Power Line Carrier

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PLCC OVERVIEW :PRESENTED BY BIMAL NANDA

Prepared By :

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RF carrier(40-500kHz)

Power Line(50Hz)

LT

CC

PAX

RTU

(AB-ETL41)PLCC TERMINAL

Power Line Carrier Communication System

Transmission line

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PLCC Technology

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-StationLine diagram

display bay-1

Line Isolator

Circuit Breaker

Bus Bar #1

Bus Bar #2

Bus Isolator 2Bus Isolator 1

Single Line digm

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 terminal

Coaxial cable

Components

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FrontBehind

Local substation

To remote

substation

CouplingCapacitor

Line Matching

Unit

PLC terminal

Coaxial

•Transformer(s)•BusBar

Line Trap

The PLC signal is routed to H.V Line

The PLC signal is not absorbed by the substation

Coupling Scheme

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= PLC signal BlockingHV Line

Substation

Line Trap = High Impedance for PLC signal Low Impedance for Power energy

Power energy

PLC Signal

Line trap function

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Corona ring Lifting lugTerminalMain coilTuning devicePedestal

Protective deviceTie rod

Line Trap Components

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Inductanceof

main Coil

LightningArrester

Seriesresistance

Tuning Capacitor

Damped single Line Trap

Line Trap is a parallel LC circuit

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Vertical Pedestal Horizontal Pedestal Suspension

Line Traps Mounting Options

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CVT : CAPACITIVE VOLTAGE TRANSFORMER

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LMU

LMU

CouplingCapacitor

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

LMU function

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Modular Coupling Device ABB 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 for transients protection

• Transformer for impedance matching and galvanic isolation between line 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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LMU functional blocks

Couplingcapacitor

ABB MCD 80 or

Linetrap

HV -line

Tx

PLC Cabinet

Rx

Substation

Coax cable

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Inter circuit

Phase-to-Ground

LMU

Cc

LT

PLC

Cc

LMDU LMUPLC

Cc

LTLT

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

AFIF

IFRF

RFIFAF

IF

PA

HH

A H= hybrid

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PLCC Panel ( type: ABB ETL 41/42)

Cabinet

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

Spe

ed

Center frequency120 Hz steps

2.0

Programmablespeech bandwidth

plus

tele protection (4 trip commands)

plus

Tele metering (FSK modem)

kHz

kHz

kHz

Multiplexing speech & data in 4 kHz raster

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- 41 System data -- complies to IEC 495

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Typical PLCC Installation

MS = Master stationPAX = Private automatic exchangePR = Protection relayPC = ComputerM = Modem

ETLETL

LTLT

CFAX

FAX

PR PC MS PAX FAX

M

PR PC RTU FAX

M

PR= Protection relayFAX = Facsimile equipmentM = ModemRTU = Remote terminal unit

cc cc

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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 PLCC communication

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RF noise in HV line two mains effects

Impulsive 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 the line

Weather effect can also be significant

RF Noise

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Typical average Noise on a 220 kV lineand for a 3 kHz Bandwidth

Voltage (kV)

Correction (dB)

33 - 14132 - 4220 0400 + 4500 + 5

Bad weather Noise

Corona Noise

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PLCC test instrument: Selective Level Meter

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PLCC test instrument : Selective Level Oscillator

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THANK YOU ALL