Electrical

What is a power line carrier communication?

This is a type of communication which is used to do the communication between the electric substations with the help of electric cables. So with the help of this, we can do telecommunication, telemonitoring, and tele-protection between the electric substations. This is a quick way of communication that is required for a safe and efficient power supply. The power line communication also carries data on the conductor which is used for AC power transmission or electric power distribution to consumers. The major advantage of this type of communication is that we are using the existing power line for the data transmission. Power line carrier communication is the most reliable and cost-effective method of distance communication.

Why do we need PLCC in a power system and what are the functions of PLCC?

  • We can quickly rectify the power failure
  • The interconnected grid system can be maintained in optimum working condition
  • Coordination of the various generating operation can be done
  • The PLCC communication would provide good operating efficiency of the power system
  • Due to the mechanical strength and the insulation level of the power lines, the reliability of the communication has been improved
  • With the help of PLCC, we can handle a big power grid
  • We can transmit data between different generating stations, substations, and control room
  • It can send or receive speech or data signals with the help of HF carrier signals
  • High-frequency signal transmission is done over the electrical power line

The PLCC would do the carrier protection relaying of the transmission line so that the inter-trip command can be issued by the relay due to the circuit breaker tripping at any one end. It would trip the circuit breaker which is close to the faulty section.

What are the factors that affect the reliability of the PLCC?

  • The amount of power out from the transmitter
  • Type of line tuner which is used
  • The number of hybrids that are used to parallel transmitters and receivers
  • The capacitance of the coupling capacitor
  • Line trap inductance
  • Voltage in the power line
  • The phase to which the PLC signal is coupled
  • Circuit length
  • Decoupling equipment at the receiving end
  • The type of modulation and demodulation circuits used in the transmitter and in the receiver
  • Signal to noise ratio

How does a PLCC operate?

The power line carrier communication is achieved by adding a modulated carrier signal to the wiring system. The transmission frequency range will be 50hz to 500khz and we can transmit all types of information. The modulated signal will be injected into the power line conductors and this will be done at the transmitting or the sending end and this transmitted signal will be filtered out at the receiving end. The power lines are high voltage lines and it is designed in a way that it will carry a huge amount of energy while the communication system is at low voltage and because of this, it can’t be directly connected to the high voltage lines.

What are the major components of PLCC?

  • Wave trap/line trap
  • Coupling capacitor
  • Protective devices
  • Coupling of filter
  • HF cable
  • Lightning arrester
  • Line matching unit

Wave trap

The wave trap or a line trap is used to trap the wave frequencies of high magnitude, it would prevent the carrier signal from entering into the substation. The wave trap will be connected to the power line in series, mostly a wave trap consists of a capacitor and inductor to do its operation.

Coupling capacitor

This device is used to do the connection of carrier equipment to the transmission line. This device would prevent the power signal from entering the PLCC and also it would allow passing the carrier signal.

Lightning arrester

This device would protect the system from lightning, this device would be mounted on the highest object of the structure. Low resistance cables are used to connect the lightning arrester to the ground, so in case if the lightning strikes or voltage spikes then it would go to the ground through the ground wire.

Line matching unit

The line matching unit is used to match the impedance of the lines, it consists of an air-core transformer and also some condensers. This device will be mounted on the base of the coupling capacitors. In order to achieve this, the line matching utilizes a balancing transformer, matching transformer, and also capacitor filter.

Earth switch

This device is used for the maintenance of LMU, this device would ground the trapped charges. So if there is any fault in the LMU or in any component then this switch can be used to ground the LMU.

HF cables

These cables are used to interconnect the PLCC station and the LMU in order to carry the high-frequency signals.

Coupling filters

This device is used to isolate the equipment connection from the power line and it can be used to match the impedance of the power line to that of the HF cable to connected equipment.

Protective equipment

Certain protective equipment is used in this system to protect the carrier equipment and also the personnel. The protective equipment is a drainage coil, arresters, and grounding switch.  

What are the advantages of power line carrier communication?

  • Maintenance of the electrical grid can be easily done
  • Power transmission can be easily done
  • Power failure problems can be easily rectified
  • Long-distance communication
  • Economical
  • Reliability
  • There is no need for separate wires for the communication
  • Power transmission and communication can be easily done on the same circuit
  • Power lines provide the easiest route between the power stations
  • The cross-sectional area of the power line is really huge and due to this, the resistance will be really low per unit length. The carrier signals won’t suffer much attenuation when compared to the telephone lines of the same length
  • When the power goes off then the PLCC would utilize the rectified AC or the main supply for its operation
  • The leakage between the conductors and ground is very less because the power lines are properly insulated
  • In a power line, there is good spacing between the conductors and this would reduce the capacitance and due to this the attenuation will be smaller at high frequencies

What are the disadvantages of PLCC?

  • The carrier currents would be attenuated in high voltage lines which are connected to the transformer
  • Noise in the power lines will be higher than the telephone lines
  • There will be a reflection on the spur lines which is connected to the high voltage lines and this would increase the attenuation and other problems
  • Proper care should be taken to protect the carrier equipment and also the persons who is using them 

What are the applications of the PLCC?

  • Protection of the power line
  • Fault indicator
  • Communication between transmission and distribution network
  • Telecommunication can be done with the help of PLCC
  • Security systems
  • Automatic meter reading

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