A lightning stroke damage calculation method and device for overhead ground wire

Abstract

The application discloses a lightning stroke damage calculation method and device for an overhead ground wire, and the method comprises the following steps: establishing a ground wire geometric model of the overhead ground wire, and performing parameter setting on the geometric model; loading a temperature field to the ground wire geometric model, and calculating a temperature distribution result; loading a structure field to the ground wire geometric model, and calculating mechanical stress applied to the ground wire geometric model and corresponding equivalent plastic strain results according to the temperature distribution result; and calculating a ground wire damage factor according to the mechanical stress and the equivalent plastic strain. In the simulation process, the coupling of the temperature field and the structure field is considered, the ground wire damage factor is calculated according to the mechanical stress and the plastic strain, the influence of the mechanical stress on the ground wire damage is considered, and therefore the accuracy of the damage calculation result is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of transmission line lightning experiment, and in particular to a lightning damage calculation method and device for overhead ground wire. BACKGROUND

[0002] In the field of overhead transmission, the overhead ground wire (also known as the lightning conductor) serves as the first line of defense against lightning, and its role is to guide lightning to itself to avoid lightning strikes on the transmission conductor. However, after the ground wire is struck by lightning, it may suffer damage defects, broken strands, or even broken lines, which pose a hidden danger to the safe and stable operation of the power grid. As the length of the transmission line circuit increases year by year, the probability of lightning strikes on the lightning conductor will further increase, and the resulting damage defects and broken line failures will become increasingly prominent, and research on lightning damage to the lightning conductor has gained increasing attention. Due to the non-repeatability of lightning, in the absence of actual lightning strike tests on the lightning conductor, research on lightning damage to the lightning conductor is generally conducted through simulation. Through finite element simulation and calculation, the damage to the lightning conductor under the action of different amplitude, waveform, and duration parameters can be analyzed, thereby determining the lightning withstand level of the lightning conductor and providing a basis for the selection of the lightning conductor. The current simulation calculation of lightning damage to the ground wire is to apply a heat source to the surface of the ground wire after constructing a complete ground wire model, calculate the temperature distribution results, and then based on the temperature distribution results, hide the parts exceeding the melting point of the material in the simulation software to obtain the damage volume. However, the existing technology does not consider the actual development process of lightning damage to the ground wire, such as the impact of mechanical force on lightning damage to the ground wire during lightning strikes, and is unable to quantify the mechanical damage caused by lightning strikes. SUMMARY

[0003] The present application provides a lightning damage calculation method and device for overhead ground wire to solve the technical problem that the existing technology does not consider the impact of mechanical force on ground wire damage when calculating the damage caused by lightning strikes on the ground wire.

[0004] To solve the above technical problems, the present application provides a lightning damage calculation method for overhead ground wire, comprising:

[0005] Establishing a ground wire geometric model of the overhead ground wire and loading a temperature field to the ground wire geometric model to calculate the temperature distribution results;

[0006] Loading a structure field to the ground wire geometric model and calculating the mechanical stress applied to the ground wire geometric model and the equivalent plastic strain results corresponding to the mechanical stress according to the temperature distribution results;

[0007] Calculating the ground wire damage factor according to the mechanical stress and the equivalent plastic strain results.

[0008] The application applies temperature field and structure field on the ground wire geometric model, and simulates mechanical stress and plastic strain by using the calculated temperature distribution result, considers the coupling of temperature field and structure field, calculates ground wire damage factor according to mechanical stress and plastic strain, and considers the influence of mechanical stress on ground wire damage, thereby improving the accuracy of damage calculation result.

[0009] Further, the ground wire geometric model of the overhead ground wire is established, and the geometric model is parameterized, specifically:

[0010] The COMSOL is used to establish the ground wire geometric model, and the structure parameters and material parameters of the ground wire geometric model are set.

[0011] Further, the temperature field is loaded to the ground wire geometric model, and the temperature distribution result is calculated, specifically:

[0012] The temperature distribution result includes: a continuous component temperature distribution result and a pulse component temperature distribution result.

[0013] According to the ground wire geometric model, the temperature field loaded to the ground wire geometric model is set to obtain a Gaussian function distribution of injected heat;

[0014] According to the Gaussian function distribution of injected heat, the continuous component temperature distribution result is calculated, the electromagnetic field is set and loaded to the ground wire geometric model, and the coupling relationship between the Gaussian function distribution of injected heat, the electromagnetic field and the temperature field is calculated to obtain the pulse component temperature result.

[0015] In the calculation of the temperature distribution result of the ground wire geometric model, the influence of the pulse component on the temperature distribution is considered in addition to the continuous component, the continuous component temperature distribution result only considers the calculation of the temperature field, and the calculation efficiency is improved; and the pulse component temperature distribution result considers the coupling effect of the temperature field and the electromagnetic field, and the calculation result has higher accuracy.

[0016] Further, the temperature field loaded to the ground wire geometric model is set, specifically: the outer surface of the ground wire geometric model is set as the adiabatic boundary of the temperature field, and the boundary heat source of the temperature field is set as the lightning stroke point; the electromagnetic field is set and loaded to the ground wire geometric model, specifically: the lightning stroke point of the geometric model is set as the current input terminal of the electromagnetic field, and the two ends of the cross section of the ground wire geometric model are set as the current grounding end of the electromagnetic field.

[0017] The application sets the boundary of temperature field and electromagnetic field, calculates the continuous component and the impulse component after setting the adiabatic boundary, the lightning stroke point, the current input terminal and the current grounding terminal, and the temperature distribution result obtained by the calculation can be used for further mechanical stress calculation, so as to consider the influence of mechanical stress on the damage result of the ground wire under lightning stroke.

[0018] Further, the expression of the injected heat Gaussian function distribution is:

[0019] Q(r, t) = 10J(r, t), r≤R;

[0020] Wherein, Q(r, t) is the injected heat Gaussian function distribution, R is the arc root radius, and J(r, t) is the current density in the lightning arc channel.

[0021] The expression of the current density in the lightning arc channel is:

[0022]

[0023] Wherein, I(t) is the lightning current, including: the current of the continuous component or the current of the impulse component, R(t) is the arc root radius, and t is the time.

[0024] Further, the structure field is loaded to the ground wire geometric model, and the mechanical stress applied to the ground wire geometric model and the equivalent plastic strain result corresponding to the mechanical stress are calculated according to the temperature distribution result, specifically:

[0025] Wherein, the mechanical stress includes: axial tension, impact force, electromagnetic force and thermal stress.

[0026] The cross section of the ground wire geometric model is set to be constrained by the structure field, and the axial tension of the ground wire geometric model is calculated; the impact force application position of the structure field is set, and the outer surface of the ground wire geometric model is set as the first fixed constraint surface of the structure field, the impact force and the electromagnetic force of the impact force application position are calculated according to the preset lightning current; the elastic modulus and the yield strength are calculated according to the temperature distribution result, and then the thermal stress of the ground wire geometric model is calculated according to the elastic modulus and the yield strength.

[0027] According to the axial tension, impact force, electromagnetic force and thermal stress, the equivalent plastic strain result of the ground wire geometric model is calculated.

[0028] The application sets the constraint of the structure field and the position of the impact force, calculates the axial tension and the impact force and electromagnetic force caused by lightning stroke, and on the other hand, calculates the thermal stress by considering the coupling of the temperature field and the structure field; by the mechanical stress and the corresponding equivalent plastic strain results, the influence caused by the mechanical stress is considered in the process of calculating the ground wire damage, thereby improving the accuracy of the calculation results.

[0029] Further, the section of the ground wire geometric model is set as the constraint of the structure field, and the axial tension of the ground wire geometric model is calculated, specifically:

[0030] One end of the section of the ground wire geometric model is set as a second constraint surface, and the axial tension is applied to the other end of the section:

[0031] The axial tension is calculated according to the minimum breaking force of the ground wire and the ground wire safety factor; wherein the expression of the axial tension is:

[0032]

[0033] Wherein, F T，max is the axial tension, f y is the minimum breaking force of the ground wire, and alpha is the ground wire safety factor.

[0034] Further, the expression of the electromagnetic force is:

[0035]

[0036] Wherein, p electromagnetic (r, t) is the electromagnetic force, r is the distance of the action point from the arc root, t is the time, mu0 is the vacuum permeability, mu0 = 4pi x 10 -7 N / A, R c is the arc root radius, and I(t) is the lightning current.

[0037] The axial tension of the ground wire is calculated by the minimum breaking force and other parameters, in addition, the electromagnetic force is calculated by the lightning current, arc root radius and other factors, the obtained various mechanical stresses further participate in the calculation process of the equivalent plastic strain and the ground wire damage factor, the influence caused by various mechanical stresses is considered in the calculation of the damage result, thereby improving the accuracy of the calculation result.

[0038] Further, the ground wire damage factor is calculated according to the mechanical stress and the equivalent plastic strain result, specifically:

[0039] According to the mechanical stress and the equivalent plastic strain result, the ground wire damage factor of several sections of the ground wire geometric model is calculated;

[0040] selecting a maximum ground wire damage factor from the ground wire damage factors of the several sections as the damage degree of the ground wire geometric model; wherein the expression of the ground wire damage factor is:

[0041]

[0042] wherein D is the ground wire damage factor, sigma is the mechanical stress, epsilon is the equivalent plastic strain result, and E is the elastic modulus of the undamaged material.

[0043] According to the calculated mechanical stress and equivalent plastic strain result, the ground wire damage factor is calculated to represent the damage degree of the ground wire when suffering from lightning stroke; and the ground wire damage factor can quantitatively show the influence of the mechanical stress on the damage result of the ground wire, and has higher accuracy.

[0044] In another aspect, the embodiment of the present application also provides a lightning stroke damage calculation device for overhead ground wire, comprising: a temperature distribution calculation module, a stress calculation module and a damage degree evaluation module;

[0045] The temperature distribution calculation module is used to establish a ground wire geometric model of the overhead ground wire, load a temperature field to the ground wire geometric model, and calculate a temperature distribution result;

[0046] The stress calculation module is used to load a structure field to the ground wire geometric model, and calculate a mechanical stress applied on the ground wire geometric model and an equivalent plastic strain result corresponding to the mechanical stress according to the temperature distribution result;

[0047] The damage degree evaluation module is used to calculate a ground wire damage factor according to the mechanical stress and the equivalent plastic strain.

[0048] The present application applies a temperature field and a structure field on the ground wire geometric model, and simulates the mechanical stress and plastic strain by using the calculated temperature distribution result, considers the coupling of the temperature field and the structure field; and calculates the ground wire damage factor according to the mechanical stress and the plastic strain, considers the influence of the mechanical stress on the damage of the ground wire, thereby improving the accuracy of the damage calculation result. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 The flowchart of one embodiment of the lightning stroke damage calculation method for overhead ground wire provided by the present application;

[0050] Figure 2 The flowchart of another embodiment of the lightning stroke damage calculation method for overhead ground wire provided by the present application;

[0051] Figure 3A flowchart of another embodiment of the lightning damage calculation method for overhead ground wires provided by the present application is shown in the figure.

[0052] Figure 4 A structural diagram of an embodiment of the lightning damage calculation device for overhead ground wires provided by the present application is shown in the figure. DETAILED DESCRIPTION

[0053] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0054] Embodiment one

[0055] Please refer to Figure 1 A flowchart of an embodiment of the lightning damage calculation method for overhead ground wires provided by the present application is shown in the figure, mainly including steps 101-103, and the details are as follows.

[0056] Step 101: Establish a ground wire geometric model of the overhead ground wire, and load a temperature field to the ground wire geometric model to obtain a temperature distribution result.

[0057] In this embodiment, first, a ground wire geometric model is built in software, and material parameters are set. Then, a temperature field and a coupling of electric field are set to act on the ground wire to simulate a lightning process, and a temperature distribution result of the ground wire is obtained.

[0058] In this embodiment, the establishment of the ground wire geometric model of the overhead ground wire is specifically: the COMSOL is used to establish the ground wire geometric model, and the structural parameters and material parameters of the ground wire geometric model are set. When the structural parameters are set, the parameters involved and the corresponding values are shown in the following table:

[0059]

[0060] When the material parameters are set in this embodiment, the parameters involved and the corresponding values are shown in the following table:

[0061]

[0062] Wherein, m.p represents melting point; a represents thermal expansion coefficient; l represents thermal conductivity; TCR represents resistance temperature coefficient; E represents elastic modulus; s b represents tensile strength.

[0063] In the embodiment, the high temperature inside the lightning arc and the Joule heat generated by the lightning current together form the high temperature ablation of the ground wire during the lightning strike process. The lightning current can be divided into two parts, i.e., the pulse component and the continuous component. Therefore, the influence of the pulse component and the continuous component on the temperature distribution needs to be considered when calculating the temperature distribution result.

[0064] Step 102: loading the structural field to the ground wire geometric model, and calculating the mechanical stress applied to the ground wire geometric model and the equivalent plastic strain result corresponding to the mechanical stress according to the temperature distribution result.

[0065] During the lightning strike process, the ground wire is subjected to various mechanical forces. Under the action of these mechanical forces, the damage of the ground wire will be further deepened. Therefore, in order to accurately calculate the ground wire damage result, the combined action of the mechanical stress and the equivalent plastic strain result on the ground wire damage needs to be considered.

[0066] Step 103: calculating the ground wire damage factor according to the mechanical stress and the equivalent plastic strain result.

[0067] Under the combined action of high temperature and mechanical force, a large number of micro defects such as holes and cracks will be formed inside the ground wire. The existence and development of these damage distributions in the remaining material will further lead to the damage of the ground wire until failure.

[0068] Therefore, in order to determine whether the lightning-struck ground wire can still maintain the performance in the structural field and evaluate the damage degree of the lightning-struck ground wire, in the embodiment, the ground wire damage factor is calculated according to the mechanical stress and the equivalent plastic strain result, specifically: the ground wire damage factors of a plurality of cross sections of the ground wire geometric model are calculated according to the mechanical stress and the equivalent plastic strain result; the maximum ground wire damage factor is selected from the ground wire damage factors of the plurality of cross sections as the damage degree of the ground wire geometric model; and the expression of the ground wire damage factor is:

[0069]

[0070] Wherein, D is the ground wire damage factor, σ is the mechanical stress, ε is the equivalent plastic strain result, and E is the elastic modulus of the undamaged material.

[0071] In the embodiment, the plurality of cross sections are obtained by taking a plane perpendicular to the axial direction of the ground wire as a sampling plane and sampling along the axial direction multiple times. The cross sections obtained by sampling obtain the equivalent plastic strain result after each mechanical stress and the structural field are applied. Then, the ground wire damage factor of the cross section is calculated according to the equivalent plastic strain result.

[0072] In the embodiment, the ground wire damage factor is 0-1, when the ground wire damage factor reaches 1, it is considered that the ground wire is completely damaged, when the ground wire damage factor is greater than 0 and less than 1, the different damage degrees of the ground wire can be judged. In addition, when the ground wire damage factor is greater than 0.9, it can also be considered that the ground wire is completely damaged.

[0073] In the embodiment, the ground wire damage factor is calculated according to the damage evolution equation after assuming that the damage is continuous and setting the microelement strength load probability distribution; the damage evolution equation of the ground wire damage model in tension is:

[0074]

[0075] Wherein, D is the ground wire damage factor, ε is the equivalent plastic strain result, ε0, α and β are material parameters, the material parameters can be obtained by setting the material parameters when the ground wire geometric model of the overhead ground wire is established. Using the damage evolution equation, taking the axial coordinate of the lightning stroke point as the origin and the axial direction as the horizontal axis, connecting all the maximum damage factors D calculated by sampling can obtain the damage curve of the ground wire, the damage curve reflects the damage degree of the ground wire, and the damage of the ground wire after lightning stroke can be evaluated.

[0076] Please refer to Figure 2 , the flowchart of another embodiment of the lightning damage calculation method for the overhead ground wire provided by the application mainly includes steps 201, 2021 and 2022, and specifically as follows:

[0077] In the embodiment, step 101 specifically includes steps 201, 2021 and 2022.

[0078] Step 201: according to the ground wire geometric model, setting the temperature field loaded to the ground wire geometric model to obtain the Gaussian function distribution of injected heat.

[0079] In the embodiment, the temperature field loaded to the ground wire geometric model is set as follows: the outer surface of the ground wire geometric model is set as the adiabatic boundary of the temperature field, and the boundary heat source of the temperature field is set as the lightning stroke point.

[0080] Generally, the amplitude of the pulse component can reach 300kA, and the duration is not more than 500us; the continuous component is a constant current of not more than 400A, and the duration is not more than 500ms. Both components exist heat conduction and joule heat to the ground wire, so in the simulation, there is a difference between the settings of the pulse component and the continuous component of the ground wire thermal excitation. However, because the continuous component current is small, the joule heat of the ground wire can be ignored, and only the temperature field is set.

[0081] In the embodiment, the expression of the injected heat Gaussian function distribution is:

[0082] Q(r, t) = 10J(r, t), r≤R;

[0083] Wherein, Q(r, t) is the injected heat Gaussian function distribution, R is the arc root radius, and J(r, t) is the current density in the lightning arc channel.

[0084] The expression of the current density in the lightning arc channel is:

[0085]

[0086] Wherein, I(t) is the lightning current, including: the current of the continuous component or the current of the pulse component, R(t) is the arc root radius, and t is the time.

[0087] Step 2021: According to the injected heat Gaussian function distribution, the continuous component temperature distribution result is calculated.

[0088] In the embodiment, when calculating the continuous component temperature distribution result, the value of the lightning current can be set to 0-400A.

[0089] Step 2022: Set and load the electromagnetic field to the ground wire geometric model, and calculate the pulse component temperature result according to the coupling relationship between the injected heat Gaussian function distribution, the electromagnetic field and the temperature field.

[0090] The temperature distribution of the ground wire under the action of the pulse component needs to set the boundary conditions of the electromagnetic field and the temperature field. In the embodiment, the setting and loading of the electromagnetic field to the ground wire geometric model is specifically: setting the lightning point of the geometric model as the current input terminal of the electromagnetic field, and setting the two ends of the cross section of the ground wire geometric model as the current grounding end of the electromagnetic field.

[0091] In the embodiment, when calculating the pulse component temperature result, the lightning current can be set as a pulse wave function, and the expression of the pulse wave function is:

[0092] I(t) = I a (e -0.015t -e -1.9t );

[0093] Wherein, I a is the amplitude of the lightning current pulse component, and the unit is A; t is the rising edge time, and the unit is s.

[0094] In the embodiment, when the electromagnetic field and the temperature field exist in the simulation model at the same time, the coupling relationship between the two needs to be considered; the electromagnetic loss caused by the electromagnetic field is expressed as Joule heat as a heat source in the temperature field, and the rise of temperature changes the electrical conductivity of the material and thus affects the specific performance of the electromagnetic loss. The expression of the coupling relationship between the electromagnetic field and the temperature field is:

[0095] P θ =P 20 [1+α(θ-20)];

[0096] Wherein, P θ is the heat source power under the temperature θ ℃, W / m3; P 20 is the heat source power under 20 ℃, that is, the electromagnetic loss heat power generated by the electromagnetic field; α is the temperature coefficient of the electrical resistivity of the steel, 1 / ℃; the coupling relationship can be realized by setting the temperature coefficient of the electrical resistivity in the material parameters.

[0097] The ground wire will have a local severe temperature rise due to the Joule heat and the heat conduction of the current generated by the electromagnetic field when suffering from lightning strike, at this time, the surface temperature of the ground wire will present a circular arc which spreads around the lightning point as the center; in the embodiment, according to the temperature distribution result, COMSOL and MATLAB are used to jointly operate the ground wire to obtain the ground wire which has a structure change.

[0098] Please refer to Figure 3 , which is a flowchart of another embodiment of the lightning damage calculation method for the overhead ground wire provided by the application, mainly including steps 3011-3013, step 302, and specifically as follows:

[0099] In the embodiment, step 102 specifically includes steps 3011 to 3013, and step 302.

[0100] In the embodiment, the mechanical stress includes axial tension, impact force, electromagnetic force and thermal stress.

[0101] Step 3011: The cross section of the ground wire geometric model is subjected to the constraint setting of the structure field, and the axial tension of the ground wire geometric model is calculated.

[0102] The overhead ground wire is fixed between the high-voltage line towers and will be subjected to continuous axial tension; however, it is difficult to accurately obtain the axial tension of the overhead line in actual engineering. In the embodiment, the axial tension of the ground wire geometric model is calculated by setting a structural field constraint on the section plane of the ground wire geometric model, specifically: one end of the section plane of the ground wire geometric model is set as a second constraint surface, and the axial tension is applied to the other end of the section plane; the axial tension is calculated according to the minimum breaking force of the ground wire and the ground wire safety factor; wherein the expression of the axial tension is:

[0103]

[0104] wherein F T，max is the axial tension, f y is the minimum breaking force of the ground wire, and a is the ground wire safety factor.

[0105] In the embodiment, when the strand in the ground wire geometric model is broken after high-temperature ablation, in the setting of the structural field, the two ends of the section plane do not contain the broken strand.

[0106] Step 3012: Set the impact force application position of the structural field, set the outer surface of the ground wire geometric model as a first fixed constraint surface of the structural field, and calculate the impact force and the electromagnetic force at the impact force application position according to the preset lightning current.

[0107] During lightning strike, the impact force will act on the ground wire due to the expansion of the arc channel; in the embodiment, the impact force is proportional to the lightning current amplitude, and acts vertically on the arc center of the lightning-stricken ground wire. For example, when the lightning current is 100 kA, the impact force is 10 Mpa.

[0108] The lightning arc not only brings the impact force, but also generates the electromagnetic force on the ground wire when the lightning current is injected into the ground wire through the arc root; therefore, in the embodiment, the expression of the electromagnetic force is:

[0109]

[0110] wherein p electromagnetic (r, t) is the electromagnetic force, r is the distance from the action point to the arc root, t is the time, μ0 is the vacuum permeability, μ0 = 4π × 10 -7 N / A, R c is the arc root radius, and I(t) is the lightning current.

[0111] Step 3013: The elastic modulus and the yield strength are calculated according to the temperature distribution result, and the thermal stress of the ground wire geometric model is calculated according to the elastic modulus and the yield strength.

[0112] In the simulation model, the coupling relationship between the temperature field and the structure field is also considered. In the coupling of the temperature field and the structure field, the increase of the material temperature causes the change of the mechanical parameters of the material; meanwhile, due to the uneven heating of the ground wire in the thermal excitation loading, the thermal stress is generated due to the inconsistent thermal expansion deformation and shrinkage deformation in the ground wire. Therefore, for the calculation of the thermal stress, the reduction of the elastic modulus and the yield strength of the material after the temperature rise is calculated. In the embodiment, the expression of the elastic modulus is as follows:

[0113] E θ = E 20℃ · k E，θ ;

[0114] Wherein, E θ and E 20℃ are the elastic modulus of the ground wire at θ℃ and 20℃ respectively, and k E，θ is the reduction coefficient of the elastic modulus.

[0115] In the embodiment, the expression of the yield strength is as follows:

[0116] R y，θ = 0.85R t，20℃ · k R，θ ;

[0117] Wherein, R y，θ is the yield strength of the ground wire at θ℃, R t，20℃ is the tensile strength of the ground wire at 20℃, and k R，θ is the reduction coefficient of the tensile strength.

[0118] Please refer to Figure 4 , which is a structural schematic diagram of an embodiment of the lightning damage calculation device for the overhead ground wire provided by the application, mainly comprising: a temperature distribution calculation module 401, a stress calculation module 402 and a damage degree evaluation module 403.

[0119] In the embodiment, the temperature distribution calculation module 401 is used to establish a ground wire geometric model of the overhead ground wire, and load a temperature field to the ground wire geometric model to calculate the temperature distribution result.

[0120] In the embodiment, the temperature distribution calculation module 401 comprises a model establishment unit; the model establishment unit is used to establish the ground wire geometric model by using COMSOL, and set the structure parameters and material parameters of the ground wire geometric model.

[0121] In the embodiment, the temperature distribution calculation module 401 further comprises a temperature field setting unit and a temperature distribution calculation unit; the temperature distribution result comprises a continuous component temperature distribution result and a pulse component temperature distribution result; the temperature field setting unit is configured to set a temperature field loaded to the ground wire geometric model according to the ground wire geometric model, to obtain a heat injection Gaussian function distribution; the temperature distribution calculation unit is configured to calculate the continuous component temperature distribution result according to the heat injection Gaussian function distribution; and set and load an electromagnetic field to the ground wire geometric model, to calculate the pulse component temperature result according to a coupling relationship between the heat injection Gaussian function distribution, the electromagnetic field and the temperature field.

[0122] The stress calculation module 402 is configured to load a structure field to the ground wire geometric model, and calculate a mechanical stress applied to the ground wire geometric model and an equivalent plastic strain result corresponding to the mechanical stress according to the temperature distribution result.

[0123] In the embodiment, the stress calculation module 402 comprises a mechanical stress calculation unit and a strain calculation unit; the mechanical stress calculation unit is configured to set a constraint of the structure field to a section plane of the ground wire geometric model, and calculate the axial tension of the ground wire geometric model; set an impact force application position of the structure field, and set an outer surface of the ground wire geometric model as a first fixed constraint surface of the structure field, to calculate the impact force and the electromagnetic force of the impact force application position according to a preset lightning current; and calculate the elastic modulus and the yield strength according to the temperature distribution result, and then calculate the thermal stress of the ground wire geometric model according to the elastic modulus and the yield strength; the strain calculation unit is configured to calculate the equivalent plastic strain result of the ground wire geometric model according to the axial tension, the impact force, the electromagnetic force and the thermal stress.

[0124] The damage degree evaluation module 403 is configured to calculate a ground wire damage factor according to the mechanical stress and the equivalent plastic strain.

[0125] The above-described specific embodiments further specifically describe the purpose, technical solutions and advantages of the present application, and it should be understood that the above-described specific embodiments are merely specific embodiments of the present application, and are not used to limit the protection scope of the present application. It should be particularly pointed out that any modification, equivalent replacement, improvement, etc. made by those skilled in the art within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for calculating lightning damage to overhead ground wires, characterized in that, include: A ground wire geometric model of the overhead ground wire is established, and a temperature field is applied to the ground wire geometric model to calculate the temperature distribution results. A structural field is loaded onto the ground geometry model, and the mechanical stress applied to the ground geometry model and the equivalent plastic strain corresponding to the mechanical stress are calculated based on the temperature distribution results. Based on the mechanical stress and the equivalent plastic strain results, the ground wire damage factor is calculated. The process of loading a structural field onto the ground geometry model and calculating the mechanical stress applied to the ground geometry model and the equivalent plastic strain corresponding to the mechanical stress based on the temperature distribution results is as follows: The mechanical stresses include: axial tension, impact force, electromagnetic force, and thermal stress. Structural field constraints are set on the cross-section of the ground wire geometric model, and the axial tension of the ground wire geometric model is calculated; the impact force application position of the structural field is set, and the outer surface of the ground wire geometric model is set as the first fixed constraint surface of the structural field; based on the preset lightning current, the impact force and the electromagnetic force at the impact force application position are calculated; based on the temperature distribution results, the elastic modulus and yield strength are calculated, and then based on the elastic modulus and yield strength, the thermal stress of the ground wire geometric model is calculated. The equivalent plastic strain result of the ground wire geometric model is calculated based on the axial tension, impact force, electromagnetic force, and thermal stress.

2. The method for calculating lightning damage to overhead ground wires as described in claim 1, characterized in that, The establishment of the overhead ground wire geometric model is specifically as follows: The ground geometry model was created using COMSOL, and its structural and material parameters were set.

3. The method for calculating lightning damage to overhead ground wires as described in claim 1, characterized in that, The process of loading a temperature field onto the ground geometry model and calculating the temperature distribution results is as follows: The temperature distribution results include: continuous component temperature distribution results and pulse component temperature distribution results; Based on the ground geometry model, the temperature field applied to the ground geometry model is set to obtain the Gaussian function distribution of the injected heat; Based on the Gaussian function distribution of the injected heat, the continuous component temperature distribution is calculated; an electromagnetic field is set and loaded onto the ground geometry model, and the pulse component temperature is calculated based on the Gaussian function distribution of the injected heat and the coupling relationship between the electromagnetic field and the temperature field.

4. The method for calculating lightning damage to overhead ground wires as described in claim 3, characterized in that, Setting the temperature field applied to the grounding geometry model specifically involves setting the outer surface of the grounding geometry model as the adiabatic boundary of the temperature field and setting the boundary heat source of the temperature field as the lightning strike point; setting and applying the electromagnetic field to the grounding geometry model specifically involves setting the lightning strike point of the geometry model as the current input terminal of the electromagnetic field and setting both ends of the cross-section of the grounding geometry model as the current grounding terminal of the electromagnetic field.

5. The method for calculating lightning damage to overhead ground wires as described in claim 4, characterized in that, The expression for the Gaussian function distribution of the injected heat is: ； in, The Gaussian function distribution of the injected heat, Let the radius be the arc root. The current density in the lightning arc channel; The expression for the current density in the lightning arc channel is: ； in, Lightning current includes either the continuous component or the pulse component. Let the radius be the arc root. For time.

6. The method for calculating lightning damage to overhead ground wires as described in claim 1, characterized in that, The process of setting structural field constraints on the cross-section of the ground wire geometric model and calculating the axial tension of the ground wire geometric model specifically involves: One end of the cutting surface of the ground geometry model is set as the second constraint surface, and the axial tension is applied to the other end of the cutting surface; The axial tension is calculated based on the minimum breaking force of the grounding wire and the grounding wire safety factor; wherein, the expression for the axial tension is: ； in, For axial tension, The minimum breaking force of the ground wire. This is the safety factor for the ground wire.

7. The method for calculating lightning damage to overhead ground wires as described in claim 1, characterized in that, The expression for the electromagnetic force is: ； in, Electromagnetic force, The distance from the point of application to the root of the arc. For time, The permeability of free space, , Let the radius be the arc root. This is the lightning current.

8. The method for calculating lightning damage to overhead ground wires as described in any one of claims 1-7, characterized in that, The ground wire damage factor is calculated based on the mechanical stress and the equivalent plastic strain results, specifically as follows: Based on the mechanical stress and the equivalent plastic strain results, the ground wire damage factor of several sections of the ground wire geometric model is calculated. The ground wire damage factor with the largest value among the ground wire damage factors of the aforementioned cross sections is selected as the damage degree of the ground wire geometric model; wherein, the expression for the ground wire damage factor is: ； in, Grounding damage factor Mechanical stress, For equivalent plastic strain results, It represents the elastic modulus of a non-damaging material.

9. A device for calculating lightning damage to overhead ground wires, characterized in that, include: Temperature distribution calculation module, stress calculation module, and damage assessment module; The temperature distribution calculation module is used to establish a ground wire geometric model of the overhead ground wire, and to load a temperature field onto the ground wire geometric model to calculate the temperature distribution results. The stress calculation module is used to load a structural field onto the ground geometry model and, based on the temperature distribution results, calculate the mechanical stress applied to the ground geometry model and the equivalent plastic strain corresponding to the mechanical stress. The damage assessment module is used to calculate the ground wire damage factor based on the mechanical stress and the equivalent plastic strain. The stress calculation module includes a mechanical stress calculation unit and a strain calculation unit; The mechanical stresses include: axial tension, impact force, electromagnetic force, and thermal stress. The mechanical stress calculation unit is used to constrain the structural field on the cross-section of the ground wire geometric model and calculate the axial tension of the ground wire geometric model; it is also used to set the impact force application position of the structural field, and set the outer surface of the ground wire geometric model as the first fixed constraint surface of the structural field, and calculate the impact force and electromagnetic force at the impact force application position according to the preset lightning current; and it is used to calculate the elastic modulus and yield strength according to the temperature distribution results, and then calculate the thermal stress of the ground wire geometric model according to the elastic modulus and yield strength. The strain calculation unit is used to calculate the equivalent plastic strain result of the ground wire geometric model based on the axial tension, impact force, electromagnetic force and thermal stress.

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