Differential protection scheme for transmission lines with end-of-line UPFC compensation using sequential current...

With the rapid growth in population, the increase in power demand has outpaced the expansion of transmission line infrastructure, often leading to overload conditions. To mitigate such challenges, Flexible AC Transmission System (FACTS) devices are widely adopted to enhance system reliability and stability. While FACTS devices significantly boost the power transfer capability of transmission lines, they can also impact the effectiveness of traditional protection relays. Among these, the Unified Power Flow Controller (UPFC) is particularly notable for its ability to regulate both active and reactive power flows independently, offering the advantages of combined series and shunt compensation. This study introduces a protection strategy based on differential current sequence components for a transmission line equipped with end-line UPFC compensation (ELUC). The proposed algorithm is validated through simulations in MATLAB Simulink and further assessed using a real-time simulator. The evaluation considers a range of scenarios including variation in fault types, fault locations, fault resistances, UPFC operating modes, simultaneous faults, and synchronization errors. The performance is thoroughly examined through real-time simulation and benchmarked against existing techniques. The results demonstrate that the proposed scheme is both selective and accurate in detecting faults under dynamic conditions.