Research on the Diagnosis and Localization Method of Cross-Bonding Cable Defects Based on Three-Phase Differential Frequency Excitation

In high-voltage network, long-distance cables use cross bonding (CB) to eliminate the sheath currents and ensure the stable operation of the power system. Existing impedance testing suffers from signal attenuation and distortion due to limited instrument output, while cross-bonding causes phase coupling and signal aliasing, which interfere with defect diagnosis and localization accuracy. These combined factors affect the accuracy of defect localization for the cables. This paper proposes a method for diagnosing and locating defects in cross-bonding cables based on three-phase differential frequency excitation. An equivalent CB cable model was constructed to analyze the relationship between defects and resonant frequency shifts. A CB cable impedance spectrum analysis method was constructed, utilizing small frequency differences and fundamental frequency information to achieve full coverage of defect information for three single-phase cables in the wide frequency range. A testing system is built to obtain impedance spectra for damaged and thermally aged cables. Based on the offset characteristics of peak frequencies, the identification of defect types was achieved. Defect types are identified based on peak frequency offsets, and a differential frequency localization function is used to locate defects with an accuracy of 0.1%, verifying the effectiveness of the method.