Plcc Overview
Transcript of Plcc Overview
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PLCC Overview
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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-Station
Line 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
substatio
n
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 Blocking
HV 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 lug
Terminal
Main coil
Tuning device
Pedestal
Protective device
Tie 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
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
AFIF
IF
RF
RF
IFAFIF
PA
HH
AH= 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 line
and for a 3 kHz Bandwidth
Voltage (kV)
Correction (dB)
33 - 14
132 - 4
220 0
400 + 4
500 + 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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