Cable fault signal evaluation method and system based on steady-state calibration

Abstract

The embodiment of the application relates to the technical field of fault detection, and provides a cable fault signal evaluation method and system based on steady-state verification, which comprises the following steps: applying a wide-frequency scanning signal with a scanning slope dynamically adjusted according to signal distortion degree to a cable to be evaluated, and obtaining an original wide-frequency response signal sequence; separating transient and steady-state response components from the original wide-frequency response signal sequence, and respectively generating transient impact characteristic parameters and steady-state nonlinear characteristic parameters; constructing a nonlinear response coupling mapping relationship between the two, substituting the transient impact characteristic parameters into the steady-state nonlinear characteristic parameters to obtain a theoretical estimation value of the steady-state nonlinear characteristic parameters, comparing the theoretical estimation value with the steady-state nonlinear characteristic parameters, and generating a coupling verification state signal according to a comparison result; and when the coupling verification state signal represents a true defect, locating the defect according to the steady-state response component, matching a defect type according to the two kinds of characteristic parameters, and generating an evaluation result containing the defect type and the position, so that the efficiency of cable fault signal evaluation is improved.

Description

Technical Field

[0001] This application relates to the field of fault detection technology, and in particular to a cable fault signal evaluation method and system based on steady-state verification. Background Technology

[0002] Currently, the broadband impedance spectroscopy / frequency domain reflection method is widely used in cable fault detection. Its basic implementation involves applying a broadband sweep signal to the cable under test, acquiring its reflection / transmission response signal, extracting the reflection coefficient spectrum or impedance spectrum by performing a frequency domain transformation on the response signal, and then determining the cable condition based on abnormal resonance peaks or impedance change characteristics in the spectrum. The effective implementation of this method typically relies on two preconditions: the sweep signal parameters are pre-set, and the analysis process is mainly based on steady-state frequency domain response data for single-domain feature extraction and interpretation. When the actual detection environment deviates from the preset conditions, this fixed sweep strategy and single-domain analysis mode can easily lead to insufficient adaptability of the system to signal quality fluctuations.

[0003] In cable field inspection scenarios, cable types are diverse, laying environments are complex, and the signal response characteristics generated by different defect types vary. With fixed sweep parameters, when the response signal is distorted due to cable structure inhomogeneity or external interference, a fixed sweep slope is insufficient to effectively excite transient defect features or ensure sufficient establishment of the steady-state response signal, thus affecting the accuracy of frequency domain feature extraction. Furthermore, relying on a single steady-state frequency domain response for interpretation makes it easy to misjudge structural reflections such as cable joints and bends as insulation defects in actual testing. Moreover, defect type identification and spatial localization often need to be performed separately in different analysis stages, increasing the complexity of the comprehensive evaluation. Summary of the Invention

[0004] This application provides a cable fault signal evaluation method and system based on steady-state verification to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, this application provides a cable fault signal evaluation method based on steady-state verification, comprising: A broadband scanning signal is applied to the cable to be evaluated, and the original broadband response signal sequence returned by the cable to be evaluated in response to the broadband scanning signal is obtained. The sweep slope of the broadband scanning signal is dynamically adjusted according to the degree of signal distortion in the original broadband response signal sequence. Transient response components and steady-state response components are separated from the original broadband response signal sequence. Transient impulse characteristic parameters are generated based on the transient response components, and steady-state nonlinear characteristic parameters are generated based on the steady-state response components. A nonlinear response coupling mapping relationship is constructed between the transient impact characteristic parameter and the steady-state nonlinear characteristic parameter. The transient impact characteristic parameter is substituted into the nonlinear response coupling mapping relationship to obtain the theoretical estimate of the steady-state nonlinear characteristic parameter. The theoretical estimate is compared with the steady-state nonlinear characteristic parameter for consistency. A coupling verification state signal is generated based on the consistency comparison result. When the coupled verification state signal is a signal characterizing a true defect, a positioning operation is performed based on the steady-state response component, and the defect type is matched based on the transient impact characteristic parameter and the steady-state nonlinear characteristic parameter to generate an evaluation result containing the defect type and defect location.

[0006] To address the aforementioned issues, this application also provides a cable fault signal evaluation system based on steady-state verification, the system comprising: A wideband scanning module is used to apply a wideband scanning signal to the cable to be evaluated and acquire the original wideband response signal sequence returned by the cable to be evaluated in response to the wideband scanning signal. The sweep slope of the wideband scanning signal is dynamically adjusted according to the degree of signal distortion in the original wideband response signal sequence. The component parameter analysis module is used to separate transient response components and steady-state response components from the original broadband response signal sequence, generate transient impulse characteristic parameters based on the transient response components, and generate steady-state nonlinear characteristic parameters based on the steady-state response components. The coupling verification module is used to construct a nonlinear response coupling mapping relationship between the transient impact characteristic parameter and the steady-state nonlinear characteristic parameter, substitute the transient impact characteristic parameter into the nonlinear response coupling mapping relationship to obtain the theoretical estimate of the steady-state nonlinear characteristic parameter, compare the consistency of the theoretical estimate with the steady-state nonlinear characteristic parameter, and generate a coupling verification state signal based on the consistency comparison result. The defect assessment module is used to perform a positioning operation based on the steady-state response component and match the defect type based on the transient impact characteristic parameter and the steady-state nonlinear characteristic parameter when the coupled verification state signal is a signal characterizing a true defect, thereby generating an assessment result containing the defect type and defect location.

[0007] Compared with the prior art, the embodiments of this application have the following beneficial effects: 1. This application embodiment applies a broadband scanning signal to the cable to be evaluated and dynamically adjusts the sweep slope according to the degree of distortion of the response signal. This enables the excitation signal to be adaptively optimized according to the actual state of the cable, avoiding the problem that fixed sweep parameters cannot effectively excite defect features when the signal is distorted. At the same time, by separating the transient response component and the steady-state response component from the original response signal and generating corresponding feature parameters respectively, a nonlinear response coupling mapping relationship between the two is constructed. The consistency comparison between the theoretical estimate and the measured steady-state parameter is used as the basis for judging whether the defect is real or fake. This overcomes the limitation that it is difficult to distinguish between structural reflection and real defects when relying on a single steady-state frequency domain response for interpretation. Furthermore, defect type matching and location positioning are integrated into the same evaluation framework, thereby improving the reliability of the evaluation results while reducing the complexity of the comprehensive evaluation.

[0008] 2. Based on the quantitative correspondence between transient impact characteristic parameters and steady-state nonlinear characteristic parameters determined by the nonlinear conductivity characteristics of local defects in cables, this application constructs a nonlinear response coupling mapping model expressed by a third-order polynomial. The transient impact characteristic parameters are then substituted into this model to obtain theoretical estimates of the steady-state nonlinear characteristic parameters. Thus, based on the established coupling verification framework, a specific mathematical expression of the coupling relationship is further provided, enabling precise quantification of the physical correlation between transient and steady-state responses. This provides a definite computational basis for consistency comparison, enhancing the reproducibility of the verification process and the stability of the judgment results. Attached Figure Description

[0009] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only one feasible implementation of the embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0010] Figure 1 A flowchart illustrating a cable fault signal evaluation method based on steady-state verification, provided for an embodiment of this application; Figure 2 This is a functional block diagram of a cable fault signal evaluation system based on steady-state verification, provided in an embodiment of this application.

[0011] The realization of the objectives, functional features and advantages of the embodiments of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0012] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0013] This application provides a cable fault signal evaluation method based on steady-state verification. The execution entity of this steady-state verification-based cable fault signal evaluation method includes, but is not limited to, at least one of the following electronic devices that can be configured to execute the method provided in this application embodiment: a server, a terminal, etc. In other words, the steady-state verification-based cable fault signal evaluation method can be executed by software or hardware installed on a terminal device or a server device. The server includes, but is not limited to, a single server, a server cluster, a cloud server, or a cloud server cluster. The server can be an independent server or a cloud server that provides basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network services, cloud communication, middleware services, domain name services, security services, content delivery networks (CDNs), and big data and artificial intelligence platforms.

[0014] Reference Figure 1 The diagram shown is a flowchart illustrating a cable fault signal evaluation method based on steady-state verification provided in an embodiment of this application. In this embodiment, the cable fault signal evaluation method based on steady-state verification includes: Pt.1. Apply a broadband scanning signal to the cable to be evaluated and obtain the original broadband response signal sequence returned by the cable to be evaluated in response to the broadband scanning signal. The sweep slope of the broadband scanning signal is dynamically adjusted according to the degree of signal distortion in the original broadband response signal sequence. In this embodiment of the application, a broadband scanning signal is applied to the cable to be evaluated, and the original broadband response signal sequence returned by the cable to be evaluated in response to the broadband scanning signal is obtained.

[0015] The wideband scanning signal has a start frequency, an end frequency, a sweep period, and a sweep slope.

[0016] The start frequency and the end frequency together define the sweep frequency range of the broadband scanning signal, which covers the fundamental resonant frequency band and the frequency band of its main harmonic components of the cable to be evaluated.

[0017] Preferably, the starting frequency of the sweep range is 10kHz and the ending frequency is 100MHz.

[0018] The selection of the start and end frequencies is based on the fact that the frequency band below 10kHz is significantly affected by the boundary conditions at the end of the cable and has insufficient signal penetration, while the frequency band above 100MHz suffers from severe high-frequency attenuation due to the increased skin effect of the cable. Neither of these frequencies can effectively carry defect feature information.

[0019] It should be noted that the specific values ​​mentioned above are exemplary, and those skilled in the art can make adaptive adjustments to the starting and ending frequencies based on actual factors such as the length, model, dielectric constant of the insulation material, and expected defect types of the cable to be evaluated.

[0020] The sweep period of a wideband scanning signal is the length of time that a complete sweep cycle takes, and its value should be sufficient to allow the cable to be evaluated to establish a stable response at each frequency point.

[0021] Preferably, the sweep frequency period ranges from 0.5 seconds to 2 seconds.

[0022] When the sweep period is less than 0.5 seconds, the electromagnetic energy inside the cable is not sufficiently built up, and the steady-state response component is covered by the excitation of the next frequency point before it has fully formed.

[0023] When the frequency sweep period is longer than 2 seconds, the time taken for a single sweep is too long, which will reduce the timeliness of the evaluation in scenarios where the cable condition changes rapidly.

[0024] The sweep slope is a quantitative representation of the rate of frequency change within the sweep cycle, and its value is equal to the sweep range width divided by the sweep cycle.

[0025] In traditional fixed frequency sweep parameter schemes, the sweep slope remains unchanged throughout the entire sweep test once it is set, and cannot be adjusted according to the actual response state of the cable.

[0026] However, in actual testing, when the original broadband response signal sequence is significantly distorted, if the sweep slope remains unchanged, it is difficult to enhance the transient excitation effect on the defect by accelerating the frequency change, nor is it possible to ensure the full establishment of the steady-state response by slowing down the frequency change.

[0027] Therefore, in this embodiment, the sweep slope of the broadband scanning signal is dynamically adjusted according to the degree of signal distortion in the original broadband response signal sequence.

[0028] The physical basis of this dynamic adjustment is that the degree of signal distortion reflects the response strength of the internal impedance discontinuity or nonlinearity of the cable to be evaluated to the frequency sweep excitation, and the response strength increases with the increase of the severity of the defect; by monitoring the degree of signal distortion and adjusting the frequency sweep slope accordingly, a closed-loop feedback link from response quality to excitation parameters is formed.

[0029] Specifically, amplitude fluctuation detection is performed on the original broadband response signal sequence of the cable to be evaluated to obtain the fluctuation amount of the amplitude of the original broadband response signal sequence at each sampling time relative to the preset reference amplitude, and this fluctuation amount is used as a quantitative characterization of the degree of signal distortion.

[0030] The preset reference amplitude is the theoretical response amplitude or factory-calibrated amplitude curve of a standard cable of the same model under the same frequency sweep parameters in a defect-free state. This reference amplitude is preset by the operator based on a large amount of historical experimental data or standard sample test results.

[0031] In one feasible implementation, the degree of signal distortion can also be quantified by the amplitude variance, peak change rate, or root mean square value of the amplitude difference between adjacent sampling points of the original broadband response signal sequence.

[0032] In another feasible implementation, the degree of signal distortion can also be characterized by the spectral entropy value of the original broadband response signal sequence or the peak factor of the time-domain waveform.

[0033] When the fluctuation exceeds the preset fluctuation threshold, the sweep slope of the broadband scanning signal is increased to enhance the transient excitation effect of the broadband scanning signal on potential defects in the cable to be evaluated, and an updated broadband scanning signal is generated based on the increased sweep slope and applied to the cable to be evaluated.

[0034] The preset fluctuation threshold is a predetermined allowable value for amplitude deviation, which is set by the operator based on a large amount of experimental data or standard sample test results.

[0035] Preferably, the preset fluctuation threshold is set to ±5% to ±10% of the reference amplitude.

[0036] When the fluctuation is lower than the preset fluctuation threshold, the sweep slope of the broadband scan signal is reduced, and an updated broadband scan signal is generated based on the reduced sweep slope and applied to the cable to be evaluated.

[0037] The specific adjustment range of the sweep slope is determined as follows: calculate the difference between the fluctuation amount and the preset fluctuation threshold, multiply the difference by the preset proportional coefficient, and then add it to the current sweep slope to form the updated sweep slope.

[0038] Preferably, the proportionality coefficient ranges from 0.1 to 0.5.

[0039] In another feasible implementation, the adjustment range of the sweep slope can also be determined by a piecewise function: when the fluctuation exceeds the threshold by a multiple in the first interval, the first adjustment step is executed; when the fluctuation exceeds the threshold by a multiple in the second interval, the second adjustment step is executed, and the second adjustment step is larger than the first adjustment step.

[0040] In another feasible implementation, the sweep rate slope can be adjusted using a proportional-integral control method, which incorporates the accumulated history of fluctuations into the calculation of the adjustment amount, in order to avoid the over-response of the sweep rate slope caused by accidental jumps in fluctuations at a single moment.

[0041] Regardless of which adjustment method is used, the increase or decrease of the sweep slope is subject to the boundary conditions of not exceeding the minimum and maximum physically realizable slopes of the wideband sweep signal.

[0042] Preferably, the maximum value of the sweep slope is limited by the maximum frequency change rate of the signal source and the high-frequency attenuation characteristics of the cable to be evaluated, while the minimum value of the sweep slope is limited by the maximum allowable time for a single sweep and the amplitude detection sensitivity of the steady-state response signal.

[0043] Obtain the original broadband response signal sequence returned by the cable to be evaluated in response to the updated broadband scan signal. This original broadband response signal sequence is the input data for subsequent separation of transient response components and steady-state response components.

[0044] Through the above dynamic adjustment mechanism, the distortion of the original broadband response signal sequence is always maintained near the preset fluctuation threshold, avoiding the problem of response signal quality degradation caused by fixed sweep parameters. This provides signal quality assurance for the reliable separation of subsequent transient response components and steady-state response components, and also creates conditions for the effective excitation of transient impulse characteristic parameters.

[0045] Pt.2. Separate transient response components and steady-state response components from the original broadband response signal sequence, generate transient impulse characteristic parameters based on the transient response components, and generate steady-state nonlinear characteristic parameters based on the steady-state response components; In the embodiments of this application, under wideband sweep excitation, the original wideband response signal sequence simultaneously contains two response components with different physical properties.

[0046] One of the components is the transient response component, which is generated by the impulse signal excited by the redistribution of the electromagnetic field inside the cable when the sweep frequency of the broadband scanning signal changes transiently. This component is extremely sensitive to sudden changes in the local impedance of the cable and is a key information carrier for characterizing the impact characteristics of defects.

[0047] Another component is the steady-state response component, which is a periodic response signal that is in the same frequency as the broadband scanning signal after the electromagnetic field inside the cable reaches dynamic equilibrium. This component has a stable characterization ability for the nonlinear conductivity characteristics of the cable and is an important basis for reflecting the degree of nonlinear distortion of defects.

[0048] However, in actual testing, transient response components and steady-state response components are superimposed in the time domain and have overlapping frequency bands. If the original broadband response signal sequence is analyzed as a whole without distinction, the impact characteristics of the transient components will be smoothed by the steady-state periodic components, and the nonlinear details of the steady-state components will be submerged by the transient impact. The two interfere with each other, resulting in distortion of defect information extraction.

[0049] Therefore, in this embodiment of the application, transient response components and steady-state response components are extracted from the original broadband response signal sequence, respectively.

[0050] The original broadband response signal sequence is truncated using a time-domain window function to capture the transient signal component generated by the sudden change in the sweep frequency rate of the broadband scanning signal in the original broadband response signal sequence, and the transient signal component is used as the transient response component.

[0051] Specifically, time-domain window function truncation refers to selecting a time window of finite width on the time axis of the original broadband response signal sequence, centered on the moment when the sweep frequency change rate changes abruptly, and extracting the signal sequence within this time window as the transient response component.

[0052] The moment when the sweep frequency change rate changes abruptly corresponds to the instant when the sweep slope is adjusted. The transient signal generated at this instant contains information about the maximum impact response of the internal defects of the cable to the frequency change.

[0053] In one feasible implementation, the time window uses a rectangular window function, where all sampling points within the window are assigned an equal weight coefficient of 1, and sampling points outside the window are assigned a weight coefficient of 0.

[0054] In another feasible implementation, the time window uses a Hanning window function or a Hamming window function, in which the weight coefficients of the sampling points within the window gradually decrease to zero from the center of the window to the edge of the window, in order to suppress the spectral leakage effect.

[0055] Preferably, the width of the time window is 1% to 5% of the sweep period.

[0056] The determination of the window width range is based on the following: when the window width is less than 1% of the sweep frequency period, the transient process that has not yet been fully presented may be truncated, resulting in the loss of feature information; when the window width is greater than 5% of the sweep frequency period, the steady-state component begins to be significantly mixed into the transient extraction result, resulting in incomplete separation.

[0057] The remaining signal sequence after removing the transient signal component is periodically truncated to extract a response signal segment that is synchronized with the sweep frequency period of the wideband scanning signal.

[0058] Periodic truncation refers to dividing the remaining signal sequence according to the periodic boundary, using the sweep period of the wideband scan signal as the length unit. Each segment obtained by the division corresponds to the response signal within a complete sweep period.

[0059] The amplitude of the intercepted response signal segment is averaged within the same period, and the periodic signal component with the same frequency as the broadband scanning signal in the response signal segment is extracted and used as the steady-state response component.

[0060] Amplitude averaging within the same period refers to the arithmetic average of the response signal amplitudes at the same phase point within multiple sweep cycles, in order to eliminate the influence of random noise and aperiodic disturbances, and retain the periodic response components that are strictly synchronized with the sweep signal.

[0061] Preferably, the number of sweep cycles involved in amplitude averaging is 8 to 32 cycles.

[0062] When the number of cycles is less than 8, the suppression effect of random noise is insufficient and the signal-to-noise ratio of the steady-state response component is low; when the number of cycles is more than 32, the time taken for a single steady-state extraction is too long and the robustness to the slow change of cable condition over time decreases.

[0063] By employing the two-stage separation strategy that combines time-domain window function truncation and periodic truncation, transient response components and steady-state response components are effectively separated in the time domain, enabling the defect feature information carried by each type of component to be extracted independently in subsequent steps without interference.

[0064] Transient impact characteristic parameters are generated based on the transient response components.

[0065] The instantaneous amplitude values ​​at each sampling time are extracted from the time-domain waveform of the transient response component, and the instantaneous amplitude values ​​are arranged according to the sampling time sequence to form the time-domain waveform envelope of the transient response component.

[0066] The envelope is a curve showing the continuous change of the instantaneous amplitude of the transient response component over time, and its shape reflects the distribution pattern of transient signal energy on the time axis.

[0067] The instantaneous amplitude is accumulated point by point along the time axis of the envelope to obtain the energy accumulation curve of the transient response component.

[0068] The energy accumulation curve represents the total amount of transient signal energy accumulated from the start of the transient to the current time. This total amount increases monotonically as the transient process progresses until it reaches a stable value when the transient energy decays completely.

[0069] The amplitude of the energy accumulation curve at each time point is traversed, and the amplitude corresponding to the time point with the largest amplitude is detected and used as the transient impact characteristic parameter.

[0070] The time point with the largest amplitude corresponds to the moment when the transient energy accumulation rate is the fastest. The cumulative amplitude at this moment comprehensively reflects the intensity and energy concentration of the transient impact signal, and this amplitude is used as a characteristic parameter of the transient impact.

[0071] Preferably, the value range of the transient impact characteristic parameter is 0.1 to 1000.

[0072] The unit of this value range is determined according to the quantization method of the signal acquisition system. Different acquisition systems can make the parameters be of the same order of magnitude through normalization processing.

[0073] The larger the transient impact characteristic parameter, the higher the energy concentration in the transient response component, and the stronger the impact response of the internal defects of the cable to frequency changes.

[0074] Steady-state nonlinear characteristic parameters are generated based on the steady-state response components.

[0075] A frequency domain transformation operation is performed on the steady-state response component to obtain the frequency domain amplitude sequence of the steady-state response component.

[0076] Frequency domain transformation converts the steady-state response components from a time domain representation to a frequency domain representation, allowing the amplitudes of different frequency components to be clearly distinguished in the frequency domain.

[0077] In one feasible implementation, the frequency domain transformation operation is implemented using the Fast Fourier Transform algorithm.

[0078] In another feasible implementation, the frequency domain transformation operation is implemented using the discrete Fourier transform algorithm.

[0079] In another feasible implementation, the frequency domain transformation operation is implemented using the chirp Z-transform algorithm, which can provide higher resolution spectrum analysis within a specific frequency band.

[0080] Preferably, the number of points in the frequency domain transformation is between 1024 and 8192.

[0081] The number of points directly affects the frequency resolution. When the number of points is too low, adjacent frequency components cannot be distinguished. When the number of points is too high, the computational load increases significantly, and the improvement in frequency resolution tends to saturate.

[0082] Extract the fundamental amplitude corresponding to the fundamental frequency from the frequency domain amplitude sequence, and extract the harmonic amplitude corresponding to the harmonic frequencies from the frequency domain amplitude sequence.

[0083] The fundamental frequency is equal to the instantaneous frequency of the broadband scanning signal, and the fundamental amplitude is the amplitude of the component in the steady-state response that has the same frequency as the excitation signal.

[0084] The harmonic frequency is an integer multiple of the fundamental frequency, and the harmonic amplitude is the amplitude of each harmonic component generated by the nonlinear distortion of the cable in the steady-state response component.

[0085] Preferably, the extracted harmonics include the second harmonic, the third harmonic, the fifth harmonic, and the seventh harmonic.

[0086] The ratio of the harmonic amplitude corresponding to each harmonic frequency to the fundamental frequency amplitude is calculated to obtain the harmonic amplitude ratio corresponding to each harmonic.

[0087] The calculation of harmonic amplitude ratio eliminates the influence of absolute amplitude fluctuations of the signal on feature extraction, making the feature parameters depend only on the degree of nonlinear distortion of the signal itself.

[0088] According to the preset weight allocation rules, each harmonic amplitude ratio is assigned a corresponding weight value, and the harmonic amplitude ratio and the corresponding weight value are weighted and integrated to generate steady-state nonlinear characteristic parameters.

[0089] The weighting rules are set based on the ability of different harmonic orders to distinguish cable defect types.

[0090] Preferably, the weight value of the second harmonic is 0.1 to 0.3, the weight value of the third harmonic is 0.3 to 0.6, the weight value of the fifth harmonic is 0.1 to 0.3, the weight value of the seventh harmonic is 0.05 to 0.15, and the sum of all weight values ​​is equal to 1.

[0091] In the embodiments of this application, through the above-mentioned frequency domain transformation, harmonic extraction, ratio calculation and weighted integration operations, the steady-state nonlinear characteristic parameter can fuse the multi-order harmonic distortion information in the steady-state response component into a single quantitative index. This index is positively correlated with the severity of nonlinear conductance defects inside the cable, providing a reliable steady-state characteristic input for subsequent coupling verification.

[0092] In this embodiment, after the transient response component and the steady-state response component are separated, transient impact characteristic parameters and steady-state nonlinear characteristic parameters are generated respectively. The two types of parameters characterize the defect's properties from different physical dimensions, providing a data foundation for subsequently constructing the nonlinear response coupling mapping relationship between the two.

[0093] Pt.3. Construct a nonlinear response coupling mapping relationship between the transient impact characteristic parameter and the steady-state nonlinear characteristic parameter. Substitute the transient impact characteristic parameter into the nonlinear response coupling mapping relationship to obtain the theoretical estimate of the steady-state nonlinear characteristic parameter. Perform a consistency comparison between the theoretical estimate and the steady-state nonlinear characteristic parameter. Generate a coupling verification state signal based on the consistency comparison result. In the embodiments of this application, at the local defects in the cable, due to factors such as aging of the insulation material, moisture, or mechanical damage, the conductivity characteristics of the defect area no longer follow the linear relationship described by Ohm's law, but exhibit significant nonlinear conductivity characteristics.

[0094] The physical essence of this nonlinear conductivity characteristic is that the charge carrier mobility in the defect region changes with the electric field strength. When a broadband scanning signal passes through the defect region, its voltage-current response curve deviates from the linear relationship, generating harmonic components and nonlinear distortion.

[0095] This nonlinear conductivity characteristic acts on both transient and steady-state processes.

[0096] During the transient process, when the sweep rate slope changes abruptly, the nonlinear conductance of the defect region causes a violent redistribution of electromagnetic energy locally, forming an impact signal with concentrated amplitude and slow decay. The intensity of this impact signal is quantified by the transient impact characteristic parameters.

[0097] During steady-state operation, when the frequency sweep signal is continuously excited at a constant frequency, the nonlinear conductance of the defect region causes harmonic components other than the fundamental frequency to be generated in the response signal. The degree of nonlinear distortion is quantified by the steady-state nonlinear characteristic parameter.

[0098] Since both types of parameters originate from the same physical source, namely the nonlinear conductivity characteristics of the defect region, there must be a deterministic quantitative correspondence between them.

[0099] However, in actual testing, the transient impact characteristic parameters are significantly affected by the excitation conditions at the moment of sudden change in the sweep frequency slope, and are highly sensitive to the presence of defects.

[0100] Steady-state nonlinear characteristic parameters are less affected by random noise and system drift, and have a stronger ability to distinguish defect types.

[0101] If a quantitative mapping relationship can be established between transient impact characteristic parameters and steady-state nonlinear characteristic parameters, the high sensitivity of the transient response can be used to confirm the existence of defects, while the high stability of the steady-state response can be used to verify the reliability of the confirmation result.

[0102] The core of this two-way verification mechanism is that the transient response and steady-state response generated by a genuine defect must satisfy this quantitative mapping relationship, while the transient response and steady-state response generated by a false defect, such as a cable joint, bending, or gradual material change, do not have this mapping relationship, thus effectively distinguishing between genuine and false defects.

[0103] Therefore, a quantitative correspondence is determined between the transient impact characteristic parameter and the steady-state nonlinear characteristic parameter, which are determined by the nonlinear conductivity characteristics of local defects in the cable, and the quantitative correspondence is used as the basis for constructing the nonlinear response coupling mapping relationship.

[0104] The nonlinear response coupling mapping relationship is established based on the quantitative correspondence, and the nonlinear response coupling mapping relationship is expressed as follows: ; in, These are the theoretical estimates of the steady-state nonlinear characteristic parameters. The transient impact characteristic parameter, The first fitting coefficient corresponds to the cubic term of the transient impact characteristic parameter. The second fitting coefficient corresponds to the quadratic term of the transient impact characteristic parameter. The third fitting coefficient is the first power term of the transient impact characteristic parameter.

[0105] The basis for determining the cubic polynomial form is that the current-voltage relationship of the nonlinear conductivity characteristics in the defect region of the cable can be mathematically expanded into a Taylor series, where the first term corresponds to the linear conductivity part, the second and third terms correspond to the dominant orders of the nonlinear conductivity part, and the higher-order terms can be ignored in practical engineering due to their small amplitude. Therefore, the cubic polynomial can accurately characterize the physical coupling relationship between the transient impact characteristic parameters and the steady-state nonlinear characteristic parameters.

[0106] The first fitting coefficient, the second fitting coefficient, and the third fitting coefficient are constant values ​​determined based on the model parameters and historical calibration data of the cable to be evaluated.

[0107] Preferably, the first fitting coefficient The value range is from 0.001 to 0.1.

[0108] Preferably, the second fitting coefficient The value range is from 0.01 to 1.0.

[0109] Preferably, the third fitting coefficient The value range is from 0.1 to 10.0.

[0110] The specific values ​​of the above fitting coefficients are determined as follows: Historical calibration data of standard cables of the same model as the cable to be evaluated under different defect levels are obtained. The historical calibration data includes the measured values ​​of transient impact characteristic parameters and steady-state nonlinear characteristic parameters of each calibration sample. The transient impact characteristic parameters of each calibration sample are used as inputs and the steady-state nonlinear characteristic parameters are used as outputs. The least squares method is used to perform cubic polynomial fitting, and the coefficient combination that minimizes the sum of squared fitting errors is solved. This coefficient combination is used as the values ​​of the first fitting coefficient, the second fitting coefficient, and the third fitting coefficient.

[0111] In one feasible implementation, the fitting coefficients can also be updated online using the recursive least squares method. That is, whenever new calibration data or field measured data is acquired, the transient impact characteristic parameter and steady-state nonlinear characteristic parameter of the data are used as new sample points to recursively correct the existing fitting coefficients, so that the mapping relationship is gradually refined as data accumulates.

[0112] In another feasible implementation, each fitting coefficient can also be globally optimized using a particle swarm optimization algorithm or a genetic algorithm, with the nonlinear function of the fitting error as the fitness function, and the coefficient combination that makes the fitness optimal is searched in the coefficient space.

[0113] The transient impact characteristic parameters are used as input parameters of the nonlinear response coupling mapping relationship. Substituted into the nonlinear response coupling mapping relationship, the theoretical estimated value of the steady-state nonlinear characteristic parameters is obtained, and the theoretical estimated value is used as the object of consistency comparison.

[0114] The difference between the theoretical estimate and the steady-state nonlinear characteristic parameter is obtained by subtracting the theoretical estimate from the steady-state nonlinear characteristic parameter.

[0115] The difference is compared with a preset coupling tolerance range, which has an upper limit and a lower limit.

[0116] When the degree of difference is within the range of the coupling tolerance, the consistency comparison is determined to be passed, and the coupling verification status signal characterizing the true defect is generated.

[0117] When the difference is outside the coupling tolerance range, the consistency comparison is determined to fail, and the coupling verification status signal characterizing the false defect is generated.

[0118] Preferably, the lower limit of the coupling tolerance range is a negative tolerance threshold, and the upper limit is a positive tolerance threshold. The tolerance threshold ranges from ±5% to ±15% of the theoretically estimated value of the steady-state nonlinear characteristic parameter.

[0119] The tolerance threshold is determined based on the following: when the tolerance threshold is less than ±5%, the system is overly sensitive to noise and normal fluctuations, and is prone to misjudging real defects as false defects; when the tolerance threshold is greater than ±15%, the system has too large a tolerance for deviations from the actual nonlinear coupling relationship, and is prone to misjudging false defects as real defects.

[0120] In another feasible implementation, the tolerance threshold can be set differently according to the type of cable to be evaluated. A wider tolerance threshold is used for long-distance high-voltage cables to tolerate the natural drift of coupling relationship caused by the gradual change of parameters along the line, while a narrower tolerance threshold is used for short-distance low-voltage cables to improve the verification sensitivity.

[0121] In another feasible implementation, the difference degree can also be replaced by the relative difference degree, that is, the difference degree is equal to the absolute value of the difference between the theoretical estimate and the steady-state nonlinear characteristic parameter divided by the absolute value of the steady-state nonlinear characteristic parameter, and the relative deviation expressed as a percentage is compared with the preset percentage tolerance threshold.

[0122] In another feasible implementation, the calculation of the difference can also introduce a weighting factor that is negatively correlated with the magnitude of the steady-state nonlinear characteristic parameter itself, so as to suppress the error amplification effect under large magnitude conditions.

[0123] Regardless of which difference calculation method or tolerance threshold setting method is used, the coupled verification status signal will binarize the consistency comparison result into two states: true defect or false defect.

[0124] When the coupling verification status signal is a signal that represents a true defect, the subsequent steps perform location and defect type matching operations.

[0125] When the coupling verification status signal is a signal that characterizes a false defect, the subsequent steps terminate and the evaluation conclusion of no defect is output.

[0126] By constructing and comparing the above-mentioned nonlinear response coupling mapping relationship, the high sensitivity of transient response and the high stability of steady-state response are mutually verified, avoiding the false alarm problem inherent in the judgment of single feature parameter threshold, and realizing the effective distinction between true defects and false defects.

[0127] Pt.4 When the coupled verification state signal is a signal characterizing a true defect, a positioning operation is performed based on the steady-state response component, and the defect type is matched based on the transient impact characteristic parameter and the steady-state nonlinear characteristic parameter to generate an evaluation result containing the defect type and defect location.

[0128] In this embodiment of the application, after the coupling verification status signal is confirmed as a genuine defect, it is necessary to further determine the spatial location of the defect on the cable and the specific type of the defect in order to form a complete evaluation conclusion.

[0129] The steady-state response component is converted from a time-domain representation to a frequency-domain representation to obtain the reflection coefficient amplitude of the steady-state response component at each frequency point. The frequency points are then associated with and arranged with the corresponding reflection coefficient amplitude to form the frequency-domain reflection coefficient curve of the steady-state response component.

[0130] The physical meaning of the frequency domain reflection coefficient curve is that each impedance discontinuity point in the cable reflects the incident signal, the amplitude of the reflected signal is positively correlated with the degree of impedance change, and the phase delay of the reflected signal reaching the measurement end is positively correlated with the distance of the impedance discontinuity point.

[0131] In the frequency domain representation, the amplitude of the reflection coefficient at each frequency point is the result of the vector superposition of the reflected signals at that frequency from all impedance discontinuities along the cable.

[0132] When a cable has a local defect, the defect acts as a significant impedance discontinuity, which will form a resonance peak at a specific frequency position on the frequency domain reflection coefficient curve.

[0133] The reflection coefficient amplitude at each frequency point of the frequency domain reflection coefficient curve is traversed. The reflection coefficient amplitude at adjacent frequency points is compared point by point. The frequency points where the reflection coefficient amplitude is convex relative to the reflection coefficient amplitude at adjacent frequency points are detected as local peak points, and the frequency value corresponding to the local peak points is extracted.

[0134] Local peak points can be detected using the first-order differential zero-crossing detection method, which involves calculating the first-order differential value of the frequency domain reflection coefficient curve at each frequency point. When the differential value changes from positive to negative, that point is the local peak point.

[0135] In one feasible implementation, the detection of local peak points can also be achieved using the second-order difference threshold method. This involves calculating the second-order difference value of the frequency domain reflection coefficient curve and identifying points where the second-order difference value is less than a preset negative threshold and the first-order difference value crosses zero as valid local peak points, thereby eliminating false peaks caused by noise.

[0136] In another feasible implementation, the detection of local peak points can also be achieved using the wavelet transform modulus maxima method. This involves performing wavelet decomposition on the frequency domain reflection coefficient curve, detecting modulus maxima at different scales, and taking the point with the largest amplitude among the modulus maxima at each scale as the local peak point. This method has stronger robustness against noise interference.

[0137] In another feasible implementation, the detection of local peak points can also be achieved using a constant false alarm rate (CFAR) detection method. This involves estimating the background noise level of the frequency domain reflection coefficient curve, setting a detection threshold that is adaptively linked to the background noise level, and identifying local extreme points whose amplitude exceeds the detection threshold as valid local peak points.

[0138] Based on the ratio between the frequency value corresponding to the local peak point and the preset wave velocity parameter of the cable to be evaluated, the location distance corresponding to the local peak point is determined, and the location distance is taken as the defect location.

[0139] Location distance is calculated using the following formula: ; in, The spatial distance from the defect location to the measuring end. The preset propagation speed of electromagnetic waves in the cable to be evaluated. This represents the frequency value corresponding to the local peak point.

[0140] The physical basis of the above formula is that the total distance that the electromagnetic wave travels from the measuring end to the defect and then reflects back to the measuring end is twice the distance of the defect. This total distance is equal to the electromagnetic wave propagation speed multiplied by the total time delay. The total time delay is proportional to the reciprocal of the resonant peak frequency in the frequency domain reflection coefficient curve. Therefore, the defect distance is equal to the wave speed divided by twice the resonant peak frequency.

[0141] Preferably, preset wave velocity parameters The value ranges from 50% to 99% of the speed of light in a vacuum.

[0142] The upper limit of this range is determined based on the relative permittivity of the cable insulation material. When the relative permittivity is close to 1, the wave speed approaches the speed of light in a vacuum. The lower limit of this range is determined based on the physical law that the wave speed decreases accordingly when the relative permittivity of the cable insulation material is large.

[0143] Specifically, the value of the preset wave velocity parameter v is determined as follows: obtain the nominal or measured value of the insulation material type and relative permittivity of the cable to be evaluated, and calculate the value of the preset wave velocity parameter based on the formula for the propagation speed of electromagnetic waves in a medium, i.e., wave velocity equals the speed of light in a vacuum divided by the square root of the relative permittivity.

[0144] When there are multiple defects in the cable, the frequency domain reflection coefficient curve may have multiple local peak points, which correspond to impedance discontinuities at different spatial locations.

[0145] At this point, the distance to each local peak point is calculated according to the above formula to obtain multiple candidate values ​​for defect locations.

[0146] When the spatial distance between several candidate values ​​among multiple defect location candidate values ​​is less than the preset spatial resolution threshold, these candidate values ​​are merged into the same defect location to eliminate redundant location results.

[0147] Preferably, the spatial resolution threshold ranges from 0.5 meters to 2 meters.

[0148] The determination of this spatial resolution threshold is based on the following: when the resolution is less than 0.5 meters, the merging conditions are too stringent, causing the same defect to be detected repeatedly; when the resolution is greater than 2 meters, the merging conditions are too lenient, causing adjacent different defects to be mistakenly merged.

[0149] By detecting local peak points of the frequency domain reflection coefficient curve and performing frequency-distance transformation, the spatial location of the defect on the cable can be quantitatively determined.

[0150] Based on the transient impact characteristic parameters and the steady-state nonlinear characteristic parameters, the defect type is matched to generate an evaluation result that includes the defect type and defect location.

[0151] Obtain a preset defect type mapping table, which records the transient impact characteristic parameter reference interval and steady-state nonlinear characteristic parameter reference mode corresponding to each defect type.

[0152] The transient impact characteristic parameter reference interval is the numerical distribution range of the transient impact characteristic parameters corresponding to the defect types.

[0153] The steady-state nonlinear characteristic parameter reference mode is the distribution pattern of the harmonic amplitude ratios corresponding to the defect types.

[0154] The defect type mapping table is constructed based on the fact that different defect types have different physical formation mechanisms and electrical performance characteristics.

[0155] Specifically, the deterioration of insulation materials with localized aging defects is gradual, and its nonlinear conductance is dominated by the third harmonic, while the transient impact characteristic parameters are usually in the medium value range.

[0156] Mechanical damage defects cause abrupt changes in conductor cross-section and electric field concentration. Its nonlinear conductance is dominated by second harmonics, and the transient impact characteristic parameters are usually in a high value range.

[0157] The contact resistance of loose joint defects exhibits strong nonlinearity with changes in current and temperature. Its harmonic spectrum is wide and its higher-order harmonic components are significant. The transient impact characteristic parameters are usually in the low value range.

[0158] Therefore, by comparing the numerical range of transient impact characteristic parameters with the harmonic distribution pattern of steady-state nonlinear characteristic parameters, the defect type can be uniquely determined.

[0159] The transient impact feature parameter is compared with the reference interval of the transient impact feature parameter corresponding to the defect type in the defect type mapping table to determine the defect type corresponding to the reference interval into which the transient impact feature parameter falls, which is taken as the first matching result.

[0160] The specific operation of the attribution comparison is as follows: determine which reference interval of the defect type in the defect type mapping table the measured value of the transient impact characteristic parameter is located in. If it is located in a certain reference interval, then the defect type corresponding to that reference interval is taken as the first matching result.

[0161] The steady-state nonlinear feature parameter is morphologically compared with the reference pattern of the steady-state nonlinear feature parameter corresponding to the defect type in the defect type mapping table to determine the defect type corresponding to the reference pattern matched by the steady-state nonlinear feature parameter, which is taken as the second matching result.

[0162] The specific operation of morphological comparison is as follows: extract the second harmonic amplitude ratio, third harmonic amplitude ratio, fifth harmonic amplitude ratio and seventh harmonic amplitude ratio from the steady-state nonlinear characteristic parameters to form a measured harmonic distribution vector. Calculate the similarity between the measured harmonic distribution vector and each reference pattern vector in the defect type mapping table, and take the defect type corresponding to the reference pattern with the highest similarity as the second matching result.

[0163] In one feasible implementation, similarity is calculated using Euclidean distance, which involves calculating the Euclidean distance between the measured harmonic distribution vector and the reference mode vector, with the vector having the smallest distance being the most similar.

[0164] In another feasible implementation, the similarity is calculated using cosine similarity, which is to calculate the cosine value of the angle between the measured harmonic distribution vector and the reference mode vector, and the one with the largest cosine value is the most similar.

[0165] In another feasible implementation, the similarity is calculated using Mahalanobis distance, which is the standardized distance between the measured harmonic distribution vector and the reference mode vector after considering the covariance relationship between each harmonic component. This method is more adaptable to the correlation between feature components.

[0166] Cross-validate the first matching result with the second matching result.

[0167] The purpose of cross-validation is that transient impact characteristic parameters are highly sensitive to the presence of defects but have relatively low discrimination of types, while the harmonic distribution pattern of steady-state nonlinear characteristic parameters has high discrimination of defect types but is greatly affected by noise. By cross-validating the two, the sensitivity of transient parameters can be used to verify whether there are mismatches in steady-state parameters due to noise, and the discrimination of steady-state parameters can be used to correct the fuzzy matching caused by possible interval overlap of transient parameters.

[0168] When the first matching result and the second matching result point to the same defect type, the defect type is taken as the defect type determined by the matching.

[0169] When the first matching result and the second matching result point to different defect types, the second matching result is used as the defect type determined by the matching.

[0170] The basis for using the second matching result as the final result is that the harmonic distribution pattern of the steady-state nonlinear characteristic parameter directly reflects the nonlinear conductance spectrum characteristics of the defect region. This spectrum characteristic has a more direct one-to-one correspondence with the physical formation mechanism of the defect. The transient impact characteristic parameter is a single numerical quantity, and the reference interval it falls into may become blurred at the interval boundary of adjacent defect types. Therefore, when the two conflict, the steady-state matching result is given priority.

[0171] The defect type determined by the matching is taken as the defect type included in the evaluation result, and the defect location determined by the positioning operation is taken as the defect location included in the evaluation result.

[0172] The defect type and defect location are combined to form a complete evaluation result and output.

[0173] By organically combining the above-mentioned location operation and defect type matching operation, the spatial location of the defect and the physical type of the defect are further quantitatively determined and identified based on the confirmation of the true defect through coupled verification, thus forming a complete evaluation link from defect confirmation to location and then to type determination.

[0174] like Figure 2 The diagram shown is a functional block diagram of a cable fault signal evaluation system based on steady-state verification provided in an embodiment of this application.

[0175] The cable fault signal assessment system based on steady-state verification described in this application embodiment can be installed in an electronic device. Depending on the functions implemented, the cable fault signal assessment system based on steady-state verification may include a broadband scanning module, a component parameter analysis module, a coupling verification module, and a defect assessment module. The module described in this application embodiment can also be referred to as a unit, which refers to a series of computer program segments that can be executed by the processor of an electronic device and can perform a fixed function, and which are stored in the memory of the electronic device.

[0176] In this embodiment, the functions of each module / unit are as follows: The wideband scanning module is used to apply a wideband scanning signal to the cable to be evaluated and obtain the original wideband response signal sequence returned by the cable to be evaluated in response to the wideband scanning signal. The sweep slope of the wideband scanning signal is dynamically adjusted according to the degree of signal distortion in the original wideband response signal sequence. The component parameter analysis module is used to separate transient response components and steady-state response components from the original broadband response signal sequence, generate transient impulse characteristic parameters based on the transient response components, and generate steady-state nonlinear characteristic parameters based on the steady-state response components. The coupling verification module is used to construct a nonlinear response coupling mapping relationship between the transient impact characteristic parameter and the steady-state nonlinear characteristic parameter, substitute the transient impact characteristic parameter into the nonlinear response coupling mapping relationship to obtain the theoretical estimate of the steady-state nonlinear characteristic parameter, compare the consistency of the theoretical estimate with the steady-state nonlinear characteristic parameter, and generate a coupling verification state signal based on the consistency comparison result. The defect assessment module is used to perform a positioning operation based on the steady-state response component and match the defect type based on the transient impact characteristic parameter and the steady-state nonlinear characteristic parameter when the coupled verification state signal is a signal characterizing a true defect, thereby generating an assessment result containing the defect type and defect location.

[0177] In the several embodiments provided by this invention, it should be understood that the disclosed methods and systems can be implemented in other ways. For example, the system embodiments described above are merely illustrative; for instance, the division of modules is only a logical functional division, and other division methods may be used in actual implementation.

[0178] Furthermore, the functional modules in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or in the form of hardware plus software functional modules.

[0179] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0180] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A cable fault signal evaluation method based on steady-state verification, characterized in that, The method includes: A broadband scanning signal is applied to the cable to be evaluated, and the original broadband response signal sequence returned by the cable to be evaluated in response to the broadband scanning signal is obtained. The sweep slope of the broadband scanning signal is dynamically adjusted according to the degree of signal distortion in the original broadband response signal sequence. Transient response components and steady-state response components are separated from the original broadband response signal sequence. Transient impulse characteristic parameters are generated based on the transient response components, and steady-state nonlinear characteristic parameters are generated based on the steady-state response components. The step of generating transient impact characteristic parameters based on the transient response components includes: extracting the instantaneous amplitude at each sampling time from the time-domain waveform of the transient response components; arranging the instantaneous amplitudes according to the sampling time sequence to form the time-domain waveform envelope of the transient response components; accumulating the instantaneous amplitudes point-by-point along the time axis of the envelope to obtain the energy accumulation curve of the transient response components; traversing the amplitude of the energy accumulation curve at each time point, and detecting the amplitude corresponding to the time point with the largest amplitude as the transient impact characteristic parameter; the step of generating steady-state nonlinear characteristic parameters based on the steady-state response components includes: […]. The steady-state response component undergoes a frequency domain transformation to obtain a frequency domain amplitude sequence. The fundamental amplitude corresponding to the fundamental frequency is extracted from the frequency domain amplitude sequence, and the harmonic amplitudes corresponding to the harmonic frequencies are extracted from the frequency domain amplitude sequence. The harmonic amplitudes corresponding to each harmonic frequency are compared with the fundamental amplitude to obtain the harmonic amplitude ratios corresponding to each harmonic. According to a preset weighting rule, corresponding weight values ​​are assigned to the harmonic amplitude ratios corresponding to each harmonic. The harmonic amplitude ratios corresponding to each harmonic are then weighted and integrated with the corresponding weight values ​​to generate steady-state nonlinear characteristic parameters. A nonlinear response coupling mapping relationship is constructed between the transient impact characteristic parameter and the steady-state nonlinear characteristic parameter. The transient impact characteristic parameter is substituted into the nonlinear response coupling mapping relationship to obtain the theoretical estimate of the steady-state nonlinear characteristic parameter. The theoretical estimate is compared with the steady-state nonlinear characteristic parameter for consistency. A coupling verification state signal is generated based on the consistency comparison result. When the coupled verification state signal is a signal characterizing a true defect, a positioning operation is performed based on the steady-state response component, and the defect type is matched based on the transient impact characteristic parameter and the steady-state nonlinear characteristic parameter to generate an evaluation result containing the defect type and defect location.

2. The cable fault signal evaluation method based on steady-state verification as described in claim 1, characterized in that, The sweep slope of the broadband scanning signal is dynamically adjusted according to the degree of signal distortion in the original broadband response signal sequence, including: Amplitude fluctuation detection is performed on the original broadband response signal sequence of the cable to be evaluated to obtain the fluctuation amount of the amplitude of the original broadband response signal sequence at each sampling time relative to the preset reference amplitude, and the fluctuation amount is used as a quantitative characterization of the degree of signal distortion. When the fluctuation exceeds the preset fluctuation threshold, the sweep slope of the broadband scanning signal is increased to enhance the transient excitation effect of the broadband scanning signal on the potential defects in the cable to be evaluated, and an updated broadband scanning signal is generated based on the increased sweep slope and applied to the cable to be evaluated. When the fluctuation amount is lower than the preset fluctuation threshold, the sweep slope of the broadband scanning signal is reduced, and an updated broadband scanning signal is generated based on the reduced sweep slope and applied to the cable to be evaluated.

3. The cable fault signal evaluation method based on steady-state verification as described in claim 1, characterized in that, The step of separating the transient response component and the steady-state response component from the original broadband response signal sequence includes: The original broadband response signal sequence is truncated using a time-domain window function to capture the transient signal component generated by the sudden change in the sweep frequency rate of the broadband scanning signal in the original broadband response signal sequence, and the transient signal component is used as the transient response component; The remaining signal sequence after removing the transient signal component is periodically truncated to extract a response signal segment that is synchronized with the sweep frequency period of the wideband scanning signal. The amplitude of the intercepted response signal segment is averaged within the same period, and the periodic signal component with the same frequency as the broadband scanning signal in the response signal segment is extracted and used as the steady-state response component.

4. The cable fault signal evaluation method based on steady-state verification as described in claim 1, characterized in that, The construction of the nonlinear response coupling mapping relationship between the transient impact characteristic parameters and the steady-state nonlinear characteristic parameters includes: The quantitative correspondence between the transient impact characteristic parameter and the steady-state nonlinear characteristic parameter determined by the nonlinear conductivity characteristics of local defects in the cable is determined, and the quantitative correspondence is used as the basis for constructing the nonlinear response coupling mapping relationship. The nonlinear response coupling mapping relationship is established based on the quantitative correspondence, and the nonlinear response coupling mapping relationship is expressed as follows: ； in, This is the theoretical estimate of the steady-state nonlinear characteristic parameter. The transient impact characteristic parameter, The first fitting coefficient corresponds to the cubic term of the transient impact characteristic parameter. The second fitting coefficient corresponds to the quadratic term of the transient impact characteristic parameter. The third fitting coefficient is the first power term of the transient impact characteristic parameter, and the first fitting coefficient, the second fitting coefficient and the third fitting coefficient are constant values ​​determined based on the model parameters and historical calibration data of the cable to be evaluated. The transient impact characteristic parameters are used as input parameters of the nonlinear response coupling mapping relationship. Substituted into the nonlinear response coupling mapping relationship, the theoretical estimated values ​​of the steady-state nonlinear characteristic parameters are obtained, and the theoretical estimated values ​​are used as the objects of consistency comparison.

5. The cable fault signal evaluation method based on steady-state verification as described in claim 1, characterized in that, The process of substituting the transient impact characteristic parameters into the nonlinear response coupling mapping relationship to obtain the theoretical estimate of the steady-state nonlinear characteristic parameters, comparing the theoretical estimate with the steady-state nonlinear characteristic parameters for consistency, and generating a coupling verification state signal based on the consistency comparison result includes: The difference between the theoretical estimate and the steady-state nonlinear characteristic parameter is obtained by subtracting the theoretical estimate from the steady-state nonlinear characteristic parameter. The difference is compared with a preset coupling tolerance range, which has an upper limit and a lower limit. When the degree of difference is within the coupling tolerance range, the consistency comparison is determined to be passed, and the coupling verification status signal characterizing the true defect is generated. When the difference is outside the coupling tolerance range, the consistency comparison is determined to fail, and the coupling verification status signal characterizing the false defect is generated.

6. The cable fault signal evaluation method based on steady-state verification as described in claim 1, characterized in that, When the coupled verification state signal is a signal characterizing a true defect, the location operation is performed based on the steady-state response component, including: The steady-state response component is converted from a time-domain representation to a frequency-domain representation to obtain the reflection coefficient amplitude of the steady-state response component at each frequency point. The frequency points are then associated with and arranged with the corresponding reflection coefficient amplitude to form the frequency-domain reflection coefficient curve of the steady-state response component. The reflection coefficient amplitude at each frequency point of the frequency domain reflection coefficient curve is traversed, and the reflection coefficient amplitude at adjacent frequency points is compared point by point. The frequency points where the reflection coefficient amplitude is convex relative to the reflection coefficient amplitude at adjacent frequency points are detected as local peak points, and the frequency value corresponding to the local peak points is extracted. Based on the ratio between the frequency value corresponding to the local peak point and the preset wave velocity parameter of the cable to be evaluated, the location distance corresponding to the local peak point is determined, and the location distance is taken as the defect location.

7. The cable fault signal evaluation method based on steady-state verification as described in claim 1, characterized in that, The step of matching defect types based on the transient impact characteristic parameters and the steady-state nonlinear characteristic parameters to generate an evaluation result containing defect type and defect location includes: Obtain a preset defect type mapping table. The defect type mapping table records the transient impact characteristic parameter reference range and steady-state nonlinear characteristic parameter reference mode corresponding to each defect type. The transient impact characteristic parameter reference range is the numerical distribution range of the transient impact characteristic parameter corresponding to each defect type. The steady-state nonlinear characteristic parameter reference mode is the distribution shape of the harmonic amplitude ratio corresponding to each defect type. The transient impact feature parameter is compared with the reference interval of the transient impact feature parameter corresponding to the defect type in the defect type mapping table to determine the defect type corresponding to the reference interval into which the transient impact feature parameter falls, which is taken as the first matching result. The steady-state nonlinear feature parameter is morphologically compared with the reference pattern of the steady-state nonlinear feature parameter corresponding to the defect type in the defect type mapping table to determine the defect type corresponding to the reference pattern matched by the steady-state nonlinear feature parameter, which is taken as the second matching result. Cross-validate the first matching result with the second matching result; When the first matching result and the second matching result point to the same defect type, the defect type is taken as the defect type determined by the matching. When the first matching result and the second matching result point to different defect types, the second matching result is used as the defect type determined by the matching, and the defect type determined by the matching is used as the defect type included in the evaluation result.

8. A cable fault signal evaluation system based on steady-state verification, characterized in that, The system is used to implement the cable fault signal evaluation method based on steady-state verification as described in any one of claims 1-7, the system comprising: A wideband scanning module is used to apply a wideband scanning signal to the cable to be evaluated and acquire the original wideband response signal sequence returned by the cable to be evaluated in response to the wideband scanning signal. The sweep slope of the wideband scanning signal is dynamically adjusted according to the degree of signal distortion in the original wideband response signal sequence. The component parameter analysis module is used to separate transient response components and steady-state response components from the original broadband response signal sequence, generate transient impulse characteristic parameters based on the transient response components, and generate steady-state nonlinear characteristic parameters based on the steady-state response components. The step of generating transient impact characteristic parameters based on the transient response components includes: extracting the instantaneous amplitude at each sampling time from the time-domain waveform of the transient response components; arranging the instantaneous amplitudes according to the sampling time sequence to form the time-domain waveform envelope of the transient response components; accumulating the instantaneous amplitudes point-by-point along the time axis of the envelope to obtain the energy accumulation curve of the transient response components; traversing the amplitude of the energy accumulation curve at each time point, and detecting the amplitude corresponding to the time point with the largest amplitude as the transient impact characteristic parameter; the step of generating steady-state nonlinear characteristic parameters based on the steady-state response components includes: […]. The steady-state response component undergoes a frequency domain transformation to obtain a frequency domain amplitude sequence. The fundamental amplitude corresponding to the fundamental frequency is extracted from the frequency domain amplitude sequence, and the harmonic amplitudes corresponding to the harmonic frequencies are extracted from the frequency domain amplitude sequence. The harmonic amplitudes corresponding to each harmonic frequency are compared with the fundamental amplitude to obtain the harmonic amplitude ratios corresponding to each harmonic. According to a preset weighting rule, corresponding weight values ​​are assigned to the harmonic amplitude ratios corresponding to each harmonic. The harmonic amplitude ratios corresponding to each harmonic are then weighted and integrated with the corresponding weight values ​​to generate steady-state nonlinear characteristic parameters. The coupling verification module is used to construct a nonlinear response coupling mapping relationship between the transient impact characteristic parameter and the steady-state nonlinear characteristic parameter, substitute the transient impact characteristic parameter into the nonlinear response coupling mapping relationship to obtain the theoretical estimate of the steady-state nonlinear characteristic parameter, compare the consistency of the theoretical estimate with the steady-state nonlinear characteristic parameter, and generate a coupling verification state signal based on the consistency comparison result. The defect assessment module is used to perform a positioning operation based on the steady-state response component and match the defect type based on the transient impact characteristic parameter and the steady-state nonlinear characteristic parameter when the coupled verification state signal is a signal characterizing a true defect, thereby generating an assessment result containing the defect type and defect location.

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