A new directional relaying approach for transmission lines considering hybrid superconducting fault current limiters

The inclusion of a superconducting fault current limiter (SFCL) in transmission lines causes transients that lead to variations in the magnitude and angle of relaying quantities such as voltage and current. This results in erroneous delta (superimposed) quantities, which create issues for existing angle-based directional relaying methods that rely on these quantities, and amplitude-based directional methods due to a reduction in magnitude of fault currents. The proposed approach computes the DQ information of the local-end current signal using the Clarke transformation. Next, the superimposed instantaneous frequency of the complex current signal is computed using the Ensemble Empirical Mode Decomposition-based Hilbert–Huang Transform (EEMD-HHT). Two threshold values, one positive and negative are used to distinguish between forward and reverse faults. The reliability and security of the proposed protection mechanism under various test scenarios are demonstrated and compared with those of existing directional schemes to validate its accuracy, efficiency, and adaptability.