Electromagnetic thermoacoustic cable detection method and apparatus

Abstract

The application discloses an electromagnetic thermoacoustic cable detection method and device, and belongs to the technical field of cable state detection. The method applies electromagnetic excitation to the cable through an excitation source and a transmitting coil or antenna, generates ultrasonic signals under electromagnetic excitation by utilizing the difference in the conductivity and permittivity distribution in the cable medium, and detects the signals through an ultrasonic sensor or array. At the same time, the excitation current signal is detected by a current transformer, the sound source distribution and the cable electrical characteristic parameter (conductivity, permittivity) distribution are inverted, the electromagnetic signals containing cable information are collected through a receiving coil or antenna, and the electromagnetic anomalies caused by defects or aging are extracted. The reconstructed sound source image, electrical characteristic parameter image and electromagnetic anomaly signal are combined to comprehensively evaluate the cable defect and aging state. The application combines the advantages of high electromagnetic detection sensitivity and high ultrasonic imaging resolution, realizes early and accurate evaluation of the internal defects and aging state of the cable, and effectively improves the safe operation level of the cable.

Description

Technical Field

[0001] This invention belongs to the field of cable condition detection technology, specifically relating to electromagnetic thermoacoustic cable detection methods and devices. Background Technology

[0002] The impact of the health status of cables with a high proportion of power cables on the safe and stable operation of the power grid cannot be ignored. With the continuous increase in the number of power cable equipment, the continuous enrichment of application scenarios, and the continuous acceleration of urban construction, the fault forms faced by power cable lines in operation are becoming more complex. The aging of insulation performance and defects in cable construction process caused by long-term operation throughout the cable's life cycle pose hidden dangers to the reliable operation of power. In order to avoid power accidents caused by power cable insulation faults and to ensure the safety and reliability of power supply operation, it is necessary to conduct regular condition inspections on the cables in operation.

[0003] Many cables put into operation in the last century have entered their "aging" stage, approaching or exceeding their design life. Faults caused by equipment aging account for a large proportion of all cable faults. Power cables may overheat due to overload, especially during periods of high load, potentially leading to overheating and ultimately aging of the cable insulation. Long-term temperature fluctuations can easily cause cable materials to age and become brittle, potentially reducing insulation performance and leading to problems such as leakage or short circuits. Local areas such as river valleys and mountainous regions may be affected by high humidity and surface contaminants. Moisture penetrating into cable joints and insulation, or untreated contaminants, can cause insulation failure or external corrosion. In cases of insulation damage or dielectric breakdown, local defects such as air bubbles, metallic and non-metallic particles within the cable can lead to partial discharge during prolonged operation, eventually resulting in complete insulation breakdown and a permanent fault. The quality and installation of cable joints can also be hidden dangers. Poor cable connections at joints or external interference (such as vibration or thermal expansion) can lead to poor contact, arcing, and localized overheating. Early detection and assessment of cable defects and aging conditions can prevent catastrophic failures.

[0004] Currently, cable defect and aging detection methods mainly include offline detection methods, online monitoring methods, and laboratory analysis methods, such as dielectric loss measurement, partial discharge monitoring, and infrared thermal imaging. Dielectric loss measurement can assess the overall aging degree of the cable but is not sensitive to local defects. Partial discharge monitoring can reflect concentrated microscopic defects inside the insulation that cause discharge, but it cannot effectively warn of situations where the overall insulation of the cable is uniformly deteriorated without the formation of obvious partial discharge points. Infrared thermal imaging can detect abnormal surface temperatures but is not sensitive to early internal aging.

[0005] In summary, existing cable testing technologies either focus on overall aging assessment with insufficient local sensitivity, or can only reflect concentrated defects that have already produced partial discharge, making it difficult to balance detection sensitivity, location accuracy, and the ability to identify early uniform degradation. To address these technical problems, there is an urgent need to develop a novel testing method that can combine the advantages of multiple physical fields to achieve early, accurate, and comprehensive evaluation of cable defects and aging conditions. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method and apparatus for detecting electromagnetic thermoacoustic cables. It employs a method combining multi-physics field coupled imaging with electromagnetic information detection, leveraging the advantages of high sensitivity in electromagnetic detection and high resolution in ultrasonic imaging. By utilizing reconstructed sound source images or electrical characteristic parameter images and electromagnetic anomaly signals, the cable condition is assessed through the sound source images, the cable's conductivity distribution, dielectric constant distribution, or electromagnetic anomaly signals, evaluating cable defects and aging status.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for testing electromagnetic thermoacoustic cables, comprising:

[0009] An excitation source applies electromagnetic excitation to the cable under test via a transmitting coil or antenna; the ultrasonic signal generated by the cable under test under electromagnetic excitation is acquired and processed;

[0010] The excitation current signal of the excitation source passing through the transmitting coil or antenna is detected using a current transformer, and the excitation current signal is processed.

[0011] Based on the processed ultrasonic signal and the excitation current signal, the sound source image is reconstructed;

[0012] The electrical characteristic parameters of the cable are reconstructed based on the reconstructed sound source image, wherein the electrical characteristic parameters include conductivity and dielectric constant;

[0013] Electromagnetic signals containing cable status information are collected by receiving coils or antennas. The collected electromagnetic signals are differentially processed with reference electromagnetic signals in the health state of the cable under test to obtain residual signals, and electromagnetic anomaly signals are extracted from the residual signals.

[0014] The reconstructed sound source image, the reconstructed electrical characteristic parameter image, and the extracted electromagnetic anomaly signal are fused together to evaluate the defects and aging status of the cable and output the evaluation results.

[0015] Furthermore, the electromagnetic excitation is in the form of a pulsed magnetic field, and the transmitting coil or antenna adopts an array-type distributed magnetic field focusing mode and is equipped with a magnetic core structure to focus the electromagnetic excitation on the test area space of the cable under test; the transmitting coil or antenna adopts a flexible thin film structure that can be closely attached to the surface of the cable under test.

[0016] Furthermore, the process of generating the ultrasonic signal is as follows: when the cable under test has sharp points, burrs, gaps, thin air gaps, bubble defects, impurities, changes in insulation performance, or structural changes, it causes discontinuous distribution or changes in conductivity or dielectric constant, which in turn leads to changes in electric field distribution, and the ultrasonic signal is generated under the electromagnetic excitation.

[0017] Furthermore, the loss term in the ultrasonic signal source is composed of an ohmic loss term and a dielectric loss term. The ohmic loss term is related to the product of the conductivity distribution and the square of the electric field strength, while the dielectric loss term is related to the product of the imaginary part of the dielectric constant, the dominant frequency of the excitation current signal, and the square of the electric field strength.

[0018] Furthermore, the method for reconstructing the sound source image is as follows: an ultrasonic sensor or an ultrasonic sensor array is arranged around the cable under test, ultrasonic signals are measured to obtain sound pressure signals, and the sound source spatial distribution inside the cable under test is inverted by a reconstruction algorithm based on the integral relationship between the sound pressure signal and the spatial distribution of the sound source; wherein the integral relationship involves the normal vector of the sound source position, the specific heat capacity at constant pressure, the volume expansion coefficient, the sound velocity, the time derivative, and the sound pressure.

[0019] Furthermore, the method for reconstructing the electrical characteristic parameter image is as follows: the main contribution source of the loss term in the sound source is determined according to the frequency of the electromagnetic excitation. When the frequency of the electromagnetic excitation is low, the ohmic loss term is the main contributor, and the conductivity distribution image is obtained by inverting the reconstructed sound source image; when the frequency of the electromagnetic excitation is high, the dielectric loss term is the main contributor, and the dielectric constant distribution image is obtained by inverting the reconstructed sound source image.

[0020] Furthermore, the method for extracting the electromagnetic anomaly signal is as follows: the difference between the acquired measured electromagnetic signal and the reference electromagnetic signal when the cable under test is in a healthy state is calculated to obtain a residual signal; wavelet transform is performed on the residual signal to obtain a high-resolution time-frequency diagram; instantaneous frequency fluctuation entropy, fundamental frequency and second harmonic phase difference, and energy distribution characteristics are extracted from the high-resolution time-frequency diagram to form an electromagnetic anomaly feature vector; the electromagnetic anomaly feature vector is input into a pre-trained convolutional neural network, and the convolutional neural network outputs the defect type and anomaly degree.

[0021] Furthermore, the multi-information fusion includes feature-level fusion and decision-level fusion.

[0022] Furthermore, in the feature-level fusion, the electrical characteristic parameter features, sound source distribution features, and electromagnetic anomaly features are concatenated into a joint feature vector; in the decision-level fusion, a weighted fusion is performed based on the joint feature vector to obtain a comprehensive evaluation result of the defects and aging status of the cable under test.

[0023] On the other hand, the present invention provides an electromagnetic thermoacoustic cable testing device, comprising:

[0024] An excitation source is used to apply electromagnetic excitation to the cable under test via a transmitting coil or antenna.

[0025] An excitation current detection module is used to acquire the excitation current signal passing through the transmitting coil or antenna;

[0026] An ultrasonic signal detection and acquisition system is used to acquire the ultrasonic signal generated by the cable under test under electromagnetic excitation.

[0027] An electromagnetic signal detection and acquisition system is used to acquire electromagnetic signals containing cable status information through a receiving coil or antenna.

[0028] The image reconstruction and condition assessment system includes a sound source image reconstruction module, an electrical characteristic parameter image reconstruction module, a defect and aging condition assessment module, and a cable condition information output and display module. The sound source image reconstruction module reconstructs a sound source image based on the ultrasonic signal and the excitation current signal. The electrical characteristic parameter image reconstruction module reconstructs an electrical characteristic parameter image of the cable under test based on the reconstructed sound source image, where the electrical characteristic parameters include conductivity and dielectric constant. The defect and aging condition assessment module performs differential processing on the acquired electromagnetic signal and a reference electromagnetic signal of the cable under test in a healthy state to obtain a residual signal, extracts an electromagnetic anomaly signal from the residual signal, and fuses the reconstructed sound source image, the reconstructed electrical characteristic parameter image, and the extracted electromagnetic anomaly signal to assess the defects and aging condition of the cable under test. The cable condition information output and display module outputs the assessment results.

[0029] Thirdly, the present invention provides an electronic device, comprising: one or more processors; and a memory for storing one or more programs; wherein, when the one or more programs are executed by the one or more processors, the one or more processors implement the aforementioned electromagnetic thermoacoustic cable detection method.

[0030] Fourthly, the present invention provides a computer-readable storage medium having executable instructions stored thereon, which, when executed by a processor, enable the processor to implement the aforementioned electromagnetic thermoacoustic cable detection method.

[0031] The beneficial effects of this invention are as follows:

[0032] Multi-physics field fusion for high detection accuracy: This invention innovatively combines electromagnetic and ultrasonic detection technologies, employing an electromagnetic-thermo-acoustic multi-physics field coupled imaging method. Electromagnetic excitation is used to achieve a sensitive response to the internal electrical characteristic parameters (conductivity, dielectric constant) of the cable, fully leveraging the high sensitivity of electromagnetic detection; simultaneously, image reconstruction is performed by detecting the ultrasonic signal induced by electromagnetic excitation, utilizing the high resolution of ultrasonic imaging. The complementary advantages of these two methods overcome the technical bottleneck of single detection methods struggling to simultaneously achieve both sensitivity and positioning accuracy.

[0033] With strong early diagnostic capabilities and broad identification dimensions, this invention can not only identify local microscopic defects in cables (such as bubbles, impurities, burrs, and gaps) by reconstructing sound source images, but also invert the distribution images of the cable's conductivity and dielectric constant, intuitively reflecting the early uniform aging and performance degradation trends of the insulation material. Furthermore, by extracting electromagnetic anomaly signals through receiving coils or antennas, it further enriches the characteristic information of the cable's condition, achieving a multi-dimensional comprehensive diagnosis from local defects to overall aging, and from physical structure to changes in electrical characteristics.

[0034] The assessment results are intuitive and have broad application prospects: By fusing and analyzing reconstructed images and electromagnetic anomaly signals, the location, morphology, and aging degree of defects inside the cable can be intuitively displayed, providing a clear and reliable basis for cable condition assessment and maintenance decisions. This method combines the precision of offline detection with the potential of online monitoring and can be widely applied to factory inspection, installation acceptance, routine inspection, and life assessment of power cables. It has significant engineering application value and promising prospects for improving the safe operation level of the power grid and reducing the failure rate.

[0035] This invention uses electromagnetic excitation, eliminating the need for direct electrical connection with the cable conductor. This avoids the secondary fault risks and poor contact problems that may be introduced by the pulse current injection method, thus achieving true non-contact detection. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the electromagnetic thermoacoustic cable testing method of the present invention.

[0037] Figure 2 Flowchart of the method for extracting electromagnetic anomaly signals from cables;

[0038] Figure 3 This is a framework diagram for the integration assessment. Detailed Implementation

[0039] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0040] like Figure 1As shown, this invention provides a method and apparatus for testing electromagnetic thermoacoustic cables. It employs electromagnetic and ultrasonic coupling, combining electromagnetic detection with the high sensitivity of electromagnetic detection and the high resolution of ultrasonic detection. The cable's conductivity, dielectric constant, and electromagnetic anomaly information reflect its defects and aging state. This invention can largely meet the urgent need for high-quality cable condition assessment and safe operation of cable facilities. Specifically, the electromagnetic thermoacoustic cable testing method of this invention includes the following steps:

[0041] The excitation source applies electromagnetic excitation to the cable through a transmitting coil or antenna; the transmitting coil adopts an array-type distributed magnetic field focusing mode, and introduces a magnetic core structure to focus the generated electromagnetic excitation on the area of ​​the cable to be tested; the transmitting coil or antenna adopts a flexible thin film design scheme, which can be closely attached to the surface of the cable.

[0042] A cable with a conductivity and dielectric constant distribution generates an ultrasonic signal under electromagnetic excitation; the ultrasonic signal is detected using an ultrasonic sensor or an ultrasonic sensor array; the detected ultrasonic signal is amplified, bandpass filtered, and then used for data acquisition.

[0043] The current signal passing through the transmitting coil or antenna is detected using a current transformer. After signal conditioning, data is acquired. The acquired ultrasonic and current signals are stored and analyzed. Sound source image reconstruction is then carried out.

[0044] Reconstruct the electrical properties of the cable, including conductivity and dielectric constant;

[0045] Electromagnetic signals containing cable status information are received using a receiving coil or antenna. The differential receiving coil or antenna is integrated into a flexible thin-film array sensor and closely attached to the outer surface of the cable. There are two ways to design the receiving coil or antenna: one is to design it separately from the excitation coil or antenna, and arrange and position it separately during detection; the other is to design it as an integrated unit with the excitation coil or antenna to eliminate the relative positional deviation between excitation and detection.

[0046] Methods for extracting electromagnetic anomaly signals from cables, such as Figure 2 As shown. The extraction of electromagnetic anomaly signals when cables are defective or aging employs feature extraction based on time-frequency analysis and defect identification methods based on deep learning. The detected electromagnetic signals are differentially amplified to eliminate common-mode interference, then bandpass filtered before being acquired by a high-speed data acquisition card. The acquired electromagnetic signals are then stored and analyzed, and the measured signals are... Reference signal for cable health status Subtraction, calculation of residual signal To eliminate the inherent electromagnetic response and environmental interference of the cable, the residual signal is transformed by wavelet to obtain a high-resolution time-frequency map. The instantaneous frequency fluctuation entropy, the phase difference between the fundamental frequency and the second harmonic, and the energy distribution characteristics are extracted from the time-frequency map to form an electromagnetic anomaly feature vector. This feature vector is input into a pre-trained convolutional neural network. The training set consists of electromagnetic anomaly feature vectors obtained by simulation or actual measurement and corresponding defect features. Finally, the anomaly features such as defect type and anomaly degree are output.

[0047] By fusing reconstructed acoustic source images, electrical characteristic parameters, and electromagnetic anomaly signals, cable condition assessment is performed to evaluate cable defects and aging status. The acoustic source image, also known as a thermal acoustic source image, reflects the absorption capacity of different cable materials and structures for electromagnetic fields. Gray-scale differences in the image further reveal abrupt changes in cable electromagnetic parameters, indicating defects and aging trends. Electrical characteristic parameters, including the cable's dielectric constant and conductivity distribution, are used to assess the overall aging status of the insulation, or to reflect cable defects and damage based on changes in these parameters. Electromagnetic anomaly signals can locate abrupt changes in the cable's physical structure and determine their severity. Comprehensive analysis of these three factors enables a complete assessment of cable defects and aging status. The cable condition information is then displayed and output.

[0048] Figure 3 The diagram shows the overall framework of the fusion evaluation. The framework consists of an excitation and detection layer, a feature extraction layer, a fusion decision layer, and an output layer. The excitation and detection layer applies electromagnetic excitation to the cable under test via a transmitting coil / antenna. A current transformer detects the current signal passing through the transmitting coil or antenna, an ultrasonic sensor or ultrasonic sensor array detects the ultrasonic signal, and a receiving coil or antenna detects the electromagnetic signal. The feature extraction layer extracts the cable's acoustic source image, electrical characteristic parameters, and electromagnetic anomaly signals. The fusion decision layer performs feature-level fusion of the electrical characteristic parameter features, acoustic source distribution features, and electromagnetic anomaly features, concatenating the three types of feature vectors into a joint feature vector. The decision-level fusion layer performs weighted fusion based on the joint feature vector. Finally, the output layer outputs the cable's defect type, degree, and aging level.

[0049] Furthermore, the electromagnetic excitation can be a variety of pulsed magnetic fields, such as pulse excitation with a certain repetition frequency or modulation signal pulse excitation with a certain width.

[0050] Furthermore, the process of generating the ultrasonic signal is as follows: Electromagnetic excitation is applied to the cable. When the cable contains sharp points, burrs, notches, thin air gaps, bubble defects, impurities, or when its insulation performance or structure changes, it causes discontinuities or changes in electrical characteristics, resulting in changes in conductivity or dielectric constant and changes in electric field distribution. Under electromagnetic excitation, ultrasonic signals are generated, producing the loss term in the ultrasonic signal source. as follows:

[0051] (1)

[0052] in, For conductivity distribution, The main frequency of the pulse excitation current signal Decision, that is , The free space permittivity, The imaginary part of the dielectric constant describes the loss. The electric field strength in the medium, Indicates location, Indicates time; sound source is .

[0053] Furthermore, the sound source image reconstruction method is as follows:

[0054] (2)

[0055] in, This refers to the spatial distribution of the sound source, i.e., the distribution of heat absorption. It is the plane where the ultrasonic transducer is located. Indicates the location of the ultrasonic transducer. It is the sound source Location The normal vector, For isobaric specific heat capacity, The coefficient of volumetric expansion. Represents the first-order time derivative. For sound pressure, The solution method is to use the known sound pressure signal measured by the ultrasonic transducer on the surface and reconstruct the sound source distribution inside the tissue through integration.

[0056] For the reconstruction of the electrical characteristic parameters of the cable, the proportion of the loss term in the sound source is determined based on the electromagnetic excitation frequency. When the excitation frequency is too low, The main one is the first item. It works; when the excitation frequency is high. The main one is the second item. It works by inverting the sound source and then inverting the conductivity or dielectric constant.

[0057] Furthermore, the excitation source is composed of a synchronous trigger controller, a signal generator, a power amplifier, and a load matching module connected in sequence. The synchronous trigger controller controls the signal generator to generate a trigger signal, which is amplified by the power amplifier and then impedance matched by the load matching module. The pulse current is then passed through the transmitting coil or antenna to generate electromagnetic excitation, which is then applied to the cable.

[0058] A current transformer is used to detect the pulse current signal output by the excitation source. After passing through the signal conditioning module, the signal is input to the third data acquisition module. The output of the third data acquisition module is connected to the input of the first data storage and signal analysis module.

[0059] An ultrasonic sensor or ultrasonic sensor array is arranged around the cable. Its output is connected to the input of a first signal amplification module. The output of the first signal amplification module is connected to the input of a first bandpass filter module. The output of the first bandpass filter module is connected to the input of a first data acquisition module. The outputs of the first data acquisition module and the third data acquisition module are connected to the input of a first data storage and signal analysis module. The output of the first data storage and signal analysis module is connected to the input of a sound source image reconstruction module. The output of the sound source image reconstruction module is connected to the input of an electrical characteristic parameter image reconstruction module and a defect and aging condition assessment module.

[0060] The output of the receiving coil or antenna is connected to the input of the second signal amplification module. The output of the second signal amplification module is connected to the input of the second bandpass filter module. The output of the second bandpass filter module is connected to the input of the second data acquisition module. The outputs of the second and third data acquisition modules are connected to the input of the second data storage and signal analysis module. The output of the second data storage and signal analysis module is connected to the input of the defect and aging condition assessment module. The output of the defect and aging condition assessment module is connected to the cable status information output and display module.

[0061] The present invention also provides an electromagnetic thermoacoustic cable testing device, comprising:

[0062] The electromagnetic thermoacoustic cable testing device consists of an excitation source, a transmitting coil or antenna, an excitation current detection module, an ultrasonic signal detection and acquisition system, an electromagnetic signal detection and acquisition system, and an image reconstruction and condition assessment system.

[0063] The excitation source is used to apply electromagnetic excitation to the cable. The excitation source consists of a synchronous trigger controller, a signal generator, a power amplifier, and a load matching module connected in sequence. The synchronous trigger controller controls the signal generator to generate a trigger signal, which is amplified by the power amplifier and then impedance matched by the load matching module. The pulse current is then passed through the transmitting coil or antenna to generate electromagnetic excitation, which is then applied to the cable.

[0064] The excitation current detection module is used to detect the current signal passing through the transmitting coil or antenna. It consists of a current transformer, a signal conditioning module, and a data acquisition module connected in sequence. The output terminal of the current transformer is connected to the input terminal of the signal conditioning module, the output terminal of the signal conditioning module is connected to the input terminal of the third data acquisition module, and the output terminal of the third data acquisition module is connected to the input terminals of the first data storage and signal analysis module and the second data storage and signal analysis module.

[0065] An ultrasonic signal detection and acquisition system comprises an ultrasonic sensor or ultrasonic sensor array, a first signal amplification module, a first bandpass filter module, a first data acquisition module, and a first data storage and signal analysis module connected sequentially. It is used to detect ultrasonic signals generated by electromagnetic excitation applied to a cable, and to store and analyze current and ultrasonic signals. The ultrasonic sensor or ultrasonic sensor array is arranged around the cable, with its output connected to the input of the first signal amplification module. The output of the first signal amplification module is connected to the input of the first bandpass filter module, the output of the first bandpass filter module is connected to the input of the first data acquisition module, and the output of the first data acquisition module is connected to the input of the first data storage and signal analysis module. The ultrasonic signal generation process is as follows: electromagnetic excitation is applied to the cable. When the cable contains sharp points, burrs, notches, thin air gaps, bubble defects, impurities, or when its insulation performance or structure changes, discontinuities or changes in electrical characteristics occur, resulting in changes in conductivity or dielectric constant and changes in electric field distribution. Under electromagnetic excitation, ultrasonic signals are generated.

[0066] The electromagnetic signal detection and acquisition system consists of a receiving coil or antenna, a second signal amplification module, a second bandpass filter module, a second data acquisition module, and a second data storage and signal analysis module connected in sequence. The output terminal of the receiving coil or antenna is connected to the input terminal of the second signal amplification module, the output terminal of the second signal amplification module is connected to the input terminal of the second bandpass filter module, the output terminal of the second bandpass filter module is connected to the input terminal of the second data acquisition module, and the output terminals of the second data acquisition module and the third data acquisition module are connected to the input terminal of the second data storage and signal analysis module.

[0067] The image reconstruction and condition assessment system consists of a sound source image reconstruction module, an electrical characteristic parameter image reconstruction module, a defect and aging condition assessment module, and a cable condition information output and display module. The output of the first data storage and signal analysis module in the ultrasonic signal detection and acquisition system is connected to the input of the sound source image reconstruction module. The output of the sound source image reconstruction module is connected to the input of the electrical characteristic parameter image reconstruction module. The outputs of the sound source image reconstruction module, the electrical characteristic parameter image reconstruction module, and the second data storage and signal analysis module in the electromagnetic signal detection and acquisition system are connected to the input of the defect and aging condition assessment module. The output of the defect and aging condition assessment module is connected to the cable condition information output and display module, thereby realizing the assessment of cable defects or aging conditions.

[0068] Thirdly, the present invention provides an electronic device, comprising: one or more processors; and a memory for storing one or more programs; wherein, when the one or more programs are executed by the one or more processors, the one or more processors implement the aforementioned electromagnetic thermoacoustic cable detection method.

[0069] Fourthly, the present invention provides a computer-readable storage medium having executable instructions stored thereon, which, when executed by a processor, enable the processor to implement the aforementioned electromagnetic thermoacoustic cable detection method.

[0070] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for testing electromagnetic thermoacoustic cables, characterized in that, include: The excitation source applies electromagnetic excitation to the cable under test through a transmitting coil or antenna; The ultrasonic signal generated by the cable under test under electromagnetic excitation is acquired and processed. The excitation current signal of the excitation source passing through the transmitting coil or antenna is detected using a current transformer, and the excitation current signal is processed. Based on the processed ultrasonic signal and the excitation current signal, the sound source image is reconstructed; The electrical characteristic parameters of the cable are reconstructed based on the reconstructed sound source image, wherein the electrical characteristic parameters include conductivity and dielectric constant; Electromagnetic signals containing cable status information are collected by receiving coils or antennas. The collected electromagnetic signals are differentially processed with reference electromagnetic signals in the health state of the cable under test to obtain residual signals, and electromagnetic anomaly signals are extracted from the residual signals. The reconstructed sound source image, the reconstructed electrical characteristic parameter image, and the extracted electromagnetic anomaly signal are fused together to evaluate the defects and aging status of the cable and output the evaluation results.

2. The method for testing electromagnetic thermoacoustic cables according to claim 1, characterized in that, The electromagnetic excitation is in the form of a pulsed magnetic field. The transmitting coil or antenna adopts an array-type distributed magnetic field focusing mode and is equipped with a magnetic core structure to focus the electromagnetic excitation on the test area of ​​the cable under test. The transmitting coil or antenna adopts a flexible thin film structure that can be closely attached to the surface of the cable under test.

3. The method for testing electromagnetic thermoacoustic cables according to claim 1, characterized in that, The process of generating the ultrasonic signal is as follows: when the cable under test has sharp points, burrs, gaps, thin air gaps, bubble defects, impurities, changes in insulation performance, or changes in structure, it causes discontinuous distribution or changes in conductivity or dielectric constant, which in turn leads to changes in electric field distribution, and the ultrasonic signal is generated under electromagnetic excitation.

4. The method for testing electromagnetic thermoacoustic cables according to claim 3, characterized in that, The loss term in the ultrasonic signal source is composed of an ohmic loss term and a dielectric loss term. The ohmic loss term is related to the product of the conductivity distribution and the square of the electric field strength, while the dielectric loss term is related to the product of the imaginary part of the dielectric constant, the dominant frequency of the excitation current signal, and the square of the electric field strength.

5. The method for testing electromagnetic thermoacoustic cables according to claim 1, characterized in that, The method for reconstructing the sound source image is as follows: an ultrasonic sensor or an ultrasonic sensor array is arranged around the cable under test, the ultrasonic signal is measured to obtain the sound pressure signal, and the sound source spatial distribution inside the cable under test is inverted by a reconstruction algorithm based on the integral relationship between the sound pressure signal and the spatial distribution of the sound source; wherein the integral relationship involves the normal vector of the sound source position, the specific heat capacity at constant pressure, the volume expansion coefficient, the sound velocity, the time derivative, and the sound pressure.

6. The method for testing electromagnetic thermoacoustic cables according to claim 1, characterized in that, The method for reconstructing the electrical characteristic parameter image is as follows: the main contribution source of the loss term in the sound source is determined according to the frequency of the electromagnetic excitation. When the frequency of the electromagnetic excitation is low, the ohmic loss term is the main contributor, and the conductivity distribution image is obtained by inverting the reconstructed sound source image. When the frequency of the electromagnetic excitation is high, the dielectric loss term is the main contributor, and the dielectric constant distribution image is obtained by inverting the reconstructed sound source image.

7. The method for testing electromagnetic thermoacoustic cables according to claim 1, characterized in that, The method for extracting the electromagnetic anomaly signal is as follows: the difference between the acquired measured electromagnetic signal and the reference electromagnetic signal of the cable under test in a healthy state is calculated to obtain a residual signal; wavelet transform is performed on the residual signal to obtain a high-resolution time-frequency diagram; instantaneous frequency fluctuation entropy, phase difference between fundamental frequency and second harmonic frequency, and energy distribution characteristics are extracted from the high-resolution time-frequency diagram to form an electromagnetic anomaly feature vector; the electromagnetic anomaly feature vector is input into a pre-trained convolutional neural network, and the convolutional neural network outputs the defect type and anomaly degree.

8. The method for testing electromagnetic thermoacoustic cables according to claim 1, characterized in that, The multi-information fusion includes feature-level fusion and decision-level fusion.

9. The method for testing electromagnetic thermoacoustic cables according to claim 8, characterized in that, In the feature-level fusion, electrical characteristic parameter features, sound source distribution features, and electromagnetic anomaly features are concatenated into a joint feature vector; in the decision-level fusion, a weighted fusion is performed based on the joint feature vector to obtain a comprehensive evaluation result of the defects and aging status of the cable under test.

10. An electromagnetic thermoacoustic cable testing device, characterized in that, include: An excitation source is used to apply electromagnetic excitation to the cable under test via a transmitting coil or antenna. An excitation current detection module is used to acquire the excitation current signal passing through the transmitting coil or antenna; An ultrasonic signal detection and acquisition system is used to acquire the ultrasonic signal generated by the cable under test under electromagnetic excitation. An electromagnetic signal detection and acquisition system is used to acquire electromagnetic signals containing cable status information through a receiving coil or antenna. An image reconstruction and condition assessment system includes a sound source image reconstruction module, an electrical characteristic parameter image reconstruction module, a defect and aging condition assessment module, and a cable condition information output and display module. The sound source image reconstruction module reconstructs a sound source image based on the ultrasonic signal and the excitation current signal. The electrical characteristic parameter image reconstruction module reconstructs an electrical characteristic parameter image of the cable under test based on the reconstructed sound source image, wherein the electrical characteristic parameters include conductivity and dielectric constant. The defect and aging condition assessment module performs differential processing on the acquired electromagnetic signal and a reference electromagnetic signal of the cable under test in a healthy state to obtain a residual signal, extracts an electromagnetic anomaly signal from the residual signal, and fuses the reconstructed sound source image, the reconstructed electrical characteristic parameter image, and the extracted electromagnetic anomaly signal to assess the defects and aging condition of the cable under test. The cable status information output and display module is used to output the evaluation results.

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