Single-end Fault Location Method for Fractional Frequency Transmission Lines based on GAM Current Reversal

• Proposes a GAM-based single-end fault location method for FFAC lines; • GAM suppresses reflections and enhances traveling wave detection; • No need for time sync or wavefront arrival calibration; • TW reversal forms a virtual fault point for precise location; • Validated on RTDS and field data with high accuracy. In fractional frequency AC (FFAC) transmission systems, fault location methods based on transient and steady-state quantities are susceptible to variations in converter control parameters. Additionally, as the fractional frequency period (60 ms) is three times that of the power frequency period (20 ms), conventional fault location algorithms relying on full-cycle power frequency sampling face challenges due to mismatched signal periodic characteristics, rendering them impractical. In contrast, signals during the initial fault stage are governed by the system’s inherent topological structure, exhibiting distinct traveling wave characteristics unaffected by dynamic adjustments of control strategies. Consequently, fault location methods based on the initial traveling wave phase effectively circumvent technical bottlenecks in FFT systems, such as control response delays and signal period widening. To address this, this paper proposes a transmission line fault location method based on generalized spatial mode current inversion. First, the generalized Aero Mode (GAM) current traveling waves are constructed using measured terminal currents from the faulted and non-faulted lines to eliminate the influence of reflections at the ends of healthy lines on the reflected waves from the fault point or remote busbar. Subsequently, leveraging the mapping relationship between traveling wave mutation points and fault locations, the wave mutation points are inversely propagated along the line to form a virtual fault point matrix and construct a location function, from which the fault distance is derived based on the mutation points. This method overcomes the bottleneck of time-domain wavefront timestamp calibration and facilitates automated single-ended traveling wave fault location. The effectiveness of the proposed method is validated using real-world transmission line fault data and RTDS simulation data, demonstrating high localization accuracy and strong robustness under diverse fault conditions.