The Adaptability Comparison between BIS and RCS for Power Cable Diagnosis

Frequency domain reflectometry (FDR) is widely used in the power cable diagnosis and localization. There are mainly two technical routes for this method: broadband impedance spectrum (BIS) and reflection coefficient spectrum (RCS). In order to clarify the adaptability of the two main techniques for power cables, this paper focuses on comparing those two main techniques in terms of the principles and diagnostic effects. First, by comparing the methods principles, it is found that both methods are based on the principle of signal folding and reflection, but the core variables and mathematical transformations are different: BIS is a global quantity derived from RCS, which increases the computational redundancy; RCS directly reflects the reflection strength of the signal and is relatively simple to compute. In addition, the diagnostic effectiveness is analyzed. Both methods can provide accurate localization for shorter lengths and capacitive defects. BIS provides the better estimate the positions of the start and end of the defect for longer length, thereby estimating the length of the defect. RCS shows better applicability for localization of inductive defects. The study results provide the theoretical basis for selecting appropriate FDR techniques in different application scenarios, and offer new perspectives for cable maintenance and fault diagnosis.