High T C Superconducting Wire Research Articles

A new benchmark problem for electromagnetic modelling of superconductors: the high-T c superconducting dynamo

The high-T c superconducting (HTS) dynamo is a promising device that can inject large DC supercurrents into a closed superconducting circuit. This is particularly attractive to energise HTS coils in NMR/MRI magnets and superconducting rotating machines without the need for connection to a power supply via current leads. It is only very recently that quantitatively accurate, predictive models have been developed which are capable of analysing HTS dynamos and explain their underlying physical mechanism. In this work, we propose to use the HTS dynamo as a new benchmark problem for the HTS modelling community. The benchmark geometry consists of a permanent magnet rotating past a stationary HTS coated-conductor wire in the open-circuit configuration, assuming for simplicity the 2D (infinitely long) case. Despite this geometric simplicity the solution is complex, comprising time-varying spatially-inhomogeneous currents and fields throughout the superconducting volume. In this work, this benchmark problem has been implemented using several different methods, including H-formulation-based methods, coupled H-A and T-A formulations, the Minimum Electromagnetic Entropy Production method, and integral equation and volume integral equation-based equivalent circuit methods. Each of these approaches show excellent qualitative and quantitative agreement for the open-circuit equivalent instantaneous voltage and the cumulative time-averaged equivalent voltage, as well as the current density and electric field distributions within the HTS wire at key positions during the magnet transit. Finally, a critical analysis and comparison of each of the modelling frameworks is presented, based on the following key metrics: number of mesh elements in the HTS wire, total number of mesh elements in the model, number of degrees of freedom, tolerance settings and the approximate time taken per cycle for each model. This benchmark and the results contained herein provide researchers with a suitable framework to validate, compare and optimise their own methods for modelling the HTS dynamo.

Experimental Test and Numerical Analysis to Estimate Permissible Transport Current Considering Protection of High-Tc Superconducting Tapes in Adiabatic Condition

High-Tc superconducting (HTS) wires have showed good capabilities as an alternative conductor for superconducting magnet. The HTS wires have more current carrying capability within high external magnetic field and its stability against external disturbance is much higher than the low temperature superconducting (LTS) wires. But the HTS wire has slower normal zone propagation (NZP) velocity which makes HTS magnets hard to be protected from unexpected hot spot. This paper presents experimental test and numerical analysis about the relation between transport current and rate of temperature rise in a hot spot. A sample which contained a HTS wire, a heater, and temperature sensor was fabricated and an experimental test on measuring normal zone propagation and temperature of the HTS wire was conducted. A numerical model was also built to estimate transient temperature rise of a winding pack model which was representing practical winding of HTS magnets. The numerical model and its numerical estimation results are expected to be a guideline about designing proper protection technique and operating current for HTS magnets.

Overview of High-temperature Superconducting Power Cable for Practical Use

A High Tc Superconducting (HTS) Cable, which has a conductor with superconducting materials discovered in 1986, has been developed since early 1990s. After 10 and several years, the HTS cable has reached to the stage of evaluation at the real grid. Improvement of the performance and progress on the productivity of HTS wires are enhancing opportunities for commercialization of the HTS cable as well as other HTS applications. Especially in the USA, several demonstration projects of the HTS cable are undergoing in order to strengthen the fragile electric power network. In the Albany project, which is one of them, the 3-in-One type HTS cable was installed in 2006 and the world first operation has been conducted with an actual configuration in the long underground duct.In Japan, a new HTS cable project supported by NEDO has just started in order to study operation, maintenance method and related technologies for operating in the actual grid.This paper describes the position of HTS cable in accord with the history of large capacity power cables, summarizes its prospects and technical problems and introduces various projects in the world.

Normal zone propagation characteristics of the HTS wires by heat energy applied

With the successful commercialization of Bi-2223 powder-in-tube wire, various attempts in the R&D of the high- T c superconducting (HTS) magnets for high magnetic field applications are being implemented actively. Operating temperature of HTS magnet has to be maintained at the designed level but the magnetic energy and mechanical disturbance can cause unstable operational temperature of HTS magnet. Especially, the generated heat energy of inner HTS winding is apt to be accumulated, so the normal region appears in HTS winding. This paper deals with the quenching characteristics of three kinds of selected Bi-2223 wires: the high current density wire (HC-A) and the high strength wire (HS-A) made by AMSC and HTS wire (HW-I) made by Innost. The Innost wire has the highest minimum quench energy (MQE). The high current density wire has the highest normal zone propagation velocity (NZPV).

１００ｍ超電導ケーブル実用性検証試験の概要

Since the discovery of High-Tc superconducting (HTSC) materials, elementary technologies of an HTSC cable system have been developed such as the manufacturing technology of a conductor wound with HTSC wires, cold dielectric properties, and thermally insulated pipes. HTSC cable models have also been constructed to evaluate these technologies. As a next step, new test project of a 100m, 66kV/1, 000A/100MVA class, three-core HTSC cable system, integrating these elementary technologies, are planned to verify the practicability of an HTSC cable system as an actual power system equipment. It is a joint project of Tokyo Electric Power Company and Sumitomo Electric Industries, Ltd., and is being conducted in collaboration with the Central Research Institute of Electric Power Industry. The purposes of this project are to prove newly developed technologies satisfying the requirement as actual deployments, to prove manufacturing abilities and installation technologies, and to conduct long-term current-voltage loading tests. The cable consists of three-core conductors placed in thermally insulated pipes having a vacuum insulation layer between them. Each conductor consists of a copper former, superconducting layers, PPLP/LN2 composite insulating layer, and superconducting shielding layers. The cable is placed at a CRIEPI test yard and is bent into U-shape at its center, partially installed into a duct 150mm in inner diameter. The following tests are scheduled, using this cable system, such as an initial cooling test, continuous rated current-voltage loading tests, load fluctuation tests, cooling cycle test between room temperature and LN2 temperature, and overloading and overvoltage withstand tests. Through these tests, problems are expected to be extracted that may be difficult to foresee in individual part tests for development of an actual level HTSC power cable system.

A high temperature superconducting winding and its techniques

A small prototype unit high T c superconducting (HTS) winding has been made using a Ag-clad (Bi,Pb) 2Sr 2Ca 2Cu 3O 10+x multifilament HTS wire. Research carried out on the HTS winding has addressed the basic concerns of the HTS wire, and consequently the HTS wire can be verified for practical applications.

Novel AC loss measurement of high Tc superconducting long wire

A novel method for AC loss measurement of a long length high T c superconducting (HTSC) wire has been investigated. An 8 m long (Bi,Pb) 2Sr 2Ca 2Cu 3O 10+ x Ag clad multifilament wire was selected to prepare a special sample in which the inductive voltage induced by AC transport currents can be cancelled. Consequently the resistive voltage of the HTSC long wire can be measured. The HTSC sample has been tested at 77 K with AC transport currents up to 3 I c and at various frequencies from 10 Hz to 1 kHz. The loss of the (Bi,Pb) 2Sr 2Ca 2Cu 3O 10+ x Ag clad wire related to its zero field AC transport current characteristics has been obtained experimentally, and results also prove that this method is effective and useful for AC loss measurement of a long length HTSC wire.

Operating principle of a high Tc superconducting saturable magnetic core fault current limiter

An electrical fault current limiter (FCL) designed with a high Tc superconducting (HTS) dc bias winding is described. The winding is prepared by using a Ag-clad (Bi,Pb)2Sr2Ca2Cu3O10+x HTS wire. The limiting behaviour of this FCL is investigated and considered with respect to operation in a 6 kV power system. The results show that the FCL limits fault currents effectively, and is a possible solution for reducing power system fault currents.

(Bi, Pb)2Sr2Ca2Cu3O10+x Ag-clad high-Tc superconducting coil and its magnetic field properties

Abstract A high Tc superconducting (HTS) (Bi, Pb)2Sr2Ca2Cu3O10+x Ag-clad multifilament wire is used to prepare a HTS coil. This anisotropic HTS wire has a strong magnetic-field-dependent critical current. which causes critical-current degradation when used in the form of a coil. The magnetic field behaviour of the HTS coil is studied with respect to its critical current and magnetic field properties. Experiments carried out include magnetic field measurements of the HTS coil. dc magnetic field, ac magnetic field and critical-current ampere-turns when used as a magnetic core bias winding. The magnetic field distribution of the HTS coil is also investigated with a magnetic field analysis program. The experimental results and analysis provide basic information for the design and operation of a HTS coil made from anisotropic HTS (Bi, Pb)2Sr2Ca2Cu3O10+x Ag-clad wire.

Magnetic field properties of Bi-2223/Ag HTS coil at 77 K

High T c superconducting (HTS) (Bi,Pb) 2Sr 2Ca 2Cu 3O 10+ x Ag clad multifilament wire, is used to prepare a HTS coil. Magnetic field behaviour of the HTS coil is studied at 77 K operation. Experiments carried out include magnetic field measurements of the HTS coil, DC magnetic field, AC magnetic field, and critical current ampere-turns when used as a magnetic core bias winding. The magnetic field distribution of the HTS coil is also investigated for use at 77 K with the anisotropic HTS wire. The experimental results and analysis provide basic information for design and operation of a HTS coil made from the present HTS (Bi,Pb) 2Sr 2Ca 2Cu 3O 10+ x Ag clad wire.

The Fabrication of High-TC Superconducting Wires, Tapes and Bulk Conductors

ABSTRACTThe results of a UK-based industrial consortium, aimed at the development of high-Tcsuperconducting wires, tapes and bulk conductors, are reviewed. The powder-in-tube method has been used to fabricate 10's of metre lengths of bismuth-based, Ag-clad, single and multi-filamentary wires. Performance highlights include current densities of 23,000Acm-2 [7A] at 77K; (zero field) for 2223 bismuth-based wire and greater than 105Acm-2 [25A] and 104cm-2 at 4.2K, zero field and 15T, respectively, for 2212-based wire. Ag-backed, 2212, tape-cast conductors have carried currents of over 60A [80,000Acnrr-2] at 4.2K; (zero field). Bulk ceramic processing techniques, sol-gel chemistry and plasma-spraying have also been used to fabricate a range of YBCO and bismuth-based components. Currents in excess of 100A have been carried in bulk 2223 bismuth-based samples at 77K.