Current-carrying Core Research Articles

Thermal protection implementation of the contact overheadline based on bay controllers of electric transport traction substations in the mining industry

The article presents the principle of thermal protection of the contact overheadlineand substantiates the possibility of practical implementation of this principle for rail electric transport in the mining industry. The algorithm for the implementation of modern digital protection of the contact overhead line as one of the functions of the controller is described. A mathematical model of thermal protection is proposed, which follows from the solution of the heat balance equation. The model takes into account the coefficient of the electrical networktopology, as well as the coefficient of consumption of the current-carrying core of the cable, which determines the reduction in the conducting section from contact erosion and the growth of oxide films. Corrections for air flows are introduced when receiving data from an external anemometer, via telemechanics protocol. The mathematical model was tested by writing a real thermal protection program in the C programming language for the bay controller, based on the circuitry of which is the STM32F407IGT6 microcontroller for the microcontroller unit. Verification tests were carried out on a serial bay controller in 2020. The graphs for comparing the calculated and actual values of temperatures, with different flow rates of the current-carrying conductor of the DC cable, are given. To obtain data, telemechanics protocols IEC 60870-104 and Modbus TCP, PLC Segnetics SMH4 were used.

Neural Network Multistage Method for The Forecasting Electrical Insulating Materials Characteristics

The solution to the problem of non-destructive monitoring of thermal processes in insulating materials is shown. The main configuration parameters of the artificial neural network are determined. A mathematical model and architecture of a neural network for the forecasting thermal fluctuation processes are developed. The architecture of a neural network with a consistently distributed structure is synthesized. A forecasting technique is proposed and functions are obtained for assessing the long-term permissible heating values of the cable current-carrying core insulating material. Temperature monitoring will allow to monitor both the condition and the throughput of the lines.

ELECTROMECHANICAL TRANSIENT PROCESSES DURING SUPPLY VOLTAGE CHANGING IN THE SYSTEM OF POLYMER INSULATION COVERING OF THE CURRENT-CARRYING CORE OF ULTRA HIGH VOLTAGE CABLES

Aim. The article is devoted to the analysis of the electromechanical transient processes in a system of three frequency-controlled electric drives based on asynchronous motors that control current-carrying core motion, as well as to the study of the effect of such processes on the modes applying three-layer polymer insulation to the current-carrying core. Technique. The study was conducted based on the concepts of electromechanics, electromagnetic field theory, mathematical physics, mathematical modeling. Results. A mathematical model has been developed to analyze transients in an electromechanical system consisting of three frequency-controlled electric drives providing current-carrying core motion of ultra-high voltage cables in an inclined extrusion line. The coordination of the electromechanical parameters of the system drives has been carried out and the permissible changes in the supply voltage at the limiting mass while moving current-carrying core of ultra-high voltage cables with applied polymer insulation have been estimated. Scientific novelty. For the first time it is determined that with the limiting mass of the current-carrying core, the electromechanical system allows to stabilize the current-carrying core speed with the required accuracy at short-term decreases in the supply voltage by no more than 27 % of its amplitude value. It is also shown that this system is resistant to short-term increases in voltage by 32 % for 0.2 s. Practical significance. Using the developed model, it is possible to calculate the change in the configuration and speed of the slack current-carrying core when applying polymer insulation, depending on the specific mass of the current-carrying core per unit length, its tension at the bottom, the torque of the traction motor and the supply voltage to achieve stable operation of the system and accurate working of the set parameters.

Global Solar Free Magnetic Energy and Electric Current Density Distribution of Carrington Rotation 2124

Solar eruptive phenomena, like flares and coronal mass ejections(CMEs) are governed by magnetic fields. To describe the structure of these phenomena one needs information on the magnetic flux density and the electric current density vector components in three dimensions throughout the atmosphere. However, current spectro-polarimetric measurements typically limit the determination of the vector magnetic field only to the photosphere. Therefore, there is considerable interest in accurate modeling of the solar coronal magnetic field using photospheric vector magnetograms as boundary data. In this work, we model the coronal magnetic field for global solar atmosphere using a nonlinear force-free field(NLFFF) extrapolation codes implemented to a synoptic maps of photospheric vector magnetic field synthesized from Vector Spectromagnetograph (VSM) on Synoptic Optical Long-term Investigations of the Sun (SOLIS) as boundary condition. Using the resulting three dimensional magnetic field, we calculate the three dimensional electric current density and free magnetic energy throughout the solar atmosphere for Carrington rotation 2124. We found that spatially, the low-lying, current-carrying core field demonstrates strong concentration of free energy in the AR core, from the photosphere to the lower corona; the coronal field becomes slightly more sheared in the lowest layer and it relaxes to the potential field configuration with height. The free energy density appears largely co-spatial with the electric current distribution.

Application of shock waves for the improvement of current-carrying properties of YBCO(123) and Bi(2223) HTSC tapes in magnetic fields

Shock waves with a leading-edge pressure of ∼1011 Pa, which were produced in a plasma focus setup, were used to increase the critical current density in YBCO(123) and Bi(2223) HTSC tapes. It was shown that the effect of chemically inactive high-temperature high-density plasma on the HTSC tapes leads to an irreversible increase in the critical current in high magnetic fields. The improvement of the current-carrying properties of the YBCO(123) HTSC tape is confirmed also by the results of scanning Hall magnetometry at 77 K. In particular, in a field of 8 T applied perpendicular to the c axis (H ⊥ c), the increase in the critical current after shock-wave treatment is ∼60%. In the case of the Bi(2223) tape, the critical current in a zero field in the sample portion subjected to shock-wave action was found to be twice as high as that in the untreated portion (100 and 50 A, respectively). The increase in the critical current can be related to a number of possible structural transformations of the superconducting core. First of all, an increase in the density of current-carrying core, which leads to an increase in weak bonds at grain boundaries, is possible. In this case, the formation of nanosized defects, which are responsible for an increase in the force of pinning of Abrikosov vortices, is also possible.

Electron–LO-phonon scattering near a current-carrying core

A calculation is presented on the scattering rates of electrons via the bulk spectrum of longitudinal optical phonons near a current-carrying core of radius R employing the Fröhlich interaction Hamiltonian. The electrons are mainly confined near the core by an electric potential and are also under the influence of the current-induced spatially inhomogeneous static azimuthal magnetic field. The external magnetic field lifts the double degeneracy of the non-zero electron’s axial wave number ( k z ) states, while that of the non-zero azimuthal quantum number ( m ) states is preserved. In fact, the k z < 0 electron’s energy subbands are found to be characterized by minima in their variations with the field. The intrasubband scattering rates show a remarkable behavior in their variations with the field. First, for weak electric potential of the nanosystem, these exhibit a strong, nonetheless inharmonic, oscillatory behavior in their variations with the field. The oscillations are, however, smoothed out as the strength of the electrical potential is increased, commencing at lower values of the field, within the same range of values of the field used. Second, for the same strength of the electric potential, there arise phase variations of the scattering rates in their variations with the field, resulting from the variation in the electron’s axial wave number.

Surface nucleation of superconductivity near a current-carrying core

A calculation is given of the azimuthal surface nucleation field of a type IIsuperconductor which hosts a current-carrying core. The spatially inhomogeneousazimuthal external magnetic field is that due to a current of uniform densitythought to be passed along the axis of a core. Upon increasing the current, the fieldincreases to a critical value at which a phase transition from the superconducting tothe normal state occurs. The magnetic field lines are parallel to the curvatureof the superconductor–core heterointerface, hence the required critical field isHc 3, the surface-sheath nucleation field.

Single-electron states near a current-carrying core

The energy spectrum of an electron confined near a current-carrying core is obtained as a function of the azimuthal applied magnetic field within the effective-mass approximation. The double degeneracy of the non-zero electron's axial wave number ( k z ) states is lifted by the current-induced magnetic field while that of the non-zero azimuthal quantum number ( m) states is preserved. A further analysis is the evaluations of the oscillator strengths for optical transitions involving the lowest-order pair of the electron's energy subbands within the dipole approximation. The radiation field is taken as that of elliptically polarized light incident along the core axis. In this polarization and within the dipole approximation, the allowed transitions are only those governed by the following specific selection rules. The azimuthal quantum numbers of the initial and final states must differ by unity while the electron's axial wave number is conserved. The azimuthal magnetic field is also found to lift the multiple degeneracies of the k z ≠0 interaction integrals as well as those of the oscillator strengths for optical transitions.

What initiates the explosion of a current-carrying conductor?

It is shown that the explosion of a conductor heated by a high-power current pulse is initiated by the nuclei of liquid phase that appear in the layer of a supersaturated vapor surrounding the liquid current-carrying core. The instant of electric explosion and the expansion velocity predicted by this scenario are confirmed by the experimental and computational data on current-induced heating of a tungsten conductor.

Semi-Classical Dynamics of an Electron near a Current-Carrying Core

The influence of a spatially inhomogeneous magnetic field on the motion of an electron near a current-carrying core is evaluated. Expressions for the velocity components perpendicular to the magnetic flux lines are obtained. These form the basis for the numerical evaluations of the trajectories of a charged particle under the influence of an azimuthal magnetic field. A discussion of the main results is also given in the context of the problem of the azimuthal critical field of a bulk type II superconductor within which a current-carrying core is embedded.

Design and first stage test of 50-meter flexible superconducting cable

A 50-meter flexible superconducting cable model is described, including a copper-stabilized Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> Sn-tape current-carrying core and cable-paper electric insulation of 13 mm total thickness which is submerged in cold helium while under working conditions. The helium-cooled inner channel is 36 mm in diameter and the outer diameter of the current-carrying core is 75 mm. Helium also flows in an annular channel between the outer surface of the core and a corrugated enclosure. The core is incorporated in a flexible cryostating envelope consisting of 4 corrugated enclosures; the two middle pipes form an annular channel for liquid nitrogen which reduces heat leaks to helium. The design of a 110 kV, 12 kA lead was developed to test the flexible superconducting cable model. For d.c. and a.c. tests of the model, a technique of inductive current introduction through a superconducting transformer is offered. A multisection transformer with a superconducting primary of insulated Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> Sn tape was manufactured, the current-carrying core being the secondary. Before assemblying, the sections were tested in a liquid helium cryostat to check the design characteristics and to determine the critical current in the winding. A.C. losses (50 Hz) in the transformer's primary were measured. The cable model was cooled by two improved helium refrigerator plants, HGU-150/4,5. Current tests were performed at a working temperature.