A cable defect positioning method and device based on wave velocity correction

Abstract

The application discloses a cable defect positioning method and equipment based on wave velocity correction, belongs to the technical field of cable local defect positioning, and is used for solving the technical problems that the existing cable defect positioning has the limitation of scene use, and the wave velocity of a defect cable is easy to change, and it is difficult to accurately position the defect position of the cable. The method comprises the following steps: based on the same endpoint of a to-be-tested cable, impedance analysis is conducted on the core and metal shielding layer of the to-be-tested cable, and cable impedance frequency domain data are obtained; the cable impedance frequency domain data are subjected to frequency calculation related to an incident signal, and a phase shift coefficient of the to-be-tested cable is determined; the corresponding cable frequency variable wave velocity is subjected to electromagnetic propagation characteristic processing related to a comprehensive characteristic sweep signal, and a cable sweep signal comprehensive wave velocity is obtained; the cable impedance frequency domain data are subjected to discretization processing based on the number of sampling points, and a cable defect positioning function and a defect positioning point distance are obtained; and local defect position information of the to-be-tested cable is determined.

Description

Technical Field

[0001] This application relates to the field of cable local defect location, and in particular to a cable defect location method and device based on wave velocity correction. Background Technology

[0002] Cables are essential tools for power transmission and distribution. Due to their small footprint and high safety and stability, they are increasingly widely used, and the cabling of power grids will be a significant future development trend. However, due to factors such as wear and tear during installation, prolonged deep underground burial, and harsh operating environments, cables are prone to various local defects such as breakage, moisture absorption, and thermal aging. If these defects are not located and eliminated in a timely manner, they will pose a serious threat to the safety and stability of the power system. Therefore, the diagnosis and location of local defects in cables is of great importance.

[0003] Frequency domain reflection based on broadband impedance spectrum is a fast, non-destructive, and accurate method for locating cable defects. Among these methods, the Fast Fourier Transform (FFT) can quickly locate cable defects and their ends, achieving good results in engineering applications. However, current FFT algorithms still have location limitations. They primarily rely on the known empirical wave velocity of the cable under test for calculation, and the accuracy of this empirical wave velocity directly affects the accuracy of defect location. Furthermore, empirical wave velocities are not universally applicable and are often inaccurate for specific cables under test; moreover, the empirical wave velocity is unknown for many cable models.

[0004] On the one hand, only a small number of cable models currently have known empirical wave velocities, severely limiting the application of existing defect location methods in these scenarios. On the other hand, the accuracy and applicability of empirical wave velocities are limited. When local defects exist in a cable, changes in the local distribution parameters of the defective segment will alter the wave velocity at that point, leading to a change in the overall wave velocity of the cable, which differs from the wave velocity of an intact cable. Summary of the Invention

[0005] This application provides a cable defect location method and device based on wave velocity correction to solve the following technical problems: existing cable defect location methods have limitations in application scenarios, and the wave velocity of defective cables is prone to change, making it difficult to accurately locate the defect position of the cable.

[0006] The embodiments of this application adopt the following technical solutions:

[0007] On one hand, this application provides a cable defect location method based on wave velocity correction, comprising: performing impedance analysis on the core and metal shielding layer of the cable under test based on the same end point of the cable under test to obtain cable impedance frequency domain data; performing frequency calculations related to the incident signal on the cable impedance frequency domain data to determine the phase shift coefficient of the cable under test; using a preset sweep frequency signal, performing electromagnetic propagation characteristics processing on the cable frequency-varying wave velocity corresponding to the phase shift coefficient to obtain the comprehensive wave velocity of the cable sweep frequency signal of the cable under test; performing discretization processing on the cable impedance frequency domain data based on the number of sampling points according to the comprehensive wave velocity of the cable sweep frequency signal to obtain the cable defect location function and the distance of the defect location point of the cable under test; and determining the local defect location information of the cable under test based on the cable defect location function and the distance of the defect location point.

[0008] This application addresses the difficulty in accurately determining wave velocity during cable defect location by employing a cable wave velocity correction algorithm to achieve accurate extraction of cable wave velocity. It has broad applicability when detecting cables with unknown empirical wave velocities, expanding the applicability of cable defect location methods to various cable types. Compared to traditional Fast Fourier Transform (FFT) location methods that rely on empirical wave velocity calculations, this application significantly reduces location errors, effectively improving the accuracy of cable defect location.

[0009] In one feasible implementation, impedance analysis is performed on the conductor and metal shield of the cable under test at the same endpoint to obtain cable impedance frequency domain data. Specifically, this includes: determining the continuity between the conductor and metal shield at the same endpoint of the cable under test; if the conductor and metal shield are disconnected and no load is connected, impedance analysis data is collected from the disconnected cable under test using an impedance analyzer to obtain first cable impedance frequency domain data; if the conductor and metal shield are conductive, impedance analysis data is collected from the conductive cable under test using the impedance analyzer to obtain second cable impedance frequency domain data; wherein the cable impedance frequency domain data includes: the first cable impedance frequency domain data and the second cable impedance frequency domain data.

[0010] In one feasible implementation, the impedance analyzer is connected to the other end of the cable under test; the first test fixture in the impedance analyzer is connected to the conductor in the other end; the second test fixture in the impedance analyzer is connected to the metal shielding layer in the other end; the other end is the opposite end of the endpoint for conducting continuity judgment.

[0011] In one feasible implementation, frequency calculations related to the incident signal are performed on the cable impedance frequency domain data to determine the phase shift coefficient of the cable under test. Specifically, this includes: based on... The phase shift coefficient β(f) is obtained; where f is the incident signal frequency of the cable under test, l is the total length of the cable under test, M(f) is the frequency domain data of the first cable impedance, N(f) is the frequency domain data of the second cable impedance, tanh is the hyperbolic tangent function, and Im is the complex function.

[0012] In one feasible implementation, before processing the electromagnetic propagation characteristics of the sweep frequency signal corresponding to the phase shift coefficient using a preset sweep frequency signal to obtain the comprehensive sweep frequency signal velocity of the cable under test, the method further includes: obtaining the cable frequency-varying velocity v(f) according to v(f)=2πf / β(f); where f is the incident signal frequency of the cable under test, and β(f) is the phase shift coefficient.

[0013] In one feasible implementation, the cable frequency-changing wave velocity corresponding to the phase shift coefficient is processed using a preset sweep frequency signal to comprehensively characterize the electromagnetic propagation characteristics of the sweep frequency signal, thereby obtaining the comprehensive wave velocity of the cable sweep frequency signal of the cable under test. Specifically, this includes: based on... The combined wave velocity v of the cable sweep frequency signal is obtained. com Where v(f) is the frequency-varying wave velocity of the cable, f is the incident signal frequency of the cable under test, and f min f is the sweep start frequency in the comprehensive characterization sweep signal. max The sweep cutoff frequency is the frequency that comprehensively characterizes the sweep frequency signal.

[0014] This application embodiment, through integral processing of the frequency-varying wave velocity of the cable, combines the comprehensive influence of wave velocity components at different frequencies on the wave velocity of the cable under test under a swept frequency signal, to obtain a wave velocity that can comprehensively characterize the propagation characteristics of the swept frequency signal in the cable under test, namely, the comprehensive wave velocity of the cable swept frequency signal. Simultaneously, the comprehensive wave velocity of the cable swept frequency signal also fully incorporates the frequency-varying effect of the cable's distributed parameters, and is also a wave velocity unique to the cable under test, conforming to the electromagnetic propagation process of a specific swept frequency signal in the cable under test.

[0015] In one feasible implementation, based on the comprehensive wave velocity of the cable sweep frequency signal, the cable impedance frequency domain data is discretized based on the number of sampling points to obtain the cable defect location function and the distance to the defect location point of the cable under test. Specifically, this includes: based on... Time data t based on the frequency domain data of the first cable impedance is obtained. kWhere n is the number of sampling points in the impedance analyzer, k is the kth data point of the n data groups in the first cable impedance frequency domain data, and Δf is the frequency interval between adjacent sweep points in the comprehensive wave velocity based on the cable sweep frequency signal; according to x k =v com ·t k / 2, to obtain the distance x of the defect location point. k ; where v com The combined wave velocity of the cable sweep frequency signal; according to The cable defect location function F is obtained. k (x); where M i (f) represents the frequency domain data of the first cable impedance at the i-th sampling point, where j and e are mathematical quantities in the discretization algorithm.

[0016] In one feasible implementation, the local defect location information of the cable under test is determined based on the cable defect location function and the distance to the defect location point. Specifically, this includes: generating a cable defect location curve related to the defect location distance based on the cable defect location function; marking the curve abrupt change peaks in the cable defect location curve to obtain marking information; identifying the horizontal coordinate information in the cable defect location curve corresponding to the marking information; and determining the local defect location information of the cable under test based on the horizontal coordinate information.

[0017] In one feasible implementation, the cable impedance frequency domain data is a data set consisting of multiple sampling point data.

[0018] On the other hand, embodiments of this application also provide a cable defect location device based on wave speed correction, the device comprising: 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 to enable the at least one processor to execute a cable defect location method based on wave speed correction as described in any of the above embodiments.

[0019] This application provides a cable defect location method and device based on wave velocity correction. Compared with the prior art, the embodiments of this application have the following beneficial technical effects:

[0020] This application addresses the difficulty in accurately determining wave velocity during cable defect location by employing a cable wave velocity correction algorithm to achieve accurate extraction of cable wave velocity. It has broad applicability when detecting cables with unknown empirical wave velocities, expanding the applicability of cable defect location methods to various cable types. Compared to traditional Fast Fourier Transform (FFT) location methods that rely on empirical wave velocity calculations, this application significantly reduces location errors, effectively improving the accuracy of cable defect location. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings:

[0022] Figure 1 A flowchart of a cable defect location method based on wave velocity correction provided in this application embodiment;

[0023] Figure 2 This is a schematic diagram of a cable defect location platform provided in an embodiment of this application;

[0024] Figure 3 This application provides a traditional algorithm positioning curve based on simulation verification for embodiments of the present application;

[0025] Figure 4 A simulation-verified wave velocity correction algorithm positioning curve is provided for embodiments of this application;

[0026] Figure 5 This application provides a traditional algorithm localization curve based on experimental verification in its embodiments.

[0027] Figure 6 A wave velocity correction algorithm positioning curve based on experimental verification is provided for embodiments of this application;

[0028] Figure 7 This is a schematic diagram of a cable defect location device based on wave velocity correction, provided as an embodiment of this application. Detailed Implementation

[0029] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. 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 application.

[0030] This application provides a cable defect location method based on wave velocity correction, such as... Figure 1 As shown, the cable defect location method based on wave velocity correction specifically includes steps S101-S105:

[0031] It should be noted that the frequency domain reflection method based on broadband impedance spectrum is a fast, non-destructive, and accurate method for locating cable defects. Compared with traditional methods such as oscillating wave partial discharge detection, dielectric response method, and time domain reflection method, the frequency domain reflection method can detect and locate localized minute defects and non-discharge defects, offering significant technical advantages. Within the frequency domain reflection method, depending on the impedance spectrum data processing algorithm, it can be further divided into linear resonance analysis (LIRA), kernel function-based integral transform method, and fast Fourier transform (FFT). Among these, the LIRA method does not consider the frequency-varying effects of cable distributed parameters at high frequencies, resulting in numerous misjudgment points. The kernel function-based integral transform method heavily relies on the accurate extraction of the cable propagation coefficient γ; however, in actual field testing, γ extraction is often distorted by various interferences, leading to less than ideal defect location results. The fast Fourier transform (FFT) method can quickly locate cable defects and their ends, achieving good results in engineering applications.

[0032] However, current FFT algorithms still have shortcomings. They mainly rely on the known empirical wave velocity of the cable under test for calculation to achieve defect location. The accuracy of the empirical wave velocity directly affects the accuracy of defect location. Furthermore, empirical wave velocities are not universally applicable and are often inaccurate for specific cables under test; moreover, the empirical wave velocity is unknown for many cable models. Therefore, this patent proposes an improved cable defect location method based on a wave velocity correction algorithm, which achieves accurate extraction of cable wave velocity and improves the accuracy and applicability of the defect location method.

[0033] S101. Based on the same end of the cable under test, perform impedance analysis on the core and metal shielding layer of the cable under test to obtain the frequency domain data of the cable impedance.

[0034] Specifically, continuity is determined between the conductor and the metal shield at the same end of the cable under test. If the conductor and the metal shield are disconnected and no load is connected, impedance analysis data is collected for the disconnected cable under test using an impedance analyzer to obtain the first cable impedance frequency domain data.

[0035] If the conductor and the metal shielding layer are in a conductive state, then the impedance analysis data of the cable under test in the conductive state is collected by an impedance analyzer to obtain the second cable impedance frequency domain data.

[0036] The cable impedance frequency domain data includes: first cable impedance frequency domain data and second cable impedance frequency domain data. The impedance analyzer is connected to the other end of the cable under test. The first test fixture in the impedance analyzer is connected to the conductor at the other end. The second test fixture in the impedance analyzer is connected to the metal shielding layer at the other end. The other end is the opposite end to the endpoint used for continuity testing.

[0037] In one embodiment, Figure 2 This is a schematic diagram of a cable defect location platform provided in an embodiment of this application, as shown below. Figure 2 As shown, the setup includes a computer, an impedance analyzer, and the cable under test. A test fixture from the impedance analyzer is connected to end A (the other end) of the cable under test. One end of the test fixture is connected to the cable core, and the other end is connected to the cable's metal shield. With the cable core and metal shield connected and disconnected at end B (one end), the impedance analyzer collects frequency domain data of the cable impedance. ① Keeping the cable core at end B disconnected from the metal shield and without any load, the frequency domain data M(f) of the cable impedance at this time is obtained (first cable impedance frequency domain data); ② Connecting the cable core at end B to the metal shield using a metal conductor, the frequency domain data N(f) of the cable impedance at this time is obtained (second cable impedance frequency domain data).

[0038] S102. Calculate the frequency of the incident signal based on the frequency domain data of the cable impedance to determine the phase shift coefficient of the cable under test.

[0039] Specifically, according to The phase shift coefficient β(f) is obtained. Where f is the incident signal frequency of the cable under test, l is the total length of the cable under test, M(f) is the frequency domain data of the first cable impedance, N(f) is the frequency domain data of the second cable impedance, tanh is the hyperbolic tangent function, and Im is the complex function.

[0040] At the same time, the phase shift coefficient β(f) is also a unique β value corresponding to each specific signal frequency.

[0041] S103. Using a preset sweep frequency signal, the cable frequency-varying wave velocity corresponding to the phase shift coefficient is processed to comprehensively characterize the electromagnetic propagation characteristics of the sweep frequency signal, thereby obtaining the comprehensive wave velocity of the cable sweep frequency signal of the cable under test.

[0042] Specifically, the frequency-dependent wave velocity v(f) of the cable is obtained according to v(f)=2πf / β(f). Where f is the incident signal frequency of the cable under test, and β(f) is the phase shift coefficient.

[0043] Furthermore, according to The combined wave velocity v of the cable sweep frequency signal is obtained. com Where v(f) is the frequency-varying wave velocity of the cable, f is the incident signal frequency of the cable under test, and f0 is the frequency of the incident signal. min To comprehensively characterize the sweep start frequency in the sweep signal, f max To comprehensively characterize the sweep cutoff frequency in the sweep signal.

[0044] As a feasible implementation method, by integrating the frequency-varying wave velocity of the cable, and considering the combined influence of wave velocity components at different frequencies on the wave velocity of the cable under test under a swept frequency signal, a wave velocity that can comprehensively characterize the propagation characteristics of the swept frequency signal in the cable under test is obtained, namely, the comprehensive wave velocity of the cable swept frequency signal. Simultaneously, the comprehensive wave velocity of the cable swept frequency signal also fully incorporates the frequency-varying effect of the cable's distributed parameters, and is unique to the cable under test, conforming to the electromagnetic propagation process of a specific swept frequency signal in the cable under test.

[0045] S104. Based on the comprehensive wave velocity of the cable sweep frequency signal, the frequency domain data of the cable impedance is discretized based on the number of sampling points to obtain the cable defect location function and the distance of the defect location point of the cable under test.

[0046] Specifically, according to Time data t based on the frequency domain data of the first cable impedance is obtained. k Where n is the number of sampling points in the impedance analyzer, k is the kth data point of the n data groups in the first cable impedance frequency domain data, and Δf is the frequency interval between adjacent sweep points in the comprehensive wave velocity based on the cable sweep frequency signal.

[0047] Furthermore, according to x k =v com ·t k / 2, to get the distance x from the defect location point. k Among them, v com This is the combined wave velocity of the cable sweep frequency signal.

[0048] Furthermore, according to Obtain the cable defect location function F k (x). Where M i (f) represents the frequency domain data of the first cable impedance at the i-th sampling point, where j and e are mathematical quantities in the discretization algorithm.

[0049] As a feasible implementation method, impedance analyzers in practice cannot sample continuously, but rather collect data in discrete points for analysis. Therefore, the obtained first cable impedance frequency domain data M(f) is actually an array of n data points, where n is also the number of sampling points of the impedance analyzer. Thus, it is necessary to discretize the cable impedance frequency domain data collected during testing based on the number of sampling points.

[0050] S105. Based on the cable defect location function and the distance between the defect location points, determine the local defect location information of the cable under test.

[0051] Specifically, based on the cable defect location function, a cable defect location curve with respect to the defect location distance is generated.

[0052] Furthermore, the abrupt peaks in the cable defect location curve are marked accordingly to obtain marking information. The horizontal coordinate information in the cable defect location curve corresponding to the marking information is then identified.

[0053] Furthermore, based on the horizontal coordinate information, the location information of local defects in the cable under test is determined.

[0054] In one embodiment, such as Figure 2 As shown, the specific location process for cable defect location based on wave velocity correction is as follows:

[0055] (1) Connect the computer, impedance analyzer, and cable under test according to the implementation platform diagram. The test fixture led out from the impedance analyzer is connected to end A of the cable under test. One end of the fixture is connected to the cable core, and the other end is connected to the cable's metal shielding layer.

[0056] (2) When the conductor at end B of the cable is connected and disconnected from the metal shielding layer respectively, the impedance frequency domain data of the cable is collected by an impedance analyzer and transmitted to the computer.

[0057] (3) The computer processes the data using a wave velocity correction algorithm to calculate the comprehensive wave velocity v of the cable sweep frequency signal. com .

[0058] (4) The computer performs data conversion algorithm processing on the frequency domain data of the cable impedance, and simultaneously substitutes the comprehensive wave velocity v of the cable sweep frequency signal. com Calculations were performed to obtain the cable defect location curve.

[0059] (5) By observing the horizontal coordinate of the sudden peak in the cable defect location curve, the location information of the corresponding local cable defect can be obtained.

[0060] Compared with traditional algorithm-based cable defect location, the wave velocity correction-based method in this application has better location accuracy:

[0061] Existing Fast Fourier Transform (FFT) defect location algorithms require knowledge of the wave velocity of the cable under test to achieve location. The accuracy of the known wave velocity directly affects the accuracy of defect location. According to simulations and actual measurements, the electromagnetic wave velocity in a cable is not a fixed value, but a function that varies with frequency.

[0062] However, current cable defect location methods typically use a fixed empirical wave velocity for a specific cable type for calculation. This approach has two main drawbacks: First, only a limited number of cable types have known empirical wave velocities, such as RG-58 communication cables and 10kV YJT type (cross-linked polyethylene insulated, copper core) distribution cables. The empirical wave velocities for most cable types, such as 35kV, 110kV, and 220kV high-voltage cables, or cables of other materials, are unknown, severely limiting the applicability of existing defect location methods in these scenarios. Second, the accuracy and applicability of empirical wave velocities need further verification. When a cable has localized defects, the wave velocity at the defective section changes due to altered local distribution parameters, leading to a change in the overall wave velocity of the cable, which differs from that of an intact cable. Furthermore, the longer and more severe the defect, the greater the change in the overall cable wave velocity. Using a fixed empirical wave velocity for calculation in such cases will result in significant location errors. Therefore, determining the appropriate wave velocity value is a crucial and challenging issue in cable defect location.

[0063] 1) Simulation Verification: The simulation object is a 100m long RG-58 coaxial cable. Two local defects are set at 30m and 80m, and the frequency sweep range is 1kHz-50MHz. Two different methods are used for comparative experiments to verify the effectiveness and superiority of the cable defect location method of this application:

[0064] ① Figure 3 A traditional algorithm positioning curve based on simulation verification is provided for embodiments of this application, such as... Figure 3 As shown, using the traditional Fast Fourier Transform algorithm, the wave velocity is taken as the empirical wave velocity of the RG-58 coaxial cable, v = 1.93 × 10⁻⁶. 8 m / s. As shown in the figure above, the cable end is located at 87.72m, and the two local defects are located at 25.8m and 70.52m respectively. These locations differ significantly from the actual cable length of 100m and defect locations of 30m and 80m. This demonstrates that the traditional Fast Fourier Transform algorithm, which uses empirical wave velocity calculations, has a significant error in positioning accuracy; that is, the location information of local defects in the tested cable has a large margin of error.

[0065] ② Figure 4 A simulation-verified wave velocity correction algorithm positioning curve is provided for embodiments of this application, such as... Figure 4 As shown, the cable end is located at 100.623m, and the two local defects are located at 29.5951m and 80.8933m respectively. Both are consistent with the actual cable length and defect location, which is a significant improvement in positioning accuracy compared with the traditional positioning algorithm in ①.

[0066] Table 1 Comparison of Simulation Results

[0067]

[0068] Table 1 shows the comparison of simulation results. As can be seen from the comparison in the table, in the simulation comparison experiment, the cable defect improvement positioning method proposed in this application reduces the positioning error of local defects and cable ends by more than 10 times compared with the traditional positioning method using empirical wave velocity calculation, which significantly improves the positioning accuracy.

[0069] 2) Experimental Verification: An RG-58 coaxial cable with a total length of 105m and a defect located at 30m was used as the test object. The frequency sweep range was 0.1MHz-50MHz. Two different methods were used for comparison to verify the effectiveness and superiority of the cable defect location improvement method proposed in this application:

[0070] ① Figure 5 This application provides an example of a traditional algorithm localization curve based on experimental verification, such as... Figure 5 As shown, using the traditional Fast Fourier Transform algorithm, the wave velocity is taken as the empirical wave velocity of the RG-58 coaxial cable, v = 1.93 × 10⁻⁶. 8 m / s. As shown in the figure above, the two local defects are located at 31.28m and 107.47m respectively, both significantly different from the actual cable length of 105m and the defect location of 30m. This indicates that the traditional Fast Fourier Transform algorithm, which uses empirical wave velocity calculations, has a large error in positioning accuracy; that is, the location information of local defects in the cable under test has a significant error in positioning accuracy.

[0071] ② Figure 6 A wave velocity correction algorithm positioning curve based on experimental verification is provided for embodiments of this application, such as... Figure 6 As shown, the two local defects are located at 30.6194m and 105.254m respectively, which are consistent with the actual cable length and defect location. Compared with the traditional positioning algorithm in ①, the positioning accuracy has been greatly improved.

[0072] Table 2 Comparison of Experimental Results

[0073]

[0074] Table 2 is a comparison table of experimental results. As shown in Table 2, the comparison of the above table shows that, in the experiment, the improved cable defect location method proposed in this application reduces the location error at the cable end by about 10 times and the location error of local defects by more than 2 times compared with the traditional location method using empirical wave velocity calculation, and the location accuracy is significantly improved.

[0075] Meanwhile, the improved cable defect location method proposed in this application can also be used for cable defect location with unknown empirical wave velocities such as 35kV, 110kV, and 220kV. It can accurately extract the wave velocities of various types of cables, further expanding the applicability of the cable defect location method in various testing scenarios.

[0076] In addition, embodiments of this application also provide a cable defect location device based on wave velocity correction, such as... Figure 7 As shown, the cable defect location device 700 based on wave velocity correction specifically includes:

[0077] At least one processor 701. And a memory 702 communicatively connected to the at least one processor 701. The memory 702 stores instructions executable by the at least one processor 701, enabling the at least one processor 701 to execute:

[0078] Impedance analysis is performed on the cable core and metal shielding layer of the cable under test based on the same end point to obtain the frequency domain data of the cable impedance.

[0079] The frequency of the incident signal is calculated from the frequency domain data of the cable impedance to determine the phase shift coefficient of the cable under test.

[0080] By using a preset sweep frequency signal, the cable frequency-varying wave velocity corresponding to the phase shift coefficient is processed to comprehensively characterize the electromagnetic propagation characteristics of the sweep frequency signal, thereby obtaining the comprehensive wave velocity of the cable sweep frequency signal of the cable under test.

[0081] Based on the comprehensive wave velocity of the cable sweep frequency signal, the frequency domain data of the cable impedance is discretized based on the number of sampling points to obtain the cable defect location function and the distance of the defect location point of the cable under test.

[0082] Based on the cable defect location function and the distance to the defect location point, the local defect location information of the cable under test is determined.

[0083] This application provides a cable defect location method, device, and medium based on wave velocity correction. By addressing the difficulty in accurately determining wave velocity during cable defect location, and based on a cable wave velocity correction algorithm, it achieves accurate extraction of the cable wave velocity. It has broad applicability when detecting cables with unknown empirical wave velocities, expanding the applicability of the cable defect location method to various cable types. Compared to the traditional Fast Fourier Transform location method that uses empirical wave velocity calculation, the location error of the embodiments in this application is significantly reduced, effectively improving the accuracy of cable defect location.

[0084] The various embodiments in this application 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 for 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.

[0085] The foregoing has described specific embodiments of this application. 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 results. Furthermore, the processes depicted in the drawings do not necessarily require the specific or sequential order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0086] The above description is merely an embodiment of this application and is not intended to limit this application. For those skilled in the art, various modifications and variations can be made to the embodiments of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the embodiments of this application should be included within the scope of the claims of this application.

Claims

1. A cable defect location method based on wave velocity correction, characterized in that, The method includes: Impedance analysis is performed on the core and metal shield of the cable under test based on the same end point to obtain the frequency domain data of the cable impedance. The frequency of the incident signal is calculated from the frequency domain data of the cable impedance to determine the phase shift coefficient of the cable under test. By using a preset sweep frequency signal, the cable frequency-varying wave velocity corresponding to the phase shift coefficient is subjected to comprehensive processing to characterize the electromagnetic propagation characteristics of the sweep frequency signal, thereby obtaining the comprehensive wave velocity of the cable sweep frequency signal of the cable under test, specifically including: according to The combined wave velocity of the cable sweep frequency signal is obtained. v com ;in, v ( f The frequency-varying wave velocity of the cable is denoted as . f The incident signal frequency of the cable under test is given. f min The sweep start frequency is the frequency that comprehensively characterizes the sweep signal. f max This refers to the sweep cutoff frequency in the comprehensive sweep signal. Based on the comprehensive wave velocity of the cable sweep frequency signal, the cable impedance frequency domain data is discretized based on the number of sampling points to obtain the cable defect location function and the distance to the defect location point of the cable under test, specifically including: according to Time data based on the frequency domain data of the first cable impedance is obtained. t k ;in, n This represents the number of sampling points in the impedance analyzer. k For the first cable impedance frequency domain data n The first data set k Data points, Δ f The frequency interval between adjacent sweep points in the comprehensive wave velocity of the cable sweep frequency signal; according to The distance to the defect location point is obtained. x k ;in, v com The combined wave velocity of the cable sweep frequency signal; according to The cable defect location function is obtained. F k (x) ;in, M i ( f ) is the first i The frequency domain data of the first cable impedance at each sampling point j as well as e All of these are mathematical quantities used in discretization algorithms; Based on the cable defect location function and the distance to the defect location point, the local defect location information of the cable under test is determined.

2. The cable defect location method based on wave velocity correction according to claim 1, characterized in that, Impedance analysis is performed on the cable core and metal shielding layer of the cable under test from the same endpoint to obtain the cable impedance frequency domain data, specifically including: The continuity between the conductor at the same end of the cable under test and the metal shielding layer is determined. If the conductor and the metal shielding layer are disconnected and no load is connected, then the impedance analysis data of the cable under test in the disconnected state is collected by an impedance analyzer to obtain the first cable impedance frequency domain data. If the conductor and the metal shielding layer are in a conductive state, the impedance analyzer is used to collect impedance analysis data of the cable under test in the conductive state to obtain the second cable impedance frequency domain data. The cable impedance frequency domain data includes: the first cable impedance frequency domain data and the second cable impedance frequency domain data.

3. The cable defect location method based on wave velocity correction according to claim 2, characterized in that, The impedance analyzer is connected to the other end of the cable under test; The first test fixture in the impedance analyzer is connected to the wire core at the other end. The second test fixture in the impedance analyzer is connected to the metal shielding layer at the other end. The other endpoint is the opposite endpoint to the endpoint used for conduction determination.

4. The cable defect location method based on wave velocity correction according to claim 1, characterized in that, The frequency of the incident signal is calculated from the frequency domain data of the cable impedance to determine the phase shift coefficient of the cable under test, specifically including: according to The phase shift coefficient is obtained. ;in, f The incident signal frequency of the cable under test is given. l The total length of the cable under test. M ( f () represents the frequency domain data of the first cable impedance. N ( f ) represents the frequency domain data of the second cable impedance, tanh is the hyperbolic tangent function, and Im is the complex function.

5. The cable defect location method based on wave velocity correction according to claim 1, characterized in that, Before processing the electromagnetic propagation characteristics of the sweep frequency signal corresponding to the phase shift coefficient using a preset sweep frequency signal to obtain the comprehensive sweep frequency signal velocity of the cable under test, the method further includes: according to The frequency-varying wave velocity of the cable is obtained. v ( f );in, f The incident signal frequency of the cable under test is given. The phase shift coefficient is denoted as .

6. The cable defect location method based on wave velocity correction according to claim 1, characterized in that, Based on the cable defect location function and the distance to the defect location point, the local defect location information of the cable under test is determined, specifically including: Based on the cable defect location function, a cable defect location curve related to the defect location distance is generated; The abrupt change peaks in the cable defect location curve are marked accordingly to obtain marking information; and the horizontal coordinate information in the cable defect location curve corresponding to the marking information is identified. Based on the horizontal coordinate information, the location information of local defects in the cable under test is determined.

7. The cable defect location method based on wave velocity correction according to claim 4, characterized in that, The cable impedance frequency domain data is a data set composed of multiple sampling point data.

8. A cable defect location device based on wave velocity correction, 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 to enable the at least one processor to perform a cable defect location method based on wave velocity correction according to any one of claims 1-7.

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