Distance Estimation for Early Three-core Cable Fault Based on Multiple Amplitude Ratio Fusion of Grounding Line Current Selected Frequency Band

Early cable faults are becoming more prevalent in urban distribution networks. In this paper, the mechanism of grounding line current signal generation and propagation in cables with early faults is analyzed to help understand the relationship among each frequency component, the fault location, and fault resistance, based on which we propose a novel distance estimation method for early faults in three-core cables using multiple amplitude ratio fusion within a selected frequency band. By combining the amplitudes of different frequency components, this approach reduces the reliance on accurate extraction of the amplitude of a single-frequency component, which is particularly suitable for detecting sub-cycle early faults. Simulation analysis and field test results demonstrate the proposed method's high accuracy in estimating the fault distance. Moreover, it is less susceptible to variations in fault conditions. These findings show that the proposed method is effective in addressing the challenge of early cable fault distance estimation in distribution networks.