Investigation on Interturn Short-Circuit Faults in an Onboard Traction Transformer for High-Speed Railway

Onboard traction transformers filled with combustible oil are vital equipment in high-speed railway systems, and their interturn short-circuit (ITSC) faults pose serious threats to transportation safety. Their unique internal structure and external system, as well as the wide range of fluctuating catenary voltages and train loads, present challenges for fault investigations. In this study, ITSC faults in an onboard traction transformer are modeled and analyzed via field-circuit coupling, in which solutions are exchanged between the magnetic field and the circuit system models by bidirectional data transfer. In particular, the conductance of a fault arc connecting adjacent turns is described by a verified diameter-based black box model, which is integrated into simulations using user-defined code. For case studies, a typical 2.5 MVA traction transformer for a high-speed railway train is simulated subject to a series of ITSC faults. The results confirm an apparent diversity in the changing patterns of the leakage flux, short-circuit current and terminal currents under different operational states of the train. This method is expected to facilitate follow-up studies on the fault detection of onboard traction transformers.