Evaluation Model of DC Current Distribution in AC Power Systems Caused by Stray Current of DC Metro Systems

With the rapid development of the DC metro system, the stray current may bring new challenges to the AC power system. Especially, the stray current of the DC metro system flowing in the AC power system may cause many serious consequences such as the corrosion of the grounding grids, plenty of harmonics, and the dc bias of transformers. Therefore, it is significant to evaluate the dc current distribution in the AC power system caused by the stray current. In order to evaluate the dc current distribution, a coupled simulation model both considering the DC metro system and the AC power system is proposed in this paper. Moreover, the earth and the grounding system are both used as the coupling elements in the proposed model. The correctness of the proposed model is verified by the comparison of the calculation results and the field test data. Furthermore, based the proposed model, the dc current distribution in the AC power system is evaluated and analyzed. The results indicate that the dc current distribution is affected by the trains operating conditions and the relative position between the DC metro system and the AC power system.