Novel method for rail insulation degradation diagnosis driven by diffusion law of stray current

• A field-circuit coupling model integrating traction power supply with stray current distribution is proposed. • A knowledge-data driven diagnostic algorithm addressing rail to earth insulation defects is Developed. • The technical requirement for synchronous monitoring of the monitoring data and the equal intervals deployment method of monitoring points are determined. The degradation of the rail to earth insulation performance is the primary factor contributing to the increased leakage of stray currents. It is difficult to locate rail to earth insulation degradation or assess their severity in urban rail transit systems. To overcome this problem, a novel diagnostic method for rail to earth insulation degradation is proposed. This method, which is based on the diffusion law of stray current and characterizes rail to earth admittance by utilizing the field circuit coupling model, utilizes multi-source synchronous monitoring data to construct the optimization algorithm and achieve precise calculation of the rail to earth admittance. The verification for the effectiveness of rail to earth insulation defect diagnosis principle by a laboratory physical simulation platform. Using actual subway line parameters, the error of the diagnostic algorithm is analyzed through cases. Most errors are below 5%. To address errors caused by uneven tunnel resistivity, a correction measure involving segmental parameter adjustments is proposed.