A quick calculation method for the current carrying capacity of horizontal pipe jacking of high voltage AC cables

Abstract

The present invention discloses a method for quickly calculating the current carrying capacity of a horizontal pipe top of a high-voltage AC cable, comprising the following steps: S1, obtaining the parameters of a submarine cable and their value ranges; S2, constructing an adaptive surface response model based on compactly supported radial basis functions and electromagnetic-thermal-fluid coupling; S3, using the constructed adaptive surface response model to quickly calculate the current carrying capacity of the cable under any submarine cable parameters. The present invention can quickly calculate the current carrying capacity under any cable parameters, while ensuring the accuracy of the calculation results, and can also greatly reduce the calculation time and reduce the calculation cost.

Description

Technical Field

[0001] The invention relates to the technical field of cables, and in particular to a method for quickly calculating the current carrying capacity of a horizontal pipe jacking of a high-voltage AC cable. Background Art

[0002] With the continuous development of the national economy and the electric power industry, power cables are increasingly widely used in power transmission and distribution lines. Accurately calculating their current carrying capacity is of great significance to improving the utilization rate of power cables and dynamically adjusting loads. The current carrying capacity of cables is mainly determined by the long-term maximum temperature of the insulating material used. For example, for the widely used cross-linked polyethylene (XLPE) cable, the long-term maximum operating temperature of the cable core conductor cannot exceed 90 degrees Celsius.

[0003] Cable horizontal pipe jacking is a common form of cable structure. The air layer between the cable in the pipe and the pipe wall is a coupling of three heat transfer modes: heat conduction, heat convection and heat radiation. The current in the cable conductor generates an electromagnetic field, which affects the heat generation of the surrounding cables, and then affects the temperature field distribution of the cable group. Therefore, the cable horizontal pipe jacking needs to couple the electromagnetic field, thermal field, and fluid field to complete the calculation of the cable current carrying capacity. In the calculation of the cable current carrying capacity, the parameters of the cable horizontal pipe jacking can be considered as input variables, and the current carrying capacity is the output variable. Therefore, the functional relationship between the cable parameters and the current carrying capacity can be reconstructed by adopting the surface response model, thereby improving the calculation efficiency and reducing the calculation cost.

[0004] The surface response model (RSM) is a method that uses mathematical statistics knowledge to establish the input-output relationship of a system (device). The core of this method is to construct an analytical solution to the input-output relationship based on the response of the system at a series of sampling points using certain basis functions. Therefore, the key problem to be solved in constructing the RSM model is to determine the appropriate basis function to construct the relationship between the output variable and the input variable. At present, the most commonly used basis function for the RSM model in computational electromagnetics is the radial basis function (RBF). The advantage of RBF is that the constructed interpolation function is very simple to process discrete sampling points of any dimension and does not require too much calculation. However, the surface response model constructed based on the fully supported radial function has the following problems: (1) the constructed function is not an "optimal" function in a "certain" sense; (2) this model has difficulty in processing irregular sampling points; (3) it cannot automatically achieve the best matching of algorithm parameters; (4) when there are many sampling points, the calculation of the reconstruction function still requires a lot of computing resources. Summary of the invention

[0005] The purpose of the present invention is to provide a method for quickly calculating the current carrying capacity of a horizontal pipe jacking of a high-voltage AC cable. The present invention can quickly calculate the current carrying capacity of a horizontal pipe jacking of a cable under any cable parameters, while ensuring the accuracy of the calculation results, and can also greatly reduce the calculation time and reduce the calculation cost.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions: a method for quickly calculating the current carrying capacity of a horizontal pipe jacking of a high-voltage AC cable, comprising the following steps:

[0007] S1. Obtaining the parameters of the horizontal cable jacking pipe and the value range of each parameter;

[0008] S2, perform parameter sampling within the feasible interval of parameters;

[0009] S3. Calculate the cable current carrying capacity at the sampling point;

[0010] S4, constructing a surface response model based on moving least squares approximation;

[0011] S5. Use the constructed surface response model to quickly calculate the cable current carrying capacity under any cable horizontal pipe jacking parameters.

[0012] In the above-mentioned method for quickly calculating the current carrying capacity of the horizontal cable jacking pipe of high-voltage AC cables, in step S1, the parameters of the horizontal cable jacking pipe include the inner diameter length of the horizontal cable jacking pipe and the outer diameter length of the horizontal cable jacking pipe.

[0013] In the aforementioned method for quickly calculating the current-carrying capacity of a horizontal pipe-jacking device for a high-voltage AC cable, in step S2, the parameter sampling is uniform sampling within a feasible parameter range, and the number of sampling points is 100.

[0014] In the aforementioned method for quickly calculating the current carrying capacity of the horizontal pipe jacking of the high-voltage AC cable, in step S3, a multi-physics field coupling model is used to calculate the eddy current field, temperature field and fluid field of the cable at the sampling point, and then the cable current carrying capacity at the sampling point of the cable is calculated by an iterative procedure, specifically including:

[0015] S3.1. Calculation of eddy current field: For a two-dimensional eddy current field, the governing equation of the vector magnetic potential under the Coulomb specification is:

[0016]

[0017] Where: is the current density, is the vector magnetic potential, σ is the conductivity, is the vector differential operator, i.e. the gradient operator; μ is the magnetic permeability, j is the complex number sign, and ω is the angular frequency;

[0018] S3.2. Calculate the temperature field: For the two-dimensional temperature field, the control equation is:

[0019]

[0020] Where: ρ is density, C p is the heat capacity at normal pressure, u is the velocity vector, k is the thermal conductivity, Q e is the heat source's heating power per unit volume, q is the heat flux density; is the temperature gradient, J is the current density vector, and E is the electric field intensity vector;

[0021] S3.3. Calculate the fluid field. The fluid field satisfies the laws of conservation of mass, momentum and energy:

[0022]

[0023] Where: I is the unit matrix, μ is the dynamic viscosity, T is the temperature of the fluid material, and F is the buoyancy caused by density change;

[0024] S3.4. Set boundary conditions, including known boundary temperature conditions, known boundary normal heat flux density conditions and convection boundary conditions:

[0025]

[0026] Where: T w is the known top tube wall temperature, q is the heat flux, α is the temperature coefficient of the conductor resistivity, T f is the fluid medium temperature;

[0027] S3.5. Consider the temperature field as a two-dimensional steady-state heat conduction problem. The conductivity σ of the conductor will change with temperature and can be expressed as:

[0028]

[0029] Where α is the temperature coefficient of the conductor resistivity, ρ0 is the resistivity of the conductor at 20°C, and T ref is the reference temperature;

[0030] S3.6. Use the chord intercept method to solve the current carrying capacity. That is, when the maximum temperature of the cable conductor reaches 90 degrees Celsius, the current at this moment is defined as the current carrying capacity of the cable. The corresponding conductor temperature is calculated by solving the temperature field, and the chord intercept method is used to calculate the cable current carrying capacity. In the iterative calculation, when |T k When the value of -90| is less than 0.01℃, the cable conductor temperature is considered to be stable at the maximum allowable temperature. At this time, the current flowing through the cable is the cable current carrying capacity.

[0031] In the aforementioned method for quickly calculating the current carrying capacity of the horizontal pipe jacking of a high-voltage AC cable, in step S4, the surface response model based on the moving least squares approximation is constructed specifically as follows:

[0032] For any f(x):R n →R, if it is known that at some series of sampling points x i ∈R D The function value on (i=1,2,…,N) is f i , then in the selected basis function Under these conditions, we first define the local approximation L of MLS. x f is:

[0033]

[0034] The basis functions satisfy:

[0035] 1) b (1) ≡1;

[0036] 2) b (i) ∈C m (R D )(i=1,2,…,n);

[0037] 3) At the given n sampling points, Independent of each other;

[0038] Then define the global projection operator Gf as: for any point x∈R D :

[0039]

[0040] To determine the coefficient a(x), use the following inner product definition of L 2 -norm, i.e.

[0041] (u,v) x =u T w(x)v;

[0042]

[0043] In the formula, z=(z(x1)z(x2)…z(x N )) T (z=u,v), w(x) is an N×N diagonal matrix whose diagonal elements are w (i) (x), w (i) (x) is the weight function of MLS;

[0044] The characteristic of MLS is the weight function w (i) (x) is a compactly supported function centered at the i-th sampling point; Gf is the least squares approximation of function f, and we have:

[0045] a(x)=A(x) -1 B(x)f;

[0046] Where: f=[f1 f2 … f N ] T ;

[0047]

[0048] B(x)=[w 1 (x)b(x1) w 2 (x)b(x2) … w N (x)b(x N )];

[0049] Thus, a surface response model based on moving least squares is obtained.

[0050] The aforementioned fast calculation method for the current carrying capacity of the horizontal pipe top of the high-voltage AC cable is used to calculate the weight function w (i) (x) is corrected to make MLS an interpolation-type approximation method. The corrected formula is as follows:

[0051]

[0052] In the formula, a is a positive number.

[0053] The aforementioned method for quickly calculating the current carrying capacity of the horizontal pipe top of a high-voltage AC cable, the weight function w (i) The selection of (x) satisfies the following conditions:

[0054] 1) In the support domain Ω x Within, w(xx i )>0;

[0055] 2) In the support domain Ω x In addition, w(xx i )=0;

[0056] 3) Normality, i.e. ∫ Ω w(xx i )dΩ=1;

[0057] 4) The weight function is || xx i ||'s monotonically decreasing function;

[0058] 5) The weight function is continuously differentiable.

[0059] The aforementioned method for quickly calculating the current carrying capacity of the horizontal pipe top of a high-voltage AC cable, the weight function w (i) (x) is a Gaussian function, a cubic spline function, or a quartic spline function.

[0060] The aforementioned method for quickly calculating the current carrying capacity of the horizontal pipe top of a high-voltage AC cable, the weight function w (i) (x) is a cubic spline function:

[0061]

[0062] Or a quartic spline function:

[0063]

[0064] In the formula: r = || xx i ||, r max is the support domain radius of the weight function.

[0065] Compared with the prior art, the present invention first determines the parameters of the cable horizontal jacking pipe and the value range of each parameter of the cable horizontal jacking pipe; secondly, the parameters are sampled within the feasible interval of the parameters; then the cable current carrying capacity at the sampling point is calculated; finally, the input-output relationship between the cable horizontal jacking pipe parameters and the cable current carrying capacity is reconstructed using the surface response model based on the moving least squares, that is, the surface response model constructed by the present invention is used to input any cable horizontal jacking pipe parameters within the feasible interval, and the cable current carrying capacity is calculated and output. Therefore, the parameter sampling adopted in the present invention ensures that the present invention is applicable to the current carrying capacity calculation under any parameters within the feasible interval of the parameters; the multi-physical field coupling model combined with the chord intercept method ensures the accuracy of the current carrying capacity calculation results at the sampling point; in view of the powerful function reconstruction ability of the moving least squares, the numerical matching accuracy of the reconstructed function and the original function is guaranteed. In summary, for any parameter within the feasible interval of the parameters, the present invention has good numerical accuracy. While ensuring the accuracy of the current carrying capacity calculation results, the present invention can also greatly reduce the calculation time and reduce the calculation cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 It is a schematic diagram of the process of the present invention;

[0067] Figure 2 It is a schematic diagram of the parameters of the horizontal cable jacking pipe of the present invention;

[0068] Figure 3 It is a flow chart for calculating the current carrying capacity of cables. DETAILED DESCRIPTION

[0069] The present invention is further described below in conjunction with the embodiments and drawings, but they are not intended to limit the present invention.

[0070] Embodiment: A method for quickly calculating the current carrying capacity of a horizontal pipe top of a high voltage AC cable, such as Figure 1 As shown, the following steps are included:

[0071] S1. Obtaining the parameters of the horizontal cable jacking pipe and the value range of each parameter;

[0072] There are two parameters for the cable horizontal pipe jacking in this embodiment (both in millimeters), such as Figure 2 As shown. They are:

[0073] The inner diameter length of the cable horizontal jacking pipe: x1∈[1500,1600];

[0074] The outer diameter length of the horizontal cable jacking pipe: x2∈[1800,1900].

[0075] S2. Parameter sampling is performed within the feasible interval of the parameters; the parameter sampling is uniform sampling within the feasible interval of the parameters, and the number of sampling points is 100.

[0076] S3. Calculate the current carrying capacity of the cable at the sampling point; for the cable in the cable top pipe, the cable is the only heat source, which includes the Joule heat generated by the conductive material and the dielectric loss of the insulation layer. The heat dissipation in the cable top pipe includes heat conduction between the cable and the surrounding medium, natural convection of air between the outer surface of the cable and the inner wall of the cable top pipe, and thermal radiation between the outer surfaces.

[0077] In this embodiment, a multi-physics field coupling model is used to calculate the eddy current field, temperature field and fluid field of the cable at the sampling point, and then the cable current carrying capacity at the sampling point of the cable is calculated through an iterative program, specifically including:

[0078] S3.1. Calculation of eddy current field: For a two-dimensional eddy current field, the governing equation of the vector magnetic potential under the Coulomb specification is:

[0079]

[0080] Where: is the current density, is the vector magnetic potential, σ is the conductivity, is the vector differential operator, i.e. the gradient operator; μ is the magnetic permeability, j is the complex number sign, and ω is the angular frequency;

[0081] S3.2. Calculation of temperature field: In cables, the heat source in the solid and fluid heat transfer field is the Joule heat generated by the cable current. The length of the cable line can be considered infinite compared to its diameter. Therefore, the temperature field of the cable arranged in the top pipe can also be simplified to two-dimensional. For the two-dimensional temperature field, its control equation is:

[0082]

[0083] Where: ρ is density, C p is the heat capacity at normal pressure, u is the velocity vector, k is the thermal conductivity, Q e is the heat source's heating power per unit volume, q is the heat flux density; is the temperature gradient, J is the current density vector, and E is the electric field intensity vector;

[0084] S3.3. Calculate the fluid field. The fluid field satisfies the laws of conservation of mass, momentum and energy:

[0085]

[0086] Where: I is the unit matrix, μ is the dynamic viscosity, T is the temperature of the fluid material, and F is the buoyancy caused by density change;

[0087] S3.4. Set boundary conditions: In order to solve the temperature field and current carrying capacity of the horizontal cable jacking pipe, the boundary conditions of the cable heat transfer problem can be summarized into three categories: the first category is the known boundary temperature; the second category is the known boundary normal heat flux density; the third category is the convection boundary condition, that is, the convection heat transfer coefficient and fluid temperature within the known boundary. These three types of boundaries are expressed as:

[0088]

[0089] Where: T w is the known top tube wall temperature, q is the heat flux, α is the temperature coefficient of the conductor resistivity, T f is the fluid medium temperature;

[0090] S3.5. Since the on-site cable laying conditions are extremely complex during cable laying, in order to reduce the complexity of the model and further ensure the smooth progress of the heat transfer finite element analysis, the following simplifications are made:

[0091] Assume that the cable in the cable jacking pipe is infinitely long and do not consider the influence of axial heat transfer. Simplify the three-dimensional model into a two-dimensional model, that is, regard the temperature field as a two-dimensional steady-state heat conduction problem. The conductivity σ of the conductor will change with temperature, expressed as:

[0092]

[0093] Where α is the temperature coefficient of the conductor resistivity, ρ0 is the resistivity of the conductor at 20°C, and T ref It is the reference temperature; the natural convection velocity in the enclosed air zone in the cable trench is relatively low, and the air in the trench can be regarded as an incompressible fluid.

[0094] S3.6. The calculation of the current carrying capacity of the cable jacking pipe is based on the calculation of the temperature field, which is the inverse process of the calculation of the electromagnetic field and the temperature field. This embodiment uses the chord intercept method to solve the current carrying capacity, that is, when the maximum temperature of the cable conductor reaches 90 degrees Celsius, the current at this moment is defined as the current carrying capacity of the cable; Figure 3 As shown, the initial value of the current can be calculated according to the IEC60287 standard. The corresponding conductor temperature is calculated by solving the temperature field, and the cable current carrying capacity is calculated by the chord intercept method. In the iterative calculation, when |Tk When the value of -90| is less than 0.01℃, the cable conductor temperature is considered to be stable at the maximum allowable temperature. At this time, the current flowing through the cable is the cable current carrying capacity.

[0095] S4, constructing a surface response model based on moving least squares approximation;

[0096] In order to quickly calculate the current carrying capacity of the cable jacking pipe, the present invention adopts a surface response model based on moving least squares approximation to reconstruct the input-output relationship between the input variable (cable horizontal jacking pipe parameter) and the output variable (cable current carrying capacity).

[0097] The moving least squares approximation (MLS) was first proposed by Shepard for low-dimensional curve fitting problems, and then Lancaster and Salkauskas extended it to high-dimensional problems. Because of its strong fitting ability, this method has been widely used in curve and surface fitting, as well as meshless algorithms, etc. in recent years.

[0098] For any f(x):R n →R, if it is known that at some series of sampling points x i ∈R D The function value on (i=1,2,…,N) is f i , then in the selected basis function Under these conditions, we first define the local approximation L of MLS. x f is:

[0099]

[0100] The basis functions satisfy:

[0101] 1) b (1) ≡1;

[0102] 2) b (i) ∈C m (R D )(i=1,2,…,n);

[0103] 3) At the given n sampling points, Independent of each other;

[0104] Then define the global projection operator Gf as: for any point x∈R D :

[0105]

[0106] To determine the coefficient a(x), use the following inner product definition of L 2-norm, i.e.

[0107] (u,v) x =u T w(x)v;

[0108]

[0109] In the formula, z=(z(x1)z(x2)…z(x N )) T (z=u,v), w(x) is an N×N diagonal matrix whose diagonal elements are w (i) (x), w (i) (x) is the weight function of MLS;

[0110] One of the characteristics of MLS is the weight function w (i) (x) is a compactly supported function centered at the i-th sampling point; therefore, the MLS approximation is a local approximation. From Gf, which is the least squares approximation of function f, we have:

[0111] a(x)=A(x) -1 B(x)f;

[0112] Where: f=[f1 f2 … f N ] T ;

[0113]

[0114] B(x)=[w 1 (x)b(x1) w 2 (x)b(x2) … w N (x)b(x N )];

[0115] Thus, the surface response model based on moving least squares is obtained. Generally speaking, MLS is not an interpolation fitting method. In order to make MLS an interpolation approximation method, the weight function is modified as follows:

[0116]

[0117] In the formula, a is a positive number. The MLS in this case is called Interpolating MLS (IMLS).

[0118] The weight function plays a very important role in the moving least squares method and has a great influence on the calculation results. Generally speaking, the weight function w (i) The selection of (x) satisfies the following conditions:

[0119] 1) In the support domain Ω xWithin, w(xx i )>0;

[0120] 2) In the support domain Ω x In addition, w(xx i )=0;

[0121] 3) Normality, i.e. ∫ Ω w(xx i )dΩ=1;

[0122] 4) The weight function is || xx i ||'s monotonically decreasing function;

[0123] 5) The weight function is continuously differentiable.

[0124] Among them, condition 2) is crucial, which can ensure that MLS is a local approximation with compact support, that is, the approximate solution only depends on the nodes in the affected area and is independent of other nodes.

[0125] The weight function is a Gaussian function, a cubic spline function or a quartic spline function, wherein when the weight function is a cubic spline function:

[0126]

[0127] When the weight function is a quartic spline function:

[0128]

[0129] In the formula: r = || xx i ||, r max is the support domain radius of the weight function.

[0130] Generally speaking, the support radius (influence domain) of the weight function has a great influence on the performance of MLS. Under the condition that the sampling points remain unchanged, the larger the support radius of the weight function, the higher the accuracy of the reconstruction function, but the locality of MLS deteriorates; under the extreme condition that the influence domain of the weight function covers all sampling points, MLS becomes a fully supported surface response model; conversely, when the support radius is smaller, the locality of MLS becomes better, but the accuracy of the reconstruction function deteriorates. In addition, in practical applications, the influence area should contain enough sampling points so that the formula a(x) = A(x) -1 A(x) in B(x)f is reversible.

[0131] The present invention uses the aforementioned moving least square method to reconstruct the functional relationship between the cable horizontal pipe jacking parameters and the cable current carrying capacity based on 100 sampling points and the target function value (cable current carrying capacity). During the reconstruction, the basis function is a quadratic basis function, and the weight function is a tri-spline function.

[0132] S5. The surface response model constructed by the above steps can be used to quickly calculate the cable current carrying capacity under any cable horizontal pipe jacking parameters. That is, by using the surface response model constructed by the present invention and inputting any cable horizontal pipe jacking parameters within the feasible range, the cable current carrying capacity can be quickly and accurately calculated and output.

[0133] In summary, the present invention first determines the parameters of the cable horizontal jacking pipe and the value range of each parameter of the cable horizontal jacking pipe; secondly, the parameters are sampled within the feasible interval of the parameters; then the cable current carrying capacity at the sampling point is calculated; finally, the input-output relationship between the cable horizontal jacking pipe parameters and the cable current carrying capacity is reconstructed using the surface response model based on the moving least squares, that is, the surface response model constructed by the present invention is used to input any cable horizontal jacking pipe parameters within the feasible interval, and the cable current carrying capacity is calculated and output. Therefore, the parameter sampling used in the present invention ensures that the present invention is applicable to the current carrying capacity calculation under any parameters within the feasible interval of the parameters; the multi-physical field coupling model combined with the chord intercept method ensures the accuracy of the current carrying capacity calculation results at the sampling point; in view of the powerful function reconstruction ability of the moving least squares, the numerical matching accuracy of the reconstructed function and the original function is guaranteed. For any parameter within the feasible interval of the parameters, the present invention has good numerical accuracy. While ensuring the accuracy of the current carrying capacity calculation results, the present invention can also greatly reduce the calculation time and reduce the calculation cost.

Claims

1. A method for quickly calculating the current carrying capacity of a horizontal pipe jacking of a high-voltage AC cable, characterized in that: The steps include: S1. Obtaining the parameters of the cable tube and the value range of each parameter; S2, perform parameter sampling within the feasible interval of parameters; S3. Calculate the cable current carrying capacity at the sampling point; S4, constructing a surface response model based on moving least squares approximation; S5, using the constructed surface response model to quickly calculate the cable current carrying capacity under any cable horizontal pipe jacking parameters; In step S4, the surface response model based on the moving least squares approximation is constructed as follows: For any f(x):R n →R, if it is known that at some series of sampling points x i ∈R D , i = 1, 2, ..., the function value on N is f i , then in the selected basis function Under these conditions, we first define the local approximation L of MLS. x f is: The basis functions satisfy: 1)、b (1) ≡1； 2)、b (i) ∈C m (R D ),i=1,2,…,n; 3) At the given n sampling points, Independent of each other; Then define the global projection operator Gf as: for any point x∈R D : To determine the coefficient a(x), use the following inner product definition of L 2 -norm, i.e. (u,v) x =u T w(x)v; In the formula, z=(z(x1) z(x2) … z(x N )) T , z = u, v, w(x) is an N × N diagonal matrix, whose diagonal elements are w (i) (x), w (i) (x) is the weight function of MLS; The characteristic of MLS is the weight function w (i) (x) is a compactly supported function centered at the i-th sampling point; Gf is the least squares approximation of function f, and we have: a(x)=A(x) -1 B(x)f; Where: f=[f1 f2…f N ] T ; B(x)=[w 1 (x)b(x1)w 2 (x)b(x2)…w N (x)b(x N )]: Thus, a surface response model based on moving least squares is obtained.

2. The method for rapidly calculating the current carrying capacity of a horizontal pipe jacking of a high-voltage AC cable according to claim 1 is characterized in that: In step S1, the parameters of the horizontal cable jacking pipe include the inner diameter length of the horizontal cable jacking pipe and the outer diameter length of the horizontal cable jacking pipe.

3. The method for rapidly calculating the current carrying capacity of a horizontal pipe jacking of a high-voltage AC cable according to claim 1 is characterized in that: In step S2, the parameter sampling is uniform sampling within the feasible interval of the parameter, and the number of sampling points is 100.

4. The method for rapidly calculating the current carrying capacity of a horizontal pipe jacking of a high-voltage AC cable according to claim 1 is characterized in that: In step S3, a multi-physics field coupling model is used to calculate the eddy current field, temperature field and fluid field of the cable at the sampling point, and then the cable current carrying capacity at the sampling point of the cable is calculated by an iterative procedure, specifically including: S3.

1. Calculation of eddy current field: For a two-dimensional eddy current field, the governing equation of the vector magnetic potential under the Coulomb specification is: Where: is the current density, is the vector magnetic potential, σ is the conductivity, is the vector differential operator, i.e. the gradient operator; μ is the magnetic permeability, j is the complex number sign, and ω is the angular frequency; S3.

2. Calculate the temperature field: For the two-dimensional temperature field, the control equation is: Where: ρ is density, C p is the heat capacity at normal pressure, u is the velocity vector, k is the thermal conductivity, Q e is the heat source's heating power per unit volume, q is the heat flux density; is the temperature gradient, J is the current density vector, and E is the electric field intensity vector; S3.

3. Calculate the fluid field. The fluid field satisfies the laws of conservation of mass, momentum and energy: Where: I is the unit matrix, μ is the dynamic viscosity, T is the temperature of the fluid material, and F is the buoyancy caused by density change; S3.

4. Set boundary conditions, which include known boundary temperature conditions, known boundary normal heat flux density conditions and convection boundary conditions: Where: T w is the known top tube wall temperature, q is the heat flux, α is the temperature coefficient of the conductor resistivity, T f is the fluid medium temperature; S3.

5. Consider the temperature field as a two-dimensional steady-state heat conduction problem. The conductivity σ of the conductor will change with temperature and can be expressed as: Where α is the temperature coefficient of the conductor resistivity, ρ0 is the resistivity of the conductor at 20°C, and T ref is the reference temperature; S3.

6. Use the chord intercept method to solve the current carrying capacity. That is, when the maximum temperature of the cable conductor reaches 90 degrees Celsius, the current at this moment is defined as the current carrying capacity of the cable. The corresponding conductor temperature is calculated by solving the temperature field, and the chord intercept method is used to calculate the cable current carrying capacity. In the iterative calculation, when |T k When the value of -90| is less than 0.01℃, the cable conductor temperature is considered to be stable at the maximum allowable temperature. At this time, the current flowing through the cable is the cable current carrying capacity.

5. The method for rapidly calculating the current carrying capacity of a horizontal pipe jacking of a high-voltage AC cable according to claim 1 is characterized in that: The weight function w (i) (x) is corrected to make MLS an interpolation-type approximation method. The corrected formula is as follows: In the formula, a is a positive number.

6. The method for rapidly calculating the current carrying capacity of a horizontal pipe jacking of a high-voltage AC cable according to claim 1 is characterized in that: The weight function w (i) The selection of (x) satisfies the following conditions: 1) In the support domain Ω x Within, w(xx i )>0; 2) In the support domain Ω x In addition, w(xx i )=0; 3) Normality, i.e. ∫ Ω w(xx i )dΩ=1; 4) The weight function is ||xx i ||'s monotonically decreasing function; 5) The weight function is continuously differentiable.

7. The method for rapidly calculating the current carrying capacity of a horizontal pipe jacking of a high-voltage AC cable according to claim 1 is characterized in that: The weight function w (i) (x) is a Gaussian function, a cubic spline function, or a quartic spline function.

8. The method for rapidly calculating the current carrying capacity of a horizontal pipe jacking of a high-voltage AC cable according to claim 7 is characterized in that: The weight function w (i) (x) is a cubic spline function: or a quartic spline function: In the formula: r = || xx i ||, r max is the support domain radius of the weight function.

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