Development of Short-Circuit Impedance Testing and Setting Calculation Device for Urban Rail Transit Catenary

Objective The line impedance of urban rail transit catenary is significantly affected by many factors such as wire material, line length, surrounding environment, etc., resulting in significant impedance differences between different lines and different time periods. However, in the setting calculation process, assessments often rely on empirical formulas, leading to inaccurate setting values and affecting the selectivity and sensitivity of the protection device. When the system encounters a short-circuit fault, false operation or refusal to operate may occur, posing a great safety hazard. Therefore, it is particularly important to develop a device that can accurately test the short-circuit impedance of the catenary and perform setting calculations. Method A low-voltage short-circuit test method is proposed. The method sets a short-circuit point at the end of the catenary and realizes the measurement of short-circuit impedance by applying low-voltage direct current at the head end of the line. A high-precisio