Electromagnetic Response of DC Type-II SC Wires Under Oscillating Magnetic Excitations

Type-II superconductors are expected to be extensively used in the designing of dc power grids due to their reduced use of space, high transport current capability, and nearly zero resistive losses. Nevertheless, these systems will have to share the right of way of the currently installed ac network, reducing the costs of development associated with the superconducting (SC) cables without the need of increasing the right of way. Under the theoretical framework of the critical state model and the numerical solution of Maxwell equations in the magneto quasi-steady approach, in this paper, we present a comprehensive study of the effects of applying an ac transverse magnetic field to a type-II SC wire of rounded cross section it utilized for direct current power transmission. Our numerical results can be used as a practical benchmark for determining the minimal losses and magnetic impact of dc SC lines subjected to external oscillating magnetic fields. The local dynamics of the flux front profile of current density, the resulting density of magnetic flux, the total magnetic moment of the wire, and the curve of ac losses for different conditions of dc current and transverse AC magnetic field are presented. Our results are compared with simplified analytical approaches, demonstrating the importance of considering the concomitant action of dc current and ac magnetic field by the use of numerical methods, mainly at low values of applied magnetic field relative to the intensity of transport current and the full penetration profile of current density.