Research On Anti-EMI Of BTM Equipment Based On Electromagnetic Topology

With the continual speed-up of high-speed railway,the corresponding traction power is increasing,which leads to increased interference on signal equipment,especially Balise Transmission Module(BTM)equipment in the Automatic Train Protection(ATP)system.According to statistical data,more than 50%of ATP-1 signalling equipment failures are BTM failures.Therefore,it is of great significance to study the interference caused by electromagnetic disturbance sources on BTM equipment and put forward pertinent anti-interference measures for anti-interference purpose.Based on the BTM anti-electromagnetic-interference research,the main work of this thesis is as follows:Firstly,under the foundation of the investigation and a large number of field cases,it is evident that the main disturbance sources on BTM equipment are high-voltage power supply lines,traction transformers,traction converters and other high-power equipment.The main coupling paths are near-field crosstalk and far-field radiation.In case of crosstalk of BTM cable,the main on-site anti-interference measures are to place the cable in the metal channel;for the radiation interference of CAU(Compact Antenna Unit),the main on-site anti-interference measures are to install metal fender around CAU.However,the above two methods are engineering experiences and lack theoretical analysis and quantitative calculation.Secondly,theoretical interpretation on shielding mechanism of shielded cables and cable channel is performed and the thesis has clarified the facts that the main factor affecting shielding effectiveness of cable channel is the change of distributed inductance between sensitive circuit and harassment circuit.The electromagnetic topology model of shielded cables placed in cable channel is established,aiming to calculate the shielding effectiveness of cable channel quantitatively.The effectiveness of the simulation model is verified by comparing simulation with experimetal results.The results of simulation and measurement show that the shielding effectiveness of the shielded cable plus channel can be improved from 10 dB(under single-shielded cable mode)to 40 dB in the frequency band of 104Hz to about 107Hz.Thirdly,after dissecting the instrinsic of metal fender shielding effectiveness,it is obvious that the attenuation function of the fender lies in diffraction effect caused by fender-obstruct.On this basis,the metal fender electromagnetic topology model is established in order to calculate the shielding effectiveness of metal fender quantitatively.Then,the validity of the simulation model is verified by comparing simulation with experiment.The simulation and measurement results show that the fender has shielding effect on far-field radiation interference.In accordance with the demarcation standard,considering the size and installation requirements of CAU,the optimum size of the fender is 645 mm x 645 mm,the height is about 510 mm,and the corresponding shielding effectiveness is 7.2 dB.