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A PRACTICAL TRAINING SEMINAR REPORT ON POWER LINE CARRIER COMMUNICATION TAKEN AT: 132 KV CHAMBLE GSS, HAWA SARAK JAIPUR DURATION: 16 june 2011 to 15 July 2011 Submitted in partially Fulfillment of the Requirements for the Degree of Bachelor of Technology In Electronics & Communication Engineering SUBMITTED TO: SUBMITTED BY: MISS PRAGYA KHAGWAL ROHIT CHOUDHARY (Dean & H.O.D.) B.Tech. 7 TH SEMESTER (Department of Elec. & Comm.)
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Plcc Report(Rohit Choudhary

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Page 1: Plcc Report(Rohit Choudhary

A

PRACTICAL TRAINING SEMINAR REPORT

ON

POWER LINE CARRIER COMMUNICATION

TAKEN AT:

132 KV CHAMBLE GSS, HAWA SARAK

JAIPUR

DURATION: 16 june 2011 to 15 July 2011

Submitted in partially Fulfillment of the Requirements for the Degree of

Bachelor of Technology

In

Electronics & Communication Engineering

SUBMITTED TO: SUBMITTED BY:

MISS PRAGYA KHAGWAL ROHIT CHOUDHARY

(Dean & H.O.D.) B.Tech. 7THSEMESTER

(Department of Elec. & Comm.)

DEPARTMENT OF ELECTRONICS & COMM. ENGINEERING

VIVEKANANDA INSTITUTE OF TECHNOLOGY(EAST), JAIPUR

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ACKNOWLEDGEMENT

We are over helmed in all humbleness and gratefulness to acknowledge our depth to all those

who have helped us to put these ideas, well above the level of simplicity and into concrete

something.

We are very thankful to all the instructors of PLCC, Jaipur for their valuable help. With the

help of their valuable suggestions, guidance and encouragement, we were able to

perform this project work.

I would also like to thank to our institution VIVEKANANDA INSTITUTE OF

TECHNOLOGY(EAST), Jaipur and faculty members of the department, who often helped

and gave me valuable guidence to prepare my presentation. Last but not the least, I would

like to thank my parents who helped me a lot in gathering different

information, collecting data and guiding me from time to time in making this project .despite

of their busy schedules ,they gave me different ideas in making this project unique.

ROHIT CHOUDHARY

B.Tech.7THSemester

VIT/ECE

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PREFACE

Summer Training is an important part of our Engineering Curriculum. The B. Tech. course

helps a student in getting acquainted with the manner in which his/her knowledge is being

practically used at a large scale. Hence, when the student switched from the process of

learning to that of implementing his/her knowledge, he/she finds an abrupt change. This is

exactly why summer training during the B. Tech. curriculum becomes all the more important.

Summer Training is prescribed for the student of Technical College as a part of the four-year

degree course of Engineering by the AICTE.

We are required to do training and it has to be completed within a particular period of time

before completion of the 3rd year and in VI semester. This training report describes each and

every detail of the work we performed to make a successful completion of project. This

report also give us a brief idea of how we move ahead step by step reaching to specific height

and ultimately completing the goal.

ROHIT CHOUDHARY

B.Tech.VII Semester

VIT/ECE

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OFFICE OF ASSISTANT ENGINEER

(PLCC)

RAJASTHAN RAJYA VIDYUT PRASARAN NIGAM

LIMITED

132KV G.S.S CHAMBAL POWER HOUSE

JAIPUR

TO WHOM SO EVER IT MAY CONCERN

This is certify that ROHIT CHOUDHARY student of B.TECH 3rd

year of Electronics & communication from VIVEKANANDA

INSTITUTE OF TECHNOLOGY (EAST), JAIPUR has attended

practical training program from 16-06-2011 to 15-07-2011

(30 working days) in this organization connected with power

line carrier communication (PLCC).

His performance during the practical training period

remained good/ very good/excellent and completed his

training with full devotion.

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Date:-03-08-2011 (MOHD. FAROOQ NIRWAN)

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CONTENTS

S. No. Topic Page

1. Acknowledgement I

2. Preface II

3. Certificate III

4. Company profile 1

5. Introduction to PLCC 2

6. Basic principle of PLCC 4

7. General description of PLCC equipment (ETI) 14

8. Applications of ETI equipments 15

9. Construction 18

10. Modes of operations 19

11. Specification of PLCC 21

12. Precautions and maintenance 23

13. Battery Charge 25

14. Advantages and Disadvantages 30

15. Conclusion 31

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COMPANY PROFILE

INTRODUCTION OF RSEB

"Rajasthan state electricity board" started working from Ist July, 1957. This is the body of big

organization and is to function under provision electricity act, like public limited companies.

The board does not have article and memorandum of association.

In order to carry out its function, its rules & regulation and his mad other necessary

administrative arrangement. After the acting of RSEB six dimensions along with 64 offices &

about 300 employees were transferred to its control by the state Govt.

The aim of RSEB is to supply electricity to entire Rajasthan State in the most economical

way. There are no possibilities of staking or electricity so the target of board is to distribute

the energy in the new area as possible. The board has to carry the business on profit without

losses.

After an efficient starting, for the better service privatization of RSEB has been done

recently, it has been divided in five main parts, they are:

1. Electricity production authority: RRVUNL

2. Electricity transmission authority: RRVPNL

3. Distribution authority for Jaipur: JVVNL

4. Distribution authority for Jodhpur: JDVVNL

5. Distribution authority for Ajmer: AVVNL

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INTRODUCTION OF PLCC

(POWER LINE CARRIER COMMUNICATION)

As electronics play a vital rote in the industrial growth, communication is also backbone of

any power system. Communication between various generating and receiving stations is very

essential for proper operation of power system. This is more so in the case of a large

interconnected systems, where a control load dispatch station has to coordinate the working

of various units to see that the system is maintained in the optimum working condition, power

line carrier communication has been found to be the most economical and reliable method of

communication for medium and long-distance in a power network. For short distance the

ordinary telephone system is using. Open wires or underground cables and in some cases

VHF wireless communication are found to be more economical as they do not involve the use

of costly high voltage coupling equipment.

In the early days of generation and utilization of electric power, the generating station was

invariably a thermal one located within or very near a city having industries acting as the

consumers of the power. However, with him introduction of hydroelectric generating stations

and extension of electricity to suburban and rural areas, the picture radically changed. The

various generating stations, located at great distances among themselves could no longer

remain isolated and self-distances among themselves could no longer remain isolated and

self-sufficient entitles. On the other hand, they soon became interconnected giving rise to

what is known as the power grid. This necessitated an economical and dependable means of

intercommunication, between various generating stations, sub-stations and control rooms.

Among many facilities that such means of communication are expected to provide, the

following are the important ones:

1. Speech transmission

2. Remote control and Tele-metering

3. Power line protection

4. Direct breaker tripping

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Many different methods are possible for sending speech or other signals from point to point

in an interconnected power grid. Some of them are as between:

1. Public Telephone Network

2. Direct Lines

3. Radio Circuits

4. Power Line Carrier Communication (PLCC)

In PLCC the higher mechanical strength and insulation level of high voltage power lines

result in increased reliability of communication and power attenuation over long-distance.

The idea of using power lines as transmission lines for communication purpose was the first

thought of at about the beginning of the century and the practical applications were made in

several countries from 1920 onwards.These systems have now developed into extremely

sophisticated and complicated PLCC systems and widely used in all modern power system.

When the distances involved are large, it will not be economical to provide separate wires for

communication purpose. In fact, for such large distances, the power lines themselves provide

a very good medium of transmission of information. So the Power Line Carrier

Communication (PLCC) is mostly used.

APPLICATION OF POEWR LINE CARRIER

COMMUNICATION

1) Protection

By using the PLCC equipment we can able to protect the power lines. If any problem occur in

the transmission of power, it will be informed to the main station by the using of power line

carrier communication.

2) Point To Point Communication

In power line carrier communication, communication occurs in between two stations. If we

want to communicate with the same station then a separate line is required. So in power line

carrier communication is a point to point communication and PLCC line never busy.

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3) Fault Indicator

If power line has any fault it will informed to power house to repair the fault. In power line

fault is very dangerous because it consists of very high voltage.

BASIC PRINCIPLE OF PLCC

In PLCC the higher mechanical strength and insulation level of high voltage power lines

result in increased reliability of communication and lower attenuation over long-distance. The

idea of using power lines as transmission lines for communication purpose was the first

thought of at about the beginning of the century and the practical applications were made in

several countries from 1920 onwards. These systems have now developed into extremely

sophisticated and complicated systems and widely used in all modern power systems.

Since telephone communication system can not be directly connected to the high voltage

lines, suitably designed coupling devices have therefore to be employed. These usually

consist of high voltage capacitors or capacitor with polaritical devices used in conjunction

with suitable line matching units 9LMU's) for matching the impedance of line to that of the

co-axial cable connecting the unit to the PLC transmit-receive equipment.

Also the carrier currents used for communication have to be prevented from entering the

power equipment used in GSS as the would result in high attenuation of even complete loss

of communication signals when earthed at isolator. To prevent this loss, wave traps or line

traps are employed. These consist of suitably designed choke coils connected in series with

the line, which offer negligible impedance to RF carrier currents. Wave traps also usual have

one or more suitable designed capacitors connected in parallel with the choke coils so as to

resonate at carrier frequencies and thus offer even higher impedance to the flow of RF

currents.

The basic arrangement of connecting the WT and coupling capacitor in PLCC

communication is shown in the above figure -

As can be seen from the sketch, the power frequency and radio frequency component are

sorted out by this arrangement. The RF in prevented from entering the stations bus and the

power frequency is blocked of coupling capacitor.

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Fig:- Basic PLCC circuit

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(1) COUPLING DEVICES

Earliest coupling devices used were antenna as similar to these used in radio work. This was

because capacitors capable of withstanding the high voltages used in transmission of

electrical power were not available at that time. The antennas used for coupling the PLC

equipment to the transmission lines were usually erected below the line and parallel to it.

They were usually more then 300 ft long and were tuned to the carrier frequency employed.

These were rather inefficient and the systems were affected but interference from nearby long

wave radio transmitters.

By about 1930, suitably paper and oil capacitors were developed which could withstand the

high voltage and serve as affectidive coupling units to PLC equipments.

A modern coupling capacitor consists of stack of flat would elements of pure cellulose paper

and aluminium coils held between insulating roads under optimum pressure to minimize

capacitance the changes with time and temperature. The interconnection is designed to

obtain.

Highest possible range withstands capacity and highest cut-off frequency. The entire stack

assembly as placed in a suitable pro claim insulating shall fill with insulation coils and

hemetically sealed by metallic flanges and gaskets of synthetic rubber with a dry nitrogen gas

cushion. The mechanical strength of the shell and flanges are carefully matched.

Coupling capacitors are designed for outdoors use and withstand normal atmospheric

phenomenon such as temperature and humidity rain, shown etc. The capacitor's used in

modern PLCC systems have a capacity between 2000 and 8000 ft. The usual value is between

3000 and 5000 ft. The units are designed to have a very low (<0.5dB). There are usually

mounted on pedestals below the line conductors.

In many cases the capacitive voltage dividers are used for communication system and voltage

is used for synchronizing purpose or voltage measurement.

Coupling is necessary because, if power of power line is flow through the communication

line it cause the burning of PLCC equipment. So overcome this problem a coupling capacitor

is used to block the flow of power into the carrier signal line.

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TYPE OF COUPLING

(A)Phase To Ground Coupling

As can be seen from the figure, the wave traps and coupling capacitors are all connected to

one conductor of the power line. The remaining two conductors, though not directly

connected to the.

Line carry a potion of the returning carrier current because these two conductors do not have

wave traps, a portion of the carrier energy is 1 lost. Also radiation losses are goes high as

earth forms a part of the circuit and the noise pickup is correspondingly higher. The method

of connecting is inefficient and the connection at the receiving and can not be made to match

the line perfectly. This is because the impedance of the line can not be calculated correctly as

it depends partly on the soil conductivity enrote the line which varies from place to place and

time to time and parity on station switching condition.

(b) Phase To Phase Coupling

This type of coupling was formally being used to improve the reliability of communication

case of breakage of one of the coupled conductors the system used double the number of

wave traps and coupling capacitors used in phase to ground and hence is costlier. This

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coupling capacitor at each and have the line are connected in parallel to the LMUs as shown

in this sketch figure-

Through this type coupling increase the reliability of communication, the attenuation,

interference from radio transmission and monitoring possibilities are all-higher than those of

phase to ground coupling. Hence this type of coupling has been discontinued and super sided

by the phase to phase coupling system.

(C) Inter Circuit Coupling

This type is coupling uses the same number of wave traps and the capacitor as two

phase coupling but the capacitance are not connected in parallel as in the case of that type of

coupling. The two power conductors used in this case may be considered as metallic go and

return lines for the carrier currents. The conductor has no appreciable influences on the

carrier currents. The third has no appreciable influence on the carrier current transmission.

Hence the switching conditions attention is less because two conductors are used instead of

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one conductor and earth. This type of coupling is more reliable over longer distance and is

generally used load dispatch work, though is lightly costlier than the two phase system.

COMPARISON OF PHASE TO PHASE AND PHASE TO

GROUND COUPLING

The phase-to-ground coupling has the advantage of requiring only half the number of wave

traps and coupling capacitors in comparison to phase-to-phase coupling. But it is inferior to

many respects as would be evident from the following points:

1. The phase-to-ground coupling has higher attenuation and unlike phase-to-phase

coupling, the attenuation varies with station switching conditions.

2. The variation of attenuation function with changes in weather condition is greater in

phase-to-ground coupling.

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3. Reflection and echoes due to mismatch difficulties are much greater in phase-to-

ground coupling.

4. Signal-to-noise ratio is poorer due to longitudinal noise voltages induced in the line.

In phase-to-phase coupling thee noise voltages tend to cancel themselves as equal

voltages are induced in the coupled conductors, which oppose each other in the

circuit.

5. Radiation from phase-to-ground case is about double than that in the other case.

6. A break or fault of some other kind will hamper the transmission in phase-to-ground

coupling much more seriously than in phase-to-phase coupling.

Hence, phase-to-ground coupling is used due to its cheapness, especially when frequency

used and distances to be covered are suitable, and radiation not particularly objectionable, as

may be the situation in sparsely populated areas.

(2) WAVE TRAPS

Wave traps- (WT's) are used between the transmission line and the power stations to avoid

carrier power dislocation in the power plant and cross talk with other power line carrier

circuits connected to the same power station. WT’s also ensure proper operating conditions

and signal levels at the PLCC transmit receive equipment irrespective of switching conditions

of the power circuits and equipment in the station.

A wave trap must satisfy the following requirements :

1) It must block the carrier currents. By blocking, we mean that the track should

attenuate the H.F. signals by at least 8 to 10dB.

2) It must carry the power frequency current safely during normal operation as well as

during short circuit fault conditions.

Constructions of Wave Traps-

All wave traps have a choke as a main part. This choke may be a single layer or a multi-layer

coils made of special aluminum alloy and is designed to carry the full load current the power

circuit continuously and also to withstand normal short circuit current in the event of a fault

on that line for a short time until the current in the event of a fault on circuit breakers clears

the fault without suffering any mechanical or thermal damages. The inductance of the choke

kvaries from 100 Micro henry's to 2 milli-henrys depending on the pass-band required. The

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100 or 200 Micro Henry wave trap will in conjuction with a suitable tuning capacitor block a

band of a few tens of KHz, the blocked land width being dependent on the carry frequency.

The one willi Henry and 2 milli-Henry traps will clock periodically teh whole range of carrier

frequency employed in PLCC a 2.o mH traps can be used without a tuning capacitor across it.

It will still block almost all carrier frequencies in use effectively, but its inherent capacitance

of about 100PF, will cause it to resonate at the high end of the PLCC band (250 to 500 KHZ).

The low indutance respant types of traps are usually wound a narrow cylindrical single layer,

whereas the high inductance broadband traps are invariably wound as large diameter

discoshed coils.

The cost of the wave trap increased with the rated power current to be carrier by it as well as

with the inductance required. A trap with a nominal rated current of 1600n Amp. Designed to

withstand a short circuit current of look. A may cost 10 times as much as trap rated for a

nominal current of 400 Amp and a short circuit current of 50 KA. Similarly a 2.0 mH tap may

cost several times as much as 100 micro-henry traps for the same nominal power current.

Therefore, wherever the nominal load currents and expected short circuit currents are high

smaller inductances are used with tuning arrangement to obtain broadband trap.

Suspension mounting of wave trap is preferred to rigid mounting on coupling capacitors as

this arrangement enables it to withstand the dynamic stresses created by short circuits better

and because it is more economical but high current, high inductance traps, which are very

heavy may have to be mounted on pedestals insulators or coupling capacitors. Wave traps are

made in various is a standard sizes and rating and to various specifications.

Standard inductances for wave trap recommended by IEC are 0.2, 0.25, 0.4, 0.5, 1.0 and 2.0

mH.

3) LIGHTNING ARRESTER

Lightning is one of the most serious causes of over voltage. If the power equipment

especially at our door's is not protected, the over voltage will cause burning of insulations.

The ground wires running over the towers provides an adequate protection against lighting

and also reduced the induced electrostatic or electromagnetic voltage but such a shield is

inadequate to protect any traveling which reaches terminals of electrical equipment and such

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waves can causes internal flash over between inter-turns of transformers and the high peack

voltage of surge may causes external flash over between terminals of the electrical equipment

which results in damage of insulators.

A good light arrester must pass the following properties:

It should not absorb any current during normal operation, but during over voltage surge it

must provide an easy way to the earth. After the first discharge of current has taken place

through then must be capable of carrying the discharge current for same interval of time

without any damage to them. After the over voltage discharge, it must be capable of

interrupting the normal frequency of current from flowing to ground as soon as voltages

reaches below down value.

In addition to tuning devices, which usually consist of a capacitor or capacitors, a lightning

arrester is invariably connected across the choke coils of the wave traps.

The lightning arrester used may be vacuum type arrester whose are over voltage lies below

the rated voltage of the tuning capacitors, but about the voltage produced across the coils

during a short circuit current surge. The lightning arrester therefore protects the tuning

capacitors against momentary over voltage caused by traveling waves. Sustained over voltage

resulting from short circuits currents are not high enough to cause the lightning arrester to be

over. Hence, a sustained are and consequent destruction of the arrester are avoided.

(4) THE TUNING CAPACITOR

Used are high voltage, high stability mica capacitors with low losses. For lower voltage class

of tuning units (with impulse test voltage rating upto 40 KV) polystyrene capacitors are used

by some manufactures. For higher voltage class of tuning units with impulse test voltage

rating upto 150 KV), capacitors with mineral oil impregnated paper die electric are used

which are similar in construction to coupling capacitors. All types are moulded in epoxy

resin. Single frequency traps have a single and double frequency traps have a double tuned

parallel resonant circuit. All the elements belonging to the tuning circuit are usually mounted

in a common housing, which can be revolved and substituted with another similar tuning

device to reasonate trap to a different frequency.

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DIAGRAM SHOWING COPUPLING ARRANGEMENT

(5) TRANSMISSION SYSTEMS

There are three different transmission methods, which can be employed for PLC

communication. They are as below:

1) Amplitude modulation with carrier and double side band transmission.

2) Amplitude modulation with a single side band suppressed carrier transmission.

3) Frequency modulation

The earlier systems used the first method. The speech frequencies transmitted were between

300 HZ to 2400 HZ when the carrier modulated with these frequencies the resulting side

bands took up a maximum bandwidth of 4800 KHZ. Thus, the available HF band was divided

into a number of channels each 5 KHZ wide with the nominal to (carrier) frequency located

in the centre o the channel, some countries attlotted 8 KHZ for each channel an these

channels could naturally transmit higher voice frequencies upto 3.4 KHZ insisted of 2.4 KHZ

and this resulted in better voice quality. Later, some manufacture retained the 8 KHZ and

used the remaining part of the channel for transmitting the telemetry information etc.

Almost all the modern PLC equipments are designed for amplitude modulation with single

side band suppressed carrier transmission. Single side band transmission has the following

advantages over a double side band transmission.

1) The bandwidth requirements per channel is exactly half that of double side band

transmission. Hence, twice the number of channels can be accommodated in the

available band of frequencies of the speech.

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2) As the receiver accepts only half the band of frequencies the noise input to the

receiver is correspondingly reduced. This results in better signal to noise ratio and

intelligibility of the speech.

6) TRUNKING CONNECTIONS FOR TYPICAL CALLS IN

THE NETWORK

A Trunking connection between Heerapura and Ajmer is shown above. For calling Ajmer for

telephone number 23 from Heerapura, the subscriber will left the telephone and he will dial

the direction number for Ajmer that is 53 and if the line is not busy, he will further dial the

station number that is 52. Now he subscriber at Heerapura will receive station tone of Ajmer.

Now on further dialing the telephone number 22, the link will be established in between

telephone number 23 of Heerapura and if a number 22 of Ajmer, in a similar manner, Ajmer

can contact Heerapura by dialing direction number 33, the station number 67 and subscriber

number 23. All directions are having different direction numbers and all stations are allotted

different stations numbers.

GENERAL DESCRIPTION OF PLCC EQUIPMENTS (ETI)

The multipurpose equipment type ETI-21 and ETI-22 transmit simultaneously speech and

multiplexed tele-operation signals in SSB technique over high voltage lines of cables.

The transmitted intelligence is suitable for

Telephone Tele-operations: - Telemetry

- Remote control

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- Remote analogue metering

- Tele-printer

Tele-protection signals for: - High voltage power equipment

- High voltage power lines

While the telephone and Tele operations facilities are typically used for economic control and

supervision of energy network. The tele-protection channels are kept continuously on hot

stand by an are used only in rare cases of a power fault for the planning of new network and

the extension of existing equipment, the ETI series offers a complete range of variation made

possible by a combination of tiers and plug-in PCB.

The equipment is built of 3 main parts-

1. The low frequency multiplex section

With the speech and up to five Tele-operations channels, together with an optional speech

compander.

2. The Carrier Frequency Section

Designed for single channels duplex or double channel duplex working in a 4 KHz or 2.5

KHz raster. The carrier frequency ranges is from 24 KHz to 500 KHz and with transmitted

power of 20 watts of a variant 100 watts.

3. Power Supply Unit

This can be operated from 110/220v, 50/60Hz or a separate battery or charger unit of 24v,

48v or 60v.

The techniques of simple side band modulation with double conversion provides frequency

equalization, automatic gain control and frequency synchronization and ensures perfect

reproduction of the transmitted intelligence, proper distribution of the transmitting power in

normal operation and for the boosting of protection trip signals enables optimum distance to

be converted.

The front panel arrangement of operational and servicing elements such as switches,

potentiometer, lambs etc. allows the non specialist to carry out maintenance of the equipment

with the aid of a built in test oscillator and handy audio test instrument, a quick test and level

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adjustment can be carried out so that with the local transmitter and receiver connected back-

to-back a complete stimulation of the PLC link in establish.

APPLICATIONS OF ETI EQUIPMENTS

The power line carrier (PLC) equipments and the associated protection signaling units are

required to be situated in the area of the high voltage apparatus, thereby facilitating

connections to the PLC' line coupling equipment. In contrast, the telephone exchange and

Tele control equipment are usually more conveniently situated in a control building some

distance from the high voltage equipment.

According to the type of installation various arrangements are possible. These are briefly

explained in the following:

1. PLCC equipment and AF Multiplexer as a Combined Unit

The majority of electricity authorities adopt this arrangement since the complete PLC is

contained in a single cabinet or rack and is easily placed in a suitable telecommunication

room. From this room the individual connections are taken directly to the associated HV

protection circuits and via an appropriate distribution frame, connections to the telephone and

Tele control equipments.

2. Remote at Multiplexer Connected by A long Cable

The case here is that the high voltage lines are terminated in the sub-stations as the edge of

the city while the associated control building or load dispatching office is situated some km.

way in the center of the city. A long 4-wire interconnection cable (Zo=600 chms) connects

the parent PLC equipment with the remote multiplexer.

Brief characteristics -

Cable Attenuation - Permitted 32 dB maximum

- Planning value 26 dB

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Frequency band - 300 to 3700 HZ

- 300 to 3400 HZ Optional

- Adjustable attenuation equalizes for loaded lines, located at both

ends.

The Facilities Available is -

- 4 wire duplex speech, from remote location.

- Duplex tele-operational channels, from remote location.

- Duplex pilot/signaling channel, from remote location.

- Possibilities for input and output connections of tele-operation

signals from PLC equipments.

- Optional: Service telephone from parent PLC equipment to opposite

PLC station.

3. Remote at Multiplexer Connected by a Short Line

When the distance between the PLC and remote multiplexer is relatively short, i.e. up to

about 3 km and in connected by a 4-wire pilot cable (Zo=600 ohm). Due to the lower cable

attenuation the line amplifier with line equalizer is unnecessary and the cable will be

terminated on the tele-operation input/notput circuit (03EA and 03EH/s respectively).

Brief Characteristics -

Remote AF Multiplexer - Cable Terminal Type KTI :

Cable attenuation:

Permitted </=7 dB with a cable distortion loss of /=2dB in the frequency band 300-

3700 Hz. This is equivalent to a distance of 3 Km. Maximum with an unloaded 600

ohms cable.

Frequency band - 300 to 3700 Hz

- 300 to 3400 Hz optional

4. Protection Signaling Over PLCC Equipments Where AF Multiplexer

Is Remote

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In addition to the remote AF multiplexer, tele-protection signaling equipment can be coupled

directly to the PLC equipment. Such an arrangement must of course be reliable and safe so

that even with a possible favour of the remote multiplexed or connecting cable the Tele

protection equipment continues to work perfectly.

This means the PLC equipment has to function fully independently of the transmit signals

from the remote multiplexer. This will be the case when a pilot signal P-1 is used from AF

multiplexer to PLC equipment. A further pilot tone P-2 of the same frequency is transmitted

from the PLC equipment to the opposite PLC station. The signaling impulses carried by the

pilot tones are looped from P-1 to P-2 in DC form at the PLC equipment. The pilot tone P-3

from the opposite stations is received directly at the remote multiplexer.

5. Repeaters

When several transmission are joined together to form a long transmission path, the ETI

equipment can serve as repeater at the intermediate stations. In each transmission section the

carrier signal will be individually regulated, syschronized and equalized and the transmitted

intelligence at each repeater station will be demodulated and passed on to the next section.

The method allows the insertion of tele-operation signals at the repeater station provided, of

course, free space in the 4 KHz band is available. The transit filter E3ET prevents the pilot

tone P-1 entering the neighboring section.

CONSTRUCTION

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The PLC equipment built in Module Electronic System (MES) is especially compact. For all

equipment variations, the single channel equipment ETI-21 can be accommodated in 3 tiers,

the double channel equipment ETI-22 in 4 tiers and the double channel, 40W equipment ETI-

22 (s) in 6 tiers. Further more, a mechanical coding system ensures all plug in units can be

inserted in their correct position.

The ABB free standing cabinet type E-35 can for example, accommodate two single channel

PLC equipments with the associated protection signaling units and an electronic trunk-dialing

unit for eight (8) telephone subscribers.

A nameplate on the front door of the carrier cabinet carriers relevant information of the PLC

link, such as equipment type, station names, carrier frequency etc.

To enable printed circuit boards to be exchanged without any readjustment being required,

there is on the rear side a strapping field for the initial programming of the system variant and

also for the system variant and also for the adjustment of the PLC equalizer. Further of

course, all terminal strips and connectors are easily accessible on the rear side.

MODES OF OPERATION

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The PLCC equipment is suitable for connecting to a telephone exchange and further more , a

4 wire remote and emergency call station can be created by operating it in parallel with the

built in service telephone equipment. The transmission facility for Tele operation working

use separate input and separate output circuit according to their classifications.

1) Telephone Facilities

The associated automatic telephone exchange (PAX) is suitable for a network with a limited

number of subscribers. Between the PAX and PLC channels, controls circuits give out-

signals for the setting up , dialing and later releasing a telephone connection and the

switching criteria between PAX and PLC equipment is performed by potential free contacts.

The PAX sending contact will, via the PLC signaling channel close an output contact in the

PLC receive and the distant end of the link.

The dialing impulses are transmitted over the combined pilot and signaling channel which

has a maximum transmitted speech of 50band. It should be noted that because of the various

possibilities of telephone switching, more functions are built into the speech circuits than are

actually needed by some PAX types.

2) Compressor And Expander (Compander)

The inclusion of a compander improves the carrier signal quality of speech and in normally

reserved for use over lines with high noise. The improvement in the signals to noise ratios is

approximately 12 db. When the speech is carried over PLC links in series, it is recommended

that only one compande r be used, the compressor being installed at the sending end of the

line and the expander in the farthest station.

The ETI series is fully wired for a later inclusion of the compander equipment when required.

3) Service Telephone

With the help of the built in speech facilities, service calls be carried out in 4 wire from the

front panel associated equipment the DC belt and the plug in 4 wire handset are supplied.

4) Supervison And Alarms

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The channels plug in supervision unit give an alarm indication if there is a failure of the tx

path, the transmitter / receiver and the power supply. Both a collective and individual alarms

are given and are indicted on the equipment with light emitting diodes (LED’s).

5) Signal Boosting

The equipment offers the possibility of signal boosting of one or two especially important

signals, for example protection signals for high voltage lines or equipment. This is advantage

during unfavorable transmission conditions caused by perhaps faults conditions on the power

line. During boosting, the less importing channels, for example the speech are disconnected

(known as disconnected channels) whereas other channels can be allowed to work normally

(non-disconnected able channels).

6) Tele-Operation Signals

Individual and adjustable Tele operation inputs are the essential requirement of the PLCC

equipment for the interfacing with the various manufacturers’ low frequency transmission

channels and for PLC through switching/transit working. The 5input and 3output possibilities

each individually adjustable and fully decoupled together with the separated terminals. For

protection signaling equipment, offer the necessary flexibility. A strapping field is provided

for choosing the various modes of operation.

7) 4 Wire Hand/Emergency Call

The equipment, especially in the extension phases can, without addition units in the HF

equipment is equipped through out with hand/emergency call telephone. This telephone with

DC bell can be connected directly via a 6-wire extension cable. The calling of the opposite

station is accomplished lifting the handset and pressing the calling button in the opposite

station after a two second delay the bell rings as the push button is pressed. By lifting the

handset the called station, the bell is automatically disconnected. After the cell is completed

both handset must be replaced. The calling tone is fixed at 1 KHz in the speech band.

SPECIFICATIONS OF PLCC

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1. General

- Carrier frequency range :- 40 to 512 KHZ

- Gross channel bandwidth :- 4 KHZ

- Useful AF band :- 300 to 3,700 KHZ

2. Permissible Room Temperature In

Climates

- Date guaranteed within reliable

     Centigrade

:- 0 to 45 degree

- Operation guarantee :- 20 to 45 degree Centigrade

3. Transmitter

R.F. Transmitting power :

- Peak envelope power :- 25 W

- Side band power :- 15 W

- Auxiliary carrier frequency :- 16 KHZ

At frequency 250 KHZ their power lower by 2 dB.

- I.F. carrier frequency :- 16 KHZ

- Pilot tone :- 3,600 HZ

- Test tone :- 1000 HZ

- Synthesizer reference frequency :- 8 KHZ

- Dummy load :- 20 OHMS

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4. Trunk Dialing

Shifting the pilot oscillator frequency of 3600 +/-30 transmits dialing criterions of a

speed of normally 1- pulses per second.

5. Power Supply

- DC supply :- 49 TO 60(-10/+25%), 180 W

Approximate maximum supply 2 percent

- Capacity :- 800 AH.

- A.C. Supply :- 220+/- 15%, 50 HZ

- Power consumption :- < 80 W

PRECAUTIONS AND MAINTENANCE

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In normal rooms the ETI equipment generally erected on an open rack on a frame of

freestanding cabinet.

The rooms for the erection of the equipment should have a dust free floor, which is washable.

The room should be well ventilated and of normal temperature & humidity and where

necessary provided with a ventilator fan having a dust filters.

The cabinets should be checked for damage before mounting.

Caution - before opening the hinged frame, make sure that the cabinet cannot tip forward.

Fault Analysis, Test Equipment And Test Procedure

(1)Test Equipments

(A) Test Oscillator

Test oscillator enables the commissioning of the PLC link without aid of external signals,

pressing the CALL button initiate a test tone of 1 KHZ which is fed to the voice amplifier and

passes through all transmit stages of the PLC equipment with the exception of the telephone

adapter. It is possible to check at any test point the DBR value printed in the front side of the

equipment is against the measured dB reading. It simplifies also the setting of the

transmitting (Tx) output power, which is measured by T (HF) on the transmitting level test

point.

(B) Dummy Load And Hf Loop Test

Faultfinding is much simplified when the HF output is connected to a definite resistive load

in place of the more or less ill defined characteristics of the power line. The ohmic load with

additional isolates the line, takes the form of a 50 ohms artificial load, which insert in place

of P3EO at the time of testing. Connecting back-to-back transmitter and receiver can test the

complete PLC equipment. This is achieved by to feeding a reduced transmitting voltage. The

dummy load automatically adjusts the receiver to accept the transmitter frequency.

(C) Audio Test

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For a quick and simple check of the equipment and audio test circuit is provided. The audio

test (voice amplifier) is to patch on the front side of the equipment to any desired signal path

and the received signal will be heard in the handset of the service telephone via amplifier.

The following signals can be checked in the AF section of the equipment: -

Speech, Tele operation/data dialing.

(2) Fault Analysis

In fault analysis the faulty devices are checked in this serial or manner:

- Telephone or Tele operation signals

- Cabling-low frequency circuits or DC power supplies

- PLC equipments

- HF transmission path

Comparisons with the transmission levels and working voltages measured under health

conditions are valuable aids to fault analysis. The back-to-back testing of the equipment using

the dummy load is also a very useful aid.The presence of AF signals in the various stages of

the equipment can be checked using the telephone handset and test load connected between

the associated measuring point and audio testing.

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BATTERY CHARGER

PLCC (Power Line Carrier Communication) works on rectified AC or main when supply

goes off. We make use of a device for proper functioning of PLCC, called BATTERY

CHARGER. this is the device that provides supply to the PLCC equipment for uninterrupted

working. It provides DC to the panel by battery of 48 V. In this type 24 batteries are

connected in series and individually per battery has approximately 2 V capacities.

1. General Description

Battery charger mainly consists of 4 sections -

1. Float charger

2. Boost charger section

3. Control section

4. Alarm section

All the four sections are situated in mounted sheet steel. The sides and tops of the frame are

provided with removable panels suitable recess has been provided in front panel to prevent

the compenent from projecting out. All meters indicating lamps, push buttons have been

mounted on front panel.

2. Technical Specifications

- Normal Input - 415 V AC 3 phase

- Input variation- +/20% of voltage

Float charger -

DC output - 50 V +/-1%

Output current - 20 to 40 ampere

Line regulation & load regulation - +/-1% individual

Ripple - 0.6 Vpp (peak to peak)

Efficiency - > 70%

Boost charger -

DC output - 43.2 to 67.2 V

Output current - 25-70 Amps.

Over load - 10%

Efficiency - > 80%

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1. Float Charger -

The float charger is basically static type 3-phase charger with stabilized output dc voltage.

The charger output dc voltage is constantly compared with standard dc reference voltage and

error voltage is again amplified. This amplified voltage control the triggering signals of all

the 3 phase bridge control rectifier, as the output voltage tends to decrease than it's selected

value, it makes the triggering signals of each thyristor of all 3 phase, to advance for firing

them, so that the output voltage remains within the specified accuracy. If the output voltage

tends to increase more than the selected value, the triggering pulses of these thyristors of all 3

phase are delayed in firing operations in such a way so that the output dc voltage is again

brought back to its stabilized voltage.

Circuit Description -

The 3-phase AC input is applied through the 3 poles 2 way switch (RS-I) and fuse F-18 to F-

20 to the float input contractor (CON-1).

The AC voltage is applied after CON-1 to the float transformer TX-1. The pilot lamp LED 4

To LED 6 indicates 'ON' condition of the float charger. The secondary of the TX -1 is

connected to the 3-phase full wave half controlled bridge rectifier, which consists of silicon

diodes D-2 to D-4, and SCR-1 to SCR-3, D-1 is the free wheeling diodes. HRC fuses F1 to

F7 protect all diodes and SCR's, Special surge circuits have also been provided to protect

SCR's.

The rectified output is filtered by the choke XL-1 and KL-2 and the capacitor bank C-1 and

C-2, which are protected by the HRC fuse F-8. The filtered DC output is protected by the

HRC fuses F-9 and LK-1. BR-1 is the bleeder is the resister for the capacitor bank.

Control Circuit of Float Charger -

The output of the charger is controlled through the electronic controller. Using phase control

of the SCR's feedback control the output. The control circuit has plug in type cards with hard

type connectors for external connections. The control circuit consists of following functional

circuits:

1. Power supply

2. UOT firing for SCR phase control

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3. Amplifier

4. DC under voltage/over voltage sensing

5. Auxiliary circuits

Power Supply:

This card provides regulated power supplies of +/-12% and u unregulated24 V used for ICs

and relays respectively, regulated output is 200 (maximum)., Auxiliary transformer TR-5 gets

supply from main transformer's phase and neutral points. The two identical secondary circuits

consisting of bridge rectifier, filter and IC regulator provide +/- 12V stabilized output and

24V unregulated DC output. The output of the bridge is filtered using L-C filter comprising

of filter Choke CH-1 and capacitor bank consisting of capacitor C-1. The capacitor is

protected by HRC fuses. BR-1 is bleeder resistance dummy load connected across the DC

output; the filtered output is then connected to the load circuit or to the battery through a

rotary switch. Shunt SH-1 is used for current limit control, which is also used for measuring

output current on ammeter. A DC volt- meter indicates the DC output voltage. An indicating

lamp indicates DC 'ON' condition. Blocking diodes are used to prevent reverse current

flowing from the battery to the charger when the charger voltage goes below the battery

voltage or charger is 'OFF'. The DC voltmeter V-2 reads voltage across the load bus.

UOT Firing Card:

There are three (3) identical firing cards, each for triggering one SCR in the main bridge.

Zener diodes DZ-1 to DZ- 6 and resistance R-15, R-16, R-17 connected to the secondary of

the TX-2, TX-2 and TX-4 clamp the positive half of the input sine wave to the Zenor voltage.

RV-1 and RV-2 are adjusted to equalize the conduction angle of the SCR's resulting in law

ripple. All SCR's at the same conduction angle +/-10% input and output adjusted to 5V. RV-2

again adjusted in full load to keep conduction angle of the SCR's equal.

C-1 beings charging at the start of the cycle, through current supplied by the R-2, RV-2 and

TR-1. When voltage across C-1 reaches the threshold value, UOT fires and C-1 discharge

through the pulse transformer. This pulse fires the main SCR via auxiliary transistor.

Output voltage control is obtained by varying the base ammeter bias of TR-1. An

increase/decrease in charging current leads to a decrease/increase in firing andgle and a

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corresponding increase/decrease in the output voltage. Senor DZ-1 limits the gate voltage of

the main SCR to the Zenor voltage.

Amplifier Card:

This card consists of two operational amplifiers IC-1 and IC-2 reference Zenor diodes DZ-1,

emitter follower TR-1 and buffer amplifier TR-3 and TR-4; IC-1 is the error detector

amplifier.

A negative reference by a Zenar diode DZ-1 and voltage sensing singles are given to the

inverting input of operational amplifier IC-1 the output is taken through a diode D-1 to the

base of transistor TR-1 from whose emitter the output is taken to the UOT driver cards. Ratio

of R-4 and R-5 determine the voltage gain of the operational amplifier and Rv-1 is used for

offset nulling.

The voltage sensing input is supplied to the OPAM IC-2 through an 'OR' gate formed by

diode D-2 & D-15. Whichever signal in higher the amplifier will respond to that signal. D-2

accepts the battery current signal while D-15 accepts the float or voltage limit signal at any

time only one of the above signals will be commanding the amplifier.

The overall working of the feedback control can be explained as follows :-

If the inverting input tends to rise or increase in loading during current limit, the output of the

operational amplifier IC-1 decrease which in turns makes the emitter voltage or TR 1 lower.

This reduces the bias on transistor TR 1 on firing cards so that charging current supplied by

them to the capacitor are reduced. Hence the triggering pulses are retarded and make the

output lower. Thus the negative feedback is complete so that the increase in output voltage

will reduce or if the unit is in load limit condition. The increase in output current will also be

reduced to bring the current to the original condition.

Resistance R-3, capacitor C-2 and also resistance R-2, capacitor C-1 are incorporated to

remove the instabilities like hunting. Operational amplifier IC-2 l liner amplifier the mv drop

across shunt. The ratio of R-14/R-15 determine the gain of the amplifier and RV-2 on sub

assemble sets the charging current. When charging current increases the mv drop across pin

No. 2 & 3 of IC-2 will increased. This voltage is applied to the base of TR-3 and TR-3

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through R-11. Transistor TR-4 will be the base current of TR-3 and TR-3 will increase the

voltage from D-2 will control in DC output voltage to keep the battery current at set level,

which can be adjusted by potentiometer RV-2.

It is desired that output of the rectifier attain its steady state value slowly rather than by step.

Fuse Fail Alarm:

Fuse Fail alarm is also available in float charger. In the event of any HRC fuse failure.

Corresponding types fuse blows and trip the corresponding relay.

2. Boost Charger Section

The battery can be charged by using the two rotatory switches provided on front panel for

coarse and fine control and that charging current can be read by ammeter A-3 provided on the

front panel. The operator must ensure that the rotatory switches are in minimum position

before switching on the boost charger.

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ADVANTGES & DISADVANTAGES OF PLCC

1. Advantages -

1. No separate wires are needed for communication purposes, as the power lines

themselves carry power as well as communication signals. Hence the cost of

constructing separate telephone lines is saved.

2. When compared with ordinary lines the power lines have appreciably higher

mechanical strength. They would normally remain unaffected under the

conditions, which might seriously damage telephone lines.

3. Power lines usually provide the shortest route between the power stations.

4. Power lines have large cross-sectional areas resulting in very low resistance

per unit length. Consequently the carrier signals suffer much less attenuation

then when they travel on usual telephone lines of equal lengths.

5. Power lines are well insulated to provide only negligible leakage between

conductors and ground even in adverse weather conditions.

6. Largest spacing between conductors reduces capacitance, which results in

smaller attenuation at high frequencies. The large spacing also reduces the

cross talk to a considerable extent.

2. Disadvantages -

1. Proper care has to be taken to guard carrier equipment and persons using them

against high voltages and currents on the lines.

2. Reflections are produced on spur lines connected to high voltage lines. This

increases attenuation and creates other problems.

3. High voltage lines have transformer connections, attenuate carrier currents. Sub-

station equipments adversely affect the carrier currents.

4. Noise introduced by power lines is far more than in case of telephone lines. This is

due to the noise generated by discharge across insulators, corona and

switching processes.

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CONCLUSION

The Practical training has proved to be knowledge buster for me and I have acquired a good

practical knowledge of the field which can’t be gained nearly by reading books. As PLCC is

the power line carrier communication that is used to transmit the signal with power line

network for such large distances, the power line themselves provides a very good medium of

transmission of information. So the power line carrier communication (PLCC) is mostly used.

The training has proved me with a good knowledge of working of PLCC and base for relating

the theoretical knowledge with the practical one. It was a very exciting adventurous and

exhaustive training which has raised my practical skills to a great extent.