. UNIT AUXILARY TRANSFORMER (UAT)
4. MINES SUBSTATION TRANSFORMER (MST)

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GENERATING TRANSFORMER:
There are total 4 generating transformer of rating 180 MVA each, which is used to
step up the voltage from 13.6 KV to 220 KV. Windings in GT are star-delta
connected.
SUBSTATION TRANSFORMER:
There are total 3 substation transformers of 40 MVA each. This is used when the
plant shut down or any unit shut down takes place. So, to start the plant/unit they
take the power from JPL so to step down the voltage. Windings in ST are star-star
connected. Unit 3 and 4 are connected to a common ST.
UNIT AUXILIARY TRANSFORMERS:
There are total 4 unit auxiliary transformers of 25 MVA each. This is used to run
the auxiliaries of the plant means once with the help of ST unit is started then the
generated power is utilized with the help of UAT. Windings in UAT are delta-star
connected.
MINES SUBSTATION TRANSFORMER:
Near DCPP there is a Dongamahua captive coal mines through which coal is
supplied to the plant. To supply power to the mines 2 MST’s are installed in the
plant of 50 MVA each.

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TRANSORMER OIL
In DCPP oil immersed transformers are used. Oil in transformer used is called
mineral oil. Transformer oil serves mainly two purposes one it is liquid insulation
in electrical power transformer and two it dissipates heat of the transformer i.e. acts
as coolant. In addition to these, this oil serves other two purposes, it helps to
preserve the core and winding as these are fully immersed inside oil and another
important purpose of this oil is, it prevents direct contact of atmospheric oxygen
with cellulose made paper insulation of windings, which is susceptible to
oxidation.
TESTING OF TRANSFORMER OIL
There are basically 2 tests which are performed generally:
 Dissolved gas analysis (DGA) test
Whenever electrical power transformer goes under abnormal thermal and
electrical stresses, certain gases are produced due to decomposition of
transformer insulating oil. Which affect the insulation of windings. when the
fault is major, the production of decomposed gases are more and they get
collected in Buchholz relay. But when abnormal thermal and electrical
stresses are not significantly high the gasses due to decomposition of
transformer insulating oil will get enough time to dissolve in the oil. Hence
by only monitoring the Buchholz relay it is not possible to predict the
condition of the total internal healthiness of electrical power transformer.
That is why it becomes necessary to analyse the quantity of different gasses
dissolved in transformer oil in service.
Actually in dissolved gas analysis of transformer oil or DGA of transformer
oil test, the gases in oil are extracted from oil and analyze the quantity of
gasses in a specific amount of oil. By observing percentages of different
gasses present in the oil, one can predict the internal condition of
transformer.
Generally the gasses found in the oil in service are hydrogen (H2),
methane(CH4), Ethane (C2H6), ethylene(C2H4), acetylene (C2H3), carbon
monoxide (CO), carbon dioxide (CO2), nitrogen(N2) and oxygen(O2).

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EQUIPMENT IN WHICH OIL IS STORED DISSOLVED GAS ANALYSIS KIT
GAS APPROVED LIMIT(ppm)
H2 100
CO2 2500
C2H2 2
CO 350
C2H4 50
C2H6 65
CH4 120
RESULT OF SAMPLE OIL

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 BREAKDOWN VOLTAGE TEST
Dielectric strength of transformer oil is also known as breakdown voltage of
transformer oil or BDV of transformer oil. Break down voltage is measured
by observing at what voltage, sparking strands between two electrodes
immerged in the oil, separated by specific gap. low value of BDV indicates
presence of moisture content and conducting substances in the oil. In this kit,
oil is kept in a pot in which one pair of electrodes are fixed with a gap of 2.5
mm between them.
Now slowly rising voltage is applied between the electrodes. Rate of rise of
voltage is generally controlled at 2 KV/s and observe the voltage at which
sparking starts between the electrodes.
That means at which voltage dielectric strength of transformer oil between
the electrodes has been broken down. Generally this measurement is taken 3
to 6 times in same sample of oil and the average value of these reading is
taken. Minimum breakdown voltage of transformer oil or dielectric strength
of transformer oil at which this oil can safely be used in transformer, is
considered as 50 KV.
BDV KIT

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INSULATION RESISTANCE TEST (MEGGER TEST)
The insulation resistance (IR) test (also commonly known as a Megger) is a
spot insulation test which uses an applied DC voltage (typically either 250V
dc, 500V dc or 1,000V dc for low voltage equipment <600V and 2,500V dc
and 5,000V dc for high voltage equipment) to measure insulation resistance
in either KΩ, MΩ or GΩ. Test should be run between each winding and
ground and between each pair of winding. Low resistance value indicates
that the transformer is the problem.
Polarization index is a variation of the IR test. It is the ratio of IR measured
after voltage has been applied for 10
minutes (R10) to the IR measured after one minute (R1), i.e.
PI = R10/R1
Low value of PI indicates that the winding may have been contaminated
with oil, dirt etc. or absorbed moistures.
IR is measured with a ‘mega-ohmmeter’. Sometimes this is called Megger
Tester after the name of the instrument first developed for this purpose.
Mega-ohmmeter generates and applies a regulated DC supply. It measures
the flow of current and IR is directly read on its dial.
Polarization index Condition of winding Measures to be taken
<1 Hazardous Dry winding
1-1.5 Bad Dry winding
1.5-2 Doubtful Drying is
recommended
2-3 Adequate
3-4 Good
>4 Excellent
In general IR & PI test are an excellent means of ascertaining winding conditions
that are contaminated or soaked with moisture. The tests are also good detecting
major flaws where the insulation is cracked or has been cut through. The test can
also detect thermal deterioration for form wound stators using thermoplastic
insulation system.

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PROTECTION OF TRANSFORMER
1) Breather- Most of the power generation companies use silica gel
breathers fitted to the conservator of oil filled transformers. The purpose
of these silica gel breathers is to absorb the moisture in the air sucked in
by the transformer during the breathing process.
When load on transformer increases or when the transformer under full
load, the insulating oil of the transformer gets heated up, expands and gets
expel out in to the conservator tank present at the top of the power
transformer and subsequently pushes the dry air out of the conservator
tank through the silica gel breather. This process is called breathing out of
the transformer.
When the oil cools down, air from the atmosphere is drawn in to the
transformer. This is called breathing in of the transformer.
During the breathing process, the incoming air may consist of moisture
and dirt which should be removed in order to prevent any damage. Hence
the air is made to pass through the silica gel breather, which will absorb
the moisture in the air and ensures that only dry air enters into the
transformer. Silica gel in the breather is blue when installed and they turn
to pink colour when they absorb moisture which indicates that the crystal
should be replaced. These breathers also have an oil cup fitted with so
that dust particles get settled down.

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2) Radiator- When an electrical transformer is loaded, the current starts
flowing through its windings. Due to this flowing of electric current, heat
is produced in the windings, this heat ultimately rises the temperature of
transformer oil. We know that the rating of any electrical equipment
depends upon its allowable temperature rise limit. Hence, if the
temperature rise of the transformer insulating oil is controlled, the
capacity or rating of transformer can be extended up to significant range.
Oil immersed power transformer is generally provided with detachable
pressed sheet radiator with isolating valves.
The working principle of radiator is very simple. It just increases the
surface area for dissipating heat of the oil. In case of electrical power
transformer, due to the transport limitation, these units are sent separately
and assembled at site with transformer main body.
Under loaded condition, warm oil increases in volume and comes to the
upper portion of the main tank. Then this oil enters in the radiator through
top valve and cools down by dissipating heat through the thin radiator
wall. This cold oil comes back to the main tank through the bottom
radiator valve. This cycle is repeated continuously till the load is
connected to the transformer. Dissipation of heat in the transformer
radiator; can be accelerated further by force air provided by means of
fans. These fans are fitted either on the radiator bank itself or fitted
nearby the bank but all the fans must be faced towards the radiator.
Sometime, the cooling rate of convectional circulation of oil is not
sufficient. That time an oil pump may be used for speeding up circulation.
Oil temperature indicator
600
-650
– ALARM – FAN ON
900
-950
– TRANSFORMER TRIP

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3) CONSERVATOR TANK- This is a cylindrical tank mounted on
supporting structure on the roof the transformer main tank. The main
function of conservator tank of transformer is to provide adequate space
for expansion of oil inside the transformer. When volume of transformer
insulating oil increases due to load and ambient temperature, the vacant
space above the oil level inside the conservator is partially occupied by
the expanded oil. Consequently, corresponding quantity of air of that
space is pushed away through breather. On other hand, when load of
transformer decreases, the transformer is switched off and when the
ambient temperature decreases, the oil inside the transformer contracts.
CONSERVATOR
INSIDE VIEW OF A CONSERVATOR

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4) BUCHHOLZ RELAY- Buchholz relay in transformer is an oil
container housed the connecting pipe from main tank to conservator tank.
It has mainly two elements. The upper element consists of a float. The
float is attached to a hinge in such a way that it can move up and down
depending upon the oil level in the Buchholz relay Container. One
mercury switch is fixed on the float. The alignment of mercury switch
hence depends upon the position of the float.
The Buchholz relay working principle of is very simple. Buchholz relay
function is based on very simple mechanical phenomenon. It is
mechanically actuated. Whenever there will be a minor internal fault in
the transformer such as an insulation faults between turns, break down of
core of transformer, core heating, the transformer insulating oil will be
decomposed in different hydrocarbon gases, CO2 and CO. The gases
produced due to decomposition of transformer insulating oil will
accumulate in the upper part the Buchholz container which causes fall of
oil level in it. Fall of oil level means lowering the position of float and
thereby tilting the mercury switch. The contacts of this mercury switch
are closed and an alarm circuit energized. Sometime due to oil leakage on
the main tank air bubbles may be accumulated in the upper part the
Buchholz container which may also cause fall of oil level in it and alarm
circuit will be energized. By collecting the accumulated gases from the
gas release pockets on the top of the relay and by analyzing them one can
predict the type of fault in the transformer.

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TRANSFORMER NOISE (HUMMING NOISE)
Transformer noise is caused by a phenomenon which causes a piece of magnetic
sheet steel to extend itself when magnetized. When the magnetization is taken
away, it goes back to its original condition. This phenomenon is scientifically
referred to as magnetostriction. A transformer is magnetically excited by an
alternating voltage and current so that it becomes extended and contracted twice
during a full cycle of magnetization.
The magnetization of any given point on the sheet varies, so the extension and
contraction is not uniform. A transformer core is made from many sheets of special
steel to reduce losses and moderate the ensuing heating effect. The extensions and
contractions are taking place erratically all over a sheet and each sheet is behaving
erratically with respect to its neighbor. Applying voltage to a transformer produces
a magnetic flux, or magnetic lines of force in the core. The degree of flux
determines the amount of magnetostriction and hence, the noise level
TRANSFORMER
SOUND
CORE SOUND
MAGNETOSTRICTIVE
FORCES
MAGNETIC FORCES
LOAD SOUND
WINDINGS STRUCTURAL PARTS
TANK AND WALL
SHUNTS
SOUND GENERATED
BY COOLING
EQUIPMENTS
COOLING FANS AND
PUMPS

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SAFETY MEASURES
• Safety helmets
• Fire extinguishers
• Emergency Exit
• First Aid Box
• Shock proof circuit system
• Maintenance of machines at regular interval
• Proper circuit breakers to protect instruments
• Welding goggles should be used during welding
• Proper alarm system
• Safe distance from rolling parts of the machines
• Safety training & tips to employees
• Arrangements for sufficient and pure drinking water
• Healthy environment for all workers
• Proper lighting system
• Proper ventilation

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CONCLUSION
The first phase of in-plant training has proved to be fruitful. It provides
opportunity to experience the working environment of such huge plant
comprising high-tech machineries.
It provides an opportunity to learn how lean low technology used at
proper place and time can save a lot of time. The employees in the plant
helped a lot and shared useful knowledge.
In- plant training has allowed the student to get an exposure for the
practical implementation to theoretical fundamentals, which would be of
great use in coming future.

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REFERENCE
 Wikipedia
 www.scribd.com
 Pdf files on JSPL annual report
 http://indianpowersector.com/home/power-station/thermal-power-plant/
 http://www.jindalsteelpower.com/businesses/raigarh.html
 www.electrical4u.com
 www.slideshare.net
 www.ijareeie.com
 Wordpress