Study On Fault Location Method Optimization Of All Parallel AT Traction Power Supply System

The all parallel autotransformer(AT)traction power supply system is widely used in high-speed railway power supply system due to its larger transmission power,lower voltage loss and longer power supply distance.However,its relatively complicated power supply structure makes it easier to occur various faults compared to other traction power supply modes,and especially the short circuit fault has the highest frequency.In order to meet the requirements of safe,reliable and economic operation of the traction power supply system,once the fault occurs,the fault should be quickly located to reduce the safety hazard caused by the power supply system power failure.Therefore,it is particularly important to accurately locate the fault position of the all parallel AT traction power supply system after the fault occurs.Firstly,the structure of the all parallel AT traction power supply system is introduced in this paper,the anti-thunder coil and power supply cable line existing in the traction substation,AT station and section post are taken into consideration in the fault location.The generalized symmetrical component method is applied to analyze the fault of the all parallel AT traction power supply system,and the corresponding sequence network diagram is obtained according to the boundary conditions corresponding to different fault types.By solving the sequence network diagram of different faults,the modified ranging formula of the all parallel AT traction power supply system is obtained.Secondly,due to the mature application of traveling wave method fault location in power system,it is applied to fault location of traction power supply system.The traveling wave method is applied to the traction power supply system for theoretical research and analysis.Because of the traction power supply system is not balanced transmission lines,the phase-mode transformation of the traction power supply system is obtained according to the voltage fluctuation equation.Considering the complex structure of the traction power supply system,this paper selects the double-ended voltage traveling wave ranging method.The effect of AT on traveling wave propagation process is verified by simulation of electromagnetic transient simulation software PSCAD/EMTDC.Thirdly,the digital signal processing method is utilized to calibrate the time when the traveling wave head reaches the measuring points at both terminals of the traction network.In this paper,the improved Hilbert-Huang transform is applied to process the traveling wave signal,and on this basis,the fault section of the overhead-cable hybrid line is obtained.The fault ranging equation obtained according to segment discriminant formula by the double-ended traveling wave method.Finally,an all parallel AT traction power supply system model with anti-thunder coil and power supply cable is built in PSCAD/EMTDC software,the modified current ratio ranging algorithm and traveling wave method ranging results are simulated and verified respectively.According to the advantages and disadvantages of the two fault location algorithms,the two algorithms are combined to obtain the optimized fault location of the all parallel AT traction power supply system.