Cable safety monitoring and early warning system

Abstract

The invention discloses a cable safety monitoring and early warning system comprising the following modules: a disturbance injection module used for injecting a double-frequency disturbance electric signal; the temperature acquisition module is used for acquiring temperature change data of each monitoring point of the cable; the residual construction module is used for constructing a two-dimensional disturbance thermal residual spectrum; the thermal evolution analysis module is used for performing wavelet packet multi-scale decomposition on the disturbance thermal residual spectrum and generating a two-dimensional thermal evolution image through an improved back projection reconstruction algorithm; the first early warning calculation module is used for acquiring a thermal response function and calculating a time partial derivative to obtain a thermal evolution trend index as a first early warning factor; the vibration acquisition module is used for acquiring a reflection waveform data set; the second early warning calculation module is used for calculating an equal-amplitude decay time symmetry rate index as a second early warning factor; and the early warning generation module is used for generating a final early warning scheme according to a preset judgment rule. According to the invention, on the basis of dual-frequency disturbance excitation and an improved back projection reconstruction algorithm, intelligent early warning of cable monitoring is realized.

Description

Technical Field

[0001] This invention relates to the field of power equipment safety monitoring technology, and in particular to a cable safety monitoring and early warning system. Background Technology

[0002] As a key component of power transmission systems, the operational safety of power cables directly affects the stability of the power grid and the reliability of power supply. With the continuous growth of urban power grid loads and the rapid increase in the number of underground cables, the operating environment of cables is becoming increasingly complex. In particular, high temperatures, humidity, mechanical stress, and aging factors can easily lead to problems such as insulation degradation, sheath cracking, and structural voids, resulting in localized overheating or breakdown faults. Therefore, research on online monitoring and early warning of cable insulation status and structural integrity has become a hot topic in the field of smart grids in recent years.

[0003] Traditional cable condition monitoring technologies mainly focus on methods such as temperature measurement, partial discharge detection, and infrared thermal imaging. For example, distributed fiber optic temperature sensors, thermocouples, and infrared cameras are used to monitor temperature changes on the cable surface or adjacent areas in real time, and the presence of anomalies is determined by combining these with set temperature thresholds. However, these technologies rely heavily on passive sensing methods, lack the ability to stimulate disturbances in deep insulation structures, struggle to detect subtle thermal anomalies in the early stages of degradation, and are easily affected by ambient temperature fluctuations and load disturbances, resulting in poor early warning accuracy.

[0004] Meanwhile, existing structural integrity monitoring methods based on vibration or ultrasonic reflection analysis are commonly used in oil and gas pipelines and rail transit. Applying them to cable monitoring presents the following challenges: (1) The internal structure of cables is mostly covered with multiple layers of materials, and the vibration signal propagation path is complex. The reflected echoes often exhibit nonlinear attenuation and multiple superposition characteristics; (2) Traditional analysis methods such as time delay judgment and frequency domain energy calculation have limited ability to distinguish local structural damage and it is difficult to extract effective abnormal indicators from higher-order features such as waveform symmetry; (3) Vibration testing and temperature analysis are usually performed separately, lacking a unified perception and fusion analysis technical framework.

[0005] Some studies have proposed active diagnostic techniques based on perturbation excitation combined with thermal imaging. These techniques involve artificially injecting current to stimulate the internal thermal response of the cable, and then recording the temperature rise trajectory using an infrared camera to aid analysis. However, these techniques often rely on image acquisition equipment, and their resolution is limited by sensor accuracy and installation conditions, making it difficult to achieve high-density monitoring along the entire cable length. Furthermore, they lack thermal response modeling and physical interpretation mechanisms, remaining at the stage of thermal image visualization. They have not yet generated quantifiable trend factor outputs, and cannot form a unified early warning system with structural reflection indicators.

[0006] Therefore, how to provide a cable safety monitoring and early warning system is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] One objective of this invention is to propose a cable safety monitoring and early warning system. Based on dual-frequency disturbance excitation and an improved back-projection reconstruction algorithm, this invention achieves intelligent early warning for cable monitoring. It combines multi-point temperature response differential and wavelet packet energy decomposition to reconstruct a two-dimensional thermal evolution image, extracting partial derivatives of the thermal response function to construct thermal degradation trend indicators. Furthermore, it introduces micro-vibration reflection waveform analysis to calculate the symmetry rate of constant amplitude attenuation time as a basis for judging structural integrity. By integrating two types of early warning factors for joint judgment, a hierarchical and location-based early warning scheme is formed, possessing advantages such as high detection accuracy, fast response speed, and wide applicability.

[0008] A cable safety monitoring and early warning system according to an embodiment of the present invention includes the following modules: The disturbance injection module is used to periodically and synchronously inject a dual-frequency disturbance electrical signal consisting of a first frequency and a second frequency into both ends of the cable. The temperature acquisition module is used to collect temperature change data at various monitoring points of the cable within a set response time window and generate a disturbance temperature response curve. The residual construction module is used to perform difference calculation between the perturbation temperature response curve and the steady temperature distribution curve to construct a two-dimensional perturbation thermal residual map. The thermal evolution analysis module is used to perform wavelet packet multi-scale decomposition on the two-dimensional perturbation thermal residual map and generate a two-dimensional thermal evolution image through an improved back-projection reconstruction algorithm. The first early warning calculation module is used to obtain the thermal response function by fitting the two-dimensional thermal evolution image and calculate the time partial derivative to obtain the thermal evolution trend index as the first early warning factor. The vibration acquisition module includes a piezoelectric vibrator and a vibration receiver. The piezoelectric vibrator is used to periodically apply millisecond excitation pulses, and the vibration receiver acquires reflected signals to obtain a reflected waveform dataset. The second early warning calculation module is used to calculate the constant amplitude attenuation time symmetry index based on the reflection waveform dataset, which serves as the second early warning factor. The early warning generation module is used to generate a final early warning scheme by jointly judging based on the first early warning factor and the second early warning factor according to preset judgment rules.

[0009] A cable safety monitoring and early warning method according to an embodiment of the present invention includes the following steps: S1. During the period when the cable is in a stable operating state, a dual-frequency disturbance electrical signal consisting of a first frequency and a second frequency is periodically injected into the cable. S2. After the dual-frequency disturbance electrical signal is injected, collect the instantaneous temperature change data of each monitoring point of the cable within the set response time window to obtain the disturbance temperature response curve. S3. Perform a difference calculation between the disturbance temperature response curve and the stable temperature distribution curve before the dual-frequency disturbance electrical signal injection to construct a disturbance thermal residual map. S4. Perform wavelet packet multi-scale decomposition on the disturbed thermal residual map and generate a two-dimensional thermal evolution image based on the improved back-projection reconstruction algorithm; S5. The thermal response function is obtained by fitting the two-dimensional thermal evolution image and the time partial derivative is calculated to obtain the thermal evolution trend index, which serves as the first early warning factor. S6. Install a piezoelectric vibrator outside the cable sheath, apply millisecond excitation pulses periodically, and have a vibration receiver collect the reflected signal to obtain a reflected waveform dataset. S7. Extract reflection peaks and find equal amplitude points for each group of waveforms in the reflection waveform dataset to obtain the equal amplitude decay time symmetry index, which serves as the second early warning factor. S8. Based on the preset judgment rules, a joint judgment is made on the first warning factor and the second warning factor to generate the final warning scheme.

[0010] Optionally, the first frequency is 5kHz and the second frequency is 11kHz. The dual-frequency disturbance signal is injected synchronously through both ends of the cable for a duration of 10ms. The dual-frequency design is used to simultaneously excite the cable medium's thermal inertial response at low frequency (5kHz) and its perturbation-sensitive response at high frequency (11kHz) to jointly obtain the cable's temperature response characteristics under different thermal diffusion time constants. Compared to a single-frequency disturbance signal, this enhances the detection resolution of minor thermal anomalies and improves the stability of early warning indicators.

[0011] Optionally, S2 specifically includes: S21. Set a response time window, which starts at the moment when the dual-frequency disturbance electrical signal injection is completed and lasts for 200ms. S22. Within the response time window, the temperature acquisition module is activated, and multiple monitoring points deployed along the cable length direction synchronously acquire the instantaneous temperature change data of the cable. S23. Arrange the instantaneous temperature change data collected from each monitoring point according to the time series to generate the corresponding temperature change curve; S24. Perform noise filtering on the temperature change curve to generate a disturbance temperature response curve. The noise filtering includes performing sliding window averaging on the temperature change curve to eliminate jitter, and applying a bandpass filter to the smoothed temperature change curve to retain the response range corresponding to the frequency components of the dual-frequency disturbance signal. The passband frequency range of the bandpass filter is matched with the first frequency of 5kHz and the second frequency of 11kHz to filter out background thermal responses unrelated to the disturbance.

[0012] Optionally, S3 specifically includes: S31. After the disturbance temperature response curve is generated, obtain the stable temperature distribution curve before the injection of the dual-frequency disturbance electrical signal within the corresponding cable monitoring cycle. The stable temperature distribution curve is the cable temperature curve collected under undisturbed conditions. S32. Register the disturbance temperature response curve and the stable temperature distribution curve on the time axis to ensure that they have the same sampling length and time correspondence. S33. Perform point-by-point difference calculation on the registered disturbance temperature response curve and the stable temperature distribution curve to calculate the residual sequence of temperature changes and form the temperature residual dataset corresponding to each monitoring point. S34. Arrange the temperature residual datasets of each monitoring point synchronously with the time series according to the spatial layout order of the cable, and construct a two-dimensional disturbance thermal residual matrix. S35. Perform pseudo-color mapping processing on the two-dimensional perturbation thermal residual matrix to convert the temperature residual values ​​into color gradients and generate a perturbation thermal residual map. The pseudo-color mapping processing includes mapping the temperature residual values ​​to a fixed color gradient range according to a piecewise linear function, with low residual values ​​corresponding to cool colors and high residual values ​​corresponding to warm colors, thereby enhancing the visualization and recognition effect of local thermal anomalies.

[0013] Optionally, S4 specifically includes: S41. Obtain the disturbed thermal residual spectrum. ,in Represents the spatial coordinates along the length of the cable. This represents the time coordinates after the injection of the dual-frequency disturbance electrical signal; S42, the perturbation thermal residual spectrum Perform two-dimensional wavelet packet multi-scale decomposition and extract each decomposition level. wavelet packet coefficients ,in Indicates the total number of decomposition levels. Indicates the first Wavelet packet coefficients of the layer; S43. Calculate the wavelet energy ratio index for each decomposition level. : ; in, Indicates the first Wavelet packet coefficients of the layer; S44. According to the preset energy threshold Select the one that satisfies The set of principal energy scales, and retain the corresponding wavelet packet coefficients for spectrum reconstruction; S45. Perform inverse wavelet packet reconstruction on the principal energy scale set to obtain the perturbed thermal residual reconstruction map. ; S46. Reconstruct the spectrum based on the perturbation thermal residual. A two-dimensional thermal evolution image is generated using an improved back-projection reconstruction algorithm. The improvement of the algorithm lies in the use of a nonlinear convolution kernel function that fuses a two-dimensional Gaussian diffusion kernel and an exponential annealing term. ; in, Represents a two-dimensional thermal evolution image. Indicates the spatial location of the perturbation thermal residual reconstruction map. and time location The value on, This represents the kernel normalization constant. Indicates the center annealing adjustment parameters. Represents an exponential function. This represents the standard deviation of heat diffusion in the spatial direction. This represents the standard deviation of heat diffusion over time.

[0014] Optionally, S5 specifically includes: S51. Obtain a two-dimensional thermal evolution image. ,in Represents the spatial coordinates along the length of the cable. This represents the time coordinates after the injection of the dual-frequency disturbance electrical signal; S52, For each spatial location Extract the spatial location Corresponding thermal evolution curve ; S53. The least squares method is used to analyze the thermal evolution curve. Perform fitting to obtain the thermal response function The thermal response function Defined as a combined function with an exponentially decaying term and a perturbation excitation recovery term: ; in, Indicates the intensity of the excitation response. Represents the rate of ascent coefficient. Indicates the attenuation coefficient. Represents the thermal steady-state offset constant; S54, Regarding the thermal response function The first-order time partial derivative yields the thermal response rate function, which is used to quantify spatial location. The changing trend of thermal disturbance response intensity; S55. Select the response time window set after the disturbance, calculate the average value of the first-order time partial derivative within the time period, and use it as the spatial location. Thermal evolution trend indicators ; S56, The thermal evolution trend index It is used as the first early warning factor and output.

[0015] Optionally, S6 specifically includes: S61. Several piezoelectric vibrators and corresponding vibration receivers are arranged at intervals along the length of the cable on the outer surface of the cable sheath. S62. Control the piezoelectric vibrator to apply excitation pulses with a duration of 1 to 10 milliseconds and an amplitude of no more than 0.5 micronewtons at a set period; S63. After each excitation pulse is applied, the vibration receiver synchronously collects the reflected signal from the internal structure of the cable sheath; S64. Record and store the waveform data of the reflected signal, and perform time-domain alignment and amplitude normalization processing on the waveform data to output the reflected waveform dataset.

[0016] Optionally, S7 specifically includes: S71. Obtain the reflected waveform dataset, which contains waveform data of multiple sets of reflected signals collected by the vibration receiver, with each set of waveforms corresponding to a complete response process within one excitation cycle; S72. Perform reflection peak extraction on each group of waveforms, find equal amplitude points on both sides of each reflection peak, record the time coordinates of each pair of equal amplitude points, and calculate the equal amplitude symmetrical time difference. ; S73. Calculate the constant amplitude decay time symmetry index (TASR) corresponding to the waveform: ; in, This indicates the number of equal amplitude point pairs in the waveform. Indicates the duration of the entire waveform; S74. The output of the constant amplitude attenuation time symmetry index TASR is used as the second early warning factor to characterize the internal structural continuity of the cable segment structure and the degree of symmetry maintenance of the reflected signal. The closer TASR is to 1, the better the structural continuity.

[0017] Optionally, S8 specifically includes: S81, Preset the first warning factor threshold With the second early warning factor threshold ,in Risk threshold as an indicator of thermal evolution trend As a lower limit for judging the structural integrity of the constant amplitude decay time symmetry index; S82. During the current monitoring cycle, obtain the first early warning factor for each monitoring point of the cable. With the corresponding second early warning factor value , representing the thermal degradation rate and structural symmetry at the corresponding spatial locations, respectively; S83. According to the preset judgment rules, a joint judgment is made based on the first warning factor and the second warning factor. The preset judgment rules include: like and If so, it is judged as a high-risk warning; like and If so, it is determined as a thermal degradation warning; like and If so, it is determined as a structural anomaly warning; like and If so, it is determined to be a safe state; S84. Generate a structured early warning record for each cable monitoring point according to the results of the preset judgment rules. The structured early warning record includes the early warning type, spatial location and timestamp. S85. Summarize the corresponding structured early warning records of each monitoring point to generate the final early warning plan.

[0018] The beneficial effects of this invention are: (1) By combining dual-frequency perturbation electrical signal injection with bandpass filtering extraction, the internal thermal response of the cable is actively excited and the temperature change characteristics of the corresponding frequency band are extracted, which effectively improves the sensitivity and identification resolution of early insulation degradation. (2) A two-dimensional thermal evolution image is constructed by using wavelet packet multi-scale decomposition and improved back projection reconstruction algorithm, and the thermal response function is fitted based on the exponential combination model, which can quantify the thermal anomaly evolution trend and form a physically interpretable first early warning factor. (3) A method for analyzing the symmetry of millisecond-level micro-vibration excitation and reflection waveforms is introduced, and the constant amplitude decay time symmetry index (TASR) is proposed, which can reflect the continuity of the cable structure and the internal defects, forming a second early warning factor for structure guidance. (4) By setting dual thresholds for thermal degradation trend and structural integrity, and outputting multi-level risk results based on joint judgment rules, the fine classification and traceable location of different types of potential faults in cables can be realized. Attached Figure Description

[0019] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the structure of a cable safety monitoring and early warning system proposed in this invention; Figure 2 This is an overall flowchart of a cable safety monitoring and early warning method proposed in this invention. Detailed Implementation

[0020] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the invention, and therefore only show the components relevant to the invention.

[0021] refer to Figure 1 A cable safety monitoring and early warning system includes the following modules: The disturbance injection module is used to periodically and synchronously inject a dual-frequency disturbance electrical signal consisting of a first frequency and a second frequency into both ends of the cable. The temperature acquisition module is used to collect temperature change data at various monitoring points of the cable within a set response time window and generate a disturbance temperature response curve. The residual construction module is used to perform difference calculation between the perturbation temperature response curve and the steady temperature distribution curve to construct a two-dimensional perturbation thermal residual map. The thermal evolution analysis module is used to perform wavelet packet multi-scale decomposition on the two-dimensional perturbation thermal residual map and generate a two-dimensional thermal evolution image through an improved back-projection reconstruction algorithm. The first early warning calculation module is used to obtain the thermal response function by fitting the two-dimensional thermal evolution image and calculate the time partial derivative to obtain the thermal evolution trend index as the first early warning factor. The vibration acquisition module includes a piezoelectric vibrator and a vibration receiver. The piezoelectric vibrator is used to periodically apply millisecond excitation pulses, and the vibration receiver acquires reflected signals to obtain a reflected waveform dataset. The second early warning calculation module is used to calculate the constant amplitude attenuation time symmetry index based on the reflection waveform dataset, which serves as the second early warning factor. The early warning generation module is used to generate a final early warning scheme by jointly judging based on the first early warning factor and the second early warning factor according to preset judgment rules.

[0022] This system overcomes the limitations of traditional single monitoring methods by introducing dual-frequency disturbance excitation to achieve active thermal response wake-up. It extracts thermal degradation trends through an improved back-projection reconstruction algorithm and physical modeling, while combining high-resolution micro-vibration detection and waveform symmetry assessment to characterize structural continuity. Finally, by fusing two types of early warning factors through preset judgment rules, it achieves collaborative identification and classified response to cable thermal degradation and structural hazards. The system as a whole possesses the advantages of simple deployment, high sensitivity, strong reliability, and wide adaptability, making it suitable for real-time cable condition assessment and early fault warning under various operating environments.

[0023] refer to Figure 2 A cable safety monitoring and early warning method includes the following steps: S1. During the period when the cable is in a stable operating state, a dual-frequency disturbance electrical signal consisting of a first frequency and a second frequency is periodically injected into the cable. S2. After the dual-frequency disturbance electrical signal is injected, collect the instantaneous temperature change data of each monitoring point of the cable within the set response time window to obtain the disturbance temperature response curve. S3. Perform a difference calculation between the disturbance temperature response curve and the stable temperature distribution curve before the dual-frequency disturbance electrical signal injection to construct a disturbance thermal residual map. S4. Perform wavelet packet multi-scale decomposition on the disturbed thermal residual map and generate a two-dimensional thermal evolution image based on the improved back-projection reconstruction algorithm; S5. The thermal response function is obtained by fitting the two-dimensional thermal evolution image and the time partial derivative is calculated to obtain the thermal evolution trend index, which serves as the first early warning factor. S6. Install a piezoelectric vibrator outside the cable sheath, apply millisecond excitation pulses periodically, and have a vibration receiver collect the reflected signal to obtain a reflected waveform dataset. S7. Extract reflection peaks and find equal amplitude points for each group of waveforms in the reflection waveform dataset to obtain the equal amplitude decay time symmetry index, which serves as the second early warning factor. S8. Based on the preset judgment rules, a joint judgment is made on the first warning factor and the second warning factor to generate the final warning scheme.

[0024] This method clarifies the logical coordination mechanism between modules, forming a complete closed-loop processing mechanism from disturbance injection to early warning generation. By periodically applying dual-frequency signals to induce internal thermal disturbances in the cable, it overcomes the problem of insufficient perception of weak thermal anomalies in traditional passive monitoring. During the thermal response process, a disturbance thermal residual map is constructed from the temperature curve differences, and trend features are extracted by combining image processing and mathematical modeling, effectively improving the quantification capability of early insulation degradation evolution. Simultaneously, in terms of structural anomaly identification, high-resolution structural features are constructed through micro-excitation and reflected wave symmetry analysis, avoiding the difficulty of traditional amplitude or frequency domain energy-based methods in dealing with micro-damage. Finally, risk level identification and spatial positioning are achieved through a joint early warning rule based on thresholds and logical judgments, demonstrating significant advantages in accurate diagnosis, rapid response, and automated execution.

[0025] In this embodiment, the first frequency is 5kHz and the second frequency is 11kHz. The dual-frequency disturbance signal is injected synchronously through both ends of the cable for a duration of 10ms. The dual-frequency design is used to simultaneously excite the thermal inertial response of the cable medium at low frequency (5kHz) and the micro-disturbance sensitive response at high frequency (11kHz) to jointly obtain the temperature response characteristics of the cable under different thermal diffusion time constants. Compared with a single-frequency disturbance signal, this enhances the detection resolution of minor thermal anomalies and improves the stability of early warning indicators.

[0026] By optimizing the frequency selection and injection method of the disturbance signal, multi-scale excitation characteristics of cable thermal response were achieved. In the dual-frequency excitation design, the low frequency (5kHz) is used to awaken the slowly varying thermal inertial response of the cable medium, while the high frequency (11kHz) is used to excite the sensitive thermal response caused by the small thermal capacity difference of the medium, thus taking into account the detection requirements of deep degradation trends and shallow abnormal disturbances. The synchronous injection method at both ends of the cable ensures the symmetry and propagation consistency of the excitation signal in spatial distribution, further improving the accuracy of spectrum reconstruction and physical modeling in the data processing process. Compared with the traditional single-frequency injection technology, this invention can significantly improve the spatial resolution and trend fitting accuracy of thermal anomaly detection, laying a high-quality foundation for thermal evolution modeling and early warning factor construction.

[0027] In this embodiment, S2 specifically includes: S21. Set a response time window, which starts at the moment when the dual-frequency disturbance electrical signal injection is completed and lasts for 200ms. S22. Within the response time window, the temperature acquisition module is activated, and multiple monitoring points deployed along the cable length direction synchronously acquire the instantaneous temperature change data of the cable. S23. Arrange the instantaneous temperature change data collected from each monitoring point according to the time series to generate the corresponding temperature change curve; S24. Perform noise filtering on the temperature change curve to generate a disturbance temperature response curve. The noise filtering includes performing sliding window averaging on the temperature change curve to eliminate jitter, and applying a bandpass filter to the smoothed temperature change curve to retain the response range corresponding to the frequency components of the dual-frequency disturbance signal. The passband frequency range of the bandpass filter is matched with the first frequency of 5kHz and the second frequency of 11kHz to filter out background thermal responses unrelated to the disturbance.

[0028] Acquiring and refining temperature data during the response process is crucial for achieving highly reliable thermal anomaly monitoring. By setting a 200ms response time window, temperature change data is rapidly acquired after the disturbance signal ends, ensuring that the acquired data reflects the main effects of the disturbance rather than environmental noise. Simultaneous acquisition of temperature change curves from multiple monitoring points enables continuous thermal response recording along the cable length. A moving average filter combined with a bandpass filter accurately preserves the response information corresponding to the disturbance frequency components, filters out background thermal fluctuations and random noise, and enhances the quality of the constructed graph.

[0029] In this embodiment, S3 specifically includes: S31. After the disturbance temperature response curve is generated, obtain the stable temperature distribution curve before the injection of the dual-frequency disturbance electrical signal within the corresponding cable monitoring cycle. The stable temperature distribution curve is the cable temperature curve collected under undisturbed conditions. S32. Register the disturbance temperature response curve and the stable temperature distribution curve on the time axis to ensure that they have the same sampling length and time correspondence. S33. Perform point-by-point difference calculation on the registered disturbance temperature response curve and the stable temperature distribution curve to calculate the residual sequence of temperature changes and form the temperature residual dataset corresponding to each monitoring point. S34. Arrange the temperature residual datasets of each monitoring point synchronously with the time series according to the spatial layout order of the cable, and construct a two-dimensional disturbance thermal residual matrix. S35. Perform pseudo-color mapping processing on the two-dimensional perturbation thermal residual matrix to convert the temperature residual values ​​into color gradients and generate a perturbation thermal residual map. The pseudo-color mapping processing includes mapping the temperature residual values ​​to a fixed color gradient range according to a piecewise linear function, with low residual values ​​corresponding to cool colors and high residual values ​​corresponding to warm colors, thereby enhancing the visualization and recognition effect of local thermal anomalies.

[0030] This step constructs a perturbation thermal residual map by calculating the point-by-point difference between the perturbation temperature response curve and the stable temperature curve, achieving an effective conversion from raw temperature data to a two-dimensional space-time structured image. Registration and alignment of the temperature curves ensure temporal consistency and data comparability in the residual calculation process, improving the stability and reliability of the map. Subsequently, by constructing a two-dimensional perturbation thermal residual matrix and performing pseudo-color mapping, subtle thermal anomalies are visually visualized as changes in color gradients, enhancing the system's ability to identify local anomalies.

[0031] In this embodiment, S4 specifically includes: S41. Obtain the disturbed thermal residual spectrum. ,in Represents the spatial coordinates along the length of the cable. This represents the time coordinates after the injection of the dual-frequency disturbance electrical signal; S42, the perturbation thermal residual spectrum Perform two-dimensional wavelet packet multi-scale decomposition and extract each decomposition level. wavelet packet coefficients ,in Indicates the total number of decomposition levels. Indicates the first Wavelet packet coefficients of the layer; S43. Calculate the wavelet energy ratio index for each decomposition level. : ; in, Indicates the first Wavelet packet coefficients of the layer; S44. According to the preset energy threshold Select the one that satisfies The set of principal energy scales, and retain the corresponding wavelet packet coefficients for spectrum reconstruction; S45. Perform inverse wavelet packet reconstruction on the principal energy scale set to obtain the perturbed thermal residual reconstruction map. ; S46. Reconstruct the spectrum based on the perturbation thermal residual. A two-dimensional thermal evolution image is generated using an improved back-projection reconstruction algorithm. The improvement of the algorithm lies in the use of a nonlinear convolution kernel function that fuses a two-dimensional Gaussian diffusion kernel and an exponential annealing term. ; in, Represents a two-dimensional thermal evolution image. Indicates the spatial location of the perturbation thermal residual reconstruction map. and time location The value on, This represents the kernel normalization constant. Indicates the center annealing adjustment parameters. Represents an exponential function. This represents the standard deviation of heat diffusion in the spatial direction. This represents the standard deviation of heat diffusion over time.

[0032] By performing two-dimensional wavelet packet multi-scale decomposition on the thermal residual map and combining principal energy scale screening with an improved back-projection reconstruction algorithm, this step achieves accurate modeling of the dynamic evolution process of cable thermal disturbance. The improved back-projection algorithm introduces a nonlinear convolution kernel function that integrates a two-dimensional Gaussian diffusion kernel and an exponential annealing adjustment term, which can effectively simulate the spatial diffusion characteristics and temporal lag effects of thermal disturbance in the medium, improving the physical consistency and anomaly localization accuracy of the reconstructed image.

[0033] In this embodiment, S5 specifically includes: S51. Obtain a two-dimensional thermal evolution image. ,in Represents the spatial coordinates along the length of the cable. This represents the time coordinates after the injection of the dual-frequency disturbance electrical signal; S52, For each spatial location Extract the spatial location Corresponding thermal evolution curve ; S53. The least squares method is used to analyze the thermal evolution curve. Perform fitting to obtain the thermal response function The thermal response function Defined as a combined function with an exponentially decaying term and a perturbation excitation recovery term: ; in, Indicates the intensity of the excitation response. Represents the rate of ascent coefficient. Indicates the attenuation coefficient. Represents the thermal steady-state offset constant; S54, Regarding the thermal response function The first-order time partial derivative yields the thermal response rate function, which is used to quantify spatial location. The changing trend of thermal disturbance response intensity; S55. Select the response time window set after the disturbance, calculate the average value of the first-order time partial derivative within the time period, and use it as the spatial location. Thermal evolution trend indicators ; S56, The thermal evolution trend index It is used as the first early warning factor and output.

[0034] By extracting the thermal evolution curves at each spatial location from a two-dimensional thermal evolution image and fitting them with a physically meaningful exponential combination model, and then calculating the time partial derivative to construct a thermal response rate index, a first early warning factor quantitatively expressing the evolution trend of thermal anomalies is formed. This process not only preserves the details of thermal disturbance changes in the time domain but also endows the trend index with clear engineering interpretability, making early warning judgments traceable and providing a basis for regulation. The introduction of the thermal evolution trend index breaks through the limitations of traditional rough criteria such as maximum temperature rise or slope, enabling higher response sensitivity and accurate identification capabilities for hidden risks such as slow degradation and early overheating.

[0035] In this embodiment, S6 specifically includes: S61. Several piezoelectric vibrators and corresponding vibration receivers are arranged at intervals along the length of the cable on the outer surface of the cable sheath. S62. Control the piezoelectric vibrator to apply excitation pulses with a duration of 1 to 10 milliseconds and an amplitude of no more than 0.5 micronewtons at a set period; S63. After each excitation pulse is applied, the vibration receiver synchronously collects the reflected signal from the internal structure of the cable sheath; S64. Record and store the waveform data of the reflected signal, and perform time-domain alignment and amplitude normalization processing on the waveform data to output the reflected waveform dataset.

[0036] By applying micro-vibration excitation to the outside of the cable sheath and collecting reflected waveform data, a non-invasive assessment of the continuity of the cable structure can be achieved.

[0037] In this embodiment, S7 specifically includes: S71. Obtain the reflected waveform dataset, which contains waveform data of multiple sets of reflected signals collected by the vibration receiver, with each set of waveforms corresponding to a complete response process within one excitation cycle; S72. Perform reflection peak extraction on each group of waveforms, find equal amplitude points on both sides of each reflection peak, record the time coordinates of each pair of equal amplitude points, and calculate the equal amplitude symmetrical time difference. ; S73. Calculate the constant amplitude decay time symmetry index (TASR) corresponding to the waveform: ; in, This indicates the number of equal amplitude point pairs in the waveform. Indicates the duration of the entire waveform; S74. The output of the constant amplitude attenuation time symmetry index TASR is used as the second early warning factor to characterize the internal structural continuity of the cable segment structure and the degree of symmetry maintenance of the reflected signal. The closer TASR is to 1, the better the structural continuity.

[0038] The high-order symmetry analysis of vibration waveforms is a significant breakthrough in the field of structural assessment. By pairing equal-amplitude points on both sides of each reflection peak in the reflected wave, the equal-amplitude time difference is statistically analyzed to obtain the TASR index. A TASR close to 1 indicates good symmetry of the reflected waveform and high structural continuity; a deviation from 1 suggests structural anomalies. This method can achieve real-time structural change perception under non-destructive conditions and without reconstructing the structural model. It is particularly suitable for detecting invisible defects such as delamination of the cladding layer and cracking of the bonding interface, and has the advantages of high resolution, automatic judgment, and no need for empirical thresholds.

[0039] In this embodiment, S8 specifically includes: S81, Preset the first warning factor threshold With the second early warning factor threshold ,in Risk threshold as an indicator of thermal evolution trend As a lower limit for judging the structural integrity of the constant amplitude decay time symmetry index; S82. During the current monitoring cycle, obtain the first early warning factor for each monitoring point of the cable. With the corresponding second early warning factor value , representing the thermal degradation rate and structural symmetry at the corresponding spatial locations, respectively; S83. According to the preset judgment rules, a joint judgment is made based on the first warning factor and the second warning factor. The preset judgment rules include: like and If so, it is judged as a high-risk warning; like and If so, it is determined as a thermal degradation warning; like and If so, it is determined as a structural anomaly warning; like and If so, it is determined to be a safe state; S84. Generate a structured early warning record for each cable monitoring point according to the results of the preset judgment rules. The structured early warning record includes the early warning type, spatial location and timestamp. S85. Summarize the corresponding structured early warning records of each monitoring point to generate the final early warning plan.

[0040] By setting dual thresholds for thermal evolution trend indicators and structural integrity indicators, and establishing clear judgment rules, a four-level classification early warning system for cable operating status has been implemented. The system can output structured early warning records based on the dual-factor values ​​of each cable segment in the current cycle, and generate information packets containing early warning type, location, and timestamps for reporting to the platform, greatly improving the system's visualization, manageability, and traceability capabilities. Compared to traditional single-factor triggered alarm mechanisms, this method has the advantages of more comprehensive anomaly identification, more detailed risk classification, and more intelligent response strategies, making it suitable for online automated operation and maintenance systems of large-scale, multi-channel cable systems.

[0041] Example 1: To verify the feasibility of this invention in practice, it was applied to the online monitoring of a high-voltage underground cable line. This line is a three-phase, three-core cross-linked polyethylene insulated cable, approximately 3.7 kilometers long, operating long-term in a core urban area with a complex geological environment, surrounded by high-density building foundations and underground facilities. Due to its long service life, it faces potential risks of thermal degradation and structural loosening.

[0042] In this embodiment, a set of sensing units is deployed every 100 meters along the cable, each set including a temperature sensor and a vibration sensor, for a total of 37 sets of nodes. The system's disturbance injection module can automatically and synchronously apply dual-frequency electrical signals to both ends of the cable, with signal frequencies set to 5kHz and 11kHz, and an injection duration of 10 milliseconds. Subsequently, within the response time window, the temperature acquisition module records instantaneous temperature response data at a sampling rate of 500Hz and calculates the difference with the historical stable temperature curve to form a two-dimensional thermal residual map. The thermal evolution image is reconstructed through wavelet packet decomposition and an improved back-projection algorithm, the thermal response function is extracted, and its first-order time partial derivative is calculated to obtain a thermal evolution trend index reflecting the changing trend of the cable insulation state.

[0043] After the thermal disturbance is completed, the system further activates the vibration acquisition module. A weak excitation pulse is applied by the piezoelectric vibrator, and the receiver collects the reflected waveform data. The system automatically extracts the constant amplitude symmetrical time characteristics and calculates the constant amplitude decay time symmetry rate (TASR) to characterize the symmetry and continuity of the cable structure. Through the joint judgment of the first and second warning factors, the system generates a warning result according to preset rules.

[0044] During two months of continuous monitoring, the system collected and processed over 50,000 sets of thermal response data and 40,000 sets of vibration waveform data. In actual operation, several cable monitoring points exhibited an increasing trend in thermal response indicators and a decreasing trend in thermal stability (TASR). The system successfully identified several of these locations as potentially high-risk sections and issued early warnings. Subsequent manual verification confirmed issues such as localized sheath peeling and structural loosening at the warning locations, validating the system's ability to identify thermal anomalies and micro-damage in real-world operating environments.

[0045] Table 1 Comparative Analysis of Cable Multi-Parameter Joint Early Warning Samples As shown in Table 1 above, the system of this invention achieves accurate quantification and classification of cable condition in two dimensions: thermal evolution trend index and TASR symmetry rate. Taking monitoring points D09 and D10 as examples, their thermal evolution trend indices are 0.0372°C / ms and 0.0381°C / ms, respectively, both significantly exceeding the set first threshold of 0.030°C / ms. Meanwhile, their TASR symmetry rates are 0.805 and 0.799, respectively, both lower than the second threshold of 0.85. Based on this, the system accurately marks them as high-risk warnings. Although the thermal evolution trend at point D12 is high, the TASR is normal, and the system identifies it as a thermal degradation warning. At point D17, the thermal trend is normal, but the structural symmetry is decreasing, and it is judged as a structural anomaly warning. At point D21, both indices are within the safe range, and the system automatically classifies it as a normal state. This table verifies the effectiveness of the dual-factor joint judgment mechanism, which can clearly distinguish different types of hidden danger sources, avoid misjudgment and omission, improve the accuracy and practicality of cable condition monitoring, and fully demonstrate the intelligent diagnosis and risk classification capabilities of this invention in complex power operation environments.

[0046] This embodiment fully verifies the adaptability and reliability of the cable safety monitoring and early warning system of this invention in complex operating environments by deploying it in actual cable lines. The system utilizes dual-frequency disturbance excitation combined with thermal response and micro-vibration detection technology to achieve dual-factor identification of cable insulation thermal degradation trends and structural continuity anomalies. It can identify potential fault segments with both heat rise and reflected waveform imbalance in advance, effectively improving the sensitivity and location accuracy of fault warnings. In actual operation, the system's early warning results are highly consistent with manual inspection results, with no missed alarms, a false alarm rate controlled within 1%, and a data processing response time of less than 1.5 seconds, meeting real-time requirements. Compared with traditional temperature threshold alarms or single-parameter analysis methods, this invention not only improves the resolution of anomaly identification but also enhances the ability to perceive early hidden dangers, providing strong data support for maintenance decisions and demonstrating significant practical value and promising prospects for widespread application.

[0047] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A cable safety monitoring and early warning system, characterized in that, Includes the following modules: The disturbance injection module is used to periodically and synchronously inject a dual-frequency disturbance electrical signal consisting of a first frequency and a second frequency into both ends of the cable. The temperature acquisition module is used to collect temperature change data at various monitoring points of the cable within a set response time window and generate a disturbance temperature response curve. The residual construction module is used to perform difference calculation between the perturbation temperature response curve and the steady temperature distribution curve to construct a two-dimensional perturbation thermal residual map. The thermal evolution analysis module is used to perform wavelet packet multi-scale decomposition on the two-dimensional perturbation thermal residual map and generate a two-dimensional thermal evolution image through an improved back-projection reconstruction algorithm. The first early warning calculation module is used to obtain the thermal response function by fitting the two-dimensional thermal evolution image and calculate the time partial derivative to obtain the thermal evolution trend index as the first early warning factor. The vibration acquisition module includes a piezoelectric vibrator and a vibration receiver. The piezoelectric vibrator is used to periodically apply millisecond excitation pulses, and the vibration receiver acquires reflected signals to obtain a reflected waveform dataset. The second early warning calculation module is used to calculate the constant amplitude attenuation time symmetry index based on the reflection waveform dataset, which serves as the second early warning factor. The early warning generation module is used to generate a final early warning scheme by jointly judging based on the first early warning factor and the second early warning factor according to preset judgment rules.

2. The cable safety monitoring and early warning system according to claim 1, characterized in that, The modules are connected in the following way: S1. During the period when the cable is in a stable operating state, a dual-frequency disturbance electrical signal consisting of a first frequency and a second frequency is periodically injected into the cable. S2. After the dual-frequency disturbance electrical signal is injected, collect the instantaneous temperature change data of each monitoring point of the cable within the set response time window to obtain the disturbance temperature response curve. S3. Perform a difference calculation between the disturbance temperature response curve and the stable temperature distribution curve before the dual-frequency disturbance electrical signal injection to construct a disturbance thermal residual map. S4. Perform wavelet packet multi-scale decomposition on the disturbed thermal residual map and generate a two-dimensional thermal evolution image based on the improved back-projection reconstruction algorithm; S5. The thermal response function is obtained by fitting the two-dimensional thermal evolution image and the time partial derivative is calculated to obtain the thermal evolution trend index, which serves as the first early warning factor. S6. Install a piezoelectric vibrator outside the cable sheath, apply millisecond excitation pulses periodically, and have a vibration receiver collect the reflected signal to obtain a reflected waveform dataset. S7. Extract reflection peaks and find equal amplitude points for each group of waveforms in the reflection waveform dataset to obtain the equal amplitude decay time symmetry index, which serves as the second early warning factor. S8. Based on the preset judgment rules, a joint judgment is made on the first warning factor and the second warning factor to generate the final warning scheme.

3. The cable safety monitoring and early warning system according to claim 2, characterized in that, The first frequency is 5kHz, the second frequency is 11kHz, and the dual-frequency disturbance electrical signal is injected synchronously through both ends of the cable for a duration of 10ms.

4. The cable safety monitoring and early warning system according to claim 2, characterized in that, S2 specifically includes: S21. Set a response time window, which starts at the moment when the dual-frequency disturbance electrical signal injection is completed and lasts for 200ms. S22. Within the response time window, the temperature acquisition module is activated, and multiple monitoring points deployed along the cable length direction synchronously acquire the instantaneous temperature change data of the cable. S23. Arrange the instantaneous temperature change data collected from each monitoring point according to the time series to generate the corresponding temperature change curve; S24. Perform noise filtering on the temperature change curve to generate a disturbance temperature response curve. The noise filtering includes performing sliding window averaging on the temperature change curve to eliminate jitter, and applying a bandpass filter to the smoothed temperature change curve to retain the response range corresponding to the frequency components of the dual-frequency disturbance signal. The passband frequency range of the bandpass filter is matched with the first frequency of 5kHz and the second frequency of 11kHz to filter out background thermal responses unrelated to the disturbance.

5. A cable safety monitoring and early warning system according to claim 2, characterized in that, S3 specifically includes: S31. After the disturbance temperature response curve is generated, obtain the stable temperature distribution curve before the injection of the dual-frequency disturbance electrical signal within the corresponding cable monitoring cycle. The stable temperature distribution curve is the cable temperature curve collected under undisturbed conditions. S32. Register the disturbance temperature response curve and the stable temperature distribution curve on the time axis to ensure that they have the same sampling length and time correspondence. S33. Perform point-by-point difference calculation on the registered disturbance temperature response curve and the stable temperature distribution curve to calculate the residual sequence of temperature changes and form the temperature residual dataset corresponding to each monitoring point. S34. Arrange the temperature residual datasets of each monitoring point synchronously with the time series according to the spatial layout order of the cable, and construct a two-dimensional disturbance thermal residual matrix. S35. Perform pseudo-color mapping processing on the two-dimensional perturbation thermal residual matrix to convert the temperature residual values ​​into color gradients and generate a perturbation thermal residual map.

6. A cable safety monitoring and early warning system according to claim 2, characterized in that, S4 specifically includes: S41. Obtain the disturbed thermal residual spectrum. ,in Represents the spatial coordinates along the length of the cable. This represents the time coordinates after the injection of the dual-frequency disturbance electrical signal; S42, the perturbation thermal residual spectrum Perform two-dimensional wavelet packet multi-scale decomposition and extract each decomposition level. wavelet packet coefficients ,in Indicates the total number of decomposition levels. Indicates the first Wavelet packet coefficients of the layer; S43. Calculate the wavelet energy ratio index for each decomposition level. : ； in, Indicates the first Wavelet packet coefficients of the layer; S44. According to the preset energy threshold Select the one that satisfies The set of principal energy scales, and retain the corresponding wavelet packet coefficients for spectrum reconstruction; S45. Perform inverse wavelet packet reconstruction on the principal energy scale set to obtain the perturbed thermal residual reconstruction map. ; S46. Reconstruct the spectrum based on the perturbation thermal residual. A two-dimensional thermal evolution image is generated using an improved back-projection reconstruction algorithm. The improvement of the algorithm lies in the use of a nonlinear convolution kernel function that fuses a two-dimensional Gaussian diffusion kernel and an exponential annealing term. ； in, Represents a two-dimensional thermal evolution image. Indicates the spatial location of the perturbation thermal residual reconstruction map. and time location The value on, This represents the kernel normalization constant. Indicates the center annealing adjustment parameters. Represents an exponential function. This represents the standard deviation of heat diffusion in the spatial direction. This represents the standard deviation of heat diffusion over time.

7. A cable safety monitoring and early warning system according to claim 2, characterized in that, S5 specifically includes: S51. Obtain a two-dimensional thermal evolution image. ,in Represents the spatial coordinates along the length of the cable. This represents the time coordinates after the injection of the dual-frequency disturbance electrical signal; S52, For each spatial location Extract the spatial location Corresponding thermal evolution curve ; S53. The least squares method is used to analyze the thermal evolution curve. Perform fitting to obtain the thermal response function The thermal response function Defined as a combined function with an exponentially decaying term and a perturbation excitation recovery term: ； in, Indicates the intensity of the excitation response. Represents the rate of ascent coefficient. Indicates the attenuation coefficient. Represents the thermal steady-state offset constant; S54, Regarding the thermal response function The first-order time partial derivative yields the thermal response rate function, which is used to quantify spatial location. The changing trend of thermal disturbance response intensity; S55. Select the response time window set after the disturbance, calculate the average value of the first-order time partial derivative within the time period, and use it as the spatial location. Thermal evolution trend indicators ; S56, The thermal evolution trend index It is used as the first early warning factor and output.

8. A cable safety monitoring and early warning system according to claim 2, characterized in that, S6 specifically includes: S61. Several piezoelectric vibrators and corresponding vibration receivers are arranged at intervals along the length of the cable on the outer surface of the cable sheath. S62. Control the piezoelectric vibrator to apply excitation pulses with a duration of 1 to 10 milliseconds and an amplitude of no more than 0.5 micronewtons at a set period; S63. After each excitation pulse is applied, the vibration receiver synchronously collects the reflected signal from the internal structure of the cable sheath; S64. Record and store the waveform data of the reflected signal, and perform time-domain alignment and amplitude normalization processing on the waveform data to output the reflected waveform dataset.

9. A cable safety monitoring and early warning system according to claim 2, characterized in that, Specifically, S7 includes: S71. Obtain the reflected waveform dataset, which contains waveform data of multiple sets of reflected signals collected by the vibration receiver, with each set of waveforms corresponding to a complete response process within one excitation cycle; S72. Perform reflection peak extraction on each group of waveforms, find equal amplitude points on both sides of each reflection peak, record the time coordinates of each pair of equal amplitude points, and calculate the equal amplitude symmetrical time difference. ; S73. Calculate the constant amplitude decay time symmetry index (TASR) corresponding to the waveform: ； in, This indicates the number of equal amplitude point pairs in the waveform. Indicates the duration of the entire waveform; S74. The output of the constant amplitude attenuation time symmetry index TASR is used as the second early warning factor to characterize the internal structural continuity of the cable segment structure and the degree of symmetry maintenance of the reflected signal. The closer TASR is to 1, the better the structural continuity.

10. A cable safety monitoring and early warning system according to claim 2, characterized in that, S8 specifically includes: S81, Preset the first warning factor threshold With the second early warning factor threshold ,in Risk threshold as an indicator of thermal evolution trend As a lower limit for judging the structural integrity of the constant amplitude decay time symmetry index; S82. During the current monitoring cycle, obtain the first early warning factor for each monitoring point of the cable. With the corresponding second early warning factor value , representing the thermal degradation rate and structural symmetry at the corresponding spatial locations, respectively; S83. According to the preset judgment rules, a joint judgment is made based on the first warning factor and the second warning factor. The preset judgment rules include: like and If so, it is judged as a high-risk warning; like and If so, it is determined as a thermal degradation warning; like and If so, it is determined as a structural anomaly warning; like and If so, it is determined to be a safe state; S84. Generate a structured early warning record for each cable monitoring point according to the results of the preset judgment rules. The structured early warning record includes the early warning type, spatial location and timestamp. S85. Summarize the corresponding structured early warning records of each monitoring point to generate the final early warning plan.

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