Study On Temperature Characteristics And Partial Discharge Characteristics Of Internal Defects In Vehicle Cable Terminal

The development of high-speed railways in China is changing rapidly,and its achievements such as speed and safety of travel are attracting attention at home and abroad,and the ensuing load on the on-board electrical equipment is increasing,resulting in more and more explosive accidents of on-board cable terminals,which seriously endanger the safety of train traffic and passenger life and property.The explosion of the cable terminal is often caused by the internal defects of the cable terminal,and the internal defects of the terminal will cause the distortion of the internal temperature field of the terminal.In order to avoid the insulation failure of the cable terminal during operation,this paper focuses on the temperature distribution and partial discharge characteristics of the internal defects of the cable terminal.This paper firstly explains the calculation model of electric and temperature fields of vehicle-mounted cable terminals.And various electrical,thermal and basic material parameters measurement devices are built,and the measurement and collation of relevant thermal,electrical and basic material parameters are completed.A three-dimensional finite element simulation calculation model of the vehicle-mounted cable terminal was established using COMSOL software.Then,the temperature distribution of the axial and radial sections at different locations of the on-board cable terminal under normal operation was studied,and the causes and change patterns were analyzed.The axial and radial temperature distributions of air gap defects,metal impurity defects and water vapor defects in different length,width and thickness dimensions are simulated and analyzed respectively.The axial and radial temperature distribution patterns inside the vehicle cable terminal with different defect types under the same conditions are studied.The experimental device for partial discharge of the vehicle-in-cable terminal is constructed and the defect model is made.The mechanism of different types of defects in the vehicle cable terminal is explained,and the equivalent model partial discharge patterns of different defect sizes and types of defects in the vehicle cable terminal are measured and analyzed.It is found that the air gap,metal impurities and water vapor defects inside the vehicle cable terminal will raise the temperature at the defects inside the vehicle cable terminal,and the defect thickness has a greater effect on the distortion of the temperature field inside the vehicle cable terminal than the defect length,and the defect width has a smaller effect on the distortion of the temperature field.The impact of air gap defects on the internal temperature field of the vehicle cable terminal is the largest,followed by metal impurity defects,and the impact of water vapor defects on the internal temperature field of the vehicle cable terminal is the smallest.The common feature of the partial discharge diagram of air gap defects is that the width of the positive and negative half-perimeter is the same,and the height of the negative half-perimeter is greater than the positive half-perimeter.The common features of the local discharge pattern of metal impurity defects are the same width of positive and negative halfperimeter,and the height of positive half-perimeter is larger than negative half-perimeter;the defect radius of water vapor defects is almost independent of the phase of the discharge area,and the width of the discharge area is basically the same;in the process of increasing the defect radius,the width of the local discharge pattern almost remains the same,and the height gradually becomes higher,and the average discharge volume and the maximum discharge volume also increase.The study provides a certain theoretical reference significance for the characterization technology of internal defects in vehicle cable terminals.