Lifetime estimation of medium voltage cables in wet environments

An analysis of the time-breakdown strength characteristics of cables with various kinds of insulations aged under essential service stressors (electrical stress, thermal stress, and water) is reported. Specifically, attention is given to MV cables with synthetic insulation and sheath installed in locations where, during service, water can enter into the insulation. The analysis revealed the main causes of cable aging. Structural properties seem to be responsible for the degradation of the insulation. A novel method for selection of insulating material, making it possible to tailor insulation with respect to required life expectancy, is presented. Methods for testing and lifetime estimation of full-size cables are given