GIS Partial Discharge Detection And Biomimetic Pattern Recognition Based On UHF Method

GIS (Gas Insulated Switchgear or Gas Insulated Substation) has been widely used in electrical power system because of its advantages such as compact structure, reliable operation and easy maintenance. At the same time, there are several disadvantages of GIS including complex structure, precious manufacture and maintenance technologies and the integrated way to install of various equipments. So that the conventional preventive test methods are hard to effectivly implement. Therefore, in case of GIS failure event, it would be very serious. In order to ensure the safe and reliable operation of GIS, a substantial amount of research works have been carried out on the GIS PD (partial discharge) detection techniques at home and abroad. One UHF (Ultra-High Frequency) PD detection method, which has superior anti-disturbance performance and high sensitivity, has become the research focus in recent years.So far, UHF PD detection of GIS is still a advancing front issue to be researched more thoroughly. The difficulties mainly include the PD mechanism and the propagation of EMW (ElectroMagnetic Wave) in GIS, development of stable and reliable detection system, construction and dimension reduction of feature space based on UHF PD signals, reasonable methods of pattern recognition for defects type in GIS, and long-term accumulation of data from experiments and local sites. In this paper, based on the PD mechanism and the propagation of EMW excited by PD current pulse in real condition of GIS, a large number of experimental data were acquired by the developed UHF PD detection system in 126kV and 252kV GIS respectively. Afterwards, using the evelope of UHF PD signals, the feature space construction and dimension reduction methods were proposed. At last, the biomimetic pattern recognition was used to classify the typical insulation defects.Firstly, the current research and application situation of UHF PD detection in GIS was reviewed. The research status and problems were summarized including characteristics of EMW propagation within GIS, UHF PD signal analysis model, defects pattern recognition, as well as detection system research and application. Afterwards, the PD mechanism excited by typical insulation defects in GIS was analyzed, and the FDTD (Finite-difference time-domain) was used to simulated the propagation of EMW excited by actual PD current pulse in the actual GIS constructure. The simulation results show that differences of rise time, oscillation attenuation, as well as frequency component existed between PD current pulse exciting and ideal Gauss pulse exciting. In addition, the existence of basin spacer, shields and three conductors in actual GIS should effect the EWM propagation such as model transfer. Subsequently, five defect models were designed and set in 126kV GIS and 252kV GIS respectively, through PD experiments, a large number of UHF PD data was acquired by the developed detection system. After that, an improved adaptive wavelet threshold was proposed to filter the white noise in UHF PD signals. At the same time, a novel feature space were presented with 37 feature parameters. To reduce the dimension of the feature space, the improved KPCA (Kernel Principal Component Analysis) and the proposed CCMDR (Correlation Coefficient Matrix Dimension Reduction), as well as the RST (Rough Set Theory) were used to depress the sapace dimension. The three algorithms have their own advantages and achieved outstanding effects.Finally, the BPR (Biomimetic Pattern Recognition) was introduced for the first time into the fields of PD pattern recognition even into electrical engineering. Based on the"understanding"and"homologous continuity", BPR completely broke the tranditional pattern recognition methods based on"division"with new features. After the discussion of basic idea, theory and implementation of BPR, a novel algorithm was improved to realize BPR and was used to classify the typical defects. The comparison with BP neural network and support vector machine demonstrates the superiority of BPR. Further more, conclusion and prospect were presented. The research results in this paper have important theoretical value and practical significance for PD mechanism, UHF PD detection, defects recognition research as well as guidance of GIS operation and maintenance.