500kV submarine cable multi-laying environment current-carrying capacity simulation and mutual influence analysis method

Abstract

The invention discloses a 500kV submarine cable multi-laying environment current-carrying capacity simulation and mutual influence analysis method, and belongs to the field of high-voltage direct-current power transmission and submarine cable engineering. In order to solve the problems that in the prior art, the calculation precision of downloading flow in a multi-laying environment is insufficient, and a quantification means is lacked for mutual influence of co-channel laying of alternating current and direct current submarine cables, the method is optimized through the following three steps: constructing a full-path thermal resistance chain network model covering six environments such as air and J-shaped pipes, and establishing a multi-environment coupling thermal circuit equation; designing an AC / DC submarine cable electromagnetic-thermal coupling analytical model, quantifying additional loss and temperature rise, and constructing a mutual influence coefficient matrix; a multi-model and multi-physics field hybrid simulation strategy is integrated to form a unified evaluation framework. The method improves the current-carrying capacity calculation precision and the safety margin, achieves the quantitative evaluation of the mutual influence of the AC and DC submarine cables, and provides support for the safe and economic design of an offshore wind power delivery system.

Description

Technical Field

[0001] This invention belongs to the field of high voltage direct current transmission technology and submarine cable engineering, specifically involving a method for simulating the current carrying capacity and analyzing the mutual influence of multiple laying environments for 500kV submarine cables. Background Technology

[0002] In recent years, with the development of offshore wind farms in my country towards larger capacity and deeper waters, 500kV submarine cables have become an important solution for offshore wind power collection and transmission. Due to the complex geological conditions and construction environment at sea, 500kV submarine cables in actual engineering projects must pass through various laying environments, including J-shaped pipes, seabed, tidal flats, direct burial pipes, and cable trenches. The thermal resistance coefficients, ambient temperatures, and boundary heat dissipation conditions vary significantly in different laying environments, resulting in nonlinear variations in the current-carrying capacity of the submarine cables. Traditional design methods are usually based on assumptions about a single laying environment or use empirical coefficients for correction, making it difficult to accurately characterize the dynamic coupling effect of current-carrying capacity in different sections. This can easily lead to insufficient capacity design margins or excessive conservatism in the submarine cables, directly affecting the safety, reliability, and economy of the offshore wind power transmission system. In onshore control centers and near-shore landing sections, there are often situations where multiple AC and DC submarine cables from different wind farms share the same laying channel. The alternating magnetic field generated by AC submarine cables during operation will induce eddy current losses and circulating current losses in the metal sheath and armor layer of adjacent DC submarine cables, leading to an additional temperature rise in the DC submarine cables. Conversely, the constant electric and magnetic field distribution of the DC submarine cables may also affect the insulation performance and metal layer losses of the AC submarine cables. Current technologies mostly adopt the assumption of independent laying and lack systematic research on the electromagnetic-thermal coupling mechanism when AC and DC submarine cables are laid in the same channel. They have also failed to establish quantitative evaluation indicators for mutual influence, posing a risk of equipment overheating, insulation degradation, or even system shutdown due to electromagnetic interference. Existing simulation methods primarily focus on single-type submarine cables or single-laying environments, exhibiting the following prominent issues: incomplete multi-physics coupling modeling, making it difficult to simultaneously solve the interactions between electromagnetic, temperature, and fluid fields; unclear thermal parameter transfer mechanisms across multiple laying environments, lacking a comprehensive thermal resistance chain modeling method encompassing the entire path from air to J-tube to seabed to tidal flats to direct burial and cable trench; lack of calculable analytical models for the mutual influence between AC and DC submarine cables, making it impossible to quantitatively assess the attenuation of DC submarine cable current carrying capacity by the amplitude, phase, and arrangement of currents from adjacent AC submarine cables; and low computational efficiency in large-scale finite element simulations, failing to meet the needs of multi-scheme comparison in engineering projects. Therefore, a current carrying capacity simulation method that integrates refined modeling of multiple laying environments with analysis of the mutual influence between AC and DC submarine cables is urgently needed to provide theoretical support and technical means for the optimized design and safe operation of 500kV offshore wind power transmission systems. Summary of the Invention

[0003] To address the issues of insufficient accuracy in calculating current carrying capacity in multi-laying environments and the lack of quantitative analysis methods for the mutual influence between AC and DC submarine cables laid in the same channel in existing 500kV submarine cable projects, this invention provides a method for simulating current carrying capacity and analyzing mutual influence of 500kV submarine cables in multi-laying environments.

[0004] The technical solution adopted in this invention is as follows: A method for simulating and analyzing the environmental current carrying capacity and mutual influence of 500kV submarine cables under multiple laying conditions, comprising the following steps:

[0005] S1: Construct a thermal resistance chain network model for the entire laying path of a 500kV AC / DC submarine cable and establish multi-environment coupled thermal circuit equations;

[0006] S2: Design an analytical model of electromagnetic-thermal coupling for AC and DC submarine cables laid in the same channel to achieve a quantitative assessment of their mutual influence;

[0007] S3: Integrating the thermal resistance chain network model of the entire laying path, the electromagnetic-thermal coupling analytical model, and the multiphysics hybrid simulation strategy into a unified submarine cable current carrying capacity assessment framework, realizing the safe and economical design of the 500kV offshore wind power transmission system.

[0008] Furthermore, the specific process of constructing the thermal resistance chain network model of the entire laying path in step S1 is as follows:

[0009] First, based on the six typical laying environments through which the 500kV submarine cable passes in sequence—air, J-tube, seabed, tidal flat, direct burial in pipe, and cable trench—parametric models of thermal resistance for each environmental section are established, thus forming thermal resistance models for the six typical laying environments.

[0010] Then, the thermal resistance models of each environmental section are coupled through temperature continuity boundary conditions to form a multi-node thermal path network from the conductor to the external environment. The thermal balance equation is established using Kirchhoff's heat flow law, so that the temperature rise of each section is expressed as the linear superposition of conductor loss, dielectric loss, metal sheath loss and external environment temperature rise, and the full-path thermal resistance chain network equation is constructed.

[0011] Finally, a multi-environment thermal parameter database is constructed. Core parameters such as soil thermal resistivity, seawater temperature, J-tube material, and cable trench size under different laying conditions are normalized to form an expandable simulation input parameter set. The parameter database is then normalized to construct a multi-environment thermal parameter normalization model. Through the integration of the thermal resistance chain network model and the parameter database, a unified description of the temperature distribution along the entire path of the 500kV submarine cable is achieved.

[0012] Furthermore, the model involved in step S1 is characterized by the following formulas: six typical laying environment thermal resistance models are shown in formulas (1)-(6), the full path thermal resistance chain network equation is shown in formulas (7)-(9), and the multi-environment thermal parameter normalization model is shown in formulas (10)-(12):

[0013] (1)

[0014] (2)

[0015] (3)

[0016] (4)

[0017] (5)

[0018] (6)

[0019] (7)

[0020] (8)

[0021] (9)

[0022] (10)

[0023] (11)

[0024] (12)

[0025] In the formula: Equivalent thermal resistance for the air-laying section; , These are the convective and radiative heat dissipation coefficients, respectively. for Total thermal resistance of the pipe section; , , These are the thermal resistances of the air inside the pipe, the pipe wall, and the seawater outside the pipe, respectively. Thermal resistance of the stratified soil of the seabed; , The radius and thermal conductivity of each soil layer; For the dynamic thermal resistance of the tidal flat section; This is the coefficient for dry and wet conditions; This is a heat capacity correction term; Thermal resistance of the directly buried pipe section; , , These are the contact, pipe wall, and soil thermal resistances, respectively. Thermal resistance of the cable trench section; , These are natural convection and thermal conductivity, respectively. For nodes temperature; For nodes Heat loss; , , These are heat flow through conduction, convection, and radiation, respectively. For conductor temperature; The ambient temperature; Soil temperature; , , , , These are the soil temperature baseline, attenuation coefficient, fluctuation amplitude, angular frequency, and phase, respectively. The convective heat transfer coefficient of seawater; For Nusselt numbers; The thermal conductivity of seawater; for Outer diameter of the tube; Equivalent contact thermal resistance; The aspect ratio; The thermal conductivity of the material; Surface roughness.

[0026] Furthermore, the specific process of designing the electromagnetic-thermal coupling analytical model and realizing the quantitative evaluation of mutual influence in step S2 is as follows:

[0027] First, based on the physical mechanism of the additional loss induced by the alternating magnetic field of AC submarine cable in the metal sheath and armor layer of DC submarine cable, the Biot-Savart law is used to calculate the time-varying magnetic flux density distribution generated by the three-phase current of AC submarine cable. The eddy current electromotive force induced in the metal layer of DC submarine cable is derived by Faraday's law of electromagnetic induction. The eddy current loss power is calculated by combining the resistance parameters of the metal layer, and an analytical model of electromagnetic coupling between AC and DC submarine cables is constructed.

[0028] Next, the risk indices VaR and CVaR are weighted and integrated using the combination coefficient method to construct a GlueVaR-type additional loss risk measurement function, which gives higher weight to the surge in losses caused by AC current imbalance and harmonic distortion under extreme operating conditions.

[0029] Then, the additional loss power calculated by the electromagnetic coupling analytical model is used as a heat source term and superimposed on the conductor loss and dielectric loss of the DC submarine cable. The temperature rise distribution of the metal sheath and insulation layer is calculated by the thermal circuit model. An insulation conductivity correction model considering the temperature feedback effect is established. The nonlinear thermal resistance parameter is approximated to several linear segments by the piecewise linearization method to achieve rapid correction of the download flow rate of the same channel.

[0030] Finally, by parametrically scanning different laying spacings, AC current amplitudes, phase arrangements, and DC operating voltages, the percentage decrease in DC submarine cable current carrying capacity and the increase in AC submarine cable insulation temperature under each combination are calculated, a mutual influence coefficient matrix is ​​constructed, and a mutual influence coefficient lookup table is formed.

[0031] Furthermore, the model involved in step S2 is characterized by the following formulas: the analytical model of electromagnetic coupling of AC / DC submarine cables is shown in formulas (13)-(17), the GlueVaR type additional loss risk measurement function is shown in formulas (18)-(20), and the mutual influence coefficient matrix is ​​shown in formulas (21)-(23):

[0032] (13)

[0033] (14)

[0034] (15)

[0035] (16)

[0036] (17)

[0037] (18)

[0038] (19)

[0039] (20)

[0040] (twenty one)

[0041] (twenty two)

[0042] (twenty three)

[0043] In the formula: To generate magnetic flux density for AC submarine cables; The vacuum permeability; Alternating current; For laying spacing; Angular frequency; To induce electromotive force; It is magnetic flux; The cross-sectional area of ​​the metal layer; This is eddy current loss; For metal layer resistance; This refers to the cable length. This represents the total loss of the DC submarine cable. It is direct current; Resistance of a conductor; For dielectric loss; For additional temperature rise; , These are the thermal resistance of the metal layer and the thermal resistance of the insulating layer, respectively. This is the harmonic correction factor; This is a risk metric. , For combined weights; Confidence level; The current carrying capacity influence coefficient of DC submarine cable; This refers to the rated current of the DC submarine cable. The temperature influence coefficient of AC submarine cable insulation; The insulation temperature of the AC submarine cable; This is the mutual influence coefficient matrix; This refers to the phase arrangement. It is a DC voltage; The ambient temperature.

[0044] Furthermore, the specific process of integrating the unified submarine cable current carrying capacity assessment framework and realizing safe and economical design in step S3 is as follows:

[0045] First, the full-path thermal resistance network model, electromagnetic-thermal coupling analytical model, and mutual influence coefficient matrix are uniformly constructed in a multi-physics hybrid simulation platform. The finite element-thermal coupling algorithm is used to achieve adaptive switching of solution methods for different laying sections. Finite element fine simulation is used for J-shaped pipe sections and cable trench sections with complex boundary conditions, while thermal circuit model is used for rapid calculation of long-distance sections in homogeneous soil. The advantages of multiple methods are complemented by the data transfer at the interface.

[0046] Then, a three-dimensional geometric model of the submarine cable was established based on the engineering design drawings, and the material properties and boundary conditions of each laying section were defined. The electromagnetic field distribution was solved by the finite element method to obtain the spatial distribution of conductor loss, metal sheath loss and additional loss.

[0047] Finally, the loss density is mapped to the thermal network nodes, and a multi-environment thermal parameter database is called to solve the temperature distribution of the entire path through the node temperature equation. The conductor temperature limit is checked according to the IEC60287 standard, and the current carrying capacity iterative check process is executed until the design requirements are met. This process ensures the calculation accuracy and stability through a hybrid simulation convergence criterion.

[0048] Furthermore, the model involved in step S3 is characterized by the following formulas: the finite element-thermal circuit coupling algorithm is shown in formulas (24)-(27), the current carrying capacity iterative verification process is shown in formulas (28)-(29), and the hybrid simulation convergence criterion is shown in formula (30):

[0049] (twenty four)

[0050] (25)

[0051] (26)

[0052] (27)

[0053] (28)

[0054] (29)

[0055] (30)

[0056] In the formula: The power loss calculated using the finite element method; Electrical conductivity; Electric field strength; Source current density; For magnetic vector position; To map to nodes Heat loss; Weights for shape functions; For the first The temperature vector of the next iteration; This is the heat conduction matrix; This is the heat capacity matrix; For the first The carrying capacity of the next iteration; This represents the current increment step size. For conductor temperature limits; This represents the convergence error of the temperature field. This is the electromagnetic field convergence error; , These are the weighting coefficients; This is the total convergence tolerance.

[0057] This invention also provides a 500kV submarine cable multi-laying environment current carrying capacity simulation and mutual influence analysis system, used to realize the 500kV submarine cable multi-laying environment current carrying capacity simulation and mutual influence analysis method as described above, including a full-path thermal resistance chain modeling module, an electromagnetic-thermal coupling analysis module, and a multi-physics field hybrid simulation evaluation module. Each module works together to realize the refined calculation of the current carrying capacity of 500kV AC and DC submarine cables and the quantitative evaluation of mutual influence in the same channel;

[0058] The full-path thermal resistance chain modeling module is used to construct a thermal resistance chain network model of the entire laying path of 500kV AC / DC submarine cable and establish multi-environment coupled thermal path equations. The thermal resistance chain network model covers six typical laying environments: air, J-tube, seabed, tidal flat, direct burial, and cable trench, and integrates a multi-environment thermal parameter database.

[0059] The electromagnetic-thermal coupling analysis module is used to establish an electromagnetic-thermal coupling analytical model for AC and DC submarine cables laid in the same channel, quantify the additional loss and additional temperature rise induced by the power frequency magnetic field of the AC submarine cable in the metal layer of the DC submarine cable, and construct the mutual influence coefficient matrix of AC and DC submarine cables.

[0060] The multiphysics hybrid simulation and evaluation module integrates the full-path thermal resistance chain network model and the electromagnetic-thermal coupling analytical model into a unified simulation platform. It uses a finite element-thermal coupling algorithm to achieve efficient solution and outputs the rated current carrying capacity, full-path temperature distribution and mutual influence evaluation results of 500kV submarine cable, supporting the safe and economical design of offshore wind power transmission systems.

[0061] The present invention also provides an electronic device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement a method for simulating and analyzing the environmental current carrying capacity and mutual influence of 500kV submarine cables under multiple laying conditions as described above.

[0062] The present invention also provides a computer program product, which, when executed by a processor, implements the above-described method for simulating the current carrying capacity and analyzing the mutual influence of multiple laying environments for 500kV submarine cables.

[0063] Advantages and beneficial effects of this invention: This invention achieves refined current-carrying capacity calculation and quantitative assessment of mutual influence within the same channel for 500kV AC / DC submarine cables under multiple laying environments, improving design accuracy and safety margin while maintaining computational efficiency. This invention constructs a distributed, scalable simulation model to replace traditional single-environment assumptions, accurately characterizing the local characteristics of different laying sections, thereby significantly improving the reliability and economy of current-carrying capacity assessment for submarine cable systems. This invention introduces risk constraints and multi-physics coupling mechanisms to effectively mitigate the impact of AC / DC electromagnetic interference, geological condition changes, and extreme environments on submarine cable operation, making submarine cable design more adaptable to the complex operating conditions of offshore wind power, and maintaining the accuracy and robustness of current-carrying capacity calculation results under different laying conditions. This invention achieves rapid assessment of AC / DC submarine cable laying within the same channel through a mutual influence coefficient matrix, significantly improving the design efficiency and safety of multi-circuit submarine cable shared channel projects. Attached Figure Description

[0064] Figure 1 This is a flowchart of the steps of the method of the present invention. Detailed Implementation

[0065] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0066] Example 1

[0067] like Figure 1 As shown, a method for simulating and analyzing the interaction of current carrying capacity in various environments for 500kV submarine cables includes the following steps:

[0068] S1: Construct a thermal resistance chain network model for the entire laying path of a 500kV AC / DC submarine cable, and establish multi-environment coupled thermal circuit equations:

[0069] First, based on the fact that 500kV submarine cables pass through six typical laying environments in the offshore wind power transmission project, namely air, J-shaped pipe, seabed, tidal flat, direct burial pipe and cable trench, this invention establishes thermal resistance models for each environmental section. For air-laid sections, a parallel model of convection and radiation heat dissipation is adopted, parameterizing ambient temperature, wind speed, and solar radiation intensity into equivalent thermal resistances. For J-shaped pipe sections, a coupled model of natural and forced convection of fluids inside and outside the pipe is constructed, considering the series structure of air thermal resistance, pipe wall thermal conductivity, and seawater convection thermal resistance outside the pipe. For seabed sections, a layered thermal resistance model of seabed soil is established, incorporating the different thermal conductivity and temperature gradient effects of silt, sand, and bedrock layers into the calculation. For tidal flat sections, considering tidal periodic flooding and exposure, a transient heat capacity correction model under alternating wet and dry boundary conditions is established. For direct-buried pipe sections, the contact thermal resistance between the cable sheath and the protective pipe, the thermal conductivity of the protective pipe, and the thermal resistance of the surrounding soil are constructed into a π-type equivalent network. For cable trench sections, a multi-heat source coupled model of natural air convection, trench wall heat conduction, and trench cover radiation heat dissipation is established. These six models constitute six typical thermal resistance models for laying environments.

[0070] Then, the full-path thermal resistance chain network equation is established. The thermal resistance models of each environmental segment are coupled through temperature continuity boundary conditions to form a multi-node thermal path network from the conductor to the external environment. Kirchhoff's heat flux law is used to establish thermal balance equations for all nodes, so that the temperature rise of each segment can be expressed as a linear superposition of conductor loss, dielectric loss, metal sheath loss, and external environment temperature rise. This thermal resistance chain network model, namely the full-path thermal resistance chain network equation, can significantly reduce the complexity of direct coupling of multi-physics fields while ensuring computational accuracy, enabling the current carrying capacity calculation of different laying environments to be performed efficiently under a unified thermal path framework.

[0071] Finally, a multi-environment thermal parameter database was constructed. Core parameters such as soil thermal resistivity, seawater temperature, J-tube material, and cable trench size measured under different laying conditions were normalized to form an scalable multi-environment thermal parameter normalization model, which serves as the simulation input parameter set. Through the integration of this thermal resistance chain network model with the parameter database, the temperature distribution along the entire path of the 500kV submarine cable is uniformly described within a thermal path state-space framework that can be used for subsequent multiphysics simulations, providing a complete and computable structure for subsequent AC / DC interaction analysis.

[0072] The model involved in step S1 is characterized by the following formulas: six typical laying environment thermal resistance models are shown in formulas (1)-(6), the full path thermal resistance chain network equation is shown in formulas (7)-(9), and the multi-environment thermal parameter normalization model is shown in formulas (10)-(12):

[0073] (1)

[0074] (2)

[0075] (3)

[0076] (4)

[0077] (5)

[0078] (6)

[0079] (7)

[0080] (8)

[0081] (9)

[0082] (10)

[0083] (11)

[0084] (12)

[0085] In the formula: Equivalent thermal resistance for the air-laying section; , These are the convective and radiative heat dissipation coefficients, respectively. for Total thermal resistance of the pipe section; , , These are the thermal resistances of the air inside the pipe, the pipe wall, and the seawater outside the pipe, respectively. Thermal resistance of the stratified soil of the seabed; , The radius and thermal conductivity of each soil layer; For the dynamic thermal resistance of the tidal flat section; This is the coefficient for dry and wet conditions; This is a heat capacity correction term; Thermal resistance of the directly buried pipe section; , , These are the contact, pipe wall, and soil thermal resistances, respectively. Thermal resistance of the cable trench section; , These are natural convection and thermal conductivity, respectively. For nodes temperature; For nodes Heat loss; , , These are heat flow through conduction, convection, and radiation, respectively. For conductor temperature; The ambient temperature; Soil temperature; , , , , These are the soil temperature baseline, attenuation coefficient, fluctuation amplitude, angular frequency, and phase, respectively. The convective heat transfer coefficient of seawater; For Nusselt numbers; The thermal conductivity of seawater; for Outer diameter of the tube; Equivalent contact thermal resistance; The aspect ratio; The thermal conductivity of the material; Surface roughness.

[0086] S2: Design an analytical model for electromagnetic-thermal coupling of AC and DC submarine cables laid in the same channel to achieve a quantitative assessment of their mutual influence.

[0087] First, based on the physical mechanism that the alternating magnetic field generated by the AC submarine cable during operation induces additional losses in the adjacent DC submarine cable's metal sheath and armor layer, an analytical model of electromagnetic coupling between AC and DC submarine cables is constructed. The Biot-Savart law is used to calculate the time-varying magnetic flux density distribution generated in space by the three-phase current of the AC submarine cable. Faraday's law of electromagnetic induction is used to derive the eddy current electromotive force induced in the metal layer of the DC submarine cable, and the eddy current loss power is calculated based on the resistance parameters of the metal layer. A weighted fusion of VaR and CVaR risk indicators is constructed using a combination coefficient method to construct a GlueVaR-type additional loss risk measurement function. Higher weights are given to the surge in losses caused by factors such as AC current imbalance and harmonic distortion under extreme operating conditions, enabling the model to balance economy and safety when assessing mutual influences.

[0088] Then, an additional temperature rise model for the DC submarine cable is established. The additional loss power calculated by the electromagnetic coupling analytical model is used as a heat source term and superimposed on the conductor loss and dielectric loss of the DC submarine cable. The temperature rise distribution of the metal sheath and insulation layer is calculated through a thermal circuit model. Considering the constant electric field characteristics of the DC submarine cable, an insulation conductivity correction model that takes into account the temperature feedback effect is established, making the dielectric loss exhibit nonlinear characteristics with temperature changes. A piecewise linearization method is used to approximate the nonlinear thermal resistance parameter into several linear segments, allowing the additional temperature rise calculation to be embedded in a mixed integer linear programming framework, enabling rapid correction of the transmission flow rate for cables laid in the same channel.

[0089] Finally, a mutual influence coefficient matrix is ​​constructed. By parametrically scanning different laying spacings, AC current amplitudes, phase arrangements, and DC operating voltages, the percentage decrease in DC submarine cable current carrying capacity and the increase in AC submarine cable insulation temperature for each combination are calculated, forming a mutual influence coefficient lookup table. This matrix can provide intuitive decision support for engineering design, quickly determining the minimum safe spacing or current carrying capacity correction coefficient that meets temperature limits through table lookup, avoiding redundant calculations in complex electromagnetic field simulations.

[0090] The model involved in step S2 is characterized by the following formulas: the analytical model of electromagnetic coupling of AC / DC submarine cable is shown in formulas (13)-(17), the GlueVaR type additional loss risk measurement function is shown in formulas (18)-(20), and the mutual influence coefficient matrix is ​​shown in formulas (21)-(23):

[0091] (13)

[0092] (14)

[0093] (15)

[0094] (16)

[0095] (17)

[0096] (18)

[0097] (19)

[0098] (20)

[0099] (twenty one)

[0100] (twenty two)

[0101] (twenty three)

[0102] In the formula: To generate magnetic flux density for AC submarine cables; The vacuum permeability; Alternating current; For laying spacing; Angular frequency; To induce electromotive force; It is magnetic flux; The cross-sectional area of ​​the metal layer; This is eddy current loss; For metal layer resistance; This refers to the cable length. This represents the total loss of the DC submarine cable. It is direct current; Resistance of a conductor; For dielectric loss; For additional temperature rise; , These are the thermal resistance of the metal layer and the thermal resistance of the insulating layer, respectively. This is the harmonic correction factor; This is a risk metric. , For combined weights; Confidence level; The current carrying capacity influence coefficient of DC submarine cable; This refers to the rated current of the DC submarine cable. The temperature influence coefficient of AC submarine cable insulation; The insulation temperature of the AC submarine cable; This is the mutual influence coefficient matrix; This refers to the phase arrangement. It is a DC voltage; The ambient temperature.

[0103] S3: Integrating the full-path thermal resistance chain network model, the electromagnetic-thermal coupling analytical model, and the multiphysics hybrid simulation strategy into a unified submarine cable current carrying capacity assessment framework, enabling the safe and economical design of a 500kV offshore wind power transmission system:

[0104] Firstly, in the design and operation analysis of 500kV submarine cable projects, this invention integrates the aforementioned full-path thermal resistance chain network model, electromagnetic-thermal coupling analytical model, and mutual influence coefficient matrix into a multi-physics hybrid simulation platform, and employs a finite element-thermal coupling algorithm for efficient solution. In the specific implementation process, a three-dimensional geometric model of the submarine cable is first established based on the engineering design drawings, defining the material properties and boundary conditions of each laying section. Then, the electromagnetic field distribution is solved using the finite element method to obtain the spatial distribution of conductor loss, metal sheath loss, and additional losses. Next, the loss density is mapped to the thermal network nodes, and a multi-environment thermal parameter database is invoked to solve the full-path temperature distribution through node temperature equations. Finally, the conductor temperature limit is checked according to the IEC60287 standard, and the current carrying capacity is iteratively adjusted until the design requirements are met; this process is the current carrying capacity iterative verification process. This hybrid simulation strategy not only significantly reduces the computational scale of pure finite element simulation but also enables rapid evaluation of 500kV AC / DC submarine cable co-laying scenarios, avoiding investment waste caused by overly conservative design.

[0105] Then, by deeply integrating electromagnetic-thermal coupling modeling with multiphysics hybrid simulation, the unified evaluation framework proposed in this invention can ensure the safe and economical operation of submarine cables under different laying environments, different levels of electromagnetic interference, and different operating conditions. Especially in the scenario of laying cables in the same channel, the mutual influence coefficient matrix can quickly quantify the weakening effect of AC submarine cables on the current carrying capacity of DC submarine cables; under complex geological conditions, the full-path thermal resistance chain model can accurately calculate the current carrying capacity bottlenecks in each section; and under the condition of large-scale wind power cluster transmission, the distributed simulation architecture makes the computation time engineering-available. This framework significantly improves the design accuracy, safety margin, and economy of 500kV submarine cable transmission systems under the condition of high-proportion offshore wind power access, with the hybrid simulation convergence criterion used to ensure the stability and accuracy of multiphysics iterative calculations.

[0106] The model involved in step S3 is characterized by the following formulas: the finite element-thermal circuit coupling algorithm is shown in formulas (24)-(27), the current carrying capacity iterative verification process is shown in formulas (28)-(29), and the hybrid simulation convergence criterion is shown in formula (30).

[0107] (twenty four)

[0108] (25)

[0109] (26)

[0110] (27)

[0111] (28)

[0112] (29)

[0113] (30)

[0114] In the formula: The power loss calculated using the finite element method; Electrical conductivity; Electric field strength; Source current density; For magnetic vector position; To map to nodes Heat loss; Weights for shape functions; For the first The temperature vector of the next iteration; This is the heat conduction matrix; This is the heat capacity matrix; For the first The carrying capacity of the next iteration; This represents the current increment step size. For conductor temperature limits; This represents the convergence error of the temperature field. This is the electromagnetic field convergence error; , These are the weighting coefficients; This is the total convergence tolerance.

[0115] This invention enables refined current-carrying capacity calculation and quantitative assessment of mutual influence within the same channel for 500kV AC / DC submarine cables under multi-laying environments, improving design accuracy and safety margin while maintaining computational efficiency. By constructing a distributed, scalable simulation model to replace traditional single-environment assumptions, this invention accurately characterizes the local characteristics of different laying sections, significantly improving the reliability and economy of current-carrying capacity assessment for submarine cable systems. Furthermore, by introducing risk constraints and multi-physics coupling mechanisms, this invention effectively mitigates the impact of AC / DC electromagnetic interference, geological condition variations, and extreme environments on submarine cable operation, making submarine cable design more adaptable to the complex conditions of offshore wind power and maintaining the accuracy and robustness of current-carrying capacity calculation results under different laying conditions. Finally, this invention achieves rapid assessment of AC / DC submarine cable laying within the same channel through a mutual influence coefficient matrix, significantly improving the design efficiency and safety of multi-circuit submarine cable shared-channel projects.

Claims

1. A method for simulating the current-carrying capacity and analyzing the mutual influence of 500kV submarine cables in various laying environments, characterized in that, Includes the following steps: S1: Construct a thermal resistance chain network model for the entire laying path of a 500kV AC / DC submarine cable and establish multi-environment coupled thermal circuit equations; S2: Design an analytical model of electromagnetic-thermal coupling for AC and DC submarine cables laid in the same channel to achieve a quantitative assessment of their mutual influence; S3: Integrating the thermal resistance chain network model of the entire laying path, the electromagnetic-thermal coupling analytical model, and the multiphysics hybrid simulation strategy into a unified submarine cable current carrying capacity assessment framework, realizing the safe and economical design of the 500kV offshore wind power transmission system.

2. The method for simulation and mutual influence analysis of environmental current carrying capacity of 500kV submarine cables under multiple laying conditions as described in claim 1, is characterized in that, The specific process of constructing the thermal resistance chain network model of the entire laying path in step S1 is as follows: First, based on the six typical laying environments through which the 500kV submarine cable passes in sequence—air, J-tube, seabed, tidal flat, direct burial in pipe, and cable trench—parametric models of thermal resistance for each environmental section are established, thus forming thermal resistance models for the six typical laying environments. Then, the thermal resistance models of each environmental section are coupled through temperature continuity boundary conditions to form a multi-node thermal path network from the conductor to the external environment. The thermal balance equation is established using Kirchhoff's heat flow law, so that the temperature rise of each section is expressed as the linear superposition of conductor loss, dielectric loss, metal sheath loss and external environment temperature rise, and the full-path thermal resistance chain network equation is constructed. Finally, a multi-environment thermal parameter database is constructed. Core parameters such as soil thermal resistivity, seawater temperature, J-tube material, and cable trench size under different laying conditions are normalized to form an expandable simulation input parameter set. The parameter database is then normalized to construct a multi-environment thermal parameter normalization model. Through the integration of the thermal resistance chain network model and the parameter database, a unified description of the temperature distribution along the entire path of the 500kV submarine cable is achieved.

3. The method for simulation and mutual influence analysis of environmental current carrying capacity of 500kV submarine cables under multiple laying conditions as described in claim 2, is characterized in that, The models involved in step S1 are characterized by the following formulas: six typical laying environment thermal resistance models are shown in formulas (1)-(6), the full path thermal resistance chain network equations are shown in formulas (7)-(9), and the multi-environment thermal parameter normalization model is shown in formulas (10)-(12): （1） （2） （3） （4） （5） （6） （7） （8） （9） （10） （11） （12） In the formula: Equivalent thermal resistance for the air-laying section; , These are the convective and radiative heat dissipation coefficients, respectively. for Total thermal resistance of the pipe section; , , These are the thermal resistances of the air inside the pipe, the pipe wall, and the seawater outside the pipe, respectively. Thermal resistance of the stratified soil of the seabed; , The radius and thermal conductivity of each soil layer; For the dynamic thermal resistance of the tidal flat section; This is the coefficient for dry and wet conditions; This is a heat capacity correction term; Thermal resistance of the directly buried pipe section; , , These are the contact, pipe wall, and soil thermal resistances, respectively. Thermal resistance of the cable trench section; , These are natural convection and thermal conductivity, respectively. For nodes temperature; For nodes Heat loss; , , These are heat flow through conduction, convection, and radiation, respectively. For conductor temperature; The ambient temperature; Soil temperature; , , , , These are the soil temperature baseline, attenuation coefficient, fluctuation amplitude, angular frequency, and phase, respectively. The convective heat transfer coefficient of seawater; For Nusselt numbers; The thermal conductivity of seawater; for Outer diameter of the tube; Equivalent contact thermal resistance; The aspect ratio; The thermal conductivity of the material; Surface roughness.

4. The method for simulation and mutual influence analysis of environmental current carrying capacity of 500kV submarine cables under multiple laying conditions as described in claim 1, characterized in that, The specific process of designing the electromagnetic-thermal coupling analytical model and realizing the quantitative evaluation of mutual influence in step S2 is as follows: First, based on the physical mechanism of the additional loss induced by the alternating magnetic field of AC submarine cable in the metal sheath and armor layer of DC submarine cable, the Biot-Savart law is used to calculate the time-varying magnetic flux density distribution generated by the three-phase current of AC submarine cable. The eddy current electromotive force induced in the metal layer of DC submarine cable is derived by Faraday's law of electromagnetic induction. The eddy current loss power is calculated by combining the resistance parameters of the metal layer, and an analytical model of electromagnetic coupling between AC and DC submarine cables is constructed. Next, the risk indices VaR and CVaR are weighted and integrated using the combination coefficient method to construct a GlueVaR-type additional loss risk measurement function, which gives higher weight to the surge in losses caused by AC current imbalance and harmonic distortion under extreme operating conditions. Then, the additional loss power calculated by the electromagnetic coupling analytical model is used as a heat source term and superimposed on the conductor loss and dielectric loss of the DC submarine cable. The temperature rise distribution of the metal sheath and insulation layer is calculated by the thermal circuit model. An insulation conductivity correction model considering the temperature feedback effect is established. The nonlinear thermal resistance parameter is approximated to several linear segments by the piecewise linearization method to achieve rapid correction of the download flow rate of the same channel. Finally, by parametrically scanning different laying spacings, AC current amplitudes, phase arrangements, and DC operating voltages, the percentage decrease in DC submarine cable current carrying capacity and the increase in AC submarine cable insulation temperature under each combination are calculated, a mutual influence coefficient matrix is ​​constructed, and a mutual influence coefficient lookup table is formed.

5. The method for simulation and mutual influence analysis of environmental current carrying capacity of 500kV submarine cables in multiple laying environments according to claim 4, characterized in that, The model involved in step S2 is characterized by the following formulas: the analytical model of electromagnetic coupling of AC and DC submarine cables is shown in formulas (13)-(17), the GlueVaR type additional loss risk measurement function is shown in formulas (18)-(20), and the mutual influence coefficient matrix is ​​shown in formulas (21)-(23): （13） （14） （15） （16） （17） （18） （19） （20） （21） （22） （23） In the formula: To generate magnetic flux density for AC submarine cables; The vacuum permeability; Alternating current; For laying spacing; Angular frequency; To induce electromotive force; It is magnetic flux; The cross-sectional area of ​​the metal layer; This is eddy current loss; For metal layer resistance; This refers to the cable length. This represents the total loss of the DC submarine cable. It is direct current; Resistance of a conductor; For dielectric loss; For additional temperature rise; , These are the thermal resistance of the metal layer and the thermal resistance of the insulating layer, respectively. This is the harmonic correction factor; This is a risk metric. , For combined weights; Confidence level; The current carrying capacity influence coefficient of DC submarine cable; This refers to the rated current of the DC submarine cable. The temperature influence coefficient of AC submarine cable insulation; The insulation temperature of the AC submarine cable; This is the mutual influence coefficient matrix; This refers to the phase arrangement. It is a DC voltage; The ambient temperature.

6. The method for simulation and mutual influence analysis of environmental current carrying capacity of 500kV submarine cables under multiple laying conditions as described in claim 1, characterized in that, The specific process of integrating the unified submarine cable current carrying capacity assessment framework and realizing safe and economical design in step S3 is as follows: First, the full-path thermal resistance network model, electromagnetic-thermal coupling analytical model, and mutual influence coefficient matrix are uniformly constructed in a multi-physics hybrid simulation platform. The finite element-thermal coupling algorithm is used to achieve adaptive switching of solution methods for different laying sections. Finite element fine simulation is used for J-shaped pipe sections and cable trench sections with complex boundary conditions, while thermal circuit model is used for rapid calculation of long-distance sections in homogeneous soil. The advantages of multiple methods are complemented by the data transfer at the interface. Then, a three-dimensional geometric model of the submarine cable was established based on the engineering design drawings, and the material properties and boundary conditions of each laying section were defined. The electromagnetic field distribution was solved by the finite element method to obtain the spatial distribution of conductor loss, metal sheath loss and additional loss. Finally, the loss density is mapped to the thermal network nodes, and a multi-environment thermal parameter database is called to solve the temperature distribution of the entire path through the node temperature equation. The conductor temperature limit is checked according to the IEC60287 standard, and the current carrying capacity iterative check process is executed until the design requirements are met. This process ensures the calculation accuracy and stability through a hybrid simulation convergence criterion.

7. The method for simulation and mutual influence analysis of environmental current carrying capacity of 500kV submarine cables in multiple laying environments according to claim 6, characterized in that, The model involved in step S3 is characterized by the following formulas: the finite element-thermal circuit coupling algorithm is shown in formulas (24)-(27), the current carrying capacity iterative verification process is shown in formulas (28)-(29), and the hybrid simulation convergence criterion is shown in formula (30): （24） （25） （26） （27） （28） （29） （30） In the formula: The power loss calculated using the finite element method; Electrical conductivity; Electric field strength; Source current density; For magnetic vector position; To map to nodes Heat loss; Weights for shape functions; For the first The temperature vector of the next iteration; This is the heat conduction matrix; This is the heat capacity matrix; For the first The carrying capacity of the next iteration; This represents the current increment step size. For conductor temperature limits; This represents the convergence error of the temperature field. This is the electromagnetic field convergence error; , These are the weighting coefficients; This is the total convergence tolerance.

8. A system for simulating and analyzing the environmental current-carrying capacity of 500kV submarine cables in multiple laying configurations, used to implement the method for simulating and analyzing the environmental current-carrying capacity of 500kV submarine cables in multiple laying configurations as described in any one of claims 1-7, characterized in that, It includes a full-path thermal resistance chain modeling module, an electromagnetic-thermal coupling analysis module, and a multi-physics hybrid simulation and evaluation module. These modules work together to achieve refined calculation of the current carrying capacity of 500kV AC / DC submarine cables and quantitative evaluation of mutual influence in the same channel. The full-path thermal resistance chain modeling module is used to construct a thermal resistance chain network model of the entire laying path of 500kV AC / DC submarine cable and establish multi-environment coupled thermal path equations. The thermal resistance chain network model covers six typical laying environments: air, J-tube, seabed, tidal flat, direct burial, and cable trench, and integrates a multi-environment thermal parameter database. The electromagnetic-thermal coupling analysis module is used to establish an electromagnetic-thermal coupling analytical model for AC and DC submarine cables laid in the same channel, quantify the additional loss and additional temperature rise induced by the power frequency magnetic field of the AC submarine cable in the metal layer of the DC submarine cable, and construct the mutual influence coefficient matrix of AC and DC submarine cables. The multiphysics hybrid simulation and evaluation module integrates the full-path thermal resistance chain network model and the electromagnetic-thermal coupling analytical model into a unified simulation platform. It uses a finite element-thermal coupling algorithm to achieve efficient solution and outputs the rated current carrying capacity, full-path temperature distribution and mutual influence evaluation results of 500kV submarine cable, supporting the safe and economical design of offshore wind power transmission systems.

9. An electronic device, characterized in that, include: The system includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement a method for simulating and analyzing the environmental current carrying capacity of a 500kV submarine cable under multiple laying conditions as described in any one of claims 1-7.

10. A computer program product, characterized in that, When the computer program / instruction is executed by the processor, it implements the method for simulation of environmental current carrying capacity and mutual influence analysis of 500kV submarine cable multi-laying as described in any one of claims 1-7.

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