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WHAT IS PLC (POWER LINE CARRIER)?

The technologies used for data transmission over power lines are called PLC (power line carrier). The conductor drawn for energy transmission can be multiplexed in the frequency domain and used for many different purposes. Among these applications, automation studies are the first to come to mind. At the beginning of the 20th century, this method was used to turn on and off street lighting in New York City and this application became the ancestor of PLC solutions. Over the past hundred years, project-specific applications have been developed and put into use for many purposes. With PLC becoming an industry standard, more widespread and integrated structures have emerged.

Other terms describing the use of the power transmission line for data transmission also describe the same technology. Other terms that have the same meaning as PLC (power-line carrier) are power line communication (PLC), power-line digital subscriber line (PDSL), mains communication, power-line telecommunications and power-line networking (PLN).

PLC technologies have a wide range of uses for different applications. From home automation to internet access (broadband over power lines BPL). However, they can basically be categorized according to the cables they can work on, i.e. the indoor network and the transmission network. Some technologies allow for use in both systems. In general, transformers used in the network prevent the propagation of the signal and cause interruptions in transmission. Meters at the entrances of houses also cause serious attenuation of the data. In order to create large networks, different solutions are needed to eliminate this problem.

In PLC technologies, many different baudrates and frequencies can be used for data transmission. However, due to the structure of power cables, the use of high frequencies is not possible and there are some limitations due to legal regulations. In particular, radio broadcast frequencies, etc. frequencies of general use are not used in PLC technologies. Since energy transmission is done with 50 Hz or 60 Hz, interference caused by harmonics is another reason for limitation. The permissible level for unlicensed use is 500 kHz and below in many countries.

A PLC SYSTEM BASICALLY CONSISTS OF THE FOLLOWING COMPONENTS:

  • Transceiver Device: Usually located in a cabinet or automation room. It is used to generate and receive the signal.
  • Combiner (hybrids) and filter: Used for transmission and re-filtering of multiple transmitters on a single line without interference.
  • Line tuner: A capacitor based device used to create a low impedance path for data communication and a high impedance path for power.
  • Line Trap: Inductance-based devices used at junctions to ensure that the data goes to the desired point. These devices, with windings tuned to the transmission frequency, prevent the transmission of data to the unwanted line and do not cause any difficulty in transmitting energy to the same path.

Reliability of a PLC system requires many factors to be in place. The main objective is to transmit a signal to the end device at a level above the receiver’s sensitivity level and SNR (signal to noise ratio). In this way, the receiving end can receive the intended message in a healthy way. If these conditions are met, the PLC system is considered reliable.

GÜVENİLİRLİĞE ETKİ EDEN FAKTÖRLER AŞAĞIDA SIRALANMIŞTIR.

  • Output power of the transmitter.
  • The number and type of combiners (hybrids) required for transceivers operating in parallel.
  • Type of line adjuster used.
  • Capacitance of the matching capacitors.
  • Type and inductance of line-splitters.
  • Voltage and physical design of the power line.
  • The phase to which the PLC signal is mapped.
  • Length of the line and transfers in the network.
  • Disconnecting and receiving equipment.
  • Type of modulation and type of demodulation circuit.
  • Received noise to signal ratio SNR (signal-to-noise ratio) value.

THE DIVERSITY IN THE USE OF PLC TECHNOLOGY IS BASED ON THE PURPOSES FOR WHICH IT IS USED. A LIST OF THE DIFFERENT USES IS PRESENTED BELOW.

LOW FREQUENCY, LONG DISTANCE:

Frequencies in the range 24-500 kHz are used. Output power is in the order of hundreds of watts. It is used for data transmission in energy transmission lines. It is used for transmission of data for monitoring and management purposes. Although mostly high voltage line is used, there are applications where neutral line is used. In new systems, OPGW technology using fiber cables is preferred. Amplitude modulation is generally preferred in these systems. The transmission of audio data is limited and compressed in the range of 300 Hz to 4,000 Hz. Depending on the distance, the output power is in the range of 0-32 dbW. Repeaters can be used where needed in the system. In these systems, data and voice can be transmitted hundreds of kilometers away.

MID FREQUENCY (100 KHZ):

  • Home Automation (narrowband): Used in increasingly widespread home automation technologies. These are systems designed to monitor and manage systems such as lighting, appliances, etc. in the home. 20-200 kHz range is used. The carrier is modulated as a digital signal. Each receiver is addressed and can be communicated individually. X10 technology has been in use since the 1970s.
  • Low Speed Narrow Band: These systems have been in use since 1922 and are still in use. It is used in remote reading and similar systems and can provide speeds of 200-800 bit/sec with 15-500 kHz signals. Applications such as control and remote metering applications, electricity network components, user meters, automatic meter reading (AMR automatic meter reading), traffic control, load management, load profile, prepaid systems, leakage control, network management are within this scope.
  • Medium Speed Narrowband: Distribution line carrier (DLC) systems can communicate at 576 kBit/sec with 9-500 kHz signal.

HIGH FREQUENCY (> 1 MHZ):

It is used for home automation and broadband internet access. Modems with data transmission rates of 256 Kbit/sec to 2.7 Mbit/sec with 1.6-80 MHz signals are used. Up to 256 users can be connected to a medium voltage transformer and the uplink speed can reach 135 Mbit/sec.

STANDARDS

Two different standards have been developed for home use, HomePlug AV and IEEE 1901. IEEE 1901 was developed based on HomePlug AV. IEEE 1901 products are therefore fully compatible with HomePlug AV products.

Different organizations have defined standards in this area. Some of them are HomePlug Powerline Alliance, Universal Powerline Association and HD-PLC Alliance. In December 2008, ITU-T established the G.hn/G.9960 recommendations as a high-speed powerline standard.

In July 2009, IEEE P1901 PLC was published as a draft for broadband. The IEEE 1901 final standard was published on February 1, 2011.