Characteristics Of Conductors Research Articles

How to measure the current–voltage characteristics of Ohmic conductors and superconductors

Abstract A comparison between two different techniques useful to measure the current–voltage (I–V) characteristics of conducting materials or devices will be presented, suitable for an undergraduate laboratory devoted to the electrical measurements. First, I–V curves of linear resistors with known nominal resistance are measured by using the simplest version of a DC method and an AC method, in order to settle the experimental procedure. Then, nonlinear I–V curves of a superconductor are measured with the same procedures at different temperatures down to 77 K.

Correlation between Ionic Conductor Characteristics and Ionotronic Pressure Sensory Performance

Correlation between Ionic Conductor Characteristics and Ionotronic Pressure Sensory Performance

Overvoltages caused by direct lightning strokes to a hybrid overhead line

This paper presents an analysis of the overvoltages caused by direct lightning strokes to a hybrid overhead line with 138 kV, 13.8 kV, and 220 V circuits. The primary focus is on medium voltage line overvoltages and their dependence on key parameters, including ground impedance, soil resistivity, stroke current front time, conductor characteristics, lightning channel impedance, insulator capacitance, conductors' sags, and tower surge impedance. Using specific models for the transmission tower and high-voltage insulators, validated through laboratory tests and EMTP simulations, critical currents are determined for varying soil resistivity and impulse impedances. The analysis confirms the line robust performance against stroke-induced backflashovers.

MEASUREMENT OF ELECTRICAL CONDUCTIVITY AND RESISTIVITY OF CU-NB18% MICROCOMPOSITE CONDUCTOR AND ITS WELDED JOINT

Systems generating strong magnetic fields are widely used in modern fundamental and applied research as well as in the most innovative industrial processes. These devices generate magnetic fields that reach 5–100 T and the conductors are subjected to a huge Lorentz force, so the conductor material must be extremely strong (UTS ≥ 700 MPa) and have a good specific electrical conductivity (IACS ≥ 60%). Since traditional conductors such as copper, aluminum, gold, and silver cannot withstand such loads, microcomposite materials have been developed that are characterized by such high strength and good specific electrical conductivity. This paper reviews the specific electrical conductivity and specific electrical resistance characteristics of conductor and factors affecting them, methods of measuring these electrical characteristics as well as properties of Cu-Nb18% microcomposite conductor. This paper also describes the methodology for measuring the specific electrical conductivity and specific electrical resistance of the Cu-Nb18% microcomposite conductor solid and with welded joint (welded by using butt welding). The comparison of application possibilities of used methodologies and obtained characteristics was carried out.

Current Flow Simulation of Assembled Conductors for Field Coils of Liquid Hydrogen-Cooled High-Temperature Superconducting Generator

High-temperature superconducting (HTS) generators that functions in combination with a hydrogen gas turbine have the potential to reduce CO2 emissions in Japan. The system can realize zero-emission power generation, and it requires no refrigerator and has almost no cooling costs by fully using the cold energy of liquid hydrogen. The ultimate goal is to commercialize a 600 MW-class liquid hydrogen-cooled HTS generator that requires a 6 kA-class assembled conductor with an outer diameter of approximately 6 mm that can conduct 6 kA at 20 K and 5 T. A technical challenge in applying assembled conductors to the field coils of generators is realizing the interlayer current distribution during steady-state operation and quick-response excitation. A conductor with four layers of 12 wires wound on a 5 mm-diameter former was experimentally and numerically studied, and the current distribution was examined. Similar waveforms were numerically obtained when the terminal resistance of each layer was set to 5/90/60/40 nΩ/m. Such variations in the terminal resistance have a slight effect on the transport characteristics of long conductors.

Full-Wave 3-D Transient Analysis With Method of Moments and Numerical Laplace Transform Including Resistive Non-Linear Elements

Methods based on both time ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> )-domain and frequency ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> )-domain have been used for electromagnetic transient (EMT) analysis using both circuit-theory and field-theory approaches. Methods based on circuit theory are fast and convenient but may become inapplicable to many engineering problems due to simplifications such as the transverse electromagnetic assumptions. Moreover, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> -domain-based techniques rely on approximate methods to account for frequency dependence, which is an essential characteristic of electric conductors, equipment and soil environment. In this paper, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> -domain solutions obtained from the method of moments (MoM) discretization of the electric field integral equation (EFIE) are converted to <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t-</i> domain using the numerical Laplace transform (NLT) by means of post-processing. This circumvents the need to formulate the EFIE and MoM based on the complex frequency which would be required for their application to conventional NLT. Hence, existing MoM implementations can be used to perform a full-wave 3-D EMT analysis for a wide range of power system applications. Examples include energizations of 3-D power system networks with fast and non-vanishing excitations such as step functions, as well as modeling non-linear elements using the piecewise linear approximation. Results from experimental measurements, finite-difference <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> -domain method, and EMT-type software confirm the validity of the proposed method for power system transients in the range of microseconds down to nanoseconds.

RKKY Interaction in Spin Valve Structure with LaAlO&lt;sub&gt;3&lt;/sub&gt; Spacer

RKKY interaction is an indirect interaction between localized magnetic moments mediated by conduction electrons. RKKY exchange interaction is mostly found in multilayer involving conductors as the non-magnetic spacer. However, recent experiment shows that LaAlO3 spacer can intermediate long-range exchange interaction even though it is an insulator. Here we study the mechanism of RKKY interaction in LaAlO3. To study the effect of charge transfer, we perform a density functional theory (DFT) approach to obtain the band structure of LaAlO3 with charge doping. Undoped LaAlO3 has an indirect band gap around 3 eV with peak valence at R symmetry point and lowest conduction point at Γ point. We show that the conducting characteristic arises from Fermi energy shifts via charge doping. By adding charge doping, we show that LaAlO3 can have conductor characteristics, in agreement with the charge transfer experiment on LaAlO3. The spin-polarized conduction electron is measurable as additional magnetization of the system. Furthermore, the conducting LaAlO3 is able to mediate RKKY interaction in spin valve structure.

Inflection point temperature characteristics of carbon fiber composite core conductors

Carbon fiber composite core conductor is a new construction, which is new overhead transmission times the capacity of the conductor. Transmission line times the capacity of the transformation project has great potential for exploration, but due to the short time put into actual operation, the research is relatively weak, and cannot accurately assess its characteristics, therefor resulting in the further promotion of carbon fiber conductor application is limited. In this paper, based on the geographical characteristics of carbon fiber conductors in actual operation, a set of" inflection point temperature" model for carbon fiber conductors is built, measuring the stall distance L, height difference angle β and initial temperature t0 of carbon fiber composite core conductor. So based on the stall distance L, height difference angle β and initial temperature t0 to calculate the carbon fiber composite core conductors, the theoretical basis at the inflection point temperature, which is for the further study of the arc sag characteristics of the multi-capacity conductor can be made.

Aerodynamic Characteristics Analysis of Iced Conductor Based on BP Neural Network

Major disasters and losses would be caused by the galloping of transmission lines. The basis for studying the galloping mechanism of transmission lines is to analyze the aerodynamic characteristics of iced conductors. The wind tunnel test is a traditional way to obtain the aerodynamic coefficients of an iced transmission line under wind load. Due to the high cost and long duration of wind tunnel tests, an experimental method based on machine learning to predict aerodynamic coefficients is proposed. Here, the steady and unsteady aerodynamic coefficients of an iced conductor under different parameters were obtained by wind tunnel test, and then the aerodynamic coefficients of the iced conductor under different parameters were predicted by machine learning. The aerodynamic coefficients of each iced conductor varied with the angle of wind attack by the wind tunnel test. The Den Hartog and Nigol coefficients determined based on the aerodynamic coefficients obtained by machine learning and wind tunnel test are in agreement. The results show the feasibility of the machine learning prediction method.

Predicting novel atomic structure of the lowest-energy Fe n P13–n (n = 0–13) clusters: A new parameter for characterizing chemical stability

A series of novel atomic structure of lowest-energy Fe n P13–n (n = 0–13) clusters via density functional theory (DFT) calculations and an unbiased structure search using Crystal structure AnaLYsis by Particle Swarm Optimization (CALYPSO) code. Our research results show that the global minimum geometry structure of neutral Fe13–n P n (n = 0–6) clusters tend to form cage structures but the lowest-energy Fe13–n P n (n = 7–13) clusters are gradually evolution from a cage structure to a chain shape geometric structure. Their geometric structure should responsible for the raise of binding energy from Fe7P6 to P13 clusters rather than chemical components. This is completely different from a linear relation of the binding energy with chemical components in our previous research for Cu n Zr13–n (n = 3–10) clusters (J. Mol. Liq. 343 117603 (2021)). Hence, in order to characterize the global chemical stability of target cluster, we proposed a new parameter (jyq = η/χ) that the chemical hardness of isolated cluster is used to be divided by its electronegativity. One of the biggest advantages of this parameter is successful coupling the ability of a resistance to redistribution of electrons and the ability to attract electrons from other system (such as atom, molecular or metallic clusters). Moreover, it is found that the P13 cluster shows typical insulator characteristics but the Fe12P1 shows typical conductor characteristics, which phenomena can be attributed to the remarkable delocalized and localized electrons in Fe12P1 and P13, respectively. In terms of nearly-free-electron mode, we also found that the number of electrons on Femi level (N(E F)) are obviously tended to toward a lower value when Fe was replaced gradually with P from Fe13 to P13, and a non-magnetic can be observed in Fe13, Fe2P11, Fe1P12, and P13 that mainly because their perfect symmetrical between spin-up and spin-down of density of states of electrons.

Numerical Simulation Analysis on the Lateral Dynamic Characteristics of Deepwater Conductor Considering the Pile-Soil Contact Models

It is important to accurately assess the interaction between the conductor and the soil to ensure the stability of the subsea wellheads during deepwater drilling. In this paper, numerical simulations were carried out to study the lateral dynamic bearing capacity of the conductor considering different contact models between the conductor and the soil. In particular, the contact surface model and contact element model were selected to study the dynamic behavior of pile–soil under a transverse periodic load. On this basis, the influence of the bending moment, the wellhead stick-up, the outer diameter (O.D.) of the conductor and the wall thickness (W.T.) of the conductor, as well as the physical parameters of the soil on the dynamic bearing capacity are discussed in detail. Analysis results show that the lateral deformation, deflection angle and von Mises stress calculated by the contact element model are greater than those calculated by the contact surface model. The maximum value of the lateral deformation and bending moment of the conductor decrease with the O.D. and W.T. of the conductor, and the cohesion and internal friction angle of the soil. However, the maximum value of the lateral deformation and bending moment of the conductor increase with the wellhead stick-up. Both the vertical force and the soil density have a negligible effect on the lateral behavior of the conductor. This study has reference value for the design and stability assessment of subsea wellheads.

Numerical Evaluation of the Transient Thermal Stability of No-Insulation Pancake Coils Wound With a REBCO-Coated Conductor With Some Defects

We have been developing large-diameter (m-class) no-insulation (NI) REBCO coil systems for applications in areas, such as medical cyclotrons and high-magnetic-field whole-body magnetic resonance imaging (MRI). NI coil technology can achieve both high thermal stability and current density, which have an in-verse relationship. Our previous studies revealed that the application of NI winding technology can allow a coil to continuously operate even when some parts of the coil windings are degraded. Accordingly, by applying the NI winding technology, the use of REBCO-coated conductors with defects or degradation, that is, coil production that allows for variations in conductor characteristics, can result in reduced costs. In this study, the transient thermal stability of NI pancake coils wound with a REBCO-coated conductor with one or more defects was analyzed and evaluated numerically. The conditions for stable operations in a coil with defects were clarified using turn-to-turn contact electrical resistance and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_OP/I_C</i> ratios as parameters. In addition, we evaluated the possibility of establishing a monitoring technology to detect the state of health of the coil by observing changes in the voltage at both ends of the coil to see if any new deterioration has occurred.

AC Loss Calculation and Analysis of Hollow Conductor for Doubly Salient Brushless DC Generator

The hollow conductor has attracted attention in variable reluctance machines (VRMs) working in harsh environment due to its good heat dissipation performance. The abundant harmonic content of the magnetic field in the slot of VRM and the complex structure of the hollow conductor make ac loss characteristics of the hollow conductor complex. Accurate and fast ac loss calculation is necessary to optimize the efficiency of VRM and provide the basis for thermal design. The doubly salient brushless dc generator (DSBLDCG), as the VRM, is analyzed in this article. First, the ac loss of the hollow conductor under a uniform alternating magnetic field is modeled numerically. The loss characteristics of hollow conductor in DSBLDCG are obtained by combining the analytical model and the simplified finite element (FE) model. Second, the refined FE model of DSBLDCG with the hollow conductor winding is established to verify the proposed method, and the influence of different structural parameters and operating conditions on the ac loss of the hollow conductor is also analyzed. Finally, the ac loss test experiment is designed for experimental verification.

Superionic conductor Ag2Se modulated CoSe2 nanosheets prepared via monometallic cation release for efficient pH-universal water electrolysis into hydrogen

Superionic conductors regulated transition metal chalcogenides are the newly emerged electrocatalyst in water electrolysis into clean hydrogen and oxygen. However, there is still much room for the development of structural design, electronic modulation and heterogeneous interface construction to improve the overall water splitting performance in pH-universal solutions, especially in alkaline and neutral mediums. Herein, using β-cyclodextrin (β-CD) and citric acid (CA) organics with abundant hydroxyl (–OH) and carboxyl (–COOH), a special Ag2Se nanoparticles-decorated CoSe2 flower-like nanosheets loaded on porous and conductive nickel foam substrate (Ag2Se-CoSe2/NF) was successfully constructed by a new method of monometallic cation release of coordinated cobalt. The Ag2Se phase exerts the nature characteristics of superionic conductors to modulate the morphological and electronic structures of CoSe2 as well as improve its conductivity. The generated rich active interfaces and abundant Se vacancy defects facilitate numerous active sites exposure to accelerate the hydrogen ion transport and charge transfer. Compared to the single-phase Ag2Se/NF-8 and CoSe2/NF, the prepared Ag2Se-CoSe2/NF-8 with a two-phase synergistic effect achieves an outstanding pH-universal electrocatalytic hydrogen production performance by water electrolysis, as evidenced by a lower overpotential (60 mV, 212 mV and 85 mV vs RHE at 10 mA cm−2 for pH = 0.36, 7.00 and 13.70, respectively). Only a voltage of 1.55 V at 10 mA cm−2 is required to implement the overall water splitting in an alkaline electrolyzer. This work provides significant guidance for the future designation and practical development of transition metal chalcogenides with superionic conductors applied in the electrocatalytic field.

Quantum Flicker Noise in Atomic and Molecular Junctions.

We report on a quantum form of electronic flicker noise in nanoscale conductors that contains valuable information on quantum transport. This noise is experimentally identified in atomic and molecular junctions and theoretically analyzed by considering quantum interference due to fluctuating scatterers. Using conductance, shot-noise, and flicker-noise measurements, we show that the revealed quantum flicker noise uniquely depends on the distribution of transmission channels, a key characteristic of quantum conductors. This dependence opens the door for the application of flicker noise as a diagnostic probe for fundamental properties of quantum conductors and many-body quantum effects, a role that up to now has been performed by the experimentally less-accessible shot noise.

[36-5-3] Stabilizer에 따른 2세대 고온 초전도 선재의 전기적 열화특성

2G High temperature superconducting(HTS) conductors are usually considered as appropriate superconductors for a superconducting coil to develop an applied superconducting apparatus such as a superconducting fault current limiter(SFCL), a superconducting cable, and a superconducting accelerator with high voltage or high ramping-up rate condition. The electrical degradation characteristics of HTS conductors due to electrical breakdown should be taken into consideration because high electric field intensity induced by high operating voltage or rapid ramping-up rate can affect the dielectric stability. In this study, the electrical degradation characteristics of 2G HTS conductors with different metal stabilizers made by SuNAM Co., Ltd. are analyzed and compared through dielectric experiments. As results, the most appropriate type of a 2G HTS conductor is recommended to manufacture superconducting apparatuses with a high voltage or rapid ramping-up rate condition.

Recent Progress in Conjugated Conducting and Semiconducting Polymers for Energy Devices

Advanced conductors (such as conducting and semiconducting polymers) are vital building blocks for modern technologies and biocompatible devices as faster computing and smaller device sizes are demanded. Conjugated conducting and semiconducting polymers (including poly(3,4-ethylenedioxythiophene) (PEDOT), polyaniline (PANI), polythiophene (PTh), and polypyrrole (PPy)) provide the mechanical flexibility required for the next generation of energy and electronic devices. Electrical conductivity, ionic conductivity, and optoelectronic characteristics of advanced conductors are governed by their texture and constituent nanostructures. Thus, precise textural and nanostructural engineering of advanced conjugated conducting and semiconducting polymers provide an outstanding pathway to facilitate their adoption in various technological applications, including but not limited to energy storage and harvesting devices, flexible optoelectronics, bio-functional materials, and wearable electronics. This review article focuses on the basic interconnection among the nanostructure and the characteristics of conjugated conducting and semiconducting polymers. In addition, the application of conjugated conducting and semiconducting polymers in flexible energy devices and the resulting state-of-the-art device performance will be covered.

Friction factor of a forced-flow cooled HTS subsize-conductor for fusion magnets

Thermal–hydraulic analyses of forced-flow cooled superconducting conductors designed for fusion magnets are typically based on 1-D mathematical models, which demand reliable predictive correlations for the transverse mass-, momentum- and energy transport processes occurring between different conductor components. Friction factor correlations, derived from pressure drop tests or Computational Fluid Dynamics (CFD) simulations of conductor samples, describe momentum transfer. High Temperature Superconductors (HTS) are promising materials to be applied in future fusion magnets, since they offer operating magnets at higher magnetic fields or higher temperatures as compared to the current conductors made of Low Temperature Superconductors (LTS). Various concepts of HTS cables for fusion applications are being developed, characterized and analysed. Recently three concepts of triplet HTS subsize-conductors for a quench experiment have been proposed by KIT. Each of them consists of three twisted CrossConductor (CroCo) strands enclosed in a stainless steel jacket, but they feature different copper stabilizer geometry. In the Option 1 and 2 conductors CroCo strands are contained in copper sheaths of different thickness, whereas in the Option 3 they are embedded in copper profiles with larger contact area. Hydraulic characteristics of such conductors were unknown. Three dedicated short dummy conductors with the geometry identical to Option 1–3 conductors were prepared by KIT to be tested for pressure drop. Option 1 and 2 samples were prepared and characterized earlier. In the present study we report the results of the hydraulic test of the Option 3 conductor, performed using demineralized water at different temperatures, as well as the outcomes of the CFD simulations using the ANSYS FLUENT commercial code. It was observed that the experimental values of friction factor in the turbulent regime are small (close to the respective values predicted by the smooth tube correlation). The friction factors obtained by the CFD simulations agreed with the experimental data within the range of measurement uncertainty. Based on experimental and simulation results we developed a friction factor correlation valid in a very wide range of Reynolds number which could be used in thermal-hydraulic analyses of similar HTS cables.

Numerical Simulation of Galloping Characteristics of Multi-Span Iced Eight-Bundle Conductors

In this article, the numerical model of the multi-span iced eight-bundle conductor is established using the nonlinear finite element method, the galloping of the line under different parameters is simulated, and the tension in the galloping process is analyzed. Based on the aerodynamic characteristics and galloping characteristics of conductors, the galloping modes, frequency characteristics, vibration amplitudes, and galloping orbits of multi-span lines under different wind velocities, span lengths, ice shape, and number of spans are analyzed, compared with those of single-span lines. It is demonstrated that there are differences in galloping characteristics between multi-span transmission lines and single-span lines. Each span of the transmission line is different, so it should be fully considered in the research of galloping prevention and control technology.

Soil impulse ionisation model based on dynamic changes of electric field

Soil ionisation has an important influence on impulse characteristics of grounding conductor. This paper introduced improvements to an existing soil ionisation model considering the influence of electric field on the change of soil resistivity, while soil resistivity is not directly dependent on soil electric field. The validity of improved soil ionisation model was verified by surge response of vertical conductor in uniform soil and horizontally stratified soil. Furthermore, the impulse experiment was carried out on horizontal conductor in soil with finite volumes. Based on experimental configuration, the corresponding calculation model was built, and calculated results were in good agreement with experimental results.