Research Of Wide Dynamic Range Partial Discharge Sensor Based On UHF Method And Design Of Monitoring System

Gas-insulated switchgear(GIS) is widely used in ultrahigh voltage transformation system in cities. Partial discharge(PD) is not only a symbol and representation of the degradation of insulation, but also leads to further deterioration. In order to improve the reliability of GIS, a large amount of research has been studied both in China and abroad, and the UHF method is proved to be highly serviceable in PD detection. So far, there are still some problems, including dynamic range, bandwidth, sampling, cost and compatibility need to be resolved.This thesis regards the GIS PD detection system as the object and focuses on the problems in the applications of detection system such as dynamic range, bandwidth, cost, compatibility and so on. By the method of logarithmic detection and the usage of FPGA, and with the equipment modeling based on IEC61850, fewer sensors are trying to be used to detect larger range of GIS as well as decrease cost, improve compatibility, and provide a technical basis for the application of partial discharge monitoring equipment. The main contents are as follows:(1) The electromagnetic theory is used for analyzing the attenuation characteristics of partial discharge in GIS qualitatively. HFSS simulation software is used for analyzing the attenuation of PD signal and mounting position of sensors quantitatively. The result shows that at least 40 d B dynamic range is needed to detect PD within 20 meters effectively.(2) In the design of the active integrated antenna, Archimedean spiral antenna and bow-tie antenna and other ultra wide bandwidth(UWB) antenna are analyzed. A variety of wide dynamic range detection methods were compared. Preliminary results revealed bow-tie antenna and logarithmic detector are suitable for GIS partial discharge detection. A sensor was made to test the performance. Experimental results show that the sensor has 44 d B dynamic range and 0.3 ~ 1.5GHz bandwidth, which is suitable for PD detection.(3) The application of time division multiplexing in this system is introduced. Anti-jamming measures in multiplexing are analyzed and improved. Collinear transmission of signal and power is achieved using frequency division multiplexing. Printed circuit board is improved with the help of the signal integrity(SI) analysis technique. Based on FPGA, the system amplifies, adjusts and filters the PD signal, samples and buffers it and then sends to PC diagnostic center.(4) Phase resolved partial discharge(RPPD) mode and record mode are analyzed and designed. According to the IEC61850(edition 2), the model of GIS’s PD online monitoring system is built, the system framework and communication system is given, which enhanced compatibility in the various stations.Finally, the PD detection system is tested in 110 k V GIS. The result shows the effectiveness of the system.