Shielding effect detection method under impact electromagnetic field

Abstract

The invention relates to the technical field of electromagnetic field shielding detection, and discloses a shielding effect detection method under an impact electromagnetic field, which comprises the following steps: setting an impact electromagnetic field simulation environment, placing a shielding shell for electromagnetic shielding in the simulated impact electromagnetic field simulation environment, placing the shielding shell in the simulation environment, and carrying out electromagnetic shielding on the shielding shell; the electromagnetic detector receiving impact electromagnetism is opened, the shielding shell sleeves the outer side of the electromagnetic detector, and the output port of the electromagnetic wave generator device simulating impact electromagnetic waves is aligned to the two sides of the shielding shell. According to the shielding effect detection method under the impact electromagnetic field, a simulation environment of the impact electromagnetic field is set, then in the simulation environment, a simulation electromagnetic generator is arranged, electromagnetic impact is carried out on a shielding shell through electromagnetic generation, then electromagnetic interference data are detected through an electromagnetic detector in the shielding shell, and the shielding effect of the shielding shell is measured. The process is simple and efficient without dismounting equipment, so that the shielding effect detection of the lightning arrester impact electromagnetic field is more convenient and efficient.

Description

Technical Field

[0001] The invention relates to the technical field of electromagnetic field shielding detection, and in particular to a shielding effect detection method under an impact electromagnetic field. Background Art

[0002] Lightning arresters are an electrical appliance used to protect electrical equipment from high transient overvoltage hazards and limit the follow-on time and often the follow-on amplitude. Because lightning arresters can be struck by lightning, a large amount of current will be generated at the moment of lightning strike. The high amplitude and transient characteristics of lightning current will generate a large amount of impact electromagnetics that can damage the lightning arrester. Therefore, a shielding shell is now set on the outside of the lightning arrester to shield the impact electromagnetic field and prevent the lightning arrester from electromagnetic interference. Electromagnetic interference refers to the normal working equipment causing incorrect information transmission or reduced shielding performance due to the surrounding electromagnetic environment, thereby ensuring the stable operation of the lightning arrester.

[0003] At present, when testing the shielding interference effect of lightning arresters, it is generally done by manually carrying a handheld testing device to the installation location of the lightning arrester to test the electromagnetic protection effect of the lightning arrester. However, such a testing process is relatively cumbersome and requires direct testing of the shielding effect, which cannot meet the shielding effect of the lightning arrester shielding shell under different conditions, making the results of the shielding effect testing insufficient. Summary of the invention

[0004] The present invention provides a method for detecting shielding effect under an impact electromagnetic field, aiming to solve the problems raised in the above background technology.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The shielding effect detection method under the impact electromagnetic field comprises the following steps:

[0007] Step 1: first set up an impact electromagnetic field simulation environment, and place the shielding shell used for electromagnetic shielding in the simulated impact electromagnetic field simulation environment;

[0008] Step 2: Put the shielding shell into the simulated environment, turn on the electromagnetic detector for receiving the impact electromagnetic, and cover the shielding shell on the outside of the electromagnetic detector;

[0009] Step 3, aligning the output port of the electromagnetic wave generator device in the simulated impact electromagnetic wave with the two sides of the shielding shell, and moving the electromagnetic wave generator device to fit the surface of the shielding shell;

[0010] Step 4, then starting the electromagnetic wave generator in the simulated impact electromagnetic field environment, and then the electromagnetic wave generator emits impact electromagnetic waves to the shielding shell of the equipment, and the empty box electromagnetic shielding effect of the shielding shell is measured;

[0011] Step 5, after completing steps 1 to 4, reset the electromagnetic wave generator device, then take out the shielding shell from the simulation environment, and then put the shielded device into the simulation environment. After placing the device, put the shielding shell on the outside of the shielded device and the electromagnetic detector;

[0012] Step 6, repeating steps 3 and 4 to test the electromagnetic shielding effect of the shielding housing loaded with the shielded device under the impact electromagnetic field;

[0013] Step 7: Calculate and analyze the electromagnetic shielding values ​​of the unloaded and loaded shielding shells detected in steps 4 and 6 to determine the shielding effect of the shielding shell.

[0014] Furthermore, the calculation formula for electromagnetic shielding effectiveness in step seven is as follows:

[0015]

[0016] Among them, E i and E t Respectively represent the electric field strength before and after shielding; 20log 10 The time value of the electromagnetic field is taken as 10μs, and 20log represents the gain or loss of the signal in the electromagnetic field.

[0017] Furthermore, the calculation formula of the electromagnetic shielding attenuation efficiency in step seven is as follows:

[0018] SE=Bq×e -μ×t

[0019] Among them, SE is the shielding effectiveness; e is a constant; μ is the linear attenuation coefficient; t is the thickness of the material; Bq is the initial electromagnetic radiation intensity.

[0020] Furthermore, the analysis and calculation formula of the shielding effectiveness in step seven is as follows:

[0021] For the electric field:

[0022] For magnetic field:

[0023] Among them, SE E SE is the shielding effectiveness, which indicates the material's ability to attenuate electric fields; H E is the shielding effectiveness, which indicates the material's ability to attenuate the magnetic field; os and E s Represents the electric field strength before and after shielding; H os and H s Represents the magnetic field strength before and after the shield.

[0024] Furthermore, in step seven, the detection data of the unloaded shielding enclosure is set as SE0, and the detection data of the loaded shielding enclosure with the shielded device is set as SE1, and the difference between SE0 and SE1 is compared to confirm the shielding effect of the material.

[0025] Furthermore, the shielding shell is made of aluminum, and the thickness of the shielding shell is 2 mm.

[0026] Furthermore, the shielded device is a lightning arrester, and the lightning arrester test current waveform includes typical waveforms of 0.25 / 100μs, 1 / 5μs, 4 / 10μs and 8 / 20μs.

[0027] Furthermore, the simulation environment set in step 1 is set by finite element analysis method, the electromagnetic generator simulates lightning, and the lightning current characteristic setting parameters are amplitude -10kA and current waveform 1 / 5μs.

[0028] Furthermore, finite element simulation was performed using the finite element analysis method. The finite element simulation temperature was set to 20 degrees Celsius, and the air relative permittivity was simulated to be 1, the relative magnetic permeability was 1, and the electrical conductivity was 0. The shielding material relative conductivity was 0.61, and the relative magnetic permeability was 1. The simulation was set to be an ideal conductor.

[0029] Furthermore, the shielding housing, electromagnetic detector and shielded device in steps 1 to 7 are all simulated and set according to the parameters of the actual device.

[0030] Compared with the prior art, the advantages and positive effects of the present invention are:

[0031] 1. The present invention sets a simulated environment for impacting an electromagnetic field, then sets a simulated electromagnetic generator in the simulated environment, uses electromagnetic generation to perform electromagnetic impact on the shielding shell, and then uses an electromagnetic detector inside the shielding shell to detect electromagnetic interference data to measure the shielding effect of the shielding shell. The process is simple and efficient, and there is no need to disassemble and assemble equipment, and manually operate the detection equipment, and the shielding effect can be simulated and detected, so that the detection of the shielding effect of the impact electromagnetic field of the lightning arrester is more convenient and efficient;

[0032] 2. The present invention divides the simulation of shielding detection into two parts: simulation of the shielding shell with no load and simulation of the loaded equipment, thereby being able to measure the shielding effect of the shielding shell itself and the shielding effect of the lightning arrester installed in the shielding shell when struck by lightning, so that the detection result of the shielding effect is more sufficient and accurate;

[0033] 3. In the present invention, the shielding effect detection method can also be simulated using real equipment. The simulated equipment is set up according to the steps, and then a physical simulation test is performed, thereby making the detection of the shielding effect more complete and improving the accuracy of the detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0035] Figure 1 This is a flowchart of the method for detecting shielding effect of the present invention. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings of the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0037] Example 1

[0038] This embodiment provides a method for detecting shielding effect under an impact electromagnetic field. Figure 1 As shown, the shielding effect detection method under the impact electromagnetic field includes the following steps:

[0039] Step 1: Simulation environment settings:

[0040] First, an impact electromagnetic field simulation environment is set up, and the shielding shell used for electromagnetic shielding is placed in the simulated impact electromagnetic field simulation environment; the simulation environment continuously increases the basic simulation parameters through the finite element analysis method, so that the operating status of the actual equipment can be simulated in the intelligent computer equipment, and the shielding effect of the shielding shell can be detected after modeling.

[0041] Step 2: Prepare electromagnetic testing equipment:

[0042] The shielding shell is placed in a simulated environment; an electromagnetic detector for receiving impact electromagnetics is turned on, and the shielding shell is put on the outside of the electromagnetic detector; the electromagnetic detector performs simulation operation in the simulated environment according to the parameters set in the existing detection instrument, thereby being able to accurately and efficiently detect the shielding effect.

[0043] Step 3: Adjust the electromagnetic wave generator:

[0044] The output port of the electromagnetic wave generator device in the simulated impact electromagnetic wave is aligned with the two sides of the shielding shell, and the electromagnetic wave generator device is moved to fit the surface of the shielding shell.

[0045] Step 4: Launch shock electromagnetic waves:

[0046] Subsequently, the electromagnetic wave generator in the simulated impact electromagnetic field environment is started, and then the electromagnetic wave generator emits impact electromagnetic waves to the shielding shell of the equipment, and the empty box electromagnetic shielding effect of the shielding shell is measured.

[0047] Step 5: Install the shielded device:

[0048] After completing steps one to four, reset the electromagnetic wave generator device, then take the shielding shell out of the simulated environment, and then put the shielded device into the simulated environment. After placing the device, put the shielding shell on the outside of the shielded device and the electromagnetic detector. At this time, the shielded device is a lightning arrester, and when the lightning arrester is installed in the shielding shell to detect the shielding effect, the simulated environment will simulate the state of thunder, causing the lightning arrester to instantly increase the current and electromagnetic field. At this time, the simulated electromagnetic interference emitted from the outside will form an impact electromagnetic field, and then the shielding effect of the shielding shell can be confirmed under actual circumstances.

[0049] Step 6: Repeat the test:

[0050] Repeat steps three and four to test the electromagnetic shielding effect of the shielding shell loaded with the shielded device under the impact electromagnetic field. By testing the shielding shell in an empty state and the state of the shielded device installed, record two sets of data for shielding shells of different materials for testing and comparison, and thus effectively confirm the shielding effect of the shielding shell under different materials and in different states.

[0051] Step 7: Data analysis:

[0052] The electromagnetic shielding values ​​of the unloaded and loaded shielding shells detected in step 4 and step 6 are calculated and analyzed to determine the shielding effect of the shielding shell.

[0053] The calculation formula for electromagnetic shielding effectiveness in step 7 is as follows:

[0054] In order to study the electric field strength of the conductor loop under the impact electromagnetic field, the center point of the conductor loop (0,-0.1m,0) is taken, and the domain point probe is set to simulate the change of the electric field strength at the conductor loop position under the conditions of no shielding and shielding shell with holes. Under the condition of no shielding, the electric field strength at the center of the conductor continues to increase from 1μs, and then the rising trend slows down. Under the condition of shielding shell with holes, the electric field strength has an obvious pulse change near 1μs, and then continues to rise, and the trend gradually slows down. Take 10μs data, and the shielding effectiveness SE E The calculation formula is as follows:

[0055]

[0056] Among them, E i and E t Represent the electric field strength before and after shielding; 20log 10The time value of the electromagnetic field is taken as 10μs, and 20log represents the gain or loss of the signal in the electromagnetic field.

[0057] Furthermore, by integrating the tangential electric field along the conductor loop, the induced voltage on the conductor can be calculated. Under 1 / 5μs conditions and shielding conditions, the induced voltage of the conductor loop is in a pulse form with a voltage amplitude of up to about 18mV and an obvious positive polarity oscillation process. It does not damage the circuit, but has a certain interference with the measurement and affects the measurement accuracy. Under the condition of a shielding shell with a window, the induced voltage is significantly reduced with a voltage amplitude of up to about 5mV, which can still affect the measurement accuracy. Under full shielding conditions, no obvious induced voltage is generated.

[0058] The calculation formula of electromagnetic shielding attenuation efficiency SE in step 7 is as follows:

[0059] SE=Bq×e -μ×t

[0060] Among them, SE is the shielding effectiveness; e is a constant; μ is the linear attenuation coefficient; t is the thickness of the material; Bq is the initial electromagnetic radiation intensity.

[0061] The electromagnetic shielding attenuation efficiency SE reflects the ability of shielding materials to resist electromagnetic interference. Shielding materials can reflect electromagnetic waves, so that electromagnetic waves are reflected after hitting the surface of the material and will not penetrate the material. Part of the electromagnetic wave energy can be absorbed by the material and converted into heat energy, reducing the propagation of electromagnetic waves. Although the material allows some electromagnetic waves to pass through, it usually weakens the intensity of the electromagnetic waves. Therefore, the reflection, absorption and penetration attenuation of the impact electromagnetic by the shielding shell are detected, and then the shielding protection effectiveness of different materials in the application of the shielding shell is judged, and the material and shielding structure of the shielding shell used for shielding protection of the lightning arrester are confirmed.

[0062] Step 7 Shielding Effectiveness SE E The analytical calculation formula is as follows:

[0063] For the electric field:

[0064] For magnetic field:

[0065] Among them, SE E SE is the shielding effectiveness, which indicates the material's ability to attenuate electric fields; H E is the shielding effectiveness, which indicates the material's ability to attenuate the magnetic field; os and E s Represents the electric field strength before and after shielding; H os and H s Represents the magnetic field strength before and after the shield.

[0066] Shielding effectiveness is related to factors such as the conductivity and thickness of the shielding material, and whether there are electrical discontinuities on the shielding body. When analyzing the shielding effectiveness, the shielding effectiveness can be quantitatively evaluated by measuring the change in the intensity of the electromagnetic field before and after the installation of the shielding body. This method involves the reflection and absorption losses when the electromagnetic wave is incident on the surface of the shielding material, as well as the attenuation of the electromagnetic wave inside the shielding material. The calculation of shielding effectiveness usually involves the difference between the electric field intensity at the time of electromagnetic wave incidence and the electric field intensity of the leakage part after shielding. The larger the difference, the higher the shielding effectiveness. By calculating and analyzing the electric and magnetic fields, the shielding effectiveness of the shielding material can be intuitively represented, which facilitates the design and selection of subsequent lightning arrester shielding protection materials.

[0067] Step seven sets the test data of the unloaded shielding enclosure as SE0, and the test data of the loaded shielding enclosure with the shielded device as SE1, compares the difference between SE0 and SE1, and confirms the shielding effect of the material.

[0068] By setting up an unloaded shielding shell, no electromagnetic field is generated inside the shielding shell, so the electromagnetic interference generated on the outside will electromagnetically impact the shielding shell. When a lightning arrester is set inside the shielding shell, after the lightning arrester is struck by lightning, the current increases instantaneously, generating an internal impact electromagnetic field. At this time, the impact electromagnetic generated from the shielding shell, the two groups of electromagnetic interference are conducted in opposite directions. At this time, it is detected whether the external impact electromagnetic field will affect the electromagnetic field of the internal lightning arrester, and then the specific shielding effect of the shielding shell in different states is confirmed, so that the shielding effect detection of the shielding shell is more sufficient and accurate.

[0069] Through the above method, the shielding effect of the shielding shell under the impact electromagnetic field can be systematically detected, providing data support for the electromagnetic shielding performance under different materials and conditions. This detection method is not only suitable for the performance evaluation of the shielding shell, but also provides a reference for the design and improvement of related equipment.

[0070] Example 2

[0071] See also Figure 1 , further improvements were made on the basis of Example 1:

[0072] The shielding shell is made of aluminum and has a thickness of 2mm. The shielding shell is designed with holes, openings and is fully enclosed. Therefore, when there are display screens and button holes, the induced voltage generated by the circuit is significantly lower than that without shielding, but there is still a certain amplitude, which can affect the signal measurement; when the shielding shell is fully enclosed, there is basically no induced voltage, which shows the application requirements of the shielding effect.

[0073] Under the same shielding structure conditions, the magnitude of the induced voltage is related to the lightning current waveform and the lightning current amplitude. When the lightning current amplitude is the same, the faster the lightning wave rise rate, the larger the induced voltage amplitude. When the lightning current waveform is the same, the larger the lightning current amplitude, the larger the induced voltage amplitude, and it is approximately linear with the increase of the amplitude. Taking 100kV0.25 / 100μs as an example, the maximum induced voltage amplitude is -1.07V when there is no shielding, and the maximum induced voltage amplitude is -0.33V when there is a hole shield. It does not damage the circuit, but affects the signal measurement.

[0074] The shielded equipment is a lightning arrester. The lightning arrester test current waveform includes typical waveforms of 0.25 / 100μs, 1 / 5μs, 4 / 10μs and 8 / 20μs. In real life, the probability of the lightning current amplitude exceeding 1kA is about 97%, the probability of exceeding 10kA is about 77%, and the probability of exceeding 100kA is about 7%. The lightning current amplitude is concentrated in the range of 1kA to 100kA. According to the above research, the lightning current amplitude of 0.25 / 100μs in the amplitude range of 1kA to 100kA is used for testing. The study shows that under the conditions of 10kA and 4 / 10μs, the induced voltage on the wire loop is in the form of pulses, the voltage amplitude can reach up to about 4mV, and there is an obvious positive polarity oscillation process under the conditions of no shielding, shielding shell with window, and full shielding. Compared with the conditions of 10kA and 4 / 10μs, the induced voltage is significantly reduced under the conditions of shielding shell with window, and the voltage amplitude can reach up to about 1.5mV, which is also lower than the conditions of 10kA and 4 / 10μs. Under the conditions of full shielding, there is no obvious The induced voltage is generated, which shows that the maximum amplitude of the induced voltage is related to the rising rate of the lightning wave head. The faster the rising rate, the larger the amplitude of the induced voltage. Under the conditions of 10kA and 0.25 / 100μs, the induced voltage on the conductor loop is in pulse form, and the voltage amplitude can reach up to about 0.11V, which is higher than that of 10kA and 1 / 5μs, and the positive polarity oscillation is relatively unobvious. Under the condition of shielding shell with window, the induced voltage is significantly reduced, and the voltage amplitude can reach up to about 30mV, which is also higher than that of 10kA and 1 / 5μs. Under the condition of full shielding, no obvious induced voltage is generated, which can verify the conclusion that the maximum amplitude of the induced voltage is related to the rising rate of the lightning wave head. The faster the rising rate, the larger the amplitude of the induced voltage, and the relationship with the subsequent wave tail time is small. Therefore, under different waveforms and different shielding conditions, the impact of the impact electromagnetic field on the arrester can be detected in time.

[0075] The simulation environment set in step 1 is set by finite element analysis. The electromagnetic generator simulates lightning. The lightning current characteristic setting parameters are amplitude -10kA and current waveform 1 / 5μs. The finite element simulation temperature is set to 20 degrees Celsius. The air relative dielectric constant is simulated as 1, the relative magnetic permeability is 1, and the conductivity is 0. The shielding material relative conductivity is 0.61 and the relative magnetic permeability is 1. The simulation is set as an ideal conductor. The current in the lightning current channel is positive from top to bottom. Considering the characteristics of lightning current, there are more negative lightning currents. Therefore, the lightning current characteristic parameters are set first. Due to the corona discharge effect around the channel, the lightning current speed is 1 / 3 of the speed of light, thereby forming a finite element simulation model. Then the finite element simulation model determines the accuracy of the shielding effect detection after simulation through the above-mentioned setting parameters.

[0076] The shielding shell, electromagnetic detector and shielded equipment in steps 1 to 7 are simulated and set according to the parameters of the actual equipment. During the simulation setting, the state of no shielding shell, shielding shell without cover, with display screen and button holes, and shielding shell covered with cover is set to be completely closed. By simulating and detecting different shielding protection states on the outside of the lightning arrester and different forms of shielding shells, the impact on the shielding effect is analyzed. The impact of the impact electromagnetic field on the internal circuit is mainly caused by the electric field. Under different conditions, the electric field strength distribution in the shielding shell is different. Under unshielded conditions, the electric field strength gradually decreases, and there is a large electric field strength at the wire loop. Under perforated shielding conditions, the electric field strength is strong at the holes and relatively weakened inward. There is a certain electric field strength at the wire loop, and under full shielding conditions, the electric field strength is close to 0, so that the effect of shielding protection can be judged, and the impact of different shielding protection on the lightning arrester is made to ensure that it provides reference significance for the subsequent design of the shielding shell.

[0077] The above are only preferred specific implementation modes of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and inventive concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for detecting shielding effect under an impact electromagnetic field, characterized in that: The following steps are involved: Step 1: first set up an impact electromagnetic field simulation environment, and place the shielding shell used for electromagnetic shielding in the simulated impact electromagnetic field simulation environment; Step 2: Put the shielding shell into the simulated environment, turn on the electromagnetic detector for receiving the impact electromagnetic, and cover the shielding shell on the outside of the electromagnetic detector; Step 3, aligning the output port of the electromagnetic wave generator device in the simulated impact electromagnetic wave with the two sides of the shielding shell, and moving the electromagnetic wave generator device to fit the surface of the shielding shell; Step 4, then starting the electromagnetic wave generator in the simulated impact electromagnetic field environment, and then the electromagnetic wave generator emits impact electromagnetic waves to the shielding shell of the equipment, and the empty box electromagnetic shielding effect of the shielding shell is measured; Step 5, after completing steps 1 to 4, reset the electromagnetic wave generator device, then take out the shielding shell from the simulation environment, and then put the shielded device into the simulation environment. After placing the device, put the shielding shell on the outside of the shielded device and the electromagnetic detector; Step 6, repeating steps 3 and 4 to test the electromagnetic shielding effect of the shielding housing loaded with the shielded device under the impact electromagnetic field; Step 7: Calculate and analyze the electromagnetic shielding values ​​of the unloaded and loaded shielding shells detected in steps 4 and 6 to determine the shielding effect of the shielding shell.

2. The method for detecting shielding effect under an impact electromagnetic field according to claim 1, characterized in that: The calculation formula for electromagnetic shielding effectiveness in step 7 is as follows: Among them, E i and E t Represent the electric field strength before and after shielding; 20log 10 The time value of the electromagnetic field is taken as 10μs, and 20log represents the gain or loss of the signal in the electromagnetic field.

3. The method for detecting shielding effect under an impact electromagnetic field according to claim 1, characterized in that: The calculation formula of electromagnetic shielding attenuation efficiency in step 7 is as follows: SE=Bq×e -μ×t Among them, SE is the shielding effectiveness; e is a constant; μ is the linear attenuation coefficient; t is the thickness of the material; Bq is the initial electromagnetic radiation intensity.

4. The method for detecting shielding effect under an impact electromagnetic field according to claim 1, characterized in that: Step 7: The analysis and calculation formula for shielding effectiveness is as follows: For the electric field: For magnetic field: Among them, SE E SE is the shielding effectiveness, which indicates the material's ability to attenuate electric fields; H E is the shielding effectiveness, which indicates the material's ability to attenuate the magnetic field; os and E s Represents the electric field strength before and after shielding; H os and H s Represents the magnetic field strength before and after the shield.

5. The method for detecting shielding effect under an impact electromagnetic field according to claim 1, characterized in that: Step seven sets the test data of the unloaded shielding enclosure as SE0, and the test data of the loaded shielding enclosure with the shielded device as SE1, compares the difference between SE0 and SE1, and confirms the shielding effect of the material.

6. The method for detecting shielding effect under an impact electromagnetic field according to claim 1, characterized in that: The shielding shell is made of aluminum material, and the thickness of the shielding shell is 2 mm.

7. The method for detecting shielding effect under an impact electromagnetic field according to claim 1, characterized in that: The shielded device is a lightning arrester, and the lightning arrester test current waveform includes typical waveforms of 0.25 / 100μs, 1 / 5μs, 4 / 10μs and 8 / 20μs.

8. The method for detecting shielding effect under an impact electromagnetic field according to claim 1, characterized in that: The simulation environment set in step 1 is set by finite element analysis method, the electromagnetic generator simulates lightning, and the lightning current characteristic setting parameters are amplitude -10kA and current waveform 1 / 5μs.

9. The method for detecting shielding effect under an impact electromagnetic field according to claim 8, characterized in that: Finite element simulation was performed using the finite element analysis method. The finite element simulation temperature was set to 20 degrees Celsius. The air relative permittivity was 1, the relative magnetic permeability was 1, and the conductivity was 0. The shielding material relative conductivity was 0.61, and the relative magnetic permeability was 1. The simulation was set to an ideal conductor.

10. The method for detecting shielding effect under an impact electromagnetic field according to claim 1, characterized in that: The shielding housing, electromagnetic detector and shielded device in steps 1 to 7 are all simulated and set according to the parameters of the actual device.

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