No abstract

No abstract

According to the different features of the DC traction network transient current in the Metro, the electromagnetic transient process of traction power supply system that should be divided into the two forms of short-circuit fault and the low-frequency oscillation was proposed. While traction network short-circuit fault happens, the system model is a weakly nonlinear first-order differential equation, which feeder current is increasing exponentially and eventually stabilized. While the load current becomes low-frequency oscillation current, the system model is a nonlinear second-order differential equation. After linear processing in unique equilibrium point neighborhood, the state space equation of linear system is built, and the structural reason of low-frequency oscillation is revealed by eigenvalue analysis method. The simulation result shows that the simulation current waveforms are consistent with the recorded current waveforms and the division of transient process is reasonable.

No abstract

This study addresses fault identification in differential protection of a V/x-type traction transformer used in a highspeed railway. To quickly and accurately identify an internal short circuit in a traction transformer, a hybrid algorithm is developed that combines intrinsic mode function (IMF) energy entropy with the correlation dimension from chaos theory. IMF energy entropy and correlation dimension are sufficiently fast and sensitive to reflect the dynamic changes in the differential-current signal from the traction transformer using different metrics; thus, this hybrid method can effectively identify an internal short circuit and magnetising inrush. Real-time simulations and actual measurements of faults illustrate the validity of the proposed method.