*PLCC Overview

*RF carrier(40-500kHz) Power Line(50Hz)LTCCPAXRTU(AB-ETL41)PLCC TERMINALPower Line Carrier Communication SystemTransmission line

*PLCC TechnologyPLCC 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.

*Sub-StationLine diagram display bay-1Single Line digmTo other S/S

* 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 LineLMUCoupling capacitorLine TrapPLCC terminalCoaxial cable Components

*FrontBehindLocal substationTo remote substationCouplingCapacitorLine MatchingUnitPLC terminalCoaxialTransformer(s)BusBar

Line Trap The PLC signal is routed to H.V Line

The PLC signal is not absorbed by the substationCoupling Scheme

*= PLC signal BlockingHV LineSubstationLine Trap = High Impedance for PLC signal Low Impedance for Power energyPower energyPLC SignalLine trap function

*Line Trap Components

*Damped single Line TrapLine Trap is a parallel LC circuit

*Vertical PedestalHorizontal PedestalSuspensionLine Traps Mounting Options

*CVT : CAPACITIVE VOLTAGE TRANSFORMER

*LMU LMU = impedance matching Transformer + high voltage Protection To prevent dangerous potential on the PLCC connectionTo match PLCC set & transmission Line LMU function

*Modular Coupling Device ABB make MCD-80

*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

*LMU functional blocks Couplingcapacitor ABB MCD 80orLinetrapHV-lineTxPLC CabinetRxSubstationCoax cable

*Inter circuitPhase-to-GroundPhase-to-PhaseHF Coupling modes

*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 H= hybrid

*PLCC Panel ( type: ABB ETL 41/42)CabinetModules

*Speech 2.0 kHzSpeech 3.4 kHz0.33.64.00.33.64.00.33.64.01200 Bd300 BdSpeedCenter frequency120 Hz steps2.0Programmablespeech bandwidthplustele protection (4 trip commands) plusTele metering (FSK modem) kHzkHzkHzMultiplexing speech & data in 4 kHz rasterSpeech 3.4 kHz

* 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

*Typical PLCC Installation MS = Master stationPAX = Private automatic exchangePR = Protection relayPC = ComputerM = Modem

*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 insulatorsEffect of bad weather on PLCC communication

*RF noise in HV line two mains effectsImpulsive Noise = Caused by atmospheric discharges, breakers and isolator close/open operationCorona 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 lineWeather effect can also be significant

RF Noise

*Typical average Noise on a 220 kV lineand for a 3 kHz BandwidthBad weather NoiseCorona Noise

Voltage (kV)Correction (dB)33- 14132- 42200400+ 4500+ 5

*PLCC test instrument: Selective Level Meter

*PLCC test instrument : Selective Level Oscillator

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