Performance evaluation and failure mode analysis of a long-term ageing test on HV submarine cables with tree-retardant XLPE insulation and factory joints

The use of TR-XLPE for the insulation of a wet design submarine cable has been a widely adopted design, however CIGRE TB 722 requires a long-term ageing test to qualify wet design insulation. Currently very few information is available in the literature regarding the long-term performance of cable systems combining factory joints and wet design. This paper presents the results of a wet ageing test preformed according to the recommendations of CIGRE TB 722 at 500 Hz in salt water (Regime B). The acceptance criteria were met, no breakdown during the water ageing occurred. In the final AC breakdown test, three samples out of six experienced a breakdown of the insulation above the set target, the remaining reached the testing equipment working limits. KEYWORDS Wet ageing; CIGRE TB 722;TR-XLPE wet cable; inter array cable; factory joints.