| In the railway transportation system, power supply system of electric traction is one of the symbols of the main railway modernization, because it can improve the transport capacity considerably and save energy, but no environmental pollution. However, this power supply system also brings heavy electric traction interference to railway signal equipments. If there are no more advanced railway signal equipment to support the power supply system, the advantage of electrified railway can’t visualize adequately. In other words, if advanced signal equipment can not prevent and eliminate all kinds of electric traction interference effectively, it can not ensure the running safety and improve the transport efficiency.The continuous distribution of alternating magnetic field exists in overhead contact line air around of25kV single-phase industrial frequency alternating current electric traction system, and its power supply circuit are asymmetric, which uses the overhead contact line and rail as the working wire. The insulation degree of rail to the earth is extremely low, traction current is separated into two parts:one part current flows. along with the rail, and the other part flows along the earth. Therefore, it will produce potential and longitudinal electro-motive force in signal equipment which are set along with the railway. At the same time, potential current will appear in all kinds of signal circuits, this electromagnetic interference directly generates obstruction to itself as well as maintenance of signal equipment.There are three electrification interference types, including conducted interference, electric induction and radiated interference. But the most serious is conducted interference, which is mainly show that the unbalanced traction current has influence on track circuit and cab signal, etc. Besides, it also has ground potential raise influence. Firstly, it makes a brief description of disturbance effect about signal system which the cause is railway electrification system in thesis. Secondly, traction power supply system of electrified railway and its interference source are introduced, then makes an analysis on principle of conducted interference. The specific performance is analysis distributing model of rail in different power supply system and determine the distribution of rail return current. Meantime, analysising the formation and influence principle of unbalanced current, building the equivalent circuit model of traction power supply system and making simulation test to pulse current. Thirdly, according to numerous factors of generating unbalanced current, makes research on anti-interference measures for unbalanced current of track circuit in electrified railway.Finally, in order to prevent electrification interference to signal equipments, which can better adapt to electric traction, comprehensive analysis system about traction current based on the VC++platform is designed. The main task is to complete the system design and giving realization scheme on the basis of demand analysize. Its major function is current data reduction after sampling, waveform display, and a detailed analysis on this data, which can reflect the traction current real-time dynamic situation for railway signal system equipments. All this analysis would provide the reliable theory basis for anti-interference, and can find effectively protection to restrain or eliminate electrified interference. It has certain practical value. |
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