A method and system for predicting the current-carrying capacity of an alternating current cable

Abstract

The application provides a kind of AC cable current-carrying capacity prediction method and system, the method comprises: obtaining the first estimated current-carrying capacity of target cable, first estimated cable parameter and environmental parameter;The first estimated current-carrying capacity, the first estimated cable parameter and the environmental parameter are input to the preset simulation model, to make the simulation model output corresponding to the first estimated current-carrying capacity first predicted temperature value, wherein the simulation model includes electromagnetic field simulation calculation model and thermal simulation calculation model;When the first predicted temperature value is in the preset temperature range, the first estimated current-carrying capacity is output as predicted current-carrying capacity;When the first predicted temperature value is not in the preset temperature range, the first estimated current-carrying capacity is iteratively updated, until the second estimated current-carrying capacity corresponding to the second predicted temperature value after updating is located in the preset temperature range, and the second estimated current-carrying capacity is output as predicted current-carrying capacity, to improve the accuracy of current-carrying capacity prediction.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of simulation calculation and power equipment insulation technology, and particularly relates to a method and system for predicting the current-carrying capacity of an alternating current cable. BACKGROUND

[0002] An alternating current power cable is an important means of power transmission in a power transmission and distribution system, and has the characteristics of wide application, complex operating environment, and high reliability requirements. The current-carrying capacity, as an important indicator for measuring the performance of the cable, is subject to various factors. If the load current is too large, the temperature of the wire core is too high, which accelerates the aging process of the insulation and shortens the service life. If the load current is too small, the utilization rate is too low, which damages the economic benefits. For a tunnel cable, the engineering requirement is that the conductor temperature cannot be higher than 90℃, that is, the current corresponding to the conductor temperature of 90℃ under stable operating conditions is the current-carrying capacity.

[0003] Since the heat dissipation of the cable is greatly affected by the arrangement and the environment of the cable passage, and the heat exchange process is relatively complex during long-distance power transmission, the current experience formula cannot accurately calculate the temperature distribution of the cable conductor over the transmission distance, cannot accurately calculate the heat dissipation characteristics of the cable under different arrangement structures, wind speeds, loop numbers, and water cooling structures, and is not accurate enough for calculating the current-carrying capacity of the long-distance transmission cable. SUMMARY

[0004] To solve the above technical problems, the present application provides a method and system for predicting the current-carrying capacity of an alternating current cable, which combines a simulation model to predict the current-carrying capacity of a target cable and improves the accuracy of current-carrying capacity prediction.

[0005] In a first aspect, the present application provides a method for predicting the current-carrying capacity of an alternating current cable, comprising:

[0006] obtaining a first estimated current-carrying capacity, a first estimated cable parameter, and an environmental parameter of a target cable;

[0007] inputting the first estimated current-carrying capacity, the first estimated cable parameter, and the environmental parameter into a preset simulation model, so that the simulation model outputs a first predicted temperature value corresponding to the first estimated current-carrying capacity, wherein the simulation model comprises an electromagnetic field simulation calculation model and a thermal simulation calculation model, and the simulation model is constructed according to the laying mode and the heat dissipation mode of the target cable;

[0008] when the first predicted temperature value is within a preset temperature range, outputting the first estimated current-carrying capacity as a predicted current-carrying capacity;

[0009] when the first predicted temperature value is not in the preset temperature range, iteratively updating the first estimated current-carrying capacity until a second predicted temperature value corresponding to a second estimated current-carrying capacity is in the preset temperature range, and outputting the second estimated current-carrying capacity as the predicted current-carrying capacity; wherein the second predicted temperature value is calculated by the simulation model according to the second estimated current-carrying capacity, the first estimated cable parameter, and the environmental parameter.

[0010] The embodiment of the present application provides a current-carrying capacity prediction method of an alternating current cable. First, a first estimated current-carrying capacity and a first estimated cable parameter of a target cable are obtained, and an environmental parameter of an environment around the target cable is obtained. Then, the parameters are input into a simulation model constructed by an electromagnetic field simulation calculation model and a thermal simulation calculation model. A first predicted temperature value corresponding to the first estimated current-carrying capacity is obtained through simulation calculation. Then, whether the first predicted temperature value is in a preset temperature range is judged based on the definition of current-carrying capacity. The first estimated current-carrying capacity is iteratively updated based on the judgment result until a second predicted temperature value corresponding to a second estimated current-carrying capacity is in the preset temperature range. The second estimated current-carrying capacity is output as the predicted current-carrying capacity. The prediction of the current-carrying capacity of the target cable is realized. Compared with the prior art, the embodiment of the present application models the target cable by using the simulation model, and indirectly predicts the current-carrying capacity of the target cable by predicting the temperature of the target cable at a preset position by using the simulation model. The current-carrying capacity is directly calculated by using an empirical formula, and the embodiment of the present application iteratively updates the first estimated current-carrying capacity so that the predicted temperature corresponding to the current-carrying capacity is in the preset temperature range. The accuracy of the prediction of the current-carrying capacity of the target cable is improved. In addition, the simulation model of the embodiment of the present application is constructed based on the laying mode and the heat dissipation mode of the target cable. The heat dissipation characteristics of the cable under different arrangement structures, wind speeds, loop numbers and water cooling structures can be effectively adapted. The accuracy and flexibility of the prediction of the current-carrying capacity of the target cable are further improved.

[0011] In a possible implementation manner, the simulation model outputs a first predicted temperature value corresponding to the first estimated current-carrying capacity, and the method comprises the following steps.

[0012] The first estimated current-carrying capacity and the first estimated cable parameter are input into the electromagnetic field simulation calculation model, so that the electromagnetic field simulation calculation model outputs loss data of the target cable by using a finite element method. The estimated cable parameter comprises an estimated cable conductor temperature and an estimated cable medium attribute. The loss data comprises unit volume conductor loss data, shielding layer loss data and sheath loss data.

[0013] inputting the estimated cable medium properties, the loss data and the environment parameters into the thermal simulation calculation model, so that the thermal simulation calculation model outputs the first conductor average temperature of the target cable by using the finite volume method, wherein the environment parameters include temperature, pressure and velocity of air flow at a tunnel entrance;

[0014] judging whether the first conductor average temperature meets a preset condition, and if so, calculating the first predicted temperature value by the thermal simulation calculation model according to the loss data and the environment parameters;

[0015] if not, iteratively updating the first estimated cable parameters and the first conductor average temperature until the updated second conductor average temperature meets the preset condition, wherein in each iteration, the current first estimated cable parameters are updated according to the current first conductor average temperature to obtain updated second estimated cable parameters, and the current first conductor average temperature is updated according to the updated second estimated cable parameters, the first estimated ampacity and the environment parameters to obtain updated second conductor average temperature.

[0016] The embodiments of the present application provide a method for outputting a first predicted temperature value of a preset position of a target cable by a simulation model. Firstly, the first estimated ampacity and the first estimated cable parameters are used to perform electromagnetic field simulation model calculation by using the finite element method to obtain loss data of the target cable. Then, the loss data is further used to perform thermal simulation model calculation by using the finite volume method to obtain conductor average temperature, and the estimated cable conductor temperature in the estimated cable parameters is updated by the conductor average temperature. Then, the updated estimated cable conductor temperature is used to generate new conductor average temperature again until the conductor average temperature meets a preset condition. This is because the initially obtained first estimated ampacity and first estimated cable parameters are rough estimates, and thus the temperature value corresponding to the first estimated ampacity cannot be accurately calculated. Therefore, the embodiments of the present application use an iterative updating method to cyclically update the first estimated cable parameters and the first conductor average temperature until the first conductor average temperature meeting the preset condition is obtained. Then, the first predicted temperature value accurately corresponding to the first estimated ampacity is calculated by using the current first estimated cable parameters. The embodiments of the present application continuously adjust input data according to output results by a simulation model until the output results meet the prediction condition of the ampacity, so that the final prediction result is more accurate, data preparation for subsequent adjustment of the first estimated ampacity is made, and the accuracy of the prediction of the target cable ampacity is further improved.

[0017] Further, the judging whether the first conductor average temperature meets a preset condition comprises:

[0018] determining whether the absolute value of the difference between the first conductor average temperature and the estimated cable conductor temperature is less than a preset threshold value, and if the absolute value of the difference is less than the preset threshold value, determining that the first conductor average temperature meets the preset condition, otherwise determining that the first conductor average temperature does not meet the preset condition.

[0019] In the embodiment of the present application, whether the current first estimated cable parameter is accurate is evaluated by determining whether the absolute value of the difference between the first conductor average temperature and the estimated cable conductor temperature is less than a preset threshold value. Since the first conductor average temperature is calculated by the simulation model according to the first estimated current-carrying capacity, the first estimated cable parameter and the environmental parameter, when the first estimated cable parameter is accurate enough, the conductor average temperature calculated by the simulation is very close to the input estimated cable conductor temperature, so the embodiment of the present application sets whether the absolute value of the difference between the first conductor average temperature and the estimated cable conductor temperature is less than a preset threshold value as a preset condition, and further improves the accuracy of the target cable current-carrying capacity prediction.

[0020] Further, the first predicted temperature value is calculated by the thermal simulation calculation model according to the loss data and the environmental parameter, including:

[0021] The estimated cable medium attribute, the loss data and the environmental parameter are input into the thermal simulation calculation model, so that the thermal simulation calculation model outputs the conductor temperature curve of the target cable in the pre-design calculation domain;

[0022] If the pre-design calculation domain is greater than or equal to the preset position of the target cable, the first predicted temperature value of the preset position of the target cable is determined according to the conductor temperature curve;

[0023] If the pre-design calculation domain is less than the preset position, the first predicted temperature value of the preset position of the target cable is calculated by a polynomial function fitting method according to the conductor temperature curve.

[0024] The embodiment of the present application provides a method for calculating a first predicted temperature value. In general, the distance between two ventilation openings of an engineering tunnel is 500 m, but the calculation amount of establishing a complete 500 m tunnel thermal simulation model is huge, so the embodiment of the present application only calculates the conductor temperature curve of the target cable in the pre-design calculation domain. When the pre-design calculation domain is less than the preset position, for example, the calculation domain is 100 m and the preset position is 500 m, the first predicted temperature value of the target cable of 500 m is calculated by a polynomial function fitting method through the conductor temperature curve of the target cable of 100 m, which effectively reduces the calculation amount, improves the calculation efficiency of the system, realizes the prediction of the temperature of the long-distance conductor, and prepares data for the subsequent prediction of the cable current-carrying capacity of long-distance transmission.

[0025] In a possible implementation, when the first predicted temperature value is not within the preset temperature range, the first estimated current capacity is iteratively updated until a second predicted temperature value corresponding to a second estimated current capacity is within the preset temperature range, and the second estimated current capacity is output as the predicted current capacity, including:

[0026] When the first predicted temperature value is less than the lower limit of the preset temperature range, the value of the first estimated current capacity is gradually increased by a preset current difference until a third predicted temperature value corresponding to a third estimated current capacity is greater than the upper limit of the preset temperature range, and the first estimated current capacity and the third estimated current capacity are used to obtain the second estimated current capacity by using a dichotomy method.

[0027] When the first predicted temperature value is greater than the upper limit of the preset temperature range, the value of the first estimated current capacity is gradually decreased by a preset current difference until a third predicted temperature value corresponding to a third estimated current capacity is less than the lower limit of the preset temperature range, and the first estimated current capacity and the third estimated current capacity are used to obtain the second estimated current capacity by using a dichotomy method.

[0028] If the second predicted temperature value corresponding to the second estimated current capacity is within the preset temperature range, the second estimated current capacity is output as the predicted current capacity.

[0029] If the second predicted temperature value corresponding to the second estimated current capacity is not within the preset temperature range, the second estimated current capacity is used as the first estimated current capacity, and the first estimated current capacity is iteratively updated.

[0030] The method for adjusting an estimated current capacity provided in the embodiments of the present application determines an adjustment manner of the current capacity according to a difference between a first predicted temperature value and a preset temperature range, gradually increases or decreases the value of the first estimated current capacity to obtain a third estimated current capacity. Then, a second estimated current capacity between the first estimated current capacity and the third estimated current capacity is calculated by using a dichotomy method, and a second predicted temperature corresponding to the second estimated current capacity is calculated by using a simulation model. If the second predicted temperature is still not within the preset temperature range, the second estimated current capacity is continuously adjusted until a predicted temperature corresponding to a certain current capacity is within the preset temperature range, and the current capacity is output as the predicted current capacity. The embodiments of the present application continuously fine tune the estimated current capacity by using a cyclic iteration manner, ensure that an optimal solution of the target cable current capacity can be found, and accurately predict the current capacity.

[0031] Further, the preset temperature range is 89-90 degrees Celsius.

[0032] Further, the thermal simulation calculation model adopts a structured network.

[0033] Further, the laying mode of the target cable is a single-loop arrangement or a multi-loop arrangement.

[0034] Further, the heat dissipation mode of the target cable is air cooling, natural convection or water cooling.

[0035] In a second aspect, an embodiment of the present application provides a current-carrying capacity prediction system of an AC cable, comprising an acquisition module, a temperature prediction module, an output module and a current-carrying capacity updating module.

[0036] The acquisition module is configured to acquire a first estimated current-carrying capacity of a target cable, first estimated cable parameters and environmental parameters.

[0037] The temperature prediction module is configured to input the first estimated current-carrying capacity, the first estimated cable parameters and the environmental parameters into a preset simulation model, so that the simulation model outputs a first predicted temperature value corresponding to the first estimated current-carrying capacity, wherein the simulation model comprises an electromagnetic field simulation calculation model and a thermal simulation calculation model, and the simulation model is constructed according to the laying mode and the heat dissipation mode of the target cable.

[0038] The output module is configured to output the first estimated current-carrying capacity as a predicted current-carrying capacity when the first predicted temperature value is within a preset temperature range.

[0039] The current-carrying capacity updating module is configured to iteratively update the first estimated current-carrying capacity when the first predicted temperature value is not within the preset temperature range, until a second predicted temperature value corresponding to a second estimated current-carrying capacity is within the preset temperature range, and output the second estimated current-carrying capacity as a predicted current-carrying capacity, wherein the second predicted temperature value is calculated by the simulation model according to the second estimated current-carrying capacity, the first estimated cable parameters and the environmental parameters. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 FIG. 1 is a flowchart of a current-carrying capacity prediction method of an AC cable according to an embodiment of the present application.

[0041] Figure 2 FIG. 2 is a schematic diagram of a cable laying mode in a current-carrying capacity prediction method of an AC cable according to an embodiment of the present application.

[0042] Figure 3 FIG. 3 is a flowchart of calculating a predicted temperature value in a current-carrying capacity prediction method of an AC cable according to an embodiment of the present application.

[0043] Figure 4 FIG. 4 is a schematic diagram of loss data corresponding to different estimated current-carrying capacities in a current-carrying capacity prediction method of an AC cable according to an embodiment of the present application.

[0044] Figure 5 A schematic diagram of a geometric model of a thermal simulation calculation model of a 100m calculation domain in a method for predicting the current-carrying capacity of an alternating-current cable according to an embodiment of the present application.

[0045] Figure 6 A schematic diagram of a thermal simulation calculation model of a 100m calculation domain in a method for predicting the current-carrying capacity of an alternating-current cable according to an embodiment of the present application.

[0046] Figure 7 A schematic diagram of a conductor temperature curve and a fitting function in a method for predicting the current-carrying capacity of an alternating-current cable according to an embodiment of the present application.

[0047] Figure 8 A schematic diagram of a detailed step flow of a method for predicting the current-carrying capacity of an alternating-current cable according to an embodiment of the present application.

[0048] Figure 9 A schematic diagram of the structure of a system for predicting the current-carrying capacity of an alternating-current cable according to an embodiment of the present application. DETAILED DESCRIPTION

[0049] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all 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 work fall within the scope of protection of the present application.

[0050] It should be noted that the step numbers in the text are only for the convenience of explaining the specific embodiments, and do not serve as the basis for determining the execution sequence of the steps. In the description of the present application, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first" and "second" can explicitly or implicitly include one or more of the features.

[0051] Embodiment One:

[0052] As shown in Figure 1 Embodiment One provides a method for predicting the current-carrying capacity of an alternating-current cable, comprising steps S1-S4:

[0053] Step S1, obtaining the first estimated current-carrying capacity, the first estimated cable parameter and the environmental parameter of the target cable;

[0054] Step S2, inputting the first estimated current-carrying capacity, the first estimated cable parameter and the environmental parameter into a preset simulation model, so that the simulation model outputs a first predicted temperature value corresponding to the first estimated current-carrying capacity, wherein the simulation model comprises an electromagnetic field simulation calculation model and a thermal simulation calculation model, and the simulation model is constructed according to the laying mode and the heat dissipation mode of the target cable;

[0055] Step S3, when the first predicted temperature value is in the preset temperature range, outputting the first estimated current-carrying capacity as a predicted current-carrying capacity;

[0056] Step S4, when the first predicted temperature value is not in the preset temperature range, iteratively updating the first estimated current-carrying capacity until a second predicted temperature value corresponding to a second estimated current-carrying capacity is in the preset temperature range, and outputting the second estimated current-carrying capacity as a predicted current-carrying capacity; wherein the second predicted temperature value is calculated by the simulation model according to the second estimated current-carrying capacity, the first estimated cable parameter and the environmental parameter.

[0057] In a preferred embodiment, the laying mode of the target cable is as shown in Figure 2 .

[0058] The embodiments of the present application provide a current-carrying capacity prediction method of an alternating current cable. First, a first estimated current-carrying capacity and a first estimated cable parameter roughly estimated for a target cable are obtained, and an environmental parameter of an environment around the target cable is obtained. Then, the parameters are input into a simulation model constructed by an electromagnetic field simulation calculation model and a thermal simulation calculation model, and a first predicted temperature value corresponding to the first estimated current-carrying capacity is obtained through simulation calculation. Then, whether the first predicted temperature value is in a preset temperature range is judged based on the definition of current-carrying capacity, and the first estimated current-carrying capacity is iteratively updated based on the judgment result until a second predicted temperature value corresponding to a second estimated current-carrying capacity is in the preset temperature range, and the second estimated current-carrying capacity is output as a predicted current-carrying capacity, so that the prediction of the current-carrying capacity of the target cable is realized. Compared with the prior art, the embodiments of the present application model the target cable by using the simulation model, and indirectly predict the current-carrying capacity of the target cable by predicting the temperature at a preset position of the target cable by using the simulation model, so that the current-carrying capacity is directly calculated by using an empirical formula, and the embodiments of the present application make the predicted temperature corresponding to the current-carrying capacity fall into the preset temperature range by iteratively updating the first estimated current-carrying capacity, so that the accuracy of the prediction of the current-carrying capacity of the target cable is improved. In addition, the simulation model of the embodiments of the present application is constructed based on the laying mode and the heat dissipation mode of the target cable, so that the heat dissipation characteristics of the cable under different arrangement structures, wind speeds, loop numbers and water cooling structures can be effectively adapted, and the accuracy and flexibility of the prediction of the current-carrying capacity of the target cable are further improved.

[0059] In a possible implementation, in step S2, the simulation model outputs a first predicted temperature value corresponding to the first estimated load flow, as shown in Figure 3 The method comprises steps S201-S204, as shown in the figure:

[0060] In step S201, the first estimated load flow and the first estimated cable parameters are input into the electromagnetic field simulation calculation model, so that the electromagnetic field simulation calculation model outputs loss data of the target cable by using a finite element method, wherein the estimated cable parameters include an estimated cable conductor temperature and an estimated cable medium attribute, and the loss data includes conductor loss data, shielding layer loss data and sheath loss data per unit volume.

[0061] In step S202, the estimated cable medium attribute, the loss data and environmental parameters are input into the thermal simulation calculation model, so that the thermal simulation calculation model outputs a first conductor average temperature of the target cable by using a finite volume method, and the environmental parameters include a temperature, a pressure and a speed of a tunnel inlet airflow.

[0062] In step S203, it is determined whether the first conductor average temperature meets a preset condition, and if the preset condition is met, the first predicted temperature value is obtained by the thermal simulation calculation model according to the loss data and the environmental parameters.

[0063] In step S204, if the preset condition is not met, the first estimated cable parameters and the first conductor average temperature are iteratively updated until a second conductor average temperature after updating meets the preset condition, and in each iteration updating process, the first estimated cable parameters are updated according to the current first conductor average temperature to obtain second estimated cable parameters after updating, and the current first conductor average temperature is updated according to the second estimated cable parameters after updating, the first estimated load flow and the environmental parameters to obtain the second conductor average temperature after updating.

[0064] The method for outputting a first predicted temperature value of a preset position of a target cable through a simulation model provided by the embodiment of the present application first adopts a finite element method to perform electromagnetic field simulation model calculation according to a first estimated current-carrying capacity and a first estimated cable parameter, obtains loss data of the target cable, then further adopts a finite volume method to perform thermal simulation model calculation according to the loss data, obtains a conductor average temperature, and updates an estimated cable conductor temperature in the estimated cable parameter through the conductor average temperature, then uses the updated estimated cable conductor temperature to generate a new conductor average temperature again until the conductor average temperature meets a preset condition. This is because the first estimated current-carrying capacity and the first estimated cable parameter obtained initially are rough estimates, and therefore the temperature value corresponding to the first estimated current-carrying capacity cannot be accurately calculated. Therefore, the embodiment of the present application adopts an iterative updating method to cyclically update the first estimated cable parameter and the first conductor average temperature until the first conductor average temperature meeting the preset condition is obtained, and then uses the current first estimated cable parameter to calculate a first predicted temperature value accurately corresponding to the first estimated current-carrying capacity. The embodiment of the present application continuously adjusts input data according to output results through a simulation model until the output results meet the prediction condition of the current-carrying capacity, so that the final prediction result is more accurate, data preparation for subsequent adjustment of the first estimated current-carrying capacity is made, and the accuracy of the prediction of the current-carrying capacity of the target cable is further improved.

[0065] In a preferred embodiment, the estimated cable medium properties include the dielectric constant, electrical conductivity, thermal conductivity of each layer of the cable, and the thermal conductivity of the tunnel soil. In step S201, the first estimated current-carrying capacity, the estimated cable conductor temperature, the dielectric constant and the electrical conductivity of each layer of the cable are input into the electromagnetic field simulation calculation model, so that the electromagnetic field simulation calculation model calculates the magnetic field, current and electric field distribution of the target cable by the finite element method, calculates the cable conductor loss, shielding layer loss and sheath loss per unit volume as the heat source condition of the thermal simulation calculation model, wherein the conductor loss, shielding layer loss and sheath loss calculation results under different estimated current-carrying capacities are as shown in FIG. 2. Figure 4 In step S202, the loss data, the thermal conductivity of each layer of the cable and the thermal conductivity of the tunnel soil are input into the thermal simulation calculation model of the 100m calculation domain, so that the thermal simulation calculation model performs thermal simulation calculation to obtain the first conductor average temperature, wherein the geometric model of the thermal simulation calculation model of the 100m calculation domain is as shown in FIG. 3, and the thermal simulation calculation model of the 100m calculation domain is as shown in FIG. 4. Figure 5 In step S202, the loss data, the thermal conductivity of each layer of the cable and the thermal conductivity of the tunnel soil are input into the thermal simulation calculation model of the 100m calculation domain, so that the thermal simulation calculation model performs thermal simulation calculation to obtain the first conductor average temperature, wherein the geometric model of the thermal simulation calculation model of the 100m calculation domain is as shown in FIG. 3, and the thermal simulation calculation model of the 100m calculation domain is as shown in FIG. 4. Figure 6 The electromagnetic field simulation model calculation based on the finite element method and the thermal simulation model calculation combined by the embodiment of the present application can accurately obtain the conductor loss, the shielding layer loss, the sheath loss, the conductor temperature distribution, the current-carrying capacity, the air temperature rise amplitude in the tunnel, etc., and has higher accuracy compared with the empirical formula.

[0066] Further, in step S203, the determining whether the first conductor average temperature satisfies a preset condition comprises:

[0067] determining whether an absolute value of a difference between the first conductor average temperature and the estimated cable conductor temperature is less than a preset threshold value, and if the absolute value of the difference is less than the preset threshold value, determining that the first conductor average temperature satisfies the preset condition, otherwise, determining that the first conductor average temperature does not satisfy the preset condition.

[0068] In a preferred embodiment, the preset threshold value is 1 degree Celsius.

[0069] In the embodiments of the present application, whether the current first estimated cable parameter is accurate is evaluated by determining whether an absolute value of a difference between the first conductor average temperature and the estimated cable conductor temperature is less than a preset threshold value. Since the first conductor average temperature is calculated by the simulation model according to the first estimated current-carrying capacity, the first estimated cable parameter and the environmental parameter, when the first estimated cable parameter is accurate enough, the conductor average temperature calculated by the simulation model is very close to the input estimated cable conductor temperature, therefore, the present application sets whether the absolute value of the difference between the first conductor average temperature and the estimated cable conductor temperature is less than a preset threshold value as a preset condition, which further improves the accuracy of the target cable current-carrying capacity prediction.

[0070] Further, in step S204, the first predicted temperature value is calculated by the thermal simulation calculation model according to the loss data and the environmental parameter, comprising:

[0071] inputting the estimated cable medium attribute, the loss data and the environmental parameter into the thermal simulation calculation model, so that the thermal simulation calculation model outputs a conductor temperature curve of the target cable in a preset calculation domain;

[0072] if the preset calculation domain is greater than or equal to a preset position of the target cable, determining the first predicted temperature value of the preset position of the target cable according to the conductor temperature curve;

[0073] if the preset calculation domain is less than the preset position, calculating the first predicted temperature value of the preset position of the target cable by a polynomial function fitting method according to the conductor temperature curve.

[0074] In a preferred embodiment, the calculation domain is 100 m, the preset position of the target cable is 500 m, and the conductor temperature curve and the fitting function are as shown in Figure 7 .

[0075] The embodiment of the present application provides a method for calculating a first predicted temperature value. In general, the distance between two ventilation openings of an engineering tunnel is 500 m, but the calculation amount of a complete 500 m tunnel thermal simulation model is huge, therefore, the embodiment of the present application only calculates the conductor temperature curve of the target cable in a pre-design calculation domain. When the pre-design calculation domain is smaller than the preset position, for example, the calculation domain is 100 m and the preset position is 500 m, the first predicted temperature value of the target cable in 500 m is obtained through the conductor temperature curve of the target cable in 100 m by using a polynomial function fitting mode, so that the calculation amount is effectively reduced, the calculation efficiency of the system is improved, the prediction of the conductor temperature of a long distance is realized, and data preparation is made for subsequent prediction of the cable ampacity of long distance transmission.

[0076] In a possible implementation, in step S4, when the first predicted temperature value is not in the preset temperature range, the first estimated ampacity is iteratively updated until the second estimated ampacity corresponding to the second predicted temperature value in the preset temperature range is obtained, and the second estimated ampacity is output as the predicted ampacity, including:

[0077] When the first predicted temperature value is less than the lower limit of the preset temperature range, the value of the first estimated ampacity is gradually increased by a preset current difference value until the third predicted temperature value corresponding to the third estimated ampacity after the increase is greater than the upper limit of the preset temperature range, and the first estimated ampacity and the third estimated ampacity are used to obtain the second estimated ampacity by using a dichotomy method;

[0078] When the first predicted temperature value is greater than the upper limit of the preset temperature range, the value of the first estimated ampacity is gradually reduced by a preset current difference value until the third predicted temperature value corresponding to the third estimated ampacity after the reduction is less than the lower limit of the preset temperature range, and the first estimated ampacity and the third estimated ampacity are used to obtain the second estimated ampacity by using a dichotomy method;

[0079] If the second predicted temperature value corresponding to the second estimated ampacity is in the preset temperature range, the second estimated ampacity is output as the predicted ampacity;

[0080] If the second predicted temperature value corresponding to the second estimated ampacity is not in the preset temperature range, the second estimated ampacity is used as the first estimated ampacity, and the first estimated ampacity is iteratively updated.

[0081] Taking the preset temperature range of 89 degrees Celsius to 91 degrees Celsius as an example, the specific operation of the above process is performed in two stages.

[0082] (1) Determine the value range of the predicted ampacity

[0083] When the predicted temperature corresponding to the first estimated current-carrying capacity is less than 89℃, the value of the first estimated current-carrying capacity is gradually increased, and the electromagnetic field simulation model calculation and the thermal simulation model calculation are performed until the predicted temperature corresponding to a third estimated current-carrying capacity exceeds 91℃. At this time, the third estimated current-carrying capacity is the maximum value, and the first estimated current-carrying capacity is the minimum value.

[0084] When the predicted temperature corresponding to the first estimated current-carrying capacity is greater than 91℃, the value of the first estimated current-carrying capacity is gradually reduced, and the electromagnetic field simulation model calculation and the thermal simulation model calculation are performed until the predicted temperature corresponding to a third estimated current-carrying capacity is less than 89℃. At this time, the third estimated current-carrying capacity is the minimum value, and the first estimated current-carrying capacity is the maximum value.

[0085] (2) The value of the current is adjusted by using the dichotomy method in the value range of the predicted current-carrying capacity, a second estimated current-carrying capacity is obtained, and the electromagnetic field simulation model calculation and the thermal simulation model calculation are performed again until the second estimated current-carrying capacity meets the judgment condition, the predicted current-carrying capacity is obtained, and is output. The detailed step flow chart of the embodiment of the application is shown in Figure 8

[0086] The embodiment of the application provides a method for adjusting the estimated current-carrying capacity. The adjustment mode of the current-carrying capacity is determined according to the difference between the first predicted temperature value and the preset temperature range, the value of the first estimated current-carrying capacity is gradually increased or reduced, and the third estimated current-carrying capacity is obtained. Then, the second estimated current-carrying capacity between the first estimated and the third estimated current-carrying capacity is calculated by using the dichotomy method, and the second predicted temperature corresponding to the second estimated current-carrying capacity is calculated through the simulation model. If the second predicted temperature is still not in the preset temperature range, the second estimated current-carrying capacity is continuously adjusted until the predicted temperature corresponding to a certain current-carrying capacity value is in the preset temperature range, and the current-carrying capacity is output as the predicted current-carrying capacity. The embodiment of the application continuously fine-tunes the estimated current-carrying capacity in a cyclic iteration manner, ensures that the optimal solution of the target cable current-carrying capacity can be found, and realizes the accurate prediction of the current-carrying capacity.

[0087] Further, the preset temperature range is 89-90 degrees Celsius.

[0088] Further, the thermal simulation calculation model adopts a structured network.

[0089] Further, the laying mode of the target cable is single-loop arrangement or multi-loop arrangement.

[0090] Further, the heat dissipation mode of the target cable is air cooling, natural convection heat exchange or water cooling heat exchange.

[0091] ​In a preferred embodiment, the embodiments of the present application can optimize different influencing factors based on the same scene. When the laying mode of the target cable is optimized, the ampacity of the cable under different laying modes can be calculated and analyzed to help the staff effectively determine the optimal cable arrangement mode. In the multi-loop arrangement mode, the ampacity of the cable arranged in the tunnel in multiple loops can be calculated and analyzed to effectively determine the most reasonable number of loops of the cable. When the wind speed of the target cable is optimized, the ampacity of the tunnel under different wind speed conditions can be calculated and analyzed to effectively determine the most reasonable wind speed value. When the heat dissipation mode of the target cable is optimized, the embodiments of the present application support the calculation and analysis of the ampacity of the cable in the tunnel with the added water cooling pipe, which can effectively determine the impact of the added water cooling pipe on the ampacity.

[0092] Embodiment two

[0093] As Figure 9 shown, accordingly, embodiment two provides an AC cable ampacity prediction system, comprising an acquisition module 10, a temperature prediction module 20, an output module 30, and an ampacity updating module 40.

[0094] The acquisition module 10 is configured to acquire a first estimated ampacity of a target cable, first estimated cable parameters, and environmental parameters.

[0095] The temperature prediction module 20 is configured to input the first estimated ampacity, the first estimated cable parameters, and the environmental parameters into a preset simulation model, so that the simulation model outputs a first predicted temperature value corresponding to the first estimated ampacity. The simulation model includes an electromagnetic field simulation calculation model and a thermal simulation calculation model, which are constructed according to the laying mode and the heat dissipation mode of the target cable.

[0096] The output module 30 is configured to output the first estimated ampacity as a predicted ampacity when the first predicted temperature value is within a preset temperature range.

[0097] The ampacity updating module 40 is configured to iteratively update the first estimated ampacity when the first predicted temperature value is not within the preset temperature range, until a second predicted temperature value corresponding to a second estimated ampacity after the update is within the preset temperature range, and output the second estimated ampacity as a predicted ampacity. The second predicted temperature value is calculated by the simulation model according to the second estimated ampacity, the first estimated cable parameters, and the environmental parameters.

[0098] The more detailed working principle and step flow of the present embodiment can be but not limited to the related records of embodiment one.

[0099] The above-described specific embodiments, purposes, technical solutions and beneficial effects of the present application are further described in detail, and it should be understood that the above-described is only a specific embodiment of the present application and is not used to limit the protection scope of the present application. It is particularly pointed out that for those skilled in the art, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method of predicting ampacity of an alternating current cable, characterized by, The method comprises: obtaining a first estimated current-carrying capacity, a first estimated cable parameter and an environmental parameter of a target cable; inputting the first estimated current-carrying capacity, the first estimated cable parameter and the environmental parameter into a preset simulation model, so that the simulation model outputs a first predicted temperature value corresponding to the first estimated current-carrying capacity, wherein the simulation model comprises an electromagnetic field simulation calculation model and a thermal simulation calculation model, and the simulation model is constructed according to a laying mode and a heat dissipation mode of the target cable; the simulation model outputs a first predicted temperature value corresponding to the first estimated current-carrying capacity, comprising: inputting the first estimated current-carrying capacity and the first estimated cable parameter into the electromagnetic field simulation calculation model, so that the electromagnetic field simulation calculation model outputs loss data of the target cable by using a finite element method, wherein the estimated cable parameter comprises an estimated cable conductor temperature and an estimated cable medium attribute, and the loss data comprises conductor loss data, shielding layer loss data and sheath loss data per unit volume; inputting the estimated cable medium attribute, the loss data and the environmental parameter into the thermal simulation calculation model, so that the thermal simulation calculation model outputs a first conductor average temperature of the target cable by using a finite volume method, and the environmental parameter comprises temperature, pressure and velocity of air flow at a tunnel entrance; determining whether the first conductor average temperature meets a preset condition, if the first conductor average temperature meets the preset condition, then according to the loss data and the environmental parameter, the first predicted temperature value is calculated by using the thermal simulation calculation model; if the first conductor average temperature does not meet the preset condition, then the first estimated cable parameter and the first conductor average temperature are iteratively updated until a second conductor average temperature after updating meets the preset condition, in each iteration updating process, the first estimated cable parameter is updated according to the current first conductor average temperature to obtain a second estimated cable parameter after updating, and the current first conductor average temperature is updated according to the second estimated cable parameter after updating, the first estimated current-carrying capacity and the environmental parameter to obtain a second conductor average temperature after updating; when the first predicted temperature value is within a preset temperature range, the first estimated current-carrying capacity is output as a predicted current-carrying capacity; when the first predicted temperature value is not within the preset temperature range, the first estimated current-carrying capacity is iteratively updated until a second predicted temperature value corresponding to a second estimated current-carrying capacity after updating is within the preset temperature range, and the second estimated current-carrying capacity is output as the predicted current-carrying capacity, wherein the second predicted temperature value is calculated by the simulation model according to the second estimated current-carrying capacity, the first estimated cable parameter and the environmental parameter.

2. A method of predicting ampacity of an AC power cable as claimed in claim 1, wherein, the determination of whether the first conductor average temperature meets the preset condition comprises: determining whether an absolute value of a difference between the first conductor average temperature and the estimated cable conductor temperature is less than a preset threshold, if the absolute value is less than the preset threshold, it is determined that the first conductor average temperature meets the preset condition, otherwise it is determined that the first conductor average temperature does not meet the preset condition.

3. A method of predicting ampacity of an AC power cable as claimed in claim 1, wherein, The first predicted temperature value is calculated according to the loss data and the environmental parameters through the thermal simulation calculation model, and the calculation includes: The estimated cable medium attribute, the loss data and the environmental parameters are input into the thermal simulation calculation model, so that the thermal simulation calculation model outputs a conductor temperature curve of the target cable in a pre-designed calculation domain; If the pre-designed calculation domain is greater than or equal to the preset position of the target cable, a first predicted temperature value of the preset position of the target cable is determined according to the conductor temperature curve; If the pre-designed calculation domain is less than the preset position, a first predicted temperature value of the preset position of the target cable is calculated through a polynomial function fitting method according to the conductor temperature curve.

4. A method of predicting ampacity of an AC power cable as defined in claim 1, characterized in that, When the first predicted temperature value is not in the preset temperature range, the first estimated current-carrying capacity is iteratively updated until a second predicted temperature value corresponding to a second estimated current-carrying capacity after the update is located in the preset temperature range, and the second estimated current-carrying capacity is output as a predicted current-carrying capacity, and the updating includes: When the first predicted temperature value is less than a lower limit of the preset temperature range, the value of the first estimated current-carrying capacity is gradually increased by a preset current difference until a third predicted temperature value corresponding to a third estimated current-carrying capacity after the increase is greater than an upper limit of the preset temperature range, and the first estimated current-carrying capacity and the third estimated current-carrying capacity are used to obtain the second estimated current-carrying capacity by using a dichotomy method; When the first predicted temperature value is greater than the upper limit of the preset temperature range, the value of the first estimated current-carrying capacity is gradually decreased by a preset current difference until a third predicted temperature value corresponding to a third estimated current-carrying capacity after the decrease is less than the lower limit of the preset temperature range, and the first estimated current-carrying capacity and the third estimated current-carrying capacity are used to obtain the second estimated current-carrying capacity by using a dichotomy method; If the second predicted temperature value corresponding to the second estimated current-carrying capacity is located in the preset temperature range, the second estimated current-carrying capacity is output as a predicted current-carrying capacity; If the second predicted temperature value corresponding to the second estimated current-carrying capacity is not located in the preset temperature range, the second estimated current-carrying capacity is taken as the first estimated current-carrying capacity, and the first estimated current-carrying capacity is iteratively updated.

5. A method of predicting ampacity of an AC power cable according to any one of claims 1-4, characterized in that, The preset temperature range is 89-90 degrees Celsius.

6. A method of predicting ampacity of an AC power cable according to any one of claims 1-4, characterized in that, The thermal simulation calculation model adopts a structured network.

7. A method of predicting ampacity of an AC power cable according to any one of claims 1-4, characterized in that, The target cable is arranged in a single loop or a multi-loop.

8. A method of predicting ampacity of an AC power cable according to any one of claims 1-4, characterized in that, The heat dissipation mode of the target cable is air cooling, natural convection or water cooling.

9. A current-carrying capacity prediction system for an alternating current cable, characterized by The method includes an acquisition module, a temperature prediction module, an output module and a current-carrying capacity updating module. The acquisition module is used to acquire a first estimated current-carrying capacity of a target cable, first estimated cable parameters and environmental parameters. The temperature prediction module is configured to input the first estimated load flow, the first estimated cable parameter and the environmental parameter into a preset simulation model, so that the simulation model outputs a first predicted temperature value corresponding to the first estimated load flow, wherein the simulation model comprises an electromagnetic field simulation calculation model and a thermal simulation calculation model, and the simulation model is constructed according to a laying mode and a heat dissipation mode of the target cable. The simulation model outputs a first predicted temperature value corresponding to the first estimated load flow, comprising: inputting the first estimated load flow and the first estimated cable parameter into the electromagnetic field simulation calculation model, so that the electromagnetic field simulation calculation model outputs loss data of the target cable by using a finite element method, wherein the estimated cable parameter comprises an estimated cable conductor temperature and an estimated cable medium attribute, and the loss data comprises conductor loss data, shielding layer loss data and sheath loss data per unit volume; inputting the estimated cable medium attribute, the loss data and the environmental parameter into the thermal simulation calculation model, so that the thermal simulation calculation model outputs a first conductor average temperature of the target cable by using a finite volume method, wherein the environmental parameter comprises temperature, pressure and velocity of air flow at a tunnel inlet; judging whether the first conductor average temperature meets a preset condition, if the first conductor average temperature meets the preset condition, calculating the first predicted temperature value by the thermal simulation calculation model according to the loss data and the environmental parameter; if the first conductor average temperature does not meet the preset condition, iteratively updating the first estimated cable parameter and the first conductor average temperature until a second conductor average temperature after updating meets the preset condition, in each iteration updating process, updating the first estimated cable parameter according to the current first conductor average temperature to obtain a second estimated cable parameter after updating, and updating the current first conductor average temperature according to the second estimated cable parameter after updating, the first estimated load flow and the environmental parameter to obtain a second conductor average temperature after updating; The output module is configured to output the first estimated load flow as a predicted load flow when the first predicted temperature value is in a preset temperature range. The load flow updating module is configured to iteratively update the first estimated load flow when the first predicted temperature value is not in the preset temperature range until a second predicted temperature value corresponding to a second estimated load flow after updating is in the preset temperature range, and output the second estimated load flow as a predicted load flow, wherein the second predicted temperature value is calculated by the simulation model according to the second estimated load flow, the first estimated cable parameter and the environmental parameter.

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