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PLCC SYSTEM by P.R.MEKAP Asst.Engineer SLDC,BBSR

PLCC SYSTEM by P.R.MEKAP Asst.Engineer SLDC,BBSR. GRIDCO POWER TRAINING CENTRE. Part -I. Overview of PLCC Systems. WT. WT. cc. cc. C. F. A. X. F. A. X. M. M. MS. PR. FAX. PC. PR. FAX. PC. RTU. PAX. MS = Master station PAX = Private automatic exchange

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PLCC SYSTEM by P.R.MEKAP Asst.Engineer SLDC,BBSR

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  1. PLCC SYSTEM byP.R.MEKAPAsst.EngineerSLDC,BBSR GRIDCO POWER TRAINING CENTRE “PLCC system” presented by P R Mekap (Tel) SLDC

  2. Part -I Overview of PLCC Systems “PLCC system” presented by P R Mekap (Tel) SLDC

  3. WT WT cc cc C F A X F A X M M MS PR FAX PC PR FAX PC RTU PAX MS = Master station PAX = Private automatic exchange PR = Protection relay PC = Computer M = Modem PR= Protection relay FAX = Facsimile equipment M = Modem RTU = Remote terminal unit Typical PLCC Installation “PLCC system” presented by P R Mekap (Tel) SLDC

  4. Topics to be discussed 1.Why PLCC is preferred in by Power Utilities? 2. What is the RF power and frequency band in PLCC? 3. Typical PLCC installation; how speech, data and protection commands are transmitted over PLCC system ? 4. PLCC link design, factors affecting performance of a PLCC link, effect of corona noise in PLCC . 5.Features of digital PLCC. “PLCC system” presented by P R Mekap (Tel) SLDC

  5. System description • PLCC is used in all power utilities as a primary communication service to transmit speech, telemetry and protection tripping commands. • PLCC system uses the HV power transmission line of the utility as a metallic medium for telecommunication. No need for laying separate telephone lines on the electric poles or hire lease lines from public telephone companies. • This is very economic, dependable and secure communication compared to any other means like HF wireless,VSAT or lease line. Cheaper thanmicrowave radio and optical fibre. PLCC communication is feasible for line length up to 800 kM . “PLCC system” presented by P R Mekap (Tel) SLDC

  6. The frequency band used for PLCC is 90 - 500kHz. Type of modulation adopted is SSB-SC as per IEC-495 specification. PLCC channel carrying voice and super imposed data has gross band width of 4kHz. • RF out put power of a PLCC transmitter is 20/40/80W depending on distance. The radio frequencies used by the power utilities for PLCC should be approved by WPC, New Delhi, Ministry of Communication Govt.of India. Government charges a licence fee for this communication too. • The RF out put of PLCC terminal is injected in to high voltage power line using a suitable high voltage HF coupling capacitor(4-10nF). Also HF traps ( 0.2 – 2mH) are inserted at both ends of the line. “PLCC system” presented by P R Mekap (Tel) SLDC

  7. Components of PLCC H.V Line Wave Trap Coupling apacitor PLCC Terminal Translates voice and data into Radio Freq. Carrier. Coaxial cable LMU “PLCC system” presented by P R Mekap (Tel) SLDC

  8. POWER FREQUENCY & CARRIER FREQUENCY WT Power Line (50Hz) CC RF carrier (40-500kHz) PAX RTU Transmission line PLCC TERMINAL (ABB-ETL41) “PLCC system” presented by P R Mekap (Tel) SLDC

  9. IF AF IF PA IF RF H H AF RF IF AF A gain RF IF IF Function of PLCC terminal R.F Signal (40 to 500 kHz) User Signal (0 to 4 kHz) Line Side User Side Frequency conversion : audio signals into radio spectrum and vice versa Amplification : Sufficient RF power to compensate the line attenuation “PLCC system” presented by P R Mekap (Tel) SLDC

  10. Wave Trap function 40- 500kHz ( HF) : Blocked WAVE Trap Behind The carrier signal is transmitted over Power Line to reach the opposite end The carrier signal is blocked by line trap; not allowed to enter inside the switch- yard Front Coupling Capacitor • Transformer(s) • BusBar Line Matching Unit Coaxial PLC terminal “PLCC system” presented by P R Mekap (Tel) SLDC

  11. Wave trap function 50 Hz (Power Freq): through pass HV Line Power energy PLC Signal Substation Line Trap =High Impedance for PLC signal Low Impedance for Power energy “PLCC system” presented by P R Mekap (Tel) SLDC

  12. Wave Traps Mounting Options Vertical Pedestal Horizontal Pedestal Suspension “PLCC system” presented by P R Mekap (Tel) SLDC

  13. Inductance of main Coil Series Lightning resistance Arrester Tuning Capacitor Wave Trap is a Band Stop filter (50-500kHz) Damped single Line Trap “PLCC system” presented by P R Mekap (Tel) SLDC

  14. Corona ring Lifting lug Terminal Main coil Tuning device Pedestal Protective device Tie rod Wave Trap assembly “PLCC system” presented by P R Mekap (Tel) SLDC

  15. Capacitive Voltage Transformer ( CVT ) “PLCC system” presented by P R Mekap (Tel) SLDC

  16. 220kV 8800 pf 8800 pf CVT LMU DISCONNECT THIS LINK COAXIAL CABLE 20mH Drain coil CVT and HF connection HF PLCC TERMINAL “PLCC system” presented by P R Mekap (Tel) SLDC

  17. LMU : Type-MCD-80, ABB make “PLCC system” presented by P R Mekap (Tel) SLDC

  18. Co-axial Cable “PLCC system” presented by P R Mekap (Tel) SLDC

  19. + Matching Protection LMU function LMU = impedance matching +high voltage Protection • To prevent dangerous potential on the PLCC connection • To match impedance of PLCC set with power Line impedance. s/s PLCC LMU Coaxial LMU “PLCC system” presented by P R Mekap (Tel) SLDC

  20. LMU functional blocks -line HV Substation Wave trap PLCC Panel Coupling capacitor Tx or Rx Coax cable ABB MCD 80 “PLCC system” presented by P R Mekap (Tel) SLDC

  21. 75ž 2 3 T A G K L H C1 1 25ž B C2 M N 2 C Z2 D Q1 C3 O P F1 L2 E C4 F Q R L1 T1 Z 1 L C E Z1 ABB- MCD 80internal wiring Coax To PLCC CVT LA E.S Drain Coil Match Trans “PLCC system” presented by P R Mekap (Tel) SLDC

  22. Built in protection devices of LMU • Drainage coil to sink the leakage currents from CC/CVT to ground. • Lightning arrester across the CVT HF terminals and ground for transients protection. • Earth switch for grounding of CVT HF terminal during maintenance. • RF Transformer for galvanic isolation between power line and PLCC terminal. “PLCC system” presented by P R Mekap (Tel) SLDC

  23. Cc LT LT LT LT LT LMU PLC Cc Cc LMDU LMU PLC Cc Cc LMDU LMU PLC HF Coupling modes Phase-to-Ground Inter circuit Phase-to-Phase “PLCC system” presented by P R Mekap (Tel) SLDC

  24. Part -II PLCC Link Design “PLCC system” presented by P R Mekap (Tel) SLDC

  25. Line loss and Noise • Signal loss factors • Taping loss (effect of PLCC terminals in parallel) • Coaxial cable attenuation ( length of the cable) • Return loss ( improper line matching ) • Coupling loss (LMU,CC, Wavetrap) • Modal coversion loss (effect of carrier current on conductors) • Line loss (type of tower, conductor type and line length) • Line loss (Bad Weather conditions; rain,frost) • Corona Noise( Swicth Yard equipments & line insulators) • White Noise ( semiconductor devices) “PLCC system” presented by P R Mekap (Tel) SLDC

  26. Loss due to Parallel Working of PLCC Parallel working of several PLCC terminals results a loss of power due to loading of transmitters by each other. This depends on frequency spacing between adjacent transmitters . It is called tapping loss and it should not exceed 2dB. “PLCC system” presented by P R Mekap (Tel) SLDC

  27. Co-axial cable Loss The RF power through coaxial cable gets attenuated by 2 to 6 dB per kM of cable length depending on carrier frequency used. “PLCC system” presented by P R Mekap (Tel) SLDC

  28. Modal conversion loss While RF power is directly coupled to one or two phase conductor(s) carrier current flows on all the three or six phase conductors running parallel. Depending on coupling methods used, the magnitude and direction of carrier current in each conductor is different. In an unfavorable mode the effect is equivalent to loss of transmit power up to3.5dB = ac “PLCC system” presented by P R Mekap (Tel) SLDC

  29. Carrier signal attenuation per mile of line length Attenuation in db/mile depends on conductor size, spacing above ground, transpositions, type of coupling and carrier frequency. It also varies periodically with weather conditions (rain and frost do affect) “PLCC system” presented by P R Mekap (Tel) SLDC

  30. f . - 3 a » + 0.071 f 10 . n d = f frequency (kHz) = d diameter of phase conductor (mm) = n number of phase conductor in bundle Line attenuation per Km = α It is the attenuation of transmit power over a line length of one kilo meter = α db “PLCC system” presented by P R Mekap (Tel) SLDC

  31. Source of RF Noise is HV line • Corona Noise = 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) • Impulsive Noise = Caused by atmospheric discharges, breakers and isolator close/open operation “PLCC system” presented by P R Mekap (Tel) SLDC

  32. Corona Noise Bad weather Noise Typical average Noise on a 220 kV line and for a 3 kHz Bandwidth “PLCC system” presented by P R Mekap (Tel) SLDC

  33. Effect of bad weather on PLCC links • 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 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. “PLCC system” presented by P R Mekap (Tel) SLDC

  34. Additional loss Depending upon line configuration , mode of coupling and number of transpositions an additional loss is considered = aadd “PLCC system” presented by P R Mekap (Tel) SLDC

  35. Channel Band Width and White Noise The noise power is proportional to noise band width of the channel. Noise bandwidth of 50 Baud voice frequency telegraphy channel is taken to be 80Hz and speech has band width of 2100Hz (300Hz-2400Hz) Noise power in a 50Bd VFT channel is calculated as follows =10 log (2100Hz/80Hz) = -14dB Meaning , Noise power in 50 Bd/80 Hz data channel is 14 dB below the noise power in 2100 Hz speech channel. In the AF mixer of the transmitter, the input signal levels for test tone, pilot tone, speech and telemetry are kept proportionate to their noise band width to maintain same SNR at the receiver. This is discussed under channel loading in next slide. “PLCC system” presented by P R Mekap (Tel) SLDC

  36. Channel LoadingPUNCOM PLCC The scheme for allocating the weights to voice and data channels is based on the noise bandwidth of each channel Speech(300-2400Hz) 2100/80 = 5.0 Pilot(3923Hz) = 50 baud 80/80 = 1.0 Signalling(3825Hz) = 50 baud 80/80 = 1.0 200baud FSK channel 360/80 = 2.12 300baud FSK channel 480/80 = 2.45 600baud FSK channel 960/80 = 3.55 1200baud FSK channel Same as speech = 5.0 Speech with 3 dB safety margin= 2 x 5 = 7 “PLCC system” presented by P R Mekap (Tel) SLDC

  37. Channel loading (ABB PLCC) “PLCC system” presented by P R Mekap (Tel) SLDC

  38. Signal Levels ( PUNCOM) Speech ( with 9dB safety margin = 23 dB above reference) Peak Envelope Power additional 9 dB as safety margin leads to difference in SNR level for speech vs data in link budget calculation. 9 dB 14 dB above reference 1kHz Test tone 14 dB 600 Bd data 10. 5 dB above reference 300 Bd data 6 dB above reference 50 Bd data 23dBm MAX Pilot (50 Bd) as reference Level PUNCOM Pilot/signaling “PLCC system” presented by P R Mekap (Tel) SLDC

  39. VF Signals Signal Levels Absolute Level at HF Output Absolute Level at input of Channel Modem dBm0 Weighting dBm dBm Speech(300-3400Hz) 0 5 +37 -16 Speech with 3dB safety margin +3 7 +40 -13 Pilot(3923Hz) -14 1 +23 -30 Signalling(3825Hz) -14 1 +23 -30 200baud Channel -8 2 +29 -24 300baud Channel -6 2.45 +31 -22 600baud Channel -3 3.55 +34 -19 1200baud Channel 0 5 +37 -16 Signal weighting and absolute levels (PUNCOM) “PLCC system” presented by P R Mekap (Tel) SLDC

  40. PLCC Link Budget It is a mathematical model representing the performance of the proposed PLCC link for the given transmit power and carrier frequency. Propagation parameters like line attenuation, modal conversion loss, coupling loss, corona noise and many other factors affecting signal quality are being considered in calculating link budget. Finally we arrive at the SNR value for the voice and data channels. SNR is expected to be higher than 45dB. A link is not at all feasible if SNR is less than 15dB. “PLCC system” presented by P R Mekap (Tel) SLDC

  41. Sample Link Budget : Boinda–Angul Puncom PLCC “PLCC system” presented by P R Mekap (Tel) SLDC

  42. Modal Conversion Loss - A (dB) 1 c Additional Loss - A (dB) 6 add = -15 + 10*LOG(1700/4000) Corona Noise for Speech - P (dBm) -33.7161107 cor Corona Noise for Data - Pcor (dBm) = -30 + 10*LOG(320/4000) Channel # 1 -40.9691001 Coupling Loss - A (dB) 6 coupl = 0.71{SQRT(364/1)/21}+364/1000 Attenuation Constant - Alpha1 0.089075947 Line Attenuation - A (dB) 11.56303787 line = alpha1*40km +2*1+6 Signal level of reference channel Pr (dBm) PEP – power[speech+data+pilot+signal ] 19.14912096 23 dB above reference Power allocation for speech Psp (dBm) 1 42.14912096 (dBm) 6 dB above reference Power allocation for data P 25.14912096 data Difference in two SNR level, because of 9 dB safety margin in speech SNR (speech) in dB 58.30 48.56 SNR (data) in dB SNR>45dB “PLCC system” presented by P R Mekap (Tel) SLDC

  43. SNR Calculation 1 - Corona Noise for speech (300-2000 Hz) = -15 + 10 log (1700/4000) =-33.7 dB 2 - Corona Noise for 300 Bd data (320 Hz) = -30 + 10 log (320/4000) =- 40.969 dB 3 – Attenuation Constant (364kHz;21 mm) = 0.71 {(364/1)/21} +364/1000 = 0.089 dB 4 – Line attenuation (40 kM) = (40 x 0.089 dB) + 2x1 + 6 = 11.563 dB 5 - Signal level of reference channel Pr (50 Bd) = PEP – power[speech+data+pilot+signal] = 43dBm – 10 log [6.3095 (1700/80) + (320/80) + (80/80) + (80/80)] 2 =19.149 dBm 6 - Power allocation for speech Psp = 23 dB above reference =19.194+23 = 42.149 dBm 7 - Power allocation for data Pdata = 6 dB above reference =19.194+6 = 25.149 dBm 8- SNR (speech) = (Psp– coupling loss– line attenuation) - corona noise for spech = 42.149 - 6 - 11.563 - (-33.7) = 58 dB 8- SNR (data) = (Pdata– coupling loss– line attenuation) - corona noise for data = 25.149 - 6 - 11.563 - (-40.969) = 49 dB Remarks : 20W PLCC operating at 320 KHz carrying speech plus data in Boinda - Angul 132 kV line (40km) gives acceptable SNR “PLCC system” presented by P R Mekap (Tel) SLDC

  44. Part -III PLCC Equipments ABB ETL series “PLCC system” presented by P R Mekap (Tel) SLDC

  45. PLCC Panel ( type: ABB ETL 41/42) Modules Cabinet “PLCC system” presented by P R Mekap (Tel) SLDC

  46. ABB PLCC terminal ETL- 41 System data -- complies to IEC 495 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 “PLCC system” presented by P R Mekap (Tel) SLDC

  47. Functional blocks of a ABB ETL41 PLCC terminal Basic equipment B5LA,B4LA AF Interfaces Power Amplifier +12V -12V + 5V Main Power Supply P4LB=AF CONV Voice interface E5LA P1LA 16-20KHZ SA MO MO MO PA P4LF P4LC H 0-4kHZ P4LG Data interface P3LB dB DE DE DE DE P3LB P4LD P4LC PILOT P4LB = AF CONV P4LC =IF CONV. P4LD= RX RF CONV P4LF=TX RF CONV P4LG = CARR GEN P1LA = POW AMP P3LB = RF HYB MO=Modulator DE = Demodulator SA = Summing Amplifier PA= Power Amplifier H = RF-Hybrid “PLCC system” presented by P R Mekap (Tel) SLDC

  48. ETL 41 module layout speech + data + protection Power amplifier 40 W P3LB RF-Hybrid B5LA Power Supply 48 VDC E5LA/B Tx-Filter P7LA Power shelf Channel 1 O4LATelcontrol interf. P4LB AF-converter O4LC 4-wirePAXintrf. P4LC IF-converter P4LA Pilot+Supervn P4LD Rx-converter P4LG Carrier synth. P4LF Tx--RF-conv. G4AE Modem NSK5 G4AA DSP-Module B4LA DC-converter G4AC Interface P7LB Channel shelf 8R 8R 4R 10R 6R 9R 4R 6R 6R 7R 6R 6R 4R NSD 50 User interface basic Power shelf “PLCC system” presented by P R Mekap (Tel) SLDC

  49. ABB_ETL 41: Modulation Scheme ( double conversion) IF range (low) AF Band IF range (high) PLCC BAND (40 –500kHz) 0-4Khz AF IF1 Carrier =16kHz IF1=16-20k IF2 Carr =640kHz 3 modulators 2 stage IF IF2=620-624K SSB-SC TX FC= 724 kHz ( Programmable) TX=100-104 “PLCC system” presented by P R Mekap (Tel) SLDC

  50. ABB_ETL 41: Demodulation Scheme (Triple conversion) IF range (low) AF Band IF range (high) PLCC BAND (40 –500kHz) RX=104-108KHz SSB-SC 4 demodulators 3 stage IF IF3=620-624 RX FC = 728 kHz (programmable) IF2=140-144 IF3 Carr =480kHz IF1 Carrier =16kHz IF2 Carr =160kHz AF=0-4Khz IF1=16-20K “PLCC system” presented by P R Mekap (Tel) SLDC

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