Method and device for determining transmission capacity of alternating-current cable after direct-current transformation, electronic equipment and storage medium

Abstract

The invention discloses a method and device for determining the transmission capacity of an alternating current cable after direct current transformation, electronic equipment and a storage medium, and belongs to the field of cable line operation, and the method comprises the steps: obtaining a cable finite element model and a cable field intensity calibration model of a simulation alternating current cable; inputting the electric field intensity threshold value of the insulating layer into the calibration model, and generating the maximum applied voltage of the alternating current cable under the direct current working condition; gradually increasing the current and performing simulation under the maximum direct-current voltage until the conductor temperature or the insulation electric field intensity reaches a threshold value, and determining the maximum direct-current carrying capacity; and finally, calculating the direct current transmission capacity of the alternating current cable based on the maximum direct current voltage and the maximum direct current carrying capacity. By implementing the invention, the problem that the transmission capacity of the alternating current cable after direct current transformation is not accurate enough in the prior art can be solved.

Description

Technical Field

[0001] This invention relates to the field of cable line operation technology, specifically to a method, apparatus, electronic device, and storage medium for determining the transmission capacity of an AC cable after DC conversion. Background Technology

[0002] With the continuous growth of urban electricity load and the increasing proportion of renewable energy integration, traditional AC cables face numerous challenges in power distribution systems, such as high capacitive current, high energy loss, and limited transmission capacity, making it difficult to meet the power supply capacity and operational flexibility requirements of high-density areas. In contrast, DC operation offers advantages such as large transmission capacity and low loss, making it an important direction for improving the utilization efficiency of existing AC cables, especially suitable for scenarios where urban cable lines cannot be expanded but capacity increases are needed. After converting AC cables to DC operation, their insulation structure, electric field distribution, and thermodynamic characteristics all change significantly. Therefore, it is essential to reasonably assess the post-conversion operating voltage and current-carrying capacity to accurately determine the cable's DC transmission capacity. This is fundamental to ensuring the long-term safe operation of the line and achieving the desired capacity increase.

[0003] However, existing technologies are not accurate enough in determining the transmission capacity of AC cables after DC conversion. They often rely on empirical values ​​to determine the maximum DC voltage and the maximum DC current carrying capacity, resulting in insufficient accuracy in determining the transmission capacity of AC cables. This fails to accurately reflect the true performance of the cables under DC conditions and limits the engineering application and promotion of AC cable DC conversion. Summary of the Invention

[0004] This invention provides a method, apparatus, electronic device, and storage medium for determining the transmission capacity of an AC cable after DC conversion, which can solve the problem that the determination of the transmission capacity of an AC cable after DC conversion is not accurate enough in the prior art.

[0005] One embodiment of the present invention provides a method for determining the transmission capacity of an AC cable after DC conversion, comprising:

[0006] A finite element model of an AC cable is obtained, along with a cable field strength calibration model for characterizing the quantitative relationship between the critical inversion field strength of the insulation layer and the DC voltage of the simulated AC cable; wherein the finite element model of the cable includes the simulated AC cable.

[0007] The preset electric field strength threshold of the insulation layer is used as the critical reversal field strength of the insulation layer and input into the cable field strength calibration model so that the cable field strength calibration model generates the corresponding DC voltage according to the preset electric field strength threshold of the insulation layer; the DC voltage corresponding to the preset electric field strength threshold of the insulation layer is used as the maximum DC voltage of the simulated AC cable.

[0008] With the conductor voltage of the simulated AC cable set to the maximum DC voltage, the current increment operation is repeatedly performed until the termination condition is met, generating the maximum DC current carrying capacity of the simulated AC cable; the termination condition is that the current conductor temperature of the simulated AC cable exceeds a preset conductor temperature threshold, or the current maximum electric field strength in the insulation layer of the simulated AC cable exceeds a preset insulation layer electric field strength threshold.

[0009] The DC transmission capacity of the AC cable is determined based on the maximum DC voltage and the maximum DC current carrying capacity.

[0010] The current increment operation includes:

[0011] Under the current DC current, based on the finite element model of the cable, the current conductor temperature of the simulated AC cable and the current maximum electric field strength in the insulation layer of the simulated AC cable are simulated and calculated; wherein, the initial DC current is a preset value;

[0012] Determine if the termination condition is met. If yes, use the previous DC current as the maximum DC current carrying capacity of the simulated AC cable; otherwise, update the current DC current according to the preset step size.

[0013] Furthermore, the finite element model of the AC cable is obtained through the following methods:

[0014] Obtain the structural and material properties of the AC cable;

[0015] Based on the structural parameters and material property parameters, finite element modeling is performed to generate a finite element model of the AC cable.

[0016] Furthermore, a cable field strength calibration model for characterizing the quantitative relationship between the critical reversal field strength of the insulation layer and the DC voltage of the simulated AC cable is obtained through the following method:

[0017] Under the condition that the conductor temperature of the simulated AC cable is set to a preset conductor temperature threshold, the critical inversion field strength of the insulation layer of the cable finite element model under various applied DC voltages is simulated.

[0018] Linear fitting is performed on each DC voltage and the corresponding critical inversion field strength of the insulation layer to generate a cable field strength calibration model that characterizes the quantitative relationship between the critical inversion field strength of the insulation layer and the DC voltage of the simulated AC cable.

[0019] Furthermore, a cable field strength calibration model for characterizing the quantitative relationship between the critical reversal field strength of the insulation layer and the DC voltage of the simulated AC cable is obtained through the following method:

[0020] Under the condition that the conductor temperature of the simulated AC cable is set to a preset conductor temperature threshold, the critical inversion field strength of the insulation layer of the cable finite element model under various applied DC voltages is simulated.

[0021] Linear fitting is performed on each DC voltage and the corresponding critical inversion field strength of the insulation layer to generate a cable field strength calibration model that characterizes the quantitative relationship between the critical inversion field strength of the insulation layer and the DC voltage of the simulated AC cable.

[0022] Furthermore, under the condition that the conductor temperature of the simulated AC cable is set to a preset conductor temperature threshold, the critical inversion field strength of the insulation layer of the cable finite element model under various applied DC voltages is simulated, including:

[0023] Set the conductor temperature of the simulated AC cable to a preset conductor temperature threshold.

[0024] For each DC voltage, the current DC voltage is applied to the finite element model of the cable, and the temperature difference between the inside and outside of the insulation layer of the simulated AC cable is adjusted until the electric field strength at each point in the current insulation layer is equal.

[0025] The electric field strength at any point within the current insulation layer is taken as the critical reversal field strength of the insulation layer under the current DC voltage applied to the cable finite element model.

[0026] Furthermore, under the current DC current, based on the finite element model of the cable, the current conductor temperature of the simulated AC cable and the current maximum electric field strength within the insulation layer of the simulated AC cable are simulated and calculated, including:

[0027] The current DC current is used as an excitation source and input into the cable finite element model so that the cable finite element model can perform electrothermal coupling calculations based on the current DC current and generate the steady-state temperature field distribution caused by the current DC current.

[0028] Extract the current conductor temperature from the steady-state temperature field distribution;

[0029] Based on the steady-state temperature field distribution, the electric field intensity distribution of the insulation layer of the simulated AC cable is determined;

[0030] The maximum electric field intensity within the insulation layer of the simulated AC cable is extracted from the electric field intensity distribution of the insulation layer.

[0031] Furthermore, the DC transmission capacity of the generated AC cable is calculated using the following formula:

[0032] P DC =2U DC ·I DC

[0033] In the formula, P DCFor the DC transmission capacity of the AC cable; U DC Maximum DC voltage; I DC This represents the maximum DC current carrying capacity.

[0034] Based on the above method embodiments, the present invention provides corresponding apparatus embodiments.

[0035] An embodiment of the present invention provides a device for determining the transmission capacity of an AC cable after DC conversion, comprising: a data acquisition module, a maximum DC voltage determination module, a maximum DC current carrying capacity module, and a DC transmission capacity determination module;

[0036] The data acquisition module is used to acquire the finite element model of the AC cable and the cable field strength calibration model used to characterize the quantitative relationship between the critical reversal field strength of the insulation layer and the DC voltage of the simulated AC cable; wherein, the finite element model of the cable includes the simulated AC cable.

[0037] The maximum DC voltage determination module is used to input a preset insulation layer electric field strength threshold as the critical reversal field strength of the insulation layer into the cable field strength calibration model, so that the cable field strength calibration model generates the corresponding DC voltage according to the preset insulation layer electric field strength threshold; and uses the DC voltage corresponding to the preset insulation layer electric field strength threshold as the maximum DC voltage of the simulated AC cable.

[0038] The maximum DC current carrying capacity module is used to repeatedly perform a current increment operation under the condition that the conductor voltage of the simulated AC cable is set to the maximum DC voltage, until a termination condition is met, thereby generating the maximum DC current carrying capacity of the simulated AC cable. The termination condition is that the current conductor temperature of the simulated AC cable exceeds a preset conductor temperature threshold, or the current maximum electric field strength in the insulation layer of the simulated AC cable exceeds a preset insulation layer electric field strength threshold. The current increment operation includes: under the current DC current, based on the finite element model of the cable, simulating and calculating the current conductor temperature and the current maximum electric field strength in the insulation layer of the simulated AC cable; wherein the initial DC current is a preset value; determining whether the termination condition is met; if yes, then using the previous DC current as the maximum DC current carrying capacity of the simulated AC cable; if no, then updating the current DC current according to a preset step size.

[0039] The DC transmission capacity determination module is used to determine the DC transmission capacity of the simulated AC cable based on the maximum DC voltage and the maximum DC current carrying capacity.

[0040] Furthermore, the DC transmission capacity determination module calculates the DC transmission capacity of the AC cable using the following formula:

[0041] P DC =2UDC ·I DC

[0042] In the formula, P DC For the DC transmission capacity of the AC cable; U DC Maximum DC voltage; I DC This represents the maximum DC current carrying capacity.

[0043] Based on the above method embodiments, the present invention provides corresponding electronic device embodiments.

[0044] An embodiment of the present invention provides an electronic device, including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, it implements the method for determining the transmission capacity of an AC cable after DC conversion as described in any of the above-described method embodiments.

[0045] Based on the above method embodiments, the present invention provides corresponding storage medium embodiments.

[0046] One embodiment of the present invention provides a storage medium storing a computer program, wherein, when the computer program is running, it controls the device where the storage medium is located to execute the method for determining the transmission capacity of an AC cable after DC conversion as described in any of the above-described method embodiments.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] This invention provides a method, apparatus, electronic device, and storage medium for determining the transmission capacity of an AC cable after DC conversion. The method acquires a finite element model of the AC cable and a predefined cable electric field strength calibration model as the basis for calculation. The calibration model characterizes the quantitative relationship between DC voltage and the critical reversal electric field strength of the insulation layer. During calculation, a preset upper limit of the safe electric field strength of the insulation layer is first input into the cable electric field strength calibration model to solve for the maximum DC voltage that the AC cable can withstand. Next, with the conductor voltage of the simulated AC cable fixed at the maximum DC voltage, an iterative simulation process of increasing DC current is used to find the upper limit of the current. This iterative process simultaneously calculates and monitors the conductor temperature and the maximum electric field strength within the insulation layer at each current step. Once either of these two indicators exceeds a preset safe threshold, the iteration stops, and the last safe current value just before exceeding the limit is determined as the maximum DC current carrying capacity. Based on the determined maximum DC voltage and maximum DC current carrying capacity, the final DC transmission capacity is calculated.

[0049] This invention obtains a finite element model of an AC cable and introduces a field strength calibration model that characterizes the quantitative relationship between the critical reversal field strength of the insulation layer and the DC voltage. Under simulation conditions, it accurately confirms the maximum DC voltage of the AC cable. Based on this, the current is gradually increased during simulation to ultimately determine the transmission capacity of the AC cable under DC operation. This method avoids the large errors in maximum DC voltage and maximum DC current carrying capacity caused by the reliance on experience in existing technologies. It provides a clear physical basis for the maximum DC voltage and maximum DC current carrying capacity, effectively reflecting the true performance of the AC cable under DC conditions, thereby improving the accuracy of determining the transmission capacity of the AC cable after DC conversion. Attached Figure Description

[0050] Figure 1 This is a flowchart illustrating a method for determining the transmission capacity of an AC cable after DC conversion, according to an embodiment of the present invention.

[0051] Figure 2 This is a schematic diagram of a device for determining the transmission capacity of an AC cable after DC conversion, according to an embodiment of the present invention. Detailed Implementation

[0052] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] like Figure 1 As shown, to address the problem of inaccurate determination of the transmission capacity of AC cables after DC conversion in the prior art, an embodiment of the present invention provides a method for determining the transmission capacity of AC cables after DC conversion, comprising at least the following steps:

[0054] Step S1: Obtain the finite element model of the AC cable and the cable field strength calibration model for characterizing the quantitative relationship between the critical reversal field strength of the insulation layer and the DC voltage of the simulated AC cable; wherein, the finite element model of the cable includes the simulated AC cable.

[0055] In an optional embodiment, the finite element model of the AC cable is obtained by:

[0056] Obtain the structural and material properties of the AC cable;

[0057] Based on the structural parameters and material property parameters, finite element modeling is performed to generate a finite element model of the AC cable.

[0058] In practical implementation, the structural parameters of the AC cable are obtained, including conductor dimensions, insulation thickness, sheath structure, overall cable diameter, and the spatial distribution order of each layer of materials. Simultaneously, the thermal and electrical properties of each layer of materials constituting the cable are acquired, including thermal conductivity, electrical conductivity, heat capacity, density, and temperature coefficient of resistivity. Next, based on these structural and material properties, a two-dimensional or three-dimensional physical model of the cable is constructed in a finite element simulation platform (such as COMSOL Multiphysics), and coupled boundary conditions are established in the electric field and thermal field modules to complete the construction of the cable finite element model. This cable finite element model can reflect key thermoelectric response characteristics such as conductor temperature distribution and changes in electric field intensity within the insulation layer under different voltage and current conditions, and serves as the basis for subsequent simulation calculations of current carrying capacity and transmission capacity.

[0059] In a preferred embodiment, a cable field strength calibration model for characterizing the quantitative relationship between the critical reversal field strength of the insulation layer and the DC voltage of a simulated AC cable is obtained in the following manner:

[0060] Under the condition that the conductor temperature of the simulated AC cable is set to a preset conductor temperature threshold, the critical inversion field strength of the insulation layer of the cable finite element model under various applied DC voltages is simulated.

[0061] Linear fitting is performed on each DC voltage and the corresponding critical inversion field strength of the insulation layer to generate a cable field strength calibration model that characterizes the quantitative relationship between the critical inversion field strength of the insulation layer and the DC voltage of the simulated AC cable.

[0062] In the specific implementation, under simulation conditions, the conductor temperature of the AC cable is fixed at a preset conductor temperature threshold, preferably the upper limit of the long-term operating temperature of the cable, to reflect the most unfavorable thermal conditions in actual operation. Under this temperature condition, based on the finite element model of the cable, multiple sets of DC voltages with different amplitudes are applied, and the steady-state maximum electric field strength corresponding to the electric field reversal of the insulation layer under each set of voltages is simulated and calculated as the critical reversal field strength of the insulation layer under the DC voltage.

[0063] The obtained DC voltage values ​​are fitted to their corresponding critical inversion field strengths in the insulation layer. A linear regression method is preferred to establish a functional relationship model between the voltage and the critical inversion field strength, thereby generating a cable field strength calibration model. This model can be used to predict the corresponding critical inversion DC voltage under any given insulation layer electric field strength threshold, serving as the basis for subsequently determining the maximum DC voltage level of the cable.

[0064] It should be noted that the so-called critical reversal refers to a special critical point under DC operating conditions where the electric field distribution within the cable insulation layer changes from the traditional "higher inside, lower outside" state to a "higher outside, lower inside" state. In this state, the conductivity on both the inner and outer sides of the insulation layer forms a symmetrical distribution due to the temperature gradient, causing the electric field intensity at all radial locations within the insulation layer to become more uniform, and the electric field intensity no longer changes significantly with radius. At this time, the maximum electric field value within the insulation layer is no longer concentrated at the conductor shielding area, but is uniformly distributed throughout the entire insulation region; that is, the electric field intensity is equal everywhere in the radial direction, and the cable enters the critical state of electric field reversal. In this state, there are no obvious areas of electric field concentration within the insulation layer, and the electrical stress distribution is more balanced, making it an important indicator for judging the operating boundary of the cable under DC conditions.

[0065] In one specific embodiment, under the condition that the conductor temperature of the simulated AC cable is set to a preset conductor temperature threshold, the critical inversion field strength of the insulation layer of the cable finite element model under various applied DC voltages is simulated, including:

[0066] Set the conductor temperature of the simulated AC cable to a preset conductor temperature threshold.

[0067] For each DC voltage, the current DC voltage is applied to the finite element model of the cable, and the temperature difference between the inside and outside of the insulation layer of the simulated AC cable is adjusted until the electric field strength at each point in the current insulation layer is equal.

[0068] The electric field strength at any point within the current insulation layer is taken as the critical reversal field strength of the insulation layer under the current DC voltage applied to the cable finite element model.

[0069] In this practical implementation, a 110kV single-core cross-linked polyethylene (XLPE) insulated cable is used as the research object. First, using finite element analysis software such as COMSOL Multiphysics, an accurate electrothermal coupling finite element model of the cable is established based on its actual structure and material parameters. In determining the maximum DC voltage, the method first sets the temperature boundary condition of the conductor in the model to a preset 70℃. Then, for a series of different DC voltage levels, independent simulation calculations are performed for each DC voltage. When simulating a specific DC voltage, the core operation is to repeatedly adjust the temperature difference between the inside and outside of the insulation layer in the simulated AC cable to change the conductivity distribution within the insulation layer until the electric field intensity distribution within the insulation layer reaches a uniform state that is equal everywhere, as monitored through post-processing. This state is defined as the critical electric field reversal state under that voltage. At this point, the uniform electric field intensity value is recorded and used as the critical reversal field strength corresponding to the current DC voltage.

[0070] Understandably, this step, by obtaining an accurate finite element model of the cable, provides a digital, virtual object for electrothermal analysis in subsequent current-increment simulations. Simultaneously, acquiring a pre-established cable field strength calibration model provides a direct and efficient calculation basis for determining the maximum DC voltage, thereby simplifying the overall process and ensuring the accuracy of subsequent analyses.

[0071] Step S2: Input the preset insulation layer electric field strength threshold as the critical reversal field strength of the insulation layer into the cable field strength calibration model so that the cable field strength calibration model generates the corresponding DC voltage according to the preset insulation layer electric field strength threshold; and use the DC voltage corresponding to the preset insulation layer electric field strength threshold as the maximum DC voltage of the simulated AC cable.

[0072] In practice, the electric field strength threshold of the insulation layer is set to 6 kV / mm. This value is crucial for ensuring the long-term safe and reliable operation of the cable. It is not the physical breakdown limit of the material (which is usually much higher), but rather an engineering design limit that takes into account material aging, manufacturing process fluctuations, and various uncertainties in actual operation, reserving sufficient safety margins on top of the breakdown limit. During operation, this electric field strength threshold is used as a known dependent variable and substituted into the previously established cable field strength calibration model for solution. Since this calibration model accurately characterizes the quantitative functional relationship between DC voltage and critical reversal steady-state field strength, the DC voltage value corresponding to when the maximum field strength is exactly equal to the 6 kV / mm safety threshold can be quickly calculated in reverse. This calculated voltage value is then determined as the maximum DC voltage at which the cable can operate safely and long-term after DC modification, and will serve as a constant input condition for subsequent calculations to determine the maximum DC current carrying capacity.

[0073] Understandably, this step clarifies the voltage limit of the cable under DC operating conditions, preventing the electric field strength of the insulation layer from exceeding the safety threshold, thereby ensuring the insulation safety and stable operation of the cable. Ultimately, the obtained DC voltage value serves as the maximum DC voltage that the simulated AC cable can withstand, guiding subsequent current-carrying capacity simulation and transmission capacity determination.

[0074] Step S3: Under the condition that the conductor voltage of the simulated AC cable is set to the maximum DC voltage, repeat the current increment operation until the termination condition is met to generate the maximum DC current carrying capacity of the simulated AC cable; the termination condition is that the current conductor temperature of the simulated AC cable exceeds the preset conductor temperature threshold, or the current maximum electric field strength in the insulation layer of the simulated AC cable exceeds the preset insulation layer electric field strength threshold.

[0075] Specifically, the current increment operation includes:

[0076] Under the current DC current, based on the finite element model of the cable, the current conductor temperature of the simulated AC cable and the current maximum electric field strength in the insulation layer of the simulated AC cable are simulated and calculated; wherein, the initial DC current is a preset value;

[0077] Determine if the termination condition is met. If yes, use the previous DC current as the maximum DC current carrying capacity of the simulated AC cable; otherwise, update the current DC current according to the preset step size.

[0078] In the specific implementation, during the simulation process, the conductor voltage of the simulated AC cable is first set to the previously determined maximum DC voltage value, serving as the voltage boundary condition for cable operation. Based on this, the system begins the simulation with a preset initial DC current value and gradually increases the DC current. After each current increase, based on the cable's finite element model, detailed thermal and electric field coupling calculations are performed to obtain the conductor temperature and the maximum electric field strength inside the insulation layer under the current DC current conditions. By continuously monitoring these two key parameters, the system determines whether the preset termination conditions have been met: whether the conductor temperature exceeds a preset conductor temperature threshold, or whether the maximum electric field strength of the insulation layer exceeds a preset insulation layer electric field strength threshold. If either condition is met, the simulation process stops, and the previously acceptable DC current value is considered the maximum DC current carrying capacity of the cable. If the termination condition is not met, the DC current continues to increase according to a preset current step size, repeating the above calculation and judgment process. Through this cycle of incrementing and judging, the maximum current carrying capacity of the cable under safe electrical and thermal parameters can be accurately obtained, providing a basis for determining the subsequent DC transmission capacity.

[0079] For example, a preset initial DC current (e.g., 300A) is used as the starting point for the calculation, and a preset current increment step is set to 50A. A simulation is performed at the initial current of 300A to calculate the conductor temperature and the maximum electric field strength within the insulation layer corresponding to that DC current. These two calculation results are then compared with preset safety thresholds (e.g., a conductor temperature threshold of 70°C and an insulation layer electric field strength threshold of 6 kV / mm). If neither calculation result exceeds its respective threshold, the current is increased by one step to 350A, and the next gradient simulation calculation is performed.

[0080] In a preferred embodiment, under the current DC current, based on the finite element model of the cable, the current conductor temperature of the simulated AC cable and the maximum electric field strength within the current insulation layer of the simulated AC cable are simulated and calculated, including:

[0081] The current DC current is used as an excitation source and input into the cable finite element model so that the cable finite element model can perform electrothermal coupling calculations based on the current DC current and generate the steady-state temperature field distribution caused by the current DC current.

[0082] Extract the current conductor temperature from the steady-state temperature field distribution;

[0083] Based on the steady-state temperature field distribution, the electric field intensity distribution of the insulation layer of the simulated AC cable is determined;

[0084] The maximum electric field intensity within the insulation layer of the simulated AC cable is extracted from the electric field intensity distribution of the insulation layer.

[0085] In the specific implementation, under the current DC current, the current conductor temperature and the maximum electric field strength within the current insulation layer of the AC cable are simulated and calculated. The process is as follows: First, the current DC current value is input as the excitation source into the conductor of the model. Then, electrothermal coupling calculations begin. The core of this calculation lies in its accurate simulation of the interaction between two physical fields: on the one hand, Joule heating is generated when current flows through the conductor, and the thermal field solver calculates the steady-state temperature field distribution when the entire cable reaches thermal equilibrium based on this heat source and the thermal conductivity and dissipation properties of the material; on the other hand, this temperature field distribution, in turn, affects the electric field because the conductivity (or resistivity) of the insulating material is highly sensitive to temperature. Therefore, when determining the electric field strength distribution of the insulation layer, the electric field solver, based on the calculated steady-state temperature field distribution and according to the material's preset "resistivity-temperature" relationship, assigns a unique resistivity value corresponding to its temperature to each point in the model, thereby generating a non-uniform "resistivity field." Finally, under the combined effect of the applied maximum DC voltage and this "resistivity field," the solver calculates the final electric field distribution. After obtaining the complete temperature and electric field distribution maps, two key single values ​​are extracted. The conductor temperature is extracted because it is a core safety indicator for assessing the cable's thermal stability and must be compared with the material's long-term permissible operating temperature threshold (e.g., 70°C) to prevent insulation material aging and damage due to overheating. Simultaneously, the maximum value is extracted from the electric field intensity distribution to compare it with the insulation's withstand voltage limit threshold (e.g., 6kV / mm) to prevent electrical breakdown. Through this coupled calculation and key value extraction process, this method allows for a comprehensive assessment of both the thermal and electrical safety states of the cable at every current gradient.

[0086] Step S4: Determine the DC transmission capacity of the AC cable based on the maximum DC voltage and the maximum DC current carrying capacity;

[0087] In an optional embodiment, the DC transmission capacity of the generated AC cable is calculated using the following formula:

[0088] P DC =2U DC ·I DC

[0089] In the formula, P DC For the DC transmission capacity of the AC cable; U DC Maximum DC voltage; I DC This represents the maximum DC current carrying capacity.

[0090] In practical implementation, because a bipolar operation mode is adopted, using two phases of the three-phase cable as positive and negative poles and one phase as the neutral line, the total transmission capacity is twice that of a single pole. Therefore, the final DC transmission capacity P... DC P is calculated using the following formula: DC =2U DC ·I DC The calculated P DC The value represents the upper limit of the transmission capacity that can be achieved after the AC cable is converted to DC.

[0091] In another specific embodiment of the present invention, in order to quantitatively evaluate the capacity increase effect of the DC transmission capacity determined by this method compared with the original AC operating conditions, it is also necessary to determine the baseline transmission capacity of the cable under the original AC operating conditions. First, using the aforementioned cable finite element model, its AC operating conditions are set in simulation software (such as COMSOL), for example, applying an AC voltage of 110 kV and setting the long-term operating temperature of the conductor to 90 degrees Celsius. Through simulation calculation, the AC current carrying capacity under these specific conditions can be obtained. Subsequently, according to the three-phase AC transmission power formula... The AC carrying capacity I AC Line voltage U AC Multiplying this by a preset power factor cosφ (e.g., 0.9) and then by the square root of three, the maximum transmission capacity P of the cable under AC conditions can be calculated. AC .

[0092] By comparing these two transmission capacity values, the specific capacity increase effect achieved by the 110 kV AC cable after DC conversion can be quantitatively confirmed, providing data support for engineering decisions.

[0093] Based on the above method embodiments, the present invention provides corresponding apparatus embodiments.

[0094] like Figure 2 As shown, an embodiment of the present invention provides a device for determining the transmission capacity of an AC cable after DC conversion, comprising: a data acquisition module, a maximum DC voltage determination module, a maximum DC current carrying capacity module, and a DC transmission capacity determination module;

[0095] The data acquisition module is used to acquire the finite element model of the AC cable and the cable field strength calibration model used to characterize the quantitative relationship between the critical reversal field strength of the insulation layer and the DC voltage of the simulated AC cable; wherein, the finite element model of the cable includes the simulated AC cable.

[0096] The maximum DC voltage determination module is used to input a preset insulation layer electric field strength threshold as the critical reversal field strength of the insulation layer into the cable field strength calibration model, so that the cable field strength calibration model generates the corresponding DC voltage according to the preset insulation layer electric field strength threshold; and uses the DC voltage corresponding to the preset insulation layer electric field strength threshold as the maximum DC voltage of the simulated AC cable.

[0097] The maximum DC current carrying capacity module is used to repeatedly perform a current increment operation under the condition that the conductor voltage of the simulated AC cable is set to the maximum DC voltage, until a termination condition is met, thereby generating the maximum DC current carrying capacity of the simulated AC cable. The termination condition is that the current conductor temperature of the simulated AC cable exceeds a preset conductor temperature threshold, or the current maximum electric field strength in the insulation layer of the simulated AC cable exceeds a preset insulation layer electric field strength threshold. The current increment operation includes: under the current DC current, based on the finite element model of the cable, simulating and calculating the current conductor temperature and the current maximum electric field strength in the insulation layer of the simulated AC cable; wherein the initial DC current is a preset value; determining whether the termination condition is met; if yes, then using the previous DC current as the maximum DC current carrying capacity of the simulated AC cable; if no, then updating the current DC current according to a preset step size.

[0098] The DC transmission capacity determination module is used to determine the DC transmission capacity of the simulated AC cable based on the maximum DC voltage and the maximum DC current carrying capacity.

[0099] Specifically, the DC transmission capacity determination module calculates and generates the DC transmission capacity of the AC cable using the following formula:

[0100] P DC =2U DC ·I DC

[0101] In the formula, P DC For the DC transmission capacity of the AC cable; U DC Maximum DC voltage; I DC This represents the maximum DC current carrying capacity.

[0102] It should be noted that the embodiments of the device described above correspond to the embodiments of the present invention described above, and can realize the method for determining the transmission capacity of AC cables after DC conversion as described in any one of the present invention. Furthermore, the embodiments of the device described above are merely illustrative. The modules described as separate components may or may not be physically separate, and the components shown as modules may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Additionally, in the accompanying drawings of the device embodiments provided by the present invention, the connection relationship between modules indicates that they have a communication connection, which can be implemented as one or more communication buses or signal lines. Those skilled in the art can understand and implement this without creative effort.

[0103] Based on the above-described method embodiments of the present invention, a corresponding embodiment of an electronic device is provided.

[0104] An embodiment of the present invention provides an electronic device, including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, it implements the method for determining the transmission capacity of an AC cable after DC conversion as described in any one of the present invention, or the processor implements the functions of each module in the above-described device embodiments.

[0105] For example, the computer program may be divided into one or more modules, which are stored in the memory and executed by the processor to complete the present invention. The one or more modules may be a series of computer program instruction segments capable of performing specific functions, which describe the execution process of the computer program in the terminal device.

[0106] The terminal device may be a desktop computer, laptop, handheld computer, or cloud server, etc. The terminal device may include, but is not limited to, a processor and a memory.

[0107] The processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor can be a microprocessor or any conventional processor. The processor is the control center of the terminal device, connecting all parts of the terminal device via various interfaces and lines.

[0108] The memory can be used to store the computer programs and / or modules. The processor implements various functions of the terminal device by running or executing the computer programs and / or modules stored in the memory and by calling data stored in the memory. The memory may mainly include a program storage area and a data storage area. The program storage area may store the operating system, applications required for at least one function, etc.; the data storage area may store data created based on the use of the mobile phone, etc. In addition, the memory may include high-speed random access memory, and may also include non-volatile memory, such as hard disk, RAM, plug-in hard disk, smart media card (SMC), secure digital card (SD), flash card, at least one disk storage device, flash memory device, or other volatile solid-state storage devices.

[0109] Based on the above method embodiments, the present invention provides corresponding storage medium embodiments;

[0110] Another embodiment of the present invention provides a storage medium including a stored computer program, wherein, when the computer program is running, the device where the storage medium is located executes the method for determining the transmission capacity of any of the AC cables after DC conversion as described above.

[0111] The aforementioned storage medium is a computer-readable storage medium, and the computer program includes computer program code, which may be in the form of source code, object code, executable file, or certain intermediate forms. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording media, USB flash drive, portable hard drive, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc.

[0112] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of those different embodiments or examples.

[0113] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for determining the transmission capacity of an AC cable after DC conversion, characterized in that, include: A finite element model of an AC cable is obtained, along with a cable field strength calibration model for characterizing the quantitative relationship between the critical inversion field strength of the insulation layer and the DC voltage of the simulated AC cable; wherein the finite element model of the cable includes the simulated AC cable. The preset electric field strength threshold of the insulation layer is used as the critical reversal field strength of the insulation layer and input into the cable field strength calibration model so that the cable field strength calibration model generates the corresponding DC voltage according to the preset electric field strength threshold of the insulation layer; the DC voltage corresponding to the preset electric field strength threshold of the insulation layer is used as the maximum DC voltage of the simulated AC cable. With the conductor voltage of the simulated AC cable set to the maximum DC voltage, the current increment operation is repeatedly performed until the termination condition is met, generating the maximum DC current carrying capacity of the simulated AC cable; the termination condition is that the current conductor temperature of the simulated AC cable exceeds a preset conductor temperature threshold, or the current maximum electric field strength in the insulation layer of the simulated AC cable exceeds a preset insulation layer electric field strength threshold. The DC transmission capacity of the AC cable is determined based on the maximum DC voltage and the maximum DC current carrying capacity. The current increment operation includes: Under the current DC current, based on the finite element model of the cable, the current conductor temperature of the simulated AC cable and the current maximum electric field strength in the insulation layer of the simulated AC cable are simulated and calculated; wherein, the initial DC current is a preset value; Determine if the termination condition is met. If yes, use the previous DC current as the maximum DC current carrying capacity of the simulated AC cable; otherwise, update the current DC current according to the preset step size.

2. The method for determining the transmission capacity of an AC cable after DC conversion as described in claim 1, characterized in that, The finite element model of the AC cable is obtained through the following methods: Obtain the structural and material properties of the AC cable; Based on the structural parameters and material property parameters, finite element modeling is performed to generate a finite element model of the AC cable.

3. The method for determining the transmission capacity of an AC cable after DC conversion as described in claim 2, characterized in that, The cable field strength calibration model, used to characterize the quantitative relationship between the critical reversal field strength of the insulation layer and the DC voltage of a simulated AC cable, is obtained through the following method: Under the condition that the conductor temperature of the simulated AC cable is set to a preset conductor temperature threshold, the critical inversion field strength of the insulation layer of the cable finite element model under various applied DC voltages is simulated. Linear fitting is performed on each DC voltage and the corresponding critical inversion field strength of the insulation layer to generate a cable field strength calibration model that characterizes the quantitative relationship between the critical inversion field strength of the insulation layer and the DC voltage of the simulated AC cable.

4. The method for determining the transmission capacity of an AC cable after DC conversion as described in claim 3, characterized in that, Under the condition that the conductor temperature of the simulated AC cable is set to a preset conductor temperature threshold, the critical inversion field strength of the insulation layer of the cable finite element model under various applied DC voltages is simulated, including: Set the conductor temperature of the simulated AC cable to a preset conductor temperature threshold. For each DC voltage, the current DC voltage is applied to the finite element model of the cable, and the temperature difference between the inside and outside of the insulation layer of the simulated AC cable is adjusted until the electric field strength at each point in the current insulation layer is equal. The electric field strength at any point within the current insulation layer is taken as the critical reversal field strength of the insulation layer under the current DC voltage applied to the cable finite element model.

5. The method for determining the transmission capacity of an AC cable after DC conversion as described in claim 4, characterized in that, Under the current DC current, based on the finite element model of the cable, the current conductor temperature and the maximum electric field strength within the insulation layer of the simulated AC cable are calculated and generated through simulation, including: The current DC current is used as an excitation source and input into the cable finite element model so that the cable finite element model can perform electrothermal coupling calculations based on the current DC current and generate the steady-state temperature field distribution caused by the current DC current. Extract the current conductor temperature from the steady-state temperature field distribution; Based on the steady-state temperature field distribution, the electric field intensity distribution of the insulation layer of the simulated AC cable is determined; The maximum electric field intensity within the insulation layer of the simulated AC cable is extracted from the electric field intensity distribution of the insulation layer.

6. The method for determining the transmission capacity of an AC cable after DC conversion as described in claim 5, characterized in that, The DC transmission capacity of the generated AC cable is calculated using the following formula: P DC =2U DC ·I DC In the formula, P DC For the DC transmission capacity of the AC cable; U DC Maximum DC voltage; I DC This represents the maximum DC current carrying capacity.

7. A device for determining the transmission capacity of an AC cable after DC conversion, characterized in that, include: Data acquisition module, maximum DC voltage determination module, maximum DC current carrying capacity module, and DC transmission capacity determination module; The data acquisition module is used to acquire the finite element model of the AC cable and the cable field strength calibration model used to characterize the quantitative relationship between the critical reversal field strength of the insulation layer and the DC voltage of the simulated AC cable; wherein, the finite element model of the cable includes the simulated AC cable. The maximum DC voltage determination module is used to input a preset insulation layer electric field strength threshold as the critical reversal field strength of the insulation layer into the cable field strength calibration model, so that the cable field strength calibration model generates the corresponding DC voltage according to the preset insulation layer electric field strength threshold; and uses the DC voltage corresponding to the preset insulation layer electric field strength threshold as the maximum DC voltage of the simulated AC cable. The maximum DC current carrying capacity module is used to repeatedly perform a current increment operation under the condition that the conductor voltage of the simulated AC cable is set to the maximum DC voltage, until a termination condition is met, thereby generating the maximum DC current carrying capacity of the simulated AC cable. The termination condition is that the current conductor temperature of the simulated AC cable exceeds a preset conductor temperature threshold, or the current maximum electric field strength in the insulation layer of the simulated AC cable exceeds a preset insulation layer electric field strength threshold. The current increment operation includes: under the current DC current, based on the finite element model of the cable, simulating and calculating the current conductor temperature and the current maximum electric field strength in the insulation layer of the simulated AC cable; wherein the initial DC current is a preset value; determining whether the termination condition is met; if yes, then using the previous DC current as the maximum DC current carrying capacity of the simulated AC cable; if no, then updating the current DC current according to a preset step size. The DC transmission capacity determination module is used to determine the DC transmission capacity of the simulated AC cable based on the maximum DC voltage and the maximum DC current carrying capacity.

8. The device for determining the transmission capacity of an AC cable after DC conversion as described in claim 7, characterized in that, The DC transmission capacity determination module calculates and generates the DC transmission capacity of the AC cable using the following formula: P DC =2U DC ·I DC In the formula, P DC For the DC transmission capacity of the AC cable; U DC Maximum DC voltage; I DC This represents the maximum DC current carrying capacity.

9. An electronic device, characterized in that, It includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein the processor executes the computer program to implement the method for determining the transmission capacity of an AC cable after DC conversion as described in any one of claims 1 to 6.

10. A storage medium, characterized in that, The storage medium includes a stored computer program, wherein, when the computer program is executed, it controls the device containing the storage medium to perform the method for determining the transmission capacity of an AC cable after DC conversion as described in any one of claims 1 to 6.

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