Research on relay protection technology of active distribution network considering different voltage levels

In recent years, the deployment of distributed photovoltaic (PV) systems equipped with Low Voltage Ride-Through (LVRT) technology in power distribution networks has seen significant growth. However, due to the relatively low short-circuit current contribution from these systems, their short-circuit characteristics diverge from those of traditional synchronous motors. This discrepancy often leads to the misoperation of conventional overcurrent protection systems, which may continue to supply power to faulted areas, thereby increasing the risk of reverse power transmission incidents. To address this challenge, an adaptive setting strategy is proposed to optimize the performance of overcurrent protection systems. The strategy is grounded in the operational principles of LVRT. By estimating fault voltage and leveraging the voltage drop effect during faults to offset the minor increase in current resulting from the current-limiting control of the PV inverter, the system’s response time is enhanced. The proposed method is validated through simulations using DIgSILENT software on both 220V and 10kV distribution systems. The results substantiate that this adaptive setting strategy, while preserving selectivity, significantly reduces the protection system's action time, thereby mitigating the risk of reverse power transmission accidents and ensuring the safety of distribution network operators and maintenance personnel.