Cable accessory fault location method and system

Abstract

The application provides a cable accessory fault positioning method and system. The method comprises the following steps: collecting reflection signals of a linear frequency modulation signal reflected at multiple impedance discontinuous points in a cable accessory; arranging all the reflection signals into a reflection signal sequence; selecting a first reflection signal in the reflection signal sequence as a selected signal; identifying bubble migration caused by insulation interface discharge at a reflection position corresponding to the selected signal according to amplitude-frequency characteristics of a nonlinear component in the selected signal; correcting an air gap of a next reflection signal in the reflection signal sequence based on the bubble migration, taking the air gap corrected signal as a new selected signal, repeating the above steps until the last reflection signal in the reflection signal sequence is corrected; and tracing and positioning a fault accessory on the cable according to the linear frequency modulation signal and each air gap corrected reflection signal. The method can eliminate the interference of the gas generated by the discharge at the insulation interface on the reflection signal.

Description

Technical Field

[0001] This application relates to the field of fault detection technology, and more specifically, to a method and system for locating faults in cable accessories. Background Technology

[0002] As the core carrier of electrical energy transmission in the power system, the safe and stable operation of cables is directly related to the reliability of power supply. Cable accessories (such as cable joints and terminals) are key components that connect cables to equipment and achieve insulation transition. Due to long-term exposure to electrical, thermal, mechanical stress and environmental factors, they are prone to becoming weak links in the cable system. The proportion of faults caused by their insulation defects remains high. Therefore, fault location of cable accessories is an important prerequisite for ensuring the safe operation of the power system.

[0003] In existing technologies, the Frequency Modulated Continuous Wave Radar with Time Reversal (FMCW-TR) method is commonly used for fault location of cable accessories. This method injects a linear frequency modulated signal into the cable and utilizes the signal reflection characteristics at the fault point, combined with a time reversal algorithm to analyze the reflected signal to determine the fault location. However, this method has significant limitations when dealing with insulation interface breakdown faults: the insulation interface breakdown process has phased characteristics, and gas is generated during the discharge process. The formed bubble region causes severe distortion of the local electric field, reducing the interface breakdown strength. At the same time, the dynamic migration of the bubbles increases the randomness of the interface discharge, resulting in multiple discrete arc discharges with random paths during the breakdown process. These discharges cause complex interference to the reflection characteristics of the linear frequency modulated signal, leading to nonlinear distortion of the reflected signal received by the FMCW-TR method, which in turn causes deviations or even errors in the fault location results. Therefore, how to eliminate the interference of gas generated by the discharge at the insulation interface on the reflected signal has become a difficult problem for the industry. Summary of the Invention

[0004] This application provides a method and system for locating faults in cable accessories, which can eliminate the interference of gas generated by discharge at the insulation interface on the reflected signal.

[0005] In a first aspect, this application provides a method for locating faults in cable accessories, including:

[0006] A continuous linear frequency modulated signal is injected into the cable through a circulator, and the reflected signals of the linear frequency modulated signal at multiple impedance discontinuities in the cable accessories are collected.

[0007] All reflected signals are arranged into a reflected signal sequence according to their reflection positions. The first reflected signal in the reflected signal sequence is selected as the selected signal, and the nonlinear component is extracted from the selected signal.

[0008] The electric field distortion coefficient at the reflection position corresponding to the selected signal is determined based on the amplitude-frequency characteristics of the nonlinear component, and the bubble migration generated by the discharge at the insulating interface at the reflection position corresponding to the selected signal is identified based on the electric field distortion coefficient.

[0009] Based on the bubble migration, the amplitude and phase of the next reflected signal in the reflected signal sequence are corrected by air gap, and the air gap corrected signal is used as the new selected signal. The above steps are repeated until the amplitude and phase of the last reflected signal in the reflected signal sequence are corrected by air gap.

[0010] Based on the linear frequency modulation signal and the reflected signal after each air gap correction, the focused energy at each location on the cable is identified, and the faulty accessories on the cable are traced and located by the positioning peak of all focused energy.

[0011] In some embodiments, arranging all reflected signals into a reflected signal sequence according to their reflection positions specifically includes:

[0012] The distance between the reflection position of each reflected signal and the sampling point is determined based on the reflection time of each reflected signal;

[0013] Arrange all the reflected signals in ascending order of the distance between the reflection position and the sampling point, and use the resulting sequence as the reflected signal sequence.

[0014] In some embodiments, extracting the nonlinear component from the selected signal specifically includes:

[0015] The selected signal is decomposed into multiple intrinsic mode functions;

[0016] Multiple signal components with nonlinear characteristics were selected by filtering out the amplitude proportion of the third harmonic component in each intrinsic mode function;

[0017] All the selected signal components are reconstructed to obtain the nonlinear components.

[0018] In some embodiments, determining the electric field distortion coefficient at the reflection location corresponding to the selected signal based on the amplitude-frequency characteristics of the nonlinear component specifically includes:

[0019] Determine the amplitude-frequency response curve of the nonlinear component;

[0020] Discretize the amplitude-frequency response curve to obtain discrete amplitude-frequency response;

[0021] The electric field distortion coefficient at the reflection location corresponding to the selected signal is extracted from the discrete amplitude-frequency characteristics.

[0022] In some embodiments, identifying the bubble migration caused by the discharge at the insulating interface at the reflection location corresponding to the selected signal based on the electric field distortion coefficient specifically includes:

[0023] The signal attenuation coefficient is determined based on the distance between the selected signal reflection location and the sampling point;

[0024] The selected signal is enhanced using the signal attenuation coefficient to obtain the enhanced signal;

[0025] Based on the covariance matrix between the enhanced signal and the linear frequency modulated signal, the migration of bubbles generated by the discharge at the insulating interface at the reflection position corresponding to the selected signal is identified.

[0026] In some embodiments, air gap correction of the amplitude and phase of the next reflected signal in the reflected signal sequence based on the bubble migration specifically includes:

[0027] The signal phase distortion vector caused by the air gap at the reflection position corresponding to the selected signal is determined based on the quantization matrix of the bubble migration.

[0028] Extract the nonlinear features of the next reflected signal in the reflected signal sequence;

[0029] The air gap correction factor is determined based on the nonlinear characteristics and the phase distortion vector.

[0030] The phase and amplitude of the next reflected signal in the reflected signal sequence are corrected by the air gap correction factor.

[0031] In some embodiments, tracing and locating faulty accessories on a cable using the location peaks of all focused energy specifically includes:

[0032] All focused energy is fitted into a fault diagnosis spectrum of the cable accessory;

[0033] The faulty accessories on the cable are located by tracing their origins based on the position coordinates of each location peak in the fault diagnosis spectrum.

[0034] Secondly, this application provides a cable accessory fault location system, comprising:

[0035] The acquisition module is used to inject a continuous linear frequency modulated signal into the cable through a circulator and to acquire the reflected signals of the linear frequency modulated signal at multiple impedance discontinuities in the cable accessories.

[0036] The processing module is used to arrange all the reflected signals into a reflected signal sequence according to the reflection position, select the first reflected signal in the reflected signal sequence as the selected signal, and extract the nonlinear component from the selected signal.

[0037] The processing module is also used to determine the electric field distortion coefficient at the reflection position corresponding to the selected signal based on the amplitude-frequency characteristics of the nonlinear component, and to identify the bubble migration generated by the discharge of the insulating interface at the reflection position corresponding to the selected signal based on the electric field distortion coefficient.

[0038] The processing module is also used to perform air gap correction on the amplitude and phase of the next reflected signal in the reflected signal sequence based on the bubble migration, and to use the air gap corrected signal as the new selected signal, repeating the above steps until the amplitude and phase of the last reflected signal in the reflected signal sequence are corrected by air gap.

[0039] The execution module is used to identify the focused energy at various locations on the cable based on the linear frequency modulation signal and the reflection signal after each air gap correction, and to trace and locate the faulty accessories on the cable by the positioning peak of all focused energy.

[0040] Thirdly, this application provides a computer device including a memory and a processor, the memory storing code, and the processor being configured to acquire the code and execute the above-described cable accessory fault location method.

[0041] Fourthly, this application provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described cable accessory fault location method.

[0042] The technical solutions provided by the embodiments disclosed in this application have the following beneficial effects:

[0043] The cable accessory fault location method and system provided in this application first injects a continuous linear frequency modulated (LFM) signal into the cable through a circulator and collects the reflected signals of the LFM signal at multiple impedance discontinuities in the cable accessory. All reflected signals are arranged into a reflected signal sequence according to their reflection positions. The first reflected signal in the sequence is selected as the chosen signal, and a nonlinear component is extracted from the chosen signal. The electric field distortion coefficient at the reflection position corresponding to the chosen signal is determined based on the amplitude-frequency characteristics of the nonlinear component. Based on the electric field distortion coefficient, bubble migration generated by insulation interface discharge at the reflection position corresponding to the chosen signal is identified. Based on the bubble migration, the amplitude and phase of the next reflected signal in the reflected signal sequence are corrected using an air gap. The air gap-corrected signal is then used as the new chosen signal. This process is repeated until the amplitude and phase of the last reflected signal in the reflected signal sequence are corrected using an air gap. The focused energy at each location on the cable is identified based on the LFM signal and each air gap-corrected reflected signal. The faulty accessory on the cable is located by tracing the location of the faulty accessory through the location peaks of all focused energies.

[0044] Therefore, this application processes the reflected signals sequentially according to their reflection distance. First, it extracts the nonlinear component from the nearest reflected signal and then extracts the electric field distortion (i.e., electric field distortion coefficient) at the reflection location from the nonlinear component. Next, it identifies the bubble migration caused by discharge at the insulation interface at the reflection location based on the electric field distortion. Then, it corrects the next reflected signal (i.e., the second closest reflected signal) based on the bubble migration. This process is repeated to correct reflected signals at different locations on the cable. Finally, the corrected signals are used to trace and locate faulty accessories on the cable. In summary, the solution of this application can eliminate the interference of gas generated by discharge at the insulation interface on the reflected signal. Attached Figure Description

[0045] Figure 1 This is an exemplary flowchart of a cable accessory fault location method according to some embodiments of this application;

[0046] Figure 2 This is an exemplary flowchart illustrating the identification of bubble migration according to some embodiments of this application;

[0047] Figure 3 This is an equivalent circuit diagram of a cable according to some embodiments of this application;

[0048] Figure 4 This is a structural schematic diagram of a cable accessory fault location system according to some embodiments of this application;

[0049] Figure 5 This is a schematic diagram of the structure of a computer device for implementing a cable accessory fault location method according to some embodiments of this application. Detailed Implementation

[0050] To better understand the technical solution of this application, the technical solution of this application will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0051] refer to Figure 1 The figure is an exemplary flowchart of a cable accessory fault location method according to some embodiments of this application. The cable accessory fault location method mainly includes the following steps:

[0052] In step 101, a continuous linear frequency modulated signal is injected into the cable through a circulator, and the reflected signals of the linear frequency modulated signal at multiple impedance discontinuities in the cable are collected.

[0053] In practice, injecting a continuous linear frequency modulated (LFM) signal into the cable via a circulator can be achieved as follows: First, connect the output port of the LFM signal generator to the first port of the circulator via a coaxial cable. Connect the second port of the circulator to the input of the cable under test via a coaxial cable with characteristic impedance matching. Then, set the parameters of the continuous LFM signal according to actual needs. These parameters include the signal's start frequency, end frequency, sweep period, and signal power, so that the signal frequency changes linearly with time according to the formula: start frequency + (end frequency - start frequency) * t / sweep period, where t is a time variable. Then, start the LFM signal generator and input the LFM signal through the first port of the circulator. Through the unidirectional transmission characteristic of the circulator, the LFM signal is injected into the cable connected to the second port without reflection, thus completing the injection of the LFM signal.

[0054] In practice, the acquisition of reflected signals from multiple impedance discontinuities in the cable accessories of the linear frequency modulated (LFM) signal can be achieved in the following way: First, the third port of the circulator is connected to the signal input channel of the signal acquisition device via a coaxial cable. At the same time, a synchronization signal from the LFM signal generator is connected to the trigger input channel of the signal acquisition device via a coaxial cable to ensure time synchronization of signal acquisition. Then, the signal acquisition device is set to a sampling period consistent with the sweep period of the LFM signal. When the LFM signal encounters an impedance discontinuity in the cable and generates a reflected signal, the reflected signal is transmitted to the signal acquisition device via the third port of the circulator. Under the control of the synchronization trigger signal, the signal acquisition device acquires the reflected signal, thereby obtaining the reflected signals from multiple impedance discontinuities in the cable accessories of the LFM signal.

[0055] It should be noted that, in this application, impedance discontinuity refers to the location in the cable where the impedance value changes abruptly, which will cause the signal to be reflected.

[0056] In step 102, all the reflected signals are arranged into a reflected signal sequence according to their reflection positions, and the first reflected signal in the reflected signal sequence is selected as the selected signal. The nonlinear component is extracted from the selected signal.

[0057] In some embodiments, arranging all reflected signals into a sequence according to their reflection positions can be achieved using the following steps:

[0058] The distance between the reflection position of each reflected signal and the sampling point is determined based on the reflection time of each reflected signal;

[0059] Arrange all the reflected signals in ascending order of the distance between the reflection position and the sampling point, and use the resulting sequence as the reflected signal sequence.

[0060] In practice, the distance between the reflection position of each reflected signal and the sampling point can be determined based on the reflection time of each reflected signal in the following way: First, obtain the time 'a' when each reflected signal is collected and the injection time 'b' of the linear frequency modulated signal. Then, use the value obtained by (ab) * signal transmission speed / 2 as the distance between the reflection position of each reflected signal and the sampling point. The signal transmission speed can be calculated based on the relative permittivity of the cable medium using the formula "signal transmission speed = speed of light / square root of relative permittivity". The relative permittivity of the cable medium is an inherent parameter of the cable and can be directly obtained by consulting the cable specification manual.

[0061] It should be noted that the reflected signal sequence in this application is a set of all reflected signals arranged according to the distance of the reflection position.

[0062] In some embodiments, the extraction of nonlinear components from a selected signal can be achieved by the following steps:

[0063] The selected signal is decomposed into multiple intrinsic mode functions;

[0064] Multiple signal components with nonlinear characteristics were selected by filtering out the amplitude proportion of the third harmonic component in each intrinsic mode function;

[0065] All the selected signal components are reconstructed to obtain the nonlinear components.

[0066] In a specific implementation, the selected signal can be decomposed into multiple intrinsic mode functions in the following way: the selected signal can be decomposed into multiple intrinsic mode functions through the Hilbert-Huang transform in the prior art.

[0067] In specific implementation, the selection of multiple signal components with nonlinear characteristics by the amplitude ratio of the third harmonic component in each intrinsic mode function can be achieved in the following way: First, perform a Fourier transform on each intrinsic mode function to obtain the frequency domain spectrum of each intrinsic mode function. Then, identify the fundamental frequency component and the third harmonic frequency component from each frequency domain spectrum. The ratio of the amplitude of the third harmonic component to the amplitude of the fundamental component in each frequency domain spectrum is taken as the amplitude ratio of the third harmonic component in each frequency domain spectrum. Then, set a ratio threshold, and identify each intrinsic mode function with an amplitude ratio greater than the ratio threshold as a signal component with nonlinear characteristics. The ratio threshold can be set to 5%. In other embodiments, the ratio threshold can also be set to other values ​​according to the actual signal characteristics of the cable accessories. This is not limited here.

[0068] In practice, the nonlinear components can be reconstructed by adding all the selected signal components together and using the sum as the nonlinear component.

[0069] It should be noted that, in this application, the nonlinear component refers to the signal component of the nonlinear part of the selected signal.

[0070] In step 103, the electric field distortion coefficient at the reflection position corresponding to the selected signal is determined based on the amplitude-frequency characteristics of the nonlinear component, and the bubble migration generated by the discharge at the insulating interface at the reflection position corresponding to the selected signal is identified based on the electric field distortion coefficient.

[0071] In some embodiments, determining the electric field distortion coefficient at the reflection location corresponding to the selected signal based on the amplitude-frequency characteristics of the nonlinear component can be achieved using the following steps:

[0072] Determine the amplitude-frequency response curve of the nonlinear component;

[0073] Discretize the amplitude-frequency response curve to obtain discrete amplitude-frequency response;

[0074] The electric field distortion coefficient at the reflection location corresponding to the selected signal is extracted from the discrete amplitude-frequency characteristics.

[0075] In specific implementation, the amplitude-frequency characteristic curve of the nonlinear component can be determined in the following way: First, the extracted nonlinear component is subjected to a fast Fourier transform to convert the time-domain nonlinear component into a frequency-domain signal, and multiple sets of amplitude-frequency data pairs consisting of discrete frequency points and their corresponding amplitude values ​​are obtained from the frequency-domain signal. Then, a cubic spline interpolation algorithm is used to interpolate all amplitude-frequency data pairs to obtain a continuous curve, which is used as the amplitude-frequency characteristic curve of the nonlinear component.

[0076] It should be noted that the amplitude-frequency response curve in this application is a curve that describes the continuous change relationship between different frequency components and their corresponding amplitude values ​​in the nonlinear component.

[0077] In specific implementation, the amplitude-frequency characteristic curve is discretized to obtain discrete amplitude-frequency characteristics. This can be achieved by discretizing the amplitude-frequency characteristic curve according to a preset sampling interval, arranging the collected data into a sequence according to the order of collection, and using this sequence as the discrete amplitude-frequency characteristic. The sampling interval can be set according to the parameters of the linear frequency modulated signal. For example, the sampling interval can be set as (terminal frequency - starting frequency) / (N times the sweep period), where N is the length of the selected signal.

[0078] It should be noted that the discrete amplitude-frequency characteristic in this application is a discrete sequence obtained by discretely sampling the amplitude-frequency characteristic curve.

[0079] In a specific implementation, the electric field distortion coefficient at the reflection position corresponding to the selected signal can be extracted from the discrete amplitude-frequency characteristics in the following way: the kurtosis value of the discrete amplitude-frequency characteristics can be calculated and used as the electric field distortion coefficient at the reflection position corresponding to the selected signal.

[0080] It should be noted that the electric field distortion coefficient in this application is a parameter value used to measure the degree of electric field distortion at the impedance discontinuity point corresponding to the selected signal. When the impedance discontinuity point is damp, discrete arc discharge will be generated at the insulation interface. Because the energy of the arc discharge is concentrated at a local frequency, the reflected signal at that point will generate a pulse peak in a specific frequency range.

[0081] In some embodiments, reference Figure 2 The figure is an exemplary flowchart illustrating the identification of bubble migration according to some embodiments of this application. In this application, the identification of bubble migration caused by the discharge of the insulating interface at the reflection position corresponding to the selected signal based on the electric field distortion coefficient can be achieved by the following steps:

[0082] In step 1031, the signal attenuation coefficient is determined based on the distance between the reflection position of the selected signal and the sampling point;

[0083] In step 1032, the selected signal is enhanced using the signal attenuation coefficient to obtain an enhanced signal;

[0084] In step 1033, the bubble migration caused by the discharge at the insulating interface at the reflection position corresponding to the selected signal is identified based on the covariance matrix between the enhanced signal and the linear frequency modulated signal.

[0085] In practice, the signal attenuation coefficient can be determined based on the distance between the reflection position of the selected signal and the sampling point in the following way: First, obtain the distance between the reflection position of the selected signal and the sampling point, as well as the attenuation constant of the cable. Then, take the negative of the product of the attenuation constant and the distance, and use the value of the natural exponential function of the negative number as the signal attenuation coefficient. The attenuation constant of the cable is an inherent parameter of the cable and can be obtained directly from the cable specification manual.

[0086] It should be noted that the signal attenuation coefficient in this application is a parameter used to measure the degree of attenuation caused by the transmission distance during the transmission of a selected signal from the reflection position to the sampling point.

[0087] In practice, the selected signal is enhanced by the signal attenuation coefficient. The enhanced signal can be obtained by dividing the amplitude of the selected signal by the signal attenuation coefficient and using the resulting signal as the enhanced signal.

[0088] It should be noted that the enhanced signal in this application is the reflected signal obtained after correcting the amplitude attenuation of the reflected signal due to distance in the transmission path.

[0089] In specific implementation, identifying the bubble migration caused by the insulation interface discharge at the reflection position corresponding to the selected signal based on the covariance matrix between the enhanced signal and the linear frequency modulated signal can be achieved in the following way: Since the bubble migration caused by the insulation interface discharge will cause the correlation between the enhanced signal and the linear frequency modulated signal to deviate, the bubble migration can be described by the covariance matrix. That is, firstly, the signal segment corresponding to the selected signal is extracted from the linear frequency modulated signal. Then, the covariance matrix between the signal segment and the selected signal is calculated. Subsequently, the covariance matrix is ​​decomposed into Jouleski and the lower triangular matrix obtained by the decomposition is used as the quantization matrix of the bubble migration caused by the insulation interface discharge at the reflection position corresponding to the selected signal. Here, extracting the signal segment corresponding to the selected signal from the linear frequency modulated signal means extracting the part of the linear frequency modulated signal that matches the reflection time interval as the corresponding signal segment based on the reflection time of the selected signal.

[0090] It should be noted that, in this application, bubble migration refers to the dynamic movement of gas generated during the breakdown discharge process caused by moisture at the insulation interface of cable accessories. During the breakdown process caused by moisture at the insulation interface, gas is generated at the insulation interface. The bubbles formed by the gas will cause severe electric field distortion near the insulation interface, and the dynamic movement of the bubbles will increase the randomness of the interface discharge, resulting in multiple discrete arc discharges with random paths at the insulation interface. This will affect the linear frequency modulation signal in the cable, causing distortion of the subsequent reflected signal.

[0091] In step 104, the amplitude and phase of the next reflected signal in the reflected signal sequence are corrected by air gap based on the bubble migration, and the air gap corrected signal is used as the new selected signal. The above steps are repeated until the amplitude and phase of the last reflected signal in the reflected signal sequence are corrected by air gap.

[0092] In some embodiments, air gap correction of the amplitude and phase of the next reflected signal in the reflected signal sequence based on the bubble migration can be achieved by the following steps:

[0093] The signal phase distortion vector caused by the air gap at the reflection position corresponding to the selected signal is determined based on the quantization matrix of the bubble migration.

[0094] Extract the nonlinear features of the next reflected signal in the reflected signal sequence;

[0095] The air gap correction factor is determined based on the nonlinear characteristics and the phase distortion vector.

[0096] The phase and amplitude of the next reflected signal in the reflected signal sequence are corrected by the air gap correction factor.

[0097] In specific implementation, the signal phase distortion vector caused by the air gap at the reflection position corresponding to the selected signal, based on the quantization matrix of the bubble migration, can be determined in the following way: First, perform eigenvalue decomposition on the bubble migration quantization matrix to extract its principal eigenvector. Then, calculate the angle between the principal eigenvector and the direction vector of the linear frequency modulated signal propagating in the cable. Next, multiply the angle by each frequency component of the linear frequency modulated signal, arrange the resulting components according to their frequency magnitude, and finally convert the arranged components into complex vectors. The resulting vector is used as the signal phase distortion vector caused by the air gap at the reflection position corresponding to the selected signal. The direction vector of the linear frequency modulated signal propagating in the cable can be set according to the phase of each frequency component, that is, arrange the phase of each frequency component according to its frequency magnitude, and use the resulting vector as the direction vector. The dimension of this direction vector must be consistent with the dimension of the principal eigenvector.

[0098] It should be noted that the signal phase distortion vector in this application is a vector characterizing the degree of distortion of the reflected signal phase at each frequency component caused by the air gap. The real and imaginary parts of this phase distortion vector correspond to the cosine and sine phase modulation components, respectively.

[0099] In a specific implementation, the nonlinear feature of the next reflected signal in the reflected signal sequence can be extracted in the following way: the same steps as "extracting nonlinear components from selected signals" in this application can be used, taking the next reflected signal in the reflected signal sequence as the selected signal, and then taking the nonlinear component of the next reflected signal in the reflected signal sequence as the nonlinear feature of the next reflected signal.

[0100] In specific implementation, the air gap correction factor can be determined based on the nonlinear characteristics and the phase distortion vector in the following manner: First, the nonlinear characteristics are converted to the frequency domain by a fast Fourier transform to obtain the amplitude and phase of each frequency component. Then, the phase values ​​of each element in the phase distortion vector are inverted, and the resulting vector is multiplied point by point with the frequency domain of the nonlinear characteristics to obtain the pre-corrected frequency domain signal. Then, the pre-corrected frequency domain signal is converted back to the time domain by an inverse fast Fourier transform. Then, the time domain signal is subjected to a Hilbert transform to construct an analytic signal to obtain its time domain envelope. Finally, the reciprocal of the time domain envelope is used as the air gap correction factor.

[0101] It should be noted that the air gap correction factor in this application is a set of amplitude correction parameters used to perform air gap correction on the next reflected signal in the reflected signal sequence.

[0102] In specific implementation, the correction of the phase and amplitude of the next reflected signal in the reflected signal sequence by the air gap correction factor can be achieved in the following way: First, the next reflected signal in the reflected signal sequence is taken as the signal to be corrected. The signal to be corrected is converted to the frequency domain by a fast Fourier transform to obtain the complex spectrum of the signal to be corrected. Then, the phase values ​​of each element in the phase distortion vector are inverted, and the resulting vector is multiplied point by point with the complex spectrum to obtain the phase-corrected frequency domain signal. Then, the phase-corrected frequency domain signal is converted back to the time domain by an inverse fast Fourier transform, and the signal converted back to the time domain is multiplied point by point with the air gap correction factor in the time domain to achieve the correction of amplitude distortion, thus obtaining the reflected signal after simultaneous correction of phase and amplitude.

[0103] It should be noted that, in this application, air gap correction refers to the process of correcting the amplitude distortion and phase shift of the reflected signal caused by the air gap in order to eliminate the influence of bubble migration on the reflected signal. Since the bubbles generated by the discharge at the insulation interface will form an air gap, causing the electric field distortion at that point, the amplitude and phase will change when the signal passes through this point, causing the downstream reflected signal to fail to truly reflect the real electrical characteristics of the downstream cable accessories, thereby interfering with the fault location of the cable accessories. Therefore, it is necessary to correct the reflected signal sequentially to avoid interference.

[0104] In step 105, the focused energy at each location on the cable is identified based on the linear frequency modulation signal and the reflected signal after each air gap correction, and the faulty accessory on the cable is located by locating the positioning peak of all focused energy.

[0105] In some embodiments, reference Figure 3 The figure is an equivalent circuit diagram of a cable according to some embodiments of this application, and is specifically described as follows: In the figure, R0, L0, G0 and C0 are the resistance, inductance, conductance and capacitance per unit length of the cable body in the normal area, respectively. For the fault area, the resistance, inductance, conductance and capacitance per unit length in the fault area are different from those in the normal area, and are represented by R1, L1, G1 and C1, respectively.

[0106] In some embodiments, identifying the focused energy at various locations on the cable based on the linear frequency modulation signal and the reflected signal corrected for each air gap can be achieved using the following steps:

[0107] The linear frequency modulated signal and the reflection signal after each air gap correction are respectively subjected to time inversion processing to obtain the corresponding inversion signal;

[0108] The inversion signals are input into the cable simulation model to obtain the focused energy at each location on the cable.

[0109] In practice, time inversion processing is performed on the linear frequency modulated signal and the reflection signal after each air gap correction to obtain the corresponding inversion signal. This can be achieved by reversing the time coordinates of the linear frequency modulated signal and the reflection signal after each air gap correction, and using the reversed signals as the corresponding inversion signals.

[0110] It should be noted that the inverted signal in this application refers to the signal obtained after performing time inversion operation on the linear frequency modulated signal and the reflected signal, that is, the signal whose amplitude remains unchanged and only the time sequence is reversed.

[0111] In practice, the inversion signals are input into the cable simulation model to obtain the focused energy at each location on the cable. This can be achieved by inputting the inversion signals into a pre-set cable simulation model. The cable simulation model can be the test cable model mentioned in the literature "Diagnosis Method of Cable Joint Moisture Defect Based on FMCW-TR". The focused energy at each location on the cable is directly output through the test cable model.

[0112] It should be noted that, in this application, focused energy is a parameter value that measures the degree of energy concentration at a specified location on the cable.

[0113] In some embodiments, tracing and locating faulty accessories on a cable using the location peaks of all focused energy can be achieved through the following steps:

[0114] All focused energy is fitted into a fault diagnosis spectrum of the cable accessory;

[0115] The faulty accessories on the cable are located by tracing their origins based on the position coordinates of each location peak in the fault diagnosis spectrum.

[0116] In practice, fitting all the focused energy into a fault diagnosis spectrum of the cable accessory can be achieved in the following way: fitting all the focused energy according to the corresponding position coordinates, and using the fitted curve as the fault diagnosis spectrum of the cable accessory.

[0117] It should be noted that the fault diagnosis spectrum in this application is an energy spectrum used to diagnose faults in cable accessories. This energy spectrum is a distance-energy curve characterizing the focused energy distribution at various locations on the cable.

[0118] In practice, the fault location of accessories on the cable can be traced and located based on the position coordinates of each location peak in the fault diagnosis spectrum as follows: First, extract all local peaks from the fault diagnosis spectrum and use each local peak as a location peak to obtain the distance coordinates of the location peak. Then, analyze the positive and negative change characteristics of each location peak. If the location peak shows a "negative then positive" characteristic, it is determined that the accessory corresponding to that location has a moisture fault. If it is "positive then negative", it corresponds to a normal accessory. Finally, match the location of the location peak that is determined to be faulty with the location information in the cable accessory installation log to determine the type and installation location of the specific fault accessory, so as to complete the traceability and location of the fault accessories on the cable.

[0119] In another aspect, in some embodiments, this application provides a cable accessory fault location system, with reference to... Figure 4 The figure is a schematic diagram of the structure of a cable accessory fault location system according to some embodiments of this application. The cable accessory fault location system 400 includes: a data acquisition module 401, a processing module 402, and an execution module 403, which are described below:

[0120] Acquisition module 401, in this application, is mainly used to inject a continuous linear frequency modulated signal into the cable through a circulator, and to acquire the reflected signals of the linear frequency modulated signal at multiple impedance discontinuities in the cable accessories.

[0121] Processing module 402, in this application, is mainly used to arrange all the reflected signals into a reflected signal sequence according to the reflection position, select the first reflected signal in the reflected signal sequence as the selected signal, and extract the nonlinear component from the selected signal.

[0122] It should be noted that the processing module 402 in this application is also used to determine the electric field distortion coefficient at the reflection position corresponding to the selected signal based on the amplitude-frequency characteristics of the nonlinear component, and to identify the bubble migration generated by the discharge of the insulating interface at the reflection position corresponding to the selected signal based on the electric field distortion coefficient.

[0123] It should be noted that the processing module 402 in this application is also used to perform air gap correction on the amplitude and phase of the next reflected signal in the reflected signal sequence based on the bubble migration, and to use the air gap corrected signal as the new selected signal, repeating the above steps until the amplitude and phase of the last reflected signal in the reflected signal sequence are corrected by air gap.

[0124] The execution module 403 in this application is mainly used to identify the focused energy at each position on the cable based on the linear frequency modulation signal and the reflection signal after each air gap correction, and to trace and locate the faulty accessories on the cable through the positioning peak of all focused energy.

[0125] In addition, this application also provides a computer device, the computer device including a memory and a processor, the memory storing code, and the processor being configured to acquire the code and execute the above-described cable accessory fault location method.

[0126] In some embodiments, reference Figure 5 The figure is a schematic diagram of the structure of a computer device for implementing a cable accessory fault location method according to some embodiments of this application. The cable accessory fault location method in the above embodiments can be implemented through... Figure 5 The computer device shown is used to implement this, and the computer device 500 includes at least one processor 501, a communication bus 502, a memory 503, and at least one communication interface 504.

[0127] Processor 501 can be a general-purpose central processing unit (CPU) or an application-specific integrated circuit (ASIC).

[0128] The communication bus 502 can be used to transmit information between the aforementioned components.

[0129] Memory 503 may be a read-only memory (ROM) or other type of static storage device capable of storing static information and instructions, random access memory (RAM) or other type of dynamic storage device capable of storing information and instructions, or electrically erasable programmable read-only memory (EEPROM), compact disc read-only memory (CD-ROM) or other optical disc storage, optical disc storage (including compressed optical discs, laser discs, optical discs, digital universal optical discs, Blu-ray discs, etc.), magnetic disks or other magnetic storage devices, or any other medium capable of carrying or storing desired program code in the form of instructions or data structures and accessible by a computer, but not limited thereto. Memory 503 may exist independently and be connected to processor 501 via communication bus 502. Memory 503 may also be integrated with processor 501.

[0130] The memory 503 stores program code for executing the solution of this application, and its execution is controlled by the processor 501. The processor 501 executes the program code stored in the memory 503. The program code may include one or more software modules. In the above embodiment, the cable accessory fault location method can be implemented by the processor 501 and one or more software modules in the program code in the memory 503.

[0131] Communication interface 504 uses any transceiver-like device to communicate with other devices or communication networks, such as Ethernet, radio access network (RAN), wireless local area networks (WLAN), etc.

[0132] In a specific implementation, as one example, a computer device may include multiple processors, each of which may be a single-core (single CPU) processor or a multi-core (multi CPU) processor. Here, a processor may refer to one or more devices, circuits, and / or processing cores used to process data (e.g., computer program instructions).

[0133] The aforementioned computer device can be a general-purpose computer device or a special-purpose computer device. In specific implementations, the computer device can be a desktop computer, a portable computer, a network server, a handheld digital assistant (PDA), a mobile phone, a tablet computer, a wireless terminal device, a communication device, or an embedded device. This application does not limit the type of computer device.

[0134] In addition, this application also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described cable accessory fault location method.

[0135] In summary, the cable accessory fault location method and system disclosed in this application firstly injects a continuous linear frequency modulated (LFM) signal into the cable through a circulator and collects the reflected signals of the LFM signal at multiple impedance discontinuities in the cable accessory; arranges all the reflected signals into a reflected signal sequence according to their reflection positions, selects the first reflected signal in the reflected signal sequence as the selected signal, and extracts the nonlinear component from the selected signal; determines the electric field distortion coefficient at the reflection position corresponding to the selected signal based on the amplitude-frequency characteristics of the nonlinear component, and identifies the bubble migration generated by the insulation interface discharge at the reflection position corresponding to the selected signal based on the electric field distortion coefficient; performs air gap correction on the amplitude and phase of the next reflected signal in the reflected signal sequence based on the bubble migration, and uses the air gap-corrected signal as the new selected signal, repeating the above steps until the amplitude and phase of the last reflected signal in the reflected signal sequence are air gap corrected; identifies the focused energy at each position on the cable based on the LFM signal and each air gap-corrected reflected signal, and traces and locates the faulty accessory on the cable through the location peaks of all focused energies.

[0136] Therefore, this application processes the reflected signals sequentially according to their reflection distance. First, it extracts the nonlinear component from the nearest reflected signal and then extracts the electric field distortion (i.e., electric field distortion coefficient) at the reflection location from the nonlinear component. Next, it identifies the bubble migration caused by discharge at the insulation interface at the reflection location based on the electric field distortion. Then, it corrects the next reflected signal (i.e., the second closest reflected signal) based on the bubble migration. This process is repeated to correct reflected signals at different locations on the cable. Finally, the corrected signals are used to trace and locate faulty accessories on the cable. In summary, the solution of this application can eliminate the interference of gas generated by discharge at the insulation interface on the reflected signal.

[0137] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0138] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A method of cable accessory fault location, characterized by, The method comprises the following steps: injecting a continuous linear frequency modulation signal into the cable through a circulator, and collecting reflected signals of the linear frequency modulation signal reflected at multiple impedance discontinuities in the cable accessory; arranging all the reflected signals into a reflected signal sequence according to the reflection positions, selecting a first reflected signal in the reflected signal sequence as a selected signal, and extracting a nonlinear component from the selected signal; determining an electric field distortion coefficient at the reflection position corresponding to the selected signal according to the amplitude-frequency characteristics of the nonlinear component, and identifying a bubble migration caused by insulation interface discharge at the reflection position corresponding to the selected signal according to the electric field distortion coefficient, wherein the bubble migration refers to the dynamic movement of the gas generated in the breakdown discharge process of the insulation interface of the cable accessory due to moisture; performing air gap correction on the amplitude and phase of a next reflected signal in the reflected signal sequence based on the bubble migration, taking the air gap corrected signal as a new selected signal, and repeating the above steps until the amplitude and phase of the last reflected signal in the reflected signal sequence are corrected; identifying focusing energy at each position on the cable according to the linear frequency modulation signal and each air gap corrected reflected signal, and locating the fault accessory on the cable through the positioning peaks of all the focusing energy.

2. The method of claim 1, wherein, The step of arranging all the reflected signals into a reflected signal sequence according to the reflection positions specifically comprises the following steps: determining the distance between the reflection position of each reflected signal and the sampling point according to the reflection time of each reflected signal; arranging all the reflected signals according to the distance between the reflection position and the sampling point from small to large, and taking the sequence obtained by the arrangement as the reflected signal sequence.

3. The method of claim 1, wherein, The step of extracting the nonlinear component from the selected signal specifically comprises the following steps: decomposing the selected signal into multiple intrinsic modal functions; screening multiple signal components containing nonlinear characteristics through the amplitude proportion of the third harmonic component in each intrinsic modal function; reconstructing all the screened signal components to obtain the nonlinear component.

4. The method of claim 1, wherein, The step of determining the electric field distortion coefficient at the reflection position corresponding to the selected signal according to the amplitude-frequency characteristics of the nonlinear component specifically comprises the following steps: determining the amplitude-frequency characteristic curve of the nonlinear component; discretizing the amplitude-frequency characteristic curve to obtain a discrete amplitude-frequency characteristic; extracting the electric field distortion coefficient at the reflection position corresponding to the selected signal from the discrete amplitude-frequency characteristic.

5. The method of claim 1, wherein, The step of identifying the bubble migration caused by insulation interface discharge at the reflection position corresponding to the selected signal according to the electric field distortion coefficient specifically comprises the following steps: determining a signal attenuation coefficient according to the distance between the reflection position of the selected signal and the sampling point; enhancing the selected signal through the signal attenuation coefficient to obtain an enhanced signal; identifying the bubble migration caused by insulation interface discharge at the reflection position corresponding to the selected signal according to the covariance matrix between the enhanced signal and the linear frequency modulation signal.

6. The method of claim 1, wherein, The step of performing air gap correction on the amplitude and phase of the next reflected signal in the reflected signal sequence based on the bubble migration specifically comprises the following steps: determining a signal phase distortion vector caused by the air gap at the reflection position corresponding to the selected signal based on a quantization matrix of the bubble migration; extracting the nonlinear characteristics of the next reflected signal in the reflected signal sequence; determining a gap correction factor according to the non-linear characteristic and the phase distortion vector; correcting the phase and amplitude of a next reflection signal in the reflection signal sequence by the gap correction factor.

7. The method of claim 1, wherein, The traceable positioning of the fault accessory on the cable through the positioning peaks of all focused energy specifically includes: fitting all focused energy into a fault diagnosis spectrum of the cable accessory; traceably positioning the fault accessory on the cable according to the position coordinates of each positioning peak in the fault diagnosis spectrum.

8. A cable accessory fault location system employing the method of any one of claims 1 to 7 for cable accessory fault location, characterised in that, The cable accessory fault positioning system includes: a collection module configured to inject a continuous linear frequency modulation signal into the cable through a circulator and collect reflection signals reflected by the linear frequency modulation signal at multiple impedance discontinuities in the cable accessory; a processing module configured to arrange all the reflection signals according to reflection positions into a reflection signal sequence, select a first reflection signal in the reflection signal sequence as a selected signal, and extract a non-linear component from the selected signal; the processing module is further configured to determine an electric field distortion coefficient at the reflection position corresponding to the selected signal according to an amplitude-frequency characteristic of the non-linear component, and identify a bubble migration caused by insulation interface discharge at the reflection position corresponding to the selected signal according to the electric field distortion coefficient; the processing module is further configured to correct the amplitude and phase of a next reflection signal in the reflection signal sequence based on the bubble migration, and take the reflection signal after the gap correction as a new selected signal, repeat the above steps until the amplitude and phase of a last reflection signal in the reflection signal sequence are corrected; an execution module configured to identify focused energy at each position on the cable according to the linear frequency modulation signal and each gap-corrected reflection signal, and traceably position the fault accessory on the cable through positioning peaks of all focused energy.

9. A computer device, comprising: The computer device includes a memory and a processor, the memory stores a code, and the processor is configured to acquire the code and execute the cable accessory fault positioning method according to any one of claims 1 to 7.

10. A computer-readable storage medium storing a computer program, the computer program comprising instructions that, when executed by a computer, cause the computer to perform the method of any one of claims 1 to 9. The computer program is executed by the processor to implement the cable accessory fault positioning method according to any one of claims 1 to 7.

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