Combustion characteristic evolution and degradation mechanism of finished fire-resistant cables exposed to different ageing conditions

Abstract

The safe operation of power system relies heavily on the fire-resistant and mechanical properties of cables, whose degradation behaviors under different ageing conditions remain a serious concern. The combustion characteristics evolution of finished cables under thermal, hygrothermal, and salt spray ageing conditions was explored, and potential degradation mechanisms were clarified by different analytical methods. The results indicate that the adverse influence of hygrothermal environmental condition on finished cable is the largest, including a decrease by 29.6 % in elongation at break, an increase by 52.4 % in total heat release, an increase by 145.8 % in maximum specific optical density, and a reduction by 16.0 % in limiting oxygen index value. The degradation mechanism of the finished cable shows that the main causes of performance degradation are the migration and decomposition of substrate, antioxidants, flame retardants, and plasticizers in the finished cable sheaths. This work highlights the key role of environmental factors in performance degradation of cables, and provides important implications for the design of high-weatherability cables and the evaluation of service cables.