Contents Introduction
In high voltage power cables, traditional paper/oil systems have now been largely superceded by polymeric insulation, notably, polyethylene. However, following their introduction in the early 1960s, many polyethylene-insulated cables failed as a result of the growth of water trees. The solution that was devised to counter this involved the extrusion of a metallic sheath around the core of the cable, such that under normal conditions, water is unable to reach the insulation. Although this is an effective means of providing a water barrier with considerable mechanical integrity, it is also costly and results in bulky cables. An alternative is to replace the traditional metallic sheath with a lightweight, aluminium foil. While this provides an effective water barrier when intact, it does not possess the same mechanical integrityas conventional designs, leaving the cable susceptible to water ingress via any punctures.
