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PLCCOverview

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RF carrier

(40-500kHz)

Power Line(50Hz)

LT

CC

PAX

RTU

(AB-ETL41)

PLCC

TERMINAL

Power Line Carrier Communication System

Transmissionline

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PLCCTechnology

PLCC system uses the same High Voltage transmission line connecting two

sub-stations for telecommunication purpose too.

PLCC is used in all power utilities as a primary communication service to transmit

speech, telemetry and protection tripping commands. This is economic and

reliable for inter grid message transfer as well as low bit rate RTU signals.

The voice/data are mixed with radio frequency carrier (40-500kHz), amplified to a

level of 10-80W RF power and injected in to high voltage power line using a

suitable coupling capacitor. The power line as a rigid long conductor parallel to

ground, guides the carrier waves to travel along the transmission line. Point to

point communication takes place between two SSB transceivers at both ends.

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Sub-

Station

Line diagramdisplay

bay-1

Line Isolator

Circuit Breaker

Bus Bar#1

Bus Bar#2

Bus Isolator 2Bus Isolator 1

Single Linedi m

To other S/S

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PLCC Terminal = Translates voice and data into High Frequency Carrier. Output Power =10 to 80W

LMU = Line Matching Unit = For impedance matching between line and coaxial cable, includes high

voltage protection devices like drainage coil(20mH), lightening arrestor(500V) and an earth switch.

Coupling Capacitor = Couples high frequency carrier with Power Line ( 4000 to10000pF)

Line Trap = Do not allow the transmitted HF carrier to enter inside the sub-station. (L = 0.5 to 2mH)

With out Line trap HF carrier get by-passed to some other line on the same bus bar and may leak

to ground ( a earth switch inside the yard provided for each bay is kept closed during maintenance)

H.V Line

LMU

Coupling

capacitor

Line Trap

PLCC

terminalCoaxial

cable

Components

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FrontBehind

Localsubstation

To

remote

substatio

n

CouplingCapacitor

LineMatching

Unit

PLC terminal

Coaxial

Transformer(s)BusBar

LineTrap

The PLCsignal isrouted toH.V Line

The PLCsignal isnotabsorbedby thesubstation

Coupling Scheme

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= PLC signal Blocking

HV Line

Substation

Line Trap = High Impedance for PLC signal

Low Impedance for Power energy

Powerenergy

PLCSignal

Line trapfunction

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Corona ring

Liftinglug

Terminal

Main coil

Tuning devicePedestal

Protective device

Tie rod

Line TrapComponents

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Inductanceof

main Coil

LightningArrester

Seriesresistance

Tuning

Capacitor

Damped single Line Trap

Line Trap is a parallel LCcircuit

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Vertical Pedestal Horizontal Pedestal Suspension

Line Traps MountingOptions

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CVT : CAPACITIVE VOLTAGE

TRANSFORMER

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LMU

LMU

Coupling

Capacitor

Line Trap

PLC

Coaxial

s/s

LMU = impedance matching Transformer

+high voltage Protection

To prevent dangerous potential on the

PLCC connection

To match PLCC set & transmission Line

Matching + Protection

LMUfunction

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Modular CouplingDeviceABB make MCD-80

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Drain coil for draining of HV leakage currents to earth.

Lightning arrester at the line terminals of coupling device fortransients protection

Transformer for impedance matching and galvanic isolation betweenline and PLCC terminal.

Earth switch for grounding of line terminals during maintenance.

High-pass or band-pass filter elements for efficient matching.

connectivity to equipment room through coaxial cable.

Elements of Coupling Device

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Inter circuit

Phase-to-Ground

LMU

Cc

LT

PLC

Cc

LMDU LMUPLC

Cc

LT

LT

Cc

LMDU LMUPLC

Cc

LT

LT

Phase-to-Phase

HF Coupling modes

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Translation : User audio signals into radio Spectrum

R.F Signal(40 to 500 kHz)

User Side Line Side

User Signal(0 to 4 kHz)

Amplification : To compensate the line attenuation

Function of PLCC

terminal

AF RF

IF

IF

gain

AF

IF

IF

RF

RF

IFAF

IF

PA

HH

AH= hybrid

PLCC Panel ( type: ABB ETL

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PLCC Panel ( type: ABB ETL41/42)

Cabine

t

Modules

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Speech 2.0 kHz

Speech 3.4 kHz

0.3 3.6 4.0

0.3 3.6 4.0

0.3 3.6 4.0

1200 Bd

300 Bd

Spee

d

Center frequency120 Hz steps

2.0

Programmable

speech bandwidth

plus

tele protection(4 trip commands)

plus

Tele metering

(FSK modem)

kHz

kHz

kHz

Multiplexing speech & data in 4 kHzraster

Speech 3.4 kHz

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Operating mode : Single side band Suppressed carrier

Frequency range: 40 to 500kHz (programmable in 4 kHz Steps)

AF Bandwidth: 4 kHz (Speech band=300 3400 Hz)

Transmitter RF output power : 40W ( +46 dBm)

Spurious suppression > 60 dB

Pilot channel : 3780 + 30 Hz

Receiver RF sensitivity : - 24 dBm

Receiver Selectivity : 70dB ( 300Hz from band

limit)

Receiver Image rejection > 80 dB

Receiver IF rejection > 80 dB

ABB PLCC terminal ETL- 41System data -- complies to IEC 495

I t ll ti

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Installation

MS = Master station

PAX = Private automatic exchange

PR = Protection relay

PC = ComputerM = Modem

E T LE T L

LTLT

CFAX

FAX

PR PC MS PAX FAX

M

PR PC RTU FAX

M

PR= Protection relay

FAX = Facsimile equipment

M = Modem

RTU = Remote terminal unit

cccc

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Losses increase for all inclement weather conditions

The worst offender is when heavy frost is formed on the line

Because of the skin effect, the carrier signal tries to propagate

on the ice instead of the conductor.

The attenuation can change as much as 4:1 depending on the

frequency.

The contaminats (on the insulators) have a larger effect when it is

raining than when the line is dry.

The worst condition is a light rain with the presence of

contaminants on the insulators

Effect of bad weather on PLCCcommunication

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RF noise in HV line two mains effectsImpulsive Noise = Caused by atmospheric discharges, breakers and isolator

close/open operation

Corona effect = Due to sequences of pulse streams caused by arcs over

conductors. It appears during positive-going half-cycle of the Line voltage

(occurrance frequency for a 50Hz 3-phase system is 150 Hz)

The corona noise could be subject to considerable variations due to

differences in the design parameters of the overhead line.

Other variations are possible due to the construction, altitude and age of theline

Weather effect can also be significant

RFNoise

Corona

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Typical average Noise on a 220 kV line

and for a 3 kHz Bandwidth

Voltage(kV)

Correction(dB)

33 - 14

132 - 4

220 0

400 + 4

500 + 5

Bad weather Noise

CoronaNoise

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PLCC test instrument: Selective Level

Meter

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PLCC test instrument : Selective LevelOscillator

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THANK YOU ALL