15-01-2013, 03:39 PM
POWER LINE CARRIER COMMUNICATION
POWER LINE.pptx (Size: 706.84 KB / Downloads: 53)
Introduction :
Fast and efficient communication is a pre-requisite for the management of modern power systems. To maintain a large power grid in optimum working condition the Central Load Despatcher has to have his command a large battery of communication systems. The lead despatcher may use the commercial PIT telephone system using open wires or under-ground Cables for communication over short distances such as communications between the load despatch centre and generating/receiving stations in the same city. Where the load despatch station is located. In some cases, VHF wireless-communication, may also be used. For communication over medium and long distances in a power network, Power Line Carrier Communication is the most economical and reliable method of communication
History of PLC Communication
Engineers started thinking about using power lines for communication at the beginning of the 20th century. Practical power line carrier communication systems cams into operation in several countries after 1920. In those early days antennae similar to those used in radio work were set to couple the telephone systems to the power lines. This Was because capacitors capable of withstanding the high voltages used in power transmission ;had not yet keen developed at that time. These antennae were more than 100 meters long and were tuned-to the carrier frequencies employed. The coupling systems using antennae were-inefficient and were affected by interference from nearby long wave radio transmitter
Components of plcc
Carrier-:
The carriers used in modern plc communication system are audio frequency current of frequency in between 24 khz and 500 khz .
Modulation-:
In plcc technology the carrier currents are modulated by voice frequency .currents and modulated currents are transmitted over the power line . frequency modulation is rarely used for speech transmission because of its considerable bandwidth requirements.
Basic Coupling arrangements
The basic arrangement of connections of wave trap and coupling capacitor for PLC communication is shown in Figure.
As can be seen from the figure, the power frequency and radio frequency currents are sorted out by this arrangement. The radio frequency currents are prevented from entering the station bus and the power frequency current is blocked by the coupling capacitor from the PLC equipment. The coupling capacitor offers low impedance to the flow of carrier frequency and thus enables the telephone equipment to be coupled safely to the high voltage power lines
INER-LINE OR INTER-CIRCUIT COUPLING
This is the same as phase-to phase coupling but with the difference that the two conductors used for communication belong to two different power circuits carried on common towers. This type of coupling is not employed where the two circuits are, carried on two separate sets of towers as it then behaves more like a double phase-to-ground coupling and is found to be impractical.
Application of PLCC
It is used to provide high speed tripping for fault covering the entire power line.
On many lines in remote location there is not a whole lot of fiber and microwave type communication equipment available. So signals are injected onto the power line to pass the above information back and forth
On some power lines carrier equipment, there is also the ability to inject voice.so some equipment can be used for communication between technical at different sub station
Conclusion
Power line communication also called mains communication is a wire less technology that is use to able to use the current electricity network for data and voice transmission. It is the fast and efficient communication system. For communication over medium and long distance in a power network it is the reliable and economical method of communication.