Kinds Of Conductors Research Articles

Effects of bending and torsion behavior on Ic degradation and microstructure of ReBCO coated conductors

The performance degradation caused by bending and torsion is crucial for the application of superconducting coated conductors. In this study, we investigated the critical current (Ic) degradation of four kinds of conductors under bending and torsion. With 1 mm resolution, the critical bending radius of STT236μm (Shanghai Superconductor Technology) conductors is 6–7 mm, and that of STT380μm conductors is 4–5 mm, and that of SAMRI (Suzhou Advanced Materials Research Institute) conductors is 4 mm. With better bending tolerance, SAMRI conductors also have a less critical twist pitch of 82–87 mm. Considering the residual thermal stress during fabrication, the longitudinal strain corresponding to 5 % Ic degradation is 0.484 %. Further, to figure out the failure mechanism of coated conductors, the micromorphology of the ReBCO layer was observed after chemical etching. The crack distribution not only verified the cause of Ic degradation under mechanical behaviors, but also helps to develop a crack-based Ic prediction method.

Study on Galloping Characteristics of Large-section Carbon Fiber Composite Core Conductor

This paper establishes the finite element galloping model of large-section carbon fiber composite core conductor, and selects three kinds of large-section conductors to analysis on galloping characteristics, i.e. carbon fiber composite core large-section conductor JLZ2X1/F2A-1660/95-492, 1,250mm2 large-section aluminum conductor steel reinforced JL1/G2A-1250/100-84/19 and 1,520mm2 aluminum conductor aluminum-alloy reinforced JL1X/LHA1-1040/550-487, thus obtaining galloping amplitudes and galloping tension values of three kinds of conductors. In addition, this paper compares the galloping characteristics of such three conductors, thus obtaining galloping characteristics of large-section carbon fiber composite core conductor. The research achievement provides technical support for anti-galloping design of carbon fiber conductor on the power transmission line.

A numerical CFD study of the wind flow distribution around the overhead conductors

The CFD numerical model of smooth circular conductor and stranded conductor are established, and the flow field distributions of these two kinds of conductors in different wind speed and diameter are analysed by using DES method. The study shows that: the numerical simulation method is applicable to the vortex-shedding simulation of smooth circular conductor and strand conductor; with the increase of wind speed, the vortex shedding frequency of transmission conductor is accelerated, the space distance of the vortex increases, the vortex street becomes irregular, and the length of the trailing vortex is significantly longer; as the diameter of the conductor increases, the sizes of wake zone and vortex are larger, and the vortex shedding frequency becomes slower; in the same diameter and inlet wind speed, the resistance and vortex street effect of the smooth circular conductor are stronger than the strand conductor.

Delamination Strengths of Different Types of REBCO-Coated Conductors and Method for Reducing Radial Thermal Stresses of Impregnated REBCO Pancake Coils

An impregnated pancake coil is composed of a REBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7-δ</sub> (REBCO)-coated conductor, a polyimide tape, and epoxy resin, so that a radial thermal stress is generated in the winding by their anisotropic thermal contraction when the coil is cooled from room temperature to 77 K or less. If this radial stress locally exceeds the delamination strength of the REBCO-coated conductor under transverse tensile stress, the coil will be degraded. Although it is important to determine the exact delamination strength of the REBCO-coated conductor to fabricate an impregnated coil that does not suffer from degradation, the delamination strengths reported until now have shown considerable variation due to the evaluation methods used. Therefore, we propose a new method for evaluating the delamination strength using small epoxy impregnated test coils, since the radial stress depends on the ratio of inner to outer diameters regardless of the coil size. The delamination strength can be obtained by investigating the ratios of inner to outer diameters that do not result in degradation. In this paper, the delamination strengths of three types of REBCO-coated conductors made with different manufacturing processes and having different configurations were evaluated. This method showed that a conductor laminated with copper plates had higher delamination strength than the other two kinds of conductors. In addition, impregnated single pancake coils whose inner diameter was 50 mm and whose outer diameter was 100 mm were fabricated using the three types of REBCO-coated conductors. Degradation was avoided in all coils by dividing the coils into a number of winding parts in the radial direction according to the delamination strength of the conductors.

Interaction of conductor with polymeric materials (XLPE/EPR) at partial discharges

A novel investigation into the behavior of the interface between an insulating material and a conductor subjected to sinusoidal stimulus is presented. Both copper and aluminum wires are used in the windings of electrical machines and also as power cable conductors. During in-service operation, partial discharges (PD) may be initiated in the insulation systems. The paper presents experimental results showing the interaction of different kinds of conductors and dielectric materials on the mechanism of partial discharges in the insulation system. The dedicated test setup is designed to perform experiments with various electrodes, with special focus on copper. Two kinds of specially prepared insulation samples were tested, ethylene propylene rubber (EPR), cross-linked polyethylene (XLPE). These insulating materials were subjected to a sinusoidal stimulus at predefined time intervals and were exposed to PD action. The paper comprises the results of PD measurements and microstructural observations performed by means of scanning electron microscope (SEM) coupled with energy dispersive analysis (EDS). The morphological and elemental analysis reveals the interaction of conductor on polymeric material degradation. Two zones were distinguished, migration and erosion. The migration of atoms of electrode material into the dielectric substrate due to PD activity was observed.

Design study of superconducting coils for the fusion DEMO plant at JAERI

A design study of the TF coil for the fusion DEMO plant at JAERI is in progress. A major issue is to estimate the maximum fields generated by the TF coils for three tokamak options and two conductor options. Three tokamak options are proposed varying the aspect ratio and the role of the CS coil. Two kinds of conductors using advanced superconducting materials are candidates for the TF coils: Nb 3Al and high temperature superconductor (HTS). In order to evaluate achievable magnetic fields, a simple method was adopted to calculate mechanical properties. The estimated maximum fields are 17–20 T by the HTS conductor and 16–17 T by the Nb 3Al conductor. There is a possibility of a 0.7 T enhancement using grading of Nb 3Al winding.

Study on dependence of AC transport current losses in YBCO‐coated conductors on distribution of critical current density and n value

AbstractWe measured AC transport current losses in three kinds of thin‐film YBCO‐coated conductors made by different processes. The results showed that the loss characteristics were different and that some of the conductors did not follow the Norris strip model which is generally believed to well explain the loss characteristics of YBCO conductors. In the paper, an analytical model in which distribution of critical current density and n value of the conductor are taken into consideration is proposed to describe the AC transport current loss characteristics more generally than the Norris strip and elliptical models. It is shown that the analytical model explains well the measured loss characteristics of the three kinds of conductors. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 152(2): 26–38, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20056

Effects of Particle Shape and Microstructure on Effective Nonlinear Response**The project supported by National Natural Science Foundation of China under Grant No. 19774042

We consider a binary granular composite medium, in which two materials have high-order nonlinearities. The effect of particle shape on effective nonlinear response (ENR) is investigated by assuming all the particles to be shaped as uniaxial ellipsoid. We discuss two types of arrangements of particles: 1) parallel axes (Case I); 2) random axes (Case II). During the process of numerical calculation, one component material is assumed to be linear, and two kinds of conductors are assumed to be at high conducting contrast. We find that: 1) the shape effect on ENR is possibly strong; 2) the enhanced ENR can even be obtained by choosing particles of appropriate ellipsoidal shapes; 3) the ENR enhancement predicted by Case I is much stronger than that by Case II.

架空送電線表面の超撥水処理によるコロナ騒音低減

The purpose of this study is to clarify the wetting property of conductors for the reduction of audible noise generated from transmission lines during rain. This report shows that the audible noise from a super-water-repellent-surface conductor is the lowest by comparative results of artifi-cial rainfall tests using four kinds of conductors with different wetting properties.

Stability of bronze processed (Nb,Ti) 3Sn superconducting wire reinforced and stabilized with CuNb in-situ composites

The stability of two kinds of conductors, CuNb ( Nb,Ti) 3 Sn and Cu ( Nb,Ti) 3 Sn has been studied in order to obtain basic information for the future compact design of high field superconducting magnets using a (Nb,Ti) 3Sn conductor stabilized with a high strength-high conductivity CuNb in-situ composite. From the results of experiments and numerical analyses on minimum quench energy (MQE) and quench front propagation velocity, it was found that there is no substantial degradation of the stability in the conductor stabilized and reinforced with CuNb in-situ composite, suggesting a possibility of the future compact design of a high field superconducting magnet using a CuNb ( Nb,Ti) 3 Sn conductor.

FEM modelling of the magnetic, thermal, electrical and mechanical transient phenomena in linear induction launchers

Finite Element Method transient modelling is used to study the behaviour of Linear Induction Launchers. A coupling between electrical and magnetic equations allows one to model all kinds of conductors as well as connections with electrical circuits. A local remeshing around the moving part is applied at the beginning of each time step in order to take into account the displacement of the conductors. Moreover, a thermal coupling enables one to take into consideration the the main characteristics of materials. >

Model coil for the International Thermonuclear Experimental Reactor (ITER) magnet systems

The model coil program for the ITER EDA includes the manufacture and testing of one Central Solenoid (CS) model coil and one Toroidal Field (TF) model coil, and test facility preparations. The CS model coil has an inner diameter of 1.6 m and produces a full field of 13 T. The TF model coil is race-track shaped with an outer dimension of 3 m/spl times/4 m. It will be tested in conjunction with an LCT coil to simulate mechanical load conditions. Different kinds of conductors can be tested as inserts to be placed in the bore of the CS model coil. Two facilities at JAERI and KfK can provide ITER-relevant conditions for testing the model coils and inserts. The model coil program will validate the ITER magnet design and the manufacturing feasibility. >

The effect of Ti conduit on the critical current in (NbTi)/sub 3/ Sn cable-in-conduit conductors

The authors investigated the effect of Ti conduit on the critical current in (NbTi)/sub 3/Sn cable-in-conduit conductors in comparison with stainless steel and copper-nickel alloy conduits. Ti has a coefficient of thermal expansion closely matching (NbTi)/sub 3/Sn and is expected to prevent the compressive thermal prestrain introduced in (NbTi)/sub 3/Sn filaments. As samples, two kinds of conductors were prepared, one consisting of seven (NbTi)/sub 3/Sn strands and the other of 36 (NbTi)/sub 3/Sn strands. The (NbTi)/sub 3/Sn strands produced by a bronze process had a diameter of 1.0 mm and a copper ratio of 2. The experimental results indicated that the critical current density in conductors with a Ti conduit and void fraction in the range of 5-46% nearly matched that of a single strand. From these results, Ti appears to be attractive as a practical conduit material for (NbTi)/sub 3/Sn cable-in-conduit conductors.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Effects of Local Conditions on Radio Direction-Finding

THE methods used for finding the direction in which Hertzian waves are incident at a radio station have now attained a high accuracy, the maximum error being well under one degree. It does not follow, however, that the methods give the direction of the sending station to the same accuracy. The waves sent out may have suffered reflections from all kinds of conductors before they reach the receiving station. Hence, especially at night-time, the apparent direction generally differs very appreciably from the true direction. A preliminary report on this subject, communicated by the Radio Research Board, was read on November 8 to the Radio section of the Institution of Electrical Engineers by Messrs. Smith-Rose and Barfield. They classify the causes of distortion under two heads: First, those which are vaguely classed as night effects and occur between sunset and sunrise. They are sometimes as large as 20°, and little is known as to their cause. Hence in practice radio-direction finding is restricted to day-time. The second causes of error are those due to conducting substances in the immediate neighbourhood of the search coil. In one experiment a metal tube 50 ft. long, semicircular in cross-section, and of radius 3 ft. 6 in. was used. When the coil was at a distance of 15 ft. from either end errors became appreciable, and when placed 15 ft. inside the tube the error was as great as 29°.