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Power Line Carrier Communication | PLCC

Published on 20/8/2018 & updated on 21/8/2018
Also called wired wireless, the Power Line carrier Communication (PLCC) has evolved a long way from its earliest use in metering at remote locations to its present day applications in home automation, high speed internet access, smart grid etc. In the early 20th century the power companies used telephones as the medium of communication for exchange of voice messages for operational support, maintenance, control etc and as a method of connectivity at remote locations. The telephone lines ran parallel to the power lines. This had so many disadvantages:

This led to the idea of inventing a more robust and less expensive method of communication. The use of power line as a method of telephony was a long thought idea and its first successful test took place in Japan in 1918. And there after its commercialization started during 1930s.

Power Line Carrier Communication

The figure 1 shows a basic PLCC network used in power substations. The Power line carrier Communication (PLCC) uses the existing power infrastructure for the transmission of data from sending to receiving end. It works in full duplex mode. PLCC system consists of three parts:
  1. The terminal assemblies include the receivers transmitters and protective relays.
  2. The coupling equipment is the combination of line tuner, coupling capacitor and the wave or line trap.
  3. The 50/60 Hz power transmission line serves as path for relaying data in the PLCC bandwidth.
diagram of plcc network

Coupling Capacitor

It forms the physical coupling link between transmission line and the terminal assemblies for the relaying of carrier signals. Its function is to provide high impedance to power frequency and low impedance to carrier signal frequencies. They are usually made up of paper or liquid dielectric system for high voltage application. The ratings of coupling capacitors range from 0.004-0.01µF at 34 kV to 0.0023-0.005µF at 765kV (source: IEEE).

Related pages
Power Line Carrier Communication | PLCC

Drain Coil

As shown in the figure 1 the purpose of drain coil is to provide high impedance for carrier frequency and low impedance for power frequency.

Line Tuner

It is connected in series with the coupling capacitor to form a resonant circuit or carrier signal frequency high pass or band pass filter. Its function is to match the impedance of the PLC terminal with the power line in order to impress the carrier frequency over the power line. In addition it also provides isolation from power frequency and transient overvoltage protection.

Line Trap or Wave Trap

It is a parallel L-C tank filter or band-stop filter connected in series with the transmission line. It presents high impedance to carrier signal frequencies and very low impedance to the power frequency. It consists of
  1. Main coil

    An inductor that is connected directly to the high voltage power line carries power frequency.
  2. Tuning device

    It may be a capacitor or a combination of capacitor, inductor and resistor, connected across the main coil in order to tune the line trap to the desired blocking frequency.
  3. Protective device

    It is usually a gap type surge arrester used to protect the line trap from damage due to transient over-voltages.
The line trap or wave trap prevents unwanted loss of carrier signal power and also prevents carrier signal transmission to adjacent power lines. Line traps or wave traps are available for narrow-band and wide-band carrier frequency blocking applications.

Power Line Channel Characteristics

Applications of PLCC in Power Systems

home automation using power lines

Limitations of PLCC




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