A method and equipment for calculating the convective thermal resistance of tunnel cables based on self-modeling theory.

Abstract

This invention relates to a method and apparatus for calculating the convective thermal resistance of tunnel cables based on self-modeling theory. The method includes the following steps: calculating the phase sheath temperature rise of the cable by scaling the data based on self-modeling theory while neglecting thermal radiation; and performing mathematical modeling based on the phase sheath temperature rise data of the cable while neglecting thermal radiation to obtain a fitted representation of the convective thermal resistance of the tunnel cable. Compared with the prior art, this invention has the advantages of rapidly obtaining the convective thermal resistance of tunnel cables, reducing computational complexity, and improving computational speed.

Description

Technical Field

[0001] This invention relates to the field of power cable operation technology, and in particular to a method for calculating the convective thermal resistance of tunnel cables based on self-modeling theory. Background Technology

[0002] Tunneling is one of the main methods for laying high-voltage cables. Due to its ease of operation and maintenance, it is widely used for 110kV and above power cables. However, because heat dissipation involves flow field calculations and there is a lack of universally accepted engineering algorithms, numerical calculations are often required for a more accurate analysis of the heat generation and dissipation problem. Compared to other underground cable laying methods, tunnel cables require more complex finite element models and greater computational loads when analyzing and calculating the cable temperature field. This is mainly because: compared to directly buried cables, air exists within cable tunnels, necessitating flow simulations when calculating cable temperature, which are complex and time-consuming; and compared to ducted and trenched cables, tunnel cables have a larger space (for rectangular tunnels, the height is generally over 2m and the width is generally 1.8-3m), making airflow calculations more time-consuming. Therefore, improving the speed of finite element calculations is particularly important for tunnel cables.

[0003] How to quickly calculate the convective thermal resistance of tunnel cables has become a technical problem that needs to be solved. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a method for calculating the convective thermal resistance of tunnel cables based on self-modeling theory.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] According to one aspect of the present invention, a method for calculating the convective thermal resistance of a tunnel cable based on self-modeling theory is provided, the method comprising the following steps:

[0007] (1) Based on the self-modeling theory, the phase sheath temperature rise in the cable is obtained by scaling proportionally while ignoring thermal radiation;

[0008] (2) Based on the temperature rise data of the outer sheath of the middle phase of the cable obtained in step (1), mathematical modeling is performed to obtain a fitting representation of the convective thermal resistance of the tunnel cable.

[0009] Preferably, the method of calculating the phase sheath temperature rise of the cable by scaling up the calculation based on self-modeling theory while neglecting thermal radiation includes:

[0010] A) Ignoring thermal radiation, randomly generate thermal loads and ambient temperatures to obtain data on the temperature rise of the outer sheath of the cable phase in a tunnel of a certain characteristic size;

[0011] B) Adjust the feature size and simultaneously adjust the corresponding multiple sets of thermal loads of the previous feature size. After scaling, obtain the temperature rise of the outer sheath of the tunnel cable under this feature size.

[0012] C) Repeat step B) After obtaining the temperature rise of the cable phase sheath under multiple characteristic dimensions, perform fitting analysis to determine the adjustment conversion factor applicable to the tunnel.

[0013] D) Based on the tunnel adjustment conversion factor in step C), calculate the temperature rise of the cable phase sheath under the new characteristic dimensions and verify it.

[0014] More preferably, the synchronous adjustment of multiple sets of thermal loads corresponding to the previous feature dimension specifically refers to:

[0015] The thermal load is calculated using the following formula, with the internal structural parameters of the cable scaled proportionally:

[0016] Q = C1 * l 3 / 4

[0017] Where C1 represents the temperature characteristics determined by the loss Q and the characteristic size l; Q is the thermal load, also known as the loss.

[0018] More preferably, the temperature rise of the phase sheath in the cable obtained by scaling down to this characteristic size specifically refers to:

[0019] First, determine the scaling range of the adjustment conversion factor and calculate the adjustment loss conversion factor under different size ratios;

[0020] Then, based on the data of the temperature rise of the outer sheath of the cable in the tunnel with the characteristic size in step A), and combined with the adjustment conversion factor under different characteristic size ratios, the temperature rise of the outer sheath of the cable in the tunnel with the characteristic size under radiation-free conditions is obtained by scaling.

[0021] More preferably, the verification specifically involves comparing the phase sheath temperature rise of the tunnel cable calculated directly by finite element method under the condition of ignoring thermal radiation with the phase sheath temperature rise result of the tunnel cable obtained by fitting the convective thermal resistance of the tunnel cable. If the maximum error of the phase sheath in each loop cable is less than the threshold, then the engineering application is satisfied.

[0022] Preferably, the fitting representation of the convective thermal resistance of the tunnel cable is obtained by: ignoring the temperature rise data of the phase sheath in the cable and referring to the calculation model of the temperature rise of the phase sheath in the three tunnel cables, obtaining a fitting representation of the convective thermal resistance of the tunnel cable.

[0023] More preferably, the fitting expression of the convective thermal resistance of the tunnel cable is represented by the formula:

[0024] t1=Q1*[ap1+ap2*power(t0,ak1)+ap3*power(t1,ak2)+ap4*power(t2,ak3)+ap5*power(t3,ak4)]+

[0025] Q2*[ap6+ap7*power(t0,ak5)+ap8*power(t1,ak6)+ap9*power(t2,ak7)+ap 10 *power(t3,ak8)]+

[0026] Q3*[ap 11 +ap 12 *power(t0,ak9)+ap 13 *power(t1,ak 10 )+ap 14 *power(t2,ak 11 )+ap 15 *power(t3,ak 12 )]+t0t2=Q1*[bp1+bp2*power(t0,bk1)+bp3*power(t1,bk2)+bp4*power(t2,bk3)+bp5*power(t3,bk4)]+

[0027] Q2*[bp6+bp7*power(t0,bk5)+bp8*power(t1,bk6)+bp9*power(t2,bk7)+bp 10 *power(t3,bk8)]+

[0028] Q3*[bp 11 +bp 12 *power(t0,bk9)+bp 13 *power(t1,bk 10 )+bp 14 *power(t2,bk 11 )+bp 15 *power(t3,bk 12 )]+t0

[0029] t3=Q1*[cp1+cp2*power(t0,ck1)+cp3*power(t1,ck2)+cp4*power(t2,ck3)+cp5*power(t3,ck4)]+

[0030] Q2*[cp6+cp7*power(t0,ck5)+cp8*power(t1,ck6)+cp9*power(t2,ck7)+cp 10 *power(t3,ck8)]+

[0031] Q3*[cp 11 +cp 12 *power(t0,ck9)+cp 13 *power(t1,ck 10 )+cp 14 *power(t2,ck 11 )+cp 15 *power(t3,ck 12 )]+t0

[0032] Where t1~t3 represent the temperature rise of the middle phase outer sheath of the first to third circuit cables, t0 represents the tunnel wall temperature, and Q1~Q3 represent the temperature rise of the tunnel wall.

[0033] For the heat flow of the first to third circuit cables, ap1 to ap 15 bp1~bp 15 cp1~cp 15 AK1~AK 12 bk1~bk 12 ,ck1~ck 12 This is the coefficient of the convective thermal resistance.

[0034] Preferably, the fitting representation of the convective thermal resistance of the tunnel cable is obtained by the McCourt iterative search method.

[0035] According to another aspect of the present invention, an electronic device is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the program to implement the method described thereon.

[0036] According to a third aspect of the present invention, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the method described thereon.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1) This invention first obtains the temperature rise data of the outer sheath of the middle phase of the cable under multiple working conditions (without radiation) at a small size. Then, based on the self-modeling theory, it obtains the temperature rise data of the outer sheath of the middle phase of the cable under multiple working conditions (without radiation) at a large cross section by scaling. Then, it obtains the fitting representation of the convective thermal resistance through mathematical modeling, which greatly reduces the computational complexity and improves the computational speed, thereby realizing the rapid acquisition of the convective thermal resistance of tunnel cables.

[0039] 2) This invention patent distinguishes between radiative heat dissipation and convective heat dissipation in finite element calculations, scales the geometric model of the tunnel cable proportionally, reduces the absolute size of the air domain, thereby reducing the computational complexity of the finite element model, increasing the calculation speed, reducing the demand for computing resources (software, personnel), facilitating implementation, and supporting the requirements of real-time load adjustment by operators. Attached Figure Description

[0040] Figure 1 A schematic diagram of heat dissipation for a single cable;

[0041] Figure 2 This is a schematic diagram of the three-stage model finite element calculation in this invention;

[0042] Figure 3 This is a schematic histogram of the temperature rise error of the outer sheath of the cable in this invention, with radiation ignored by 100% of the dimensions.

[0043] Figure 4 This is a schematic diagram showing the temperature rise error distribution of the outer sheath of each loop of the cable in this invention, with radiation ignored by 100% of the dimensions.

[0044] Figure 5 This is a flowchart illustrating the method for calculating the convective thermal resistance of tunnel cables in this invention. Detailed Implementation

[0045] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0046] Example 1

[0047] This embodiment relates to a method for calculating the convective thermal resistance of tunnel cables based on self-modeling theory.

[0048] The calculation principle of this method is introduced below, including:

[0049] (1) Self-modeling theory

[0050] In heat transfer, natural convection is divided into open-space natural convection and confined-space natural convection. Open-space natural convection refers to natural convection where the development of the thermal boundary layer is not disturbed or hindered, and is not limited by geometric dimensions. For open-space natural convection, there exists an experimental correlation as shown in equation (1):

[0051]

[0052] Among them, Num Nusselt number at the qualitative temperature, Gr is the Grashof number, Pr is the Prandtl number, and C and n are constants determined experimentally. m Substituting the definitions of the three dimensionless numbers Gr, Pr into equation (2), we have:

[0053]

[0054] Where h is the convective heat transfer coefficient (W / m) 2 ·K), l is the characteristic length (m), k is the thermal conductivity of the fluid (W / m·K), and Grashof number (Gr): g is the acceleration due to gravity, a v The fluid's volumetric expansion coefficient is given by ΔT, where ΔT is the temperature difference, l is the characteristic length, ν is the kinematic viscosity, and Prandtl number (Pr) is the coefficient of volumetric expansion. μ is viscosity, c p Where λ is the specific heat capacity at constant pressure, and λ is the wavelength.

[0055] Experimental results show that for turbulent natural convection (Gr>4.65×10), 9 ), the exponent n = 1 / 3 (vertical direction) or 1 / 4 (horizontal direction), substituting it into equation (2) and simplifying, we get:

[0056]

[0057] Equation (3) shows that, in the case of turbulent natural convection, the surface heat transfer coefficient h of natural convection is a quantity independent of the characteristic length l. This characteristic is called the self-modeling of natural convection. Utilizing this characteristic, when establishing a physical model of turbulent natural convection, a model with a smaller size than that required to equal the given characteristic number can be used for research.

[0058] (2) Self-modeling analysis of tunnel convection

[0059] For tunnel cables, firstly, their surface temperature is generally below 60-70°C, limiting convection development; secondly, the total cable cross-section is relatively small compared to the tunnel cross-section. Therefore, the heat dissipation space of tunnel cables can be considered as large-space natural convection, making it suitable for the self-modeling theory of natural convection. This provides a possibility for simplification in subsequent calculations.

[0060] To quickly obtain the phase sheath temperature of the cable under different loads, the phase sheath temperature and temperature distribution in the cable calculated in a small space should be basically consistent with those under large space conditions after self-modeling simplification. For cables, a horizontal arrangement is generally adopted, and the corresponding equations (1) to (3) can be converted into:

[0061]

[0062] Num =C(Gr·Pr) 1 / 4 (5)

[0063]

[0064] This leads to the conclusion that:

[0065]

[0066] Where π is the ratio of a circle's diameter to its circumference.

[0067] As can be seen from equation (7), C1 represents the temperature characteristics under the given loss Q and characteristic size l (cable diameter). If the cable phase sheath temperature and temperature distribution in the small space are basically consistent with those under the large space condition, i.e., C1 remains unchanged, the loss Q can be adjusted synchronously when the characteristic size l changes, so that the value of C1 remains unchanged, and thus the cable phase sheath temperature under different sizes can be obtained with the same value. If the characteristic size is reduced to 50% of the original size, according to equation (7), the corresponding Q should be adjusted to 59.4% of the original loss, and the volumetric heat rate should be 237.8% of the original. Considering that tunnels are different from completely large-space natural convection, and the cable cross-section to tunnel cross-sectional area ratio is different, the adjusted value may need to be adjusted slightly. However, if the adjustment range between different sizes can be kept consistent under the same tunnel and cable layout conditions, it can also meet the needs of subsequent engineering analysis.

[0068] Heat dissipation analysis of tunnel cables

[0069] For tunnel cables, firstly, their surface temperature is generally below 60-70°C. According to equation (2), the wavelength of their radiation band is 8.45-10.6 μm (corresponding to a surface temperature of 0-70°C), which is far from the main radiation band range of nitrogen and oxygen. Therefore, the air inside the tunnel can be considered as transparent to radiation, i.e., it does not participate in the radiation heat dissipation process. At this time, the radiation inside the tunnel only occurs between the outer sheath of each phase of the cable and the tunnel wall.

[0070] Based on the above analysis, from a heat transfer perspective, radiation and convection are relatively independent. Therefore, the heat dissipation capacity of tunnel cables can be considered separately in terms of thermal resistance, and the two can be regarded as a parallel relationship. Taking a single cable as an example, such as... Figure 1 As shown, where R rad For radiative heat dissipation thermal resistance, R fli For convective heat dissipation thermal resistance, R cab For the thermal resistance of the cable body, T cor T represents the core temperature. ski For skin temperature, T amb Q represents the ambient temperature. cab Q represents the heat generated by the cable (excluding heat generated by sheath circulating currents, eddy currents, and insulation dielectric losses).rad Q represents the heat dissipation due to radiation. fli This refers to convective heat dissipation.

[0071] According to the principles of heat transfer, radiative heat dissipation is expressed as:

[0072]

[0073] The relationship between the outer sheath temperature rise, the core temperature rise, and the cable's heat generation is as follows:

[0074] T cor -T ski =Q cab *R cab (9)

[0075] The balance between heat generation and heat dissipation is as follows:

[0076] Q cab =Q rad +Q fli (10)

[0077] Based on this, if the convective heat dissipation R is modeled mathematically... fli Representing it in some form will enable rapid computation.

[0078] The method includes:

[0079] (1) Calculate the phase sheath temperature rise in the cable by scaling based on the self-modeling theory:

[0080] A) Ignoring thermal radiation, randomly generate thermal loads and ambient temperatures to obtain data on the temperature rise of the outer sheath of the cable phase in a tunnel of a certain characteristic size;

[0081] B) Adjust the thermal load of the characteristic dimension and the corresponding previous characteristic dimension to obtain the temperature rise of the cable phase sheath under that characteristic dimension;

[0082] C) Repeat step B) After obtaining the temperature rise of the cable phase sheath under multiple characteristic dimensions, perform fitting analysis to determine the loss adjustment coefficient applicable to the tunnel.

[0083] D) Calculate the temperature rise of the cable phase sheath under the new characteristic dimensions to verify the above conclusions;

[0084] (2) Fitting representation of convection thermal resistance: Through mathematical modeling, the relationship between the convection thermal resistance of the cable tunnel and the thermal load and ambient temperature is obtained by the McCourt iterative search method, that is, the mathematical representation of the convection thermal resistance.

[0085] Computational models such as Figure 2The three-circuit model was used, and the finite element method was employed for calculation. The tunnel was selected as 0.75m * 0.5m, and ideal gas information was used for the air. The thermal conductivity of the three cables (1, 2, and 3) was non-uniform, with the copper conductor selected as 380 and the XLPE material as 0.3. The conductor diameter was 2.5cm, and the insulation layer thickness was 1.25cm. Random ambient temperature was used as the tunnel wall temperature (first-type boundary condition), and the volume heat flux density varied randomly. The iteration step was 1500 steps, and the relaxation factor was 0.5. Thermal radiation was not considered in the calculation.

[0086] Each cable circuit is set to the same radiation surface. According to thermal field knowledge, when the cables are arranged vertically, the temperature of the upper phase is higher than that of the middle and lower phases; when the cables are arranged horizontally, the temperature of the middle phase is higher than that of the side phases. Considering that the operating current is limited by the highest temperature point, we mainly focus on the highest temperature point in the outer sheath of each cable circuit, that is, the outer sheath temperature of the middle phase, and then obtain the core temperature through formula (10).

[0087] Application of proportional scaling: Setting the tunnel size to 0.75m * 0.5m as 100%, the phase temperature rise of the tunnel cable under sizes of 25%, 50%, 100%, 200%, and 300% is calculated. The internal structural parameters of the cable are scaled proportionally, and the thermal load (loss) is calculated according to formula (7). Trial calculations determine the adjustment factor to be 0.87 * the adjustment factor when scaling to 200%-100%, 100%-50%, and 50%-25%, as shown in Table 1. The 0.87 factor will be slightly adjusted depending on environmental changes.

[0088] Table 1

[0089] Size ratio 25％ 50％ 100％ 200％ Conversion factor 0.210 0.354 0.595 1.000 Body heat rate conversion factor 13.454 5.657 2.378 1.000 Adjusting the conversion factor 0.138 0.268 0.517 1.000 Adjust the conversion factor for body heat rate 8.860 4.282 2.069 1.000

[0090] Table 2 shows the phase temperature rise in tunnel cables under different operating conditions, calculated using 25% of the dimensions under radiation-free conditions.

[0091] Table 2

[0092]

[0093]

[0094] Using the adjustment loss conversion factor obtained in Table 1 and the data in Table 2, the phase temperature rise in a 100% dimensional tunnel cable under radiation-free conditions can be obtained after scaling, as shown in Table 3.

[0095] Table 3

[0096]

[0097]

[0098] Fitting the convection thermal resistance:

[0099] Using the cable temperature rise data for non-radiative heat dissipation shown in Table 3, and referring to the phase sheath temperature rise calculation model for three-circuit tunnel cables, i.e.

[0100] t1=Q1*[ap1+ap2*power(t0,ak1)+ap3*power(t1,ak2)+ap4*power(t2,ak3)+ap5*power(t3,ak4)]+Q2*[ap6+ap7*power(t0,ak5)+ap8*power(t1,ak6)+ap9*power(t2,ak7)+ap 10 *power(t3,ak8)]+Q3*[ap 11 +ap 12 *power(t0,ak9)+ap 13 *power(t1,ak 10 )+ap 14 *power(t2,ak 11 )+ap 15 *power(t3,ak 12 )]+t0

[0101] t2=Q1*[bp1+bp2*power(t0,bk1)+bp3*power(t1,bk2)+bp4*power(t2,bk3)+bp5*power(t3,bk4)]+Q2*[bp6+bp7*power(t0,bk5)+bp8*power(t1,bk6)+bp9*power(t2,bk7)+bp 10 *power(t3,bk8)]+Q3*[bp 11 +bp 12 *power(t0,bk9)+bp 13 *power(t1,bk 10 )+bp 14 *power(t2,bk 11 )+bp 15 *power(t3,bk 12 )]+t0

[0102] t3=Q1*[cp1+cp2*power(t0,ck1)+cp3*power(t1,ck2)+cp4*power(t2,ck3)+cp5*power(t3,ck4)]+Q2*[cp6+cp7*power(t0,ck5)+cp8*power(t1,ck6)+cp9*power(t2,ck7)+cp10 *power(t3,ck8)]+Q3*[cp 11 +cp 12 *power(t0,ck9)+cp 13 *power(t1,ck 10 )+cp 14 *power(t2,ck 11 )+cp 15 *power(t3,ck 12 )]+t0 (11)

[0103] Where t1~t3 represent the temperature rise of the middle phase outer sheath of the first to third circuit cables, t0 represents the tunnel wall temperature, Q1~Q3 represent the heat flux of the first to third circuit cables, and ap1~ap 15 bp1~bp 15 cp1~cp 15 AK1~AKB 12 bk1~bk 12 ,ck1~ck 12 This is the coefficient of the convective thermal resistance.

[0104] The parameters were estimated using the Levenberg-Marquardt method and the general global optimization method. The fitting results of the convective thermal resistance parameters of each cable (first, second and third circuits) at 100% size are shown in Tables 4-1 to 4-3.

[0105] Table 4-1

[0106]

[0107]

[0108] Table 4-2

[0109] parameter Best estimate parameter Best estimate bp1 8.508788348 bk1 0.678507342 bp2 -0.109458204 bk2 0.224659693 bp3 -0.769844412 bk3 -0.255821273 bp4 -12.17282707 bk4 -5.896365174 bp5 -0.552233482 bk5 0.85433153 bp6 -2.003798321 bk6 0.544910502 bp7 0.146131889 bk7 -0.129273873 bp8 -0.564120903 bk8 0.204687232 bp9 6.8325211 bk9 0.113258358 bp10 0.767637392 bk10 -3.280638287 bp11 0.662435266 bk11 -1.121946598 bp12 1.490045093 bk12 0.294441171 bp13 -1.58E+01 bp14 -0.100438147 bp15 -0.874366953 Correlation coefficient (R) 0.9993

[0110] Table 4-3

[0111] parameter Best estimate parameter Best estimate cp1 -3.56618 ck1 0.196536 cp2 -3.83559 ck2 1.620738 cp3 -0.00158 ck3 0.042544 cp4 -10.4373 ck4 0.119374 cp5 16.13762 ck5 0.022015 cp6 -0.05954 ck6 -7.06645 cp7 -1.46948 ck7 0.263383 cp8 -3.65117 ck8 0.102383 cp9 -0.95337 ck9 0.43955 cp10 3.141496 ck10 -0.19389 cp11 -23.1629 ck11 -0.05272 cp12 1.531759 ck12 -0.64925 cp13 32.58937 cp14 2.775604 cp15 -2.57379 Correlation coefficient (R) 0.9996

[0112] Example 2

[0113] This embodiment also relates to the application of a method for calculating the convective thermal resistance of tunnel cables based on self-modeling theory. The effect of the convective thermal resistance application is reflected in the estimation of the temperature rise of the phase sheath in the cable under the condition of ignoring thermal radiation. Under 100% size, 15 sets of data were randomly selected for direct finite element calculation (ignoring thermal radiation), and the results of the comprehensive application of formula (11) under the convective thermal resistance fitting were compared as shown in Table 5 below, unit: K. Error statistics and verification are shown in Table 6, and the error histogram is shown below. Figure 3 As shown, the error distribution diagram is as follows: Figure 4 As shown.

[0114] Table 5

[0115]

[0116] Table 6

[0117]

[0118] Error statistics show that:

[0119] (1) The maximum error of the outer sheath of each phase in each circuit cable is less than 3K, which can meet the requirements of engineering applications;

[0120] (2) There were no significant differences between groups, indicating that the fitting effect on the thermal resistance of the phase sheath in each loop cable was comparable;

[0121] (3) Judging from the error distribution plot QQ plot, it is basically near the straight line, which can be considered to follow a normal distribution.

[0122] In conclusion, the fitting of the thermal resistance can be considered reliable and can meet the actual needs of engineering.

[0123] The examples show that:

[0124] (1) By scaling the tunnel dimensions proportionally and adjusting the heat load (loss) synchronously, the sheath temperature of the middle phase of the cable under different dimensions can be obtained. The heat load (loss) calculation based on equation (7) is reliable. Considering that tunnels are different from completely large spaces with natural convection, and the difference in the ratio of cable cross-section to tunnel cross-sectional area, the adjusted values ​​may need to be adjusted slightly.

[0125] (2) The examples show that it is feasible to handle the convection part in the temperature rise calculation of large cross-section cable tunnels by scaling based on the self-modeling theory, which will significantly improve the overall temperature rise calculation efficiency and convenience.

[0126] In practical applications:

[0127] 1) Obtain cable phase sheath temperature rise data under multiple operating conditions (without radiation) in a small size;

[0128] 2) Based on equation (7) and its adjustment coefficient, the temperature rise data of the cable phase sheath under multiple working conditions under large cross-section (without radiation) is obtained by scaling.

[0129] 3) Fitting representation of convective thermal resistance: Through mathematical modeling, the relationship between the convective thermal resistance of the cable tunnel and the thermal load and ambient temperature is obtained through the McCourt iterative search method, that is, the mathematical representation of the convective thermal resistance.

[0130] This invention patent allows for the relative separation of radiative and convective heat dissipation in finite element calculations. This facilitates the scaling of the geometric model of tunnel cables based on the natural convection self-modeling theory, reducing the absolute size of the air domain, thereby decreasing the computational complexity of the finite element model, increasing computational speed, reducing the demand for computing resources (software, personnel), facilitating implementation, and supporting the requirement for real-time load adjustment by operators.

[0131] Example 3

[0132] The electronic device of this invention includes a central processing unit (CPU), which can perform various appropriate actions and processes according to computer program instructions stored in read-only memory (ROM) or loaded from a storage unit into random access memory (RAM). Various programs and data required for device operation can also be stored in the RAM. The CPU, ROM, and RAM are interconnected via a bus. Input / output (I / O) interfaces are also connected to the bus.

[0133] Multiple components in the device are connected to the I / O interface, including: input units such as keyboards and mice; output units such as various types of displays and speakers; storage units such as disks and optical discs; and communication units such as network interface cards (NICs), modems, and wireless transceivers. The communication unit allows the device to exchange information / data with other devices through computer networks such as the Internet and / or various telecommunications networks.

[0134] The processing unit executes the various methods and processes described above. For example, in some embodiments, the methods may be implemented as computer software programs tangibly contained in a machine-readable medium, such as a storage unit. In some embodiments, part or all of the computer program may be loaded and / or installed on the device via ROM and / or a communication unit. When the computer program is loaded into RAM and executed by the CPU, one or more steps of the methods described above may be performed. Alternatively, in other embodiments, the CPU may be configured to execute the methods by any other suitable means (e.g., by means of firmware).

[0135] The functions described above in this document can be performed, at least in part, by one or more hardware logic components. For example, exemplary types of hardware logic components that can be used, without limitation, include: Field Programmable Gate Arrays (FPGAs), Application-Specific Integrated Circuits (ASICs), Application Standard Products (ASSPs), System-on-Chip (SoCs), Complex Programmable Logic Devices (CPLDs), and so on.

[0136] The program code used to implement the methods of the present invention can be written in any combination of one or more programming languages. This program code can be provided to a processor or controller of a general-purpose computer, special-purpose computer, or other programmable data processing device, such that when executed by the processor or controller, the program code causes the functions / operations specified in the flowcharts and / or block diagrams to be implemented. The program code can be executed entirely on the machine, partially on the machine, as a standalone software package partially on the machine and partially on a remote machine, or entirely on a remote machine or server.

[0137] In the context of this invention, a machine-readable medium can be a tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, apparatus, or device. A machine-readable medium can be a machine-readable signal medium or a machine-readable storage medium. Machine-readable media can include, but are not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination of the foregoing. More specific examples of machine-readable storage media include electrical connections based on one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fibers, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the foregoing.

[0138] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for calculating the convective thermal resistance of tunnel cables based on self-modeling theory, characterized in that, The method includes the following steps: Step 1: Based on the self-modeling theory, the phase sheath temperature rise in the cable is obtained by scaling proportionally while ignoring thermal radiation; Step 2: Based on the temperature rise data of the outer sheath of the middle phase of the cable obtained in Step 1, perform mathematical modeling to obtain a fitted representation of the convective thermal resistance of the tunnel cable. The method for calculating the phase sheath temperature rise of a cable by scaling up the process while neglecting thermal radiation, based on self-modeling theory, includes: A) Ignoring thermal radiation, randomly generate thermal loads and ambient temperatures to obtain data on the temperature rise of the outer sheath of the cable phase in a tunnel of a certain characteristic size; B) Adjust the feature size and simultaneously adjust the corresponding multiple sets of thermal loads of the previous feature size. After scaling, obtain the temperature rise of the outer sheath of the tunnel cable under this feature size. C) Repeat step B) After obtaining the temperature rise of the cable phase sheath under multiple characteristic dimensions, perform fitting analysis to determine the adjustment conversion factor applicable to the tunnel; D) Based on the tunnel adjustment conversion factor in step C), calculate the temperature rise of the cable phase sheath under the new characteristic dimensions and verify it.

2. The method for calculating the convective thermal resistance of tunnel cables based on self-modeling theory according to claim 1, characterized in that, The aforementioned synchronous adjustment of multiple sets of thermal loads corresponding to the previous characteristic dimension specifically refers to: The thermal load is calculated using the following formula, with the internal structural parameters of the cable scaled proportionally: ； in, C 1 represents loss Q With feature size l The temperature characteristics under a given condition; Q is the thermal load, also known as loss.

3. The method for calculating the convective thermal resistance of tunnel cables based on self-modeling theory according to claim 1, characterized in that, The specific details of obtaining the phase sheath temperature rise of the cable under this characteristic size through proportional scaling are as follows: First, determine the scaling range of the adjustment conversion factor and calculate the adjustment loss conversion factor under different size ratios; Then, based on the data of the temperature rise of the outer sheath of the cable in the tunnel with the characteristic size in step A), and combined with the adjustment conversion factor under different characteristic size ratios, the temperature rise of the outer sheath of the cable in the tunnel with the characteristic size under radiation-free conditions is obtained by scaling.

4. The method for calculating the convective thermal resistance of tunnel cables based on self-modeling theory according to claim 1, characterized in that, The verification specifically involves comparing the phase sheath temperature rise of the tunnel cable calculated directly by finite element method under the condition of ignoring thermal radiation with the phase sheath temperature rise result of the tunnel cable obtained by fitting the convective thermal resistance of the tunnel cable. If the maximum error of the phase sheath in each loop cable is less than the threshold, then the engineering application is satisfied.

5. The method for calculating the convective thermal resistance of tunnel cables based on self-modeling theory according to claim 1, characterized in that, The specific method for obtaining the fitting representation of the convective thermal resistance of the tunnel cable is as follows: ignoring the temperature rise data of the phase sheath in the cable and referring to the calculation model of the phase sheath temperature rise in a three-circuit tunnel cable, a fitting representation of the convective thermal resistance of the tunnel cable is obtained.

6. The method for calculating the convective thermal resistance of tunnel cables based on self-modeling theory according to claim 5, characterized in that, The fitting expression for the convective thermal resistance of the tunnel cable is represented by the following formula: ； ； ； in, t 1~ This refers to the temperature rise of the middle phase outer sheath of the first through third circuit cables. t 0 represents the tunnel wall temperature. ~ For the heat flow of the first to third circuit cables, ~ , ~ , ~ , ~ , ~ , ~ This is the coefficient of the convective thermal resistance.

7. The method for calculating the convective thermal resistance of tunnel cables based on self-modeling theory according to claim 1, characterized in that, The fitting representation of the convective thermal resistance of the tunnel cable was obtained by the McCourt iterative search method.

8. An electronic device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the program, it implements the method as described in any one of claims 1 to 7.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the method as described in any one of claims 1 to 7.

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