Development of a Cable Degradation Diagnosis Method Based on Propagation Constant

This paper presents a frequency-domain approach to quantify cable insulation degradation based on regression coefficients extracted from the propagation constant of the cable model. The resistance, inductance, capacitance, and conductance (RLCG) parameters are determined from the cable’s geometry and dielectric properties. Insulation degradation is then simulated by stepwise increases in conductance, following the reference thresholds specified in IEEE 400 standard. The attenuation and phase constants are regressed to extract first-order coefficients, which are then normalized against anchor values representing normal, warning, and critical states. A unified health index (HI), ranging from 0 to 1, is constructed through sensitivity-based weighting and anchor-locked mapping. Simulation results confirm that the proposed HI index increases monotonically with insulation degradation severity and remains stable across different materials and geometrical configurations. The method provides reproducible thresholds, requires no site-specific calibration, and can be readily extended to field applications for online cable condition monitoring.