Pulsed eddy current based thermal shrinkable cable shield damage detection method and apparatus

Abstract

The application discloses a thermal contraction type cable shielding layer damage detection method and device based on pulse eddy current, relates to the technical field of cable shielding layer damage detection, and comprises the following steps: arranging a pulse eddy current probe on the outer surface of a cable, applying a preset pulse excitation, collecting an original transient electromagnetic response signal and constructing a reference phase signal; performing synchronous phase-sensitive demodulation, extracting in-phase components and quadrature components, and obtaining a phase purification signal; based on the difference between the spatial statistical characteristics of the shielding layer response and the conductor response, performing spatial joint reconstruction on the phase purification signal to obtain a purified reconstruction signal; based on the purified reconstruction signal, extracting damage features, judging the damage of the cable shielding layer, and positioning the damage area; the application effectively solves the problems that in the existing pulse eddy current detection, the electromagnetic response of the internal conductor and the shielding layer response are highly superimposed, are difficult to separate, and the damage features are easily covered by noise and spatial fluctuations, resulting in insufficient shielding layer damage recognition sensitivity and positioning accuracy.

Description

Technical Field

[0001] This invention relates to the field of cable shielding damage detection technology, and more specifically, to a heat-shrinkable cable shielding damage detection method and equipment based on pulsed eddy currents. Background Technology

[0002] Heat-shrinkable cables are widely used in power transmission and distribution, electrical equipment connections, and complex operating environments due to their convenient installation, good sealing performance, and high mechanical strength. These cables typically have a metallic shielding layer outside the conductor insulation layer to balance the electric field distribution, suppress electromagnetic interference, and improve operational safety. However, under the influence of long-term operation, installation, heat-shrinking construction, mechanical stress, and environmental aging, the cable shielding layer is prone to damage such as breakage, thinning, localized ablation, or poor contact. If shielding layer damage is not detected in time, it may lead to partial discharge, insulation degradation, or even cable failure, posing a threat to the safe operation of the power system. Therefore, effective and reliable non-destructive testing of the heat-shrinkable cable shielding layer is of significant engineering importance.

[0003] Existing testing methods for cable shielding mainly include DC resistance testing, power frequency or high frequency impedance testing, ultrasonic testing, and eddy current testing based on electromagnetic induction. Among these, pulsed eddy current testing technology has been gradually introduced into the field of cable shielding condition assessment due to its advantages such as non-contact operation, sensitivity to surface and near-surface defects, and high detection efficiency. This technology applies broadband pulse excitation to the object under test and analyzes the resulting transient electromagnetic response, thereby reflecting the integrity of the conductive structure and changes in electromagnetic properties.

[0004] However, existing pulsed eddy current testing methods for heat-shrinkable cables, a multi-layered composite structure, still have significant shortcomings. On one hand, the internal conductors and external shielding layers are highly coaxially distributed in space, resulting in significant superposition of their electromagnetic responses in both the time and frequency domains. The strong response of the internal conductors often masks the subtle damage characteristics of the shielding layer, leading to insufficient detection sensitivity and reliability. Existing methods often rely on simple time window truncation or band filtering for signal separation, making it difficult to effectively distinguish the phase and attenuation characteristics of different structural layers in complex transient responses. On the other hand, existing technologies typically analyze detection signals from single points or independent locations, neglecting the statistical correlation of spatial distribution along the cable axis. When shielding layer damage exhibits localized or gradual characteristics, the detection results are easily affected by noise, installation gaps, and fluctuations in operating conditions, leading to misjudgments or inaccurate positioning. Summary of the Invention

[0005] To overcome the above-mentioned defects of the prior art, embodiments of the present invention provide a heat-shrinkable cable shielding layer damage detection method and device based on pulsed eddy currents, which effectively solves the problems of insufficient sensitivity and positioning accuracy of shielding layer damage identification caused by the high superposition and difficulty in separation of the electromagnetic response of the internal conductor and the response of the shielding layer in the existing pulsed eddy current detection, and the damage characteristics being easily masked by noise and spatial fluctuations.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] In a first aspect, this application provides a method for detecting damage to the shielding layer of a heat-shrinkable cable based on pulsed eddy currents. The method includes: arranging a pulsed eddy current probe on the outer surface of the heat-shrinkable cable under test, applying a preset pulse excitation to the probe, and acquiring the original transient electromagnetic response signal; performing synchronous phase-sensitive demodulation on the original transient electromagnetic response signal, extracting its in-phase and quadrature components to obtain a phase cleanup signal; based on the spatial statistical characteristic difference between the shielding layer response and the conductor response, performing spatial joint reconstruction on the phase cleanup signal to obtain a cleanup reconstruction signal that enhances the shielding layer characteristics; extracting damage features based on the cleanup reconstruction signal, and judging the cable shielding layer damage and locating the damage area through the damage features.

[0008] In one embodiment, synchronous phase-sensitive demodulation of the original transient electromagnetic response signal further includes constructing a reference phase signal. Specific steps include: obtaining the excitation timing parameters of the pulse excitation control signal to determine the phase starting point, and generating a phase reference point sequence corresponding to the pulse repetition period; synchronously acquiring the pulsed eddy current transient response signal and preprocessing it according to the phase reference point sequence; performing time-frequency decomposition and signal reconstruction on the preprocessed signal to obtain a time-domain signal containing the main phase information; extracting the instantaneous phase of the time-domain signal, and performing phase continuity processing and smoothing denoising to generate a continuous and smooth reference phase signal.

[0009] In one embodiment, synchronous phase-sensitive demodulation is performed on the original transient electromagnetic response signal to extract its in-phase and quadrature components, thereby obtaining a phase-cleaned signal. This includes: synchronously multiplying and filtering the original transient electromagnetic response signal with both in-phase and quadrature reference signals to obtain in-phase and quadrature component signals; performing characteristic analysis and selective separation on the in-phase and quadrature component signals based on the differences in phase delay and attenuation rate between the shielding layer and the conductor; and reconstructing the signal based on the selective separation results to obtain the phase-cleaned signal.

[0010] In one embodiment, the original transient electromagnetic response signal is synchronously multiplied and filtered with both an in-phase reference signal and a quadrature reference signal to obtain in-phase and quadrature component signals. This includes: preprocessing the original transient electromagnetic response signal to obtain a signal to be processed; performing synchronous multiplication operations on the signal to be processed with both the in-phase and quadrature reference components to obtain in-phase and quadrature multiplication signals; and performing low-pass filtering on the in-phase and quadrature multiplication signals to obtain the in-phase and quadrature component signals.

[0011] In one embodiment, characteristic analysis is performed on the in-phase component signal and the quadrature component signal, including: selecting a response attenuation interval based on the in-phase component signal and the quadrature component signal, and extracting the transient attenuation characteristics and phase delay characteristics of the attenuation interval; performing comparative analysis on the transient attenuation characteristics and phase delay characteristics; and generating corresponding time interval markers in the in-phase component signal and the quadrature component signal according to the comparative analysis results, wherein the time interval markers are used to calibrate the phase component region dominated by the shielding layer response.

[0012] In one embodiment, region determination is performed based on the spatial statistical characteristics difference between the shielding layer response and the conductor response. Based on the determination result, the phase cleanup signal is spatially reconstructed using adaptive regularization to obtain a cleanup reconstruction signal with enhanced shielding layer characteristics. This includes: acquiring phase cleanup signals from multiple spatial locations distributed along the axial direction of the cable under test to form a preliminary cleanup signal set; pairing signals from adjacent spatial locations in the preliminary cleanup signal set to obtain multiple adjacent signal pairs to acquire a spatial correlation index; determining, based on the spatial correlation index, whether the dominant component of the signal at each spatial location is a shielding layer dominant response region or a local abnormal region; and performing spatial joint reconstruction using an adaptive regularization method based on the determination result to obtain a cleanup reconstruction signal with enhanced shielding layer characteristics.

[0013] In one embodiment, obtaining the purified reconstructed signal with enhanced shielding layer characteristics further includes: assigning initial regularization intensity parameters to the corresponding phase purified signal based on the determination results of the dominant signal components at each spatial location; constructing a reconstruction objective function based on the regularization intensity parameters, the reconstruction objective function including a data consistency constraint term and a spatial regularization constraint term; iteratively solving the problem by minimizing the reconstruction objective function, and dynamically updating the regularization intensity parameters according to the spatial continuity changes of the current reconstruction results; terminating the iteration and outputting the purified reconstructed signal when the amplitude of the reconstructed signal change between adjacent spatial locations meets a preset condition.

[0014] In one embodiment, damage features are extracted based on the cleaned and reconstructed signal. Damage to the cable shielding layer is determined and the damaged area is located based on the damage features. This includes: extracting phase features from the cleaned and reconstructed signal and performing fusion processing to generate a comprehensive damage feature index; establishing a background reference benchmark based on the comprehensive damage feature index; identifying the damage location by the degree of deviation between the comprehensive damage feature index and the background reference benchmark; merging spatially adjacent damage locations into a continuous damage area; determining the range and degree of damage of each damage area based on the spatial distribution of the comprehensive damage feature index within the damage area; and outputting the damage assessment and location results.

[0015] In one embodiment, the extent and degree of damage of each damage area are determined based on the spatial distribution of comprehensive damage characteristic indicators within the damage area, including: performing boundary correction on the initial spatial location range based on spatial change gradient analysis of damage characteristic indicators to obtain the corrected damage area range; performing adaptive weighted optimization on the degree of damage within the corrected damage area; and performing secondary analysis based on the weighted optimization results to determine the final refined damage area range and distribution characteristics.

[0016] Secondly, this application provides an electronic device, comprising:

[0017] Memory, used to store computer programs;

[0018] A processor is used to execute the computer program to implement the steps of the aforementioned pulsed eddy current-based heat-shrinkable cable shield damage detection method.

[0019] As can be seen from the above technical solutions, the embodiments of this application have the following advantages:

[0020] By constructing a reference phase signal and performing synchronous phase-sensitive demodulation, the shielding layer response and the internal conductor response can be effectively separated, significantly enhancing the shielding layer characteristic signal. By utilizing spatial statistical characteristics and adaptive reconstruction methods, the sensitivity and robustness of the signal to shielding layer damage are improved. Based on the normalized fusion and spatial distribution analysis of comprehensive damage characteristic indicators, the accurate location of the damaged area and the assessment of the degree of damage are realized, thereby improving the reliability and practicality of the detection. Attached Figure Description

[0021] Figure 1 A schematic diagram of the process for detecting damage to the heat-shrinkable cable shielding layer based on pulsed eddy currents, provided in an embodiment of this application.

[0022] Figure 2 This is a structural diagram of an electronic device provided in an embodiment of this application.

[0023] Figure 3 Line graph for determining spatial correlation index provided in the embodiments of this application. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0025] Reference Figure 1 As shown in the schematic diagram, the method for detecting damage to the heat-shrinkable cable shielding layer based on pulsed eddy currents provided by this invention includes the following steps:

[0026] S101, A pulsed eddy current probe is arranged on the outer surface of the heat-shrinkable cable to be tested, and a preset pulse excitation is applied to the pulsed eddy current probe to collect the original transient electromagnetic response signal corresponding to the pulse excitation and construct a reference phase signal.

[0027] In this process, a pulsed eddy current probe is positioned on the outer surface of the heat-shrinkable cable under test. A fitting method matching the probe structure is selected based on the cable diameter to ensure a stable contact between the probe's excitation coil and receiving coil and the cable surface, guaranteeing effective coupling of the excitation magnetic field to the cable's shielding layer. A preset pulse excitation is applied to the probe's excitation coil to simultaneously generate transient eddy current fields in the cable's shielding layer and internal conductors. Driven by this pulse excitation, the receiving coil acquires transient electromagnetic response signals that strictly correspond to each pulse excitation, and these signals are recorded as the original response sequence to ensure the synchronization of excitation and response in the time domain.

[0028] In this embodiment, constructing a reference phase signal includes:

[0029] Acquire a pulse excitation control signal and extract excitation timing parameters based on the pulse excitation control signal. The excitation timing parameters include the trigger time, rise time, and repetition period.

[0030] Specifically, the rising edge detection of the pulse excitation control signal at a fixed threshold is used to determine the pulse triggering time; the average period of multiple consecutive triggering times is calculated using the sliding window averaging method to obtain the pulse repetition period; and the rising edge time is determined by obtaining the time it takes for the pulse voltage to rise from 10% to 90%.

[0031] Based on the excitation timing parameters, key waveform feature points of the pulse excitation signal are identified, including rising edge inflection point, peak time, and falling edge zero point.

[0032] Based on the key waveform feature points, the corresponding phase start point is determined, and a sequence of phase reference points corresponding to each cycle is generated according to the pulse repetition period for periodic alignment of the reference phase.

[0033] Specifically, based on key waveform feature points, the corresponding phase start point is determined, and the phase start point is selected according to priority order (rising edge inflection point → peak value → falling edge zero point).

[0034] Based on the phase reference point sequence, the transient response signal synchronized with the reference point is obtained from the pulse eddy current receiving channel, and preprocessed to obtain the preprocessed signal for time-frequency decomposition.

[0035] The preprocessing includes band-limited filtering, baseline correction, and amplitude normalization of the signal.

[0036] Based on the spectral characteristics of the preprocessed signal, a wavelet envelope basis is selected (one of Db4 to Db10 from the Daubechies wavelet family is chosen as the wavelet envelope basis), and the number of decomposition levels is determined. This is based on the sampling frequency. With the lowest recognition frequency according to Determine the number of decomposition layers ;

[0037] Based on the determined wavelet packet basis and decomposition level, wavelet packet decomposition is performed on the preprocessed signal to obtain the sequence of all node coefficients of the Lth level, which is used to extract the target frequency band components.

[0038] Based on the node coefficient sequence, the energy of each node is calculated, and the node with the highest energy is selected as the dominant mode node.

[0039] The specific formula for calculating the energy is as follows:

[0040]

[0041] In the formula, Let be the energy of the k-th wavelet packet node. Let t be the node coefficient sequence of the k-th wavelet packet node in the L-th layer, and t be the index of the time sampling point.

[0042] Perform inverse wavelet packet transform on the main modal node to obtain a time-domain signal containing the main phase information for instantaneous phase extraction;

[0043] For time-domain signals, an analytic signal is constructed using the Hilbert transform, and the instantaneous phase is obtained by taking the amplitude of the analytic signal.

[0044] The instantaneous phase is demodulated and expanded by 2π, and then denoised by smoothing filtering to form a continuous and smooth reference phase signal. The reference phase signal includes an in-phase reference component and a quadrature reference component, which are used to characterize the difference between the shielding layer response and the internal conductor response in the phase domain.

[0045] It should be noted that by constructing a reference phase signal, a stable, periodic phase reference that is strictly synchronized with the pulse excitation can be provided for the transient response signal in subsequent phase-sensitive detection. This enables the extraction of in-phase and quadrature components to accurately distinguish between the shielding layer response and internal conductor interference, significantly improving the conductor suppression effect, enhancing the identifiability of the shielding layer characteristic signal, and providing a reliable phase reference for subsequent damage feature extraction and localization, thereby improving the detection accuracy, stability, and anti-interference capability.

[0046] S102, synchronous phase-sensitive demodulation is performed on the original transient electromagnetic response signal and the reference phase signal to extract the in-phase component and the quadrature component, and the shielding layer response and the internal conductor response are separated to obtain a phase purification signal dominated by the shielding layer response.

[0047] In this embodiment, the original transient electromagnetic response signal and the reference phase signal are synchronously phase-sensitively demodulated to extract the in-phase and quadrature components, and the shielding layer response and the internal conductor response are separated to obtain a phase-cleaned signal dominated by the shielding layer response, including:

[0048] The original transient electromagnetic response signal is preprocessed, including time alignment and amplitude normalization, to obtain the transient signal to be processed for phase-sensitive demodulation.

[0049] The transient signal to be processed is synchronously multiplied with the in-phase reference component and the quadrature reference component at each time step to obtain the corresponding in-phase product signal and quadrature product signal, thereby mapping the original transient electromagnetic response signal to the phase component space based on the reference phase.

[0050] Low-pass filtering is performed on the in-phase product signal and the quadrature product signal respectively to filter out the high-frequency modulation component introduced by the product operation, and only the low-frequency or DC component consistent with the trend of the reference phase change is retained, so as to obtain the in-phase component signal and the quadrature component signal of the transient signal to be processed respectively.

[0051] Based on the differences in phase delay and attenuation rate of the electromagnetic responses generated by the shielding layer and the internal conductor under pulsed eddy current excitation, the characteristics of the in-phase component signal and the quadrature component signal are analyzed to determine the target phase component region dominated by the shielding layer response.

[0052] Based on the characteristic analysis results, the in-phase component signal and the quadrature component signal are selectively separated to weaken the phase component corresponding to the internal conductor and highlight the phase component corresponding to the shielding layer, thereby achieving effective separation of the shielding layer response and the internal conductor response in the phase domain.

[0053] The selective separation specifically involves: firstly, based on the determined dominant phase component region of the shielding layer and the dominant phase component region of the internal conductor, assigning a high retention weight to the phase component region determined to be dominated by the shielding layer response and a low weight to the phase component region determined to be dominated by the internal conductor response in both the in-phase and quadrature component signals; subsequently, weighting the in-phase and quadrature component signals at each sampling time with their corresponding weights to reduce the contribution of the internal conductor phase component to the overall signal.

[0054] The in-phase component signal and the quadrature component signal after selective separation are reconstructed to obtain a phase-cleaned signal that is dominated by the electromagnetic response of the shielding layer and whose phase influence of the internal conductor is significantly suppressed.

[0055] Among them, the in-phase reference component refers to the reference signal component that maintains zero phase difference with the pulse excitation signal in terms of time reference and phase, and is used to characterize the in-phase relationship with the excitation signal in the transient electromagnetic response; the quadrature reference component refers to the reference signal component that is strictly synchronized with the in-phase reference component in time but differs from it by 90° in phase, and is used to characterize the quadrature phase relationship with the excitation signal in the transient electromagnetic response; the in-phase component signal refers to the demodulated signal that reflects the in-phase response characteristics with the excitation signal after synchronous phase-sensitive demodulation of the original transient electromagnetic response signal and the in-phase reference component and low-pass filtering; the quadrature component signal refers to the demodulated signal that reflects the phase lag or lead characteristics with the excitation signal after synchronous phase-sensitive demodulation of the original transient electromagnetic response signal and the quadrature reference component and low-pass filtering.

[0056] Furthermore, step S102 also includes a sub-step, based on the difference in phase delay and attenuation rate of the electromagnetic responses generated by the shielding layer and the internal conductor under pulsed eddy current excitation, to perform characteristic analysis on the in-phase component signal and the quadrature component signal, including:

[0057] For in-phase and quadrature component signals, corresponding in-phase and quadrature time series are constructed according to the sampling timing sequence consistent with the original transient electromagnetic response signal, so that each time series reflects the time evolution characteristics of the transient electromagnetic response on different phase components.

[0058] For in-phase and orthogonal time series, starting from the end of the pulse excitation, a response decay interval of a preset duration is selected as the time range for transient electromagnetic diffusion characteristic analysis.

[0059] For in-phase and quadrature time series within the decay interval, the corresponding amplitude and amplitude change rate are extracted as transient decay characteristics.

[0060] Based on the peak amplitude times of the in-phase and quadrature time series within the attenuation interval, the time delay of each phase component relative to the pulse excitation time is determined as a phase delay feature reflecting the difference in electromagnetic response propagation depth.

[0061] By comparing and analyzing the transient attenuation characteristics and phase delay characteristics, when a certain phase component simultaneously meets the discrimination conditions that the amplitude change rate is greater than a preset threshold and the phase delay is less than a preset delay threshold, the phase component is determined to be the target phase component whose response is mainly based on the cable shield layer.

[0062] Based on the comparative analysis results, corresponding time interval markers are generated in the in-phase time series and the orthogonal time series to identify the phase component region where the shielding layer response is dominant.

[0063] It should be noted that by utilizing the inherent differences in phase delay and attenuation rate between the shielding layer and the internal conductor for characteristic analysis, it is possible to achieve fine differentiation of different physical response sources in the time and phase domains. Thus, without relying on structural priors or additional sensing information, it is possible to innovatively achieve adaptive identification and calibration of the phase component dominated by the shielding layer response.

[0064] S103, based on the difference in spatial statistical characteristics between the shielding layer response and the conductor response, the region is determined, and based on the determination result, the phase purification signal is spatially reconstructed through adaptive regularization to obtain a purification reconstruction signal with enhanced shielding layer characteristics.

[0065] In this embodiment, region determination is performed based on the spatial statistical characteristics difference between the shielding layer response and the conductor response. Based on the determination result, the phase cleanup signal is spatially reconstructed using adaptive regularization to obtain a cleanup reconstruction signal with enhanced shielding layer characteristics, including:

[0066] The phase cleanup signals corresponding to multiple spatial positions distributed along the axial direction of the cable under test are acquired to form a preliminary cleanup signal set for the corresponding spatial positions. Each phase cleanup signal has been obtained after synchronous phase-sensitive demodulation and selective separation of phase components.

[0067] For signals at adjacent spatial locations in the preliminary purified signal set, they are paired according to spatial location order to obtain adjacent signal pairs, ensuring that each pair of adjacent signals corresponds to the phase component at the same sampling time.

[0068] Based on the adjacent signal pairs, spatial correlation indices between each spatial location and its adjacent spatial locations are obtained, and the spatial correlation indices are used to characterize the continuity of the phase purification signal in the spatial dimension.

[0069] like Figure 3As shown, each spatial location is determined according to the spatial correlation index. If the spatial correlation index is higher than the preset continuity threshold, it is determined to be the shielding layer's dominant response area. If the spatial correlation index is lower than the preset continuity threshold, it is determined to be a local abnormal area where there may be residual conductor interference.

[0070] Based on the judgment results, spatial joint reconstruction is performed using adaptive regularization to obtain a purified reconstruction signal with enhanced shielding layer characteristics.

[0071] Furthermore, based on the adjacent signal pairs, a spatial correlation index between each spatial location and its adjacent spatial locations is obtained, specifically:

[0072] Based on adjacent signal pairs, the phase cleanup signals corresponding to each pair of adjacent spatial locations are time-aligned according to a unified sampling timing sequence;

[0073] Based on the aligned adjacent signal pairs, trend features reflecting the phase cleanup signal change characteristics are extracted for each pair of adjacent signals within a preset time window. The trend features include the amplitude change direction and the first-order time difference, which are used to characterize the evolution trend of the phase response within the time window.

[0074] Based on trend characteristics, the trend direction of adjacent spatial locations at corresponding time sampling points is compared point by point. When the trend change direction of adjacent signals at corresponding time locations is consistent, the time location is determined to be a point of consistent trend.

[0075] The time sampling points that are determined to be trend consistency points are statistically analyzed, and the proportion of the number of trend consistency points to the total number of sampling points in the preset time window is calculated to obtain a statistical measure representing the degree of trend consistency between adjacent spatial locations.

[0076] The trend consistency statistic is used as a spatial correlation index between the corresponding spatial location and its adjacent spatial locations. The larger the value of the spatial correlation index, the stronger the continuity of the phase purification signal response at that spatial location.

[0077] It should be noted that by using the consistency of the changing trends of adjacent phase purification signals as a spatial correlation index, the impact of noise and local amplitude anomalies on correlation calculation can be effectively reduced, thus reflecting the continuity characteristics of the shielding layer response in the spatial dimension more robustly and reliably.

[0078] Furthermore, step S103 also includes a sub-step: based on the judgment result, spatial joint reconstruction is performed using adaptive regularization to obtain a purified reconstruction signal that enhances the characteristics of the shielding layer, including:

[0079] Based on the judgment results, an initial regularization intensity parameter is determined for the phase purification signal corresponding to each spatial location. Specifically, for spatial locations that are determined to be the dominant response area of ​​the shielding layer, a first regularization intensity parameter is assigned, and for local abnormal areas that are determined to be potentially affected by residual conductor interference, a second regularization intensity parameter greater than the first regularization intensity parameter is assigned.

[0080] Based on the regularization intensity parameter, a reconstruction objective function for joint spatial reconstruction of phase-cleaned signals is constructed, and minimizing the reconstruction objective function is used as the reconstruction criterion.

[0081] The specific calculation formula for the reconstructed objective function is as follows:

[0082]

[0083] In the formula, For the final output purified and reconstructed signal, Let t be the phase cleanup signal corresponding to the i-th spatial location, and t be the time sampling index. This is a data consistency constraint term used to constrain the difference between the cleaned reconstructed signal and the corresponding phase cleaned signal at each spatial location. It constrains the reconstruction result to be as close as possible to the original signal in the time domain, preventing over-smoothing or deviation from the physical true response. Let be the regularization intensity parameter for the i-th spatial location. This is a spatial regularization constraint term used to constrain the amplitude of signal variation in the cleaned and reconstructed signals at adjacent spatial locations. It constrains signal variations between adjacent spatial locations, enhances spatial continuity, and suppresses local anomalies (such as residual conductor interference).

[0084] The reconstruction objective function is solved iteratively. In each iteration, based on the continuous change of the current reconstruction result in the spatial dimension, that is, the change amplitude of the current cleaned reconstruction signal between adjacent spatial positions is obtained. If the change amplitude of the cleaned reconstruction signal at a certain spatial position is higher than the preset spatial stability threshold, the regularization intensity parameter corresponding to that spatial position is increased by a preset multiple. If the change amplitude of the reconstruction signal at a certain spatial position is lower than the spatial stability threshold, the regularization intensity parameter corresponding to that spatial position is decreased by a preset multiple. The regularization intensity parameter corresponding to each spatial position is adaptively updated, so that the regularization intensity parameter is adaptively adjusted with the change of spatial response stability.

[0085] If the amplitude of the reconstructed signal change between adjacent spatial locations is less than a preset convergence threshold in a preset number of consecutive iterations, the iteration process is terminated, and the final reconstructed purified reconstructed signal with enhanced shielding layer response characteristics and suppressed residual conductor response is output.

[0086] It should be noted that the above-mentioned spatial joint reconstruction method can effectively suppress residual conductor interference and local abnormal signals while maintaining the original shielding layer response characteristics, thereby achieving the continuity and feature enhancement of the shielding layer response in the spatial dimension, and thus significantly improving the accuracy and reliability of cable shielding layer damage detection.

[0087] S104: Based on the purified and reconstructed signal, extract damage features, determine the damage to the cable shielding layer according to the damage features, and locate the corresponding damage area.

[0088] The purified and reconstructed signal is a transient time sequence signal obtained after phase purification and spatial joint reconstruction, which is mainly based on the shielding layer response, and the spatial sequence of the purified and reconstructed signal is constructed according to the spatial position order.

[0089] In this embodiment, damage features are extracted based on the purified reconstructed signal, and damage to the cable shielding layer is determined according to these features. The corresponding damaged areas are then located, including:

[0090] The purification and reconstruction signal of each spatial location is segmented within a preset time range after the excitation ends, and divided into multiple time sub-windows including an early time window and a subsequent time window.

[0091] The phase energy values ​​of the purified and reconstructed signals within each time sub-window are calculated respectively. Based on the ratio of the phase energy of the early time window to the phase energy of the whole time range, a phase energy concentration feature is constructed to characterize the energy distribution characteristics of the shielding layer response in the time dimension.

[0092] The specific calculation formula for the phase energy concentration characteristic is as follows:

[0093]

[0094] In the formula, Let be the phase energy concentration characteristic value at spatial location i, representing the proportion of energy in the early time window to the total energy. Let be the transient response amplitude of the purified reconstructed signal at spatial location i at time sampling point t, and N be the total number of sub-windows within the time range. This represents the number of child windows in the early time window. Let m be the set of sampling points within the m-th time sub-window. For the energy of the early time window, This represents the total energy over the entire time span.

[0095] For the purification and reconstruction signal corresponding to each spatial location, the amplitude difference between adjacent time sampling points is calculated within the time sub-window to obtain the first-order amplitude change rate of the phase amplitude with time, and a phase decay curve is constructed accordingly.

[0096] Based on the phase attenuation curve, the degree of fluctuation of the attenuation rate within a preset time range is calculated as a phase attenuation consistency characteristic, which is used to reflect the degree of influence of shielding layer damage on the electromagnetic diffusion process.

[0097] The specific formula for calculating the degree of fluctuation is as follows:

[0098]

[0099] In the formula, For the degree of fluctuation, The total number of sampling points within the time range. The set of all sampling points within the time range. Let be the first-order rate of change of the signal amplitude at time t. It is the mean of the first-order amplitude change rate.

[0100] The phase features, including phase energy concentration features and phase attenuation consistency features, are normalized and compared with preset corresponding feature thresholds. When all phase features exceed their respective preset abnormal thresholds, the normalized features are weighted and summed to obtain a comprehensive damage feature index.

[0101] In the spatial sequence of the purified and reconstructed signal, a spatial segment with a change amplitude of comprehensive damage characteristic index less than a preset change threshold and continuous spatial distribution is selected as the healthy background area.

[0102] Statistical analysis is performed on the comprehensive damage characteristic indicators within the healthy background area to obtain a background reference benchmark, which includes a background reference value and its fluctuation range.

[0103] The background reference value is the mean of the comprehensive damage characteristic index of all spatial locations within the healthy background segment, and the fluctuation range is the standard deviation of the comprehensive characteristic index within the healthy background segment, which quantifies its volatility.

[0104] The comprehensive damage characteristic index at other spatial locations is compared with the background reference value by performing a relative deviation analysis. When the deviation of the comprehensive damage characteristic index at a certain spatial location from the background reference value exceeds the preset damage judgment condition (i.e., exceeds the preset deviation threshold), the spatial location is judged as the cable shielding layer damage location.

[0105] For spatial points identified as damage locations, a continuity analysis is performed according to the spatial location order, and multiple spatial locations that are adjacent and continuously meet the damage determination conditions are merged into the same damage area.

[0106] Based on the spatial distribution of comprehensive damage characteristic indicators within the damaged area, the spatial range and damage severity distribution characteristics of the damaged area are determined.

[0107] Damage assessment results and damage area location results of the output cable shielding layer, including the spatial location range, spatial distribution characteristics and severe damage locations of each damage area.

[0108] It should be noted that by performing time-domain segmented analysis on the purified reconstructed signal at each spatial location, the phase energy concentration and phase attenuation consistency features are extracted. A comprehensive damage feature index is constructed through normalization, threshold determination, and weighted combination. Combined with statistical analysis of healthy background segments in the spatial sequence, adaptive deviation determination is achieved. At the same time, spatial continuity is used to merge adjacent abnormal locations, thereby achieving accurate judgment and location of cable shielding damage. The innovation of this method lies in making full use of time-phase characteristics and spatial continuity information, which makes damage identification highly reliable, has high spatial resolution, strong noise resistance, and significantly reduces the risk of misjudgment caused by single feature anomalies.

[0109] Furthermore, step S104 also includes a sub-step: determining the spatial range and damage severity distribution characteristics of the damaged area based on the spatial distribution of comprehensive damage characteristic indicators within the damaged area, specifically:

[0110] The minimum and maximum values ​​of the continuous spatial location indices in the damaged region are respectively used as the initial spatial location range of the damaged region, and the initial spatial location range includes the initial start position and the initial end position.

[0111] Calculate the spatial change gradient of the comprehensive damage characteristic index. If the spatial change gradient is continuously greater than the preset gradient threshold, the corresponding spatial position is included in the damage area, thereby expanding outward to correct the starting or ending position. When the spatial change gradient is less than the gradient threshold, stop the boundary expansion and finally determine the spatial position range of the corrected damage area, including the starting and ending positions.

[0112] The specific calculation formula for the spatial variation gradient is as follows:

[0113]

[0114] In the formula, For spatial variation gradient, Let be the comprehensive damage characteristic index for the i-th spatial location. This is the comprehensive damage characteristic index for the (i-1)th spatial location.

[0115] Within the corrected damage area, the comprehensive damage characteristic index corresponding to each spatial location is normalized to obtain a normalized damage degree sequence.

[0116] Based on the normalized damage degree sequence, damage degree distribution features are extracted, including local peak positions, length of continuous high-value segments, and overall damage gradient.

[0117] Among them, the local peak position is the spatial position that satisfies that its normalized damage degree is greater than that of the adjacent spatial positions and is greater than the preset peak threshold; the length of the continuous high value segment is the number of spatial positions where the normalized damage degree is continuously greater than the preset high value threshold; the overall damage gradient is the slope value obtained by linearly fitting the normalized damage degree with the spatial position, which is used to characterize the trend of damage degree change along the spatial direction.

[0118] The phase decay consistency characteristics, phase energy concentration characteristics, and normalized damage degree consistency are normalized and weighted summed to obtain adaptive weight coefficients.

[0119] Among them, normalized damage consistency refers to a measure of whether the normalized damage index at two or more spatially adjacent measurement locations maintains relative similarity, smoothness and continuity in terms of numerical magnitude and trend of change. It is used to reflect the spatial stability and reliability of damage characteristics.

[0120] The normalized damage level consistency is calculated using the following formula:

[0121]

[0122] In the formula, To normalize the consistency of damage levels, Let represent the normalized damage level at the i-th spatial location. The normalized damage level is the (i-1)th spatial location. This represents the maximum difference in damage severity pre-calculated within the damaged area. The closer the normalized damage severity consistency is to 1, the more consistent the damage severity is between adjacent spatial locations.

[0123] The normalized damage degree is weighted using the adaptive weight coefficients. By performing boundary gradient analysis (i.e., obtaining the spatial location range of the damage area) and extracting spatial distribution features on the weighted damage degree sequence, a refined spatial location range and spatial distribution features of the damage area are obtained, highlighting the location of local severe damage.

[0124] Specifically, highlighting the location of severe local damage involves: based on the local peak position in the refined spatial distribution characteristics, if the local peak position of a certain spatial location simultaneously satisfies: greater than its adjacent positions before and after it; and greater than a preset severe damage threshold, then the location is determined to be the center point of severe damage; extending from the center point of severe damage to both sides, spatial locations that continuously satisfy the condition that the local peak position is greater than a preset secondary threshold are merged into the same severe damage sub-segment to obtain the severe damage location.

[0125] It should be noted that by determining the initial range of the damaged area based on comprehensive damage characteristic indicators, and then using spatial variation gradients to adaptively expand and finely correct the boundary of the damaged area, a normalized damage degree and its spatial distribution characteristics analysis are introduced within the damaged area. Adaptive weights are constructed by combining phase attenuation consistency, phase energy concentration, and spatial consistency. This process not only suppresses the influence of noise and isolated anomalies, but also highlights severely damaged locations with spatial continuity and high damage degree. Ultimately, this achieves refined, quantitative, and highly reliable positioning of the cable shielding layer damage location, damage range, and damage degree distribution.

[0126] Furthermore, embodiments of this application also disclose an electronic device, Figure 2 This is a structural diagram of an electronic device 20 according to an exemplary embodiment. The content of the diagram should not be construed as limiting the scope of this application.

[0127] Figure 2 This is a schematic diagram of the structure of an electronic device 20 provided in an embodiment of this application. Specifically, the electronic device 20 may include: at least one processor 21, at least one memory 22, a power supply 23, a communication interface 24, an input / output interface 25, and a communication bus 26. The memory 22 stores a computer program, which is loaded and executed by the processor 21 to implement the relevant steps in the pulsed eddy current-based heat-shrinkable cable shielding damage detection method disclosed in any of the foregoing embodiments. Alternatively, the electronic device 20 in this embodiment may specifically be a computer.

[0128] In this embodiment, the power supply 23 is used to provide operating voltage for each hardware device on the electronic device 20; the communication interface 24 can create a data transmission channel between the electronic device 20 and external devices, and the communication protocol it follows can be any communication protocol applicable to the technical solution of this application, and is not specifically limited here; the input / output interface 25 is used to acquire external input data or output data to the outside world, and its specific interface type can be selected according to specific application needs, and is not specifically limited here.

[0129] The processor 21 may include one or more processing cores, such as a 4-core processor or an 8-core processor. The processor 21 may be implemented using at least one hardware form selected from DSP (Digital Signal Processing), FPGA (Field-Programmable Gate Array), and PLA (Programmable Logic Array). The processor 21 may also include a main processor and a coprocessor; the main processor is used for processing data during wake-up.

[0130] A processor that processes data in standby mode is also called a CPU (Central Processing Unit); a coprocessor is a low-power processor that processes data in standby mode. In some embodiments, processor 21 may integrate a GPU (Graphics Processing Unit), which is responsible for rendering and drawing the content that the display screen needs to show. In some embodiments, processor 21 may also include an AI (Artificial Intelligence) processor, which is used to handle computational operations related to machine learning.

[0131] In addition, the memory 22, as a carrier for resource storage, can be a read-only memory, random access memory, disk or optical disk, etc. The resources stored thereon can include operating system 221, computer program 222, etc., and the storage method can be temporary storage or permanent storage.

[0132] The operating system 221 manages and controls the various hardware devices and computer programs 222 on the electronic device 20 to enable the processor 21 to perform calculations and processing on the massive amounts of data 223 in the memory 22. It can be Windows Server, Netware, Unix, Linux, etc. The computer program 222, in addition to including a computer program capable of performing the pulsed eddy current-based heat-shrinkable cable shield damage detection method disclosed in any of the foregoing embodiments, may further include computer programs capable of performing other specific tasks. The data 223 may include data received by the electronic device from external devices, as well as data collected by its own input / output interface 25.

[0133] The above formulas are all dimensionless calculations. The formulas are derived from software simulations based on a large amount of collected data to obtain the most recent real-world results. The preset parameters in the formulas are set by those skilled in the art according to the actual situation.

[0134] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, in the form of a computer program product.

[0135] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0136] In addition, the functional modules in the various embodiments of this application can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0137] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0138] In conclusion, the above description is only a preferred embodiment of the present invention and is 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 detecting damage to a heat-shrinkable cable shield layer based on pulsed eddy currents, characterized in that, The method comprises the following steps: arranging a pulse eddy current probe on the outer surface of the to-be-tested heat-shrinkable cable, applying a preset pulse excitation to the probe, and collecting an original transient electromagnetic response signal; synchronously performing phase-sensitive demodulation on the original transient electromagnetic response signal, extracting in-phase and quadrature components thereof, and obtaining a phase-purified signal; based on the spatial statistical characteristic difference between the shield layer response and the conductor response, performing regional determination, and based on the determination result, performing spatial joint reconstruction on the phase-purified signal through adaptive regularization to obtain a purified reconstructed signal with enhanced shield layer characteristics, comprising: obtaining a preliminary purified signal set composed of phase-purified signals at multiple spatial positions distributed along the axial direction of the to-be-tested cable; pairing signals at adjacent spatial positions in the preliminary purified signal set to obtain multiple adjacent signal pairs to obtain a spatial correlation index; determining, according to the spatial correlation index, that the signal dominant component at each spatial position is a shield layer dominant response region or a local abnormal region; based on the determination result, performing spatial joint reconstruction through an adaptive regularization method to obtain a purified reconstructed signal with enhanced shield layer characteristics; the purified reconstructed signal with enhanced shield layer characteristics further comprises: according to the determination result of the signal dominant component at each spatial position, assigning an initial regularization strength parameter to the corresponding phase-purified signal; based on the regularization strength parameter, constructing a reconstruction objective function, wherein the reconstruction objective function comprises a data consistency constraint term and a spatial regularization constraint term; iteratively solving based on the criterion of minimizing the reconstruction objective function, and dynamically updating the regularization strength parameter according to the spatial continuity change of the current reconstruction result; when the change amplitude of the reconstruction signal between adjacent spatial positions meets a preset condition, terminating the iteration and outputting the purified reconstructed signal; based on the purified reconstructed signal, extracting a damage feature, and determining and positioning a cable shield layer damage through the damage feature.

2. The pulsed eddy current based thermal shrinkage cable shield damage detection method of claim 1, wherein, The synchronous phase-sensitive demodulation of the original transient electromagnetic response signal further comprises constructing a reference phase signal, and the specific steps comprise: determining a phase starting point based on the excitation timing parameter of the pulse excitation control signal, and generating a phase reference point sequence corresponding to the pulse repetition period; synchronously collecting the pulse eddy current transient response signal based on the phase reference point sequence and performing preprocessing; performing time-frequency decomposition and signal reconstruction on the preprocessed signal to obtain a time-domain signal containing main phase information; extracting the instantaneous phase of the time-domain signal and performing phase continuity processing and smoothing denoising to generate a continuous and smooth reference phase signal.

3. The pulsed eddy current based thermal shrinkage cable shield damage detection method of claim 1, wherein, The synchronous phase-sensitive demodulation of the original transient electromagnetic response signal, the extraction of the in-phase component and the quadrature component, and the obtaining of the phase-purified signal comprise: synchronously multiplying and filtering the original transient electromagnetic response signal with the in-phase reference signal and the quadrature reference signal to obtain in-phase component signals and quadrature component signals; based on the difference characteristics of the phase delay and the attenuation rate of the shield layer response and the conductor response, performing characteristic analysis and selective separation on the in-phase component signals and the quadrature component signals; performing reconstruction processing according to the selective separation result to obtain the phase-purified signal.

4. The pulsed eddy current based thermal shrinkage cable shield damage detection method of claim 3, wherein, The original transient electromagnetic response signal is respectively multiplied with the in-phase reference signal and the quadrature reference signal, and the in-phase component signal and the quadrature component signal are obtained through filtering processing. The original transient electromagnetic response signal is preprocessed to obtain a to-be-processed signal; The to-be-processed signal is respectively multiplied with the in-phase reference component and the quadrature reference component to obtain the in-phase product signal and the quadrature product signal; The in-phase product signal and the quadrature product signal are low-pass filtered to obtain the in-phase component signal and the quadrature component signal.

5. The pulsed eddy current based thermal shrinkage cable shield damage detection method of claim 3, wherein, The in-phase component signal and the quadrature component signal are analyzed, including: Based on the in-phase component signal and the quadrature component signal, a response attenuation interval is selected, and transient attenuation characteristics and phase delay characteristics of the attenuation interval are extracted; The transient attenuation characteristics and the phase delay characteristics are compared and analyzed; According to the comparison and analysis result, corresponding time interval markers are generated in the in-phase component signal and the quadrature component signal, and the time interval markers are used to mark the phase component region dominated by the shielding layer response.

6. The pulsed eddy current based thermal shrinkage cable shield damage detection method of claim 1, wherein, The damage characteristics are extracted based on the purified reconstruction signal, the cable shielding layer damage is judged and the damage region is located through the damage characteristics, including: Phase characteristics are extracted from the purified reconstruction signal and fusion processing is performed to generate a comprehensive damage characteristic index; A background reference benchmark is established based on the comprehensive damage characteristic index, and the damage position is identified by the deviation degree of the comprehensive damage characteristic index and the background reference benchmark; Spatially adjacent damage positions are combined into continuous damage regions, and the range and damage degree of each damage region are determined according to the spatial distribution of the comprehensive damage characteristic index in the damage region, and the damage evaluation and positioning result is output.

7. The pulsed eddy current based thermal shrinkage cable shield damage detection method of claim 6, wherein, The range and damage degree of each damage region are determined according to the spatial distribution of the comprehensive damage characteristic index in the damage region, including: Based on the spatial variation gradient analysis of the damage characteristic index, the initial spatial position range is boundary corrected to obtain a corrected damage region range; The damage degree in the corrected damage region is adaptively weighted and optimized; Based on the weighted optimization result, secondary analysis is performed to determine the final refined damage region range and distribution characteristics.

8. An electronic device, comprising: It includes: A memory for saving a computer program; A processor for executing the computer program to realize the steps of the pulse eddy current based thermal contraction cable shielding layer damage detection method according to any one of claims 1 to 7.

Images