Curvularia lunata drives biodeterioration of PVC secondary cable insulation involving surface colonization, moisture retention and chemical deterioration.

Microbial degradation of cable insulation materials is a critical issue affecting the reliability of power systems. In this study, metagenomic analysis was employed to reveal the microbial community structure on contaminated substation cables, identifying Curvularia lunata as a dominant fungal species in high-voltage environments. Subsequently, a specific strain, Curvularia lunata B3, was isolated and identified for further investigation. To assess its specific impact on insulation performance, artificial inoculation experiments were conducted on secondary cable samples. Multi-dimensional characterization techniques, including SEM, WCA measurements, halogen moisture analysis, FTIR, XPS, and LCR digital bridge testing, were utilized to evaluate material degradation. The results demonstrated that C. lunata colonization caused significant surface erosion, characterized by the formation of holes and furrows. This physical damage was accompanied by a marked decrease in hydrophobicity, with the water contact angle dropping from 88.30 ± 0.79° to 78.27 ± 1.27°, and a gradual increase in water content to approximately 1.2% over 60 days. Chemical analysis revealed that microbial activity induced oxidation and dechlorination of the PVC insulation, evidenced by the reduction of C-Cl bonds and the emergence of oxygen-containing functional groups. These physicochemical alterations significantly compromised the electrical insulation of the cables, as evidenced by a marked decrease in series resistance (Rs) and an increase in series capacitance (Cs). This study elucidates the mechanisms of fungal erosion on cable insulation and provides a scientific basis for developing targeted protective strategies in power systems.