The Principle Analysis And Realization Of High-speed Railway Cable Temperature Monitoring

With the rapid development of high-speed railway,power cables have been widely used in high-speed railway system with their unique advantages.However,due to the complexity of the actual operation of the high-speed railway and the influence of the quality of the cable itself,the number of incidents of aging and burnt-out of high-speed railway cables is increasing,which seriously affects the normal operation of the high-speed railway.As the fault of high-speed railway cable is mostly accompanied by temperature rise,this thesis designs a high-speed railway cable temperature monitoring system to perform online monitoring and over-temperature alarms on the high-speed railway cable temperature to reduce the probability of high-speed railway cable accidents.First,a brief introduction to the high-speed railway cable and its joints is made,and the principle of thermal aging and heating of the cable insulation is analyzed,which provides a theoretical basis for the temperature monitoring of the high-speed railway cable.As the heat and loss of high-speed railway cables are closely related to the high-speed railway load current,the digital characteristics of the high-speed railway load are analyzed,and an equivalent thermal circuit model of the high-speed railway cable is established.At the same time,in view of the frequent fluctuations of the high-speed railway load current,a method of using the high-speed railway load current to calculate the cable loss and then substituting the equivalent thermal circuit model to calculate the cable conductor temperature is studied,which provides a basis for the fault prediction of the high-speed railway cable.Secondly,according to the overall scheme design of the system,the system design requirements are completed,and the functions of temperature acquisition,time reading,data storage,alarm and 485 communication of the lower computer hardware are realized.At the same time,in view of the situation that the power supply is turned off and the lower computer device stops working due to misoperation at the scene,a power supply circuit based on double D flip-flops is designed,which can avoid the power supply interruption caused by misoperation or external interference,and effectively prevent the loss of data acquisition.Then,the upper computer management system is programmed with C#,which realizes the functions of temperature dynamic display,curve drawing,data download,file opening and saving,over-temperature alarm and so on.According to the characteristics of frequent fluctuations in load current of high-speed railway,the load current statistics function is designed.At the same time,the BP neural network algorithm is introduced and a prediction model is established to predict the temperature of the cable conductor through the current value,the ambient temperature and the cable skin temperature.Finally,two sets of simulation experiments are designed and completed.The temperature measurement accuracy of the monitoring system is improved through temperature calibration experiments,and the temperature measurement accuracy and reliability of the monitoring system designed in this thesis are verified through simulation experiments.At the same time,a thermal circuit model based on the average load current is used to calculate the temperature of the cable conductor under fluctuating load,and good results are obtained.Finally,the cable conductor temperature and fault prediction are analyzed,and it is concluded that the occurrence of cable faults can be predicted by the change of cable conductor temperature,and the feasibility of cable conductor temperature prediction is verified by the BP neural network algorithm.