Hysteresis Losses Analysis in 2G HTS Cables

The Russian Scientific R&D Cable Institute is involved in many projects on R&D high-temperature superconducting (HTS) power cables including those made of modern second generation (2G) HTS wires. Evaluation of ac losses and methods for the reduction of the ac losses are important in the design of the cables. A fine experimental technique has been developed and implemented to measure ac losses in representative cable models with a length of ~5 m. However, only calculation can provide ac loss prediction in cases when it could be difficult to make measurements. Thus, we need a comprehensive simulation model to calculate ac losses. In HTS cables made of 2G wires, the main ac loss is a hysteresis loss, which only numerical simulation can predict for full-size 2G cables. We develop a finite-element method model to solve the electromagnetic problem for the calculation of ac losses. The model takes into account the strong nonlinear resistivity of the HTS materials, the hysteresis behavior of the magnetic substrate, the nonuniformity of critical current density across the tapes of the cable, and the possible ferromagnetism of a substrate. The model also takes into account any geometrical aspect of the 2G HTS cables. The details of the model and comparisons of calculations with our measurements of the ac losses are presented.