Changes in insulation condition of dry cured XLPE cables over a 6-year period

The service experience with dry cured XLPE cables is good and their internal failure rate is much lower than is the case for the older steam cured cables. However, water tree aging also occurs in dry cured cables, unless the insulation is protected against moisture by water barriers. Since 2001, a series of diagnostic measurements has been carried out on in total 58 dry cured XLPE cable sections without water barrier. The cables were installed in 10 kV to 20 kV networks in the period between 1979 and 1996. The objective of these measurements has been to get an assessment of the insulation condition and the rate of change in insulation condition for these cable sections and the results are presented in the paper.