Report on PLCC

ECE-B/2015-2016/PIET, JAIPUR

POWER LINE CARRIER COMMUNICATION

CHAPTER-1

JVVNL AT A GLANCE

1.1 BRIEF HISTORY OF JVVNL

The Rajasthan State Electricity Board was constituted with effect from 1st July,1957 by Government of 57 dated the 28th June,1957 under the Electricity (Supply) Act,1948 which enactment has for its object, the coordinated development and rationalization of generation and supply of electricity on a regional basis throughout the country in the most efficient and economical way. Government of Rajasthan on 1 9th July 2000, issued a gazette notification unbundling Rajasthan State Electricity Board into Rajasthan Rajya Vidyut Utpadan Nigam Ltd.(RVUN), the generation Company; Rajasthan Rajya Vidyut Prasaran Nigam Ltd.,(RVPN), the transmission Company and the three regional distribution companies namely

Jaipur Vidyut Vitran Nigam Ltd.,(JVVNL)

Ajmer Vidyut Vitran Nigam Ltd.(AVVNL)

Jodhpur Vidyut Vitran Nigam Ltd.(JdVVNL)

JVVNL is the largest government organization of Jaipur in the field of Electrical and

Electronics. The duration of my training was 60 days and in these days I was given a chance

to increase my knowledge of my branch. These 60 days of training were very helpful for me

to increase my knowledge. This presentation is made to share my experiences with

everyone. The content is fully true to my knowledge. The main purpose of going training is

to enhance our knowledge in practical field. I got a chance to implement my theoretical

knowledge in practical world.

JAIPUR VIDYUT VITRAN NIGAM LIMITED (Jaipur Discom) is engaged in distribution

and supply of electricity in 12 districts of Rajasthan, namely Jaipur, Dausa, Alwar,

Bharatpur, Dholpur, Kota, Bundi, Baran, Jhalawar, Sawaimadhopur, Tonk and Karauli.

HEERAPURA POWER HOUSE Provides the pathway for power within whole of Jaipur.

1



This Power House builds, maintains and operates the high-voltage electric transmission system that helps to keep the lights on, businesses running and communities strong. Complete Address - NH-8, Jaipur Ajmer Exp Highway, Near 200 FT By Pass, Ajmer Road, Jaipur Pin - 302021 (Ward no - 19).

Electrical power is generated, transmitted in the form of alterna ting current. The electric power produced at the power stations is delivered to the consumers through a large network of transmission & distribution. The transmission network is inevitable long and high power lines are necessary to maintain a huge block of power source of generation to the load centers to inter connected.

Fig 1.1: JVVNL MAIN OFFICE AT JAPUR

1.2 STAFF AT JVVNL

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Name Designation Contact number

Mr. Sanjay Malhotra, IAS

Chairman Discom`s 91-141-2747064

Mr. B. K. Dosi, IAS Managing Director 91-141-2744965Mr. Deepak Srivastava

Director (Finance) 91-141-2740451

Mr. G. R. Chaudhary Director (Technical) 91-141-2740341Mr. S.C. Dinker DirectorMr. B. K. Dosi, IAS Managing Director 91-141-2744965Mr. Deepak Srivastava

Director (Finance) 91-141-2740451

Mr. Girish Goyal Company Secretary 91-141-2742802Mr. S. L. Gujjar CE (O & M)-Jaipur Zone 91-141-2202403Mr. P.C. Sharma CE (O & M)-Bharatpur

Zone91-05644-236080

Mr. Naveen Arora CE (O & M)-Kota Zone91-0744-2450066

1.3 CONCLUSION

This part of report gives information of our learning and exposure level in the company. It

also enlightens the readers about various departments relevant to EC branch present at the

JVVNL.

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CHAPTER-2

INTRODUCTION OF PLCC

2.1 INTRODUCTION

As electronics play a vital role 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 large

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

of various unit to see that the system is maintained in the optimum working condition.

Power line carrier communication has been found to be the most economical & reliable

method of communication for the medium and long distance in the power network. For

short distance the ordinary telephone phone system is used. Open wire or underground cable

and in some cases VHF wireless communication is found to be more economical as they do

not involve the use of costly high voltage coupling equipment. In PLCC the higher

mechanical strength and insulation level of high voltage power line result in increased

reliability of communication & lower attenuation over long distance.

PLCC is used for establishing speech/ data communication between two stations using a

power line. PLCC is an approach to utilize the existing power lines for the transmission of

information. In today’s world every house and building has properly installed electricity

lines. By using the existing AC power lines as a medium to transfer the information, it

becomes easy to connect the houses with a high speed network access point without

installing new wirings.

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

to transmit information at high speed. Now days this technology is finding wide use in

building as it avoids the need of extra wiring. The data collected from different sensors is

transmitted on these power lines thereby also reducing the maintenance cost of the 4



additional wiring. In some countries this technology is also used to provide Internet

connection.

Fig 2.1: POWER LINE CARRIER COMMUNICATION

2.1.1 COMMNICATION SYSTEM IN PLCC

Power generation and transmission need a good &healthy communication system for proper

functioning of the power system and to give uninterrupted supply to the consumers.

Power line carrier communication (PLCC) is mainly used for telecommunication, tele-

protection and tele-monitoring between electrical substations through power lines at high

voltages, such as 110 kV, 220 kV, 400 kV. In a PLCC system the communication is

established through the power line. PLCC integrates the transmission of communication

signal and 50/60 Hz power signal through the same electric power cable. The audio

frequency is carried by a carrier frequency and the range of carrier frequency is from 50

5



kHz to 500 kHz. The voice signal is converted /compressed into the 300 Hz to 4000 Hz

range, and this audio frequency is mixed with the carrier frequency. The modulation

generally used in these systems is amplitude modulation. The carrier frequency range is

allocated to include the audio signal, protection and the pilot frequency. The pilot frequency

is a signal in the audio range that is transmitted continuously for failure detection. The

carrier frequency is again filtered, amplified and transmitted. The transmission of these HF

carrier frequencies will be in the range of 0 to +32db. This range is set according to the

distance between substations. Different types of power line communications use different

frequency bands, depending on the signal transmission characteristics of the power wiring

used. PLCC can be used for interconnecting PBXs. The electricity board in India has an

internal network PLCC between PBXs.

Fig 2.2: Power Lines

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.

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Main data transmission system for telemetry and tele control are:

1. Use of telephone lines

2. Use of separate cables

3. Power carrier communication

4. Radio wave micro wave channel

2.2 OPERATING PRINICIPAL

The communication device used for the communication over the power lines is a MODEM,

commonly known as Power Line MODEM (PLM). It works as both transmitter and

receiver, i.e., it transmits and receives data over the power lines. A power line modem not

only modulates the data to transmit it over the power lines and but also demodulates the

data it receives from the power lines. By using modulation techniques, binary data stream is

keyed on to a carrier signal and then coupled on to the power lines by PLM. At the receiver

end another PLM detects the signal and extracts the corresponding bit stream.

7



Fig 2.3: Block Diagram of PLCC

The above image shows the working of a PLCC system. Data is processed before

transmission on power lines according to the above figure. First data is modulated & filtered

and then by using couplers, it is sent over the power lines.

2.3 CONCLUSION

The training program of JVVNL for students in technical field & higher education provides

a good platform for practical training & to understand the basic & complex concepts of

electronic equipment`s and kits. A fair and educational environment at JVVNL helps the

students like us to learn the basic of electronics equipment`s and components to be used at

appropriate places. The industrial training arranged for us has been proved to be beneficial

in context of our knowledge and experience. 8



CHAPTER-3

EQUIPMENT

3.1 INTRODUCTION

There are two types of equipment is used in power line carrier communication, which is

indoor and outdoor equipment. Both are very helpful to wit how to power line carrier

communication done.

3.2 OUTDOOR EQUIPMENT:-

The equipment`s installed out the control room are called outdoor equipment.

3.2.1 LINE TRAP 9



It is also called "Wave trap". It is connected in series with the power (transmission) line. It

blocks the high frequency carrier waves (24 KHz to 500 KHz) and let power waves (50Hz -

60Hz) to pass through. It is basically an inductor of rating in millinery.

Fig 3.1: Line Trap

Fig 3.2: Circuit diagram of Line Trap

3.2.2 CAPACITOR VOLTAGE TRANSFORMER

It allows to pass the frequency to line. It provides low impedance path for carrier energy to

HV line and blocks the power frequency. Circuit by being a high impedance path easily.

3.2.3 LINE MATCHING UNIT

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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. It is also used for matching the impedance of the power line and HF cable.

3.2.4 BALANCING TRANSFORMER (BT)

Balancing transformer (BT) is used when phase to phase communication system is used for

balancing the two LMU. The diagram of balancing transformer is shown in figure 3.3. As

shown in diagram is very less in size but it is play a vital role in power line carrier

communication.

Fig 3.3: Balancing Transformer (BT)

3.2.5 HIGH FREQUENCY CABLE (HFC)

It is used to carry the signal from PLCC cabinet to switch yard.

3.3 INDOOR EQUIPMENT:-

The equipment`s installed in the control room are called indoor equipment. 11



3.3.1 EPAX

It consist of PLCC carrier equipment and related electromechanically switching

equipment`s like EPAX to provide voice communication.

Fig 3.4: EPAX

3.3.2 CARRIER TREMINAL

The 9505 PLC terminals are intended for transmission of speech, telemetering, teleidication

and tele protection in the signal carrier frequency.

3.3.3 BATTERY CHARGER

It is used for 48 volts DC supply

3.3.4 LIGTHING ARRESTER

The lighting arrestor against high voltage surges caused by atmospheric effects or switching operations protects the wave traps .The nominal discharge current

of this lighting arrester is selected to suit that of the substation lighting arrester behind the wave trap. The tuning elements however have been rated at

20to30%.

The lighting arrester used may be vacuum type arrester whose are over voltage lies below the rated voltage of the tuning capacitor, but about the voltage

produced across the coil during a short circuit current surge. Therefore it protects the tuning capacitors against momentary over voltages caused by traveling

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waves. Sustained over voltages resulting from short circuit currents are not high enough to cause the lighting arrester to be over. Hence, sustained and

consequent destruction of the arrester are avoided.

High voltages high stability mica capacitors with low losses are used .For low voltages class of tuning units (up to 40kv) polystyrene capacitor are used .For

high voltage class of tuning units (up to 150kv) .Capacitors with mineral oil impregnated paper dielectric are used which are similar in construction to the

coupling capacitor . All types are molded in epoxy resin .Single frequency traps have double tuned parallel resonant circuit. All elements belonging to the

tuning circuit are usually mounted in a common housing which can be resolved and substituted with another similar tuning device to resonate the trap to a

different frequency.

The drainage coil has a pondered iron core serves to ground the power frequency charging to appear in the output of the unit .The coarse voltage arrester

consist of air gap, which spark over at about 2kv and protect the matching unit against line surges .

Fig 3.5: Lighting Arrestor

3.3.5 POWER LINE CARRIER COMMUNICATION CABINET

It is installed in control room. It has two sections:

Transmitter: In this, voice frequency (VF) is amplified and then modulated to

intermediate frequency (IF) and amplified, modulated into HF and then transmitted.

Receiver: In this section HF signal is received and then demodulated from HF to

IF and connected to the tale phone.

3.4 CONCLUSION

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There are various equipment which we used in power line carrier communication field such

as line matching unit, wave trap etc. After getting all sound knowledge about equipment we

can easily understand all about power line carrier communication. At JVVNL for students

in technical field & higher education provides a good platform for practical training.

CHAPTER – 4

MODES OF COUPLING TO POWER LINE

4.1 INTRODUCTION

Power transmission lines have usually three conductors, one for each phases running

between points to point. This presents many different configurations for coupling to carrier

equipment. The most important technical problem in a power line carrier is to devise

methods and equipment to couple the low voltage and high frequency carrier set to the high

voltage and low frequency power line. During the annual stages of carrier operation on

power lines, and aerial wire of more than 300 feet length, supported on power line structure,

was used. On one end of it was connected the output from carrier equipment. While the

aerial coupled the signals to power lines mainly due to the capacitance between them. The

modern practice is to achieve the coupling by connecting a capacitor between the carrier

terminal and high voltage line. The particular value of the capacitor is a compromise

between two conflicting requirements

4.2 PHASE TO GROUND COUPLING

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Carrier terminals are connected between one phase conductor and ground. The wage traps and coupling capacitors are all connected to one conductor of the

power line. The remaining two conductor do not have wave traps a portion of carrier energy is lost and also radiated losses are high as the connection at the

receiving end cannot be made to match the line perfectly.

Fig 4.2: PHASE TO GROUND COUPLING

4.3 PHASE TO PHASE COUPLING

It provides metallic go and return paths to the carrier currents. In this case the uncoupled conductor does not have any appreciable influence on the

transmission.

15



Fig 4.3: PHASE TO PHASE COUPLING

4.4 INTER CIRCUIT COUPLING

It provides metallic go and return paths to the carrier currents. In this case the uncoupled conductor does not have any appreciable influence on the

transmission.

Fig 4.4: INTER CIRCUIT COUPLING 16



4.5 CONCLUSION

There are various coupling equipment`s which we used in power line carrier communication field such as phase to phase coupling, phase to ground coupling etc. After getting all sound knowledge about coupling equipment`s we can easily understand that how is it work. Coupling is most important topic in power line carrier communication without it, power communication is impossible.

CHAPTER – 5

ESSENTIAL UNITS

5.1 INTRODUCTION

There are basically five essential unit of power line. These are coupling capacitor, line

matching unit, wave trap, battery charger and float charger. All are very helpful to

understand about power line carrier communication.

5.2 COUPLING CAPACITOR

The important role of coupling capacitor in carrier operation over power lines has already been mentioned. Their special features are that they are rated to

withstand the high voltages and are insulated to same degree as the line or the other high voltage equipment. Now they are made up of oilpaper and due to their

large size are preferably installed outdoors.

Necessary devices for protection against high voltages like spark gap; drain coil and grounding switch are contained in a box at the base of the coupling

capacitor.

5.3 WAVE TRAP

Wave traps or line traps are used between the transmission line and power station to avoid carrier power dislocation in the power plant and cross talk with

17



other power line carrier circuits connected to the same power station. They offer high impedance to carrier frequencies but pass 50 cycles power currents

easily. They can be resonated at a single carrier frequency with a parallel capacitor. The tuning capacitors are protected against the surge voltages by a spark

gap arranged in parallel.

Fig 5.3: Wave Trap

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Fig 5.3(a): Wave Trap (Line trap)

5.3.1 FEATURE OF WAVE TRAP

Epoxy resins compatible with the glass fiber under thermal hock condition.

Aluminum constructions throughout with current carrying connections yielded.

No maintenance required.

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It can withstand extreme temperature fluctuations and weather condition.

Finish given by sand blasting and treating with specially modified epoxy resin paints.

Tuning element design using sophisticated programs run on advanced computers and the components carefully selected to give the optimum performance

under all condition of service. Atmospheric pollution and climatic changes do not affect the performance. No creep age path dues to the encapsulation of mains

coil. Some conductors are used to minimize loss due to eddy currents. The terminal supporting spider reinforced to withstand the short circuit forces during

fault conditions .Insulation material used much higher than class f requirements of temperature. Corona ring provided to maintain the RIV voltage levels low

and within specified limits.

5.3.1 CONSTRUCTION

The main coil windings are encapsulated by roving continuous filament fiber glass that has been impregnated with a specially selected epoxy resin hardener

system. The epoxy resin fiberglass composite is then cured according to a programmed temperature schedule. This process results in high mechanical strength

and heat distortion temperature above 160degree Celsius. The inherent bonding properties of the fiberglass resin composite system convert coil into compact

solid package. The mechanical strength required to withstand specified short circuit current is achieved by winding sufficient filament fiberglass around the

conductor. The two ends of the coils are reinforced with additional fiberglass roving to take up the severe stresses on the end turns of the coil caused by high

voltage surges or external short circuit. The main coil windings are terminated at each end on aluminum flat called spider arm. The spider arm bearing the

termination is further reinforced to carry the high short time current.

The tuning pack is connected in parallel with the main coil to provide high impedance to the desired carrier frequency .The type of tuning pack used will

depend on whether a single frequency, two frequencies and band of frequencies is to be blocked. Wideband tuning is most suitable for multichannel

application as relatively constant impedance is obtained over broad frequency band .The tuning pack is designed to have a minimum specified resistive

component over the entire blocking range so that these wave trap will not be detuned by the widely variable value of the station reactance’s. Tuning packs can

be supplied with fixed bandwidths to suit customer requirements. The minimum blocking impedance in the range 400ohms to 1000ohms can be given as

required. Tuning pack is constructed using high quality and closed tolerance capacitors, carefully designed non-securable inductors and non-inductive high

watt resistors .The components are individually tested and assembled inside a fiberglass tube .This is then completely filled with a special grade resin mixture

and sealed. This encapsulation protects them from the environment and mechanical shocks ensuring stability over long period of service.

The lighting arrestor against high voltage surges caused by atmospheric effects or switching operations protects the wave traps .The nominal discharge

current of this lighting arrester is selected to suit that of the substation lighting arrester behind the wave trap. The tuning elements however have been rated at

20to30% more than maximum residual voltage of the lighting arrestor at the maximum discharge currents.

20



5.4 LINE MATCHING UNIT

LMU is also called the coupling filter. It consists of the matching transformer and tuning capacitor to suit the individual requirement of the coupling equipment

and is generally tuned too wide band of carrier frequencies (100-450 kHz typical).

5.4.1 LIGHTING ARRESTER

In addition to tuning devices which usually consists of a capacitor. It is invariable connected across the choke coil of wave trap.

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

the rated voltage of the tuning capacitor, but about the voltage produced across the coil

during a short circuit current surge. Therefore it protects the tuning capacitors against

momentary over voltages caused by traveling waves. Sustained over voltages resulting from

short circuit currents are not high enough to cause the lighting arrester to be over. Hence,

sustained and consequent destruction of the arrester are avoided.

5.4.2 TUNING CAPACTIOR

High voltages high stability mica capacitors with low losses are used .For low voltages class of tuning units (up to 40kv) polystyrene capacitor are used .For

high voltage class of tuning units (up to 150kv) .Capacitors with mineral oil impregnated paper dielectric are used which are similar in construction to the

coupling capacitor . All types are molded in epoxy resin .Single frequency traps have double tuned parallel resonant circuit. All elements belonging to the

tuning circuit are usually mounted in a common housing which can be resolved and substituted with another similar tuning device to resonate the trap to a

different frequency.

5.4.3 DRAINAGE COIL

The drainage coil has a pondered iron core serves to ground the power frequency charging to appear in the output of the unit .The coarse voltage arrester

consist of air gap, which spark over at about 2kv and protect the matching unit against line surges .

5.4.4 EARTH SWITH

As the coupling device is inserted between the low voltages terminal of the coupling capacitor and earth, the earth switch is provided to ensure a temporary

direct earthing of the coupling capacitor during maintenance or commissioning.

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Fig 6.3.4: Earth Switch

5.5 BATTERY CHARGER

5.5.1 GENERAL DISCRIPTION

The battery charging system is intended to:

Keep the 50v-200AH, 350AH & 600AH Battery on trickle or boost charge as

required.

Supply DC power to the Sub-Station.

The Battery charge mainly consists of 4 sections which are:-

Float charge section.

Boost charge section.

Control section.

Alarm circuit.

All the four section are housed in a floor mounted sheet steel enclosures with a rigid angle

framework for mounting of components. The sides and top of the frame are provided with

removable panels. The rear portion consists of 2 nos. of hinged panels. A suitable recess has

been provided in the front panel to prevent the components from projecting out. All meter,

indicating lamp, push buttons have been mounted on the front panel.

The completed panel rests on two 75-mm channels on two sides.

The float charge essentially consists of a three phase transformer rectifier set for automatic

regulation of DC output. The float charge is means to supply regulated DC voltage to the

load and keep the battery on trickle charge. The boost charge section is initial or refresher charging of the 50 V-200AH, 350 AH & 600 AH battery as per manufacturer’s specifications.

22



This section essentially consists of a manually controlled (by rotary switches) three phase transformer rectifier set. In case of float charge

failure the boost charge can be put in emergency use to supply DC voltage to the load by reducing the boost charging voltage and using voltage

dropping diodes.

5.6 BOOST CHARGER SECTION

5.5.1 CIRCUIT DISCRIPTION

Boost charge is used to charge the battery after power resumption i.e. charging process. The input supply is switched ON means of Rotary

switch RS1, three Nos. HRC Fuses F21 to F23have been provided for over current protection. Ac Contactor CON-2 have also been

provided.TX6 steps down the input AC voltage to suitable level. Necessary taps are provided in the primary of the transformer to cater for

varying input that may prevail at the sub-station. The necessary voltage of TX6 is applied to a bridge rectifier, which consists of six silicon

diodes D6 to D11 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 diode are protected by capacitors and resistances against whole storage effects and transient over

voltage and also by HRC fuse.

5.6.2 ALARM ASSOCIATED TO THE BOOST CHARGER

The Boost charge has audio visual alarms similar to float charger used for indication of

faults.

5.6.3 OPERATION OF CHARGER

The float boost charger can be switches ‘ON’ means of selector switch RS1 thus at a time

only one charge 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 by passed through the contacts of DC contactor. This enable complete voltage appearing

on the load. In case of mains fail also the entire battery voltage is available on load though

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

contactor is open.

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Load voltage can be adjusted by VDD switch RS8 as per the requirement main switch RS9

have been provided to isolate the charger from load & battery. When the selector switch

RS9 have is in charger mode then it will supplying load as well as trickle charge the battery

in float mode & boost charge the batteries mode when the switch RS9 is in Main Mode then

load will be supplies by the battery.

CHAPTER – 6

EPAX

6.1 INTRODUCTION

As on today PLCC carrier equipment and related digital switching in which we use

microprocessor, provides non- blocking switching on line diagnostic, integrated voice and

data communication, redundancy.

The system employs stored program control (SPC) using pulse code modulation (PCM) and

time division multiplexing (TDM) confirming to latest CCITT standards. The system has

networking capability as well.An 8*24 Line MELTEL EPAX consist of 14 slot cabinet system that consists of following cards:- .

6.2 POWER SUPPLY CARD

It gives input signal of -48 and output of +5volt,-12volt ,+12volt & Ring 75VRMS. The 24



input -48 volt also serves as feed voltage to the extensions. It makes use of air cooling using

a fan operating on -12 volt DC.

6.3 CENTRAL PROCESSING CARD

It carries out all the control function in EPAX.

These functions include the following:

Call processing

Line supervision

Digit out pulsing over trunk link etc…..

A DISPLAY circuit is provided on the CPU board. This circuit contains two seven segment

LED displays and two switches. Display indicated the error code of the fault occurred in the

system. This will also indicate the type of fault occurred in the system on the pressing the

‘ACV’ (advance) switches. The second switch, ‘ALM CLR’, is used for the stopping the

alarm from the ‘BUZZER’ mounted on the CPU board, which gives audible alarm on any

fault occurrence in the system

6.4 DIGITAL SWITCH CARD (DSWIC CARD)

This card consists of a PCM switch which does the VOICE SWITCHING. In this module

the following circuits are present.

Tone generator.

Music-on-hold circuit.

Two DTMF receiver circuits.

PCM clock generating circuit.

A basic tone oscillator generates a 440 Hz single tone, which is fed to a CODEC. Dual tone

also can be generated. The codec injects the digitized tone samples into the PCM stream at

time slot 1 of highway zero.

PCM clock, 2.048 MHz, and frame sync signal are generated and distributed to other

module through a buffer.

When a P&T subscriber is kept waiting instead of HOLD TONE, pleasant music can be sent 25



with this music circuit. The music is generated internally. There is also an option for

connecting external music of customer’s choice.

To identify the digits dialed from telephones DTMF receivers are used. There are 2 DTMF

present in the card.

6.5 LINE INTERFACE CIRCUIT

The LIC is the analogue LINE INTERFACE CIRCUIT module. It provides interface for 4

analogue extension lines.

The following are the functions of LIC.

Feeding DC voltages to the telephone instrument.

Detection of telephone hook-status and dialing.

Connection / disconnection of ringing to the telephone.

Transmitting, receiving and processing of speech signals.

Generation of time slots for the equipment’s

6.5.1 ACTIVE DC FEED CIRCUIT

This circuit feed -48V DC to the telephone while blocking the speech signals frompassing through the DC feed circuit itself, to avoid any loss of speech signals .

6.5.2 HOOK STATE SENSOR

It becomes active whenever an extension handset is lifted. The digits dialed from the telephones are identified through this HOOK-STATE SENSOR only.

6.5.3 RINGING

Ring is given to the telephone connected to the system by command from the CPU

module. These ringing signals are generated in the power supply unit.

Ringing is disconnected either by a command from CPU card or when the telephone

handset is lifted off the hook.

26



6.5.4 REGULATOR

The power supply is regulated before supplying to the speech IC’s since regulated

supply is generated in each LIC; it helps to reduce the power supply noise in speech

signals.

6.5.5 SPEECH

The speech signal coming from the telephone instruments is sampled, filtered PCM

coded and sent to the DSWIC module. This sample will be switched to another

extension which is listening .On the listening side, the PCM word is converted into an

analogue sample amplified and sent to the telephone instrument. The CODEC (Coder

Decoder IC) does most of the above function. To reduce power consumption, the

CODEC is enabled only when the hook state signal is active. The hybrid transformer

does the ‘2 wire to 4 wire conversion’ of speech and vice versa.

6.5.6 COMMUNICATION & TIME SLOT GENERATION

The transmission of information like Hook state and Ring control data between LIC

and CPU is done by buffers which are enabled only when necessary. Transmission

of digitized voice signals is done only when any subscriber connected to that card

goes off hook.

A TIME SLOT GENERATOR is used to generate the time slot signal for each line.

The CPU card identifies the presence if a LIC module in the exchange by reading the

card presence information from LIC.

6.6 E & M TRUNK & INTERFACE CARD (EMTIC)

When a subscriber of one exchange wants to call a subscriber of another exchange in the

network, the module sends the seizing signal and followed by the digits to the far exchange.

When the required subscriber of the far exchange picks up the handset the module connects

the speech path between both the subscribers.

Alternatively, when the module receives the seizing signal & the digits from the far

27



exchange, it sends RING to the local subscriber and connects the speech path when the

subscriber lifts the handset.

The module also provides the TIE LINE STATUS/FAULT indications.

Apart from these functions, EMTIC does the Generation of necessary time slots and

processing of speech signals

6.7 DIGITAL OPTIONAL CARD

The DOPT is optional module, which contains the Following circuit.

6.7.1 PARITY CONFERENCE CIRCUIT

A maximum of local subscribers can have a conferencing the conference circuit.

The speech signals of all 4 subscribers are sent to this module from DSWIC module. Care is

taken not to send his/her own speech to subscribers. So, a subscriber. Listen to the voices of

all other subscribers and not his/her own voice.

6.7.2 DTMF TRANSMITTER

It is used for transmitting the signal.

6.7.3 DTMF RECEIVER

It is used for receiving the signal.

6.7.4 PAGING AMPLIFIER CIRCUIT

Paging announcement can be done using this circuit the preamplifier output is available for

the customer to connect power amplifier and loud speakers.

Other circuits like Regulator, Speech, Communication and Time slot generation circuits are

similar to the LIC. A potential free contact of the alarm relay is provided to which an

external alarm circuit cab be connected. This will be activated when a faith of serious nature

occurs. 28



6.8 MAINTENANCE & TRACING FAULT PROCEDURE

This section helps the operator to maintain the equipment and attend top common faults,

which may occurs in practice the following points must be borne by the operator.

All connection should be thoroughly checked. The control circuit boards should be

inserted firmly in their respective sockets before energizing the battery charger

All mounting Bolts\screws should be checked before energizing as loose mounting

cause vibrations.

The charger should be switching off once in every month and the connections and

mountings should be checked.

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

The instruction manual and the drawings should be referred initially to avoid any

wrong operation.

6.9 CONCLUSION

There are various switch and card which we used in power line carrier communication field.

It`s very helpful to understand about it. Switch and cards are play the most important vital

role in power line carrier communication without it we cannot imagine it.

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CHAPTER – 7

TELEOPERATAION & ALARM FACILITIES

7.1 MODES OF OPERATION

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

4- wire remote/ emergency call stations can be created by operating it in parallel with the

built-in service telephone equipment. The transmission facilities for teleoperation working

use separate input and separate output circuits according to their classification.

When 4 KHz equipment carries simultaneous speech and teleoperation signals, they are

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

two parts. The lower part of the band is used for speech and the upper part for teleoperation

signals.

7.2 TELEPHONE FACILITIES

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

no. of subscribers. Between PAX and the PLCC channel, control circuits give out signals

for the setting- up, dialling and later releasing a telephone connection and the switching 30



criteria between PAX and PLC. The PAX sending contact will, via the PLCC signalling

channel, close an output contact in the PLCC receiver at the distant end of the link.

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

has a maximum transmitting speed of 50 baud.

7.3 COMPRESSOR & EXPANDER (COMPANDER)

The inclusion of the Compander improves the carrier signal quality of the speech and is

normally reserved for use over lines with high noise. The improvement over Signal to Noise

Ratio (SNR) is approximately 12dB. When the speech is carried over several PLCC links in

series, it is recommended that only one compander is used, the compressor being installed at

the sending end of the line and the expander in the farthest receiving station.

7.3.1 4-WIRE HAND/EMERGENCY CALL

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

equipment, are equipped throughout with hand/emergency call telephone. These telephones

with the DC Bell can connected directly via a 6-wire extension cable. The calling of the

opposite station is accomplished by lifting the handset and pressing the calling button. In

the opposite station after a two-second delay the bell rings as long as the push button is set.

By lifting the handset in 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.

7.3.2 SERVICE TELEPHONE

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

the front panel.

7.4 GENERAL DESCRIPTION OF ETI EQUIPMENT

The multipurpose equipment type ETI21 and ETI22 transmits simultaneously Speech and

multiplexed Teleoperation signals in SSB technique over high voltage lines or cables.

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The transmitted intelligence is suitable for

Telephony

Teleoperation; for example

Telemetry

Remote control

Remote analog metering

Tele-printer

Tele-protection signaling, for example

High voltage power equipment

High voltage power lines

7.4.1 CARRIER FREQENCY SECTION

Designed for a single channel duplex (ETI21) or double channel duplex (ETI22) working in

a 4 kHz or 2.5 kHz raster. The carrier frequency ranges from 24 kHz to 500 kHz and with a

transmitted power of 20 watts or as a variant, 100 watts (ETI101 and 1020). This can be

operated from 110/220 volts, 50/60 Hz or a separate battery/charger unit of 24 volts, 48

volts or 60 volts. The technique of single side band modulation with double conversion

provides frequency equalization, automatic gain control and frequency synchronization and

ensures perfect reproduction of the transmitted intelligence.

7.4.2 THE LOW FREQUENCY MULTIPLE SECTION

With speech and upto five teleoperation channels, together with an optional speech

compander.

7.5 ETI CARRIER POWER SUPPLY

Power supply unit 48/60 V DC B5EC

Regulator B3EA

24 V Stabilizer B3EB

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7.5.1 TRANSMITTER

Transmit IF modulator P3EA

Transmit IF Filter E3EA

Transmit RF Modulator P3EB

Transmit Prefilter E3EB

Power Amplifier 25 W P5EA

Power Amplifier 50 W N5EA

Transmit Filter E5EA

RF Hybrid 100 W P3EO

7.5.2 RECEIVER

Receive RF Filter E3EC

Receive RF modulator P3EC

Receive Filter E3ED

IF & AGC Amplifier P3EDa

Receive IF Demodulator P3EFa

Receive IF Demodulator P3EFb

Signal output O3EHa

Signal output O3ES

Supervision I O3EIa

7.5.3 AF MULTIPLEXER

Signal Input O3EAa

Signal Adapter O3EC

Pilot /Dial Module O3ED

Pilot/Dial Module O3EDa

Pilot/Dial Module O3PEQ

Telephone Adapter O3EEa

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Voice Amplifier O3EGa

Voice Amplifier O3EGb

Voice Filter 2000 Hz E3EF

Voice Filter 2400 Hz E3EH

Voice Filter 3400 Hz E3EL

Compander O3EB

7.5.4 ETI ADDITIONAL PARTS

Dummy Load 20 W P3EG

Test Meter N3FL

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ADVANTAGE & DISADVANTAGE

ADVANTAGE

No separated wires are needed for communication purposes, as the power lines

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

constructing separate telephone lines is saved.

When compared with ordinary lines the power lines have appreciabry higher

mechanical strength. They would normally remain unaffected under the condition

which might seriously damage telephone lines.

Power lines usually provided the shortest route between the power stations.

Power line has large cross-section area resulting in very low resistance per unit

length. Consequently the carrier signals suffer much less attenuation then when

does they travel on usual telephone lines of equal lengths.

Power lines are well insulated to provide only negligible leakage between

conductors and ground even in adverse weather conditions.

DISADVANTAGE

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

against high voltages and currents on the lines.

Reflection is used on spur lines connected to high voltage lines. This increases

35



attenuation and creates other problems.

High voltage lines have transformer connections which attenuates carrier currents.

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

process.

It is obvious that an effective power line carrier system must overcome these and

many other difficulties. So we should use this system very carefully.

LIMITATIONS

1. Electro-Magnetic Radiation Issues

2. Addressing issue

3. Security

4. Noise interference

5. Regulatory and standardization issues

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APPLICATION

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. Telecommunication: Data transmission for different types of communications like

telephonic communication, audio, video communication can be made with the use of

PLCC technology.

4. Security Systems: In monitoring houses or businesses through surveillance cameras,

PLCC technology is far useful.

5. Automatic Meter Reading – Automatic Meter reading applications use the PLCC

technology to send the data from home meters to Host Central Station.

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CONCULISON

I have gained a wonderful experience and practical knowledge in this training period.

Although the time period provided was very short for allotted task. Yet I wanted to do many

things in detail. After doing this training I got sufficient confidence for doing such type

works for industrial applications.

I also learnt the importance of PLCC in power system, without PLCC a large power system

cannot be assumed. For communication purpose between the power systems, PLCC plays a

vital role. For better reliability between interconnected systems PLCC is must.

I am also thankful to those who had been helpful during my training period

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APPLENDIX

TECHNICAL SPECIFICATION

Normal Input : 415 V AC 3 Phase.

Input Variation : +10% of Normal Voltage.

FLOAT SECTION

DC Output : 50 V +1%

Output Current : 20\25\40Amps.

Line regulation : Better than +1%

Load regulation : Better than +1%

Ripple : 0.6Vpp.

Efficiency : More than 75%

BOOST SECTION

DC Output : 43.2 to 67.2 V DC

Output Current : 25\40\70Amps.

Over Load : 10%

Efficiency : More than 75%

39



REFERENCES

1. http ://ieeexplore.ieee.org/xpl/articleDetails.jsp?reload=true&arnumber=6201240

2. http://www.hindawi.com/journals/jece/2013/712376/

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communication-plcc

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matching-unit-in-power-line-carrier-communication-PLCC

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http://www.quora.com/What-is-the-use-of-a-wave-trap-coupling-capacitor-and-line-matching-unit-in-power-line-carrier-communication-PLCC

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https://www.linkedin.com/pulse/20140910024219-302442873-power-line-carrier-communication-plcc

https://www.linkedin.com/pulse/20140910024219-302442873-power-line-carrier-communication-plcc

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http://as.wiley.com/WileyCDA/WileyTitle/productCd-0470740302.html

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http://www.crcnetbase.com/doi/pdfplus/10.1201/b16540-15

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Communications

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doi=10.1.1.453.176&rep=rep1&type=pdf

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Standard.ANSI/IEEE std 643-1980. IEEE, 1980.

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Report on PLCC

Engineering

Transcript of Report on PLCC