35876044 Plcc Overview
Transcript of 35876044 Plcc Overview
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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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