Irregular cable cluster current-carrying capacity calculation method based on finite element method

Abstract

The invention relates to an irregular cable cluster current-carrying capacity calculation method based on a finite element method, and belongs to the technical field of electric power. The method comprises the following steps: S1, acquiring parameters such as a cable structure and material attributes; s2, simplifying and establishing a multi-physical field coupling model of the cable, wherein the multi-physical field coupling model comprises an electromagnetic field model, a temperature field model and a fluid field model; s3, establishing a physical model of an irregular cable cluster under channel laying by using software, and constructing an electromagnetic-thermal-flow multi-physical field coupled finite element model according to the structural characteristics and laying mode of the cable by combining the electromagnetic and thermal parameters of the cable and the surrounding materials of the cable; grid division is carried out on the model; and S4, in combination with a whale optimization algorithm, setting an objective function and constraint conditions, and calculating the current-carrying capacity of the irregular cable cluster under channel laying. According to the method, the multi-physics field coupling model is constructed, and the whale optimization algorithm is combined, so that the problem that irregularly arranged cable resources in the channel are not fully utilized is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of electric power and relates to a method for calculating the current carrying capacity of an irregular cable cluster based on a finite element method. Background Art

[0002] Current carrying capacity is one of the key parameters of cable operation, which is directly related to the transmission capacity, operation efficiency and service life of the cable. The current carrying capacity depends on the combined influence of the cable's main structure, laying method and environmental conditions. Accurately calculating the current carrying capacity of the cable can not only improve the utilization rate of cable resources, but also effectively avoid safety hazards such as excessive temperature rise, insulation aging or fault tripping caused by overload, which is of great significance to ensure the safe and reliable operation of the cable.

[0003] In urban distribution networks, cable trench laying is a very common laying method. However, due to the rapid growth of urban distribution load demand and imperfect historical planning, the phenomenon of dense accumulation of cables in cable trenches is very common. Dense accumulation will cause a series of complex thermal effect problems. When the cable is running, the heat in the trench is difficult to dissipate effectively due to the current carrying heat, and the heat transfer between the cables will further aggravate the overall temperature rise. In this case, the thermal field distribution in the cable trench is usually more uneven, and the area with higher local temperature may cause the cable to overheat and directly affect the current carrying capacity of the cable.

[0004] Compared with other laying methods, the heat dissipation capacity of densely packed cable groups is significantly reduced, which leads to a significant decrease in the current carrying capacity of the cable compared to a single cable. If the thermal field distribution and current carrying capacity are not accurately calculated in time, thermal failures may occur during cable operation due to insufficient heat dissipation. Therefore, thermal calculation of densely packed cable groups in cable trenches is particularly necessary. Accurate thermal calculation and current carrying capacity prediction can provide a scientific basis for the optimal laying of cables and ensure the safety and stability of the cable system under existing conditions.

[0005] At present, the methods for calculating the current carrying capacity of cables mainly include the following methods:

[0006] (1) IEC standard analytical method, under the premise that the cable conductor temperature is at the working temperature of the insulation material, the temperature and heat flux distribution and current carrying capacity of different layers of the cable are calculated through analytical formulas. The IEC method relies on the empirical formula provided by the standard and is suitable for simple geometric shapes and steady-state heat conduction conditions, but has poor adaptability to complex working conditions.

[0007] (2) Finite difference method: By dividing the continuous solution domain into discrete grid nodes, the partial derivative relationship in the control equation is approximated by the difference equation. Different grid density can be selected according to the required accuracy. The calculation process of the finite difference method is relatively simple and suitable for solving regular-shaped regions, but its adaptability to complex geometry or nonlinear problems is limited.

[0008] (3) Finite volume method: divide the solution area into several small control volumes, describe the change of physical quantity in each volume through the integral form of conservation equation, and calculate the transmission volume between volumes. However, the finite volume method has poor adaptability to complex geometry, large interpolation error, lower accuracy than the finite element method, complex boundary condition processing, and strong dependence on meshing and stability.

[0009] (4) Finite element method has high calculation accuracy and can adapt to complex geometric shapes and nonlinear problems, but its calculation amount is large and has high requirements for model and mesh division. Summary of the invention

[0010] In view of this, the purpose of the present invention is to provide a method for calculating the current-carrying capacity of irregular cable clusters based on the finite element method. In view of the problem that the cluster cable resources under irregular channel arrangement are not fully utilized, the electromagnetic field is solved to calculate the loss of each layer of the cable, and the complex proximity effect and skin effect of the cable are directly simulated and calculated. At the same time, the relationship between the resistivity of metal materials and temperature is considered, and the three heat conduction modes of natural convection of air, thermal radiation and solid heat conduction are coupled in the heat transfer model to achieve the mutual coupling of electromagnetic field, temperature field and fluid field. Combined with the whale optimization algorithm, the maximum current-carrying capacity of the cable cluster is solved with the constraint that the temperature of each cable does not exceed 90°C.

[0011] In order to achieve the above object, the present invention provides the following technical solutions:

[0012] A method for calculating the current carrying capacity of an irregular cable cluster based on a finite element method, specifically comprising the following steps:

[0013] S1: Obtain parameters such as cable structure and material properties;

[0014] S2: Simplify and establish a multi-physics field coupling model of the cable, including electromagnetic field model, temperature field model and fluid field model;

[0015] S3: Use software to establish physical modeling of irregular cable clusters under trench laying, combine electromagnetic and thermal parameters of cables and surrounding materials, and build electromagnetic-thermal-fluid multi-physics field coupled finite element model according to the structural characteristics and laying method of cables; then mesh the model;

[0016] S4: Combined with the whale optimization algorithm, the objective function and constraints are set to calculate the current carrying capacity of irregular cable clusters under trench laying.

[0017] Further, in step S2, an electromagnetic field model is constructed, specifically including: treating the cable channel as a two-dimensional plane field, assuming that the electromagnetic field around it is constant, and the conductivity σ of the conductor and the armor layer i The variation law with temperature is shown in formula (1), and the loss of each layer of the cable is shown in formulas (2) to (4);

[0018]

[0019] J=-jωσ i A+J s (3)

[0020]

[0021] In the formula, ρ 20 The metal resistivity at 20°C; α 20 is the temperature coefficient of metal resistivity; T is the changing temperature; T ref Take 20℃; ω is the angular frequency, rad / s; A is the vector magnetic potential of each layer, Wb / m; σ i is the electrical conductivity of the material, S / m; μ is the magnetic permeability, H / m; J is the current density of each layer, A / m 2 ; J s is the source current density, A / m 2 ; P is the power loss per unit length of each layer, W / m; S is the cross-sectional area, m 2 .

[0022] Further, in step S2, a temperature field model is constructed, specifically including: for the area with internal heat source, i.e., the cable conductor and armor layer, the solid thermal conduction partial differential equation is as shown in formula (5); for the area without internal heat source, i.e., other layers of the cable, trench wall and soil, etc., the solid thermal conduction partial differential equation is as shown in formula (6);

[0023]

[0024] Where T is the temperature of the corresponding medium (for example, the solid medium is soil, trench wall, cable, etc., and the fluid is air), q v is the internal heat source, x and y are the horizontal and vertical directions of the two-dimensional plane.

[0025] Further, in step S2, a fluid field model is constructed, specifically including: the air in the channel mainly dissipates heat through natural convection, and by calculating the Rayleigh number, it can be determined that the air flow form in the channel is turbulent; this model uses the standard k-ε turbulence model to describe the heat transfer and flow process of the fluid, where k is the turbulent pulsation kinetic energy per unit mass of the fluid, and ε is the dissipation rate of k; the natural convection of the air around the cable in the channel must follow the three most basic conservation laws, namely, the law of conservation of mass, the law of conservation of momentum, and the law of conservation of energy, and the control equations are shown in equations (7) to (9);

[0026]

[0027] Where u and v are the air velocity on the x and y axes respectively; ρ is the air density; θ is the angle between the gravitational acceleration and the x-axis; β is the air expansion coefficient; η is the air dynamic viscosity; p is the air pressure scalar; T f is the initial temperature of the air, T is the temperature of the air; λ is the thermal conductivity of the air; g is the acceleration due to gravity.

[0028] Further, in step S3, according to the temperature field model established in the heat transfer process, its boundary conditions can be divided into the following three categories:

[0029] The first type of boundary condition: the boundary temperature function is known, as shown in formula (10);

[0030] T| Γ =T w (10)

[0031] Where T is the temperature of the corresponding medium, Γ is the integration boundary; T w is the known boundary temperature;

[0032] The second type of boundary condition: the normal heat flux density of the boundary is known, as shown in formula (11);

[0033]

[0034] Where n is the normal vector, λ is the thermal conductivity, q is the known heat flux density;

[0035] The third type of boundary condition: convection heat transfer boundary condition, its form is shown in formula (12);

[0036]

[0037] Where h is the convective heat transfer coefficient; T f is the fluid temperature.

[0038] Furthermore, in step S3, different grid sizes are used for different regions during grid division; fine grid division is performed in the cable and air regions in the trench, and conventional grid division is performed in the trench wall and surrounding soil regions.

[0039] Further, in step S4, the calculation model of the objective function f of the cable cluster current carrying capacity is:

[0040]

[0041] Where, I is the expected value of the current carrying capacity of the cross section, which is a constant; I k is the load of the kth cable, n is the total number of cable loops, T k is the conductor temperature of the kth cable.

[0042] The beneficial effect of the present invention is that the existing technology does not adequately handle proximity effect, skin effect and complex thermal field in the calculation of cable current carrying capacity, and its accuracy and applicability are limited. The present invention solves the problem of cable thermal management and current carrying capacity calculation under complex fields by constructing a multi-physics field coupling model and combining the whale optimization algorithm, thereby improving the accuracy of current carrying capacity calculation.

[0043] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0045] Figure 1 A flow chart of a method for calculating the current carrying capacity of irregular cable clusters based on the finite element method provided by the present invention;

[0046] Figure 2 This is a simplified schematic diagram of a cable physical model in an embodiment of the present invention;

[0047] Figure 3 A physical model of an irregular cable cluster laid in a trench in an embodiment of the present invention;

[0048] Figure 4 The process of feeding for whales;

[0049] Figure 5 Flowchart of the algorithm optimized for whales. DETAILED DESCRIPTION

[0050] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0051] See also Figure 1 to Figure 5 The present invention provides a method for calculating the current carrying capacity of irregular cable clusters based on the finite element method, such as Figure 1 As shown in the figure, the method mainly includes the following parts: (1) establishing a finite element model of the cable through the structural parameters, material thermal parameters, laying conditions and boundary conditions of the cable; (2) combining electromagnetic-thermal-fluid multi-physics field coupling to perform finite element calculations; (3) combining the whale optimization algorithm, setting the objective function and constraints to calculate the maximum current carrying capacity of the cable cluster.

[0052] Example:

[0053] 1. Construct a cable cluster model under electromagnetic-thermal-fluid multi-physics field coupling

[0054] 1) Taking a three-core cable as an example, the cable structure and material properties are obtained, as shown in Table 1 and Table 2.

[0055] Table 1 Three-core cable structure

[0056] structure Thickness(mm) Outer diameter(mm) conductor - 18.4 Conductor shield 0.8 20.0 Insulation layer 4.5 29.0 Insulation shield 0.8 30.6 Inner sheath 2.0 69.936 Armor layer 1.0 71.936 Outer sheath 3.5 78.936

[0057] Table 2 Three-core cable and surrounding material properties

[0058]

[0059]

[0060] 2) Cable physical model

[0061] The simplified cable physical model of a three-core cable is as follows Figure 2As shown in the figure, the functions of the various parts of the three-core cable structure are as follows: the core is the core of the cable and is responsible for transmitting electrical energy; the inner and outer semiconductor layers respectively play the role of electric field isolation to avoid electromagnetic interference, while improving the contact between the insulation layer and the core to prevent partial discharge; the insulation layer is wrapped around the core to play the role of electrical isolation to ensure the safe transmission of electrical energy. The inner and outer semiconductor layers effectively improve the reliability of the cable by reducing electric field concentration and improving contact performance, preventing current leakage or signal interference, and ensuring long-term stable operation. The overall structure ensures that the cable works safely and stably under high voltage or complex environments.

[0062] Since the conductor shield and insulation shield are very thin and the mesh is too small, it is easy to cause model convergence problems and increase the amount of calculation. The conductor shield and insulation shield do not generate heat and have no effect on the thermal field of the cable. Therefore, they are attributed to the insulation layer in the simulation calculation.

[0063] Since the axial length of the cable is much larger than its longitudinal length, a two-dimensional simulation model can be established for research. Figure 3 Physical model for finite element simulation analysis of irregular cable clusters laid in trenches.

[0064] 3) Multi-physics mathematical model

[0065] (1) Electromagnetic field model

[0066] When the conductor is excited by AC, an alternating magnetic field will be generated inside. Under the influence of this magnetic field, electromagnetic loss will occur in each layer of the cable. Since the length of the cable is much larger than its diameter, it can be treated as a two-dimensional plane field. Assuming that the electromagnetic field around it is constant, the conductivity σ of the conductor and the armor layer i The variation law with temperature is shown in formula (1), and the loss of each layer of the cable is shown in formulas (2) to (4).

[0067]

[0068] J=-jωσ i A+J s (3)

[0069]

[0070] In the formula, ρ 20 The metal resistivity at 20°C; α 20 is the temperature coefficient of metal resistivity; T is the changing temperature; T ref Take 20℃; ω is the angular frequency, rad / s; A is the vector magnetic potential of each layer, Wb / m; σ i is the electrical conductivity of the material, S / m; μ is the magnetic permeability, H / m; J is the current density of each layer, A / m 2 ; Js is the source current density, A / m 2 ; P is the power loss per unit length of each layer, W / m; S is the cross-sectional area, m 2 .

[0071] (2) Temperature field model

[0072] For regions with internal heat sources (such as cable conductors and armor layers), the partial differential equation for solid heat conduction is shown in equation (5).

[0073] For areas without internal heat sources (such as other layers of cables, trench walls, soil, etc.), the partial differential equation for solid heat conduction is shown in equation (6).

[0074]

[0075] (3) Fluid field model

[0076] The air in the channel mainly dissipates heat through natural convection. By calculating the Rayleigh number, it can be determined that the air flow in the channel is turbulent. This model uses the standard k-ε turbulence model (k is the turbulent pulsation kinetic energy per unit mass of fluid, and ε is the dissipation rate of k) to describe the heat transfer and flow process of the fluid. The natural convection of the air around the cable in the channel must follow the three most basic conservation laws, namely the law of conservation of mass, the law of conservation of momentum, and the law of conservation of energy. The control equations are shown in equations (7) to (9).

[0077]

[0078] Where u and v are the air velocity on the x and y axes respectively; ρ is the air density; θ is the angle between the gravitational acceleration and the x-axis; β is the air expansion coefficient; η is the air dynamic viscosity; p is the air pressure scalar; T f is the initial temperature of the air, T is the temperature of the air; λ is the thermal conductivity of the air; g is the acceleration due to gravity.

[0079] (4) Model boundary conditions

[0080] According to the temperature field model established by the heat transfer process, its boundary conditions can be divided into the following three categories:

[0081] The first type of boundary condition: the boundary temperature function is known, as shown in formula (10);

[0082] T Γ =T w (10)

[0083] Where T is the temperature of the corresponding medium, Γ is the integration boundary; T w is the known boundary temperature;

[0084] The second type of boundary condition: the normal heat flux density of the boundary is known, as shown in formula (11);

[0085]

[0086] Where n is the normal vector, λ is the thermal conductivity, q is the known heat flux density;

[0087] The third type of boundary condition: convection heat transfer boundary condition, its form is shown in formula (12);

[0088]

[0089] Where h is the convective heat transfer coefficient; T f is the fluid temperature.

[0090] (5) Meshing and finite element calculation

[0091] The physical model of the cable cluster in the trench is established using software, and then the model is meshed. In order to ensure the accuracy of the calculation results and shorten the calculation time as much as possible, the meshing method of different mesh sizes is adopted in different regions. Fine meshing is performed in the cable and trench air area, and conventional meshing is performed in the trench wall and surrounding soil area.

[0092] 2. Cable cluster current carrying capacity calculation method based on WOA optimization algorithm

[0093] 1) WOA optimization algorithm

[0094] The WOA algorithm is a meta-inspired optimization algorithm that simulates information sharing among whale groups and uses whale bubble nets to prey. The core idea of ​​the whale algorithm is to continuously find the optimal solution to the optimization problem by simulating the group behavior of whales. Figure 4 As shown in the figure, it shows the hunting process of whales in nature. In terms of local development, the WOA algorithm has the ability of the humpback whale to shrink and surround prey and spiral hunting; at the same time, it has the characteristics of random search for prey to ensure the global optimization ability of the algorithm. Figure 5 As shown in the figure, the WOA algorithm mainly includes three processes: surrounding prey, capturing prey, and searching for prey.

[0095] (1) Surrounding the prey

[0096] Humpback whales identify prey and share information, allowing the group of whales to surround the prey. When the group of whales surrounds the prey, they will adjust the vector to determine the appropriate position and direction of the optimal solution. The process is shown in equations (13) and (14):

[0097] D=|CX * (t)-X(t)| (13)

[0098] X(t+1)=X* (t)-AD (14)

[0099] Where t is the current iteration number; X is the current position; X * is the current best position. If a better position is found during the iteration, X * Updated with the number of iterations; A and C are coefficients.

[0100] (2) Hunting prey

[0101] Whales use a spiral hunting method to catch prey, that is, they spit out bubbles along a contracting spiral line and gradually approach the prey. The process is shown in equations (15) and (16).

[0102] X(t+1)=D′e bl cos(2πl)+X * (t) (15)

[0103] X(t+1)=X * (t)-AD (16)

[0104] Where b is the logarithmic spiral adjustment parameter; l is a random number [0,1]; is the distance between the whale and the prey, and the calculation formula is as follows:

[0105] D′=|X * (t)-X(t)| (17)

[0106] (3) Searching for prey

[0107] Humpback whales conduct random searches based on the relative positions of individuals. The mathematical expression is as follows:

[0108] D=|CX rand (t)-X(t)| (18)

[0109] X(t+1)=X rand (t)-AD (19)

[0110] Where, X rand is a position vector, indicating the position of the randomly selected whale of the previous generation.

[0111] The vector |A| is used as a control parameter to determine the way the whale updates its position. When |A|>1, a search method is used to find the global optimal solution. When |A|<1, a shrinking and wrapping method is used to find the optimal solution.

[0112] 2) Cable cluster current carrying capacity calculation model

[0113] In order to obtain the maximum current-carrying capacity of the cable group, the difference between a constant I (which can be understood as the expected value of the current-carrying capacity of the section) and the load current of the cable group is minimized as the objective function, and the maximum operating temperature of each cable does not exceed 90°C as a constraint condition, and the current-carrying capacity is calculated, as shown in the formula:

[0114]

[0115] In the formula, I k is the load of the kth cable, n is the total number of cable loops, T k is the conductor temperature of the kth cable.

[0116] The present invention provides a method for calculating the current carrying capacity of an irregular cable cluster based on the finite element method and the whale optimization algorithm. First, the multi-physical field coupling model of the cable is simplified and established, and a finite element model including the electromagnetic field, temperature field and fluid field is constructed. Then (1) the cable is reasonably physically modeled, and the electromagnetic and thermal parameters of the cable and its surrounding materials are extracted. According to the structural characteristics and laying method of the cable, a finite element model of electromagnetic-thermal-fluid multi-physical field coupling is constructed; (2) the finite element model is meshed, and environmental parameters and load parameters are input. The thermal field and flow field distribution in the model are solved by the whale optimization algorithm. Combined with the constraint that the conductor temperature does not exceed 90°C, the maximum current carrying capacity of the cable cluster is calculated.

[0117] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A method for calculating the current carrying capacity of irregular cable clusters based on the finite element method, characterized in that: The method specifically comprises the following steps: S1: Obtain parameters of cable structure and material properties; S2: Simplify and establish a multi-physics field coupling model of the cable, including electromagnetic field model, temperature field model and fluid field model; S3: Use software to establish physical modeling of irregular cable clusters under trench laying, combine electromagnetic and thermal parameters of cables and surrounding materials, and build electromagnetic-thermal-fluid multi-physics field coupled finite element model according to the structural characteristics and laying method of cables; then mesh the model; S4: Combined with the whale optimization algorithm, the objective function and constraints are set to calculate the current carrying capacity of irregular cable clusters under trench laying.

2. The method for calculating the current carrying capacity of irregular cable clusters according to claim 1, characterized in that: In step S2, an electromagnetic field model is constructed, specifically including: treating the cable channel as a two-dimensional plane field, assuming that the electromagnetic field around it is constant, and the conductivity σ of the conductor and the armor layer i The variation law with temperature is shown in formula (1), and the loss of each layer of the cable is shown in formulas (2) to (4); J=-jωσ i A+J s (3) In the formula, ρ 20 The metal resistivity at 20°C; α 20 is the temperature coefficient of metal resistivity; T is the changing temperature; T ref Take 20℃; ω is the angular frequency; A is the vector magnetic potential of each layer; σ i is the electrical conductivity of the material; μ is the magnetic permeability; J is the current density of each layer; J s is the source current density; P is the power loss per unit length of each layer; S is the cross-sectional area.

3. The method for calculating the current carrying capacity of irregular cable clusters according to claim 1, characterized in that: In step S2, a temperature field model is constructed, specifically including: for the area with internal heat source, i.e., the cable conductor and armor layer, the solid thermal conduction partial differential equation is as shown in formula (5); for the area without internal heat source, i.e., other layers of the cable, trench wall and soil, the solid thermal conduction partial differential equation is as shown in formula (6); In the formula, T is the temperature of the corresponding medium, q v is the internal heat source, x and y are the horizontal and vertical coordinate directions of the two-dimensional plane.

4. The method for calculating the current carrying capacity of irregular cable clusters according to claim 1, characterized in that: In step S2, a fluid field model is constructed, specifically including: the air in the channel dissipates heat through natural convection, and the air flow form in the channel is determined to be turbulent by calculating the Rayleigh number; the standard k-ε turbulence model is used to describe the heat transfer and flow process of the fluid, where k is the turbulent pulsation kinetic energy per unit mass of the fluid, and ε is the dissipation rate of k; the natural convection of the air around the cable in the channel must follow the three most basic conservation laws, namely, the law of conservation of mass, the law of conservation of momentum, and the law of conservation of energy, and the control equations are shown in equations (7) to (9); Where u and v are the air velocity on the x and y axes respectively; ρ is the air density; θ is the angle between the gravitational acceleration and the x-axis; β is the air expansion coefficient; η is the air dynamic viscosity; p is the air pressure scalar; T f is the initial temperature of the air, T is the temperature of the air; λ is the thermal conductivity of the air; g is the acceleration due to gravity.

5. The method for calculating the current carrying capacity of irregular cable clusters according to claim 1, characterized in that: In step S3, according to the temperature field model established in the heat transfer process, its boundary conditions are divided into the following three categories: The first type of boundary condition: the boundary temperature function is known, as shown in formula (10); T Γ =T w (10) Where T is the temperature of the corresponding medium, Γ is the integration boundary; T w is the known boundary temperature; The second type of boundary condition: the normal heat flux density of the boundary is known, as shown in formula (11); Where n is the normal vector, λ is the thermal conductivity, q is the known heat flux density; The third type of boundary condition: convection heat transfer boundary condition, its form is shown in formula (12); Where h is the convective heat transfer coefficient; T f is the fluid temperature.

6. The method for calculating the current carrying capacity of irregular cable clusters according to claim 1, characterized in that: In step S3, the grid is divided into different regions using different grid sizes; fine grid division is performed in the cable and air regions in the trench, and conventional grid division is performed in the trench wall and surrounding soil regions.

7. The method for calculating the current carrying capacity of irregular cable clusters according to claim 1, characterized in that: In step S4, the calculation model of the objective function f of the cable cluster current carrying capacity is: Where, I is the expected value of the current carrying capacity of the cross section, which is a constant; I k is the load of the kth cable, n is the total number of cable loops, T k is the conductor temperature of the kth cable.

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