Improved Three-Region Moisture Migration Model for Calculating the Ampacity of 220 kV Submarine Cables Buried in Tidal Flats

The accurate calculation of current-carrying capability (ampacity) in submarine cables is essential for ensuring their safe operation. This paper proposes an improved three-region finite element (FEM) model to accurately calculate the ampacity of 220 kV three-core AC submarine cables buried in tidal flats, with a specific focus on moisture migration effects. First, the impact of different soil thermal resistivity coefficients on the critical temperature location was thoroughly investigated. Based on the observed characteristics of critical temperature changes, a novel three-region submarine cable ampacity calculation model that incorporates moisture migration was developed. The study further examines the influence of varying external soil thermal resistivity, burial depth, and air temperature on the ampacity. The results reveal that soil thermal resistivity significantly influences the position of the critical temperature point, which shifts farther from the cable center as the thermal resistivity increases. The proposed improved three-region model more accurately simulates the impact of actual soil moisture migration on the cable temperature field by finely dividing the thermal domain around the cable. This model demonstrates superior accuracy and applicability compared to the IEC 60287 standard calculation methods. This research provides a robust theoretical foundation for accurately calculating the ampacity of submarine cables in tidal flat environments, which is crucial for ensuring their safe operation and extending their service life.