Research On Electromagnetic Compatibility And Risk Of Speed Sensors In Train Control System

Speed sensor provides speed information to train control system,which was very necessary to ensure the normal operation of speed sensor.However,as a sensitive device,the speed sensor was susceptible to electromagnetic interference.At present,the main method to solve the electromagnetic compatibility(EMC)problem was the application of the EMC standard test,but the electromagnetic environment of Electric Multiple Units(EMU)was complex,and facing the situation of exceeding the standard limit.If we set too strict standards,it would make the product too expensive.To solve this problem,a risk assessment can be made on the electromagnetic compatibility of the speed sensor,and appropriate measures can be taken based on the assessment results.The main research contents of this article are:(1)Firstly,I started with the "three elements" and researched the speed sensor's disturbance source and transmission path.Secondly,I summarized the characteristics of the three types of disturbance sources and verified them on site.Thirdly,I studied the path of disturbance transmission,and established the model of high-voltage cable and vehicle body,Then I explained the process of over-voltage from high-voltage cable to vehicle body.In addition,I modeled and simulated the vehicle body to study the overvoltage distribution.At the same time,I established the circuit model of the whole vehicle to study the transmission of over-voltage between carriage.Finally,I modeled and simulated the speed sensor to study the situation that the speed sensor was damaged by breakdown and the signal line was disturbed.(2)For the EMC risk of speed sensor,I gave the definition of EMC risk,and I studied several risk analysis methods.Combined with the actual electromagnetic environment of the speed sensor,I used the Monte Carlo method to simulate all disturbances as much as possible.I also established an interference model of the speed sensor,and simulated the impact of various disturbances by simulation software.Based on the method of failure mode and effects analysis,I analyzed the risk problem of the speed sensor and summarized the risks of speed sensors.The main research results are as follows:(1)Model research on the process of speed sensor subjected to electromagnetic interference.The disturbance sources included the over-voltage of lifting pantograph,pantograph arcing when the train passing through the Neutral-Zone area and other types of pantograph arcing.The lifting pantograph would cause a large over-voltage to the vehicle body,and its peak voltage is as high as 8-10 k V,which would seriously affect the operation of speed sensor and may burn the speed sensor.The distribution of overvoltage on the vehicle body is as follows: the potential under the high-voltage cable was the largest,and the potential on both sides of the vehicle was also high.The overvoltage of the vehicle where the pantograph was located was high,and the reflected voltage of the vehicle head was also high.There are two situations for the speed sensor being interfered.The overvoltage breakdown burned the sensor,or the disturbance pulse was coupled to the speed sensor signal line to affect the count of the sensor.(2)Research on EMC risk of speed sensor.The risk faced by the speed sensor was low and would not cause accidents that affect personal safety.Electromagnetic interference causes low speed measurement error.Regarding the problem of burning down the speed sensor,the peak value of the overvoltage of each vehicle of the EMU was different,and the probability of burning down the speed sensor in different bogies was different.The damage of a single sensor was not serious due to the redundant structure of Automatic Train Operation system.The probability of multiple sensors burning down at the same time was very low,owing to the peak value of overvoltage in some carriage was low.In summary,I studied the electromagnetic compatibility and risk of speed sensors.The whole process of the speed sensor interfered was modeled and analyzed.Study the risks of speed sensors.Risk analysis was used as a supplementary method for EMC testing to improve the deficiencies and enhance the safety of the system.