Comprehensive Control of Reflux Safety Parameters Based on Flexible Grounding Scheme in DC Railway Electrification System

Currently, the excessive rail potential (RP) and stray current (SC) are disasters to the safety of equipment and staff in dc railway electrification system (dc RES). However, abnormal increase of RP and SC still exists and the coupling relationship between RP and SC with the complex grounding scheme has not been clarified. In this article, a flexible grounding scheme (FGS) is proposed to realize the comprehensive control of RP and SC with dynamic operation of multitrain. By establishing the simulation model of dc RES with FGS, the coupling mechanism of the abnormal increase between RP and SC is clarified. In order to prove the effectiveness of FGS, simulation results of dc RES with ungrounded scheme, over voltage protection device (OVPD) grounded scheme and FGS are compared. Field tests of reflux safety parameter (RSP) are carried out in Hefei Metro Line 2 with different grounding resistance. Simulations and field tests show that coupling effect between RP and SC at multiple stations is obvious, and FGS can realize the comprehensive control of RP and SC effectively.