Sequence components-based distance protection for lines connected to inverter-based resources during asymmetrical faults

The connection of Inverter-based Resources (IBRs) could introduce significant underreach and overreach for distance protection. Conventionally, a strong AC grid is assumed to connect to IBRs, which could generate significant fault currents during faults. This high-magnitude fault current can facilitate the correct operation of the grid-side relay. However, that assumption does not hold in weak systems, where reduced fault current contributed from the AC system can potentially lead to underreach and overreach for distance protection at the grid side. To address challenges at the grid side, this paper proposes a sequence components-based protection algorithm that uses the open-circuit characteristic of the negative-sequence network on the IBR side. The performance of the proposed algorithm is validated using the Real-Time Digital Simulator (RTDS) across a wide range of scenarios, including variations in fault resistances, fault locations, line lengths, IBR injection strategies, and system operating conditions. The simulation results demonstrate that the algorithm can accurately calculate the fault distance under all investigated conditions, including in both strong and weak systems. In addition, the proposed algorithm only uses local measurements and does not require communication channels. Therefore, it could provide a robust and cost-effective solution for grid-side protection in lines connected to IBRs.