Cable steady-state current-carrying capacity calculation method, device and equipment and storage medium

Abstract

The application provides a cable steady-state current-carrying capacity calculation method, device and equipment and a storage medium, and belongs to the technical field of power cables. The method comprises the following steps: modeling each loop cable in the target tunnel respectively, and obtaining a plurality of first numerical calculation models correspondingly; determining the allowable load current of each loop cable when the loop cable is put into operation under the condition of no forced ventilation by using the current-carrying capacity calculation process of each first numerical calculation model; modeling all loop cables in the target tunnel, and obtaining a second numerical calculation model; determining the maximum inflow flow rate that meets the forced ventilation enabling condition by using the current-carrying capacity calculation process of the second numerical calculation model; and calculating the steady-state current-carrying capacity of the target loop cable in the target tunnel under the forced ventilation condition that the inflow flow rate is equal to the maximum inflow flow rate by using the second numerical calculation model. The above method realizes accurate calculation of the steady-state current-carrying capacity of the cable considering the multi-cable laying loop and the forced ventilation of the tunnel, and ensures safe and reliable operation of the cable.

Description

Technical Field

[0001] This application belongs to the technical field of power cables, and specifically relates to a method for calculating the steady-state current-carrying capacity of cables, a device for calculating the steady-state current-carrying capacity of cables, a machine-readable storage medium, and a computer device. Background Art

[0002] The steady-state current-carrying capacity of a cable refers to the maximum current that the cable can carry during long-term continuous operation under conditions such as a specific ambient temperature and laying method. During the operation of the cable, losses occur in the conductor core and the metal sheath, resulting in an increase in the internal temperature of the cable. The steady-state current-carrying capacity of the cable is limited by the maximum temperature tolerance of the internal insulation material of the cable. Factors such as the laying environment and laying method of the cable affect the heat dissipation of the cable, and thus affect the steady-state current-carrying capacity of the cable. When the load current of the cable exceeds the steady-state current-carrying capacity, it will cause the internal temperature of the cable to be too high, accelerate the aging of the cable, and reduce the service life of the cable. When the load current of the cable is low, it will result in the underutilization of the power transmission capacity of the cable, causing serious waste of resources. Therefore, accurately calculating the steady-state current-carrying capacity of the cable can ensure the safe operation of high-voltage cables while reducing investment costs and improving economic efficiency.

[0003] Currently, high-voltage cable lines are mostly laid in cable tunnels, and multiple cable circuits of different models and specifications are arranged therein. In addition, an auxiliary ventilation system is generally installed in the tunnel. For such complex working conditions, the traditional methods applied to the calculation of the steady-state current-carrying capacity of high-voltage cables have their limitations. For example, the analytical solution is only applicable to the calculation of the current-carrying capacity of cables with a relatively simple operating environment. Moreover, the research of technicians in this field mainly focuses on the optimization and improvement of numerical calculation models, etc., ignoring the applicability of numerical calculation models under actual engineering working conditions. Summary of the Invention

[0004] The purpose of the embodiments of this application is to provide a method for calculating the steady-state current-carrying capacity of cables, a device for calculating the steady-state current-carrying capacity of cables, a machine-readable storage medium, and a computer device, so as to overcome the defect that in the prior art, the traditional method is not applicable to the calculation of the steady-state current-carrying capacity when there are multiple circuits and different models of cables in the tunnel and there is forced ventilation.

[0005] To achieve the above object, a first aspect of the present application provides a method for calculating the steady-state current-carrying capacity of a cable. The method for calculating the steady-state current-carrying capacity of a cable includes: respectively modeling each loop cable in the target tunnel to obtain respective first numerical calculation models; using the current-carrying capacity calculation processes of the respective first numerical calculation models to correspondingly determine the allowable load current when each loop cable is put into operation under the condition of no forced ventilation; modeling all loop cables in the target tunnel to obtain a second numerical calculation model; using the current-carrying capacity calculation process of the second numerical calculation model to determine the maximum inflow velocity that meets the forced ventilation enabling condition when all loop cables are put into operation according to the corresponding load current under the condition of forced ventilation; using the second numerical calculation model to calculate the steady-state current-carrying capacity of the target loop cable in the target tunnel under the forced ventilation condition where the inflow velocity is equal to the maximum inflow velocity.

[0006] In a specific embodiment of the present application, the first numerical calculation model is a two-dimensional numerical calculation model; the step of respectively modeling each loop cable in the target tunnel to obtain respective first numerical calculation models includes: obtaining the actual engineering parameters of each loop cable in the target tunnel and its surrounding space; simulating the natural air flow in the target tunnel using turbulent boundary conditions; for any loop cable in the target tunnel, based on the actual engineering parameters and the turbulent boundary conditions, performing finite element modeling of the loop cable and its surrounding space to obtain a first numerical calculation model for performing multiple two-dimensional physical field simulations when the loop cable is put into operation.

[0007] In a specific embodiment of the present application, the second numerical calculation model is a two-dimensional numerical calculation model; the step of modeling all loop cables in the target tunnel to obtain a second numerical calculation model includes: obtaining the actual engineering parameters of each loop cable in the target tunnel and its surrounding space; simulating the natural air flow in the target tunnel using turbulent boundary conditions; based on the actual engineering parameters and the turbulent boundary conditions, performing finite element modeling of all loop cables and their surrounding space to obtain a second numerical calculation model for performing multiple two-dimensional physical field simulations when all loop cables are put into operation according to the corresponding load current.

[0008] In a specific embodiment of the present application, using the current-carrying capacity calculation processes of the respective first numerical calculation models to correspondingly determine the allowable load current when each loop cable is put into operation under the condition of no forced ventilation includes: using the respective first numerical calculation models to respectively calculate the steady-state current-carrying capacity of each loop cable under the condition of no forced ventilation; for any loop cable, taking the steady-state current-carrying capacity of the loop cable under the condition of no forced ventilation as the full-load capacity, and determining the allowable load current when the loop cable is put into operation under the condition of no forced ventilation, where the load current does not exceed the full-load capacity.

[0009] In a specific embodiment of the present application, the second numerical calculation model is a two-dimensional numerical calculation model; the process of calculating the current-carrying capacity using the second numerical calculation model is used to determine the maximum inflow velocity that meets the forced ventilation enabling condition when all loop cables are put into operation according to the corresponding load current under forced ventilation conditions, including: using the process of calculating the current-carrying capacity of the second numerical calculation model to determine the two-dimensional air temperature field along the cable cross-section in the target tunnel when all loop cables are put into operation under no forced ventilation conditions; using the second numerical calculation model to simulate the change of the two-dimensional air temperature field along the cable cross-section in the target tunnel under forced ventilation conditions, and determining the maximum equivalent inflow velocity that meets the forced ventilation enabling condition.

[0010] In a specific embodiment of the present application, using the second numerical calculation model to simulate the change of the two-dimensional air temperature field along the cable cross-section in the target tunnel under forced ventilation conditions and determining the maximum equivalent inflow velocity that meets the forced ventilation enabling condition includes: for any one of a plurality of sequentially increasing inflow velocity setting values, using the second numerical calculation model to simulate the change of the two-dimensional air temperature field along the cable cross-section in the target tunnel under the forced ventilation condition where the inflow velocity is equal to this inflow velocity setting value, and obtaining the average temperature of the air environment in the target tunnel after the change; fitting the curve of the average temperature of the air environment in the target tunnel changing with the inflow velocity setting value, and determining the critical equivalent inflow velocity that causes the forced ventilation system connected to the target tunnel to stop operating according to this curve, and determining the critical equivalent inflow velocity as the maximum equivalent inflow velocity that meets the forced ventilation enabling condition.

[0011] In a specific embodiment of the present application, for any one of a plurality of sequentially increasing inflow velocity setting values, using the second numerical calculation model to simulate the change of the two-dimensional air temperature field along the cable cross-section in the target tunnel under the forced ventilation condition where the inflow velocity is equal to this inflow velocity setting value includes: for any one inflow velocity setting value, establishing an inflow boundary condition where the inflow velocity is equal to this inflow velocity setting value and the inflow direction is along the normal direction of the target tunnel wall to simulate the forced ventilation condition in the target tunnel; adding the inflow boundary condition to the second numerical calculation model; using the second numerical calculation model after adding the inflow boundary condition to simulate the change of the two-dimensional air temperature field along the cable cross-section in the target tunnel.

[0012] The second aspect of the present application provides a cable steady-state current-carrying capacity calculation device, which includes: a first module for respectively modeling each loop cable in the target tunnel to obtain respective first numerical calculation models; a second module for using the current-carrying capacity calculation processes of the respective first numerical calculation models to respectively determine the allowable load current when each loop cable is put into operation under the condition of no forced ventilation; a third module for modeling all loop cables in the target tunnel to obtain a second numerical calculation model; a fourth module for using the current-carrying capacity calculation process of the second numerical calculation model to determine the maximum inflow velocity that meets the forced ventilation enabling condition when all loop cables are put into operation according to the corresponding load current under the condition of forced ventilation; a fifth module for using the second numerical calculation model to calculate the steady-state current-carrying capacity of the target loop cable in the target tunnel under the forced ventilation condition where the inflow velocity is equal to the maximum inflow velocity.

[0013] The third aspect of the present application provides a computer device, including a memory, a processor, and a computer program stored on the memory and executable on the processor, and when the processor executes the program, it implements the cable steady-state current-carrying capacity calculation method according to the first aspect of the present application.

[0014] The fourth aspect of the present application provides a machine-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, it implements the cable steady-state current-carrying capacity calculation method according to the first aspect of the present application.

[0015] In the above technical solution, first, the load current of each loop cable in the target tunnel is determined by using the first numerical calculation model for calculating the current-carrying capacity of a single loop cable, and then the maximum inflow velocity that meets the forced ventilation enabling condition is determined. On this basis, the steady-state current-carrying capacity of the cable loop under the forced ventilation condition where the inflow velocity is equal to the aforementioned maximum inflow velocity is determined by using the second numerical calculation model for calculating the current-carrying capacity of multiple loop cables in the same cable tunnel. The entire calculation process is based on the numerical method, considering the complex working conditions of multiple loops, different specifications and models of cables, and the existence of forced ventilation, realizing the accurate calculation of the cable steady-state current-carrying capacity, and having a wide application range.

[0016] Other features and advantages of the embodiments of the present application will be described in detail in the subsequent specific implementation part. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings are used to provide a further understanding of the embodiments of the present application, and constitute a part of the specification, and are used to explain the embodiments of the present application together with the following specific implementation, but do not constitute a limitation to the embodiments of the present application. In the drawings: Figure 1 The schematic flowchart of the cable steady-state current-carrying capacity calculation method according to the embodiment of the present application is shown; Figure 2 The figure shows a schematic diagram of a first numerical calculation model for calculating the steady-state current-carrying capacity of a single-circuit cable; Figure 3 The figure shows a schematic diagram of a second numerical calculation model for calculating the steady-state current-carrying capacity of multiple cables in the same cable tunnel; Figure 4 The figure shows a schematic diagram of the added inflow boundary condition in the second numerical calculation model; Figure 5 The figure shows a curve graph of the change of the ambient temperature in the cable tunnel with the inflow velocity; Figure 6 The figure shows a curve graph of the change of the conductor temperatures of 500 kV cables and 220 kV cables in the cable tunnel with the inflow velocity; Figure 7 The figure shows a schematic diagram of the temperature distribution of a 500 kV AC cable when the load current is 2293 A; Figure 8 The figure shows a block diagram of the composition of a computer device according to an embodiment of the present application.

[0018] Description of the reference numerals In the figure, 1, copper conductor; 2, conductor shielding layer; 3, insulating layer; 4, insulating shielding layer; 5, buffer layer; 6, metal aluminum sheath; 7, anticorrosive asphalt; 8, outer sheath; 9, outer semiconductive layer; 10, air in the cable tunnel; 11, cable tunnel; 12, soil. Detailed implementation manners

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. It should be understood that the specific implementation manners described herein are only for explaining and illustrating the embodiments of the present application, and are not used to limit the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present application.

[0020] It should be noted that if there are directional indications (such as up, down, left, right, front, back...) involved in the embodiments of the present application, the directional indications are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0021] In addition, if the embodiments of the present application involve descriptions such as "first" and "second", the descriptions of "first", "second", etc. are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions between various embodiments may be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or impossibilities, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present application.

[0022] The technical terms involved in this application are explained as follows.

[0023] Steady-state current-carrying capacity of cables: It refers to the maximum current that a cable can carry during long-term continuous operation under specific environmental temperature, laying method and other conditions. The steady-state current-carrying capacity of cables is in contrast to the transient current-carrying capacity. Among them, in the traditional analytical solution for cable current-carrying capacity based on IEC standards, IEC60287 is mainly used for calculating the rated value of the steady-state current-carrying capacity (also known as: rated current-carrying capacity), while IEC-60853 is mainly used for calculating the transient current-carrying capacity.

[0024] In an existing technology, a method for calculating the current-carrying capacity of multi-circuit cables in a ventilation tunnel based on a thermal circuit model is disclosed. The technical route of this method is: on the basis of a one-dimensional thermal circuit model, an iterative method is used to calculate the steady-state current-carrying capacity of cables under multi-cable circuit and tunnel forced ventilation conditions. This method is only applicable to the working conditions where the cables in the tunnel are of the same specification and model. For the complex working conditions with various different specification and model cables in actual engineering applications, this steady-state current-carrying capacity calculation method has limitations. Its limitations are specifically reflected in: under the working conditions where the cables in the tunnel are of the same specification and model, after calculating the equivalent parameters of multi-circuit cables in the ventilation tunnel, the equivalent external thermal resistance, equivalent resistance, metal sheath loss coefficient and metal armor loss coefficient are obtained. With these equivalent parameters of multi-circuit cables, the current-carrying capacity of each circuit is solved. If at least two of the multi-circuit cables in the tunnel have different specification and model cables, in this working condition, the calculation process of the above-mentioned equivalent parameters of multi-circuit cables will not be applicable.

[0025] In another existing technology, a method for calculating the current-carrying capacity of cables considering the ventilation characteristics of cable trenches is disclosed. The technical route of this method is: on the basis of the finite element method, the wind speed values and air temperatures at multiple positions in the cable trench are obtained, the temperature at the cable installation position is calculated, and finally the steady-state current-carrying capacity of the cable is calculated using an equivalent one-dimensional thermal circuit model. This method does not couple the electromagnetic field and temperature field of high-voltage cables with the air flow field of the surrounding laying environment, resulting in a large deviation in the calculated steady-state current-carrying capacity of the cable.

[0026] The above-mentioned method for calculating the steady-state current carrying capacity of high-voltage cables has limitations when facing the following complex operating conditions: Cable tunnels often contain multiple cable circuits, with at least two circuits having different specifications and models, and the tunnels are also subject to forced ventilation. Therefore, it is impossible to accurately calculate the steady-state current-carrying capacity of cables of different specifications laid in forced-ventilation cable tunnels, making it difficult to provide guidance for practical engineering projects.

[0027] Therefore, this application provides a method for calculating the steady-state current carrying capacity of cables, which can accurately calculate the steady-state current carrying capacity of cables under the above-mentioned complex working conditions. By applying this method, accurate steady-state current carrying capacity data of cables can be provided for the design, construction and operation and maintenance of cable lines laid in tunnels. Corresponding operations can be performed based on the steady-state current carrying capacity data, such as changing the material, size and electrical parameters of multiple cables in the design of cable lines laid in tunnels. For example, during operation and maintenance, the real-time load current of the cable can be adjusted according to the steady-state current carrying capacity of the cable to ensure the safe and reliable operation of the cable.

[0028] Specifically, the cable steady-state current carrying capacity calculation method provided in this application realizes the steady-state current carrying capacity calculation through the following process: modeling each circuit cable in the target tunnel to obtain each first numerical calculation model; using the current carrying capacity calculation process of each first numerical calculation model to determine the allowable load current of each circuit cable when it is put into operation under the condition of no forced ventilation; modeling all circuit cables in the target tunnel to obtain a second numerical calculation model; using the current carrying capacity calculation process of the second numerical calculation model to determine the maximum inflow velocity that satisfies the forced ventilation activation condition when all circuit cables are put into operation under the corresponding load current under the condition of forced ventilation; using the second numerical calculation model to calculate the steady-state current carrying capacity of the target circuit cable in the target tunnel under the forced ventilation condition where the inflow velocity is equal to the maximum inflow velocity.

[0029] Understandably, the ratio between the allowable load current and the steady-state current carrying capacity of a cable during operation is usually determined based on the actual engineering conditions. For example, in actual engineering, the cable is operated at 40% to 60% of the steady-state current carrying capacity, meaning that the actual load current of the cable during operation is 40% to 60% of the steady-state current carrying capacity.

[0030] Furthermore, the first numerical calculation model is a mathematical model for calculating the steady-state current carrying capacity of a single-circuit cable. It performs a multi-physics coupling process simulation of the single-circuit cable. Each first numerical calculation model corresponds to a single-circuit cable in the target tunnel. For any single-circuit cable, the allowable load current under the condition of no forced ventilation is determined by using the corresponding first numerical calculation model.

[0031] Furthermore, the target loop cable is one or more of the multiple loop cables in the target tunnel, determined based on the steady-state current carrying capacity calculation requirements in the specific application.

[0032] In this regard, the above-mentioned technical solution of this application proposes a framework for calculating the steady-state current carrying capacity of cables based on numerical methods. The calculation framework includes: First, modeling each loop cable in the target tunnel to obtain a first numerical calculation model for calculating the steady-state current carrying capacity of a single loop cable. Each first numerical calculation model corresponds one-to-one with each loop cable in the target tunnel. Based on the first numerical calculation model, the steady-state current carrying capacity of a single loop cable without considering forced ventilation is calculated, and then the allowable load current of the cable during operation is calculated. Second, modeling all loop cables in the target tunnel to obtain a second numerical calculation model. Using the second numerical calculation model, the maximum inflow velocity that satisfies the forced ventilation activation condition is determined when all loop cables are put into operation at the corresponding load current under forced ventilation conditions. Third, using the second numerical calculation model, the steady-state current carrying capacity of the target loop cable in the target tunnel is calculated under forced ventilation conditions where the inflow velocity is equal to the maximum inflow velocity obtained in the second step.

[0033] The numerical calculation framework proposed in this application enables accurate calculation of the steady-state current carrying capacity of cables under complex working conditions, as mentioned in this application, and has a wide range of applications. Specifically, it fully considers complex working conditions and realistically simulates the laying environment of tunnel cables under actual engineering conditions, resulting in high accuracy of the calculated steady-state current carrying capacity of cables. Secondly, unlike the analytical solution method which requires consideration of the specific laying method of cables due to the proximity effect and skin effect between cables in different loops when modeling a one-dimensional thermal circuit model, the calculation framework proposed in this application is not limited by the specific laying method of cables. It is applicable to common cable laying methods in tunnels, such as triangular laying and straight laying. Furthermore, it is applicable not only to AC cables but also to DC cables.

[0034] Figure 1 The flowchart shown is a specific embodiment of the cable steady-state current carrying capacity calculation method described above in this application. The specific embodiment includes the following steps 202 to 210.

[0035] Step 202: Model each circuit cable in the target tunnel to obtain the corresponding first numerical calculation model.

[0036] Preferably, to reduce computational load, shorten computation time, and reduce the demand for terminal computing power, in a specific implementation of this application, the first numerical calculation model is a two-dimensional numerical calculation model based on the finite element method. Therefore, step 202 includes steps a1 to a3.

[0037] Step a1: Obtain the actual engineering parameters of each circuit cable and its surrounding space within the target tunnel.

[0038] Step a2: Simulate the natural airflow inside the target tunnel using turbulent boundary conditions.

[0039] Step a3: For any loop cable in the target tunnel, based on the actual engineering parameters of each loop cable and its surrounding space in the target tunnel and the turbulent boundary conditions, perform finite element modeling of the loop cable and its surrounding space to obtain the first numerical calculation model for performing multiple two-dimensional physical field simulations of the loop cable during operation.

[0040] Specifically, the two-dimensional physical field includes electromagnetic fields and temperature fields. In the first numerical calculation model, the finite element solution equations and boundary conditions for the electromagnetic field and the temperature field are based on a standard embodiment, and will not be described in detail here. Since forced ventilation is not considered for the time being, i.e., only natural air convection is involved in the environment surrounding the cable loop, the establishment of boundary conditions for the temperature field finite element solution can also refer to a standard embodiment.

[0041] Understandably, to model the single-circuit cable and its surrounding space in the target tunnel and obtain the first numerical calculation model, it is necessary to first obtain the actual engineering parameters of the single-circuit cable and its surrounding space. Actual engineering parameters refer to the input parameters required for simulating various two-dimensional physical fields when the single-circuit cable is in operation. These include the material and structural dimensions of the cable's metallic parts, as well as related simulation input parameters for the cable's metallic parts; the material and structural dimensions of the cable's non-metallic parts, as well as related simulation input parameters for the cable's non-metallic parts; and the structural dimensions of the target tunnel and related simulation input parameters. The relevant simulation input parameters for the cable's metallic parts include electrical parameters related to the cable's current-carrying capacity calculation. The relevant simulation input parameters for the target tunnel include the parameters required for setting thermal boundary conditions.

[0042] Therefore, by using steps a1 to a3 to model a two-dimensional numerical calculation model of a single-loop cable using the finite element method, the current-carrying capacity of the cable under the complex operating conditions described in this application can be calculated rapidly. Thus, the cable current-carrying capacity calculation method proposed in this application simultaneously possesses the characteristics of high calculation accuracy, simple and efficient calculation process, and wide applicability.

[0043] To illustrate the specific application process of steps a1 to a3, we take the modeling of individual single-circuit cables in an actual cable tunnel as an example. The modeling is based on the finite element method to obtain two-dimensional finite element numerical calculation models (the first numerical calculation model) corresponding to each individual single-circuit cable, without considering heat transfer along the cable axis. Details are as follows.

[0044] The cable tunnel contains four 500kV AC ground cables (Cable A) and four 220kV AC ground cables (Cable B). Cable A and Cable B have different specifications and models. Figure 2 As shown, the cables in the cable tunnel are laid in a triangular configuration. For cable A, its conductor cross-sectional area is 2500 mm². 2 In a single circuit, all three cables have identical structural dimensions. Taking one phase cable as an example, the layers from the inside out are: copper conductor 1, conductor shielding layer 2, insulation layer 3, insulation shielding layer 4, buffer layer 5, aluminum sheath 6, anti-corrosion asphalt 7, outer sheath 8, and outer semiconductive layer 9. The spacing between the cables in the triangular arrangement is 0 mm. For cable B, its conductor cross-sectional area is 2500 mm². 2 It also adopts a triangular laying method.

[0045] Figure 2 The image shows a single-loop cable (cable A or cable B) and its surrounding space, which includes naturally flowing air, a cable tunnel made of concrete, and soil. Figure 2 The following are shown in order: air inside the cable tunnel 10, cable tunnel 11, and soil 12.

[0046] Based on the actual engineering parameters of the single-circuit cable and its surrounding space, the following assumptions are made when modeling the single-circuit cable and its surrounding space: the heat generated by the single-circuit cable comes from the electromagnetic loss of the copper conductor and the aluminum sheath. The hysteresis loss and dielectric hysteresis loss in the electromagnetic loss are ignored, and only the resistance loss is considered.

[0047] Meanwhile, the boundary conditions set during the modeling process are as follows: the naturally flowing air inside the target tunnel is set as a turbulent boundary condition; the thermal conductivity of the target tunnel is set to 1.8 W / (m·K); the thermal conductivity of the soil is set to 1.0 W / (m·K); the inner radius of the target tunnel is 1.8 m; the distance between the target tunnel and the soil surface is 2 m; the upper boundary of the soil is set to the ambient temperature, and since the upper surface of the soil will undergo convective heat transfer with the ambient environment, the convective heat transfer coefficient between the upper surface of the soil and the ambient environment is set to 10 W / (m·K). 2 •K); The left and right boundaries of the soil are set as thermally insulated boundary conditions; The lower boundary of the soil is set to a fixed temperature of 18℃.

[0048] When modeling a single-loop cable and its surrounding space, since the conductivity of metallic materials is temperature-dependent, the calculation methods for the unit length loss of copper conductors and aluminum sheaths are shown in Formula 1 and Formula 2 below: (Formula 1); (Formula 2).

[0049] In the formula: This represents the loss per unit length of metal, expressed in W / m. I c This represents the electric current flowing through a metal, measured in amperes (A). T c This indicates the temperature of the metal, expressed in °C. express T c Resistance of a metal at a given temperature, measured in Ω. This indicates the DC resistance of a metal at 20°C, expressed in Ω. This represents the temperature coefficient of DC resistance of a metal, with units of 1 / ℃.

[0050] When modeling a single-loop cable and its surrounding space, the simulation input parameters for the copper conductor and the aluminum sheath are shown in Table 1, and the simulation input parameters for the non-metallic materials of the single-loop cable are shown in Table 2.

[0051] Table 1

[0052] Table 2

[0053] Step 204: Using the current carrying capacity calculation process of each first numerical calculation model, determine the allowable load current of each circuit cable when it is put into operation under conditions without forced ventilation.

[0054] Understandably, for any loop cable, after modeling the loop cable, the steady-state current carrying capacity of the loop cable under conditions without forced ventilation can be determined through the simulation process of the corresponding first numerical calculation model. Based on the steady-state current carrying capacity of the loop cable and the proportion of cable load capacity in actual engineering applications, the allowable load current of the loop cable when it is put into operation can be determined.

[0055] Specifically, step 204 includes the following steps b1 to b2.

[0056] Step b1: Calculate the steady-state current carrying capacity of each circuit cable under conditions without forced ventilation using each of the first numerical calculation models.

[0057] Step b2: For any loop cable, take the steady-state current carrying capacity of the loop cable under no-forced ventilation conditions as the full load capacity, and determine the allowable load current of the loop cable when it is put into operation under no-forced ventilation conditions. The load current shall not exceed the full load capacity.

[0058] Step b2 converts the steady-state current carrying capacity calculated in step b1 into the allowable load current during operation, thus taking into account the cable current load in actual engineering conditions. The load current that fits the actual engineering conditions supports the subsequent calculation of the cable steady-state current carrying capacity under forced ventilation conditions. Especially for multi-circuit cables with large differences in actual engineering conditions, step b2 can differentiate their differences in actual engineering conditions.

[0059] For example, in actual engineering conditions, cables are typically operated at 40% to 60% of their full load capacity, for example, the load current is 60% of the full load capacity.

[0060] After modeling the single-circuit cable and its surrounding space, a two-dimensional finite element numerical calculation model for calculating the steady-state current carrying capacity of the cable in a high-voltage single-circuit tunnel is obtained. Understandably, the cable structure, simulation input parameters, and boundary conditions can be adjusted according to actual engineering applications. Based on the aforementioned two-dimensional finite element numerical calculation model, multiple two-dimensional physical field simulations of the single-circuit cable during operation are performed. Using 90℃ as the temperature threshold for the copper conductor (the allowable temperature for long-term operation), the steady-state current carrying capacity of the 500kV AC terrestrial cable under ambient temperatures of 30℃ and 35℃ without forced ventilation is calculated to be 2051A and 1982A, respectively. The steady-state current carrying capacity of the 220kV AC terrestrial cable under ambient temperatures of 35℃ without forced ventilation is calculated to be 1907A. Comparison with the analytical solution shows that the calculation results of the aforementioned two-dimensional finite element numerical calculation model differ from those of the analytical solution by no more than 10%, verifying the correctness of the model. The results are shown in Table 3 below.

[0061] Table 3

[0062] exist After calculating the steady-state current carrying capacity of the 500kV AC terrestrial cable and the 220kV AC terrestrial cable, and considering that the tunnel cable operates at 60% of its full load capacity in actual engineering conditions, the load current of the 500kV AC terrestrial cable is 1189.2A (1982A×60%), and the load current of the 220kV AC terrestrial cable is 1144.2A (1907A×60%).

[0063] Step 206: Model all loop cables in the target tunnel to obtain the second numerical calculation model.

[0064] Understandably, the second numerical calculation model is a numerical calculation model for multi-circuit cables in the same tunnel, which is different from the first numerical calculation model used to calculate the steady-state current carrying capacity of a single-circuit tunnel cable.

[0065] In one specific implementation, the second numerical calculation model is a two-dimensional numerical calculation model. Referring to the modeling process of the first numerical calculation model, step 206 includes the following steps c1 to c3.

[0066] Step c1: Obtain the actual engineering parameters of each circuit cable and its surrounding space within the target tunnel.

[0067] Step c2: Simulate the natural airflow inside the target tunnel using turbulent boundary conditions.

[0068] Step c3: Based on the actual engineering parameters of each loop cable and its surrounding space within the target tunnel and the turbulent boundary conditions, perform finite element modeling of the loop cable and its surrounding space to obtain a second numerical calculation model for performing multiple two-dimensional physical field simulations of all loop cables operating at their corresponding load currents.

[0069] Taking the modeling of four 500kV AC ground cables and four 220kV AC ground cables contained in the actual cable tunnel as an example, through steps c1 to c3, a cable current carrying capacity calculation model (second numerical calculation model) for eight circuit cables in the same cable tunnel is obtained. Figure 3 As shown, the four 220kV AC land cables are located above the four 500kV AC land cables.

[0070] Step 208: Using the current carrying capacity calculation process of the second numerical calculation model, determine the maximum inflow velocity that satisfies the forced ventilation activation conditions when all circuit cables are put into operation according to the corresponding load current under forced ventilation conditions.

[0071] An auxiliary forced ventilation system is installed within the target tunnel to provide forced convection air. Unlike natural convection, forced convection refers to flow caused by a pressure difference generated by external forces. The forced ventilation system in the cable tunnel is controlled by the real-time temperature within the tunnel. For example, the forced ventilation system starts operating when the air temperature inside the tunnel reaches 40°C and stops operating when the air temperature drops below 35°C. Therefore, the maximum inflow velocity required to meet the forced ventilation activation conditions is the critical inflow velocity. If the inflow velocity of the forced ventilation system exceeds this critical inflow velocity, the air temperature inside the tunnel falls below 35°C, and the forced ventilation activation conditions are not met, causing the forced ventilation system to stop operating.

[0072] In one specific implementation of this application, a temperature field simulation of the cable and its surrounding space is performed using a two-dimensional second numerical calculation model to determine the change process of air temperature distribution in the target tunnel with the inflow velocity of the forced ventilation system. The critical inflow velocity, i.e., the maximum inflow velocity that satisfies the forced ventilation activation condition, is then calculated as the maximum equivalent inflow velocity. Thus, step 208 includes the following steps d1 to d2.

[0073] Step d1: Using the simulation process of the second numerical calculation model, determine the two-dimensional air temperature field along the cable cross-section inside the target tunnel when all loop cables are put into operation according to the corresponding load current under conditions without forced ventilation.

[0074] Step d2: Use the second numerical calculation model to simulate the change of the two-dimensional air temperature field along the cable cross section in the target tunnel under forced ventilation conditions, and determine the maximum equivalent inflow velocity that meets the forced ventilation activation conditions.

[0075] Therefore, in the above technical solution, to minimize the computational load, shorten the computation time, and reduce the demand on terminal computing power, a two-dimensional temperature field simulation based on a second numerical calculation model is used. The maximum equivalent inflow velocity is determined by utilizing the simulated air temperature distribution within the tunnel that varies with the inflow velocity. This effectively satisfies the maximum inflow velocity required to activate forced ventilation, simplifying and accelerating the calculation process for the maximum inflow velocity. It is evident that the cable steady-state current-carrying capacity calculation method proposed in this application is simple and efficient, specifically reflected in: a two-dimensional first numerical calculation model; a two-dimensional second numerical calculation model; and the equivalent calculation of the maximum inflow velocity required to activate forced ventilation based on the two-dimensional second numerical calculation model.

[0076] In one specific implementation, step d2 includes: obtaining a plurality of sequentially increasing inflow velocity setting values; for any one of the sequentially increasing inflow velocity setting values, using a second numerical calculation model to simulate the change of the two-dimensional air temperature field along the cable cross-section in the target tunnel under forced ventilation conditions where the inflow velocity is equal to the inflow velocity setting value, to obtain the average temperature of the air environment in the target tunnel after the change; fitting a curve of the average temperature of the air environment in the target tunnel changing with the inflow velocity setting value, determining the critical equivalent inflow velocity that causes the forced ventilation system connected to the target tunnel to stop operating based on the curve, and determining the critical equivalent inflow velocity as the maximum equivalent inflow velocity that satisfies the forced ventilation activation conditions.

[0077] Understandably, after fitting the curve of the average temperature of the air environment in the target tunnel changing with the set value of the inflow velocity, the equivalent inflow velocity corresponding to the air environment temperature threshold in the curve is determined as the maximum equivalent inflow velocity that satisfies the forced ventilation activation condition. The air environment temperature threshold is the maximum value of the average temperature of the air environment in the target tunnel that enables the forced ventilation system to operate. If the average temperature of the air environment in the target tunnel is lower than the air environment temperature threshold, the forced ventilation system stops operating.

[0078] Specifically, to simulate forced ventilation conditions, an inflow boundary condition is added to the second numerical calculation model. Specifically, step d2 includes: for any given inflow velocity setting, establishing an inflow boundary condition where the inflow velocity is equal to that setting and the inflow direction is along the normal direction of the target tunnel wall, to simulate forced ventilation conditions within the target tunnel; adding the inflow boundary condition to the second numerical calculation model; and using the second numerical calculation model with the added inflow boundary condition to simulate the change in the two-dimensional air temperature field along the cable cross-section within the target tunnel.

[0079] For example, after establishing such Figure 3 After the second numerical calculation model shown, the model was used to simulate the two-dimensional temperature field along the cross-section of the cable in the actual cable tunnel when all circuit cables were put into operation according to the corresponding load current under the condition of no forced ventilation. At this time, the conductor temperature of the 500kV AC ground cable was 103.54℃ and the conductor temperature of the 220kV AC ground cable was 101.67℃, both of which exceeded the maximum operating temperature of 90℃. The average temperature of the air in the actual cable tunnel was 78.50℃.

[0080] Understandably, to determine the maximum equivalent inflow velocity that meets the conditions for forced ventilation activation, the design parameters of the forced ventilation system for the actual cable tunnel connection are obtained in advance. The design parameters of the forced ventilation system are: the forced ventilation system starts operating when the ambient temperature inside the tunnel reaches 40℃, and stops operating when the ambient temperature is below 35℃.

[0081] Based on this, after determining the average air temperature inside the actual cable tunnel when all circuit cables are connected at their corresponding load currents under conditions of no forced ventilation, an inflow boundary condition is added to the second numerical calculation model to simulate the forced ventilation condition in the cable tunnel, such as... Figure 4 As shown, the turbulence length in the turbulence boundary condition is set based on the tunnel geometry, and the turbulence intensity can be referenced from empirical values ​​for indoor air flow, for example, set to 0.05. As the inflow velocity increases, the average temperature of the air inside the tunnel shows a decreasing trend, such as... Figure 5 As shown. Calculations show that when the forced ventilation system is set to an inflow velocity of 0.028 m / s, the ambient temperature inside the tunnel (characterized by the average temperature of the air inside the tunnel) is 35℃. Therefore, the maximum equivalent inflow velocity is determined to be 0.028 m / s.

[0082] As the ambient temperature inside the tunnel decreases, the temperature of the cable conductor also decreases, such as... Figure 6 As shown, when the inflow velocity of the forced ventilation system is 0.028 m / s, the conductor temperature of the 500kV AC terrestrial cable is 49.74℃ and the conductor temperature of the 220kV AC terrestrial cable is 51.09℃, neither of which exceeds the maximum operating temperature of 90℃.

[0083] Step 210: Calculate the steady-state current carrying capacity of the target loop cable in the target tunnel under forced ventilation conditions where the inflow velocity is equal to the maximum inflow velocity determined in the previous step, using the second numerical calculation model.

[0084] Specifically, to simulate forced ventilation conditions, the inflow boundary condition for simulating forced ventilation is as follows: the inflow velocity is equal to the maximum inflow velocity determined in the previous step, and the inflow direction is along the normal direction of the tunnel wall. Then, keeping the load current of the non-target loop cable in the target tunnel constant, the load current of the target loop cable is increased. Through iteration, this continues until the conductor temperature of the target loop cable reaches the long-term operating allowable temperature. The load current corresponding to the conductor temperature of the target loop cable reaching the long-term operating allowable temperature is determined as the steady-state current carrying capacity of the target loop cable under multi-loop and forced ventilation conditions.

[0085] For example, taking one of the 500kV AC ground cables in the aforementioned actual cable tunnel as the target circuit cable, and the other circuit cables as non-target circuit cables, in... Figure 3 The second numerical calculation model shown adds an inflow boundary condition with the equivalent inflow velocity as the maximum equivalent inflow velocity determined in step 208. That is, in the inflow boundary condition simulating forced ventilation, the equivalent inflow velocity is 0.028 m / s, and the inflow direction is along the normal direction of the tunnel wall. Keeping the load current of the non-target loop cable unchanged, the load current of the target loop cable is increased. When the conductor temperature reaches 90°C, the corresponding load current is the steady-state current carrying capacity of the target loop cable under multi-loop and forced ventilation conditions. Figure 7 The diagram shows the temperature distribution of the target circuit cable when the conductor temperature reaches 90℃. When the load current of the target circuit cable is 2293A, the conductor temperature of the target circuit cable reaches 90℃. That is, under the complex working conditions of multiple cables installed in the tunnel, with two different specifications of cables among the multiple cables, and forced ventilation in the tunnel, the steady-state current carrying capacity of the 500kV AC terrestrial cable is 2293A.

[0086] In summary, unlike existing technologies, the embodiments of this application propose a numerical method-based framework for calculating the steady-state current carrying capacity of cables, applicable to the following complex working conditions: multiple circuits of cables of different specifications and models exist in the tunnel, and forced ventilation is present within the tunnel. Preferably, both the first numerical calculation model for calculating the steady-state current carrying capacity of a single circuit cable and the second numerical calculation model for calculating the steady-state current carrying capacity of multiple circuits of cables in the same tunnel are finite element two-dimensional numerical calculation models. That is, when the finite element two-dimensional numerical calculation model performs the cable steady-state current carrying capacity calculation, it simulates a two-dimensional planar field, does not consider the heat transfer along the cable axis, and assumes that cable heat dissipation also occurs along its cross-section. Simultaneously, based on the simulation of the two-dimensional temperature field by the second numerical calculation model, the change in ambient temperature within the tunnel with the inflow velocity of the forced ventilation system is determined, thereby equivalently determining the maximum inflow velocity that satisfies the forced ventilation activation condition, which serves as the equivalent inflow velocity for calculating the steady-state current carrying capacity of the target circuit cable under multi-circuit and forced ventilation conditions. This reduces the computational load, shortens the calculation time, enables rapid and accurate calculation of the cable steady-state current carrying capacity under complex working conditions, and has a wide range of applications.

[0087] The following is a specific application example based on the above calculation process framework. The steady-state current carrying capacity of the target loop cable in tunnel C is calculated using the cable steady-state current carrying capacity calculation method provided in this specific application example. Then, corresponding operation and maintenance operations are performed based on the calculated steady-state current carrying capacity of the target loop cable. In this example, multiple loop high-voltage cables are laid in tunnel C, and these loop high-voltage cables have at least two different specifications and models. The cores of these high-voltage cables are copper conductors. The specific calculation process for the steady-state current carrying capacity of the target loop cable in tunnel C includes steps S1 to S8.

[0088] Step S1: Based on the finite element method, a two-dimensional numerical calculation model is obtained for calculating the steady-state current carrying capacity of a single-circuit tunnel cable.

[0089] Step S2: Input the simulation input parameters of the target loop cable into the above two-dimensional numerical calculation model. Under the condition of no forced ventilation, with the copper conductor reaching the allowable temperature for long-term operation as the termination condition for iteration, calculate the steady-state current carrying capacity of the target loop cable.

[0090] Step S3: Input the simulation input parameters of the non-target loop cable into the two-dimensional finite element numerical calculation model constructed in step S1. Under the condition of no forced ventilation, with the copper conductor reaching the allowable temperature for long-term operation as the iteration termination condition, calculate the steady-state current carrying capacity of the non-target loop cable.

[0091] Step S4: Considering that the cable operates at 60% of its full load capacity in actual engineering, calculate the allowable load current of each circuit cable during operation based on the steady-state current carrying capacity obtained in steps S2 and S3.

[0092] Step S5: Based on the finite element method, a two-dimensional finite element numerical calculation model is obtained for calculating the steady-state cable current carrying capacity of multi-circuit tunnel cables in the same tunnel.

[0093] Step S6: After obtaining the steady-state current carrying capacity of various types of cables under single-circuit, no-forced ventilation conditions, refer to the cable load in actual engineering conditions, and use the two-dimensional finite element numerical calculation model constructed in step S5 to calculate the tunnel air environment temperature distribution of various types of cables under no-ventilation conditions and actual application load conditions.

[0094] Step S7: Based on the tunnel air environment temperature distribution obtained in step S6, add inflow boundary conditions to the two-dimensional finite element numerical calculation model constructed in step S5 to simulate forced ventilation in the tunnel, and calculate the maximum equivalent inflow velocity through steps d1 to d2.

[0095] Step S8: After obtaining the maximum equivalent inflow velocity, keep the load current of the non-target calculated cable circuit unchanged (i.e., keep it at 60% of the full load capacity), and increase the load current of the target calculated cable circuit. When the conductor temperature of the target calculated cable circuit reaches the allowable temperature for long-term operation, the corresponding load current is the steady-state current carrying capacity of the target circuit cable under the conditions of multiple circuits, different specifications and models of cables, and tunnel forced ventilation.

[0096] Corresponding to the cable steady-state current carrying capacity calculation method provided in the above embodiments, this application embodiment also provides a cable steady-state current carrying capacity calculation device, which includes: a first module, used to model each circuit cable in the target tunnel respectively, and obtain each first numerical calculation model accordingly; a second module, used to determine the allowable load current of each circuit cable when it is put into operation under the condition of no forced ventilation by using the current carrying capacity calculation process of each first numerical calculation model; a third module, used to model all circuit cables in the target tunnel and obtain a second numerical calculation model; a fourth module, used to determine the maximum inflow velocity that meets the forced ventilation activation condition when all circuit cables are put into operation under the condition of forced ventilation according to the corresponding load current by using the current carrying capacity calculation process of the second numerical calculation model; and a fifth module, used to calculate the steady-state current carrying capacity of the target circuit cable in the target tunnel under the forced ventilation condition where the inflow velocity is equal to the maximum inflow velocity by using the second numerical calculation model.

[0097] Specifically, the cable steady-state current carrying capacity calculation device can achieve, for example... Figure 1 The embodiments shown and other related method embodiments in this application. The process by which each module in the cable steady-state current carrying capacity calculation device provided in this application implements its respective function can be specifically referred to the foregoing. Figure 1 The descriptions of the embodiments shown and other related method embodiments are not repeated here.

[0098] It should be noted that the information interaction and execution process between the above modules are based on the same concept as the method embodiments of this application. Their specific functions and technical effects can be found in the method embodiments section, and will not be repeated here. Furthermore, all of the above modules can be applied to computing devices that include memory and a processor.

[0099] This application also provides a machine-readable storage medium storing a program that, when executed by a processor, implements the above-described method for calculating the steady-state current carrying capacity of cables.

[0100] This application provides a processor for running a program, wherein the program executes the above-described cable steady-state current carrying capacity calculation method during runtime.

[0101] In one embodiment, a computer device is also provided, which may be a terminal, and its internal structure diagram may be as follows: Figure 8 As shown in the figure, the computer device includes a processor A01, a network interface A02, a display screen A04, an input device A05, and a memory (not shown) connected via a system bus. The processor A01 provides computing and control capabilities. The memory includes internal memory A03 and a non-volatile storage medium A06. The non-volatile storage medium A06 stores an operating system B01 and a computer program B02. The internal memory A03 provides an environment for the operation of the operating system B01 and the computer program B02 stored in the non-volatile storage medium A06. The network interface A02 is used for communication with external terminals via a network connection. When the computer program is executed by the processor A01, it implements a method for calculating the steady-state current carrying capacity of a cable. The display screen A04 can be a liquid crystal display (LCD) or an e-ink display. The input device A05 can be a touch layer covering the display screen, buttons, a trackball, or a touchpad mounted on the computer device casing, or an external keyboard, touchpad, or mouse.

[0102] Those skilled in the art will understand that Figure 8 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0103] In one embodiment, the cable steady-state current-carrying capacity calculation device provided in this application can be implemented as a computer program, and the computer program can be implemented in such a way as... Figure 8The device operates on the computer shown. The computer's memory can store various program modules that make up the cable steady-state current-carrying capacity calculation device. The computer program, composed of these program modules, causes the processor to execute the steps in the cable steady-state current-carrying capacity calculation methods of the various embodiments of this application described in this specification.

[0104] This application provides an electronic device, which includes a processor, a memory, and a program stored in the memory and executable on the processor. When the processor executes the program, it implements the above-described method for calculating the steady-state current carrying capacity of cables.

[0105] This application also provides a computer program product that, when executed on a data processing device, is adapted to execute a program that initializes the steps of the various method embodiments described above.

[0106] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0107] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0108] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0109] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0110] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0111] Memory may include non-persistent memory in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory is an example of computer-readable media.

[0112] Computer-readable media include both permanent and non-permanent, removable and non-removable media, which can store information using any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.

[0113] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0114] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A method for calculating the steady-state current carrying capacity of a cable, characterized in that, The method for calculating the steady-state current carrying capacity of the cable includes: Each circuit cable in the target tunnel is modeled separately, and corresponding first numerical calculation models are obtained. The current carrying capacity calculation process of each first numerical calculation model is used to determine the allowable load current of each circuit cable when it is put into operation under the condition of no forced ventilation. Model all loop cables within the target tunnel to obtain a second numerical calculation model; The current carrying capacity calculation process of the second numerical calculation model is used to determine the maximum inflow velocity that satisfies the forced ventilation activation condition when all circuit cables are put into operation according to the corresponding load current under forced ventilation conditions. The steady-state current carrying capacity of the target loop cable in the target tunnel is calculated using the second numerical calculation model under forced ventilation conditions where the inflow velocity is equal to the maximum inflow velocity.

2. The method for calculating the steady-state current carrying capacity of a cable according to claim 1, characterized in that, The first numerical calculation model is a two-dimensional numerical calculation model; the step of modeling each loop cable in the target tunnel to obtain each corresponding first numerical calculation model includes: Obtain the actual engineering parameters of each circuit cable and its surrounding space within the target tunnel; The natural airflow within the target tunnel was simulated using turbulent boundary conditions. For any loop cable within the target tunnel, based on the actual engineering parameters and the turbulent boundary conditions, finite element modeling of the loop cable and its surrounding space is performed to obtain a first numerical calculation model for performing multiple two-dimensional physical field simulations of the loop cable during operation.

3. The method for calculating the steady-state current carrying capacity of a cable according to claim 1, characterized in that, The second numerical calculation model is a two-dimensional numerical calculation model; the modeling of all loop cables within the target tunnel to obtain the second numerical calculation model includes: Obtain the actual engineering parameters of each circuit cable and its surrounding space within the target tunnel; The natural airflow within the target tunnel was simulated using turbulent boundary conditions. Based on the actual engineering parameters and the turbulent boundary conditions, finite element modeling of all loop cables and their surrounding space is performed to obtain a second numerical calculation model for performing multiple two-dimensional physical field simulations of all loop cables when they are put into operation with the corresponding load current.

4. The method for calculating the steady-state current carrying capacity of a cable according to claim 1, characterized in that, The current-carrying capacity calculation process of each first numerical calculation model is used to determine the allowable load current of each circuit cable under conditions of no forced ventilation, including: The steady-state current carrying capacity of each loop cable under conditions without forced ventilation is calculated using the first numerical calculation model. For any loop cable, the steady-state current carrying capacity of the loop cable under no-forced ventilation conditions is taken as the full-load capacity. The allowable load current of the loop cable under no-forced ventilation conditions is determined, and the load current does not exceed the full-load capacity.

5. The method for calculating the steady-state current carrying capacity of a cable according to claim 1, characterized in that, The current-carrying capacity calculation process of the second numerical calculation model determines the maximum inflow velocity that satisfies the forced ventilation activation conditions when all circuit cables are put into operation at the corresponding load current under forced ventilation conditions, including: The current carrying capacity calculation process of the second numerical calculation model is used to determine the two-dimensional air temperature field along the cable cross-section in the target tunnel when all loop cables are put into operation at the corresponding load current under the condition of no forced ventilation. The second numerical calculation model is used to simulate the change of the two-dimensional air temperature field along the cable cross section in the target tunnel under forced ventilation conditions, and the maximum equivalent inflow velocity that meets the forced ventilation activation conditions is determined.

6. The method for calculating the steady-state current carrying capacity of a cable according to claim 5, characterized in that, The second numerical calculation model is used to simulate the change of the two-dimensional air temperature field along the cable cross-section inside the target tunnel under forced ventilation conditions, and the maximum equivalent inflow velocity that satisfies the forced ventilation activation conditions is determined, including: For any one of the multiple inflow velocity settings that are increased sequentially, the second numerical calculation model is used to simulate the change of the two-dimensional air temperature field along the cable cross section in the target tunnel under the forced ventilation condition where the inflow velocity is equal to the inflow velocity setting value, so as to obtain the average temperature of the air environment in the target tunnel after the change. The curve of the average temperature of the air environment inside the target tunnel changing with the set value of the inflow velocity is fitted. Based on the curve, the critical equivalent inflow velocity that causes the forced ventilation system connected to the target tunnel to stop operating is determined. The critical equivalent inflow velocity is determined as the maximum equivalent inflow velocity that satisfies the conditions for the activation of forced ventilation.

7. The method for calculating the steady-state current carrying capacity of a cable according to claim 6, characterized in that, For any one of a plurality of sequentially increasing inflow velocity settings, the second numerical calculation model is used to simulate the change in the two-dimensional air temperature field along the cable cross-section within the target tunnel under forced ventilation conditions where the inflow velocity equals that inflow velocity setting. This includes: For any given inflow velocity setting, establish an inflow boundary condition where the inflow velocity is equal to that setting and the inflow direction is along the normal direction of the target tunnel wall, in order to simulate the forced ventilation conditions inside the target tunnel. The inflow boundary condition is added to the second numerical calculation model; The change of the two-dimensional air temperature field along the cable cross-section inside the target tunnel was simulated using a second numerical calculation model after incorporating the aforementioned inflow boundary conditions.

8. A cable steady-state current carrying capacity calculation device, characterized in that, The cable steady-state current carrying capacity calculation device includes: The first module is used to model each loop cable in the target tunnel and obtain the corresponding first numerical calculation model. The second module is used to determine the allowable load current of each circuit cable when it is put into operation under conditions without forced ventilation by utilizing the current carrying capacity calculation process of each first numerical calculation model. The third module is used to model all loop cables in the target tunnel to obtain the second numerical calculation model. The fourth module is used to determine the maximum inflow velocity that satisfies the forced ventilation activation condition when all circuit cables are put into operation according to the corresponding load current under forced ventilation conditions, using the current carrying capacity calculation process of the second numerical calculation model. The fifth module is used to calculate the steady-state current carrying capacity of the target loop cable in the target tunnel under forced ventilation conditions where the inflow velocity is equal to the maximum inflow velocity, using the second numerical calculation model.

9. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the cable steady-state current carrying capacity calculation method according to any one of claims 1 to 7.

10. A machine-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the cable steady-state current carrying capacity calculation method according to any one of claims 1 to 7.

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