Cable Defects Location Method Based on M-sequence with Broadband Impedance Spectroscopy

This paper suggests a method for locating cable defects using M-sequence with Broadband Impedance Spectroscopy (BIS). In this paper, the principles of M-sequence signal generation and noise reduction by cross-correlation algorithm are introduced. A platform has been constructed for the thermal aging and BIS measurement of 10 kV cable samples. Local thermal aging defects with different aging temperatures and times were introduced in the cable samples. The measured BIS data were analyzed using M-sequence and IFFT methods. Results indicate a notable decrease in noise levels in the positioning waveforms generated using the M-sequence method, with a more pronounced reflection peak at the defective point. The peak reflection of a defect caused by local thermal aging in the positioning waveform is bimodal, indicating variations in the distributed capacitance at the specific thermal aging point of the cable. The defect is located at the midpoint of the reflection peak. The reflection peak's amplitude rises with longer aging time and higher temperature.