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The power carrier is a unique communication method of the power system. The power carrier communication is a technology that uses an existing power line to carry out high-speed transmission of analog or digital signals through a carrier method. The most important feature is that there is no need to re-establish the network, and as long as there is a wire, data transfer can be performed.
However, the power line carrier communication has the following shortcomings, leading to the main application of PLC - "electric power access" can not be used on a large scale:
1. The distribution transformer has a blocking effect on the power carrier signal, so the power carrier signal can only be transmitted within the area of ​​one distribution transformer;
2. There is a large signal loss (10dB-30dB) between the three-phase power lines. When the communication distance is very close, signals may be received between different phases. General power carrier signals can only be transmitted on single-phase power lines;
3. Different signal coupling methods have different losses for the power carrier signal, and the coupling methods are wired-earth coupling and line-neutral coupling. Compared with the line-to-neutral coupling method, the line-to-ground coupling method has less loss than a dozen dB of power carrier signal, but the line-to-ground coupling method is not suitable for all areas of the power system;
4. The power line has its own inherent impulse interference. Currently used AC power is 50HZ and 60HZ. Its cycle is 20ms and 16.7ms. In each AC cycle, there are two peaks. Two peaks will bring two pulse interference, that is, there is a fixed 100HZ or 120HZ pulse on the power line. Interference, interference time is about 2ms, because the interference must be dealt with. There is a method of using the waveform to transmit data within a short time after 0 o'clock. However, due to the short time at 0 o'clock, the actual application and synchronization of the AC waveform are not well controlled, and the modern communication data frame is relatively long, so it is difficult to apply;
5. The power line causes high cuts in the carrier signal. When the load on the power line is heavy, the line impedance can reach 1 ohm or less, resulting in high reduction of the carrier signal. In practical applications, the point-to-point carrier signal can be transmitted to several kilometers when the power line is unloaded. But when the load on the power line is heavy, it can only transmit tens of meters.
Although technical problems will eventually be solved and overcome with the development of time, from the perspective of the current domestic broadband network construction, the time and space reserved for the PLC is not sufficient. Since 2000, major operators have launched a large number of broadband access services such as ADSL, optical fiber, and wireless networks, leaving the living space for power lines to access the Internet, and have been constantly being compressed by other access methods. Now, apart from its application in remote meter reading, PLC has no original rhetoric.
With the rise of the topic of home intelligence system, it also brought a new stage for the development of PLC technology. In the current home intelligence system, the home intelligence system based on the PC is the most popular. The concept of this system is that with the popularity of computers, all the data that household appliances need to be processed can be delivered to the PC. This requires building a data transmission network between home appliances and PCs. Now everyone is optimistic about wireless, but in the home environment, the feature of “multiple walls†seriously affects the quality of wireless transmission, especially in the villas and on the floor. This defect is even more pronounced in residential houses. If a dedicated wired network is set up, besides increasing the cost, it will be very difficult and cumbersome to change the location of the home appliances in the daily life in the future. This will bring opportunities for the power carrier communication that does not require new wires.
The biggest characteristic of PLC: There is no need to re-establish the network, as long as there are wires, data transmission can be carried out, which has undoubtedly become one of the best solutions to resolve this smart home data transmission. At the same time, because the data is only transmitted in the home range, the five major problems that hamper PLC applications will be greatly reduced. Remote control of home appliances can also be realized through the traditional network first connected to the PC and then controlled by home appliances. PLC modulation The cost of the demodulation module is also much lower than that of the wireless module.
The current application areas mainly focus on home intelligence, smart utilities (such as remote meter reading systems, remote street lamp monitoring systems, etc.), and industrial intelligence (such as data collection of various types of equipment). Technically, power carrier communication is no longer a category of point-to-point communication, but highlights the concept of open network architecture, making each control node (controlled device) form a network for centralized control, and currently has a network in power carrier applications. Few companies have agreements and network concepts. There are Echelon's Lonworks network abroad, and Risecomm's Ruiscon Intelligent Control Network. Their network protocols are written according to the international standard protocol EIA709.1, EIA709.2.
List two examples of application areas:
Application case I: The smart home smart home control network can be implemented with power line carrier technology. The principle is to integrate the power carrier technology into each appliance and use the existing power line of the household as the carrier communication medium to realize the smart device. Communication and Control. The interconnection and interaction of smart appliances in the smart home control network will bring you high-quality living experience and enjoyment of life:
Check all electrical status at any time. Any switch Centrally controls all smart electrical devices in the home. Sets off specific electrical appliances, such as scene lights, etc., to keep abreast of home security situations, such as security, fire alarms, and detection of gas leaks. Remote home appliances through the Internet or telephone Control Application Case 2: Remote Meter Reading System (AMR)
Remote automatic meter reading (AMR) system is one of the important applications of intelligent control network. It can enable power suppliers to reduce management costs while improving service quality; and gives users the opportunity to make full use of various power plans (such as time-of-use price) to save expenses and enjoy a variety of facilities.
System features remote automatic meter reading remote control meter pull real-time query user power meter usage group copy or individual selection reading can be integrated with the charging system according to the grid load peak-valley time segmentation electricity price divided time reading meter and Billing Control Illegal Stealing Actions Reduce Manpower Costs and Management Costs Automatically Save Historical Data for Reading Data from Statistical Electric Meters, Analyze Line Loss Estimates, and Estimate Electrical Losses Caused by Meter Errors
The application of power carrier technology in the industry
Power line communication is PLC, which is an abbreviation of English Power line Communication.