Use of 3D-FEM Tools to Improve Loss Allocation in Three-Core Armored Cables

Loss allocation through analytical expressions in three-core lead-sheathed armored cables is challenging due to the complex geometry of this type of cable, commonly employed in submarine energy transmission systems (involving twisted conductors, sheaths and armor). Most of the expressions of the IEC standard 60287 have not been properly adapted for three-core armored cables, leading to inaccurate values for the different losses, so important efforts are currently devoted to improving them. In this work, an improved ultra-shortened 3D finite element model (FEM) is employed for developing an in-depth analysis of the electromagnetic interactions that take place in 6 real cables, being especially focused on those aspects that are not considered in the IEC standard. As a result, important conclusions are derived regarding the losses in conductors and sheaths, which introduce different corrections for improving the accuracy of the IEC expressions. The new formulation is then employed to propose a simplified experimental armor loss allocation procedure. This is virtually applied through the FEM tool to more than 700 cable configurations, showing a remarkable improvement in the loss allocation over the IEC standard and previous experimental procedures.