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Hürth, Germany

Noe M.,Karlsruhe Institute of Technology | Hobl A.,Nexans SuperConductors | Tixador P.,Neel G2Elab CRETA | Martini L.,Ricerca Systema Energetico RSE | Dutoit B.,Ecole Polytechnique Federale de Lausanne
IEEE Transactions on Applied Superconductivity

In recent years many large scale demonstrators and prototypes of superconducting fault current limiters have been successfully developed and tested. Within the European Project ECCOFLOW (www.eccoflow.org), it is the first time that a resistive-type superconducting fault current limiter is developed for two different locations and that a permanent installation is foreseen. The limiter has a rating of 20 kV and 1 kA and will be tested in a busbar and transformer feeder application. The paper summarizes the conceptual design of this innovative limiter and reports in detail about the development of the superconducting limiting elements, their integration into a cryostat and the design of the whole limiter including cooling and grid integration. As a main result it can be summarized that the ECCOFLOW limiter fulfills all requirements according to the two different specifications. Approximately 3 km of 12 mm wide YBCO tape will be used to realize a three phase system. © 2002-2011 IEEE. Source

Obradors X.,Autonomous University of Barcelona | Martinez-Julian F.,Autonomous University of Barcelona | Zalamova K.,Autonomous University of Barcelona | Vlad V.R.,Autonomous University of Barcelona | And 10 more authors.
Physica C: Superconductivity and its Applications

After briefly reviewing the present understanding of the nucleation process of YBCO films, a new approach is presented to enhance the stability of c-axis nucleation in epitaxial chemical solution deposited YBCO thin films derived from TFA precursors. We show that with silver addition to the TFA precursor c-axis nucleation can be reached in a wide range of temperature thus keeping high percolating J c. We argue that silver reduces supersaturation and makes more stable the c-axis nuclei without modifying T c. Additional advantages of silver addition are an enhanced surface smootheness and a reduced porosity of the YBCO films. The second reported topic relates to the discovery of an adverse relationship between percolating J c and YBCO films mesostrain, as determined through X-ray diffraction line broadening. We show that mesostrain is enhanced in processes leading to inefficient strain healing at grain boundaries, for instance annealing times too short or growth temperatures too low. It is suggested that the strained regions at the low angle grain boundaries lead to a weak link behavior which can be microscopically understood on the basis of pair formation prevention, as proposed by the bond contraction pairing model. Source

Hobl A.,Nexans SuperConductors | Goldacker W.,Karlsruhe Institute of Technology | Dutoit B.,Ecole Polytechnique Federale de Lausanne | Martini L.,RSE SpA | And 2 more authors.
IEEE Transactions on Applied Superconductivity

The European project ECCOFLOW aims at a versatile resistive-type superconducting fault current limiter. For the first time, such a device will be tested at two different sites. The project partners have developed a superconducting fault current limiter design based on REBCO tapes with respect to the specifications provided by two hosting utilities. The limiter will operate at 1 kA at a rated voltage of 24 kV, and will be tested in both a busbar and a transformer feeder application. The design started with extensive investigations on the superconductor tape properties, especially with respect to the limitation behavior in all possible scenarios, and subsequent wide-range modeling of its in-grid behavior. The general integrated layout provides a limitation time of up to 1 s. The limiter is cooled using Gifford-McMahon cryocoolers to recondense the evaporated nitrogen. The present status of production and testing will be presented as well. © 2012 IEEE. Source

Elschner S.,Karlsruhe Institute of Technology | Elschner S.,Mannheim University of Applied Sciences | Kudymow A.,Karlsruhe Institute of Technology | Brand J.,Karlsruhe Institute of Technology | And 10 more authors.
Physica C: Superconductivity and its Applications

Within the German project ENSYSTROB a 3-phase resistive fault current limiter for medium voltage applications (12 kV, 533 A rms) was designed, built, tested and installed in the grid for a one year's field test. The superconducting modules are made of YBCO coated conductors and replace the modules of an already successfully tested limiter on the basis of BSCCO 2212 bulk material. The components are multifilar spirals equipped with pairs of 12 mm wide YBCO tapes. The single components were characterized with respect to critical current, AC losses and limitation behavior under all possible operation conditions. The finally mounted limiter was successfully tested with respect to high voltage and limitation according to the standards of the customer. It is now installed and operating in its field test location. Finally we give a first comparison of both materials with respect to the different operational aspects. Source

Elschner S.,Mannheim University of Applied Sciences | Kudymow A.,Karlsruhe Institute of Technology | Fink S.,Karlsruhe Institute of Technology | Goldacker W.,Karlsruhe Institute of Technology | And 5 more authors.
IEEE Transactions on Applied Superconductivity

A new German government funded project for a resistive fault current limiter has started in September 2009 (ENSYS-TROB) and is presented. The consortium includes partners from industry, research centers and utilities. It aims the construction of a 3-phase medium voltage current limiter (12 kV, 800 A) for the protection of the domestic supply in a power plant. A special feature of this application is the presence of large in-rush currents (4100 Ap for 50 ms, 1800 A for 15 s). The superconducting components are bifilar pancake coils consisting of pairs of YBCO-tapes in face to back configuration. Successful limitation experiments on prototype components with prospective currents in the whole range are shown. Also the stability with respect to high voltage could be demonstrated. The AC-losses under normal operation are shown, by simulation and experiment, to be smaller than the heat input of the current leads. The current limiting components are compared with similar elements based on BSCCO 2212 bulk material (Nexans SuperConductors). © 2011 IEEE. Source

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