Electrical tests of a triaxial HTS cable prototype

Abstract

A high-temperature superconducting (HTS) transmission cable based on the cold-dielectric concept with an HTS shield makes it possible to house all three phases inside a single cryostat without causing large degradation and loss due to magnetic fields generated by the neighboring phases. A further optimization can be realized by making the three phases concentric to each other. No shielding layer is required in such a triaxial configuration. It would be more compact and require only about one-half of the HTS tapes as that of three separately shielded phases. A 1.5-m-long triaxial HTS cable prototype has been fabricated and tested. Each phase consists of two layers of BSCCO-2223 HTS tapes. Electrical tests of the cable included the direct current (dc) V-I curve and alternating current (ac) loss measurements. The ac losses were measured both electrically and calorimetrically. A finite-element thermal modeling was performed to check the calorimetric calibration. Individual phase ac losses indicate good agreement with the monoblock theory. Three-phase ac loss is close to that of the sum of the three individual phases. There is no measurable excess ac loss due to the presence of the other concentric phases. A total three-phase ac loss of about 1 W/m was measured at the design operating current of 1250 A.