Report on PLCC

POWER LINE CARRIER COMMUNICATION
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ECE-B/2015-2016/PIET, JAIPUR
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.

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

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1.2 STAFF AT JVVNL
Name Designation Contact number
Mr. Sanjay Malhotra, IAS Chairman Discom`s 91-141-2747064
Mr. B. K. Dosi, IAS Managing Director 91-141-2744965
Mr. Deepak Srivastava Director (Finance) 91-141-2740451
Mr. G. R. Chaudhary Director (Technical) 91-141-2740341
Mr. S.C. Dinker Director
Mr. B. K. Dosi, IAS Managing Director 91-141-2744965
Mr. Deepak Srivastava Director (Finance) 91-141-2740451
Mr. Girish Goyal Company Secretary 91-141-2742802
Mr. S. L. Gujjar CE (O & M)-Jaipur Zone 91-141-2202403
Mr. P.C. Sharma CE (O & M)-Bharatpur Zone 91-05644-236080
Mr. Naveen Arora CE (O & M)-Kota Zone 91-0744-2450066
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
additional wiring. In some countries this technology is also used to provide Internet
connection.

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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
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

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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.
Main data transmission system for telemetry and tele control are:
1. Use of telephone lines
2. Use of separate cables

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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.
Fig 2.3: Block Diagram of PLCC

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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.

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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
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

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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
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.

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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.
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

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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 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

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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
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.

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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
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.

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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.
Fig 4.3: PHASE TO PHASE COUPLING

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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
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.

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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 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.

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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.
 It can withstand extreme temperature fluctuations and weather condition.

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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

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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.
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

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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.
Fig 6.3.4: Earth Switch

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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. 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.

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

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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.

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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
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

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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
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.

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 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 from
passing 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.
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

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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
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.

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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.
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 Boltsscrews 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.

31
 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.

32
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
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

33
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.
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

34
 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
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

35
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
Voice Amplifier O3EGa
Voice Amplifier O3EGb
Voice Filter 2000 Hz E3EF
Voice Filter 2400 Hz E3EH
Voice Filter 3400 Hz E3EL
Compander O3EB

36
7.5.4 ETI ADDITIONAL PARTS
Dummy Load 20 W P3EG
Test Meter N3FL

37
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
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.

38
LIMITATIONS
1. Electro-Magnetic Radiation Issues
2. Addressing issue
3. Security
4. Noise interference
5. Regulatory and standardization issues

39
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.

40
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

41
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 : 202540Amps.
 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 : 254070Amps.
 Over Load : 10%
 Efficiency : More than 75%

42
REFERENCES
1. http://ieeexplore.ieee.org/xpl/articleDetails.jsp?reload=true&arnumber=6201240
2. http://www.hindawi.com/journals/jece/2013/712376/
3. http://web.archive.org/web/20090214043341/http://www.rempli.org/
4. http://www.isplc.org/docsearch/Proceedings/1997/pdf/0563_001.pdf
5. yamar.com/home/dcbus-ics
6. http://www.crcnetbase.com/doi/pdfplus/10.1201/b16540-15
7. http://web.archive.org/web/20090520004013/http://www.powerq.com.my/telecomm
unication/distribution-line-carrier-system
9. https://www.iiit.kit.edu/english/2161.php
10. http://www.ijsrp.org/research-paper-0714/ijsrp-p3152.pdf
11. http://research.ijcaonline.org/comnet/number1/comnet1001.pdf
12. http://as.wiley.com/WileyCDA/WileyTitle/productCd-0470740302.html
13. http://web.archive.org/web/20090520004013/http://www.powerq.com.my/telecomm
unication/distribution-line-carrier-system
14. https://www.linkedin.com/pulse/20140910024219-302442873-power-line-carrier-
communication-plcc
15. http://www.quora.com/What-is-the-use-of-a-wave-trap-coupling-capacitor-and-line-
matching-unit-in-power-line-carrier-communication-PLCC
16. http://www.finetopix.com/showthread.php?19780-Ebook-Power-Line-
Communications

43
17. http://cdn.intechopen.com/pdfs-wm/5558.pdf
18. http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.453.176&rep=rep1&type
=pdf
19. http://www.isplc.org/docsearch/Proceedings/1999/pdf/0566_001.pdf
20. IEEE Guide for Power-Line Carrier Applications. An American National
Standard.ANSI/IEEE std 643-1980. IEEE, 1980.

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