Cable health state evaluation method and system based on single-end open circuit impedance spectrum

Abstract

The application discloses a kind of cable health state evaluation method and system based on single-end open circuit impedance spectrum, belong to nondestructive testing and impedance spectrum analysis technical field.This method only needs to carry out frequency sweep test at one end of cable and keep open circuit at the end, after obtaining wideband input impedance spectrum, extract real part data and identify resonance extreme point;The upper and lower envelope lines are constructed by extreme point interpolation, and the high-frequency characteristic impedance and attenuation constant of the full frequency band are derived;Further, the distributed parameters of the cable are calculated by combining the phase constant.By comparing the characteristics of the distributed parameters, the health status of the cable can be accurately evaluated, and the physical mechanism can effectively distinguish between thermal aging and moisture damage.The application eliminates the cumbersome of double-end cooperation test, does not need to intercept samples, greatly saves the test time, has wide applicability and strong anti-interference ability.

Description

Technical Field

[0001] This invention relates to the field of nondestructive testing and impedance spectroscopy analysis technology, specifically to a method and system for assessing the health status of cables based on single-ended open-circuit impedance spectroscopy. Background Technology

[0002] As a critical hub in modern power transmission systems, power cables are subjected to a combination of stresses from heat, electricity, machinery, and the environment during long-term service. This often leads to insulation aging and localized damage, such as overall thermal aging and large-area water treeing. If these potential defects are not detected in time, they can easily develop into breakdown faults, seriously threatening the safe and stable operation of the power grid. Therefore, accurately assessing the health status of cables and promptly identifying aging types is of great significance for ensuring the reliability of power systems.

[0003] Currently, cable health status assessment methods suffer from the following technical limitations. First, sampling-based testing methods (such as polarization / depolarization current methods and frequency domain dielectric spectroscopy) typically require taking cable samples for laboratory testing. This is not only time-consuming and labor-intensive but also lacks representativeness, making it difficult to perform non-destructive testing on in-service cables. Second, methods based on two-sided impedance spectroscopy require testing at the cable's beginning and necessitate end-to-end coordination to switch between open and short circuits to obtain open and short-circuit impedances. This is extremely difficult for long-distance or buried cables, significantly increasing testing complexity and labor costs. Third, while existing single-ended impedance spectroscopy methods save time on end-to-end coordination, most methods can only determine the degree of aging by calculating the dielectric loss tangent, failing to comprehensively obtain the cable's distributed parameters (distributed resistance, distributed inductance, distributed capacitance, and distributed conductance). Therefore, they struggle to accurately identify different aging types, such as effectively distinguishing between thermal aging and moisture damage.

[0004] To address the aforementioned issues, there is an urgent need for a cable health status assessment method that can obtain complete cable distribution parameters and accurately identify aging types using only single-end open-circuit testing. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a cable health status assessment method and system based on single-ended open-circuit impedance spectrum. By applying a sweep frequency signal to one side of the cable and keeping the end open, the distributed parameter data of the cable can be obtained and the cable aging type can be identified. No end short-circuit coordination or double-ended synchronization is required, which greatly reduces the operational difficulty and time cost of on-site testing.

[0006] This invention is achieved through the following technical solution: In a first aspect, this application provides a method for assessing the health status of cables based on single-ended open-circuit impedance spectrum, comprising the following steps: Step 1: Obtain the real part data of the broadband input impedance spectrum under the open-circuit state of the cable end, and identify the resonant extreme points of the real part data as the frequency changes. Step 2: Calculate the high-frequency phase constant of the cable based on the resonant frequency difference between adjacent resonant extreme points; Step 3: Based on the resonant extreme points, interpolate to construct the full-frequency envelope of the real part of the input impedance spectrum; Step 4: Extract the high-frequency characteristic impedance of the cable based on the full-band envelope; Step 5: Calculate the high-frequency attenuation constant of the cable based on the full-band envelope and the high-frequency characteristic impedance; Step 6: Calculate the distributed parameters of the cable by combining the high-frequency phase constant, the high-frequency attenuation constant and the high-frequency characteristic impedance, and evaluate the health status of the cable based on the distributed parameters.

[0007] Preferably, identifying the resonant extrema of the real part data as a function of frequency in step 1 specifically includes: A computer-based peak-finding algorithm is used to identify the resonant peaks and troughs of the real part data as the frequency changes, and to obtain the extreme point sequence corresponding to each resonant peak and the extreme point sequence corresponding to each resonant trough. The extreme point sequence includes the resonant frequency and real part amplitude corresponding to the extreme point.

[0008] Preferably, the calculation of the high-frequency phase constant of the cable in step 2 specifically includes: Extract the resonant frequency difference between adjacent in-phase extreme points, wherein the in-phase extreme points include adjacent peaks and peaks, or adjacent troughs and troughs; Calculate the high-frequency phase constant based on the cable length and the resonant frequency difference. The calculation formula is:

[0009] in, The length of the cable to be tested. The difference in resonant frequency between adjacent extreme points. f This refers to a frequency point.

[0010] Preferably, the resonant frequency difference is determined in the following way: Calculate the frequency difference between all adjacent peaks and the frequency difference between all adjacent troughs in the entire high-frequency band. Take the average value of each calculated frequency difference and use the average value as the resonant frequency difference in the calculation.

[0011] Preferably, constructing the full-frequency envelope of the real part of the input impedance spectrum in step 3 specifically includes: The identified resonant extreme points are separated by type to obtain the discrete point set of peaks and the discrete point set of troughs; An interpolation algorithm is used to perform curve interpolation on the discrete point set of peaks and the discrete point set of troughs respectively, and the upper envelope and lower envelope of the real part of the input impedance spectrum are constructed to form a full-band envelope.

[0012] Preferably, step 4, extracting the high-frequency characteristic impedance of the cable based on the full-band envelope, specifically includes: For each frequency point, calculate the geometric mean of the upper and lower envelopes to obtain the resistive component of the characteristic impedance that varies with frequency. The stable value of the resistive component of the characteristic impedance in the high-frequency band is taken as the high-frequency characteristic impedance of the cable.

[0013] Preferably, the calculation of the high-frequency attenuation constant of the cable in step 5 specifically includes: The high-frequency attenuation constant at each frequency point is calculated based on the upper envelope and the high-frequency characteristic impedance, forming a frequency-varying data sequence of the high-frequency attenuation constant as a function of frequency. The calculation formula is as follows:

[0014] in, The upper envelope amplitude, For high-frequency characteristic impedance, The length of the cable to be tested is given.

[0015] Preferably, step 6, calculating the cable's distributed parameters, specifically includes: The high-frequency propagation constant is synthesized from the high-frequency phase constant and the high-frequency attenuation constant; Based on the high-frequency propagation constant and high-frequency characteristic impedance, the distributed parameters of the cable, including distributed resistance, distributed inductance, distributed conductance, and distributed capacitance, are calculated using transmission line theory.

[0016] Preferably, the step of assessing the cable health status based on distribution parameters specifically includes: Retrieve a reference model of the distribution parameters of a healthy cable of the same specifications and material as the cable under test; The distributed parameters of the cable under test are compared with the reference model, and the relative changes of each parameter are calculated. If the distributed conductivity increases significantly while the distributed capacitance remains unchanged or decreases slightly, it is determined that the cable has undergone overall thermal aging. If the distributed capacitance increases significantly and the distributed conductivity increases substantially, it is determined that the cable has become damp overall or has experienced large-area water treeing aging.

[0017] Secondly, this application also provides a cable health status assessment system based on single-ended open-circuit impedance spectrum, comprising: Impedance spectrum acquisition module is used to acquire the real part data of broadband input impedance spectrum under open circuit state at the end of cable, and identify the resonant extreme points of the real part data as the frequency changes. The phase constant calculation module is used to calculate the high-frequency phase constant of the cable based on the resonant frequency difference between adjacent resonant extreme points. An envelope construction module is used to construct the full-frequency envelope of the real part of the input impedance spectrum by interpolation based on the resonant extreme points. Characteristic impedance extraction module, used to extract the high-frequency characteristic impedance of the cable based on the full-band envelope; The attenuation constant calculation module is used to calculate the high-frequency attenuation constant of the cable based on the full-band envelope and the high-frequency characteristic impedance. The health status assessment module is used to calculate the distributed parameters of the cable by combining the high-frequency phase constant, the high-frequency attenuation constant and the high-frequency characteristic impedance, and to assess the health status of the cable based on the distributed parameters.

[0018] Compared with the prior art, the present invention has the following beneficial technical effects: This application proposes a cable health status assessment method based on single-ended open-circuit impedance spectrum. Based on transmission line theory and impedance spectrum analysis, it obtains the real part data of the broadband input impedance spectrum of the cable through single-ended open-circuit testing. The propagation constant and characteristic impedance of the cable are decoupled using the resonant extrema, and then the complete distributed parameters are calculated to achieve health status assessment. This method only requires single-ended open-circuit testing to obtain all data, without the need for end-to-end coordination or double-ended synchronization, significantly reducing the difficulty and time cost of on-site testing. It overcomes the limitation of existing single-ended testing, which can only obtain the dielectric loss tangent, achieving accurate decoupling of complete distributed parameters. Based on the differentiated response characteristics of distributed capacitance and distributed conductance, it can highly sensitively distinguish between thermal aging and moisture damage types, providing a more reliable decision-making basis for cable operation and maintenance.

[0019] This application also proposes a cable health status assessment system based on single-ended open-circuit impedance spectrum, an electronic device, and a computer storage medium, which possess all the advantages of the aforementioned cable health status assessment method based on single-ended open-circuit impedance spectrum. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This invention provides a cable health status assessment based on single-ended open-circuit impedance spectrum. Figure 2 This is a schematic diagram showing the connection between the cable and the impedance analyzer of the present invention; Figure 3 This is a diagram showing the real part of the impedance spectrum and its approximate upper and lower envelopes of the present invention. Figure 4 This is a high-frequency characteristic impedance curve of the present invention; Figure 5 This is a comparison chart of the distribution parameters of the cable under different damage types according to the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0023] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0024] A method for assessing cable health status based on single-ended open-circuit impedance spectrum includes the following steps: Step 1: Obtain the broadband input impedance spectrum under the open-circuit condition at the end of the cable; Step 2: Extract the real part data of the input impedance spectrum and identify the resonant extrema of the real part data as the frequency changes; Step 3: Calculate the high-frequency phase constant of the cable based on the resonant frequency difference between adjacent resonant extreme points; Step 4: Based on the resonant extreme points, interpolate to construct the full-band upper and lower envelopes of the real part of the input impedance spectrum; Step 5: Extract the high-frequency characteristic impedance of the cable based on the full-band upper and lower envelopes; Step 6: Combine the full-band upper and lower envelopes with the high-frequency characteristic impedance to calculate the high-frequency attenuation constant of the cable; Step 7: Combine the high-frequency phase constant and the high-frequency attenuation constant to synthesize the high-frequency propagation constant, and calculate the overall distributed parameters of the cable in conjunction with the high-frequency characteristic impedance; Step 8: Compare the overall distributed parameters with the distributed parameter model of the baseline health state to assess the cable health state and identify the aging type.

[0025] This evaluation method only requires applying a sweep frequency signal to one side of the cable and keeping the end open to obtain all data, without the need for end short-circuiting or double-end synchronization, significantly reducing the operational difficulty and time cost of on-site testing. It also overcomes the technical bottleneck of existing single-end testing, which can only obtain the dielectric loss tangent. Through the envelope algorithm, it successfully decouples and calculates complete distributed parameters such as distributed resistance, distributed inductance, distributed capacitance, and distributed conductance across the entire frequency band of the cable. Based on this, and using the decoupled distributed capacitance and conductance, it can accurately and sensitively distinguish between "overall thermal aging" and "moisture / water tree aging" from the perspective of the physical mechanism of the insulation material, providing a more reliable basis for cable operation and maintenance and life prediction.

[0026] Example 1 See Figure 1 This embodiment provides a cable health status assessment method based on single-ended open-circuit impedance spectrum, applicable to insulation status detection of single-core coaxial cables. For example... Figure 2 As shown, the cable under test consists of a conductor, an insulation layer, and a shielding layer from the inside out. During testing, the test fixtures of the precision impedance analyzer are connected to the conductor and the shielding layer at the beginning of the cable under test, respectively, with the cable end kept open.

[0027] The method extracts the real part of the broadband input impedance spectrum obtained from single-ended open-circuit testing of the cable, identifies resonant extrema, constructs the envelope, and decouples parameters to calculate the cable's distributed parameters. These parameters are then compared with a baseline health status to achieve cable health assessment and aging type identification. Specifically, the method includes the following steps: Step 1: Obtain the broadband input impedance spectrum under the open-circuit condition at the end of the cable; Based on a precision impedance analyzer, with the cable end kept open as the test condition, a wideband sweep signal is injected at the cable head to obtain the complex spectrum data of the input impedance at the cable head as a function of frequency, including the real and imaginary parts of the impedance.

[0028] S1.1, see reference Figure 2 The cable under test is a single-core coaxial cable, whose structure, from the inside out, includes a conductor, an insulation layer, and a shielding layer. The test fixtures of the precision impedance analyzer are connected to the conductor and the shielding layer at the beginning of the cable under test, respectively, and the end of the cable is kept in an open circuit state.

[0029] S1.2 Control the precision impedance analyzer to perform a wide-band sweep, and set the sweep range to cover the resonant frequency band of the cable (e.g., 1MHz to 100MHz). Obtain the input impedance spectrum at the beginning of the cable The input impedance spectrum is complex data, including the real part. and the virtual part ; This step obtains the broadband input impedance spectrum of the cable under open-circuit conditions at the end through single-ended testing, eliminating the need for end-to-end coordination or double-ended synchronization, significantly reducing the operational difficulty and time cost of on-site testing. The open-circuit condition at the end causes the input impedance spectrum to exhibit obvious resonance characteristics, providing a data foundation for subsequent extreme point extraction and envelope construction.

[0030] In some embodiments, the precision impedance analyzer may be replaced by a vector network analyzer or a broadband impedance meter; The sweep frequency range can be adaptively adjusted according to the cable length and the expected resonant frequency.

[0031] Step 2: Identify the resonant extrema based on the real part of the impedance spectrum; Using the input impedance spectrum obtained in step 1 as input, the real part data of the impedance spectrum is extracted. The computer peak finding algorithm is used to identify the resonant peaks (maximums) and resonant troughs (minimums) of the real part data as the frequency changes, and the amplitude of each extreme point and its corresponding resonant frequency are recorded.

[0032] S2.1 Input impedance spectrum obtained from step 1 Extracting real part data The real part data reflects the variation of the resistive component of the cable input impedance with frequency.

[0033] S2.2, Using a computer peak-finding algorithm to analyze real data Perform extreme point identification and extract the first extreme point. i The sequence of extreme points corresponding to each resonant peak ( , ), and the j The sequence of extreme points corresponding to each resonant trough ( , );in, f This represents the resonant frequency corresponding to the extreme point. Z This represents the real part magnitude corresponding to the extreme point.

[0034] This step extracts the real part of the impedance spectrum and identifies resonant extrema, thus obtaining the oscillatory characteristics of the cable's input impedance under open-circuit conditions. The frequency distribution of these extrema is directly related to the cable's phase constant, while their amplitude attenuation is directly related to the attenuation constant, providing crucial feature point data for subsequent phase constant calculation and envelope construction.

[0035] In some embodiments, the computer peak-finding algorithm may be replaced by an extremum detection method based on the rate of change of derivatives or a peak identification method based on curve fitting.

[0036] Step 3: Using the adjacent resonant extreme points extracted in Step 2 as input, calculate the resonant frequency difference between adjacent in-phase extreme points, and extract the high-frequency phase constant of the cable based on the cable length.

[0037] S3.1 Extract the resonant frequency difference between adjacent in-phase extreme points (i.e., adjacent peaks or troughs) in step 2. .

[0038] S3.2, Based on cable length The resonant frequency difference between adjacent extreme points Calculate the high-frequency phase constant The calculation formula is:

[0039] in, The length of the cable to be tested. This represents the difference in resonant frequency between adjacent extreme points.

[0040] By utilizing the physical relationship between the frequency difference between the resonant extrema of the input impedance under open-circuit conditions and the cable phase constant, the phase constant can be directly calculated from single-ended test data. This method avoids the cumbersome double-ended coordination required by traditional methods, achieving rapid and accurate extraction of the phase constant.

[0041] In some embodiments, to reduce errors caused by field measurement noise, the frequency difference between all adjacent peaks and the frequency difference between all adjacent troughs within the entire high-frequency band can be calculated separately, and the average value of all the above frequency differences can be taken as the final value. Substitute into the calculation to significantly improve the phase constant. The calculation accuracy.

[0042] Step 4: Construct a full-frequency continuous envelope of the real part of the impedance spectrum based on the resonant extreme points using an interpolation algorithm.

[0043] Using the discrete points of the resonant peaks and valleys identified in step 2 as input, interpolation algorithms are used to perform curve interpolation on the discrete points of the peaks and valleys respectively, constructing the upper and lower envelopes of the real part of the impedance spectrum, thus forming the full-band envelope.

[0044] S4.1 Separate the resonant extrema points identified in step 2 according to their type to obtain the discrete peak point set ( , ) and the discrete point set of the trough ( , ).

[0045] S4.2. An interpolation algorithm is used to perform curve interpolation on the discrete points of the wave crest to construct the upper envelope of the real part of the impedance spectrum. .

[0046] S4.3. An interpolation algorithm is used to perform curve interpolation on the discrete points of the troughs to construct the lower envelope of the real part of the impedance spectrum. .

[0047] Based on the resonant characteristics of the real part of the cable input impedance at high frequencies, an upper and lower envelope is constructed using an interpolation algorithm. This effectively filters out fluctuations caused by resonant oscillations and extracts the overall attenuation trend of the real part of the impedance. The construction of this continuous envelope transforms discrete extreme points into a continuous function that can be calculated across the entire frequency band, providing crucial intermediate parameters for subsequent calculations of characteristic impedance and attenuation constant.

[0048] In some embodiments, the interpolation algorithm may be replaced by spline interpolation, polynomial fitting, or piecewise linear interpolation.

[0049] To verify the accuracy of the envelope construction, please refer to [link / reference]. Figure 3 . Figure 3 The figure shows the extracted real part of the impedance spectrum and its approximate upper and lower envelopes. The horizontal axis represents frequency f, and the vertical axis represents the real part of the impedance. .like Figure 3 As shown by the solid black line, the real part of the impedance exhibits a typical characteristic of oscillatory decay as the frequency increases. This embodiment accurately extracts... Figure 3 The peaks and troughs are marked with circles; the approximate upper and lower envelopes (shown as dashed lines in the figure) constructed based on the interpolation algorithm perfectly enclose all discrete extreme points. Figure 3 It can be seen that the discrete extrema are well distributed on the envelope boundary of the impedance curve, which fully proves the rationality of ignoring specific small terms to derive the envelope formula and the accuracy of the interpolation algorithm in this invention.

[0050] Step 5: Extract the high-frequency characteristic impedance of the cable based on the constructed full-band envelope.

[0051] The upper envelope constructed in step 4 and lower envelope Using the upper and lower envelopes as input, the geometric mean is calculated to obtain the high-frequency characteristic impedance of the cable. .

[0052] S5.1, For each frequency point f Calculate the upper envelope and lower envelope The geometric mean value is used to obtain the resistive component of the characteristic impedance as a function of frequency. The calculation formula is:

[0053] S5.2. In the high-frequency band (above 15MHz in this embodiment), the reactance component of the cable is extremely small, the phase angle of the characteristic impedance approaches zero, and the overall characteristic is purely resistive. Therefore, the obtained resistive component can be... Directly considered as the high-frequency characteristic impedance of the cable .

[0054] According to transmission line theory under high-frequency approximation conditions, the upper envelope of the real part of the input impedance is approximated as follows: The lower envelope is approximately... .because Therefore, the geometric mean of the two exactly cancels out the exponential oscillation term and is directly equal to the resistive component of the characteristic impedance. This method, based on the physical premise of high-frequency pure resistivity, cleverly avoids the pre-calculation of the attenuation constant, and achieves accurate and independent decoupled extraction of characteristic impedance.

[0055] Figure 4 This includes the characteristic impedance extracted in this embodiment (thick solid line) and the theoretically derived characteristic impedance value (dashed line). For example... Figure 4 As shown, limited by low-frequency approximation conditions and sampling frequency, the extracted values ​​fluctuate to some extent before 15MHz; however, in the high-frequency range after 15MHz, the extracted characteristic impedance values ​​become extremely stable and highly consistent with the theoretical values. This proves that the method of using envelope-based reverse impedance estimation in the high-frequency range is highly reliable.

[0056] Step 6: Calculate the high-frequency attenuation constant of the cable by combining the full-band envelope and high-frequency characteristic impedance. .

[0057] The upper envelope constructed in step 4 and the high-frequency characteristic impedance extracted in step 5 Using the input as input, and based on the mathematical relationship between the attenuation constant, envelope, and characteristic impedance, calculate the cable's attenuation constant as a function of frequency. .

[0058] S6.1, The characteristic impedance obtained in step 5 and the upper envelope amplitude corresponding to each frequency point. Substitute into the following formula to calculate the high-frequency attenuation constant. :

[0059] S6.2, Traverse each frequency point within the frequency band f By calculating point by point using the above formula, the high-frequency attenuation constant corresponding to each frequency point can be obtained. At the same time, a frequency-varying data sequence is formed in which the high-frequency attenuation constant changes with frequency.

[0060] By inversely calculating the attenuation constant through the relationship between the envelope and characteristic impedance, the loss component in the cable propagation characteristics can be accurately extracted. Unlike characteristic impedance, which tends to stabilize at high frequencies, the attenuation constant is essentially a frequency-varying parameter that increases with frequency due to the skin effect of the conductor and the polarization loss of the insulating medium at high frequencies. The amplitude and rate of change of this parameter curve are directly related to the insulation aging state of the cable, providing an accurate real-part data basis for subsequent decoupling of distributed parameters across the entire frequency band.

[0061] In some embodiments, the attenuation constant can be calculated using the lower envelope instead of the upper envelope, and a smoother sequence can be used as the final high-frequency attenuation constant. To improve accuracy.

[0062] Step 7: Combine the high-frequency propagation constant and the high-frequency characteristic impedance to calculate the complete distributed parameters of the cable.

[0063] The high-frequency phase constant from step 3 and the high-frequency attenuation constant in step 6 As input, determine the high-frequency propagation constant. Combined with high-frequency characteristic impedance The distributed parameters of the cable, including distributed resistance, are calculated using transmission line theory. R Distributed inductance L Distributed conductivity G Distributed capacitance C .

[0064] S7.1, Based on the high-frequency attenuation constant and high-frequency phase constant Synthetic high-frequency propagation constant The calculation formula is:

[0065] S7.2, Based on the high-frequency propagation constant and characteristic impedance Calculate the four distributed parameters of the cable using the following formula:

[0066]

[0067] in, ω is the angular frequency.

[0068] By utilizing the relationship between characteristic impedance and propagation constant in transmission line theory, four distributed parameters of the cable across the entire frequency band were successfully decoupled and calculated. This breakthrough allows single-ended testing to move beyond simply obtaining the single parameter of dielectric loss tangent, enabling a comprehensive analysis of the cable's physical characteristics and providing a data foundation for the precise identification of aging types.

[0069] Step 8: By comparing the calculated distribution parameters with the baseline health status model, assess the cable health status and identify the aging type.

[0070] Using the distributed resistance, distributed inductance, distributed conductance, and distributed capacitance calculated in step 7 as inputs, the distributed parameter reference model of the baseline health state is retrieved, and the variation characteristics of each parameter are compared and analyzed. Based on the variation trends of distributed conductance and distributed capacitance, the health state and aging type of the cable are determined.

[0071] S8.1. Retrieve a reference model of the distribution parameters of a healthy cable with the same specifications and materials as the cable under test from the knowledge database.

[0072] S8.2 Compare the distributed parameters of the cable under test with the benchmark model and calculate the relative changes of each parameter.

[0073] S8.3 Determine the aging type based on the characteristics of changes in distribution parameters: If the distributed conductance G increases significantly while the distributed capacitance C remains unchanged or decreases slightly, it is determined that the cable has undergone overall thermal aging. If the distributed capacitance C increases significantly and the distributed conductivity G also increases substantially, it is determined that the cable has become damp overall or has experienced large-area water tree aging.

[0074] S8.4. Based on the degree of change of each distributed parameter, output the cable health status assessment result, including levels such as healthy, warning, abnormal, and severe.

[0075] By utilizing the different response characteristics of distributed conductivity and distributed capacitance to thermal aging and moisture damage, accurate identification of aging types is achieved. Thermal aging mainly leads to increased dielectric loss (G increase), while moisture simultaneously leads to increased dielectric constant (C increase) and leakage current (G increase). This difference in physical mechanism provides a theoretical basis for distinguishing between the two damage types in this invention, offering more reliable decision support for cable operation and maintenance and life prediction.

[0076] In some embodiments, the reference model for the distribution parameters of the baseline health status can be established by measuring healthy cable samples or obtained by theoretical calculation; the aging type can be further subdivided into mild, moderate and severe levels.

[0077] This embodiment verifies its feasibility by constructing an analytical model of the transmission line using MATLAB. The parameters for a healthy cable are set as l=70m, core outer diameter 3.52mm, and insulation outer diameter 9.30mm.

[0078] Combination Figure 5 The damage type identification logic of the present invention will be described in detail. Figure 5The graphs show the changes in distributed parameters of cables under different damage types, visually illustrating the relationship between distributed capacitance, distributed resistance, and distributed conductance and frequency. Figure 5 In the diagram, solid lines represent healthy conditions, thick dashed lines represent thermal aging, and dotted lines represent damp conditions. (The diagram is used to illustrate this.) Figure 5 By comparing the parameter characteristics, the following two types of damage can be clearly distinguished: 1) Overall thermal aging (insulation material deterioration): The cable operates under high temperature and high load for a long time, resulting in increased dielectric loss, but no obvious water ingress in the physical structure. At this time, the calculated distributed conductivity G increases significantly, while the distributed capacitance C remains unchanged or decreases slightly.

[0079] 2) Overall moisture absorption (large-area water tree): Harsh cable laying environment causes moisture to penetrate the insulation layer, increasing the dielectric constant of the water. In this case, the calculated distributed capacitance C increases significantly, and the distributed conductance G also increases substantially due to the increased leakage current caused by moisture.

[0080] This invention utilizes the characteristic differences between the distributed capacitance C and distributed conductance G mentioned above to achieve accurate differentiation between "thermal aging" and "moisture absorption" based on physical mechanisms using only single-end measurement data.

[0081] By utilizing the different response characteristics of distributed conductivity G and distributed capacitance C to thermal aging and moisture damage, accurate identification of aging types is achieved, providing more reliable decision support for cable operation and maintenance and life prediction.

[0082] Example 2 A cable health status assessment system based on single-ended open-circuit impedance spectrum, comprising: Impedance spectrum acquisition module is used to acquire the real part data of broadband input impedance spectrum under open circuit state at the end of cable, and identify the resonant extreme points of the real part data as the frequency changes. The phase constant calculation module is used to calculate the high-frequency phase constant of the cable based on the resonant frequency difference between adjacent resonant extreme points. An envelope construction module is used to construct the full-frequency envelope of the real part of the input impedance spectrum by interpolation based on the resonant extreme points. Characteristic impedance extraction module, used to extract the high-frequency characteristic impedance of the cable based on the full-band envelope; The attenuation constant calculation module is used to calculate the high-frequency attenuation constant of the cable based on the full-band envelope and the high-frequency characteristic impedance. The health status assessment module is used to calculate the distributed parameters of the cable by combining the high-frequency phase constant, the high-frequency attenuation constant and the high-frequency characteristic impedance, and to assess the health status of the cable based on the distributed parameters.

[0083] It should be noted that, in the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of modules is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple modules may be combined or integrated into another device, or some features may be ignored or not executed. The modules described as separate components may or may not be physically separated. The components shown as modules may be one or more physical units, that is, they may be located in one place or distributed in multiple different places. Some or all of the modules can be selected to achieve the purpose of the solution in this embodiment according to actual needs.

[0084] Furthermore, in the various embodiments of the present invention, the modules can be integrated into one processing unit, or each module can exist physically separately, or two or more modules can be integrated into one unit. The integrated unit described above can be implemented in hardware or as a software functional unit.

[0085] An electronic device provided in this application includes a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, it implements the steps of the cable health status assessment method based on single-ended open-circuit impedance spectrum as described in any of the above embodiments.

[0086] Another electronic device provided in this application embodiment may further include: an input port connected to a processor for transmitting multimodal data collected by an external acquisition device to the processor; a display unit connected to the processor for displaying the processor's processing results to the outside world; and a communication module connected to the processor for enabling communication between the electronic device and the outside world. The display unit may be a display panel, a laser scanning display, etc.; the communication method adopted by the communication module includes, but is not limited to, Mobile High Definition Link (HML), Universal Serial Bus (USB), High Definition Multimedia Interface (HDMI), and wireless connection (including Wi-Fi, Bluetooth, Bluetooth Low Energy, and IEEE 802.11s-based communication technology).

[0087] This application provides a computer-readable storage medium storing a computer program. When executed by a processor, the computer program implements the steps of the cable health status assessment method based on single-ended open-circuit impedance spectrum as described in any of the above embodiments.

[0088] For descriptions of relevant parts of the cable health status assessment system, electronic device, and computer-readable storage medium based on single-ended open-circuit impedance spectrum provided in this application's embodiments, please refer to the detailed description of the corresponding parts in the cable health status assessment method based on single-ended open-circuit impedance spectrum provided in this application's embodiments, which will not be repeated here. Furthermore, parts of the technical solutions provided in this application that are consistent with the implementation principles of corresponding technical solutions in the prior art have not been described in detail to avoid excessive elaboration.

[0089] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for assessing cable health status based on single-ended open-circuit impedance spectrum, characterized in that, Includes the following steps: Step 1: Obtain the real part data of the broadband input impedance spectrum under the open-circuit state of the cable end, and identify the resonant extreme points of the real part data as the frequency changes. Step 2: Calculate the high-frequency phase constant of the cable based on the resonant frequency difference between adjacent resonant extreme points; Step 3: Based on the resonant extreme points, interpolate to construct the full-frequency envelope of the real part of the input impedance spectrum; Step 4: Extract the high-frequency characteristic impedance of the cable based on the full-band envelope; Step 5: Calculate the high-frequency attenuation constant of the cable based on the full-band envelope and the high-frequency characteristic impedance; Step 6: Calculate the distributed parameters of the cable by combining the high-frequency phase constant, the high-frequency attenuation constant and the high-frequency characteristic impedance, and evaluate the health status of the cable based on the distributed parameters.

2. The cable health status assessment method based on single-ended open-circuit impedance spectrum according to claim 1, characterized in that, Step 1, identifying the resonant extrema of the real part data as a function of frequency, specifically includes: A computer-based peak-finding algorithm is used to identify the resonant peaks and troughs of the real part data as the frequency changes, and to obtain the extreme point sequence corresponding to each resonant peak and the extreme point sequence corresponding to each resonant trough. The extreme point sequence includes the resonant frequency and real part amplitude corresponding to the extreme point.

3. The cable health status assessment method based on single-ended open-circuit impedance spectrum according to claim 1, characterized in that, Step 2, calculating the high-frequency phase constant of the cable, specifically includes: Extract the resonant frequency difference between adjacent in-phase extreme points, wherein the in-phase extreme points include adjacent peaks and peaks, or adjacent troughs and troughs; Calculate the high-frequency phase constant based on the cable length and the resonant frequency difference. The calculation formula is: in, The length of the cable to be tested. The difference in resonant frequency between adjacent extreme points. f This refers to a frequency point.

4. The cable health status assessment method based on single-ended open-circuit impedance spectrum according to claim 3, characterized in that, The resonant frequency difference is determined in the following way: Calculate the frequency difference between all adjacent peaks and the frequency difference between all adjacent troughs in the entire high-frequency band. Take the average value of each calculated frequency difference and use the average value as the resonant frequency difference in the calculation.

5. The cable health status assessment method based on single-ended open-circuit impedance spectrum according to claim 1, characterized in that, Step 3, which involves constructing the full-frequency envelope of the real part of the input impedance spectrum, specifically includes: The identified resonant extreme points are separated by type to obtain the discrete point set of peaks and the discrete point set of troughs; An interpolation algorithm is used to perform curve interpolation on the discrete point set of peaks and the discrete point set of troughs respectively, and the upper envelope and lower envelope of the real part of the input impedance spectrum are constructed to form a full-band envelope.

6. The cable health status assessment method based on single-ended open-circuit impedance spectrum according to claim 1, characterized in that, Step 4, which involves extracting the high-frequency characteristic impedance of the cable based on the full-band envelope, specifically includes: For each frequency point, calculate the geometric mean of the upper and lower envelopes to obtain the resistive component of the characteristic impedance that varies with frequency. The stable value of the resistive component of the characteristic impedance in the high-frequency band is taken as the high-frequency characteristic impedance of the cable.

7. The cable health status assessment method based on single-ended open-circuit impedance spectrum according to claim 6, characterized in that, Step 5, calculating the high-frequency attenuation constant of the cable, specifically includes: The high-frequency attenuation constant at each frequency point is calculated based on the upper envelope and the high-frequency characteristic impedance, forming a frequency-varying data sequence of the high-frequency attenuation constant as a function of frequency. The calculation formula is as follows: in, The upper envelope amplitude, For high-frequency characteristic impedance, The length of the cable to be tested is given.

8. The cable health status assessment method based on single-ended open-circuit impedance spectrum according to claim 1, characterized in that, Step 6, calculating the cable's distributed parameters, specifically includes: The high-frequency propagation constant is synthesized from the high-frequency phase constant and the high-frequency attenuation constant; Based on the high-frequency propagation constant and high-frequency characteristic impedance, the distributed parameters of the cable, including distributed resistance, distributed inductance, distributed conductance, and distributed capacitance, are calculated using transmission line theory.

9. The cable health status assessment method based on single-ended open-circuit impedance spectrum according to claim 1, characterized in that, The assessment of cable health status based on distributed parameters specifically includes: Retrieve a reference model of the distribution parameters of a healthy cable of the same specifications and material as the cable under test; The distributed parameters of the cable under test are compared with the reference model, and the relative changes of each parameter are calculated. If the distributed conductivity increases significantly while the distributed capacitance remains unchanged or decreases slightly, it is determined that the cable has undergone overall thermal aging. If the distributed capacitance increases significantly and the distributed conductivity increases substantially, it is determined that the cable has become damp overall or has experienced large-area water treeing aging.

10. A cable health status assessment system based on single-ended open-circuit impedance spectrum, characterized in that, include: Impedance spectrum acquisition module is used to acquire the real part data of broadband input impedance spectrum under open circuit state at the end of cable, and identify the resonant extreme points of the real part data as the frequency changes. The phase constant calculation module is used to calculate the high-frequency phase constant of the cable based on the resonant frequency difference between adjacent resonant extreme points. An envelope construction module is used to construct the full-frequency envelope of the real part of the input impedance spectrum by interpolation based on the resonant extreme points. Characteristic impedance extraction module, used to extract the high-frequency characteristic impedance of the cable based on the full-band envelope; The attenuation constant calculation module is used to calculate the high-frequency attenuation constant of the cable based on the full-band envelope and the high-frequency characteristic impedance. The health status assessment module is used to calculate the distributed parameters of the cable by combining the high-frequency phase constant, the high-frequency attenuation constant and the high-frequency characteristic impedance, and to assess the health status of the cable based on the distributed parameters.

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