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Power line carrier communcation.
Detailed study and Applications.
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From Kurukshetra

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  2. 2. PLCC is a technology which uses power lines asphysical media for data transmission•PLCC can offer a "no new wires” solution becausethe infrastructure has already been established.•PLCCs are used for transmitting data at a rapidspeed through a power line in a house, an office, abuilding, and a factory, etc. 2
  3. 3. 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. 3
  4. 4.  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. Here, the existing alternating current (AC) power wires serve as a transmission medium by which information is relayed from a transmitter or control station to one or more receivers or loads connected downstream from an AC source. 4
  5. 5. • The telephone communication system cannot be directly connected to the high voltage lines, which is therefore done by suitably designed coupling devices.• These usually consist of high voltage capacitor with polarity devices used in conjunction with suitable line matching unit (LMU) for matching the impedance of line to that of the coaxial cable connecting the unit to the PLC transmit-receive equipment. 5
  6. 6. H.V Line Line COMPONENTS Trap Coupling capacitor Coaxial cable LMU PLCC terminal 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 - Does 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) . 6
  7. 7. COMPONENTS Behind Front Line Trap To remote substation Coupling The PLC Capacitor signal is routed to Line H.V Line •Transformer(s) Matching •BusBar Unit The PLC signal is not Coaxial absorbed by the Local substation substation PLC terminal 7
  8. 8. Line trap function = PLC signal Blocking HV Line Power energy PLC SignalSubstation Line Trap = 1. High Impedance for PLC signal 2. Low Impedance for Power energy
  9. 9. Line Traps Mounting Options Vertical Pedestal Horizontal Pedestal Suspension 9
  10. 10. LINE MATCHING UNIT FUNCTION Line Trap LMU = Couplingimpedance matching Transformer s/s Capacitor+ high voltage Protection LMU PLC Coaxial To prevent dangerous potential on the PLCC connectionTo match PLCC set & transmission Line Matching + Protection LMU 10
  11. 11. Elements of Coupling Device• 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. 11
  12. 12. The PLCC Modem is in the form of a ready-to-go circuit module, which is capable oftransferring data over the power cable atthe low voltage end of the power transformerof a 3-phase/ 4-wire distribution network.A pair of Embedded PLCC Modems connectedon the power line can provide low speed bi-directional data communication at a baudrate of 9600 bps. 12
  13. 13. 13
  14. 14. Communication InterfaceThe Communication Interface provides serialcommunication between the Embedded PLCC Boardand a PC.The board uses a standard RS-232/UART port forcommunication with a COM port on a PC. In Caseon board RS-232 level translator is not needed aTTL interface is also provided. It can be used with,for example, a PC running a terminal program suchas Hyperterminal for use under Windows 14
  16. 16. Communication Interface 16
  17. 17. TECHNOLOGYThe Embedded PLCC modem is based on the Differential Code Shift Keying(DCSK) Technology. This technology in Power Line Carrier (PLCC)communication is well known for its high immunity to electrical noisepersistent in the power line. Other suppliers use narrow band modulation,which are sensitive against single tone noise sources. The external Analoguefront end (AFE) ensures high line drivability even at low impedances. TheEmbedded PLCC modem has many mechanisms to make the communicationmore robust.These are built-in hardware features such as:• FEC (Forward Error Correction)• CSMA/CA (Carrier Sense Multiple Access / Carrier Avoidance)• LQI (Line Quality Indication)• Three Different communication modesStandard Mode, Robust Mode,Extremely Robust Mode) 17
  18. 18. Typical PLCC Installation LT LT cc cc C FX A ETL ETLFXA M M PR PC MS PAX FAX PR PC RTU FAX LT= Line Trap MS = Master station CC = Coupler Capacitor PAX = Private automatic exchange PR= Protection relay PR = Protection relay FAX = Facsimile equipment PC = Computer M = Modem M = Modem RTU = Remote terminal unit
  20. 20. DUAL STREET LIGHT CONTROLLER NODEThe above schematic is a typical dual street light controller node.Each such node can monitor and control two street lights at atime.● The IO control can turn ON/OFF each light independently.● The sensor and IO control unit can detect ON/OFF status ofeach streetlight and can also detect burn out condition of eachlight as well.● This has an ambiance light sensor for autonomous operation.With this feature, the street light can be automatically turned ONif the surrounding light intensity goes below a preset threshold.Similarly, the light can be turned OFF, if ambiance light detected ishigher than a preset threshold.● This can measure the amount of energy consumed by each ofthe lights so as to report to the central station its energy usage. 20
  21. 21. Power line NodeThe nodes are the modules which are fixed in the street lights.The central station essentially speaks to this node, via theconcentrator, for its application. The system has the followingarchitecture. 21
  22. 22. AUTOMATIC METER READINGThe need of AMR :The distributor must be capable of connecting the customers, getting the readingfrom their meter, and to disconnect them if necessary. This will enable him to knowthe amount of energy each customer uses and this can be compares with the totalconsumption. If a customer is not paying the bill, the office personnel can disconnecthim with a single command. When he clears the dues, the connection can be re-established from the office itself. The disconnection- re connection can beprogrammed, eliminating the human effort required and also, making it corruptionfree. The server at the office is getting all the customer’s reading and thus the billingprocess can be automated. The different systems of the AMR are:• Telemetry• Wireless communication• Communication through Optical cables• Communications using the power lines 22
  23. 23. AUTOMATIC METER READINGIn the Power Line Carrier Communications, theremote metering unit is capable of receiving anddecoding the communication signals, and to respondaccordingly. If the meter can be controlled from thedistributors’ office, almost all types of thefts can beprevented and the power quality can be assured atthe consumer premises. The use of power linecarrier communication minimizes the amount ofcapital required for the infrastructure. The existingsystem can be converted to the new system with theintroduction of certain components. 23
  24. 24. AMR USING PLCC 24
  25. 25. Embedded PLCC modem hardware is used for both PLCC Masterdevice and nodes (Slave device). A 3 pin jumper setting is provided onthe board, connecting the jumper to pin 1 and pin 2 configure thedevice as Master ( concentrator ) while connecting it to pin 2 and 3configure the device as node.5-2 Setting Up the User InterfaceThe demo requires a minimum two PCs with Microsoft® XP® OS. Onone PC, PLCC Master emulation code runs and sends data toEmbedded PLCC modem (Master device) via RS232 interface which inturn sends data over power lines to node device connected to anotherPC via RS232 interface running node emulation code. 25
  26. 26. 26
  27. 27. PLCC Panel ( type: ABB ETL 41/42) Modules Cabinet 27
  28. 28. ADVANTAGES OF PLCC• No separate wires are needed for communication purpose.• Both communication and power transfer can be possible on same circuit.• Power lines provides the shortest route between the power station.• Higher mechanical strength.• Increased reliability.• Lower attenuation over long distance.• Implementation cost is reduced.
  29. 29. EFFECT OF BAD WEATHER ON PLCC COMMUNICATIONLosses increase for all severe 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 contaminants (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 29
  30. 30. Typical applications of PLCC are•Street light control,•Automatic Meter Reading,•HVAC control,•Low Speed Data Networks,•Signs and Information Display,• Fire and Security Alarm etc. 30
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