Research On Electromagnetic Radiation Emission Characteristics And Interference Mechanism Of Traction Network

With the rapid development of China’s electrified high-speed railway and comprehensive transportation hub,the electromagnetic environment around the electrified high-speed railway is becoming more and more complex,and the impact on the surrounding communication cables and sensitive equipment is becoming more and more difficult to predict.The electromagnetic emission of overhead line of traction network system is an important part of railway electromagnetic environment,so it needs to be studied.The impact of large current on the traction network is extreme,which will cause strong electromagnetic wave impact on the empty line of the traction network,and may cause interference or even damage to the surrounding equipment.The short-circuit test of the traction network can simulate this phenomenon.Similarly,when the train passes through the electric phase separation,the off-line arc of pantograph and catenary will be generated,and the generation of arc will also stimulate the overhead line system of traction grid to generate electromagnetic emission.With the continuous acceleration of electrified high-speed trains and the continuous improvement of traction power,the intensity of electromagnetic emission on the empty line of traction grid is also greatly increased.Based on the transmission line theory,the current distribution and electromagnetic emission on the overhead line system of electrified high-speed railway traction network are modeled and calculated in this paper.Corresponding to the two cases of traction network short-circuit test and train over-current phase separation,the electromagnetic emission of overhead line of traction network is studied,and its amplitude frequency characteristics are given.The electromagnetic interference of electromagnetic emission to the test equipment is calculated,and the electromagnetic interference when the proposed electrified railway enters the airport protection area is analyzed.The main contents of the paper can be summarized as follows:(1)The distribution parameter calculation of overhead line system of traction network is studied.The calculation method of distribution parameters of transmission line model is given for overhead line of traction network.The effect of frequency on the calculation of Carson formula and Sunder formula was compared in the calculation of overhead line-loss-earth impedance,and a more accurate Sunder formula was selected.The finite difference method is used to calculate the overhead line parameter matrix in tunnel.Because of the non-uniform distribution of the overhead line parameter matrix in traction network,the calculation amount is very large.Therefore,neural network is introduced to optimize the calculation,and only a small number of samples are computed to map the desired parameter matrix.(2)Electromagnetic emission on overhead line of traction network under high current impact is studied.A multi-conductor overhead line model was constructed to simulate the electrified traction network system,and Kambiz Afrooz finite-difference time domain method was used to solve the model.Considering the existence of tunnels,the model was divided into two loops along the axial direction,namely,the overhead line-lossy ground loop and the overhead line-tunnel loop.The boundary conditions were optimized by truncation and impedance matching method.The current distribution on the overhead line and the amplitude-frequency characteristics of electromagnetic emission were calculated.The traction network short circuit test is used to simulate the extreme electrical condition of high current impact,and the calculated results are compared with the measured results to verify the validity of the model.(3)The electromagnetic emission on the overhead lines of the traction network is studied when electrified trains pass the neutral section.Here,two models are constructed for analysis: one is the field-line coupling model for the overhead line of the traction net irradiated by the electromagnetic field generated by the off-line arc of the arch net;the other is the conduction current source excitation model for the conduction current of the off-line arc itself.According to the different running positions of electrified trains,the model is subdivided into four different transient states.Considering the different parameters of overhead line-vehicle body,overhead line-lossy ground and overhead line-tunnel,the model is solved in sections.Finally,the current distribution on the overhead line of each model is given,and the corresponding electromagnetic emission value is calculated.(4)According to the above calculation results,the related EMC problems of overhead line electromagnetic emission of electrified traction grid are studied.Firstly,the electromagnetic emission caused by large current impact on electrified traction network and the electromagnetic interference to weak current equipment are analyzed,the electromagnetic interference coupling mechanism is given,and the solution is put forward.Then,the influence of electromagnetic emission from traction network on airport conduction signal when the proposed electrified high-speed railway passes through the airport protection area is analyzed,and the safety distance of electrified railway electric phase separation area is calculated.Finally,the amplitude frequency characteristics of total electromagnetic emission of electrified traction network are summarized,and a new fitting curve based on neural network is given,which makes the prediction of electromagnetic emission value of electrified railway more accurate.