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S.K.CHAUDHARY EDUCATIONAL TRUST’S

SHANKARA INSTITUTE OF TECHNOLOGY

KUKAS, JAIPUR

DEPARTMENT OF ELECTRONICS &COMMUNICATION

SESSION (2015-2016)

A SUMMER TRAINING REPORT

SUBMITTED IN PARTIAL FULFILLMENT FOR AWARD OF DEGREE OF

BACHELOR OF TECHNOLOGY

RAJASTHAN TECHNICAL UNIVERSITY, KOTA (RAJASTHAN)

RAJASTHAN RAJYA VIDYUT PRASARAN

NIGAM LIMITED, JAIPUR

DURATION OF TRAINING:- 60 DAYS

DATE OF TRAINING:-25.05.2015 TO 25.07.2015

SUBMITTED TO SUBMITTED BY

Mr. ASHUTOSH MISHRA RAMANAND SAGAR

H.O.D B.TECH (VIITH SEM)

(ECE DEPARTMENT) (12ESIEC047)

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PREFACE

The objective of a practical training is to learn something about industries practically and to

be familiar with a working style of a technical worker to adjust simply according to industrial

environment. As a part of academic syllabus of four year degree course in ECE, every student

is required to undergo practical training of 60 days. We are student of 3rd year ECE and this

report is written on the basis of practical knowledge acquired by our batch of 4 students

during the period of practical training taken at PLCC section of 132 KV, Chambal G.S.S

(Grid Substation) Jaipur.

This report deals with the equipments their relation and their general operating principle.

Sincere efforts have been made to present this report on PLCC with relevant diagrams and

proper description.

Inspire of all our best efforts, some unintentional errors might have eluded, it is requested to

neglect

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ACKNOWLEDGEMENT

I am grateful to Mr. R. P. Meena (Assistant engineer) for providing me an opportunity to

work as a trainee in PLCC section of Chambal G.S.S. I am thankful to Mr. Rajesh Chander

Singh (R.M-II) all other technical staff of PLCC of their valuable practical guidance and

their keen interest in my training.

I am very grateful to Mr. Ashutosh Mishra (HOD of ECE Department) to give me

opportunity to go under training at PLCC SECTION 132 KV, CHAMBAL G.S.S.,

JAIPUR as I was very enthusiastic about this. I am also very thankful to our seminar in-

charge Mr. Rajesh Kanwadia(Assistant professor of ECE Depatment and Ms. Shweta

Agarwal(Assistant professor of ECE Department).

I am thankful to my batch- mate and as well as my training colleague.

RAMANAND SAGAR

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INDEX

S.NO. TOPIC PAGE NO.

Chapter 1 INTRODUCTION TO PLCC………………………………………………… 1-2

Chapter 2 HISTORY………………………………………………………………………3-3

Chapter 3 BASIC PRINCIPAL OF PLCC………………………………………………..4-6

Chapter 4 EQUIPMENTS USED IN PLCC………………………………………………..7

4.1 OUTDOOR EQUIPMENTS…………………………………………………..7

4.2 INDOOR EQUIPMENTS……………………………………………………..7

Chapter 5 MAIN COMPONENTS OF PLCC……………………………………………...8

5.1 COUPLING CAPACITOR……………………………………………………8-9

5.2 LINE TRAP-UNIT/ WAVE TRAP…………………………………………...10

5.3 TRANSMITTER AND RECIVER……………………………………………10

5.4 HYPBRIDS AND FILTER…………………………………………………….11

5.5 LINE TUNERS………………………………………………………………..11

5.6 PROTECTION AND EAETHING OF COUPLING EQUIPMENTS………..12

5.7 LIGHTNING ARRESTER…………………………………………………….12

5.8 DRINAGE COIL………………………………………………………………13

5.9 LINE MATCHING UNIT……………………………………………………..13

5.10 CO-AXIAL CABLE…………………………………………………………13

Chapter 6 BASIC COUPLING ARRANGEMENT………………………………………..14

6.1 TYPES OF COUPLING……………………………………………………….15

6.1.1 PHASE TO GROUND COUPLING…………………………………………15

6.1.2 PHASE TO PHASE COUPLING……………………………………………15

6.1.3 INTERLINE COUPLING……………………………………………………16

6.2 COMPARISION OF PHASE TO PHASE AND GROUND COUPLING…17-18

Chapter 7 INDOOR EQUIPMENTS……………………………………………………….19

7.1 RTU (REMOTE TERMINAL UNIT)…………………………………………19

7.2 EPAX 2003(PLCC)…………………………………………………………….19

7.3 BATTERY BANK………………………………………………………………20

Chapter 8 CONSTRUCTION OF PLCC……………………………………………….21-22

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Chapter 9 SPECIFICATION OF PLCC……………………………………………………23

9.1 GENERAL…………………………………………………………………….23

9.2 TRANSMITTER………………………………………………………………23

9.3 TRUNK DIALING……………………………………………………………23

9.4 POWER SUPPLY……………………………………………………………..24

9.5 CAUTION……………………………………………………………………..24

Chapter 10 GENERAL DISCRIPTION OF PLCC EQUIPMENTS……………………….25

10.1 TELEPHONY AND TELE-OPERATION…………………………………..25

10.2 TELE-PROTECTION SIGNALS……………………….………………25-26

Chapter 11 APPLICATION OF ETI EQUIPMENTS……………………………………...27

11.1 PLC EQUIPMENTS AND COMBINED UNIT…………………………….27

11.2 REMOTE AT MULTIPLEXER CONNECTED BY A LONG CABLE…….28

11.3 BRIEF CHARACTERSTICS……………………………………………….28

11.4 REMOTE AT MULTIPLEXER CONNECTED BY A SHORT LINE……..28

11.5 PROTECTION SIGNALLING OVER PLCC EQUIPMENT………………28

11.6 REPEATERS…………………………………………………………………28

Chapter 12 MODE OF OPERATION………………………………………………………29

12.1.1 TELEPHONE FASCILITIES……………………………………………..29

12.1.2 COMPRESSOR AND EXPANDER………………………………………29

12.1.3 FOR WIRE HAND/ EMERGENCY CALL………………………………29

12.1.4 SERVICE TELEPHONE………………………………………………….30

12.1.5 TELE-OPERATION SIGNAL…………………………………………….30

12.1.6 SIGNAL BOOSTING……………………………………………………..30

12.2 FAULT ANALYSIS & TEST PROCEDURES………………………….30

12.2.1 TEST EQUIPMENTS……………………………………………………..31

12.2.3 FAULT ANALYSIS………………………………………………………..31

Chapter 13 BATTERY CHARGER………………………………………………………..32

13.1 GENERAL DESCRIPTION…………………………………………………32

13.2 TECHNICAL SPECIFICATION…………………………………………….33

13.3 FLOAT CHARGER SECTION………………………………………………33

13.3.1 CIRCUIT DESCRIPTION…………………………………………………33

13.3.2 FUSE FAIL ALARM……………………………………………………….34

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13.4 BOOST CHARGER………………………………………………………….34

13.4.1DESCRIPTION OF CIRCUITS……………………………………………34

13.4.2OPERATION OF CHARGER………………………………………….34-35

Chapter 14 APPLICATION OF PLCC……………………………………………………36

Chapter 15 ADVANTAGE AND DISADVANATAGE OF PLCC………………………37

Chapter 16 PRECAUTIONS & MAINTENANCE………………………………………38

Chapter 17 CONCLUSION………………………………………………………………39

Chapter 18 REFRENCES…………………………………………………………………34

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LIST OF FIGURES

S.NO TOPICS PAGE NO.

FIG3.1 AM and FM.............................................…………………………….............06

FIG3.2 PLCC indoor Equipment...................................................................................07

FIG3.3 PLCC outdoor Equipment…………….......…….............................................07

FIG 3.4 Typical PLCC System..........…………...........................…….........................08

FIG 5.1 PLCC component-coupling capacitor...................……...................................11

FIG 5.2 Wave Trap...................................................................................……….........11

FIG 5.3 Transmitter and Reciver...............……………...........................………........12

FIG 5.4 Protection and Earthing of Coupling Equipments............................................14

FIG 5.5 Lightning Arrester……….………...................................................................14

FIG 6.1 Basic coupling arrangement......................................………….......................16

FIG 6.2 Phase to Ground Coupling...............................................................................17

FIG 6.3 Phase to Phase coupling...................................................................................18

FIG 6.4 Inter Circuit Coupling......................................................................................19

FIG 7.1 Indoor Unit.....................................................................………......................21

FIG 13.1 Battery Charger................................................................................................34

FIG 13.2 Block Diagram of Float snd Boost Charger.....................................................34

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INTRODUCTION OF RSEB

The history of power development in Rajasthan goes back to the year 1949, when 19 princely

states merged to form Rajasthan. At that time,

Electric power was confined to very few towns and electricity was considered a luxury. The

total number of towns and villages electrified at that time did not exceed 42 and the installed

generating capacity was only 13.27 MW. However, with the formation of Rajasthan State

Electricity Board (RSEB) on 1st July 1957, power sector in Rajasthan received priority and

power projects began to mushroom all over State.

Rajasthan State Electricity Board Companies Government of Rajasthan on 19th July

2000,issued a gazette notification unbundling Rajasthan State Electricity Board into five

different companies so that board will run efficiently.

1. Rajasthan RajyaVidyutUtpadan Nigam Ltd.(RVUN), the generation Company.

2. Rajasthan Rajya Vidyut Prasaran Nigam Ltd.,(RVPN), the transmission Company.

3. Jaipur Vidyut Vitran Nigam Ltd.,(JVVNL) , a regional distribution company.

4. Ajmer Vidyut Vitran Nigam Ltd.(AVVNL) a regional distribution company.

5. Jodhpur Vidyut Vitran Nigam Ltd.(JDVVNL) a regional distribution company.

Rajasthan State Electricity Board Companies Functions

The Generation Company owns and operates the thermal power stations at Kota and

Suratgarh, Gas based power station at Ramgarh, Hydel power station at Mahi and mini hydel

stations in the State. The Transmission Company operates all the 765kV, 400kV, 220 kV and

132 kV electricity lines and system in the State. The three distribution Companies operate and

maintain the electricity system below 132kV in

the State in their respective areas.[1]

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CHAPTER 1

INTRODUCTION TO PLCC

(POWER LINE CARRIER COMMUNICATION)

The basic idea of this project into get benefit by transmitting /receiving data as well as power through HF (high frequency)cables. Power Line Communication (PLC) is a communication technology that enables sending data over existing power cables. This means that, with just

power cables running to an electronic device (for example) one can both power it up and at the same time control/retrieve data from it in a half-duplex manner.

Use of PLCC in modern electrical power system is mainly for telemetry and tele control. Tele

means remote. Telemetry refers to science of measurement from remote location. Different

types of data transmission system can be used depending upon the network requirement and

conditions.

Main data transmission system for telemetry and tele-control are:

1. Use of telephone lines

2. Use of separate cables

3. Power Line carrier communication

4. Radio wave micro wave channel [2]

PLCC is said to be backbone of Electrical transmission system. For large power system

power line carrier communication is used for

1. Speech transmission

2. Data transmission and

3.Protection of transmission lines.

Carrier current has a frequency range of30 to200 kHz in USA 80 to 500 kHz in UK,24 kHz

to 500 kHz in INDIA.

NEED OF PLCC

1. To cope up with ever increasing size of power grid

2. Need for economic and reliable means of intercommunication between various

generating station, substation and control room

3. Avoid dependence of busy telephone lines

Each end of transmission line is provided withidentical PLCC equipment consisting

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ofequipment:

1. Transmitters and Receivers

2. Hybrids and Filters

3. Line Tuners

4. Line Traps

5. Power amplifier

6. Coupling capacitor

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CHAPTER 2

HISTORY

The idea of using an existing medium to send the communication signals is as old as the

telegraph itself. But it had not been possible until the recent decades. The first significant step

in the field was when two patents were issued to American Telephone and Telegraph

Company in the name of 'Carrier Transmission over Power Circuits' in 1920. After four years

later in 1924 two other patents were filed for the systems transmitting and receiving

communication signals over three phase power lines.

Harsh characteristics of the power cables were the key problem in further development.

Researchers were involved to overcome the unpredictable characteristics of the power lines.

Since the early 1980, spread spectrum power line communication was the main focus of the

research. This technology is now developed far better than that initial improvement and is

promising a reliable utilization in home automation and security systems.

This technology has been in wide use since 1950 and was mainly used by the grid stations to

transmit information at high speed.[3]

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CHAPTER 3

BASIC PRINCIPAL OF PLCC

Power-line communications systems operate by adding a modulated carrier

signal on one conductor, on two conductors or on all three conductors of a high-

voltage AC transmission line. Different types of power-line communications use

different frequency bands. Since the power distribution system was originally

intended for transmission of AC power at typical frequencies of 50 or 60 Hz,

power wire circuits have only a limited ability to carry higher frequencies. So,

allotted frequencies range for this purpose is from 24 to500 kHz, with

transmitter power levels up to hundreds of watts.[4]

To carry out this communication there is a need of modulation. For PLCC,

generally amplitude modulation (AM) is used.

Fig-3.1( AM and FM)

In amplitude modulation, the amplitude (signal strength) of the carrier wave is

varied according to modulating signal. Sometimes frequency modulation is also

used if transmitting medium is optical fiber instead of coaxial cable.[5]

PLCC has some equipment inside the PLCC room and some part in switch yard.

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Fig- 3.2 (PLCC indoor Equipment)

Carrier signal which is generated by oscillator is modulated with message signal

with the help of modem, there after it is allowed to pass through band pass

filter; output of band pass filter is amplified before transmission via hybrid

section, this modulated signal is transmitted through high frequency co-axial

cable to yard.

Fig- 3.3 (PLCC outdoor Equipment)

Since telephone communication system cannot directly connected to the high

voltage lines suitably designed coupling devices have therefore to be employed.

These usually consists of high voltage capacitor or capacitor with polarized

devices used in conjunction with suitable lines matching unit (LMU’s) for

matching the impedance of line to that of the coaxial cable connecting the unit

to the PLCC transmit-receive equipment.

To sectionalize the transmission network and protect against failures, a "wave

trap" is connected in series with the power (transmission) line. They consist of

one or more sections of resonant circuits, which block the high frequency carrier

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waves (24 kHz to 500 kHz) and let power frequency current (50 Hz – 60 Hz)

pass through. Wave traps are used in switchyard of most power stations to

prevent carrier from entering the station equipment. Each wave trap has

alighting arrester to protect it from surge voltages.

A coupling capacitor is used to connect the transmitters and receivers to the high

voltage line. This provides low impedance path for carrier energy to HV line but

blocks the power frequency circuit by being a high impedance path. The

coupling capacitor may be part of a capacitor voltage transformer used for

voltage measurement.

Fig-3.4( Typical PLCC system)

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CHAPTER 4

EQUIPMENTS USED IN PLCC

4.1EQUIPMENTS OF SUB-STATION OR OUTDOOR EQUIPMENT

1) Lightning arrester

2) Wave traps.

3) Drainage coils

4) LMU

5) Earthing switch

6) CC/CVT

7) Co-axial cable

4.2INDOOR EQUIPMENT

1) PLCC panel

2) Battery bank

3) Battery charger

4) EPBAX

5) RTU

6) Modem

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CHAPTER 5

Main Components of PLCC

5.1 Coupling Capacitor

Couples high frequency carrier with power line (4000-10000pF)

Fig-5.1(PLCC component - Coupling Capacitor)

Coupling capacitor connects the carrier equipment to the transmission line. The coupling

capacitor’s capacitance is of such a value that it offers low impedance to carrier frequency

(1/ωC) but high impedance to power frequency (50 Hz).

For example 2000pF capacitor offers 1. 5MΩ to50 Hz but 150Ω to 500 kHz.

Thus coupling capacitor allows carrier frequency signal to enter the carrier equipment.

To decrease the impedance further and make the circuit purely resistive so that there is

nonreactive power in the circuit, low impedance is connected in series with coupling

capacitor to form resonance at carrier frequency.[2]

5.2 Line trap Unit /WAVE TRAP-

Do not allow the transmitted HFcarrier to enter inside the sub-station. without line trap HF

carrier get bypassed to some other line on the same bus bar and may leak to ground.

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Fig-5.2 (WAVE TRAP)

The carrier energy on the transmission line must be directed toward the remote line terminal

and not toward the station bus and it must be isolated from bus impedance variations. This

task is performed by the line trap. The line trap is usually a form of a parallel resonant circuit

which is tuned to the carrier energy frequency.

A parallel resonant circuit has high impedance at its tuned frequency, and it then causes most

of the carrier energy to flow toward the remote line terminal. The coil of the line trap

provides a low impedance path for the flow of the power frequency energy.

Since the power flow is rather large at times, the coil used in a line trap must be large in terms

of physical size. Hence a line trap unit /Wave trap is inserted between bus bar and connection

of coupling capacitor to the line. It is a parallel tuned circuit comprising of inductance (L) and

Capacitance (C).It has low impedance (lessthan0.1)for power frequency (50 Hz) and high

impedance to carrier frequency .This unit prevents the high frequency carrier signal from

entering the neighboring line.

Tuning Device (T.D.):

These are used with high voltage, high stability mica capacitors with no losses. For lower

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voltage class of tuning units (with impulse test voltage rating up to 40 KV)

Polystyrene capacitors are used by some manufactures. For higher voltage class of

tuning units with impulse test voltage rating up to 150 KV, capacitors with mineral oils

impregnated paper dielectric are used which rare

similar in construction to coupling capacitors all types are mounted in epoxy resin.

Single frequency traps have a single and double frequency traps and double tuned parallel

resonant circuits.

All the elements belonging to the tuning circuits are usually mounted in a common housing,

which can be resolved and substituted with another similar tuning device to resonate trap to a

different frequency.[2]

5.3 Transmitters and Receivers:-

The carrier transmitters and receivers are usually mounted in a rack or cabinet in the control

house, and the line tuner is out in the switchyard .This then means there is a large distance

between the equipment and the tuner, and the connection between the two is made using a co-

axial cable.

Fig-5.3(PLCC component-Transmitters and receivers)

The coaxial cable provides shielding so that noise cannot get into the cable and cause

interference. The coaxial cable is connected to the line tuner which must be mounted at the

base of the coupling capacitor. If there is more than one transmitter involved per terminal the

signal must go through isolation circuits, typically hybrids , before connection to the line

tuner.[2]

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5.4 Hybrids and Filters :-

The purpose of the hybrid circuits is to enable the connection of two or more transmitters

together on one coaxial cable without causing intermediation distortion due to the signal from

one transmitter affecting the output stages of the other transmitter. Hybrids may also be

required between transmitters and receivers, depending on the application. The hybrid circuits

can, of course, cause large losses in the carrier path and must be used appropriately. High

/low -pass and band-pass networks may also be used, in some applications, to isolate carrier

equipment from each other.[2]

5.5.Line Tuners:-

The purpose of the line tuner in conjunction with the coupling capacitor is to provide low

impedance path for the carrier energy to the transmission line and a high impedance path to

the power frequency energy.

The line tuner /coupling capacitor combination provides a low impedance path to the power

line by forming a series resonant circuit tuned to the carrier frequency.

On the other hand, the capacitance of the coupling capacitor is high impedance to the power

frequency energy. Even though the coupling capacitor has high impedance at power

frequencies, there must be a path to ground in order that the capacitor may do its job. This

function is provided by the drain coil, which is in the base of the coupling capacitor. The

drain coil is designed to be low impedance at the power frequency and because of its

inductance it will have high impedance to the carrier frequency.

Thus the combination of the line tuner, coupling capacitor, and the drain coil provide the

necessary tools for coupling the carrier energy to the transmission line and blocking the

power frequency energy. One last function of the line tuner is to provide matching of

impedance between carrier coaxial cable, usually 50 to 75 ohms, and the power line which

will have an impedance of 150 to 500ohms.[2]

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5.6. Protection and earthing of couplingequipment:-

Over voltage can be caused due to lightning, switching and sudden loss of load etc.

They produce stress on coupling equipment and line trap units. Non linier resistor in series

with protective gap is connected across the line trap unit and inductor of coupling unit.

The gap is adjusted to spark at a set value of over voltage.

Coupling unit and PLCC equipment are earthed through a separate and dedicated system,

so that ground potential rise of station ear thing system does not affect the reference voltage

level /Power supply common ground of the PLCC equipment.[2]

Fig-5.4 Fig-5.5

5.7.Lightning arrester :

A lightning arrester (in Europe: surge arrester) is a device used on electrical power systems

and telecommunications systems to protect the insulation and conductors of the system from

the damaging effect of lightning. The typical lightning arrester has a high-voltage terminal

and a ground terminal. When a lightning surge (or switching surge, which is very similar)

travels along the power line to the arrester, the current from the surge is diverted through the

arrestor, in most cases to earth.

5.8.Drainage coil :

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When supply is given, all equipments start working. Wave trap block high frequency signals

like 200khz and pass low frequency signal like 50hz and coupling capacitor passes the high

frequency signals of 200 kHz and blocks low frequency signal of 50 Hz. During all this

process if any leakage current flows due to any distortion, then this drainage coil arrests all

leakage current and ground it so that it does not cause any harm to the network.

5.9 Line Matching Unit:-

The out-put of PLCC is connected to the line matching unit before to the power lines to

achieve the proper impedance matching in between PLCC Equipments and power line.

LMU is a composite unit consisting of Drain Coil, Isolation transformer with Lightning

Arrester on its both the sides, a Tuning Device and an earth switch. Tuning Device is the

combination of R-L-C circuits which act as filter circuit. LMU is also known as Coupling

Device. Together with coupling capacitor, LMU serves the purpose of connecting effectively

the Audio/Radio frequency signals to either transmission line or PLC terminal and protection

of the PLCC unit from the over voltages caused due to transients on power system.

5.10 CO-AXIAL CABLE :-

This is used for inter connection between PLCC & L.M.U. for carrying the high frequency

signal.

CHAPTER 6

BASIC COUPLING ARRANGEMENT

The power frequency and radio frequency currents are sorted by this arrangement.

Carrier currents are prevented to enter station bus by wave trap and power frequency current

is blocked by coupling capacitor, from the PLC equipment.

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Hence we get power current at the bus and carrier current at PLC equipment.

Earth switch is used at the time of maintenance of LMU.

Lightening Arrestor is used to protect the system from the damaging effect of lightening.

Drainage coil has a pondered iron core serves to ground the power frequency

charging to appear in the output of the unit.

Fig-6.1 (Basic coupling arrangement)

6.1TYPES OF COUPLING

6.1.1Phase to ground coupling

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Fig-6.2 (Phase to Ground Coupling)

This figure describes that the wave trap 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 portion 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 gone 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 end cannot be made to

match the line perfectly. This is because the impedance of the line cannot be calculated

correctly as it depends partly on the soil conductivity enroot the line which varies from place

to place and time to time and partly on station switching condition.

6.1.2 Phase to phase coupling

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Fig-6.3 (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

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

Through this type of coupling there is increment in the reliability of communication, the

attenuation, the 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.

6.1.3 Inter linecoupling.

Fig-6.4( Inter circuit coupling)

This is the same as phase to phase coupling but with the difference that the two conductors

used for communication belong to two-different power circuits carrier on common towers.

This type of coupling is not employed where the two circuits are carrier on two separate sets

of towers as it then behaves more like a double phase to ground coupling and is found to be

impracticable.

This type of coupling is even more reliable than phase-to-phase coupling on the same circuit

than it permits operation with one of the two circuits opened out and founded for maintenance

xxv

purpose.

Inter phase or inter systems coupling are always employed on 220KV and 400KV lines where

the interference levels are therefore also used on very long 110KV lines where attenuation

becomes a problem. This type of coupling permit higher reliability of operation under breaker

conductor conditions and are always employed where carrier line protection systems are

employed.

6.2.Comparison of phase to phase and phase to ground coupling:-

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

traps and coupling capacitors in comparison to phase-to-ground. 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.

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 voltage induced in the line. In

phase-to-phase coupling the noise voltage tend to 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 the other case.

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

used and distance to be covered is suitable, and radiation not particularly objectionable, as

may be the situation in sparsely populated areas.

xxvi

CHAPTER 7

INDOOR EQUIPMENTS

Fig-7.1(Indoor unit)

7.1.R.T.U (REMOTE TERMINAL UNIT) :

• Interface with the electrical network to be monitored/controlled.

• Collects, filters& processes the power system data and transmits it to the control center.

• Receives the control commands from the control centre.

7.2.EPAX 2003(PLCC):-

The EPAX system 2003 (PLCC version) is an advanced, state of art, stored program

microprocessor controlled exchange, using 8-bit microprocessor. The control functions are

implemented with digital hardware and voice switching is done with TDM technique. The

microprocessor control ensures most reliable switching because the system employs only

electronic circuit. It eliminates periodic preventive maintenance and makes system noiseless

unlike conventional electromechanical exchanges. The PA2003 (PLCC) system accepts

decaying dialing pulses and is therefore compatible with rotary dialing instruments or pulsing

xxvii

type button telephone instruments. The PA2003 (PLCC) system has been specially designed

to be connected to be connected to another PAX through power line carrier communication

equipment. This system is intended to be a direct replacement for the electromechanical

exchange now in use in power generation system and industries. The exchange can interface

directly with PLCC terminal on one hand and the existing telephone sets all the others. Hence

the exchange software has been designed to meet all the existing needs of the presently used

electromechanical exchange.

7.3.BATTERY BANK:-

In case main supply is off, battery bank supply required amount of supply power.

Now a day care-free VARLA BATTERR is used.

VARLA stands for

xxviii

CHAPTER 8

CONSTRUCTION OF PLCC

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. Furthermore, a mechanical coding system

ensures all plug in units can only be inserted in their correct position.

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

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

unit for 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 adjustment of the PLC equalizer.[6]

DESCRIPTION OF PANEL CARDS [6]

PLCC section contains different card which enable it to do its work properly. This card is

specified by the some number and contains inbuilt circuit that performs accordingly.

Different card have different specification these specification can be summed in following

way:-

E3EC Receiver RF Filter

N3FL Test matter

P3EO RF hybrid

E5EA Transmit filter

B5EC Power supply

xxix

B3EA 40 VOLT REGULATOR

B3EB 24 VOLT REGULATOR

P5EA POWER AMPLIFIER

O3EI SUPERVISION

P3EC RECEIVE IF DEMODULATOR

E3ED RECEIVE IF FILTER

P3ED RF & AGC AMPIFIER

P3EF RECEIVE IF MODULATOR

O3EH SIGNAL OUTPUT PIOLT

O3EE TELEPHONE ADAPTOR

O3EG VOICE AMPIFIER

E3EF VOCE FILTER

O3EA TELE OPERATIONAL INPUT

O3ED EXPANDER OR COMPANDER

O3EC SIGNAL ADAPTOR

O3ED DIAL MODULE PIOLT TONE

P3EA TRANSMIT IF MODULATOR

E3EA TRASMIT IF FILTER

P3EB TRANSMIT RADIO FREQUENCY

MODULATOR

E3EB TRANSMIT PER FILTER

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CHAPTER 9

SPECIFICATION OF PLCC

9.1.General:-

1. Carrier frequency range : - 40to512KHZ

2. Gross channel band witch :- 4 kHz

3. Useful AF band : - 300to3700KHZ

Permissible room temperature in climates

1. Data guaranteed within reliable :-0 to 45 degree

centigrade

2. Operation guarantee :-20 to 45 degree

centigrade

3. Frequency stability of RF.F oscillator :-5HZ

9.2.TRANSMITTER

1. R.F. transmitting power

2. Peak envelope power :-25W

3. Side band power :-15W

4. Auxiliary carrier frequency :-16 KHz

At frequency 250 KHZ their power lower by 2 db

1. I.F. carrier frequency :-16 KHz

2. Pilot tone :-3600 Hz

3. Test tone :-1000 Hz

4. Synthesizer reference frequency :-8 KHz

5. Dummy load :-20 OHMS

9.3.TRUNK DIALING

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

speed of normally 1- pulses per second.

9.4.POWER SUPPLY

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

Approximate maximum supply 2 percent

2. Capacity :-800AH

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

4. Power consumption :- <80W

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

freestanding cabinet.

The room 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 and humidity and where

necessary provided with a ventilator fan having a dust filters.

The cabinets should be checked for damage before mounting.

Cabinets should prevent from tilting when opened.

9.5.Caution:-

Before opening the hinged frame, make sure that the cabinet can not tip forward.[6]

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CHAPTER 10

GENERAL DESCRIPTION OF PLCC EQUIPMENTS

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:

10.1.Telephony tele-operations:-

1. Telemetry

2. Remote control

3. Remote analogue metering

4. Tele-printer

10.2.Tele –protection signals for: -

1. high voltage power equipment

2. 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

standby and are used only in rare cases of a power fault for the planning of new networks 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 made of 3 main parts:

1. The low frequency multiplex section:-with the speech and up to 5 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 raster. The carrier frequency range

from 24 KHz to 500 KHz and with transmitted power of 20 Watts or a variant

100 Watts.

3. Power supply unit:- which 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

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

connected back-to-back a complete stimulation of the PLC link is established.

xxxiv

CHAPTER 11

APPLICATION 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’s line coupling equipment. In contrast, the telephone exchange and

Tele control equipments 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 as follows:-

11.1.PLC 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 frame, connections to the telephone and Tele control

equipments.

11.2.Remote at multiplexer connected by a long cable:-

The case 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. away in

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

parent PLC equipments with the remote multiplexer.

11.3.Brief characteristics:-

Cable Attenuation - permitted 32 dB maximum

Planning value 26 dB

Frequency band - 300 to 3700 HZ

300 to 3400 HZ Optimal

Adjustable attenuation equalizes for loaded lines, located at both ends .

The facilities available are:-

1. 4 wire duplex speech, from remote location.

2. Duplex tele-operational channels, from remote location.

3. Duplex pilot/signaling channel, from remote location.

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4. Possibilities for input and output connections of tele-operation signals from

PLC equipment.

5. Optional: service telephone from parent PLC equipment to opposite PLC

station.

11.4Remote 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 KMs, And is 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/output circuit (03EA and 03EH/S respectively).

11.5.Protection signaling over PLC equipments where AF Multiplexer is

Remote:-

Tele-protection equipment can be coupled directly to the PLC equipment. This means the

PLC 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 station is

received directly at the remote multiplexer.

11.6.Repeaters:-

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

ETI equipment can serve as repeaters at the intermediate station. In each transmission section

the carrier signal will be individually regulated, synchronized and equalized and the

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

station.

xxxvi

CHAPTER 12

MODE OF OPERATION

The PLC equipment is suitable for connecting to a telephone exchange and further more, a 4

wire remote/emergency call station can be created by operating it in parallel with the built in

service telephone equipment. The transmission facilities for tele operation working

(telemetry, tele-control and protection signals) use separate input and separate output circuits

according to their classifications.

When 4-Khz equipment carries simultaneously the speech and Tele operation signals , they

are transmitted in frequency multiplex and accordingly the audio frequency band is divided

into two parts. The lower part is used for speech and the upper part for tele operation signals.

12.1.1.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 receiver and

the distant end of the link.

12.1.2.Compressor and Expander:-

The inclusion of a Compander improves the carrier signal quality of the 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 several PLC links in series, it

is recommended that only one Compander be used, the compressor being installed at the

sending end of the line and the expander in the farthest receiving station. The ETI series is

fully wired for a later inclusion of the compander equipment when required.

12.1.3.For wire hand/emergency call:-

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

equipment is equipped throughout with hand/emergency call telephone. This telephone with

DC dell 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 2 second delay the bell rings as long as the push button is pressed. By lifting

xxxvii

the handset the called station, the bell is automatically disconnected. After the call is

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

band.

12.1.4.Service telephone:-

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

the front panel associated equipment, including the DC belt and the plug in 4 wire handset are

supplied.

12.1.5.Tele-operation signals:-

Individual and adjustable Tele operation inputs are the essential requirements of the PLC

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

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

possibilities, each individually adjustable and fully de-coupled 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.

12.1.6.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

advantageous during unfavorable transmission condition caused by perhaps fault 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-disconnect -able channels).

The arrangement of speech and Tele operation channels fall into one of three categories and is

achieved by connecting to one of the following input:-

1. The disconnect able bus (D)

2. The non-disconnect able bus (ND)

3. Signal boosting bus (B) with a predetermined amplification.

12.2.Fault analysis, test equipment and test procedure:-

12.2.1Test equipments:-

xxxviii

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

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

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

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

equipment is against the measured dB reading. The following signals can be checked in the

AF section of the equipment:-speech, tele operation/data dialing.

12.2.2Fault analysis:-

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

1. Telephone or Tele operation signals

2. Cabling low frequency circuits or DC power supplies

3. PLC Equipment

4. HF transmission path

Comparisons with the transmissions levels and working voltages measured under healthy

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.

xxxix

CHAPTER 13

BATTERY CHARGER

Fig-13.1(Battery charger) Fig-13.2(Block Dia. Of Float Charger and Boost Charger)

PLCC works on rectified AC or main, when make supply goes off. We use of a device for

proper functioning of PLCC, called BATTERY CHARGER. This is the device that provides

xl

supply to the PLCC equipment for uninterrupted working. It provides DC to the panel by

battery of 48V. In this type 24 batteries are connected in series and individually per battery

has approximately 2V capacities.

13.1.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 component from projecting out. All meters indicating lamps, push buttons have been

mounted on front panel.

13.2.Technical specifications:-

1. Normal input :- 415 V AC 3 Phase

2. Input variation :- +/- 20% of voltage

Float charger:-

1. Efficiency :- >70%

2. Line regulation & load regulation :- +/- 1% individual

3. Ripple :- 0.6 V PP (Peak to peak)

Boost charger:-

1. DC output :- 43.2 to 67.2 V

2. Output current: - 25-70 Amps.

3. Over load :- 10%

4. Efficiency :- >80%

13.3.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 controls the triggering signals of

all the 3 thrusters of 3 phase bridge control rectifier, as the output voltage tends to decrease

xli

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.

13.3.1.Circuit description:-

The 3-phase AC output 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). 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 1 liner amplifier )drop mV across shunt. The ratio of the amplifier and RV-2

on sub assembly sets the charging current increases the mV drop across pin No. 2 & 3 of IC-2

will be increased. This voltage is applied to the base of TR-4 through R-11. Transistor TR-4

will be the base current of TR-3 will increase the voltage from D-2 will control the voltage

correcting operational amplifier IC-1. This will result in decrease 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 values slowly rather than by

step.

13.3.2.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.

13.4.Boost charger section:-

13.4.1.Description of circuit:-

Boost charger is used to charge the batteries after power resumption. The input supply is

switched on mains of rotator switch RS-1, three numbers HRC fuse. F-21 to F-23 has been

provided for over current protection. AC contractor CON-2 has also been provided.

Transformer-6 steps down the input AC voltage to suitable level. Necessary taps are provided

in the primary of transformer to cater for varying input voltage that may prevail at sub-

station. The secondary voltage of transformer-6 is applied to a bridge rectifier, which consists

of 6 silicon diodes D-6 to D-11, for rectification of AC to DC. These diodes are mounted on

individual heat sinks for cooling so that junction temperature of the device is within specified

limit. The diodes are protected by capacitors and resistances against have storage effects and

xlii

transmit over voltage in also by HRC fuses F-10 to F-15.

The battery can be charged by using the two rotator 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.

13.4.2.Operation of charger:-

The float or boost charger can be switches ‘ON’ by means of selector switch RS-1. Thus at a

time only one charger either float or boost can be operated.

When the charger is operated in float mode the battery is on float charge and all the VDD’s

are bypassed through the contacts of DC contractor. This enables complete voltage appearing

on the load. In case of mains fall also the entire battery voltage is available on load through

contacts of DC contractor. When the charger is operated on boost mode, the contacts of DC

contractor are opened. Load voltage can be adjusted by VDD switch RS-8 as per the

requirement main switch RS-9 have been provided to isolate the charger from load and

battery. When the selector switch RS-9 is in charger mode then it will supplying load as well

as trickle charger. The batteries in float and boost charger, the batteries mode when the switch

RS-9 is in mains mode, then the load will be supplied by the battery and the charger is totally

isolated from battery for charger mains purpose.[9]

xliii

CHAPTER 14

APPLICATIONS OF PLCC

PLCC technology can be deployed into different types of applications in order to provide

economic networking solutions. Hence merging with other technologies it proves useful in

different areas. These are few key areas where PLC communications are utilized:

1. Transmission & Distribution Network: PLCC was first adopted in the

electrical transmission and distribution system to transmit information at a fast rate.

2. Home control and Automation: PLCC technology is used in home control

and automation. This technology can reduce the resources as well as efforts for

activities like power management, energy conservation, etc.

3. Entertainment: PLCC is used to distribute the multimedia content throughout

the home.

4. Telecommunication: Data transmission for different types of communications

like telephonic communication, audio, video communication can be made with the

use of PLCC technology.

5. Security Systems: In monitoring houses or businesses through surveillance

cameras, PLCC technology is far useful.

6. Automatic Meter Reading :Automatic Meter reading applications use the

PLCC technology to send the data from home meters to Host Central Station[7]

xliv

CHAPTER 15

ADVANTAGES& DISADVANTAGES OF PLCC

15.1.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 the 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

than 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.

15.2.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 corrections, attenuation 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.It is obvious that an effective power lines

carrier system must overcome these and many other

difficulties.

xlv

CHAPTER 16

PRECAUTIONS& MAINTENANCE

1. All connections should be thoroughly checked.

2. The control circuit boards should be inserted far firmly in their respective

sockets before energizing the battery charger.

3. All mounting bolts/screws should be checked before energizing as loose

mounting will cause vibrations.

4. The charger should be switched off once in every month and the connections

and mounting should be checked.

5. The battery terminals should be connected first and the AC input after that.

xlvi

CHAPTER 17

CONCLUSION

Companies used Power Line Communication to maintain power grid due to past low data rate

communication needs. High data-rate communication over low-tension lines is one of the

major applications in new technologies. Power Line Carrier Communication offers symmetric

as well as two way communication along with a permanent connection. Load management

and meter reading from a distance are the two Primary motivations for Power line

communications in future. In Automatic Meter Reading electronic data that is the meter

reading is transmitted over power lines from a distant place back to the substation where the

reading has to be noted, then the reading is relayed to a central computer in the utility's main

office. Hence this would be considered a type of fixed network system.

In today world power-line-communication is being used for many applications to control

various systems such as street lighting or energy management systems. In homes the so called

"baby-phones" are very popular in which power line communication is used in which low

quality analogue voice signals is transmitted through a 230V mains wiring. In comparison to

the old analogue systems used for communications, digital data which is transferred using the

power-line as communication media is a very useful alternative for domestic applications,

particularly for devices which are already connected to the mains (e.g. washing machines or

refrigerators, linked together for energy management). Power line communication saves the

biggest part of installation costs if it is used in buildings where electric wiring is already

present hence no need for wiring separately for communication. Hence power line

communication meets the customers’ needs for low cost.

Indoor power line communication should not be mixed with outdoor power Line

communications as both are different from one another regarding the availability. The indoor

power line communication is capable to transmit information at a rate of 2400bps (bits per

second) at a very low cost. For domestic applications this rate of data transmission is good

enough as in most of the cases in domestic applications the devices have to transmit only

control signals such as on/off, dimming values etc.

xlvii

REFRENCES

[1] http://www.rajasthandirect.com/government-department/rajasthan-state-electricity-board

[2] http://electrical-engineering-portal.com/power- line-career-communication-plcc

[3] http://www.engineersgarage.com/articles/plcc-power- line-carrier-communication

[4] en.m.wikipedia.org/wiki/Power-line_communication

[5] en.m.wikipedia.org/wiki/Amplitude_modulation

[6] Manual of ETI equipment

A.B.B(Asea Brown Bowery Ltd)

[7] ] http://www.engineersgarage.com/articles/plcc-power-line-carrier-communication

[8] [ N.N.Biswas and Edition-1975], “Principles of carrier communication”.

Page no.101-103

[9].Manual on Battery Charger

Omega Electroics

[10] slideshare.net/mobile/vishu_angira/power- line-career-communication