Inter-Strand Coupling Losses in Superconducting Power Cables Without Coaxial Magnetic Shielding

(Received 4 June 1996, revised 19 September 1996, accepted 20 September 1996)

Abstract
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.