Temperature rise evaluation method, device, equipment, medium and product of cable core of buried cable group

Abstract

The invention provides a temperature rise evaluation method, device and equipment for a cable core of a buried cable group, a medium and a product, and relates to the technical field of power cables. The method comprises the following steps: dividing the cross section of a cable group into a cable part and a soil part through an isotherm; establishing a transient thermal circuit model; wherein the transient thermal circuit model comprises an equivalent circuit of the cable part and an equivalent circuit of the soil part, and the equivalent circuit of the cable part comprises a self-heating structure of each cable and a mutual heating structure between two adjacent cables; determining optimal parameters of the transient thermal circuit model according to a genetic algorithm; and based on the transient thermal circuit model, calculating a temperature rise curve of each cable core along with time change. According to the invention, the transient temperature rise of the cable core can be rapidly and accurately calculated.

Description

Technical Field

[0001] The present invention belongs to the technical field of power cables, and in particular relates to a method, device, equipment, medium and product for evaluating the temperature rise of a cable core of an underground cable group. Background Art

[0002] In large and medium-sized cities, the cable rate continues to increase. For cables of 110kV and below, direct burial in the soil and laying in pipes are common methods.

[0003] The typical method for calculating the temperature rise of the core of underground power cables is the International Electrotechnical Commission (IEC) series of standards. However, the IEC method is cumbersome when calculating the transient core temperature rise. With the popularization of numerical calculation methods such as finite element and the widespread application of various tool software, the use of numerical calculation methods such as finite element to calculate the temperature field of power cables under various laying conditions and operating conditions has gradually become the mainstream. However, the finite element method requires researchers to have a strong theoretical foundation and operational skills, and is often used in the study of typical complex lines. Due to its computational complexity and long calculation time, it is difficult to meet the rapidity requirements under conditions such as emergency loads.

[0004] In order to meet the requirements of rapidity and convenience in dynamic current-carrying capacity assessment, relevant personnel have been studying the use of thermal circuit models to calculate the transient core temperature rise of buried power cables. To fully tap the current-carrying capacity of power cables and improve the utilization rate of power cables, it is necessary to study transient thermal circuit models that can quickly and accurately calculate the transient core temperature rise of cables. However, most of the existing thermal circuit models are limited to the cable self-heating model, or the cable group is decomposed into a self-heating model and a mutual heating model, and the self-heating model and the mutual heating model are solved separately. This solution method is complex and difficult to operate, especially it is difficult to ensure the accuracy of mutual heating. Some researchers added inductance to the thermal circuit model to simulate the delayed transfer process of heat flow, but the parameters of the inductance are difficult to grasp. Some researchers proposed to calculate the parameters of resistance and capacitance components by soil stratification. Although the accuracy is improved, the complexity of the operation is increased, and it is still based on the method of separating self-heating and mutual heating. Summary of the invention

[0005] In view of this, an embodiment of the present invention provides a method, device, equipment, medium and product for evaluating the temperature rise of a cable core of an underground cable group, so as to quickly and accurately calculate the transient temperature rise of the cable core.

[0006] In a first aspect, an embodiment of the present invention provides a method for evaluating the temperature rise of a cable core of an underground cable group, comprising: The cross section of the cable group is divided into a cable part and a soil part by an isotherm; Establish a transient heat circuit model; wherein the transient heat circuit model includes an equivalent circuit of the cable part and an equivalent circuit of the soil part, and the equivalent circuit of the cable part includes a self-heating structure of each cable and a mutual heating structure between two adjacent cables; Determine the optimal parameters of the transient thermal circuit model based on the genetic algorithm; Based on the transient thermal circuit model, the temperature rise curve of each cable core changing with time is calculated.

[0007] In a possible implementation, in the equivalent circuit of the cable part, the self-heating structure is represented by two branches of two thermal resistors and two thermal capacitors, and the mutual heating structure is represented by a T-type branch of two thermal resistors and one thermal capacitor; the equivalent circuit of the soil part is represented by two branches of two thermal resistors and two thermal capacitors.

[0008] In a possible implementation, the optimal parameters of the transient thermal circuit model are determined according to a genetic algorithm, including: The transient temperature rise of each cable core under step load is calculated by finite element method, and the finite element method solution is obtained; Generate the parameters of the transient heat circuit model according to the genetic algorithm, and use the sum of squares of the transient heat circuit model solution corresponding to the parameters and the finite element method solution at each time point as the fitness function to iteratively optimize the parameters of the transient heat circuit model; After the convergence conditions are met, the optimal parameters are determined according to the optimal fitness function.

[0009] In a possible implementation, based on the transient thermal circuit model, the temperature rise curve of each cable core over time is calculated, including: Establish the heat flow differential equations of each node in the transient heat circuit model; According to the heat flow differential equation, the fourth-order Runge-Kutta equation is determined, and the voltage value sequence of each node is estimated by the fourth-order Runge-Kutta method; From each node, the corresponding node of each cable core is determined, and based on the voltage value sequence of the corresponding node, the temperature rise curve of each cable core changing with time is determined.

[0010] In one possible implementation, the voltage value sequence of each node is estimated by a fourth-order Runge-Kutta method, including: The voltage derivatives at each node are estimated by the fourth-order Runge–Kutta method; Interpolation is performed at different intermediate time points based on the voltage derivative to obtain a voltage value sequence.

[0011] In a possible implementation, the method further includes: according to , update the voltage derivative of each node; in, yis the voltage derivative; n is the current time step of the node; h is the time step; i Number the cables; k i1 , k i2 , k i3 , k i4 are the voltage derivatives of the four stages of the fourth-order Runge–Kutta method.

[0012] In a second aspect, an embodiment of the present invention provides a temperature rise assessment device for a cable core of an underground cable group, comprising: Establish a module for dividing the cross section of the cable group into a cable part and a soil part through an isotherm; establish a transient thermal circuit model; wherein the transient thermal circuit model includes an equivalent circuit of the cable part and an equivalent circuit of the soil part, and the equivalent circuit of the cable part includes a self-heating structure of each cable and a mutual heating structure between two adjacent cables; An optimization module, used to determine the optimal parameters of the transient thermal circuit model based on a genetic algorithm; The calculation module is used to calculate the temperature rise curve of each cable core over time based on the transient thermal circuit model.

[0013] In a third aspect, an embodiment of the present invention provides an electronic device, including a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the method in the first aspect or any possible implementation of the first aspect is implemented.

[0014] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, it implements the method in the first aspect or any possible implementation of the first aspect.

[0015] In a fifth aspect, an embodiment of the present invention provides a computer program product, including a computer program, which, when executed by a processor, implements the method in the first aspect or any possible implementation manner of the first aspect.

[0016] In an embodiment of the present invention, the cross section of the cable group is divided into a cable part and a soil part by an isotherm, and a comprehensive transient thermal circuit model is directly established, that is, there is no need to separate it into a self-heating thermal circuit model and a mutual heating thermal circuit model. The transient thermal circuit model includes an equivalent circuit of the cable part and an equivalent circuit of the soil part. The equivalent circuit of the cable part includes the self-heating structure of each cable and the mutual heating structure between two adjacent cables. The cable and the soil are respectively equivalent, which enhances the reliability of the calculation, improves the calculation efficiency, and avoids the complexity of the solution. According to the genetic algorithm, the optimal parameters of the transient thermal circuit model are determined, and the accuracy of the model is further improved. When the cable current or loss changes, the temperature rise of the cable body can be directly solved by the transient thermal circuit model. In addition, for the calculation of different numbers of cables, it is only necessary to add or reduce several groups of branch parts in the model, which improves the convenience of the calculation. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The isothermal distribution characteristics of the buried cable group provided by the embodiment of the present invention are Figure 1 ; Figure 2 The isothermal distribution characteristics of the buried cable group provided by the embodiment of the present invention are Figure 2 ; Figure 3 It is a flow chart of a method for evaluating the temperature rise of a cable core of an underground cable group provided by an embodiment of the present invention; Figure 4 is a structural diagram of a transient thermal circuit model provided by an embodiment of the present invention; Figure 5 is a flow chart of a particle swarm solving algorithm provided by an embodiment of the present invention; Figure 6 It is a finite element cable temperature rise diagram provided by an embodiment of the present invention; Figure 7 It is a cable temperature rise diagram of a thermal circuit model provided by an embodiment of the present invention; Figure 8 The error comparison provided by the embodiment of the present invention is Figure 1 ; Fig. 9 The error comparison provided by the embodiment of the present invention is Figure 2 ; Fig.10 The error comparison provided by the embodiment of the present invention is Figure 3 ; Fig.11 It is a structural diagram of a temperature rise assessment device for a cable core of an underground cable group provided by an embodiment of the present invention; Fig.12 It is a structural diagram of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0018] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0019] Figure 1 and Figure 2 : is a schematic diagram of an application scenario of a temperature rise assessment method for a buried cable group core provided by an embodiment of the present invention, wherein Figure 1 is the isothermal distribution characteristics of the underground cable group of two cables, Figure 2 The isothermal distribution characteristics of the buried cable group of three cables. It can be seen that there are multiple isotherms outside the cable group. If any of the isotherms is used as the boundary, the entire area can be divided into two parts, namely the area inside the isotherm and the area outside the isotherm. On the isotherm, the losses of all cables inside diffuse to the outside through the isotherm. Inside the isotherm, the losses of multiple cables are transmitted to the isotherm respectively. At the same time, there is mutual heat transfer between cables.

[0020] Currently, there is no direct thermal circuit model that reflects the laying of cable groups to calculate the cable core temperature. Therefore, this embodiment provides a new transient thermal circuit model for buried cables, which can directly construct a complete transient thermal circuit model based on the cable group without separating it into self-heating and mutual heating thermal circuit models, and use the Runge-Kutta algorithm to calculate the cable core temperature rise, thereby accurately grasping the thermal state of the power cable throughout its life cycle, deeply exploring the dynamic current carrying capacity of the power cable, and improving the utilization rate of the power cable.

[0021] See also Figure 3 , which shows a flow chart of the implementation of the temperature rise assessment method of the cable core of the buried cable group provided by an embodiment of the present invention, which is described in detail as follows: Step S301, dividing the cross section of the cable group into a cable part and a soil part by an isotherm.

[0022] Here, the isotherm is a virtual concept proposed when establishing the transient thermal circuit model, not a specific isotherm selected in practice. The isotherm divides the cross section of the cable group into two parts: the cable body and part of the soil are inside the isotherm, and the soil is outside the isotherm.

[0023] Step S302, establishing a transient thermal circuit model; wherein the transient thermal circuit model includes an equivalent circuit of the cable part and an equivalent circuit of the soil part, and the equivalent circuit of the cable part includes a self-heating structure of each cable and a mutual heating structure between two adjacent cables.

[0024] In this embodiment, each cable to the isotherm is represented by a two-branch model, and cables are represented by a T-type model; and the soil outside the isotherm is represented by a two-branch model to the environment.

[0025] Taking a cable group with two cables as an example, the transient thermal circuit model established is as follows: Figure 4As shown. Through trial calculation, each cable to isotherm and isotherm to ambient temperature can be represented by two branches with two thermal resistances and two thermal capacitances, and the transient temperature rise calculation results that meet the engineering requirements can be obtained. If only one branch is used, the error is large. If more branches are used, the complexity of the entire thermal circuit model will increase. Therefore, in Figure 4 In the figure, the temperature at the T4 node is the isotherm, the left side is the equivalent circuit of the cable part, and the right side is the equivalent circuit of the soil part. W1 and W2 are the heat sources of the two buried cables, R 11 , R 12 , C 11 , C 12 is the self-heating structural parameter of the first cable, R 21 , R 22 , C 21 , C 22 are the self-heating structural parameters of the second cable, R5, R6, C4, C5 are the equivalent thermal resistance and thermal capacity parameters of the soil part, and R3, R4, C3 are the mutual heating structural parameters between the two cables.

[0026] In some embodiments, when the cable group contains more cables, the transient thermal circuit model only needs to add corresponding self-heating structures and mutual heating structures. For example, when there are three cables, one set of self-heating structure parameters is added, and one set of mutual heating structure parameters is added between the second and third cables, which improves the convenience of calculation.

[0027] Step S303: determining the optimal parameters of the transient thermal circuit model according to the genetic algorithm.

[0028] The above thermal resistance and heat capacity parameters are equivalent parameters, which are difficult to calculate with accurate formulas. Here, the finite element method can be used to calculate the transient temperature rise of the cable core under step load. After obtaining the transient temperature rise, the genetic algorithm is used to optimize the solution and determine the optimal parameters of the transient thermal circuit model.

[0029] Step S304, based on the transient thermal circuit model, calculate the temperature rise curve of each cable core over time.

[0030] According to the transient thermal circuit model mentioned above, after the thermal resistance, thermal capacitance parameters, and the heating of the cable body are known, the node heat flow and temperature rise at each time step can be calculated step by step, where T 11 、T 21 The temperature rise of the node is the temperature rise curve of the cores of the two directly buried cables changing with time.

[0031] In an embodiment of the present invention, the cross section of the cable group is divided into a cable part and a soil part by an isotherm, and a comprehensive transient thermal circuit model is directly established, that is, there is no need to separate it into a self-heating thermal circuit model and a mutual heating thermal circuit model. The transient thermal circuit model includes an equivalent circuit of the cable part and an equivalent circuit of the soil part. The equivalent circuit of the cable part includes the self-heating structure of each cable and the mutual heating structure between two adjacent cables. The cable and the soil are respectively equivalent, which enhances the reliability of the calculation, improves the calculation efficiency, and avoids the complexity of the solution. According to the genetic algorithm, the optimal parameters of the transient thermal circuit model are determined, and the accuracy of the model is further improved. When the cable current or loss changes, the temperature rise of the cable body can be directly solved by the transient thermal circuit model. In addition, for the calculation of different numbers of cables, it is only necessary to add or reduce several groups of branch parts in the model, which improves the convenience of the calculation.

[0032] In some embodiments, the implementation process of the above step S303 may include: Step S3031, calculating the transient temperature rise of each cable core under a step load by using the finite element method to obtain a finite element method solution result.

[0033] When calculating using the finite element method, first set the soil boundary conditions and basic parameters (such as surface temperature, deep ground temperature, cable burial depth, soil initial thermal conductivity, density, specific heat capacity, surface convection heat transfer coefficient, etc.), then build a buried cable temperature field calculation model, set constant temperature boundary conditions, and calculate the transient cable core temperature by applying losses to the cable.

[0034] Step S3032, generating parameters of the transient thermal circuit model according to the genetic algorithm, and using the sum of squares of the transient thermal circuit model solution corresponding to the parameters and the finite element method solution at each time point as the fitness function to iteratively optimize the parameters of the transient thermal circuit model.

[0035] The calculation process of genetic algorithm can be found in Figure 5 shown.

[0036] (1) Set the time step, duration, heat flow, and sample temperature rise data. Set the population size, number of iterations, and upper and lower limits of the initial value.

[0037] (2) Based on the generated transient thermal circuit model parameters and the known cable core loss, the cable core temperature rise is calculated, and the value of the fitness function is calculated.

[0038] (3) Obtain the optimal fitness. Since the fitness function is the sum of the squares of the difference between the solution of the transient thermal circuit model and the solution of the finite element method at each time point, the smaller its value, the better.

[0039] (4) Determine whether the optimal fitness meets the convergence conditions. If so, end the iteration. If not, adjust the population size, number of iterations, and the upper and lower limits of the initial value, and return to step 2.

[0040] Step S3033, after the convergence condition is met, the optimal parameters are determined according to the optimal fitness function.

[0041] After obtaining the optimal parameters, the cable loss can be changed, and the calculation results of the transient thermal circuit model and the finite element method can be compared and tested to verify the accuracy and versatility of the transient thermal circuit model.

[0042] In some embodiments, the above step S304 can be implemented by a fourth-order Runge-Kutta method. Figure 4 The transient thermal circuit model of is taken as an example, and the implementation process is as follows: According to the node temperature rise and branch heat flow of the transient thermal circuit model, the heat flow differential equations of the seven nodes shown can be written through the node current equation:

[0043] Among them, i w1 、i w2 is the cable heat flow, T 11 , T 12 , T 21 , T 22 , T3, T4, T5 are the temperature rises of each node, T a is the ambient temperature.

[0044] The fourth-order Runge-Kutta equation is further formulated based on the differential equations listed above (where the voltage represents the node temperature rise): (1) Calculate the voltage derivative of each node. The voltage derivative of each node is calculated through four stages of the fourth-order Runge-Kutta method:

[0045] Where j = 1-4; u1 = Tn 11 、u2=Tn 12 、u3=Tn 21 、u4=Tn 22 , u5=Tn3, u6=Tn4, u7=Tn5, are the temperature values ​​of each node at the nth moment respectively; k 11 , k 21 , k 31 , k 41 , k 51 , k 61 , k 71 represent the initial estimates of the voltage derivatives at each node.

[0046] (2) These voltage derivatives are then used to interpolate at different intermediate time points to more accurately update the voltage value sequence:

[0047] (3) Update the voltage derivative of each node using the following formula:

[0048] in, y is the voltage derivative; n is the current time step of the node; h is the time step, here it is 1 minute; i Number the cables; k i1 , k i2 , k i3 , k i4 are the voltage derivatives at four stages of the fourth-order Runge-Kutta method. With this method, the voltage value can be updated in each time step.

[0049] (4) Finally, determine the corresponding node of each cable core, i.e., T 11 , T 21 , and based on T 11 , T 21 The voltage value sequence is used to determine the temperature rise curve of each cable core changing with time.

[0050] The embodiment of the present invention can quickly and accurately calculate the transient temperature rise of the cable core under step load by establishing a transient thermal circuit model of the direct buried power cable. The model has high calculation efficiency, high accuracy, simple structure and is easy to solve. When the cable current or loss changes, the temperature rise of the cable body can be directly solved by the transient thermal circuit model. For the calculation of multiple cables, only a few groups of branch parts need to be added, thereby improving the convenience of calculation. At the same time, external conditions such as soil are equivalent to resistance and capacitance parameters, which enhances the reliability of calculation, improves the calculation efficiency, and avoids the complexity of solution.

[0051] In some specific embodiments, the ambient temperature is set to 30°C, the loss of each cable core is 18w, the calculation step is 5 minutes, a total of 500 hours, 30,000 minutes, and the cable core temperature calculated by the finite element method can be obtained as follows: Figure 6 As shown ( Figure 6 Only the temperature rise data for the first cable are shown).

[0052] According to the obtained cable core temperature rise, the transient thermal circuit model parameters are obtained by genetic algorithm as follows: C 11 =202.2169;C12 =25658;C 21 =197.1832; C 22 =23126;C3=1404.69;C4=85652;C5=10640;R 11 =0.7707; R 12 =0.2309; R 21= 0.7612; R 22 =0.2335; R3=1.2006; R4=1.2124; R5=0.08549; R6=0.01986.

[0053] The transient thermal circuit model is used to calculate the cable core temperature rise under the same conditions. Figure 7 shown.

[0054] The calculation results of the finite element method are compared with those of the transient thermal circuit model. The temperature error curves of the two cables are shown in Figure 8 shown.

[0055] By comparison, it can be seen that the errors of the two calculation methods are small. However, since the parameters of the transient thermal circuit model are obtained by using the genetic algorithm through the results of finite element calculation, in order to ensure the accuracy and universality of the results, the transient thermal circuit model results need to be verified and analyzed. Fig. 9 The losses of the two cables added are 17w and 15w. Fig.10 The losses of the two added cables are 20W and 12W. During the calculation over a period of time, the error gradually approaches 0 and reaches stability, which shows that this embodiment has good accuracy and versatility.

[0056] By comparing the results of finite element temperature calculation, the embodiments of the present invention can ensure a high accuracy in cable core temperature calculation, thereby accurately grasping the thermal state of the power cable, exploring the dynamic current carrying capacity of the power cable, and improving the utilization rate and operation and maintenance management level of the power cable.

[0057] It should be understood that the order of execution of the steps in the above embodiment does not necessarily mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0058] The following is an embodiment of the device of the present invention. For details not described in detail therein, reference may be made to the corresponding method embodiment described above.

[0059] Fig.11 The schematic diagram of the structure of the temperature rise assessment device for the cable core of the buried cable group provided in this embodiment is shown. For the convenience of explanation, only the part related to the embodiment of the present invention is shown, which is described in detail as follows: like Fig.11As shown, the temperature rise assessment device 110 for the cable core of an underground cable group includes: Establish module 111, which is used to divide the cross-section of the cable group into a cable part and a soil part through an isotherm; establish a transient thermal circuit model; wherein the transient thermal circuit model includes an equivalent circuit of the cable part and an equivalent circuit of the soil part, and the equivalent circuit of the cable part includes a self-heating structure of each cable and a mutual heating structure between two adjacent cables.

[0060] The optimization module 112 is used to determine the optimal parameters of the transient thermal circuit model according to a genetic algorithm.

[0061] The calculation module 113 is used to calculate the temperature rise curve of each cable core over time based on the transient thermal circuit model.

[0062] In a possible implementation, in the equivalent circuit of the cable part, the self-heating structure is represented by two branches of two thermal resistors and two thermal capacitors, and the mutual heating structure is represented by a T-type branch of two thermal resistors and one thermal capacitor; the equivalent circuit of the soil part is represented by two branches of two thermal resistors and two thermal capacitors.

[0063] In a possible implementation, the optimization module 112 is used to: The transient temperature rise of each cable core under step load is calculated by finite element method, and the finite element method solution is obtained; Generate the parameters of the transient heat circuit model according to the genetic algorithm, and use the sum of squares of the transient heat circuit model solution corresponding to the parameters and the finite element method solution at each time point as the fitness function to iteratively optimize the parameters of the transient heat circuit model; After the convergence conditions are met, the optimal parameters are determined according to the optimal fitness function.

[0064] In a possible implementation, the calculation module 113 is used to: Establish the heat flow differential equations of each node in the transient heat circuit model; According to the heat flow differential equation, the fourth-order Runge-Kutta equation is determined, and the voltage value sequence of each node is estimated by the fourth-order Runge-Kutta method; From each node, the corresponding node of each cable core is determined, and based on the voltage value sequence of the corresponding node, the temperature rise curve of each cable core changing with time is determined.

[0065] In a possible implementation, the calculation module 113 is used to: The voltage derivatives at each node are estimated by the fourth-order Runge–Kutta method; Interpolation is performed at different intermediate time points based on the voltage derivative to obtain a voltage value sequence.

[0066] In a possible implementation, the calculation module 113 is used to: according to , update the voltage derivative of each node; in, y is the voltage derivative; n is the current time step of the node; h is the time step; i Number the cables; k i1 , k i2 , k i3 , k i4 are the voltage derivatives of the four stages of the fourth-order Runge–Kutta method.

[0067] In an embodiment of the present invention, the cross section of the cable group is divided into a cable part and a soil part by an isotherm, and a comprehensive transient thermal circuit model is directly established, that is, there is no need to separate it into a self-heating thermal circuit model and a mutual heating thermal circuit model. The transient thermal circuit model includes an equivalent circuit of the cable part and an equivalent circuit of the soil part. The equivalent circuit of the cable part includes the self-heating structure of each cable and the mutual heating structure between two adjacent cables. The cable and the soil are respectively equivalent, which enhances the reliability of the calculation, improves the calculation efficiency, and avoids the complexity of the solution. According to the genetic algorithm, the optimal parameters of the transient thermal circuit model are determined, and the accuracy of the model is further improved. When the cable current or loss changes, the temperature rise of the cable body can be directly solved by the transient thermal circuit model. In addition, for the calculation of different numbers of cables, it is only necessary to add or reduce several groups of branch parts in the model, which improves the convenience of the calculation.

[0068] Fig.12 Schematic diagram of an electronic device provided by an embodiment of the present invention. Fig.12 As shown, the electronic device 12 of this embodiment includes: a processor 120 and a memory 121. The memory 121 stores a computer program 122. When the processor 120 executes the computer program 122, the steps in the above-mentioned method embodiments are implemented. Alternatively, when the processor 120 executes the computer program 122, the functions of each module / unit in the above-mentioned device embodiments are implemented.

[0069] Exemplarily, the computer program 122 may be divided into one or more modules / units, which are stored in the memory 121 and executed by the processor 120 to implement the present invention. The one or more modules / units may be a series of computer program instruction segments capable of implementing specific functions, which are used to describe the execution process of the computer program 122 in the electronic device 12.

[0070] The electronic device 12 may include, but is not limited to, a processor 120 and a memory 121. Those skilled in the art will appreciate that Fig.12 It is only an example of the electronic device 12 and does not constitute a limitation of the electronic device 12. It may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, the electronic device 12 may also include input and output devices, network access devices, buses, etc.

[0071] The processor 120 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or the processor may be any conventional processor, etc.

[0072] The memory 121 may be an internal storage unit of the electronic device 12, such as a hard disk or memory of the electronic device 12. The memory 121 may also be an external storage device of the electronic device 12, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. equipped on the electronic device 12. Further, the memory 121 may also include both an internal storage unit of the electronic device 12 and an external storage device. The memory 121 is used to store the computer program 122 and other programs and data required by the electronic device 12. The memory 121 may also be used to temporarily store data that has been output or is to be output.

[0073] For the convenience and simplicity of description, only the division of the above functional modules / units is used as an example for illustration. In actual applications, the above functions can be assigned to different functional modules / units as needed. The above modules / units can be implemented in the form of hardware, software, or a combination of hardware and software.

[0074] The embodiment of the present invention further provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, the methods in the above method embodiments are implemented.

[0075] The embodiment of the present invention further provides a computer program product, including a computer program. When the computer program is executed by a processor, the methods in the above method embodiments are implemented.

[0076] The computer program includes computer program code, which may be in source code form, object code form, executable file or some intermediate form, etc. Computer readable media may include: any entity or device capable of carrying computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signal, telecommunication signal and software distribution medium, etc.

[0077] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments. If there is no special explanation and logical conflict, the terms and / or descriptions between different embodiments are consistent and can be referenced to each other. The technical features in different embodiments can be combined to form a new embodiment according to their internal logical relationship.

[0078] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention.

Claims

1. A method for evaluating the temperature rise of a cable core of an underground cable group, characterized in that: include: The cross section of the cable group is divided into a cable part and a soil part by an isotherm; Establishing a transient heat circuit model; wherein the transient heat circuit model includes an equivalent circuit of the cable part and an equivalent circuit of the soil part, and the equivalent circuit of the cable part includes a self-heating structure of each cable and a mutual heating structure between two adjacent cables; Determining optimal parameters of the transient thermal circuit model according to a genetic algorithm; Based on the transient thermal circuit model, the temperature rise curve of each cable core changing with time is calculated.

2. The method for evaluating the temperature rise of the cable core of an underground cable group according to claim 1, characterized in that: In the equivalent circuit of the cable part, the self-heating structure is represented by two branches of two thermal resistors and two thermal capacitors, and the mutual heating structure is represented by a T-shaped branch of two thermal resistors and one thermal capacitor; The equivalent circuit of the soil portion is represented by two branches of two thermal resistances and two thermal capacitances.

3. The temperature rise assessment method of the cable core of an underground cable group according to claim 1, characterized in that: Determining the optimal parameters of the transient thermal circuit model according to the genetic algorithm includes: The transient temperature rise of each cable core under step load is calculated by finite element method, and the finite element method solution is obtained; Generate the parameters of the transient heat circuit model according to the genetic algorithm, and use the sum of squares of the transient heat circuit model solution corresponding to the parameters and the finite element method solution at each time point as the fitness function to iteratively optimize the parameters of the transient heat circuit model; After the convergence conditions are met, the optimal parameters are determined according to the optimal fitness function.

4. The method for evaluating the temperature rise of the cable core of an underground cable group according to any one of claims 1 to 3, characterized in that: The step of calculating the temperature rise curve of each cable core over time based on the transient thermal circuit model includes: Establishing heat flow differential equations for each node in the transient heat circuit model; According to the heat flow differential equation, a fourth-order Runge-Kutta equation is determined, and a voltage value sequence of each node is estimated by a fourth-order Runge-Kutta method; From each node, the corresponding node of each cable core is determined, and based on the voltage value sequence of the corresponding node, the temperature rise curve of each cable core changing with time is determined.

5. The method for evaluating the temperature rise of the cable core of an underground cable group according to claim 4, characterized in that: The method of estimating the voltage value sequence of each node by the fourth-order Runge-Kutta method includes: The voltage derivatives at each node are estimated by the fourth-order Runge–Kutta method; Interpolation is performed at different intermediate time points according to the voltage derivative to obtain a voltage value sequence.

6. The method for evaluating the temperature rise of the cable core of an underground cable group according to claim 5, characterized in that: The method further comprises: according to , update the voltage derivative of each node; in, y is the voltage derivative; n is the current time step of the node; h is the time step; i Number the cables; k i1 , k i2 , k i3 , k i4 are the voltage derivatives of the four stages of the fourth-order Runge–Kutta method.

7. A temperature rise assessment device for a buried cable group core, characterized in that: include: Establishing a module for dividing the cross section of a cable group into a cable part and a soil part by an isotherm; Establishing a transient heat circuit model; wherein the transient heat circuit model includes an equivalent circuit of the cable part and an equivalent circuit of the soil part, and the equivalent circuit of the cable part includes a self-heating structure of each cable and a mutual heating structure between two adjacent cables; An optimization module, used for determining the optimal parameters of the transient thermal circuit model according to a genetic algorithm; The calculation module is used to calculate the temperature rise curve of each cable core over time based on the transient thermal circuit model.

8. An electronic device, characterized in that: The method comprises a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the method according to any one of claims 1 to 6 when executing the computer program.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

10. A computer program product, characterized in that The method comprises a computer program, which implements the steps of the method according to any one of claims 1 to 6 when the computer program is executed by a processor.

Images