A cable shielding effectiveness evaluation method, device, equipment and medium

Abstract

The present invention discloses a method, device, equipment and medium for evaluating the shielding effectiveness of cables. The evaluation method comprises the following steps: Step 1: Determine the importance of the influencing factor δ(q,p,s,h), where q is the braided cable material, p is the shape of the braided small hole, s is the braiding density, and h is the braided mesh thickness; Step 2: Calculate the transfer impedance Z L ; Step 3: If the transfer impedance Z L Less than the limit Z T , then the judgment condition is met; Step 4: If the transfer impedance Z L Not less than the limit value Z T , then optimize the influencing factors and go to step 2 until the judgment condition is met. The cable shielding effectiveness simulation comprehensive evaluation method of the present invention predicts and evaluates the shielding effectiveness of the cable before it is manufactured, thereby reducing production and testing costs.

Description

Technical Field

[0001] The invention belongs to the field of cable detection, and in particular relates to a method for evaluating the shielding effectiveness of a high-voltage cable. Background Art

[0002] High-voltage cables play the role of transmitting electric energy in the electric vehicle motor drive system. The output electric energy of the high-voltage power battery pack is supplied to the motor controller and the three-phase AC drive motor through high-voltage shielded cables. Its slender structure is an efficient electromagnetic interference receiving or transmitting antenna, which often becomes the weak link of the electromagnetic compatibility performance of the motor drive system, and is usually the main reason for the failure of the mandatory regulations test of the whole vehicle. At the same time, the electromagnetic interference radiated by the cable also has a great impact on the normal operation of the electrical components in the car. Therefore, in order to reduce the electromagnetic interference radiated from the high-voltage cable, high-voltage cables generally use shielded cables with different shielding effectiveness. Today's research and analysis on the shielding effectiveness of cables is mainly reflected in two categories: "test method" and "analytical analysis method". Among them, the "test method" focuses on the research of cable shielding effectiveness test methods and test devices; the "analytical analysis method" focuses on analyzing the influence of cable parameters on the shielding effect. For example, the patent document "CN110531172A-A method for measuring the shielding effectiveness of high-voltage cables for electric vehicles" proposes a method for measuring the shielding effectiveness of high-voltage cables for electric vehicles based on a network analyzer and a current probe, which solves the problem that the impedance matching conditions for measuring the shielding effectiveness of high-voltage shielded cables for existing electric vehicles are difficult to meet, and reduces the difficulty of measuring the shielding effectiveness of shielded cables. The patent document "CN201911089247.4-A method for testing the shielding effectiveness of multi-core special cables" involves a method for testing the shielding effectiveness of multi-core special cables, which can effectively assess and verify the electromagnetic compatibility of multi-core cables. The patent document "CN109375020A-A device and method for testing the shielding effectiveness of high-voltage cables for new energy vehicles" provides a device and method for testing the shielding effectiveness of high-voltage cables for new energy vehicles, which can realize rapid testing of the shielding effectiveness of high-voltage cables of different specifications. The patent document "CN201910618093.7-A method for designing the radius of a braided shielding layer based on shielding effectiveness" analyzes and obtains a quantitative relationship between the shielding effectiveness of the cable and the radius of the shielding layer.

[0003] The current technology has the following problems: 1. It is impossible to evaluate the shielding effectiveness of shielded cables before they are manufactured. Once the test fails, it will cause problems such as high cable manufacturing costs and long rectification cycles. 2. The production cycle and production cost of the test device are high. There are differences in the test devices produced by different testing institutions. The shielding effectiveness test results of the cable are highly dependent on the consistency and reliability of the test device and test layout. At present, there is no unified test device and test method recognized by the state. 3. The shielding effectiveness of the cable is related to many factors. The non-ideality of the braided mesh structure and the complexity of the electromagnetic coupling effect of the holes at different frequencies make it difficult to achieve accurate analytical calculation methods. Summary of the invention

[0004] In order to solve the problems that have not been solved by the above technologies, the present invention proposes a cable shielding effectiveness simulation comprehensive evaluation method.

[0005] The present invention aims to solve one of the related technical problems at least to some extent.

[0006] The present invention provides a cable shielding effectiveness simulation comprehensive evaluation method, which can propose cable parameter design indicators in the early stage of cable design, thereby avoiding the problems of high cable production and manufacturing costs, long rectification cycle, etc. In addition, based on the method described in the present invention, it can be evaluated in a short time whether different shielded cables meet the shielding requirements, thereby avoiding the problems of long cable testing time and over-reliance on testing equipment; at the same time, on the premise of meeting the target parameters, it can comprehensively consider multi-dimensional parameters such as material cost, process difficulty, reliability, etc., to provide more reliable parameter design for different application environments, thereby avoiding over-design of shielding effectiveness.

[0007] To achieve the above object, a first aspect of the present invention provides a method for evaluating cable shielding effectiveness, comprising the following steps:

[0008] Step 1: Determine the importance of the influencing factor δ(q,p,s,h), where q is the braided cable material, p is the shape of the braided holes, s is the braiding density, and h is the braided mesh thickness;

[0009] Step 2: Calculate the transfer impedance Z L ;

[0010] Step 3: If the transfer impedance Z L Less than the limit Z T , then the judgment condition is met;

[0011] Step 4: If the transfer impedance Z L Not less than the limit value Z T , then optimize the influencing factors and go to step 2 until the judgment conditions are met.

[0012] To achieve the above object, a second embodiment of the present invention provides a device for evaluating cable shielding effectiveness, which includes:

[0013] A determination module is used to determine the importance of the influencing factor δ(q,p,s,h), where q is the braided cable material, p is the shape of the braided small hole, s is the braiding density, and h is the braided mesh thickness;

[0014] Calculation module for calculating transfer impedance Z L ;

[0015] Judgment module, used for transfer impedance Z L Less than the limit Z T In the case of , the judgment condition is met;

[0016] Optimization module for transfer impedance Z L Not less than the limit value Z T In this case, the influencing factors are optimized and then the calculation module is switched until the judgment conditions are met.

[0017] To achieve the above-mentioned purpose, the third aspect of the present invention proposes an electronic device, including a memory and a processor; wherein the processor runs a program corresponding to the executable program code by reading the executable program code stored in the memory, so as to implement the cable effectiveness shielding evaluation method provided in the first aspect of the present invention.

[0018] To achieve the above-mentioned purpose, the fourth aspect of the present invention proposes a non-temporary computer-readable storage medium having a computer program stored thereon, characterized in that when the program is executed by a processor, the cable effectiveness shielding evaluation method provided by the first aspect of the present invention is implemented.

[0019] The present invention proposes indicators for the shielding effectiveness of cables according to the electromagnetic radiation emission limit requirements of new energy vehicles, so as to perform an importance analysis of the factors affecting the shielding effectiveness of cables according to the shielding effectiveness target parameters, and optimize and adjust the parameter values ​​affecting the shielding effectiveness of cables according to the results of the parameter analysis of the importance of the factors, and use high-precision simulation software to obtain the parameter design that meets the target, so as to achieve the purpose of efficiently evaluating and improving the shielding effectiveness of cables. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Flowchart of the evaluation method for cable shielding effectiveness

[0021] Figure 2 Cross section of a single-layer shielded cable model

[0022] Figure 3 Cross section of double shielded cable model

[0023] Figure 4 The transfer impedance limit requirement is

[0024] Figure 5 The shielding effectiveness transfer impedance frequency curve under the target parameters

[0025] Figure 6 Structure diagram of the device for evaluating cable shielding effectiveness

[0026] Figure 7 A schematic diagram of the structure of an electronic device DETAILED DESCRIPTION

[0027] Embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with specific same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but are not to be construed as limitations on the present invention.

[0028] The process of the cable shielding effectiveness evaluation method described in the present invention is as follows: Figure 1 shown.

[0029] Step 1: Determine the importance of the impact factor δ(q,p,s,h).

[0030] In the finite element simulation software, a single-layer shielded cable model and a double-layer shielded cable model are established according to the cable data sheet. The cross-sectional views are as follows: Figure 2 As shown in Figure 3, the single-layer shielded cable model consists of five parts: copper core, internal insulation layer, internal shielding layer, air gap, and external insulation layer; the double-layer shielded cable model consists of five parts: copper core, internal insulation layer, internal shielding layer, external shielding layer, and external insulation layer.

[0031] Since the shielding effectiveness of the cable is related to parameters such as the braided cable material q, the shape of the braided holes p, the braiding density / coverage s, and the braided mesh thickness h, the importance analysis of the influencing factors δ(q, p, s, h) is then carried out. Based on the finite element simulation software, the above influencing factors are taken as independent variables and calculated using the finite element simulation software to obtain the shielding effectiveness of the cable under different braided cable materials q, the shape of the braided holes p, the braiding density / coverage s, and the braided mesh thickness h. According to the above independent variable parameters, the importance of the influencing factors δ(q, p, s, h) of the cable shielding effectiveness is established. By establishing the importance of the influencing factors, the influence of different factors on each frequency band of the target parameters can be clarified, thereby providing guidance for the prediction, evaluation and optimization design of the shielding effectiveness.

[0032] Step 2: Calculate the transfer impedance Z L .

[0033] Target parameter transfer impedance Z L The value is determined according to the vehicle's requirements for electromagnetic radiation emission limits. First, the importance of the influencing factors is normalized, and the finite element simulation software is used to set the plane wave as the excitation source for the shielding effectiveness calculation. The electromagnetic field radiation boundary conditions are set for the single-layer shielded cable model or the double-layer shielded cable model, and the electric field Ez, magnetic field H, induced voltage and surface current of the shielded cable are calculated. Finally, the transfer impedance Z of the shielded cable is calculated. L .

[0034] Step 3: If the transfer impedance Z L Less than the limit Z T , then the judgment condition is met.

[0035] like Figure 4 As shown, the transfer impedance Z of the cable that meets the shielding effectiveness L Must be lower than Figure 2 The limit line is shown. The horizontal axis represents the frequency in (MHz). In order to observe the obvious change relationship of the curve in the wide frequency domain, the horizontal axis is represented logarithmically (0.001, 0.1, 1, 10); the vertical axis represents the transfer impedance in mΩ / m (or mOhom / m, milliohm / meter). The transfer impedance is a parameter for evaluating the shielding effectiveness of cables. The smaller the value, the better the shielding effect.

[0036] Z L and the target parameter limit Z T For comparison, if Z L <Z T , the cable meets the shielding effectiveness target requirements and the simulation comprehensive evaluation is completed.

[0037] Step 4: If the transfer impedance Z L Greater than or equal to the limit value Z T , then optimize the influencing factors and go to step 2 until the judgment conditions are met.

[0038] If Z L >=Z T , then according to the importance of the influencing factors δ(q',p',s',h'), the parameters of the model are optimized until the conditions are met.

[0039] Furthermore, in step 2, calculating the transfer impedance includes the following steps:

[0040] First, the influencing factor importance parameter δ(q,p,s,h) is normalized to obtain the influencing factor importance δ'(q,p,s,h), which is calculated as follows:

[0041]

[0042] Then, using the finite element simulation software HFSS, set the plane wave as the excitation source for shielding effectiveness calculation, and the calculation formula is:

[0043]

[0044] Among them, E inc is the incident wave, E0 is the electric field polarization vector, k0 is the wave number in free space, k is the propagation vector, and r is the direction vector.

[0045] Set the electromagnetic field radiation boundary condition for the single-layer / double-layer shielded cable model. The calculation formula is:

[0046]

[0047] Among them, E tan is the tangential component of the surface electric field, K0 is the phase constant In free space, μ=μ0≈4π×10 -7 H / m; ε=ε0≈8.85×10 -12 F / m, j is

[0048] The ideal electric and magnetic boundary conditions are:

[0049] Then set the frequency domain calculation range, which is consistent with the target parameter range (9kHz~30MHz), and simulate the electric field and magnetic field distribution of the shielded cable.

[0050] Secondly, through the mathematical relationship between voltage, current, electric field and magnetic field, the induced voltage and surface current of the cable are obtained. The calculation formula is:

[0051]

[0052] Where I0 is the current flowing through the outer surface of the shielding layer, It is the effective voltage value between the core wire and the shielding layer per unit length. z is the longitudinal electric field component, S e is the inner surface of the cable shield, A e For S e The area of ​​the region, l is the closed curve outside the cross section of the shielding layer, and H is the tangential component of the magnetic field vector along l.

[0053] Finally, the transfer impedance Z of the shielded cable is calculated using the software post-processing function. L , the calculation formula is

[0054]

[0055] Furthermore, the transfer impedance limit ZT It is not a fixed value, but changes according to the frequency. When the frequency is greater than 2 Hz, the limit value Z T 100 milliohms / meter; when the frequency is less than 2 Hz, the limit value Z T It is 60 milliohms / meter.

[0056] Furthermore, the impact factor optimization in step 3, that is, if Z L >Z T , then according to the importance of the influencing factors δ(q,p,s,h), the key influencing factors of the over-standard frequency band are identified, and the parameters (q,p,s,h) of the model are optimized and designed in a targeted manner.

[0057] For example: Figure 5 The frequency band of the medium-to-high frequency band is 6-10MHz. According to the analysis of the importance of the influencing factors δ(q,p,s,h), the key influencing factors of 6-10MHz are s and h, and the values ​​of the importance influencing factors s and h are closely related to the target parameter Z. L There is a certain positive correlation in the concerned frequency band; similarly, the key factors affecting 10-30MHz can be analyzed. Therefore, by optimizing the values ​​of the influencing factors q, p, s, and h, the importance of the key factors under the exceeding standard condition δ(q', p', s', h') is obtained.

[0058] The optimized impact factor importance δ(q',p',s',h') is used as a parameter to go to step 2 for transfer impedance calculation. Finally, Z L Compare with the target parameters until Z is met L <Z T , complete the comprehensive evaluation of simulation.

[0059] On the premise of meeting the target parameter of shielding effectiveness, the simulation analysis method described in the present invention is used to reasonably select the influencing factors of cable shielding effectiveness: parameters such as braided cable material q, shape of braided holes p, braiding density / coverage s, and braided mesh thickness h, and comprehensively consider multi-dimensional parameters such as material cost, process difficulty, and reliability to provide more reliable parameter design for different application environments, thereby avoiding excessive design of shielding effectiveness.

[0060] To achieve the above-mentioned purpose, the second embodiment of the present invention provides a cable shielding effectiveness evaluation device 100, Figure 6 , which includes:

[0061] The determination module 11 is used to determine the importance of the influencing factor δ(q,p,s,h), where q is the braided cable material, p is the shape of the braided small hole, s is the braiding density, and h is the braided mesh thickness.

[0062] Calculation module 12, used to calculate the transfer impedance ZL .

[0063] The judgment module 13 is used for transferring the impedance Z L Less than the limit Z T , the judgment condition is met.

[0064] Optimization module 14 for impedance Z L Not less than the limit value Z T In this case, the influencing factors are optimized and then transferred to the calculation module until the judgment conditions are met.

[0065] To achieve the above-mentioned purpose, the third aspect of the present invention provides an electronic device 200, see Figure 7 , including a memory 21 and a processor 22. The processor 22 runs a program corresponding to the executable program code by reading the executable program code stored in the memory 21, so as to implement the cable effectiveness shielding evaluation method provided by the embodiment of the first aspect of the present invention.

[0066] To achieve the above-mentioned purpose, the fourth aspect of the present invention provides a non-temporary computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the cable effective shielding evaluation method provided by the first aspect of the present invention.

[0067] The key technical points of the present invention include a comprehensive evaluation method for cable shielding effectiveness simulation that takes into account the influence of various cable parameters, proposes an index of the importance of influencing factors, and flexibly optimizes and improves the design of the model according to the target parameter requirements. The present invention is not limited to the evaluation analysis and parameter design of the only variable of cable shielding effectiveness. The method is applicable to cables in different application environments, such as providing reliability parameter design by comprehensively considering multi-dimensional goals such as material cost, process difficulty, and reliability.

[0068] The present invention can provide a targeted design method for cable shielding effectiveness indicators. By utilizing the cable shielding effectiveness simulation comprehensive evaluation method described in the present invention, the shielding effectiveness of the cable can be predicted and evaluated before it is manufactured, thereby reducing production and testing costs. At the same time, the cable parameters are optimized and designed according to the influencing factor importance analysis method proposed in the present invention, thereby shortening the design and rectification cycle and providing more reliable parameter design guidance for cables in different application environments, thereby avoiding blind over-design.

[0069] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for evaluating cable shielding effectiveness, characterized in that: include: Step 1: Determine the importance of the influencing factor δ(q,p,s,h), where q is the braided cable material, p is the shape of the braided holes, s is the braiding density, and h is the braided mesh thickness; Step 2: Calculate the transfer impedance Z L ; include: S1: Normalize the impact factor importance parameter δ(q,p,s,h) and calculate it as follows: S2: Based on HFSS software, the electric field and magnetic field distribution of the shielded cable are simulated; S3: Calculate the induced voltage and surface current of the cable. The calculation formula is: Where I0 is the current flowing through the outer surface of the shielding layer, E is the effective voltage value between the core wire and the shielding layer per unit length. z is the longitudinal electric field component, S e is the inner surface of the cable shield, A e For S e The area of ​​the region, l is the closed curve outside the cross section of the shielding layer, and H is the tangential component of the magnetic field vector along l; S4: Calculate the transfer impedance Z of the shielded cable L , the calculation formula is: Step 3: If the transfer impedance Z L Less than the limit Z T , then the judgment condition is met; Step 4: If the transfer impedance Z L Not less than the limit value Z T , then according to the importance of the influencing factor δ(q,p,s,h), the key influencing factors of the over-standard frequency band are identified, and by optimizing the values ​​of the influencing factors q,p,s,h, the key factor importance δ(q',p',s',h') under the over-standard condition is obtained. The optimized key factor importance δ(q',p',s',h') is used as a parameter to go to step 2 for transfer impedance calculation, and finally Z L Compare with the target parameters until Z is met L <Z T , complete the comprehensive evaluation of simulation.

2. The cable shielding effectiveness evaluation method according to claim 1, characterized in that: When the frequency is greater than 2 Hz, the limit value Z T 100 milliohms / meter; When the frequency is less than 2 Hz, the limit value Z T It is 60 milliohms / meter.

3. A device for evaluating cable shielding effectiveness, characterized in that: include: A determination module is used to determine the importance of the influencing factor δ(q,p,s,h), where q is the braided cable material, p is the shape of the braided small hole, s is the braiding density, and h is the braided mesh thickness; Calculation module for calculating transfer impedance Z L ; include: S1: Normalize the impact factor importance parameter δ(q,p,s,h) and calculate it as follows: S2: Based on HFSS software, the electric field and magnetic field distribution of the shielded cable are simulated; S3: Calculate the induced voltage and surface current of the cable. The calculation formula is: Where I0 is the current flowing through the outer surface of the shielding layer, E is the effective voltage value between the core wire and the shielding layer per unit length. z is the longitudinal electric field component, S e is the inner surface of the cable shield, A e For S e The area of ​​the region, l is the closed curve outside the cross section of the shielding layer, and H is the tangential component of the magnetic field vector along l; S4: Calculate the transfer impedance Z of the shielded cable L , the calculation formula is: Judgment module, used for transfer impedance Z L Less than the limit Z T In the case of , the judgment condition is met; Optimization module for transfer impedance Z L Not less than the limit value Z T In the case of exceeding the standard, the influencing factors are optimized and then transferred to the calculation module until the judgment conditions are met; specifically, according to the influencing factor importance δ(q, p, s, h), the key influencing factors of the frequency band exceeding the standard are identified, and the key factor importance δ(q', p', s', h') under the exceeding standard condition is obtained by optimizing the values ​​of the influencing factors q, p, s, h. The optimized key factor importance δ(q', p', s', h') is used as a parameter to transfer to step 2 for transfer impedance calculation, and finally Z L Compare with the target parameters until Z is met L <Z T , complete the comprehensive evaluation of simulation.

4. An electronic device, characterized in that: include: processor; a memory for storing instructions executable by the processor; The processor is configured to execute a cable shielding effectiveness evaluation method as described in any one of claims 1 to 2.

5. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, a cable shielding effectiveness evaluation method as claimed in any one of claims 1 to 2 is implemented.

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