Multi-core tunnel cable steady-state temperature rise rapid prediction method and electronic equipment

Abstract

The invention relates to a multi-core tunnel cable steady-state temperature rise rapid prediction method and electronic equipment, and the method comprises the steps: symmetrically decomposing a multi-core tunnel cable body into a plurality of parts, and selecting one part to be equivalent to an independent single-core cable; establishing a simplified single equivalent single-core cable steady-state thermal circuit model for the independent single-core cable; the inter-core mutual heating effect influence is equivalent to a coupling coefficient, the inter-cable mutual heating effect influence is equivalent to mutual heating resistance, and the coupling coefficient and the mutual heating resistance are coupled to a multi-loop equivalent single-core cable steady-state thermal circuit model; and correcting the cable core temperature of the multi-loop equivalent single-core cable by adopting the coupling coefficient to obtain the cable core temperature of the multi-core and multi-loop tunnel cable. Compared with the prior art, the method has the advantages that the steady-state temperature rise of the multi-core tunnel cable can be quickly and accurately predicted, and the like.

Description

Technical Field

[0001] The present invention relates to the field of steady-state temperature rise prediction of tunnel cables, and particularly to a method for rapidly predicting the steady-state temperature rise of multi-core tunnel cables. Background Art

[0002] Multi-core tunnel cables represented by three-core cables are composed of multiple metal conductors that are wound around each other. They have the advantages of small floor area, stable structure, high mechanical strength, and strong anti-destruction ability, so they are widely used under various laying conditions. However, compared with single-core cables, multi-core tunnel cables have an irregularly shaped filling layer between the cable core and the outer sheath, resulting in poor heat dissipation performance. In addition, there is mutual inductance between the cable conductors, making it difficult to predict the actual temperature of the cable core. Therefore, accurately predicting the temperature of the cable core of multi-core cables in practice poses a great challenge.

[0003] Traditionally, the methods for calculating the temperature of the cable core of multi-core cables mainly include the finite element method and the analytical calculation method based on IEC standards. The finite element method calculates the temperature of the cable core by numerically solving the control equations corresponding to the physical model through finite elements. Its advantage is relatively accurate calculation, but its disadvantages are large computational resource requirements, complex solution process, and long time consumption, which are not conducive to practical engineering applications. The analytical calculation method based on IEC standards is easy to implement and fast to solve, and is suitable for practical engineering. However, most current research focuses on single-core cables. For multi-core cables, most research directly imitates the thermal circuit model of single-core cables to give the thermal circuit model of multi-core cables, and the corresponding changes are only parameters such as material structure, number of layers, thermal resistance value, and heat capacity value, or the thermal circuit model of multi-core cables is deduced from the empirical formula for calculating the current-carrying capacity of multi-core cables in the IEC standard. Since multi-core cables have multiple conductors, the thermal circuit models of multi-core cables established by the above methods cannot accurately represent the heat transfer from the cable conductors to the surface. If a thermal circuit model of the overall structure of a multi-core cable is established, due to the many influencing factors considered and the complex thermal circuit composition, it is not convenient for practical application. Therefore, establishing a simplified prediction model that conforms to the heat transfer characteristics of multi-core cables and forming a simple method for accurately predicting the temperature of the conductors of multi-core tunnel cables are crucial in the current research on cable temperature prediction.

[0004] After retrieval, the Chinese invention patent application publication number CN119106574A discloses a method for predicting the steady-state temperature rise of a multi-circuit tunnel cable. The method includes the following steps: obtaining a sample data set of the multi-circuit tunnel cable; performing data preprocessing on the obtained sample data set to construct a BP neural network model; constructing a Hybrid Improved Particle Swarm Optimization (HIPSO) algorithm, which is formed by fusing Sinusoidal chaotic mapping, dynamically adjusting the inertia weight, T-distribution perturbation, and Gaussian-Cauchy hybrid mutation; using the constructed HIPSO algorithm to optimize the BP neural network model to obtain an optimal BP neural network model, and establishing a HIPSO-BPNN cable core temperature prediction model; using the HIPSO-BPNN cable core temperature prediction model to predict the steady-state temperature rise of the multi-circuit tunnel cable to obtain the predicted value of the highest core temperature. This existing invention application has problems such as the need for a large amount of data sets composed of finite element calculations for neural network calculations and the complex structure of the algorithm itself.

[0005] How to achieve rapid and accurate prediction of the temperature rise of a multi-core tunnel cable has become a technical problem to be solved. Summary of the Invention

[0006] The purpose of the present invention is to overcome the defects of the above-mentioned existing technologies and provide a method for rapidly predicting the steady-state temperature rise of a multi-core tunnel cable.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] According to one aspect of the present invention, there is provided a method for rapidly predicting the steady-state temperature rise of a multi-core tunnel cable. The method includes the following steps:

[0009] Step S1: Symmetrically decompose the multi-core tunnel cable body into multiple parts, and select one of the parts to be equivalent to an independent single-core cable.

[0010] Step S2: Calculate the thermal resistance of each layer of materials of the independent single-core cable and the thermal resistance of the external laying environment, and establish a simplified steady-state thermal circuit model of a single equivalent single-core cable.

[0011] Step S3: Establish a physical model of a single multi-core tunnel cable, solve the highest core temperature of the multi-core tunnel cable under different load currents through finite element analysis, and solve the highest core temperature of the multi-core cable according to the simplified steady-state thermal circuit model of a single equivalent single-core cable established in Step S1. The influence of the inter-core mutual heating effect is equivalent to a coupling coefficient.

[0012] Step S4: Expand the steady-state thermal circuit model of a single equivalent single-core cable into a steady-state thermal circuit model of a multi-circuit equivalent single-core cable, and equivalent the influence of the inter-cable mutual heating effect to an inter-thermal resistance, and couple it into the steady-state thermal circuit model of the multi-circuit equivalent single-core cable.

[0013] Step S5: Correct the core temperature of the multi - loop equivalent single - core cable using the coupling coefficient to obtain the core temperature of the multi - core multi - loop tunnel cable.

[0014] Preferably, in step S1, the specific method of symmetrically decomposing the multi - core tunnel cable body into multiple parts is as follows: Starting from the geometric center of the multi - core tunnel cable, connect the tangent points of two cores and extend to the outer surface of the cable. Each decomposed part contains one core and the same content of inter - layer filling material.

[0015] Preferably, the process of establishing the simplified steady - state thermal circuit model of a single equivalent single - core cable in step S2 includes: Establishing the steady - state thermal circuit model of a single equivalent single - core cable along the shortest path from the core to the outer sheath surface of the cable. The thermal circuit model includes insulation layer thermal resistance, filling layer thermal resistance, inner sheath thermal resistance, outer sheath thermal resistance, convective thermal resistance, radiative thermal resistance, tunnel wall thermal resistance, and soil thermal resistance.

[0016] Preferably, the starting node of the simplified steady - state thermal circuit model of a single equivalent single - core cable is the core temperature of the cable, and the ending node is the external environmental temperature of the cable tunnel.

[0017] Preferably, the coupling coefficient is used to correct the deviation of the highest core temperature of the multi - core cable obtained by solving the steady - state thermal circuit model of a single equivalent single - core cable; the coupling coefficient C c is a function of the load current I, that is, C c = f(I), and this function is obtained by fitting the coupling coefficients of the physical models of single - root multi - core tunnel cables under different current conditions.

[0018] Preferably, the physical model of the single - root multi - core tunnel cable includes a single - root multi - core cable, an air layer, a tunnel wall, and a soil layer, involving three heat transfer methods: conduction, convection, and radiation.

[0019] Preferably, the process of coupling the mutual thermal resistance into the steady - state thermal circuit model of the multi - loop equivalent single - core cable includes: Equivalent the influence of the mutual heating effect of the remaining cables except the cable to be predicted on the cable to be predicted as the mutual thermal resistance, and couple it into the steady - state thermal circuit model of the single equivalent single - core cable of the cable to be predicted to obtain the steady - state thermal circuit model of the multi - loop equivalent single - core cable considering the mutual heating effect between cables.

[0020] Preferably, the mutual thermal resistance is used to characterize the influence of the mutual heating effect of one loop of the cable by the remaining loops, and its calculation formula is as follows:

[0021]

[0022] In the formula, C m is the correction coefficient; ΔT air,i is the temperature rise of the air in the tunnel caused by the heat generation of a neighboring loop i; Qk is the heat generation of the circuit to be solved under the current I k ; N is the number of circuits; R m is the mutual thermal resistance of the multi-circuit cable.

[0023] Preferably, in the step S5, the process of obtaining the core temperature of the multi-core multi-circuit tunnel cable is as follows:

[0025]

[0026] where Tc”'max is the core temperature of the multi-core multi-circuit cable, C c is the coupling coefficient, and Tc”max is the core temperature of the cable calculated by using the established steady-state thermal circuit model of the multi-circuit equivalent single-core cable.

[0027] According to another aspect of the present invention, there is provided an electronic device, including a memory and a processor, where a computer program is stored on the memory, and when the processor executes the program, the method described above is implemented.

[0028] Compared with the prior art, by symmetrically decomposing the multi-core tunnel cable to establish a simplified steady-state thermal circuit model of a single equivalent single-core cable, the present invention comprehensively considers the influences of the multi-core cable structure, load change, and mutual heating effect under multi-circuit laying, so as to realize the prediction of the steady-state temperature rise of the multi-core tunnel cable, and has the following beneficial effects:

[0029] 1) By simplifying the multi-core tunnel cable into a single-core cable, the present invention establishes a steady-state thermal circuit model of a single equivalent single-core cable along the shortest path from the core to the surface of the cable outer sheath, greatly simplifies the complex multi-core thermal circuit model into an equivalent single-core thermal circuit model, thereby reducing the complexity of the model and improving the prediction speed.

[0030] 2) The present invention equates the inter-cable mutual heating effect to the mutual thermal resistance, realizes the expansion of the steady-state thermal circuit model of the multi-circuit equivalent single-core cable after coupling it into the steady-state thermal circuit model of the single equivalent single-core cable, and equates the influence of the inter-core mutual heating effect to the coupling coefficient to correct the core temperature of the multi-circuit equivalent single-core cable, thereby realizing the accurate prediction of the core temperature of the multi-core multi-circuit tunnel cable.

[0031] 3) By comparing the result of solving the thermal circuit model with the result of the method of solving the thermal circuit model & correcting the coupling coefficient of the present invention, it is verified that the prediction result of the method of the present invention is significantly better than the result of solving the thermal circuit model, and is very close to the result of finite element calculation, that is, a very accurate prediction is realized by using a simple algorithm. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a schematic flow chart of the method of the present invention;

[0033] Figure 2 It is a simplified schematic diagram of the sectional structure decomposition of a three-core cable in an embodiment of the present invention;

[0034] Figure 3 It is a schematic diagram of the physical model of a single three-core tunnel cable in an embodiment of the present invention;

[0035] Figure 4 It is a schematic diagram of the steady-state thermal circuit model of a single equivalent single-core tunnel cable established in an embodiment of the present invention;

[0036] Figure 5 It is a schematic diagram of the physical model of a three-core four-circuit tunnel cable established in an embodiment of the present invention;

[0037] Figure 6 It is a schematic diagram of the steady-state thermal circuit model of an equivalent single-core cable considering the mutual heating effect between multiple circuits in an embodiment of the present invention;

[0038] Figure 7 It is a schematic diagram of the calculation flow of the core temperature decomposition of a three-core four-circuit tunnel cable in an embodiment of the present invention;

[0039] Figure 8 It is a schematic diagram of the comparison of the deviation and relative deviation between the calculation results of the method of the present invention and the finite element method. Specific Embodiments

[0040] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0041] The present invention application addresses the problems such as the difficulty in theoretically predicting the core temperature rise of multi-core tunnel cables and the complexity of the thermal circuit model. It comprehensively considers the influences of the multi-core cable structure, load changes, and tunnel laying environment. By re-dividing the complex multi-core cable into independent parts, each independent part is equivalent to a single-core cable, and then a thermal circuit model of a single equivalent single-core cable is obtained. And the coupling coefficient C of the mutual heating effect between cores is obtained through the finite element method c , to correct the core temperature of the multi-core cable. At the same time, considering that the multi-circuit multi-core cables laid in the tunnel will be affected by the mutual heating effect between cables during normal operation, the thermal resistance of the mutual heating effect is introduced into the thermal circuit model, so that the proposed simplified prediction method for the core temperature of multi-core cables effectively solves the problem of difficult prediction of the core temperature of multi-core cables in practical engineering applications and can be applied to the application scenarios of multi-circuit tunnel laying.

[0042] Embodiment 1

[0043] This embodiment relates to a method for quickly predicting the steady-state temperature rise of a multi-core tunnel cable, as follows Figure 1 , including the following steps:

[0044] Step 1: According to the number of cable cores of the multi-core cable and the symmetry of the circumferential structure distribution, the multi-core cable body is symmetrically decomposed into multiple parts, and one of them is selected as the research object.

[0045] The multi-core cable is equally divided into multiple parts according to the number of cable cores. The specific division method is as follows: starting from the geometric center of the multi-core cable, connecting the tangent points of two cable cores and extending to the outer surface of the cable. Each decomposed part contains one cable core and the same content of interlayer filling material. Each equally divided part is equivalent to an independent single-core cable, and this equivalent single-core cable is used as the research object.

[0046] Step 2: Calculate the thermal resistance of each layer of the cable material and the thermal resistance of the external laying environment for the selected part, and establish a simplified steady-state thermal circuit model of a single equivalent single-core cable for preliminary prediction of the cable core temperature.

[0047] A steady-state thermal circuit of a single equivalent single-core cable is established along the shortest path from the cable core to the outer surface of the cable sheath. The thermal circuit model includes insulation layer thermal resistance, filling layer thermal resistance, outer sheath thermal resistance, convective thermal resistance, radiative thermal resistance, tunnel wall thermal resistance, soil thermal resistance, etc. The starting node of the thermal circuit model is the cable core temperature T c , and the termination node is the external environment temperature T of the cable tunnel sur .

[0048] Step 3: Establish a physical model of a single multi-core tunnel cable, solve the highest temperature of the cable cores of the multi-core cable under different load currents through finite element method, and solve the highest temperature of the cable cores of the multi-core cable according to the simplified steady-state thermal circuit model of a single equivalent single-core cable. By equating the influence of the mutual heating effect between cores to the coupling coefficient C c , to correct the deviation of the highest temperature of the cable cores of the multi-core cable solved by the steady-state thermal circuit model of a single equivalent single-core cable, so as to obtain the accurate value of the cable core temperature of the multi-core cable.

[0049] The established two-dimensional physical model of a single multi-core cable laid in a tunnel includes parts such as a single multi-core cable, an air layer, a tunnel wall, and a soil layer, involving three heat transfer methods: conduction, convection, and radiation. The load current of the multi-core cable is a variable parameter, and the highest temperature T of the cable cores is calculated by the finite element method cmax . At the same time, according to the simplified steady-state thermal circuit model of a single equivalent single-core cable established in Step 2, the highest temperature Tc'max of the cable cores is solved. Based on the finite element solution results, the deviation of the thermal circuit model solution is corrected through the coupling coefficient C c , and the coupling coefficient C c is a function of the load current I, that is, C c = f(I).

[0050] Step 4: Expand the single - cable equivalent single - core cable steady - state thermal circuit model established in Step 2 into a multi - loop equivalent single - core cable steady - state thermal circuit model. Equivalent the influence of the mutual heating effect of the other cables except the cable to be predicted on this cable as a mutual thermal resistance and couple it into the thermal circuit model. On this basis, use the coupling coefficient C c to correct the core temperature of the multi - loop equivalent single - core cable, and thus obtain the core temperature of the multi - core multi - loop cable.

[0051] Use the mutual thermal resistance to deal with the thermal influence of all adjacent cables (referred to as neighboring cables) except the cable to be predicted on the cable to be predicted, and add the mutual thermal resistance to the single - cable equivalent single - core cable steady - state thermal circuit model of the cable to be predicted. The specific steps are as follows: Make the neighboring cables no - load, and then apply different load currents to each neighboring loop in turn to obtain the current I i of a certain loop and the corresponding relationship T air with the air temperature rise T air,i (I i ). At the same time, knowing the loss Q k of the cable to be predicted, according to R m,i = ΔT air,i (I i ) / Q k calculate the mutual thermal resistance of a certain loop cable at this time. Finally, according to R m = C m ∑R m,i calculate the mutual thermal resistance, where the correction coefficient C m is used to make the calculation of R m more accurate. Use the established multi - loop equivalent single - core cable steady - state thermal circuit model to calculate the cable core temperature Tc”max, and the product Tc”'max = Cc·Tc”max of it and the coupling coefficient C c is the final result, that is, the core temperature of the multi - core multi - loop cable.

[0052] Step 5: Compare the core temperature of the multi - core multi - loop cable calculated by the calculation method in Step 4 with that calculated by the finite - element method, and verify the correctness of the rapid prediction method for the steady - state temperature rise of the multi - core tunnel cable core.

[0053] Use the finite - element method to calculate the core temperature T cmax of the multi - core multi - loop cable under different working conditions, and compare it with the calculation result Tc”'max of the simplified prediction model proposed by the present invention to verify the correctness of the method of the present invention.

[0054] Example 2

[0055] This example also relates to a rapid prediction method for the steady - state temperature rise of multi - core tunnel cables, taking the common three - core tunnel cable as an example. Figure 2It is a schematic diagram of the sectional structure decomposition of a three-core cable. The figure includes some dimensions and specific structures of a certain three-core cable, which are evenly distributed in a finished product shape with the geometric center of the cable as the origin. The overall structure includes a copper conductor, an XLPE insulation layer, a metal shielding layer, a filling layer, an inner sheath, an armor layer, and an outer sheath from the inside to the outside. Figure 2 The decomposition process of the three-core tunnel cable is as follows: First, one-third of the cable is selected for research with a certain cable core as the center, and this part of the cable is equivalent to a single-core cable, and then a steady-state thermal circuit model of a single equivalent single-core tunnel cable is established.

[0056] Figure 3 The following is a schematic diagram of the physical model of a single three-core tunnel cable established in this embodiment. Figure 4 The following is a steady-state thermal circuit model of a single equivalent single-core cable obtained after the decomposition and simplification of the three-core cable. Figure 4 Among them, R i , R f , R is , R j are the thermal resistances of the cable insulation layer, the filling layer, the inner sheath, and the outer sheath respectively. R cv , R rad , R w , R s are the convective thermal resistance, the radiative thermal resistance, the tunnel layer thermal resistance, and the soil layer thermal resistance respectively. Q c , Q d , Q ms , Q a are the heat losses of the cable core, the insulation layer, the metal shielding layer, and the armor layer respectively. T c , T i , T a , T j , T iw , T ew , T sur are the cable core temperature, the cable insulation layer temperature, the cable armor layer temperature, the cable outer sheath temperature, the tunnel inner wall temperature, the tunnel outer wall temperature, and the cable tunnel external environment temperature respectively. In the thermal circuit model, the magnitudes of the relevant parameters are determined by the IEC standard and finite element calculation.

[0057] For regular structural layers such as the insulation layer, the filling layer, the inner sheath, and the outer sheath of the three-core cable that are in a circular ring shape, the thermal resistance calculation formula is:

[0058]

[0059] In the formula, r1 and r2 are the inner and outer circle radii of the circular ring respectively, in m; ρ th is the thermal resistivity of the corresponding material, in K·m / W; π is the pi.

[0060] For the thermal resistance of the filling layer of a three-core cable with an irregular shape, the shape factor method is selected for calculation. The shape factor S is a geometric parameter that reflects the influence of the shape structure on the heat conduction process, and its magnitude is only related to the shape and size of the heat-conducting object. The filling layer of the three-core cable is located between the cable metal shielding layer and the inner sheath layer, as shown in the blue part of Figure 2 As shown. When calculating using the shape factor method, the cable metal shielding layer and the inner sheath layer are used as isothermal surfaces. Three cable cores are deducted, and only the filling layer material between the two isothermal surfaces is extracted for calculation. From the definition of the shape factor, it is easy to know the relationship between the thermal resistance of the heat-conducting medium in the cable filling layer and the shape factor:

[0061]

[0062] In the formula, λ is the thermal conductivity of the heat-conducting material between the two isothermal surfaces, W / m·K; S is the shape factor of the filling layer; n is the number of cable cores; r f 、r ms 、r cc are the radius of the cable filling layer, the radius of the metal shielding layer, and the distance from the geometric center of the cable to any cable core, respectively, m.

[0063] For a rectangular tunnel wall with a regular shape, its thermal resistance calculation formula is:

[0064]

[0065] In the formula, ρ th is the thermal resistivity of the tunnel wall material, K·m / W; l w is the thickness of the tunnel wall, m; S w is the cross-sectional area of the tunnel wall, m 2 .

[0066] For the soil layer outside the tunnel, its thermal resistance calculation formula is:

[0067]

[0068] In the formula, ρ s is the thermal resistivity of the soil, K·m / W; L T is the distance from the tunnel center to the ground surface, m; a is the width of the inner wall of the cable tunnel, m.

[0069] The calculation results or expressions of the thermal resistances of each layer in the thermal circuit model are shown in Table 1. Among them, the thermal resistances of the filling layer, inner sheath, armor layer, and outer sheath are all three times the overall thermal resistance. Since the armor layer is made of metal steel and has a much higher thermal conductivity compared to other materials, the thermal resistance of the armor layer can be ignored. Here, the three times refers to the fact that the thermal resistance of one-third of the three-core cable material after the symmetrical decomposition of the three-core cable body and the thermal resistance of the other two-thirds part are in a parallel relationship. Therefore, in the thermal circuit calculation, the thermal resistance calculated based on one-third of the three-core cable material needs to be multiplied by three. The thermal resistance values in Table 1 are already the results after multiplying by 3 in the calculation.

[0070] Table 1

[0071]

[0072] In Table 1, R i , R f , R in , R j are the thermal resistances of the cable insulation layer, filling layer, inner sheath, and outer sheath respectively, and R w and R s are the thermal resistances of the tunnel layer and the soil layer respectively. The thermal resistance R air of the tunnel air layer is composed of the convective thermal resistance R cv and the radiative thermal resistance R rad in parallel. The expressions of the two are as follows:

[0073]

[0074] In the formula, D is the outer diameter of the cable, m; ε is the surface emissivity of the cable; σ = 5.67×10 -8 W·m -2 ·K -4 is the blackbody radiation constant; T j and T iw are the average temperatures of the outer surface of the cable and the inner wall surface of the tunnel respectively, K; A is the surface area of convective heat transfer, m 2 ; h(I) is the convective heat transfer coefficient on the cable surface, W / m 2 ·K, which is a function of the load current I and can be determined based on finite element calculation. The fitting result is as follows:

[0075] h(I) = kI + b = 0.00409I + 3.0265

[0076] Apply a variable load current to a single three-core cable, and the output parameter is the maximum temperature T cmax of the cable core. At the same time, solve the maximum temperature Tc'max of the cable core according to the established simplified thermal circuit model. Based on the finite element solution result, correct the calculation result of the improved thermal circuit model, and pass the deviation generated by the solution result of the thermal circuit model through the coupling coefficient C cis corrected, and the coupling coefficient C c is a function of the load current I:

[0077] C c = f(I)

[0078] The coupling coefficient C of the three-core cable under different working conditions c The solution results are shown in Table 2,

[0079] Table 2

[0080] Current I / A 200 300 400 500 600 700 <![CDATA[Coupling coefficient C c > 0.9975 1.0087 1.0246 1.0456 1.0728 1.1074

[0081] The coupling coefficients in Table 2 above are fitted to a function of current, and the fitting results are as follows:

[0082] C c = -4.27889·10 -5 ·I + 2.886445·10 -7 ·I 2 + 0.99513

[0083] According to the obtained fitting formula of the coupling coefficient, 5 groups of random load currents are selected, and the finite element method is used to verify the correctness of the coupling coefficient C c The results of the three calculation methods under different working conditions are shown in Table 3.

[0084] Table 3

[0085] Current I / A 278 344 442 631 692 <![CDATA[Cable core temperature (finite element) T cmax / K]]> 305.72 312.89 326.51 364.18 380.10 <![CDATA[Cable core temperature (thermal circuit solution & Cc correction) T cmax / K]]> 305.62 312.72 326.47 364.32 379.91 <![CDATA[Cable core temperature (thermal circuit solution) T cmax / K]]> 303.77 313.23 330.59 374.42 391.25 <![CDATA[Finite element and thermal circuit solution & C c Deviation between corrections / K]]> 0.10 0.17 0.04 0.14 0.19 Deviation between finite element and thermal circuit solutions / K 1.95 0.34 4.08 10.24 11.15

[0086] As can be seen from Table 3, the calculation results of the thermal circuit solution & C c correction method are significantly better than those of the thermal circuit model solution: the calculation results of the thermal circuit solution & C c correction method and the finite element calculation are extremely close, and the average deviation between the two is only 0.126 K, which is much smaller than the deviation between the thermal circuit solution model and the finite element calculation (5.552 K). Moreover, as the load current increases, the deviation between the thermal circuit solution & C c correction method and the finite element calculation results only increases within a small range, while the deviation between the thermal circuit solution model and the finite element calculation results shows a sharp increasing trend, indicating that the method of the present invention has great advantages in predicting the steady-state temperature rise of the core of a single three-core cable.

[0087] Based on the physical model of the three-core four-circuit tunnel cable as Figure 5 shown, the core temperature is predicted. Figure 6The figure shows a steady-state thermal circuit model of an equivalent single-core cable considering the mutual heating effect among multiple circuits. The thermal circuit model consists of five parts: the simplified heat source and thermal resistance of the cable body, the convective and radiative thermal resistances in the tunnel, the mutual thermal resistance, the tunnel wall thermal resistance, and the soil layer thermal resistance. Compared with the laying of a single three-core cable, the thermal circuit model of a three-core four-circuit cable adds a mutual thermal resistance R m , which is used to characterize the influence of the mutual heating effect of other circuits on a certain circuit cable. Its calculation formula is as follows:

[0088]

[0089] In the formula, C m is a correction coefficient used to make the solution of R m more accurate; ΔT air,i is the temperature rise of the air in the tunnel caused by the heat generation of a certain adjacent circuit, in K; Q k is the heat generation of the circuit to be solved under the current I k , in W; N is the number of circuits, where N = 4.

[0090] Figure 7 The figure shows the decomposition calculation flow chart of the three-core four-circuit cable proposed by the method of the present invention. The decomposition calculation process is as follows:

[0091] 1) Decompose the single three-core cable body into three parts, select one part as the research object, and equivalent this part of the cable to a single-core cable. Correct the deviation caused by the mutual heating effect between cores through the coupling coefficient C c .

[0092] 2) Through finite element calculation, when the adjacent cables are under no-load conditions, apply different load currents to each adjacent circuit in turn, and obtain the temperature rise of the air in the tunnel when each adjacent circuit operates alone. Equivalent the influence of the mutual heating effect between cables caused by the temperature rise of the air in the tunnel to the mutual thermal resistance R m , and couple the mutual thermal resistance into the thermal circuit to correct the core temperature of the three-core cable to be calculated.

[0093] 3) Combine the correction of the mutual heating effect between cores of the single three-core cable and the correction of the mutual heating effect between cables of the four-circuit cable into the calculation of the three-core four-circuit tunnel cable to obtain accurate calculation results.

[0094] Through finite element calculation, the temperature rise of the air in the tunnel when the other circuits except the circuit to be solved operate alone under different load currents, and the heat generation of the circuit to be solved under different currents are obtained. The solution results of the mutual thermal resistance are shown in Table 4.

[0095] Table 4

[0096] Serial number I / A <![CDATA[ΔT air,2 / K]]> <![CDATA[ΔT air,3 / K]]> <![CDATA[ΔT air,4 / K]]> <![CDATA[Q i / W]]> 1 0 0 0 0 0 2 200 1.75 1.75 1.78 6.092 3 300 4.12 4.11 4.15 14.69 4 400 7.21 7.2 7.24 26.46 5 500 11.58 11.58 11.63 44.21

[0097] Fitting the data in Table 4, the mutual thermal resistances R m,2 and R m,3 and R m,4 generated when circuits 2, 3, and 4 operate independently can be obtained, as shown in the following formula:

[0098]

[0099] Summing up R m,2 and R m,3 and R m,4 and performing deviation correction based on C m , the total mutual thermal resistance R m can be obtained. It can be seen that R m is a function of the load currents of the other three circuits. Substituting the obtained mutual thermal resistance into the thermal circuit model of the three-core four-circuit cable, the core temperature Tc”max can be obtained by solving the thermal circuit model. The product Tc”'max = Cc·Tc”max of it and the coupling coefficient C c is the final result. Under different working conditions, the simplified prediction model and the finite element method are respectively used to predict the core temperature, and then the prediction effect is verified.

[0100] Figure 8 The figure shows the deviation distribution diagram between the calculation results of the simplified prediction model and the finite element method under different working conditions. It can be seen from the figure that the simplified prediction model proposed by the present invention can better predict the core temperature of the three-core four-circuit cable. The maximum deviation compared with the finite element calculation is 2.26K, indicating that the prediction accuracy of the method of the present invention is relatively high, which can meet the needs of engineering practice, and the model is easy to implement, has a wide application range, and broad application prospects.

[0101] Example 3

[0102] The electronic device of the present invention includes a central processing unit (CPU), which can execute various appropriate actions and processes according to the computer program instructions stored in the read-only memory (ROM) or the computer program instructions loaded from the storage unit into the random access memory (RAM). In the RAM, various programs and data required for device operation can also be stored. The CPU, ROM, and RAM are connected to each other through a bus. The input / output (I / O) interface is also connected to the bus.

[0103] Multiple components in the device are connected to the I / O interface, including: an input unit, such as a keyboard, a mouse, etc.; an output unit, such as various types of displays, speakers, etc.; a storage unit, such as a disk, an optical disc, etc.; and a communication unit, such as a network card, a modem, a wireless communication transceiver, etc. The communication unit allows the device to exchange information / data with other devices through a computer network such as the Internet and / or various telecommunication networks.

[0104] The processing unit executes the various methods and processes described above. For example, in some embodiments, the method may be implemented as a computer software program tangibly embodied 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 onto the device via the ROM and / or the communication unit. When the computer program is loaded into the 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 method by any other suitable means (e.g., by means of firmware).

[0105] The functions described above herein may be performed at least in part by one or more hardware logic components. By way of example and not limitation, the types of hardware logic components that may be used include: field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), application specific standard products (ASSPs), system on a chip (SOCs), complex programmable logic devices (CPLDs), and the like.

[0106] The program code for implementing the method of the present invention may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general purpose computer, a special purpose computer, or other programmable data processing device, such that the program codes, when executed by the processor or controller, cause the functions / operations specified in the flowchart and / or block diagram to be implemented. The program code may be executed entirely on the machine, partially on the machine, as a stand-alone software package partially on the machine and partially on a remote machine, or entirely on the remote machine or server.

[0107] In the context of the present invention, a machine-readable medium may be a tangible medium that can contain or store a program for use by or in connection with an instruction execution system, apparatus, or device. A machine-readable medium may be a machine-readable signal medium or a machine-readable storage medium. A machine-readable medium may include, but is 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 a machine-readable storage medium would include an electrical connection based on one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0108] As described above, it is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for rapidly predicting the steady-state temperature rise of a multi-core tunnel cable, characterized in that, The method includes the following steps: Step S1, symmetrically decompose the multi-core tunnel cable body into multiple parts, and select one of the parts to be equivalent to an independent single-core cable; Step S2, calculate the thermal resistance of each layer of materials of the independent single-core cable and the thermal resistance of the external laying environment, and establish a simplified steady-state thermal circuit model of a single equivalent single-core cable; Step S3, establish a physical model of a single multi-core tunnel cable, solve the highest temperature of the cable core of the multi-core tunnel cable under different load currents through finite element method, and solve the highest temperature of the cable core of the multi-core cable according to the simplified steady-state thermal circuit model of a single equivalent single-core cable established in Step S1, and equivalent the influence of the mutual heating effect between cores to a coupling coefficient; Step S4, expand the steady-state thermal circuit model of a single equivalent single-core cable into a steady-state thermal circuit model of a multi-loop equivalent single-core cable, equivalent the influence of the mutual heating effect between cables to a mutual thermal resistance, and couple it into the steady-state thermal circuit model of the multi-loop equivalent single-core cable; Step S5, use the coupling coefficient to correct the temperature of the cable core of the multi-loop equivalent single-core cable to obtain the temperature of the cable core of the multi-core multi-loop tunnel cable.

2. The rapid prediction method for the steady-state temperature rise of a multi-core tunnel cable according to claim 1, characterized in that, In Step S1, the specific method of symmetrically decomposing the multi-core tunnel cable body into multiple parts is as follows: starting from the geometric center of the multi-core tunnel cable, connect the tangent points of two cable cores and extend to the outer surface of the cable. Each decomposed part contains one cable core and the same content of interlayer filling material.

3. A method for rapidly predicting the steady-state temperature rise of a multi-core tunnel cable according to claim 1, characterized in that, The process of establishing a simplified steady-state thermal circuit model of a single equivalent single-core cable in Step S2 includes: establishing a steady-state thermal circuit model of a single equivalent single-core cable along the shortest path from the cable core to the outer sheath surface of the cable. The thermal circuit model includes insulation layer thermal resistance, filling layer thermal resistance, inner sheath thermal resistance, outer sheath thermal resistance, convective thermal resistance, radiative thermal resistance, tunnel wall thermal resistance, and soil thermal resistance.

4. A method for rapidly predicting the steady-state temperature rise of a multi-core tunnel cable according to claim 1, characterized in that, The starting node of the simplified steady-state thermal circuit model of a single equivalent single-core cable is the cable core temperature, and the ending node is the external environment temperature of the cable tunnel.

5. A method for rapidly predicting the steady-state temperature rise of a multi-core tunnel cable according to claim 1, characterized in that, The coupling coefficient is used to correct the deviation of the highest temperature of the cable core of a multi-core cable solved by the steady-state thermal circuit model of a single equivalent single-core cable; the coupling coefficient C c is a function of the load current I, that is, C c = f(I), and this function is obtained by fitting the coupling coefficients of the physical models of single multi-core tunnel cables under different current conditions.

6. A method for rapidly predicting the steady-state temperature rise of a multi-core tunnel cable according to claim 1, characterized in that, The physical model of a single multi-core tunnel cable includes a single multi-core cable, an air layer, a tunnel wall, and a soil layer, and involves three heat transfer methods: conduction, convection, and radiation.

7. A method for quickly predicting the steady-state temperature rise of a multi-core tunnel cable according to claim 1, characterized in that, The process of coupling the mutual thermal resistance into the steady-state thermal circuit model of a multi-loop equivalent single-core cable includes: equivalent the influence of the mutual heating effect of the remaining cables except the cable to be predicted on the cable to be predicted to a mutual thermal resistance, and couple it into the steady-state thermal circuit model of a single equivalent single-core cable of the cable to be predicted to obtain a steady-state thermal circuit model of a multi-loop equivalent single-core cable considering the mutual heating effect between cables.

8. A method for quickly predicting the steady-state temperature rise of a multi-core tunnel cable according to claim 1, characterized in that, The mutual thermal resistance is used to characterize the influence of the mutual heating effect of other loops on a certain loop of cable, and its calculation formula is as follows: Where C m is the correction coefficient; ΔT air,i is the temperature rise of the air in the tunnel caused by the heat generation of a neighboring circuit i; Q k is the heat generation of the circuit to be solved under the current I k ; N is the number of circuits; R m is the mutual thermal resistance of the multi-circuit cable.

9. A method for rapidly predicting the steady-state temperature rise of a multi-core tunnel cable according to claim 1, characterized in that, In Step S5, the process of obtaining the temperature of the cable core of the multi-core multi-loop tunnel cable is as follows: Among them, Tc”'max is the core temperature of the multi-core and multi-circuit cable, C c is the coupling coefficient, and Tc”max is the core temperature of the cable calculated using the established steady-state thermal circuit model of the multi-circuit equivalent single-core cable.

10. An electronic device, comprising a memory and a processor, wherein a computer program is stored on the memory, characterized in that When the processor executes the program, it implements the method described in any one of claims 1 to 9.

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