Correlation of electrical and mechanical properties in accelerated aging of LV nuclear power plant cables

Abstract

This paper presents the results of mechanical and electrical tests carried out to assess the condition of XLPE and EPR low-voltage cables installed in nuclear power plants. Cable samples underwent accelerated aging under simultaneous thermal and gamma-radiation stresses. In order to obtain significant results in a reasonable time, the dose rates were higher than the operation values, so that diffusion-limited oxidation could occur. Electrical measurements were performed through dielectric spectroscopy (frequency range: 10−2–106 Hz), while the degradation state of cable insulation was assessed by tensile testing and density measurements. Results on XLPE insulation show that elongation at break and electrical properties are not correlated when diffusion-limited oxidation strongly affects tensile testing and, in this case, the correlation with density is preferable. EPR-based insulation, more homogeneously aged, presents a good correlation between electrical and mechanical properties, as well as density.