Cable insulation fault location method, device, terminal and storage medium

Abstract

The present invention provides a method, device, terminal and storage medium for locating cable insulation faults, the method comprising: obtaining a broadband impedance spectrum of a cable obtained by applying an incident signal to the cable; calculating a time domain spectrum of a reflected signal based on a time domain spectrum of the incident signal and a broadband impedance spectrum; determining a positioning spectrum based on the time domain spectrum of the reflected signal and the propagation speed of the incident signal; wherein the positioning spectrum includes the amplitude of the reflected signal corresponding to each position on the cable; determining the insulation fault type of the cable, or the insulation fault type and insulation fault position of the cable based on each reflected signal amplitude in the positioning spectrum; wherein the insulation fault type includes capacitive insulation fault and / or resistive insulation fault. The present invention converts the broadband impedance spectrum of the cable reflection signal into a positioning spectrum, and the insulation fault type of the cable can be determined only by the amplitude of the reflected signal at each coordinate in the positioning spectrum, which can improve the efficiency of cable detection.

Description

Technical Field

[0001] The present invention relates to the technical field of cable diagnosis, and in particular to a method, device, terminal and storage medium for locating cable insulation faults. Background Art

[0002] In the operation of cables, different types of faults often occur due to insulation damage. Among the current cable insulation faults, only resistive faults are generally considered. In addition to resistive faults, there are also some local faults in the cable insulation, that is, there is no overall breakdown of the insulation, but only partial breakdown and damage in the insulation. The insulation resistance of the cable has not decayed by several orders of magnitude. Due to the large insulation margin reserved in the cable manufacturing, its insulation can still withstand higher voltages. However, the existence of this type of insulation fault will affect the change of the capacitance parameter in the cable characteristic impedance, thereby causing changes in the local characteristic impedance.

[0003] At present, the detection and positioning methods for resistive faults mainly rely on traveling wave positioning method, sound positioning method, etc., while the positioning method for capacitive faults is mainly based on partial discharge signal positioning. To achieve the positioning and detection of different types of insulation faults in cables, multiple systems need to work together to complete it, and the detection efficiency is low. Summary of the invention

[0004] The embodiments of the present invention provide a method, device, terminal and storage medium for locating cable insulation faults to solve the problem of low cable detection efficiency.

[0005] In a first aspect, an embodiment of the present invention provides a method for locating a cable insulation fault, comprising:

[0006] Acquire a broadband impedance spectrum of the cable by applying an incident signal to the cable;

[0007] Calculate the time domain spectrum of the reflected signal based on the time domain spectrum of the incident signal and the broadband impedance spectrum;

[0008] Determine a positioning spectrum based on the time domain spectrum of the reflected signal and the propagation speed of the incident signal; wherein the positioning spectrum includes the amplitude of the reflected signal corresponding to each position on the cable;

[0009] The insulation fault type of the cable, or the insulation fault type and insulation fault location of the cable is determined based on the amplitude of each reflected signal in the positioning spectrum; wherein the insulation fault type includes capacitive insulation fault and / or resistive insulation fault.

[0010] In a possible implementation, determining the insulation fault type of the cable based on the amplitude of each reflected signal in the positioning map includes:

[0011] If there are two upward convex peaks in the positioning map, and the distance between the two upward convex peaks is less than a preset threshold, the insulation fault type of the cable is a capacitive insulation fault.

[0012] In a possible implementation, determining the insulation fault type of the cable based on the amplitude of each reflected signal in the positioning map includes:

[0013] If there is a concave peak in the positioning spectrum, the insulation fault type of the cable is resistive insulation fault.

[0014] In a possible implementation, calculating the time domain spectrum of the reflected signal based on the time domain spectrum and the broadband impedance spectrum of the incident signal includes:

[0015] The self-reflection coefficient of each section of the cable is calculated based on the broadband impedance spectrum. The calculation formula is:

[0016]

[0017] The cable segment containing the load end is segment 0, the impedance mismatch point is the node between each cable segment, n is a natural number, Z (n) is the broadband impedance spectrum of the nth cable segment, S (n) represents the reflection coefficient of the nth cable segment, Z 0 (n) represents the characteristic impedance of the nth section of cable;

[0018] Based on the target window function, the time domain spectrum of the incident signal and the self-reflection coefficient of each cable segment, the time domain spectrum of the reflected signal is calculated by the inverse fast Fourier transform algorithm. The calculation formula is:

[0019] S i (w) = FFT(s i (t))

[0020] s r (t) = abs[IFFT(S i (w)W(N)S (n)* )]

[0021] Among them, s i (t) is the time domain spectrum of the incident signal, S i (w) is the frequency domain spectrum of the incident signal, W(N) is the target window function, and its length N is equal to S i The number of sampling points of (w), S (n)* For S (n) The conjugate extended signal of the negative frequency domain is equal to the conjugate of the corresponding positive frequency domain value, S (n) is the self-reflection coefficient of the nth cable segment, s r (t) is the time domain spectrum of the reflected signal.

[0022] In a possible implementation, the target window function is a Blackman window function.

[0023] In a possible implementation, determining a positioning spectrum based on a time domain spectrum of a reflected signal and a propagation speed of an incident signal includes:

[0024] The time domain spectrum of the reflected signal is multiplied by the propagation speed of the incident signal to obtain the spatial domain spectrum of the reflected signal, and the spatial domain spectrum is used as the positioning map.

[0025] In a second aspect, an embodiment of the present invention provides a device for locating a cable insulation fault, comprising:

[0026] An acquisition module, used for acquiring a broadband impedance spectrum obtained by applying an incident signal to the cable;

[0027] A time domain calculation module, used for calculating the time domain spectrum of the reflected signal based on the time domain spectrum and the broadband impedance spectrum of the incident signal;

[0028] A spatial calculation module, used to determine a positioning spectrum based on a time domain spectrum of a reflected signal and a propagation speed of an incident signal; wherein the positioning spectrum includes an amplitude of a reflected signal corresponding to each position on the cable;

[0029] The fault determination module is used to determine the insulation fault type of the cable based on the amplitude of each reflected signal in the positioning spectrum.

[0030] In a third aspect, an embodiment of the present invention provides a terminal, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the steps of the method described in the first aspect or any possible implementation manner of the first aspect are implemented.

[0031] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the method described in the first aspect or any possible implementation method of the first aspect are implemented.

[0032] The present invention provides a method, device, terminal and storage medium for locating cable insulation faults, the method comprising: obtaining a broadband impedance spectrum of a cable obtained by applying an incident signal to the cable; calculating a time domain spectrum of a reflected signal based on a time domain spectrum of the incident signal and a broadband impedance spectrum; determining a positioning spectrum based on the time domain spectrum of the reflected signal and the propagation speed of the incident signal; wherein the positioning spectrum includes the amplitude of the reflected signal corresponding to each position on the cable; determining the insulation fault type of the cable, or the insulation fault type and insulation fault position of the cable based on each reflected signal amplitude in the positioning spectrum; wherein the insulation fault type includes capacitive insulation fault and / or resistive insulation fault. The present invention converts the broadband impedance spectrum of the cable reflection signal into a positioning spectrum, and the insulation fault type of the cable can be determined only by the amplitude of the reflected signal at each coordinate in the positioning spectrum, without the need for partial discharge, and without the need for adding additional operations and calculation processes, thereby improving the efficiency of cable detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0034] Figure 1 This is an application scenario diagram of a cable insulation fault location method provided by an embodiment of the present invention;

[0035] Figure 2 is a flow chart of an implementation of a method for locating a cable insulation fault provided by an embodiment of the present invention;

[0036] Figure 3 It is a positioning spectrum corresponding to different incident signals provided by an embodiment of the present invention;

[0037] Figure 4 is a schematic diagram of an equivalent circuit of cable transmission parameters provided by an embodiment of the present invention;

[0038] Figure 5 It is a positioning map of a simulated cable model provided by an embodiment of the present invention;

[0039] Figure 6 It is a positioning map of a simulated cable model provided by an embodiment of the present invention;

[0040] Figure 7 It is a positioning map of a simulated cable model provided by an embodiment of the present invention;

[0041] Figure 8 It is a positioning spectrum before and after windowing of the reflection signal provided by an embodiment of the present invention;

[0042] Fig. 9 It is a structural schematic diagram of a cable insulation fault positioning device provided by an embodiment of the present invention;

[0043] Fig.10 is a schematic diagram of a terminal provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0044] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention.

[0045] In order to make the purpose, technical solutions and advantages of the present invention more clear, specific embodiments will be described below in conjunction with the accompanying drawings.

[0046] Figure 1 This is an application scenario diagram of the cable insulation fault location method provided by an embodiment of the present invention. Figure 1 As shown, the terminal of the tested cable is electrically connected to the switch cabinet, transformer and other equipment, and the other end of the cable can be open or short-circuited. Use alligator clips to connect the core conductor of the cable and the ground shield layer respectively, and then connect the alligator clips to the No. 1 test port of the network analyzer, and use the S11 mode to measure its broadband impedance spectrum. After the impedance spectrum measurement is completed, the method provided by the present invention is used to determine the positioning spectrum, and then determine the insulation fault type and insulation fault location in the tested cable.

[0047] See also Figure 2 , which shows a flow chart of the implementation of the cable insulation fault location method provided by an embodiment of the present invention, and is described in detail as follows:

[0048] Step 201 : obtaining a broadband impedance spectrum of the cable obtained by applying an incident signal to the cable.

[0049] In this embodiment, at present, the technology of positioning using broadband impedance spectroscopy (BIS) mainly adopts the method of directly performing an inverse fast Fourier transform algorithm (IFFT) on the characteristic parameters related to BIS or reflection coefficient. Such an algorithm actually sets the incident signal to a swept frequency signal with a constant power spectrum. The swept frequency signal has been applied when measuring BIS with a network analyzer. Compared with the pulse signal used by TDR, its power distribution is uniform, and the attenuation and dispersion probability of the traveling wave during the conduction process is low. After obtaining BIS, when the swept frequency signal is used for algorithm calculation, due to the large high-frequency signal component, truncation with any window function will cause time domain aliasing of the signal, generating a large amount of ripples in the time domain, namely the Gibbs effect. Figure 3 The positioning spectra of different incident signals are compared. Since the power of Gaussian pulse is concentrated in the frequency domain, the distortion of the original waveform is small when the high-frequency part is cut off, which weakens the oscillation of the reflected signal during the conduction process. Compared with the traditional time domain reflectometry (TDR), this embodiment selects Gaussian pulse as the incident signal to ensure that the signal is less attenuated when transmitted in the cable.

[0050] Step 202: Calculate the time domain spectrum of the reflected signal based on the time domain spectrum and the broadband impedance spectrum of the incident signal.

[0051] In this embodiment, a time domain reflection signal (TDR signal) is obtained by an inverse fast Fourier transform algorithm (IFFT), and the calculation formula is as follows:

[0052] S i (w) = FFT(s i (t))

[0053] s r (t) = abs[IFFT(S i (w)W(N)S (n)* )]

[0054] Among them, s i (t) and S i (w) are the time domain spectrum and frequency domain spectrum of the incident signal, respectively. The frequency domain signal contains positive and negative spectra; W(N) is the window function, whose length N is equal to S i (w) the number of sampling points; S (n)* For S (n) The conjugate extended signal of the negative frequency domain is equal to the conjugate of the corresponding positive frequency domain value, S (n) is the self-reflection coefficient of the nth cable segment; s r (t) is the time domain spectrum of the reflected signal, which reflects the transmission process of the reflected signal in the time domain.

[0055] Step 203: Determine a positioning spectrum based on the time domain spectrum of the reflected signal and the propagation speed of the incident signal, wherein the positioning spectrum includes the amplitude of the reflected signal corresponding to each position on the cable.

[0056] In this embodiment, the cable positioning signal can be obtained by multiplying the time domain spectrum by the propagation speed of the signal in the cable. The propagation speed of the traveling wave signal in the medium can be approximately calculated using the following formula:

[0057]

[0058] s r (l) = 2vs r (t)

[0059] Where v is the propagation speed of electromagnetic waves in power cables, which is approximately equal to 1.978×10 8 m / s,μ 0 is the vacuum permeability, ε 0 represents the vacuum dielectric constant, ε r Indicates the relative dielectric constant of the cross cable material, s r (l) is the spatial domain spectrum of the reflected signal, and this embodiment uses the signal as a positioning spectrum.

[0060] Step 204, determining the insulation fault type of the cable, or the insulation fault type and insulation fault location of the cable based on the amplitudes of each reflected signal in the positioning map; wherein the insulation fault type includes capacitive insulation fault and / or resistive insulation fault.

[0061] In this embodiment, among the current cable insulation faults, only resistive insulation faults are generally considered, and according to the type of resistive insulation fault, it is divided into high-resistance insulation fault and low-resistance insulation fault. A fault in which the DC resistance at the cable fault point is greater than the cable characteristic impedance is a high-resistance insulation fault; a fault in which the DC resistance at the cable fault point is less than the cable characteristic impedance is a low-resistance insulation fault. In addition to the above-mentioned insulation faults, there are also some local faults of cable insulation in the cable, that is, there is no overall breakdown of the insulation, but only partial breakdown and damage in the insulation (such as defects such as electric trees and water trees generated in the cable insulation). The insulation resistance of the cable has not decayed by several orders of magnitude. Due to the large insulation margin reserved in the cable manufacturing, its insulation can still withstand higher voltages. However, the existence of this type of insulation fault will affect the change of the capacitance parameter in the cable characteristic impedance, thereby causing a change in the local characteristic impedance. This type of local insulation fault is a capacitive insulation fault.

[0062] In a possible implementation, determining the insulation fault type of the cable based on the amplitude of each reflected signal in the positioning map includes:

[0063] If there are two upward convex peaks in the positioning map, and the distance between the two upward convex peaks is less than a preset threshold, the insulation fault type of the cable is a capacitive insulation fault.

[0064] In this embodiment, the relationship between the insulation fault type of the cable and the location map is determined through simulation experiments. The specific derivation and simulation process is as follows:

[0065] First, the length of the simulated cable is set to 1 km. The simulated spectrum range is 100 kHz to 100 MHz, the spectrum sampling step is 100 kHz, and the simulation parameter settings of the 10 kV cable are shown in Table 1:

[0066] Table 1

[0067] Conductivity / (S / m) Relative dielectric constant Outer diameter / mm Thickness / mm Wire core <![CDATA[5.71×10 7 ]]> <![CDATA[1×10 4 ]]> 8 — Inner semiconductive layer <![CDATA[2×10 -3 ]]> 100 8.2 0.1 insulation <![CDATA[1×10 -17 ]]> 2.3 17.2 4.5 Outer semiconductive layer <![CDATA[2×10 4 ]]> 100 17.5 0.15 Copper shield <![CDATA[5.71×10 7 ]]> <![CDATA[1×10 4 ]]> 17.5 —

[0068] When an insulation fault occurs in the cable, the distribution parameters in this area will change. At this time, the cable transmission parameters can be equivalent to Figure 4 The impedance circuit shown. Set the cable segment including the load end as segment 0, the impedance mismatch point as the node between the cable segments, the nth segment of the cable includes the n-1th segment of the cable, and then calculate the BIS by recursion:

[0069]

[0070]

[0071] Where n is a natural number, Z (n-1) and Z (n) is the BIS of segment n-1 and segment n, S (n) represents the reflection coefficient of the nth segment, γ (n) represents the propagation coefficient of the nth segment, Z 0 (n) represents the characteristic impedance of the nth segment, l (n-1) and l (n) is the length of the n-1th and nth cable segments.

[0072] Among them, Z (n) The impedance spectrum parameters in the impedance transformation need to be calculated through the transfer function of the cable, and the cable positioning spectrum is further obtained through the transfer function. The impedance transformation formula is as follows:

[0073]

[0074] Among them, S (n) is the self-reflection coefficient of the nth cable segment, Z (n) is the BIS of the nth cable segment, Z ref (n) is the reference impedance of the nth cable segment. The calculation formula of the reference impedance is as follows:

[0075]

[0076] r c 、r s Respectively represent the radius of the core and metal shielding layer, μ 0 is the vacuum permeability, ε 0 represents the vacuum dielectric constant, ε r Represents the relative dielectric constant of cross-linked polyethylene.

[0077] Next, six groups of simulation cable models corresponding to different insulation fault types were established. The parameters of the simulation cables are shown in Table 2. 0 , C 0 The conductivity and capacitance distribution parameters of the cable without defects are shown in Table 1. The cable length is set to 1 km. The incident signal uses a Gaussian pulse function, the window function uses a Blackman window function, and the reference impedance is set to 30.95Ω.

[0078] Table 2

[0079] Group No. Conductivity distribution parameters Capacitance distribution parameters Fault location 1# <![CDATA[2G 0 ]]> <![CDATA[C 0 ]]> 595m~605m 2# <![CDATA[1×10 8 G 0 ]]> <![CDATA[C 0 ]]> 595m~605m 3# <![CDATA[G 0 ]]> <![CDATA[1.014C 0 ]]> 595m~605m 4# <![CDATA[G 0 ]]> <![CDATA[1.181C 0 ]]> 595m~605m 5# <![CDATA[2G 0 ]]> <![CDATA[1.181C 0 ]]> 595m~605m 6# <![CDATA[G 0 ~2G 0 ]]> <![CDATA[C 0 ~1.181C 0 ]]> 575m~625m

[0080] Figure 5 The positioning maps of cables 3# and 4# are shown, wherein cable 3# simulates the capacitance change in the early growth stage of insulation faults such as water trees and electrical trees. Such faults occurring locally in the cable insulation do not cause significant changes in insulation conductivity (the rate of change is less than 50%), and this tiny change in conductivity does not cause differences in the positioning maps, but the capacitance change caused by it has a very obvious effect on the cable positioning map; the positioning map of cable 4# simulates the capacitance change in the late growth stage of water trees and electrical trees. Figure 5 Two reflection peaks are shown, located at the beginning (594.43m) and the end (605.26m) of the fault section, with errors of 0.69‰ and 0.26‰ respectively. The influence of the capacitance effect on the positioning spectrum is reflected in the change point of the capacitance. The greater the change in capacitance, the greater the peak value of the reflection peak. Therefore, the local increase in capacitance shows the waveform characteristics of two superimposed reflection peaks on the positioning spectrum. In addition, it should be noted that the tail of the reflection peak wave will be partially leaked in the time domain, and the amplitude of the end of the reflection peak increases, which reduces the sensitivity of the defect end to detect other defects.

[0081] Figure 6 The positioning maps of 5# and 6# cables are shown, where the 5# cable simulates the situation where the conductivity and capacitance change simultaneously, and the changes of the conductivity parameters and capacitance parameters are set to be sudden changes at the defect point; the 6# cable and the 5# cable have the same parameter settings, except that a 20m transition zone is set at both ends of the defect of the 6# cable, and the conductivity and capacitance increase linearly and uniformly in the transition zone. Figure 6It can be seen that the fault sites of cables 5# and 6# both present two reflection peak waveforms, indicating that the capacitance parameter is the main reason for the reflection at the fault site. The reflection peak of cable 5# has a large peak value and a steeper peak, while the reflection peak of cable 6# has a smaller peak value and a smoother waveform. This confirms that when a capacitive defect occurs, the peak value of the reflection peak is positively correlated with the change in capacitance. In actual operation, when the cable has defects such as water seepage or water trees or electrical branches, the possibility of a sudden change in capacitance at a certain point is small. Therefore, when using the positioning map to evaluate the degree of capacitive defects, the degree of insulation fault development cannot be evaluated based solely on the peak value of the reflection peak. It is necessary to refer to the energy of the reflected wave (the integral of the reflection peak in the time domain) at the same time to obtain a more accurate evaluation result.

[0082] In a possible implementation, determining the insulation fault type of the cable based on the amplitude of each reflected signal in the positioning map includes:

[0083] If there is a concave peak in the positioning spectrum, the insulation fault type of the cable is resistive insulation fault.

[0084] In this embodiment, Figure 7 The location maps of cables 1# and 2# are shown, where cable 1# simulates a high-resistance fault with an extremely high resistance value, and cable 2# simulates a high-resistance fault with a relatively low resistance value. Figure 7 It can be seen that the weak conductivity change of cable 1# cannot be identified, which means that the change of cable insulation resistance less than 1 order of magnitude is unlikely to cause transflection phenomenon for broadband incident signals. When the insulation resistance is reduced to the MΩ level, the conductivity of the cable is about 10 -9 At this time, a reflection peak appears at 590m-610m in the positioning spectrum, and the peak value of the reflection peak is located at 600.69m, which is located at the fault center, with an error of 0.69‰. The peak value is reduced by 44.6% (6.88×10 -5 ).

[0085] In a possible implementation, calculating the time domain spectrum of the reflected signal based on the time domain spectrum and the broadband impedance spectrum of the incident signal includes:

[0086] The self-reflection coefficient of each section of the cable is calculated based on the broadband impedance spectrum. The calculation formula is:

[0087]

[0088] The cable segment containing the load end is segment 0, the impedance mismatch point is the node between each cable segment, n is a natural number, Z (n) is the broadband impedance spectrum of the nth cable segment, S (n) represents the reflection coefficient of the nth cable segment, Z 0 (n) represents the characteristic impedance of the nth section of cable;

[0089] Based on the target window function, the time domain spectrum of the incident signal and the self-reflection coefficient of each cable segment, the time domain spectrum of the reflected signal is calculated by the inverse fast Fourier transform algorithm. The calculation formula is:

[0090] S i (w) = FFT(s i (t))

[0091] s r (t) = abs[IFFT(S i (w)W(N)S (n)* )]

[0092] Among them, s i (t) is the time domain spectrum of the incident signal, S i (w) is the frequency domain spectrum of the incident signal, W(N) is the target window function, and its length N is equal to S i The number of sampling points of (w), S (n)* For S (n) The conjugate extended signal of the negative frequency domain is equal to the conjugate of the corresponding positive frequency domain value, S (n) is the self-reflection coefficient of the nth cable segment, s r (t) is the time domain spectrum of the reflected signal.

[0093] In this embodiment, the relationship between the broadband impedance spectrum and the cable self-reflection coefficient in the following formula can be used, and the cable self-reflection coefficient is taken as an unknown variable to calculate the self-reflection coefficient of each cable segment in the cable based on the broadband impedance spectrum:

[0094]

[0095]

[0096] The cable segment including the load end is segment 0, the impedance mismatch point is the node between the cable segments, n is a natural number, Z (n-1) and Z (n) is the BIS of the n-1th cable and the nth cable, S (n) represents the self-reflection coefficient of the nth cable segment, γ (n) represents the propagation coefficient of the nth cable segment, Z 0 (n) represents the characteristic impedance of the nth cable segment, l (n-1) and l (n) is the length of the n-1th and nth cable segments.

[0097] When performing inverse fast Fourier transform calculations, truncating the spectrum of a non-periodic function will cause spectrum leakage, while adding a window function can have a better suppressive effect on spectrum leakage. Figure 8The positioning map before and after windowing when there is no defect is shown. Figure 8 It can be seen that the introduction of the window function significantly reduces the vibration of the cable tail end signal and improves the recognition sensitivity.

[0098] In a possible implementation, the target window function is a Blackman window function.

[0099] In this embodiment, the Blackman window function has a better effect of suppressing the side lobes, and can greatly improve the sensitivity of recognition.

[0100] In a possible implementation, determining a positioning spectrum based on a time domain spectrum of a reflected signal and a propagation speed of an incident signal includes:

[0101] The time domain spectrum of the reflected signal is multiplied by the propagation speed of the incident signal to obtain the spatial domain spectrum of the reflected signal, and the spatial domain spectrum is used as the positioning map.

[0102] In this embodiment, the time domain spectrum is the amplitude of the signal at each moment. The amplitude of the signal at each position in the cable can be obtained by multiplying the time domain spectrum by the speed at which the signal propagates in the cable. Then, the cable insulation fault is located based on the space domain spectrum. The location of the abnormal amplitude is the location of the cable outlet insulation fault.

[0103] The method for locating cable insulation faults provided by an embodiment of the present invention includes: obtaining a broadband impedance spectrum of a cable obtained by applying an incident signal to the cable; calculating a time domain spectrum of a reflected signal based on a time domain spectrum of the incident signal and a broadband impedance spectrum; determining a positioning spectrum based on the time domain spectrum of the reflected signal and the propagation speed of the incident signal; wherein the positioning spectrum includes the amplitude of the reflected signal corresponding to each position on the cable; determining the insulation fault type of the cable, or the insulation fault type and insulation fault position of the cable based on each reflected signal amplitude in the positioning spectrum; wherein the insulation fault type includes capacitive insulation fault and / or resistive insulation fault. Through the present invention, the broadband impedance spectrum of the cable reflection signal is converted into a positioning spectrum, and the insulation fault type of the cable can be determined only by the amplitude of the reflected signal at each coordinate in the positioning spectrum, without the need for partial discharge, and without the need to add additional operations and calculation processes, thereby improving the efficiency of cable detection.

[0104] It should be understood that the order of execution of the steps in the above embodiment does not necessarily mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0105] The following is an embodiment of the device of the present invention. For details not described in detail therein, reference may be made to the corresponding method embodiment described above.

[0106] Fig. 9The following is a schematic diagram showing the structure of a cable insulation fault location device provided by an embodiment of the present invention. For ease of description, only the parts related to the embodiment of the present invention are shown, which are described in detail as follows:

[0107] like Fig. 9 As shown, the cable insulation fault positioning device 9 includes:

[0108] An acquisition module 91 is used to acquire a broadband impedance spectrum obtained by applying an incident signal to the cable;

[0109] A time domain calculation module 92, used to calculate the time domain spectrum of the reflected signal based on the time domain spectrum and the broadband impedance spectrum of the incident signal;

[0110] A spatial calculation module 93, used to determine a positioning spectrum based on the time domain spectrum of the reflected signal and the propagation speed of the incident signal; wherein the positioning spectrum includes the amplitude of the reflected signal corresponding to each position on the cable;

[0111] The fault determination module 94 is used to determine the insulation fault type of the cable based on the amplitude of each reflection signal in the positioning spectrum.

[0112] In a possible implementation, the fault determination module 94 is specifically configured to:

[0113] When there are two upward convex peaks in the positioning map and the distance between the two upward convex peaks is less than a preset threshold, it is determined that the insulation fault type of the cable is a capacitive insulation fault.

[0114] In a possible implementation, the fault determination module 94 is specifically configured to:

[0115] When there is a concave peak in the positioning spectrum, it is determined that the insulation fault type of the cable is a resistive insulation fault.

[0116] In a possible implementation, the time domain calculation module 92 is specifically used for:

[0117] The self-reflection coefficient of each section of the cable is calculated based on the broadband impedance spectrum. The calculation formula is:

[0118]

[0119] The cable segment containing the load end is segment 0, the impedance mismatch point is the node between each cable segment, n is a natural number, Z (n) is the broadband impedance spectrum of the nth cable segment, S (n) represents the reflection coefficient of the nth cable segment, Z 0 (n) represents the characteristic impedance of the nth section of cable;

[0120] Based on the target window function, the time domain spectrum of the incident signal and the self-reflection coefficient of each cable segment, the time domain spectrum of the reflected signal is calculated by the inverse fast Fourier transform algorithm. The calculation formula is:

[0121] S i (w) = FFT(s i (t))

[0122] s r (t) = abs[IFFT(S i (w)W(N)S (n)* )]

[0123] Among them, s i (t) is the time domain spectrum of the incident signal, S i (w) is the frequency domain spectrum of the incident signal, W(N) is the target window function, and its length N is equal to S i The number of sampling points of (w), S (n)* For S (n) The conjugate extended signal of the negative frequency domain is equal to the conjugate of the corresponding positive frequency domain value, S (n) is the self-reflection coefficient of the nth cable segment, s r (t) is the time domain spectrum of the reflected signal.

[0124] In a possible implementation, the target window function is a Blackman window function.

[0125] In a possible implementation, the space calculation module 93 is specifically used for:

[0126] The time domain spectrum of the reflected signal is multiplied by the propagation speed of the incident signal to obtain the spatial domain spectrum of the reflected signal, and the spatial domain spectrum is used as the positioning map.

[0127] The cable insulation fault positioning device provided by the embodiment of the present invention includes: an acquisition module, which is used to obtain a broadband impedance spectrum obtained by applying an incident signal to the cable; a time domain calculation module, which is used to calculate the time domain spectrum of the reflected signal based on the time domain spectrum of the incident signal and the broadband impedance spectrum; a spatial calculation module, which is used to determine the positioning spectrum based on the time domain spectrum of the reflected signal and the propagation speed of the incident signal; wherein the positioning spectrum includes the reflected signal amplitude corresponding to each position on the cable; and a fault determination module, which is used to determine the insulation fault type of the cable based on each reflected signal amplitude in the positioning spectrum. The present invention converts the broadband impedance spectrum of the cable reflection signal into a positioning spectrum, and the insulation fault type of the cable can be determined only by the reflected signal amplitude of each coordinate in the positioning spectrum, without the need for partial discharge, and without adding additional operations and calculation processes, which can improve the efficiency of cable detection.

[0128] Fig.10 is a schematic diagram of a terminal provided by an embodiment of the present invention. Fig.10As shown, the terminal 10 of this embodiment includes: a processor 100, a memory 101, and a computer program 102 stored in the memory 101 and executable on the processor 100. When the processor 100 executes the computer program 102, the steps in the above-mentioned embodiments of the method for locating the cable insulation fault are implemented, for example, Figure 2 Alternatively, when the processor 100 executes the computer program 102, the functions of the modules in the above-mentioned device embodiments are realized, for example, Fig. 9 The functions of modules 91 to 94 are shown.

[0129] Exemplarily, the computer program 102 may be divided into one or more modules / units, which are stored in the memory 101 and executed by the processor 100 to implement the present invention. The one or more modules / units may be a series of computer program instruction segments capable of implementing specific functions, which are used to describe the execution process of the computer program 102 in the terminal 10. For example, the computer program 102 may be divided into Fig. 9 Modules 91 to 94 are shown.

[0130] The terminal 10 may be a computing device such as a desktop computer, a notebook, a PDA, or a cloud server. The terminal 10 may include, but is not limited to, a processor 100 and a memory 101. Those skilled in the art will appreciate that Fig.10 It is only an example of the terminal 10 and does not constitute a limitation on the terminal 10. The terminal 10 may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, the terminal may also include input and output devices, network access devices, buses, etc.

[0131] The processor 100 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc.

[0132] The memory 101 may be an internal storage unit of the terminal 10, such as a hard disk or memory of the terminal 10. The memory 101 may also be an external storage device of the terminal 10, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card (FlashCard), etc. equipped on the terminal 10. Further, the memory 101 may also include both an internal storage unit of the terminal 10 and an external storage device. The memory 101 is used to store the computer program and other programs and data required by the terminal. The memory 101 may also be used to temporarily store data that has been output or is to be output.

[0133] The technicians in the relevant field can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In practical applications, the above-mentioned function allocation can be completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated in a processing unit, or each unit can exist physically separately, or two or more units can be integrated in one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of this application. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, which will not be repeated here.

[0134] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0135] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0136] In the embodiments provided by the present invention, it should be understood that the disclosed devices / terminals and methods can be implemented in other ways. For example, the device / terminal embodiments described above are only schematic. For example, the division of the modules or units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0137] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0138] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0139] If the integrated module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by the processor, the steps of the above-mentioned cable insulation fault positioning method embodiments can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device that can carry the computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signal, telecommunication signal and software distribution medium. It should be noted that the content contained in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practices in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practices, computer-readable media does not include electrical carrier signals and telecommunication signals.

[0140] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A method for locating cable insulation faults, characterized in that: include: Acquire a broadband impedance spectrum of the cable by applying an incident signal to the cable; Calculate the time domain spectrum of the reflected signal based on the time domain spectrum of the incident signal and the broadband impedance spectrum; Determine a positioning spectrum based on the time domain spectrum of the reflected signal and the propagation speed of the incident signal; wherein the positioning spectrum includes the amplitude of the reflected signal corresponding to each position on the cable; Determining the insulation fault type of the cable, or the insulation fault type and insulation fault location of the cable based on the amplitude of each reflected signal in the positioning spectrum; wherein the insulation fault type includes capacitive insulation fault and / or resistive insulation fault; The calculating the time domain spectrum of the reflected signal based on the time domain spectrum of the incident signal and the broadband impedance spectrum comprises: The self-reflection coefficient of each section of the cable is calculated based on the broadband impedance spectrum, and the calculation formula is: The cable segment containing the load end is segment 0, the impedance mismatch point is the node between each cable segment, n is a natural number, Z (n) is the broadband impedance spectrum of the nth cable segment, S (n) represents the reflection coefficient of the nth cable segment, Z0 (n) represents the characteristic impedance of the nth section of cable; Based on the target window function, the time domain spectrum of the incident signal and the self-reflection coefficient of each cable segment, the time domain spectrum of the reflected signal is calculated by the inverse fast Fourier transform algorithm. The calculation formula is: S i (w)=FFT(s i (t)) s r (t)=abs[IFFT(S i (w)W(N)S (n)* )] Among them, s i (t) is the time domain spectrum of the incident signal, S i (w) is the frequency domain spectrum of the incident signal, W(N) is the target window function, and its length N is equal to S i The number of sampling points of (w), S (n)* For S (n) The conjugate extended signal of the negative frequency domain is equal to the conjugate of the corresponding positive frequency domain value, S (n) is the self-reflection coefficient of the nth cable segment, s r (t) is the time domain spectrum of the reflected signal.

2. The method for locating cable insulation fault according to claim 1, characterized in that: The determining the insulation fault type of the cable based on the amplitude of each reflected signal in the positioning spectrum includes: If there are two upward convex peaks in the positioning map, and the distance between the two upward convex peaks is less than a preset threshold, then the insulation fault type of the cable is a capacitive insulation fault.

3. The method for locating cable insulation fault according to claim 1, characterized in that: The determining the insulation fault type of the cable based on the amplitude of each reflected signal in the positioning spectrum includes: If there is a concave peak in the positioning map, the insulation fault type of the cable is a resistive insulation fault.

4. The method for locating cable insulation fault according to claim 1, characterized in that: The target window function is a Blackman window function.

5. The method for locating cable insulation fault according to any one of claims 1 to 4, characterized in that: The determining of the positioning spectrum based on the time domain spectrum of the reflected signal and the propagation speed of the incident signal includes: The time domain spectrum of the reflected signal is multiplied by the propagation speed of the incident signal to obtain the space domain spectrum of the reflected signal, and the space domain spectrum is used as a positioning spectrum.

6. A device for locating cable insulation faults, characterized in that: include: An acquisition module, used for acquiring a broadband impedance spectrum obtained by applying an incident signal to the cable; A time domain calculation module, used to calculate the time domain spectrum of the reflected signal based on the time domain spectrum of the incident signal and the broadband impedance spectrum; A spatial calculation module, used to determine a positioning spectrum based on the time domain spectrum of the reflected signal and the propagation speed of the incident signal; wherein the positioning spectrum includes the amplitude of the reflected signal corresponding to each position on the cable; A fault determination module, used to determine the insulation fault type of the cable based on the amplitude of each reflected signal in the positioning spectrum; The time domain calculation module is specifically used for: The self-reflection coefficient of each section of the cable is calculated based on the broadband impedance spectrum, and the calculation formula is: The cable segment containing the load end is segment 0, the impedance mismatch point is the node between each cable segment, n is a natural number, Z (n) is the broadband impedance spectrum of the nth cable segment, S (n) represents the reflection coefficient of the nth cable segment, Z0 (n) represents the characteristic impedance of the nth section of cable; Based on the target window function, the time domain spectrum of the incident signal and the self-reflection coefficient of each cable segment, the time domain spectrum of the reflected signal is calculated by the inverse fast Fourier transform algorithm. The calculation formula is: S i (w)=FFT(s i (t)) s r (t)=abs[IFFT(S i (w)W(N)S (n)* )] Among them, s i (t) is the time domain spectrum of the incident signal, S i (w) is the frequency domain spectrum of the incident signal, W(N) is the target window function, and its length N is equal to S i The number of sampling points of (w), S (n)* For S (n) The conjugate extended signal of the negative frequency domain is equal to the conjugate of the corresponding positive frequency domain value, S (n) is the self-reflection coefficient of the nth cable segment, s r (t) is the time domain spectrum of the reflected signal.

7. The cable insulation fault positioning device according to claim 6, characterized in that: The fault determination module is specifically used for: When there are two upward convex peaks in the positioning map and the distance between the two upward convex peaks is less than a preset threshold, it is determined that the insulation fault type of the cable is a capacitive insulation fault.

8. A terminal comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method for locating a cable insulation fault as claimed in any one of claims 1 to 5 are implemented.

9. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the method for locating cable insulation faults as claimed in any one of claims 1 to 5 are implemented.

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