Assessment of Ageing in the Insulation of HVDC Model Cables under Thermo-electric Stress

International audienceThe assessment of insulating materials regarding space charge features is one important aspect of HVDC cable development. Whereas most of space charge characterization is achieved under relatively short stressing time, it is important to understand if there is an evolution of materials behavior during long time under stresses, including service stresses such as combination of electrical and thermal stresses along with polarity reversal. Our purpose in this communication is to present the implementation of long term ageing tests on crosslinked polyethylene materials in such a way that relevant and valuable information can be gained as a function of stressing time. The designed stress cycle on model cables encompasses maximum fields up to 90 kV/mm at the inner semiconductor and temperature up to 100°C with repetitive grounding or polarity reversal. The stressing time is up to 18 months. The electrical and physicochemical characterizations techniques as well as the first ageing results are presented