Research On Residual Current On-Line Monitoring Technology For Rural Electric Network User Based On Short-Range Communication

With the frequently occurrence of residual current fault in rural areas, farmer's power supply stability and reliability are becoming worse, and their lives and property safety are under great threat.To prevent residual current fault and locating faults quickly and efficiently, residual current on-line monitoring technology is applied.A kind of low voltage Residual Current On-Line Monitoring technology for rural power grid is studied in this dissertation.The technology consists of Residual Current Acquirer, Data Coordinator, On-Line Monitoring Software. Electrician could obtain real-time residual current and voltage information of farmers in power supply zone through Monitoring Software, and solving residual current fault base on information uploaded by Acquier.At first, this dissertation introduces the research background, and summarizes development history of residual current measuring and On-Line Monitoring technology. Then, three residual current measuring methods (electromagnetic, Hall effect, magnetic modulation) and three amplitude quantization methods (maximum, average, RMS) are discussed. A modified quantization method of "maximum" is presented. Moreover, the Overall design scheme is presented based on functional and performance requirements analysis of the system, the system consists of Residual Current Acquirer, Data Coordinator, On-Line Monitoring Software.Then, dividing Residual Current Acquier into several modules (main chip, residual current measuring, voltage measuring, ZigBee, power supply and backup power supply) based on it's functionality requirements, schematic of each module are designed, and a 4cm ×5cm PCB of the Acquire is developed via Altium Designer. Besides, ZigBee application layer communication protocols, main program and ZigBee configuration process are developed based on schematics. A mechanical structure similar to C45 Residual Current Device is also designed for Residual Current Acquirer. Data Coordinator is designed According to its functionality requirements, the Coordinator consists of ZigBee module, power supply module, storage module and real-time clock module and multi-mode communication module (Bluetooth, GPRS, RS485 Bus), schematic of each module and overall PCB of the Coordinator arc also designed. Besides, programs including data storage scheme, GPRS and Bluetooth communication protocol, RS485 Bus communication protocol and main program are designed for Data Coordinator based on the schematic.In addition, Monitoring Software that includes B/S structure based On-Line Monitoring Software and Android On-Line Monitoring APP is discussed. The B/S structure based On-Line Monitoring Software contains Socket communications program and On-Line Monitoring Web program, the Socket communications program is designed based on Socket and IPC Mechanisms; the On-Line Monitoring Web program consists of front-end Web page, back-end MySQL, back-end PHP script, PHP script communicating with Socket communication program via IPC Mechanism achives real-time data and parameter configuration&read functionality in On-Line Monitoring Web program. Device scanning&connecting UI and monitoring UI of Android On-Line Monitoring APP arc designed, and UML class diagram of each UI's Activity class, Bluetooth connection management class, SQLite database management class and other tool class are designed.Finally, A charging and discharging test, calibration test, power consumption test on Residual Current Acquirer were finished. Residual Current Acquires are connected with Data Coordinator via ZigBee. Then, the system was installed in both Zaoyang, Hubei and Yiwu, Zhejiang power supply zone. Testing the whole system through B/S structure based On-Line Monitoring Software, Android On-Line Monitoring APP and Commix Serial Port Tool. The test result shows that the residual current online monitoring system can record the residual current faults, Overvoltage and loss of voltage in the installed power supply zone, the system also supports residual current and voltage real-time query, helps electricians deal with the residual current faults in power supply zone.