Analysis Of Dc Traction Reflux System And Research On Related Problems In Rail Potential

DC traction supply system is widely used in metro, light rail and industry and mining enterprises. In our country, urban rail transit is at a peak of development stage and a safe and reliable operation of DC traction system is the basic need of urban rail transit. It is very important to study the analysis of parameters, the restrict of rail potential, the control of stray current corrosion and related questions.Because of the frequently acceleration or deceleration of the train, the DC traction current flows in reflux system may dramaticly changed. Besides, the current direction may also shift for regenerative braking and the running of train. The reflux current have a high low-frequency content, however, the reflux rail is consisted of conductor which is made up of ferromagnetic material with large section and very irregular shape, skin effect and saturation characteristic play significant efficient on the transient resistance and inner inductance of rail. The mutual inductance between ballast and tunnel structure reinforced grid may also influence the parameters of reflux system. According to the equivalent cylinder method, this thesis deduced the compute method of transient parameters in reflux system and made a contract with the analyzed result of finite element .The measured and calculated data show that the transient shift of electrical parameters in reflux system should be taken into consideration in analysis of DC-traction rail potential and stray current, besides, it's unfavorable to directly use DC resistance parameters to calculate and analyze.The reflux system model based on transient parameters is a set of partial differential equation. This thesis proposed a crisscross modified iterative format for the model and computed the stability condition of the iterative format. Combined with the actual line condition, the thesis also did numerical simulation. We can see from the computed result that the transient parameter model is more according with the actual situation than the existed model, which supplies reference and basis for the design of reflux system and assessment of stray current. According to the solving process of the model, the thesis used sensitivity analysis to discuss the influence of various parameters of reflux system to stray current and potential, thus, according to the actual conditions, the thesis proposed a method that increase capacitance of rail to limit abnormal rail potential, and the simulation results show that this method is a feasible rail potential restrictions.This thesis studied the measure method of reflux system, according to the shift form of transient parameter model in reflux system, it proposed an on-line parameter test method based on wavelet-least square theory and operated time partial differential to wavelet space and then we can get its discrete form. Using the once complete algorithm of least squares parameters estimate, we can do the identification. It's no need to know the rail current and boundary conditions, therefore, the operation performance of the test method is improved.The transient parameters of reflux rail cause the rail potential rise. If many trains start at the same time, it may cause the operation of rail potential restricting equipment and then the corrosion of stray current may dramaticly increased. This thesis studied the influence of multi-train starting on rail potential and proposed an optimized model with less start coincidence of trains by adjusting the stop time of trains and reducing total traction current. According to the actual line, the paper used particle swarm algorithm to do optimization calculation.