CN111426919A - Basin-type insulator detection device based on laser-induced ultrasound - Google Patents

Abstract

A pot-type insulator detection device based on laser-induced ultrasound, the laser control system of which controls the laser excitation system to output pulsed laser light. The pulsed laser is directly irradiated on the carbon nano-reinforced medium attached to the surface of the basin insulator to be tested. The photodetector placed at the edge of the laser incident path receives the residual light of the pulsed laser emitted by the laser excitation system as a synchronous trigger signal of the signal detection and processing system to start the signal detection and processing system. Under the excitation of the pulsed laser, the carbon nano-enhanced medium generates high-intensity and high-frequency ultrasonic signals inside the basin insulator. The air-coupled ultrasonic transducer placed on the surface of the basin insulator to be detected receives the ultrasonic signal, which is amplified and filtered by the signal detection and processing system. Computer acquisition system acquisition. The ultrasonic signal is decomposed into different frequency ranges by wavelet packet decomposition, and then the matrix composed of wavelet packet coefficients is used to represent the signal state at a certain depth of the defect, and the defect state is characterized according to different signal states.

Description

Pot-type insulator detection device based on laser-induced ultrasound

technical field

The invention relates to a pot-type insulator detection device.

Background technique

The main connotation of Nondestructive Testing (NDT) technology is to ensure that, on the premise of not compromising the performance of the tested object, the detection of heat, sound, light, electricity, magnetism, etc. caused by abnormal internal structure or defects of the material is used. The change of the reaction is to detect the material, parts and structure of the detected object, so as to judge the reliability, integrity, continuity and some physical properties of the detected object. Non-destructive testing involves many disciplines and technical fields such as physics, materials science, and electronic information technology.

At present, the conventional detection methods for basin insulators include ultrasonic detection, pulse current detection, X-ray detection, infrared thermal imaging detection and acoustic emission detection technology, etc. The traditional detection technology has achieved good results in the detection of basin insulators, but It is impossible for any single method to achieve highly sensitive detection of all pot insulators, especially for the detection of micro defects and fatigue damage. Insulator defect detection device.

Patent CN201910405768.X "GIS basin insulator detection device and method based on shell vibration signal" directly uses electronic circuit to detect the vibration signal of basin insulator. Compared with the intact basin insulator, the overall waveform of the faulty basin insulator The change trend is basically the same, but the waveform amplitude of the vibration signal of the basin-type insulator with defects is obviously reduced, thereby realizing the non-destructive testing of the basin-type insulator. The detection operation of this method is complicated, complex electronic circuits need to be built, and at the same time, misjudgment is easy to occur, the detection is inaccurate, and it is easily interfered by noise signals. There are also non-destructive testing methods based on ultrasonic signals, such as the patent CN201910509272.7 "A method and system for ultrasonic testing of internal defects of GIS epoxy insulation". This method directly uses an ultrasonic instrument to generate ultrasonic signals, and the ultrasonic testing system detects standard parts and obtains standard parts. The defect-free reflected wave waveform is obtained; the defect evaluation method is used to evaluate the bubbles and cracks in the epoxy insulation, and then, the basin-type insulator is continuously inspected along the moving path of the probe. The ultrasonic signal mode generated by it is single, and it cannot detect the surface defects and internal defects of the basin insulator at the same time.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the disadvantages of complex operation, high cost, low detection sensitivity and high risk of existing contact non-destructive testing, and to propose a basin-type insulator testing device based on laser-induced ultrasound.

The detection and detection device of the present invention includes a laser control system, a laser excitation system, a photoelectric detector, a basin-type insulator to be detected, an ultrasonic receiving system and a signal detection and processing system. The laser control system is connected with the laser excitation system, and the laser excitation system includes a pulsed laser, a laser collimation system and an optical lens, and is used to realize the excitation of the carbon nano-enhanced medium by the focused laser. The carbon nano-reinforced medium is uniformly coated on the surface of the basin-type insulator to be tested, and the coating thickness is less than 100 microns. The ultrasonic receiving system is connected to the output end of the signal detection and processing system. The photodetector receives the residual light of the pulsed laser emitted by the pulsed laser as the synchronization trigger signal of the signal detection and processing system, and starts the signal detection and processing system to synchronize with the laser excitation system and the ultrasonic receiving system. Work. The ultrasonic receiving system uses an air-coupled ultrasonic transducer to achieve non-contact reception of ultrasonic signals. The air-coupled ultrasonic transducer and the measured basin insulator are coupled through air, and the detection surface of the air-coupled ultrasonic transducer The insulator surface is vertical.

In the invention, the surface of the basin-type insulator to be detected is coated with a carbon nano-reinforced dielectric film. The laser excitation system includes a pulsed laser, a laser collimation system and an optical lens. The laser excitation system is used to realize the excitation of the carbon nano-reinforced medium by the focused laser. The laser beam emitted by the laser pulse laser coincides with the main axis of the laser collimator and the main axis of the optical lens, and the laser collimator expands the laser beam emitted by the pulse laser. And collimation, the optical lens is focused on the collimated laser beam, and its focus is focused on the carbon nano-enhanced dielectric film closely attached to the surface of the basin insulator. Due to the high photoacoustic conversion efficiency of the carbon nano-enhanced medium, under the thermoelastic mechanism, the carbon nano-enhanced medium film and the surface of the basin insulator generate broadband ultrasonic waves simultaneously. The ultrasonic wave propagates inside the basin insulator and is placed on the surface of the basin insulator to be tested. The air-coupled ultrasonic transducer receives ultrasonic signals; the detection surface of the air-coupled ultrasonic transducer is perpendicular to the surface of the basin-type insulator to be tested, and the ultrasonic signal is processed by the computer after the air-coupled ultrasonic transducer receives the ultrasonic signal. The process characterizes the defect state and reconstructs the thermoacoustic source distribution.

The described method for characterizing the defect state is described as follows: the received ultrasonic signal is firstly decomposed into different frequency ranges by using wavelet packet decomposition, and then a matrix composed of wavelet packet coefficients is used to characterize the signal state at a certain depth of the defect, Different defect states are characterized according to different signal states, so as to realize highly sensitive and fast nondestructive detection of basin insulator defects.

The described method for reconstructing the distribution of thermoacoustic sources is as follows:

When the laser is irradiated on the carbon nano-reinforced medium, the heat conduction equation of the carbon nano-reinforced medium is:

Among them, ρ is the density of the carbon nano-enhanced medium, C is the specific heat capacity of the carbon nano-enhanced medium, T is the temperature, κ is the thermal conductivity of the carbon nano-enhanced medium solid, Q is the laser energy absorbed by the carbon nano-enhanced medium, and t is the temperature variable;

The displacement equation generated by the ultrasonic signal is:

为梯度算子。Among them, λ is the Lame coefficient of the carbon nano-reinforced medium, μ is the shear modulus of the carbon nano-reinforced medium, u is the displacement vector generated in the basin insulator, β is the thermoelastic coupling coefficient, β=α(3λ+ 2μ), α is the thermal expansion coefficient,

is the gradient operator.

The distribution of thermal sound source βΔT is reconstructed jointly by equation (1) and equation (2).

The specific working process of the detection device of the present invention is as follows:

The laser control system is connected to the laser excitation system. The laser control system first outputs a synchronous trigger signal. After receiving the synchronous trigger signal, the laser excitation system starts the laser to output pulsed laser light. The output pulsed laser energy is 100-600mJ, and the pulse width is less than 20 microseconds. , the pulsed laser is collimated by a laser collimation system, and is directed directly on the carbon nano-enhanced medium closely attached to the surface of the basin insulator to be detected. The photodetector placed at the edge of the laser incident path receives the residual light of the pulsed laser emitted by the laser excitation system as the synchronous trigger signal of the signal detection and processing system, and starts the signal detection and processing system to work. Under the excitation of pulsed laser, the carbon nano-reinforced medium on the surface of the basin insulator to be tested generates high-intensity and high-frequency ultrasonic waves inside the basin type insulator due to the thermal bomb or ablation mechanism, and the ultrasonic wave propagates inside the basin type insulator. The air-coupled ultrasonic transducer receives the ultrasonic signal, and the signal detection and processing system pre-amplifies, filters and amplifies the ultrasonic signal received by the air-coupled ultrasonic transducer, and then collects the ultrasonic signal by the computer acquisition system. The ultrasonic signal of the characterizes the defect state and reconstructs the thermoacoustic source distribution.

The carbon nano-reinforced medium has the characteristics of high laser absorption rate, high thermal conductivity, low specific heat capacity and high thermal expansion coefficient, and the nanostructure of the carbon nano-reinforced medium makes the heat transfer rate of the carbon nano-reinforced medium to the surrounding medium extremely fast, and has a high heat transfer rate. Young's modulus, so the use of carbon nano-reinforced medium as a laser ultrasonic transducer can generate high-amplitude and high-frequency ultrasonic signals. The ultrasonic signal propagates in the basin insulator. When the basin insulator contains defects such as cracks, bubbles, impurities, etc., its acoustic impedance changes, and the defect state in the basin insulator is judged by the received echo signal, so as to realize the non-destructive testing of the basin insulator.

The ultrasonic signal generated by the invention has the characteristics of high amplitude, wide frequency, rich acoustic modes, etc., high detection accuracy and high detection efficiency, and has wide application prospects.

Description of drawings

1 is a schematic diagram of the system structure of the present invention;

In the figure, 1 laser control system, 2 laser excitation system, 3 photodetector, 4 basin insulator to be detected, 5 ultrasonic receiving system, 6 signal detection and processing system.

Detailed ways

The present invention is further described below with reference to the accompanying drawings and specific embodiments.

As shown in FIG. 1 , the detection device of the present invention includes a laser control system 1 , a laser excitation system 2 , a photodetector 3 , a basin-type insulator to be detected 4 , an ultrasonic receiving system 5 and a signal detection and processing system 6 . The laser control system 1 is connected to the laser excitation system 2, and the pulsed laser light emitted by the laser excitation system 2 is focused on the basin-type insulator 4 to be detected. The basin-type insulator 4 to be detected is coupled with the air-coupled ultrasonic transducer of the ultrasonic receiving system 5 through air; the ultrasonic receiving system 5 is connected to the signal detection and processing system 6 . The photodetector 3 is placed at the edge of the laser incident path, and is connected to the signal detection processing system 6 .

The detection surface of the air-coupled ultrasonic transducer is perpendicular to the surface of the basin insulator 4 to be tested.

The laser excitation system 2 includes a laser excitation system including a pulsed laser, a laser collimation system and an optical lens, which is used to realize the excitation of the carbon nano-reinforced medium by the focused laser. The laser beam emitted by the pulsed laser coincides with the main axis of the laser collimation system and the main axis of the optical lens. The laser collimation system expands and collimates the laser beam emitted by the pulsed laser, and then the optical lens focuses the collimated laser beam. Focus it on the carbon nano-enhanced medium uniformly coated on the surface of the basin insulator 4 to be tested.

The photodetector 3 starts the signal detection and processing system 6 to work synchronously with the laser excitation system 2 and the ultrasonic receiving system 5 by receiving the residual light of the pulsed laser emitted by the pulsed laser as the synchronization trigger signal of the signal detection and processing system 6 . The coating thickness of the carbon nano-reinforced medium is less than 100 microns. Due to the high laser ultrasonic conversion efficiency of the carbon nano-enhanced medium, a high-intensity and high-frequency ultrasonic signal is generated inside the basin insulator 4 to be tested. The air-coupled ultrasonic transducer receives the ultrasonic signal, and the detection surface of the air-coupled ultrasonic transducer is perpendicular to the surface of the basin-type insulator 4 to be tested. After the air-coupled ultrasonic transducer receives the ultrasonic signal, the computer analyzes the ultrasonic signal. Processed to characterize the defect state and reconstruct the thermoacoustic source distribution.

The concrete working process of the detection device of the present invention is as follows:

The laser control system 1 first outputs a synchronous trigger signal, and the laser excitation system 2 starts the laser to output pulsed laser after receiving the synchronous trigger signal. The output pulsed laser energy is 100-600mJ, and the pulse width is less than 20 microseconds. The pulsed laser passes through the optical lens and the laser beam. The straightening system is used for collimation and focusing on the carbon nano-enhanced medium closely attached to the surface of the basin insulator 4 to be detected. The photodetector 3 placed on the edge of the laser incident path receives the residual light of the pulsed laser emitted by the laser excitation system 2 as a synchronous trigger signal of the signal detection and processing system 6, and starts the signal detection and processing system 6, the laser excitation system 2 and the ultrasonic receiving system. 5. Synchronous work; the coating thickness of the carbon nano-enhanced medium on the surface of the basin insulator 4 to be detected is less than 100 microns. Under the excitation of the pulsed laser, due to the thermal elastic or ablation mechanism of the carbon nano-enhanced medium, high-strength and High-frequency ultrasonic waves propagate inside the basin insulator 4 to be tested. The detection surface of the air-coupled ultrasonic transducer is perpendicular to the surface of the basin-type insulator 4 to be tested. The air-coupled ultrasonic transducer placed on the surface of the basin-type insulator 4 to be tested receives ultrasonic signals. After the ultrasonic signal received by the ultrasonic transducer is pre-amplified, filtered and secondary amplified, the ultrasonic signal is collected by the computer acquisition system, and then the computer uses the collected ultrasonic signal to characterize the defect state and reconstruct the thermal sound source distribution.

The described method for characterizing the defect state is described as follows: first, the collected ultrasonic signal is decomposed into different frequency ranges by using wavelet packet decomposition, and then a matrix composed of wavelet packet coefficients is used to characterize the signal state at a certain depth of the defect. The signal states represent different defect states and realize non-destructive testing of the basin insulator 4 to be tested.

The method for reconstructing the distribution of the reconstructed thermoacoustic source is as follows:

When the laser is irradiated on the carbon nano-reinforced medium, the thermal conduction process of the carbon nano-reinforced medium can be expressed as:

Among them, ρ is the density of the carbon nano-enhanced medium, C is the specific heat capacity of the carbon nano-enhanced medium, T is the temperature, κ is the thermal conductivity of the carbon nano-enhanced medium solid, Q is the laser energy absorbed by the carbon nano-enhanced medium, and t is the temperature variable. Due to the very short laser pulse width, the thermal stress generated by the thermoelastic mechanism or the ablation mechanism results in an uneven temperature distribution, thereby generating a displacement field in the basin insulator 4 to be tested:

为梯度算子。Among them, λ is the Lame coefficient of the carbon nano-reinforced medium, μ is the shear modulus of the carbon nano-reinforced medium, u is the displacement vector generated in the basin insulator, β is the thermoelastic coupling coefficient, β=α(3λ+ 2μ), α is the thermal expansion coefficient,

is the gradient operator.

The basin insulator 4 to be tested is a solid medium, and ultrasonic propagation is a body wave, so the displacement field can be decomposed into the longitudinal wave wave equation (3) and the shear wave wave equation (4):

横波波速

为拉普拉斯算符，Φ为纵波的势函数Ψ为横波的势函数，t为时间，下标L表示纵波，S表示横波。Among them, the longitudinal wave velocity

Shear wave velocity

is the Laplace operator, Φ is the potential function of the longitudinal wave, Ψ is the potential function of the shear wave, t is the time, the subscript L represents the longitudinal wave, and S represents the shear wave.

分布。Combined with equation (5) and equation (6), the thermal sound source generated in the basin insulator 4 to be detected is solved by equation (3) and equation (4)

distributed.

As will be appreciated by those skilled in the art, the embodiments of the present application may be provided as a method, a system, or a computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) having computer-usable program code embodied therein.

The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present application. It will be understood that each flow and/or block in the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to the processor of a general purpose computer, special purpose computer, embedded processor or other programmable data processing device to produce a machine such that the instructions executed by the processor of the computer or other programmable data processing device produce Means for implementing the functions specified in a flow or flow of a flowchart and/or a block or blocks of a block diagram.

These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory result in an article of manufacture comprising instruction means, the instructions The apparatus implements the functions specified in the flow or flow of the flowcharts and/or the block or blocks of the block diagrams.

These computer program instructions can also be loaded on a computer or other programmable data processing device to cause a series of operational steps to be performed on the computer or other programmable device to produce a computer-implemented process such that The instructions provide steps for implementing the functions specified in the flow or blocks of the flowcharts and/or the block or blocks of the block diagrams.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: the present invention can still be Modifications or equivalent replacements are made to the specific embodiments of the present invention, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention shall be included within the protection scope of the claims of the present invention.

Claims (6)

1. A basin-type insulator detection device based on laser-induced ultrasound, characterized in that: the detection device comprises a laser control system (1), a laser excitation system (2), a photodetector (3), a basin-type to be detected The insulator (4), the ultrasonic receiving system (5) and the signal detection and processing system (6), the laser control system (1) is connected to the laser excitation system (2), and the pulsed laser emitted by the laser excitation system (2) is focused on the basin to be detected. On the insulator (4), the basin-type insulator (4) to be detected is coupled with the air-coupled ultrasonic transducer of the ultrasonic receiving system (5) through air; the ultrasonic receiving system (5) receives the ultrasonic signal and is processed by the signal detection and processing system (6). ) to process the ultrasonic signal; the photodetector (3) is placed on the edge of the laser incident path, and is connected with the signal detection and processing system (6) to provide a synchronous trigger signal for the detection signal processing system. 2. The detection device according to claim 1, characterized in that: the laser excitation system (2) comprises a pulsed laser, a laser collimation system and an optical lens; the laser excitation system (2) is used to realize focusing laser on carbon The excitation of the nano-enhanced medium, the laser beam emitted by the pulsed laser coincides with the main axis of the laser collimation system and the main axis of the optical lens, the laser collimation system expands and collimates the laser beam emitted by the pulsed laser, and the optical lens aligns the collimated The laser beam is focused, and its focus is focused on the carbon nano-reinforced medium uniformly coated on the surface of the basin-type insulator (4) to be detected. 3. The detection device according to claim 1 is characterized in that: the photodetector (3) is used as the synchronous trigger signal of the signal detection processing system (6) by receiving the residual light of the pulsed laser emitted by the pulsed laser, and starts The signal detection and processing system (6) works synchronously with the laser excitation system (2) and the ultrasonic receiving system (5). 4. The detection device according to claim 1, characterized in that: the ultrasonic signal propagates inside the basin-type insulator (4) to be detected, and the air-coupled ultrasonic transducer placed on the surface of the basin-type insulator (4) to be detected The ultrasonic signal is received by the air-coupled ultrasonic transducer; the detection surface of the air-coupled ultrasonic transducer is perpendicular to the surface of the basin-type insulator (4) to be tested. After the air-coupled ultrasonic transducer receives the ultrasonic signal, the ultrasonic signal is processed by the computer to characterize the defect. state and reconstruct the thermoacoustic source distribution. 5. The detection device according to claim 4, wherein the method for characterizing the defect state is to decompose the received ultrasonic signal into different frequency ranges by using wavelet packet decomposition, and use a matrix composed of wavelet packet coefficients. Characterize the signal state at a certain depth of the defect, and characterize different defect states according to different signal states, so as to realize the non-destructive inspection of the basin insulator to be inspected. 6. The detection device according to claim 4, wherein the method for reconstructing the distribution of thermal sound sources is as follows: When the laser is irradiated on the carbon nano-reinforced medium, the heat conduction equation of the carbon nano-reinforced medium is:

Among them, ρ is the density of the carbon nano-enhanced medium, C is the specific heat capacity of the carbon nano-enhanced medium, T is the temperature, κ is the thermal conductivity of the carbon nano-enhanced medium solid, Q is the laser energy absorbed by the carbon nano-enhanced medium, and t is the temperature variable; The displacement equation generated by the ultrasonic signal is:

Among them, λ is the Lame coefficient of the carbon nano-reinforced medium, μ is the shear modulus of the carbon nano-reinforced medium, u is the displacement vector generated in the basin insulator, β is the thermoelastic coupling coefficient, β=α(3λ+ 2μ), α is the thermal expansion coefficient,

is the gradient operator; The distribution of thermal sound source βΔT is reconstructed jointly by equation (1) and equation (2).

Images