Sequence Impedance Calculation in Three-Core, Double-Layer Armored Power Cables: Accurate and Efficient Modeling Approaches

The increasing deployment of three-core (3C) double-layer armored (DWA) submarine power cables necessitates accurate and computationally efficient methods for sequence-impedance calculation. Existing analytical formulations are limited to single-layer armor (SWA) configurations and rely on simplifying assumptions that can restrict their applicability, especially at high frequencies. In this paper, a computationally efficient three-dimensional finite-element method (3D FEM), based on an extension of the short-twisted periodicity concept, is proposed and adopted as the reference solution. The method explicitly captures the helical geometry of both armor layers, longitudinal magnetic field components, and frequencydependent skin and proximity effects. In parallel, a 2.5D method of moments -…