Field line coupling time domain modeling method, device and equipment of bent shielded cable and medium

Abstract

The invention discloses a field line coupling time domain modeling method, device and equipment for a bent shielded cable and a medium, and relates to the field of electromagnetic compatibility and electromagnetic field numerical calculation, and the method comprises the steps: decomposing the bent shielded cable into an inner transmission line system and an outer transmission line system according to a cable shielding layer; the shielding cable structure is removed, and FDTD is used for simulating electromagnetic field distribution generated in the area where the shielding cable is located; dividing the shielding cable according to FDTD grids, and establishing an outer transmission line equation; performing differential discretization on the outer transmission line equation by adopting an FDTD method to obtain transient voltage and current response of each point along an outer layer; extracting current along a shielding outer layer, and establishing an inner transmission line equation; and performing differential discretization on the internal transmission line equation by adopting an FDTD method to obtain transient voltage and current responses of each point along the core wire and the terminating load. According to the method, a time domain finite difference method, a transmission line equation theory and an interpolation technology are combined, and synchronous calculation of space electromagnetic field radiation and transient response of a shielding cable bending shielding outer layer and a core wire is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electromagnetic compatibility and electromagnetic field numerical calculation, and particularly relates to a field-line coupling time-domain modeling method, device, equipment and medium for a curved shielding cable. BACKGROUND

[0002] With the increasingly complex space electromagnetic environment, strong electromagnetic pulses such as lightning electromagnetic pulses and nuclear electromagnetic pulses can couple through cables in various electronic and electrical equipment to generate strong interference voltage and current signals, thereby damaging the cable termination circuit. In order to avoid the direct irradiation of space electromagnetic pulses on the cable, a shielding layer is usually added outside the cable to form a shielding cable structure. However, the shielding layer is usually designed in a woven form, and the energy of strong electromagnetic pulses at high frequency can still penetrate through the holes in the woven shielding layer to the cable core and generate interference signals. Moreover, due to the limitation of the layout of the equipment circuit, the shielding cable is usually arranged in a curved form in the equipment. Therefore, it is of great significance and engineering application value to develop a field-line coupling time-domain modeling method for the curved shielding cable under the action of space electromagnetic field, so as to realize the rapid prediction of electromagnetic interference of the shielding cable.

[0003] When using full-wave algorithms such as the Finite-Difference Time-Domain (FDTD) method to simulate the electromagnetic coupling problem of the shielding cable, the three-dimensional structure of the shielding cable must be meshed. Due to the fine structure of the woven shielding layer of the shielding cable, the amount of meshing is large and the calculation efficiency is low. In order to avoid direct modeling of the fine shielding cable structure, based on the transmission line equation theory, a variety of efficient field-line coupling hybrid algorithms are studied. Among them, the BLT equation is the most classical in the frequency domain algorithm, and the FDTD-SPICE hybrid algorithm and the FDTD-TL hybrid algorithm are the most widely used in the time domain algorithm. For strong electromagnetic pulses, which are wideband signals, the BLT equation has low calculation efficiency because it can only calculate the interference response of the cable termination load at a single frequency point at a time. The FDTD-SPICE algorithm and the FDTD-TL algorithm can obtain the transient interference response of the shielding cable under the action of strong electromagnetic pulses at a time, but the FDTD-SPICE algorithm needs to establish an SPICE equivalent circuit model of the electromagnetic coupling of the shielding cable, and the theoretical derivation process is relatively complex. Moreover, the shielding cable transient response can only be calculated after the simulation of the strong electromagnetic pulse space radiation field is completed, which is low in efficiency for long-time simulation. The FDTD-TL algorithm has a simple derivation process, and the core idea is to construct the inner and outer transmission line systems of the shielding cable and solve them using the FDTD central difference format, so as to calculate the space electromagnetic field and the shielding cable transient response synchronously. However, this method is currently only used for electromagnetic coupling calculation of straight shielding cables.

[0004] In view of the above problems, it is urgent to study a field-line coupling modeling method suitable for curved shielding cables to realize fast calculation of electromagnetic interference response of shielding cables under space strong electromagnetic pulse irradiation, so as to provide technical support for shielding protection design and performance evaluation of various cables. SUMMARY

[0005] In view of the defect that the existing technology cannot efficiently process field-line coupling time-domain modeling of curved shielding cables, the present application provides an efficient field-line coupling time-domain method, device, equipment and medium, which realizes fast calculation of electromagnetic interference response of curved shielding cables under space electromagnetic field.

[0006] The present application provides a field-line coupling time-domain modeling method of curved shielding cables, comprising: According to the shielding layer of the cable, the curved shielding cable is divided into an outer transmission line system composed of a curved shielding outer layer and a grounding plate, and an inner transmission line system composed of a shielding inner layer and a core wire; The structure of the curved shielding cable is removed, the FDTD grid is used to subdivide the physical structure of the grounding plate, and the FDTD method is used to simulate the electromagnetic field distribution generated by the space strong electromagnetic pulse in the area where the curved shielding cable is located; The curved shielding cable is divided according to the FDTD grid, the calculation formula of the unit length distribution parameter of the curved shielding outer layer is derived, the interpolation technology is combined to obtain the tangential electric field and the vertical direction electric field at any position along the line of the curved shielding outer layer, and the transmission line equation representing the electromagnetic coupling of the outer transmission line system is established; The transmission line equation of the outer transmission line system is discretized by the FDTD method, and the transient voltage and current response of each point along the line of the curved shielding outer layer are obtained by iterative solution; The current along the line of the shielding outer layer is extracted, the shielding layer transfer impedance is introduced into the inner transmission line system, the equivalent distribution source term of the core wire is obtained, and the transmission line equation representing the electromagnetic coupling of the inner transmission line system is established; The transmission line equation of the inner transmission line system is discretized by the FDTD method, and the transient voltage and current response of each point along the line of the core wire and the termination load are obtained by iterative solution.

[0007] In some examples, the transmission line equation representing the electromagnetic coupling of the outer transmission line system is: , wherein, represents the direction and position of the shielding outer layer of each segment of the cable after division, which is determined by the starting point and end point coordinates of each segment of the cable, and respectively represent the voltage and current of the shielding outer layer of each segment of the cable, and are the unit length inductance and capacitance distribution parameters of the shielding outer layer of each segment of the cable, and These are the equivalent distributed voltage source and distributed current source for the outer shielding layer of each cable segment, respectively.

[0008] In some instances, , , and The spatial electromagnetic field obtained from FDTD simulation is used to determine the location. , ,in, This indicates the height of the starting point of each cable segment from the ground. This represents the electric field in the vertical direction between the starting point of each cable segment and the ground plane. This represents the tangential electric field along the center of each cable segment.

[0009] In some instances, , ,in, M This indicates the number of segments in each section of the cable. b Indicates the inner diameter of the outer shielding layer. i This represents the i-th segment of the sub-cable. Indicates the sub-cable number i The height of the center of the segment Represents the permeability of free space. It represents the vacuum permittivity.

[0010] In some instances, the transmission line equation characterizing the electromagnetic coupling of the internal transmission line system is: , in, and These represent the distributed inductance and capacitance parameters per unit length of each cable core segment. and These represent the voltage and current of each cable core segment, respectively. For DC transfer resistor, To transfer inductance.

[0011] Secondly, the present invention provides a field-line coupling time-domain modeling device for bent shielded cables, comprising: The decomposition unit is used to decompose the curved shielded cable into an outer transmission line system consisting of the outer curved shield and the ground plane, and an inner transmission line system consisting of the inner shield and the core wire, according to the cable shield layer. Electromagnetic distribution simulation unit is used to remove the curved shielded cable structure. The physical structure of the ground plane is partitioned using FDTD mesh. The electromagnetic field distribution generated by a strong electromagnetic pulse in the area where the curved shielded cable is located is simulated by the FDTD method. The outer transmission equation establishing unit divides the curved shielded cable according to the FDTD grid, deduces a calculation formula of the unit length distribution parameter of the curved shield outer layer, and obtains the tangential electric field and the vertical direction electric field at an arbitrary position along the curved shield outer layer by using an interpolation technology, so as to establish a transmission line equation representing electromagnetic coupling of the outer transmission line system; The outer transmission equation solving unit is configured to discretize the transmission line equation of the outer transmission line system by using the FDTD method, and iteratively solve the transient voltage and current response of each point along the curved shield outer layer. The inner transmission equation establishing unit is configured to extract the current along the shield outer layer, introduce the inner transmission line system through the shield layer transfer impedance, obtain the equivalent distribution source term of the core wire, and establish a transmission line equation representing electromagnetic coupling of the inner transmission line system. The inner transmission equation solving unit is configured to discretize the transmission line equation of the inner transmission line system by using the FDTD method, and iteratively solve the transient voltage and current response of each point along the core wire and the terminated load.

[0012] In a third aspect, the present application provides a computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the method according to any one of the above aspects when executing the computer program.

[0013] In a fourth aspect, the present application provides a computer readable storage medium, which stores a computer program, wherein the computer program is executable on a processor to implement the steps of the method according to any one of the above aspects.

[0014] Overall, compared with the prior art, the above technical solutions conceived by the present application can achieve the following beneficial effects: The electromagnetic coupling transmission line equation model of the inner and outer transmission line systems suitable for electromagnetic coupling analysis of the curved shielded cable is derived and established, and the FDTD method is used to solve the transmission line equations of the inner and outer transmission line systems, respectively, so that the fast synchronous calculation of the spatial electromagnetic field radiation and the transient response of the shield layer and the core wire of the shielded cable is realized. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0016] Figure 1 is a method flowchart provided by the embodiments of the present application; Figure 2 is a structure schematic diagram of the curved coaxial cable on the grounding plate provided by the embodiments of the present application; Figure 3 is a decomposition schematic diagram of an inner and outer transmission line system of a curved shielding cable provided by an embodiment of the present application; Figure 4 is a FDTD calculation schematic diagram of a space electromagnetic field around a curved shielding cable provided by an embodiment of the present application; Figure 5 is a FDTD grid division schematic diagram of a curved shielding cable provided by an embodiment of the present application; Figure 6 is a calculation schematic diagram of an electric field along a line vertical direction and a tangential electric field of a curved shielding outer layer provided by an embodiment of the present application; Figure 7 is a calculation schematic diagram of a unit length distribution parameter of a curved shielding outer layer provided by an embodiment of the present application; Figure 8 is a comparison diagram of a voltage response on a load 14 obtained by a field line coupling time domain algorithm and CST simulation provided by an embodiment of the present application; Figure 9 is a device schematic diagram provided by an embodiment of the present application; Figure 10 is a computer device schematic diagram provided by an embodiment of the present application. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person skilled in the art without creative work fall within the protection scope of the present application.

[0018] In the following description, specific embodiments of the present application will be described with reference to steps and symbols executed by one or more computers, unless otherwise specified. Therefore, these steps and operations will be mentioned several times by a computer, and the computer execution referred to herein includes operations of a computer processing unit represented by electronic signals in a structured form. The operation transforms the data or maintains it at a location in the memory system of the computer, which can reconfigure or otherwise change the operation of the computer in a manner known to those skilled in the art. The data structure maintained by the data has a specific characteristic defined by the data format at the physical location of the memory. However, the principles of the present application are described in the above description, which does not represent a limitation, and those skilled in the art will understand that the following steps and operations can also be implemented in hardware.

[0019] The term "module" or "unit" as used herein can be seen as a software object executing on the computing system. Different components, modules, engines and services herein can be seen as implementing objects on the computing system. While the apparatus and methods herein are preferably implemented in software, it is understood that they can be implemented in hardware, and that they fall within the scope of the present invention.

[0020] It is to be understood that the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. It is further understood that the terms "comprising," "including," "containing," and "having" and the like, when used in the specification, specify the presence of stated features, integers, steps, operations, elements, and / or components but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It is further understood that when an element or layer is referred to as being "on" or "connected to" another element or layer, it can be directly on or connected to the other element or layer or intervening elements or layers can be present. In addition, the term "connected" or "coupled" as used herein refers to any connection or coupling, either direct or indirect, between otherwise isolated components. The term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0021] The embodiments of the present application are described taking the electromagnetic coupling of nuclear electromagnetic pulse acting on the curved coaxial cable as an example.

[0022] Figure 2 The electromagnetic coupling model of nuclear electromagnetic pulse acting on the curved coaxial cable includes a grounding plate 1, a coaxial cable shielding layer 2, a coaxial cable core wire 3, a filling material 4, a shielding layer initial end load 5, a shielding layer terminal end load 6, a core wire initial end load 7, a core wire terminal end load 8, and an incident wave 9. Nodes 10, 11, 12, 13, and 14 are fixed nodes on the coaxial cable, which are used to generate a coaxial cable wiring path, and are set by the user according to modeling requirements in actual use. The size of the grounding plate 1 is L c × W c The inner radius of the shielding layer 2 is b The radius of the core wire 3 is a The relative dielectric constant of the filling material 4 is The loads 4, 5, 6, and 7 are resistors, and the resistance values of the resistors can be defined by the user. The incident wave 9 is a nuclear electromagnetic pulse, and the waveform expression is wherein V / m, s -1 , s -1 . L c , W c ,b 、 a and The specific parameter values can be set by oneself.

[0023] As shown in Figure 1 , the implementation flow of the present application includes the following steps: Step 1, the coaxial cable is divided into an outer transmission line system composed of a curved shield outer layer and a ground plate, and an inner transmission line system composed of a shield inner layer and a core wire according to the shielding layer, as shown in Figure 3 .

[0024] Step 2, the coaxial cable is removed, and the FDTD grid is used to subdivide the physical structure of the ground plate, and the electromagnetic field distribution in the area where the shielded cable is located is obtained by full-wave simulation by the FDTD method, as shown in Figure 4 .

[0025] Step 3, the coaxial cable is divided into multiple sub-cables using the FDTD grid, as shown in Figure 5 , and the electromagnetic coupling of each segment of the sub-cable outer transmission line system is irradiated by the nuclear electromagnetic pulse, which can be represented by the transmission line equation as: (1) (2) Wherein, l represents the direction and position of the shield outer layer of each segment of the sub-cable, which is determined by the starting point and end point coordinates of each segment of the sub-cable. and represent the voltage and current of the shield outer layer of each segment of the sub-cable, and are the unit length inductance and capacitance distribution parameters of the shield outer layer of each segment of the sub-cable. and are the equivalent distributed voltage source and distributed current source of the shield outer layer of each segment of the sub-cable, which can be represented as: (3) (4) and are determined by the spatial electromagnetic field obtained by the above FDTD simulation, and the calculation formula is: (5) (6) Here, represents the height of the starting point of each segment of the sub-cable from the ground, represents the vertical direction electric field between the starting point of each segment of the sub-cable and the ground plate, This represents the tangential electric field along the center of each cable segment. Since a bent coaxial cable will not fall on the edges of the entire FDTD grid, and The electric field needs to be calculated from the entire FDTD grid using interpolation, such as... Figure 6 As shown.

[0026] For each cable segment, the distribution parameters per unit length of the outer shield can be calculated by weighted averaging using an empirical formula, expressed as: (7) in, M This indicates the number of segments in each section of the cable. b Indicates the inner diameter of the outer shielding layer. i Indicates the first sub-cable i part, Indicates the sub-cable number i The height of the center position of the segment, such as Figure 7 As shown. Capacitance per unit length of the outer shielding layer of each cable segment. It can be done through formula get.

[0027] Step 4: Discretize the transmission line equations of the external transmission line system using the center difference scheme of the FDTD method, and obtain the FDTD iterative solution formulas for the voltage and current along the shielded outer layer and the terminated load, thereby quickly calculating the transient voltage and current response at each point along the shielded outer layer and the terminated load.

[0028] Step 5: The electromagnetic coupling of the transmission line system within each segment of the coaxial cable is modeled using transmission line equations, as follows: (8) (9) in, and These represent the distributed inductance and capacitance parameters per unit length of each cable core segment. and These represent the voltage and current of each section of the cable core. For DC transfer resistor, To transfer inductance.

[0029] Step 6: Discretize the transmission line equations of the internal transmission line system using the center difference scheme of the FDTD method to obtain the FDTD iterative solution formulas for the voltage and current along the core line and the terminated load, thereby quickly calculating the transient voltage and current responses at each point along the core line and the terminated load.

[0030] Step 7, as follows Figure 8 As shown, taking the RG58 coaxial cable as the calculation object, the results are given in Lc =2.0m, W c =1.0m、 a =0.47mm, b=1.475mm Under the conditions of a resistance of 50 ohms for loads 5-8, and coordinates of nodes 10-14 as (0.5, 0.5, 0.03) m, (0.5, 0.75, 0.033) m, (0.5, 1.0, 0.03) m, (0.5, 1.25, 0.027) m, and (0.5, 1.5, 0.03) m respectively, and an incident wave 9 being a nuclear electromagnetic pulse, the voltage response on load 8 calculated by the field-line coupling time-domain algorithm provided by this invention and the electromagnetic field simulation software CST shows that the calculation results of the two methods have a good agreement, verifying the correctness of this invention.

[0031] In another embodiment of the present invention, to facilitate better implementation of the method provided in the embodiments of the present invention, an apparatus based on the above method is also provided. The meanings of the terms used are the same as in the above method, and specific implementation details can be found in the description of the method embodiments.

[0032] Please see Figure 9 , Figure 9 This is a schematic diagram of the structure of a device provided in an embodiment of the present invention. The device may include a decomposition unit 901, an electromagnetic distribution simulation unit 902, an external transmission equation establishment unit 903, an external transmission equation solving unit 904, an internal transmission equation establishment unit 905, and an internal transmission equation solving unit 906, wherein: The decomposition unit 901 is used to decompose the curved shielded cable into an outer transmission line system consisting of the outer curved shielding layer and the ground plane, and an inner transmission line system consisting of the inner shielding layer and the core wire, according to the cable shielding layer. Electromagnetic distribution simulation unit 902 is used to remove the curved shielded cable structure. The physical structure of the ground plane is partitioned using FDTD mesh. The electromagnetic field distribution generated by a strong electromagnetic pulse in the area where the curved shielded cable is located is simulated by the FDTD method. The external transmission equation is established in unit 903. The curved shielded cable is divided according to the FDTD grid. The calculation formula of the unit length distribution parameter of the curved shield outer layer is derived. Combined with the interpolation technique, the tangential electric field and the vertical electric field at any position along the curved shield outer layer are obtained. The transmission line equation characterizing the electromagnetic coupling of the external transmission line system is established. The external transmission equation solving unit 904 is used to perform differential discretization of the transmission line equation of the external transmission line system using the FDTD method, and iteratively solve to obtain the transient voltage and current response at each point along the curved outer shield layer. The inner transmission equation establishment unit 905 is used to extract the current along the outer shield layer, introduce it into the inner transmission line system through the shield layer transfer impedance, obtain the equivalent distributed source term of the core wire, and establish the transmission line equation characterizing the electromagnetic coupling of the inner transmission line system. The internal transmission equation solving unit 906 is used to perform differential discretization of the transmission line equation of the internal transmission line system using the FDTD method, and iteratively solve to obtain the transient voltage and current response at each point along the core line and the terminated load.

[0033] The specific implementation methods of each unit can be referred to the description of the above method embodiments, and the embodiments of the present invention will not be repeated.

[0034] In another embodiment of the present invention, a computer device is also provided, such as... Figure 10 As shown, it illustrates a structural schematic diagram of a computer device involved in an embodiment of the present invention, specifically: The computer device may include components such as a processor 1001 with one or more processing cores, a memory 1002 with one or more computer-readable storage media, a power supply 1003, and an input unit 1004. Those skilled in the art will understand that... Figure 10 The computer device structure shown does not constitute a limitation on the computer device and may include more or fewer components than shown, or combine certain components, or have different component arrangements. Wherein: The processor 1001 is the control center of the computer device. It connects various parts of the computer device via various interfaces and lines. By running or executing software programs and / or modules stored in the memory 1002, and by calling data stored in the memory 1002, it performs various functions of the computer device and processes data, thereby providing overall monitoring of the computer device. Optionally, the processor 1001 may include one or more processing cores; preferably, the processor 1001 may integrate an application processor and a modem processor, wherein the application processor mainly handles the operation of the storage medium, user interface, and application programs, and the modem processor mainly handles wireless communication. It is understood that the modem processor may not be integrated into the processor 1001.

[0035] The memory 1002 can be used to store software programs and modules, and the processor 1001 executes various function applications and data processing by running the software programs and modules stored in the memory 1002. The memory 1002 can mainly include a program storage area and a data storage area, wherein the program storage area can store application programs required by at least one function (such as a sound playing function, an image playing function, etc.) of the operation storage medium, and the like; and the data storage area can store data created according to the use of the computer device, etc. In addition, the memory 1002 can include a high-speed random access memory, and can also include a non-volatile memory such as at least one magnetic disk storage device, a flash memory device, or other volatile solid-state memory device. Accordingly, the memory 1002 can also include a controller to provide the processor 1001 with access to the memory 1002.

[0036] The computer device further includes a power supply 1003 for supplying power to various components. Preferably, the power supply 1003 can be logically connected to the processor 1001 through a power management storage medium, so as to realize functions such as management of charging, discharging, and power consumption management through the power management storage medium. The power supply 1003 can also include one or more than one direct current or alternating current power supply, a rechargeable storage medium, a power failure detection circuit, a power converter or inverter, a power state indicator, and the like.

[0037] The computer device can also include an input unit 1004, which can be used to receive input digital or character information, and generate keyboard, mouse, joystick, optical or trackball signal inputs related to user settings and function controls.

[0038] Although not shown, the computer device can also include a display unit, etc., which will not be described here. Specifically, in the embodiment, the processor 1001 in the computer device loads the executable file corresponding to the process of one or more than one application program into the memory 1002 according to the following instructions, and runs the application program stored in the memory 1002 by the processor 1001, so as to realize the steps in the above method embodiments.

[0039] Those skilled in the art can understand that all or part of the steps of the various methods of the above embodiments can be completed by instructions, or by related hardware controlled by the instructions, which can be stored in a computer readable storage medium and loaded and executed by a processor.

[0040] To this end, the embodiment of the present application provides a computer readable storage medium, which stores a computer program, and the computer program is loaded by a processor to execute the steps in any one of the methods provided by the embodiments of the present application.

[0041] The specific implementation of the above operations can refer to the foregoing embodiments, which will not be described here again.

[0042] The computer readable storage medium can include a read only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, etc.

[0043] Due to the computer program stored in the computer readable storage medium, the steps in any method provided by the embodiments of the present application can be executed, thus the beneficial effects of any method provided by the embodiments of the present application can be achieved, which will be described in the foregoing embodiments and will not be described here again.

[0044] The above describes in detail the field line coupling time domain modeling method, device, equipment and medium of the bend shielding cable provided by the embodiments of the present application, the principle and implementation mode of the present application are described by applying specific examples in this paper, the above embodiment is only used to help understand the method of the present application and its core idea; at the same time, for the skilled in the art, according to the idea of the present application, the specific implementation mode and application range will be changed, in view of the above, the content of the specification should not be understood as the limitation of the present application.

Claims

1. A method of time-domain modeling of field-line coupling of a flex-shielded cable, characterized by, include: Based on the cable shielding layer, the curved shielded cable is decomposed into an outer transmission line system consisting of the outer curved shielding layer and the ground plane, and an inner transmission line system consisting of the inner shielding layer and the core wire. The bent shielded cable structure was removed, and the physical structure of the ground plane was meshed using FDTD mesh. The electromagnetic field distribution generated by a strong electromagnetic pulse in the area where the bent shielded cable was located was simulated using the FDTD method. Based on the FDTD grid, the bending shielded cable is divided, the calculation formula for the unit length distribution parameter of the bending shield outer layer is derived, and the tangential electric field and the vertical electric field at any position along the bending shield outer layer are obtained by combining interpolation technology. The transmission line equation characterizing the electromagnetic coupling of the external transmission line system is established. The FDTD method is used to differentially discretize the transmission line equations of the external transmission line system and iteratively solve them to obtain the transient voltage and current responses at various points along the outer layer of the curved shield. Extract the current along the outer shielding layer, introduce it into the inner transmission line system through the shielding layer transfer impedance, obtain the equivalent distributed source term of the core wire, and establish the transmission line equation characterizing the electromagnetic coupling of the inner transmission line system. The transmission line equations of the internal transmission line system are differentially discretized using the FDTD method, and the transient voltage and current responses at various points along the core line and the terminated loads are obtained through iterative solution.

2. The method of claim 1, wherein, The transmission line equation characterizing the electromagnetic coupling of the external transmission line system is: ， wherein, denote the direction and position of the shielding outer layer of each segment sub-cable after division, which are determined by the start and end coordinates of each segment sub-cable, and denote the voltage and current of the shielding outer layer of each segment sub-cable, respectively, and denote the inductance per unit length and the capacitance distribution parameter of the shielding outer layer of each segment sub-cable, respectively, and denote the equivalent distribution voltage source and the distribution current source of the shielding outer layer of each segment sub-cable, respectively.

3. The method of claim 2, wherein, , , and are determined from the spatial electromagnetic field obtained by FDTD simulation, , wherein, denotes the height of the start of each segment of the sub-cable from the ground, denotes the vertical electric field between the start of each segment of the sub-cable and the ground plate, denotes the tangential electric field along the line at the center position of each segment of the sub-cable.

4. The method of claim 3, wherein, , wherein, M represents the number of segments into which the sub-cable is divided, b represents the inner diameter of the outer shield, i represents the i-th segment of the sub-cable, represents the height of the center position of the i-th segment of the sub-cable, i represents the height of the center position of the i-th segment of the sub-cable, represents the vacuum permeability, represents the vacuum permittivity.

5. The method of claim 4, wherein, The transmission line equation characterizing the electromagnetic coupling of the internal transmission line system is: ， wherein, and L and C represent the per-unit length distributed inductance and capacitance parameters of the sub-cable core, and V and I represent the voltage and current of the sub-cable core, is the DC transfer resistance, is the transfer inductance.

6. An apparatus for time domain modeling of field line coupling of a flexshield cable, characterized by, include: The decomposition unit is used to decompose the curved shielded cable into an outer transmission line system consisting of the outer curved shield and the ground plane, and an inner transmission line system consisting of the inner shield and the core wire, according to the cable shield layer. Electromagnetic distribution simulation unit is used to remove the curved shielded cable structure. The physical structure of the ground plane is partitioned using FDTD mesh. The electromagnetic field distribution generated by a strong electromagnetic pulse in the area where the curved shielded cable is located is simulated by the FDTD method. The external transmission equation is established by dividing the curved shielded cable according to the FDTD grid, deriving the calculation formula of the unit length distribution parameter of the curved shield outer layer, and combining the interpolation technique to obtain the tangential electric field and the vertical electric field at any position along the curved shield outer layer, thus establishing the transmission line equation characterizing the electromagnetic coupling of the external transmission line system. The external transmission equation solving unit is used to perform differential discretization of the transmission line equation of the external transmission line system using the FDTD method, and iteratively solve to obtain the transient voltage and current response at each point along the outer bending shield layer. The inner transmission equation establishment unit is used to extract the current along the outer shield layer, introduce it into the inner transmission line system through the shield layer transfer impedance, obtain the equivalent distributed source term of the core wire, and establish the transmission line equation characterizing the electromagnetic coupling of the inner transmission line system. The internal transmission equation solving unit is used to perform differential discretization of the transmission line equations of the internal transmission line system using the FDTD method, and iteratively solve to obtain the transient voltage and current responses at each point along the core line and the terminated load.

7. The apparatus of claim 6, wherein, The transmission line equation characterizing the electromagnetic coupling of the external transmission line system is: ， wherein, denote the direction and position of the shielding outer layer of each segment sub-cable after division, which are determined by the start and end coordinates of each segment sub-cable, and denote the voltage and current of the shielding outer layer of each segment sub-cable, respectively, and are the inductance and capacitance per unit length of the shielding outer layer of each segment sub-cable, respectively, and are the equivalent distributed voltage source and distributed current source of the shielding outer layer of each segment sub-cable, respectively.

8. The apparatus of claim 7, wherein, The transmission line equation characterizing the electromagnetic coupling of the internal transmission line system is: ， wherein, and L and C represent the per-unit length distributed inductance and capacitance parameters of the sub-cable core, and V and I represent the voltage and current of the sub-cable core, R is the DC transfer resistance, L is the transfer inductance.

9. A computer device, comprising a memory, a processor, and a computer program stored in the memory and capable of running on the processor, wherein the processor implements the steps of the method according to any one of claims 1 to 5 when executing the computer program.

10. A computer readable storage medium, having stored thereon a computer program, wherein the computer program, when executed by a processor, implements the steps of the method according to any one of claims 1 to 5.

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