Long-term electrical performance and life model fitting of XLPE and EPR insulated cables

The results of life tests performed on cross-linked polyethylene (XLPE) and ethylene propylene rubber (EPR) cable models are presented and discussed. The performances of the two insulating materials when subjected to electrical stress are compared on the basis of characteristic parameters derived by the best-fitting life models. It is found that while EPR is well described by linear models, XLPE data fit curvi-linear life models, showing tendency to electrical threshold. Hence the fundamental parameter for XLPE characterization is the threshold value, while the voltage endurance coefficient should be used to characterize EPR. Considerations on test and data-processing methodologies, as well as insulation design, point out the criteria to be used for the two models