Waveform Shape Normalization for Single-Phase-to-Ground Faults in Resonant Grounding Systems: Edge-Lightweight Location via Zero-Sequence Coupling Invariance

To address the limitations of existing single-phase-to-ground fault detection methods in resonant grounding systems, including narrow grounding resistance adaptability, low noise immunity, and high computational burden, this paper proposes an edge-lightweight location method based on zero-sequence coupling invariance and waveform shape normalization. Firstly, at the theoretical level, we reveal that at the fault instant, the zero-sequence coupled quantity (ZSCQ) exhibits fixed amplitude and polarity distributions inside and outside the fault feature path (FFP), independent of grounding resistance. This serves as the foundation for subsequent signal processing and location algorithm design. Secondly, a lightweight waveform shape normalization process is devised to effectively suppress noise and unbalance components while enhancing the initial transient features of ZSCQ. This transforms signals into highly consistent characteristics amenable to further processing. Furthermore, using the normalized waveform feature value (NWFV), we propose an adaptive threshold cascading location algorithm that integrates polarity and amplitude information to ensure rapid location and high robustness. Finally, the entire solution achieves edge-lightweight implementation, substantially reducing computational and communication overhead, thereby enabling efficient execution on terminal devices.