Application of stepped-frequency waveform reflectometry to locating and characterizing line-like aging faults in cables

Soft fault detection technology helps to detect insulation aging in cables to ensure safe and stable operation of modern power system. However, for line-like aging faults, insulation degradation can cause a change in phase velocity, resulting in inaccurate fault locations. Thus, the improved stepped-frequency waveform reflectometry (SFWR) method is proposed to evaluate line-like aging faults in cables, mainly including the impedance mismatch compensation technique and the diagnosis strategy for line-like aging faults. The impedance mismatch compensation technique eliminates the effect of impedance mismatch at the head end of the cable by simply using measurement signals, ensuring an accurate assessment of reflected signals. The diagnostic strategy begins by identifying the presence of line-like aging faults through polarities and cable tail end location. Then, the phase velocity at the line-like aging fault can be extract from the reflected signal at the head end of this fault, which in turn corrects the offset locations. Simulations and experiments show that the improved SFWR method proposed in this paper can accurately evaluate line-like aging faults in cables.