Inter-strand coupling losses in superconducting power cables without coaxial magnetic shielding

This paper deals with computations of inter-strand coupling losses in superconducting power cables with Room Temperature Dielectric (RTD), in which no coaxial shielding of magnetic field is provided. In three-phase circuits, magnetic fields produced by neighbouring phases induce in the third one significant currents through contact resistances between strands, owing to their helical winding around the cable axis with a pitch inversion between each layer. Analytic expressions are first derived for a simple cable model, with only two strand layers (single ''bilayer''), with or without taking internal screening effects into account. The validity Limit of these computations is determined. Then a generalization to a real n-layer is proposed and the development shows that a homogenization procedure can be performed on the radial coordinate, in some specific cases.