Cable impedance spectroscopy defect positioning method and system

Abstract

The invention discloses a cable impedance spectroscopy defect positioning method and system, and belongs to the technical field of cable defect localization, and the method comprises the steps: measuring a to-be-detected cable through an impedance analyzer, obtaining a head end input impedance spectrum of the to-be-detected cable, comparing the head end input impedance spectrum with a head end input impedance spectrum of a healthy cable, and judging whether the to-be-detected cable has a defect or not; if defects exist, a plurality of pieces of temperature data in the circumferential direction of the intermediate joint are collected, whether the to-be-detected cable is aged or not is judged through the temperature difference between the peak value temperature data and the valley value temperature data, if not, the obtained head end input impedance spectrum of the to-be-detected cable is utilized, the frequency domain reflection method is directly used for conducting defect positioning on the cable, and if aging occurs, the frequency domain reflection method is used for determining the defect of the to-be-detected cable. And if not, compensating the obtained head end input impedance spectrum of the cable to be detected according to the aging degree, and carrying out defect positioning on the cable by using a frequency domain reflection method based on the compensated head end input impedance spectrum. According to the invention, interference of non-uniform aging on defect positioning can be weakened, and accurate positioning of cable defects is realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of cable defect positioning, and particularly relates to a cable impedance spectrum defect positioning method and system. BACKGROUND

[0002] At present, with the continuous increase of the number of urban distribution network cables in operation and the operation time limit, the defect positioning of cross-linked polyethylene (XLPE) cables gradually becomes the research focus of the power industry. At present, the cable defect positioning technologies mainly include impedance method, partial discharge method and reflection method. Due to the disadvantages of large error, low sensitivity, complicated measurement steps and great influence of external signals of the impedance method and the partial discharge method, the reflection method is commonly used to detect cable defects in actual engineering.

[0003] The reflection method commonly refers to the frequency domain reflection method, that is, a low-voltage high-frequency signal is input into the cable, the broadband impedance spectrum information of the cable is measured, then the impedance spectrum function is converted from the broadband domain to the time domain through a related algorithm, and thus the graph of the internal impedance matching condition of the cable with the cable length can be obtained, and the point with the most serious impedance mismatching condition is the specific position of the cable defect.

[0004] However, the actual distribution network cable is easily aged under the action of electric field force in the long-term high-voltage environment (10 kV and above), and the aging is often uneven and universal, which can cause a large amount of useless impedance mismatching information in the impedance spectrum function obtained by the frequency domain reflection method, so that the local part with the real defect is shielded, and the accurate positioning of the cable defect by the operation and maintenance personnel is seriously affected. SUMMARY

[0005] The present application provides a cable impedance spectrum defect positioning method and system, which can weaken the interference of uneven aging on defect positioning and realize the accurate positioning of the cable defect.

[0006] The present application provides the following technical solutions: In a first aspect, a cable impedance spectrum defect positioning method is provided, comprising: measuring the to-be-measured cable by using an impedance analyzer, obtaining the head-end input impedance spectrum of the to-be-measured cable, and comparing the head-end input impedance spectrum of the to-be-measured cable with the head-end input impedance spectrum of a healthy cable to determine whether the to-be-measured cable has a defect; if the to-be-measured cable has a defect, a plurality of temperature data in the circumferential direction of the intermediate joint are collected, the temperature difference between the peak value and the valley value of the temperature data is used to determine whether the to-be-measured cable is aged, if the to-be-measured cable is not aged, the head-end input impedance spectrum of the to-be-measured cable is used to directly position the defect of the cable by using the frequency domain reflection method, and if the to-be-measured cable is aged, the head-end input impedance spectrum of the to-be-measured cable is compensated according to the aging degree, and the defect of the cable is positioned by using the frequency domain reflection method based on the compensated head-end input impedance spectrum.

[0007] Optionally, the temperature data of the intermediate joint is collected in the circumferential direction, and the temperature difference between the peak and valley temperature data is used to determine whether the cable under test has aged, specifically: The temperature data of the intermediate joint is collected by six temperature sensors uniformly arranged in the circumferential direction of the intermediate joint of the cable under test; The Fourier third harmonic model is used to curve fit the collected temperature data to obtain the surface peak and valley temperatures of the intermediate joint, and the maximum temperature difference of the intermediate joint is obtained; It is determined whether the maximum temperature difference of the intermediate joint of the cable under test exceeds a set threshold value, if it exceeds, it has aged, otherwise it has not aged.

[0008] Optionally, the curve fitting form is: ; Wherein, is the position angle variable is the temperature, is the direct current component, is the number of harmonics, and are the sine term coefficient and the cosine term coefficient of the k harmonic, respectively.

[0009] Optionally, the obtained input impedance spectrum of the first end of the cable under test is compensated according to the aging degree, and the specific way is: ; Wherein, is the impedance value of the cable under test after aging compensation, is the impedance value corresponding to the frequency point f in the input impedance spectrum of the first end of the cable under test, is the aging temperature rise compensation coefficient, is the maximum temperature difference of the intermediate joint of the cable under test, is the temperature coefficient function fitted in advance by aging data.

[0010] Optionally, the input impedance spectrum of the first end of the healthy cable is obtained by transmission line theory, specifically, the healthy cable is equivalent to a distributed parameter model, the distributed parameters are modeled, the distributed parameters of the healthy cable are obtained, and then the input impedance of the first end of the healthy cable is obtained by the ratio of the voltage and current at any position away from the first end of the cable.

[0011] In the second aspect, a cable impedance spectrum defect positioning system is provided, comprising: An impedance analyzer is used to measure the cable under test to obtain the input impedance spectrum of the first end of the cable under test; The defect judging module is configured to compare the first-end input impedance spectrum of the to-be-tested cable with the first-end input impedance spectrum of the healthy cable, and determine whether the to-be-tested cable has defects. The aging judging module is configured to, when the to-be-tested cable has defects, acquire a plurality of temperature data in the circumferential direction of the intermediate joint, and determine whether the to-be-tested cable has aging by using the temperature difference between the peak and valley temperature data. The defect positioning module is configured to, when the to-be-tested cable has no aging, directly use the frequency domain reflection method to position the defects of the cable by using the acquired first-end input impedance spectrum of the to-be-tested cable; and when the to-be-tested cable has aging, compensate the acquired first-end input impedance spectrum of the to-be-tested cable according to the aging degree, and position the defects of the cable by using the frequency domain reflection method based on the compensated first-end input impedance spectrum.

[0012] Optionally, the aging judging module comprises: The temperature sensors are evenly arranged in the circumferential direction of the intermediate joint of the to-be-tested cable. The acquisition sub-module is configured to acquire the temperature data of the intermediate joint. The temperature difference acquisition module is configured to perform curve fitting on the acquired temperature data by using a Fourier third harmonic model, to obtain the peak and valley temperature of the surface of the intermediate joint, and to obtain the maximum temperature difference of the intermediate joint. The aging determination sub-module is configured to determine whether the maximum temperature difference of the intermediate joint of the to-be-tested cable exceeds a set threshold value, and if yes, aging occurs, otherwise, no aging occurs.

[0013] In a third aspect, a computer device is provided, comprising a processor and a memory; when the processor executes a computer program stored in the memory, the steps of the cable impedance spectrum defect positioning method of any one of the first aspect are implemented.

[0014] In a fourth aspect, a computer readable storage medium is provided for storing a computer program; when the computer program is executed by a processor, the steps of the cable impedance spectrum defect positioning method of any one of the first aspect are implemented.

[0015] Compared with the prior art, the present application has the following beneficial effects: The application can compensate the input impedance spectrum of the first end of the to-be-tested cable according to the uneven aging degree of the cable by measuring the temperature difference data of the intermediate joint of the to-be-tested cable to determine the uneven aging condition of the to-be-tested cable; finally, the accurate defect position is obtained through the frequency domain impedance spectrum method; the input impedance spectrum of the to-be-tested cable after compensation can eliminate a large amount of useless impedance mismatch information, avoid the local shielding of the real defect of the to-be-tested cable, thereby effectively reducing the interference of uneven aging on the cable defect positioning, and realizing the accurate positioning of the cable defect; the cable impedance spectrum defect positioning method has high practicability, and the operator only needs to connect the detection equipment at the power distribution node to quickly generate a defect position report, thereby greatly improving the inspection efficiency; through early discovery and accurate positioning of potential defects, the expansion of faults can be avoided, the operation and maintenance cost is reduced, and the stability of the power distribution network is significantly enhanced. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a flow chart of the cable impedance spectrum defect positioning method of the application; Figure 2 is an equivalent distributed parameter circuit diagram of a healthy cable of the application; Figure 3 is a schematic diagram of the arrangement position of six temperature sensor probes of the application; Figure 4 is a radial temperature distribution diagram of a cable containing uneven aging defects and no defects of the application; Figure 5 is a flow chart for judging whether the cable has uneven aging or not of the application; Figure 6 is a radial temperature distribution diagram under different current conditions of the application; Figure 7 is an impedance spectrum diagram of a healthy cable without defects of the application; Figure 8 is an impedance spectrum diagram of a to-be-tested cable containing defects of the application; Figure 9 is a fitting curve of the surface temperature of the to-be-tested cable of the application; Figure 10 is an impedance spectrum diagram of the to-be-tested cable after aging compensation of the application. DETAILED DESCRIPTION

[0017] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and should not be used to limit the scope of protection of the present invention. It should be noted that the term "comprising" and any variations thereof in the specification, claims and the above-mentioned drawings of the present invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products or devices.

[0018] Example 1 like Figure 1 As shown, a method for locating defects in cable impedance spectrum is provided, including: Step S1: Use an impedance analyzer to measure the cable under test and obtain the input impedance spectrum at the beginning of the cable under test.

[0019] The structure of the impedance analyzer can refer to existing technology, and the measurement method of the impedance analyzer for the cable under test can also refer to existing technology.

[0020] Step S2: Compare the input impedance spectrum of the cable under test with that of a healthy cable to determine if the cable under test has a defect. If the cable under test has no defect, the defect location process ends. If a defect exists, collect several temperature data points around the intermediate joint and use the temperature difference between the peak and valley values ​​to determine if the cable under test has aged. If no aging has occurred, use the obtained input impedance spectrum of the cable under test to directly locate the defect using the frequency domain reflection method. If aging has occurred, compensate the obtained input impedance spectrum of the cable under test according to the degree of aging, and use the frequency domain reflection method to locate the defect based on the compensated input impedance spectrum.

[0021] In this embodiment, the method of comparing the input impedance spectrum of the cable under test with that of a healthy cable to determine whether the cable under test has a defect can refer to existing technologies. Generally, it is as follows: directly determine whether the impedance spectra are consistent. If they are consistent, the cable under test does not have a defect. If they are inconsistent, the cable under test has a defect.

[0022] The input impedance spectrum at the beginning of the healthy cable is obtained through transmission line theory. Specifically, the healthy cable is equivalent to a distributed parameter model, and the distributed parameters are modeled to obtain the distributed parameters of the healthy cable. Then, the input impedance at the beginning of the healthy cable is obtained by the ratio of voltage and current at any position from the beginning of the cable.

[0023] More specifically, according to transmission line theory, under high-frequency conditions, a cable should be equivalent to a distributed parameter model, and its distributed parameter equivalent circuit is as follows: Figure 2As shown in the figure, , , , These represent the distributed resistance, distributed inductance, distributed capacitance, and distributed conductance of the cable per unit length. d x This refers to a tiny unit of a cable.

[0024] At high frequencies, the various distribution values ​​of a cable can be calculated from relevant parameters such as the cable's actual material, structure, and dimensions. The distribution parameters per unit length of cable can be approximated as: ; ; ; ; in, The angular frequency of the input signal. ; The vacuum permeability; and These are the cable core radius and the inner radius of the metal shielding layer, respectively. and These are the conductivity of the cable core and the conductivity of the metal shielding layer, respectively. The dielectric constant of the insulating layer; The conductivity of the insulating layer.

[0025] With a total length of l In a cable, the end where the signal input is located is designated as the beginning (origin), and the load end is designated as the end (terminus). The cable can be positioned at any point from the beginning. x voltage at and current It can be represented as: ; ; In the formula: and These are the incident voltage and the reflected voltage, respectively. The propagation coefficient of the cable; The characteristic impedance of a healthy cable.

[0026] The propagation coefficient and characteristic impedance of a cable are determined by its type and structure, and can be obtained by the following formula: ; ; ; In the formula: is the attenuation constant, representing the attenuation characteristics of the wave; is the phase constant, representing the phase shift characteristics of the wave; This refers to the speed at which electromagnetic waves propagate in the cable. The frequency of the incident signal; The wavelength of the electromagnetic wave in the cable.

[0027] In step S2, such as Figure 5 As shown, the determination of whether the cable under test has aged is as follows: Step a: Collect temperature data of the intermediate joint by using six temperature sensors that are evenly arranged around the circumference of the intermediate joint of the cable under test.

[0028] The six temperature sensors are arranged around the cable under test as follows: Figure 3 As shown, the cable cores are distributed symmetrically in three phases, and simulation results indicate that thermal defects can cause abnormal temperature rises in approximately one-sixth of the circumferential area of ​​the joint's outer surface. Based on this, six temperature measurement points are evenly distributed at 60° intervals along the circumference to achieve full-area monitoring of the circumferential thermal gradient characteristics. Simultaneously, six evenly distributed temperature data points are collected, and cable aging is assessed based on the severity of the temperature rise.

[0029] Specifically, the intermediate joint of a three-core cable is a crucial connecting element in power transmission and distribution systems, and its operating condition affects the stability of power transmission. Intermediate joints operate under high current and high voltage conditions for extended periods, making them highly susceptible to localized overheating due to electrothermal coupling, which gradually leads to uneven aging of the cable itself. Therefore, monitoring the condition of cable intermediate joints is an important measure to ensure the safe operation of power systems, helping to detect potential problems early, reduce the risk of failure, and improve system reliability.

[0030] The steady-state temperature field analysis of cable joints can be reduced to the problem of heat conduction modeling in a multi-physics coupled system. The heat source distribution induced by the Joule heating effect of the conductor material constitutes the non-homogeneous term of the temperature field governing equation, while the nonlinear modulation of the material's conductivity by the temperature field forms a two-way coupling mechanism between the electromagnetic and thermal fields.

[0031] The governing equations for the temperature field are derived based on Fourier's law and the law of conservation of energy, and their expression in rectangular coordinates is as follows: ; in, Density, unit: kg / m³ 3 ; Specific heat capacity, unit: J / (kg·℃); Thermal conductivity; Heat generated by a current-carrying conductor. Convective heat dissipation mainly includes three parts: heat conduction, heat convection, and heat radiation.

[0032] The outer surface of the cable joint can be considered as being in direct contact with air, and according to the heat dissipation formula by convection, we have: ; where, h is the air heat transfer coefficient, and the value is usually 10; n represents the normal direction; is the outer surface temperature, is the initial ambient temperature, and the unit is K.

[0033] A finite element simulation model of the cable joint with insulation aging was established in COMSOL software. The temperature of the cable joint in normal operation under the condition of room temperature of 20℃ can be obtained as shown in Figure 4 , wherein Figure 4 (a) and (b) are respectively the temperature distribution diagrams of the cable joint with insulation aging and the normal healthy cable. It can be seen from Figure 4 that the aging phase of the cable joint with insulation aging has a significant temperature rise compared with the normal healthy cable, so the aging condition of the three-phase cable can be judged by monitoring the temperature rise of the cable joint.

[0034] Step b: using the Fourier third harmonic model to fit the temperature data collected multiple times to obtain the surface peak and valley temperatures of the joint, and the maximum temperature difference of the joint.

[0035] Fourier series has shown significant advantages in cable joint surface temperature distribution modeling. Based on the orthogonality and harmonic decomposition principle, it can strictly satisfy the periodic boundary condition and highly accurately approximate the nonlinear temperature distribution characteristics (such as local extreme value, multi-peak shape) by superimposing sine and cosine basis functions of different frequencies. After multiple simulation data fitting, it is found that the Fourier third harmonic model has the best fitting degree, and the curve fitting form is: ; where, is the temperature of the position angle variable , is the direct current component, is the number of harmonics, and are respectively the sine term coefficient and the cosine term coefficient of the k th harmonic.

[0036] Draw the fitting function curve. Ideally, there are 3 peaks within the period 360° of the fitting curve. If not, analyze the curve according to the principle that the temperature will not change abruptly to determine the position of the wire core. Change the probe position to measure a new set of temperature data and re-Fourier fit until the temperature within the period has 3 peaks.

[0037] In this embodiment, the feasibility of the method for identifying heat generation due to crimping defects in cable intermediate joints was also determined through simulation. A simulation model of the cable intermediate joint was built based on finite element theory to simulate the radial temperature distribution on the outer surface of the joint corresponding to the center of the splice pipe with a single-phase moderate heat generation defect under different current conditions. Figure 6 As shown, Figure 6 Figures (a), (b), and (c) show the radial temperature distribution under current conditions of 200A, 300A, and 400A, respectively. Figure 6 It can be seen that the current condition only affects the magnitude of the maximum radial temperature difference, and does not affect the relationship between the maximum radial temperature difference under the heat-generating defect and the maximum radial temperature difference under normal conditions. The severity of the defect can be judged by the ratio of the maximum radial temperature difference under the heat-generating defect to the maximum radial temperature difference under normal conditions.

[0038] Step c: Determine whether the maximum temperature difference of the intermediate joint of the cable under test exceeds the set threshold. If it does, aging has occurred; otherwise, no aging has occurred. The set threshold can be determined based on expert experience.

[0039] In step S2, the input impedance spectrum of the cable under test obtained based on the aging degree compensation is specifically as follows: ; in, The impedance value of the cable under test after aging compensation. The frequency point in the input impedance spectrum of the cable under test. f The corresponding impedance value, This is the aging temperature rise compensation coefficient. The maximum temperature difference at the intermediate joint of the cable under test. This is a temperature coefficient function pre-fitted using aging data.

[0040] Temperature coefficient It is a function determined through experimental calibration, and its specific form is related to the cable's insulation material (such as XLPE) and aging type. In one specific implementation, By different aging levels (corresponding to different A broadband impedance spectrum test was performed on a cable sample, and the test data was fitted to an Nth-order polynomial to determine: ; In the formula, , and All of these are fitting coefficients obtained through experimental calibration, and under normal circumstances... n For 2-4, This refers to frequency, measured in MHz.

[0041] Due to aging, a large number of strong polar carbonyl and hydroxyl groups appear inside the XLPE of the cable insulation layer. These newly added permanent dipoles will produce significant orientation polarization under the action of an external electric field, significantly increasing the dielectric constant of the cable. The dielectric constant in turn affects the distributed capacitance of the cable, thereby affecting the characteristic impedance and propagation coefficient, causing the cable impedance spectrum to experience impedance mismatch phenomena, affecting the positioning of actual defects.

[0042] In this embodiment, the defect positioning of the cable using the frequency domain reflection method can refer to the prior art. Specifically, the obtained head-end input impedance spectrum of the cable to be measured is inverse Fourier transformed when no aging occurs, or the compensated head-end input impedance spectrum is inverse Fourier transformed when aging occurs, and the time domain reflection diagram is obtained by inverse Fourier transformation. The position of the defect point is read on the diagram.

[0043] Embodiment 2 A specific application example is given.

[0044] A 10kV XLPE cable is taken as the research object, and a cable model with a total length of 100m is built on the Matlab platform. The basic parameters are shown in Table 1. The lower limit of the frequency is set to 10kHz, the upper limit of the frequency is set to 60MHZ, and the cable end is open. The impedance spectrum of the healthy cable is shown in Figure 7 .

[0045] Table 1 Cable basic simulation parameters

[0046] Subsequently, a local damage defect is set at 70m, with a defect length of 0.15m. Uneven aging occurs at other positions of the cable, and the aging degree is different. The head-end input impedance spectrum of the cable to be measured obtained at this time is shown in Figure 8 .

[0047] The temperature data at 0° (360°), 60° (420°), 120°, 180°, 240°, and 300° (46.26℃, 46.34℃, 47.85℃, 46.24℃, 46.21℃, 45.26℃) are selected. The Fourier series is expanded to the third harmonic, and the fitting result is shown in Figure 9 . The peak temperature of the joint surface obtained by fitting is 47.9℃, with an error of only 0.1% compared with the simulation peak temperature of 47.85℃; the lowest surface temperature is 45.18℃, with an error of only 0.2% compared with the simulation peak temperature of 45.26℃, and the fitting effect is good. The maximum temperature difference obtained by the fitting curve is 2.72℃, which is 0.13℃ different from the simulation maximum temperature difference of 2.59℃, and the temperature difference error is 5%. According to the maximum temperature difference of 0.76℃ under normal no-defect conditions, it can be known that the cable is aging.

[0048] According to the maximum temperature difference 2.72℃ obtained by the fitting curve, the input impedance spectrum at the first end is corrected, and the defect positioning of the cable is performed using the frequency domain reflection method, and the defect positioning result in Matlab is shown as Figure 10 The simulation result shows that after the compensation, the defect positioning result of the cable only has obvious peak values at the first end of the cable, the defect positioning position 69.5257m and the end of the cable 100.132m, the number and amplitude of the interference peaks at the other positions are greatly reduced, and the waveforms are basically stable, which is beneficial to the correct judgment of the cable defect position by the inspection personnel. It can be seen that the method has important practical value.

[0049] Table 2 Comparison of positioning results before and after compensation

[0050] It can be seen from Table 2 that the compensated cable has not only better positioning accuracy, but also better performance in resolution (ratio of amplitude at defect to amplitude at end).

[0051] Example 3 A cable impedance spectrum defect positioning system is provided, comprising: an impedance analyzer configured to measure a to-be-measured cable and obtain a first-end input impedance spectrum of the to-be-measured cable; a defect judgment module configured to compare the first-end input impedance spectrum of the to-be-measured cable with a first-end input impedance spectrum of a healthy cable and determine whether the to-be-measured cable has a defect; an aging judgment module configured to, when the to-be-measured cable has a defect, collect a plurality of temperature data around a circumferential direction of an intermediate joint of the to-be-measured cable, and determine whether the to-be-measured cable has aging by using a temperature difference between a peak value and a valley value of the temperature data; a defect positioning module configured to, when the to-be-measured cable has no aging, directly use a frequency domain reflection method to perform defect positioning of the cable by using the obtained first-end input impedance spectrum of the to-be-measured cable, and, when the to-be-measured cable has aging, compensate the obtained first-end input impedance spectrum of the to-be-measured cable according to an aging degree, and perform defect positioning of the cable by using the frequency domain reflection method based on the compensated first-end input impedance spectrum.

[0052] Further, the aging judgment module comprises: six temperature sensors uniformly arranged around a circumferential direction of an intermediate joint of the to-be-measured cable; a collection sub-module configured to collect temperature data of the intermediate joint; a temperature difference acquisition module configured to perform curve fitting on the collected temperature data by using a Fourier third harmonic model, obtain a peak value and a valley value of surface temperature of the intermediate joint, and obtain a maximum temperature difference of the intermediate joint; ​The aging determination sub-module is configured to determine whether the maximum temperature difference of the intermediate joint of the cable under test exceeds a set threshold value, and if yes, aging occurs, otherwise, no aging occurs.

[0053] Embodiment 4 The present application provides a computer device, comprising a processor and a memory; wherein the processor implements the steps of the cable impedance spectrum defect positioning method when executing the computer program stored in the memory.

[0054] The more specific process of the above method can refer to the corresponding content disclosed in the foregoing embodiments, which will not be repeated here.

[0055] Embodiment 5 The present application provides a computer readable storage medium for storing a computer program; the computer program is executed by the processor to implement the steps of the cable impedance spectrum defect positioning method.

[0056] The more specific process of the above method can refer to the corresponding content disclosed in the foregoing embodiments, which will not be repeated here.

[0057] The embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts of each embodiment can be referred to each other. For the system, device and storage medium disclosed in the embodiments, since they correspond to the method disclosed in the embodiments, the description is relatively simple, and the related parts can be referred to the method part.

[0058] Those skilled in the art can clearly understand that the technology in the embodiments of the present application can be realized by means of software and necessary general hardware platform. Based on this understanding, the technical solutions in the embodiments of the present application can be embodied in the form of software product, which can be stored in storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., including a plurality of instructions to make a computer device (which can be a personal computer, server, or network device, etc.) execute the method described in the embodiments or some parts of the embodiments.

[0059] The above is only the preferred embodiment of the present application, and the protection scope of the present application is not limited to the above-mentioned embodiments. Any technical solution falling within the concept of the present application shall fall within the protection scope of the present application. It should be noted that, for ordinary skilled in the art, some improvements and refinements without departing from the principles of the present application shall be considered as the protection scope of the present application.

Claims

1. A method of cable impedance spectroscopy defect location, characterized by, The method comprises the following steps: measuring the to-be-tested cable by using an impedance analyzer to obtain a first-end input impedance spectrum of the to-be-tested cable, and comparing the first-end input impedance spectrum of the to-be-tested cable with a first-end input impedance spectrum of a healthy cable to determine whether the to-be-tested cable has defects; if the to-be-tested cable has defects, collecting a plurality of temperature data around the intermediate joint in the circumferential direction, and determining whether the to-be-tested cable has aged by using a temperature difference between the peak temperature data and the valley temperature data; if the to-be-tested cable has not aged, directly positioning defects of the cable by using the frequency domain reflection method based on the obtained first-end input impedance spectrum of the to-be-tested cable; if the to-be-tested cable has aged, compensating the obtained first-end input impedance spectrum of the to-be-tested cable according to the aging degree, and positioning defects of the cable by using the frequency domain reflection method based on the compensated first-end input impedance spectrum.

2. The method of claim 1, wherein, The method of collecting the plurality of temperature data around the intermediate joint in the circumferential direction and determining whether the to-be-tested cable has aged by using the temperature difference between the peak temperature data and the valley temperature data comprises the following steps: collecting temperature data of the intermediate joint by using six temperature sensors which are uniformly arranged around the intermediate joint in the circumferential direction of the to-be-tested cable; performing curve fitting on the collected temperature data by using a Fourier third harmonic model to obtain the peak temperature data and the valley temperature data on the surface of the intermediate joint, and to obtain a maximum temperature difference of the intermediate joint; determining whether the maximum temperature difference of the intermediate joint of the to-be-tested cable exceeds a set threshold value; if the maximum temperature difference exceeds the set threshold value, the to-be-tested cable has aged; otherwise, the to-be-tested cable has not aged.

3. The method of claim 2, wherein, The curve fitting is in the form of: ； wherein is a position angle variable is a temperature, is a direct current component, is a number of harmonics, and are respectively a sine term coefficient and a cosine term coefficient of the k harmonic.

4. The method of claim 1, wherein, The method of compensating the obtained first-end input impedance spectrum of the to-be-tested cable according to the aging degree comprises the following steps: ； wherein, is the impedance value of the cable under test after aging compensation, is the frequency point in the input impedance spectrum of the head end of the cable under test f corresponding impedance value, is the aging temperature rise compensation coefficient, is the maximum temperature difference of the intermediate joint of the cable under test, is the temperature coefficient function fitted in advance through aging data.

5. The method of claim 1, wherein, The first-end input impedance spectrum of the healthy cable is obtained by using a transmission line theory; specifically, the healthy cable is equivalent to a distributed parameter model, the distributed parameters are modeled, the distributed parameters of the healthy cable are obtained, and then the first-end input impedance of the healthy cable is obtained by using a ratio of a voltage and a current at any position away from the first end of the cable.

6. A cable impedance spectroscopy defect location system characterized by, The method comprises the following steps: an impedance analyzer is used to measure the to-be-tested cable to obtain a first-end input impedance spectrum of the to-be-tested cable; a defect determination module is used to compare the first-end input impedance spectrum of the to-be-tested cable with a first-end input impedance spectrum of a healthy cable to determine whether the to-be-tested cable has defects; an aging determination module is used to collect a plurality of temperature data around an intermediate joint in the circumferential direction when the to-be-tested cable has defects, and to determine whether the to-be-tested cable has aged by using a temperature difference between the peak temperature data and the valley temperature data; a defect positioning module is used to directly position defects of the cable by using the frequency domain reflection method based on the obtained first-end input impedance spectrum of the to-be-tested cable when the to-be-tested cable has not aged; when the to-be-tested cable has aged, the defect positioning module is used to compensate the obtained first-end input impedance spectrum of the to-be-tested cable according to the aging degree, and to position defects of the cable by using the frequency domain reflection method based on the compensated first-end input impedance spectrum.

7. A cable impedance spectroscopy defect location system according to claim 6, wherein, The aging determination module comprises: six temperature sensors which are uniformly arranged around the intermediate joint in the circumferential direction of the to-be-tested cable; a collection sub-module is used to collect temperature data of the intermediate joint; a temperature difference acquisition module is used to perform curve fitting on the collected temperature data by using a Fourier third harmonic model to obtain the peak temperature data and the valley temperature data on the surface of the intermediate joint, and to obtain a maximum temperature difference of the intermediate joint. An aging determination sub-module is configured to determine whether the maximum temperature difference of the intermediate joint of the cable under test exceeds a set threshold value, and if so, aging occurs, otherwise, no aging occurs.

8. A computer device, comprising: The method comprises the steps of: obtaining a cable impedance spectrum of the cable under test; determining a cable impedance spectrum defect of the cable under test; and locating the cable impedance spectrum defect.

9. A computer-readable storage medium, characterized in that, A computer program product is configured to store a computer program, and the computer program is configured to be executed by a processor to implement the steps of the method for locating a cable impedance spectrum defect according to any one of claims 1-5.

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