Ac loss reduction of multilayer superconducting power transmission cables by using narrow coated conductors

The ac loss characteristics of coated conductors are dominated by the magnetic field component normal to their superconductor layer. Multilayer cables as well as monolayer cables consisting of 4 mm-wide coated conductors (named 4 mm cables) and those consisting of 2 mm-wide coated conductors (named 2 mm cables) were designed, and numerical electromagnetic field analyses were performed in their cross sections to calculate their ac losses. Trapezoidal lateral critical current density J(c) distributions with shoulders as well as uniform ones were assumed in coated conductors for the analyses. The former models the degraded J(c) near the edges of coated conductors. In the case of the monolayer, the calculated ac losses of the 2 mm cables were comparable to those of the 4 mm cables. In the cases of the multilayers, the calculated ac losses of the 2 mm cables were obviously less than those of the 4 mm cables. The degraded J(c) near the edges of coated conductors more seriously affects the ac loss characteristics of the 2 mm cables than those of the 4 mm cables. However, even if we consider the influence of the degraded J(c) near the edges of coated conductors, 2 mm-wide coated conductors are more profitable than 4 mm-wide coated conductors in multilayer cables from the viewpoint of ac loss reduction.