Current-carrying capacity prediction method and system of AC cable

Abstract

The invention provides a current-carrying capacity prediction method and system for an AC cable. The method comprises the steps of obtaining a first estimated current-carrying capacity, a first estimated cable parameter and an environmental parameter of a target cable; the first estimated current-carrying capacity, the first estimated cable parameters and the environmental parameters are input into a preset simulation model, so that the simulation model outputs a first predicted temperature value corresponding to the first estimated current-carrying capacity, and the simulation model comprises an electromagnetic field simulation calculation model and a thermal simulation calculation model; when the first predicted temperature value is in a preset temperature range, outputting the first predicted current-carrying capacity as predicted current-carrying capacity; and when the first predicted temperature value is not within the preset temperature range, iteratively updating the first estimated current-carrying capacity until a second predicted temperature value corresponding to the updated second estimated current-carrying capacity is within the preset temperature range, and outputting the second estimated current-carrying capacity as the predicted current-carrying capacity, thereby improving 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 in particular to a method and system for predicting the current carrying capacity of an AC cable. Background Art

[0002] AC power cable is an important means of power transmission in the power transmission and distribution system. It has the characteristics of wide application, complex operating environment, and high reliability requirements. As an important indicator to measure the performance of cables, the current carrying capacity is restricted by many factors. If the load current is too large, the core temperature will be too high, which will accelerate the insulation aging process and shorten the service life; if the load current is too small, the economic benefits will be damaged due to low utilization. For tunnel cables, the engineering requires that the conductor temperature cannot be higher than 90°C, that is, the current corresponding to the conductor temperature reaching 90°C under stable operating conditions is the current carrying capacity.

[0003] Since the heat dissipation of cables is greatly affected by the layout method and the cable channel environment, and the heat exchange process during long-distance cable transmission is relatively complicated, the current empirical formula cannot accurately calculate the temperature distribution law of the cable conductor over the transmission distance, and cannot accurately calculate the heat dissipation characteristics of cables under different layout structures, wind speeds, number of loops and water-cooling structures. It is not accurate enough for calculating the current carrying capacity of cables for long-distance transmission. Summary of the invention

[0004] In response to the above technical problems, the present application provides a method and system for predicting the current carrying capacity of an AC cable, which combines a simulation model to predict the current carrying capacity of a target cable, thereby improving the accuracy of the current carrying capacity prediction.

[0005] In a first aspect, an embodiment of the present application provides a method for predicting the current carrying capacity of an AC 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 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 includes an electromagnetic field simulation calculation model and a thermal simulation calculation model, and the simulation model is constructed according to the laying method and heat dissipation method 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 within the preset temperature range, the first estimated current-carrying capacity is iteratively updated until the second predicted temperature value corresponding to the updated second estimated current-carrying capacity 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 based on the second estimated current-carrying capacity, the first estimated cable parameters and the environmental parameters.

[0010] The embodiment of the present application provides a method for predicting the current carrying capacity of an AC cable. First, a roughly estimated first estimated current carrying capacity and a first estimated cable parameter of a target cable are obtained, as well as the environmental parameters of the surrounding environment of the target cable. Then, these 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 by simulation calculation. Then, based on the definition of current carrying capacity, it is judged whether the current first predicted temperature value is within a preset temperature range, and the first estimated current carrying capacity is iteratively updated based on the judgment result until the second predicted temperature value corresponding to the updated second estimated current carrying capacity is within the preset temperature range, and the second estimated current carrying capacity is output as the predicted current carrying capacity, thereby realizing the prediction of the current carrying capacity of the target cable. Compared with the prior art, the embodiment of the present application uses a simulation model to model the target cable, and uses the simulation model to predict the temperature of the preset position of the target cable to indirectly predict the current carrying capacity of the target cable, thereby avoiding the use of an empirical formula to directly calculate the current carrying capacity. At the same time, 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 falls within the preset temperature range, thereby improving the accuracy of the prediction of the current carrying capacity of the target cable. In addition, the simulation model of the embodiment of the present application is constructed based on the laying method and heat dissipation method of the target cable, and can effectively adapt to the heat dissipation characteristics of the cable under different layout structures, wind speeds, number of loops and water cooling structures, further improving the accuracy and flexibility of the prediction of the current carrying capacity of the target cable.

[0011] In a possible implementation, the simulation model outputs a first predicted temperature value corresponding to the first estimated current carrying capacity, including:

[0012] Inputting the first estimated current carrying capacity and the first estimated cable parameters into the electromagnetic simulation calculation model, so that the electromagnetic simulation calculation model outputs loss data of the target cable using a finite element method, wherein the estimated cable parameters include estimated cable conductor temperature and estimated cable dielectric properties, and the loss data include conductor loss data per unit volume, shielding layer loss data, and sheath loss data;

[0013] Inputting the estimated cable dielectric properties, loss data and the environmental parameters into the thermal simulation calculation model so that the thermal simulation calculation model outputs the average temperature of the first conductor of the target cable using a finite volume method, wherein the environmental parameters include the temperature, pressure and velocity of the tunnel inlet airflow;

[0014] Determine whether the average temperature of the first conductor meets a preset condition, and if so, calculate the first predicted temperature value through the thermal simulation calculation model according to the loss data and the environmental parameters;

[0015] If the preset condition is not met, the first estimated cable parameters and the first conductor average temperature are iteratively updated until the updated second conductor average temperature meets the preset condition. In each iterative update process, the current first estimated cable parameters are updated according to the current first conductor average temperature to obtain the 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 current carrying capacity and the environmental parameters to obtain the updated second conductor average temperature.

[0016] The embodiment of the present application provides a method for outputting a first predicted temperature value of a preset position of a target cable through a simulation model. First, according to the first estimated current carrying capacity and the first estimated cable parameter, the electromagnetic field simulation model is calculated using the finite element method to obtain the loss data of the target cable, and then the thermal simulation model is calculated using the finite volume method based on the loss data to obtain the average conductor temperature, and the estimated cable conductor temperature in the estimated cable parameter is updated by the conductor average temperature, and then a new conductor average temperature is generated again using the updated estimated cable conductor temperature until the conductor average temperature meets the preset conditions. This is because the first estimated current carrying capacity and the first estimated cable parameter obtained initially are both 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 update method to cyclically update the first estimated cable parameter and the first conductor average temperature until the first conductor average temperature that meets the preset conditions is obtained, and then the first predicted temperature value that accurately corresponds to the first estimated current carrying capacity is calculated using the current first estimated cable parameter. The embodiment of the present application continuously adjusts the input data according to the output result through the simulation model until the output result meets the prediction condition of the current carrying capacity, so that the final prediction result is more accurate, prepares data for the subsequent adjustment of the first estimated current carrying capacity, and further improves the accuracy of the prediction of the current carrying capacity of the target cable.

[0017] Further, the determining whether the average temperature of the first conductor meets a preset condition includes:

[0018] Determine 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; if so, determine that the first conductor average temperature meets the preset condition; otherwise, determine 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 judging 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. Since the first conductor average temperature is calculated by the simulation model according to the first estimated current carrying capacity, the first estimated cable parameters and the environmental parameters, when the first estimated cable parameters are accurate enough, the conductor average temperature calculated by simulation will be very close to the input estimated cable conductor temperature. Therefore, 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 as a preset condition, which further improves the accuracy of the target cable current carrying capacity prediction.

[0020] Further, the obtaining the first predicted temperature value by calculating the thermal simulation calculation model according to the loss data and the environmental parameters includes:

[0021] Inputting the estimated cable dielectric properties, the loss data and the environmental parameters into the thermal simulation calculation model, so that the thermal simulation calculation model outputs a conductor temperature curve of the target cable within a preset calculation domain;

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

[0023] If the preset calculation domain is smaller than the preset position, a first predicted temperature value of the preset position of the target cable is calculated and obtained by polynomial function fitting according to the conductor temperature curve.

[0024] The embodiment of the present application provides a method for calculating the first predicted temperature value. Under normal circumstances, the distance between the two ventilation openings of the tunnel in the project is 500m, but the calculation amount of establishing a complete 500m 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 preset calculation domain. When the preset calculation domain is smaller than the preset position, for example, the calculation domain is 100m and the preset position is 500 meters, the first predicted temperature value of the target cable at 500m is obtained by calculating the conductor temperature curve within 100m of the target cable through a polynomial function fitting method, which effectively reduces the amount of calculation, 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 current carrying capacity of the cable for long-distance transmission.

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

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

[0027] When the first predicted temperature value is greater than the upper temperature limit of the preset temperature range, gradually reduce the value of the first estimated current carrying capacity by a preset current difference until the third predicted temperature value corresponding to the reduced third estimated current carrying capacity is less than the lower temperature limit of the preset temperature range, and use a dichotomy method on the first estimated current carrying capacity and the third estimated current carrying capacity to obtain the second estimated current carrying capacity;

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

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

[0030] The embodiment of the present application provides a method for adjusting the estimated current carrying capacity, and the adjustment method of the current carrying capacity is determined according to the difference between the first predicted temperature value and the preset temperature range, and the value of the first estimated current carrying capacity is gradually increased or decreased to obtain the third estimated current carrying capacity. 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 by the simulation model. If the second predicted temperature is still not within the preset temperature range, the second estimated current carrying capacity is adjusted continuously until the predicted temperature corresponding to a certain current carrying capacity value is within the preset temperature range, and the current carrying capacity is output as the predicted current carrying capacity. The embodiment of the present application continuously fine-tunes the estimated current carrying capacity through a cyclic iteration method to ensure that the optimal solution for the current carrying capacity of the target cable can be found, so as to achieve accurate prediction of the current carrying capacity.

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

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

[0033] Furthermore, the target cable is laid in a single-loop arrangement or a multi-loop arrangement.

[0034] Furthermore, the heat dissipation method of the target cable is air cooling, natural convection heat exchange or water cooling heat exchange.

[0035] In a second aspect, an embodiment of the present application provides a current carrying capacity prediction system for an AC cable, including an acquisition module, a temperature prediction module, an output module, and a current carrying capacity update module;

[0036] Wherein, the acquisition module is used to acquire the first estimated current carrying capacity, the first estimated cable parameters and the environmental parameters of the target cable;

[0037] The temperature prediction module is used 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 includes an electromagnetic field simulation calculation model and a thermal simulation calculation model, and the simulation model is constructed according to the laying method and heat dissipation method of the target cable;

[0038] The output module is used for outputting 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 used to iteratively update the first estimated current carrying capacity when the first predicted temperature value is not within the preset temperature range, until the second predicted temperature value corresponding to the updated second estimated current carrying capacity is within the preset temperature range, and output the second estimated current carrying capacity as the predicted current carrying capacity; wherein the second predicted temperature value is calculated by the simulation model based on the second estimated current carrying capacity, the first estimated cable parameters and the environmental parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 : A flow chart of a method for predicting the current carrying capacity of an AC cable provided in an embodiment of the present application.

[0041] Figure 2 : A schematic diagram of a cable laying method in a method for predicting the current carrying capacity of an AC cable provided in an embodiment of the present application.

[0042] Figure 3 : A schematic diagram of a flow chart for calculating a predicted temperature value in a method for predicting the current carrying capacity of an AC cable provided in an embodiment of the present application.

[0043] Figure 4 : A schematic diagram of loss data corresponding to different estimated current carrying capacities in a current carrying capacity prediction method for an AC cable provided in an embodiment of the present application.

[0044] Figure 5 : Schematic diagram of the geometric model of the thermal simulation calculation model of the 100m calculation domain in the current carrying capacity prediction method of an AC cable provided in an embodiment of the present application.

[0045] Figure 6 : Schematic diagram of the thermal simulation calculation model of a 100m calculation domain in a method for predicting the current carrying capacity of an AC cable provided in an embodiment of the present application.

[0046] Figure 7 : Schematic diagram of conductor temperature curve and fitting function in a method for predicting the current carrying capacity of an AC cable provided in an embodiment of the present application.

[0047] Figure 8 : A schematic diagram of the detailed steps of a method for predicting the current carrying capacity of an AC cable provided in an embodiment of the present application.

[0048] Fig. 9 : A structural diagram of a current carrying capacity prediction system for an AC cable provided in an embodiment of the present application. DETAILED DESCRIPTION

[0049] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0050] It should be noted that the step numbers in the text are only for the convenience of explanation of the specific embodiments and do not serve to limit the order in which the steps are executed. In the description of this application, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0051] Embodiment 1:

[0052] like Figure 1 As shown, embodiment 1 provides a method for predicting the current carrying capacity of an AC cable, comprising steps S1-S4:

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

[0054] Step S2, inputting 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 includes an electromagnetic field simulation calculation model and a thermal simulation calculation model, and the simulation model is constructed according to the laying method and heat dissipation method of the target cable;

[0055] Step S3: 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;

[0056] Step S4. When the first predicted temperature value is not within the preset temperature range, iteratively update the first estimated current-carrying capacity until the second predicted temperature value corresponding to the updated second estimated current-carrying capacity is within the preset temperature range, and output the second estimated current-carrying capacity as the predicted current-carrying capacity; wherein the second predicted temperature value is calculated by the simulation model based on the second estimated current-carrying capacity, the first estimated cable parameters and the environmental parameters.

[0057] In a preferred embodiment, the target cable is laid as follows: Figure 2 shown.

[0058] The embodiment of the present application provides a method for predicting the current carrying capacity of an AC cable. First, a roughly estimated first estimated current carrying capacity and a first estimated cable parameter of a target cable are obtained, as well as the environmental parameters of the surrounding environment of the target cable. Then, these 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 by simulation calculation. Then, based on the definition of current carrying capacity, it is judged whether the current first predicted temperature value is within a preset temperature range, and the first estimated current carrying capacity is iteratively updated based on the judgment result until the second predicted temperature value corresponding to the updated second estimated current carrying capacity is within the preset temperature range, and the second estimated current carrying capacity is output as the predicted current carrying capacity, thereby realizing the prediction of the current carrying capacity of the target cable. Compared with the prior art, the embodiment of the present application uses a simulation model to model the target cable, and uses the simulation model to predict the temperature of the preset position of the target cable to indirectly predict the current carrying capacity of the target cable, thereby avoiding the use of an empirical formula to directly calculate the current carrying capacity. At the same time, 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 falls within the preset temperature range, thereby improving the accuracy of the prediction of the current carrying capacity of the target cable. In addition, the simulation model of the embodiment of the present application is constructed based on the laying method and heat dissipation method of the target cable, and can effectively adapt to the heat dissipation characteristics of the cable under different layout structures, wind speeds, number of loops and water cooling structures, further improving the accuracy and flexibility of the prediction of the current carrying capacity of the target cable.

[0059] In a possible implementation, in step S2, the simulation model outputs a first predicted temperature value corresponding to the first estimated current carrying capacity, such as Figure 3 As shown, it includes steps S201 to S204:

[0060] Step S201, inputting the first estimated current carrying capacity and the first estimated cable parameters into the electromagnetic simulation calculation model, so that the electromagnetic simulation calculation model outputs the loss data of the target cable using a finite element method, wherein the estimated cable parameters include the estimated cable conductor temperature and the estimated cable dielectric properties, and the loss data include the conductor loss data per unit volume, the shielding layer loss data, and the sheath loss data;

[0061] Step S202, inputting the estimated cable dielectric properties, the loss data and the environmental parameters into the thermal simulation calculation model, so that the thermal simulation calculation model outputs the average temperature of the first conductor of the target cable using a finite volume method, wherein the environmental parameters include the temperature, pressure and velocity of the airflow at the tunnel inlet;

[0062] Step S203, judging whether the average temperature of the first conductor meets a preset condition, and if so, obtaining the first predicted temperature value by calculating through the thermal simulation calculation model according to the loss data and the environmental parameters;

[0063] Step S204: If the preset condition is not met, the first estimated cable parameters and the first conductor average temperature are iteratively updated until the updated second conductor average temperature meets the preset condition. In each iterative update process, 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 current carrying capacity and the environmental parameters to obtain an updated second conductor average temperature.

[0064] The embodiment of the present application provides a method for outputting a first predicted temperature value of a preset position of a target cable through a simulation model. First, according to the first estimated current carrying capacity and the first estimated cable parameter, the electromagnetic field simulation model is calculated using the finite element method to obtain the loss data of the target cable, and then the thermal simulation model is calculated using the finite volume method based on the loss data to obtain the average conductor temperature, and the estimated cable conductor temperature in the estimated cable parameter is updated by the conductor average temperature, and then a new conductor average temperature is generated again using the updated estimated cable conductor temperature until the conductor average temperature meets the preset conditions. This is because the first estimated current carrying capacity and the first estimated cable parameter obtained initially are both 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 update method to cyclically update the first estimated cable parameter and the first conductor average temperature until the first conductor average temperature that meets the preset conditions is obtained, and then the first predicted temperature value that accurately corresponds to the first estimated current carrying capacity is calculated using the current first estimated cable parameter. The embodiment of the present application continuously adjusts the input data according to the output result through the simulation model until the output result meets the prediction condition of the current carrying capacity, so that the final prediction result is more accurate, prepares data for the subsequent adjustment of the first estimated current carrying capacity, and further improves the accuracy of the prediction of the current carrying capacity of the target cable.

[0065] In a preferred embodiment, the estimated cable dielectric properties include the dielectric constant, conductivity, thermal conductivity of each layer of the cable, and thermal conductivity of tunnel soil. In step S201, the first estimated current carrying capacity, the estimated cable conductor temperature, the dielectric constant and conductivity of each layer of the cable are input into the electromagnetic simulation calculation model, so that the electromagnetic simulation calculation model calculates and solves the magnetic field, current and electric field distribution of the target cable through the finite element method, and 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 capacity are as follows: 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 average temperature of the first conductor, wherein the geometric model of the thermal simulation calculation model of the 100m calculation domain is as follows: Figure 5 As shown, the thermal simulation calculation model of the 100m calculation domain is as follows Figure 6 The embodiment of the present application adopts a method combining the calculation of the electromagnetic field simulation model based on the finite element method with the calculation based on the thermal simulation model, which can accurately obtain the conductor loss, shielding layer loss, sheath loss, conductor temperature distribution, current carrying capacity, temperature rise amplitude of the air in the tunnel, etc., and has higher accuracy than the empirical formula.

[0066] Further, in step S203, the determining whether the average temperature of the first conductor meets a preset condition includes:

[0067] Determine 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; if so, determine that the first conductor average temperature meets the preset condition; otherwise, determine that the first conductor average temperature does not meet the preset condition.

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

[0069] In the embodiment of the present application, whether the current first estimated cable parameter is accurate is evaluated by judging 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. Since the first conductor average temperature is calculated by the simulation model according to the first estimated current carrying capacity, the first estimated cable parameters and the environmental parameters, when the first estimated cable parameters are accurate enough, the conductor average temperature calculated by simulation will be very close to the input estimated cable conductor temperature. Therefore, 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 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 obtained by calculating the thermal simulation calculation model according to the loss data and the environmental parameters, including:

[0071] Inputting the estimated cable dielectric properties, the loss data and the environmental parameters into the thermal simulation calculation model, so that the thermal simulation calculation model outputs a conductor temperature curve of the target cable within a preset calculation domain;

[0072] If the preset calculation domain is greater than or equal to the preset position of the target cable, determining a 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 smaller than the preset position, a first predicted temperature value of the preset position of the target cable is calculated and obtained by polynomial function fitting 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 fitting function are as follows: Figure 7 shown.

[0075] The embodiment of the present application provides a method for calculating the first predicted temperature value. Under normal circumstances, the distance between the two ventilation openings of the tunnel in the project is 500m, but the calculation amount of establishing a complete 500m 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 preset calculation domain. When the preset calculation domain is smaller than the preset position, for example, the calculation domain is 100m and the preset position is 500 meters, the first predicted temperature value of the target cable at 500m is obtained by calculating the conductor temperature curve within 100m of the target cable through a polynomial function fitting method, which effectively reduces the amount of calculation, 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 current carrying capacity of the cable for long-distance transmission.

[0076] In a possible implementation, in step S4, when the first predicted temperature value is not within a preset temperature range, iteratively updating the first estimated current carrying capacity until a second predicted temperature value corresponding to an updated second estimated current carrying capacity is within the preset temperature range, and outputting the second estimated current carrying capacity as a predicted current carrying capacity, including:

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

[0078] When the first predicted temperature value is greater than the upper temperature limit of the preset temperature range, gradually reduce the value of the first estimated current carrying capacity by a preset current difference until the third predicted temperature value corresponding to the reduced third estimated current carrying capacity is less than the lower temperature limit of the preset temperature range, and use a dichotomy method on the first estimated current carrying capacity and the third estimated current carrying capacity to obtain the second estimated current carrying capacity;

[0079] If the second predicted temperature value corresponding to the second estimated current carrying capacity is within the preset temperature range, outputting the second estimated current carrying capacity as the predicted current carrying capacity;

[0080] If the second predicted temperature value corresponding to the second estimated current carrying capacity is not within the preset temperature range, the second estimated current carrying capacity is used as the first estimated current carrying capacity, and the first estimated current carrying capacity is continuously updated iteratively.

[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 carried out in two stages:

[0082] (1) Determine the range of predicted current carrying capacity

[0083] When the predicted temperature corresponding to the first estimated current carrying capacity is less than 89° C., 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° C. 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° C., 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 lower than 89° C. 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 current value is adjusted by binary division within the above-mentioned predicted current carrying capacity range to obtain a second estimated current carrying capacity, and the electromagnetic field simulation model calculation and the thermal simulation model calculation are re-performed until the second estimated current carrying capacity meets the judgment condition, and the predicted current carrying capacity is obtained and output. The detailed step flow chart of the embodiment of the present application is shown in FIG. Figure 8 shown.

[0086] The embodiment of the present application provides a method for adjusting the estimated current carrying capacity, and the adjustment method of the current carrying capacity is determined according to the difference between the first predicted temperature value and the preset temperature range, and the value of the first estimated current carrying capacity is gradually increased or decreased to obtain the third estimated current carrying capacity. 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 by the simulation model. If the second predicted temperature is still not within the preset temperature range, the second estimated current carrying capacity is adjusted continuously until the predicted temperature corresponding to a certain current carrying capacity value is within the preset temperature range, and the current carrying capacity is output as the predicted current carrying capacity. The embodiment of the present application continuously fine-tunes the estimated current carrying capacity through a cyclic iteration method to ensure that the optimal solution for the current carrying capacity of the target cable can be found, so as to achieve accurate prediction of the current carrying capacity.

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

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

[0089] Furthermore, the target cable is laid in a single-loop arrangement or a multi-loop arrangement.

[0090] Furthermore, the heat dissipation method 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 scenario. When optimizing the laying method of the target cable, the current carrying capacity of the cable under different laying methods can be calculated and analyzed to help the staff effectively determine the optimal cable layout method; in the multi-circuit layout method, the current carrying capacity of the cable with multiple circuits in the tunnel can be calculated and analyzed to effectively determine the most reasonable number of circuits for the cable. When optimizing the wind speed of the target cable, the embodiments of the present application can calculate and analyze the current carrying capacity under different wind speed conditions in the tunnel to effectively determine the most reasonable wind speed value. When optimizing the heat dissipation method of the target cable, the embodiments of the present application support the calculation and analysis of the current carrying capacity of the cable with water cooling pipes added in the tunnel, which can effectively determine the impact of adding water cooling pipes on the current carrying capacity.

[0092] Embodiment 2:

[0093] like Fig. 9 As shown, accordingly, embodiment 2 provides a current carrying capacity prediction system for an AC cable, comprising an acquisition module 10, a temperature prediction module 20, an output module 30 and a current carrying capacity update module 40;

[0094] Wherein, the acquisition module 10 is used to acquire the first estimated current carrying capacity, the first estimated cable parameters and the environmental parameters of the target cable;

[0095] The temperature prediction module 20 is used 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 includes an electromagnetic field simulation calculation model and a thermal simulation calculation model, and the simulation model is constructed according to the laying method and heat dissipation method of the target cable;

[0096] The output module 30 is used 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;

[0097] The current carrying capacity updating module 40 is used to iteratively update the first estimated current carrying capacity when the first predicted temperature value is not within the preset temperature range, until the second predicted temperature value corresponding to the updated second estimated current carrying capacity is within the preset temperature range, and output the second estimated current carrying capacity as the predicted current carrying capacity; wherein the second predicted temperature value is calculated by the simulation model based on the second estimated current carrying capacity, the first estimated cable parameters and the environmental parameters.

[0098] The more detailed working principle and step flow of this embodiment can refer to, but are not limited to, the relevant records of Embodiment 1.

[0099] The specific embodiments described above further describe the purpose, technical solutions and beneficial effects of the present application in detail. It should be understood that the above description is only a specific embodiment of the present application and is not intended to limit the scope of protection 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 should be included in the scope of protection of the present application.

Claims

1. A method for predicting the current carrying capacity of an AC cable, characterized in that: include: 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 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 includes an electromagnetic field simulation calculation model and a thermal simulation calculation model, and the simulation model is constructed according to the laying method and heat dissipation method of the target cable; 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; When the first predicted temperature value is not within the preset temperature range, the first estimated current-carrying capacity is iteratively updated until the second predicted temperature value corresponding to the updated second estimated current-carrying capacity 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 based on the second estimated current-carrying capacity, the first estimated cable parameters and the environmental parameters.

2. A method for predicting the current carrying capacity of an AC cable according to claim 1, characterized in that: The simulation model outputs a first predicted temperature value corresponding to the first estimated current carrying capacity, including: Inputting the first estimated current carrying capacity and the first estimated cable parameters into the electromagnetic simulation calculation model, so that the electromagnetic simulation calculation model outputs loss data of the target cable using a finite element method, wherein the estimated cable parameters include estimated cable conductor temperature and estimated cable dielectric properties, and the loss data include conductor loss data per unit volume, shielding layer loss data, and sheath loss data; Inputting the estimated cable dielectric properties, the loss data and the environmental parameters into the thermal simulation calculation model so that the thermal simulation calculation model outputs the average temperature of the first conductor of the target cable using a finite volume method, wherein the environmental parameters include the temperature, pressure and velocity of the airflow at the tunnel inlet; Determine whether the average temperature of the first conductor meets a preset condition, and if so, calculate the first predicted temperature value through the thermal simulation calculation model according to the loss data and the environmental parameters; If the preset condition is not met, the first estimated cable parameters and the first conductor average temperature are iteratively updated until the updated second conductor average temperature meets the preset condition. In each iterative update process, the current first estimated cable parameters are updated according to the current first conductor average temperature to obtain the 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 current carrying capacity and the environmental parameters to obtain the updated second conductor average temperature.

3. A method for predicting the current carrying capacity of an AC cable according to claim 2, characterized in that: The determining whether the average temperature of the first conductor meets a preset condition includes: Determine 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; if so, determine that the first conductor average temperature meets the preset condition; otherwise, determine that the first conductor average temperature does not meet the preset condition.

4. A method for predicting the current carrying capacity of an AC cable according to claim 2, characterized in that: The step of calculating the first predicted temperature value by using the thermal simulation calculation model according to the loss data and the environmental parameters includes: Inputting the estimated cable dielectric properties, the loss data and the environmental parameters into the thermal simulation calculation model, so that the thermal simulation calculation model outputs a conductor temperature curve of the target cable within a preset calculation domain; If the preset calculation domain is greater than or equal to the preset position of the target cable, determining a first predicted temperature value of the preset position of the target cable according to the conductor temperature curve; If the preset calculation domain is smaller than the preset position, a first predicted temperature value of the preset position of the target cable is calculated and obtained by polynomial function fitting according to the conductor temperature curve.

5. The method for predicting the current carrying capacity of an AC cable according to claim 1, characterized in that: When the first predicted temperature value is not within the preset temperature range, iteratively updating the first estimated current carrying capacity until a second predicted temperature value corresponding to the updated second estimated current carrying capacity is within the preset temperature range, and outputting the second estimated current carrying capacity as the predicted current carrying capacity, comprising: When the first predicted temperature value is less than the lower temperature limit of the preset temperature range, gradually increase the value of the first estimated current carrying capacity by a preset current difference until the third predicted temperature value corresponding to the increased third estimated current carrying capacity is greater than the upper temperature limit of the preset temperature range, and use a dichotomy method on the first estimated current carrying capacity and the third estimated current carrying capacity to obtain the second estimated current carrying capacity; When the first predicted temperature value is greater than the upper temperature limit of the preset temperature range, gradually reduce the value of the first estimated current carrying capacity by a preset current difference until the third predicted temperature value corresponding to the reduced third estimated current carrying capacity is less than the lower temperature limit of the preset temperature range, and use a dichotomy method on the first estimated current carrying capacity and the third estimated current carrying capacity to obtain the second estimated current carrying capacity; If the second predicted temperature value corresponding to the second estimated current carrying capacity is within the preset temperature range, outputting the second estimated current carrying capacity as the predicted current carrying capacity; If the second predicted temperature value corresponding to the second estimated current carrying capacity is not within the preset temperature range, the second estimated current carrying capacity is used as the first estimated current carrying capacity, and the first estimated current carrying capacity is continuously updated iteratively.

6. A method for predicting the current carrying capacity of an AC cable according to any one of claims 1 to 5, characterized in that: The preset temperature range is 89-90 degrees Celsius.

7. A method for predicting the current carrying capacity of an AC cable according to any one of claims 1 to 5, characterized in that: The thermal simulation calculation model adopts a structured network.

8. A method for predicting the current carrying capacity of an AC cable according to any one of claims 1 to 5, characterized in that: The target cable is laid in a single-loop arrangement or a multi-loop arrangement.

9. A method for predicting the current carrying capacity of an AC cable according to any one of claims 1 to 5, characterized in that: The heat dissipation method of the target cable is air cooling, natural convection heat exchange or water cooling heat exchange.

10. A current carrying capacity prediction system for an AC cable, characterized in that: It includes an acquisition module, a temperature prediction module, an output module and a current carrying capacity update module; Wherein, the acquisition module is used to acquire the first estimated current carrying capacity, the first estimated cable parameters and the environmental parameters of the target cable; The temperature prediction module is used 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 includes an electromagnetic field simulation calculation model and a thermal simulation calculation model, and the simulation model is constructed according to the laying method and heat dissipation method of the target cable; The output module is used for outputting the first estimated current carrying capacity as a predicted current carrying capacity when the first predicted temperature value is within a preset temperature range; The current carrying capacity updating module is used for iteratively updating the first estimated current carrying capacity when the first predicted temperature value is not within the preset temperature range, until the second predicted temperature value corresponding to the updated second estimated current carrying capacity is within the preset temperature range, and outputting the second estimated current carrying capacity as the predicted current carrying capacity; 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.

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