Mechanism Analysis of Sympathetic Inrush in Traction Network Cascaded Transformer based on Flux Linkage-Current Circuit Model

There may be sympathetic inrush in traction substation transformer when electric multiple unit passing neutral section devices, which may result in the misoperation of different protection and back-up protection. This paper proposes a new mechanism analysis method of sympathetic inrush in traction network cascaded transformer based on flux linkage-current circuit model. This paper firstly build the equivalent circuit of the traction network and electric multiple unit (EMU) coupling system through analyzing its structure, and then build flux linkage-electrical current model for each unit of the equivalent circuit, all of which make up the flux linkage-current circuit model. Based on the flux Linkage-current circuit model, this paper analyses the reason why the sympathetic inrush of the traction substation transformer produces and the influence of remanence, over-phase closing phase angle, line impedance and transformer saturation on the sympathetic inrush. A simulation is carried out in this paper, and the sympathetic inrush of the traction substation is resulted from the superposition of the DC flux linkage and AC flux linkage over the critical saturation flux linkage which goes into the flux saturation area.