Fault characteristics and protection methods for long distribution lines with grid-forming IBDG integration

Grid-forming inverter-based distributed generation (IBDG) is an effective means to address low voltage issues at the end of long distribution lines in remote areas. However, existing distribution protection methods are not suitable for this scenario. By analyzing the voltage phase angles of grid-forming IBDG that meet low voltage remediation requirements, the boundary phase angle conditions corresponding to ”minimum line loss” and ”minimum inverter current” are derived. Based on this, the distribution characteristics of short-circuit currents in long distribution networks are analyzed, and the limitations of traditional three-stage current protection methods are revealed through a regional discussion. An adaptive current protection method is proposed, which automatically adjusts protection device parameters by real-time calculation of regional intersection positions and currents. The effectiveness of this method is verified through simulations. The simulation results confirm the accuracy of the proposed boundary conditions and fault characteristic analysis, demonstrating that the proposed adaptive current protection method can effectively address short-circuit scenarios in long distribution networks with grid-forming IBDG integration.