TRAINING

REPORT ON

DURGAPUR PROJECTS LIMITED

DURGAPUR,

(WEST BENGAL).

A Training Report Submitted

In Partial Fulfillment of the Requirementsfor the award of Degree of

Bachelor of TechnologyIn

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 22.2 Water Works 22.3 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 99.2 Magnetic Balance Test 99.3 Magnetizing Current Test 109.4 Dielectric Test 10

10.10.1 Axillary DC Control Power System Design of 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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INFRASTRUCTURELAND: 1910 acres comprising 1060 acres for plant 850 acres for township.

Water Works

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.

TRANSFORMERS

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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

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 TransformerIt 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 TransformersThese 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 alternatingelectriccurrents.

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 TransformersAn 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.

BUSBARS

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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 BREAKERSA 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 breakersRated 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 breakersWith 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 breakersA 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 breakersA 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.

ISOLATERS

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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.

INSULATORSAn 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.

RELAYS

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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.

PROTECTION OF SUBSTATION

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LIGHTNING ARRESTORSA 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 PROTECTIONTransformers 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.

Conservator and 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.

Conductors

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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)

S.No. Names Size(mm)*1. Rabbit 6/1/3.552. Panther 30/7/3.003. Zebra 54/7/3.004. Moose 54/7/3.53

*No. Of strands / No. Of steel Strands/diameter of strands

Aluminum Conductor Aluminum AlloyReinforced (ACAR)

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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.

Transformer Ratio 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 Test of Transformer

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 Test of 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 of Transformer

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 of DC Auxiliary System // Single-battery and charger application

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/

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