The evolution characteristics of leakage current in traction network surge arresters under complex operating conditions

Due to frequent load fluctuations, significant impacts, and substantial harmonic distortion on heavy-load railways, leakage currents monitored by surge arresters exhibit considerable variation. This leads to abnormal operations, causing changes in lightning counters and affecting maintenance scheduling for surge arresters. To effectively monitor the operational status of surge arresters on heavy-load railways, this paper analyzes their tripping characteristics under common operating conditions based on actual railway operations. A PSCAD-based simulation model for heavy-load railways was established, revealing that under harmonic overvoltage conditions, the effective tripping current of arresters farther from the load is significantly lower—often half or less than that of arresters closer to the load. The magnitude of leakage currents on both sides remains nearly constant regardless of train load position. When grid-side faults flow through traction transformers into the catenary system, short-circuit faults do not affect surge arrester leakage currents. However, open-circuit faults cause surge arrester operating currents to exhibit periodic currents near 20 Hz, with peak operating currents corresponding to overvoltage peaks. Operational overvoltage generates a short-duration operating current of approximately 1100µA, 2.5 times the normal operating level, lasting milliseconds. Lightning overvoltage operating characteristics resemble operational overvoltage but exhibit higher amplitudes and shorter durations. Furthermore, this paper analyzes the leakage current of surge arresters from mathematical, frequency, and power consumption perspectives to distinguish their operational states, thereby enhancing the accuracy and intelligence of online monitoring for surge arresters.