Temperature- and Time-Resolved Gas Release Coupled with Degradation of an Overheated Medium-Voltage Cable PVC Outer Jacket

Overheating of polymeric cable materials is a major contributor to insulation aging, electrical failure, and fire risk in power systems, particularly in densely installed urban underground cable corridors where heat dissipation is limited and early-stage defects are difficult to identify. Although gas-detection approaches are promising for non-invasive overheating monitoring, their practical value depends on identifying material- and lay-er-specific volatile products and clarifying how their release evolves with temperature and time. Herein, volatile products released from the PVC outer jacket of a YJV22-8.7/15 kV-3 × 185 medium-voltage cable were investigated using headspace gas chromatography–mass spectrometry (GC-MS). Temperature- and time-dependent evolution was estimated for selected marker species, and the associated degradation behavior was correlated with chemical/structural and electrical changes using ATR-FTIR, KPFM, and dielectric measurements. The number and observed headspace levels of organic components increased substantially with severe overheating, reaching more than 20 dominant components at 200 °C. 2-Ethylhexanol (2-EH) was observed across the studied range and reached approximately 300 × 10−6 (volume fraction) at 200 °C for 60 min while remaining at or below approximately 50 × 10−6 at temperatures up to 140 °C. Benzene was observed mainly at severe overheating, whereas DOTP was first observed at 140 °C among the tested conditions, reaching approximately 40 × 10−6 at 140 °C for 5 min and exceeding 300 × 10−6 under more severe conditions. KPFM showed surface roughness increasing from 7.70 to 43.39 nm, and the real permittivity increased by up to 13.9% at 50 Hz. These results provide a temperature- and time-resolved headspace dataset for the tested cable outer jacket and relate its organic-gas profile to surface and dielectric changes.