Application of magnesium diboride in saturated core fault current limiters

A fault current limiter (FCL) is a nonlinear device with negligible impedance under normal conditions, which is able to switch to a high impedance state as soon as the current passing through it exceeds a given threshold. Among the various FCL topologies, saturated core fault current limiters have recently reached the demonstration phase in medium- to high-voltage networks. ASG Power Systems has assembled and tested a 36 kV rated saturated core type fault current limiter which uses superconducting solenoids to provide the saturating flux. The evolution and functionality of this implementation will be described here in detail

Thermal treatments for biaxially textured Cu-Ni alloys for YBCO coated conductors

We have studied the thermal treatments necessary to texture Cu-Ni alloys in view of applications as substrate for the YBCO coated conductors. Several alloy compositions chosen in order to avoid magnetism of the tapes have been elaborated by the rolling (RABiTS) method. Analyses of the texture as a function of annealing temperature have been done by X-ray and neutron diffractions, pole figures by EBSD and X-rays. The results show that the annealing temperature is dependant of the alloy composition and must be determined precisely for each composition. Good biaxial textures have been obtained on these cheap alloys

First tests of a 800 kJ HTS SMES

SMES using high critical temperature superconductors are interesting for high power pulsed sources. Operation at temperatures above 20 K makes cryogenics easier, enhances stability and improves operation as pulsed power source. In the context of a DGA (Delegation Generate pour l'Armement) project, we have designed and constructed a 800 kJ SMES. The coil is wound with Nexans conductors made of Bi-2212 PIT tapes soldered in parallel. The coil consists in 26 superposed simple pancakes wound and bonded on sliced copper plates coated with epoxy. The rated current is 315 A for an energy of 814 kJ. The external diameter of the coil is 814 mm and its height 222 mm. The cooling at 20 K is only performed by conduction from cryocoolers to make cryogenics very friendly and invisible for the SMES users. The cooling down has been successfully carried out and the thermal system works as designed. After a brief description of the SMES design and construction, some tests will be presented. From a current of 244 A, the SMES delivered 425 kJ to a resistance with a maximum power of 175 kW.Comment: 5 page

Industrial Cu-Ni alloys for HTS coated conductor tape

Copper rich Cu-Ni alloys have been textured with the RABiTS method in order to get non-magnetic and cost efficient substrates for coated conductor wires. The study is focused on two industrial compositions: Cu55Ni45 (Constantan) and Cu70Ni30. Studies on surface roughness have been done. The effects of annealing conditions (temperature and atmosphere) on the grain boundaries deepness were analyzed. Electrolytic polishing was also applied to improve the surface quality. RX pole figures and micro hardness measurements have been achieved on samples annealed up to 950°C. Attention has been paid to the rolling texture and to the annealing processes. The rolling texture has been found to be mainly copper-type (C, S and B contributions). Beginning of recrystallization occurred between 400°C and 600°C and stabilized between 900°C to 950°C, depending on the nickel content of the alloy. Finally both samples, rolled and annealed under the appropriate conditions, have been characterized. Pole figure measurements gave the global in plane and out of plane disorientations of our samples which are in-plane 7.4° and out-plane (RD) 4.3° for both samples. EBSD maps have shown the details of the distribution and have allowed us to quantify the ratio between cubic {100} and twined {122} orientations

Cooling Considerations for the Long Length HVDC Cables Cryostat within BEST PATHS Project

HVDC cables have been identified as the preferred solution for future pan-European grids for the transmission over long distances of the large power produced by renewable energy farms which are generally located far for the consumption places. The European project Best Paths has been launched to identify the remaining barriers and propose some innovative solutions to achieve such envisioned grids. As superconductivity offers very attractive and efficient solutions vision studies for long-distance superconducting power transmission lines are conducted. The superconducting technology under study is based on the MgB$_{2}$ conductor cooled with one-phase liquid hydrogen. A flexible cryostat with 15 to 25 K core cooling and with additional shield cooling using liquid nitrogen or hydrogen gas is required. For long length cables the limiting parameters are the cryostat heat load and the pressure drop. The calculation results show the interdependencies of the maximum length between neighboring cooling sections with the heat load on shield and core, mass flows and pressure drop, enthalpy change, viscosity, friction factors and cryostat geometry. The calculations are carried out for different fluid options and diameters, and the corresponding results are presented and discussed

Modélisations numériques des pertes en régime variable dans des tubes supraconducteurs

Les pertes AC dans les câbles supraconducteurs générées par un environnement variable dans le temps impactent la cryogénie et donc la faisabilité industrielle des dispositifs supraconducteurs. Nexans est aujourd'hui sur le point de réaliser des fils cylindriques supraconducteurs pour des câbles de forte puissance. Aucune étude numérique n'a pour l'instant porté sur le calcul des pertes AC dans un ou plusieurs tubes. Cet article présente les étapes de création d'un modèle de calcul de pertes à l'aide d'un logiciel d'éléments finis pour une nouvelle géométrie :tube ou cylindre supraconducteur. La non-linéarité des formules E-J ainsi que les problèmes de convergence ont été traités par l'implémentation d'une formulation en H pour la résolution numérique. Les résultats ont été comparés aux formules analytiques. Dans le but de vérifier l'exactitude du modèle, une série de mesures expérimentales a aussi été réalisée sur un ruban supraconducteur industriel.</p

SCARLET – A European Effort to Develop HTS and MgB2 Based MVDC Cables

Superconducting cables have been proven in a variety of pilot projects and utility installations, demonstrating several of their advantages, including compact size and low energy losses, which can make the technology economically attractive for certain applications. It is clear though that different applications impose different requirements and challenges, but also opportunities for the cables. An interesting application is high-power DC transfer at medium voltage (MVDC). The high-current capability of the superconductor allows for a reduction in voltage while maintaining or increasing the power transfer level. In this way, one MVDC superconducting cable can replace one or more conventional high-voltage DC cables. In the European project SCARLET (Superconducting cables for sustainable energy transition), two types of MVDC cables will be developed, one based on HTS and one on MgB2 materials. Additionally, protection requirements will be considered, including the development of a modular DC fault current limiter for 10 kA. A main motivation for the development is the elimination of costly high-voltage converter stations when going from high to medium voltage, e.g., for offshore wind power plants. Another feature is the combined hydrogen and electricity transmission from generation sites to industry or mobility end users. This paper describes the superconducting MVDC cable concept as well as the main challenges and research needed to develop and type test the cables.SCARLET – A European Effort to Develop HTS and MgB2 Based MVDC CablesacceptedVersio

Application of magnesium diboride in saturated core fault current limiters

A fault current limiter (FCL) is a nonlinear device with negligible impedance under normal conditions, which is able to switch to a high impedance state as soon as the current passing through it exceeds a given threshold. Among the various FCL topologies, saturated core fault current limiters have recently reached the demonstration phase in medium- to high-voltage networks. ASG Power Systems has assembled and tested a 36 kV rated saturated core type fault current limiter which uses superconducting solenoids to provide the saturating flux. The evolution and functionality of this implementation will be described here in detail

Dichotomic Decision Optimization for the Design of HVDC Superconducting Links

Superconducting links are an innovative solution for bulk power transmission, distinguished by their compact dimensions, high efficiency and small environmental footprint. As with any new technology field, there is a large amount of design possibilities for such links, each of them having a profound impact on the system configuration. For instance, changing the material can imply a change in the working temperature from 20 to 70 K and has consequences on the maximum link length. This article presents the dichotomic decision possibilities for the optimized design of a high-power superconducting link, focusing on some of the key components of the cable system. The complex design optimization process is exemplified using the European project Best Paths, in which the first 3-gigawatt-class superconducting cable system was designed, optimized, manufactured, and successfully tested