Research on Electromagnetic Loss Characteristics of Submarine Cables

The electromagnetic losses of submarine cables are mainly caused by the metal shielding layer to prevent the water tree effect and the armor layer that strengthens the strength of the submarine cables.While these losses cause the temperature of submarine cable to rise,and temperature variation will in turn change the conductivity of its metal layer material.In this paper,the electric-magnetic-thermal multi-physical field coupling of the electromagnetic loss variation of the submarine cable is realized by establishing a full coupling system containing Fourier’s law and Maxwell-Ampère’s Law for the photoelectric composite submarine cable.The multi-physical field coupling model is solved and analyzed by using the finite elementmethod.Firstly,the loss of each layer of the optoelectronic composite submarine cable is analyzed,and the lossof eachlayer of the submarine cable and themainfactors leading to the loss of the submarine cable are given.Secondly,the influence of environmental temperature,ampacity and armor layer on the electromagnetic loss of submarine cables is studied,and the main operating factors affecting the electromagnetic loss of submarine cables are summarized.The research shows that the influence of ambient temperature can be ignored,and the loss of shielding layer and armor layer increases with the increase of ampacity,but the impact of shielding layer loss is greater.Finally,this paper studies the electromagnetic loss of each metal layer of the submarine cable and the influence of the laying spacing on the electromagnetic loss.The research results show that the two ways of improving the conductivity of the armor layer and reducing the relative permeability of the armor layer can effectively reduce the loss of each metal layer in the cable structure and increase the current carrying capacity when the tensile strength of the armor layer meets the requirements for single-core and threecore photoelectric composite submarine cables laid horizontally.At the same time,increasing the laying spacing will increase the loss,but it can improve the overall current carrying capacity of the cable.The research in this paper provides a theoretical basis for the design of submarine cable carrying capacity,and also provides a reference for the optimization design of submarine cable structures.

Analysis of Temperature Rise Characteristics and Fatigue Damage Degree of ACSR Broken Strand

In this paper,the research on ACSR temperature of broken strand and fatigue damage after broken strand is carried out.Conduct modeling and Analysis on the conductor through AnsoftMaxwell software.The distribution of magnetic force lines in the cross section of the conductor after strand breaking and the temperature change law of the conductor with the number of broken strands are analyzed.A model based on electromagnetic theory is established to analyze the distribution of magnetic lines of force in the cross section of the conductor after strand breaking and the temperature variation law of the conductor with the number of broken strands.The finite element analysis results show that with the increase in the number of broken strands,the cross-sectional area of the conductor decreases,the magnetic line of force of the inner conductor at the broken strand becomes denser and denser,and the electromagnetic loss of the conductor becomes larger and larger.Therefore,the temperature of the conductor at the broken strand becomes higher and higher.Then,the current carrying experiment of conductor is carried out for LGJ-240/30 conductor.It is found that the temperature rise at the junction of inner and outer layers at the broken strand is particularly obvious,and the temperature of inner aluminumconductor at the broken strand also increases with the increase of broken strand.According to the analysis of experimental data,with the increase of broken strands,the antivibration ability and service life of the conductor decrease.At the same time,under certain conditions of broken strand,the fatigue life of conductor increases with the increase of temperature.

TRANSIENT TEMPERATURE FIELD IN ACTIVE THRUST MAGNETIC BEARING

A transient temperature field model in a thrust magnetic bearing is built in which the heat resources come mainly from the eddy-current loss of solid cores and the copper loss of coils. The transient temperature field, system temperature rise and the thermo-equilibrium state during the rotor starting-up are calculated considering only the copper loss and the eddy-current loss. The numerical results indicate that the temperatures in coils and in magnets rise rapidly, their thermo-equilibrium states are formed within a short time. The temperatures in a thrust-disk and in a rotor rise slowly, their thermo-equilibrium states are formed aller a long period time. The temperatures of the thrust-disk and the rotor are far higher than the temperatures of coils and/or magnets aller the thermo-equilibrium state has come into being.

Boosting electromagnetic wave absorption of Ti_(3)AlC_(2) by improving effective electrical conductivity

Electromagnetic wave-absorbing(EMA)materials at high temperatures are limited by poor conduction loss(L_(c)).However,adding conductors simultaneously increases the conduction loss and interfacial polarization loss,leading to a conflict between impedance matching(Z_(in)/Z_(0))and electromagnetic wave loss.This will prevent electromagnetic waves from entering the EMA materials,finally reducing overall absorbing performance.Here,the effective electrical conductivity(σ)is enhanced by synchronizing particle size and grain number of Ti_(3)AlC_(2) to increase the conduction loss and avoid the conflict between the impedance matching and the electromagnetic wave loss.As a result,the best-absorbing performance with an effective absorption bandwidth(EAB)of 4.8 GHz(10.6–15.4 GHz)at a thickness of only 1.5 mm is realized,which is the best combination of wide absorption bandwidth and small thickness,and the minimum reflection loss(RL_(min))reaches−45.6 dB at 4.1 GHz.In short,this work explores the regulating mechanism of the EMA materials of effective electrical conductivity by simulated calculations using the Vienna ab-initio Simulation Package(VASP)and COMSOL as well as a series of experiments,which provide new insight into a rational design of materials with anisotropic electrical conductivity.

Multispectral ErBO_(3)@ATO porous composite microspheres with laser and electromagnetic wave compatible absorption

The high-speed advances in electromagnetic(EM)wave and laser detection technology have accelerated the innovation of absorbing materials toward specific multi-band compatibility.It is difficult to achieve dual absorption of EM waves and near-infrared lasers by absorbing materials in a single frequency band;the design of high-performance laser-EM wave multi-band compatible absorbing materials is imminent.Herein,ErBO_(3)@ATO(erbium borate/antimony-doped tin oxide)porous composite microspheres with an average size of 15-20μm are produced solvothermal method and self-assembly,which exhibit excellent laser-EM wave compatible absorption.The porous structure on the surface of ErBO_(3)microspheres provides heterogeneous nucleation sites for ATO particle deposition.The minimum reflectivity of the composite for1.06 and 1.54μm lasers is 9.59%and 4.79%,which is0.57%and 3.78%lower than those of pure ATO particles,respectively.The composites containing 70 wt%porous ErBO_(3)@ATO reveal the minimum reflection loss(RL)value of-31.6 dB,and an effective absorption band width reaches 2.08 GHz at 2.5 mm thickness.The mechanism of near-infrared laser and EM wave compatible absorption is the synergistic effect of the energy level transition of ErBO_(3)and the dielectric loss of ATO,coupled with the large surface area and porous structure of the micro spheres.Therefore,the designed porous ErBO_(3)@ATO composite microspheres can be an attractive choice for lasers and EM wave high-quality compatible absorption.