A method, device and medium for locating cable defects based on instantaneous frequency compensation

Abstract

This specification discloses a cable defect location method based on instantaneous frequency compensation. The method includes: generating an incident signal of the cable to be tested using a computer, and acquiring the waveform of the reflected signal corresponding to the incident signal; performing time-frequency conversion on the reflected signal to obtain the time-frequency domain distribution of the reflected signal, and normalizing the time-frequency domain distribution to obtain the normalized time-frequency domain distribution of the reflected signal; determining the correspondence between time and frequency in the reflected signal based on the instantaneous frequency corresponding to each time point in the normalized time-frequency domain distribution; determining the frequency domain attenuation distortion coefficient of the reflected signal based on the model of the cable to be tested, and compensating the reflected signal according to the correspondence and the frequency domain attenuation distortion coefficient to obtain a time-domain compensated signal of the reflected signal; compensating a preset cross-correlation function according to the time-domain distribution of the time-domain compensated signal to generate a corresponding defect location curve, and determining the defect location of the cable to be tested based on the defect location curve.

Description

Technical Field

[0001] This specification relates to the field of power system detection technology, and in particular to a cable defect location method, equipment and medium based on instantaneous frequency compensation. Background Technology

[0002] Cables are electrical tools used for power transmission, and due to their small footprint, they are particularly important in urban power supply systems. However, factors such as long-term high-load operation, manufacturing process errors, and wear and tear during installation can cause localized defects in cables. If these localized defects are not located, detected, and repaired in a timely manner, they may develop into serious permanent faults, leading to power outages, resulting in significant economic losses and even endangering personal safety. Therefore, to avoid losses caused by power outages, defect location in cables is a crucial process in cable maintenance.

[0003] Currently, cable defect location methods include time-domain reflection and frequency-domain reflection. Time-domain reflection analyzes incident pulse or step signals in the cable in the time domain; however, this method can only locate severe faults. Frequency-domain reflection, on the other hand, sweeps the frequency of the incident signal and transforms the frequency information into a distance-related cable defect location curve, which can locate weak defects, but its sensitivity is limited. Therefore, existing technologies combine the advantages of both time-domain and frequency-domain reflection to obtain the time-frequency domain reflection method. The current time-frequency domain reflection method transforms the time-domain waveform of a specific incident signal into the time-frequency domain and then amplifies the defect information based on a cross-correlation function. While it offers rich information and high location sensitivity, as the incident signal propagates through the cable, the signal amplitude attenuates and the phase is distorted. This reduces the location amplitude or even causes the signal to be submerged in noise, making defect identification impossible. Summary of the Invention

[0004] To address the aforementioned technical problems, this specification provides one or more embodiments of a cable defect location method, device, and medium based on instantaneous frequency compensation.

[0005] One or more embodiments of this specification employ the following technical solutions:

[0006] This specification provides one or more embodiments of a cable defect location method based on instantaneous frequency compensation, the method comprising:

[0007] The computer generates an incident signal of the cable to be tested and acquires the waveform of the reflected signal corresponding to the incident signal.

[0008] The reflected signal is converted to a time-frequency domain to obtain the time-frequency domain distribution of the reflected signal, and the time-frequency domain distribution is normalized to obtain the normalized time-frequency domain distribution of the reflected signal.

[0009] Based on the instantaneous frequencies corresponding to each time point in the normalized time-frequency domain distribution, the correspondence between time and frequency in the reflected signal is determined.

[0010] The frequency domain attenuation and distortion coefficient of the reflected signal is determined based on the model of the cable to be tested. The reflected signal is then compensated according to the correspondence and the frequency domain attenuation and distortion coefficient to obtain the time domain compensated signal of the reflected signal. The frequency domain attenuation and distortion coefficient includes: frequency domain amplitude attenuation coefficient and frequency domain phase distortion coefficient.

[0011] The preset cross-correlation function is compensated according to the time-domain distribution of the time-domain compensated signal to generate a corresponding defect location curve, and the defect location of the cable to be tested is determined based on the defect location curve.

[0012] Optionally, in one or more embodiments of this specification, the step of generating the incident signal of the cable under test and acquiring the reflected signal corresponding to the incident signal of the cable under test specifically includes:

[0013] The incident signal parameters of the incident signal are acquired, and the incident signal parameters are transmitted to a waveform generator based on a preset electrical connection to obtain the incident signal waveform of the cable under test generated by the waveform generator; wherein, the waveform generator is electrically connected to the computer;

[0014] The incident signal waveform is incident onto the cable under test based on one end of the T-type interface between the waveform generator and the cable under test;

[0015] The reflected signal waveform, which corresponds to the incident signal waveform of the cable under test, is acquired from the other end of the T-type interface of the cable under test by the oscilloscope; wherein the oscilloscope is electrically connected to the computer.

[0016] Optionally, in one or more embodiments of this specification, determining the correspondence between time and frequency in the reflected signal based on the instantaneous frequencies corresponding to each time point in the normalized time-frequency domain distribution specifically includes:

[0017] Extract the time-frequency distribution curves corresponding to each time point in the normalized time-frequency domain distribution;

[0018] Obtain the frequency corresponding to the maximum amplitude in the time-frequency distribution curve, so as to approximate the corresponding frequency as the instantaneous frequency of the reflected signal at each time point;

[0019] Based on the relationship between each time point and the instantaneous frequency, the correspondence between time and frequency in the reflected signal is determined.

[0020] Optionally, in one or more embodiments of this specification, the frequency domain attenuation and distortion coefficient of the reflected signal is determined based on the model of the cable to be tested, and the reflected signal is compensated according to the correspondence and the frequency domain attenuation and distortion coefficient to obtain a time domain compensated signal of the reflected signal, specifically including:

[0021] The frequency domain attenuation and distortion coefficient of the signal cable is measured to determine the frequency domain attenuation and distortion coefficient of the reflected signal corresponding to the model of the cable under test.

[0022] The time-domain compensation formula for the reflected signal is determined based on the correspondence and the frequency-domain attenuation distortion coefficient, and the reflected signal is compensated based on the time-domain compensation formula to obtain the time-domain compensated signal of the reflected signal.

[0023] The time-domain compensation formula is as follows: Wherein, R(t) is the time-domain compensated signal of the reflected signal, r(t) is the reflected signal before compensation, γ' and γ” respectively identify the frequency domain amplitude attenuation coefficient and the frequency domain phase distortion coefficient, f is the instantaneous frequency of the reflected signal, and t is the time it takes for the signal to be reflected back to the beginning of the cable under test.

[0024] Optionally, in one or more embodiments of this specification, a preset cross-correlation function is compensated according to the time-domain distribution of the time-domain compensated signal to generate a corresponding defect location curve, specifically including:

[0025] The time-domain compensation signal and the incident signal distribution are converted to time-frequency data to obtain the time-domain distribution of the time-domain compensation signal and the time-frequency distribution of the incident signal, respectively.

[0026] Based on the time-domain distribution of the reflected signal and the time-domain distribution of the incident signal, a preset cross-correlation function between the incident signal and the reflected signal is determined;

[0027] The time-domain distribution of the reflected signal in the preset cross-correlation function is replaced by the time-domain distribution of the time-domain compensated signal to achieve compensation for the preset cross-correlation function and obtain the compensated cross-correlation function.

[0028] The compensation cross-correlation function is transformed based on the distance parameter to generate the corresponding defect location curve.

[0029] Optionally, in one or more embodiments of this specification, time-frequency conversion is performed on the incident signal to obtain the time-frequency domain distribution of the incident signal, specifically including:

[0030] Obtain the Hilbert transform and preset rectangular window function of the reflected signal;

[0031] The time-frequency domain distribution formula of the incident signal is constructed based on the Hilbert transform of the reflected signal and the preset rectangular window function.

[0032] The incident signal is converted to time frequency based on the time-frequency domain distribution formula to obtain the time-frequency domain distribution of the incident signal.

[0033] Optionally, in one or more embodiments of this specification, determining the defect location of the cable to be inspected based on the defect location curve specifically includes:

[0034] Obtain the first peak and the second peak in the defect location curve; wherein, the first peak is the maximum peak in the defect location curve, and the second peak is smaller than the first peak but larger than other peaks in the defect location curve except for the first peak;

[0035] The distance corresponding to the first peak value is taken as the beginning of the cable under test, and the distance corresponding to the second peak value is taken as the end of the cable under test.

[0036] The peak value between the beginning and end of the cable under test is obtained as the defect peak value, and the defect location of the cable under test is determined based on the distance corresponding to the defect peak value.

[0037] Optionally, in one or more embodiments of this specification, the compensated cross-correlation function is transformed based on a distance parameter to generate a corresponding defect location curve, specifically including:

[0038] Obtain the distance between the first and last ends of the cable under test, and test the transmission time of the acquired signal at the first and last ends.

[0039] The average wave velocity of the signal in the cable under test is obtained based on the distance and the transmission time.

[0040] The time of the reflected signal in the compensated cross-correlation function is obtained, and the conversion relationship between the distance and the time is determined based on the time and the average wave velocity. The compensated cross-correlation function is then converted based on the conversion relationship to obtain the corresponding defect location curve.

[0041] This specification provides one or more embodiments of a cable defect location device based on instantaneous frequency compensation. The device includes:

[0042] At least one processor; and,

[0043] A memory communicatively connected to the at least one processor; wherein,

[0044] The memory stores instructions executable by the at least one processor, which, when executed by the at least one processor, enable the at least one processor to:

[0045] The computer generates an incident signal of the cable to be tested and acquires the waveform of the reflected signal corresponding to the incident signal.

[0046] The reflected signal is converted to a time-frequency domain to obtain the time-frequency domain distribution of the reflected signal, and the time-frequency domain distribution is normalized to obtain the normalized time-frequency domain distribution of the reflected signal.

[0047] Based on the instantaneous frequencies corresponding to each time point in the normalized time-frequency domain distribution, the correspondence between time and frequency in the reflected signal is determined.

[0048] The frequency domain attenuation and distortion coefficient of the reflected signal is determined based on the model of the cable to be tested. The reflected signal is then compensated according to the correspondence and the frequency domain attenuation and distortion coefficient to obtain the time domain compensated signal of the reflected signal. The frequency domain attenuation and distortion coefficient includes: frequency domain amplitude attenuation coefficient and frequency domain phase distortion coefficient.

[0049] The preset cross-correlation function is compensated according to the time-domain distribution of the time-domain compensated signal to generate a corresponding defect location curve, and the defect location of the cable to be tested is determined based on the defect location curve.

[0050] This specification provides one or more embodiments of a non-volatile computer storage medium storing computer-executable instructions, wherein the computer-executable instructions are configured as follows:

[0051] The computer generates an incident signal of the cable to be tested and acquires the waveform of the reflected signal corresponding to the incident signal.

[0052] The reflected signal is converted to a time-frequency domain to obtain the time-frequency domain distribution of the reflected signal, and the time-frequency domain distribution is normalized to obtain the normalized time-frequency domain distribution of the reflected signal.

[0053] Based on the instantaneous frequencies corresponding to each time point in the normalized time-frequency domain distribution, the correspondence between time and frequency in the reflected signal is determined.

[0054] The frequency domain attenuation and distortion coefficient of the reflected signal is determined based on the model of the cable to be tested. The reflected signal is then compensated according to the correspondence and the frequency domain attenuation and distortion coefficient to obtain the time domain compensated signal of the reflected signal. The frequency domain attenuation and distortion coefficient includes: frequency domain amplitude attenuation coefficient and frequency domain phase distortion coefficient.

[0055] The preset cross-correlation function is compensated according to the time-domain distribution of the time-domain compensated signal to generate a corresponding defect location curve, and the defect location of the cable to be tested is determined based on the defect location curve.

[0056] The above-described at least one technical solution adopted in the embodiments of this specification can achieve the following beneficial effects:

[0057] By normalizing the instantaneous frequencies at each time point in the time-frequency domain distribution, a correspondence between time and frequency in the reflected signal was constructed. Then, based on this correspondence, the frequency-domain attenuation law was converted into a time-domain attenuation law. This allows for attenuation compensation of the reflected signal using the frequency-domain attenuation distortion coefficient, resulting in a time-domain compensated signal. This attenuation compensation method amplifies the defect information in the reflected signal, solving the problem of decreased positioning sensitivity caused by signal propagation. It also avoids the problem of reduced positioning amplitude and inability to locate defects due to signal amplitude attenuation and phase distortion. Attached Figure Description

[0058] To more clearly illustrate the technical solutions in the embodiments or prior art of this specification, the drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this specification. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings:

[0059] Figure 1 A schematic flowchart of a cable defect location method based on instantaneous frequency compensation provided in the embodiments of this specification;

[0060] Figure 2 This specification provides a schematic diagram of the device structure for locating cable defects in a certain application scenario, as shown in the embodiments of this specification.

[0061] Figure 3 This is a schematic diagram of the normalized time-frequency domain distribution of the reflected signal in a certain application scenario provided in the embodiments of this specification;

[0062] Figure 4 This is a schematic diagram illustrating the extraction of instantaneous frequencies of reflected signals at various time points in a specific application scenario provided in this embodiment of the specification.

[0063] Figure 5 This is a schematic diagram of the reflected signal waveform in a certain application scenario provided in the embodiments of this specification;

[0064] Figure 6 A waveform diagram of the time-domain compensation signal of the reflected signal in a certain application scenario provided in the embodiments of this specification;

[0065] Figure 7 A schematic diagram comparing defect location curves before and after compensation in a certain application scenario provided in the embodiments of this specification;

[0066] Figure 8 A schematic diagram of the internal structure of a cable defect location device based on instantaneous frequency compensation, provided for an embodiment of this specification;

[0067] Figure 9 This is a schematic diagram of the internal structure of a non-volatile storage medium provided in the embodiments of this specification. Detailed Implementation

[0068] This specification provides a method, device, and medium for locating cable defects based on instantaneous frequency compensation.

[0069] Due to their excellent transmission performance and small footprint, cables have become an essential power transmission tool for urban electricity use. However, during the manufacturing process, cables may have minor defects due to factors such as process errors. If operated for too long in adverse environments such as humidity or high temperature, it can cause local aging of the cable, resulting in deterioration of the cable insulation. If the cable is not replaced in time, it may lead to a power outage of the entire line, causing huge economic losses to the power industry and users.

[0070] To address these issues, power companies regularly inspect cables to locate and repair defects. Existing cable defect location methods include time-domain reflection, frequency-domain reflection, and time-frequency-domain reflection. However, time-domain reflection can only locate severe faults, and frequency-domain reflection has limited sensitivity. While the current time-frequency-domain reflection method combines the advantages of both methods, it involves transforming the time-domain waveform of a specific incident signal to the time-frequency domain and then amplifying the defect information based on a cross-correlation function. As the incident signal propagates through the cable, amplitude attenuation and phase distortion occur, reducing the location amplitude or even rendering the defect undetectable due to noise.

[0071] Therefore, to address the aforementioned problems and provide a cable defect location method that can further amplify defect information and improve the sensitivity of the time-frequency domain reflection method, this specification provides a cable defect location method based on instantaneous frequency compensation. By normalizing the instantaneous frequencies corresponding to each time point in the time-frequency domain distribution, a correspondence between time and frequency in the reflected signal is constructed. Then, based on this correspondence and the frequency domain attenuation distortion coefficient, attenuation compensation is applied to the reflected signal to obtain a time-domain compensated signal. This attenuation compensation amplifies the defect information, solves the problem of decreased location sensitivity caused by signal propagation, and avoids the problem of reduced location amplitude and inability to locate defects due to signal amplitude attenuation and phase distortion.

[0072] To enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this specification, and not all embodiments. Based on the embodiments of this specification, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this specification.

[0073] like Figure 1 As shown, this specification provides a flowchart of a cable defect location method based on instantaneous frequency compensation in one or more embodiments. Figure 1 As can be seen, in one or more embodiments of this specification, a cable defect location method based on instantaneous frequency compensation includes the following steps:

[0074] S101: The computer generates the incident signal of the cable to be tested and acquires the waveform of the reflected signal corresponding to the incident signal.

[0075] like Figure 2 As shown, in one embodiment of this specification, the computer designs the incident signal parameters of the cable to be tested, thereby generating the corresponding incident signal. The incident signal parameters include a signal period influence factor, a signal frequency influence factor, the signal time center, and the signal frequency center, etc. For example, in a certain application scenario of this specification, the expression of the incident signal generated based on the incident signal parameters is as follows:

[0076] Where t is the time it takes for the signal to reflect back to the cable end, Re represents the real part, α is the signal periodicity factor, β is the signal frequency factor, j is the imaginary unit, t0 is the time center of the signal, and f0 is the frequency center of the signal. After the computer generates the incident signal, it transmits the incident signal to the cable under test based on the waveform generator, so that the computer can obtain the reflected signal waveform corresponding to the incident signal.

[0077] Specifically, such as Figure 2 As shown in one or more embodiments of this specification, generating an incident signal of the cable under test and acquiring a reflected signal corresponding to the incident signal of the cable under test specifically includes the following processes:

[0078] First, the incident signal parameters of the computer-designed incident signal are obtained, and these parameters are transmitted to the waveform generator based on preset electrical connections, thereby obtaining the incident signal waveform of the cable under test generated by the waveform generator; wherein, by Figure 2It is known that the waveform generator is electrically connected to the computer to acquire the incident signal transmitted by the computer. Then, the incident signal waveform is incident onto the cable under test through one end of the T-junction of the waveform generator and the cable under test, so that the computer can acquire the signal waveform output from the other end of the T-junction of the cable under test, which is acquired by the oscilloscope. This signal waveform is the reflected signal waveform corresponding to the incident signal waveform of the cable under test. Among them, by... Figure 2 It is known that the oscilloscope is electrically connected to the computer, thereby transmitting the reflected signal waveform acquired by the oscilloscope to the computer, so that the computer can perform subsequent analysis to determine the location of the cable defect.

[0079] S102: Perform time-frequency conversion on the reflected signal to obtain the time-frequency domain distribution of the reflected signal, and normalize the time-frequency domain distribution to obtain the normalized time-frequency domain distribution of the reflected signal.

[0080] Because existing time-domain reflection methods can only locate severe faults, while frequency-domain reflection methods have limited sensitivity, this specification selects a time-frequency domain reflection method, which combines the advantages of both methods, to locate cable defects. Therefore, in one embodiment, the reflected signal is first converted from time to frequency to obtain its time-frequency domain distribution. Furthermore, to achieve data standardization and avoid the influence of dimensional indices on the analysis results, the time-frequency domain distribution is normalized to obtain a normalized time-frequency domain distribution of the reflected signal. The normalization technique used is existing in the field and will not be described further here.

[0081] Furthermore, in one or more embodiments of this specification, time-frequency conversion is performed on the reflected signal to obtain the time-frequency domain distribution of the incident signal. Specifically, this includes the following steps: First, to facilitate analysis and obtain the Hilbert transform of the reflected signal, a pre-set rectangular window function is obtained to avoid interference from cross-terms of multi-component signals such as the incident and reflected signals. The rectangular window function is not limited here. Then, based on the Hilbert transform of the reflected signal and the pre-set rectangular window function, a time-frequency domain distribution formula for the incident signal is constructed. The incident signal is then time-frequency converted according to the constructed time-frequency domain distribution formula to obtain the time-frequency domain distribution of the incident signal. In a certain application scenario of this specification, the time-frequency domain distribution formula is as follows:

[0082] Among them W P denoted as , where f is the instantaneous frequency of the signal; || represents the amplitude of the result; τ is the time variable used for integration; w(τ) is the rectangular window function; sh is the Hilbert transform of the reflected signal; * represents taking the complex conjugate; j is the imaginary unit.

[0083] S103: Based on the instantaneous frequencies corresponding to each time point in the normalized time-frequency domain distribution, determine the correspondence between time and frequency in the reflected signal.

[0084] In order to convert the signal attenuation pattern in the frequency domain into a pattern in the time domain, this specification extracts the instantaneous frequency corresponding to each time point in the normalized time-frequency distribution obtained in step S102 above, thereby determining the correspondence between time and frequency in the reflected signal, so as to convert the signal attenuation pattern in the frequency domain into a pattern in the time domain for subsequent attenuation compensation.

[0085] Specifically, based on the instantaneous frequencies corresponding to each time point in the normalized time-frequency domain distribution, the correspondence between time and frequency in the reflected signal is determined, which includes the following steps:

[0086] like Figure 3 The diagram shown is a normalized time-frequency domain distribution of the reflected signal in a certain application scenario provided in this specification embodiment. The plane corresponding to a certain time point can be extracted from this normalized time-frequency domain distribution. For example, ti represents the i-th time point, and its corresponding plane can be extracted to obtain... Figure 4 The diagram shown illustrates the extraction of instantaneous frequencies at various time points of the reflected signal. This involves extracting the plane of the normalized time-frequency domain distribution at each time point to obtain the corresponding time-frequency distribution curve. The frequency f corresponding to the maximum amplitude in the time-frequency distribution curve is then obtained. P (t i This method approximates the corresponding frequency as the instantaneous frequency of the reflected signal at time *ti*. Based on the relationship between each time point and the instantaneous frequency, the correspondence between time and frequency in the reflected signal is determined. Thus, based on this correspondence, the instantaneous frequency can be obtained from the known signal's time-domain waveform, achieving the goal of converting the signal attenuation law in the frequency domain into a law in the time domain, laying the foundation for subsequent steps.

[0087] S104: Determine the frequency domain attenuation and distortion coefficient of the reflected signal based on the model of the cable to be tested, and compensate the reflected signal according to the correspondence and the frequency domain attenuation and distortion coefficient to obtain the time domain compensated signal of the reflected signal; wherein, the frequency domain attenuation and distortion coefficient includes: frequency domain amplitude attenuation coefficient and frequency domain phase distortion coefficient.

[0088] To improve the sensitivity of cable location by compensating for the time-domain waveform, and to address the problem in existing time-frequency domain reflection methods where the incident signal attenuates in amplitude and distorts in phase as it propagates through the cable, leading to reduced location amplitude or even failure to identify defects due to the signal being submerged in noise, one or more embodiments of this specification determine the frequency-domain attenuation and distortion coefficients of the reflected signal, including frequency-domain amplitude attenuation coefficients and frequency-domain phase distortion coefficients, based on the cable model to be tested. Then, according to the obtained correspondence, the time-domain attenuation law corresponding to the frequency-domain attenuation and distortion coefficients is determined, thereby compensating for the reflected signal based on the amplitude attenuation coefficients and phase distortion coefficients to obtain a time-domain compensated signal for the reflected signal.

[0089] Specifically, in one or more embodiments of this specification, the frequency domain attenuation and distortion coefficient of the reflected signal is determined based on the model of the cable to be tested, and the reflected signal is compensated according to the correspondence and the frequency domain attenuation and distortion coefficient to obtain the time domain compensated signal of the reflected signal. The specific steps include:

[0090] First, the frequency domain attenuation and distortion coefficient of the signal cable is measured to determine the frequency domain attenuation and distortion coefficient of the reflected signal corresponding to the cable model under test. Then, based on the correspondence and the frequency domain attenuation and distortion coefficient, a time-domain compensation formula for the reflected signal is determined. The reflected signal is then compensated based on this time-domain compensation formula to obtain the time-domain compensated signal. The time-domain compensation formula is as follows:

[0091] Where R(t) is the time-domain compensated signal of the reflected signal, r(t) is the reflected signal before compensation, γ' and γ” denote the frequency domain amplitude attenuation coefficient and frequency domain phase distortion coefficient, respectively, f is the instantaneous frequency of the reflected signal, and t is the time it takes for the signal to reflect back to the beginning of the cable under test. At this point, since the relationship between time and frequency has already been established based on the above steps, the compensation formula actually only contains the time variable, thus a time-domain compensation model can be constructed. Figure 5 and Figure 6 Taking a 159m long RG58 cable with a defect at 68m as an example. Incident signal parameter settings: α = 1.2 × 10⁻⁶. 14 s -2 β is taken as 9.8 × 10 13 s -2 t0 is 0s and f0 is 5MHz, representing the acquired reflected signal and the compensated time-domain signal. A comparison shows that, in the case of… Figure 5 After performing time-frequency conversion and instantaneous frequency extraction on the reflected signal, the waveform of the reflected signal is compensated according to the above time-domain compensation formula to obtain the following result: Figure 6The diagram shows a comparison between the waveform of the time-domain compensated reflected signal and the original reflected signal. Figure 6 It can be seen that the compensation for time-domain attenuation greatly improves the reflected signal and further amplifies the defect information in the reflected signal.

[0092] S105: Compensate the preset cross-correlation function according to the time-domain distribution of the time-domain compensation signal to generate a corresponding defect location curve, and determine the defect location of the cable to be tested based on the defect location curve.

[0093] After obtaining the time-domain compensated signal corresponding to the reflected signal in step S104, to address the issue of decreased defect identification accuracy caused by amplitude attenuation and phase distortion in traditional methods that amplify defect information based on the cross-correlation function determined by the incident and reflected signals, this embodiment improves the preset cross-correlation function based on the compensated time-domain compensated signal. Specifically, it compensates the preset cross-correlation function according to the time-domain distribution of the compensated signal, thereby generating a defect location curve corresponding to the cable under test based on the compensated cross-correlation function. The defect location of the cable under test is then determined using this defect location curve.

[0094] Specifically, in one or more embodiments of this specification, a preset cross-correlation function is compensated according to the time-domain distribution of the time-domain compensated signal to generate a corresponding defect location curve, which specifically includes the following process:

[0095] Time-frequency conversion is performed on the distributions of the time-domain compensated signal and the incident signal to obtain the time-domain distribution of the time-domain compensated signal and the time-frequency distribution of the incident signal, respectively. Then, based on the time-domain distributions of the reflected signal and the incident signal, a preset cross-correlation function between the incident signal and the reflected signal is determined. In a certain application scenario of this specification, the preset cross-correlation function is as follows:

[0096] Where C(t) is the cross-correlation function, t' is the combined variable of time t and signal half-period Ts, and WPr and WPs are the time-frequency distributions of the reflected and incident signals, respectively. To compensate the cross-correlation function based on the time-domain compensated signal after reflection signal compensation, the time-domain distribution of the reflected signal in the preset cross-correlation function is replaced with the time-domain distribution of the compensated signal, thereby achieving compensation for the preset cross-correlation function and obtaining the compensated cross-correlation function. Since actual positioning uses distance as the abscissa of the positioning curve, the corresponding defect positioning curve of the cable to be inspected is generated by transforming the compensated cross-correlation function based on the distance parameter. For example... Figure 7As shown, after compensating the preset cross-correlation function based on the time-domain compensation signal, the peak value of the obtained positioning curve at the defect is also significantly improved, which means that the positioning sensitivity of the cable defect positioning technology based on the time-frequency domain reflection method is improved.

[0097] After obtaining the defect location curve of the cable to be inspected, the defect location of the cable to be inspected is determined based on the defect location curve, specifically including: obtaining the first peak and the second peak in the defect location curve; such as Figure 7 As shown, the first peak value is the largest peak value in the defect location curve, and the second peak value is smaller than the first peak value but larger than all other peak values ​​in the defect location curve except for the first peak value. The distance corresponding to the first peak value is taken as the beginning of the cable under test, and the distance corresponding to the second peak value is taken as the end of the cable under test. The peak value between the beginning and end of the cable under test is obtained as the defect peak value, and the defect location of the cable under test is determined based on the distance corresponding to the defect peak value. Figure 7 The positioning curve shown in this specification, in a certain application scenario, uses the largest peak value as the cable head and the second largest peak value as the cable tail. The peak value between these two values ​​is then identified as a defect. Figure 7 The defect, after compensation, was located at 67.65m, which is very close to the actual 68m.

[0098] Furthermore, the compensated cross-correlation function is transformed based on the distance parameter to generate a corresponding defect location curve. Specifically, this includes: obtaining the distance between the beginning and end of the cable under test; testing the transmission time of the signal at the beginning and end; obtaining the average wave velocity of the signal in the cable under test based on the base distance and transmission time; obtaining the time of the reflected signal in the compensated cross-correlation function; determining the distance-time conversion relationship based on time and average wave velocity; and then transforming the compensated cross-correlation function according to the conversion relationship to obtain the corresponding defect location curve.

[0099] like Figure 8 As shown in the figure, this specification provides an internal structure diagram of a cable defect location device based on instantaneous frequency compensation.

[0100] Depend on Figure 8 It is known that a cable defect location device based on instantaneous frequency compensation includes:

[0101] At least one processor; and,

[0102] A memory communicatively connected to the at least one processor; wherein,

[0103] The memory stores instructions executable by the at least one processor, which, when executed by the at least one processor, enable the at least one processor to:

[0104] An incident signal is generated for the cable to be tested, and the waveform of the reflected signal corresponding to the incident signal is obtained.

[0105] The reflected signal is converted to a time-frequency domain to obtain the time-frequency domain distribution of the reflected signal, and the time-frequency domain distribution is normalized to obtain the normalized time-frequency domain distribution of the reflected signal.

[0106] Based on the instantaneous frequencies corresponding to each time point in the normalized time-frequency domain distribution, the correspondence between time and frequency in the reflected signal is determined.

[0107] The frequency domain attenuation and distortion coefficient of the reflected signal is determined based on the model of the cable to be tested. The reflected signal is then compensated according to the correspondence and the frequency domain attenuation and distortion coefficient to obtain the time domain compensated signal of the reflected signal. The frequency domain attenuation and distortion coefficient includes: frequency domain amplitude attenuation coefficient and frequency domain phase distortion coefficient.

[0108] The preset cross-correlation function is compensated according to the time-domain distribution of the time-domain compensated signal to generate a corresponding defect location curve, and the defect location of the cable to be tested is determined based on the defect location curve.

[0109] like Figure 9 As shown in the figure, this specification provides a schematic diagram of the internal structure of a non-volatile storage medium.

[0110] Depend on Figure 9 It is known that a non-volatile storage medium stores computer-executable instructions, which are capable of:

[0111] An incident signal is generated for the cable to be tested, and the waveform of the reflected signal corresponding to the incident signal is obtained.

[0112] The reflected signal is converted to a time-frequency domain to obtain the time-frequency domain distribution of the reflected signal, and the time-frequency domain distribution is normalized to obtain the normalized time-frequency domain distribution of the reflected signal.

[0113] Based on the instantaneous frequencies corresponding to each time point in the normalized time-frequency domain distribution, the correspondence between time and frequency in the reflected signal is determined.

[0114] The frequency domain attenuation and distortion coefficient of the reflected signal is determined based on the model of the cable to be tested. The reflected signal is then compensated according to the correspondence and the frequency domain attenuation and distortion coefficient to obtain the time domain compensated signal of the reflected signal. The frequency domain attenuation and distortion coefficient includes: frequency domain amplitude attenuation coefficient and frequency domain phase distortion coefficient.

[0115] The preset cross-correlation function is compensated according to the time-domain distribution of the time-domain compensated signal to generate a corresponding defect location curve, and the defect location of the cable to be tested is determined based on the defect location curve.

[0116] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the embodiments of apparatus, devices, and non-volatile computer storage media are basically similar to the method embodiments, so the descriptions are relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0117] The foregoing has described specific embodiments of this specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims may be performed in a different order than that shown in the embodiments and may still achieve the desired result. Furthermore, the processes depicted in the drawings do not necessarily require the specific or sequential order shown to achieve the desired result. In some embodiments, multitasking and parallel processing are possible or may be advantageous.

[0118] The above description is merely one or more embodiments of this specification and is not intended to limit this specification. Various modifications and variations can be made to the one or more embodiments of this specification by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of one or more embodiments of this specification should be included within the scope of the claims of this specification.

Claims

1. A cable defect location method based on instantaneous frequency compensation, characterized in that, The method includes: The computer generates an incident signal of the cable to be tested and acquires the waveform of the reflected signal corresponding to the incident signal. The reflected signal is converted to a time-frequency domain to obtain the time-frequency domain distribution of the reflected signal, and the time-frequency domain distribution is normalized to obtain the normalized time-frequency domain distribution of the reflected signal. Based on the instantaneous frequencies corresponding to each time point in the normalized time-frequency domain distribution, the correspondence between time and frequency in the reflected signal is determined. The frequency domain attenuation and distortion coefficient of the reflected signal is determined based on the model of the cable to be tested. The reflected signal is then compensated according to the correspondence and the frequency domain attenuation and distortion coefficient to obtain the time domain compensated signal of the reflected signal. The frequency domain attenuation and distortion coefficient includes: frequency domain amplitude attenuation coefficient and frequency domain phase distortion coefficient. The preset cross-correlation function is compensated according to the time-domain distribution of the time-domain compensated signal to generate a corresponding defect location curve, and the defect location of the cable to be tested is determined based on the defect location curve. The step of determining the frequency domain attenuation and distortion coefficient of the reflected signal based on the model of the cable under test, and compensating the reflected signal according to the correspondence and the frequency domain attenuation and distortion coefficient to obtain the time domain compensated signal of the reflected signal, specifically includes: The frequency domain attenuation and distortion coefficient of the signal cable is measured to determine the frequency domain attenuation and distortion coefficient of the reflected signal corresponding to the model of the cable under test. The time-domain compensation formula for the reflected signal is determined based on the correspondence and the frequency-domain attenuation distortion coefficient, and the reflected signal is compensated based on the time-domain compensation formula to obtain the time-domain compensated signal of the reflected signal. The time-domain compensation formula is as follows: Wherein, R(t) is the time-domain compensated signal of the reflected signal, r(t) is the reflected signal before compensation, γ' and γ'' respectively identify the frequency domain amplitude attenuation coefficient and the frequency domain phase distortion coefficient, f is the instantaneous frequency of the reflected signal, and t is the time it takes for the signal to be reflected back to the beginning of the cable under test.

2. The cable defect location method based on instantaneous frequency compensation according to claim 1, characterized in that, The process of generating the incident signal of the cable under test and acquiring the reflected signal corresponding to the incident signal of the cable under test specifically includes: The incident signal parameters of the incident signal are acquired, and the incident signal parameters are transmitted to a waveform generator based on a preset electrical connection to obtain the incident signal waveform of the cable under test generated by the waveform generator; wherein, the waveform generator is electrically connected to the computer; The incident signal waveform is incident onto the cable under test based on one end of the T-type interface between the waveform generator and the cable under test; The reflected signal waveform, which corresponds to the incident signal waveform of the cable under test, is acquired from the other end of the T-type interface of the cable under test by the oscilloscope; wherein the oscilloscope is electrically connected to the computer.

3. The cable defect location method based on instantaneous frequency compensation according to claim 1, characterized in that, Based on the instantaneous frequencies corresponding to each time point in the normalized time-frequency domain distribution, the correspondence between time and frequency in the reflected signal is determined, specifically including: Extract the time-frequency distribution curves corresponding to each time point in the normalized time-frequency domain distribution; Obtain the frequency corresponding to the maximum amplitude in the time-frequency distribution curve, so as to approximate the corresponding frequency as the instantaneous frequency of the reflected signal at each time point; Based on the relationship between each time point and the instantaneous frequency, the correspondence between time and frequency in the reflected signal is determined.

4. The cable defect location method based on instantaneous frequency compensation according to claim 1, characterized in that, The step of compensating the preset cross-correlation function according to the time-domain distribution of the time-domain compensated signal to generate the corresponding defect location curve specifically includes: The time-domain compensation signal and the incident signal distribution are converted to time-frequency data to obtain the time-domain distribution of the time-domain compensation signal and the time-frequency distribution of the incident signal, respectively. Based on the time-domain distribution of the reflected signal and the time-domain distribution of the incident signal, a preset cross-correlation function between the incident signal and the reflected signal is determined; The time-domain distribution of the reflected signal in the preset cross-correlation function is replaced by the time-domain distribution of the time-domain compensated signal to achieve compensation for the preset cross-correlation function and obtain the compensated cross-correlation function. The compensation cross-correlation function is transformed based on the distance parameter to generate the corresponding defect location curve.

5. The cable defect location method based on instantaneous frequency compensation according to claim 1, characterized in that, Performing time-frequency conversion on the incident signal to obtain its time-frequency domain distribution specifically includes: Obtain the Hilbert transform and preset rectangular window function of the reflected signal; The time-frequency domain distribution formula of the incident signal is constructed based on the Hilbert transform of the reflected signal and the preset rectangular window function. The incident signal is converted to time frequency based on the time-frequency domain distribution formula to obtain the time-frequency domain distribution of the incident signal.

6. The cable defect location method based on instantaneous frequency compensation according to claim 1, characterized in that, Based on the defect location curve, the location of the defect in the cable under test is determined, specifically including: Obtain the first peak and the second peak in the defect location curve; wherein, the first peak is the maximum peak in the defect location curve, and the second peak is smaller than the first peak but larger than other peaks in the defect location curve except for the first peak; The distance corresponding to the first peak value is taken as the beginning of the cable under test, and the distance corresponding to the second peak value is taken as the end of the cable under test. The peak value between the beginning and end of the cable under test is obtained as the defect peak value, and the defect location of the cable under test is determined based on the distance corresponding to the defect peak value.

7. The cable defect location method based on instantaneous frequency compensation according to claim 4, characterized in that, The process of transforming the compensated cross-correlation function based on the distance parameter to generate a corresponding defect location curve specifically includes: Obtain the distance between the first and last ends of the cable under test, and test the transmission time of the acquired signal at the first and last ends. The average wave velocity of the signal in the cable under test is obtained based on the distance and the transmission time. The time of the reflected signal in the compensated cross-correlation function is obtained, and the conversion relationship between the distance and the time is determined based on the time and the average wave velocity. The compensated cross-correlation function is then converted based on the conversion relationship to obtain the corresponding defect location curve.

8. A cable defect location device based on instantaneous frequency compensation, characterized in that, The device includes: At least one processor; and, A memory communicatively connected to the at least one processor; wherein, The memory stores instructions executable by the at least one processor, which, when executed by the at least one processor, enable the at least one processor to: The computer generates an incident signal of the cable to be tested and acquires the waveform of the reflected signal corresponding to the incident signal. The reflected signal is converted to a time-frequency domain to obtain the time-frequency domain distribution of the reflected signal, and the time-frequency domain distribution is normalized to obtain the normalized time-frequency domain distribution of the reflected signal. Based on the instantaneous frequencies corresponding to each time point in the normalized time-frequency domain distribution, the correspondence between time and frequency in the reflected signal is determined. The frequency domain attenuation and distortion coefficient of the reflected signal is determined based on the model of the cable to be tested. The reflected signal is then compensated according to the correspondence and the frequency domain attenuation and distortion coefficient to obtain the time domain compensated signal of the reflected signal. The frequency domain attenuation and distortion coefficient includes: frequency domain amplitude attenuation coefficient and frequency domain phase distortion coefficient. The preset cross-correlation function is compensated according to the time-domain distribution of the time-domain compensated signal to generate a corresponding defect location curve, and the defect location of the cable to be tested is determined based on the defect location curve. The step of determining the frequency domain attenuation and distortion coefficient of the reflected signal based on the model of the cable under test, and compensating the reflected signal according to the correspondence and the frequency domain attenuation and distortion coefficient to obtain the time domain compensated signal of the reflected signal, specifically includes: The frequency domain attenuation and distortion coefficient of the signal cable is measured to determine the frequency domain attenuation and distortion coefficient of the reflected signal corresponding to the model of the cable under test. The time-domain compensation formula for the reflected signal is determined based on the correspondence and the frequency-domain attenuation distortion coefficient, and the reflected signal is compensated based on the time-domain compensation formula to obtain the time-domain compensated signal of the reflected signal. The time-domain compensation formula is as follows: Wherein, R(t) is the time-domain compensated signal of the reflected signal, r(t) is the reflected signal before compensation, γ' and γ'' respectively identify the frequency domain amplitude attenuation coefficient and the frequency domain phase distortion coefficient, f is the instantaneous frequency of the reflected signal, and t is the time it takes for the signal to be reflected back to the beginning of the cable under test.

9. A non-volatile storage medium storing computer-executable instructions, characterized in that, The computer-executable instructions are capable of: The computer generates an incident signal of the cable to be tested and acquires the waveform of the reflected signal corresponding to the incident signal. The reflected signal is converted to a time-frequency domain to obtain the time-frequency domain distribution of the reflected signal, and the time-frequency domain distribution is normalized to obtain the normalized time-frequency domain distribution of the reflected signal. Based on the instantaneous frequencies corresponding to each time point in the normalized time-frequency domain distribution, the correspondence between time and frequency in the reflected signal is determined. The frequency domain attenuation and distortion coefficient of the reflected signal is determined based on the model of the cable to be tested. The reflected signal is then compensated according to the correspondence and the frequency domain attenuation and distortion coefficient to obtain the time domain compensated signal of the reflected signal. The frequency domain attenuation and distortion coefficient includes: frequency domain amplitude attenuation coefficient and frequency domain phase distortion coefficient. The preset cross-correlation function is compensated according to the time-domain distribution of the time-domain compensated signal to generate a corresponding defect location curve, and the defect location of the cable to be tested is determined based on the defect location curve. The step of determining the frequency domain attenuation and distortion coefficient of the reflected signal based on the model of the cable under test, and compensating the reflected signal according to the correspondence and the frequency domain attenuation and distortion coefficient to obtain the time domain compensated signal of the reflected signal, specifically includes: The frequency domain attenuation and distortion coefficient of the signal cable is measured to determine the frequency domain attenuation and distortion coefficient of the reflected signal corresponding to the model of the cable under test. The time-domain compensation formula for the reflected signal is determined based on the correspondence and the frequency-domain attenuation distortion coefficient, and the reflected signal is compensated based on the time-domain compensation formula to obtain the time-domain compensated signal of the reflected signal. The time-domain compensation formula is as follows: Wherein, R(t) is the time-domain compensated signal of the reflected signal, r(t) is the reflected signal before compensation, γ' and γ'' respectively identify the frequency domain amplitude attenuation coefficient and the frequency domain phase distortion coefficient, f is the instantaneous frequency of the reflected signal, and t is the time it takes for the signal to be reflected back to the beginning of the cable under test.

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