Current Distribution Investigation of a Laboratory-Scale Coaxial Two-HTS-Layer DC Prototype Cable

A laboratory-scale dc HTS prototype cable has been built and tested. The cable consists of two layers of HTS YBCO tapes with lengths of 1 m. In order to investigate the current distribution among the two HTS layers, the dc measurement was first performed to the cable wound with only the inner HTS layer in advance of the measurement of the completed cable with both layers. The contact resistances relevant to each HTS layer obtained from the measurement are considered as constant parameters to obtain the current of each HTS layer. It turns out that the nonuniform current distribution among each layer in the dc condition mainly results from the contact resistance with operating current less than the cable critical current and tends to become uniform when the operating current increases toward the cable critical current. A modified 2-D H-formulation, which takes into account the voltage drop due to the joint parts of the cable termination, has been applied to simulate the current distribution of the cable. A good consistency is obtained between the experimental and numerical modeling results.