The influence of accelerated aging procedures on the correlation of electrical and mechanical properties of LV nuclear power plant cables

This paper presents results of accelerated life tests having the purpose to single out the diagnostic characteristics of electrical and mechanical properties for XLPE low-voltage cables used in nuclear power plants. In this work, XLPE-insulated cables were aged under two different conditions, the first consisting in the simultaneous application of temperature and gamma radiation, the second involving thermal aging followed by irradiation at room temperature. The dielectric response in the frequency range 10^-2-10⁶ Hz was investigated through dielectric spectroscopy, while the degradation conditions of cable insulation was assessed by tensile testing and density measurements. Results show that sequential aging could be ineffective for the purpose of simulating the service insulation ageing, because it can lead to a very limited amount of cable degradation. Simultaneous aging, on the contrary, can affect significantly material properties. In particular, it has been found that the imaginary part of permittivity at 100 kHz could be a suitable aging marker, correlated with the degree of oxidation.