One of the challenges with cables in deep waters is the high topside tension caused by the weight of the cable and the risk of overloading the conductor. Keeping the cable weight as low as possible is therefore a key parameter to reach deep waters. One way to reduce the cable weight is to replace the copper conductor in the cable with an aluminium conductor.
When using aluminium conductor in a wet design XLPE cable (no water barrier) there is a risk of local corrosion of aluminium that forms porous structures in the inner semiconductor, leading to accelerated ageing of the XLPE insulation. This phenomenon is known as Stress-Induced Electrochemical Degradation (SIED). SIED has so far only been seen in service-aged cables, which had been exposed to external mechanical damage causing water penetration in the conductor. It has also been found that the deterioration of the inner semicon is more severe when the cable is mechanically stressed. In order to learn more about the risk of SIED in a wet XLPE cable an extensive ageing test program has been carried out. This paper summarizes the results from this testing.