“THERMAL POWER PLANT”
ELECTRICAL & ELECTRONICS
DR. C.V. RAMAN INSTITUTE OF
SIPAT SUPER THERMAL POWER
CORP. (NTPC SIPAT)
MR. PRAVIN PATEL
(EEE 4 TH SEM)
This is to certify that the project report entitled as
NATIONAL THERMAL POWER PLANT has been done
by PRATIK GUPTA during his vocational training period
from 20-06-13 to 20-07-13 at “SIPAT SUPER THERMAL
POWER PROJECT” is a record of studies, site experience
and keen interest to the subject and analysis carried out by
him under my supervision and guidance. This is a part of
partial fulfilment of their vocational training programme.
Guided by:1. MR. SHALABH SAHRMA
3. MR. Dilip Khalatkar
4. MR. P.K. DAS
The training work has been carried out and the report
prepared by me during 20th June to 20th July 2013 under
the guidance of faculties ntpc ltd/sipat thermal power
plant and organised by employ development centre,
human resource development.
This is the original work carried out by me and not has
been taken from any other sources nor been submitted to
any institute or organisation as a fulfilment of any other
I hereby convey my deep and sincere gratitude in all humbleness to
5. MR. SHALABH SAHRMA
7. MR. Dilip Khalatkar
8. MR. P.K. DAS
Who provided me with an opportunity to learn under their
gracious guidance, meticulous care and throughout the training.
Their personal supervision and guidance has enabled me to
complete this Project. I also thankfully acknowledgement the
assistance received from MR PRAVIN PATEL and others for their
co-operation during the preparation of this project report. The
project report would not have been shaped in this form without
their encouragement and guidance.
Introduction of NTPC
Introduction about Project
Production of Electricity
Principal of Steam Power Plant
Coal Handling Plant
Coal Handling Plant Power Distribution
Demineral Plant(DM Plant)
Coal ,Water and Steam Cycle
H.T. Switch gear
L.T. Switch gear
Generators and Transformers
INTRODUCTION OF NTPC
India’s largest power company, NTPC was set up in 1975 to accelerate power
development in India. NTPC is emerging as a diversified power major with
presence in the entire value chain of the power generation business. Apart from
power generation, which is the mainstay of the company, NTPC has already
ventured into consultancy, power trading, ash utilization and coal mining. NTPC
ranked 337th in the ‘2012, Forbes Global 2000’ ranking of the World’s biggest
companies. NTPC became a Maharatna company in May, 2010, one of the only
The total installed capacity of the company is 41,184 MW (including JVs) with 16
coal based and 7 gas based stations, located across the country. In addition
under JVs, 7 stations are coal based & another station uses naptha/LNG as fuel
and 2 renewable energy projects. The company has set a target to have an
installed power generating capacity of 1,28,000 MW by the year 2032. The
capacity will have a diversified fuel mix comprising 56% coal, 16% Gas, 11%
Nuclear and 17% Renewable Energy Sources(RES) including hydro. By 2032,
non fossil fuel based generation capacity shall make up nearly 28% of NTPC’s
NTPC has been operating its plants at high efficiency levels. Although the
company has 17.75% of the total national capacity, it contributes 27.40% of
total power generation due to its focus on high efficiency.
In October 2004, NTPC launched its Initial Public Offering (IPO) consisting of
5.25% as fresh issue and 5.25% as offer for sale by Government of India. NTPC
thus became a listed company in November 2004 with the Government holding
89.5% of the equity share capital. In February 2010, the Shareholding of
Government of India was reduced from 89.5% to 84.5% through Further Public
Offer. The rest is held by Institutional Investors and the Public.
At NTPC, People before Plant Load Factor is the mantra that guides all HR related
policies. NTPC has been awarded No.1, Best Workplace in India among large
organizations and the best PSU for the year 2010, by the Great Places to Work
Institute, India Chapter in collaboration with The Economic Times.
The concept of Corporate Social Responsibility is deeply ingrained in NTPC's
culture. Through its expansive CSR initiatives, NTPC strives to develop mutual
trust with the communities that surround its power stations.
INTRODUCTION ABOUT PROJECT
Sipat Super Thermal Power Station is located at Sipat in Bilaspur district in state of Chhattisgarh.
The power plant is one of the coal based power plants of NTPC. The coal for the power plant is
sourced from Dipika Mines of South Eastern Coalfields Limited.
The project has an installed capacity of 2980 MW consisting of two stages, stage one which got
commissioned late was of 3 units of 660 MW each involving super-critical boilers technology and
stage two consisted of 2 units of 500 MW each.
Stage Unit Number Installed Capacity (MW) Date of Commissioning Status
2012 June 
Sipat' is a small developing town, approximately 22 kilometers away from Bilaspur, Chhattisgarh, the
second largest city in Chhattisgarh. It has been in news due to setup of new power plant by NTPC
Limited in that area. The project was started on 2001 by Indian former Prime Minister Mr. Atal Bihari
Vajpayee.NTPC Sipat has total installed capacity of 2980 MW.NTPC Sipat has two stages: Stage-I
comprises 3 units of 660MW each and Stage-II comprises 2 units of 500MW each. The thermal power
generation in NTPC sipat Stage-II is based on "Super Critical Boiler Technology" which is the
advanced technology in thermal power generation. NTPC Limited has helped this town in developing
by providing business prospective in that area and by providing education, healthcare facilities.
PRODUCTION OF ELECTRICITY
The means and steps involved in the production of electricity in a coal-fired power station are
The coal, brought to the station by train or other means, travels from the coal handling plant by
conveyer belt to the coal bunkers, from where it is fed to the pulverizing mills which grinds it as fine
as face powder. The finely powdered coal mixed with pre-heated air is then blown into the boiler by
fan called Primary Air Fan where it burns, more like a gas than as a solid in convectional domestic or
industrial grate, with additional amount of air called secondary air supplied by Forced Draft Fan. As
the coal has been grounded so finely the resultant ash is also a fine powder. Some of this ash binds
together to form lumps which fall into the ash pits at the bottom of the furnace. The water
quenched ash from the bottom of the furnace is conveyed to pits for subsequent disposal or sale.
Most of ash, still in fine particles form is carried out of the boiler to the precipitators as dust, where
it is trapped by electrodes charged with high voltage electricity. The dust is then conveyed by water
to disposal areas or to bunkers for sale while the cleaned flue gases pass on through ID Fan to be
discharged up the chimney.
Meanwhile the heat released from the coal has been absorbed by the many kilometres of tubing
which line the boiler walls. Inside the tubes is the boiler feed water which is transformed by the
heat into the steam at high pressure and temperature. The steam super-heated in further tubes
(Super Heater) passes to the turbine where it is discharged through the nozzles on the turbine
blades. Just the energy of the wind turns the sail of the wind-mill, so the energy of the steam,
striking the blades, makes the turbine rotate.
Coupled to the end of the turbine is the rotor of the generator – a large cylindrical magnet, so that
when the turbine rotates the rotor turns with it. The rotor is housed inside the stator having heavy
coils of copper bars in which electricity is produced through the movement of the magnetic field
created by the rotor. The electricity passes from the stator winding to the step-up transformer which
increases its voltage so that it can be transmitted efficiently over the power lines of the grid.
The steam which has given up its heat energy is changed back into water in the condenser so that it
is ready for re-use. The condenser contains many kilometres of tubing through which the colder is
constantly pumped. The steam passing around the tubes looses the heat and is rapidly changed back
to water. But the two lots of water (i.e. boiler feed water & cooling water) must NEVER MIX. The
cooling water is drawn from the river, but the boiler feed water must be absolutely pure, far purer
than the water we drink, if it is not to damage the boiler tubes. Chemistry at the power station is
largely the chemistry of water.
To condense the large quantities of steam, huge and continuous volume of cooling water is
essential. In most of the power stations the same water is to be used over and over again. So the
heat which the water extracts from the steam in the condenser is removed by pumping the water
out to the cooling towers. The cooling towers are simply concrete shells acting as huge chimneys
creating a draught (natural/mechanically assisted by fans) of air. The water is sprayed out at the top
of towers and as it falls into the pond beneath it is cooled by the upward draught of air. The cold
water in the pond is then circulated by pumps to the condensers. Inevitably, however, some of the
water is drawn upwards as vapours by the draught and it is this which forms the familiar white
clouds which emerge from the towers seen sometimes.
Why bother to change steam from the turbine back into water if it has to be heated up again
immediately? The answer lies in the law of physics which states that the boiling point of water is
related to pressure. The lower the pressure, the lower the temperature at which water boils. The
turbine designer want as low boiling point of water as possible because he can only utilize the
energy of the steam – when the steam changes back into water he can get NO more work out of it.
So a condenser is built, which by rapidly changing the steam back into water creates a vacuum. This
vacuum results in a much lower boiling point which, in turns, means he can continue getting work
out of the steam well below 100 degree Celsius at which it would normally change into water.
Principle of the Steam Power Plant
The working principle of a steam plant is based upon the Rankine cycle.
Generally steam is taken as the working medium due to its ability to be stable
and that it’s readily stable. The flow of steam in the plant can be very easily be
understood by the flow diagram of the plant. A graph plotted between the
temperature and the entropy would indicate the technical details of the
working by the rankine cycle. The entropy of a system can be understood as an
index of degradation of energy.
PLANT FLOW DIAGRAM
COAL HANDLING PLANT
Introduction: NTPC SIPAT gets its coal supply mainly from dipka mines. The coal being filled in the wagons of the
rail reaches plant. The purpose of this plant is to convey the coal to the bunker in the size not larger
than 20mm.It handles and transports the coal to the bunker from the wagons by passing through
various conveyors, transfer points, crusher houses, etc.
Type of unloading the coal: 1. Manual Unloading: -Previously, manpower was used for unloading the wagons. But it was very
time consuming and more workers were required for the job to be done.
2. Box in (using wagon tippler for unloading): -For this method, Indian Railway grants 10 hours for
unloading the 58 wagons. In this method, Wagons are separated and tippled by using wagon
tippler. The Beetle Feeder is used to move the wagon on wagon tippler. The coal from the
wagons gets accumulated in The Track Hopper. At this time; the size of the coal is approximately
3. BOBR: - Indian Railway grants only 2.5 hours for Unloading 58 BOBR wagons. This is an advanced
technology in which we use the compressor system.
In Bottom Open Bottom Release (BOBR) technology the wagons are opened from side. Pressure
is applied by the compressor to open the bottom gates of the wagon so that the coal gets
released over the track hopper and wagon get unloaded quickly.
Various equipment used in CHP: 1. WAGON TIPPLER: - The wagon tippler is a most important device in thermal power project. The
Wagon tippler turns back the wagon at 135-degree angle and the structure of the wagon tippler
is to be very heavy. Upper side of the wagon is fixed with the many angles for supporting the
wagon. When the wagon is fixed on the Platform then whole platform is turned back and the
coal fall down in the wagon tippler hopper. The unloading time of the Rack is 6hours
2. PADDLE FEEDER: - They have been installed on conveyors below the manual
hopper. There are 6 nos. of paddle feeders, 3 on each conveyer. 3 Paddle Feeders of each
conveyer move to and fro within a limiting range. The rotating part of the paddle feeder is called
as plough wheel. Plough wheel has 6 blades. By the rotation of the plough wheel, the coal of the
track hopper gets accumulated between the blades and is discharged on the conveyor below it.
3. VIBRATING FEEDER: They have been installed below the track hoppers of wagon tippler.
The coal is accumulated over the vibrating feeder so by giving vibrations to the vibrating feeder
we discharge the coal from track hopper to the conveyors. Their main purpose is to provide
uniform feeding on the conveyors. The vibrating feeders consist of a tray to which vibrator body
is fixed on the rear end.
4. TRANSFER POINTS: -Transfer Point is provided with flap gate and Conveyer. In transfer Point the
coal is transferred from one conveyer to other conveyer.
5. PRIMARY CRUSHER (ROTARY BREAKER): - In Primary Crusher House, the coal breaks in Rotary
Breaker. Here the coal comes from the Transfer point; breaks here and the stone fall down to a
separate place. Coal is converted from 300mm to 150mm size.
Part of the Primary Crusher House – a- Rotary Breaker b- Belt Feeder
6. SECONDARY CRUSHER (RING GRANULATOR): In Secondary crusher House first the
magnetic part separate from the coal and then feed to the Secondary Crusher. This Crusher
breaks the coal in 20mm size and coal is sent to the Flap Gate and then feeded to the conveyer.
The Secondary crusher is hammer type. H.T. motor are used for breaking of the coal.
Specifications are 700KW 6.6KVMotor.
7. CROSS BELT MAGNETIC SEPRATORS: They will remove the ferrous particles, which passes
along with the coal. It consists of electromagnet around which a belt is moving. It is suspended
from top, perpendicular to the conveyor belt at certain height. Whenever any iron particle
passes below the CBMS, it is attracted by the magnet and stick to the cross belt below it. The
CBMS capacity is of 50kg.
8. METAL DETECTOR: -The purpose of installation is to detect any metallic piece passing through
the conveyor. Whenever the pieces pass below the search coil of the metal detector, it gives the
trip command to the conveyor. Simultaneously, sand bag marker will fall on the conveyor belt so
that the metal can be searched easily and removed.
STACKER/RECLAIMER: -It is a very important device. The whole Structure of it is called Super
Structure. It stacks the excessive coal and reclaims the coal on its requirement. It is a two-way
10. TRANSFER TOWER: -Here the coal is send to the Tipper. Transfer Tower is provided with a coal
11. TIPPER: - The Tipper is a three-way device to feed the coal in Bunker. It is moveable device. It
is move on its track.
12. BUNKER: - Here the coal is collected from the tipper and stored. The capacity of the bunker for
Stage-I is 4800MT & Stage-II is 8700MT
DEMINERAL (DM) PLANT
INTRODUCTION: -Water is required in plant for many purposes like for formation of steam, for removal of ash, for
safety during fire, etc. But the water required for the formation of steam should be perfectly devoid
of minerals because if minerals are present in the steam and the steam strike the blades of the
turbine, then due to being high in pressure it produces scars or holes on the turbine blades.
PURIFICATION OF WATER: Water is purified in DM plant through a chain of processes as under: -1.
Carbon filter – Water taken from the river is first sent to the carbon filter for the removal of
carbon contents in the water.
Strong acid cation exchanger – After passing through the carbon filter, water is sent to the
strong acid cation exchanger, which is filled with the concentrated HCL. The acid produces
anions, which get combined with the cations present in the water.
Strong base anion exchanger – After that the water is sent to the strong base anion
exchanger, which is filled with the concentrated NaOH.The base produces cations, which get
combined with the anions present in the water.
Mixed bed exchanger – And then water is sent to the chamber of mixed bed exchanger
where the remaining ions are removed. This is the last stage of purification.
COAL, WATER & STEAM CYCLES
R.C Feeder: It is an induction motor driven device, which determine the Quantity of coal
enter in the pulverize mill.
Pulverization mill: Pulverization means exposing a large surface area to the action of oxygen
.Two Types of mill are used in the plant.
Ball mail: A ball mill operates normally under suction. A large drum partly filled with steel
balls, is used in this mill .The drum is rotated slowly while coal is fed in to it .The ball
pulverize the coal by crushing.
Contact mail: This mill uses impact principle. All the grinding elements and the primary air
fan are mounted on a single shaft. The flow of air carries coal to the primary stage where it is
reduced to a fine granular state by impact with a series of hammers.
Boiler Feed Pump
High Pressure Heater 5, 6
Low Pressure Heater 1, 2, 3
Feed Regulating station
1. DERATER: Feed strong tank of water. To produce sufficient pressure before feeding to B.F.D.
.Filter the harmful chemicals.
2. FEED REGULATING STATIONS: Control the quantity of water in to boiler drum.
3. ECONOMISER: Flux gases coming out of the boilers carry lot of heat. An economizer extracts a
part of this heat from the flue gases and uses it for heating the feed water.
4.DRAFTS SYSTEM: In forced draft system the fan is installed near the base of the boiler furnace.
This fan forces air through the furnace, economizer, air preheater and chimney. In an induced draft
system, the fan is installed near the base of Chimney.
Boiler Drum (Steam chamber)
BOILER: Boiler drum consists two chambers water chamber, steam chamber. Before
Entering in super heater the steam is going in to boiler drum, where the boiler drum filtered
the moisture and stored in to water chamber.
SUPER HEATER: The function of super heater is to remove the last traces of moisture from
the saturated steam leaving the tube boiler. The temperature is approx.530 oC.
TURBINE: Steam turbine converts the heat energy in to mechanical energy and drives the
alternator. The velocity attained during expansions depends on initial and final heat content
of the steam. Turbine having number of stages in which the pressure drops takes place.
OPERATIONG VOLTAGE - 6.6KV
For low voltage circuits fuses may be used to isolate the faulty circuit. For voltage higher than 3.3 kV
isolation is achieved by circuit breaker.
Requirement of circuit breaker:
After occurrence of fault the switchgears must isolate the faulty circuit as quickly as possible
i.e. keeping the delay to minimum.
It should not operate when an over current flows under healthy condition.
Basic principal of operation of circuit breaker:
Circuit breaker consists of a fix contact and sliding contact into which moves a moving contact. The
end of moving contact it attached to a handle that can be manually operated or may operate
automatically with the help of mechanism that has a trip coil energized by secondary of CT. Under
normal condition the secondary of CT is not energized sufficiently to trip the coil but under false
condition the coil is energized fully to operate the trip coil and the circuit breaker is operated.
MOCB (Minimum oil circuit breaker)
SF6 (Sulphur hexafluoride circuit breaker)
Here oil and SF6 are used to quench the arc.
L.T SWITCH GEAR
OPERATING VOLTAGE- 415VOLT
TYPES OF CIRCUIT BREAKER: - Air break circuit breaker
Air brake circuit breaker:
The arc interruption process of air- based circuit breaker is based on the natural deionization of
gases by cooling action. The arc is resilient and can be stretched, and has a resistance, which can be
increased both by length and confinement. Hence the arc resistance is increased by stretching the
arc and as the resistance increases to higher value, the short circuit current drops to zero and arc is
Reducing the phase difference between the system voltage and the short circuit current assure that
when the are current is interrupt at its zero value, the recovery voltage has very low value at its not
allowed to reach 2-3 times the value of the system peak voltage, a phenomenon that occurs in most
cases, when arc current is interrupted at low power factor.
GENERATORS AND TRANSFORMERS
INTRODUCTIONThe auxiliaries in a plant can be divided into two categories1.
URGENT AUXILIARIES- the urgent auxiliaries are those, which are associated with running of
SERVICE AUXILIARIES- the service auxiliaries are those whose loss would not affect output.
GENERATOR SPECIFICATIONSTURBO GENERATOR (gen1, gen2)
Volts of stator
Amperes of stator
Volts of rotor
Amperes of rotor
Water (stator)& hydrogen (rotor)
STATIC EXCITATION SYSTEM-The generators in stage -1(u-1&u-2) have this excitation
system. Static excitation system has slip ring and carbon brush arrangement. It consists of
step down transformer, converter and AVR (automatic voltage regulator).
BRUSHLESS EXCITATION SYSTEM –The generators in stage -2(U-3, U-4& &U- 5) have this
excitation system. It has two exciters, one is main exciter and other is pilot exciter.
STATOR PROTECTION- The neutral of star connected winding is connected to primary of
neutral grounding transformer, so that earth fault current is limited by over voltage relay.
DIFFERENTIAL PROTECTION- In case of phase-to-phase fault generator is protected by
longitudinal differential relay.
ROTOR PROTECTION- Rotor winding may be damaged by earth faults or open circuits. The
field is biased by a dc voltage, which causes current to flow through the relay for an earth
fault anywhere on the field system.
OVER SPEED PROTECTION – Mechanically over speed device that is usually in the form of
centrifugally operated rings mounted on the rotor shaft, which fly out and close the stop
valves if the speed of the set increase more than 10%.
OVER VOLTAGE PROTECTION – It is provided with an over voltage relay. The relay is usually
induction pattern. The relay open the main circuit break and the field switch if the over
SEAL OIL SYSTEM – Hydrogen in the generator is under very high pressure. There is a
possibility of this hydrogen to come out of gaps, which is very hazardous. So, seal oil is used
to seal the gaps so that hydrogen doesn’t come out.
LUBRICATION OIL SYSTEM –Turbine lubrication-oil system seeks to provide proper
lubrication of turbo generator bearings and operation of barring gear. Pumps are used to
circulate lubrication-oil inside the generator. The oil of the lubrication and the governing
system is cooled in the oil coolers. The cooling medium for these coolers is circulating water.
TYPE PF TRANSFORMERS—
UNIT AUXILIARY TRANSFORMER: --This is a step down transformer. The primary receives
from generator and secondary supplies a 6.6 KV bus. This is oil cooled. These are 8 in
NEUTRAL GROUNDED TRANSFORMER: --This transformer is connected with supply coming
out of UAT in stage-2. This is used to ground the excess voltage if occurs in the secondary of
UAT in spite of rated voltage.
GENRATOR TRANSFORMER: -- This is a step up transformer. This supply gets its primary
Supply from generator and its secondary supplies the switchyard from where it is
transmitted to grid. This transformer is oil cooled. The primary of this transformer is
connected in star. The secondary is connected in delta. These are four in number.
STATION TRANSFORMER: --This transformer has almost the same rating as the generator
transformer. Its primary is connected in delta and secondary in star. It is a step down
transformer. These are 4 in number.
Generator transformer (GT-1 & GT-2)
Type of cooling
Rated HV and IV (MVA)
Rated LV (MVA)
No Load Voltage HV (KV)
No Load Voltage IV (KV)
No Load Voltage LV (KV)
Line current HV (Amps)
Line current IV (Amps)
Line current LV (Amps)
Temp rise coil oC
Temp rise winding oC
Neural grounded transformer (NGT)
Type of cooling
No load voltage HV (volts)
No load voltage LV (volts)
Line current HV (Amps)
Line current LV (Amps)
Temp rise oil oC
Temp rise winding
Type of Cooling
No Load Voltage HV (volts)
No Load Voltage LV (volts)
Line Current HV (Amps)
Line Current LV (Amps)
Temp rise oil oC
Temp rise winding oC
DC system is generally used for control and protection operation, as AC supply is not fully
dependable. To maintain constant supply in case of power failure we use DC supply.
DC system consists of a battery charger. These are the mode of energy storage.
The battery charging equipment comprises of trickle charger, quick charger, battery panel, main
distribution board and switch control and signaling board.
In battery PbO2 used as positive plate and Pb as negative plate.
Battery charger normally operates in two modes.
Float charging: It is constant voltage mode and works as a trickle charger.
Boost charging: It is constant current mode and works as a quick charger.
This charger is fed from three-phase ac supply and gives a dc-stabilized output at rated full load
current. The variation of the dc output voltage is limited to +/- 1% for 0 to 100% load variation and
simultaneously ac voltage variation of +/- 10% of frequency variation of +/- 5% from 50 Hz.
The rectification is obtained through full bridge controlled silicon rectifier. Stack comprising of these
SCR and three diode with the surge suppression RC network connected across each SCR and diode.
As we know that electrical energy can’t be stored like cells, so what we generate should be
consumed instantaneously. But as the load is not constants therefore we generate electricity
according to need i.e. the generation depends upon load. The yard is the places from where the
electricity is send outside. It has both outdoor and indoor equipments.
SINGLE LINE DIAGRAM OF 220KV SWITCH YARD-
CAPACITOR VOLTAGE TRANSFORMER
The code for circuit breaker is 52. An electric power system needs some form of switchgear
in order to operate it safely & efficiently under both normal and abnormal conditions.
Circuit breaker is an arrangement by which we can break the circuit or flow of current. A circuit
breaker in station serves the same purpose as switch but it has many added and complex features.
The basic construction of any circuit breaker requires the separation of contact in an insulating fluid
that servers two functions:
It extinguishes the arc drawn between the contacts when circuit breaker opens.
It provides adequate insulation between the contacts and from each contact to earth.
The insulating fluids commonly used in circuit breakers are:
Oil which produces hydrogen for arc excitation.
Ultra high vacuum
The Specifications of the circuit breaker used are:
CROMPTON GREAVES LTD.
AIR BLAST CIRCUITREAKER
RATED LIGHTING IMPULSE
25 - 40KA
RATED NORMAL CURRENT
2000 A TO 4000 A
RATED CLOSING VOLTAGE
220 V DC
RATED OPENING VOLTAGE
220 V DC
It saves the transformer and reactor from over voltage and over currents. We have to use the
lightning arrester both in primary and secondary of transformer and in reactors.
A meter is provided which indicates the surface leakage and internal grading current of arrester.
Green – arrester is healthy
Red – arrester is defective.
In case of red we first de-energize the arrester and then do the operation.
AIR BREAK EARTHING SWITCH:
The code of earthling switch is 5, 6, 7.The work of this equipment comes into picture when we want
to shut down the supply for maintenance purpose. This help to neutralize the system from induced
voltage from extra high voltage. This induced power is up to 2KV in case of 400 KV lines.
The specification of earthling switch is:
S & S POWER
MOTOR VOLT (AC)
CONTROL VOLT (DC)
Bus bars generally are of high conductive aluminum conforming to IS-5082 or copper of
adequate cross section .Bus bar located in air –insulated enclosures & segregated from all other
components .Bus bar is preferably cover with polyurethane.
Current Transformer (CT):
A current transformer is a type of instrument transformer designed to provide a current in its
secondary winding proportional to the alternating current flowing in its primary
Current Transformer Diagram
They are commonly used in metering and protective relaying in the electrical power
industry where they facilitate the safe measurement of large currents, often in the
presence of high voltages.
The current transformer safely isolates measurement and control circuitry from the
high voltages typically present on the circuit being measured.
Current transformers are used extensively for measuring current and monitoring the
operation of the power grid. The CT is typically described by its current ratio from
primary to secondary. Often, multiple CTs are installed as a "stack" for various uses
(for example, protection devices and revenue metering may use separate CTs).
Similarly potential transformers are used for measuring voltage and monitoring the
operation of the power grid.
Capacitive Voltage Transformer (CVT):
A capacitor voltage transformer (CVT) is a transformer used in power systems to step-down extra
high voltage signals and provide low voltage signals either for measurement or to operate a
protective relay. In its most basic form the device consists of three parts: two capacitors across
which the voltage signal is split, an inductive element used to tune the device to the supply
frequency and a transformer used to isolate and further step-down the voltage for the
instrumentation or protective relay as shown in figure below.
The device has at least four terminals, a high-voltage terminal for connection to the high voltage
signal, a ground terminal and at least one set of secondary terminals for connection to the
instrumentation or protective relay. CVTs are typically single-phase devices used for measuring
voltages in excess of one hundred kilovolts where the use of voltage transformers would be
uneconomical. In practice the first capacitor, C1, is often replaced by a stack of capacitors connected
in series.This results in a large voltage drop across the stack of capacitors that replaced the first
capacitor and a comparatively small voltage drop across the second capacitor C2, and hence the
On completion of my vocational training at Feroze Gandhi Unchahar Thermal
Power Project, Unchahar I have come to know about how the very necessity of
our lives nowadays i.e., electricity is generated. What all processes are needed
to generate and run the plant on a 24x7 basis.
NTPC Unchahar is one the plants in India to be under highest load factor
for the maximum duration of time and that to operating at highest plant
efficiencies. This plant is an example in terms of working efficiency and
management of resources to all other thermal plants in our country. The
operating plf of the NTPC as compared to the rest of country is the highest
with 87.54% the highest since its inception.
The training gave me an opportunity to clear my concepts from practical point
of view with the availability of machinery of such large rating.