Study on the influence of transient processes in pantograph-catenary contact-loss on the characteristics of glue rail insulation

Electrified railways are complex electromagnetic systems that feature strong-weak electrical interactions and the coexistence of dynamic and static components. In this system, rails serve dual roles as signaling circuits and traction return channels. With the increase in operating speeds and the optimization of operational strategies, greater traction currents and more frequent traction switching when passing neutral zones pose higher demands on the signaling system’s EMI immunity, and the insulation joints’ voltage tolerance. This paper investigates the impact of pantograph-catenary contact-loss during train passing neutral zones on the return current cut-off insulation joints (referred to as ‘cut-off joints’). First, a circuit model is established based on the traction return system principles and the cut-off joints’ configuration scheme. Key model parameters are determined to clarify the mechanisms, influencing factors, and coupling paths of transient pulses during the contact-loss process. The propagation characteristics of these pulses in rails are analyzed. The results indicate that in typical scenarios, cut-off joints experience an impulse voltage peak of 4 kV and a frequency of 109 kHz as the train exits the neutral zone. Using the ANSYS Maxwell platform, a finite element modeling simulation is conducted to analyze the electric field distribution of the insulation joint structure under both ideal and defect conditions when subjected to impulse voltages. Finally, all results are validated through field tests, and optimization suggestions are proposed. This study contributes to fault tracing in glue rail insulation, provides a basis for setting electrical standards, and offers guidance for designing stationary current channels.