Water penetration in the insulation of medium-voltage cables

This paper presents further results on the insulation water content of different types of medium voltage extruded cables under simulated field conditions. The goal is to evaluate the amount of water penetration in the insulation when the cables are thermally cycled. Cables are XLPE or TRXLPE insulated, with or without a jacket, steam or dry cured. Conditioning of the cables was performed in a water tank, at 90°C maximum outside conductor temperature, 1×U_o, applied voltage and no water in the strands. After 2-3 years of conditioning, the results indicate that thermal cycling leads effectively to water ingress in the TRXLPE cable insulation, but to a much greater level for the unjacketed one. On the other hand, the steam and dry cured unjacketed XLPE insulations show an opposite behavior