The impact of electric vehicle (EV) penetration and smart charging on the coordination of overcurrent protection in distribution networks is investigated in this paper. High demand for EV charging drastically changes short-circuit levels and can make trouble to adjusting the coordination time interval (CTI) between primary and backup relays, even when the system was working perfectly in the first place. In order to sort this out, a two-stage framework is proposed in this paper. First, a multi-agent-based coordination scheme is run under a base case with no EVs, to adjust the settings of the backup relays in a radial feeder so that a minimum time interval of 0.3s is met in all zones. Then, keeping these relay settings fixed, the effect of increasing EV penetration (0–100%) is evaluated by modeling the incremental contribution of EV chargers to fault currents in different zones of the feeder. A simple penetration-dependent smart charging approach is proposed, which gradually limits the effective charging electricity beyond a penetration threshold, thereby decreasing EV-driven fault cutting-edge contributions. Simulation effects show that, without clever charging, the CTI in downstream zones pretty decreases with EV penetration, decreasing the coordination margin. With the proposed clever charging method, a big part of this margin is recovered, and in upstream zones the CTI is completely preserved above the target value, highlighting the benefits of coordinated protection and charging manage in EV-rich distribution networks.
