SUMMER TRAINING REPORT

ON

MAINTENCE SERVICE SHOP TRACTION ASSEMBLY SHOP

ELECTRICAL LAB TTC and COLONY

Submitted in partial fulfillment of the

Requirement for the award of the

Degree of

BACHELOR OF TECHNOLOGY

IN

(Electronics & Communication Engineering)

BY

Rahul Kumar

Under the Guidance of

AMIT SINGH

Ashoka Institute of Technology & Management, Pahariya, Sarnath, Varanasi

U.P. Technical University

SEPTEMBER 2015

2

CERTIFICATE

This is to certify that Training Report entitled, “MAINTENCE SERVICE SHOP, TRAC-

TION ASSEMBLY SHOP , ELECTRICAL LAB TTC and COLONY ” which is submitted

by Rahul kumar in partial fulfillment of the requirement for the award of degree B. Tech. in

Department of Electronics & Communication Engineering of U. P. Technical University, is

a record of the candidate own work carried out by him under my supervision. The matter

embodied in this summer training is original and has not been submitted for the award of

B.Tech degree.

(Anupam Kumar)

Date : HOD of Department of Electronics & Communication Engg

Objective of the project is satisfactory / unsatisfactory

Examiner- 1 Examiner-11

3

CERTIFICATE

This is to certify that Rahul Kumar bearing Registration no. GL21216843 has completed ob-

jective formulation of training titled, “MAINTENCE SERVICE SHOP, TRACTION AS-

SEMBLY SHOP, ELECTRICAL LAB TTC and COLONY ” under my guidance and su-

pervision. To the best of my knowledge, the present work is the result of her original investiga-

tion and study. No part of the summer training is has ever been submitted for any other degree

at any University.

The industrial training is fit for submission and the partial fulfillment of the condi-

tions for the award of Bachelor of Technology.

( AMIT SINGH)

Signature and Name of the Research Supervisor

Designation

Ashoka Institute of Technology & Management

Pahariya, Sarnath , Varanasi Utter Pradesh

U.P. Technical University, Lucknow

Date:

4

DECLARATION

I Rahul Kumar, Roll No- GL21216843, student of B.Tech. (Electronics & Communication En-

gineering ) 4th year of Ashoka Institute Of Technology And Management, Varanasi, hereby

declare that my training report on “ DIESEL LOCOMOTIVE WORKS ” is an original and

authenticated word done by me and the best of my knowledge and belief.

I further declare that it has not been submitted elsewhere by any person in any of

the institutes for the degree of bachelor’s of Technology.

Signature

Name : Rahul Kumar

Branch : E.C.E. (4th year)

Roll No : GL21216843

5

Acknowledgement

Summer training has an important role in exposing the real life situation in an industry. It

was a great experience for me to work on training at DIESEL LOCOMOTIVE WORK-

SHOP through which I could learn to work in a professional environment.

I would like to thank the people who guided me and have been a constant source of inspiration

throughout the tenure of my summer training.

I express my sincere thanks and regards to the principle of technical training center, DLW

for giving me the opportunity of training in Diesel Locomotive Works, Varanasi.

I also wish my deep sense of gratitude to Mr. Anupam Kumar (HOD: Electronics and

communication Engineering), and Training Coordinator. Saurabh Verma, Mrs Anuja

Singh and other faculty members of ECE department of Ashoka Institute Of Technology and

Management whose guidance and encouragement made my training successful.

Signature

Name : Rahul Kumar

Branch: E.C.E. (4th year)

Roll No: GL21216843

6

ABSTRACT

The industrial training report of DLW(DIESEL LOCOMOTIVE WORKS) is various trade.

i.e. Electronics and communication , Electrical, Mechanical, Electrical & Electronics and many

Diploma holders are participated .The content of my industrial topic MAINTENCE SERVICE

SHOP (ELECT), TRACATION ASSEMBLY SHOP,ELECTRICAL LAB TTC and COLO-

NY.

In Maintence Service Shop, we are discus about how to remove defect from the circuit board

and any part of system. The second is TAS (Traction Assembly Shop), I learn about assemble

of loco engine. After completed the Traction Assembly Shop going to discus about Electrical

lab. Than the last of my section is Colony, in this shop I learn to explain the system of colony

line distribution and how to generate high power electricity.

this report is written on the basis of practical knowledge of acquired by me during the period of

practical training taken at, Diesel Locomotive Works Varanasi. This report is presented in very

simple & understanding language and it is comprise of four sections namely MAINTENCE

SERVICE SHOP (ELECT), TRACATION ASSEMBLY SHOP, ELECT LAB TTC and

COLONY areas.

7

Content

History of Diesel Locomotive Works

Chapter 1 Maintenance Service Shop

Objective

1.1 Winding shop

1.2 Battery

1.3 Meter

1.4 Electronic lab

Chapter 2 TRACTION ASSEMBLY SHOP

Objective

2.1 Control Panel (C.P)

2.2 Alternator

2.3 Traction Motors

2.4 16 Cylinder Diesel Engine

2.5 Master Control

2.6 Cab

2.7 Auxiliary Generator & Exciter

2.8 Governor

2.9 Crank Case Exhauster

2.10 Mechanical Assembly

Chapter 3Electrical lab of TTC

Objective

3.1 Control panel

3.2 Basic different of ALCO & GM loco/engin

3.3 side view of diesel loco

Chapter 4COLONY

4.1 From the power station to the home

4.2 Electrical substation model (side-view)

4.3 Element of a substation

4.4 Step up & step down tranformers

4.5 Busbars

4.6 Circuit breakers

8

4.7 Isolators

4.8 Insulators

4.9 Relays

4.10 Relay used in controlling panel of substation

4.11 Capacitor bank

9

History of DLW

The Diesel Locomotive Works (DLW) in Varanasi, India, is a production unit owned by Indian

Railways, that manufactures diesel-electric locomotives and its spare parts. It is the largest die-

sel-electric locomotive Manufacture in India. Locally it is abbreviated as D.L.W. It is located

in the Manduadih area on the outskirts of the metropolitan city of Varanasi.

Diesel Locomotive Works is an ISO 9002 certified manufacturer of diesel electric locomotive

and is one of the biggest industrial complexes in eastern part of the country. Diesel Locomotive

Works was set up in 1961 with technical collaboration from M/s. ALCO/USA with a modest

beginning of manufacturing 4 locos 1964, today DLW is the largest Diesel Locomotive manu-

facturer in the world, and the largest in Asia. In order to capture export market & widen its

product range. Indian railway entered in to a contract for Transfer of Technology (TOT) with

M/s. General Motors, USA for manufacture of 4000 HP state of the art locos at DLW. After

assimilation of this technology, DLW will become the only factory in the world capable of

producing ALCO as well as General Motors designs of locomotives.

Dlw is only manufacture of diesel –electric locomotive with both ALCOand GENERAL MO-

TORS Technologies in the world.

DLW exports locos to SRILANKA , MALAYSIA, BANGLADESH, TANZANIA, VIETAN-

NAM.

Fig. Technical training center of DLW

Chapter

1

10

Maintenance Service Shop

Introduction

Maintenance, repair, and overhaul involve fixing any sort of mechanical, plumbing or electri-

cal device should it become out of order or broken (known as repair, unscheduled, or casualty

maintenance). It also includes performing routine actions which keep the device in working

order (known as scheduled maintenance) or prevent trouble from arising (preventive mainte-

nance). MRO may be defined as, "All actions which have the objective of retaining or restoring

an item in or to a state in which it can perform its required function. The actions include the

combination of all technical and corresponding administrative, managerial, and supervision

actions.

Fig. 1.1 Maintenance shop of DLW

MSS is the unit in which Maintenance & repair the device that include:

1. Winding shop

2. Electronics lab

3. Battery shop

4. Meter shop

Chapter

2

11

1.1 winding shop

A step motor is a constant output power transducer, where power is defined as

torque multiplied by speed. This means motor torque is the inverse of motor speed. To help

understand why a step motor’s power is independent of speed, we need to construct

(figuratively) an ideal step motor,

An ideal step motor would have zero mechanical friction, its torque would be

proportional to ampere-turns and its only electrical characteristic would be inductance.

Ampere-turns simply mean that torque is proportional to the number of turns of wire in the

motor’s stator multiplied by the current passing through those turns of wire.

Anytime there are turns of wire surrounding a magnetic material such as the iron in the motor’s

stator, it will have an electrical property called inductance. Inductance describes the energy

stored in a magnetic field anytime current passes through this coil of wire.

Fig.1.2 Internal part of 3-phase moter

1.2 Electronics lab

There is a full-fledged Electronic Lab to cater to maintenance need of highly sophisticated

CNC machines and component / subassembly level trouble shooting of PCBs, Servo Drives,

and Microprocessor based controllers and electronic units. This Lab also supports other Zonal

Railways in repair of PCBs.

Important Machines:-

(i) Reverse Engineering System:

It helps tracing PCB tracks between components in given circuit board whose detail is not pro-

vided by the OEM.

12

(ii) Automatic Test Equipment:

With its library having more than 30,000 components details, it helps in-circuit testing of digi-

tal and analog devices mounted on latest PCBs.

Fig.1.3 A view of Electronics Lab in Dlw

1.3 Battery Shop

An electricbatteryis a device consisting of two or moreelectrochemicalcellsthat convert stored

chemical energy into electrical energy. Each cell has a positive terminal, orcathode, and a

negative terminal, oranode. The terminal marked positive is at a higher electrical potential en-

ergy than is the terminal marked negative. The terminal marked positive is the source of elec-

trons that when connected to an external circuit will flow and deliver energy to an external de-

vice. When a battery is connected to an external circuit,Electrolytesare able to move as ions

within, allowing the chemical reactions to be completed at the separate terminals and so deliver

energy to the external circuit. It is the movement of those ions within the battery which allows

current to flow out of the battery to perform work.[1]Although the termbatterytechnically

means a device with multiple cells, single cells are also popularly called batteries.

Fig.1.4 Internal part of battery

13

Chemical action during discharge

Pbo2 + H2 + H2SO4= PBSO4 + 2H2O ( at + Ve )------ (i)

Pb + SO4 = PbSO4 (at – Ve ) --------------- (ii)

Chemical action during charging

PbSO4 + H2 = Pb + H2SO4(at – Ve )------------- (iii)

PbSO4 + SO4 + 2H2O = PbO2 +2H2O ( at + Ve )------- (iv)

1.4 Meter Shop

Meter (in locomotive) is a device that measure,s the amount of loco speed, air

pressure ,Fuel, diesel pressure, power of electricity and meter-calibration etc..

Fig.1.5 A view of Meter Lab in Dlw

14

TRACTION ASSEMBLY SHOP

Traction assembly shop is the unit in which all the locomotive parts are assembled that

includes:

1. CP (Control Panel)

2. Alternator

3. Traction Motors

4. 16 cylinder Diesel Engine

5. Master Control

6. Cab

7. Auxiliary Generator & Excited

8. Governor

9. Crank Case Exhauster

10. Mechanical Assembly

2.1 Control Panel

The CP or the Control Panel (wrt WG3A loco) consists of:

a) Control Switch

b) Display Unit

c) LED Panel

d) Microprocessor based Control Unit

e) Reverser

f) BKT

g) Valves

h) Hooter

i) CK1/CK2/CK3

The top portion of CP has sensors and relays connected to the microprocessor unit. The

display unit of microprocessor shows working condition of items in engine (electrical

Chapter

3

15

equipments apart from engine). The LED Panel displays the overload, auxiliary generator

failure, hot engine, rectilinear fuse blown, etc. The battery ammeter shows the charging

state of the batteries. REV: Field wiring goes to reverser (REV) and hence it is used to

control the polarity of the field which in turn controls the direction of train. BKT: It is a

switch which in one direction is used to motor the loco while in other it is used for dy-

namic braking. Microprocessor based Control Unit: On-board microprocessors control

engine speed, fuel injection, and excitation of the alternator. These computers also inter-

connect with improved systems to detect slipping or sliding of the driving wheels, pro-

ducing faster correction and improved adhesion. An additional function of the micropro-

cessor is to monitor performance of all locomotive systems, thereby increasing their reli-

ability and making the correction of problems easier. Hooter: It is a vigilance control de-

vice (VCD) to keep the driver alert. If the driver isn’t doing anything with the controls for

over a minute, the hooter ‘hoots’ and brings the engine speed to the normal speed (low)

without asking the driver. It can only be reset after 2 minutes and hence the driver will be

held responsible for delay in reaching the next station.

Fig.2.1 Control Panel of WG3A loco

Dynamic braking

It is the use of the electric traction motors of a railroad vehicle as generators when slow-

ing the vehicle. It is termed rheostatic if the generated electrical power is dissipated as

heat in brake grid resistors, and regenerative if the power is returned to the supply line.

16

Dynamic braking lowers the wear of friction-based braking components, and additionally

regeneration can also lower energy consumption.

During braking, the motor fields are connected across either the main traction generator

(diesel-electric loco) or the supply (electric locomotive) and the motor armatures are

connected across either the brake grids or supply line. The rolling locomotive wheels turn

the motor armatures, and if the motor fields are now excited, the motors will act as gen-

erators.

For a given direction of travel, current flow through the motor armatures during braking

will be opposite to that during motoring. Therefore, the motor exerts torque in a direction

that is opposite from the rolling direction. Braking effort is proportional to the product of

the magnetic strength of the field windings, times that of the armature windings. In DLW

Locomotives the braking method used is rheostatic, i.e. the traction motors behave as

generators (separately excited) and their electrical power is dissipated in brake grid re-

sistors. This method is used for minimising speed of the loco. The loco actually comes to a

halt due to factors like air resistance, friction with the rail, etc.

2.2 Alternator

An alternator converts kinetic energy (energy of motion) into electrical energy. All re-

cently manufactured automobiles rely on alternators to charge the battery in the ignition

system and supply power to other electrical equipment. Alternators are sometimes called

AC generators because they generate alternating current (AC).

Electric current can be generated in two ways: The magnet may rotate inside the coil, or

the coil may rotate in a magnetic field created by a magnet. The component that remains

stationary is called the stator, and the component that moves is called the rotor. In alter-

nators, the coil is the stator and the magnet is the rotor. A source of mechanical power, i.e.

the diesel engine turns the rotor.

In WDM-3D and WDM-3A locos, the diesel engine’s mechanical output is used to run the

shaft of the Alternator. The alternating output of the Alternator is then rectified to DC via

solid-state rectifiers and is fed to traction motors (DC) that run the loco wheels. Thus

they operate on AC-DC Traction mechanism. WDG4 and WDP4 locos have AC-AC traction

with microprocessor control, i.e. AC Traction motors are used thus eliminating the mo-

17

tor commutator and brushes The result is a more efficient and reliable drive that re-

quires relatively little maintenance and is better able to cope with overload conditions.

Why not feed direct DC to the traction motors via DC generators?

In a DC generator, the rotor is the coil. Alternators normally rotate the magnet,

which is lighter than the coil. Since alternators are built to spin the lighter component in-

stead of 10

the heavier one, they generally weigh only one-third as much as generators of the same

capacity. DC generators, in particular, require more maintenance because of wear on the

parts that brush against one another in the commutator switch and the stress of rotating

the heaviest component instead of the lightest. Also, when generators are run at higher

speeds, electricity tends to arc, or jump the gap separating metal parts. The arcing dam-

ages parts and could make generators hazardous to touch. Alternators can run at high

speeds without arcing problems.

Fig.2.2 Alternator

2.3 Traction Motor

It’s an electric motor providing the primary rotational torque of the engine, usually for

conversion into linear motion (traction).

Traction motors are used in electrically powered rail vehicles such as electric multiple

units and electric locomotives, other electric vehicles such as electric milk floats, eleva-

tors and conveyors as well as vehicles with electrical transmission systems such as die-

sel-electric and electric hybrid vehicles. Traditionally, these are DC series-wound motors,

usually running on approximately 600 volts.

18

Fig.2.3 Traction motors

2.4 16 Cylinder Diesel Engine

It is an internal-combustion engine in which heat caused by air compression ignites the

fuel. At the instant fuel is injected into a diesel engine’s combustion chambers, the air in-

side is hot enough to ignite the fuel on contact. Diesel engines, therefore, do not need

spark plugs, which are required to ignite the air-fuel mixture in gasoline engines. The

Diesel engine has 16 cylinders. Pistons inside the cylinders are connected by rods to a

crankshaft. As the pistons move up and down in their cylinders, they cause the crankshaft

to rotate. The crankshaft’s rotational force is carried by a transmission to a drive shaft,

which turns axles, causing mechanical output. Eight 8V and four 2V Batteries are used in

series to run a more powerful starter motor, which turns the crankshaft to initiate igni-

tion in a diesel engine for the first time.

Fig.2.4 diesel engine of ALCO loco

19

2.5 Master Control

It’s the unit that has the handles to regulate the speed of the loco as well as the direction

of motion. It has numbering from 0-9 and each increment causes rise in speed in forward

direction. It can also be used to reverse the direction of motion by pushing the handle in

the opposite sense. It is present on the control desk of the cab.

2.6 Cab

It’s the driver’s cabin with 2 control desks, the Control Panel (CP) and chairs for the driv-

er. The Cab is at one end of the locomotive with limited visibility if the locomotive is not

operated cab forward. Each control desk has the Independent SA9 brake for braking of

the engine alone and Auto Brake A9 for the braking of the entire loco. It also has the fol-

lowing components:

v LED Panel

v Buttons of various engine LED lights (front and side)

v Automatic sand throw button (to prevent sliding of wheels on inclined

tracks)

v Master Control

v Gauges to monitor booster air pressure and fuel & lube oil pressures.

v Speedometer

v Service Brakes (Independent and Auto brakes described above)

v Emergency Brake (Type of Air brake to halt the train in the distance

nearly equal to the length of the train, to be used only during an emergen-

cy)

2.7 Auxiliary Generator and Exciter

The Alternator has these two components. The exciter and the auxiliary generator consist

of two armatures on a single shaft. The auxiliary generator supplies a constant voltage of

around 72V for supplying power to charge the battery for the control equipment and to

power the locomotive lights. The Exciter supplies excitation for the main generator. Start-

ing of Engine The supply from the batteries is given to the exciter. The exciter has arma-

ture and field windings. Hence it starts rotating as it receives the supply voltage. The Ex-

20

citer is coupled with the rotor of the alternator which in turn is connected with the pro-

peller shaft. When the propeller rotates at a particular rpm, the

engine gets started. It’s just like starting a bike. The ‘kick’ must be powerful enough to

start its engine. Later the engine runs on diesel oil (fuel). As soon as the engine starts, the

auxiliary generator also coupled with the alternator starts charging the batteries. Its po-

tential is maintained at ~72V.

Fig .2.5 Auxiliary generator

2.8 Governor

It is the device that has the following functions:

1. To control engine speed

2. Deliver fuel (Diesel oil) according to load

3. To mediate electrical demand and diesel engine output.

2.9 Crank case exhauster

It is the device used to evacuate the diesel engine chamber.

Fig.2.6 Crank case

21

2.10 Mechanical Assembly

All mechanical parts on the engine apart from the above mentioned units may be

grouped in this category. It essentially consists of:

v Base frame

v Wheels

v Air Brakes

v Batteries

v Sand Box

v Vacuum brakes

v Fuel tank (Loco fuel oil tank capacity is 3000L) etc

Air Braking System of Locomotives: On a train, the brake shoes are pressed directly

against the wheel rim. A compressor generates air pressure that is stored in air tanks.

Air hoses connect the brakes on all the train cars into one system. Applying air pressure

into the system releases the brakes, and releasing air pressure from the system applies

the brack.

22

Electrical lab of TTC

Introduction

Starting of traning of electrical lab of TTC (Technical traning centre) of DLW. I have seen

about 28 panal (trainers) of different subject . I come know the capab- ility of electrical ring is

going to be advance as regarding gidence to the tranise.

The complate syllabus of 1961 of operanties is present here. For guidedence

tomainhouseandothertranises.Process of the locomotive of diffferent type are convert to

electrical point of view.

In this shop, we are discus about basic idea of assemble the loco,control panel , engine type ,

governer, locomotive control system etc…

There are two type of locomotive engine(rail engine ).

1. ALCO (AMERICAN LOCO COMPANY) <4000 HP

2. GM (GENERAL MOTER) or HHP (HIGH HORSE POWER ) >4000HP

3.1 control panel

control panel is a flat often vertical area where control or monitoring instruments are displayed.

ÿ Protection

1. Metering

2. Indication

3. breaker

Chapter

4

23

3.2 Basic different of ALCO & GM loco/engin

3.3 side view of diesel loco

Fig 3.1 Part name of loco

1) Head light 2) Inertial Filter Air Inlet 3) Starting Fuse and Battery Knife Switch

4) Handrails 5) Cooling System Air 6) Radiator and Fan Access

7) Coupler “E” Type 8) Sanding Box (8) 9) Jacking Pads (4)

10) Wheels (6 ) 11) Fuel Tank 12) Compressed Air System Main Reservoir

13) Battery Box 14) Trucks (3 axle 3 motor HTSC type) Qty. 2

15) Underframe 16) Dynamic Brake Grids 17) Dynamic Brake Fans (2)

Discription ALCO GM

Loco WDM3D,WDP3A WDG4, WDP4

Gross horse power 3100 , 3600 4500 , 4400

Transmision AC - DC AC – AC

Traction moter DC Series Ac -induction

Governer Medha,cimence Medha, simplex

24

ColonyIntroduction

Electricity transmission is the process of transfer-

ring electrical energy to consumers. Electrical en-

ergy generated at power facilities is transmitted at

high voltages through overhead power lines and

cables.Thosetransmission lines connect to substa-

tionswhich transform the power to lowervoltages

for distribution to consumers through the distribu-

tion system.

4.1 From the Power Station to the Home

Inside a generating station, turbines use the driving force of water to set electrons in motion

and generate alternating current.

Fig 4.1 Electricity transmition from the power station to customer

Chapter

5

25

Electricity from the power station has a long way to go before reaching your home.

1. The voltage of the current produced by a generating station can reach 13,800 volts, like

at the Robert-Bourassa generating facility.

2. Thanks to the voltage step-up transformer located in the generating station’s

switchyard, the electricity is transmitted at much higher voltages, from 44,000 to

765,000 volts.

3. Once in the transmission system, electricity from each generating station is combined

with electricity produced elsewhere.

4. The electricity passes through cables which are suspended from towers. These towers

are arranged in a series from the generating stations to source substations–which lower

the voltage–and then reach the satellite substations, which further reduce the voltage.

5. Leaving the satellite substations, electricity travels through underground lines. At some

distance from the substations, the distribution system goes from underground to over-

head, and transformers attached to poles lower the voltage one last time. Inside our

homes, we use either 120 volts to power our televisions, radios and other regular elec-

trical appliances, or 240 volts for the appliances that require a strong current like the

dryer or stove.

6. Electricity is consumed as soon as it is produced. It is transmitted at a very high speed,

close to the speed of light (300,000 km/s).

4.2 Electrical substation model (side-view)

Fig: 4.2 1.Primary power lines 2.Ground wire 3.Overhead lines 4.Lightning arrester

5.Disconnect switch 6.Circuit breaker 7.Current transformer 8.Transformer for meas-

urement of electric voltage 9.Main transformer 10.Control building 11.Security fence

12.Secondary power lines

26

4.3 Elements of a substation

Substations generally have switching, protection and control equipment, and transformers.

In a large substation, circuit breakers are used to interrupt any short circuits or overload cur-

rents that may occur on the network. Smaller distribution stations may use recloser circuit

breakers or fuses for protection of distribution circuits. Substations themselves do not usually

have generators, although a power plant may have a substation nearby. Other devices such as

capacitors and voltage regulators may also be located at a substation.

Substations may be on the surface in fenced enclosures, underground, or located in special-

purpose buildings. High-rise buildings may have several indoor substations. Indoor substations

are usually found in urban areas to reduce the noise from the transformers, for reasons of ap-

pearance, or to protect switchgear from extreme climate or pollution conditions.

Where a substation has a metallic fence, it must be properly grounded to protect people from

high voltages that may occur during a fault in the network. Earth faults at a substation can

cause a ground potential rise. Currents flowing in the Earth's surface during a fault can cause

metal objects to have a significantly different voltage than the ground under a person's feet;

this touch potential presents a hazard of electrocution

4.4 Step-up and Step-down Transformers

This is a very useful device, indeed. With it, we can easily multiply or divide voltage and cur-

rent in AC circuits. Indeed, the transformer has made long-distance transmission of electric

power a practical reality, as AC voltage can be “stepped up” and current “stepped down” for

reduced wire resistance power losses along power lines connecting generating stations with

loads. At either end (both the generator and at the loads), voltage levels are reduced by trans-

formers for safer operation and less expensive equipment. A transformer that increases voltage

from primary to secondary (more secondary winding turns than primary winding turns) is

called a step-up transformer. Conversely, a transformer designed to do just the opposite is

called a step-down transformer.

Step-up and step-down transformers for power distribution purposes can be gigantic in propor-

tion to the power transformers previously shown, some units standing as tall as a home. The

following photograph shows a substation transformer standing about twelve feet tall.

27

Fig 4.3 (a)Substation transformer. Fig 4.3 (b) Block diagram

REVIEW:

∑ Transformers “step up” or “step down” voltage according to the ratios of primary to

secondary wire turns.

∑ A transformer designed to increase voltage from primary to secondary is called a step-up

transformer. A transformer designed to reduce voltage from primary to secondary is called

a step-down transformer.

∑ The transformation ratio of a transformer will be equal to the square root of its primary to

secondary inductance (L) ratio.

28

∑

By being able to transfer power from one circuit to another without the use of interconnect-

ing conductors between the two circuits, transformers provide the useful feature of electri-

cal isolation.

Transformers designed to provide electrical isolation without stepping voltage and current

either up or down are called isolation transformers.

4.5 BUSBARS

It an electrical conductor, maintained at a specific voltage and capable of carrying a high

current, usually used to make a common connection between several circuits in a system

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 alisation.

∑ Duplicate bus bar system

In large stations it is important that break downs and maintenance should interfere as little as

possible with continuity of supply to achieve this, duplicate bus bar system is used. Such a

system consists of two bus bars, a main bus bar and a spare bus bar with the help of bus cou-

pler, which consist of the circuit breaker and isolator.

In substations, it is often desired to disconnect a part of the system for general maintenance

and repairs. An isolating switch or isolator accomplishes this. Isolator operates under no load

condition. It does not have any specified current breaking capacity or current making capaci-

ty. In some cases isolators are used to breaking charging currents or transmission lines.

While opening a circuit, the circuit breaker is opened first then isolator while closing a circuit

the isolator is closed first, then circuit breakers. Isolators are necessary on supply side of cir-

29

cuit breakers, in order to ensure isolation of the circuit breaker from live parts for the purpose

of maintenance.

A transfer isolator is used to transfer main supply from main bus to transfer bus by using bus

coupler (combination of a circuit breaker with two isolators), if repairing or maintenance of

any section is required.

4.6 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. Unlike a fuse, which operates once and then must be re-

placed, a circuit breaker can be reset (either manually or automatically) to resume normal oper-

ation. Circuit breakers are made in varying sizes, from small devices that protect an individual

household appliance up to large switchgear designed to protect high voltage circuits feeding an

entire city. There are different types of circuit breakers which are:-

1. Low-voltage circuit breakers

Low-voltage (less than 1,000 VAC) types are common in domestic, commercial and industrial

application, and include Miniature Circuit Breaker (MCB) and Molded Case Circuit Breaker

(MCCB).

Fig 4.4 Circuit breaker

2. Magnetic circuit breakers

Magnetic circuit breakers use a solenoid (electromagnet) whose pulling force increases

with the current. Certain designs utilize electromagnetic forces in addition to those of the

solenoid

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Fig 4.5 Magnetic circuit breakers

3 .Thermal magnetic circuit breakers

Thermal magnetic circuit breakers, which are the type found in most distribution boards, incor-

porate both techniques with the electromagnet responding instantaneously to large surges in

current (short circuits) and the bimetallic strip responding to less extreme but longer-term over-

current conditions. The thermal portion of the circuit breaker provides an "inverse time" re-

sponse feature, which trips the circuit breaker sooner for larger over currents.

Fig 4.6 Thermal magnetic circuit breakers

4. Common trip breakers

Three-pole common trip breaker for supplying a three-phase device. This breaker has a 2A rat-

ing. When supplying a branch circuit with more than one live conductor, each live conductor

must be protected by a breaker pole. To ensure that all live conductors are interrupted when

any pole trips, a "common trip" breaker must be used. These may either contain two or three

tripping mechanisms within one case, or for small breakers, may externally tie the poles to-

gether via their operating handles.

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Fig 4.7Three-pole common trip breaker

5. 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. Usually electronically

controlled, though some modelsare microprocessor controlled via an integral electronic trip

unit, often used for main power distribution in large industrial plant, where the breakers are

arranged in draw-out enclosures for ease of maintenance.

Fig 4.8 Air circuit breakers

6. Vacuum circuit breakers

with rated current up to 6,300 A, and higher for generator circuit breakers. These breakers in-

terrupt the current by creating and extinguishing the arc in a vacuum container.

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Fig 4.9 Vacuum circuit breakers

7. Oil circuit breakers

A high-voltage circuit breaker in which the arc is drawn in oil to dissipate the heat and extin-

guish the arc; the intense heat of the arc decomposes the oil, generating a gas whose high pres-

sure produces a flow of fresh fluid through the arc that furnishes the necessary insulation to

prevent a restrike of the arc.

The arc is then extinguished, both because of its elongation upon parting of contacts and be-

cause of intensive cooling by the gases and oil vapor. They are further of two types: Bulk Oil

Circuit Breaker (BOCB) and Minimum Oil Circuit Breaker (MOCB).

Fig 4.10 Oil circuit breakers

8. Sulfur hexafluoride (Sf6) high-voltage circuit breakers

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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 incorpo-

rated into compact gas-insulated switchgear.

Fig 4.11 Sulfur hexafluoride (Sf6) high-voltage circuit breakers

4.7 ISOLATERS

In electrical engineering, a disconnector, disconnect switch or isolator switch is used to ensure

that an electrical circuit is completely 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. High-voltage isolation

switches are used in electrical substations to allow isolation of apparatus such as circuit break-

ers, transformers, and transmission lines, for maintenance. The disconnector is usually not in-

tended for normal control of the circuit, but only for safety isolation. Disconnector can be op-

erated either manually or automatically (motorized disconnector).

Unlike load break switches and circuit breakers, disconnectors lack a mechanism for suppres-

sion of electric arc, which occurs when conductors carrying high currents are electrically inter-

rupted. Thus, they are off-load devices, intended to be opened only after current has been inter-

rupted by some other control device. Safety regulations of the utility must prevent any attempt

to open the disconnector while it supplies a circuit. Standards in some countries for safety may

require either local motor isolators or lockable overloads (which can be padlocked).

Disconnectors have provisions for a padlock so that inadvertent operation is not possible (lock-

out-tag out). In high-voltage or complex systems, these padlocks may be part of a trapped-key

interlock system to ensure proper sequence of operation. In some designs, the isolator switch

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has the additional ability to earth the isolated circuit thereby providing additional safety. Such

an arrangement would apply to circuits which inter-connect power distribution systems where

both ends of the circuit need to be isolated.

Fig 4.12 Isolaters circuit

4.8 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. The most common used material for the manufacture of insulator is

porcelain. There are several types of insulators (e.g. pin type, suspension type, post insulator

etc.) and their use in substation will depend upon the service requirement.

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. The conductor passes through this groove

and is tied to the insulator with annealed wire of the same material as the conductor. Pin type

insulators are used for transmission and distribution of elec

tric power at voltages up to 33 kV. Beyond operating voltage of 33 kV, the pin type insulators

become too bulky and hence uneconomical.

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Fig 4.13Pin type insulator

∑ Suspension insulator

For voltages greater than 33 kV, it is a usual practice to use suspension type insulators shown

in Figure. Consist of a number of porcelain discs connected in series by metal links in the form

of a string. The conductor is suspended at the bottom end of this string while the other end of

the string is secured to the cross-arm of the tower. The number of disc units used depends on

the voltage.

Fig 4.14Suspension insulator

∑ 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 insulators are used as strain insulators. However, for

high voltage transmission lines, strings of cap-and-pin (disc) insulators are used, attached to the

crossarm in a horizontal direction. When the tension load in lines is exceedingly high, such as

at long river spans, two or more strings are used in parallel.

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Fig 4.15Strain insulator

∑ Shackle insulator

In early days, the shackle insulators were used as strain insulators. But now a day, they are fre-

quently used for low voltage distribution lines. Such insulators can be used either in a horizon-

tal position or in a vertical position. They can be directly fixed to the pole with a bolt or to the

cross arm.

Fig 4.16Shackle insulator

4.9 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 re-

lays detect the fault and supply the information to the circuit breaker.The electrical quantities

which may change under fault condition are voltage, frequency, current, phase angle. When a

short circuit occurs at any point on the transmission line the current flowing in the line increas-

es to the enormous value.This result in a heavy current flow through the relay coil, causing the

relay to operate by closing its contacts. This in turn closes the trip circuit of the breaker making

the circuit breaker open and isolating the faulty section from the rest of the system. In this way,

the relay ensures the safety of the circuit equipment from the damage and normal working of

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the healthy portion of the system.

Relay works on two main operating principles:-

∑ Electromagnetic Attraction

∑ Electromagnetic Induction

4.10 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. If this differential quantity is equal or greater than

the pickup value, the relay will operate and open the circuit breaker to isolate the faulty sec-

tion.

Fig 4.17Differential Relay

∑ Over Current Relay

This type of relay works when current in the circuit exceeds the predetermined value. The ac

tuating source is the current in the circuit supplied to the relay from a current transformer.

These relay are used on A.C. circuit only and can operate for fault flow in the either direction.

This relay operates when phase to phase fault occurs.

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Fig 4.17Over Current Relay

∑ 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.

Fig 4.18Earth fault relay

∑ 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.

Fig 4.19Tripping Relay

∑ Auxiliary Relay

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An auxiliary relay is used to indicate the fault by glowing bulb or showing various flags.

Fig 4.20Auxiliary relay

4.11 Capacitor bank

The load on the power system is varying being high during morning and evening which in-

creases the magnetization current. This result in the decreased power factor. The low power

factor is mainly due to the fact most of the power loads are inductive and therefore take lagging

currents. The low power factor is highly undesirable as it causes increases in current, resulting

in additional losses. So in order to ensure most favorable conditions for a supply system from

engineering and economic stand point it is important to have power factor as close to unity as

possible. In order to improve the power factor come device taking leading power should be

connected in parallel with the load. One of such device can be capacitor bank. The capacitors

draw a leading current and partly or completely neutralize the lagging reactive component of

load current.

Main functions of Capacitor Bank are:-

∑ Supply Reactive Power

∑ Improve Terminal Voltage

∑ Improve Power Factor

Fig 4.21Capacitor bank

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Reference

ÿ www.wikipedia.in/dlw

ÿ www.powershow.comview706e8

ÿ www.google.com/dlw

ÿ www.slideshare.in/summerreport7457

ÿ www.irieen.indianrailways.gov.inview_sectionreport