Method, device, equipment, medium and product for evaluating temperature rise of buried cable group cable cores

Abstract

The present invention provides a method, device, equipment, medium and product for evaluating the temperature rise of the cable cores of a buried cable group, relating to the technical field of power cables. The method includes: dividing the cross-section of the cable group into a cable part and a soil part by an isothermal line; 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 an inter-heating structure between two adjacent cables; determining the optimal parameters of the transient thermal circuit model according to a genetic algorithm; and calculating the temperature rise curve of each cable core changing with time based on the transient thermal circuit model. The present invention can quickly and accurately calculate the transient temperature rise of the cable cores.

Description

Technical Field

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

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

[0003] The typical method for calculating the temperature rise of the cable cores of buried power cables is the series of standards of the International Electrotechnical Commission (IEC). However, the IEC method is relatively cumbersome when calculating the transient temperature rise of the cable cores. With the popularization of numerical calculation methods such as the finite element method and the wide application of various tool software, it has gradually become the mainstream to use numerical calculation methods such as the finite element method to calculate the temperature field of power cables under various laying conditions and operating conditions. However, the finite element method requires researchers to have strong theoretical foundations and operating skills, and is often applied to the research of typical complex lines. Due to its calculation 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 rapidity and convenience in the evaluation of dynamic current-carrying capacity, relevant personnel have been researching the use of a thermal circuit model to calculate the transient temperature rise of the cable cores of buried power cables. To fully exploit the current-carrying capacity of power cables and improve the utilization rate of power cables, it is necessary to study a transient thermal circuit model that can quickly and accurately calculate the transient temperature rise of the cable cores. However, most of the existing thermal circuit models are limited to the self-heating model of the cable, 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 add inductance to the thermal circuit model to simulate the delay transfer process of heat flow, but the parameters of the inductance are difficult to grasp. Some researchers propose to calculate the parameters of resistance and capacitance elements by the method of soil stratification. Although the accuracy is improved, the complexity of the operation is increased, and it is still a method based on the separate solution of self-heating and mutual-heating. Summary of the Invention

[0005] In view of this, the embodiments of the present invention provide a method, device, equipment, medium and product for evaluating the temperature rise of the cable cores of a buried cable group, so as to quickly and accurately calculate the transient temperature rise of the cable cores.

[0006] In a first aspect, the embodiments of the present invention provide a method for evaluating the temperature rise of the cable cores of a buried cable group, including:

[0007] Dividing the cross-section of the cable group into a cable part and a soil part by an isothermal line;

[0008] 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 an inter-heating structure between two adjacent cables;

[0009] Determine the optimal parameters of the transient thermal circuit model according to the genetic algorithm;

[0010] Based on the transient thermal circuit model, calculate the temperature rise curve of each cable core varying with time.

[0011] In a possible implementation manner, in the equivalent circuit of the cable part, the self-heating structure is represented by a two-branch circuit with two thermal resistances and two heat capacities, the inter-heating structure is represented by a T-shaped branch circuit with two thermal resistances and one heat capacity; the equivalent circuit of the soil part is represented by a two-branch circuit with two thermal resistances and two heat capacities.

[0012] In a possible implementation manner, according to the genetic algorithm, determining the optimal parameters of the transient thermal circuit model includes:

[0013] Calculate the transient temperature rise of each cable core under a step load by the finite element method to obtain the solution result of the finite element method;

[0014] Generate the parameters of the transient thermal circuit model according to the genetic algorithm, and use the sum of squared differences between the solution result of the transient thermal circuit model corresponding to the parameters and the solution result of the finite element method at each time point as the fitness function to iteratively optimize the parameters of the transient thermal circuit model;

[0015] After meeting the convergence condition, determine the optimal parameters according to the optimal fitness function.

[0016] In a possible implementation manner, based on the transient thermal circuit model, calculating the temperature rise curve of each cable core varying with time includes:

[0017] Establish the heat flow differential equations of each node in the transient thermal circuit model;

[0018] Determine the fourth-order Runge-Kutta equations according to the heat flow differential equations, and estimate the voltage value sequence of each node by the fourth-order Runge-Kutta method;

[0019] Determine the corresponding nodes of each cable core from each node, and based on the voltage value sequence of the corresponding nodes, determine the temperature rise curve of each cable core varying with time.

[0020] In a possible implementation manner, estimating the voltage value sequence of each node by the fourth-order Runge-Kutta method includes:

[0021] Estimate the voltage derivative of each node by the fourth-order Runge-Kutta method;

[0022] Interpolate according to the voltage derivative at different intermediate time points to obtain a sequence of voltage values.

[0023] In a possible implementation, the method further includes:

[0024] According to , update the voltage derivative of each node;

[0025] wherein, y is the voltage derivative; n is the current time step of the node; h is the time step; i is the cable number; k i1 , k i2 , k i3 , k i4 are the voltage derivatives of the four stages of the fourth-order Runge-Kutta method.

[0026] In a second aspect, an embodiment of the present invention provides a temperature rise evaluation device for the cable cores of a buried cable group, including:

[0027] A building module, configured to divide the cross-section of the cable group into a cable part and a soil part through an isothermal line; 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 the self-heating structure of each cable and the mutual-heating structure between two adjacent cables;

[0028] An optimization module, configured to determine the optimal parameters of the transient thermal circuit model according to the genetic algorithm;

[0029] A calculation module, configured to calculate the temperature rise curve of each cable core changing with time based on the transient thermal circuit model.

[0030] In a third aspect, an embodiment of the present invention provides an electronic device, including a memory and a processor, the memory stores a computer program, and when the processor executes the computer program, it implements the method in the first aspect or any possible implementation manner of the first aspect above.

[0031] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, which stores a computer program, and when the computer program is executed by a processor, it implements the method in the first aspect or any possible implementation manner of the first aspect above.

[0032] In a fifth aspect, an embodiment of the present invention provides a computer program product, including a computer program, and when the computer program is executed by a processor, it implements the method in the first aspect or any possible implementation manner of the first aspect above.

[0033] In the embodiment of the present invention, an isothermal line is used to divide the cross-section of a cable group into a cable part and a soil part, and a comprehensive transient thermal circuit model is directly established, that is, it is not necessary to be separated into a self-heating thermal circuit model and an interactive heating thermal circuit model. The transient thermal circuit model includes the equivalent circuit of the cable part and the equivalent circuit of the soil part. The equivalent circuit of the cable part includes the self-heating structure of each cable and the interactive 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, further improving the accuracy of the model. When the cable current or loss changes, the temperature rise of the cable body can be directly solved through the transient thermal circuit model. In addition, for the calculation of different numbers of cables, only a few groups of branch parts need to be added or reduced in the model, improving the convenience of the calculation. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is the isothermal line distribution characteristic of the buried cable group provided by the embodiment of the present invention Figure 1 ;

[0035] Figure 2 is the isothermal line distribution characteristic of the buried cable group provided by the embodiment of the present invention Figure 2 ;

[0036] Figure 3 is the flow chart of the temperature rise evaluation method of the cable core of the buried cable group provided by the embodiment of the present invention;

[0037] Figure 4 is the structure diagram of the transient thermal circuit model provided by the embodiment of the present invention;

[0038] Figure 5 is the flow chart of the particle swarm optimization algorithm provided by the embodiment of the present invention;

[0039] Figure 6 is the finite element cable temperature rise diagram provided by the embodiment of the present invention;

[0040] Figure 7 is the thermal circuit model cable temperature rise diagram provided by the embodiment of the present invention;

[0041] Figure 8 is the error comparison provided by the embodiment of the present invention Figure 1 ;

[0042] Figure 9 is the error comparison provided by the embodiment of the present invention Figure 2 ;

[0043] Figure 10 is the error comparison provided by the embodiment of the present invention Figure 3 ;

[0044] Figure 11 It is the structural diagram of the temperature rise evaluation device for the buried cable group cable core provided by the embodiment of the present invention;

[0045] Figure 12 It is the structural diagram of the electronic device provided by the embodiment of the present invention. Specific embodiments

[0046] Next, the embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0047] Figure 1 and Figure 2 are the schematic diagrams of the application scenarios of the temperature rise evaluation method for the buried cable group cable core provided by the embodiment of the present invention, where Figure 1 is the isothermal line distribution characteristic of the buried cable group with two cables, Figure 2 is the isothermal line distribution characteristic of the buried cable group with three cables. It can be seen that there are multiple isothermal lines outside the cable group. If any one of the isothermal lines is used as the boundary, the entire area can be divided into two parts, namely the area inside the isothermal line and the area outside the isothermal line. On the isothermal line, the losses of all internal cables are diffused to the outside through the isothermal line. And inside the isothermal line, the losses of multiple cables are respectively transmitted to the isothermal line. At the same time, there is also mutual heat transfer between the cables.

[0048] Currently, there is no direct thermal path model for the laid cable group to calculate the core temperature. Therefore, this embodiment provides a new transient thermal path model for buried cables, which can directly construct a complete transient thermal path model according to the cable group, without the need to be separated into self-heating and mutual-heating thermal path models, and uses the Runge-Kutta algorithm to calculate the temperature rise of the cable core, so as to accurately grasp the thermal state of the power cable throughout its life cycle, deeply explore the dynamic current-carrying capacity of the power cable, and improve the utilization rate of the power cable.

[0049] See Figure 3 , which shows the implementation flowchart of the temperature rise evaluation method for the buried cable group cable core provided by the embodiment of the present invention, and is described in detail as follows:

[0050] Step S301, divide the cross-section of the cable group into a cable part and a soil part through an isothermal line.

[0051] Here, the isothermal line is a virtual concept proposed when establishing the transient thermal path model, rather than a certain actual selected isothermal line. The isothermal line divides the cross-section of the cable group into two parts. Inside the isothermal line are the cable body and part of the soil, and outside the isothermal line is the soil.

[0052] Step S302, establish a transient thermal path model; wherein, the transient thermal path model includes the equivalent circuit of the cable part and the 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 adjacent two cables.

[0053] In this embodiment, each cable to the isothermal line is represented by a two-branch model, and the cables are represented by a T-type model; while the soil outside the isothermal line to the environment is represented by a two-branch model.

[0054] Taking a cable group with two cables as an example, the established transient thermal circuit model is as Figure 4 shown. Through trial calculations, each cable to the isothermal line and the isothermal line to the ambient temperature can both be represented by a two-branch with two thermal resistances and two heat capacities, and 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 , the temperature at node T4 is the temperature of the isothermal line. 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 are the self-heating structure parameters of the first cable, R 21 , R 22 , C 21 , C 22 are the self-heating structure parameters of the second cable, R5, R6, C4, and C5 are the equivalent thermal resistance and heat capacity parameters of the soil part, and R3, R4, and C3 are the mutual-heating structure parameters between the two cables.

[0055] In some embodiments, when the cable group contains more cables, the transient thermal circuit model only needs to add the corresponding self-heating structure and mutual-heating structure. For example, when there are three cables, add another set of self-heating structure parameters and add a set of mutual-heating structure parameters between the second and third cables, which improves the convenience of calculation.

[0056] Step S303: Determine the optimal parameters of the transient thermal circuit model according to the genetic algorithm.

[0057] The above thermal resistance and heat capacity parameters are all equivalent parameters and 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 a step load. After obtaining the transient temperature rise, use the genetic algorithm to optimize and solve to determine the optimal parameters of the transient thermal circuit model.

[0058] Step S304: Based on the transient thermal circuit model, calculate the temperature rise curve of each cable core changing with time.

[0059] According to the above transient thermal circuit model, after knowing the thermal resistance, heat capacity parameters, and the heat generation of the cable body, the node heat flow and temperature rise at each time step can be gradually calculated, where T 11 , T 21The temperature rise of the node is the temperature rise curve of the cores of two directly buried cables varying with time.

[0060] In the embodiments of the present invention, a cross-section of a cable group is divided into a cable part and a soil part by an isothermal line, and a comprehensive transient thermal circuit model is directly established, that is, it is not necessary to be separated into a self-heating thermal circuit model and an interactive 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 a self-heating structure of each cable and an interactive 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, further improving the accuracy of the model. When the cable current or loss changes, the temperature rise of the cable body can be directly solved through the transient thermal circuit model. In addition, for the calculation of different numbers of cables, only a few groups of branch parts need to be added or reduced in the model, improving the convenience of the calculation.

[0061] In some embodiments, the implementation process of the above step S303 may include:

[0062] Step S3031, calculate the transient temperature rise of each cable core under a step load by the finite element method to obtain the solution result of the finite element method.

[0063] When calculating by the finite element method, first set the soil boundary conditions and basic parameters (such as surface temperature, deep ground temperature, cable burial depth, initial soil thermal conductivity, density, specific heat capacity, surface convective heat transfer coefficient, etc.), then build a calculation model of the temperature field of the buried cable, set the constant temperature boundary conditions, and calculate the transient core temperature of the cable by applying losses to the cable.

[0064] Step S3032, according to the genetic algorithm, generate the parameters of the transient thermal circuit model, and use the sum of the squared differences between the solution results of the transient thermal circuit model corresponding to the parameters and the solution results of the finite element method at each time point as the fitness function, and iteratively optimize the parameters of the transient thermal circuit model.

[0065] The calculation process of the genetic algorithm can be referred to Figure 5 as shown.

[0066] (1) Set the time step, duration, heat flow, and sample temperature rise data. Set the population size, number of iteration steps, and upper and lower limits of the initial values.

[0067] (2) According to the generated parameters of the transient thermal circuit model and the known core losses, calculate the core temperature rise, and calculate the value of the fitness function.

[0068] (3) Obtain the optimal fitness. Since the fitness function is the sum of the squared differences between the solution results of the transient thermal circuit model and the solution results of the finite element method at each time point, the smaller its value, the better.

[0069] (4) Determine whether the optimal fitness meets the convergence condition. If it meets, end the iteration. If it does not meet, adjust the population size, the number of iteration steps, and the upper and lower limits of the initial values, and return to step 2.

[0070] In step S3033, after meeting the convergence condition, determine the optimal parameters according to the optimal fitness function.

[0071] After obtaining the optimal parameters, the cable loss can be changed to conduct a comparative test on the calculation results of the transient thermal circuit model and the finite element method to verify the accuracy and generality of the transient thermal circuit model.

[0072] In some embodiments, the above step S304 can be implemented by the fourth-order Runge-Kutta method. Taking Figure 4 the transient thermal circuit model as an example, the implementation process is as follows:

[0073] According to the node temperature rise and branch heat flow of the transient thermal circuit model, through the node current equation, the heat flow differential equations of its seven nodes can be written:

[0074]

[0075] Among them, i w1 , i w2 are the cable heat flows, T 11 , T 12 , T 21 , T 22 , T3, T4, T5 are the temperature rises of each node, and T a is the ambient temperature.

[0076] Further list the fourth-order Runge-Kutta equations based on the above-listed differential equations (where the voltage represents the node temperature rise):

[0077] (1) Calculate the voltage derivative of each node. The voltage derivative of each node is calculated through the four stages of the fourth-order Runge-Kutta method:

[0078]

[0079] Among them, 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; k 11 , k 21 , k 31 , k 41 , k 51 , k 61 , k71 respectively represent the preliminary estimates of the voltage derivatives of each node.

[0080] (2) After that, use these voltage derivatives to interpolate at different intermediate time points to more accurately update the voltage value sequence:

[0081]

[0082] (3) Update the voltage derivative of each node using the following formula:

[0083]

[0084] where y is the voltage derivative; n is the current time step of the node; h is the time step, which is 1 minute here; i is the cable number; k i1 , k i2 , k i3 , k i4 are the voltage derivatives of the four stages of the fourth-order Runge-Kutta method. Through this method, the voltage value can be updated within each time step.

[0085] (4) Finally, determine the corresponding nodes of each cable core, that is, T 11 , T 21 , and based on the voltage value sequences of T 11 , T 21 , determine the temperature rise curve of each cable core over time.

[0086] By establishing a transient thermal circuit model for directly buried power cables, the embodiments of the present invention can quickly and accurately calculate the transient temperature rise of the cable core under step load. This model has high calculation efficiency, high accuracy, a 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 through 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 calculation convenience. At the same time, external conditions such as soil are equivalent to resistance and capacitance parameters, enhancing the calculation reliability, improving the calculation efficiency, and avoiding the complexity of the solution.

[0087] In some specific embodiments, the ambient temperature is set to 30 °C, the loss of each cable core is 18 w, 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 Figure 6 shown ( Figure 6 only the temperature rise data of the first cable is shown).

[0088] Based on the obtained temperature rise of the cable core, the parameters of the transient thermal circuit model are obtained by using the genetic algorithm as follows:

[0089] C 11 = 202.2169; C 12 = 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.

[0090] The temperature rise of the cable core under the same conditions is calculated by using the transient thermal circuit model as Figure 7 shown.

[0091] 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 as Figure 8 shown.

[0092] It can be seen from the comparison 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 based on the results of finite element calculation, in order to ensure the accuracy and generality of the results, it is necessary to verify and analyze the results of the transient thermal circuit model. Figure 9 The losses of the two added cables are 17 w and 15 w, Figure 10 The losses of the two added cables are 20 w and 12 w. During a period of calculation, the error gradually approaches 0 and reaches stability, indicating that the present embodiment has good accuracy and generality.

[0093] By comparing the results of finite element temperature calculation, the embodiment of the present invention can ensure a high accuracy rate in the calculation of the cable core temperature, 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.

[0094] It should be understood that the magnitudes of the sequence numbers of the steps in the above embodiments do not mean the order of execution is prior or subsequent. The execution order of each process should be determined according to its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.

[0095] The following is the device embodiment of the present invention. For the details not described in detail herein, reference can be made to the corresponding method embodiment above.

[0096] Figure 11The structural schematic diagram of the temperature rise evaluation device for the cable cores of the buried cable group provided in this embodiment is shown. For the sake of convenience of description, only the parts related to the embodiments of the present invention are shown and are described in detail as follows:

[0097] As Figure 11 shown, the temperature rise evaluation device 110 for the cable cores of the buried cable group includes:

[0098] A building module 111, configured to divide the cross-section of the cable group into a cable part and a soil part through an isothermal line; 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 an inter-heating structure between two adjacent cables.

[0099] An optimization module 112, configured to determine the optimal parameters of the transient thermal circuit model according to the genetic algorithm.

[0100] A calculation module 113, configured to calculate the temperature rise curve of each cable core changing with time based on the transient thermal circuit model.

[0101] In a possible implementation manner, in the equivalent circuit of the cable part, the self-heating structure is represented by a two-branch circuit of two thermal resistances and two heat capacities, and the inter-heating structure is represented by a T-shaped branch circuit of two thermal resistances and one heat capacity; the equivalent circuit of the soil part is represented by a two-branch circuit of two thermal resistances and two heat capacities.

[0102] In a possible implementation manner, the optimization module 112 is configured to:

[0103] Calculate the transient temperature rise of each cable core under a step load through the finite element method to obtain the solution result of the finite element method;

[0104] Generate the parameters of the transient thermal circuit model according to the genetic algorithm, and use the sum of the squared differences between the solution results of the transient thermal circuit model corresponding to the parameters and the solution results of the finite element method at each time point as the fitness function to iteratively optimize the parameters of the transient thermal circuit model;

[0105] After meeting the convergence condition, determine the optimal parameters according to the optimal fitness function.

[0106] In a possible implementation manner, the calculation module 113 is configured to:

[0107] Establish the heat flow differential equations of each node in the transient thermal circuit model;

[0108] Determine the fourth-order Runge-Kutta equation according to the heat flow differential equations, and estimate the voltage value sequence of each node through the fourth-order Runge-Kutta method;

[0109] From each node, determine the corresponding node of each cable core, and based on the voltage value sequence of the corresponding node, determine the temperature rise curve of each cable core varying with time.

[0110] In a possible implementation, the calculation module 113 is configured to:

[0111] Estimate the voltage derivative of each node by the fourth-order Runge-Kutta method;

[0112] Interpolate according to the voltage derivative at different intermediate time points to obtain the voltage value sequence.

[0113] In a possible implementation, the calculation module 113 is configured to:

[0114] According to , update the voltage derivative of each node;

[0115] Wherein, y is the voltage derivative; n is the current time step of the node; h is the time step size; i is the cable number; k i1 、 k i2 、 k i3 、 k i4 are the voltage derivatives of the four stages of the fourth-order Runge-Kutta method.

[0116] In the embodiments of the present invention, the cross-section of the cable group is divided into a cable part and a soil part by an isothermal line, and a comprehensive transient thermal circuit model is directly established, that is, it is not necessary to be separated into a self-heating thermal circuit model and an interactive 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 interactive 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, further improving the model accuracy. When the cable current or loss changes, the temperature rise of the cable body can be directly solved through the transient thermal circuit model. In addition, for the calculation of different numbers of cables, only a few groups of branch parts need to be added or reduced in the model, improving the convenience of the calculation.

[0117] Figure 12 is a schematic diagram of the electronic device provided by the embodiments of the present invention. As Figure 12As 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 method embodiments are implemented. Alternatively, when the processor 120 executes the computer program 122, the functions of each module / unit in the above device embodiments are implemented.

[0118] Exemplarily, the computer program 122 can be divided into one or more modules / units. The one or more modules / units are stored in the memory 121 and executed by the processor 120 to complete the present invention. The one or more modules / units can be a series of computer program instruction segments capable of performing specific functions, and the instruction segments are used to describe the execution process of the computer program 122 in the electronic device 12.

[0119] The electronic device 12 may include, but is not limited to, a processor 120 and a memory 121. Those skilled in the art can understand that Figure 12 merely examples of the electronic device 12, which do not constitute a limitation on the electronic device 12, may include more or fewer components than shown in the figure, or combine certain components, or different components. For example, the electronic device 12 may also include input / output devices, network access devices, buses, etc.

[0120] The processor 120 may be a central processing unit (CPU), or may also be other general-purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0121] 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 and an external storage device of the electronic device 12. 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 the data that has been output or will be output.

[0122] For the convenience and simplicity of description, only the above division of each functional module / unit is used as an example. In practical applications, the above functions may be allocated to different functional modules / units according to needs. The above modules / units may be implemented in the form of hardware, or in the form of software, or in the form of a combination of hardware and software.

[0123] The embodiment of the present invention also 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.

[0124] The embodiment of the present invention also 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.

[0125] Wherein, the computer program includes computer program code, and the computer program code may be in the form of source code, object code, executable file or some intermediate form, etc. The computer-readable medium may include: any entity or device capable of carrying the computer program code, a recording medium, a USB flash drive, a mobile hard disk, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc.

[0126] In the above embodiments, the descriptions of each embodiment have their own emphases. For the parts not detailed or recorded in a certain embodiment, reference may be made to the relevant descriptions of other embodiments. Without special instructions and logical conflicts, the terms and / or descriptions between different embodiments are consistent and can be mutually referred to. The technical features in different embodiments can be combined to form new embodiments according to their internal logical relationships.

[0127] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention, and should all be included within 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 temperature rise assessment method 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.

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