Cable structure optimization method and system, program product and electronic equipment

Abstract

The embodiment of the invention belongs to the technical field of cable manufacturing, and particularly relates to a cable structure optimization method and system, a program product and electronic equipment, a cable structure model is established according to cable parameters to be optimized, steady-state current-carrying capacity under set laying conditions and a metal sheath grounding mode is acquired, a cable line model is further established, and load parameters are set; corresponding steady-state and transient-state voltage and current waveforms are obtained through simulation, an electricity-heat-flow multi-physics field coupling model of the cable is established by further combining cable parameters, and the current-carrying capacity, the electric field intensity of an insulating layer and the short-circuit capacity of a metal sheath under steady-state and transient-state operation conditions are obtained through simulation; and in combination with a simulation result and a cable design standard formula, calculating and determining the value range of the optimal cable insulation thickness and metal sheath thickness. By constructing a multi-simulation collaborative optimization framework, the current-carrying capacity, the electric field intensity, the short-circuit capacity and other key indexes are accurately obtained, and the problem of high-voltage cable structure size design is solved.

Description

Technical Field

[0001] The embodiments of this invention belong to the field of cable manufacturing technology, specifically cable structure optimization methods, systems, program products, and electronic devices. Background Technology

[0002] To meet the demands of power transmission projects requiring "large capacity, long distance, and large cross-section," the transmission voltage levels of cables are constantly increasing. However, the increase in voltage levels and transmission capacity also leads to a significant rise in the induced voltage on the cable's metallic sheath and the amplitude of the circulating current in the sheath, which can easily exceed safety limits. This not only poses a major hazard to personal electric shock and the safe operation of equipment, but also causes a series of chain reactions such as increased cable losses, intensified heating, and shortened lifespan.

[0003] To address these issues, cable structure is typically optimized during the design phase. However, traditional structural design relies primarily on relevant specifications or empirical formulas. This approach fails to adequately consider the unique laying conditions, grounding methods, and actual operating conditions of specific projects, potentially leading to designs that are either overly conservative (high cost) or insufficient (high risk), and thus cannot be optimized to meet the specific needs of the user.

[0004] To overcome the shortcomings of standard designs, cable simulation technology has been introduced into the design process. Currently, commonly used professional simulation software in the industry each has its own characteristics, but also inherent limitations. Using any single software cannot comprehensively and accurately solve the aforementioned problems. For example: Current carrying capacity calculation software (such as CYMCAP software) is based on thermal circuit models and is good at calculating the current carrying capacity of cables under steady-state operation according to cable design standards. However, its models are difficult to simulate the transient operating conditions of power systems (such as power frequency overvoltage and lightning overvoltage), which limits its application scope. Electromagnetic transient analysis software (such as ATP / EMTP software) is based on circuit models and can effectively simulate voltage and current waveforms in steady-state and transient states of power systems. However, the initial values ​​for its current carrying capacity analysis require manual setting of load parameters, which affects the objectivity of the results. More importantly, its model is based on the impedance matrix and can only reflect electromagnetic coupling relationships. It cannot realize the coupling analysis of multiple physical fields such as electricity, heat, and fluid, and cannot accurately calculate the impact of temperature field on cable performance. Multiphysics coupling simulation platforms (such as COMSOL software) can accurately simulate the electro-thermal-current coupling process of cables, but they are difficult to set up in simulating complex external transient conditions of power systems (such as circuit breaker operation and lightning intrusion waves), which challenges their practicality.

[0005] In summary, the prior art has the following core problems: the traditional design method relies on standards and is too rough; and the simulation tool has a single function, the model is simple, and each software is independent of each other, lacking cooperation, resulting in a large deviation between the simulation analysis result and the actual operating condition, and insufficient reliability. SUMMARY

[0006] To solve the technical problems in the background art, the present application provides a cable structure optimization method, system, program product and electronic device, which builds a multi-simulation cooperative optimization framework to solve the problem of high-voltage cable structure size design. The method uses cable parameters to determine the steady-state current-carrying capacity, and then uses it as a key parameter to further simulate the voltage and current waveforms under power system transient operating conditions. Finally, these simulation results are analyzed by electric-thermal-flow multi-physical field coupling analysis, so as to accurately obtain key indicators such as current-carrying capacity, electric field strength and short-circuit capacity. Finally, the best thickness range of the cable insulation layer and the metal sheath is optimized and determined.

[0007] To achieve the above-mentioned purpose, the present application adopts the following technical solutions: The first embodiment of the present application discloses a cable structure optimization method, comprising the following steps: Step S1, obtaining cable parameters to be optimized; Step S2, establishing a cable structure model according to the cable parameters, updating the cable structure model using the arrangement mode, laying conditions and metal sheath grounding mode in the cable parameters, and obtaining the steady-state current-carrying capacity using the updated cable structure model; Step S3, establishing a cable line model according to the cable parameters, updating the cable line model using the system operating condition and the laying conditions and metal sheath grounding mode in the cable parameters, determining the load parameter according to the obtained steady-state current-carrying capacity and the system operating condition, and obtaining the steady-state and transient voltage and current waveforms under the corresponding load parameter using the updated cable line model; Step S4, establishing an electric-thermal-flow multi-physical field coupling model of the cable according to the cable parameters, using the obtained steady-state and transient voltage and current waveforms as the excitation source of the electric-thermal-flow multi-physical field coupling model, and obtaining the current-carrying capacity, electric field strength of the insulation layer and short-circuit capacity of the metal sheath under the steady-state and transient operating conditions; Step S5, calculating and determining the preferred cable insulation thickness and metal sheath thickness value range according to the current-carrying capacity, electric field strength of the insulation layer and short-circuit capacity of the metal sheath under the steady-state and transient operating conditions, and combining the cable design standard formula.

[0008] As a further improvement, the cable parameters include cable structure, geometric size, material property, arrangement mode, laying spacing, laying condition and metal sheath grounding mode; the arrangement mode includes at least one of horizontal laying, vertical laying, equilateral triangle laying and inverted triangle laying; the laying condition includes at least one of tunnel laying, pipe laying, cable trench laying, direct buried laying and backflow cable arrangement mode; the metal sheath grounding mode includes at least one of cross-connection with both ends directly grounded and cross-connection with one end grounded through a protector.

[0009] As a further improvement, step S2 is specifically: Step S2.1, constructing a cable structure model according to the cable structure, geometric size and material property in the cable parameters; Step S2.2, updating the cable structure model according to the arrangement mode, laying condition and metal sheath grounding mode; Step S2.3, obtaining the steady-state carrying capacity by using the updated cable structure model according to the conductor maximum operating temperature and operating voltage class.

[0010] As a further improvement, step S3 is specifically: Step S3.1, establishing a cable line model according to the cable structure, geometric size, material property and arrangement mode in the cable parameters; Step S3.2, updating the cable line model according to the system operating condition, laying condition and metal sheath grounding mode; the system operating condition includes at least one of power frequency overvoltage, temporary overvoltage, operating overvoltage and lightning overvoltage; Step S3.3, determining the load parameter based on the system operating condition and the steady-state carrying capacity, obtaining the sheath induced voltage and sheath circulating current under the steady-state and transient operating conditions by using the updated cable line model, and forming the steady-state and transient voltage and current waveforms.

[0011] As a further improvement, after step S3.3, it further includes: verifying whether the sheath induced voltage and the sheath circulating current of the cable model are lower than the corresponding safety threshold; if the corresponding safety threshold is exceeded, returning to adjust the arrangement mode or the metal sheath grounding mode and recalculating until the requirements are met.

[0012] As a further improvement, step S4 is specifically: Step S4.1, establishing a multi-dimensional geometric model of the cable according to the cable structure, geometric size, material property and arrangement mode in the cable parameters; Step S4.2, updating the multi-dimensional geometric model according to the laying condition and the metal sheath grounding mode, and obtaining an electro-thermal-fluid multi-physical field coupling model including electromagnetic field, temperature field and flow field; Step S4.3, the steady-state and transient voltage and current waveforms obtained in step S3 are loaded into the electro-thermal-flow multi-physical field coupling model as an excitation source, and the current-carrying capacity, the electric field intensity of the insulation layer and the short-circuit capacity of the metal sheath under the steady-state and transient operating conditions are obtained.

[0013] As a further improvement, after step S4.3, it further comprises: comparing the obtained current-carrying capacity with the steady-state current-carrying capacity obtained in step S2; if the deviation exceeds a predetermined tolerance, the current-carrying capacity obtained by the multi-physical field simulation is fed back to step S3, the load parameter is updated, and the simulation is performed again until the result converges.

[0014] The second embodiment of the present application discloses a cable structure optimization system, comprising: a cable parameter acquisition module configured to acquire cable parameters to be optimized; a first simulation analysis module configured to establish a cable structure model according to the cable parameters, update the cable structure model using the arrangement mode, laying condition and metal sheath grounding mode in the cable parameters, and obtain the steady-state current-carrying capacity using the updated cable structure model; a second simulation analysis module configured to establish a cable line model according to the cable parameters, update the cable line model using the system operating conditions and the laying condition and metal sheath grounding mode in the cable parameters, determine the load parameter according to the obtained steady-state current-carrying capacity and the system operating conditions, and obtain the steady-state and transient voltage and current waveforms under the corresponding load parameter using the updated cable line model; a third simulation analysis module configured to establish an electro-thermal-flow multi-physical field coupling model of the cable according to the cable parameters, use the obtained steady-state and transient voltage and current waveforms as the excitation source of the electro-thermal-flow multi-physical field coupling model, and obtain the current-carrying capacity, the electric field intensity of the insulation layer and the short-circuit capacity of the metal sheath under the steady-state and transient operating conditions; a cable structure size optimization design module configured to calculate and determine the preferred value range of the cable insulation thickness and the metal sheath thickness according to the current-carrying capacity, the electric field intensity of the insulation layer and the short-circuit capacity of the metal sheath under the steady-state and transient operating conditions, and in combination with the cable design standard formula.

[0015] The third embodiment of the present application discloses a computer program product comprising computer readable instructions which, when executed on an electronic device, cause the electronic device to implement the above-mentioned cable structure optimization method.

[0016] The fourth embodiment of the present application discloses an electronic device comprising at least one processor and a memory connected to the processor, the memory being configured to store a computer program; the processor is configured to execute the computer program, so that the electronic device can implement the above-mentioned cable structure optimization method.

[0017] Compared with the prior art, the above one or more technical solutions have the following beneficial effects: By constructing the progressive simulation architecture of "steady-state ampacity calculation-transient electromagnetic simulation-multi-physical field coupling analysis", the advantages of each simulation link are complemented and data closed-loop verification is realized, effectively solving the problem of insufficient precision caused by model simplification and single software function in traditional design, and providing accurate data support for cable structure size optimization in the whole process and under multiple working conditions. During the multi-simulation cooperation, the specific arrangement mode, laying conditions and grounding mode of the cable and other parameters are fully considered to affect the performance of the cable, so as to establish a thermal circuit model considering the specific laying conditions, a circuit model reflecting the actual grounding mode, and finally realize multi-physical field coupling analysis through simulation, solve the problem that the traditional design method is too rough and cannot consider the specific engineering conditions, realize the fine design based on the specific engineering conditions, and avoid the problem of overly conservative or insufficient design. BRIEF DESCRIPTION OF DRAWINGS

[0018] The drawings accompanying the specification of this application form a part thereof, serve to provide further understanding of the application, and together with the description of the exemplary embodiments of the application given below, serve to explain the application, and do not constitute an improper limitation on the application.

[0019] Figure 1 A cable structure optimization flowchart is provided for one or more embodiments of the application; Figure 2 A schematic diagram of importing cable parameters based on ampacity calculation software is provided for one or more embodiments of the application; Figure 3 A schematic diagram of establishing a cable structure model based on ampacity calculation software is provided for one or more embodiments of the application; Figure 4 A schematic diagram of setting operating temperature and voltage level based on ampacity calculation software is provided for one or more embodiments of the application; Figure 5 A schematic diagram of importing cable parameters based on electromagnetic transient analysis software is provided for one or more embodiments of the application; Figure 6 A schematic diagram of constructing a cable line model based on electromagnetic transient analysis software is provided for one or more embodiments of the application; Figure 7 A schematic diagram of obtaining cable line steady-state and transient voltage and current waveforms based on electromagnetic transient analysis software is provided for one or more embodiments of the application; Figure 8 A schematic diagram of importing cable parameters based on a multi-physical field simulation coupling platform is provided for one or more embodiments of the application; Figure 9A schematic diagram of a coupled model of electromagnetic field, temperature field and flow field of a cable line built on a multiphysics simulation coupling platform, provided for one or more embodiments of the present invention; Figure 10 This is a schematic diagram illustrating the acquisition of cable current carrying capacity, insulation electric field strength, and metal sheath short-circuit capacity under steady-state and transient operating conditions using a multiphysics simulation coupling platform, provided for one or more embodiments of the present invention. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0022] The current carrying capacity calculation software, electromagnetic transient analysis software, and multiphysics coupling simulation platform involved in this invention are not limited to specific software types, as long as they can meet the relevant functions such as current carrying capacity calculation, electromagnetic transient analysis, and multiphysics simulation.

[0023] In describing the specific embodiments of the present invention, the current carrying capacity calculation software is illustrated using CYMCAP software as an example. The electromagnetic transient analysis software can be PSCAD software, ATP / EMTP software, or other software capable of electromagnetic transient analysis. The specific embodiments are illustrated using ATP / EMTP software as an example. The multiphysics simulation coupling platform is illustrated using COMSOL software as an example. The aforementioned software is only used to exemplify the technical process and core concept of the present invention and does not constitute a reliance on, recommendation, or limitation of any specific commercial software product. The core concept of the present invention lies in utilizing the synergistic cooperation of multiple tools, such as current carrying capacity calculation software, electromagnetic transient analysis software, and multiphysics simulation coupling platform, to achieve the technical effects of the present invention.

[0024] Those skilled in the art should understand that, in the actual implementation of this invention, any similar software tool that meets the input / output requirements and functional needs of this invention can be used as a substitute, as long as it can achieve the corresponding current carrying capacity calculation, electromagnetic transient analysis, or multiphysics coupling simulation functions, and meets the data interface and process coordination requirements specified in this invention. All software tools commonly used or available in the field fall within the scope of this invention.

[0025] Example 1: like Figure 1 As shown, the cable structure optimization method includes the following steps: S1, obtaining cable parameters, including cable structure, geometric size, material property, arrangement mode, laying spacing, laying condition and metal sheath grounding mode; S2, importing the cable parameters into the ampacity calculation software, and establishing a cable structure model in the ampacity calculation software to obtain the steady-state ampacity under the laying condition and the metal sheath grounding mode; S3, importing the obtained steady-state ampacity and cable parameters into the electromagnetic transient analysis software, establishing a cable line model in the electromagnetic transient analysis software and setting load parameters to obtain steady-state and transient voltage and current waveforms under the laying condition and the metal sheath grounding mode; S4, importing the obtained steady-state and transient voltage and current waveforms and cable parameters into the multi-physical field simulation coupling platform, establishing an electro-thermal-flow coupling model of the cable in the multi-physical field simulation coupling platform to obtain simulation calculation results under steady-state and transient operating conditions, including ampacity, electric field strength of the insulation layer, and short-circuit capacity of the metal sheath; S5, determining an optimal cable structure size value range according to the obtained simulation calculation results and combining design standard formulas, and the optimal structure size includes insulation thickness and metal sheath thickness.

[0026] S1, obtaining cable parameters, including cable structure, geometric size, material property, arrangement mode, laying spacing, laying condition and metal sheath grounding mode.

[0027] The cable structure includes a conductor, an inner semi-conductive shielding layer, an insulation layer, an outer semi-conductive shielding layer, a buffer layer, a metal sheath layer, an outer sheath, and an extruded semi-conductive layer.

[0028] The geometric size of the cable is pre-set according to design standards or experience.

[0029] The material property of the cable is pre-set according to design standards or experience.

[0030] The arrangement mode of the cable includes at least one of horizontal laying, vertical laying, equilateral triangle laying, and inverted triangle laying.

[0031] The laying condition includes at least one of tunnel laying, pipe laying, cable trench laying, direct burial laying, and backflow cable arrangement mode.

[0032] The metal sheath grounding mode includes at least one of cross-connection and direct grounding at both ends, and cross-connection and grounding at one end through a protector. S2, importing the cable parameters into the ampacity calculation software, and establishing a cable structure model in the ampacity calculation software to obtain the steady-state ampacity under the laying condition and the metal sheath grounding mode.

[0033] Specifically comprising the following steps: S2.1, import cable structure, geometry, material properties, establish cable structure model in ampacity calculation software.

[0034] The established cable structure model is shown in Figure 2 The conductor is four segments, made of copper, with a diameter of 64 mm, and the conductor shield has a diameter of 68 mm; the insulation is cross-linked polyethylene (XLPE) with a diameter of 112 mm, the semi-conducting insulation shield has a diameter of 116 mm, the aluminum sheath layer has a diameter of 118 mm, the polyethylene jacket has a diameter of 126 mm, and the overall cable diameter is 126 mm.

[0035] S2.2, set cable arrangement, laying conditions and metal sheath grounding mode in ampacity calculation software, update the cable structure model, as shown in Figure 3 The cable arrangement is "cross bonded cable system, equal minor section lengths"; The laying condition is "single conductor cables NOT touching"; The metal sheath grounding mode is "sheaths cross bonded, flat configuration".

[0036] S2.3, set the maximum operating temperature of the conductor and the operating voltage level in the ampacity calculation software, and obtain the steady-state ampacity under the corresponding laying conditions and metal sheath grounding mode using the updated cable structure model.

[0037] As shown in Figure 4 The set maximum operating temperature of the conductor is "90°C", and the operating voltage level is "110KV".

[0038] The set maximum operating temperature of the conductor complies with existing standards (such as IEC 60840, IEC 62067), for example 90°C for XLPE.

[0039] ​​S3. Importing the obtained steady-state load current and cable parameters into the electromagnetic transient analysis software, establishing a cable line model in the electromagnetic transient analysis software and setting load parameters, and obtaining steady-state and transient voltage and current waveforms under laying conditions and metal sheath grounding modes.

[0040] wherein the load parameters are determined according to the operating voltage and the steady-state load current; and the steady-state and transient voltage and current waveforms are voltage and current waveforms of the cable line under normal operating conditions, internal and external overvoltage faults.

[0041] Specifically, the method comprises the following steps: S3.1. Importing the cable structure, geometric dimensions, material properties and arrangement mode into the electromagnetic transient analysis software, and establishing a cable line model.

[0042] Figure 5 An interface for importing required parameters in the electromagnetic transient analysis software is shown, as shown in Table 1.

[0043] Table 1. Parameter import interface of the electromagnetic transient analysis software

[0044] S3.2. Setting system operating conditions, laying conditions and metal sheath grounding modes in the electromagnetic transient analysis software, and updating the cable line model.

[0045] Figure 6 A constructed cable line model is shown, wherein the cable line is located between a power supply side and a power station side, a simulated single-phase grounding fault is introduced at the power station side, and a simulated lightning stroke condition is introduced between the power supply side and the power station side.

[0046] The system operating conditions include internal and external overvoltages, i.e., power frequency overvoltage, temporary overvoltage, operating overvoltage and lightning overvoltage.

[0047] When setting the power frequency / temporary overvoltage, the overvoltage multiple and duration are determined according to specific design requirements.

[0048] When setting the operating overvoltage, it is determined whether the overvoltage is caused by air switching, load switching or other operations according to specific design requirements, and a standard waveform (such as 250 / 2500 μs) is given.

[0049] When setting the lightning overvoltage, the lightning current amplitude and waveform (such as 8 / 20 μs) are determined according to specific design requirements.

[0050] S3.3, import the operating voltage and the steady-state load current in step S2 into the electromagnetic transient analysis software to determine the load parameters, analyze the shield induced voltage and the sheath circulating current under the steady-state and transient operating conditions by using the updated cable line model, and obtain the steady-state and transient voltage and current waveforms of the cable line. The obtained waveform diagram is shown in Figure 7 The embodiment takes the voltage waveform as an example, Figure 7 The upper half of the waveform shows that the horizontal coordinate is time (ms) and the vertical coordinate is voltage (kV), and the lower half of the waveform shows that the horizontal coordinate is time (ms) and the vertical coordinate is voltage (MV).

[0051] In the embodiment, not only the steady-state and transient voltage and current waveforms of the cable line are obtained, but also key quantitative results are obtained, for example, the maximum transient induced voltage that can occur on the shield (used to check the selection of the shield protector), the short-circuit current amplitude and duration flowing through the metal sheath when the system is short-circuited (used for subsequent calculation of the metal sheath thickness).

[0052] Check whether the shield induced voltage and the circulating current are within a safe range (for example, the IEC 60287 suggests that the shield voltage is limited to within 60 V). If the limit is exceeded, return to S1 to adjust the arrangement mode or the grounding mode.

[0053] After step S3.3, the method further includes: checking whether the shield induced voltage and the sheath circulating current of the cable model are lower than corresponding safety thresholds; and if the corresponding safety thresholds are exceeded, returning to adjust the arrangement mode or the metal sheath grounding mode and recalculating until the requirements are met.

[0054] S4, import the obtained steady-state and transient voltage and current waveforms and cable parameters into a multi-physical field simulation coupling platform, establish an electro-thermal-flow coupling model of the cable in the multi-physical field simulation coupling platform, and obtain simulation calculation results under steady-state and transient operating conditions, including the load current, the electric field intensity of the insulation layer, and the short-circuit capacity of the metal sheath. Specifically, the method includes the following steps: S4.1, import the cable structure, geometric dimensions, material properties, and arrangement mode into the multi-physical field simulation coupling platform, and establish a multi-dimensional geometric model of the cable in the multi-physical field simulation coupling platform. The established multi-dimensional geometric model is shown in Figure 8 .

[0055] S4.2, set the laying conditions and the metal sheath grounding mode in the multi-physical field simulation coupling platform, update the multi-dimensional geometric model, obtain an electro-thermal-flow multi-physical field coupling model, and the electro-thermal-flow multi-physical field coupling model includes the coupling conditions of the electromagnetic field, the temperature field, and the flow field of the cable line. The established coupling model is shown in Figure 9 .

[0056] When laying in air, the flow field refers to the heat convection and heat conduction in air. For tunnel laying, the heat dissipation of air flow needs to be calculated; for direct burial laying, the soil heat conduction is mainly considered.

[0057] S4.3, the voltage and current waveform in step 3 is introduced into the multi-physical field simulation coupling platform as an excitation source, and the electromagnetic field, temperature field and flow field characteristics of the cable under steady-state and transient operating conditions are analyzed by using the electro-thermal-flow multi-physical field coupling model to obtain the cable current-carrying capacity, insulation electric field strength and metal sheath short-circuit capacity under corresponding steady-state and transient operating conditions. The simulation results are shown in Figure 10

[0058] In this embodiment, the "current-carrying capacity" calculated by the multi-physical field simulation coupling platform and the "current-carrying capacity" calculated by the current-carrying capacity calculation software in S2 are compared for verification.

[0059] If the deviation is large, it means that the thermal circuit model of the current-carrying capacity calculation software is too simplified, and the more accurate multi-physical field coupling results in the multi-physical field simulation coupling platform should be used as the reference, and the new current-carrying capacity is fed back to step S3 to update the load parameters in the electromagnetic transient analysis software and re-perform the transient simulation.

[0060] After step S4.3, it also includes: comparing the obtained current-carrying capacity with the steady-state current-carrying capacity obtained in step S2; if the deviation exceeds the predetermined tolerance, the current-carrying capacity is fed back to step S3 to update the load parameters and re-perform the simulation calculation until the results converge.

[0061] S5, according to the simulation calculation results, combined with the design standard formula, the preferred cable structure size value range is determined, and the preferred structure size includes the insulation thickness and the metal sheath thickness. Based on the electro-thermal-flow field coupling simulation results in step S4.3 and the design standard formula, the current-carrying capacity, the insulation electric field strength and the metal sheath short-circuit capacity are calculated and determined.

[0062] In this embodiment, the calculated insulation thickness is the minimum insulation thickness required under power frequency and impulse voltage, and the actual design thickness needs to ensure that the maximum electric field strength is less than the allowable field strength of the material (considering the safety factor) under various operating conditions.

[0063] In this embodiment, the metal sheath thickness is the minimum metal sheath thickness required to meet the short-circuit thermal stability, and the actual design thickness also needs to consider the safety redundancy.

[0064] The cable insulation layer thickness calculation method is as follows: Among them, , ​​​The insulation thicknesses under power frequency and impulse voltage, respectively, mm; and The maximum system line voltage and the system lightning impulse voltage, respectively, kV; , The temperature coefficients of the breakdown strength under power frequency and impulse voltage, respectively; , The aging coefficients of the breakdown strength under power frequency and impulse voltage, respectively; , The safety coefficients of the breakdown strength under power frequency and impulse voltage, respectively; , The minimum breakdown strengths determined by the power frequency and impulse breakdown voltages conforming to Weibull distribution, kV / mm, respectively.

[0065] For cross-linked polyethylene insulated cables, the temperature coefficients and the safety coefficients are usually constant values, and the calculation formula of the aging coefficient is as follows: ; In the formula, is the life index; is the life of the cable insulation under long-term working voltage, usually 40 years; is the duration of the short-time withstand voltage test of the cable insulation, usually 1 hour.

[0066] The key to determining the thickness of the cable insulation lies in determining the minimum breakdown strength and the life index of the insulation, which are as follows: ; ; In the formula, is the test field strength; is the life at the set reliability level; is a constant; , are the electric field strengths of the sample under the two test voltages, respectively; , are the breakdown times of the sample under the two electric field strengths, respectively.

[0067] Based on the calculation results of the above formula, simulation results, empirical constants and test data, the preferred thickness of the cable insulation layer can be determined.

[0068] The determination of the thickness of the metal sheath matches the maximum fault current and the duration under the system power frequency and impulse overvoltage.

[0069] The calculation method of the thickness of the metal sheath is as follows: ; ; ; wherein, is the short circuit current allowed; is the short circuit current (RMS value valid throughout the short circuit) calculated on adiabatic basis, A; is the short circuit duration, s; is the cross section of the metallic sheath, ; is the final temperature; is the initial temperature; is the specific heat of the fluid at 0℃; is the specific heat of the fluid at 20℃; is the fluid resistance at 20℃; is the heat loss coefficient.

[0070] Based on the calculation results of the above formula, simulation results, empirical constants and test data, the preferred thickness of the metallic sheath can be determined.

[0071] The traditional design method mainly relies on specifications and empirical formulas, and cannot fully consider the laying conditions, grounding methods and operating conditions of specific projects. The scheme can accurately input the specific arrangement method, laying conditions and grounding method of the cable and fully consider the influence of these factors on the performance of the cable in the simulation process. Through the thermal circuit model considering the specific laying conditions established by the ampacity calculation software, the circuit model reflecting the actual grounding method is constructed by the electromagnetic transient analysis software, and finally the multi-physical field coupling analysis is realized through the multi-physical field simulation coupling platform, so as to realize the fine design based on the specific engineering conditions and avoid the problems of over-conservative or insufficient design.

[0072] The technical route of multi-software collaborative simulation is adopted, and the advantages of various software or tools are fully utilized. By inputting the calculated steady-state ampacity as the load parameter of transient analysis, and then inputting the simulated transient voltage and current waveform as the excitation source of multi-physical field simulation, a complete simulation chain is formed, which not only solves the problem of artificial setting of load parameters in electromagnetic transient analysis, but also overcomes the difficulty of multi-physical field simulation platform in simulating complex power grid transient conditions.

[0073] The prior art cannot accurately reflect the actual operating conditions due to independent use of each software and simple model. The scheme establishes a more actual cable simulation model through multi-software cooperation and multi-physical field coupling analysis. In particular, through the multi-physical field simulation coupling platform, the electric-thermal-fluid multi-physical field coupling analysis can accurately simulate the influence of the temperature field on the electrical performance of the cable and the influence of the fluid field on the heat dissipation of the cable, thereby greatly improving the accuracy of the simulation results. At the same time, by combining the transient simulation results with the multi-physical field analysis, the performance of the cable under fault conditions can be more accurately evaluated.

[0074] The traditional design method lacks precise prediction ability of cable performance. The scheme can output accurate calculation results of key performance parameters such as current-carrying capacity, insulation electric field strength, and metal sheath short-circuit capacity through multi-software cooperative simulation. Based on these results, combined with the design standard formula, the optimal value range of the insulation thickness and the metal sheath thickness can be scientifically determined, which not only ensures the safe operation of the cable, but also avoids waste of materials, providing reliable quantitative basis for the optimization design of cable structure size.

[0075] Embodiment two: The cable structure optimization system comprises: The cable parameter acquisition module is configured to acquire the cable parameters to be optimized, including cable structure, geometric size, material property, arrangement mode, laying spacing, laying condition, and metal sheath grounding mode. The first simulation analysis module is configured to establish a cable structure model in the current-carrying capacity calculation software according to the cable parameters, and acquire the steady-state current-carrying capacity under the laying condition and the metal sheath grounding mode. The second simulation analysis module is configured to import the obtained steady-state current-carrying capacity together with the cable parameters into the electromagnetic transient analysis software, establish a cable line model and set load parameters, and obtain the steady-state and transient voltage and current waveforms under the laying condition and the metal sheath grounding mode through simulation. The third simulation analysis module is configured to import the obtained steady-state and transient voltage and current waveforms together with the cable parameters into the multi-physical field simulation coupling platform, establish an electric-thermal-fluid multi-physical field coupling model of the cable, and obtain the current-carrying capacity, the electric field strength of the insulation layer, and the short-circuit capacity of the metal sheath under the steady-state and transient operating conditions through simulation. The cable structure size optimization design module is configured to calculate and determine the value range of the preferred cable insulation thickness and metal sheath thickness according to the current-carrying capacity, the electric field strength of the insulation layer, and the short-circuit capacity of the metal sheath under the steady-state and transient operating conditions, combined with the cable design standard formula.

[0076] A collaborative simulation link of "load flow calculation→ electromagnetic transient analysis→ multi-physical field simulation" is constructed. The steady-state load flow is accurately calculated by software, and the load parameters for transient analysis are obtained by combining the operating voltage, which solves the problem of relying on experience setting; then the complex power grid transient is simulated, and the high-precision waveform is output as the excitation source of simulation, which overcomes the difficulty of setting external transient conditions. Finally, through multi-physical field coupling verification, a closed loop with complementary advantages is formed.

[0077] Not only the steady-state performance is concerned, but also the transient fault simulation such as lightning and operating overvoltage is introduced to realize the full life cycle coverage of the cable from normal operation to extreme fault. The electric field strength of the insulation layer under lightning instantaneous and the thermal stability performance of the metal sheath under short-circuit current can be accurately evaluated in the design stage, which completely changes the traditional static design mode, changes the post-validation to pre-prediction, and significantly improves the system safety margin.

[0078] Through the multi-physical field simulation platform, the electromagnetic field, temperature field and fluid field are solved synchronously, and the whole process of current heat generation, heat dissipation and temperature effect on electrical characteristics is accurately simulated. The error of traditional isolated model is avoided, and the prediction accuracy of load capacity, temperature distribution and other key indicators is far superior to conventional methods, providing a solid data foundation for optimization design.

[0079] The short-circuit capacity and electric field strength parameters obtained by simulation are combined with the standard design formula to convert into the insulation layer and metal sheath thickness optimization value range which can directly guide production. This method can effectively avoid overdesign under the premise of ensuring safety, and realize the best balance between cost control and performance guarantee.

[0080] Example three: A computer program product includes computer readable instructions that, when executed on an electronic device, cause the electronic device to implement the above cable structure optimization method.

[0081] An optimization framework of multi-software collaborative simulation is constructed to solve the problem of high-voltage cable structure size design. This method uses load flow calculation software to calculate the steady-state load flow, and then inputs it as a key parameter into electromagnetic transient analysis software to accurately simulate the voltage and current waveform under power system transient conditions. Finally, these results are imported into a multi-physical field simulation coupling platform for electro-thermal-fluid multi-physical field coupling analysis, so as to accurately obtain key indicators such as load capacity, electric field strength and short-circuit capacity. Finally, the best thickness range of cable insulation layer and metal sheath is optimized and determined.

[0082] Example four: An electronic device comprises at least one processor and a memory connected with the processor, the memory is used for storing a computer program; the processor is used for executing the computer program, so that the electronic device can realize the cable structure optimization method.

[0083] By constructing an optimization framework of multi-software collaborative simulation, the problem of high-voltage cable structure size design is solved. The method uses the ampacity calculation software to calculate the steady-state ampacity, and then inputs it as a key parameter into the electromagnetic transient analysis software to accurately simulate the voltage and current waveform under the transient working condition of the power system. Finally, these results are imported into the multi-physics field simulation coupling platform for electric-thermal-flow multi-physics field coupling analysis, so as to accurately obtain the key indicators such as ampacity, electric field strength and short-circuit capacity, and finally optimize and determine the best thickness range of the cable insulation layer and metal sheath.

[0084] The above is only a preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for optimizing a cable structure, characterized by, The method comprises the following steps: Step S1, obtaining cable parameters to be optimized; Step S2, establishing a cable structure model according to the cable parameters, updating the cable structure model by using arrangement mode, laying condition and metal sheath grounding mode in the cable parameters, and obtaining steady-state ampacity by using the updated cable structure model; Step S3, establishing a cable line model according to the cable parameters, updating the cable line model by using system operation conditions and laying condition and metal sheath grounding mode in the cable parameters, determining load parameters according to the obtained steady-state ampacity and the system operation conditions, and obtaining steady-state and transient voltage and current waveforms under corresponding load parameters by using the updated cable line model; Step S4, establishing an electro-thermal-flow multi-physical field coupling model of the cable by using the obtained steady-state and transient voltage and current waveforms as excitation sources of the electro-thermal-flow multi-physical field coupling model, and obtaining ampacity, electric field intensity of the insulation layer and short-circuit capacity of the metal sheath under steady-state and transient operation conditions; Step S5, calculating and determining the value range of the preferred cable insulation thickness and metal sheath thickness by combining the cable design standard formula according to the ampacity under the steady-state and transient operation conditions, the electric field intensity of the insulation layer and the short-circuit capacity of the metal sheath.

2. The cable structure optimization method of claim 1, wherein, In step S1, the cable parameters include cable structure, geometric size, material property, arrangement mode, laying spacing, laying condition and metal sheath grounding mode; the arrangement mode includes at least one of horizontal laying, vertical laying, equilateral triangle laying and inverted triangle laying; the laying condition includes at least one of tunnel laying, pipe laying, cable trench laying and direct buried laying; and the metal sheath grounding mode includes at least one of cross interconnection with both ends directly grounded and cross interconnection with one end grounded through a protector.

3. The cable structure optimization method of claim 1, wherein, In step S2, the method comprises the following steps: Step S2.1, constructing a cable structure model according to the cable structure, geometric size and material property in the cable parameters; Step S2.2, updating the cable structure model according to the arrangement mode, laying condition and metal sheath grounding mode; Step S2.3, obtaining the steady-state ampacity by using the updated cable structure model according to the maximum operating temperature of the conductor and the operating voltage level.

4. The cable structure optimization method of claim 1, wherein, In step S3, the method comprises the following steps: Step S3.1, establishing a cable line model according to the cable structure, geometric size, material property and arrangement mode in the cable parameters; Step S3.2, updating the cable line model according to the system operation conditions, laying condition and metal sheath grounding mode; The system operation conditions include at least one of power frequency overvoltage, temporary overvoltage, operating overvoltage and lightning overvoltage; Step S3.3, determining load parameters based on the system operation conditions and the steady-state ampacity, obtaining the sheath induced voltage and sheath circulating current under steady-state and transient operation conditions by using the updated cable line model, and forming the steady-state and transient voltage and current waveforms.

5. The cable structure optimization method of claim 4, wherein, After step S3.3, further comprising: checking whether the shield induced voltage and the sheath loop current of the cable model are lower than the corresponding safety threshold; if the corresponding safety threshold is exceeded, returning to adjust the arrangement mode or the metal sheath grounding mode, and recalculating until the requirements are met.

6. The cable structure optimization method of claim 1 wherein, Step S4, specifically: Step S4.1, establishing a multi-dimensional geometric model of the cable according to the cable structure, geometric dimensions, material properties and arrangement mode in the cable parameters; Step S4.2, updating the multi-dimensional geometric model according to the laying conditions and the metal sheath grounding mode to obtain an electro-thermal-flow multi-physical field coupling model containing electromagnetic field, temperature field and flow field; Step S4.3, loading the steady-state and transient voltage and current waveforms obtained in step S3 into the electro-thermal-flow multi-physical field coupling model as excitation sources to obtain the ampacity, electric field strength of the insulation layer and short-circuit capacity of the metal sheath under steady-state and transient operating conditions.

7. The cable structure optimization method of claim 6, wherein, After step S4.3, further comprising: comparing the obtained ampacity with the steady-state ampacity obtained in step S2; if the deviation exceeds the predetermined tolerance, feeding back the ampacity to step S3 to update the load parameters and re-perform simulation calculation until the results converge.

8. A cable structure optimization system characterized by, Comprise: A cable parameter acquisition module configured to acquire cable parameters to be optimized; A first simulation analysis module configured to establish a cable structure model according to the cable parameters, update the cable structure model using the arrangement mode, laying conditions and metal sheath grounding mode in the cable parameters, and obtain the steady-state ampacity using the updated cable structure model; A second simulation analysis module configured to establish a cable line model according to the cable parameters, update the cable line model using the system operating conditions and the laying conditions and metal sheath grounding mode in the cable parameters, determine the load parameters according to the obtained steady-state ampacity and system operating conditions, and obtain the steady-state and transient voltage and current waveforms under the corresponding load parameters using the updated cable line model; A third simulation analysis module configured to establish an electro-thermal-flow multi-physical field coupling model of the cable according to the cable parameters, use the obtained steady-state and transient voltage and current waveforms as excitation sources of the electro-thermal-flow multi-physical field coupling model, and obtain the ampacity, electric field strength of the insulation layer and short-circuit capacity of the metal sheath under steady-state and transient operating conditions; A cable structure size optimization design module configured to calculate and determine the preferred value range of the cable insulation thickness and the metal sheath thickness according to the ampacity, electric field strength of the insulation layer and short-circuit capacity of the metal sheath under steady-state and transient operating conditions, and in combination with the cable design standard formula.

9. A computer program product, characterised in that, Comprise computer readable instructions, when the computer readable instructions run on an electronic device, make the electronic device realize the steps in the cable structure optimization method of any one of claims 1-7.

10. An electronic device, comprising: Comprise at least one processor and a memory connected to the processor, the memory is used to store a computer program; the processor is used to execute the computer program, so that the electronic device can realize the steps in the cable structure optimization method of any one of claims 1-7.

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