Field-circuit coupling numerical simulation method for calculating high-voltage tunnel cable space thermal field distribution

Abstract

The invention discloses a field-circuit coupling numerical simulation method for calculating spatial thermal field distribution of a high-voltage tunnel cable, and belongs to the technical field of energy research, and the simulation method specifically comprises the following steps: S1, simulating important geometric parameters collected and recorded by a simulation system according to high-voltage tunnel cable equipment which is actually put into operation; the method can comprehensively analyze the temperature field distribution of the cable system under the conditions of different loads, tunnel structures, laying modes and the like, improves the precision and reliability of temperature monitoring, and compared with the traditional technology, reduces the computing resources, accurately simulates the operation condition of the KM-level long-distance tunnel cable, improves the analyzability of the simulation result, and reduces the construction cost. According to the method, the engineering reference precision of practical application is deepened, the temperature field distribution condition of the high-voltage tunnel cable in a long-time operation state can be analyzed, and the method has important engineering application value and particularly has great significance in operation monitoring, fault early warning and optimization design of the high-voltage tunnel cable.

Description

Technical Field

[0001] The invention relates to the technical field of energy research, and in particular to a field-circuit coupling numerical simulation method for calculating the spatial thermal field distribution of a high-voltage tunnel cable. Background Art

[0002] With the development of the power industry and the continuous advancement of the transformation of new power systems, the proportion of clean energy power generation, mainly photovoltaic and wind power, has increased significantly. In this context, high-voltage cables, an important equipment for large-scale energy transmission, play an increasingly important role. However, cables often cause operating failures due to excessive temperatures, resulting in economic losses. Therefore, the temperature changes during the operation of cables deserve in-depth study.

[0003] At present, the distributed optical fiber temperature measurement system in high-voltage cable tunnels only monitors the temperature field on the cable surface, and cannot directly reflect the temperature distribution inside the cable, especially near the core. In addition, the temperature field distribution on the cable surface varies greatly under different loads, different tunnel structures, different laying methods, and different operating environments. The operation and maintenance personnel rely heavily on manual experience to judge the operation status of the cable, and lack the data support of theoretical calculations and simulation models, resulting in low utilization of monitoring data, false alarms and missed alarms, and unable to effectively support cable line fault warnings. The support capacity for operation and maintenance business is insufficient. It is urgent to reasonably use the existing massive distributed optical fiber temperature measurement data and develop an efficient and accurate high-voltage cable operation simulation model on this basis.

[0004] However, in terms of the feasibility and effectiveness of analog temperature sensors, numerical simulation, as an auxiliary research method, is increasingly being used to reveal the temperature change characteristics of cables under various operating conditions. This simulation research is crucial to the principle and appearance design of the sensor.

[0005] In addition, most of the current studies have not fully considered the analysis of the entire operation characteristics of the tunnel cable. Few studies have fully considered the electric-thermal-fluid multi-physics field coupling factors of the tunnel cable under actual operating conditions and solved the temperature field distribution of the entire cable. Therefore, it is particularly important to invent a field-circuit coupling numerical simulation method for calculating the spatial thermal field distribution of high-voltage tunnel cables.

[0006] After searching, Chinese Patent No. CN118393236A discloses a device and method for measuring the temperature field distribution of a power cable. The invention realizes dynamic monitoring of the temperature field at each position of the power cable by constructing a slidable observation device, but it is unable to comprehensively analyze the temperature field distribution of the cable system under different loads, tunnel structures, laying methods and other conditions, which reduces the accuracy and reliability of temperature monitoring; in addition, Chinese Patent No. CN118310650A discloses an online cable temperature monitoring device. The invention is based on Bragg grating sensing technology and adopts a dual-wavelength differential demodulation method. By effectively eliminating the influence of stress on the Bragg grating sensor, the device can realize high-precision monitoring of the cable temperature. However, it is not conducive to analyzing the temperature field distribution of high-voltage tunnel cables under long-term operation, and cannot provide convenience for industrial applications; for this reason, we propose a field-circuit coupling numerical simulation method for calculating the spatial thermal field distribution of high-voltage tunnel cables. Summary of the invention

[0007] The purpose of the present invention is to solve the defects in the prior art and to propose a field-circuit coupling numerical simulation method for calculating the spatial thermal field distribution of high-voltage tunnel cables.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] The field-circuit coupling numerical simulation method for calculating the spatial thermal field distribution of high-voltage tunnel cables is as follows:

[0010] S1. According to the actual high-voltage tunnel cable equipment put into operation, the simulation system collects and records the important geometric parameters, thermal parameters of the materials of each component of the high-voltage tunnel cable, and its electrostatic parameters and other basic equipment characteristic parameters;

[0011] S2. The user inputs the basic characteristic parameters of the tunnel cable operation environment that need to be simulated and calculated through the simulation interface APP;

[0012] S3. Based on the acquired parameter data, a three-dimensional simulation model is built through a simulation system;

[0013] S4. Based on the key operating characteristic parameters obtained, define the conditional assumptions, initial and constraint conditions in the model, reasonably simplify the model solution, and determine the calculation range of the simulation model;

[0014] S5. Design a corresponding finite element meshing method and solve the simulation model through a nonlinear transient solver;

[0015] S6. The three-dimensional data of the electric field and temperature field calculated by the back-end simulation model are converted into a visual form of three-dimensional graphics or thermal maps after real-time processing and displayed on the one-stop simulation interface.

[0016] As a further solution of the present invention, the important geometric parameters in S1 specifically include tunnel height, three-phase cable shape and three-phase cable spacing;

[0017] The thermal parameters and electrostatic parameters of the materials of the components of the high-voltage tunnel cable described in S1 specifically include thermal conductivity, constant-pressure heat capacity and dielectric constant.

[0018] As a further solution of the present invention, the basic characteristic parameters of the tunnel cable operating environment in S2 include tunnel temperature, tunnel air humidity and tunnel material during operation.

[0019] As a further solution of the present invention, the simulation system in S3 specifically includes a parameter acquisition module, a model building module and a model solving module;

[0020] The parameter acquisition module is used to acquire key geometric parameters, physical parameters of the high-voltage tunnel cable and environmental characteristic parameters input by the user;

[0021] The model building module is used to establish a three-dimensional geometric model of a high-voltage tunnel cable that meets actual dimensions using COMSOL Multiphysics software, and to establish a complete multi-physics coupling model based on magnetic fields, circuits, solid heat transfer, and Navier-Stokes fluid heat transfer equations;

[0022] The model solving module is used to define constraint conditions, design a finite element mesh partitioning scheme for the simulation calculation area, perform simulation calculations on the obtained model, and record the results.

[0023] As a further solution of the present invention, the model building module establishes a complete multi-physics field coupling model based on magnetic field, circuit, solid heat transfer, and Navier-Stokes fluid heat transfer equations, specifically including a magnetic field model, a circuit model, and a physical heat transfer model;

[0024] The multi-physics field coupling model simulates the spatial distribution characteristics of the temperature field of the high-voltage tunnel cable during long-term operation under real conditions, and displays it intuitively and visually through a three-dimensional geometric model.

[0025] As a further solution of the present invention, the simulation system is connected to a database for simulation modeling, including an insulation material library, an electrode configuration library, a tunnel cable geometry library, an experimental platform model template library, a heat transfer model library and a physical parameter library;

[0026] The insulating material library, electrode configuration library and tunnel cable geometry library are used to simulate the geometry and material properties of actual tunnel cables;

[0027] The experimental platform model template library is used to quickly import commonly used experimental platform model frameworks;

[0028] The heat transfer model library and physical parameter library are used to import gas parameters, current parameters, voltage parameters, heat conduction parameters, temperature change rules, etc., and are used to model and realize physical processes such as heat conduction, thermal radiation, and thermal convection, and to add a heat transfer condition mechanism to the model components that have been modeled, and to make the model modeling produce changes in appearance and color according to physical rules, and to determine the voltage, current, temperature and other parameters of the entire model operation.

[0029] As a further solution of the present invention, the finite element meshing method described in S5 uses triangular units or quadrilateral units to perform adaptive meshing through a nonlinear algorithm and a generalized α time domain method, and the local refinement area creates a three-dimensional mesh by rotating and extending the two-dimensional mesh.

[0030] As a further solution of the present invention, the one-stop simulation interface in S6 specifically includes a model input module, a data management module and a result visualization module;

[0031] The model input module is used to transmit the data input by the user and imported by the system to the back-end simulation system;

[0032] The data management module is used to manage internal data, including externally imported simulation files and simulation results calculated by the back-end simulation system;

[0033] The result visualization module is used to convert the simulation data obtained by the back-end simulation system into a visualization form that is easy to analyze, and provide an interactive interface with the user.

[0034] As a further solution of the present invention, the one-stop simulation interface is connected to a database for storing data, including input task data, external environment data, temperature distribution data, and magnetic field distribution data. There is also a user interaction interface library for storing elements for interaction between the APP and the user.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. The field-circuit coupling numerical simulation method for calculating the spatial thermal field distribution of high-voltage tunnel cables can accurately restore the heat transfer process of high-voltage tunnel cables during long-term operation, and obtain the refined distribution characteristics of the spatial thermal field around the tunnel cables from a comprehensive three-dimensional perspective. It can comprehensively analyze the temperature field distribution of the cable system under different loads, tunnel structures, laying methods and other conditions. Compared with traditional technologies, the present invention reduces computing resources while accurately simulating the operating conditions of KM-level long-distance tunnel cables through field-circuit coupling technology, thereby improving the analyzability of simulation results and deepening the engineering reference accuracy for practical applications.

[0037] 2. The field-circuit coupling numerical simulation method for calculating the spatial thermal field distribution of high-voltage tunnel cables constructs a cable tunnel model under the electric-heat-flow multi-physical field, and simulates the temperature distribution of tunnel cables under different loads, tunnel structures, laying methods, operating environments, faults and non-faults based on the finite element method. It is helpful to analyze the temperature field distribution of high-voltage tunnel cables under long-term operation, which is of great significance for the operation and laying optimization of tunnel cables. In addition, in terms of high-voltage cable temperature monitoring, it accurately simulates the temperature field distribution of high-voltage cables at the KM level, and clarifies the influence of changes in operating parameters on the spatial temperature distribution characteristics of tunnel cables. It can provide a reference for the appearance design of the temperature monitoring device and the selection of the monitoring method, provide convenience for industrial applications, and has important engineering application value, especially for the operation monitoring, fault warning and optimization design of high-voltage tunnel cables. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0039] Figure 1 This is a flow chart of the field-circuit coupling numerical simulation method for calculating the spatial thermal field distribution of high-voltage tunnel cables proposed by the present invention;

[0040] Figure 2 A schematic diagram of the logic framework of a simulation system for a field-circuit coupling numerical simulation method for calculating the spatial thermal field distribution of high-voltage tunnel cables proposed in the present invention;

[0041] Figure 3 A schematic diagram of an equivalent model of a cable joint and a terminal circuit for a field-circuit coupling numerical simulation method for calculating the spatial thermal field distribution of a high-voltage tunnel cable proposed in the present invention;

[0042] Figure 4 This is a three-dimensional simulation effect diagram and APP interface of the field-circuit coupling numerical simulation method proposed in the present invention for calculating the spatial thermal field distribution of high-voltage tunnel cables. DETAILED DESCRIPTION

[0043] Reference Figure 1 , a field-circuit coupling numerical simulation method for calculating the spatial thermal field distribution of high-voltage tunnel cables is proposed. The specific steps of the simulation method are as follows:

[0044] According to the high-voltage tunnel cable equipment actually put into operation, the simulation system collects and records the important geometric parameters, thermal parameters of the materials of each component of the high-voltage tunnel cable, and the electrostatic parameters of the basic equipment characteristic parameters.

[0045] It should be further explained that the important geometric parameters include tunnel height, three-phase cable shape and three-phase cable spacing; thermal parameters of the materials of each component of the high-voltage tunnel cable and its electrostatic parameters, including thermal conductivity, constant-pressure heat capacity and dielectric constant.

[0046] The user inputs the basic characteristic parameters of the tunnel cable operating environment that need to be simulated and calculated through the simulation interface APP.

[0047] In addition, it should be noted that the basic characteristic parameters of the tunnel cable operating environment include the tunnel temperature, tunnel air humidity and tunnel material during operation.

[0048] Based on the obtained parameter data, a three-dimensional simulation model is built through the simulation system.

[0049] For details, please refer to Figure 2-4 ,The simulation system specifically includes a parameter acquisition module, a model building module and a model solving module.

[0050] The parameter acquisition module is used to obtain the key geometric parameters, physical parameters and environmental characteristic parameters of the high-voltage tunnel cable input by the user; the model building module is used to use COMSOL Multiphysics software to establish a three-dimensional geometric model of the high-voltage tunnel cable that meets the actual size, and to establish a complete multi-physics field coupling model based on the magnetic field, circuit, solid heat transfer, and Navier-Stokes fluid heat transfer equations; the model solving module is used to define constraints, design a finite element mesh division scheme for the simulation calculation area, perform simulation calculations on the obtained model, and record the results.

[0051] In addition, it should be noted that the three-dimensional geometric model has priority over the electrostatic conduction model and the physical heat transfer model coupling;

[0052] Among them, reference Figure 3 It can be seen that the specific construction principle of the multi-physics field coupling model is as follows:

[0053] According to Maxwell's equations, the vector magnetic potential A is introduced

[0054]

[0055] The magnetic flux density is spiral, or divergence-free. This means that the magnetic field can be written as the curl of other vector fields, as shown in equation (1);

[0056] The control equation of the electric field module is:

[0057]

[0058] Formula (2) is the differential form of Maxwell-Ampere's law, J is the current density vector, A / m3. It shows that the curl of the magnetic field intensity H at a certain point is equal to the current density at that point.

[0059] J=σE (3)

[0061] In formula (3), σ is the conductivity, S / m, and E is the electric field intensity vector, V / m. This shows that the current density is proportional to the electric field.

[0062] The equivalent circuit model of the cable usually includes components such as resistance, inductance, and capacitance. 0 , L 0 , C 0 , G 0 They are the distributed resistance, inductance, capacitance and conductance per unit length of the cable respectively.

[0063] Cable conductor temperature and resistance R 0 The relationship between them is:

[0064]

[0065] In formula (4), ρ is the conductor resistivity at 20℃, Ω / m; α1 is the temperature coefficient of copper, ℃; T is the conductor temperature, K.

[0066] Distributed capacitance C of the cable 0 The calculation formula is:

[0067]

[0068] Formula (5): ε is the relative dielectric constant of insulation; ε 0 is the dielectric constant of vacuum.

[0069] Distributed inductance L of the cable 0 The calculation formula is:

[0070] L 0 =L i +L e (6)

[0072] L i , L e The calculation formula is as follows:

[0073]

[0074] In formula (6) and (7): μ 0 is the vacuum permeability; L i is the internal inductance; L e is the external inductor.

[0075] Figure 3 In the figure, the radial structural thermal resistance of each layer is linearly superimposed to obtain the total radial structural thermal resistance of the cable. yk is the radial structural thermal resistance of the cable connector or body, where R yi (i=A、B 1 , C 1 ) is the radial structural thermal resistance of the cable joint, and its value is equal to the linear superposition of the radial structural thermal resistance of each layer of the joint. yj (j=D 1 、E 1 、F 1 , G 1 H 1 ) represents the radial structural thermal resistance between the aluminum sheath and the conductor of the cable body, and its value is equal to the linear superposition of the structural thermal resistances of each layer of the body;

[0076] According to the law of conservation of energy, the governing equation of the temperature field is expressed as follows:

[0077]

[0078] In formula (8), ρ is density, kg / m3; is temperature, °C; t is time, s; C is heat capacity, J / (kg·°C); is thermal conductivity, W / (m·°C); u is fluid velocity, m / s; Q is heat source, J. The first term on the left side of formula (8) is the heat accumulation term, which characterizes the heat storage capacity of the heat transfer medium; the second term is the fluid convection term, which is used to describe the heat convection process; the first term on the right side is the heat conduction term; and the second term represents the heat source.

[0079] Finally, the above formulas are combined to obtain the control equation of the tunnel cable under the coupling of electrical, thermal and fluid multi-physics fields:

[0080]

[0081] The meaning of each parameter in formula (9) is explained in formula (8).

[0082] It should be further explained that the model building module establishes a complete multi-physics field coupling model based on the magnetic field, circuit, solid heat transfer, and Navier-Stokes fluid heat transfer equations, specifically including a magnetic field model, a circuit model, and a physical heat transfer model; the multi-physics field coupling model simulates the spatial distribution characteristics of the temperature field of high-voltage tunnel cables running for a long time in a real environment, and intuitively visualizes it through a three-dimensional geometric model.

[0083] The simulation system is connected to a database for simulation modeling, including an insulation material library, an electrode configuration library, a tunnel cable geometry library, an experimental platform model template library, a heat transfer model library and a physical parameter library;

[0084] Among them, the insulation material library, electrode configuration library and tunnel cable geometry library are used to simulate the geometry and material properties of actual tunnel cables; the experimental platform model template library is used to quickly import the commonly used experimental platform model framework; the heat transfer model library and physical parameter library are used to import gas parameters, current parameters, voltage parameters, heat conduction parameters, temperature change rules, etc., which are used to model and realize physical processes such as heat conduction, thermal radiation and thermal convection, and add a heat transfer condition mechanism to the modeled model components, and make the model modeling produce changes in appearance and color according to physical rules, and determine the voltage, current, temperature and other parameters of the entire model operation.

[0085] Based on the key operating characteristic parameters obtained, define the conditional assumptions, initial and constraint conditions in the model, reasonably simplify the model solution, and determine the calculation scope of the simulation model.

[0086] Design the corresponding finite element meshing method and solve the simulation model through the nonlinear transient solver.

[0087] It should be noted that the finite element meshing method uses triangular elements or quadrilateral elements to perform adaptive meshing through a nonlinear algorithm and a generalized α-time domain method, and the local refinement area creates a three-dimensional mesh by rotating and extending the two-dimensional mesh.

[0088] The three-dimensional data of the electric field and temperature field calculated by the back-end simulation model are converted into three-dimensional graphics or thermal map visualization after real-time processing and displayed on the one-stop simulation interface.

[0089] Specifically, refer to Figure 4 ,The one-stop simulation interface specifically includes a model input module, a data management module and a result visualization module.

[0090] The model input module is used to transmit the data input by the user and imported by the system to the back-end simulation system; the data management module is used to manage the internal data, including the simulation files imported from the outside and the simulation results calculated by the back-end simulation system; the result visualization module is used to convert the simulation data obtained by the back-end simulation system into a visualization form that is easy to analyze, and provide an interactive interface with the user.

[0091] It should be further explained that the one-stop simulation interface is connected to a database for storing data, including input task data, external environment data, temperature distribution data, and magnetic field distribution data. There is also a user interaction interface library for storing elements for the APP to interact with users.

Claims

1. A field-circuit coupling numerical simulation method for calculating the spatial thermal field distribution of high-voltage tunnel cables, characterized in that: The specific steps of the simulation method are as follows: S1. According to the actual operation of high-voltage tunnel cable equipment, the simulation system collects and records important geometric parameters, thermal parameters of various components and materials of high-voltage tunnel cables, and basic equipment characteristic parameters of electrostatic parameters; S2. The user inputs the basic characteristic parameters of the tunnel cable operation environment that need to be simulated and calculated through the simulation interface APP; S3. Based on the acquired parameter data, a three-dimensional simulation model is built through a simulation system; S4. Based on the key operating characteristic parameters obtained, define the conditional assumptions, initial and constraint conditions in the model, reasonably simplify the model solution, and determine the calculation range of the simulation model; S5. Design a corresponding finite element meshing method and solve the simulation model through a nonlinear transient solver; S6. The three-dimensional data of the electric field and temperature field calculated by the back-end simulation model are converted into a visual form of three-dimensional graphics or thermal maps after real-time processing and displayed on the one-stop simulation interface.

2. The field-circuit coupling numerical simulation method for calculating the spatial thermal field distribution of high-voltage tunnel cables according to claim 1 is characterized in that: The important geometric parameters described in S1 specifically include tunnel height, three-phase cable shape, and three-phase cable spacing; The thermal parameters and electrostatic parameters of the materials of the components of the high-voltage tunnel cable described in S1 specifically include thermal conductivity, constant-pressure heat capacity and dielectric constant.

3. The field-circuit coupling numerical simulation method for calculating the spatial thermal field distribution of high-voltage tunnel cables according to claim 1 is characterized in that: The basic characteristic parameters of the tunnel cable operating environment described in S2 include the tunnel temperature, tunnel air humidity and tunnel material during operation.

4. The field-circuit coupling numerical simulation method for calculating the spatial thermal field distribution of high-voltage tunnel cables according to claim 1 is characterized in that: The simulation system described in S3 specifically includes a parameter acquisition module, a model building module and a model solving module; The parameter acquisition module is used to acquire key geometric parameters, physical parameters of the high-voltage tunnel cable and environmental characteristic parameters input by the user; The model building module is used to establish a three-dimensional geometric model of a high-voltage tunnel cable that meets actual dimensions using COMSOL Multiphysics software, and to establish a complete multi-physics coupling model based on magnetic fields, circuits, solid heat transfer, and Navier-Stokes fluid heat transfer equations; The model solving module is used to define constraint conditions, design a finite element mesh partitioning scheme for the simulation calculation area, perform simulation calculations on the obtained model, and record the results.

5. The field-circuit coupling numerical simulation method for calculating the spatial thermal field distribution of high-voltage tunnel cables according to claim 4 is characterized in that: The model building module establishes a complete multi-physics field coupling model based on magnetic field, circuit, solid heat transfer, and Navier-Stokes fluid heat transfer equations, specifically including a magnetic field model, a circuit model, and a physical heat transfer model; The multi-physics field coupling model simulates the spatial distribution characteristics of the temperature field of the high-voltage tunnel cable during long-term operation under real conditions, and displays it intuitively and visually through a three-dimensional geometric model.

6. The field-circuit coupling numerical simulation method for calculating the spatial thermal field distribution of high-voltage tunnel cables according to claim 1 is characterized in that: The finite element meshing method described in S5 uses triangular elements or quadrilateral elements to perform adaptive meshing through a nonlinear algorithm and a generalized alpha time domain method, and the local refinement area creates a three-dimensional mesh by rotating and extending the two-dimensional mesh.

7. The field-circuit coupling numerical simulation method for calculating the spatial thermal field distribution of high-voltage tunnel cables according to claim 1 is characterized in that: The one-stop simulation interface in S6 specifically includes a model input module, a data management module and a result visualization module; The model input module is used to transmit the data input by the user and imported by the system to the back-end simulation system; The data management module is used to manage internal data, including externally imported simulation files and simulation results calculated by the back-end simulation system; The result visualization module is used to convert the simulation data obtained by the back-end simulation system into a visualization form that is easy to analyze, and provide an interactive interface with the user.

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