CN116894365A - Method for simulating specific energy consumption of ferromagnetic substances outside power transmission wire - Google Patents
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Abstract
The invention belongs to the technical field of electric power, and discloses a method for simulating the specific energy consumption of an external ferromagnetic substance of a power transmission wire, which comprises the following steps: based on the basic principle of a magneto-quasi static field and eddy current effect analysis, selecting ferromagnetic substances, damper and wires and establishing a model; analyzing the energy consumption of the ferromagnetic substance based on a finite element analysis method, simulating the ferromagnetic substance under different current carrying capacities, and calculating, comparing and analyzing the consumption value of the ferromagnetic substance under different current carrying capacities by utilizing Ansoft Maxwell; defining the current loading and the thickness of the ferromagnetic substance, and simulating and analyzing different distances between the ferromagnetic substance and the conducting wire; the current loading capacity and the distance between the ferromagnetic substance and the wire are limited, the thicknesses of different ferromagnetic substances are simulated and analyzed, the loss generated by the electric power fitting and the ferromagnetic substance under the condition that the wire is electrified with alternating currents with different effective values is obtained, and the energy consumption reasons generated by the ferromagnetic substance outside the wire at different thicknesses and different distances are obtained.
Description
Technical Field
The invention belongs to the technical field of electric power, and particularly relates to a method for simulating specific energy consumption of an external ferromagnetic substance of a power transmission wire.
Background
At present, the power industry generally advocates energy conservation and emission reduction, and people do a lot of researches on the power transmission and distribution energy conservation direction, but most of research works aim at reducing the energy consumption of a power transmission wire and produce a lot of excellent achievements, and overhead line electric power fittings which play an important role in assisting and protecting a circuit transmission line pay less attention. The overhead line electric power fitting has important influence on the protection and smooth operation of the power transmission and distribution line, and is an indispensable component part of the overhead line. For a long time, electric power fittings used for overhead lines are mostly made of ferromagnetic substance related materials in China. The electric power fitting has the advantages of good mechanical property, convenience in casting and processing and the like, but has the defects of thick and heavy structure, high maintenance cost, large recycling difficulty and the like. In addition, the power consumption of the ferromagnetic material power fitting is huge compared with that of other alloy materials, but the power loss is small in proportion to the total power transmission, so that enough attention is not paid. In addition, at present, for electric field analysis of a power system, huge equipment energy consumption such as power consumption of a load of a transformer generator of a power transmission line is mostly calculated by using simulation software, such as power flow calculation by a computer. In actual life production, the energy consumption of auxiliary devices of some electric power systems is not negligible, and electromagnetic field analysis is rarely discussed and deeply discovered.
Because a plurality of electric power fittings exist outside the power transmission line, electric energy loss can be inevitably generated, the energy consumption of the ferromagnetic substances outside the power transmission line can be better simulated by adopting a finite element analysis method, a more accurate energy consumption value can be obtained, and the energy consumption of the ferromagnetic substances outside the power transmission line can be better evaluated for the power industry so as to ensure the powerful promotion of energy conservation and emission reduction.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a method for simulating the specific energy consumption of ferromagnetic substances outside a power transmission wire, which solves the problems that in the prior art, based on a finite element analysis method, related models of the power transmission wire, an electric power fitting, ferromagnetic substances outside the power transmission wire and the like are constructed, simulation is carried out, then different carrying capacities are simulated, the energy consumption of the ferromagnetic substances is simulated and analyzed, then the influence rules of the energy consumption of the ferromagnetic substances with different thicknesses and different distances are simulated, and physical explanation is carried out, and the energy consumption influence factors of the electric power fitting are explored, and then the physical mechanism explanation is carried out.
The aim of the invention can be achieved by the following technical scheme:
a method for simulating the specific energy consumption of ferromagnetic substances outside a power transmission wire comprises the following steps:
based on the basic principle of the quasi-static magnetic field and the analysis of the eddy current effect, the types of ferromagnetic substances, anti-vibration hammers and wires are selected and a model is built;
analyzing the energy consumption of the ferromagnetic substance based on a finite element analysis method, performing simulation experiments on the ferromagnetic substance under different current carrying capacities, calculating the loss value of the ferromagnetic substance under different current carrying capacities by using an Ansoft Maxwell field calculator, and comparing and analyzing the loss value;
limiting the current loading and the thickness of the ferromagnetic substance, performing simulation experiments on different distances between the ferromagnetic substance and the wire based on different interval theoretical analysis between the ferromagnetic substance and the wire, and analyzing simulation results;
and limiting the current load and the distance between the ferromagnetic substance and the lead, performing simulation experiments on the thicknesses of different ferromagnetic substances, and analyzing simulation results to obtain factors and energy consumption values which influence the specific energy consumption of the ferromagnetic substances.
Further, the basic principle of the magneto-quasi-static field is as follows:
the time-varying magnetic field is formed by conducting current density J C (t) and Displacement Current DensityCo-generation, if there is J in the low-frequency electromagnetic field C ＞＞J D Equivalent to->The effect of the displacement current can be ignored at this time; at this time, maxwell time-varying magnetic field and time-varying electric field should satisfy:
wherein H is magnetic field intensity, J is current density, B is magnetic induction intensity, D is point flux density,is Hamiltonian, t is time.
Further, the eddy current effect is:
a metal conductor is placed in the time-varying magnetic field, and because the alternating magnetic field can generate an alternating electric field, electrons in the metal conductor can be gathered to generate an electric field, namely induced electromotive force, under the action of the electric field; since the internal structure of the metal conductor is continuous and there is a closed path, an induced electromotive force forms an induced current in the conductor path, and the induced current is generally in eddy current distribution, so the induced current is called an eddy current, the induced current generated by the induced electromotive force causes the field quantity in the metal to tend to be in surface distribution, the field quantity is smaller as the distance from the surface is further, the phenomenon is called a skin effect, and in a magneto-quasi-static field, the following basic equation set is satisfied:
wherein D is the spot flux density, gamma is the electrical conductivity,the magnetic induction density is Hamiltonian, B is magnetic induction density, and t is time;
and the skin depth formula is as follows:
where d is skin depth, ω is angular frequency, μ is permeability, and γ is conductivity.
Further, the types of the power transmission wire, the damper and the ferromagnetic substance are selected as follows:
the power transmission wire is selected from steel-cored aluminum stranded wires with the cross section area of 400mm2, the diameter of 26.82mm and the length of 2000 mm;
the damper FD-5 having a length of 500mm was selected;
the ferromagnetic material is cast iron plate with width and height of 500mm and thickness of 3mm.
Further, the model is built as: and the damper FD-5 is positioned in the middle of the wire, the damper FD-5 is symmetrical about the vertical line of the central axis of the wire, the center position of the front surface of the cuboid block in the middle of the damper FD-5 is aligned with the center of the wire, and the ferromagnetic substance is vertically arranged on one side of the wire.
Further, the finite element analysis method is used for analyzing the energy consumption of the ferromagnetic substance, and the method comprises the following steps:
the ferromagnetic substance is put into the time-varying magnetic field, and because the alternating magnetic field can generate an alternating electric field, electrons in the ferromagnetic substance can be gathered to generate an electric field, namely induced electromotive force, because a conduction path exists in the ferromagnetic substance, the induced electromotive force gradually induces current, and the induced current is generally distributed in an eddy current shape, so that eddy current is also called eddy current, the eddy current can not flow outwards, and the energy loss caused by heating of the ferromagnetic substance is eddy current loss;
when current is introduced into the lead, the generated electromagnetic field is a magneto-quasi-static field, so that the magnetic induction intensity B generated at one point inside the object is as follows:
wherein I is the current flowing into the lead; mu 0 is vacuum magnetic permeability, 4 pi multiplied by 10 -7 H/m; μr is the relative permeability of the material; r is the distance between a certain point in the ferromagnetic substance and a wire;
since the ferromagnetic substance itself is a conductor, the alternating magnetic field generates an induced electromotive force ε in its plane perpendicular to the magnetic lines of force:
ε＝αfB m S
wherein α is a constant; f is the frequency of the alternating magnetic field; b (B) m Is the maximum magnetic induction intensity; s is the cross section area of the ferromagnetic substance perpendicular to the direction of magnetic force lines;
eddy current loss W of ferromagnetic material in one period according to Maxwell's equation e Can be expressed as:
wherein a is a constant; f is the frequency of the alternating magnetic field, d is the thickness of the electric ferromagnetic substance, B m Is the maximum magnetic induction intensity; ρ is the resistivity of the electrically ferromagnetic substance;
combined typeThe method can obtain:
wherein a is a constant; f is the frequency of the alternating magnetic field, d is the thickness of the electric ferromagnetic substance, B m Is the maximum magnetic induction intensity; ρ is the resistivity of the electrically ferromagnetic substance; mu 0 is vacuum magnetic permeability, 4 pi multiplied by 10 -7 H/m; μr is the relative permeability of the material; r is the distance from a certain point in the ferromagnetic substance to the conducting wire.
Further, the simulation experiments of the different current carrying capacities of the ferromagnetic substances are as follows: when the ferromagnetic substance is simulated under different current carrying capacities, the ferromagnetic substance with the thickness of 3mm is selected, the distance between the ferromagnetic substance and the wire is kept to be 100mm, and the effective value of the current introduced into the wire is changed.
Further, the theoretical analysis of the different distances between the ferromagnetic substance and the conducting wire is as follows:
the ferromagnetic substance is put into the time-varying magnetic field, because the alternating magnetic field can generate an alternating electric field, electrons in the ferromagnetic substance can be gathered to form an electric field and an induced electromotive force due to the action of the electric field, and because a closed loop exists, the induced electromotive force can further form an induced current, the current can generally become eddy-current distribution, and the induced electromotive force on the ferromagnetic substance is as follows according to Lenz's law and Faraday electromagnetic induction law:
wherein e is an induced electromotive force; k is the eddy current loss coefficient of the hardware material;is the intensity of magnetic flux; b, magnetic induction intensity is in direct proportion to the current I passing through the lead; s is the cross section area perpendicular to the direction of magnetic force lines in the hardware fitting; t is time;
will be described inSubstituted +.>Is obtained by:
wherein K is the eddy current loss coefficient of the hardware fitting material, R is the distance between the lead and the ferromagnetic substance, mu 0 is the vacuum magnetic permeability, and 4 pi is multiplied by 10 -7 H/m; μr is the relative permeability of the material; i is the current which is introduced into the lead, S is the cross-sectional area perpendicular to the direction of magnetic force lines in the hardware fitting, and t is the time.
Further, the simulation experiment on different distances between the ferromagnetic substance and the conducting wire is as follows: the ferromagnetic substance thickness was defined as 3mm, with a distance gradually increasing from 100mm to 1000mm, with a distance of 100mm for each increase.
Further, the simulation experiment on the thickness of different ferromagnetic substances is as follows: the distance between the ferromagnetic substance and the center of the wire is defined as 100mm, and the thickness of the ferromagnetic substance is gradually increased from 3mm to 27mm, and the thickness is increased by 3mm each time.
The invention has the beneficial effects that:
the invention quantitatively analyzes the loss generated by the electric power fitting and the ferromagnetic substance under the condition that the wires are electrified with alternating currents with different effective values, is more accurate than the traditional empirical formula, analyzes the energy consumption reasons generated by the ferromagnetic substance outside the wires at different thicknesses and different distances, and provides relevant experience for energy conservation and emission reduction measures carried out in the electric power industry.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described, and it will be obvious to those skilled in the art that other drawings can be obtained according to these drawings without inventive effort.
FIG. 1 is a schematic flow diagram of an embodiment of the present invention;
FIG. 2 is a diagram of simulation models of FD-5 and wires in an Ansoft Maxwell according to an embodiment of the present invention;
FIG. 3 is an overall model of an external ferromagnetic substance of a wire in an Ansoft Maxwell according to an embodiment of the present invention;
FIG. 4 is a graph of the effective value 650A of the wire through-flow of an embodiment of the present invention, the magnetic induction of a ferromagnetic substance;
FIG. 5 is a graph of ohmic loss cloud of ferromagnetic material for the effective value 650A of wire current according to an embodiment of the present invention;
FIG. 6 is a graph of ohmic loss cloud of ferromagnetic material with a thickness of 3mm and a distance of 100mm from the center of the wire according to an embodiment of the present invention;
FIG. 7 is a graph of ohmic loss cloud of ferromagnetic material at a thickness of 3mm and a distance of 500mm from the center of the wire according to an embodiment of the present invention;
FIG. 8 is an ohmic loss cloud of ferromagnetic material with a thickness of 3mm and a distance of 1000mm from the center of the wire according to an embodiment of the present invention;
FIG. 9 is a graph showing the variation of the energy consumption of a fixed ferromagnetic substance with a thickness of 3mm, varying the distance from the ferromagnetic substance according to an embodiment of the present invention;
FIG. 10 is a graph showing the variation of the energy consumption of a ferromagnetic substance with varying thickness, with a fixed ferromagnetic substance at a distance of 100mm from a wire in accordance with an embodiment of the present invention;
FIG. 11 is an ohmic loss cloud of ferromagnetic material with a distance of 100mm from the center of the wire and a thickness of 3mm according to an embodiment of the present invention;
FIG. 12 is an ohmic loss cloud of ferromagnetic material with a distance of 100mm from the center of the wire and a thickness of 15mm according to an embodiment of the present invention;
FIG. 13 is an ohmic loss cloud of ferromagnetic material with a distance of 100mm from the center of the wire and a thickness of 27mm according to an embodiment of the present invention;
FIG. 14 is a cross-sectional view of a ferromagnetic substance with a distance of 100mm from the center of the wire and a thickness of 15mm according to an embodiment of the present invention;
FIG. 15 is a cross-sectional view of a ferromagnetic substance with a distance of 100mm from the center of the wire and a thickness of 21mm according to an embodiment of the present invention;
FIG. 16 is a cross-sectional view of a ferromagnetic substance with a distance of 100mm from the center of the wire and a thickness of 27mm according to an embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
As shown in fig. 1, a method for simulating the specific energy consumption of a ferromagnetic substance outside a power transmission wire comprises the following steps:
based on the basic principle of the quasi-static magnetic field and the analysis of the eddy current effect, the types of ferromagnetic substances, anti-vibration hammers and wires are selected and a model is built;
analyzing the energy consumption of the ferromagnetic substance based on a finite element analysis method, performing simulation experiments on the ferromagnetic substance under different current carrying capacities, calculating the loss value of the ferromagnetic substance under different current carrying capacities by using an Ansoft Maxwell field calculator, and comparing and analyzing the loss value;
limiting the current loading and the thickness of the ferromagnetic substance, performing simulation experiments on different distances between the ferromagnetic substance and the wire based on different interval theoretical analysis between the ferromagnetic substance and the wire, and analyzing simulation results;
and limiting the current load and the distance between the ferromagnetic substance and the lead, performing simulation experiments on the thicknesses of different ferromagnetic substances, and analyzing simulation results to obtain factors and energy consumption values which influence the specific energy consumption of the ferromagnetic substances.
The above steps are further described below.
S1, selecting the types of ferromagnetic substances, damper and wires and establishing a model based on the basic principle of a magneto quasi-static field and analysis of eddy current effect.
(1) Magneto-quasi-static field theory
The time-varying magnetic field is formed by conducting current density J C (t) and Displacement Current DensityCo-generation, if there is J in the low-frequency electromagnetic field C ＞＞J D Equivalent to->The effect of the displacement current can be neglected at this time. At this time, maxwell time-varying magnetic field and time-varying electric field should satisfy:
wherein H is magnetic field intensity, J is current density, B is magnetic induction intensity, D is point flux density,is Hamiltonian, t is time.
(2) Vortex effect
The metal conductor is placed in the time-varying magnetic field, and because the alternating magnetic field can generate an alternating electric field, electrons in the metal conductor can be gathered to generate an electric field, namely induced electromotive force, under the action of the electric field. Since the inner structure of the metal conductor is continuous and there is a closed path, the induced electromotive force in turn forms an induced current in the conductor path. Such currents typically become eddy current distributions. Thus, such induced currents are referred to as eddy currents. The induced current generated by the induced electromotive force tends to make the field amount in the metal to be distributed toward the surface, and the field amount becomes smaller as the distance from the surface is increased, which is called skin effect. In a magneto-quasi-static field, the following basic equation set is satisfied:
wherein D is the spot flux density, gamma is the electrical conductivity,the magnetic flux is Hamiltonian, B is magnetic induction intensity, and t is time.
And the skin depth formula is as follows:
where d is skin depth, ω is angular frequency, μ is permeability, and γ is conductivity.
(3) Model selection and model establishment of power transmission wire, damper and ferromagnetic substance
1) Transmission conductor model selection
In view of the fact that the current carrying capacity can affect a range of electrical parameters such as magnetic induction, current density and ohmic loss distribution. And the actual rated current-carrying capacity is combined for comprehensive consideration. And allows for the type of wire to be selected that is a relatively common type for high voltage overhead line sites.
In summary, a steel-cored aluminum strand with a cross-sectional area of 400mm2 and a diameter of 26.82mm is selected, and the rated current-carrying capacity of the wire of the specification is 500A. Meanwhile, the length of the transmission conductor model needs to be considered when the transmission conductor model is built, the length of the conductor is not too short in selection, the boundary effect is obvious easily, the simulation efficiency is reduced due to too long, and therefore the length of the conductor is selected to be 2000mm.
2) Damper model selection
Since a steel-cored aluminum strand having a cross-sectional area of 400mm2 is selected, the damper type FD-5 can be selected according to the wire type. Thereby, a length of 500mm of its corresponding damper FD-5 can be obtained. The FD-5 damper is also a common protection fitting for high-voltage overhead lines, has a certain practical significance for simulating the model, and can provide a certain reference value for practical energy conservation, emission reduction and other measures. The simulation diagram is shown in fig. 2.
3) Ferromagnetic material model selection
The shape of the ferromagnetic substance outside the actual overhead line is very complex, and the characteristic is very inconvenient to study. Therefore, the invention is to design ferromagnetic substance for simulation purpose, and the feasibility and the simplicity are considered, so a cast iron plate with width and height of 500mm and thickness of 3mm is selected, and the distance from the wire is 100mm. The subsequent simulation experiment for changing different thicknesses is to change the thickness of the ferromagnetic substance by 3-27mm, and simulate each time by adding 3mm. The simulation experiment for changing different distances is to change the distance between the ferromagnetic substance and the wire by 100-1000mm, and simulate the distance by increasing 100mm each time. A simulation diagram of the whole environment is shown in fig. 3.
4) Model building
And the damper FD-5 is matched with the power transmission wire, so that the damper FD-5 is positioned in the middle of the wire, and the damper FD-5 is symmetrical about the perpendicular line of the central axis of the wire, so that the influence of the boundary effect of the wire port can be reduced. The center of the front surface of the cuboid block in the middle of the damper FD-5 is aligned with the center of the lead, so that the field quantity distribution of ferromagnetic substances can be better observed, and the distribution rule can be better summarized. The ferromagnetic substance is vertically disposed on one side of the wire.
S2, analyzing the energy consumption of the ferromagnetic substance based on a finite element analysis method, performing simulation experiments on the ferromagnetic substance under different current carrying capacities, calculating the loss value of the ferromagnetic substance under different current carrying capacities by using an Ansoft Maxwell field calculator, and comparing and analyzing the loss value.
(1) Analysis of ferromagnetic material energy consumption based on finite element analysis
A ferromagnetic substance is placed in the time-varying magnetic field, and because the alternating magnetic field can generate an alternating electric field, electrons in the ferromagnetic substance can be gathered to generate an electric field, namely induced electromotive force, due to the action of the electric field. Since a conduction path exists inside the ferromagnetic substance, the induced electromotive force gradually induces a current. And such induced currents are generally distributed in an eddy current, also called eddy currents. The eddy current cannot flow outwards, so that the ferromagnetic substance generates heat to cause energy loss, namely eddy current loss.
When current is introduced into the lead, the generated electromagnetic field is a magneto-quasi-static field, so that the magnetic induction intensity B generated at one point inside the object is as follows:
wherein I is the current flowing into the lead; mu 0 is vacuum magnetic permeability, 4 pi multiplied by 10 -7 H/m; μr is the relative permeability of the material; r is the distance from a certain point in the ferromagnetic substance to the conducting wire.
Since the ferromagnetic substance itself is a conductor, the alternating magnetic field generates an induced electromotive force ε in its plane perpendicular to the magnetic lines of force:
ε＝αfB m S
wherein α is a constant; f is the frequency of the alternating magnetic field; b (B) m Is the maximum magnetic induction intensity; s is the cross-sectional area of the ferromagnetic substance perpendicular to the direction of magnetic force lines.
Eddy current loss W of ferromagnetic material in one period according to Maxwell's equation e Can be expressed as:
wherein a is a constant; f is the frequency of the alternating magnetic field, d is the thickness of the electric ferromagnetic substance, B m Is the maximum magnetic induction intensity; ρ is the resistivity of the electrically ferromagnetic substance.
Combined typeThe method can obtain:
from the above equation, the eddy current loss of the ferromagnetic substance increases as the alternating magnetic frequency, the thickness of the ferromagnetic substance, the current passing through the wire, and the magnetic permeability of the ferromagnetic substance increase. Meanwhile, the eddy current loss of the electric ferromagnetic substance decreases as the distance between the electric ferromagnetic substance and the wire and the resistivity of the electric ferromagnetic substance increase.
(2) Simulation experiment of different current-carrying capacities of ferromagnetic substances
The invention is a control variable, when the ferromagnetic substance is simulated under different current carrying capacities, the ferromagnetic substance with the thickness of 3mm is selected, the distance between the ferromagnetic substance and the wire is kept to be 100mm, and the effective value of the current introduced into the wire is changed. When the effective value of the power frequency is 500A, 650A and 800A, other secondary parts are hidden to obtain a magnetic induction density cloud picture and an ohmic loss distribution cloud picture of the ferromagnetic substance. A magnetic induction cloud and ohmic loss distribution cloud are shown 650A as shown in fig. 4.
(3) Analysis of simulation results of different current carrying capacities of ferromagnetic substances
As can be seen from the obtained fig. 4, the maximum magnetic induction intensity of the ferromagnetic substance is about 0.2T when the effective value of the supplied power frequency current is 650A. And the middle magnetic induction intensity of the cast iron plate is large, and the magnetic induction intensity of the upper end and the lower end is small. The magnetic induction intensity is inversely proportional to the distance between one point on the ferromagnetic substance and the wire, so that the middle part of the cast iron plate is close to the wire, the magnetic induction intensity is large, the upper end and the lower end of the cast iron plate are far away from the wire, and the magnetic induction intensity is obviously reduced. The magnetic induction density cloud patterns of ferromagnetic substances are distributed symmetrically, and a little asymmetry is caused by superposition of an induction electromagnetic field on the electric power fitting and an electromagnetic field generated by a wire.
Looking at the ohmic loss cloud chart, as shown in fig. 5, the energy consumption distribution is basically symmetrical, a small amount of asymmetry is generated due to the fact that induced current is generated in the electric power fitting, and the magnetic field generated by the induced current influences the magnetic field generated by the lead, so that ohmic loss is influenced. The ferromagnetic loss was 0.461W based on an Ansoft Maxwell field calculator. And table 1 also shows the energy consumption variation, indicating that the theory is correct.
S3, limiting the current loading and the thickness of the ferromagnetic substance, carrying out simulation experiments on different distances between the ferromagnetic substance and the conducting wire based on different interval theoretical analysis between the ferromagnetic substance and the conducting wire, and analyzing simulation results.
(1) Defining current load and thickness of ferromagnetic material, and making theoretical analysis of different spacing between ferromagnetic material and wire
As can be seen from the magnetic induction map 4, the magnetic induction is inversely related to the distance, and the larger the distance is, the smaller the magnetic induction is. Ferromagnetic substances are placed in the time-varying magnetic field, and because the alternating magnetic field can generate an alternating electric field, electrons in the ferromagnetic substances can be gathered under the action of the electric field to form an electric field and induce electromotive force. The induced electromotive force in turn forms an induced current due to the closed loop. Such currents typically become eddy current distributions. According to lenz's law and faraday's law of electromagnetic induction, the induced electromotive force on a ferromagnetic substance is:
wherein e is an induced electromotive forceThe method comprises the steps of carrying out a first treatment on the surface of the K is the eddy current loss coefficient of the hardware material;is the intensity of magnetic flux; b, magnetic induction intensity is in direct proportion to the current I passing through the lead; s is the cross section area perpendicular to the direction of magnetic force lines in the hardware fitting; t is time.
Will be described inSubstituted +.>Is obtained by:
wherein K is the eddy current loss coefficient of the hardware fitting material, R is the distance between the lead and the ferromagnetic substance, mu 0 is the vacuum magnetic permeability, and 4 pi is multiplied by 10 -7 H/m; μr is the relative permeability of the material; i is the current which is introduced into the lead, S is the cross-sectional area perpendicular to the direction of magnetic force lines in the hardware fitting, and t is the time.
When the distance between the ferromagnetic substances is changed and the thickness is unchanged, the relative magnetic permeability of the ferromagnetic substances is 400 constant, the current is 500A constant, and therefore, the distance R only affects the induced electromotive force, the resistance is constant because the thickness of the ferromagnetic substances is unchanged, the induced electromotive force is reduced along with the increase of the distance, and the generated eddy current loss is reduced.
(2) Limiting the current loading and the thickness of the ferromagnetic substance, performing simulation experiments on different distances between the ferromagnetic substance and the conducting wire, and analyzing simulation results
The simulation selects to limit the thickness of the ferromagnetic substance to 3mm, the distance is gradually increased from 100mm to 1000mm, and the distance added each time is 100mm. The distance is increased uniformly, the sampling point number is proper, and the change trend of the law can be well reflected. Meanwhile, other electrical parameters should be kept consistent, materials of the electric power fitting, the lead and the ferromagnetic substance are kept unchanged, and the effective value of the lead-in current is unified to be 500A.
And in order to clearly show the trend of variation, three ohmic loss clouds with distances of 100mm, 500mm and 1000mm can be selected as fig. 6, 7 and 8, respectively, and tables 2 and 9 are made for analysis of energy consumption. From fig. 9, it can be seen that the energy consumption gradually decreases with increasing distance, and the energy consumption is in inverse proportion, so that the energy consumption accords with the theoretical deduction.
S4, limiting the current loading and the distance between the ferromagnetic substance and the conducting wire, carrying out simulation experiments on the thicknesses of different ferromagnetic substances, analyzing simulation results, and carrying out theoretical analysis on the reasons of the thickness change and loss change of the ferromagnetic substances.
(1) And defining the thickness of the ferromagnetic substance and the distance between the wires, performing simulation experiments on the thicknesses of different ferromagnetic substances, and analyzing simulation results.
The simulation limits that the distance between the ferromagnetic substance and the center of the lead wire is 100mm, the thickness of the ferromagnetic substance is gradually increased from 3mm to 27mm, and the thickness is increased by 3mm each time. The thickness is increased uniformly, the sampling point is proper, and the change trend of the law can be better reflected. For the obvious representation of the energy consumption change law, ohmic loss cloud charts with the thickness of 3mm, 9mm, 15mm, 21mm and 27mm are selected for display, and are respectively shown in fig. 11, 12 and 13. By observing the ohmic losses of ferromagnetic substances of different thickness, it can be seen that in the thickness range of 3-15mm, the ohmic loss density of ferromagnetic substances increases in some areas as the thickness increases. But after a ferromagnetic substance thickness of 15mm, the ohmic loss density remains substantially unchanged after some regions have been slightly reduced. The energy consumption data obtained by changing the thickness is shown in Table 3, and it is clear from Table 3 that the energy consumption of the ferromagnetic substance gradually increases as the thickness increases at a ferromagnetic substance thickness of 3 to 15mm, and after the thickness increases at 15mm, the energy consumption of the ferromagnetic substance slightly decreases and then becomes stable at substantially 0.9W. In order to more intuitively show the change rule, a graph is made according to the energy consumption data obtained by simulation, as shown in fig. 10.
(2) And defining the distance between the thickness of the ferromagnetic substance and the conducting wire, and carrying out theoretical analysis on simulation results of the thicknesses of different ferromagnetic substances.
When ferromagnetic materialThe distance between the mass and the center of the lead is 100mm, and the thickness loss change reason of the ferromagnetic substance is changed: the ferromagnetic material is cast iron, the relative permeability is 400, the conductivity is 1.5 multiplied by 106S/m, and the angular velocity is 100 pi rad/S because the power frequency current frequency is 50Hz, and the skin depth d=2.9 mm of the cast iron can be obtained by a skin depth calculation formula. Based on the knowledge of electromagnetic field, the field intensity value at depth d is only the surface field intensity due to the fact that each skin depth d is lowered
As the depth increases exponentially with the field strength decreases, it is believed that eddy currents exist in the depth range of 5.8-8.7mm (2-3 d), above which eddy currents are substantially negligible. Because the eddy current exists on the front side and the back side of the iron plate, the eddy current can be generated at 11.6-17.4mm (4-6 d) at maximum. According to simulation results, the energy consumption of the ferromagnetic material is increased from 0.29W to 1.17W when the thickness of the ferromagnetic material is increased from 3mm to 15mm, and the ferromagnetic material basically accords with the skin effect rule of the vortex field. When the thickness increases again, the energy consumption drops slightly and then remains substantially unchanged at 0.9W.
From FIG. 10, it can be seen that the energy in the range of 11.6-17.4mm exhibits a phenomenon that the middle is large and the ends are slightly smaller, probably due to the increase in thickness, but the conductivity is large and constant, expressed by the resistance expressionIt is known that the increase in resistance is very small, and the induced electromotive force generated by the alternating magnetic field remains substantially unchanged, resulting in a slight decrease in the eddy current generated and thus a decrease in the energy consumption of the ferromagnetic substance. The ferromagnetic material is 5.17 times the skin depth at 15mm thickness, and is in the middle region of 11.6-17.4mm, so that the loss is maximum. Meanwhile, the thickness interval of 3mm adopted by the invention is basically consistent with the skin depth, so that each simulation can obviously show the result of skin effect generation.
Further, the most direct factor affecting ohmic losses in terms of the present invention is eddy current loss, which is the most dominant factor affecting the magnitude of current flowing through ferromagnetic substances. To verify the theory, the invention carries out simulation of horizontal and vertical sections of ferromagnetic substances, and the theory is supplemented and perfected by observing current density distribution, because the current density distribution starts to slightly decline at the thickness of 15mm and then basically keeps unchanged, so that in order to better show the change rule of the ferromagnetic substances at the thickness of 15-27mm, simulation results at the thicknesses of 15mm, 21mm and 27mm are shown in fig. 14, 15 and 16 respectively.
As can be seen from the current density profile, the transverse eddy current density is greater than the longitudinal eddy current density because the longitudinal direction is relatively close to the wire, and the eddy current flow is generally along the surface of the cross section according to lenz's law. It can also be seen that the maximum eddy current density is 5.4X104A/m 2 and that the eddy current density generally decreases as the thickness of the ferromagnetic substance increases from 15mm to 27 mm. The gradual increase in energy consumption is due to the gradual increase in eddy currents when the thickness is varied from 3 to 15mm, the increase being due to the ferromagnetic material thickness being in the range of 2 to 3 times the skin depth. When the thickness is increased backwards, the eddy current is concentrated and distributed on the surface and in 2-3 skin depths, and current hardly exists when the eddy current is larger than the surface and the skin depths, and the induced electromotive force of the ferromagnetic substance is basically unchanged, so that the current density is reduced due to the slight increase of the theoretical resistance, and the theory is basically consistent.
Specifically, the ferromagnetic material changes the energy consumption change of different current carrying capacities, the thickness of the ferromagnetic material is limited, and the energy consumption change of the ferromagnetic material from the change is shown in table 2. The ferromagnetic substance distance is defined, and the energy consumption changes of different ferromagnetic substance thicknesses are shown in table 3.
TABLE 1
TABLE 2
TABLE 3 Table 3
In the description of the present specification, the descriptions of the terms "one embodiment," "example," "specific example," and the like, mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The foregoing has shown and described the basic principles, principal features and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the foregoing embodiments, which have been described in the foregoing description merely illustrates the principles of the invention, and that various changes and modifications may be made therein without departing from the spirit and scope of the invention, which is defined in the appended claims.
Claims (10)
1. A method for simulating the specific energy consumption of a ferromagnetic substance outside a power transmission wire, comprising the steps of:
based on the basic principle of the quasi-static magnetic field and the analysis of the eddy current effect, the types of ferromagnetic substances, anti-vibration hammers and wires are selected and a model is built;
analyzing the energy consumption of the ferromagnetic substance based on a finite element analysis method, performing simulation experiments on the ferromagnetic substance under different current carrying capacities, calculating the loss value of the ferromagnetic substance under different current carrying capacities by using an Ansoft Maxwell field calculator, and comparing and analyzing the loss value;
limiting the current loading and the thickness of the ferromagnetic substance, performing simulation experiments on different distances between the ferromagnetic substance and the wire based on different interval theoretical analysis between the ferromagnetic substance and the wire, and analyzing simulation results;
and limiting the current load and the distance between the ferromagnetic substance and the lead, performing simulation experiments on the thicknesses of different ferromagnetic substances, and analyzing simulation results to obtain factors and energy consumption values which influence the specific energy consumption of the ferromagnetic substances.
2. The method for simulating the specific energy consumption of the ferromagnetic substance outside the power transmission wire according to claim 1, wherein the basic principle of the magneto-quasi-static field is as follows:
the time-varying magnetic field is formed by conducting current density J C (t) and Displacement Current DensityCo-generation, if there is J in the low-frequency electromagnetic field C ＞＞J D Equivalent to->The effect of the displacement current can be ignored at this time; at this time, maxwell time-varying magnetic field and time-varying electric field should satisfy:
wherein H is magnetic field intensity, J is current density, B is magnetic induction intensity, D is point flux density,is Hamiltonian, t is time.
3. A method for simulating energy consumption of ferromagnetic substances outside a power transmission line according to claim 1, wherein the eddy current effect is:
a metal conductor is placed in the time-varying magnetic field, and because the alternating magnetic field can generate an alternating electric field, electrons in the metal conductor can be gathered to generate an electric field, namely induced electromotive force, under the action of the electric field; since the internal structure of the metal conductor is continuous and there is a closed path, an induced electromotive force forms an induced current in the conductor path, and the induced current is generally in eddy current distribution, so the induced current is called an eddy current, the induced current generated by the induced electromotive force causes the field quantity in the metal to tend to be in surface distribution, the field quantity is smaller as the distance from the surface is further, the phenomenon is called a skin effect, and in a magneto-quasi-static field, the following basic equation set is satisfied:
wherein D is the spot flux density, gamma is the electrical conductivity,the magnetic induction density is Hamiltonian, B is magnetic induction density, and t is time;
and the skin depth formula is as follows:
where d is skin depth, ω is angular frequency, μ is permeability, and γ is conductivity.
4. The method for simulating the specific energy consumption of the ferromagnetic substance outside the power transmission line according to claim 1, wherein the power transmission line, the damper and the ferromagnetic substance are selected from the group consisting of:
the power transmission wire is selected from steel-cored aluminum stranded wires with the cross section area of 400mm2, the diameter of 26.82mm and the length of 2000 mm;
the damper FD-5 having a length of 500mm was selected;
the ferromagnetic material is cast iron plate with width and height of 500mm and thickness of 3mm.
5. A method for simulating energy consumption of external ferromagnetic substances of a power transmission line according to claim 1, wherein said model is built up as: and the damper FD-5 is positioned in the middle of the wire, the damper FD-5 is symmetrical about the vertical line of the central axis of the wire, the center position of the front surface of the cuboid block in the middle of the damper FD-5 is aligned with the center of the wire, and the ferromagnetic substance is vertically arranged on one side of the wire.
6. The method for simulating the energy consumption of the characteristics of the ferromagnetic substance outside the power transmission wire according to claim 1, wherein the analysis of the energy consumption of the ferromagnetic substance based on the finite element analysis method is as follows:
the ferromagnetic substance is put into the time-varying magnetic field, and because the alternating magnetic field can generate an alternating electric field, electrons in the ferromagnetic substance can be gathered to generate an electric field, namely induced electromotive force, because a conduction path exists in the ferromagnetic substance, the induced electromotive force gradually induces current, and the induced current is generally distributed in an eddy current shape, so that eddy current is also called eddy current, the eddy current can not flow outwards, and the energy loss caused by heating of the ferromagnetic substance is eddy current loss;
when current is introduced into the lead, the generated electromagnetic field is a magneto-quasi-static field, so that the magnetic induction intensity B generated at one point inside the object is as follows:
wherein I is the current flowing into the lead; mu 0 is vacuum magnetic permeability, 4 pi multiplied by 10 -7 H/m; μr is the relative permeability of the material; r is the distance between a certain point in the ferromagnetic substance and a wire;
since the ferromagnetic substance itself is a conductor, the alternating magnetic field generates an induced electromotive force ε in its plane perpendicular to the magnetic lines of force:
ε＝αfB m S
wherein α is a constant; f is the frequency of the alternating magnetic field; b (B) m Is the maximum magnetic induction intensity; s is the cross section area of the ferromagnetic substance perpendicular to the direction of magnetic force lines;
according to maxwell's equations,eddy current loss W of ferromagnetic material in one period e Can be expressed as:
wherein a is a constant; f is the frequency of the alternating magnetic field, d is the thickness of the electric ferromagnetic substance, B m Is the maximum magnetic induction intensity; ρ is the resistivity of the electrically ferromagnetic substance;
combined typeThe method can obtain:
wherein a is a constant; f is the frequency of the alternating magnetic field, d is the thickness of the electric ferromagnetic substance, B m Is the maximum magnetic induction intensity; ρ is the resistivity of the electrically ferromagnetic substance; mu 0 is vacuum magnetic permeability, 4 pi multiplied by 10 -7 H/m; μr is the relative permeability of the material; r is the distance from a certain point in the ferromagnetic substance to the conducting wire.
7. The method for simulating the specific energy consumption of the ferromagnetic substance outside the power transmission wire according to claim 1, wherein the simulation experiments of the different current carrying capacities of the ferromagnetic substance are as follows: when the ferromagnetic substance is simulated under different current carrying capacities, the ferromagnetic substance with the thickness of 3mm is selected, the distance between the ferromagnetic substance and the wire is kept to be 100mm, and the effective value of the current introduced into the wire is changed.
8. The method for simulating the specific energy consumption of the ferromagnetic substance outside the power transmission wire according to claim 1, wherein the theoretical analysis of the different distances between the ferromagnetic substance and the wire is:
the ferromagnetic substance is put into the time-varying magnetic field, because the alternating magnetic field can generate an alternating electric field, electrons in the ferromagnetic substance can be gathered to form an electric field and an induced electromotive force due to the action of the electric field, and because a closed loop exists, the induced electromotive force can further form an induced current, the current can generally become eddy-current distribution, and the induced electromotive force on the ferromagnetic substance is as follows according to Lenz's law and Faraday electromagnetic induction law:
wherein e is an induced electromotive force; k is the eddy current loss coefficient of the hardware material;is the intensity of magnetic flux; b, magnetic induction intensity is in direct proportion to the current I passing through the lead; s is the cross section area perpendicular to the direction of magnetic force lines in the hardware fitting; t is time;
will be described inSubstituted +.>Is obtained by:
wherein K is the eddy current loss coefficient of the hardware fitting material, R is the distance between the lead and the ferromagnetic substance, mu 0 is the vacuum magnetic permeability, and 4 pi is multiplied by 10 -7 H/m; μr is the relative permeability of the material; i is the current which is introduced into the lead, S is the cross-sectional area perpendicular to the direction of magnetic force lines in the hardware fitting, and t is the time.
9. The method for simulating the specific energy consumption of the ferromagnetic substance outside the power transmission wire according to claim 1, wherein the simulation experiment on the different distances between the ferromagnetic substance and the wire is: the ferromagnetic substance thickness was defined as 3mm, with a distance gradually increasing from 100mm to 1000mm, with a distance of 100mm for each increase.
10. The method for simulating the specific energy consumption of the ferromagnetic substances outside the power transmission wire according to claim 1, wherein the simulation experiment on the thickness of the different ferromagnetic substances is: the distance between the ferromagnetic substance and the center of the wire is defined as 100mm, and the thickness of the ferromagnetic substance is gradually increased from 3mm to 27mm, and the thickness is increased by 3mm each time.
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