Semi-quantitative analysis of photoluminescence in thermoelectrically aged cables: I-identification of optical signatures

Photoluminescence measurements have been carried out along the radius of the insulation of un-aged and thermo-electrically aged HVAC cables. A specific emission, with maximum at 400 nm has been isolated in the emission spectrum of cross-linked polyethylene insulation in the vicinity of the semi-conducting screens. Complementary measurements on lab-compounded samples were carried in order to unravel the nature of the emitting species. It is shown that the antioxidant ¿or its derivatives- used for the semi-conducting screens are at the origin of this emission and exhibit significant diffusion within the bulk of the insulation. The evolution of the shape of the photoluminescence spectra with thermal ageing is presented and a procedure for decomposing emission spectra into the contributing elementary processes is proposed.