Thermal disaster risk assessment method based on stranded conductor structure parametric modeling

Abstract

The invention discloses a thermal disaster risk assessment method based on stranded conductor structure parameterized modeling. The method comprises the following steps of performing digital modeling; anisotropic heat conduction calculation: calculating an axial heat conduction coefficient and a radial heat conduction coefficient of the wire core; performing multi-physics field coupling simulation; a dynamic failure criterion; and carrying out risk quantification output, setting a safety time threshold value, and finally outputting the risk level and the safety margin index of the current lead. According to the thermal disaster risk assessment method based on stranded wire structure parametric modeling, parametric modeling and anisotropic heat conductivity coefficient calculation are performed on stranded wires, so that the thermal disaster assessment reliability is improved; the accurate and reversible quantitative mapping relation between key twisting structure parameters such as the wire core diameter, the twisting density and the twisting pitch and the axial and radial anisotropic heat conductivity coefficients of the wire is established, so that model simulation can be directly carried out in the design stage of the twisted wire, the parameters of the twisted wire are optimized, and the safety coefficient of the finally produced twisted wire is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of conductor thermal risk assessment methods, and in particular to a thermal disaster risk assessment method based on parametric modeling of a twisted conductor structure. Background Art

[0002] Conductor thermal risk assessment refers to the process of systematically identifying, analyzing, and quantifying the temperature rise caused by current flowing through the conductor, which may lead to a series of adverse consequences (such as insulation aging and failure, fire, equipment damage, system failure, personal injury, etc.).

[0003] According to the invention patent application with publication number: CN111859802B and publication date: 2021-10-01, a method, system and device for calculating the steady-state temperature of an overhead conductor are disclosed. The present invention calculates the heat dissipation coefficient of a non-contact reference body by acquiring environmental data, inputs the heat dissipation coefficient of the non-contact reference body into a pre-trained association model, obtains the heat dissipation coefficient of the overhead conductor, and finally calculates the heat dissipation power of the overhead conductor under the same environmental data. The steady-state temperature of the overhead conductor is calculated based on the heat dissipation power of the overhead conductor and the heat dissipation coefficient of the overhead conductor. Its main technical effects are: the steady-state temperature of the overhead conductor is evaluated in a non-contact manner, the electromagnetic interference caused by the overhead conductor to the temperature measuring device is avoided, the influence of the temperature measuring device on the surface temperature of the overhead conductor and the damage to the temperature measuring device caused by the heating of the overhead conductor are avoided, and the accuracy of the surface temperature measurement of the overhead conductor is improved.

[0004] In the existing technology, the assessment of conductor thermal disaster risk is mainly based on the assumption of homogeneous materials, ignoring the anisotropic thermal conductivity characteristics of twisted conductors, resulting in serious distortion in the prediction of the internal true temperature distribution and hot spot formation. The temperature rise calculation is performed based on a single thermal conductivity coefficient, which leads to inaccurate assessment of the thermal risk of twisted conductors. Therefore, a thermal disaster risk assessment method based on parametric modeling of twisted conductor structure is proposed to solve the problem of inaccurate thermal risk assessment of twisted conductors in the existing conductor thermal disaster risk assessment method. Summary of the Invention

[0005] The purpose of the present invention is to provide a thermal disaster risk assessment method based on parametric modeling of twisted conductor structure, aiming to solve the problem that the conductor thermal disaster risk assessment method in the prior art is inaccurate in thermal risk assessment of twisted conductors.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for thermal disaster risk assessment based on parametric modeling of twisted conductor structure, comprising the following steps: Digital modeling, collecting basic parameters of the twisted conductor, building a three-dimensional calculation model, and calculating the volume fraction of the metal core and insulation layer and the helical angle of the metal core through the three-dimensional calculation model; Anisotropic thermal conductivity calculation, calculate the axial thermal conductivity and radial thermal conductivity of the metal wire core wrapped by the insulation layer; Multi-physics coupling simulation, coupling Joule heating, external radiation heat flow and anisotropic heat transfer equations to perform calculations, outputting the change in internal temperature distribution of the conductor over time under power-on or external radiation conditions, i.e. dynamic temperature field data; Dynamic failure criterion: Coupled with dynamic temperature field data, predict the critical time of the flammable and melting temperatures of the insulation layer of the twisted conductor, calculate the time when the insulation layer reaches the melting temperature and flammable temperature, and output the melting temperature time and flammable temperature time of the insulation layer; Risk quantification output, set the safety time threshold, calculate the melting critical time and combustion critical time based on the melting temperature time and the flammable temperature time, and output the risk level and safety margin index by comparing the melting critical time and combustion critical time with the safety time threshold.

[0007] As an example, the basic parameters of the stranded conductor include the diameter d of a single core, the number of cores n, the radius of the total core, and the diameter of the core. , insulation layer thickness and the material properties of the stranded conductors; For a twisted conductor, n cores are twisted axially with insulation between the cores. The volume fraction of the metal core is calculated. The three-dimensional calculation model calculates the cross-sectional area of ​​a single metal wire core, the total proportion of wire cores within the cross-sectional area per unit length, and the proportion of insulation material.

[0008] Preferably, the specific calculation formula for the cross-sectional area of ​​the single metal wire core is: ; Where d is the diameter of a single core of the input twisted conductor; The total proportion of wire cores within the cross-sectional area per unit length is expressed as: ; ; in, is the total cross-sectional area of ​​the conductor core; The proportion of insulation material is expressed as: .

[0009] Preferably, the core helix angle is calculated according to the following formula: ; Where D is the diameter of the metal wire core, , p is the twist lay pitch of the metal wire core.

[0010] Preferably, the axial thermal conductivity and radial thermal conductivity of the stranded conductor are calculated based on the thermal conductivity of the metal core wire, the thermal conductivity of the insulation layer, the number of cores, and the core radius; The spiral arrangement of the core results in the axial heat conduction projection being: ; Axial heat is mainly conducted through the continuous metal core and the filled insulation material. The axial thermal conductivity is calculated as: ; .

[0011] Preferably, when the heat flow passes vertically through the metal core and the insulation layer, the radial thermal conductivity is calculated according to the following formula: ; .

[0012] As a preference, for a helically twisted core, the radial thermal conductivity depends only on the material distribution and microstructure within the cross section. Using the equivalent medium theory, the calculation formula is as follows: .

[0013] Preferably, in the multi-physics field coupling simulation, for the metal wire core, the anisotropic heat conduction equation based on the cylindrical coordinate system is expressed as: ; in, is Joule heat, is the axial thermal conductivity, is the radial thermal conductivity; ; in, is the overall resistivity of the twisted conductor; The equivalent density is: ; ; For the insulating layer, the heat conduction equation based on the cylindrical coordinate system is established as: ; Add a radiation surface in the axial position on the insulation layer and add radiation heat flow Input, then the boundary is: ; For other boundaries, natural convection or adiabatic conditions are maintained.

[0014] Preferably, the dynamic failure criterion is calculated by coupling the thermal conductivity of the insulating sheath and the thermal conductivity of the metal core to determine the time when the insulating sheath reaches the melting temperature or the flammable temperature.

[0015] Preferably, the safety margin index is specifically a ratio of the actual critical time to the safety time threshold.

[0016] In the above technical solution, the present invention provides a thermal disaster risk assessment method based on parametric modeling of twisted conductor structure, which has the following beneficial effects: By performing parametric modeling and calculating the anisotropic thermal conductivity of twisted conductors, the reliability of thermal hazard assessment is improved. An accurate and reversible quantitative mapping relationship is established between key twisted structural parameters such as core diameter, twist density, and lay length and the axial / radial anisotropic thermal conductivity of the conductors. This allows direct model simulation during the twisted conductor design stage, thereby optimizing the parameters of the twisted conductors and improving the safety factor of the final produced twisted conductors. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments described in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0018] Figure 1 A flowchart provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0020] like Figure 1 As shown, a thermal disaster risk assessment method based on parametric modeling of a twisted conductor structure includes the following steps: Digital modeling, collecting basic parameters of twisted conductors, building a three-dimensional calculation model, and calculating the volume fractions of the metal and insulation layers and the helix angle of the metal core through the three-dimensional calculation model; Anisotropic thermal conductivity calculation, calculate the axial thermal conductivity and radial thermal conductivity of the wire core; Multi-physics coupling simulation, coupling Joule heating, external radiation heat flow and anisotropic heat transfer equations to perform calculations, outputting the change in internal temperature distribution of the conductor over time under power-on or external radiation conditions, i.e. dynamic temperature field data; Dynamic failure criterion: Coupled with dynamic temperature field data, predict the critical time of the flammable and melting temperatures of the insulation layer of the twisted conductor, calculate the time when the insulation layer reaches the melting temperature and flammable temperature, and output the melting temperature time and flammable temperature time of the insulation layer; Risk quantification output, set the safety time threshold, calculate the melting critical time and combustion critical time based on the melting temperature time and the flammable temperature time, and output the risk level by comparing the melting critical time and the combustion critical time with the safety time threshold.

[0021] Collect basic data of twisted conductors, including the diameter d of a single core inside the twisted conductor, the number n of bus cores inside the twisted conductor, and the radius of the bus core , insulation layer thickness and the material properties of the stranded conductors; The material properties of the stranded conductors include: Metal core: thermal conductivity ,density , specific heat ; Thermal conductivity of the filling insulation material ,density , specific heat ; Insulation layer: thermal properties 、 、 .

[0022] Based on the basic data of twisted conductors, a three-dimensional calculation model is constructed. The specific calculations include the cross-sectional area of ​​a single metal wire core, the total proportion of wire cores per unit length of cross-sectional area (the filling rate of the wire core), and the proportion of insulation material.

[0023] The cross-sectional area of ​​a single metal wire core is expressed as: ; Where d is the diameter of a single core of the input twisted conductor; The total proportion of wire cores per unit length cross-sectional area (filling rate): ; ; in, is the total cross-sectional area of ​​the conductor core; The proportion of insulation material is expressed as: .

[0024] By digitizing the geometric structure of the input twisted conductor, quantitative input is provided for subsequent calculations, avoiding errors in empirical assumptions.

[0025] By inputting parameters such as wire core diameter, number of core wires, and insulation layer thickness, a three-dimensional calculation model is constructed to calculate the volume fraction of the metal conductor, the volume fraction of the insulation layer, and the helix angle of the metal wire core.

[0026] The specific calculation formula for the core helix angle is: ; Where D is the diameter of the metal wire core, , lay length p; Calculate the geometry-physical property mapping relationship: Calculate the volume fraction of the metal conductor and the volume fraction of the insulation layer through the "model assumption of the twisted wire core structure", and then obtain the overall equivalent physical property parameters through the volume fraction wait.

[0027] By modeling the twisted conductors with structured arrays, the macroscopic geometric parameters (such as the twist pitch p, the diameter D of the metal core) and the microscopic material distribution (such as the volume fraction of the metal core, the volume fraction of the insulation) of the twisted conductors as well as the core heat transfer geometric characteristics (such as the core helix angle) can be realized. This mapping overcomes the geometric difficulty of traditional methods in simplifying complex three-dimensional twisted structures into computable physical parameters, providing high-fidelity structural input for subsequent anisotropic thermal conductivity calculations.

[0028] In the anisotropic thermal conductivity calculation, it is necessary to calculate the axial thermal conductivity and radial thermal conductivity of the wire core; Specifically, the input parameters are: thermal conductivity of the metal core wire , Thermal conductivity of the filling insulation material , Number of twisted wire cores n, Bus core radius .

[0029] For the calculation of axial thermal conductivity, the spiral arrangement of the core leads to the following axial thermal conductivity projection: ; Furthermore, axial heat is mainly conducted through the continuous metal core and the filled insulation material. The axial thermal conductivity is calculated as: ; .

[0030] In calculating the radial heat transfer coefficient, the radial heat flow path is extremely complex and difficult to accurately model due to the complex alternating arrangement and uneven contact between the metal wires and the insulating filler material within the stranded conductor structure. The radial heat transfer path passes through alternating layers of metal wire and insulation material, with the radial direction being perpendicular to the conductor axis. The heat flow path is complex due to the stranded structure. The model assumes that the radial arrangement of the wires and filler can be approximated as the thermal conductivity path of the composite material. It is important to note that the radial heat flow path is confined to the cross-section and is independent of the strand pitch of the stranded conductor.

[0031] As one of the embodiments provided by the present invention, when the heat flow passes vertically through the metal core and the insulation layer, the radial thermal conductivity is calculated according to the following formula: ; .

[0032] As another embodiment provided by the present invention, the core is spiral-shaped, and its radial thermal conductivity depends only on the material distribution and microstructure within the cross section, using the equivalent medium theory. Specifically, the following formula is used for calculation: ; The effective medium principle is suitable for sparsely distributed cylindrical wire cores, and the diameter of the metal wire core is less than 0.3mm.

[0033] As another embodiment provided by the present invention, the equivalent medium theory may be replaced by a Bruggeman symmetric model. The Bruggeman model describes the interaction between the metal core and the insulating material by solving nonlinear equations.

[0034] It accurately and quantitatively describes the inherent and critical anisotropic heat conduction directionality of twisted conductors, breaking through the limitations of traditional homogeneous models.

[0035] The final output is the axial thermal conductivity of the entire core wrapped by the insulation layer and radial thermal conductivity .

[0036] Multi-physics coupling simulation enables seamless, dynamic, and bidirectional coupling of Joule heating, external radiation heat flow (complex boundary conditions), and internal anisotropic heat transfer equations.

[0037] In this calculation step, the parameters that need to be input are: Joule heat , axial thermal conductivity , radial thermal conductivity , the density of the metal core and specific heat capacity , the density of the filling material and specific heat capacity , the density of the insulation layer and specific heat capacity .

[0038] The anisotropic heat conduction equation based on the cylindrical coordinate system for the metal wire core is expressed as: ; in, is Joule heat, is the axial thermal conductivity, is the radial thermal conductivity; ; in, is the overall resistivity of the twisted conductor; The equivalent density is: ; ; For the insulating layer, the heat conduction equation based on the cylindrical coordinate system is established as: ; Add a radiation surface in the axial position on the insulation layer and add radiation heat flow Input, then the boundary is: ; For other boundaries, natural convection or adiabatic conditions are maintained.

[0039] In this calculation process, the finite element method (FEM) or finite difference method (FDM) is used to divide the grid in the spatial discretization solution process, and the implicit time integration (such as the Crank-Nicolson method) is used to ensure stability for transient problems in the time discretization solution process.

[0040] The final output calculation results are: the change of temperature distribution of the metal core layer and insulation layer of the twisted conductor over time under power-on or external radiation conditions, that is, dynamic temperature field data.

[0041] During the solution process, the finite difference model (FDM) algorithm was optimized to address the characteristics of transient and high-gradient temperature fields. An adaptive mesh refinement strategy was used to accurately capture local hotspots, and customized preprocessing techniques were introduced to ensure numerical stability and computational efficiency under strong nonlinear and transient coupling conditions. This enables the model to faithfully reproduce the actual thermal response of conductors under extreme dynamic conditions such as arc fires and transient overloads, whereas traditional models are prone to numerical divergence or prediction distortion in such scenarios.

[0042] Specifically, the adaptive grid refinement strategy is a conventional strategy in the prior art and will not be described in detail here.

[0043] The dynamic failure criterion combines the dynamic temperature field data output by the multi-physics field coupling module to achieve real-time and accurate prediction of the critical time (tcritical) for the insulation layer to reach the flammable temperature and melting temperature.

[0044] In this module, the parameters that need to be input are: thermal conductivity of the metal core ,density and specific heat ; Thermal conductivity of the filling insulation material ,density and specific heat , thermal physical parameters of the insulation layer 、 、 , temperature resistance threshold ; and the structural parameters of the stranded conductor: single core wire diameter d, total number of core wires n, total core radius , insulation layer thickness ; Radiation parameters: , absorption rate .

[0045] It should be noted that the radiation parameters are measured experimentally, obtained from the material database, or determined according to environmental conditions.

[0046] Critical temperature determination: set the flammable temperature according to the type of insulation material (such as XLPE, PVC) and melting temperature By numerically solving the equations provided in the above embodiment, the time for the insulation layer to reach the melting temperature or the flammable temperature is calculated and recorded as , .

[0047] Risk quantification output Set the safety time threshold. The safety time threshold is After solving the above model, the temperature field inside the conductor and the insulation layer at different times is obtained, and the insulation layer reaches the flammable temperature through the cycle. and melting temperature Time required and , calculate the critical time Then, by comparing the critical time with the system safety time threshold , to output the risk level.

[0048] Specifically, when , output the risk level of the current twisted conductor as low risk; when , output the risk level of the current twisted conductor as medium risk; when , output the risk level of the current twisted conductor as high risk; The ratio of the actual critical time to the system safety requirement is the safety margin index, which is expressed as: ; Among them, when: When the output current twisted conductor thermal risk assessment is safe; when , output the current twisted conductor thermal risk assessment as requiring early warning; when When , the output indicates that the thermal risk assessment of the current twisted conductor requires immediate treatment.

[0049] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0050] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0051] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0052] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0053] Specific embodiments are used in the present invention to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas. At the same time, for those skilled in the art, according to the ideas of the present invention, there may be changes in the specific implementation methods and application scopes. In summary, the contents of this specification should not be understood as limiting the present invention.

[0054] The embodiments of the present application also provide a specific implementation of an electronic device capable of implementing all steps of the method in the above embodiments. The electronic device specifically includes the following contents: Processor, memory, communications interface, and bus; The processor, memory, and communication interface communicate with each other via the bus. The processor is configured to call the computer program in the memory. When the processor executes the computer program, all steps of the method in the above embodiment are implemented. For example, when the processor executes the computer program, the following steps are implemented: Digital modeling, collecting basic parameters of the twisted conductor, building a three-dimensional calculation model, and calculating the volume fraction of the metal core and insulation layer and the helical angle of the metal core through the three-dimensional calculation model; Anisotropic thermal conductivity calculation, calculate the axial thermal conductivity and radial thermal conductivity of the metal wire core wrapped by the insulation layer; Multi-physics coupling simulation, coupling Joule heating, external radiation heat flow and anisotropic heat transfer equations to perform calculations, outputting the change in internal temperature distribution of the conductor over time under power-on or external radiation conditions, i.e. dynamic temperature field data; Dynamic failure criterion: Coupled with dynamic temperature field data, predict the critical time of the flammable and melting temperatures of the insulation layer of the twisted conductor, calculate the time when the insulation layer reaches the melting temperature and flammable temperature, and output the melting temperature time and flammable temperature time of the insulation layer; Risk quantification output, set the safety time threshold, calculate the melting critical time and combustion critical time based on the melting temperature time and the flammable temperature time, and output the risk level and safety margin index by comparing the melting critical time and combustion critical time with the safety time threshold.

[0055] The embodiments of the present application also provide a computer-readable storage medium capable of implementing all the steps of the method in the above embodiments. The computer-readable storage medium stores a computer program. When the computer program is executed by a processor, all the steps of the method in the above embodiments are implemented. For example, when the processor executes the computer program, the following steps are implemented: Digital modeling, collecting basic parameters of the twisted conductor, building a three-dimensional calculation model, and calculating the volume fraction of the metal core and insulation layer and the helical angle of the metal core through the three-dimensional calculation model; Anisotropic thermal conductivity calculation, calculate the axial thermal conductivity and radial thermal conductivity of the metal wire core wrapped by the insulation layer; Multi-physics coupling simulation, coupling Joule heating, external radiation heat flow and anisotropic heat transfer equations to perform calculations, outputting the change in internal temperature distribution of the conductor over time under power-on or external radiation conditions, i.e. dynamic temperature field data; Dynamic failure criterion: Coupled with dynamic temperature field data, predict the critical time of the flammable and melting temperatures of the insulation layer of the twisted conductor, calculate the time when the insulation layer reaches the melting temperature and flammable temperature, and output the melting temperature time and flammable temperature time of the insulation layer; Risk quantification output, set the safety time threshold, calculate the melting critical time and combustion critical time based on the melting temperature time and the flammable temperature time, and output the risk level and safety margin index by comparing the melting critical time and combustion critical time with the safety time threshold.

[0056] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between the various embodiments can be referenced across them. Each embodiment focuses on the differences from other embodiments. In particular, for hardware + program embodiments, since they are generally similar to method embodiments, their description is relatively simple. For relevant parts, reference can be made to the description of the method embodiments. Although the embodiments in this specification provide method operation steps as described in the embodiments or flowcharts, more or fewer operation steps may be included based on conventional or non-inventive means. The order of steps listed in the embodiments is merely one of many possible execution sequences and does not represent the only execution sequence. When implemented in a practical device or end product, the methods shown in the embodiments or figures may be executed sequentially or in parallel (for example, in a parallel processor or multi-threaded processing environment, or even a distributed data processing environment). The terms "comprise," "comprising," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, product, or apparatus comprising a set of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, product, or apparatus. Without further limitation, this does not preclude the presence of additional identical or equivalent elements in a process, method, product, or apparatus comprising the elements described. For ease of description, the above devices are described as functionally divided into various modules. Of course, when implementing the embodiments of this specification, the functions of each module can be implemented in the same or multiple software and / or hardware components, or a module implementing the same function can be implemented by a combination of multiple sub-modules or sub-units. The device embodiments described above are merely illustrative. For example, the division of units described is merely a logical functional division. In actual implementation, other divisions may be used, such as combining or integrating multiple units or components into another system, or omitting or disabling some features. Furthermore, the coupling or direct coupling or communication connection shown or discussed between devices or units may be through interfaces, or indirect coupling or communication connection between devices or units, and may be electrical, mechanical, or other forms. The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device produce the instructions for implementing the process Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0057] Those skilled in the art will appreciate that the embodiments of this specification can be provided as methods, systems, or computer program products. Therefore, the embodiments of this specification may take the form of entirely hardware embodiments, entirely software embodiments, or embodiments combining software and hardware. Furthermore, the embodiments of this specification may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk drives, CD-ROMs, optical storage devices, etc.) containing computer-usable program code. The various embodiments in this specification are described in a progressive manner, and similar parts between the various embodiments can be referenced across them. Each embodiment focuses on the differences from other embodiments. In particular, since the system embodiments are generally similar to the method embodiments, their description is relatively simple; for relevant parts, reference can be made to the description of the method embodiments. Throughout this specification, reference to the terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the embodiments of this specification.

[0058] In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples, unless they contradict each other. The above is only an embodiment of the embodiment of this specification and is not intended to limit the embodiment of this specification. For those skilled in the art, the embodiment of this specification may have various changes and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiment of this specification shall be included within the scope of the claims of the embodiment of this specification.

Claims

1. A thermal disaster risk assessment method based on parametric modeling of twisted conductor structure, characterized in that: The following steps are involved: Digital modeling, collecting basic parameters of the twisted conductor, building a three-dimensional calculation model, and calculating the volume fraction of the metal core and insulation layer and the helical angle of the metal core through the three-dimensional calculation model; Anisotropic thermal conductivity calculation, calculate the axial thermal conductivity and radial thermal conductivity of the metal wire core wrapped by the insulation layer; Multi-physics coupling simulation, coupling Joule heating, external radiation heat flow and anisotropic heat transfer equations to perform calculations, outputting the change in internal temperature distribution of the conductor over time under power-on or external radiation conditions, i.e. dynamic temperature field data; Dynamic failure criterion: Coupled with dynamic temperature field data, predict the critical time of the flammable and melting temperatures of the insulation layer of the twisted conductor, calculate the time when the insulation layer reaches the melting temperature and flammable temperature, and output the melting temperature time and flammable temperature time of the insulation layer; Risk quantification output, set the safety time threshold, calculate the melting critical time and combustion critical time based on the melting temperature time and the flammable temperature time, and output the risk level and safety margin index by comparing the melting critical time and combustion critical time with the safety time threshold.

2. The thermal disaster risk assessment method based on parametric modeling of twisted conductor structure according to claim 1 is characterized in that: The basic parameters of the stranded conductor include the diameter d of a single core, the number of cores n, the total core radius , insulation layer thickness and the material properties of the stranded conductors; For a twisted conductor, n cores are twisted axially with insulation between the cores. The volume fraction of the metal core is calculated. The three-dimensional calculation model calculates the cross-sectional area of ​​a single metal wire core, the total proportion of wire cores within the cross-sectional area per unit length, and the proportion of insulation material.

3. The thermal disaster risk assessment method based on parametric modeling of twisted conductor structure according to claim 2 is characterized in that: The specific calculation formula for the cross-sectional area of ​​a single metal wire core is: ； Where d is the diameter of a single core of the input twisted conductor; The total proportion of wire cores within the cross-sectional area per unit length is expressed as: ； ； in, is the total cross-sectional area of ​​the conductor core; The proportion of insulation material is expressed as: 。 4. The thermal disaster risk assessment method based on parametric modeling of twisted conductor structure according to claim 2 is characterized in that: The core helix angle is calculated according to the following formula: ； Where D is the diameter of the metal wire core, , p is the twist lay pitch of the metal wire core.

5. The thermal disaster risk assessment method based on parametric modeling of twisted conductor structure according to claim 1 is characterized in that: Calculate the axial thermal conductivity and radial thermal conductivity of the stranded conductor based on the thermal conductivity of the metal core wire, the thermal conductivity of the insulation layer, the number of cores and the core radius; The spiral arrangement of the core results in the axial heat conduction projection being: ； Axial heat is mainly conducted through the continuous metal core and the filled insulation material. The axial thermal conductivity is calculated as: ； 。 6. The thermal disaster risk assessment method based on parametric modeling of twisted conductor structure according to claim 5 is characterized in that: For the case where the heat flow passes vertically through the metal core and the insulation layer, the radial thermal conductivity is calculated according to the following formula: ； 。 7. The thermal disaster risk assessment method based on parametric modeling of twisted conductor structure according to claim 5, characterized in that: For spirally twisted cores, the radial thermal conductivity depends only on the material distribution and microstructure within the cross section. Using the equivalent medium theory, the calculation formula is as follows: 。 8. The thermal disaster risk assessment method based on parametric modeling of twisted conductor structure according to claim 1 is characterized in that: In the multi-physics coupling simulation, for the metal wire core, the anisotropic heat conduction equation based on the cylindrical coordinate system is expressed as: ； in, is Joule heat, is the axial thermal conductivity, is the radial thermal conductivity; ； in, is the overall resistivity of the twisted conductor; The equivalent density is: ； ； For the insulating layer, the heat conduction equation based on the cylindrical coordinate system is established as: ； Add a radiation surface in the axial position on the insulation layer and add radiation heat flow Input, then the boundary is: ； For other boundaries, natural convection or adiabatic conditions are maintained.

9. The thermal disaster risk assessment method based on parametric modeling of twisted conductor structure according to claim 1, characterized in that: The dynamic failure criterion is calculated by coupling the thermal conductivity of the insulating sheath and the thermal conductivity of the metal core to determine the time when the insulating sheath reaches the melting temperature or the flammable temperature.

10. The thermal disaster risk assessment method based on parametric modeling of twisted conductor structure according to claim 1, characterized in that: The safety margin index is specifically a ratio of the actual critical time to the safety time threshold.

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