Predicting failure of dynamic subsea cables by electrical insulation breakdown due to water treeing

Paper in proceeding, 2023

The study presents numerical models and a methodology that can be used to study and simulate the growth of water trees in the insulation materials under a combination of cyclic electrical stresses and mechanical stresses (cable motions-induced). A fracture-mechanics-based model is presented that combines the effect of these stresses to determine the growth rate of water tree defects and the service life of the insulation materials around a conductor. A study case with two dynamic power cables installed between a wave energy converter and a hub is used to demonstrate the methodology for different sea state conditions. The results show that the cable fails significantly earlier when motion-induced mechanical stresses and electrical stresses are taken into account compared to when only the mechanical stresses were considered. A sensitivity analysis for selected material parameters is also presented to highlight the factors that significantly influence the cable service life prediction.