The effects of seasonal factors on life and reliability of high voltage ac cables subjected to load cycles

In previous articles by this author, a procedure was set up and validated for life and reliability evaluation of HV cables subjected to the time-varying electro-thermal stress associated with the typical daily cycles of conductor current. In this paper, the procedure is improved to account for the effects of seasonal factors, by taking for every season different daily cycles of cable current, as well as different values of thermal resistivity and temperature of the soil. The procedure is applied to a case-study HVAC XLPE-insulated cable. The results show that the fraction of life and reliability lost by cable insulation is strongly dependent on seasonal factors, in particular on soil resistivity and temperature, and the vast majority of cable life and reliability is lost within the hot (summer) season.