Analysis and Diagnosis of Shielded Cable Faults Based on Finite-Element Method and Time-Reversal Time-Frequency Domain Reflectometry

Due to the electrical, thermal, and mechanical stress, the insulating materials of cable undergo a slow aging process in service, which leads to the decline of insulation performance. Besides, friction frequently occurs when the cable is moving or vibrating, which will easily cause mechanical damage including frays and chafes. Both aging and damage will cause the characteristic impedance to change. Therefore, it is of great significance for the safe operation of the cable to analyze the variations of characteristic impedance and to make an effective diagnosis. In this article, a two-dimensional model of the cable containing defects is first built, and the characteristic impedance of the model is calculated by the finite-element method (FEM). Meanwhile, a quantitative analysis of the characteristic impedance under two defect types is carried out. Second, combining the space-time focusing of time-reversal and the time-frequency characteristics of reflectometry, the time-reversal time-frequency domain reflectometry (TRTFDR) is proposed to diagnose the cable faults. Based on the distributed parameters calculated by the FEM, the TRTFDR simulation model is established to study the judgment of different faults. Finally, the validity of this method is verified by experiments.