Coupled Field–Circuit Modeling and Analysis for Interturn Short-Circuit Faults in an Onboard Traction Transformer

Onboard traction transformers are essential electrical equipment in high-speed railway systems, and their interturn faults can seriously threaten the safety of rail transportation. In this digest, a coupled field–circuit model of an onboard traction transformer with interturn short-circuit (ITSC) faults is built, in which the magnetic field is calculated together with the external circuit through transient data exchange. Moreover, a cybernetic arc model is adopted for the simulation of the time-varying conductance of the fault arc, and the effect of the traction rectifier control system is also considered in the circuit domain. As a study case, a typical 6.5 MVA/25 kV onboard traction transformer on a China Railway Highspeed (CRH)-1 electric multiple unit (EMU) was modeled and simulated in a 25 kV traction system. With fault occurrence, the flux distribution is markedly distorted, and the short-circuit current reaches 7.8 kA at its maximum. The proposed method and representative findings enrich fundamental studies on the internal faults of the onboard traction transformers.