A method and system for detecting a GIS component based on laser ultrasound

Abstract

The application relates to a GIS component detection method and system based on laser ultrasound, and belongs to the technical field of nondestructive testing. The method comprises the following steps: emitting a pulsed laser beam to a GIS component to be detected, obtaining an ultrasonic echo signal generated by the GIS component to be detected based on the pulsed laser beam; extracting sum-frequency double power spectrum and difference-frequency double power spectrum in the ultrasonic echo signal by using a frequency spectrum screening method; obtaining the nonlinearity of the GIS component to be detected based on the ratio of the sum-frequency double power spectrum and the difference-frequency double power spectrum; if the nonlinearity of the GIS component to be detected is greater than a preset threshold, it is determined that the GIS component to be detected has defects; and if the nonlinearity of the GIS component to be detected is less than or equal to the preset threshold, it is determined that the GIS component to be detected has no defects. The application can judge whether the GIS component has defects by analyzing sum-frequency components and difference-frequency components in the ultrasonic echo signal generated by the GIS component under the excitation of a laser pulsed beam, and has high sensitivity and resolution.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nondestructive testing, in particular to a GIS component detection method and system based on laser ultrasound. BACKGROUND

[0002] The main connotation of nondestructive testing (NDT) technology is to ensure that the use performance of the detected object is not damaged, and to detect the material, parts and structure of the detected object by using the changes of heat, sound, light, electricity, magnetism and other reactions caused by the existence of internal structure abnormalities or defects, so as to judge the reliability, integrity, continuity and physical performance of the detected object.

[0003] At present, the methods for nondestructive testing of GIS components include ultrasonic detection, pulse current detection, X-ray detection, infrared thermal imaging detection and acoustic emission detection, etc., but these detection methods cannot accurately detect the micro defects existing in the GIS components. For example, in the patent with publication number CN112268753A, a GIS basin-type insulator detection device and method based on shell vibration signal are provided. Since the waveform amplitude of the vibration signal of the basin-type insulator with defects is relatively smaller than that of the vibration signal of the perfect basin-type insulator, the method directly detects the vibration signal of the basin-type insulator by using an electronic circuit, compares the detected vibration signal with the vibration signal of the standard basin-type insulator, and judges whether the basin-type insulator contains defects. However, when the basin-type insulator contains micro bubbles, cracks or foreign matters, etc., the vibration signal generated by these defects is very weak, and in a complex electromagnetic environment, these weak vibration signals will also be covered by environmental noise, so that the final detected vibration signal is basically consistent with the vibration signal of the standard basin-type insulator, resulting in inaccurate detection results.

[0004] In summary, the existing GIS component detection methods cannot detect and accurately detect the micro defects in the GIS components. SUMMARY

[0005] Therefore, the technical problem to be solved by the present application is to overcome the problem that the existing GIS component detection method cannot accurately detect the micro defects existing in the GIS components.

[0006] To solve the above technical problems, the present application provides a GIS component detection method based on laser ultrasound, comprising:

[0007] emitting a pulse laser beam to the GIS component to be detected, and acquiring an ultrasonic echo signal generated by the GIS device to be detected based on the pulse laser beam;

[0008] extracting a sum-frequency double power spectrum and a difference-frequency double power spectrum in the ultrasonic echo signal by using a spectrum filtering method, obtaining the nonlinearity of the GIS component to be detected based on a ratio of the sum-frequency double power spectrum and the difference-frequency double power spectrum;

[0009] If the nonlinearity of the GIS component to be detected is greater than a preset threshold, it is determined that the GIS component to be detected has defects; if the nonlinearity of the GIS component to be detected is less than or equal to the preset threshold, it is determined that the GIS component to be detected has no defects.

[0010] Preferably, after it is determined that the GIS component to be detected has defects, the method further comprises:

[0011] calculating a first difference value between the sum-frequency double power spectrum and a standard sum-frequency double power spectrum, and taking a ratio of the first difference value and the standard sum-frequency double power spectrum as a sum-frequency damage coefficient of the GIS component to be detected, so as to judge the defect severity of the GIS component to be detected based on the sum-frequency damage coefficient;

[0012] The standard sum-frequency double power spectrum is a sum-frequency double power spectrum in an ultrasonic echo signal generated by the GIS component in a non-defect state based on the pulsed laser beam.

[0013] Preferably, after it is determined that the GIS component to be detected has defects, the method further comprises:

[0014] calculating a second difference value between the difference-frequency double power spectrum and a standard difference-frequency double power spectrum, and taking a ratio of the second difference value and the standard difference-frequency double power spectrum as a difference-frequency damage coefficient of the GIS component to be detected, so as to judge the defect severity of the GIS component to be detected based on the difference-frequency damage coefficient;

[0015] The standard difference-frequency double power spectrum is a difference-frequency double power spectrum in an ultrasonic echo signal generated by the GIS component in a non-defect state based on the pulsed laser beam.

[0016] Preferably, the sum-frequency double power spectrum is:

[0017] B1(w1,w2,w1+w2)=E[U(w1),U(w2),U * (w1+w2)],

[0018] wherein B1(w1,w2,w1+w2) represents the sum-frequency double power spectrum, E[] represents taking a mathematical expectation, U(w1) represents a signal component with a frequency of w1 in the ultrasonic echo signal, U(w2) represents a signal component with a frequency of w2 in the ultrasonic echo signal, and U * (w1+w2) represents a complex conjugate of a sum-frequency component of the signal component with the frequency of w1 and the signal component with the frequency of w2 in the ultrasonic echo signal;

[0019] The difference frequency bispectrum is:

[0020] B2(w1, w2, w1-w2) = E[U(w1), U(w2), U * (w1-w2)],

[0021] where B1(w1, w2, w1-w2) represents the difference frequency bispectrum, U * (w1-w2) represents the complex conjugate of the difference frequency component of the signal component with frequency w1 and the signal component with frequency w2 in the ultrasonic echo signal.

[0022] Preferably, the calculation formula of the nonlinearity of the GIS component to be detected is:

[0023]

[0024] where NL represents the nonlinearity of the GIS component to be detected.

[0025] Preferably, the calculation formula of the sum frequency damage coefficient of the GIS component to be detected is:

[0026]

[0027] where S1 represents the sum frequency damage coefficient of the GIS component to be detected, B1(w1, w2, w1+w2) represents the sum frequency bispectrum, and B1 ′ (w1, w2, w1+w2) represents the standard sum frequency bispectrum.

[0028] Preferably, the calculation formula of the difference frequency damage coefficient of the GIS component to be detected is:

[0029]

[0030] where S2 represents the difference frequency damage coefficient of the GIS component to be detected, B2(w1, w2, w1-w2) represents the difference frequency bispectrum, and B2 ′ (w1, w2, w1-w2) represents the standard difference frequency bispectrum.

[0031] Preferably, the method further comprises: simultaneously emitting the pulsed laser beam to the GIS component to be detected by using a plurality of laser ultrasonic sensors.

[0032] Preferably, the ultrasonic echo signal generated by the GIS device to be detected based on the pulsed laser beam is represented as:

[0033]

[0034] where u(x, t) represents the ultrasonic echo signal generated by the GIS device to be detected based on the pulsed laser beam, and Ai A (w) represents the signal amplitude of the frequency w in the ultrasonic echo signal i j A (w) represents the signal amplitude of the frequency w in the ultrasonic echo signal j k (w) represents the signal wave number of the frequency w in the ultrasonic echo signal i k (w) represents the signal wave number of the frequency w in the ultrasonic echo signal i k (w) represents the signal wave number of the frequency w in the ultrasonic echo signal j k (w) represents the signal wave number of the frequency w in the ultrasonic echo signal j k (w) represents the signal wave number of the frequency w in the ultrasonic echo signal, M and N are constants, and α represents a nonlinear coefficient.

[0035] The application also provides a GIS component detection system based on laser ultrasound, comprising:

[0036] A laser ultrasound sensor is configured to emit a pulsed laser beam to a GIS component to be detected.

[0037] An interferometer is configured to acquire an ultrasonic echo signal generated by the GIS device to be detected based on the pulsed laser beam.

[0038] A host computer is in communication connection with the interferometer, and specifically comprises:

[0039] A signal processing module is configured to extract sum frequency double power spectrum and difference frequency double power spectrum in the ultrasonic echo signal by using a frequency spectrum screening method, and obtain the nonlinearity of the GIS component to be detected based on the ratio of the sum frequency double power spectrum and the difference frequency double power spectrum.

[0040] A defect detection module is configured to determine that the GIS component to be detected has defects if the nonlinearity of the GIS component to be detected is greater than a preset threshold, and determine that the GIS component to be detected has no defects if the nonlinearity of the GIS component to be detected is less than or equal to the preset threshold.

[0041] ​The GIS component detection method based on laser ultrasound provided in the application calculates the nonlinearity of the GIS component to be detected to determine whether the GIS component to be detected has defects by extracting the sum frequency component and the difference frequency component in the ultrasound echo signal generated by the GIS component to be detected under the excitation of the laser pulse beam; since the laser pulse beam acts on the GIS component, the GIS component generates an ultrasound echo signal, when defects exist in the GIS component, the defects change the propagation characteristics of the ultrasound echo signal, causing strong scattering and reflection of the ultrasound echo signal, thereby generating a sum frequency signal higher than the original frequency and a difference frequency signal lower than the original frequency with high intensity, even if only a tiny defect exists in the GIS component, the defect area still becomes a nonlinear scattering source, thereby generating a more significant sum frequency signal and difference frequency signal compared to the defect-free state, therefore, the application uses laser ultrasound to perform nondestructive testing on the GIS device, judges whether the GIS component has defects by analyzing the sum frequency component and the difference frequency component in the ultrasound echo signal generated by the GIS component under the excitation of the laser pulse beam, can accurately detect tiny defects in the GIS component, and has high sensitivity and resolution. BRIEF DESCRIPTION OF DRAWINGS

[0042] In order to make the content of the application more easily understood, the application will be further described in detail below according to specific embodiments of the application and in conjunction with the drawings, in which:

[0043] Figure 1 The flowchart of the GIS component detection method based on laser ultrasound provided in the application is shown in

[0044] Figure 2 The schematic diagram of the application provided for emitting a laser pulse beam to the GIS component to be detected is shown in DETAILED DESCRIPTION

[0045] The application will be further described below in conjunction with the drawings and specific embodiments, so that those skilled in the art can better understand the application and implement it, but the embodiments are not limiting the application.

[0046] Please refer to Figure 1 , Figure 1 The GIS component detection method based on laser ultrasound provided in the application is shown in the drawing, and the method specifically includes:

[0047] S10: Emitting a pulse laser beam to the GIS component to be detected, and acquiring an ultrasound echo signal generated by the GIS device to be detected based on the pulse laser beam;

[0048] S20: Extracting the sum frequency double power spectrum and the difference frequency double power spectrum in the ultrasound echo signal by using the frequency spectrum screening method, and calculating the nonlinearity of the GIS component to be detected based on the ratio of the sum frequency double power spectrum and the difference frequency double power spectrum.

[0049] S30: If the nonlinearity of the GIS component to be detected is greater than the preset threshold, it is determined that the GIS component to be detected has a micro-crack defect; if the nonlinearity of the GIS component to be detected is less than or equal to the preset threshold, it is determined that the GIS component to be detected does not have a micro-crack defect.

[0050] When the laser pulse beam acts on the GIS component, the GIS component will generate an ultrasonic echo signal. When defects exist in the GIS component, these defects will change the propagation characteristics of the ultrasonic echo signal, causing strong scattering and reflection of the ultrasonic echo signal, thereby generating high-frequency sum frequency signals and low-frequency difference frequency signals with higher intensity than the original frequency. Even if only a small defect exists in the GIS component, the defect area will still become a nonlinear scattering source, thereby generating more significant sum frequency signals and difference frequency signals compared to the defect-free state. Therefore, the present application uses laser ultrasonic to perform nondestructive testing on GIS equipment, and judges whether the GIS component has defects by analyzing the sum frequency components and difference frequency components in the ultrasonic echo signal generated by the GIS component under the excitation of the laser pulse beam. The small defects in the GIS component can be accurately detected, and the sensitivity and resolution are high.

[0051] Specifically, the ultrasonic echo signal generated by the GIS component to be detected under the excitation of the laser pulse beam in step S10 is:

[0052]

[0053] wherein u(x, t) represents the ultrasonic echo signal generated by the GIS component to be detected based on the pulse laser beam, A i represents the signal amplitude of the frequency w i in the ultrasonic echo signal, A j represents the signal amplitude of the frequency w j in the ultrasonic echo signal, k i represents the signal wave number of the frequency w i in the ultrasonic echo signal, k j represents the signal wave number of the frequency w j in the ultrasonic echo signal, and M and N are constants, and a represents the nonlinear coefficient.

[0054] The frequency spectrum screening principles involved in extracting the sum frequency double power spectrum and the difference frequency double power spectrum from the above ultrasonic echo signal include: after Fourier transform is performed on the above ultrasonic echo signal, U(w) is obtained, and U(w) needs to satisfy: 1, the signal component U(w1) at the frequency w1 is not 0; 2, the signal component U(w2) at the frequency w2 is not 0; 3, the sum frequency component U(w1+w2) of the signal component at the frequency w1 and the signal component at the frequency w2 is not 0; 4, the difference frequency component U(w1-w2) of the signal component at the frequency w1 and the signal component at the frequency w2 is not 0; 5, 6、 wherein, is the phase of the signal component U(w1), is the phase of the signal component U(w2), is the phase of the sum frequency component U(w1+w2), is the phase of the difference frequency component U(w1-w2).

[0055] Specifically, the sum frequency double power spectrum in step S20 is:

[0056] B1(w1,w2,w1+w2)=E[U(w1),U(w2),U * (w1+w2)],

[0057] wherein, B1(w1,w2,w1+w2) represents the sum frequency double power spectrum, E[] represents taking mathematical expectation, U(w1) represents the signal component at the frequency w1 in the ultrasonic echo signal, U(w2) represents the signal component at the frequency w2 in the ultrasonic echo signal, U * (w1+w2) represents the complex conjugate of the sum frequency component of the signal component at the frequency w1 and the signal component at the frequency w2 in the ultrasonic echo signal;

[0058] The difference frequency double power spectrum is:

[0059] B2(w1,w2,w1-w2)=E[U(w1),U(w2),U * (w1-w2)],

[0060] wherein, B1(w1,w2,w1-w2) represents the difference frequency double power spectrum, U * (w1-w2) represents the complex conjugate of the difference frequency component of the signal component at the frequency w1 and the signal component at the frequency w2 in the ultrasonic echo signal.

[0061] Based on the above sum frequency double power spectrum and the difference frequency double power spectrum, the nonlinearity of the GIS component to be detected is represented as:

[0062]

[0063] wherein NL represents the nonlinearity of the GIS component to be detected.

[0064] Further, when the defect in the GIS component is more serious, the sum frequency component in the ultrasonic echo signal generated thereby tends to be more significant, because a larger defect will introduce stronger nonlinear scattering and reflection effects. Generally speaking, the increase in the sum frequency component is proportional to the size of the defect. Therefore, after determining that the GIS component to be detected has a defect, the embodiments of the present application can further analyze the sum frequency double power spectrum to determine the severity of the defect.

[0065] Specifically, in some embodiments of the present application, after determining that the GIS component to be detected has a defect, the method further comprises:

[0066] calculating a first difference between the sum frequency double power spectrum and the standard sum frequency double power spectrum, and taking the ratio of the first difference to the standard sum frequency double power spectrum as a sum frequency damage coefficient of the GIS component to be detected, so as to determine the severity of the defect in the GIS component to be detected based on the sum frequency damage coefficient.

[0067] wherein the standard sum frequency double power spectrum is the sum frequency double power spectrum in the ultrasonic echo signal generated by the GIS component in a non-defective state based on the pulsed laser beam.

[0068] Specifically, the calculation formula of the sum frequency damage coefficient of the GIS component to be detected is:

[0069]

[0070] wherein S1 represents the sum frequency damage coefficient of the GIS component to be detected, B1(w1, w2, w1+w2) represents the sum frequency double power spectrum, and B1 ′ (w1, w2, w1+w2) represents the standard sum frequency double power spectrum.

[0071] Unlike the sum frequency component, when the defect in the GIS component is more serious, the difference frequency component in the ultrasonic echo signal generated thereby will also change, but this change is not monotonous increase or monotonous decrease. However, regardless of whether the difference frequency component increases or decreases, the difference between the difference frequency component in the ultrasonic echo signal of the GIS component to be detected and the difference frequency component in the ultrasonic echo signal of the GIS component in a non-defective state can still reflect the severity of the defect, i.e., the larger the defect size of the GIS component to be detected, the larger the difference between the difference frequency component in the ultrasonic echo signal of the GIS component to be detected and the difference frequency component in the ultrasonic echo signal of the GIS component in a non-defective state. Therefore, after determining that the GIS component to be detected has a defect, the embodiments of the present application can further analyze the difference frequency double power spectrum to determine the severity of the defect.

[0072] Specifically, in some embodiments of the present application, after determining that the GIS component to be detected has a defect, the method further comprises:

[0073] a second difference value between the difference frequency double power spectrum and the standard difference frequency double power spectrum is calculated, and a ratio of the second difference value to the standard difference frequency double power spectrum is taken as a difference frequency damage coefficient of the GIS component to be detected, so as to judge the defect severity of the GIS component to be detected based on the difference frequency damage coefficient;

[0074] The standard difference frequency double power spectrum is a difference frequency double power spectrum in an ultrasonic echo signal generated by the GIS component in a non-defective state based on the pulsed laser beam.

[0075] Specifically, the calculation formula of the difference frequency damage coefficient of the GIS component to be detected is as follows:

[0076]

[0077] The difference frequency damage coefficient of the GIS component to be detected is calculated based on the sum frequency double power spectrum and the difference frequency double power spectrum in each ultrasonic echo signal. ′ The standard difference frequency double power spectrum is a difference frequency double power spectrum in an ultrasonic echo signal generated by the GIS component in a non-defective state based on the pulsed laser beam.

[0078] Optionally, in some embodiments of the present application, the pulsed laser beam emitted to the GIS component to be detected can be emitted by one laser ultrasonic sensor to the GIS component to be detected;

[0079] In some other embodiments of the present application, a plurality of laser ultrasonic sensors can be used to form a laser ultrasonic sensor array, and all the laser ultrasonic sensors are controlled to emit laser pulse beams to the GIS device to be detected at the same time, which specifically includes:

[0080] The plurality of laser ultrasonic sensors are used to emit laser pulse beams to the GIS component to be detected at the same time, and a plurality of ultrasonic echo signals generated by the GIS component to be detected under the excitation of the laser pulse beams are acquired;

[0081] The sum frequency double power spectrum and the difference frequency double power spectrum in each ultrasonic echo signal are extracted respectively, and a nonlinearity of the GIS component to be detected is calculated based on the sum frequency double power spectrum and the difference frequency double power spectrum in the ultrasonic echo signal.

[0082] The size of each nonlinearity and a preset threshold value is judged, if there is a nonlinearity of the GIS component to be detected greater than the preset threshold value, it is determined that the GIS component to be detected has a defect; if all the calculated nonlinearities are less than or equal to the preset threshold value, it is determined that the GIS component to be detected has no defect.

[0083] For example, as Figure 2As shown, in one specific example of the present application, six laser ultrasonic sensors are used to form an ultrasonic laser sensor array, A1 is a GIS component to be detected, and A2-A7 are laser ultrasonic sensors. By adjusting the laser energy of each laser ultrasonic sensor, acoustic energy focusing at different positions of the GIS component to be detected can be achieved, so that defects in the GIS component to be detected can be more accurately detected.

[0084] Based on the laser-ultrasound-based GIS component detection method provided in the above embodiments, the present application further provides a laser-ultrasound-based GIS component detection system, which specifically comprises:

[0085] a laser ultrasonic sensor, configured to emit a pulsed laser beam to the GIS component to be detected;

[0086] an interferometer, configured to acquire an ultrasonic echo signal generated by the GIS device based on the pulsed laser beam;

[0087] a host computer, in communication connection with the interferometer, which specifically comprises:

[0088] a signal processing module, configured to extract sum-frequency double power spectrum and difference-frequency double power spectrum in the ultrasonic echo signal by using a frequency spectrum screening method, and obtain the nonlinearity of the GIS component to be detected based on the ratio of the sum-frequency double power spectrum and the difference-frequency double power spectrum;

[0089] a defect detection module, configured to determine that the GIS component to be detected has defects if the nonlinearity of the GIS component to be detected is greater than a preset threshold, and determine that the GIS component to be detected has no defects if the nonlinearity of the GIS component to be detected is less than or equal to the preset threshold.

[0090] Specifically, the wavelength of the pulsed laser beam output by the laser ultrasonic sensor can be 1064 nm or 532 nm.

[0091] Optionally, the laser ultrasonic sensor and the interferometer can be controlled wirelessly through the host computer, or directly through the control panel of the sensor and the interferometer.

[0092] The laser-ultrasound-based GIS component detection method provided by the present application can be applied to the detection of the metal shell of the GIS component, the detection of the pot-type insulator, and the defect detection of the metal and non-metal parts of other GIS components.

[0093] Those skilled in the art will appreciate that embodiments of the application can be devised for a method, a system, or a computer program product. Accordingly, the present application can be embodied in the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application can take the form of a computer program product on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage devices, etc.) embodying computer readable program code.

[0094] The present application is described in reference to the flowchart illustrations and / or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams.

[0095] These computer program instructions can also be stored in a computer- readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instructions which implement the functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams.

[0096] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams.

[0097] Obviously, the above-described embodiments are only examples and are not intended to limit the present application. Based on the above description, those skilled in the art can make other variations and modifications of the present application without departing from the present application. Neither requiring nor intending to limit the present application to the exact forms of implementations shown and described, the application is to cover all modifications and variations as long as they come within the scope of the present application.

Claims

1. A method for detecting GIS components based on laser ultrasound, characterized in that, include: A pulsed laser beam is emitted toward the GIS component to be tested, and the ultrasonic echo signal generated by the GIS component to be tested based on the pulsed laser beam is acquired. The sum-frequency dual-power spectrum and difference-frequency dual-power spectrum of the ultrasonic echo signal are extracted using a spectral screening method. The nonlinearity of the GIS component under test is obtained based on the ratio of the sum-frequency dual-power spectrum to the difference-frequency dual-power spectrum. The sum-frequency dual-power spectrum is: ， in, Represents the sum-frequency dual power spectrum. This represents taking the mathematical expectation. This indicates that the frequency in the ultrasonic echo signal is The signal components, This indicates that the frequency in the ultrasonic echo signal is The signal components, This indicates that the frequency in the ultrasonic echo signal is The signal components and frequencies are The complex conjugate of the sum and frequency components of the signal components; The difference-frequency dual power spectrum is: ， in, Represents the difference-frequency dual power spectrum. This indicates that the frequency in the ultrasonic echo signal is The signal components and frequencies are The complex conjugate of the difference frequency component of the signal component; If the nonlinearity of the GIS component to be tested is greater than a preset threshold, the GIS component to be tested is determined to have a defect; if the nonlinearity of the GIS component to be tested is less than or equal to the preset threshold, the GIS component to be tested is determined to have no defect.

2. The GIS component detection method based on laser ultrasound according to claim 1, characterized in that, After determining that the GIS component to be tested has a defect, the method further includes: Calculate the first difference between the sum-frequency dual power spectrum and the standard sum-frequency dual power spectrum, and use the ratio of the first difference to the standard sum-frequency dual power spectrum as the sum-frequency impairment coefficient of the GIS component to be tested, so as to determine the severity of the defect of the GIS component to be tested based on the sum-frequency impairment coefficient; The standard sum-frequency dual power spectrum is the sum-frequency dual power spectrum of the ultrasonic echo signal generated by the pulsed laser beam in the non-defect state of the GIS component.

3. The GIS component detection method based on laser ultrasound according to claim 1, characterized in that, After determining that the GIS component to be tested has a defect, the method further includes: Calculate the second difference between the difference frequency dual power spectrum and the standard difference frequency dual power spectrum, and use the ratio of the second difference to the standard difference frequency dual power spectrum as the difference frequency damage coefficient of the GIS component to be tested, so as to determine the severity of the defect of the GIS component to be tested based on the difference frequency damage coefficient; The standard difference frequency dual power spectrum is the difference frequency dual power spectrum in the ultrasonic echo signal generated by the pulsed laser beam in the non-defect state of the GIS component.

4. The GIS component detection method based on laser ultrasound according to claim 1, characterized in that, The formula for calculating the nonlinearity of the GIS component to be tested is: ， in, This indicates the nonlinearity of the GIS component to be tested.

5. The GIS component detection method based on laser ultrasound according to claim 2, characterized in that, The formula for calculating the sum-frequency impairment coefficient of the GIS component to be tested is as follows: ， in, This represents the sum-frequency impairment coefficient of the GIS component to be tested. Represents the sum-frequency dual power spectrum. This represents the standard and frequency dual power spectrum.

6. The GIS component detection method based on laser ultrasound according to claim 3, characterized in that, The formula for calculating the difference frequency impairment coefficient of the GIS component to be tested is as follows: ， in, This represents the difference frequency impairment coefficient of the GIS component to be tested. Represents the difference-frequency dual power spectrum. This represents the standard difference frequency dual power spectrum.

7. The GIS component detection method based on laser ultrasound according to claim 1, characterized in that, The method of emitting pulsed laser beams to the GIS component under test includes: simultaneously emitting pulsed laser beams to the GIS component under test using multiple laser ultrasonic sensors.

8. The GIS component detection method based on laser ultrasound according to claim 1, characterized in that, The ultrasonic echo signal generated by the pulsed laser beam based on the GIS component to be detected is represented as follows: ， in, This indicates that the GIS component under test is based on the ultrasonic echo signal generated by the pulsed laser beam. This indicates that the frequency in the ultrasonic echo signal is The signal amplitude, This indicates that the frequency in the ultrasonic echo signal is The signal amplitude, This indicates that the frequency in the ultrasonic echo signal is signal wavenumber, This indicates that the frequency in the ultrasonic echo signal is signal wavenumber, , It is a constant. This represents the nonlinear coefficient.

9. A GIS component inspection system based on laser ultrasound, characterized in that, include: A laser ultrasonic sensor is used to emit pulsed laser beams toward the GIS component to be inspected; An interferometer is used to acquire the ultrasonic echo signal generated by the GIS component under test based on the pulsed laser beam; The host computer, which is communicatively connected to the interferometer, specifically includes: The signal processing module is used to extract the sum-frequency dual power spectrum and the difference-frequency dual power spectrum from the ultrasonic echo signal using a spectrum filtering method, and to obtain the nonlinearity of the GIS component to be detected based on the ratio of the sum-frequency dual power spectrum and the difference-frequency dual power spectrum. The defect detection module is used to determine that the GIS component under test has a defect if the nonlinearity of the GIS component under test is greater than a preset threshold, and to determine that the GIS component under test does not have a defect if the nonlinearity of the GIS component under test is less than or equal to the preset threshold.

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