| The dissertation is supported by the National Natural Science Foundation of China, namely “Study on Insulation Fault Mechanism and Residual Life Estimation Methods of High-voltage Mining Cable”(No. 51377113). That is the research of the surface electrical tracking of 10 kV ethylene propylene rubber insulated cables and its fault diagnosis method.Now, the 10 kV power supply has been widely used in mining. And mine used mobile cable has been used as the transmission cable. Its main insulation layer is made of Ethylene Propylene Rubber(EPR). EPR has excellent weather resistance, water resistance, heat resistance, corrosion resistance, and good flexibility and dielectric properties. However, the mining conditions are complex. Normally, the cable is affected by a variety of aging factors, which caused the insulation deterioration and damaged. Such as the outer sheath of cable damaged due to drag. In this role, the main insulation layer and metal shielding layer of cable can be exposed. It is easy to cause the surface discharge and surface electrical tracking formed. In addition, the high voltage cable connection in the connection cavity of the mine electrical equipment often does not make special processing, exposed to the outside directly. If the joints are handled improperly or with contaminants on the surface, the surface discharge can be occurred under the action of lower voltage and surface electrical tracking formed along the insulation surface. The irreversible damage can be produced by the surface electrical tracking. And the insulation gradually deterioration until failure.According to the aforementioned problems about EPR insulation used in 10 kV mining cable, the electrical tracking on EPR surf ace has been selected as the research object. The formation and destruction mechanism of surface electrical tracking and its diagnosis method have been studied based on the theory and test. The specific research content are as follows:Based on the operating environment of mining used EPR cable, the surface discharge condition of mining used EPR cable in different electric field distribution have been studied firstly. And the surface electrical tracking is analyzed after the test. Then the electrical tracking performance of EPR has been studied according to the IEC60587. Finally, the effect of contamination to EPR has been analyzed.On the basis of experimental analysis, the Insulation Resistance, Polarization-Depolarization Current and Return Voltage are selected to characterize the degree of electrical tracking on EPR surface. Then the effect of measuring voltage, measuring temperature and the size of surface electrical tracking are analyzed in detail.Based on the difference of Insulation Resistance, PolarizationDepolarization Current and Return Voltage curve under different electrical size and contamination degree, some typical characteristic parameters are extracted from the three curves.The basic theory of fuzzy theory and neural network was introduced in this paper. Based on the analysis of the advantages and disadvantages of the two combined to form a fuzzy neural network, the fault diagnosis function was achieved. Mainly rely on LabVIEW software platform, the preparation of the feature extraction process was written. The appropriate membership function was selected to deal with the original feature data, and then the neural network was trained to diagnose the fault.The results show that the study of surface discharge progress under different electric field distribution is helpful to known the effects of electric field distribution on the initial discharge, the development process of discharge and the formation of electrical tracking deeply. Evaluation of the EPR resistance to electrical tracking performance can be achieved through the IEC60587. The selected typical characteristic parameters combined with Fuzzy Neural Network fault diagnosis method, which can identify and classify the degree of surface electrical tracking and the type and degree of insulation contamination. |
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