Single-ended fault location method for multi-terminal overhead-cable hybrid transmission line using alternating search algorithm

With rapid urbanization and power grid expansion, multi-terminal overhead-cable hybrid transmission lines have been increasingly utilized. However, the significant differences between overhead lines and cables, combined with the complexity of multi-terminal structures, lead to complicated refraction and reflection of travelling waves (TWs). Therefore, conventional single-ended TW-based fault location methods, which rely on accurate identification of reflected waves and a high sampling frequency in the MHz range, are not suitable. To address this issue, the paper proposes an enhanced TW-based fault location method based on waveform similarity. First, this method incorporates a frequency-dependent multi-terminal hybrid transmission line analytical model to reproduce fault transient voltage waveforms. On this basis, dynamic time warping and normalized mean square error collaborative similarity metrics are established to evaluate calculated and actual fault transient waveform characteristics, and the sensitivity analysis of the similarity metrics shows that there is a coupling relationship among the fault variables. Then, a variable-step, dual-metric alternating search algorithm is proposed to accurately identify fault variables (e.g., fault inception angle, fault resistance, and fault distance). Finally, simulation results using PSCAD/EMTDC demonstrate that the proposed method can accurately locate the fault at a sampling frequency of 200 kHz, is less affected by fault resistance, and does not require data synchronization.