Cable temperature simulation model construction method and system based on multi-field coupling

Abstract

The invention discloses a cable temperature simulation model construction method and system based on multi-field coupling, and relates to the technical field of multi-physical field coupling simulation and tunnel cables, and the method comprises the steps: constructing a three-dimensional geometric model based on actual cable structure parameters and cable tunnel three-dimensional scanning data; physical field parameters are set for all layers of materials of the cable and peripheral media of the tunnel, boundary heat dissipation conditions are defined, two-dimensional grid division is conducted on the model according to the axial symmetry characteristic of the cross section of the cable, processing frequency load current excitation is applied, electromagnetic field distribution is solved, and a three-dimensional steady-state temperature field control equation is constructed; and solving three-dimensional temperature distribution of the cable and tunnel environment, establishing a bidirectional coupling relationship between an electromagnetic field and a temperature field, and iteratively updating Joule loss power and temperature field distribution by dynamically adjusting conductor conductivity until a convergence condition is met. According to the invention, real-time monitoring and early warning of the temperature along the cable are realized, and detection and response at the initial stage of a fault are ensured, so that the operation safety and reliability of a power system are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of multi-physical field coupling simulation and tunnel cable, and particularly relates to a cable temperature simulation model construction method and system based on multi-field coupling. BACKGROUND

[0002] As an important medium for power transmission, the stable working state of high-voltage cable is crucial to guarantee the power supply quality and safety of the power system. However, long-time running high-voltage cable is easily affected by factors such as insulation aging, mechanical damage, poor installation quality, etc., leading to faults in the intermediate joint part and the conductor, and even explosion accidents in severe cases. According to statistics, the intermediate joint fault accounts for about 63% of the main causes of high-voltage cable fire accidents. When the high-voltage cable fails, the leakage current increases, causing the conductor loss to intensify, and the heat generated at the fault point accumulates, causing the temperature to rise. This high temperature not only damages the insulation layer of the cable, but also endangers the surrounding facilities, especially in relatively closed environments such as cable tunnels and trenches. Once an explosion occurs, it will pose a serious safety hazard.

[0003] Current high-voltage cable temperature monitoring technologies mainly include infrared imaging, point temperature sensing, and distributed optical fiber sensing, etc. However, these methods can usually only monitor the external temperature of the cable, and the monitoring accuracy and spatial resolution are limited. Point sensors have monitoring blind spots and cannot achieve high-precision distributed monitoring of the internal conductor temperature of the cable. Moreover, they have limited efficiency when facing randomly distributed fault locations, making it difficult to achieve comprehensive monitoring and early warning. Distributed optical fiber sensing can solve the problem of comprehensive monitoring of randomly distributed fault locations, but it cannot achieve internal temperature monitoring of the cable. SUMMARY

[0004] In view of the above existing problems, the present application provides a cable temperature simulation model construction method and system based on multi-field coupling, to solve the problems that the existing technology can only monitor the external temperature of the cable, and the monitoring accuracy and spatial resolution are limited, and cannot achieve internal temperature monitoring of the cable.

[0005] To solve the above technical problems, a cable temperature simulation model construction method based on multi-field coupling is proposed, which includes,

[0006] Based on the actual cable structure parameters and the three-dimensional scanning data of the cable tunnel, a three-dimensional geometric model is constructed, and physical field parameters of cable layer materials and tunnel peripheral media in the three-dimensional geometric model are set, and boundary heat dissipation conditions are defined; according to the axial symmetry characteristics of the cable cross section, two-dimensional grid division is performed on the three-dimensional geometric model, and a working frequency load current excitation is applied, and electromagnetic field distribution is solved; the Joule loss power is taken as a heat source term, combined with the heat conduction, heat convection and heat radiation mechanism, a three-dimensional steady-state temperature field control equation is constructed, and the three-dimensional temperature distribution of the cable and the tunnel environment is solved; a two-way coupling relationship between the electromagnetic field and the temperature field is established, and the conductor conductivity is dynamically adjusted, and the Joule loss power and the temperature field distribution are iteratively updated until the convergence condition is met.

[0007] As a preferred scheme of the cable temperature simulation model construction method based on multi-field coupling provided by the application, the three-dimensional geometric model is constructed by determining the size of the conductor and the insulating layer according to the rated current and voltage level of the cable, obtaining the tunnel structure parameters through environmental scanning data, and integrating the spatial layout of the cable and the tunnel to construct a three-dimensional geometric model containing the geometric characteristics of the high-voltage cable layer and the tunnel environment.

[0008] The high-voltage cable layer includes a copper conductor, a conductor shielding layer, an XLPE insulating layer, an insulating shielding layer, a water-blocking layer, an air layer, a corrugated aluminum sheath and an outer sheath, and the influence of uneven distribution of the air layer on the geometric model is ignored.

[0009] The setting of the physical field parameters includes setting the electrical conductivity, thermal conductivity, heat capacity, density, relative dielectric constant and magnetic permeability parameters.

[0010] As a preferred scheme of the cable temperature simulation model construction method based on multi-field coupling provided by the application, the boundary heat dissipation conditions are defined by setting the natural convection heat transfer coefficient of the upper surface of the cable tunnel and the air, setting the constant temperature condition of the lower boundary, and setting the heat balance condition of the left and right boundaries with the normal heat flux density being zero.

[0011] As a preferred scheme of the cable temperature simulation model construction method based on multi-field coupling provided by the application, the two-dimensional grid division includes dividing the area according to the electromagnetic field intensity gradient and the temperature gradient distribution, using dense grid on the surface of the cable conductor and the insulating interface, and using sparse grid in the soil and sheath area.

[0012] As a preferred scheme of the cable temperature simulation model construction method based on multi-field coupling provided by the application, the solving of the electromagnetic field distribution includes generating an electromagnetic field excitation source based on the working frequency current excitation, solving the electromagnetic field by ignoring the quasi-steady-state equation of displacement current, and calculating the heat source power of the conductor and the insulating layer according to the relationship between the current density and the magnetic field intensity.

[0013] The construction of the three-dimensional steady-state temperature field control equation comprises mapping the heat source power to a heat source term of a three-dimensional geometric model, defining a heat transfer equation in combination with heat conduction, heat convection and heat radiation mechanisms, and performing numerical solution of the three-dimensional steady-state temperature field control equation through a discretization method.

[0014] As a preferred scheme of the cable temperature simulation model construction method based on multi-field coupling, the two-way coupling relationship between the electromagnetic field and the temperature field is established by adjusting the conductivity of the conductor according to the temperature distribution, updating the material parameters through a linear relationship, feeding back the updated conductivity, regenerating the heat source power, and repeating the iteration until the temperature residual error meets the preset threshold.

[0015] The relationship between the conductivity and the temperature is represented as:

[0016]

[0017] wherein σ is the conductivity, σ 20 is the conductivity at the reference temperature, and α is the resistance temperature coefficient, T is the temperature, and T amb is the reference ambient temperature.

[0018] The electromagnetic-thermal coupling control equation is represented as:

[0019]

[0020] wherein σ is the conductivity, is the Laplace operator, T is the temperature, Q is the heat source term, that is, the heat generated per unit volume, J is the current density, and λ is the thermal conductivity.

[0021] As a preferred scheme of the cable temperature simulation model construction method based on multi-field coupling, the temperature residual error determination comprises calculating the global maximum temperature change and comparing it with the preset tolerance, and when the convergence is not achieved, the conductivity and the heat source power are updated and the next round of iteration is entered.

[0022] The convergence condition comprises setting a tolerance range of the temperature change and defining a maximum number of iterations.

[0023] As a preferred scheme of the cable temperature simulation model construction system based on multi-field coupling, the system comprises a geometric modeling module, a material and boundary parameter configuration module, a mesh division and optimization module, and an electromagnetic-thermal field dynamic coupling simulation module.

[0024] The geometric modeling module is configured to construct a three-dimensional geometric model based on the actual structural parameters of the high-voltage cable and three-dimensional laser scanning data of the cable tunnel.

[0025] The material and boundary parameter configuration module is configured to define physical field parameters of each layer of the cable and the peripheral medium, including conductivity, thermal conductivity, heat capacity and density, and set boundary heat dissipation conditions.

[0026] The mesh division and optimization module is configured to simplify the three-dimensional model into a two-dimensional axisymmetric model according to the axisymmetric characteristics of the cable cross section, encrypt the mesh in key areas, use coarse mesh in the outer sheath and soil area, and balance simulation accuracy and resource consumption by dynamically adjusting the mesh density.

[0027] The electromagnetic-thermal field dynamic coupling simulation module is configured to apply a working frequency load current excitation, solve electromagnetic field distribution based on a simplified Maxwell equation set, calculate Joule loss power of the conductor and the insulating layer, construct a three-dimensional temperature field control equation by combining heat conduction, heat convection and heat radiation mechanisms with the Joule loss power as a heat source term, solve temperature distribution by a finite element method, establish a two-way coupling relationship between the electromagnetic field and the temperature field, dynamically adjust the conductivity of the conductor according to the temperature distribution, and iteratively update the heat source power and the temperature field until convergence.

[0028] A computer device includes a memory and a processor, the memory stores a computer program, and the processor implements the steps of the method for constructing a cable temperature simulation model based on multi-field coupling when executing the computer program.

[0029] A computer readable storage medium stores a computer program, and the computer program implements the steps of the method for constructing a cable temperature simulation model based on multi-field coupling when executed by a processor.

[0030] The beneficial effects of the present application: the present application is based on the actual cable structure parameters and the cable tunnel three-dimensional scanning data to construct a three-dimensional geometric model, and set the physical field parameters for the cable layer material and the tunnel peripheral medium in the model, and define the boundary heat dissipation conditions, realize the accurate simulation of the actual cable and its tunnel environment, provide a reliable basic model for temperature field simulation, improve the accuracy and reliability of the simulation model; according to the axial symmetry characteristics of the cable cross section, the two-dimensional grid division is carried out on the three-dimensional geometric model, and the working frequency load current excitation is applied, the electromagnetic field distribution is solved, the accurate modeling of the high-voltage cable layer and the tunnel environment is realized, and the fineness of the simulation model is improved; the joule loss power is taken as the heat source term, combined with the heat conduction, heat convection and heat radiation mechanism, the three-dimensional steady-state temperature field control equation is constructed, and the three-dimensional temperature distribution of the cable and the tunnel environment is solved, through reasonable boundary condition setting, the stability and accuracy of the simulation model are improved; the two-way coupling relationship between the electromagnetic field and the temperature field is established, the conductor conductivity is adjusted according to the temperature distribution, and the material parameters are updated through the linear relationship, the updated conductivity is fed back, the heat source power is regenerated, and the iteration is repeated until the temperature residual error meets the preset threshold, the dynamic interactive simulation of the electromagnetic field and the temperature field is realized, so that the simulation model can more truly reflect the temperature change of the cable in the actual operation; and by calculating the global maximum temperature change and comparing with the preset tolerance, the tolerance range of the temperature change and the maximum iteration number are set as the convergence condition, to ensure the convergence and stability of the simulation process. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creating laborious work.

[0032] Figure 1 The overall flow chart of the cable temperature simulation model construction method based on multi-field coupling provided by an embodiment of the present application.

[0033] Figure 2 The cable conductor temperature calculation flow chart of the cable temperature simulation model construction method based on multi-field coupling provided by an embodiment of the present application.

[0034] Figure 3 The grid division result schematic diagram of the cable temperature simulation model construction method based on multi-field coupling provided by an embodiment of the present application.

[0035] Figure 4 The cable temperature simulation result schematic diagram of the cable temperature simulation model construction method based on multi-field coupling provided by an embodiment of the present application.

[0036] Figure 5 The system scheme flow chart of the cable temperature simulation model construction system based on multi-field coupling provided by an embodiment of the present application. DETAILED DESCRIPTION

[0037] In order to make the above objectives, features and advantages of the present application more apparent, specific embodiments of the present application are described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work should fall within the protection scope of the present application.

[0038] In the following description, a large number of specific details are set forth in order to facilitate a thorough understanding of the present application. However, the present application can be implemented in other different manners than those described, and those skilled in the art can make similar generalizations without departing from the spirit and scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0039] Secondly, the term "one embodiment" or "an embodiment" as used herein means that a specific feature, structure or characteristic described can be included in at least one implementation of the present application. The term "in one embodiment" appearing in different places in the specification does not mean the same embodiment, nor does it mean that the embodiments are mutually exclusive or alternative to each other.

[0040] The present application is described in detail in conjunction with the schematic diagram. In the detailed description of the embodiments of the present application, the cross-sectional view of the device structure is locally enlarged without the general proportion for the convenience of description, and the schematic diagram is only an example, which should not limit the scope of protection of the present application herein. In addition, the three-dimensional spatial dimensions of length, width and depth should be included in actual manufacture.

[0041] Meanwhile, in the description of the present application, it should be noted that the terms "up, down, in and out" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first, second or third" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0042] Unless otherwise defined, the terms "mounting, connecting, associating" in the present application should be interpreted broadly, for example: it can be fixed connection, detachable connection or integral connection; it can also be mechanical connection, electrical connection or direct connection, it can also be indirectly connected through intermediate medium, or it can be the internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0043] Embodiment 1, reference Figure 1 and Figure 2 The first embodiment of the present application provides a cable temperature simulation model construction method based on multi-field coupling, comprising:

[0044] S1: based on the actual cable structure parameters and the three-dimensional scanning data of the cable tunnel, a three-dimensional geometric model is constructed, and the physical field parameters of the cable layer materials and the tunnel peripheral medium in the three-dimensional geometric model are set, and the boundary heat dissipation conditions are defined.

[0045] The three-dimensional geometric model includes determining the conductor and insulation layer size according to the rated current and voltage level of the cable, obtaining the tunnel structure parameters through environmental scanning data, and integrating the spatial layout of the cable and the tunnel to construct a three-dimensional geometric model containing the geometric characteristics of the high-voltage cable layer and the tunnel environment.

[0046] The high-voltage cable layer includes copper conductor, conductor shielding layer, XLPE insulation layer, insulation shielding layer, water-blocking layer, air layer, corrugated aluminum sheath and outer sheath, and the influence of uneven distribution of the air layer on the geometric model is ignored; the setting of the physical field parameters includes setting the conductivity, thermal conductivity, heat capacity, density, relative dielectric constant and magnetic permeability parameters.

[0047] It should be noted that the geometric model of the cable tunnel can be obtained by three-dimensional laser scanning in the field, and the geometric model of the high-voltage cable is determined by the actual structure size of each layer of the cable. The uneven distribution of the air layer of the high-voltage cable caused by gravity and external force is ignored in the simulation process; the arrangement of the high-voltage cable in the cable tunnel is simulated by a detailed geometric model, which avoids the errors that may be caused by a simplified model, simplifies the model by ignoring the influence of uneven distribution of the air layer, improves the calculation efficiency, and has little effect on the accuracy of the results.

[0048] Further, the definition of the boundary heat dissipation condition includes the setting of the natural convection heat transfer coefficient of the upper surface of the cable tunnel and the air, the setting of the constant temperature condition of the lower boundary, and the setting of the heat balance condition of the normal heat flux density of the left and right boundaries.

[0049] It should be further pointed out that the boundary conditions of the cable trench temperature field equation are the contact surfaces of the soil and the cable tunnel and the ground surface air, the near-surface air temperature is taken as the ambient temperature, and heat is dissipated to the outside air in a natural convection manner, the lower boundary is the soil layer, the temperature of the deep soil layer is taken as constant, which is suitable for constant temperature boundary conditions, the normal temperature gradient of the soil layer on the left side and the right side is constant and is 0, and the heat balance boundary conditions are set on the two side boundaries; the temperature gradient and the heat balance conditions are set according to actual boundary conditions, so that the model is closer to the real working condition, and the accuracy of the response of the simulation result to temperature change is ensured, and the natural convection of the upper boundary further improves the authenticity of the model and reduces the assumption deviation.

[0050] S2: According to the axial symmetry of the cable cross section, a two-dimensional grid division is performed on the three-dimensional geometric model, and a working frequency load current excitation is applied, and electromagnetic field distribution is solved.

[0051] Further, the two-dimensional grid division includes discretizing the structure by using a finite element simulation software to divide the continuous physical space into a limited number of grid units so as to be processed by a computer; wherein the grid division steps are: geometry processing, grid generation, refinement adjustment and quality check, the quality of the grid directly affects the accuracy and calculation efficiency of the simulation result, high-quality grid division can ensure the accuracy and efficiency of the calculation, denser grid distribution makes the calculation more accurate, and coarser regions can improve the calculation efficiency, and this way can effectively balance the simulation accuracy and time cost. According to the physical field characteristics (such as temperature gradient, electromagnetic field intensity), the regions are divided, and finer grids are set in key regions (such as conductor surface and insulation layer), and coarser grids are used in other regions.

[0052] In the embodiments of the present application, the solving of the electromagnetic field distribution includes: based on the two-dimensional axial symmetry model, applying a working frequency load current excitation, solving a simplified Maxwell equation set to obtain electromagnetic field distribution, and calculating the Joule loss power of the conductor and the insulation layer.

[0053] In an optional embodiment, the solving of the electromagnetic field distribution includes: constructing a complete three-dimensional geometric model, and performing full-domain three-dimensional grid division on the cable and the tunnel, the conductor surface and the insulation layer adopt uniform density grids, a working frequency current excitation is applied, and the electromagnetic field distribution is solved based on a complete three-dimensional Maxwell equation set.

[0054] In another optional embodiment, the solving of the electromagnetic field distribution includes: calculating the conductor Joule loss, using a static magnetic field equation, and estimating the heat source power through the current density.

[0055] The solving of the simplified Maxwell equation set is represented as:

[0056]

[0057] where H is the magnetic field strength, J is the current density, B is the magnetic induction, A is the magnetic vector potential, E is the electric field strength, σ is the electrical conductivity, J e is the external excitation current density, v is the velocity, is the Laplace operator.

[0058] The control equation of the high-voltage cable conductor part with load current is:

[0059]

[0060] The control equation of the high-voltage cable conductor part without load current is:

[0061]

[0062] where, is the Laplace operator, μ is the magnetic permeability, A is the magnetic vector potential, J e is the external excitation current density, ω is the angular frequency, σ is the electrical conductivity, j is the imaginary unit; a voltage excitation of 110 kV is applied to the conductor, electromagnetic field simulation results are obtained, two-dimensional Maxwell simulation can simplify the calculation and save time, and can accurately reflect the electromagnetic characteristics of the high-voltage cable, because the cable cross section is symmetrical, only two-dimensional cross section needs to be calculated to meet the modeling requirements.

[0063] S3: Taking the Joule loss power as a heat source term, combining heat conduction, heat convection and heat radiation mechanisms, a three-dimensional steady-state temperature field control equation is constructed, and a three-dimensional temperature distribution of the cable and the tunnel environment is solved.

[0064] In the embodiment of the application, the construction of the three-dimensional steady-state temperature field control equation includes mapping the heat source power to the heat source term of the three-dimensional geometric model, defining the heat transfer equation by combining the heat conduction, heat convection and heat radiation mechanisms, and numerically solving the three-dimensional steady-state temperature field control equation by a discretization method.

[0065] In an alternative embodiment, the construction of the three-dimensional steady-state temperature field control equation includes retaining the heat conduction and convection terms in the temperature field control equation, setting the natural convection coefficient and constant temperature environment in the boundary condition, and solving the simplified heat transfer equation by the finite element method.

[0066] In another alternative embodiment, the construction of the three-dimensional steady-state temperature field control equation includes using a fixed convection heat transfer coefficient, referencing industry experience values in the boundary condition to avoid real-time calculation of the convection coefficient, and solving the temperature field distribution based on fixed parameters.

[0067] The heat conduction formula is expressed as:

[0068]

[0069] wherein q is the heat flux, i.e. the heat passing through a unit area per unit time, Φ is the heat flow, S is the surface area through which the heat passes, λ is the thermal conductivity, T a is the temperature of the object, and x is the coordinate in the x direction of a three-dimensional space;

[0070] The heat radiation formula is expressed as:

[0071] R = εS b σ b T b 4

[0072] wherein R is the radiation heat transfer, i.e. the heat exchanged due to thermal radiation, ε is the emissivity, i.e. the ratio of the radiation ability of the actual surface to that of a black body, S b is the surface area, i.e. the surface area through which the radiation heat transfer occurs, σ b is the black body radiation constant, with a value of 5.67 x 10 -8 W / (m 2 ·K), and T b is the absolute temperature;

[0073] The heat convection formula is expressed as:

[0074] q = hΔT c

[0075] wherein q is the heat flux, i.e. the heat passing through a unit area per unit time, ΔT c is the error between the surface of the object and the fluid, and h is the convective heat transfer coefficient of the surface of the object

[0076] In the solution of the temperature field of the cable, the solid heat conduction control equation is:

[0077]

[0078] wherein T is the temperature, Q is the heat source term, i.e. the heat generated per unit volume, ρ is the material density, c is the specific heat capacity, t is the time variable in the heat conduction process, λ x is the thermal conductivity of the material in the x direction, λ y is the thermal conductivity of the material in the y direction, and λ z is the thermal conductivity of the material in the z direction, and x, y and z are the three-dimensional space coordinates.

[0079] S4: a bidirectional coupling relationship between the electromagnetic field and the temperature field is established, and the electrical conductivity of the conductor is dynamically adjusted, the Joule loss power and the temperature field distribution are iteratively updated until the convergence condition is met.

[0080] The establishing of the bidirectional coupling relationship between the electromagnetic field and the temperature field comprises adjusting the conductivity of the conductor according to the temperature distribution, updating the material parameters through a linear relationship, feeding back the updated conductivity, regenerating the heat source power, and repeating the iteration until the temperature residual error meets the preset threshold.

[0081] Wherein, in the working state of the high-voltage cable with the continuously changing load current, the resistivity of the copper conductor is affected by the actual temperature; when the conductor temperature rises, the resistivity also increases; additional electromagnetic loss also causes further heating of the conductor, and the relationship between the conductivity and the temperature in this process is represented as:

[0082]

[0083] Wherein, σ is the conductivity, σ 20 is the conductivity at the reference temperature, and α is the resistivity temperature coefficient, T is the temperature, and T amb is the reference ambient temperature.

[0084] The dynamic adjustment of the conductivity of the conductor is represented as:

[0085]

[0086] Wherein, q v is the electric charge, K e is a set of eddy current density parameters, and σ is the conductivity.

[0087] The Joule heat generated by the energization of the cable conductor is taken as the heat source term for temperature field calculation, and according to the law of conservation of energy and the Fourier heat conduction law, the electromagnetic-thermal coupling control equation is represented as:

[0088]

[0089] Wherein, σ is the conductivity, is the Laplace operator, T is the temperature, Q is the heat source term, i.e., the heat generated per unit volume, J is the current density, and λ is the thermal conductivity.

[0090] The temperature residual error determination comprises calculating the global maximum temperature change and comparing it with the preset tolerance, and when it does not converge, updating the conductivity and the heat source power and entering the next round of iteration;

[0091] The convergence condition comprises comparing the difference between the current iteration temperature field and the previous result, and when any of the following conditions is met, it is determined to be converged: the temperature residual error criterion, the global maximum temperature change is less than or equal to 0.1℃; the iteration number limit, reaching the preset maximum iteration number of 100 times, forced to terminate to prevent infinite loop, when it does not converge, updating the temperature for the next round of iteration of the electromagnetic-thermal field coupling; and converged, ending the calculation.

[0092] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present application, and they should be covered in the scope of the claims of the present application.

[0093] Embodiment 2, refer to Figure 3 and Figure 4 For an embodiment of the present application, a cable temperature simulation model construction method based on multi-field coupling is provided. In order to verify the beneficial effects of the present application, scientific demonstration is carried out through experiments.

[0094] According to the actual working condition, the height, width, thickness of the tunnel wall, the size of the cable support in the tunnel, the size of the cable, including the thickness of the copper conductor, the conductor shielding layer, the XLPE insulation layer, the insulation shielding layer, the water blocking layer, the air layer, the corrugated aluminum sheath and the outer sheath, etc. are obtained.

[0095] The 110kv high-voltage cable tunnel is geometrically modeled. According to the obtained cable model and voltage grade, the material parameters related to magnetic field in the finite element calculation process need to be set, that is, relative permittivity, relative permeability, resistivity, and the material parameters related to thermal field of the cable peripheral medium, that is, thermal conductivity, constant pressure heat capacity, density, as shown in Table 1 and Table 2:

[0096] Table 1 Cable body material parameter table

[0097]

[0098]

[0099] Table 2 Temperature field parameter table of cable peripheral medium

[0100]

[0101] According to the environmental conditions of the cable tunnel engineering, the solid heat transfer parameters in the finite element calculation process are set, the convective heat transfer coefficient of the cable trench upper surface and air is 5W / (m2*K), the left and right boundary method is 0, and the lower boundary is constant temperature 20℃.

[0102] The model is meshed, the free triangular mesh type is set, the tunnel part unit size is "normal", the soil part is divided by "roughening", and the conductor current is set by bisection method, so that the conductor temperature is constantly close to 90℃, and the final carrying capacity is 1735A.

[0103] Embodiment 3, refer to Figure 5For the third embodiment of the present application, the embodiment provides a cable temperature simulation model construction system based on multi-field coupling, including a geometric modeling module, a material and boundary parameter configuration module, a mesh division and optimization module, and an electromagnetic-thermal field dynamic coupling simulation module.

[0104] The geometric modeling module is configured to construct a three-dimensional geometric model based on actual structural parameters of the high-voltage cable and three-dimensional laser scanning data of the cable tunnel.

[0105] The material and boundary parameter configuration module is configured to define physical field parameters for each layer of material of the cable and the peripheral medium, including electrical conductivity, thermal conductivity, heat capacity, and density, and set boundary heat dissipation conditions.

[0106] The mesh division and optimization module is configured to simplify the three-dimensional model into a two-dimensional axisymmetric model according to the axisymmetric characteristics of the cable cross section, and to encrypt the mesh in key areas, to use coarse mesh in the outer sheath and soil area, and to balance simulation accuracy and resource consumption by dynamically adjusting the mesh density.

[0107] The electromagnetic-thermal field dynamic coupling simulation module is configured to apply a working frequency load current excitation, to solve the electromagnetic field distribution based on the simplified Maxwell equation set, to calculate the Joule loss power of the conductor and the insulating layer, to construct a three-dimensional temperature field control equation by combining the heat conduction, heat convection, and heat radiation mechanisms with the Joule loss power as the heat source term, and to solve the temperature distribution by the finite element method to establish a two-way coupling relationship between the electromagnetic field and the temperature field, to dynamically adjust the electrical conductivity of the conductor according to the temperature distribution, and to iteratively update the heat source power and the temperature field until convergence.

[0108] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and are not limiting, and although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application, and all should be covered in the scope of the claims of the present application.

[0109] Embodiment 4, the fourth embodiment of the present application, which is different from the first two embodiments, is:

[0110] If the functions are implemented in the form of software function units and sold or used as independent products, they can be stored in a computer readable storage medium. Based on this understanding, the technical solutions of the present application or the part of the technical solutions that essentially contribute to the prior art or the part of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes a plurality of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in the various embodiments of the present application. The aforementioned storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a magnetic disk or an optical disk, and various media that can store program codes.

[0111] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered a list of executable instructions for implementing logic functions, and can be specifically embodied in any computer-readable medium for use by an instruction execution system, apparatus, or device, such as a computer-based system, a system including a processor, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions, or in conjunction with these instructions execution systems, apparatuses, or devices. For the purpose of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate, or transport programs for use by an instruction execution system, apparatus, or device, or in conjunction with these instruction execution systems, apparatuses, or devices.

[0112] More specific examples (a non-exhaustive list) of the computer-readable medium include the following: an electrical connection having one or more wires (electrical devices), a portable computer diskette (magnetic devices), a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM). In addition, the computer-readable medium can even be paper or other suitable medium on which the program can be printed, as the program can be electronically obtained, for example, by optical scanning of the paper or other medium, followed by editing, interpreting, or otherwise processing, if necessary, in other suitable ways to be electronically obtained, and then stored in the computer memory.

[0113] It should be understood that aspects of the application can be implemented in hardware, software, firmware or combinations thereof. In the embodiments described above, various steps or methods can be implemented, for example, by software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, and in another embodiment, any of the following technology, known in the art, or combinations thereof, can be used: discrete logic circuitry having logic gates for implementing logic functions upon an application of data signals, application specific integrated circuits having appropriate combinational logic gates, programmable gate arrays (PGA), field programmable gate arrays (FPGA), and the like.

Claims

1. A method for constructing a cable temperature simulation model based on multi-field coupling, characterized by: include, Based on the actual cable structure parameters and the 3D scanning data of the cable tunnel, a 3D geometric model is constructed. The physical field parameters of the cable layer material and the surrounding medium of the tunnel are set in the 3D geometric model, and the boundary heat dissipation conditions are defined. According to the axisymmetric characteristics of the cable cross section, the three-dimensional geometric model is divided into two-dimensional grids, and the power frequency load current excitation is applied to solve the electromagnetic field distribution; Taking Joule loss power as the heat source term and combining the mechanisms of heat conduction, heat convection, and heat radiation, the three-dimensional steady-state temperature field control equation is constructed, and the three-dimensional temperature distribution of the cable and tunnel environment is solved; A bidirectional coupling relationship between the electromagnetic field and the temperature field is established, and the conductor conductivity is dynamically adjusted. The Joule loss power and temperature field distribution are iteratively updated until the convergence conditions are met.

2. The method for constructing a cable temperature simulation model based on multi-field coupling according to claim 1, wherein: The construction of the three-dimensional geometric model includes determining the dimensions of the conductor and insulation layer according to the rated current and voltage level of the cable, obtaining tunnel structural parameters through environmental scanning data, and integrating the spatial layout of the cable and tunnel to construct a three-dimensional geometric model that includes the geometric characteristics of the high-voltage cable layer and the tunnel environment; The high-voltage cable layer includes copper conductor, conductor shield, XLPE insulation layer, insulation shield, water-blocking layer, air layer, corrugated aluminum sheath and outer sheath, and the influence of uneven distribution of air layer on the geometric model is ignored; The setting of physical field parameters includes setting electrical conductivity, thermal conductivity, heat capacity, density, relative permittivity and magnetic permeability parameters.

3. The method for constructing a cable temperature simulation model based on multi-field coupling according to claim 2, wherein: The boundary heat dissipation conditions are defined as follows: setting the natural convection heat transfer coefficient between the upper surface of the cable tunnel and the air; setting the constant temperature condition of the lower boundary; and setting the thermal equilibrium condition that the normal heat flux density of the left and right boundaries is zero.

4. The method for constructing a cable temperature simulation model based on multi-field coupling according to claim 3, wherein: The two-dimensional grid division includes dividing the area according to the electromagnetic field intensity gradient and temperature gradient distribution, using a dense grid on the cable conductor surface and insulation interface, and using a sparse grid in the soil and sheath area.

5. The method for constructing a cable temperature simulation model based on multi-field coupling according to claim 4, characterized in that: The electromagnetic field distribution is solved by generating an electromagnetic field excitation source based on power frequency current excitation, solving the electromagnetic field by using a quasi-steady-state equation ignoring displacement current, and calculating the heat source power of the conductor and the insulation layer based on the relationship between current density and magnetic field strength; The construction of the three-dimensional steady-state temperature field control equation includes mapping the heat source power to the heat source term of the three-dimensional geometric model, defining the heat transfer equation in combination with heat conduction, heat convection and heat radiation mechanisms, and numerically solving the three-dimensional steady-state temperature field control equation through a discretization method.

6. The method for constructing a cable temperature simulation model based on multi-field coupling according to claim 5, wherein: Establishing a bidirectional coupling relationship between the electromagnetic field and the temperature field includes adjusting the conductor conductivity according to the temperature distribution, updating the material parameters through a linear relationship, feeding back the updated conductivity, regenerating the heat source power, and repeating the iteration until the temperature residual meets a preset threshold; The relationship between conductivity and temperature is expressed as: Where σ is the conductivity, σ 20 is the conductivity at the reference temperature, α is the temperature coefficient of resistance, T is the temperature, T amb is the reference ambient temperature; The electromagnetic-thermal coupling control equation is expressed as: Where σ is the conductivity, is the Laplace operator, T is the temperature, Q is the heat source term, that is, the heat generated per unit volume, J is the current density, and λ is the thermal conductivity.

7. The method for constructing a cable temperature simulation model based on multi-field coupling according to claim 6, wherein: The temperature residual determination includes calculating the global maximum temperature change and comparing it with the preset tolerance. If convergence is not achieved, the conductivity and heat source power are updated and the next iteration is started. The convergence conditions include setting the tolerance range of temperature variation and defining the maximum number of iterations.

8. A system using the method for constructing a cable temperature simulation model based on multi-field coupling according to any one of claims 1 to 7, characterized in that: It includes geometric modeling module, material and boundary parameter configuration module, meshing and optimization module, and electromagnetic-thermal field dynamic coupling simulation module; The geometric modeling module is used to construct a three-dimensional geometric model based on the actual structural parameters of the high-voltage cable and the three-dimensional laser scanning data of the cable tunnel; The material and boundary parameter configuration module is used to define physical field parameters for each layer of cable material and the surrounding medium, including electrical conductivity, thermal conductivity, heat capacity and density, and to set boundary heat dissipation conditions; The meshing and optimization module is used to simplify the three-dimensional model into a two-dimensional axisymmetric model based on the axisymmetric characteristics of the cable cross-section, and to use dense meshes in key areas and coarsened meshes in the outer sheath and soil areas. The module also dynamically adjusts the mesh density to balance simulation accuracy and resource consumption. The electromagnetic-thermal field dynamic coupling simulation module is used to apply power frequency load current excitation, solve the electromagnetic field distribution based on the simplified Maxwell equations, calculate the Joule loss power of the conductor and insulation layer, use the Joule loss power as the heat source term, and construct a three-dimensional temperature field control equation combining heat conduction, heat convection and heat radiation mechanisms. The temperature distribution is solved using the finite element method, a bidirectional coupling relationship between the electromagnetic field and the temperature field is established, the conductor conductivity is dynamically adjusted according to the temperature distribution, and the heat source power and temperature field are iteratively updated until convergence.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method for constructing a cable temperature simulation model based on multi-field coupling according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method for constructing a cable temperature simulation model based on multi-field coupling according to any one of claims 1 to 7 are implemented.

Images