Typical Defect Study of HVAC Power Cable Through Distortion Analysis of Grounding Current

As the service life increases, the latent defects of power cables gradually become apparent, threatening the normal operation of cable lines. This study simulates two typical defects of power cables under laboratory conditions, the thermal aging and the insulation scratch. The grounding current signals of cable specimens are collected under three defect levels. The Variational Mode Decomposition (VMD), which is improved by the Particle Swarm Optimization (PSO) algorithm, and the Lorentz chaotic synchronous system are both adopted to analyze the grounding current distortion from different dimensions. A correlation has been established between the harmonic characteristics of grounding currents, the graphical features of distortion, and the typical cable defects. The results indicate that the grounding current of thermally aged cables primarily consists of the
$3^{\text{rd}}, 9^{\text{th}}$
and
$13^{\text{th}}$
harmonics, and the dynamic error scatter plot takes the form of a flat ellipse. In contrast, the harmonic content of insulation-scratched cables is generally lower, and the dynamic error scatter plot contains two elliptical lines tangent at the top. This study will provide guidance and reference for the condition assessment and defect determination of power cables.