Condition Assessments of 50-Year Old Low Voltage Power Cables

This paper presents the results of laboratory condition assessments conducted for six low voltage power cables removed from service after 50 years of operation in an industrial facility. The laboratory work involved an in-depth evaluation of the mechanical, thermal, and chemical properties of the cable insulation polymers using techniques such as elongation at break, oxidation induction temperature, visual and microscope inspections, and Fourier-transform infrared spectroscopy. The results of this testing revealed that four of the six cables exhibited evidence of substantial insulation degradation including poor mechanical properties, significant amounts of cracking, low thermal stability, and high concentrations of chemical compounds that form as a result of age-related degradation. In addition to the condition assessments, a root cause analysis was conducted for two of the four degraded cables to identify the source of the extensive insulation degradation. This evaluation involved laboratory materials characterization and analysis using tests such as scanning electron microscopy with energy dispersive spectroscopy. In addition, an evaluation of the operating lifetime of the insulation polymers in their nominal operating environment was performed. The results of these assessments revealed that the degradation observed in these materials was caused by long-term exposure to the service conditions at the facility.