The Emi Analysis And Protection Of Contact Loss Between The Pantograph And Catenary Based On Transmission Line Theory

With the rapid development of high-speed railway technology in China,the speed of train is increasing constantly,which brings convenience to people and inevitably brings some problems of electromagnetic interference at the same time.Research data shows that the off-line phenomenon between pantograph and catenary of train supply system is more and more frequent with the increase of the train speed.The off-line of the pantograph and catenary will produce very voltage interference to the equipment on the train.Meanwhile the off-line arc radiation electromagnetic pulse of the pantograph and catenar will be also be produced,which will cause electromagnetic interference to the sensitive electronic equipment around the railway and on the vehicle.Therefore,electromagnetic interference by the pantograph-catenary off-line is a potential threat to the rain safety,and has become an important research content in the field of railway electromagnetic compatibility(EMC).Based on the transmission line theory,the distribted-parameters model of off-line electromagnetic interference is established,the electromagnetic interference(EMI)of off-line between pantograph and catenaryis studied in this paper,and the protection of the off-line electromagnetic interference is discussed in the end.The main work of this thesis is briefly summarized as follows:(1)The classical black-box models of arc,Cassie arc model,Mayr arc model and Habedank arc model,are presented.According to the characteristics of pantegraph-catenary off-line arc,the Habedank arc model is modified and the train speed factor is added,and the off-line arc model of pantograph and catenary is obtained.Based on the off-line arc model of pantograph and catenary combined with traction power supply system,the distribution parameter model of off-line arc of pantograph and catenary is established.The lumped electrical parameters of off-line pantograph and catenary are analyzed,and the lumped parameter model is used to solve the off-line electromagnetic interference characteristics of pantograph and catenary.The results show that the lumped parameter model can reflect the phenomenon of off-line overvoltage of pantograph and catenary.However,the lumped parameter model is no longer suitable for the study of off-line high frequency electromagnetic interference between pantograph and catenary.(2)Because the lumped parameter model is no longer suitable for off-line high frequency electromagnetic interference of pantograph and catenary,a parameter model of off-line arc distribution of pantograph and catenary is established in this paper.Based on the off-line arc distribution parameter model of pantograph and catenary,the characteristics of off-line arc of pantograph and catenary are calculated,and the voltage and current characteristic curve of off-line arc of pantograph and catenary is obtained.The influence of train running speed and off-line position of bow-net on the voltage and current of off-line arc of bow-net is analyzed.(3)Combined with the case of the PWM encoder's electromagnetic compatibility in Brazillian EMU(Electric Multiple Units),the time domain response of off-line electromagnetic interference to transmission line terminal conduction interference and radiation interference is studied.The typical pulse excitation source is used to replace the electromagnetic interference of off-line arc.The terminal time-domain response results of transmission line conduction interference and radiation interference are obtained by theoretical calculation,and the results are verified,and the correctness of the calculated results is proved.At the same time,it is proved that the influence of off-line electromagnetic interference of pantograph and catenary on vehicle sensitive electronic equipment can not be ignored.(4)Two kinds of non-uniform transmission lines,gradual and abrupt non-uniform transmission lines,are studied respectively.The uniform transmission line is modified to a certain extent,and the formula for calculating the terminal response of asymptotically non-uniform transmission line is obtained.The voltage response of the transmission line with increasing height and the terminal voltage of the sine-cosine transmission line is obtained by using the formula.For the mutant non-uniform transmission line,the microwave network parameter method is proposed to study,the theoretical formula for solving the mutant non-uniform transmission line by microwave network method is derived,and the terminal response of the transmission line is calculated by deducing the formula.Finally,the practical test is carried out in the laboratory,and the measured data are in good agreement with the theoretical results,which proves the correctness of the microwave network parameter method in solving the mutant non-uniform transmission line.(5)Two kinds of protection methods of off-line electromagnetic interference from pantograph and catenary are studied:adding shielding measures and adding TVS tube at the end of sensitive equipment.Firstly,the shielding effectiveness of reinforced concrete to off-line arc of bow and catenary is studied:the shielding effectiveness of reinforced concrete is calculated theoretically,and then the shielding effectiveness of reinforced concrete in a subway station is measured and compared with the calculated results.The correctness of the theoretical calculation is proved,and the reinforced concrete has a good shielding effect on the off-line arc of pantograph and catenary.Then the electromagnetic protection effect of TVS tube on the electromagnetic interference of off-line arc between pantograph and catenary is analyzed:TVS tube is a nonlinear load.In order to simplify the calculation,a piecewise linear technique is proposed to discretize the volt-ampere characteristic curve of TVS tube.The suppression effect of TVS tube on electromagnetic interference is obtained by using linear impedance instead of linear impedance on each discrete section,and then the results are verified,and the feasibility of piecewise linear technique for solving nonlinear load is proved.At the same time,it is proved that TVS tube has a good suppression effect on electromagnetic interference.Finally,combined with the railway practice,the corresponding suggestions for off-line electromagnetic interference protection of pantograph and catenary are given.