Research And Achievement On Metro Catenary Fault Lacation

Metro has an obvious advantage to improve urban public transport pressure, and now in China many big cities are making great efforts to build metro. Metro traction line system fault is a common fault in actual operation, in order to reduce the losses because of outage it is important to ensure DC traction line system security and stability, and to quickly achieve fault location and renew normal power supply. So in this paper we develop the research about metro catenary fault location, and the main fault simulation is about to feeder cable’s low-impedance fault, high-impedance fault and catenary main line’s short-circuit fault.In this paper we give a brief introduction about the structure of metro traction power supply system and the significance of metro catenary fault location. Fault analysis method (impendance method) and traveling wave method are the main fault location methods for power system transmission line, both the methods have their own applicable transmission lines, accuracy and correlation algorithms. Combination metro catenary line this thesis decides to use traveling wave method to achieve fault location and discuss its applicability in DC short-distance power transmission lines.It is given a detailed expatiation on the basic theory of traveling wave in this paper, by the model of uniform lossless conductor we do some mathematical deduces on wave velocity, wave impedance, wave equation and traveling wave refraction and reflection. Also it has instructions for some key technology problems and their solutions in traveling wave method fault location. Wavelet transform theory provides a good mathematical foundation for the realization of traveling wave fault location. Through wavelet transform we find out transient singular points of traveling wave signal, and the singular points correspond to wavelet transform modulus maxima points. From the singular points we acquire time information on fault, then calculate the fault distance based on time information. The wavelet transform has been widely used in power system transmission lines wave traveling method fault location.This thesis gives the equivalent mathematical model of metro DC traction line system, and calculates DC-side short-circuit current. Using MATLAB/SIMULINK we build a metro traction power supply system pulse rectifier simulation model and catenary DC-side proximal end short-circuit and remote end short-circuit simulation model. The simulation results show24-pulse rectifier has better power quality and metro traction power supply system catenary DC-side proximal end short-circuit has a very large short-cicuit impulse current. Finally we use low-voltage pulse reflection method to realize faultlocation for metro catenary feeder cable low-impedance and pulse current method (DC high-voltage flashover method and impulse high-voltage flashover method) for high-impedance. Acquisition metro catenary short-circuit current signal and analysis the fault signal using wavelet transform, then calculation fault distance from time information. The result indicats the error is also in the ideal range. The simulation verifies traveling wave method is feasible for metro catenary short distance DC line. In theory the accuracy has certain guiding significance for the actual metro catenary fault investigation.