Design and implementation of intelligent meter reading system

With the rapid development of the information industry, the continuous improvement of communication, electronic and computer technologies, the use of communication technology to expand the application of computers in various fields of the power industry has become more and more widespread. In China, although many power departments in many regions have achieved automation of electricity billing management to varying degrees, manual meter reading still accounts for a large proportion in China, and various errors caused by human factors are very common. Therefore, the Power Bureau has made a strategic deployment of "one household, one meter, centralized meter reading" in 3 to 5 years across the country, advocating intelligent meter reading systems. The intelligent meter reading system
　　 
currently mainly includes: wired communication technology and power carrier communication technology. As a traditional method, wired communication technology has an advantage in its stability. However, the wired communication wiring project is huge and easily damaged by human beings. At the same time, the residential buildings have been built, and it is difficult for residents to accept it if the wires are pulled on the wall surface. Power carrier communication technology can effectively solve the above problems. It uses the existing AC power line as a communication line, eliminating the unrealistic wiring project, and has obvious advantages. At the same time, the intelligent meter reading system is also suitable for household life meters such as water meters and gas meters.

1 Basic hardware composition and principle of the system
　　
The intelligent meter reading system based on power line carrier communication refers to a system in which the master station reads the information of the recorded values ​​(window values) of the electric energy of multiple electric energy meters in a centralized manner through the power line carrier communication channel.

1 System composition
　　
diagram 1 is mainly composed of carrier electric meters (equipped with a collection terminal or collection module for collecting the electric energy information of user electric energy meters), concentrators (according to the instructions of the host computer, control the transmission and reception of all electric meter readings in the line), channels (generally using the PSTN public telephone network) and host computers (such as community meter reading control centers, mainly meter reading management systems) and other equipment.

1.2 System Working Principle
　　
According to the designed instructions, the computer communicates with the concentrator through the community control center. According to the communication protocol between the control center software and the concentrator, the community control center controls the program of the concentrator. The concentrator works according to the various circuits in the concentrator, communicates the instructions to be sent and received with each carrier meter through the power line, and receives various data measured by the meter. Each carrier meter also accepts the setting program of the concentrator, transmits information to each other or entrusts a carrier meter to forward the information to the concentrator. In the whole process, it is controlled by the program execution function set by the concentrator to form an intelligent adaptive relay communication system.
　　
However, in the process of power line transmission, there are various noises and signal attenuation generated by switching power supplies, variable frequency motors and other communication equipment. The various interferences caused by this greatly reduce the success rate of the carrier communication system communication, hindering the development of the intelligent meter reading system. In view of the above situation, we will install the KQ-100E carrier communication transceiver module in the concentrator and carrier meter in this system. It is a powerful MODEM with good signal-to-noise ratio, reduces interference, increases transmission distance, and greatly optimizes the traditional meter reading system.

1.3 Specific performance indicators of KQ-100E module
　　 
(1) The microcomputer control end of the transceiver module consists of three ports: RX, TX, and R/T, all of which are TTL level. 

(2) The +5 V end is connected to a +5 V ± 5% DC power supply; the VAA end is the transmission power supply, which can be a DC unregulated power supply. The current is 300 mA when transmitting (0 mA when not transmitting), and VAA can be selected between 9 and 15 V; the two AC ends can be directly connected to the live and neutral wires of the mains, or to the live and ground wires; and the live and neutral wire communication method can be used for long-distance outdoor communication.

(3) KQ-100E can communicate serially with a single-chip microcomputer, or with a microcomputer through an RS232 serial port. The zero-crossing carrier module and the microcomputer interface adopt 1 200 B/S communication, serial asynchronous 10-bit mode, 1 start bit, 8 data bits, and 1 stop bit. 

(4) Adopting FSK zero-crossing carrier communication mode, the test proves that in a 10 kV transformer area, 100% successful communication can be achieved at any time. Since KQ-100E is a zero-crossing transmission module, data can only be correctly transmitted on the same-phase power line. However, my country uses three-phase power supply. Therefore, there must be a three-phase power supply in the concentrator, and it can ensure that the three phases of the concentrator can transmit data. The specific steps are as follows: three modules are used in the concentrator to connect A, B, and C phases respectively, and then CD4053 is used to switch multiple PTT, RX, TX and other signals when the single-chip microcomputer is controlled. This is costly and bulky, but there is no interference and switching life. The specific reference is shown in Figure 2.

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2 System Software Design

The connection between KQ-100E and the microcontroller is shown in Figure 3.　　

89 2 M, baud rate 1 200 b/s) as follows: 

(1) Send port program:　

RT bit p1.0　

(2) Receiving port program:

3 Conclusion
　　
Since the current operation of China's power grid is not particularly standardized, coupled with the interference caused by various natural factors, the power line has high shear, high noise and high deformation, which poses a great obstacle to power line carrier communication. People are looking for various methods, such as appropriate error control technology, spread spectrum technology and dynamic relay technology to solve this problem. Practice has proved that the intelligent meter reading system equipped with carrier transceiver module has the characteristics of fast data collection, high communication success rate and good lightning resistance. It is believed that this intelligent meter reading will realize the real "local network", unified billing and unified revenue, and achieve energy management automation throughout the society.
　　
References

[1] Liu Guihua, Ma Jianguo. Design and implementation of power line carrier home appliance network control system [J]. Electronic
Engineer, 2001, (3).

[2] LM1893/LM2893 carrier-current transceiver [C]. National Semiconductor Corporation, 1995.

[3] Shao Yuan, Zhong Ju, Zhou Zhaomao. A review of low-voltage user centralized meter reading system [J]. Automation of Electric Power Systems, 1999, 23(17).

［4］Wang Dayuan, Liu Xinwei. Research on remote control using power line carrier [J]. Journal of Shenyang Education College, 1999, (4)

［5］Ma Hongfeng, Chen Jinpeng. Anti-interference measures in low voltage power line carrier system [J]. Journal of Lanzhou Polytechnic College, 2001, (1).