Electrical

Power line carrier communication

Introduction to power line carrier communication

Power line carrier communication is a method of using the existing power lines for communication, so information can be transmitted by the help of power lines. Nowadays every house and buildings have properly installed electricity lines so the existing power lines can be used for the connection of high-speed network access point without the installation of new wires. Power line carrier communication is the most economical and reliable method of communication for medium and long-distance in a power network. Power line communication system uses a high voltage transmission line connecting two substations for telecommunication purpose. So there are mainly two tasks the first one is power transfer and the second one is communication and both of this is carried out by sending two signals along the same line.

What are the advantages of PLCC over other communication methods

PLCC uses existing power lines for the communication so it has many advantages over other traditional communication methods. The main advantage of power line carrier communication is the reduced cost because of utilizing the existing power lines. In case of a power supply for a whole building, the main cables are dropped through-out the building and it bears all the load thruster by equipment or devices run on electricity. If PLCC modem is used in such an area no additional wiring or cable is needed as PLCC uses this power lines only and data is sent on this by equipotential coupling circuitry using modulator and its retrieved at the receiver’s side using demodulator so elimination of the wires and cables is the biggest advantage and the users doesn’t have to pay taxes for this because they are using the existing power lines.

PLCC operating principle

The communication device for the PLCC system is a built-in modem which will transmit and receives data over the power line, both the MIU and DCM contain the PLM device. A binary data stream is keyed onto a carrier signal by means of the frequency shift keying technique and the signal is coupled onto the power line by PLM. At the receiving end, an identical PLM will detect the signal and convert it back to the binary data stream

The basic circuit of PLCC

Coupling capacitor

It is a high voltage capacitor which is connected between the power line and the LMU. This capacitor will block the power signal entering the PLCC and it allows to pass the carrier signal so its capacitance is kept in a way that it is negligible for the power signal frequency and significant for carrier signal frequency. A coupling capacitor exhibits low impedance to the carrier signal and high impedance for the power signal. in the absence of the coupling capacitor, high voltage signal will enter the PLCC panel and destroys the modulator and demodulator circuitry.

Lightning arrestor

It is used in the system to protect the system from the damages caused by the lightning and from high voltage spikes from the transmission line. Lightning arrestors are connected to the ground by low resistance cables so whenever high voltage spikes strike to the lightning arrestor it goes to the ground through ground wire and thus it prevents the LMU from high voltage AC spikes

Line matching unit

It is used for the proper impedance matching between the power line and the PLCC panel. Line matching unit is connected between the CC and PLCC panel. Coaxial cable is used for interconnection between PLCC and LMU. If a high-frequency wave is not terminated then the terminating load is not equal to the characteristic impedance, reflection occurs and it will cause power loss in a circuit and to avoid this impedance matching is done.

Wave trap

It is a parallel combination of coil, tuning device and lightning arrestor. It offers negligible impedance to the power signal and at the same time high impedance to the carrier signal. The output of the wave trap is given to yard, out-put of the yard is internally connected to PLCC panel.

Earth switch

It is used at the time of maintenance of LMU. Before inspection of LMU, one must close the switch so that the power signal goes to earth.

Types of coupling

Phase to ground coupling

In this type of coupling-out of three we use one wire for communication the wave traps and coupling capacitors are all connected to one conductor of the power line and the remaining two conductors, though not directly connected to the line carry a portion of the carrier energy which is lost.

Phase to phase coupling

In this type of coupling-out of three wires, we use two wires for communication and the advantage of this coupling is that if one wire is damaged then communication will take place by another wire

Applications of PLCC

  • Information can be transmitted at a fast rate
  • Voice message can be transmitted
  • Home automation and control
  • Telecommunication
  • Current and voltage can be checked from distant locations
  • PLCC can be used as a security system it can be done by monitoring houses or business through surveillance camera

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