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The use of high temperature superconducting (HTS) materials for power transmission cable applications is being realized in several utility demonstration projects. Tape testing on short-sample cables is conducted to determine the suitability of HTS tapes for use in different cable designs. Testing includes deter- mining the DC critical current, ac loss and overcurrent behavior in a wound cable configuration. The short-sample cable configuration is similar in physical respects, such as winding diameter, winding pitch, application of dielectric, to a practical length cable. With more attention being paid to the short-circuit fault protection, the over-current pulse behavior of the cable will be tested thoroughly. The temperature history of the cable in the radial direction and the re-cooling of the cable will be monitored and compared with a model calculation. This paper describes the testing and results from one such series of tests of a short-sample cable made with copper laminated HTS tapes for use in future projects. [ABSTRACT FROM AUTHOR]

The Ultera/ORNL team have built and tested 3-m and 5-m triaxial cables rated at 3 and 1.3 kA-rms, respectively. The three concentric superconducting phases are made of BSCCO-2223 HTS tapes, separated by layers of cold-dielectric tapes. A copper braid is added as the grounding shield on the outside of the three active phases. Tests of these cables were performed at temperatures ranging from 70 to 84 K. AC loss data reconfirmed the previous result on a 1.5-m prototype cable that the total 3-phase ac loss is about the sum of the calculated ac losses of the three concentric phases. These and other test results of the 1,3 and 3 kA cables will be used to construct a second S-m triaxial cable rated at 3 kA-rms, 15 kV. Preliminary test results supporting this new cable and the associated termination are summarized. [ABSTRACT FROM AUTHOR]

An investigation of the current distribution in a three- phase triaxial superconducting cable is underway to study phase imbalances under steady-state operation and to assist in the construction of a transient model to study operational impacts of the cable in a power grid. The triaxial cable consists of three superconducting concentric phases inside a copper shield, with each phase composed of multiple layers of BSCCO tape wound helically in opposite directions. Current distribution among the phases of the cable is determined by using an electric circuit (EC) model containing the self and mutual inductances resulting from both axial and tangential fields. An ac loss term is also included in the model. Building on the EC model, a lumped cable model is used to investigate the effects of the triaxial cable on a power grid when faults are applied to the system. Cable lengths practical for future applications (∼40 km) are considered. [ABSTRACT FROM AUTHOR]

The impact of Ni-5at%W substrates on ac loss and inductance of HTS cables was examined. Two 1.2-m prototype cables were made with stainless steel laminated BSCCO tapes and were wound on a 25.4 mm diameter former. Each cable consisted of two layers of 15 BSCCO tapes wound at opposite lay angles and has an estimated critical current of 3000 A at 77 K. One cable had four additional layers of 4.8 mm wide Ni-Sat % W tape co-wound with the BSCCO tapes to simulate a commercial second generation IITS cable. The Ni-5at%W tapes had the same width as the BSCCO and a thickness of 50 microns. Through the use of a coaxial copper ground, the cable inductance was measured at room temperature and liquid nitrogen (77 K) using high frequency rf measurement techniques. Experimental results for the cable inductance and ac loss were compared against numerical calculations to determine the significance of the Ni-5at%W substrate contribution. Results indicate that inductance and ac loss changes from these substrates in commercial cables should be small. [ABSTRACT FROM AUTHOR]

In support of second generation HTS conductor development for ac applications, transport ac loss measurements were conducted on a series of RABiTS-processed YBa2Cu3Ox (YBCO) coated conductors with different nickel alloy substrates and copper stabilization at 77 K. Each 1-cm wide sample had a critical current density between 1.0 and 2.0 MA/cm² and had either a 75 μm Ni-5at%W substrate or a 75 μmNi-10%Cr-2%W substrate with 2-μm nickel overlayer. Samples with copper stabilization had a 50-μm strip of 1 cm wide copper laminated to a 3-μm thick silver coated YBCO sample. Using thermal and electrical measurement techniques, the ac losses were measured as a function of the peak current ratio at 60 Hz. Experimental results were compared to the Norris thin strip and elliptical models to determine the influence of the ferromagnetic loss of the substrate and the copper lamination on the total ac loss. [ABSTRACT FROM AUTHOR]