By: - Shubham Pati Tripathi

Electronics and Communication Engineering

NIT Agartala

Contents

Acknowledgement

Preface

Introduction

Shop 1: Electronics Lab

Shop 2: MRS

Shop 3: SCADA

Shop 4: Telephone Exchange

Conclusion

Acknowledgement I would sincerely like to thank the employees and the officers of DLW, VARANASI for their help and support during the vocational training. Despite their busy schedules, they took time out and explained to us the various aspects of the working of the plant and technological knowhow. I would sincerely like to thank Shri Amit Kumar (ACWI/Elect.), Miss. Ratna Singh (SSE/Telephone Exchange) and other JEs who were instrumental in arranging the vocational training at DLW Varanasi, and without whose help and guidance the training could not have materialized. I express my deep sense of gratitude to the Principal, TTC for given me such a great opportunity

Preface

The objective of this training is to learn something about industries

practically and to be familiar with the working style of the technical

world to adjust simply according to the industrial environment.

In this practical world practical knowledge is very important, apart

from the theoretical learning in the college, an industrial training

provides a platform to explore real life experiences of hat we learn

and working around industry professionals help to build a better

spectrum of professional life as an engineer.

My training at DLW, Varanasi was focused on the electronics and

communication related fields in the wide range of jobs in Diesel and

Electrical Engine production.

Introduction to 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 diesel-electric locomotive manufacturer in India.

Founded in 1961, the DLW rolled out its first locomotive three years later, on

January 3, 1964. It manufactures locomotives which are variants based on the

original ALCO designs dating to 1960s and the GM EMD designs of the 1990s.

DLW has an annual production capacity of 250 locomotives and plans to

increase it to 275 based on the current demand.

About the Training

Diesel Locomotive Works (DLW) has many Workshops for learning and visiting.

These workshops are HWS, HMS, EES, ETS, LMS, LAS, EL, SAS,RS, HTS, LFS, PS,

TMS, TAS, SMS,MRS, LAS, TE, LPS, SCADA and LTS etc. These are the workshops

in the Diesel Locomotive Works (DLW) where student get knowledge about

practical experience.

There are some workshops in TTC (Technical Training Centre) like Fitting shop,

Machine Shop and Welding Shop.

In Diesel Locomotive Works (DLW) I have visited 4 Works shop in four weeks.

These works shop are Electronics lab, Main Receiving Substation (MRS), SCADA

and Telephone Exchange.

Shop 1-Electronics Lab

The lab deals in following areas:

PCB repair tool for third-party repair

shops.

Small to medium volume production.

Card edge testing with the QT-200.

IC testing is performed by QT-200.

QT-200

The lab also deals with maintenance jobs. It is of two types:

BREAKDOWN MAINTENANCE

In this case of maintenance, repair can be done after the break down occur.

Breakdown of machine can occur due to unpredicted failure of components

which cannot be prevented or due to gradual wear and tear of the part.

PREVENTIVE MAINTENANCE

In this case maintenance is done on the basis of predication checking.

This is sometimes called “maintenance maintenance “or “systematic point

maintenance”. It is an extremely important function for the reduction of

maintenance cost, less expenditure of repairs etc.

• Reduction in production downtime.

• Lesser over-time pay for maintenance personnel.

• Lesser number of standby equipments in needed.

• Less expenditure of repairs.

• Due to planned spare parts replacement, lesser spare parts are needed

to remain in store all time.

• Greater safety to employees because of reduced breakdown.

Three devices were introduced at this lab:-

1. Relay

2. Contactor

3. IGBT

RELAY:

It is an EAS which controls the electrical power flow. There are of following

types:

Relay

Controlling Relay Protection Relay

EMR SSR OLR Microprocessor Relay

Power consumption in controlling Relay is lesser compared to Protection Relay.

Protection Relay is used to detect isolated faults in transmission or distribution

system.

Classification based on pole and throw

Application: - Railway signalling relays are large considering the mostly small

voltages (less than 120 V) and currents (perhaps 100 mA) that they switch.

Contacts are widely spaced to prevent flashovers and short circuits over a

lifetime that may exceed fifty years. BR930 series plug-in relays are widely

used on railways following British practice. These are 120 mm high, 180 mm

deep and 56 mm wide and weigh about 1400 g, and can have up to 16

separate contacts, for example, 12 make and 4 break contacts.

CONTACTOR:

A contactor is an electrically controlled switch used for switching an electrical

power circuit, similar to a relay except with higher current ratings. A contactor

is controlled by a circuit which has a much lower power level than the switched

circuit.

It is an electro-mechanical device which has a fixed part and a movable part.

Application: - A magnetic starter is a device designed to provide power to

electric motors. It includes a contactor as an essential component, while also

providing power-cut-off, under-voltage, and overload protection.

IGBT:

An insulated-gate bipolar transistor (IGBT) is a three-terminal power

semiconductor device primarily used as an electronic switch which, as it was

developed, came to combine high efficiency and fast switching. It switches

electric power in many modern appliances: variable-frequency drives (VFDs),

electric cars, trains, variable speed refrigerators, lamp ballasts, air-conditioners

and even stereo systems with switching amplifiers. Since it is designed to turn

on and off rapidly, amplifiers that use it often synthesize complex waveforms

with pulse-width modulation and low-pass filters. In switching applications

modern devices feature pulse repetition rates well into the ultrasonic range—

frequencies which are at least ten times the highest audio frequency handled

by the device when used as an analog audio amplifier.

The IGBT combines an isolated-gate FET for the control input and a bipolar

power transistor as a switch in a single device.

Cross section of a typical IGBT showing internal connection of MOSFET and Bipolar Device

An IGBT cell is constructed similarly to a n-channel vertical construction power

MOSFET except the n+ drain is replaced with a p+ collector layer, thus forming

a vertical PNP bipolar junction transistor. This additional p+ region creates a

cascade connection of a PNP bipolar junction transistor with the surface n-

channel MOSFET.

Shop 2-Main Receiving Substation (MRS)

MRS receives main supply from UPPCL at 33kv.

This is step down with 7.5MVA transformer. The 33kv feeder is transformed

into two 11kv feeder with a bus coupler in between.

There are two types of distribution techniques:

1. Ring System- Under this system, each substation is connected to the

distribution system with two different transmission lines coming from the

MRS. Hence the substations receive power from any one of the lines.

Generator

SUB 1 SUB 5

SUB 2 SUB 4

SUB 3

2. Radial System-A single main line runs down the MRS and various

substations are connected to it forming branches.

Generator SUB 1 SUB 2 SUB 3

The MRS follows the ring type distribution system for supplying power

to DLW. The advantage of ring type system is that each substation is fed

from two sides. If in case one line is faulted then the substation is fed by

other line. But major disadvantage of ring type system is that it is too

costly.

Safety Precautions at MRS: The most important responsibility while handling

such high power is safety of the employees and equipments. The following

measures are undertaken at MRS for protection-

1. Protection Relays:

i. Over Current Relay- It is set at the current limit of the device with lowest

current rating.

ii. Differential Relay- It prevents imbalance in current in different phases.

iii. Negative Phase Sequence Relay- It detects if the R-Y-B sequence is put

wrongly.

iv. Under/Over Voltage Relay

v. Reverse Power Relay- Prevents clashing of power from different sources.

2. Air Circuit Breaker (ACB) - Air Circuit Breaker is a device used to provide over

current and Short Circuit Protection for circuits ranging from 800 Amps to

10000 Amps. One should not be confused between Air Circuit Breaker and Air

Blast Circuit Breaker. Air Circuit Breakers are usually used in low voltage

applications below 450 volts.

ACBs are being replaced by SF6 Circuit Breakers in a phased manner.

The gaseous medium SF6 possesses excellent dielectric and arc quenching

properties. After arc extinction, the dissociated gas molecules recombine

almost completely to reform SF6. This means that practically no

loss/consumption of the quenching medium occurs. The gas pressure can be

very simply and permanently supervised. This function is not needed where

the interrupters are sealed for life.

Shop 3- SCADA

Supervisory control and data acquisition (SCADA) is a control system

architecture that uses computers, networked data communications and

graphical user interfaces for high-level process supervisory management, but

uses other peripheral devices such as programmable logic controllers and

discrete PID controllers to interface to the process plant or machinery. The

operator interfaces which enable monitoring and the issuing of process

commands, such as controller set point changes, are handled through the

SCADA supervisory computer system. However, the real-time control logic or

controller calculations are performed by networked modules which connect to

the field sensors and actuators.

A SCADA system is used to control physical output through logical input.

In DLW, SCADA is used to control power flow to all sections in the factory and

colony. It is also being upgraded to control motors and all other equipments in

the facility.

The SCADA systems are installed at MRS and all substations and controls are

provided accordingly. The MRS SCADA system acts as parent to all other

substations, i.e.- It’s commands will override all other substations.

A general SCADA screen showing different equipments and substations.

Shop 4-Telephone Exchange

Provides telephone connections to the administrative blocks and colony

area.

The exchange works on a D.C. supply of 50V obtained from battery set

which is connected in parallel to the charger which is operating on 230V

A.C.

The exchange is designed to perform satisfactorily for line loop

resistance of 1000 ohm for each subscriber.

The voltage required when two subscribers talk is 12V.

Block Diagram of Telephone Exchange

Parts in a Telephone exchange:-

Internal Distribution Frame (IDF) - In if the framing of jumper is done .

The cables which are coming out of the exchange are terminated in IDF

and in MDF

1. Crown type

2. Block type

Main Distribution Frame (MDF) - Exchange is also provided in the rack

type of tag block which is called MDF which is the main distribution

frame. In MDF we mount the fuse hold tag at the Back of the Block and

jumper in front.

Distribution Board (DB) - it is the box board in which cable pads are

distributed according to the number which are to be provided near the

distribution .DB are installed after accretion interval of the distance

making a proper distribution of cable which is easier with the consumer.

Distribution Pole- Distribution poles are much nearer to the consumer

here it is easier to take cables from the consumer.

Faults in a Telephone Exchange:-

There are three types of faults-

1. Line Contacts – It mean that the drop wire is connected either with a

pole or a tree if is broken down and a husky voice is obtain when we

ring.

2. Line Earth – It means that drop wire breaks on its own when it touches a

pole or a tree; a soft humming sound comes when we dial a number.

3. Line Disc - The wire has been broken down.

Conclusion

The Four weeks Training program lasted from 01-June-2016 to

28-June-2016 with one week each spent at Electronics Lab, MRS, Telephone

Exchange and SCADA.

A certificate of completion of training was provided

(No. Voc./TTC/DLW/16/1438).

The training program was very fruitful and I got to learn about various new

devices and process undertaken at an industry. My interactions with the

industry professionals gave me an idea of practical life of an engineer.