Waveform similarity-based robust pilot protection for transmission lines

This paper proposes a robust pilot protection scheme based on waveform similarity that restricts the influence of outliers in fault line identification. By comparing two refactoring currents constructed using the time-domain sampling values of currents at the two terminals of a transmission line, a waveform similarity algorithm called the Kendall's Tau coefficient (KTC) is employed to distinguish two different datasets of a protected transmission line. A reliable fault identification is realized under different fault types, distances, and resistances. Proposed criteria that are robust against to current transformer saturation, synchronization error, and noise are proposed. The KTC is based on simply the rank order instead of the metric value and thus limits outliers to a moderate level, ensuring protection safety in cases where outliers that cannot be eliminated completely are included in the current waveforms. The simulation results demonstrate the excellent performance of the proposed robust pilot protection scheme.