Enhancing Instantaneous Overcurrent Protection Selectivity in Power Lines Using Resistive Superconducting Fault Current Limiters

Traditional instantaneous overcurrent protection schemes encounter significant challenges in power lines, particularly when line impedances are low, resulting in minimal differences in fault current magnitudes for faults occurring at various segments in the power line. This condition compromises selectivity, leading to poor relay coordination, misoperation, and delayed fault clearing. This study presents an advanced solution through the design and strategic placement of Resistive-type Superconducting Fault Current Limiters (r-SFCLs) along power line segments to enhance protection selectivity and system reliability. The r-SFCL dynamically introduces substantial impedance upon fault detection, effectively reducing fault current magnitudes downstream and creating distinct, easily discriminated current levels at each segment. This clear differentiation enables instantaneous overcurrent relays to operate swiftly and selectively. A detailed self-activated r-SFCL model, incorporating realistic superconducting behavior, is developed and simulated within a practical 33 kV power line system using MATLAB/Simulink. Simulation results under various fault conditions show marked improvements in relay sensitivity and instantaneous selectivity. Strategically inserting multiple r-SFCLs across line segments yields a selectivity margin greater than 25% between fault current magnitudes of line segments, ensuring accurate fault localization and fast clearing without affecting normal load stability. These findings confirm the usage of r-SFCLs as effective and practical devices to enhance instantaneous overcurrent protection, strengthening system resilience and reliability in modern distribution networks.