Semi-quantitative analysis of photoluminescence in thermoelectrically aged cables: II-analysis of a population of cables

A set of thermo-electrically aged cross-linked polyethylene-insulated HVAC cables has been characterized by photoluminescence measurements. The photoluminescence spectra have been decomposed into a set of seven bands representing the response of three contributions to the emission: bulk cross-linked polyethylene emission, fluorescence of the antioxidant used in the semi-conducting screens of the cables, peaking at 400 nm, and an emission at 540 nm that has been correlated to the yellowing of the cables observed during thermal ageing. From the analysis of the cable radius dependence of these emissions, it is shown that traces of the antioxidant can be found in the 14 mm-thick insulation after less than 5000 h of ageing at 90 degC. The emissions related to the antioxidant and to yellowing appear dependent on the cable manufacturing process.