A high-voltage cable lead seal ultrasonic phased array full-focusing imaging detection method, device and computer program product

Abstract

The application discloses a high-voltage cable lead seal ultrasonic phased array full focusing imaging detection method and device and a computer program product. The detection system parameters and the high-voltage cable lead seal parameters are acquired, the propagation time of ultrasonic waves in the curved surface interface is calculated based on the double-layer medium full focusing imaging principle and the Fermat principle, a point spread function calculation model considering the geometric attenuation, the unit directivity and the interface transmission loss is established, the main lobe width and the side lobe level are extracted from the model as key characteristic parameters, the optimal probe spacing is determined by taking the side lobe level being less than or equal to a preset threshold as a constraint condition and taking the minimization of the main lobe width as an optimization target, the full matrix data are collected by adopting the optimal probe spacing and full focusing image reconstruction is carried out, and the internal defects of the high-voltage cable lead seal are identified and positioned. The application solves the problems of imaging artifacts and resolution loss caused by the cylindrical curved surface structure of the high-voltage cable lead seal, realizes scientific and quantitative optimization of the probe spacing, and has high consistency and reliability of the detection result.

Description

Technical Field

[0001] This invention relates to the field of power equipment monitoring technology, specifically to a method, device, and computer program product for ultrasonic phased array full-focusing imaging detection of high-voltage cable lead seals. Background Technology

[0002] High-voltage cable lead seals are core sealing and protective components for cable terminals and intermediate joints, functioning to prevent external moisture, humidity, and corrosive media from penetrating the cable insulation layer. Once the lead seal fails, it can easily lead to insulation breakdown due to moisture; statistics show that approximately 30% of high-voltage cable faults originate from this problem. During the casting process of the lead seal, internal defects such as porosity, shrinkage cavities, and slag inclusions are prone to occur; during on-site installation, process defects such as welding cracks and incomplete welds may also occur. hot In long-term operation under multi-field coupling, the aforementioned defects will continue to expand, eventually leading to the loss of sealing function. Therefore, early detection of minute defects inside the lead seal using high-precision non-destructive testing methods is crucial for ensuring the safe and stable operation of the power grid.

[0003] Ultrasonic phased array total focusing (TFM) is based on full matrix acquisition (FMC) technology, acquiring all emitted signals. The receiving unit receives the A-scan signal and performs point-by-point synthesis and focusing on each pixel within the detection area, theoretically providing uniform high-resolution imaging of the entire detection area, and is recognized as the "gold standard" of ultrasonic phased array imaging. However, high-voltage cable seals have a typical cylindrical curved surface structure. Under actual detection conditions, the distance between the probe and the seal surface will significantly change the propagation path and focusing characteristics of the ultrasonic waves. If the probe spacing is not set properly, it will introduce severe phase distortion and energy dispersion, resulting in strong artifacts and resolution loss in the image, making it difficult to accurately identify tiny pores with a diameter of less than 0.5 mm and microcracks with a length of less than 1 mm, and even leading to missed detections and misjudgments.

[0004] Existing ultrasonic phased array testing technologies for curved parts mainly rely on custom-made acoustic wedges or experience-based adjustment of probe spacing. Custom-made wedges require individual design and fabrication for lead seals with different curvatures, which is not only costly and lacks versatility, but also makes it difficult to guarantee the coupling quality between the wedges and the lead seal surface. On the other hand, experience-based probe spacing adjustment relies entirely on the operator's subjective judgment, lacking scientific quantitative basis, resulting in inconsistent and unreliable test results that fail to meet engineering requirements. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method, device and computer program product for ultrasonic phased array full-focus imaging detection of high-voltage cable lead seals, so as to overcome the technical bottleneck of ultrasonic detection of curved surface structures of high-voltage cable lead seals and improve the accuracy and reliability of detection.

[0006] To solve the above-mentioned technical problems, the present invention provides a method for ultrasonic phased array full-focusing imaging detection of high-voltage cable lead seals, comprising: Step S1: Obtain the detection system parameters and the high-voltage cable lead seal parameters. The detection system parameters include the ultrasonic phased array probe parameters, the acoustic parameters of the coupling medium and the lead seal material, and the high-voltage cable lead seal parameters include the lead seal surface profile function and the location range of the defect to be detected. Step S2: Based on the imaging principle of dual-layer medium total focusing method, Fermat's principle is used to calculate the propagation time of ultrasonic waves from the probe to the target pixel and back to the probe. Step S3: Based on the propagation time, establish a point spread function calculation model that comprehensively considers geometric attenuation, unit directivity, and interface transmission loss, and calculate the point spread function under different probe spacings; Step S4: Extract the main lobe width and side lobe level from the calculated point spread function as key feature parameters; Step S5: Determine the optimal probe spacing with the sidelobe level being less than or equal to a preset threshold as a constraint and the main lobe width being minimized as the optimization objective. Step S6: Collect full matrix data using the optimal probe spacing, and perform full-focus image reconstruction on the full matrix data to identify and locate internal defects in the high-voltage cable lead seal.

[0007] Preferably, the ultrasonic phased array probe parameters include the number of elements, center frequency, element spacing, element length, array aperture, and bandwidth; the coupling medium acoustic parameters include longitudinal wave velocity and density; the lead seal material acoustic parameters include longitudinal wave velocity, transverse wave velocity, and density; and the lead seal surface profile function is determined according to the geometry of the lead seal as either a convex or concave cylindrical surface function.

[0008] Preferably, in step S2, the calculation of the ultrasonic wave propagation time using Fermat's principle specifically includes: The lead seal surface of the high-voltage cable is discretized into intervals. The set of points, in which The ultrasonic wavelength in the coupling medium; In the set of discrete points, the propagation time is calculated by solving the equation in which the first derivative of the propagation time with respect to the x-coordinate of the transmission point is zero, thus finding the transmission point that satisfies Fermat's principle.

[0009] Preferably, in step S3, the point spread function calculation model is established in the following manner: For point targets located inside the lead seal, a 4-cycle sinusoidal pulse signal modulated by the Hanning window is generated as the excitation signal. The excitation signal is delayed using the propagation time to obtain the original signal response of each transmit-receive unit pair; The original signal response is corrected by comprehensively considering geometric attenuation, unit directivity, and interface transmission loss; The point spread function of the point target is obtained by superimposing the corrected signals of all transmit-receive unit pairs.

[0010] Preferably, the correction of the original signal response that comprehensively considers geometric attenuation, unit directivity, and interface transmission loss is specifically performed through the geometric attenuation coefficient of the transmission path. Geometric attenuation coefficient of the receiving path , Directivity coefficient of the transmitting unit , Directivity coefficient of the receiving unit Interface transmission coefficient of the transmission path Interface transmission coefficient with receiving path accomplish: Geometric attenuation coefficient of the transmission path and the geometric attenuation coefficient of the receiving path They are respectively:

[0011]

[0012] in, This represents the distance from the transmitting unit to the transmission point of the ultrasonic wave at the couplant-lead seal interface. This represents the distance from the transmission point of the ultrasonic wave to the target pixel. This represents the distance from the target pixel to the transmission point of the ultrasonic wave. This represents the distance from the transmission point to the receiving unit of the ultrasonic wave. Directivity coefficient of the transmitting unit and the directivity coefficient of the receiving unit They are respectively:

[0013]

[0014] in, The length of the piezoelectric element; The center frequency; The longitudinal wave velocity in the coupling medium; The angle of incidence of the ultrasonic wave in the coupling medium along the transmission path; The angle of refraction of the ultrasonic wave in the coupling medium during the receiving path; Interfacial transmission coefficient of the emission path Interface transmission coefficient with receiving path They are respectively:

[0015] in, and These are the densities of the coupling medium and the lead seal, respectively. The longitudinal wave velocity within the lead seal; The angle of refraction of the ultrasonic wave within the lead seal in the transmission path; The angle of incidence of the ultrasonic wave in the lead seal is the angle of incidence of the ultrasonic wave in the receiving path.

[0016] Preferably, in step S4, the main lobe width is calculated using the -6dB descent method, and the side lobe level is calculated using the peak search method; specifically including: Extract the lateral distribution of the point spread function at the depth of the point target; Find the maximum value of the lateral distribution, and determine two points on both sides of the maximum value where the amplitude drops by 6dB. Use the distance between these two points as the main lobe width. After excluding the main lobe region in the lateral distribution, the largest side lobe peak is found, and the decibel value of the ratio of the side lobe peak to the maximum value is taken as the side lobe level.

[0017] Preferably, in step S5, the preset threshold is -20dB, and the step of determining the optimal probe spacing includes: Traverse the range of probe spacing to be tested, and calculate the point spread function, main lobe width, and side lobe level for each probe spacing according to the preset step size; Select probe spacings with sidelobe levels less than or equal to -20dB; The probe spacing with the smallest main lobe width is selected from the filtered probe spacings as the optimal probe spacing.

[0018] Preferably, in step S6, after bandpass filtering and denoising preprocessing of the acquired full matrix data, the full-focusing image reconstruction is performed; and the reconstructed image is quantitatively evaluated using signal-to-artifact ratio SAR and array performance index API, wherein:

[0019] in, The maximum amplitude within the signal region; is the root mean square value of the amplitude within the artifact region; The area of ​​pixels in the image whose amplitude is within 6 dB below the maximum value; The wavelength of the ultrasonic wave inside the lead seal.

[0020] The present invention also provides an ultrasonic phased array full-focusing imaging detection device for high-voltage cable lead seals, comprising: One or more processors; Memory; One or more applications, wherein the one or more applications are stored in the memory and configured to be executed by the one or more processors, the one or more applications being configured to perform the high-voltage cable lead seal ultrasonic phased array full-focus imaging detection method.

[0021] The present invention also provides a computer program product, including computer instructions, which instruct a computer device to perform the operation corresponding to the ultrasonic phased array full-focus imaging detection method for high-voltage cable lead seals.

[0022] The beneficial effects of this invention are as follows: By establishing a precise point spread function calculation model, this invention fundamentally solves the technical problem of image artifacts and resolution loss in ultrasonic phased array full-focusing imaging caused by the cylindrical curved surface structure of high-voltage cable lead seals. This method comprehensively considers the influence of geometric attenuation, element directivity, and interface transmission loss on imaging quality, and can accurately predict the point spread function response under different probe spacings. By using a sidelobe level less than or equal to a preset threshold as a constraint and minimizing the main lobe width as the optimization objective, it achieves scientific quantitative optimization of the probe spacing, enabling the clear identification of micropores with a diameter less than 0.5 mm and microcracks with a length less than 1 mm, effectively avoiding missed detections and misjudgments.

[0023] This invention elevates the determination of probe spacing from relying on operator subjective experience to objective calculation based on a physical model, fundamentally ensuring the consistency and reliability of test results and fully meeting the stringent requirements of standardized on-site testing in power grids. Furthermore, this method eliminates the need for custom-designed acoustic wedges for lead seals with different curvatures; it only requires inputting the lead seal surface profile function, material acoustic parameters, and probe parameters to automatically solve for the optimal probe spacing. It boasts strong versatility and low operating costs.

[0024] Regarding the detection process, the optimized calculations of this invention are completed in one go before detection, eliminating the need for repeated on-site adjustments. Combined with full-matrix capture and full-focus image reconstruction, detection efficiency is significantly improved. Quantitative evaluation of the reconstructed image using signal-to-artifact ratio and array performance indicators provides an objective basis for defect identification, further enhancing the reliability of the detection results. Furthermore, this invention's method does not rely on specific hardware, is adaptable to various ultrasonic phased array systems, and can be extended to two-dimensional arrays to achieve three-dimensional imaging, providing strong technical support for the comprehensive health characterization of high-voltage cable lead seals. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic flowchart of an ultrasonic phased array full-focusing imaging detection method for high-voltage cable lead seals according to Embodiment 1 of the present invention.

[0027] Figure 2 This is a schematic diagram illustrating the calculation process of the propagation time of the two-layer medium TFM in an embodiment of the present invention.

[0028] Figure 3 This is a schematic diagram of the point spread function calculation and feature extraction process in an embodiment of the present invention. Detailed Implementation

[0029] The following description of the embodiments is taken with reference to the accompanying drawings, which illustrate specific embodiments in which the invention can be implemented.

[0030] Please refer to Figure 1 As shown, Embodiment 1 of the present invention provides a method for ultrasonic phased array full-focusing imaging detection of high-voltage cable lead seals, comprising: Step S1: Obtain the detection system parameters and the high-voltage cable lead seal parameters. The detection system parameters include the ultrasonic phased array probe parameters, the acoustic parameters of the coupling medium and the lead seal material, and the high-voltage cable lead seal parameters include the lead seal surface profile function and the location range of the defect to be detected. Step S2: Based on the imaging principle of dual-layer medium total focusing method, Fermat's principle is used to calculate the propagation time of ultrasonic waves from the probe to the target pixel and back to the probe. Step S3: Based on the propagation time, establish a point spread function calculation model that comprehensively considers geometric attenuation, unit directivity, and interface transmission loss, and calculate the point spread function under different probe spacings; Step S4: Extract the main lobe width and side lobe level from the calculated point spread function as key feature parameters; Step S5: Determine the optimal probe spacing with the sidelobe level being less than or equal to a preset threshold as a constraint and the main lobe width being minimized as the optimization objective. Step S6: Collect full matrix data using the optimal probe spacing, and perform full-focus image reconstruction on the full matrix data to identify and locate internal defects in the high-voltage cable lead seal.

[0031] As can be seen from the above steps, the embodiments of the present invention are based on quantitative analysis of point spread function, which can automatically calculate the optimal probe spacing before detection, effectively suppress image artifacts caused by curved surface structures, improve imaging resolution, and ensure accurate identification of minute defects inside the lead seal of high-voltage cables.

[0032] The technical principle of this invention lies in the fact that the curved surface structure of the high-voltage cable lead seal acts as an acoustic lens in ultrasonic testing, altering the propagation direction and focusing characteristics of ultrasonic waves. When the probe spacing does not match the curvature of the surface, it causes defocusing of the ultrasonic waves inside the lead seal, manifested as an increase in the main lobe width and side lobe level of the point spread function, leading to decreased image resolution and increased artifacts. This invention establishes a precise point spread function calculation model to quantitatively analyze the imaging quality under different probe spacings, thereby finding the optimal probe spacing that minimizes the main lobe width of the point spread function and keeps the side lobe level below an acceptable threshold, achieving the best imaging effect.

[0033] Specifically, in this embodiment of the invention, step S1 is used to obtain the detection system parameters and the high-voltage cable lead seal parameters. The detection system parameters include the ultrasonic phased array probe parameters, the acoustic parameters of the coupling medium and the lead seal material, and the high-voltage cable lead seal parameters include the lead seal surface profile function and the location range of the defect to be detected. Further, the ultrasonic phased array probe parameters include the number of elements, center frequency, element spacing, element length, array aperture, and bandwidth; the coupling medium acoustic parameters include the longitudinal wave velocity and density; and the lead seal material acoustic parameters include the longitudinal wave velocity, transverse wave velocity, and density. The lead seal surface profile function is determined based on the actual geometry of the lead seal. For common cylindrical curved lead seals, it can be represented as either an outwardly convex type or an inwardly concave type. The location range of the defect to be detected is determined based on the thickness of the lead seal and the areas prone to defects.

[0034] Step S2 is fundamental to achieving high-quality TFM imaging, and its core lies in accurately locating the transmission point of ultrasound at the coupling agent-lead seal interface. Since the lead seal surface is curved, the propagation path of the ultrasound from the probe to the target pixel is not a straight line, but rather refracts at the interface. According to Fermat's principle, ultrasound propagates along the path with the shortest propagation time; therefore, the location of the transmission point needs to be determined by solving an equation where the first derivative of the propagation time with respect to the x-coordinate of the transmission point is zero.

[0035] Please combine Figure 2 As shown, for an N-element linear ultrasonic phased array probe, let the transmitting element be... The receiving unit is The target pixel in the region of interest is The amplitude of that pixel is obtained by superimposing the A-scan signals of all transmit-receive unit pairs according to the propagation time delay:

[0036] in, For the full matrix capture data, the first The first launch unit, the first A scan signal corresponding to each receiving unit; For ultrasonic waves from the transmitting unit propagate to target pixel Time; For ultrasonic waves from the target pixel propagated to the receiving unit The time.

[0037] Because ultrasound travels at different speeds in the coupling medium and the lead seal, refraction occurs at the interface, and the propagation time can be expressed as:

[0038]

[0039] in, The longitudinal wave velocity in the coupling medium; The longitudinal wave velocity within the lead seal; For ultrasonic waves from the transmitting unit Transmission point at the coupling agent-lead seal interface The distance; For ultrasonic waves to travel from the transmission point To the target pixel The distance; For ultrasonic waves from the target pixel Transmission point at the coupling agent-lead seal interface The distance; For ultrasonic waves to travel from the transmission point to receiving unit The distance; This is the surface profile function for the lead seal of a high-voltage cable.

[0040] According to Fermat's principle, ultrasound waves propagate along the path with the shortest propagation time, therefore the transmission point... The propagation time should have a first derivative with respect to the x-coordinate of the transmission point that is zero.

[0041]

[0042] Substituting the above propagation time formula into Fermat's principle equation, we obtain the equation satisfied by the transmission point:

[0043]

[0044] in, For the transmitting unit The x-coordinate; For receiving unit The x-coordinate; For surface profile function in The first derivative at that point.

[0045] The above transmission point equation is solved using a grid search method, discretizing the lead seal surface into points with intervals of [missing information]. The point set (where The method involves finding the transmission point that satisfies Fermat's principle among discrete points (where the wavelength of the ultrasonic wave in the coupling medium is 1), and then calculating the accurate propagation time. This method offers high accuracy, is easy to implement, and can meet the requirements of real-time detection.

[0046] The point spread function (PSF) describes the response of an imaging system to an ideal point target and is a core indicator for evaluating the resolution and artifact level of an imaging system. The PSF calculation model established in step S3 of this invention comprehensively considers multiple factors affecting ultrasound imaging quality, including geometric attenuation, element directivity, and interface transmission loss, and can accurately predict imaging quality under different probe spacings.

[0047] Please combine Figure 3 As shown, for point targets located inside the lead seal The calculation process of its point spread function is as follows: (1) Applying the propagation time calculation method in step S2, the propagation time from all transmitting units is obtained. Target transmission time and from point targets To all receiving units transmission time ; (2) Generate a 4-cycle sinusoidal pulse signal modulated by the Hanning window as the excitation signal for the system:

[0048] in, The center frequency of the ultrasonic phased array probe is given. A 4-cycle sinusoidal pulse signal modulated with a Hanning window can effectively simulate the transmission signal characteristics of an actual ultrasonic probe.

[0049] (3) The excitation signal is delayed by the propagation time to obtain the original signal response of each transmit-receive unit pair:

[0050] (4) Considering the effects of geometric attenuation, element directivity, and interface transmission loss on the signal, the original signal response is corrected:

[0051] in, and These are the geometric attenuation coefficients for the transmission and reception paths, respectively; and These are the directivity coefficients for the transmitting and receiving units, respectively; and These are the interface transmission coefficients for the transmission and reception paths, respectively.

[0052] The geometric attenuation coefficient describes the spherical diffusion loss of ultrasound during propagation:

[0053]

[0054] The element directivity coefficient describes how the radiation and reception characteristics of a piezoelectric element change with angle:

[0055]

[0056] in, The length of the piezoelectric element; The angle of incidence of the ultrasonic wave in the coupling medium along the transmission path; The angle of refraction of the ultrasonic wave in the coupling medium during the receiving path; This is the Singer function.

[0057] The interfacial transmission coefficient describes the energy transmittance of ultrasound at the interface between two media:

[0058] in, and These are the densities of the coupling medium and the lead seal, respectively. The angle of refraction of the ultrasonic wave within the lead seal in the transmission path; Let be the angle of incidence of the ultrasonic wave within the lead seal in the receiving path. According to Snell's law, .

[0059] (5) The correction signals of all transmit-receive unit pairs are superimposed to obtain the point target. Point spread function:

[0060] in, and From the transmitting unit To pixel and from pixels to receiving unit The spread time.

[0061] Next, in step S4, two key feature parameters, the main lobe width (MLW) and the side lobe level (SLL), are extracted from the point spread function.

[0062] The main lobe width determines the lateral resolution of the imaging system; the smaller the main lobe width, the higher the resolution. The side lobe level determines the artifact level of the imaging system; the lower the side lobe level, the fewer the artifacts. This invention uses the -6dB descent method to calculate the main lobe width and the peak search method to calculate the side lobe level. These two methods are standard methods for evaluating the point spread function in the field of ultrasound imaging.

[0063] At the depth of the point target At this point, extract the lateral distribution of the spread function. , recorded as .

[0064] The main lobe width was calculated using the -6dB descent method: [Find...] maximum value Then find the maximum value on both sides. two points and The width of the main lobe is the distance between these two points:

[0065] The sidelobe level is calculated using the peak search method: in After excluding the main lobe region, find the largest side lobe peak. The sidelobe level is the difference between the peak value and the maximum value of the main lobe.

[0066] Step S5 uses the sidelobe level ≤ -20dB as a constraint and the minimization of the main lobe width as the optimization objective to determine the optimal probe spacing.

[0067] The optimization strategy employed in this invention is to first ensure that the image artifact level is within an acceptable range, and then pursue the highest possible resolution based on this. According to industrial inspection standards, when the sidelobe level is below -20dB, image artifacts will not affect defect identification. Therefore, this invention sets the preset threshold for the sidelobe level to -20dB, first filters out all probe spacings that meet this constraint, and then selects the spacing with the smallest main lobe width as the optimal probe spacing.

[0068] The specific steps are as follows: (1) Traverse all probe spacings to be tested Step size is Calculate the point spread function and its characteristic parameters for each probe spacing. and ; (2) Filter out those that meet the requirements probe spacing set ; (3) Select the probe spacing with the smallest main lobe width from set H as the optimal probe spacing. :

[0069] The optimal probe spacing may differ for defects with different curvatures and depths. This invention can calculate the optimal probe spacing for each defect depth individually, or it can calculate a comprehensive optimal probe spacing to meet the imaging requirements of the entire detection area.

[0070] After determining the optimal probe spacing, step S6 uses the determined optimal probe spacing to collect full matrix data, perform TFM image reconstruction, and identify and locate internal defects in the lead seal of the high-voltage cable.

[0071] Specifically, the ultrasonic phased array probes are first adjusted to the optimal probe spacing position. Then, full-matrix acquisition data is collected. After preprocessing the data, such as bandpass filtering and noise reduction, the TFM algorithm is applied for image reconstruction. Finally, the reconstructed images are analyzed to identify and locate defects inside the lead seal.

[0072] To quantitatively assess imaging quality, two evaluation metrics are used: signal-to-artifact ratio (SAR) and array performance index (API).

[0073] in, The maximum amplitude within the signal region; is the root mean square value of the amplitude within the artifact region; The area of ​​pixels in the image whose amplitude is within 6 dB below the maximum value; The wavelength of the ultrasonic wave inside the lead seal.

[0074] A higher SAR value indicates a better signal-to-noise ratio and fewer artifacts in the image; a lower API value indicates a higher image resolution.

[0075] The following example, using ultrasonic phased array TFM imaging for the lead seal of a 110kV high-voltage cable, illustrates the implementation process of this invention: First, determine the parameters of the detection system and the high-voltage cable seal. A 64-element linear ultrasonic phased array probe is used, with a center frequency of... unit spacing , unit length Array aperture The bandwidth is 83%. The coupling medium uses medical-grade ultrasound coupling agent, and its longitudinal wave velocity... ,density The seal material is pure lead, and its longitudinal wave velocity is... ,density The surface profile of a high-voltage cable lead seal is a cylindrical curved surface. For a convex lead seal, its surface profile function is: For a concave lead seal, its surface profile function is: ,in In this embodiment, the radius of curvature of the lead seal is... The defects to be detected are located inside the lead seal at depths of 5mm, 10mm, and 15mm.

[0076] Next, based on the principle of two-layer dielectric total focusing imaging, the propagation time of the ultrasonic wave is calculated. The lead seal surface is discretized into segments with intervals of [missing information]. The set of points, in which Therefore, the discrete interval is 0.0592 mm. The transmission point equation is solved using a grid search method to find transmission points that satisfy Fermat's principle among discrete surface points, and then the propagation time of each transmitter-receiver unit to the target pixel is calculated.

[0077] Then, a point spread function calculation model was established. The probe spacing test range was 20mm to 130mm, with a step size of 10mm. For each probe spacing, the point spread function of point targets at depths of 5mm, 10mm, and 15mm was calculated. The specific process was as follows: First, the propagation time from each element to the point target was calculated. Then, a 4-cycle 5MHz sinusoidal pulse signal modulated by a Hanning window was generated. The original signal response was obtained by delaying the pulse signal using the propagation time. Next, the geometric attenuation, element directivity, and interface transmission loss coefficient were calculated to correct the signal. Finally, the corrected signals of all transmit-receive element pairs were superimposed to obtain the point spread function at that probe spacing.

[0078] Next, the main lobe width and side lobe levels are extracted from the point spread function. The lateral distribution of the PSF is extracted at the depth of the point target, the main lobe width is calculated using the -6dB descent method, and the side lobe levels are calculated using the peak search method.

[0079] Next, the optimal probe spacing was determined. The preset sidelobe level threshold was -20dB, and all probes satisfying SLL≤ were selected. The probe spacing is set to 20dB, and then the spacing with the smallest main lobe width is selected as the optimal probe spacing. For the convex lead seal in this embodiment, the optimal probe spacing is 20mm when the defect depth is 10mm; for the concave lead seal, the optimal probe spacing is 70mm when the defect depth is 10mm.

[0080] Finally, the optimal probe spacing was used for detection. The probes were adjusted to the optimal spacing position, and medical ultrasound coupling agent was evenly applied to ensure good coupling. Full-matrix acquisition data was collected, and after 3-7MHz bandpass filtering preprocessing, the TFM algorithm was applied for image reconstruction. To quantitatively evaluate imaging quality, two evaluation metrics were used: signal-to-artifact ratio (SAR) and array performance index (API). The wavelength of the ultrasonic wave inside the lead seal.

[0081] Experimental results show that when using the optimal probe spacing determined by the method of this invention, the SAR of the concave lead seal TFM image can reach a maximum of 33dB, which is about 45 times lower than the detection results using an inappropriate probe spacing (40mm). The API of the convex lead seal TFM image can be reduced to a minimum of 2.2, which is about 3.1 times higher than the detection results using a 130mm probe spacing. This invention can clearly identify micropores with a diameter of 0.5mm and microcracks with a length of 1mm, with a defect location error of less than 0.2mm.

[0082] Corresponding to the ultrasonic phased array full-focusing imaging detection method for high-voltage cable lead seals in Embodiment 1 of the present invention, Embodiment 2 of the present invention also provides an ultrasonic phased array full-focusing imaging detection device for high-voltage cable lead seals, comprising: One or more processors; Memory; One or more applications, wherein the one or more applications are stored in the memory and configured to be executed by the one or more processors, the one or more applications being configured to perform the high-voltage cable lead seal ultrasonic phased array full-focus imaging detection method.

[0083] Corresponding to the ultrasonic phased array full-focusing imaging detection method for high-voltage cable lead seals in Embodiment 1 of the present invention, Embodiment 3 of the present invention also provides a computer program product, including computer instructions, which instruct computer equipment to perform the operation corresponding to the ultrasonic phased array full-focusing imaging detection method for high-voltage cable lead seals.

[0084] Preferably, the processor can be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor, or the processor can be any conventional processor. The processor is the control center of the device, connecting various parts of the device through various interfaces and lines.

[0085] The memory mainly includes a program storage area and a data storage area. The program storage area can store the operating system, applications required for at least one function, etc., while the data storage area can store related data, etc. Furthermore, the memory can be a high-speed random access memory, or a non-volatile memory, such as a plug-in hard drive, a SmartMedia Card (SMC), a Secure Digital (SD) card, and a Flash Card, or other volatile solid-state storage devices.

[0086] It should be noted that the above-mentioned devices may include, but are not limited to, processors and memory, as will be understood by those skilled in the art.

[0087] For the working principle and process of the above embodiments, please refer to the description of Embodiment 1 of the present invention, which will not be repeated here.

[0088] Compared with existing technologies, this invention has the following significant advantages: By establishing a precise point spread function calculation model, this invention fundamentally solves the technical problem of image artifacts and resolution loss in ultrasonic phased array full-focusing imaging caused by the cylindrical curved surface structure of high-voltage cable lead seals. This method comprehensively considers the influence of geometric attenuation, element directivity, and interface transmission loss on imaging quality, and can accurately predict the point spread function response under different probe spacings. By using a sidelobe level less than or equal to a preset threshold as a constraint and minimizing the main lobe width as the optimization objective, it achieves scientific quantitative optimization of the probe spacing, enabling the clear identification of micropores with a diameter less than 0.5 mm and microcracks with a length less than 1 mm, effectively avoiding missed detections and misjudgments.

[0089] This invention elevates the determination of probe spacing from relying on operator subjective experience to objective calculation based on a physical model, fundamentally ensuring the consistency and reliability of test results and fully meeting the stringent requirements of standardized on-site testing in power grids. Furthermore, this method eliminates the need for custom-designed acoustic wedges for lead seals with different curvatures; it only requires inputting the lead seal surface profile function, material acoustic parameters, and probe parameters to automatically solve for the optimal probe spacing. It boasts strong versatility and low operating costs.

[0090] Regarding the detection process, the optimized calculations of this invention are completed in one go before detection, eliminating the need for repeated on-site adjustments. Combined with full-matrix capture and full-focus image reconstruction, detection efficiency is significantly improved. Quantitative evaluation of the reconstructed image using signal-to-artifact ratio and array performance indicators provides an objective basis for defect identification, further enhancing the reliability of the detection results. Furthermore, this invention's method does not rely on specific hardware, is adaptable to various ultrasonic phased array systems, and can be extended to two-dimensional arrays to achieve three-dimensional imaging, providing strong technical support for the comprehensive health characterization of high-voltage cable lead seals.

[0091] The above description is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for ultrasonic phased array full-focusing imaging detection of lead seals on high-voltage cables, characterized in that, include: Step S1: Obtain the detection system parameters and the high-voltage cable lead seal parameters. The detection system parameters include the ultrasonic phased array probe parameters, the acoustic parameters of the coupling medium and the lead seal material, and the high-voltage cable lead seal parameters include the lead seal surface profile function and the location range of the defect to be detected. Step S2: Based on the imaging principle of dual-layer medium total focusing method, Fermat's principle is used to calculate the propagation time of ultrasonic waves from the probe to the target pixel and back to the probe. Step S3: Based on the propagation time, establish a point spread function calculation model that comprehensively considers geometric attenuation, unit directivity, and interface transmission loss, and calculate the point spread function under different probe spacings; Step S4: Extract the main lobe width and side lobe level from the calculated point spread function as key feature parameters; Step S5: Determine the optimal probe spacing with the sidelobe level being less than or equal to a preset threshold as a constraint and the main lobe width being minimized as the optimization objective. Step S6: Collect full matrix data using the optimal probe spacing, and perform full-focus image reconstruction on the full matrix data to identify and locate internal defects in the high-voltage cable lead seal.

2. The method according to claim 1, characterized in that, The parameters of the ultrasonic phased array probe include the number of elements, center frequency, element spacing, element length, array aperture, and bandwidth; the acoustic parameters of the coupling medium include longitudinal wave velocity and density; the acoustic parameters of the lead seal material include longitudinal wave velocity, transverse wave velocity, and density; and the surface profile function of the lead seal is determined according to the geometry of the lead seal as either a convex or concave cylindrical surface function.

3. The method according to claim 1, characterized in that, In step S2, the calculation of ultrasonic wave propagation time using Fermat's principle specifically includes: The lead seal surface of the high-voltage cable is discretized into intervals. The set of points, in which The ultrasonic wavelength in the coupling medium; In the set of discrete points, the propagation time is calculated by solving the equation in which the first derivative of the propagation time with respect to the x-coordinate of the transmission point is zero, thus finding the transmission point that satisfies Fermat's principle.

4. The method according to claim 1, characterized in that, In step S3, the point spread function calculation model is established in the following way: For point targets located inside the lead seal, a 4-cycle sinusoidal pulse signal modulated by the Hanning window is generated as the excitation signal. The excitation signal is delayed using the propagation time to obtain the original signal response of each transmit-receive unit pair; The original signal response is corrected by comprehensively considering geometric attenuation, unit directivity, and interface transmission loss; The point spread function of the point target is obtained by superimposing the corrected signals of all transmit-receive unit pairs.

5. The method according to claim 4, characterized in that, The correction to the original signal response, which comprehensively considers geometric attenuation, unit directivity, and interface transmission loss, is specifically achieved through the geometric attenuation coefficient of the transmission path. Geometric attenuation coefficient of the receiving path , Directivity coefficient of the transmitting unit , Directivity coefficient of the receiving unit Interface transmission coefficient of the transmission path Interface transmission coefficient with receiving path accomplish: Geometric attenuation coefficient of the transmission path and the geometric attenuation coefficient of the receiving path They are respectively: in, This represents the distance from the transmitting unit to the transmission point of the ultrasonic wave at the couplant-lead seal interface. This represents the distance from the transmission point of the ultrasonic wave to the target pixel. This represents the distance from the target pixel to the transmission point of the ultrasonic wave. This represents the distance from the transmission point to the receiving unit of the ultrasonic wave. Directivity coefficient of the transmitting unit and the directivity coefficient of the receiving unit They are respectively: in, The length of the piezoelectric unit; The center frequency; The longitudinal wave velocity in the coupling medium; The angle of incidence of the ultrasonic wave in the coupling medium along the transmission path; The angle of refraction of the ultrasonic wave in the coupling medium during the receiving path; Interfacial transmission coefficient of the emission path Interface transmission coefficient with receiving path They are respectively: in, and These are the densities of the coupling medium and the lead seal, respectively. The longitudinal wave velocity within the lead seal; The angle of refraction of the ultrasonic wave within the lead seal in the transmission path; The angle of incidence of the ultrasonic wave in the lead seal is the angle of incidence of the ultrasonic wave in the receiving path.

6. The method according to claim 1, characterized in that, In step S4, the main lobe width is calculated using the -6dB descent method, and the side lobe level is calculated using the peak search method; specifically including: Extract the lateral distribution of the point spread function at the depth of the point target; Find the maximum value of the lateral distribution, and determine two points on both sides of the maximum value where the amplitude drops by 6dB. Use the distance between these two points as the main lobe width. After excluding the main lobe region in the lateral distribution, the largest side lobe peak is found, and the decibel value of the ratio of the side lobe peak to the maximum value is taken as the side lobe level.

7. The method according to claim 1, characterized in that, In step S5, the preset threshold is -20dB, and the step of determining the optimal probe spacing includes: Traverse the range of probe spacing to be tested, and calculate the point spread function, main lobe width, and side lobe level for each probe spacing according to the preset step size; Select probe spacings with sidelobe levels less than or equal to -20dB; The probe spacing with the smallest main lobe width is selected from the filtered probe spacings as the optimal probe spacing.

8. The method according to claim 1, characterized in that, In step S6, after bandpass filtering and denoising preprocessing of the acquired full matrix data, the full-focus image reconstruction is performed; furthermore, the reconstructed image is quantitatively evaluated using signal-to-artifact ratio SAR and array performance index API, wherein: in, The maximum amplitude within the signal region; is the root mean square value of the amplitude within the artifact region; The area of ​​pixels in the image whose amplitude is within 6 dB below the maximum value; The wavelength of the ultrasonic wave inside the lead seal.

9. A high-voltage cable lead seal ultrasonic phased array full-focusing imaging detection device, characterized in that, include: One or more processors; Memory; One or more applications, wherein the one or more applications are stored in the memory and configured to be executed by the one or more processors, the one or more applications being configured to perform the ultrasonic phased array full-focusing imaging detection method for high-voltage cable lead seals as described in any one of claims 1 to 8.

10. A computer program product, characterized in that, Includes computer instructions that instruct a computer device to perform the operation corresponding to the ultrasonic phased array full-focus imaging detection of high-voltage cable lead seals as described in any one of claims 1 to 8.

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