Method and system for transient time domain analysis of multi-core cables

Abstract

The application provides a method and system for transient time domain analysis of a multi-core cable. The method comprises: obtaining initial parameters of the multi-core cable, the initial parameters being obtained by operating the FDTD algorithm, and the multi-core cable being a cable including at least two conductors in an armor; updating the initial parameters to obtain target parameters; operating the target parameters according to the MTL algorithm to obtain an operation result, the operation result being used to represent a result of the transient time domain analysis of the multi-core cable. In the scheme, a new transient time domain analysis scheme for the multi-core cable is designed, and the scheme is used for the transient time domain analysis of the multi-core cable. First, the parameters in the FDTD algorithm are updated, so that the FDTD grid discretization solving is not needed, and then the MTL algorithm is used for analysis, the strong coupling of the FDTD-MTL algorithm is realized, and the overall transient simulation efficiency of the multi-core cable is greatly improved under the premise of ensuring the simulation precision.

Description

Technical Field

[0001] This application relates to the field of transient time-domain analysis technology for multi-core cables, and more specifically, to a transient time-domain analysis method, apparatus, and system for multi-core cables. Background Technology

[0002] A power cable is a type of electrical energy and signal transmission line, typically composed of four layers: the innermost layer consists of one or more conductive copper wires; outside these wires is a layer of plastic (serving as insulation and dielectric); outside this insulation is a thin mesh-like conductive shield (usually copper or an alloy, referred to in this design as a metal armor layer); and finally, the outermost insulating material acts as the sheath. Due to its strong anti-interference capability and high energy density per unit volume, power cables are widely used in power transmission, information transmission, electrified railways, and other fields. These fields also place higher demands on the stable operation of power cables.

[0003] Multi-core power cables refer to cables with two or more insulated cores within their armor. When there is alternating current or an alternating electromagnetic field in the conductor, the current inside the conductor is no longer uniformly distributed; the current concentrates in the conductor's "skin," a phenomenon known as the skin effect. This means that the current is concentrated in a thin outer layer of the conductor, with the current density increasing closer to the surface, while the actual current inside the conductor is relatively small. This results in increased conductor resistance and consequently, increased power loss. Multi-core power cables effectively reduce the increased resistance caused by the skin effect, decrease power loss due to heat generation along the cable, and improve power transmission efficiency.

[0004] When performing electromagnetic transient overvoltage analysis on power transmission systems containing multi-core power cables, it is crucial to accurately analyze electromagnetic propagation and reflection within the multi-core power cables, as well as the matching and electromagnetic coupling effects between the multi-core power cables and other transmission systems. This allows for the overall optimization of cable connection methods, extending cable lifespan, and improving system reliability. Current solutions often employ the FDTD (finite difference time domain) algorithm for time-domain electromagnetic transient simulation of power cables. Traditional FDTD algorithms require discretizing the entire computational domain using orthogonal grids. The size and number of discrete grids must be determined based on the geometric dimensions of the simulated object and the degree of electromagnetic field distortion in adjacent areas. For multi-core power cables, radial dimensions can be as small as millimeters, while axial dimensions can be as large as hundreds of meters, resulting in extremely large spatial spans. Therefore, current FDTD algorithms are relatively inefficient for transient time-domain analysis of multi-core power cables. Summary of the Invention

[0005] The main objective of this application is to provide a transient time-domain analysis method, apparatus, and system for multi-core cables, so as to at least solve the problem that the current FDTD algorithm in the prior art has low efficiency in transient time-domain analysis of multi-core power cables.

[0006] To achieve the above objectives, according to one aspect of this application, a transient time-domain analysis method for a multi-core cable is provided, comprising: obtaining initial parameters of the multi-core cable, wherein the initial parameters are obtained by calculation using the FDTD algorithm, and the initial parameters include at least one of the following: initial dielectric constant, initial permeability, wherein the multi-core cable is a cable having at least two conductors within its armor layer; updating the initial parameters to obtain target parameters; and performing calculations on the target parameters according to the MTL algorithm to obtain a calculation result, wherein the calculation result is used to characterize the result of transient time-domain analysis of the multi-core cable.

[0007] Optionally, when the initial parameters include the initial dielectric constant and the initial permeability, the target parameters include the dielectric constant and permeability. Updating the initial parameters to obtain the target parameters includes: calculating a correction coefficient according to a first formula, wherein the first formula is...

[0008]

[0009] m represents the correction coefficient, which is used to update the initial parameters, r d The radius from the center of the multi-core cable to the outer edge of the armor layer is expressed as Δs, where Δs is the FDTD grid size. The initial dielectric constant is updated according to the second formula: ε'=mε to obtain the dielectric constant, where ε' represents the dielectric constant and ε represents the initial dielectric constant. The initial permeability is updated according to the third formula: μ'=mμ to obtain the permeability, where μ' represents the permeability and μ represents the initial permeability.

[0010] Optionally, when the multi-core cable includes three conductors, the calculation result includes the current value flowing through each conductor, the voltage between each conductor and the armor, the total current value of the multi-core cable, and the current value of the armor. The target parameters are calculated according to the MTL algorithm to obtain the calculation result, which includes: obtaining the first mutual inductance, second mutual inductance, first mutual capacitance, second mutual capacitance, and magnetic field vector in the multi-core cable. The first mutual inductance is the mutual inductance between the x-phase conductor and the armor; the second mutual inductance is the mutual inductance between the x-phase conductor and the y-phase conductor; the first mutual capacitance is the mutual capacitance between the x-phase conductor and the armor; the second mutual capacitance is the mutual capacitance between the x-phase conductor and the y-phase conductor; x and y are not equal, where x represents A, B, or C, and y represents A, B, or C. The magnetic field vector is the magnetic field strength of the induced magnetic field generated by the multi-core cable. The system calculates the following: a first current value, a second current value, and a third current value based on the first mutual capacitance and the second mutual capacitance; a first voltage value, a second voltage value, and a third voltage value based on the first mutual inductance and the second mutual inductance; wherein the first current value is the current flowing through phase A conductor, the second current value is the current flowing through phase B conductor, and the third current value is the current flowing through phase C conductor; the first voltage value is the voltage between phase A conductor and the armor layer, the second voltage value is the voltage between phase B conductor and the armor layer, and the third voltage value is the voltage between phase C conductor and the armor layer; the system calculates the total current value of the multi-core cable based on the magnetic field vector; the system calculates the difference between the total current value and the target current value to obtain the current value of the armor layer; wherein the target current value is the sum of the first current value, the second current value, and the third current value.

[0011] Optionally, obtaining the first mutual inductance, second mutual inductance, first mutual capacitance, and second mutual capacitance in the multi-core cable includes: calculating the first mutual inductance according to a fourth formula, wherein the fourth formula is:

[0012]

[0013] L xx The first mutual inductance is represented by μ0, which represents the free permeability. r The relative permeability r of a dielectric material a R represents the radius of each phase conductor. b.x r represents the distance between the center of the x-phase conductor and the center of the armor layer. c The inner radius of the sheath conductor is represented, and the dielectric is located between each conductor and the sheath; the second mutual inductance is calculated according to the fifth formula, wherein the fifth formula is:

[0014]

[0015] L xyRepresenting the second mutual inductance, θ xy The coefficient C represents the spatial angle between the x-phase conductor and the y-phase conductor. n The calculation formula is:

[0016]

[0017] The first mutual capacitance is calculated according to the sixth formula, wherein the sixth formula is:

[0018]

[0019] C xx ε represents the first mutual capacitance, ε0 represents the dielectric constant, and ε r The relative permittivity of the dielectric is represented; the second mutual capacitance is calculated according to the seventh formula, wherein the seventh formula is:

[0020]

[0021] Among them, C xy This indicates the second mutual compatibility.

[0022] Optionally, calculating the first current value, the second current value, and the third current value based on the first mutual capacitance and the second mutual capacitance, and calculating the first voltage value, the second voltage value, and the third voltage value based on the first mutual inductance and the second mutual inductance, includes: calculating the first current value, the second current value, and the third current value according to an eighth formula, wherein the eighth formula is:

[0023]

[0024] l represents the axial distance of the multi-core cable, s characterizes the complex frequency domain, and I A I represents the first current value. B Indicates the second current value, I C C represents the third current value. xx Indicates the first mutual compatibility, C xy V represents the second mutual compatibility. x This represents the voltage between the x-phase conductor and the armor layer; the first voltage value, the second voltage value, and the third voltage value are calculated according to the ninth formula, wherein the ninth formula is:

[0025]

[0026] L xx L represents the first mutual inductance. xy V represents the second mutual inductance. A V represents the first voltage value. B This represents the second voltage value, V. C This indicates the third voltage value.

[0027] Optionally, after calculating the first current value, the second current value, and the third current value based on the first mutual capacitance and the second mutual capacitance, and calculating the first voltage value, the second voltage value, and the third voltage value based on the first mutual inductance and the second mutual inductance, the method further includes: converting the first current value, the second current value, and the third current value into a time-domain form according to a tenth formula, wherein the tenth formula is:

[0028]

[0029] Δt is the FDTD time step, and q represents the number of time steps; the first voltage value, the second voltage value, and the third voltage value are converted into time-domain form according to the eleventh formula, wherein the eleventh formula is:

[0030]

[0031] Optionally, calculating the total current value of the multi-core cable based on the magnetic field vector includes: calculating the total current value according to the twelfth formula, wherein the twelfth formula is:

[0032]

[0033] The total current value is represented by H, the magnetic field vector is represented by i, j, and k, which are the magnetic field vector position numbers based on the FDTD grid number, and Δy and Δz are the dimensions of the FDTD grid in the Y and Z directions, respectively.

[0034] Optionally, obtaining the magnetic field vector in the multi-core cable includes: calculating the magnetic field vector according to the thirteenth formula, wherein the thirteenth formula is:

[0035]

[0036]

[0037]

[0038] Where μ represents the magnetic permeability, σ m E represents the permeability, q represents the time step, and E represents the magnetic permeability. x E y E z Let σ represent the electric field vectors in three orthogonal directions, ε represent the equivalent conductivity in the corresponding space, ε represent the dielectric constant in the corresponding space, x represent the first direction, y represent the second direction, and z represent the third direction. Δx, Δy, and Δz represent the dimensions of the FDTD mesh in the three orthogonal directions x, y, and z, respectively. H x H y Hz These are the magnetic field vectors in three orthogonal directions, i, j, and k are the electric field vector position numbers based on the FDTD grid number, and the electric field vector is the electric field intensity vector of the electric field generated by the multi-core cable.

[0039] According to another aspect of this application, a transient time-domain analysis apparatus for a multi-core cable is provided, comprising: an acquisition unit for acquiring initial parameters of the multi-core cable, wherein the initial parameters are obtained by calculation using the FDTD algorithm, and the initial parameters include at least one of the following: initial dielectric constant, initial permeability, wherein the multi-core cable is a cable having at least two conductors within its armor layer; an update unit for updating the initial parameters to obtain target parameters; and a calculation unit for performing calculations on the target parameters according to the MTL algorithm to obtain a calculation result, wherein the calculation result is used to characterize the result of transient time-domain analysis of the multi-core cable.

[0040] According to another aspect of this application, a transient time-domain analysis system for a multi-core cable is provided, comprising: one or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the one or more programs including methods for performing transient time-domain analysis of any of the described multi-core cables.

[0041] By applying the technical solution of this application, a new transient time-domain analysis scheme for multi-core cables is designed. This scheme performs transient time-domain analysis on multi-core cables. First, the parameters in the FDTD algorithm are updated, so that it is no longer necessary to solve the problem by discretization through the FDTD mesh and then use the MTL algorithm for analysis. This realizes strong coupling of the FDTD-MTL algorithm and significantly improves the overall transient simulation efficiency of multi-core cables while ensuring simulation accuracy. Attached Figure Description

[0042] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0043] Figure 1 A schematic diagram of the FDTD grid space is shown;

[0044] Figure 2 A schematic diagram of the electromagnetic field vectors in the grid space of the FDTD is shown;

[0045] Figure 3 A schematic diagram showing electromagnetic field vectors orbiting each other is shown;

[0046] Figure 4A hardware structure block diagram of a mobile terminal for performing a transient time-domain analysis method for multi-core cables, according to an embodiment of this application, is shown.

[0047] Figure 5 A flowchart illustrating a transient time-domain analysis method for a multi-core cable according to an embodiment of this application is shown.

[0048] Figure 6 A schematic diagram of the cross-section of a multi-core cable is shown;

[0049] Figure 7 This diagram illustrates the segmentation of the FDTD mesh in this scheme.

[0050] Figure 8(a) shows a schematic diagram of the first FDTD-based mesh and cable outer surface correction coefficient in this scheme;

[0051] Figure 8(b) shows a schematic diagram of the second FDTD-based mesh and cable outer surface correction coefficient in this scheme;

[0052] Figure 9 A schematic diagram of the port of a multi-core cable is shown;

[0053] Figure 10 A flowchart illustrating another transient time-domain analysis method for multi-core cables is shown.

[0054] Figure 11 A structural block diagram of a transient time-domain analysis device for a multi-core cable provided according to an embodiment of this application is shown.

[0055] The above figures include the following reference numerals:

[0056] 102. Processor; 104. Memory; 106. Transmission device; 108. Input / output device; 10. Armor layer; 11. Conductor; 12. Dielectric. Detailed Implementation

[0057] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0058] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0059] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0060] Currently, time-domain electromagnetic transient simulation of power cables (multi-core cables in this scheme) is mainly implemented based on the finite-difference time-domain (FDTD) algorithm. This algorithm discretizes the computational space and time into a finite number of spatiotemporal units. Each spatial unit contains six orthogonal electric and magnetic field vectors to discretize the interior and structure of the simulated object, making the spatial distribution of electromagnetic fields within each unit approximately uniform. The time unit (also known as the time step) is used to discretize the time-varying curves of the electromagnetic fields, allowing for the solution of transient electromagnetic coupling problems using a static steady-state approach. After the electromagnetic fields are discretized by the FDTD spatiotemporal units, their iterative equations can be directly derived from Maxwell's equations, yielding second-order accurate results. The application scope is not limited by newly added mathematical model assumptions; therefore, theoretically, this algorithm can solve any form of electromagnetic transient case for simulated objects of arbitrary structures. Furthermore, the FDTD algorithm has advantages such as wideband simulation characteristics, strong computational stability, and ease of parallel computing, and is currently widely used in fields such as power, communication, bioelectromagnetism, and optics.

[0061] Traditional FDTD algorithms require discretizing the entire computational domain using orthogonal meshes. The size and number of meshes must be determined based on the geometric dimensions of the simulated object and the degree of electromagnetic distortion in the adjacent region. For multi-core power cables (also known as multi-core cables), their radial dimensions are as small as millimeters, while their axial dimensions are as large as hundreds of meters, resulting in extremely large spatial spans. When discretizing power cables using the classic FDTD mesh, the following problems will inevitably arise if the simulation requirements for both axial and radial dimensions are to be met simultaneously:

[0062] 1) The computation time is long. For the radial structure of discrete cables (multi-core cables), the axial mesh size needs to be reduced. However, since the FDTD algorithm needs to satisfy the Kronte stability criterion, the time step is also reduced accordingly. This results in the electromagnetic transient process of the same time length needing to be calculated more times, which passively prolongs the computation time.

[0063] 2) It consumes a lot of memory. In order to simultaneously meet the discretization accuracy of the radial direction of the cable and the extension dimension of the axial direction, it is necessary to cover the axial dimension of the power cable with a small-sized grid, which leads to a sharp increase in memory consumption and reduces computational efficiency.

[0064] 3) Poor computational stability. To partially solve the problem of modeling cables across axial and radial scales, non-uniform mesh modeling is usually used. However, for model construction with a span of millimeters to hundreds of meters, an extremely non-uniform mesh is required. This approach often causes the calculation results to diverge, which seriously reduces the computational stability.

[0065] 4) Large calculation error. In order to improve the overall calculation performance, multi-core power cables are treated as solid conductors in engineering simulations. This ignores the electromagnetic transient propagation of each phase conductor in the cable armor, resulting in a significant increase in calculation error.

[0066] The classic FDTD algorithm is a global discrete-time simulation algorithm. Its computational domain includes not only all simulated models but also the regions between and adjacent to the simulated objects. Before solving the electromagnetic field domain, the entire computational domain needs to be discretized into a set of parallelepiped spatial elements using an FDTD orthogonal mesh, such as... Figure 1 As shown. The electromagnetic field within each spatial cell is assumed to be uniformly distributed. Regions with drastic changes in the electromagnetic field should have a finer mesh size, such as the air-soil interface and the metal-dielectric interface. Regions with slow changes in the electromagnetic field can use a larger mesh size, such as the interior of air or soil. Taking the lower left vertex of each parallelepiped spatial cell as the initial point, electric field vectors E pointing in the XYZ orthogonal directions are defined on the three edges connected to the initial point. x E y E z The magnetic field vectors H, perpendicular to the three planes connected to the origin, are defined pointing in the three orthogonal directions X, Y, and Z. x H y H z ,like Figure 2 As shown. The electric field vector and magnetic field vector in each direction need to be set with corresponding material parameters according to their relative spatial positions, including conductivity σ, dielectric constant ε, and magnetic permeability μ.

[0067] When a set of FDTD meshes are arranged together to form the FDTD computational domain, the electromagnetic field vectors are spatially staggered by half a spatial step (i.e., the spatial cell size), and the electromagnetic vectors surround and encircle each other. That is, the electric field vector in a certain direction is surrounded by four magnetic field vectors, and vice versa. Figure 3As shown, the electromagnetic field vectors are also staggered by half a time step, meaning the overall electric field vector and the overall magnetic field vector are always 0.5Δt apart. These spatiotemporal characteristics satisfy the solution characteristics of Maxwell's discrete equations, allowing for alternating step-by-step solutions of the electric and magnetic field vectors. Typically, a complete electromagnetic transient analysis requires tens of thousands of step-by-step iterations until a preset convergence condition is met (e.g., the simulation results tend to a constant value or begin to form periodic changes) or the preset number of iterations is reached.

[0068] As described in the background section, the current FDTD algorithm in the prior art has low efficiency in performing transient time-domain analysis on multi-core power cables. To solve the above problems, the embodiments of this application provide a transient time-domain analysis method, apparatus and system for multi-core cables.

[0069] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0070] The methods and embodiments provided in this application can be executed on a mobile terminal, computer terminal, or similar computing device. Taking running on a mobile terminal as an example, Figure 4 This is a hardware structure block diagram of a mobile terminal for a transient time-domain analysis method for multi-core cables according to an embodiment of the present invention. Figure 4 As shown, a mobile terminal may include one or more ( Figure 4 Only one is shown in the diagram. A processor 102 (which may include, but is not limited to, a microprocessor MCU or a programmable logic device FPGA, etc.) and a memory 104 for storing data are also shown. The mobile terminal may further include a transmission device 106 for communication functions and an input / output device 108. Those skilled in the art will understand that... Figure 4 The structure shown is for illustrative purposes only and does not limit the structure of the mobile terminal described above. For example, the mobile terminal may also include components that are more... Figure 4 The more or fewer components shown, or having the same Figure 4 The different configurations shown.

[0071] The memory 104 can be used to store computer programs, such as application software programs and modules, like the computer program corresponding to the device information display method in this embodiment of the invention. The processor 102 executes various functional applications and data processing by running the computer program stored in the memory 104, thereby implementing the above-described method. The memory 104 may include high-speed random access memory and non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory. In some instances, the memory 104 may further include memory remotely located relative to the processor 102, and these remote memories can be connected to the mobile terminal via a network. Examples of the aforementioned networks include, but are not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof. The transmission device 106 is used to receive or send data via a network. Specific examples of the aforementioned networks may include wireless networks provided by the mobile terminal's communication provider. In one example, the transmission device 106 includes a network interface controller (NIC), which can be connected to other network devices via a base station to communicate with the Internet. In one example, the transmission device 106 may be a radio frequency (RF) module, which is used to communicate with the Internet wirelessly.

[0072] This embodiment provides a transient time-domain analysis method for multi-core cables running on mobile terminals, computer terminals, or similar computing devices. It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Furthermore, although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in a different order than that shown here.

[0073] Figure 5 This is a flowchart illustrating a transient time-domain analysis method for a multi-core cable according to an embodiment of this application. Figure 5 As shown, the method includes the following steps:

[0074] Step S201: Obtain the initial parameters of the multi-core cable. The initial parameters are obtained by calculation using the FDTD algorithm. The initial parameters include at least one of the following: initial dielectric constant and initial permeability. The multi-core cable is a cable with at least two conductors in its armor layer.

[0075] Specifically, taking three-phase power cables as an example, such as Figure 6 As shown, three parallel cylindrical conductor structures are assembled within the metal armor layer 10. Figure 6 The image shows a cross-section of a multi-core cable, which may include three conductors 11.

[0076] This scheme only considers the case of undamaged power cables, that is, the electromagnetic coupling inside and outside the armor only occurs at the cable ends. The coupling effect between the cable armor structure and the electromagnetic field of the external environment is analyzed by the FDTD algorithm.

[0077] Step S202: Update the initial parameters to obtain the target parameters;

[0078] Specifically, the FDTD algorithm mainly solves the electromagnetic coupling problem between the armor structure and the external environment (such as damaged soil, metal cable clamps, metal structural components, etc.). The cable model needs to be built on the edge of the FDTD spatial cell, and its radial dimension is much smaller than the FDTD mesh size. However, this scheme does not need to use the FDTD mesh to discretize and solve its radial structure. Therefore, the initial parameters can be updated to obtain the target parameters.

[0079] Step S203: Perform calculations on the target parameters according to the MTL algorithm to obtain the calculation results, wherein the calculation results are used to characterize the results of transient time-domain analysis of the multi-core cable.

[0080] Specifically, the electromagnetic wave propagation and reflection between the phase conductors within the armor layer are simulated based on the multi-conductor transmission line method (MTL). This method can also be applied to a structure in which three or more parallel cylindrical conductors are assembled within a metal armor layer.

[0081] This embodiment presents a novel transient time-domain analysis scheme for multi-core cables. This scheme performs transient time-domain analysis on multi-core cables by first updating the parameters in the FDTD algorithm. This eliminates the need for discretization through the FDTD mesh and subsequent analysis using the MTL algorithm, achieving strong coupling between the FDTD and MTL algorithms. This significantly improves the overall transient simulation efficiency of multi-core cables while ensuring simulation accuracy.

[0082] Specifically, the MTL (Multiconductor Transmission Line) algorithm is an analysis algorithm for multiconductor transmission lines. Multiconductor transmission lines are electromagnetic composite systems composed of a group of metallic wires, used to transmit various waveforms and signals. They are also ideal tools for transmitting pulsed and continuous signals. They are key components of high-frequency laser transmission and pulsed systems, and can also be used for low-frequency signal transmission. One of the most important properties of multiconductor transmission lines is their ability to efficiently transmit waveforms, thus achieving signal transmission. The application of multiconductor transmission line theory has two main aspects: the analysis of wire boundary conditions and the establishment of wire models. The analysis of wire boundary conditions first considers the details of the boundary layer structure, including impedance, resistance, and inductive potential. Then, it examines the impact on the entire wire transmission system and its significant role in waveform transmission. The establishment of wire models is the foundation for realizing the transmission and conductivity performance of multiconductor systems and is the core technology for analyzing the theory and practice of multiconductor transmission lines. It includes identifying various wire parameters, studying and analyzing system models, estimating various transmission parameters, exploring wire transmission characteristics, and conducting simulation and complexity analysis of conductor systems. The research and development of multiconductor transmission line technology is a deep study from the perspective of the physical essence and wire technology. First, it's essential to understand the nature of the conductors, deeply analyzing their geometric structure and its impact on the transmission system, as well as the influence of complex electromagnetic field structures. Second, it's necessary to study the conductor's dispersion characteristics, the nonlinear and divergent characteristics of coupled isolated systems, and the special transmission signal processing techniques used to achieve high-resolution transmission. Finally, it's crucial to understand the theoretical foundation of complex conductor transmission systems, including analog transmission, comprehensive analysis, and electromagnetic compatibility analysis. Multi-conductor transmission line theory not only covers the core technologies of transmission systems but also introduces new mathematical methods and theoretical models, which can be effectively applied to various novel transmission systems. From a practical application perspective, research on multi-conductor transmission lines plays a vital role in the design and management of complex communication systems. They help improve the efficiency and stability of transmission systems, enhance transmission quality, meet necessary field electromagnetic compatibility requirements, achieve high-speed waveform transmission, and optimize signal processing.

[0083] A multi-conductor transmission line (MTL) is a transmission line composed of multiple conductors. Common MTLs have two, three, four, or even N conductors. MTLs are widely used in high-speed digital communication, radio frequency communication, microwave technology, radar systems, and other fields. The characteristics of MTLs are their ability to transmit multiple signals, high transmission efficiency, and strong anti-interference capabilities. Two-conductor MTLs are widely used in digital communication fields such as Ethernet, USB, and HDMI; three-conductor MTLs are widely used in radio frequency communication, microwave technology, and antennas; and four-conductor MTLs are widely used in radar systems and high-speed data transmission. The design and analysis of MTLs require consideration of the conductors' electromagnetic properties, capacitance, inductance, and impedance matching. Currently, the research and application of MTLs has become one of the hot topics in the field of electronic technology.

[0084] The FDTD algorithm primarily addresses the electromagnetic coupling problem between the armor structure and the external environment (such as damaged soil, metal cable clamps, and metal structural components). The model's configuration within the FDTD mesh is as follows: Figure 7 As shown. The cable model needs to be constructed on the edge of the FDTD space cell. Its radial dimension is much smaller than the FDTD mesh size, that is, it is not necessary to discretize and solve its radial structure with the help of the FDTD mesh. The axial dimension of the model is discretized into several segments by the FDTD mesh in the corresponding direction. Each segment of the model coincides in space with the electric field vector at the corresponding position.

[0085] To avoid using the FDTD algorithm for transient time-domain analysis of the cable after obtaining initial parameters, and considering that the cable contains multiple conductors, it is necessary to correct some initial parameters to prevent the parameters obtained by the FDTD algorithm from being unsuitable for subsequent MTL analysis. Given that the initial parameters include the initial dielectric constant and initial permeability, and the target parameters include the dielectric constant and permeability, updating the initial parameters to obtain the target parameters can be achieved through the following steps:

[0086] The correction coefficient is calculated according to the first formula, where the first formula is:

[0087]

[0088] m represents the aforementioned correction coefficient, which is used to update the aforementioned initial parameters, r dThe radius from the center of the multi-core cable to the outer edge of the armor layer is expressed as Δs, which is the FDTD grid size. As shown in Figure 8(a), the initial dielectric constant is updated according to the second formula: ε'=mε to obtain the dielectric constant, where ε' represents the dielectric constant and ε represents the initial dielectric constant. As shown in Figure 8(b), the initial permeability is updated according to the third formula: μ'=mμ to obtain the permeability, where μ' represents the permeability and μ represents the initial permeability.

[0089] In this scheme, the multi-core cable can be solved without using the FDTD mesh for discretization. Instead, an equivalent multi-core cable model is constructed by correcting the material parameters of the electric and magnetic field vectors adjacent to the multi-core cable (i.e., constructing a virtual multi-core cable containing the actual parameters of various multi-core cables). Specifically, the initial dielectric constants corresponding to the four orthogonal electric field vectors perpendicular to the axis of the multi-core cable model are multiplied by correction coefficients to obtain the updated dielectric constant ε', which replaces the initial dielectric constant in the FDTD iterative formula. Next, the initial permeability corresponding to the four orthogonal magnetic field vectors surrounding the axis of the line model is divided by correction coefficients to obtain the corrected permeability μ', which replaces the initial permeability in the FDTD iterative formula. This corrects the parameters obtained by the FDTD algorithm without requiring further solution using the FDTD algorithm, ensuring high accuracy for subsequent transient time-domain analysis using the MTL algorithm.

[0090] In multi-core, multi-layer cables, since the current value of a multi-core cable is related to mutual capacitance, mutual capacitance can be used to calculate multiple current values ​​in the multi-core cable. Similarly, since the voltage value of a multi-core cable is related to mutual inductance, mutual inductance can be used to calculate multiple voltage values ​​in the multi-core cable. In specific implementation processes, such as... Figure 6As shown, when the multi-core cable includes three conductors, the calculation results include the current value flowing through each conductor, the voltage between each conductor and the armor layer, the total current value of the multi-core cable, and the current value of the armor layer. The calculation results are obtained by performing calculations on the target parameters according to the MTL algorithm, which can be achieved through the following steps: obtaining the first mutual inductance, second mutual inductance, first mutual capacitance, second mutual capacitance, and magnetic field vector in the multi-core cable. The first mutual inductance is the mutual inductance between the x-phase conductor and the armor layer; the second mutual inductance is the mutual inductance between the x-phase conductor and the y-phase conductor; the first mutual capacitance is the mutual capacitance between the x-phase conductor and the armor layer; the second mutual capacitance is the mutual capacitance between the x-phase conductor and the y-phase conductor; x and y are not equal, where x represents A, B, or C, and y represents A, B, or C. The magnetic field vector is the induced magnetic field generated by the multi-core cable. The magnetic field strength vector is calculated; the first current value, the second current value, and the third current value are calculated based on the first mutual capacitance and the second mutual capacitance; the first voltage value, the second voltage value, and the third voltage value are calculated based on the first mutual inductance and the second mutual inductance, wherein the first current value is the current value flowing through the A-phase conductor, the second current value is the current value flowing through the B-phase conductor, and the third current value is the current value flowing through the C-phase conductor; the first voltage value is the voltage between the A-phase conductor and the armor layer, the second voltage value is the voltage between the B-phase conductor and the armor layer, and the third voltage value is the voltage between the C-phase conductor and the armor layer; the total current value of the multi-core cable is calculated based on the magnetic field vector; the difference between the total current value and the target current value is calculated to obtain the current value of the armor layer, wherein the target current value is the sum of the first current value, the second current value, and the third current value.

[0091] In this scheme, the process of obtaining the calculation results is a process of transient time-domain analysis of multi-core cables. It can solve for the current values ​​of each phase conductor (including the first current value, the second current value, and the third current value) and the voltage between each phase conductor and the armor layer (including the first voltage value, the second voltage value, and the third voltage value). This simplifies the electromagnetic coupling solution process of complex structures, improves the calculation stability, and thus further improves the efficiency of transient time-domain analysis of multi-core and multi-layer power cables.

[0092] Specifically, within the metallic armor of a multi-core cable, the current conduction, reflection, and electromagnetic coupling relationships between phase conductors and between phase conductors and the metallic armor are analyzed using the multi-conductor transmission line method (MTL). To describe the geometric relationships within the metallic armor, three sets of conductors can be defined as phase A, phase B, and phase C, with the armor and each phase conductor filled with a dielectric material.

[0093] In the specific implementation process, obtaining the first mutual inductance, second mutual inductance, first mutual capacitance, and second mutual capacitance in the above multi-core cable can be achieved through the following steps:

[0094] The first mutual inductance is calculated according to the fourth formula, where the fourth formula is:

[0095]

[0096] L xx The first mutual inductance is represented by μ0, which represents the free permeability. r The relative permeability r of a dielectric material a R represents the radius of each phase conductor. b.x r represents the distance between the center of the x-phase conductor and the center of the aforementioned armor layer. c This indicates the inner radius of the aforementioned armor conductor, such as... Figure 6 As shown, the dielectric 12 is located between each conductor 11 and the armor layer 10; the second mutual inductance is calculated according to the fifth formula, wherein the fifth formula is:

[0097]

[0098] L xy Representing the second mutual inductance mentioned above, θ xy The coefficient C represents the spatial angle between the x-phase conductor and the y-phase conductor. n The calculation formula is:

[0099]

[0100] The first mutual capacitance mentioned above is calculated according to the sixth formula, where the sixth formula is:

[0101]

[0102] C xx This represents the first mutual capacitance mentioned above, where ε0 represents the dielectric constant, and ε r The relative permittivity of the aforementioned dielectric is represented; the second mutual capacitance is calculated according to the seventh formula, wherein the seventh formula is:

[0103]

[0104] Among them, C xy This indicates the second mutual compatibility mentioned above.

[0105] In this scheme, since the first mutual inductance is related to the permeability, the second mutual inductance is related to the spatial angle between the two conductors, the first mutual capacitance is related to the dielectric constant, and the second mutual capacitance is related to the spatial angle between the two conductors, the first mutual inductance can be calculated using the fourth formula, the second mutual inductance using the fifth formula, the first mutual capacitance using the sixth formula, and the second mutual capacitance using the seventh formula. Because the data obtained using each formula is relatively accurate, the first mutual inductance, the second mutual inductance, the first mutual capacitance, and the second mutual capacitance can be used to further perform transient time-domain analysis on the multi-core cable, thereby further ensuring that the data obtained from the subsequent transient time-domain analysis is relatively accurate.

[0106] The first current value, the second current value, and the third current value can be obtained according to specific calculation formulas. Similarly, the first voltage value, the second voltage value, and the third voltage value can also be obtained according to specific calculation formulas. In some embodiments, the first current value, the second current value, and the third current value are calculated based on the aforementioned first mutual capacitance and the aforementioned second mutual capacitance. The first voltage value, the second voltage value, and the third voltage value are calculated based on the aforementioned first mutual inductance and the aforementioned second mutual inductance. This can be achieved through the following steps:

[0107] The first current value, the second current value, and the third current value are calculated according to the eighth formula, where the eighth formula is:

[0108]

[0109] l represents the axial distance of the aforementioned multi-core cable, s characterizes the complex frequency domain, and I A I represents the first current value mentioned above. B I represents the second current value mentioned above. C C represents the third current value mentioned above. xx Indicates the first mutual compatibility mentioned above, C xy V represents the second mutual compatibility mentioned above. x This represents the voltage between the x-phase conductor and the aforementioned armor layer; the first voltage value, the second voltage value, and the third voltage value are calculated according to the ninth formula, wherein the ninth formula is:

[0110]

[0111] L xx L represents the first mutual inductance mentioned above. xy V represents the second mutual inductance mentioned above. A This represents the first voltage value mentioned above, V. B This represents the second voltage value mentioned above, V. C This indicates the third voltage value mentioned above.

[0112] In this scheme, three different conductors (first conductor, second conductor, and third conductor) are first defined, denoted as A, B, and C respectively. Then, the first current value, second current value, and third current value are calculated more accurately according to the eighth formula, and the first voltage value, second voltage value, and third voltage value are calculated more accurately according to the ninth formula. In this way, the current values ​​of each phase conductor flowing through the multi-core cable can be obtained more accurately. Subsequently, the transient time-domain analysis of the multi-core multilayer cable can be performed more accurately based on the current values ​​of each phase conductor.

[0113] Specifically, the first current value, the second current value, and the third current value obtained in the eighth formula above, and the first voltage value, the second voltage value, and the third voltage value obtained in the ninth formula are expressions in the frequency domain.

[0114] Since the FDTD algorithm performs calculations in the time domain, the data obtained in the frequency domain can be converted into a time domain form. To efficiently and accurately convert the data obtained in the frequency domain into a time domain form, after calculating the first current value, the second current value, and the third current value based on the first mutual capacitance and the second mutual capacitance, and calculating the first voltage value, the second voltage value, and the third voltage value based on the first mutual inductance and the second mutual inductance, the above method further includes the following steps:

[0115] According to the tenth formula, the first current value, the second current value, and the third current value are converted into time-domain form, where the tenth formula is:

[0116]

[0117] Δt is the FDTD time step, and q represents the number of time steps; according to the eleventh formula, the first voltage value, the second voltage value, and the third voltage value are converted into time-domain form, where the eleventh formula is:

[0118]

[0119] In this scheme, the tenth formula can be used to convert the current value flowing through each phase conductor into a time-domain expression, and the eleventh formula can be used to convert the voltage value between each phase conductor and the armor layer into a time-domain expression. This scheme can efficiently and accurately convert the data obtained in the frequency domain into the time domain form, so that the total current value can be calculated in the time domain later.

[0120] The total current value can also be obtained according to a specific calculation formula. In the specific implementation process, the total current value of the multi-core cable is calculated based on the above magnetic field vector, which can be achieved through the following steps:

[0121] The total current value is calculated according to the twelfth formula, where the twelfth formula is:

[0122]

[0123] The total current value is represented by H, the magnetic field vector is represented by i, j, and k, which are the magnetic field vector position numbers based on the FDTD grid number, and Δy and Δz are the dimensions of the FDTD grid in the Y and Z directions, respectively.

[0124] In this scheme, the total current flowing through the multi-core cable can actually be calculated based on the specific magnetic field vector, and the total current value I of each segment of the multi-core cable is... t The total current value of the multi-core cable in the X direction can be calculated by loop integration of the magnetic field vector surrounding the multi-core cable in the FDTD calculation region. Taking the m-th segment of the multi-core cable in the X direction as an example, the twelfth calculation formula can be used to calculate the total current value of the multi-core cable in the X direction. This can provide a more accurate total current value flowing through the multi-core cable. Subsequently, the transient time-domain analysis of the multi-core cable can be further performed more accurately based on the total current value.

[0125] Specifically, given the first current value, the second current value, the third current value, and the total current value, the current value of the armor layer can be calculated using the fourteenth formula, which is: in, This indicates the current value of the armor layer.

[0126] In some embodiments, obtaining the magnetic field vector in the aforementioned multi-core cable can be achieved through the following steps:

[0127] The magnetic field vector is calculated according to formula thirteen, where formula thirteen is:

[0128]

[0129]

[0130]

[0131] Where μ represents the magnetic permeability, σ m E represents the permeability, q represents the time step, and E represents the magnetic permeability. x E y E z Let σ represent the electric field vectors in three orthogonal directions, ε represent the equivalent conductivity in the corresponding space, ε represent the permittivity in the corresponding space, x represent the first direction, y represent the second direction, and z represent the third direction. Δx, Δy, and Δz represent the dimensions of the FDTD mesh in the three orthogonal directions (x, y, z), respectively. x H y H zThese are the magnetic field vectors in three orthogonal directions, i, j, and k are the electric field vector position numbers based on the FDTD grid number, and the electric field vectors are the electric field intensity vectors of the electric field generated by the multi-core cable.

[0132] In this scheme, the magnetic field vector of the multi-core cable can be calculated using Formula 13. Since the data obtained by Formula 13 is relatively accurate, the magnetic field vector can be used to further perform transient time-domain analysis on the multi-core cable, thereby further ensuring that the data obtained by the subsequent transient time-domain analysis is relatively accurate.

[0133] Specifically, at the port of a multi-core cable, on the one hand, the voltage between the metal armor and each phase conductor is exposed to the air and no longer shielded by the armor. This needs to be considered in the FDTD algorithm's calculation of the electric field difference, meaning the end voltage obtained from transmission line theory is output to the FDTD algorithm. On the other hand, to consider the connection between each phase conductor and the external circuit, the current value of a section of the circuit outside the cable needs to be substituted into the transmission line theory calculation. The current in this section of the circuit is obtained by the loop integration of the magnetic field vector in the FDTD calculation region, meaning the extended circuit current obtained from the FDTD algorithm is output to the transmission line theory. The port structure of a multi-core cable is as follows: Figure 9 As shown, the three conductor segments indicated by dashed lines represent the extended circuits of phase A, phase B, and phase C conductors. Taking phase A conductor of a multi-core cable as an example, its extended conductor extends along the X direction. The current in this extended circuit segment is solved using the twelfth formula, and the magnetic field vector at its port is...

[0134]

[0135] The updated formula is the fifteenth formula, which is:

[0136]

[0137] This scheme also involves the calculation of the electric field vector, which can be obtained using the sixteenth formula. The sixteenth formula is:

[0138]

[0139]

[0140]

[0141] The core idea of ​​this scheme can be summarized as follows: 1) A hybrid algorithm is used to model and simulate the cable model. The electromagnetic coupling between the armor structure of the multi-core power cable and the external environment is analyzed by the FDTD algorithm. Furthermore, by correcting the material coefficients in the adjacent areas of the cable model, the cable model is efficiently constructed in a large-size FDTD mesh, eliminating the need to discretize the cable structure using a fine mesh; 2) The electromagnetic coupling between the phase conductors within the armor and between the phase conductors and the armor is analyzed by the multi-conductor transmission line method (MTL). The current in each phase conductor and the voltage between each phase conductor and the armor are coupled by mutual inductance and mutual capacitance matrices. 3) Since the loss of the power cable conductor material is not considered, the electromagnetic fields inside and outside the armor layer in the middle of the cable can be decoupled for analysis, that is, the FDTD and MTL algorithms do not need to consider information interaction in the middle of the cable; 4) At the port of the cable, the current of the extended circuit of each phase conductor is calculated by FDTD and substituted into the voltage distribution of MTL for solution, and the voltage at the port of each phase conductor is calculated by MTL and substituted into the magnetic field distribution of FDTD for solution; 5) Repeat the iterative loop of the FDTD-MTL hybrid algorithm, and output the calculation results when the number of iteration steps or the convergence requirement is met.

[0142] To enable those skilled in the art to better understand the technical solution of this application, the implementation process of the transient time-domain analysis method for multi-core cables of this application will be described in detail below with reference to specific embodiments.

[0143] This embodiment relates to a specific transient time-domain analysis method for multi-core cables, such as... Figure 10 As shown, it includes the following steps:

[0144] (1) Establish models such as multi-core power cables according to actual needs (including all formulas in this scheme, specifically the formulas derived from this model), and define network discretization and time step.

[0145] The computational domain is reasonably determined based on the actual model size required for simulation. This domain generally extends outward by about 50% beyond the area containing all simulated objects to eliminate the effects of boundary effects, stray signal reflection, etc. Secondly, the mesh discretization scheme is determined according to the model's topology. In areas containing finely structured simulated objects, the mesh size needs to be appropriately refined, while in areas where the electromagnetic field changes slowly, the mesh size is increased, thus simultaneously considering simulation accuracy and efficiency. For power cable modeling, the model is attached to an edge of the FDTD mesh, with its radial dimension smaller than the FDTD mesh size. The axial dimension is discretized by the FDTD mesh into several cable segments, each coinciding with the corresponding electric field vector. The cable radial direction does not need to be solved through FDTD mesh discretization; instead, equivalent modeling is performed by correcting the dielectric constant and permeability of the adjacent region of the cable model, modifying the first, second, and third formulas.

[0146] The range of time steps for the FDTD algorithm is determined by the minimum FDTD discrete grid size, and must satisfy the Courant-Friedrich-Levy (CFL) criterion to prevent problems such as data divergence, oscillation, and non-convergence that may occur in time-domain calculations, which is expressed as the seventeenth formula:

[0147]

[0148] Where Δx, Δy, and Δz are the minimum FDTD mesh sizes in the three orthogonal directions x, y, and z, respectively, and c is the speed of light propagation in the corresponding medium. Generally, the FDTD time step can be selected from the maximum value in the seventeenth formula to reduce the number of simulations and improve simulation efficiency.

[0149] (2) Set the necessary solution parameters such as material parameters, load, and number of iteration steps.

[0150] Based on the spatial location of the simulated object, set the conductivity, dielectric constant, and permeability of the response in the FDTD mesh. Depending on the actual requirements, set loads at specified locations in the form of spatial electromagnetic fields or lumped circuit parameter elements. Determine the total number of iterations based on the transient process to be simulated, or set convergence conditions for the calculation results (such as the simulation results tending to a constant value or beginning to form periodic changes) based on the required computational accuracy.

[0151] (3) Calculate the electric field value over the entire FDTD domain and correct the electric field vector coinciding with the cable.

[0152] The iterative process involves the electric field vector value of the previous time step and the four magnetic field vectors surrounding the electric field vector. The specific update equation is shown in Formula 16.

[0153] In one feasible approach, since the power cable model described above only considers a lossless conductor, i.e., an equipotential body with no potential difference inside or on the surface of the conductor, the FDTD electric field vectors coinciding with the power cable must all be assigned a value of 0, i.e., E l q =0 (Eighteenth Formula).

[0154] (4) Calculation of voltage distribution on dielectric based on the multi-conductor transmission line method (MTL)

[0155] Using the eleventh formula, combining the currents of each phase conductor in the first half of the time step and the voltages between each phase conductor and the metal armor layer in the previous time step, the axial voltage distribution within the metal armor layer at the current time step is calculated based on the time-domain discrete multi-conductor transmission line method.

[0156] (5) Calculate the magnetic field value over the entire FDTD domain, and correct the magnetic field value at the cable port to account for the port voltage.

[0157] The magnetic field vector across the entire domain is calculated iteratively using the classical FDTD magnetic field vector update equation. The specific formula is shown in Formula Thirteen.

[0158] The permeability is generally set to 0. The magnetic field vector update equation at the cable port should take into account the influence of the port voltage on the electric field vector difference, and the fifteenth formula should be used to correct the magnetic field vector update equation.

[0159] (6) Calculate the current distribution in each phase conductor based on the multi-conductor transmission line method (MTL).

[0160] The current of each phase conductor, the total current of the power cable, and the current of the metal armor layer are solved sequentially using the tenth, twelfth, and fourteenth formulas at the current time step.

[0161] (7) Repeat steps (3)-(6). When the number of iterations or the convergence requirement is met, output the calculation results.

[0162] Following steps (3)-(6), the electric field vector and magnetic field vector in the calculation region are repeatedly iterated and solved. Each iteration is equivalent to updating and estimating the electromagnetic field quantity in the calculation region in time to the next time step Δt, thus realizing the step-by-step solution of the electromagnetic field quantity in time. When the number of iterations or the convergence condition meets the preset conditions, the electromagnetic field calculation is terminated and the calculation result is output.

[0163] This proposal presents a time-domain simulation model for multi-core power cables based on a hybrid FDTD-MTL algorithm. This model uses the metal armor as a boundary for electromagnetic decoupling analysis in the middle section of the cable. The electromagnetic transient processes within the armor are analyzed using the MTL algorithm, while the electromagnetic coupling outside the armor is analyzed using FDTD. Efficient interaction of the computational information from the two algorithms is achieved at the cable port, realizing strong coupling between the hybrid algorithm-based field-circuit coupling analysis and the FDTD-MTL algorithm. This significantly improves the overall efficiency of electromagnetic transient simulation for power cables while ensuring simulation accuracy, enabling efficient time-domain transient solution analysis of power cables. This provides a theoretical basis and important technical support for the overall optimization of cable connection methods, extending cable life, and improving system operational reliability.

[0164] The key points of this scheme are: 1) The power cable is constructed into an equivalent cable model in the FDTD mesh, without the need for fine FDTD mesh discretization; 2) Based on the assumption of a high-conductivity metallic armor layer, the electromagnetic analysis inside and outside the armor layer in the middle section of the cable is decoupled; 3) The FDTD-MTL hybrid algorithm is used for solving the problem, with the electromagnetic transient process inside the armor layer analyzed by the MTL algorithm and the electromagnetic coupling outside the armor layer analyzed by the FDTD algorithm; 4) Through real-time and efficient interaction at the cable port, strong coupling of FDTD and MTL can be achieved as a whole; 5) Field-circuit coupling analysis can be naturally realized, improving the coverage depth and breadth of electromagnetic analysis; 6) The position and structure of each phase conductor inside the armor layer can be freely defined.

[0165] The advantages of this scheme are as follows: 1) The power cable layout scheme involves modifying the material parameters of adjacent areas and constructing an equivalent cable model in the FDTD mesh. The radial dimension of the model can be smaller than the FDTD mesh size, while the axial dimension is segmented using the FDTD mesh, thereby increasing the single time step, reducing memory usage, and improving the algorithm's computational efficiency; 2) Based on the actual simulation requirements of electrical engineering, it is assumed that the coupled electromagnetic field cannot penetrate the high-conductivity metal armor layer. Therefore, the electromagnetic analysis inside and outside the armor layer in the middle section of the cable can be decoupled, laying the foundation for the implementation of the hybrid algorithm; 3) The FDTD-MTL hybrid algorithm is used for solving the problem, and the electromagnetic transient process inside the armor layer is solved using M... 4) At the cable port, by using the real-time and efficient interaction between the extended circuit current calculated by FDTD and the phase conductor-armor voltage calculated by MTL, strong coupling between FDTD and MTL can be achieved as a whole; 5) FDTD is a field algorithm and MTL is a circuit algorithm. By constructing a hybrid algorithm, field-circuit coupling analysis can be naturally achieved, improving the coverage depth and breadth of electromagnetic analysis; 6) A complete analytical formula is constructed inside the armor, which can meet the free position structure definition of each phase conductor inside the armor, without the constraints of axisymmetry, etc.

[0166] This application also provides a transient time-domain analysis device for multi-core cables. It should be noted that this device can be used to execute the transient time-domain analysis method for multi-core cables provided in this application. This device is used to implement the above embodiments and preferred embodiments; details already described will not be repeated. As used below, the term "module" can refer to a combination of software and / or hardware that performs a predetermined function. Although the device described in the following embodiments is preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated.

[0167] The transient time-domain analysis device for multi-core cables provided in the embodiments of this application will be described below.

[0168] Figure 11 This is a structural block diagram of a transient time-domain analysis device for a multi-core cable according to an embodiment of this application. Figure 11 As shown, the device includes:

[0169] The acquisition unit 100 is used to acquire the initial parameters of the multi-core cable, wherein the initial parameters are obtained by calculation using the FDTD algorithm, and the initial parameters include at least one of the following: initial dielectric constant, initial permeability, and the multi-core cable is a cable that includes at least two conductors within its armor layer.

[0170] The update unit 200 is used to update the initial parameters to obtain the target parameters;

[0171] The calculation unit 300 is used to perform calculations on the target parameters according to the MTL algorithm to obtain the calculation results, wherein the calculation results are used to characterize the results of transient time-domain analysis of the multi-core cable.

[0172] This embodiment presents a novel transient time-domain analysis scheme for multi-core cables. This scheme performs transient time-domain analysis on multi-core cables by first updating the parameters in the FDTD algorithm. This eliminates the need for discretization through the FDTD mesh and subsequent analysis using the MTL algorithm, achieving strong coupling between the FDTD and MTL algorithms. This significantly improves the overall transient simulation efficiency of multi-core cables while ensuring simulation accuracy.

[0173] To avoid using the FDTD algorithm for transient time-domain analysis of the cable after obtaining initial parameters, and considering that the cable contains multiple conductors, some initial parameters need to be corrected. This is to prevent the parameters obtained by the FDTD algorithm from being unsuitable for subsequent MTL analysis. Given that the initial parameters include the initial dielectric constant and initial permeability, and the target parameters include dielectric constant and permeability, the update unit includes a first calculation module, a first update module, and a second update module. The first calculation module calculates correction coefficients according to a first formula, wherein the first formula is...

[0174]

[0175] m represents the aforementioned correction coefficient, which is used to update the aforementioned initial parameters, r d The radius from the center of the multi-core cable to the outer edge of the armor layer is expressed as Δs, where Δs is the FDTD grid size. The first update module is used to update the initial dielectric constant according to the second formula: ε'=mε, to obtain the dielectric constant, where ε' represents the dielectric constant and ε represents the initial dielectric constant. The second update module is used to update the initial permeability according to the third formula: μ'=mμ, to obtain the permeability, where μ' represents the permeability and μ represents the initial permeability.

[0176] In this scheme, the multi-core cable can be solved without using the FDTD mesh for discretization. Instead, an equivalent multi-core cable model is constructed by correcting the material parameters of the electric and magnetic field vectors adjacent to the multi-core cable (i.e., constructing a virtual multi-core cable containing the actual parameters of various multi-core cables). Specifically, the initial dielectric constants corresponding to the four orthogonal electric field vectors perpendicular to the axis of the multi-core cable model are multiplied by correction coefficients to obtain the updated dielectric constant ε', which replaces the initial dielectric constant in the FDTD iterative formula. Next, the initial permeability corresponding to the four orthogonal magnetic field vectors surrounding the axis of the line model is divided by correction coefficients to obtain the corrected permeability μ', which replaces the initial permeability in the FDTD iterative formula. This corrects the parameters obtained by the FDTD algorithm without requiring further solution using the FDTD algorithm, ensuring high accuracy for subsequent transient time-domain analysis using the MTL algorithm.

[0177] In multi-core, multi-layer cables, since the current value of the multi-core cable is related to mutual capacitance, mutual capacitance can be used to calculate multiple current values ​​in the multi-core cable. Similarly, since the voltage value of the multi-core cable is related to mutual inductance, mutual inductance can be used to calculate multiple voltage values. Specifically, in the case of a multi-core cable containing three conductors, the calculation results include the current value flowing through each conductor, the voltage between each conductor and the armor layer, the total current value of the multi-core cable, and the current value of the armor layer. The calculation unit includes an acquisition module, a second calculation module, a third calculation module, and a fourth calculation module. The acquisition module is used to acquire the first mutual inductance, the second mutual inductance, the first mutual capacitance, the second mutual capacitance, and the magnetic field vector in the multi-core cable. The first mutual inductance is the mutual inductance between the x-phase conductor and the armor layer; the second mutual inductance is the mutual inductance between the x-phase conductor and the y-phase conductor; the first mutual capacitance is the mutual capacitance between the x-phase conductor and the armor layer; and the second mutual capacitance is the mutual capacitance between the x-phase conductor and the y-phase conductor. x and y are not equal, and x represents A or... B or C, y represents A or B or C, and the above magnetic field vector is the magnetic field strength vector of the induced magnetic field generated by the above multi-core cable; the second calculation module is used to calculate the first current value, the second current value and the third current value according to the first mutual capacitance and the second mutual capacitance, and to calculate the first voltage value, the second voltage value and the third voltage value according to the first mutual inductance and the second mutual inductance, wherein the first current value is the current value flowing through the A phase conductor, the second current value is the current value flowing through the B phase conductor, the third current value is the current value flowing through the C phase conductor, the first voltage value is the voltage between the A phase conductor and the above armor layer, the second voltage value is the voltage between the B phase conductor and the above armor layer, and the third voltage value is the voltage between the C phase conductor and the above armor layer; the third calculation module is used to calculate the total current value of the above multi-core cable according to the above magnetic field vector; the fourth calculation module is used to calculate the difference between the above total current value and the target current value to obtain the current value of the above armor layer, wherein the target current value is the sum of the above first current value, the above second current value and the above third current value.

[0178] In this scheme, the process of obtaining the calculation results is a process of transient time-domain analysis of multi-core cables. It can solve for the current values ​​of each phase conductor (including the first current value, the second current value, and the third current value) and the voltage between each phase conductor and the armor layer (including the first voltage value, the second voltage value, and the third voltage value). This simplifies the electromagnetic coupling solution process of complex structures, improves the calculation stability, and thus further improves the efficiency of transient time-domain analysis of multi-core and multi-layer power cables.

[0179] In the specific implementation process, the acquisition module includes a first calculation submodule, a second calculation submodule, a third calculation submodule, and a fourth calculation submodule. The first calculation submodule is used to calculate the aforementioned first mutual inductance according to the fourth formula, wherein the aforementioned fourth formula is:

[0180]

[0181] L xx The first mutual inductance is represented by μ0, which represents the free permeability. r The relative permeability r of a dielectric material a R represents the radius of each phase conductor. b.x r represents the distance between the center of the x-phase conductor and the center of the aforementioned armor layer. c The term "inner radius" represents the inner radius of the aforementioned armor layer conductor, and the aforementioned dielectric is located between each conductor and the aforementioned armor layer; the second calculation submodule is used to calculate the aforementioned second mutual inductance according to the fifth formula, wherein the aforementioned fifth formula is:

[0182]

[0183] L xy Representing the second mutual inductance mentioned above, θ xy The coefficient C represents the spatial angle between the x-phase conductor and the y-phase conductor. n The calculation formula is:

[0184]

[0185] The third calculation submodule is used to calculate the first mutual capacitance mentioned above according to the sixth formula, wherein the sixth formula is:

[0186]

[0187] C xx This represents the first mutual capacitance mentioned above, where ε0 represents the dielectric constant, and ε r The fourth calculation submodule is used to calculate the second mutual capacitance according to the seventh formula, wherein the seventh formula is:

[0188]

[0189] Among them, C xy This indicates the second mutual compatibility mentioned above.

[0190] In this scheme, since the first mutual inductance is related to the permeability, the second mutual inductance is related to the spatial angle between the two conductors, the first mutual capacitance is related to the dielectric constant, and the second mutual capacitance is related to the spatial angle between the two conductors, the first mutual inductance can be calculated using the fourth formula, the second mutual inductance using the fifth formula, the first mutual capacitance using the sixth formula, and the second mutual capacitance using the seventh formula. Because the data obtained using each formula is relatively accurate, the first mutual inductance, the second mutual inductance, the first mutual capacitance, and the second mutual capacitance can be used to further perform transient time-domain analysis on the multi-core cable, thereby further ensuring that the data obtained from the subsequent transient time-domain analysis is relatively accurate.

[0191] The first current value, the second current value, and the third current value can be obtained according to specific calculation formulas. Similarly, the first voltage value, the second voltage value, and the third voltage value can also be obtained according to specific calculation formulas. In some embodiments, the second calculation module includes a fifth calculation submodule and a sixth calculation submodule. The fifth calculation submodule is used to calculate the aforementioned first current value, the aforementioned second current value, and the aforementioned third current value according to an eighth formula, wherein the aforementioned eighth formula is...

[0192]

[0193] l represents the axial distance of the aforementioned multi-core cable, s characterizes the complex frequency domain, and I A I represents the first current value mentioned above. B I represents the second current value mentioned above. C C represents the third current value mentioned above. xx Indicates the first mutual compatibility mentioned above, C xy V represents the second mutual compatibility mentioned above. x This represents the voltage between the x-phase conductor and the aforementioned armor layer; the sixth calculation submodule is used to calculate the aforementioned first voltage value, the aforementioned second voltage value, and the aforementioned third voltage value according to the ninth formula, wherein the aforementioned ninth formula is:

[0194]

[0195] L xx L represents the first mutual inductance mentioned above. xy V represents the second mutual inductance mentioned above. A This represents the first voltage value mentioned above, V. B This represents the second voltage value mentioned above, V. C This indicates the third voltage value mentioned above.

[0196] In this scheme, three different conductors (first conductor, second conductor, and third conductor) are first defined, denoted as A, B, and C respectively. Then, the first current value, second current value, and third current value are calculated more accurately according to the eighth formula, and the first voltage value, second voltage value, and third voltage value are calculated more accurately according to the ninth formula. In this way, the current values ​​of each phase conductor flowing through the multi-core cable can be obtained more accurately. Subsequently, the transient time-domain analysis of the multi-core multilayer cable can be performed more accurately based on the current values ​​of each phase conductor.

[0197] Since the FDTD algorithm is performed in the time domain, the data obtained in the frequency domain can be converted into a time domain form. To efficiently and accurately convert the frequency domain data into a time domain form, the device further includes a first conversion unit and a second conversion unit. The first conversion unit is used to calculate a first current value, a second current value, and a third current value based on the first mutual capacitance and the second mutual capacitance, and to calculate a first voltage value, a second voltage value, and a third voltage value based on the first mutual inductance and the second mutual inductance. Then, it converts the first current value, the second current value, and the third current value into a time domain form according to a tenth formula, wherein the tenth formula is:

[0198]

[0199] Δt is the FDTD time step, and q represents the number of time steps; the second conversion unit is used to convert the first voltage value, the second voltage value, and the third voltage value into time-domain form according to the eleventh formula, wherein the eleventh formula is:

[0200]

[0201] In this scheme, the tenth formula can be used to convert the current value flowing through each phase conductor into a time-domain expression, and the eleventh formula can be used to convert the voltage value between each phase conductor and the armor layer into a time-domain expression. This scheme can efficiently and accurately convert the data obtained in the frequency domain into the time domain form, so that the total current value can be calculated in the time domain later.

[0202] The total current value can also be obtained according to a specific calculation formula. In the specific implementation, the third calculation module includes a seventh calculation submodule. The seventh calculation submodule is used to calculate the above total current value according to the twelfth formula, where the above twelfth formula is:

[0203]

[0204] The total current value is represented by H, the magnetic field vector is represented by i, j, and k, which are the magnetic field vector position numbers based on the FDTD grid number, and Δy and Δz are the dimensions of the FDTD grid in the Y and Z directions, respectively.

[0205] In this scheme, the total current flowing through the multi-core cable can actually be calculated based on the specific magnetic field vector, and the total current value I of each segment of the multi-core cable is... t The total current value of the multi-core cable in the X direction can be calculated by loop integration of the magnetic field vector surrounding the multi-core cable in the FDTD calculation region. Taking the m-th segment of the multi-core cable in the X direction as an example, the twelfth calculation formula can be used to calculate the total current value of the multi-core cable in the X direction. This can provide a more accurate total current value flowing through the multi-core cable. Subsequently, the transient time-domain analysis of the multi-core cable can be further performed more accurately based on the total current value.

[0206] In some embodiments, the acquisition module includes an eighth calculation submodule, which is used to calculate the magnetic field vector according to the thirteenth formula, wherein the thirteenth formula is:

[0207]

[0208]

[0209]

[0210] Where μ represents the magnetic permeability, σ m E represents the permeability, q represents the time step, and E represents the magnetic permeability. x E y E z Let σ represent the electric field vectors in three orthogonal directions, ε represent the equivalent conductivity in the corresponding space, ε represent the permittivity in the corresponding space, x represent the first direction, y represent the second direction, and z represent the third direction. Δx, Δy, and Δz represent the dimensions of the FDTD mesh in the three orthogonal directions (x, y, z), respectively. x H y H z These are the magnetic field vectors in three orthogonal directions, i, j, and k are the electric field vector position numbers based on the FDTD grid number, and the electric field vectors are the electric field intensity vectors of the electric field generated by the multi-core cable.

[0211] In this scheme, the magnetic field vector of the multi-core cable can be calculated using Formula 13. Since the data obtained by Formula 13 is relatively accurate, the magnetic field vector can be used to further perform transient time-domain analysis on the multi-core cable, thereby further ensuring that the data obtained by the subsequent transient time-domain analysis is relatively accurate.

[0212] The aforementioned transient time-domain analysis device for multi-core cables includes a processor and a memory. The acquisition unit, update unit, and calculation unit are all stored as program units in the memory, and the processor executes these program units to achieve the corresponding functions. All of the above modules are located in the same processor; alternatively, the modules may be located in different processors in any combination.

[0213] The processor contains a kernel, which retrieves the corresponding program unit from memory. One or more kernels can be configured, and adjusting kernel parameters can address the low efficiency of current FDTD algorithms for transient time-domain analysis of multi-core power cables.

[0214] The memory may include non-permanent memory in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM, and the memory includes at least one memory chip.

[0215] This invention provides a computer-readable storage medium including a stored program, wherein, when the program is executed, it controls the device containing the computer-readable storage medium to perform the transient time-domain analysis method for the multi-core cable.

[0216] This invention provides a processor for running a program, wherein the program executes the transient time-domain analysis method for the multi-core cable.

[0217] This application also provides a transient time-domain analysis system for multi-core cables, including one or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, and the one or more programs include methods for performing any of the aforementioned transient time-domain analysis methods for multi-core cables.

[0218] This invention provides a device including a processor, a memory, and a program stored in the memory and executable on the processor. When the processor executes the program, it implements at least the following steps of a transient time-domain analysis method for multi-core cables.

[0219] This application also provides a computer program product that, when executed on a data processing device, is adapted to perform the steps of an initialization transient time-domain analysis method having at least the following multi-core cable.

[0220] It is obvious to those skilled in the art that the modules or steps of the present invention described above can be implemented using general-purpose computing devices. They can be centralized on a single computing device or distributed across a network of multiple computing devices. They can be implemented using computer-executable program code, and thus can be stored in a storage device for execution by a computing device. In some cases, the steps shown or described can be performed in a different order than those described herein, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. Thus, the present invention is not limited to any particular combination of hardware and software.

[0221] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0222] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0223] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0224] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0225] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0226] Memory may include non-persistent memory in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory is an example of computer-readable media.

[0227] Computer-readable media includes both permanent and non-permanent, removable and non-removable media that can store information using any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic magnetic disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.

[0228] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0229] As can be seen from the above description, the embodiments of this application achieve the following technical effects:

[0230] 1) The transient time-domain analysis method for multi-core cables in this application designs a new transient time-domain analysis scheme for multi-core cables. This scheme performs transient time-domain analysis on multi-core cables. First, the parameters in the FDTD algorithm are updated, so that it is no longer necessary to solve the problem by FDTD mesh discretization and then use the MTL algorithm for analysis. This realizes the strong coupling of the FDTD-MTL algorithm and significantly improves the overall transient simulation efficiency of multi-core cables while ensuring simulation accuracy.

[0231] 2) The transient time-domain analysis device for multi-core cables in this application designs a new transient time-domain analysis scheme for multi-core cables. This scheme performs transient time-domain analysis on multi-core cables. First, the parameters in the FDTD algorithm are updated, so that it is no longer necessary to solve the problem by discretization through the FDTD mesh and then use the MTL algorithm for analysis. This realizes the strong coupling of the FDTD-MTL algorithm and significantly improves the overall transient simulation efficiency of multi-core cables while ensuring simulation accuracy.

[0232] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method of transient time domain analysis of a multi-core cable, characterized by, include: The initial parameters of a multi-core cable are obtained, wherein the initial parameters are calculated using the finite-difference time-domain (FDTD) algorithm, and the initial parameters include at least one of the following: initial dielectric constant and initial permeability. The multi-core cable is a cable that includes at least two conductors within its armor layer. The initial parameters are updated to obtain the target parameters; The target parameters are calculated using the Multi-Conductor Transmission Line (MTL) algorithm to obtain the calculation results, which are used to characterize the results of transient time-domain analysis of the multi-core cable. When the multi-core cable includes three conductors, the calculation result includes the current value flowing through each conductor, the voltage between each conductor and the armor, the total current value of the multi-core cable, and the current value of the armor. The target parameters are calculated using the Multi-Conductor Transmission Line (MTL) algorithm to obtain the calculation result, which includes: acquiring the first mutual inductance, second mutual inductance, first mutual capacitance, second mutual capacitance, and magnetic field vector in the multi-core cable. The first mutual inductance is the mutual inductance between the x-phase conductor and the armor; the second mutual inductance is the mutual inductance between the x-phase conductor and the y-phase conductor; the first mutual capacitance is the mutual capacitance between the x-phase conductor and the armor; the second mutual capacitance is the mutual capacitance between the x-phase conductor and the y-phase conductor; x and y are not equal, where x represents A, B, or C, and y represents A, B, or C. The magnetic field vector is the magnetic field vector of the induced magnetic field generated by the multi-core cable. The field strength vector is used to calculate the first, second, and third current values ​​based on the first and second mutual capacitances, and the first, second, and third voltage values ​​based on the first and second mutual inductances. The first current value is the current flowing through phase A, the second current value is the current flowing through phase B, and the third current value is the current flowing through phase C. The first voltage value is the voltage between phase A and the armor layer, the second voltage value is the voltage between phase B and the armor layer, and the third voltage value is the voltage between phase C and the armor layer. The total current value of the multi-core cable is calculated based on the magnetic field vector. The difference between the total current value and the target current value is calculated to obtain the current value of the armor layer, where the target current value is the sum of the first, second, and third current values.

2. The method of claim 1, wherein, Given that the initial parameters include the initial dielectric constant and the initial permeability, and the target parameters include the dielectric constant and permeability, updating the initial parameters yields the target parameters, including: The correction coefficient is calculated according to the first formula, where the first formula is: ， denotes the correction factor for updating the initial parameters, denotes the radius of the center of the multi-core cable to the outer edge of the armor, is the FDTD grid size; According to a second formula: updating the initial dielectric constant to obtain the dielectric constant, wherein, represents the dielectric constant, represents the initial dielectric constant; According to the third formula: The initial permeability is updated to obtain the permeability, wherein, Indicates the permeability, This represents the initial permeability.

3. The method of claim 1, wherein, Obtaining the first mutual inductance, second mutual inductance, first mutual capacitance, and second mutual capacitance in the multi-core cable includes: The first mutual inductance is calculated according to the fourth formula, wherein the fourth formula is: ， This indicates the first mutual inductance. Represents the permeability of free space. Represents the relative permeability of a dielectric material. Indicates the radius of each phase conductor. This represents the distance between the center of the x-phase conductor and the center of the armor layer. This indicates the inner radius of the armor layer conductor, and the dielectric is located between each conductor and the armor layer; The second mutual inductance is calculated according to the fifth formula, wherein the fifth formula is: ， represents the second mutual inductance, represents the spatial angle between the x-phase conductor and the y-phase conductor, the coefficient The calculation formula of the coefficient is ； The first mutual capacitance is calculated according to the sixth formula, wherein the sixth formula is: ， represents the first mutual capacitance, represents the dielectric constant, represents the relative dielectric constant of the dielectric; The second mutual capacitance is calculated according to the seventh formula, wherein the seventh formula is: ， wherein represents the second mutual capacity.

4. The method of claim 1, wherein, Calculating a first current value, a second current value, and a third current value based on the first mutual capacitance and the second mutual capacitance, and calculating a first voltage value, a second voltage value, and a third voltage value based on the first mutual inductance and the second mutual inductance, including: The first current value, the second current value, and the third current value are calculated according to the eighth formula, wherein the eighth formula is: ， This indicates the axial distance of the multi-core cable. Characterizing the complex frequency domain, This represents the first current value. This indicates the second current value. This indicates the third current value. This indicates the first mutual compatibility. This indicates the second mutual compatibility. This represents the voltage between the x-phase conductor and the armor layer; The first voltage value, the second voltage value, and the third voltage value are calculated according to the ninth formula, wherein the ninth formula is: ， represents the first mutual inductance, represents the second mutual inductance, represents the first voltage value, represents the second voltage value, represents the third voltage value.

5. The method of claim 4, wherein, After calculating a first current value, a second current value, and a third current value based on the first mutual capacitance and the second mutual capacitance, and calculating a first voltage value, a second voltage value, and a third voltage value based on the first mutual inductance and the second mutual inductance, the method further includes: The first current value, the second current value, and the third current value are converted into time-domain form according to the tenth formula, wherein the tenth formula is: ， for the FDTD time step, denotes the time step number; The first voltage value, the second voltage value, and the third voltage value are converted into time-domain form according to the eleventh formula, wherein the eleventh formula is: 。 6. A device for transient time domain analysis of a multi-core cable, characterized by include: An acquisition unit is used to acquire the initial parameters of a multi-core cable, wherein the initial parameters are obtained by calculation using the finite-difference time-domain (FDTD) algorithm, and the initial parameters include at least one of the following: initial dielectric constant, initial permeability, and the multi-core cable is a cable that includes at least two conductors within its armor layer; An update unit is used to update the initial parameters to obtain the target parameters; The calculation unit is used to calculate the target parameters according to the Multi-Conductor Transmission Line (MTL) algorithm to obtain the calculation result, wherein the calculation result is used to characterize the result of transient time-domain analysis of the multi-core cable. When the multi-core cable includes three conductors, the calculation result includes the current value flowing through each conductor, the voltage between each conductor and the armor layer, the total current value of the multi-core cable, and the current value of the armor layer. The calculation unit includes an acquisition module, a second calculation module, a third calculation module, and a fourth calculation module. The acquisition module is used to acquire the first mutual inductance, the second mutual inductance, the first mutual capacitance, the second mutual capacitance, and the magnetic field vector in the multi-core cable. The first mutual inductance is the mutual inductance between the x-phase conductor and the armor layer; the second mutual inductance is the mutual inductance between the x-phase conductor and the y-phase conductor; the first mutual capacitance is the mutual capacitance between the x-phase conductor and the armor layer; the second mutual capacitance is the mutual capacitance between the x-phase conductor and the y-phase conductor; x and y are not equal, where x represents A, B, or C, and y represents A, B, or C. The magnetic field vector is the magnetic field strength vector of the induced magnetic field generated by the multi-core cable. The second calculation module... The module is used to calculate a first current value, a second current value, and a third current value based on the first mutual capacitance and the second mutual capacitance, and to calculate a first voltage value, a second voltage value, and a third voltage value based on the first mutual inductance and the second mutual inductance. The first current value is the current flowing through phase A conductor, the second current value is the current flowing through phase B conductor, and the third current value is the current flowing through phase C conductor. The first voltage value is the voltage between phase A conductor and the armor layer, the second voltage value is the voltage between phase B conductor and the armor layer, and the third voltage value is the voltage between phase C conductor and the armor layer. The third calculation module is used to calculate the total current value of the multi-core cable based on the magnetic field vector. The fourth calculation module is used to calculate the difference between the total current value and the target current value to obtain the current value of the armor layer. The target current value is the sum of the first current value, the second current value, and the third current value.

7. A system for transient time domain analysis of a multi-core cable, characterized by include: One or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the one or more programs including a transient time-domain analysis method for a multi-core cable according to any one of claims 1 to 5.

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