A Two-Terminal Steady-state Ranging Method for Short Circuit Fault in Subway Traction Network Based on T-Type Equivalent Rail-Ground Transition Resistance

Aiming at the low accuracy of short-circuit fault impedance method in subway traction network, a double-ended impedance ranging algorithm based on the T-type equivalent of rail-to-ground transition resistance is proposed. Perform T-type equivalent transformation on rail resistance and rail-ground transition resistance, collect voltage and current data with the detection device of the adjacent traction substation, and substitute it into the T-type equivalent algorithm to locate faults. The short-circuit fault of metro traction network is simulated by MATLAB. The effects of different rail ground transition resistance, different equivalent algorithms, different fault locations and measurement errors of voltage and current detection devices on the ranging accuracy of T-type equivalent algorithm are discussed, and the ranging results are compared with those of classical impedance method. The simulation results show that the distance measurement accuracy of the T-type equivalent algorithm is hardly affected by the change of the rail-to-ground transition resistance. When the fault location is 900m and the rail-to-ground transition resistance is
$\mathbf{3}\mathbf{\Omega}\cdot \mathbf{km}$
, the distance measurement result is 895.21m, and the rail-to-ground transition resistance is 895.21m. When it is
$\mathbf{50}\mathbf{\Omega}\cdot \mathbf{km}$
, the distance measurement result is 892.27m. The traditional classical impedance method has a maximum ranging error of 91.59m, a relative error percentage of 30.53%, a minimum error of 10.25m, and a relative error of 3.42%. The T-type equivalent ranging method has a maximum error of 19.88m and a relative error percentage of 6.63%, the minimum error is 2.93m, and the relative error is 0.98%. Four equivalent transformations are performed on the rail-ground loop resistance respectively, and the simulation ranging results are basically the same. At the same time, when the measurement error of the measuring device is within the normal allowable range, the fluctuation of the voltage and current data will not affect the T-type equivalent algorithm.