Preprint of "Fault Location in Distribution Networks Using Apparent Inductance-based Algorithm "

Accurate fault location is essential for rapid service restoration in distribution networks. However, modern active distribution networks (ADNs) with high penetration of distributed energy resources (DERs) challenge conventional methods through multi-source fault contributions, bidirectional power flows, and converter-limited fault currents. This paper presents a time-domain fault location method for both passive distribution networks (PDNs) and ADNs, based on a three-sample apparent inductance estimator using local voltage and current measurements. The estimator exploits the strong correlation between line inductance and fault distance, with reduced sensitivity to fault resistance compared to classical impedance approaches. Its performance is evaluated on a 22 kV, 20 km distribution feeder, covering three fault types, four fault resistance levels (5–500 Ω), four fault locations, EN 50160-compliant harmonic distortion, and DER penetration levels from 0 to 80%. Under ideal sinusoidal conditions, relative location errors remain below 2% for low-resistance faults. In ADNs, the method achieves errors below 5% for low-resistance faults across all fault types, with accuracy decreasing for high-resistance faults at high DER penetration. A sensitivity analysis confirms practical robustness across SNR, load current, THD, and DER penetration.