High repair cost is one of the main reasons that the use of synthetic dielectrics like XLPE is more conservative for submarine cables than for underground cables. The repair time is 3 times as long for submarine cables as for underground cable.
Detection of weak points is challenging on extruded insulation and the problem increase with the voltage and the insulation thickness. Therefore the need for knowledge on how different contaminants impact the electrical properties under demanding conditions is str ong. Organic and oxidised particles can be generated at different processing steps and such contaminants can reduce the electrical life of the cable. Data on how oxidised particles impact mechanisms like water treeing, electrical treeing and thermal degra dation are lacking in the literature.
The main categories for the research and development work will be to identify, to reproduce, to introduce and to detect oxidised particles. Actual contaminants will be determined and classified from granules detecte d by pellets checking systems used by Nexans and DOW. Short and long term properties of the contaminants will be examined on artificial contaminants. These contaminants will be introduced in model cables. Then the impact on demanding conditions like high electrical stress, high service temperature and dynamic mechanical stress will be determined.