Research On The On-line Monitoring System For Leakage Current Of Catenary Polluted Insulator

As the key component of railway traction power supply system for railway, catenary is the indispensable infrastructure for the realization of railway electrification. Catenary insulator, which is the critical structure, realizes the mechanical connection between catenary and other devices in the electrified railway, playing an important role in the reliable operation of the catenary. Nowadays, the high-speed railway continues to grow stronger in China, and the operating environment of the catenary also becomes more complicated, the influence of insulation insulators performance for railway safety and reliable operation is increasing. If catenary insulator causes a flashover since polluted, the reliable operation of tractive power supply system and the safe operation of the train will be directly affected. So, on-line monitoring to property of insulator becomes particularly urgent and important at the moment.Firstly, this thesis studies the formation of the phenomena that insulating surface discharges and the mechanism insulator flashovers. Through a comparative analysis of characterizing insulator insulation performance parameters methods, it shows that insulator leakage currents have such features: easy to collect, suitable for on-line monitoring, comprehensive information can be contained and dynamic intuitively reflect the performance of the insulator, so using catenary insulator leakage current characterizes insulating property of insulator. Meanwhile, those important characteristic parameters needed by on-line monitoring of insulator leakage current can be determined, which include effective value of power frequency leakage current(Ie), maximum value(Imax), frequency characteristic and environmental parameter, etc. And then through the analyses of feasibility, function and performance requirements of the system, an overall design scheme of system has been improved and determined. In other words, site monitoring, remote monitoring and evaluation of insulator can be done by using distributed insulator leakage current monitoring extension. The chips such as master digital signal processor, analog to digital converter can be selected on the basis of system function design requirements, and all sorts of function circuit units were been designed using the selected chips, including power circuit, central control and peripheral circuit, signal processing circuit, leakage current signal change and calculation unit, close proximity or remote serial port communication unit, etc.; the exploitation of high speed and precision data acquisition, storage and transmission program has been completed under the CCS development environment; designing an extracting program to analyze leakage current characteristic, which includes extraction of the maximum, calculation of effective values, screening of special data, counting of high-frequency impulse and so on; simultaneously, use LabVIEW to build a remote monitoring and diagnosis software of catenary insulator leakage current, with the function of leakage current full-wave monitoring, characteristic quantity display, data storage, and fast fourier transformation analysis. The leakage current on-line monitoring system is chiefly featured by complete functions, easy to operation and management, real-time multi-task.Use the system mentioned above to finish the data acquisition and feature analysis of which characteristics are known, comparing the theoretical result with the testing result, and complete the testing and calibration about diagnostic monitoring system. Then the practical test to leakage current of diagnostic monitoring system can be carried out in high voltage laboratory, and the result shows that, the designed catenary polluted insulator leakage current monitoring system has the following characteristics: high-speed and accuracy when collecting the signal of leakage current; calculation and analysis to characteristic quantity are reasonable and precise; signal waveform can be visually shown; property of insulator can be accurately monitored; PC operation of monitoring system is simple and convenient, and stored data can be applied to insulator pollution flashover prediction, etc.