Voltage Actuated Transmission Line Protection Scheme Applying Signal Processing Techniques

For the protection of a two-terminal transmission line, this research developed a method for fault recognition by analyzing voltage data using Stockwell transform (ST) and Hilbert transform (HT). The HT is used to process the voltage signals and compute a Hilbert amplitude frequency index (HAFI). ST is also used to get the Stockwell summation median index from the voltage signals (SSMI). The combined fault index is calculated by multiplication of HAFI and SSMI (CFI). Hilbert Stockwell Derivative Fault Index (HSDFI) is computed by differentiating the CFI and comparing it to a pre-set threshold value for identifying problematic phases. Numbers of faulty phases are utilized to classify defective occurrences. The Hilbert Stockwell derivative ground fault index (HSDGFI), which is generated by processing the zero sequence currents, is used to detect ground involvement during a failure. Line to ground (LG) faults, double line (LL) faults, double line to ground (LLLG) faults, and three phase faults with ground (LLLG) are among the faults investigated. Results of this study have been verified in MATLAB.