This document provides a training report on Durgapur Projects Limited (DPL) in Durgapur, West Bengal. It includes an introduction to DPL, which was established in 1958 and consists of coke oven batteries, by-product plant, and water works. The report then describes the infrastructure at DPL including land area and water works. It discusses the different types of substations observed during training, including 11kV, 33kV, and 132kV switching substations. The report also summarizes key components of substations like transformers, busbars, circuit breakers, isolators, insulators, and relays. It provides details on different types of each component.

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TRAINING
REPORT ON
DURGAPUR PROJECTS LIMITED
DURGAPUR,
(WEST BENGAL).
A
Training Report Submitted
In Partial Fulfillment of the Requirements
for the award of Degree of
Bachelor of Technology
In
Electrical Engineering
By
AYON KUMAR GON ARINDAM DAS
(12001614122) (12001613024)
PALLABI PANDIT SUBRATA DAS
(12001614130) (120016141309)
DR. B C ROY ENGINEERING COLLEGE,DURGAPUR

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Table of contents
ACKNOWLEDGEMENT i
1. Introduction 1
1.1 About DPL, Durgapur. 1
2.
2.1 Infrastructure 2
2.2 Water Works 2
2.3 Substations 2
3. Transformers 3
3.1 Types of Transformers 3
3.1.1 Power transformer 3
3.1.2 Instrument transformer 3
3.1.3 Autotransformer 3
4. Busbars, Circuit Breakers 4
4.1 Oil circuit breaker 4
4.2 Air blast circuit breaker 4
4.3 Sulphur hexafluoride circuit breaker (SF6)circuit breaker 4
4.4 Vacuum circuit breaker 4
5. Isolators, Insulators 5
5.1 Types of Insulators 5
5.1.1 Pin type Insulators 5
5.1.2 Suspension type Insulators 5
5.1.3 Strain type Insulators 5
5.1.4 Shackle type Insulators 5

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6. Relay 6
6.1 Relay 6
6.2 Relays used in control panel of substation 6
6.2.1 Differential relay 6
6.2.2 Over current relay 6
6.2.3 Earth Fault relay 6
6.2.4 Tripping relay 6
6.2.5 Auxiliary relay 6
7. Protection of substation 7
7.1 Transformer protection (Lightning Arrester) 7
7.2 Buchholz Relay 7
7.3 Conservation and breather 7
7.4 Marshalling box 7
7.5 Fuse 7
7.6 Bus Coupler 7
8. Conductors 8
8.1 AAC 8
8.2 AAAC 8
8.3 ACSR(Types used) 8
8.4 ACAR 8
9. Transformer Testing 9-11
9.1 Transformer Ratio Test 9
9.2 Magnetic Balance Test 9
9.3 Magnetizing Current Test 10
9.4 Dielectric Test 10
10.
10.1 Axillary DC Control Power System Designof Substation 12

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10.2 Elements of DC Axillary Supply 12
11. 11kV Switching Substation at Water Works 13
12. 33kV Switching Substation at City Centre 14
13. 132kV Switching Substation at A-B Zone, DPL 15
14. Conclusion 16
References 17

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ACKNOWLEDGEMENT
The project has been prepared based on the vocational training
undergone in a highly esteemed organization of Eastern region, a
pioneer in Generation, Transmission & Distribution of power, one of the
most technically advanced & largest thermal power stations in West
Bengal, the Durgapur Project Limited (DPL), Durgapur. We would like
to express our heartfelt gratitude to the authorities of DPL and Dr. B C
Roy Engineering College for providing us such an opportunity to
undergo training in the thermal power plant of DPL. We would also
thank its esteemed engineers for the plethora of knowledge and the
experience they have shared with us during the training period.
We would like to give special thanks to Mr. B K Lal (training co-
ordinator) for giving us the chance to be a trainee in DPL.
Last but not the least we would like to thank THE ALMIGHTY GOD
without whom this would not have been dreamt of.

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INTRODUCTION
The DURGAPUR PROJECT LIMITED (DPL) was established in 1958
by Dr. Bidhan Chandra Roy. It consists of coke oven batteries, by
product plant, and water works. It is under the administrative control of
the Government of West Bengal.
DPL is the first undertaking of the state government which has been
engaged in development of infrastructure for industries and was given
the stature of industries. It has helped in development of various large,
medium and small scale industry in and around Durgapur.
It produces coke oven gas, supply water and electricity. DPL’s coke
oven complex is India’s largest merchant cookery producing coke of
global quality. The plant has rail and linking with Kolkata, Siliguri and
Dhanbad and sea port at an elevation 73m above sea level.
Our interest is regarding the transmission and distribution of power from
DPL through its various switching stations.

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INFRASTRUCTURE
LAND: 1910 acres comprising 1060 acres for plant 850 acres for township.
WaterWorks
Originally commissioned with a capacity of MGD in 1960, the water works was expanded up to
a capacity of 41 MSD of water treatment of DVC for use of company’s plant, township and other
industries and domestic consumers.
SUBSTATIONS
A substation is a part of an electrical generation, transmission and distribution system.
Substations transform voltage from high too low, or the reverse, or perform any of several other
important functions. Between the generating station and consumer, electric power may flow
through several substations at different voltage levels. Substations may be owned and operated
by an electrical utility, or may be owned by a large industrial or commercial customer.A
substation may include transformers to change voltage levels between high transmission voltages
and lower distribution voltages, or at the interconnection of two different transmission voltages.
The substations we observed during our Industrial Training at DPL, Durgapur were: -
 11kV Switching station at Water Works at DPL.
 33kV Switching Station at City Centre.
 132kV Switching Station at DPL.
Unit No Year of commissioning Present capacity Renovated capacity
I. 10.08.60 30MW Scrap
II. 10.06.60 30MW Scrap
III. 23.06.64 70MW Decommissioned
IV. 29.06.64 70MW Decommissioned
V. 04.07.66 77MW Decommissioned
VI. 01.01.87 110MW 110MW
VII. 01.03.08 300MW 300MW
VIII. 01.10.14 250MW 250MW

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TRANSFORMERS
Transformer is a static machine, which transforms the potential of alternating current at same
frequency. It means the transformer transforms the low voltage into high voltage & high voltage
to low voltage at same frequency. It works on the principle of static induction principle.
TYPES OF TRANSFORMERS
1. Power Transformer
It is used for the transmission purpose at heavy load, high
voltage greater than 33 KV & 100% efficiencies. It also having
a big in size as compare to distribution transformer, it used
in generating station and Transmission substation at high
insulation level.
2. Instrument Transformers
These transformers are used for the measurement purposes at that points where standard
voltmeters and ammeters cannot be used. They are of two types: -
a) CURRENT TRANSFORMER
A current transformer (CT) is used for
measurement of alternating
electriccurrents.
b) POTENTIAL OR VOLTAGE TRANSFORMER
Voltage transformers (VT) (also called potential
transformers (PT)) are a parallel connected type
of instrument transformer, used for metering and
protection in high-voltage circuits or phasor phase
shift isolation.
3. Auto Transformers
An autotransformer is an electrical transformer with only
one winding. The "auto" prefix refers to the single coil acting
on itself and not to any kind of automatic mechanism. In an
autotransformer, portions of the same winding act as both
the primary and secondary sides of the transformer.

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BUSBARS
When numbers of generators or feeders operating at the same voltage have to be directly
connected electrically, bus bar is used as the common electrical component. Bus bars are made
up of copper rods operate at constant voltage. The following are the important bus bars
arrangements used at substations:
 Single bus bar system
 Single bus bar system with section allocation.
 Duplicate bus bar system
CIRCUIT BREAKERS
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. There are different types of circuit breakers which are: -
1. Air circuit breakers
Rated current up to 6,300 A and higher for generator circuit
breakers. Trip characteristics are often fully adjustable
including configurable trip thresholds and delays.
2. Vacuum circuit breakers
With rated current up to 6,300 A, and higher for generator circuit
breakers. These breakers interrupt the current by creating and
extinguishing the arc in a vacuum container.
3. Oil circuit breakers
A high-voltage circuit breaker in which the arc is drawn in oil to
dissipate the heat and extinguish the arc; the intense heat of the arc
decomposes the oil.
4. Sulfur hexafluoride (Sf6) high-voltage circuit breakers
A sulfur hexafluoride circuit breaker uses contacts surrounded by
sulfur hexafluoride gas to quench the arc. They are most often used
for transmission-level voltages and may be incorporated into
compact gas-insulated switchgear.

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ISOLATERS
In electrical engineering, a disconnector, disconnect switch or isolator
switch is used to ensure that an electrical circuit iscompletely
de-energized for service or maintenance. Such switches are often found
in electrical distribution and industrial applications, where machinery must
have its source of driving power removed for adjustment or repair.
INSULATORS
An electrical insulator is a material whose internal electric charges do not flow freely, and
therefore make it very hard to conduct an electric current under the influence of an electric field.
The insulator serves two purposes. They support the conductors (bus bar) and confine the current
to the conductors. Different types of insulator are: -
 Pin type insulator
As the name suggests, the pin type insulator is mounted on a pin on the
cross-arm on the pole. There is a groove on the upper end of the insulator.
 Suspension insulator
For voltages greater than 33 kV, it is a usual practice to use
suspension type insulators shown in Figure.
 Strain insulator
A dead end or anchor pole or tower is used where a straight section of
line ends, or angles off in another direction. These poles must
withstand the lateral (horizontal) tension of the long straight section
of wire. In order to support this lateral load, strain insulators are used.
For low voltage lines (less than 11 kV),
 Shackle insulator
In early days, the shackle insulators were used as strain insulators.

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RELAYS
In a power system it is inevitable that immediately or later some failure does occur somewhere in
the system. When a failure occurs on any part of the system, it must be quickly detected and
disconnected from the system. Rapid disconnection of faulted apparatus limits the amount of
damage to it and prevents the effects of fault from spreading into the system. For high voltage
circuits relays are employed to serve the desired function of automatic protective gear. The
relays detect the fault and supply the information to the circuit breaker.
Relay works on two main operating principles: -
 Electromagnetic Attraction
 Electromagnetic Induction
RELAY USED IN CONTROLLING PANEL OF SUBSTATION
 Differential Relay
A differential relay is one that operates when vector difference of the
two or more electrical quantities exceeds a predetermined value.
 Over Current Relay
This type of relay works when current in the circuit exceeds the
predetermined value.
 Earth Fault Relay
This type of relay sense the fault between the lines and the earth.
It checks the vector sum of all the line currents. If it is not equal
to zero, it trips.
 Tripping Relay
This type of relay is in the conjunction with main relay. When main
relay sense any fault in the system, it immediately operates the trip
relay to disconnect the faulty section from the section.
 Auxiliary Relay
An auxiliary relay is used to indicate the fault by glowing bulb
or showing various flags.

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PROTECTION OF SUBSTATION
LIGHTNING ARRESTORS
A lightning arrestor is a device used in power systems and telecommunications systems to
protect the insulation and conductors of the system from the damaging effects of lightning.
TRANSFORMER PROTECTION
Transformers are totally enclosed static devices and generally oil immersed chances of fault
occurring on them are very easy rare, however the consequences of even a rare fault may be very
serious unless the transformer is quickly disconnected from the system. This provides adequate
automatic protection for transformers against possible faults. Various protection methods used
for transformers are: -
 Buchholz Relay
Buchholz relay is a safety device mounted on some oil-filled power
transformers and reactors, equipped with an external overhead oil
reservoir called a conservator. The Buchholz Relay is used as a
protective device sensitive to the effects of dielectric failure inside
the equipment.
 Conservatorand Breather
A conservator is used to maintain the oil level up too predetermined
value in the transformer main tank by placing it above the level of
the top of the tank. Breather is connected to conservator tank for the
purpose of extracting moisture as it spoils the insulating properties
of the oil.
 Marshalling box
It has two meter which indicate the temperature of the oil and
winding of main tank.
 FUSE:
A fuse is a short piece of wire or thin strip which melts when
excessive current through it for sufficient time.
 BUS COUPLER:
The bus coupler consists of circuit breaker and isolator.

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Conductors
In physics and electrical engineering, a conductor is an object or type of material which permits
the flow of electric charges in one or more directions.
All Aluminum Conductors (AAC)
All Aluminum-Alloy Conductor (AAAC)
Aluminum Conductor Steel Reinforced
(ACSR)
Names of ASCRs
*No. Of strands / No. Of steel Strands/diameter of strands
Aluminum Conductor Aluminum Alloy
Reinforced (ACAR)
S.No. Names Size(mm)*
1. Rabbit 6/1/3.55
2. Panther 30/7/3.00
3. Zebra 54/7/3.00
4. Moose 54/7/3.53

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Transformer Testing
For confirming the specifications and performances of an electrical power transformer it has to
go through numbers of testing procedures. The transformer testing performed before
commissioning the transformer at site is called pre-commissioning test of transformer. These
tests are done to assess the condition of transformer after installation and compare the test results
of all the low voltage tests with the factory test reports.
TransformerRatio Test
The performance of a transformer largely depends upon perfection of specific turns or voltage
ratio of transformer. So transformer ratio test is an essential type test of transformer. The
procedure of transformer ratio test is simple. We just apply three phase 415 V supply to HV
winding, with keeping LV winding open. The we measure the induced voltages at HV and LV
terminals of transformer to find out actual voltage ratio of transformer. We repeat the test for all
tap position separately.
Magnetic Balance TestofTransformer
Magnetic balance test of transformer is conducted only on three phase transformers to check the
imbalance in the magnetic circuit.
There are three limbs side by side in a core of transformer. One phase winding is wound in one
limb. The voltage induced in different phases depends upon the respective position of the limb in
the core. The voltage induced in different phases of transformer in respect to neutral terminals
given in the table below.
Magnetizing Current Testof Transformer
Magnetizing current test of transformer is performed to locate defects in the magnetic core
structure, shifting of windings, failure in turn to turn insulation or problem in tap changers. These
conditions change the effective reluctance of the magnetic circuit, thus affecting the current
required to establish flux in the core.
Generally, there are two similar higher readings on two outer limb phases on transformer core
and one lower reading on the centre limb phase, in case of three phase transformers. An
agreement to within 30% of the measured exciting current with the previous test is usually
considered satisfactory.
Caution: This magnetizing current test of transformer is to be carried out before DC
resistance measurement.

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Dielectric Tests ofTransformer
Dielectric tests of transformer are one kind of insulation test. This test is performed to ensure the
expected over all insulation strength of transformer. There are several test performed to ensure
the required quality of transformer insulation, dielectric test is one of them. Dielectric tests of
transformer are performed in two different steps, first one called Separate source voltage
withstand test of transformer, where a single phase power frequency voltage of prescribed level,
is applied on transformer winding under test for 60 seconds while the other windings and tank
are connected to the earth and it is observed that whether any failure of insulation occurs or not
during the test. Second one is induced voltage test of Transformer where, three phase voltage,
twice of rated secondary voltage is applied to the secondary winding for 60 second by keeping
the primary of the transformer open circuited. The frequency of the applied voltage should be
double of power frequency too. Here also if no failure of insulation, the test is successful. In
addition to dielectric tests of transformer there are other type test for checking insulation of
transformer, such as lightning impulse test, switching impulse test and partial discharge test.

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Auxiliary DC Control Power System Design for Substations
The most critical component of a protection, control and
monitoring (PCM) system is the auxiliary dc control power
system. Failure of the dc control power can render fault
detection devices unable to detect faults, breakers unable
to trip for faults, local and remote indication too become
inoperable, etc. In many cases, the dc system is not redundant,
which makes reliability an extremely important consideration
in the overall design.
.
Elements ofDC Auxiliary System //Single-battery and chargerapplication
The main components of the system are battery, charger and
distribution switchboard including the DC system monitoring
relay a typical installation, especially with batteries of
considerable size, the batteries are installed in a separate
battery room. The ventilation of the battery room shall be
adequate, considering the type and size of the battery.
Auxiliary power supply switchboard

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1. 11kV Switching Substation at Water Works, DPL
To supply industrial and drinking water to the residents of DPL township, the company
maintains its captive water storage facility. It has its own water treatment plant. While
water pumping capacity remains at 35 million gallons per day (MGD), the water
treatment capacity has been augmented by 6 MGD to 41 MGD. It also houses a 11kV
Switching substation alongside a transformer workshop.
The single line diagram of the Substation is as: -

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2. 33kV Switching Substation at City Centre.
Located near to the City Centre Bus Stand, the Switching Substation supplies power to
Junction Mall, Webel, Suhatta, SAIL, and Village nearby. It converts 33kV to 11kV or
directly switches the 33kV supply line coming from two feeder.
The Single Line Diagram of the Substation is as: -

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3. 132kV Switching Substation at A-B Zone, DPL
Located alongside DPL gate no.-1, the Switching Substation receives two feeder lines
directly from DPL. The Single Line Diagram of the substation is as: -

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CONCLUSION
Now from this report we can conclude that electricity plays an important role in our life.
We are made aware of how the transmission of electricity is done. We too came to know about
the various parts of the Substation system.
The Durgapur Projects Limited has got radio communication in microwave range in
order to transmit and receive data with various Substations in Durgapur to get reliable
transmission and distribution of electricity.

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References
1. www.yahooanswers.com
2. www.britannica.com
3. www.webopedia.com
4. www.encyclopedia.com
5. www.worldbook.com
6. www.encyclopediadramatica.com/