Study On Ultra-high-frequency Partial Discharge On-line Monitoring In Scanning And Comparing Method

Partial Discharge （PD） is a sign of electrical equipment insulation fault and alsois a cause of insulation fault. On-line PD monitoring is very important content incondition-based maintenance. On the basis of research and analysis of the on-line PDmonitoring technique，anti-interference technique and pattern recognition technique athome and abroad, this paper designs a new type of UHF PD monitoring system withscanning and comparing method, and anti-interference method, pattern recognitionmethod that used in the system. The main work of this paper is as follows：According to PD has the feature of cycle repeatability under power frequencyvoltage, this paper designs a signal feature extraction method by pulse potential scancomparison and statistics. And the UHF PD monitoring system does not rely on A/DAcquisition System to extract PD characteristic quantity and PD spectrum. This paperconcretely explains the principle and work flow of the UHF PD monitoring system withscanning and comparing method, and introduces the way of eliminatinginterference.The scan acquisition unit of the system is composed of the high-frequencyfilter and amplifier, Field－Programmable Gate Array （FPGA） and high-frequencycomparator, which realizes signal spot digitization and signal transfers the signals to PCby Ethernet.This system has the feature of small data size, transforming the signal to digitalform in-place, excellent expandability, and small size of the components. According tothese characteristic，the paper design distributed partial discharge on-line monitoringsystem and partial discharge live monitoring device. And analysis the advantages of thissystem in the engineering application。This paper describes the hardware structure，andemphatically introduces the microstrip antenna and the3rd order Hilbert antenna. Thepaper explains the meaning of the antenna parameters, such as VSWR, the radiatingpattern and gain. There are multiple sets of multi-way selector switch and filteramplifier for live.The paper concretely explains the operation status of the system in the laboratoryand field. Studies have shown that the system can a long time continuously acquireUHF discharge signals and on-line monitor PD of electrical equipment. The system canextract the characteristic quantities of UHF partial discharge signals and draw partialdischarge φ-V-n spectrum. The paper confirms that the acquired data and the discharge spectrum can show the basic characteristics of partial discharge signals by comparingthe experimental data of scanning systems and traditional systems. The paper evaluatesthe performance of system site utilization and gives the picture of the installed on-sitesystem.In this paper，author take typical discharge defects in GIS as a pattern recognitionobject. After standardized processing collected data, the system draws dischargespectrum and analyses phase and amplitude characteristics. The paper show statisticalcharacteristic quantity of PD spectrum which are suitable for the collected data feature.The paper selects wide difference characteristic quantity to construct vectors for SVMby comparing. At last, the paper identifies the discharge defect by using support vectormachine and bintree algorithm.