Power Line Carrier Communication


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Power Line Carrier Communication

  1. 1. Seminar on, Power Line Career Communication DEPARTMENT OF ELECTRICAL ENGINEERING Submitted to: Dr. Abhimanyu Mohapatra, & Dr. Ranjan Ku. Jena Lecturers , Dept of Electrical Engineering, CET. submitted by: Soumya Mishra Regd no-0901106013
  2. 2.    Fast and efficient communication is a prerequisite for the management of modern power systems. To maintain a large power grid in optimum working condition,the central load despatcher has to have at his command a large battery of communication systems. For this the load dispatcher may use the commercial P&T telephone system using underground cables or open wires or VHF wireless communication.
  3. 3.  a. b. c. But for communication over medium and long distances in a power network,Power Line Carrier Communication is the most economical and reliable method of communication. This is because of : The higher mechanical strength and insulation level of HV powerlines. Lower attenuation over longer distances. Absence of additional communication lines.
  4. 4.  Like any other communication system in PLCC the three basic blocks of communication are: 1) transmitter 2) Channel and 3) Receiver
  5. 5.  In PLCC we use wired channel of communication.
  6. 6.   The idea of Power line communication came into picture in 20th century and practically this idea came into operation in several countries after 1920. In early time antennae similar to those used in radio work were being used to couple telephone systems into powerline systems.
  7. 7.   But due to their inefficiency owing to their length and interference with nearby long wave radio transmitters they were replaced by oil and paper capacitors by about 1930. These coupling capacitors could withstand high voltages and serve as effective coupling devices for power line carrier communication.
  8. 8. These early PLC communication systems today handle not only speech communication but also:  Telemetry  Tele-signaling  Tele-control  Tele-printer  Tele-protection signals. 
  9. 9.  1. 2. 3.     The various components of PLC communication includes: Carrier Signals Modulation Coupling arrangements Wave traps Coupling capacitors Drainage coil The line matching unit
  10. 10.   The carrier signals used in modern PLC systems are audio frequency currents of frequencies between 24khz to 500khz. The use of audio frequency carrier currents enables several channels of communication to be held over a single physical circuit.
  11. 11. The frequency limits are decided basing on the following points:  Ease of separation between power frequency and radio frequency  Cost of coupling equipments  Radiation losses  Signal to noise ratio in the communication circuit  Interference to and from other services
  12. 12.   We use the word modulation to mean the systematic alteration of one waveform, called the carrier, according to the characteristic of another waveform, the modulating signal or the message. In Continuous Wave (CW) modulation schemes, the carrier is a sinusoid.
  13. 13. The various advantages of modulation are:  Ease of radiation  Efficient transmission  Multiplexing  Frequency assignment  Improvement of signal to noise ratio
  14. 14.  The four important types of linear modulation schemes are: 1) Double Sideband, Suppressed Carrier (DSB-SC) 2) Double Sideband, Large Carrier (DSB-LC) (also called conventional AM or simply AM) 3) Single Sideband (SSB) 4) Vestigial Sideband (VSB)
  15. 15.  Let gm denotes the amplitude sensitivity (or gain constant) of the modulator, with the units per volt (we assume that m(t ) and Ac are in volts). Then the modulator output s (t ) is, s (t ) = gm m(t ) (Ac cos(ωc t )) For convenience, let gm = 1. Then, s (t ) = Ac m(t )cos(ωc t )
  16. 16. i. ii. There are two popular methods for generation of single side band sinals: Frequency discrimination method Phase discrimination method
  17. 17.  Frequency discrimination method Conceptually, it is a very simple scheme. First generate a DSB signal an then filter out the unwanted sideband.
  18. 18.     This scheme requires: two product modulators two π/2 phase shifters and an adder. One of the phase shifter is actually a Hilbert transformer (HT); it should provide a π/2 phase shift for all the components in M(f ) .
  19. 19.   The received SSB signal is multiplied by the local carrier which is of the same frequency and phase as the carrier used at the transmitter. In the output we get the spectrum centered at ± 2fc which will be eliminated by the LPF following v (t ).
  20. 20. Wave traps: Wave traps prevent the carrier currents from entering into the power equipments in the stations removing the chances of:  High attenuation  Complete loss of signals 
  21. 21.  o o These wave traps consist of choke coils connected in series with the power lines and offer: Negligible impedance to power frequency currents But a suitably high impedance to the radio frequency carrier currents.
  22. 22. Vertical Pedestal Suspension
  23. 23. Corona ring Lifting lug Terminal Main coil Tuning device Pedestal Protective device Tie rod
  24. 24. Modern coupling capacitors are designed to obtain,  Highest possible surge withstand capacity  Highest cutoff frequency  Lowest series resistance at carrier frequencies.
  25. 25.  The drainage coil serves to ground the power frequency charging current of the capacitor and allows the carrier frequency current to appear in the output of the unit. The line matching unit: It consists of the matching transformer and tuning capacitors and is generally tuned to a wide band of carrier frequencies(100450khz).
  26. 26.     Phase to ground coupling Phase to phase coupling Inter line or inter circuit coupling CVT coupling
  27. 27. Advantages:  More economical than all others.  Disadvantages:  Loss of carrier current.  Carrier energy & radiation losses are more.  Noise pick ups are correspondingly higher. Applications:  Short or unimportant lines where carrier protection is not essential.
  28. 28. Advantages:  The third conductor has no appreciable effect on carrier current transmission.  Switching conditions have little effect on transmission.  Signal attenuation is less.  More reliable over longer distances. Application:  Used in load dispatch work.
  29. 29. Advantages:  It is more reliable than phase to phase coupling on the same circuit as it permits operation with one of the two circuits opened out & grounded for maintenance.  More reliable under broken conductor conditions. Applications:  In 220kv and 400kv lines where interference levels are high.  In long110kv lines where attenuation is a problem.
  30. 30. Cabinet Module
  31. 31.    Now a day PLC communication is finding application in domestic and many corporate sectors also. Spread spectrum is the main field of research these days. Very soon this system will have a wide range of applications due to its reliability, fastness and more economic features.
  32. 32. Thank You