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Power Line Carrier Communication (PLCC)
electrical-engineering-portal
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Ltd)

Introduction
Major goal/Application of PLCC
Main Components of PLCC:
1
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Line trap Unit
3
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Hybrids and Filters
5
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Master Oscillator and Amplifiers
7
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Tele means remote
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Different types of data transmission system can be used depending upon the network requirement and
conditions
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Use of telephone lines
2
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Power Line carrier communication
4
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Carrier current has a frequency range of 30 to 200 kHz in USA and 80 to 500 kHz in UK
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Transmitters and Receivers
2
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Line Tuners
4
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Power amplifier
6
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The output of relay goes to modem of PLCC
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Major goal/Application of PLCC
PLCC in modern electrical power system substation is mainly used for following purpose:

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1
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To trip the line circuit breaker nearest to the fault, this is done by:
a) Distance protection relay (V/I characteristics)
b) Differential comparison method
c) Phase comparison method
2
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Carrier telemetring, electrical quantities that are telemetered are kW, kVA, kVAR, Voltage and
Power factor etc
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The goal is to get a signal level to the remote
terminal that is above the sensitivity of the
receiver, and with a signal-to-noise ratio
(SNR) well above the minimum, so that the
receiver can make a correct decision based
on the information transmitted
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The factors affecting reliability are:

PLCC scheme

1
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2
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3
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4
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5
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6
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7
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8
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9
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10
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11
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The above list may not be all inclusive, but these are the major factors involved in the success or failure of a PLC
channel
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Coupling Capacitor

Coupling capacitor
connects the carrier
equipment to the
transmission line
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PLCC component – Coupling Capacitor

For example 2000pF capacitor offers 1
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Thus coupling capacitor allows carrier frequency signal to enter the carrier equipment
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2
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This task is performed by the line trap
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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
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Since the power flow is rather large at times, the coil used in a line trap must be large in terms of physical size
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It is
a parallel tuned circuit comprising of inductance (L) and capacitance (C)
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1?)
for power frequency (50 Hz) and high impedance to carrier frequency
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3
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This then means there is a large distance between the equipment and the tuner, and the connection between the
two is made using a coaxial cable
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The coaxial cable is
connected to the line tuner which
must be mounted at the base of
the coupling capacitor
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PLCC component – Transmitters and receivers

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4
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Hybrids may also be required between transmitters and receivers, depending on the
application
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High/low-pass and band-pass networks may also be used, in some applications, to isolate carrier equipment
from each other
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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
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On the other hand, the capacitance of the coupling capacitor is high impedance to the power frequency energy
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This function is provided by the drain coil, which is in the base of the
coupling capacitor
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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
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6
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Oscillator can be crystal oscillator with which operation for a particular bandwidth can be achieved
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The output of oscillator is fed to amplifier so that loses in transmission can be compensated
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They are mainly: Losses in coupling equipment which are constant losses for a given carrier frequency
bandwidth
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Frequency spacing is a
process using different
carrier frequency in two
adjacent transmission
lines
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PLCC component – Master oscillator and amplifiers

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7
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They produce stress on coupling equipment and line trap units
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The gap is adjusted to spark at a set value of over voltage
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In this regard that is earthing of PLCC and other communication/Instrumentation/Electronic equipment please
refer to NEC Article 645 for data centers (IT equipment
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Immune to noise in processing and storage stages,
as it is completely digital
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Digital: Require less no
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3
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4
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5
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(Analog processing is limited
by the availability of devices to perform desired
functions, while)

Protection and earthing of coupling equipment

6
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7
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Therefore, digital systems more reliably reproduce the desired
responses in spite of temperature variations or component aging
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In addition, in digital circuits there is little need for component matching
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Simplified Production: Lower Parts count and improved testability
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Transposition may introduce additional attenuation which can generally not be predicted with simple rules
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Forbidden Frequency Ranges may be determined as explained in CIGRE Paper 35-02, Senn/Morf – Optimum
PLC Arrangement on Transposed Single Circuit power Lines – (August, 1984)
In critical cases, however, computer calculation may be necessary, for which the following data is
required:
1
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Sag of conductors (between towers)
3
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Number of conductors per phase (single or if bundle spacing)
5
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Number of strands at the circumference (outer strands)
7
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Same information (a) to (g) for ground wires
9
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Sketch of phasing arrangement showing type and number of transpositions and distance between

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transpositions (if double system, each scheme required separately)
11
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12
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Available carrier frequency range
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Typical signal to noise ratio calculation by considering a line of 295 kilometers
Frequency line section: 140/144 KHz
Line Voltage: 400 KV
Line configuration: 3 transpositions at equal distance
Line length: 295 Kms
Conductor diameter: 31
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of bundles per conductor: Two
Overall loss = Line attenuation + Coupling loss
Line attenuation (aL) = a1 x L + 2a C + aadd
Where:
a1 = attenuation constant of the lowest loss made in dB per Km
ac = model conversion loss in dB
aadd = additional loss caused by discontinuities e
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coupling circuits, transposition etc
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of bundles
Line configuration = No of transposition at equal intervals
Upon substituting corresponding values with certain approximation we get a1:
a1 = 0
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029 x 295 + 2 x 0 + 10 = 8
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55 dB
Coupling Loss = Loss in Coupling equipment + tapping loss + paralleling loss + by pass losses in case
of bypasses + cable loss
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6 + 1 + 0 + 0
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1 dB
Overall loss = Line attenuation + Coupling loss = 18
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1 = 24
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2 KHz bandwidth = -13
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0 dB
Noise level in speech band (300 – 2400 Hz) = -15
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55 + 6
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65 = 10
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35 -(-15
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85 dB (considering PLC terminal power output as 20 watts)
= 28
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