Nexans (Germany)

The SuperRail project is the world’s first installation of a high-temperature superconducting (HTS) cable system for commercial operation in a railway electric grid. The aim is to increase traffic capacity and achieve national low-carbon emission targets by strengthening the railway grid. The project involves the development, manufacture, installation, and operation of an HTS DC cable system at Paris’ Montparnasse railways station. Due to limited available rights-of-way, conventional cable technologies are not feasible, making HTS cable technology the only viable solution for supplying power to the railway tracks in such a dense urban area. Two HTS cables are installed in parallel. Each one can carry 2.25 MW and support fault conditions of 67 kA for 100 ms due to their direct connection to the transmissions grid. In order to validate the HTS cable system design and the accessories performances, a complete 35-m HTS cable type test loop was installed and tested at the SNCF Railway Test Agency. This paper shows the results, including dielectric performance, current carrying capacity and fault current tests. The HTS cable system successfully passed all the tests, and the design has been fully qualified.

We describe how the contribution of crystallographic texture to the anisotropy of the resistivity of polycrystalline samples can be estimated by averaging over crystallographic orientations through a geometric mean approach. The calculation takes into account the orientation distribution refined from neutron diffraction data and literature values for the single crystal resistivity tensor. The example discussed here is a melt-cast processed Bi2Sr2CaCu2O8+δ (Bi-2212) polycrystalline tube in which the main texture component is a <010> fiber texture with relatively low texture strength. Experimentally-measured resistivities along the longitudinal, radial, and tangential directions of the Bi-2212 tube were compared to calculated values and found to be of the same order of magnitude. Calculations for this example and additional simulations for various texture strengths and single crystal resistivity anisotropies confirm that in the case of highly anisotropic phases such as Bi-2212, even low texture strengths have a significant effect on the anisotropy of the resistivity in polycrystalline samples.

The optimization of a HTS cable design with respect to AC-losses is of crucial importance for the economic viability of the respective concept. However the experimental determination of AC-losses is not straightforward since for short cable samples the distribution of current among the super-conducting tapes is mainly determined by the contact resistances of the individual tapes. The resulting inhomogeneous current distribution definitely falsifies the results. To solve this experimental problem we present a new experimental technique. The setup is a 2m-long three phase concentric cable model for which, within each phase, the superconducting tapes (up to 30) are connected in series. The Cu-braid backwards conductors were assembled in a rotational symmetric cage type arrangement, such that their self fields at the cable cancel. If experimental peculiarities of this setup, as the strong inductive coupling between the phases and the suitable positioning of the voltage contact leads, are correctly taken into account, the currents can be controlled independently and the electrical properties of the cable can be measured unambiguously. In this paper preliminary results are presented. The work is part of the German government funded cable project AMPACITY (1 km / 20 kV/ 2 kA)

In recent years significant progress has been made in the development of high temperature superconducting (HTS) power devices, in particular cables and fault current limiters. Several field tests of large scale prototypes for both applications have been successfully accomplished and the technologies are getting closer to commercialization. In this paper the German AmpaCity project will be introduced and its objectives will be described. Furthermore, the conceptual design of the HTS cable system and the major developments which have been achieved so far, as well as the current status of the project will be reported. (4 pages)

This paper deals with the magnetic properties of bulk high temperature superconducting cylinders used as magnetic shields. We investigate, both numerically and experimentally, the magnetic properties of a hollow cylinder with two axial slits which cut the cylinder in equal halves. Finite element method modelling has been used with a three-dimensional geometry to help us in understanding how the superconducting currents flow in such a cut cylinder and therefore how the magnetic shielding properties are affected, depending on the magnetic field orientation. Modelling results show that the slits block the shielding current flow and act as an ‘entrance channel’ for the magnetic flux lines. The contribution of the slits to the total flux density that enters the cylinder is studied through the angle formed between the applied field and the internal field. The modelled data agree nicely with magnetic shielding properties measured on a bulk Bi-2212 hollow cylinder at 77 K. The results demonstrate that the magnetic flux penetration in such a geometry can be modelled successfully using only two parameters of the superconductor (constant Jc and n value), which were determined from magnetic measurements on the plain cylinder.

Underground high temperature Superconductor (HTS) power cables have attracted extensive interest in recent years due to their potential for high power density. With funding support from the United States Department of Energy (DOE), the world's first transmission voltage level HTS power cable has been designed, fabricated and permanently installed in Long Island Power Authority (LIPA) grid. The HTS cable was successfully commissioned on April 22, 2008. In 2007, a new DOE Superconductor Power Equipment (SPE) program to address the outstanding issues for integrating HTS cables into the utility grid was awarded to the current project team (LIPA II). The goal of the LIPA II is to develop and install a replacement phase conductor manufactured using AMSC's second generation wire. In addition to the replacement of the phase conductor, the team will also address the outstanding components development necessary for full scale integration into a power grid including integral management of thermal shrinkage of the cable conductor, optimization of the cryostat design to mitigate the implications of potential cable damage, and the development and demonstration of a field splice in the operating utility grid and modular higher efficiency refrigeration system. This paper will report on the progress and status of LIPA II program. In addition, in-grid operation experience of existing 1G HTS Power cable is presented.

Nexans experience in developing all CSD processes for coated conductors with the YBCO/CGO/LZO/Ni-5% W RABITS architecture is summarized. The chosen CC architecture has a principal disadvantage that the next layer only clones, but more often deteriorates the out-of-plane texture of the previous layer (in average by ~ 20% for LZO). Depending on the quality of RABITS, this may increase the amount of grain boundaries (GBs) not transparent for the supercurrent close to the percolation limit for the current-breaking path, which explains low and poorly reproducible Jc. Modifying the buffer architecture by introducing CGO seed layer suppresses deterioration of the out-of-plane texture. Another approach, extending the range of acceptable grain misorientations by selective doping YBCO GBs with Ca is shown not possible using the current MOD-TFA process because of decomposition of initial Y123 to disordered Y124 and Y247 during pyrolysis of the second MOD layer. Possible ways of further development are discussed.

Applicability of 1 GW class hybrid energy transfer line of hydrogen and electricity is investigated in this report. Hydrogen refrigeration station is placed on every 10 km of the unit section. The rated current is 10 kA, and operation voltage is 100 kV (+ 50 kV and −50 kV for ground). Delivery capacity of the liquid hydrogen is 100 tons per day. The HETL consists of the SC cable, electrical insulation layer, channel for liquid hydrogen, inner corrugated tube, vacuum space for thermal insulation and outer corrugated tube. The special multi-filamentary MgB2 wire was developed to improve the Ic performance against bending strain. When the pressure of liquid hydrogen increases, boiling temperature of liquid hydrogen becomes high. Pressurization of liquid hydrogen enables to expand operation temperature region of the MgB2 cable, and to absorb the head loss of the installation route. To obtain the operation temperature from 20 K to 25 K, pressure of liquid hydrogen from 0.4 to 0.6 MPa was chosen. When the heat leak into the liquid hydrogen is 1.0 W/m (expected value), the temperature at the outlet becomes 21.8 K. It was confirmed that this HETL is one of the attractive energy transportation system which combines hydrogen fuel and SC power transmission.

The US Department of Energy is currently funding the design, development and demonstration of the first long length, transmission level voltage, cold dielectric, high temperature superconductor power cable. The cable is designed for permanent installation in the long island power authority (LIPA) grid and will be able to carry 574 MVA at a voltage of 138 KV. The project is led by American Superconductor and the team is comprised of Nexans, Air Liquide and LIPA. This paper will describe the goals of the project, an overview of the cable design, refrigeration system and site design. It will also include the statistics of the HTS wire manufactured for this project, the results of the qualification testing on a prototype 30 meter cable and the preparation work of the refrigerator system. The cable will be completed and put into service in the LIPA grid in 2007.

Efforts to increase critical current density (Jc) and engineering current density (JE) in round multifilament Bi‐2212/Ag wires have included studies of the effect of precursor composition. Variations in the cation ratios in the precursor have a number of effects on conductor processing and properties, including the melt temperature, the relative sharpness of the melting event, the crystallization behavior including secondary phase formation and growth, and the peak Jc and JE attainable. Multifilamentary wires and dip coated tapes made from four precursors with different cation ratios were studied using an experimental matrix of heat treatments that systematically varied melt temperature, cooling rate, annealing temperature, and annealing time. Average Jc and JE were determined for all samples. In addition two different levels of Ag additions were given to two of the cation ratios, and subjected to the same heat treatment matrix. The results showed a strong dependence of microstructure and Jc on cation ratio and heat treatment parameters, but not obviously on Ag addition in multifilament Bi‐2212/Ag wires. The highest JE of 1580 A/mm2 (Jc of 6140 A/mm2) at 4.2 K, 0 T and JE of 312 A/mm2 (Jc of 1160 A/mm2) at 20 K, 2 T were obtained in 0.81 mm wire with the precursor composition of Bi:Sr:Ca:Cu = 2.17:1.94:0.89:2.00.