The Study Of Traction Current Reflux To The Insulation Joint Burning In The High Railway Station

In recent years,there have been many mechanical insulation joints and rail burning faults on the Beijing-Shanghai,Shanghai-Nanjing and Wuhan-Guangzhou and other lines,the reason is that the electric arc is occurred in the insulation section.This paper mainly analyzes the fundamental cause of ac arc based on the arc generation mechanism,and studies the solution to suppress arc generation.The main contents are as follow:1)Based on the power supply system of AT power supply system,the combination algorithm of conductor impedance and the calculation method of each parameter are studied in the power supply system.Firstly,the traction substation of AT power supply system is analyzed in detail,especially for the Scott transformer,and the simulation model of traction substation is established accordingly.Next,this thesis introduce the autotransformer in AT,and establishes simulation model.And then,the simulation model of CRH380 BL was built in MATLAB,and the correctness of the model was verified according to the THD value of the measured current in the model network.2)By applying the electric contact theory into the wheel/rail contact model,the mathematical model of effective contact area between wheel/rail is established according to the condition of the insulated joint at the cut-off point in the station.During the modeling of the actual contact area of the wheel/rail,it is necessary to take into account the influence of the irregularity of the wheel and rail surface and the pollution film layer on the surface of the rail.In order to obtain the actual contact area of wheel track and the change curve of contact resistance over time,the MATLAB program is designed to solve the mathematical model.And then,by analyzing the curve features and relevant data,this model can be equivalent to Mayr arc model.The design basis of relevant parameters can be obtained afterwards.3)According to the serious situation of the electric arc discharge of different models in the Jiayuguan high-speed railway station,the corresponding ac arc model is selected.The root cause of arc generation in the cut-off point insulation section is that in the short period of time,there is greater difference between the two sides of the insulation section,and the current on both sides is broken,which can be obtained by analyzing the simulation results of the MATLAB model.Besides,aiming at the fundamental cause of ac arc generation,a low pass filter is designed to provide a channel for the backflow of the traction current at the cut-off point insulation section in this thesis.Considering the insulating section of the track circuit signal blocking effect,the designed filter can effectively block the carrier frequency signal with frequency of 50 Hz and above.At the same time,the traction current backflow with power frequency(50Hz)can pass under the undistorted condition as far as possible.