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Notes on PLCC
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MSETCL RTC Padghe Batch 7 (dt.12/7/2013)
Power Line Carrier Communication
( B2B & D2D)
To communicate is Human Nature
We communicate to
Convey feelings.
Express agreements.
Express love.
Learn/ Teach
Share knowledge
Communico (Latin)
TelephoneA user end instrument that is used to transmit &
receive Voice frequency signals.
Voice frequency is audio range used for transmission of Speech. ( 300 Hz to 3400 Hz)
Telephone bandwidth for a Single voice frequency channel is 4 KHz.
Telephone Bandwidth is 4 KHz 1000 Hz
2000 Hz
3000 Hz
4000 Hz
5000 Hz
6000 Hz
Dialing Communication
Modulation & Demodulation
LINE IN LINE OUT (LILO) Arrangement
Existing PLCC link ABB make ETL
PLCC links after LILO
1. Line Section 1 use existing PLCTs(ABB)2. Line section 2 use new PLCTs (ABB or BPL)
Frequency plan
Freq. Band in KHz UFreq. Band in
KHzU
Freq. Band in KHz
UFreq. Band in
KHzU
Freq. Band in KHz
U Freq. Band in KHz U
100-104 168-172 236-240 304-308 372-376 440-444
104-108 172-176 240-244 308-312 376-380 444-448
108-112 176-180 244-248 312-316 380-384 448-452
112-116 180-184 248-252 316-320 384-388 452-456
116-120 184-188 252-256 320-324 388-392 456-460
120-124 188-192 256-260 324-328 392-396 460-464
124-128 192-196 260-264 328-332 396-400 464-468
128-132 196-200 264-268 332-336 400-404 468-472
132-136 200-204 268-272 336-340 404-408 472-476
136-140 204-208 272-276 340-344 408-412 476-480
140-144 208-212 276-280 344-348 412-416 480-484
144-148 212-216 280-284 348-352 416-420 484-488
148-152 216-220 284-288 352-356 420-424 488-492
152-156 220-224 288-292 356-360 424-428 492-496
156-160 224-228 292-296 360-364 428-432 496-500
160-164 228-232 296-300 U 364-368 432-436
164-168 232-236 300-304 U 368-372 436-440
Sr no. PLCC link Frequency in KHz Overlapping of allotted frequencies with the
available links.
1 400KV Pune PGCIL Lonikand S/S(with PC)
124/128U128/124U (400KV PGCIL- Padghe)
2 400KV Pune PGCIL Lonikand S/S(with PC)
160/168URx 160 (400KV PGCIL- Padghe)
Rx 168 (400KV PGCIL- Chakan
3 400KV Pune PGCIL Lonikand S/S
336/340UTx 340 (400KV PGCIL- Chakan)
4 400KV Pune PGCIL Lonikand S/S
352/356UCan be used.
5 400KV Pune PGCIL Lonikand S/S
228/232U228/232U (400KV PGCIL- Parali-II). Link
not yet commissioned. Hence can be used.
6 400KV Pune PGCIL Lonikand S/S
248/264UCan be used.
Approved Frequencies for 400 KV Lonikand I PGCIL line
Sr
no.
PLCC link Frequency in KHz Remarks
1 400KV Pune PGCIL Lonikand S/S ( With PC)
352/356U
2 400KV Pune PGCIL Lonikand S/S ( With PC)
228/232ULink not yet commissioned at
400KV Pune PGCIL- Parali-II.
Hence can be used.
3 400KV Pune PGCIL Lonikand S/S
248/264U
4 400KV Pune PGCIL Lonikand S/S
336/360U336KHz is already approved as
above.
5 400KV Pune PGCIL Lonikand S/S
328/348UBeing spare during shifting of
400KV Lonikand Parali I &
panel reduction at 400KV
Lonikand-II.
6 400KV Pune PGCIL Lonikand S/S
488/496U432/488UL is approved for 220KV
Lonikand I- VSNL. Can be
modified.
( 428/456 U KHz)Or (96/92 U KHz)
( 232/108 UL KHz)Or 480/ 488 UL KHz
RxTxRx TxRx Tx
Frequency space4 + 4 = 8 KHz required
Frequency space4 + 4 +4 +4 = 16 KHz required
For Single ch. Max 56 no. of PLCT & Twin ch. Max.28 no.of PLCTs can be used .
Rx
Tx
Rx
Tx
Speech signal
Protection signal
Data Signal Carrier
Amplitude Modulated Signal
AMsignal
fm
fm
fm fc
fc + fm
fc - fm
fc
PLCC link
PLCT are used as a pair one at each end
Each PLCT is designated for a set of Tx & Rx freq.
These freq may be Separate Or Adjacent.
The corresponding PLCT at the other end will be designated for the reverse value of Tx/Rx freq.
The ch freq. will be either in 4 KHz or 8 KHz BW depending upon single ch or Twin ch.
Features of PLCT
Mode of Transmission Amplitude Modulation (Single Sideband with Suppressed Carrier)
Carrier Frequency 50 to 500 KHz
Nominal carrier frequency band in either direction of transmission 4 KHz
Power output of PLC Terminal 20 or 40 Watt
Supply voltage- 48 V DC with + pole earthed
ProtectionFrequency
Guard Frequency
Pilot Frequency
Data Freq. Dial Freq. Speech Freq.
Carrier Frequency
Wave Trap or Line trap
Wave traps are series connected
Parallel tuned circuit.
Main components
L (main Coil)
Tuning pot
LA (protective device)
For a well designed Wave trap insertion loss is 1 to 3 dB & blocking attenuation is 8 to 10 dB
Do you know dB (decibel) unit ? Decibel dB denotes Logarithmic comparison between
two signals I/P & O/P.
Power ratio = 10 Log (P2/P1)
Voltage ratio = 20 Log (V2/V1)
Basic units dBm & dBu
dBm = Power levels above, below or at 1 milli watt.
One milli watt power w.r.to 600 ohms is referred as reference power.
dBu = Voltage levels above, below or at 775 millivolts.
Tuning Pot & LA
Pedestal WT
Exercise
Select Blocking Band for PLCT having Frequency 96/92 U KHz
Coupling Capacitor / CVT The main Purpose of CC is twofold
1. Protection of PLCC terminals from Extra HighVoltage.
2. Passing the HF signal with minimum attenuation.
One end of the CC must be securely connected to ground otherwise Over voltages up to the magnitude of the operating voltage may occur on the equipment side of the Capacitor.
Capacitive Voltage Transformer CVT
CVT consists of CC & Voltage transformer
CC for Carrier communication & Voltage Transformer for Monitoring or control.
CVT HF point
Line Matching Unit (LMU)
R
150E
125E
75E
To PLCC Terminal
22
21
20
19
18
17
24
23
28
27
MARSHALLING BOX A To CC/CVT
ESLADC
16
15
14
13
MARSHALLING BOX B
DC
LA ES
To CC/CVT
16
15
14
13
C S
MT
BT- Balancing Transformer
MT- Matching Transformer
DC- Drain Coil
ES- Earth Switch
LA- Lightning Arrestor
S- shield of Co-axial cable
C- Conductor of C-axial cable
LMU is mounted on the structure that supports the CC /CVT
ExerciseSelect the pass band of LMU for PLCT having frequency 96/92 U KHz.
Pass bands
35 90 KHz50 90 KHz
90 500 KHz
3 Elements Protection device
Drain Coil
LA
Earth switch
Insulated single Conductor Lead in wire To connect CC to the LMU, use an
insulted single conductor lead in wire.
Bare conductor & Co axial cable should not be used.
Stray capacitance & leakage to ground will increase the losses of LMU & bandwidth.
The connection between the CC & LMU is high impedance point in the series tuned circuit formed by the tuning inductor & CC.
HF Cable or Coaxial Cable
Coaxial cable is a Two conductor cable made of a single conductor surrounded by a braided wire jacket with a plastic insulating material separating the two.
The coaxial cable provides Shielding so that noise can not get into the cable and cause interference .
The characteristic impedance of the co ax cable is either
75 ohms or 125 ohms.
Characteristic Impedance
Ch impedance of a transmission line is defined as the ratio of the Voltage to the current of a traveling wave on a line of infinite length.
Ch impedance of line, Z = 276 Log (D/r)
where D distance between conductors & r is radius of conductor.
Ch. Impedance is also known as Surge impedance due to the temporarily resistive behavior of any length transmission line.
ABB Make Coupling device Connections
ExerciseFind the mistakes in this picture
Hints -
1. Make, Type & Frequency of PLCT.
2. Selection of Passband of LMU.
3. Selection of Blocking band of Line trap.
4. PLCC Phase to Phase coupling.
5. Main HF Cable & HF loop connections.
Coupling schemes---Economic ,Engineering & common sense
Mode 1 coupling
Center ph to Outer ph (No Mode 3)
Center ph to Ground ( No mode 2)
Outer ph to outer ph with Ground return (No mode 2)
Outer ph to Ground ( All 3 modes)
Inter circuit
Phase-to-Ground
LMU
Cc
LT
PLC
Cc
LMDU LMUPLC
Cc
LT
LT
Cc
LMDU LMUPLC
Cc
LT
LT
Phase-to-Phase
PLCC Coupling
Modal analysis Modal analysis is a mathematical tool similar to
symmetrical components used for analyzing unbalanced faults on three ph power system.
It can be shown that no. of natural Nodes is equal to the no. of conductors involved in the propagation.
For example, 3 nodes in the case of a single circuit line with 2 earth wires earthed at each tower.
The ph conductor V or I can be resolved into 3 sets of natural mode components at any point on a lossy, reflection free three ph line.
Mode distribution for a 3 ph line
Mode 1 is least attenuated & least frequency dependent
more frequency dependent & has more attenuation than Mode1
Mode 3 is the highest attenuated mode & is propagated on all 3 phases & returns via
the ground
Mode components for various types of coupling
a) Center phase to Ground couplingb) Outer phase to Ground coupling
c) Center to Outer Push Pull coupling
d) Outer to Outer Push push coupling
Substation A
Substation B
Zone 1 (A & B)Zone 1 (A)Zone 2 (B)
Zone 1 (B)Zone 2 (A)
Line Fault PUTTDistance relay( 21), Main I, Main II
Conductor snapping Tree fault Bird fault
In case of 400 KV line, Main I & Main II are parallel commands.M I ,M II should be operated simultaneously.
Substation A Substation B
Substation FaultDirect Trip Protection
Over Voltage LBB
Reactor Protection Busbar Hand trip
86ROV all commands are routed through 86ROV except Hand trip
85 LO receive command is routed through 85LO relay.
Conventional 3 Zone Protection
Distance Relay 21
Distance Relay 21
400 220
Z 1 0 0
Z 2 300 400
Z3 500 700
Carrier aided Protection
Distance Relay 21
Distance Relay 21
Protection Coupler
Protection Coupler
Trip logic Conventional & Carrier aided protection
Carrier aided Protection
In the absence of communication link, the operation of End zone fault is longer & auto reclosing is not possible.
Carrier aided protection scheme is used for simultaneoustripping of near & far end circuit breakers
Protection Coupler equipments can be used along with PLCC terminals for Tele protection requirements.
Principle of operation
Under normal conditions, i.e. when there is no fault in the line, guard frequency or frequencies G1 & G2 will be continuously transmitted through the PLC channel for monitoring the healthiness of the equipment.
In the event of operation of protection due to fault the guard signals will be cut & corresponding trip signals will be transmitted in the Speech band.
Speech & any other Data transmission are interrupted while the trip signals are being transmitted.
Relay Interface
1G4AC
Slot no. 15
Relay Interface
2G4AC
Slot no. 21
DSP
D A
D AD A
C
DSP Module G4AA Slot no.10Start A
Tx Command A AF Tx
BOOST
Pilot
Tx Speech
Relay Interface
1G4AC
Slot no. 15
Relay Interface
2G4AC
Slot no. 21
DSP
D A
D AD A
C
AlarmTx,Rx,COM 1,2
DSP Module G4AA Slot no.10
Rx command A
Rx aux O/P A
AF Rx
Rx Speech
AGC
ALARM
NSD 50 Trip Frequencies
Command A 872 Hz Command B 1090 Hz
A & B Permissive Trip/ Uncoded Commands
Command C 654 Hz / 1526 Hz Command D 654 Hz / 1745 Hz
C &D Direct Trip / Coded Commands
A,B,C & D Commands are transmitted in Speech band
Transmission time ,Security & Dependability
The Performance of a protection coupler is assessed by The Transmission time
The Security ( Unwanted command probability)
The Dependability ( Missing command probability)
Permissive & Direct
This scheme is used for protection of power line with Distance relay.
Tripping can only take place at the receiving end if a tripping signal is being received and local protection relay detects a fault.
Transmission Time 12ms
Command Prolongation (Trip Extension) time- 20ms
The tripping command from the protection coupler goes directlyto the circuit breaker.
Transmission Time 26 ms
Command Prolongation time- 100 ms
ABB ETL 41 ABB ETL 41 ABB ETL 41ABB ETL 41 ABB ETL 41
Main I Main II Direct Trip Sp Dialing Sp Express
M I Own M II Own Direct trip Own
M I Parallel
M II Parallelv
Utilization of PLCC panels (3P+2S)
A AB B C
Modified Utilization (2P+2/1S)
ABB ETL 41 ABB ETL 41 ABB ETL 41ABB ETL 41
Channel I Channel II Speech Dialing
A AB B
M II Own Direct trip Own
v
v
v
M I Parallel
M II Parallel
Direct trip Parallel
Speech Express
C C
OR
ABB ETL 41 ABB ETL 42A AB B
M II Own
v
v
v
M I Parallel
M II Parallel
Direct trip Parallel
C C
Channel I Channel II Speech Dialing/Express
Twin Channel Panel
M I Own
M I Own
Direct trip Own
ABB ETL 41
Relay Interface 2
Opto coupler
Solid state C
Alarm Contact
Opto coupler
Solid state C
Relay Interface 1
Opto coupler
Solid state C
Opto coupler
Solid state C
DSP Card
G4AA G4AC G4AC
Protection Coupler ABB Make NSD 50
Alarm Contact
Slot no. 10 Slot no. 15Slot no. 21
DSP
Relay Panel Protection coupler
Opto coupler
Solid state
Contact
Alarm Contact
Trip Send Contact in RP
Carrier Receive Relay in RP
Carrier Healthy relay in RP
85X
30X
RP K102
RP K877
RP K173
RP K169
RP K161
RP K169
Distance
Relay 21
ETL 41 84/80 KHzwith
NSD 50
ETL 41 80/84 KHz with
NSD 50
M I
M II
DT
M I
M II
DT
ETL 41 96/92 KHzwith
NSD 50
ETL 41 92/96 KHz with
NSD 50
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