A Novel Approach for Design of DC HTS Cable

High temperature superconducting (HTS) cable is one of important apparatus in future smart-grid. Direct current (DC) HTS cable can provide secure and reliable transmission of electric power at the gigawatt level with several hundreds of kA and kV. Since the magnetic field of cable seriously degrades the critical current of HTS superconductor and then the current capacity, modern power converters often introduce alternating currents (AC) at other frequencies even filters reduce the magnitude of those ripple currents which resulting into ac loss since systems used to convert AC to direct current (DC) produce some current variations which are usually at frequencies of multiple power frequency. In order to reduce this loss, unlike the conventional uniform current design in AC HTS cable, a novel approach is proposed for minimizing the loss as small as possible by adjusting the inductive reactance of each layer so that the ratios of AC current amplitude to critical current are always same in layers. The magnetic field distribution and critical current are simulated by finite element method (FEM). The calculations show that the new approaches can reduce ac loss, improve efficiency, which are potential for DC current transmission HTS cable application.