Short-term thermal endurance characterization of polymeric cable insulating materials. Use of oxidative stability measurements

In this paper, a method which provides thermal endurance characterization in significantly shorter duration than that required by IEC 216 Standard is presented. The method proposed resorts to measurements of oxidative stability to estimate the activation energy of the degradation process which is deemed to prevail in the range of test and service temperatures, as well as to a conventional thermal life test of suitable length. By this way, slope and location of the thermal endurance line are determined. Comparisons between the results provided by the proposed method and characterizations made according to IEC 216 are presented, referring to the most common insulating materials for HV cables, that is, crosslinked polyethylene and ethylene-propylene rubber. It is shown that, considering different diagnostic properties, both temperature index and halving interval obtained by the proposed method are very close to the values derived by applying IEC 216.