Method and device for positioning cable hidden danger defect based on broadband characteristic impedance spectroscopy, electronic equipment and storage medium

Abstract

The invention discloses a method and device for positioning cable hidden danger defects based on broadband characteristic impedance spectroscopy, electronic equipment and a storage medium. The method comprises the following steps: measuring a head end broadband characteristic impedance spectrum when the tail end of a to-be-measured cable is open-circuited and short-circuited; calculating a characteristic impedance spectrum according to the open-circuit and short-circuit impedance spectrums; obtaining a reference pseudo frequency according to the relative dielectric constant of the main insulating layer of the to-be-measured cable; determining a reference frequency list based on the reference pseudo frequency; analyzing the characteristic impedance spectrum by adopting a digital lock-in amplifier analysis algorithm; and determining the position of the hidden defect in the cable according to the analysis result. According to the method, parameter information such as a propagation coefficient rule and an impedance spectrum reference value of a healthy cable does not need to be obtained, the limitation of an existing FFT method and an IT method is solved, high-precision positioning of weak hidden danger defects of the cable is achieved, the frequency domain reflection method based on the broadband impedance spectrum has more practical operation performance, and the method is suitable for preventive maintenance of an electric power system and has good application prospects. And the method has higher field application capability.

Description

Technical Field

[0001] The present disclosure relates to the field of electrical engineering, and particularly to a method, apparatus, electronic device, and storage medium for locating hidden dangers and defects of a cable based on a broadband characteristic impedance spectrum. Background Art

[0002] The frequency domain reflectometry has the potential to identify weak faults in power cables, and the cable impedance spectrum is the main object of study in the frequency domain reflectometry. Through the frequency domain reflectometry, potential hidden dangers and defects in power cables can be detected in advance, avoiding losses that may be caused by their development into serious faults, which is of great significance for the operation and maintenance inspection of cables.

[0003] Currently, the main objects of study in the frequency domain reflectometry are the cable's beginning impedance spectrum (BIS) and reflection coefficient spectrum (RCS). When testing, the cable end needs to be kept open or short-circuited. The analysis paradigm is to design an algorithm for a test result. In the currently disclosed analysis algorithms, the fast Fourier transform (FFT) or integral transform (IT) method is mainly used to analyze the cable impedance spectrum. However, both of these methods have their respective drawbacks.

[0004] The FFT method analyzes the tested impedance spectrum alone, and the obtained positioning step size is affected by the selected time window and sampling rate, and it is lacking in locating more minute hidden dangers and defects.

[0005] The IT method needs to analyze the healthy impedance spectrum and the tested impedance spectrum together. By comparing the difference in the analysis results of the integral transforms of the two impedance spectra, more minute defects are located. However, the kernel function used in the integral transform needs to accurately know the law of the propagation coefficient of the ideal healthy cable with frequency change, and the impedance spectrum of the healthy cable needs to be known, which has problems in actual operation. For cables in service, they can be tested in advance. For cables that have been in service, testing cannot be achieved, and only the ideal cable impedance spectrum can be calculated based on all the structural parameters and electrical parameters of the ideal healthy cable. However, this is very difficult in actual operation because it is impossible to accurately know each parameter that affects the impedance spectrum of the healthy cable, which will affect the final test result.

[0006] Therefore, a technical solution that can locate more minute hidden dangers and defects of the cable and overcome the drawbacks of existing solutions is needed. Summary of the Invention

[0007] The present disclosure proposes a solution for locating hidden dangers and defects of a power cable based on a broadband characteristic impedance spectrum, which can achieve precise positioning of minute defects without accurately knowing the law of the propagation coefficient and impedance spectrum of the healthy cable.

[0008] According to an embodiment of the present disclosure, a method for locating hidden dangers and defects of a cable based on a broadband characteristic impedance spectrum is proposed, including:

[0009] Measure the broadband characteristic impedance spectrum Z of the first end when the end of the cable under test is open-circuited open and measure the broadband characteristic impedance spectrum Z of the first end when the end of the cable under test is short-circuited short ;

[0010] Calculate the broadband characteristic impedance spectrum Z of the cable under test according to the following formula char :

[0011] Z char (i) = sqrt(Z open (i) * Z short (i)),

[0012] where Z open (i) represents the i-th data point in the broadband characteristic impedance spectrum Z open of the first end, and Z short (i) represents the i-th data point in the broadband characteristic impedance spectrum Z short of the first end, and Z char (i) represents the i-th data point in the broadband characteristic impedance spectrum Z char ; sqrt represents the square root operation;

[0013] Obtain a reference pseudo-frequency for determining the frequency interval of impedance spectrum analysis according to the relative dielectric constant of the main insulation layer of the cable under test;

[0014] Determine a list of reference frequencies corresponding to each data point to be analyzed in the positioning interval to be analyzed of the cable under test based on the reference pseudo-frequency;

[0015] Using the list of reference frequencies, analyze the broadband characteristic impedance spectrum Z of the cable under test as a pseudo-time domain signal based on the digital lock-in amplifier analysis algorithm to obtain an analysis result DLIA(Z char ); char )

[0016] Determine the location of potential defects in the cable according to DLIA(Z char ).

[0017] In some embodiments, measuring the broadband characteristic impedance spectrum Z of the first end when the end of the cable under test is open-circuited open and measuring the broadband characteristic impedance spectrum Z of the first end when the end of the cable under test is short-circuited short , including:

[0018] Select a preset number of discrete frequency points within a preset frequency range;

[0019] Measure the impedance value of the first end of the cable under test at each discrete frequency point when the end is open-circuited to obtain the broadband characteristic impedance spectrum Z open ;

[0020] Measure the impedance values at the head end of the cable to be measured at each discrete frequency point when the end of the cable to be measured is short - circuited, and obtain the head - end broadband characteristic impedance spectrum Z short .

[0021] In some embodiments, the reference pseudo - frequency f is obtained according to the following formula 0 :

[0022] f 0 = 2*sqrt(epsilon) / (c*N 0 ),

[0023] where epsilon is the relative permittivity of the main insulation layer of the cable to be measured, c is the speed of light, and N 0 is the number of data points analyzed per meter.

[0024] In some embodiments, according to the following formula, determine the reference frequency list F corresponding to each data point to be analyzed in the positioning interval to be analyzed

[0025] F = [l 1 *N 0 *f 0 :f 0 :l 2 *N 0 *f 0 ,

[0026] where [l 1 *N 0 *f 0 :f 0 :l 2 *N 0 *f 0 represents an arithmetic progression from l 1 *N 0 *f 0 to l 2 *N 0 *f 0 with a step size of f 0 , where l 1 and l 2 are the start and end points of the positioning interval to be analyzed, and f 0 is the reference pseudo - frequency.

[0027] In some embodiments, using the reference frequency list, based on the digital lock - in amplifier analysis algorithm, analyze the broadband characteristic impedance spectrum Z of the cable to be measured char as a pseudo - time - domain signal to obtain the analysis result DLIA(Z char ), including: for the k - th data point to be analyzed,

[0028] Select cos(w kt) as the first reference signal, multiply it with the broadband characteristic impedance spectrum Z char and obtain the X component through low-pass filtering, where w k is the k-th frequency in the reference frequency list;

[0029] Select sin(w k t) as the second reference signal, multiply it with the broadband characteristic impedance spectrum Z char and obtain the Y component through low-pass filtering;

[0030] According to the X and / or Y components, obtain the analysis result corresponding to the k-th data point to be analyzed.

[0031] In some embodiments, determining the location of potential defects in the cable according to DLIA(Z char ) includes:

[0032] Identifying peak points in the waveform diagram of DLIA(Z char );

[0033] Determine the location where potential defects exist according to the abscissa corresponding to the peak points.

[0034] According to an embodiment of the present disclosure, a device for locating potential defects in a cable based on a broadband characteristic impedance spectrum is also proposed, including:

[0035] An open-circuit and short-circuit impedance measurement unit for measuring the broadband characteristic impedance spectrum Z open at the head end when the end of the cable under test is open-circuited, and measuring the broadband characteristic impedance spectrum Z short at the head end when the end of the cable under test is short-circuited;

[0036] A broadband characteristic impedance calculation unit for calculating the broadband characteristic impedance spectrum Z char of the cable under test according to the following formula:

[0037] Z char (i) = sqrt(Z open (i) * Z short (i)),

[0038] where Z open (i) represents the i-th data point in the head-end broadband characteristic impedance spectrum Z open , Z short (i) represents the i-th data point in the head-end broadband characteristic impedance spectrum Z short , Z char (i) represents the i-th data point in the broadband characteristic impedance spectrum Z char , and sqrt represents the square root operation;

[0039] A reference pseudo-frequency calculation unit, configured to obtain a reference pseudo-frequency for determining an impedance spectrum analysis frequency interval according to the relative permittivity of the main insulation layer of the cable to be measured;

[0040] A reference frequency list calculation unit, configured to determine a reference frequency list corresponding to each data point to be analyzed in the positioning interval to be analyzed of the cable to be measured based on the reference pseudo-frequency;

[0041] A digital lock-in amplifier algorithm analysis unit, configured to use the reference frequency list to analyze the broadband characteristic impedance spectrum Z of the cable to be measured char as a pseudo-time domain signal to obtain an analysis result DLIA(Z char );

[0042] A hidden danger positioning unit, configured to determine the position of a hidden danger defect in the cable according to DLIA(Z char );

[0043] In some embodiments, the open-circuit and short-circuit impedance measurement unit is configured to:

[0044] Select a preset number of discrete frequency points within a preset frequency range;

[0045] Measure the impedance value at the head end of the cable to be measured at each discrete frequency point when the end of the cable to be measured is open-circuited, to obtain the head-end broadband characteristic impedance spectrum Z open ;

[0046] Measure the impedance value at the head end of the cable to be measured at each discrete frequency point when the end of the cable to be measured is short-circuited, to obtain the head-end broadband characteristic impedance spectrum Z short ;

[0047] In some embodiments, the reference pseudo-frequency calculation unit is configured to calculate the reference pseudo-frequency f according to the following formula 0 :

[0048] f 0 = 2 * sqrt(epsilon) / (c * N 0 ),

[0049] where epsilon is the relative permittivity of the main insulation layer of the cable to be measured, c is the speed of light, and N 0 is the number of data points analyzed per meter.

[0050] In some embodiments, the reference frequency list calculation unit is configured to determine a reference frequency list F according to the following formula:

[0051] F = [l 1 * N 0 * f 0 : f 0 : l 2 * N0 *f 0 ,

[0052] wherein, [l 1 *N 0 *f 0 :f 0 :l 2 *N 0 *f 0 represents an arithmetic progression from l 1 *N 0 *f 0 to l 2 *N 0 *f 0 with a step size of f 0 , where l 1 and l 2 are the start and end points of the positioning interval to be analyzed, and f 0 is the reference pseudo-frequency.

[0053] According to an embodiment of the present disclosure, an electronic device is provided, which includes a memory and a processor. The memory is used to store computer instructions that can run on the processor, and the processor is used to implement the method described in any one of the above when executing the computer instructions.

[0054] According to an embodiment of the present disclosure, a computer-readable storage medium is provided, on which a computer program is stored. When the program is executed by a processor, the method described in any one of the above is implemented.

[0055] The solution for locating hidden defects in power cables based on broadband characteristic impedance spectrum proposed by the present disclosure calculates the characteristic impedance spectrum by analyzing the impedance spectra measured in open-circuit and short-circuit states, without the need to know the propagation coefficient law and impedance spectrum of healthy cables, overcoming the limitation of the IT method that requires a large amount of healthy cable parameter information in practical applications. Compared with the FFT method, this solution is not limited by the time window and sampling rate and can achieve higher-precision positioning. By using the characteristic impedance spectrum as a pseudo-time-domain signal for digital lock-in amplifier analysis, this solution can effectively identify and locate smaller hidden defects. This solution is simple to operate and only requires measuring two states of open circuit and short circuit, facilitating its popularization and application in practical engineering. In addition, experimental verification shows that this solution is significantly superior to the existing FFT method and IT method in locating hidden defects in power cables and has strong practical value.

[0056] Other features and advantages of the technical solution proposed by the present disclosure are described in detail below. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the specification and, together with the description, serve to explain the principles of the specification.

[0058] Figure 1 A flow chart of a method for locating hidden defects of cables according to an embodiment of the present disclosure is shown.

[0059] Figure 2 A schematic diagram showing a broadband characteristic impedance spectrum of a head end when a cable end is open-circuited and a broadband characteristic impedance spectrum of a head end when a cable end is short-circuited, obtained according to an exemplary embodiment of the present disclosure.

[0060] Figure 3 A schematic diagram showing a broadband characteristic impedance spectrum of a cable obtained according to an exemplary embodiment of the present disclosure is shown.

[0061] Figure 4a , Figure 4b and Figure 4c A schematic diagram of analyzing and locating cable hidden danger faults according to an exemplary embodiment of the present disclosure and a schematic diagram of analyzing and locating cable hidden danger faults using the prior art are respectively shown.

[0062] Figure 5 It is a schematic diagram of the structure of an electronic device shown in at least one embodiment of the present disclosure. DETAILED DESCRIPTION

[0063] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. Instead, they are merely examples of devices and methods consistent with some aspects of the present disclosure as detailed in the appended claims.

[0064] The disclosed embodiments may be applied to a computer system / server that may operate with numerous other general or special computing system environments or configurations. Examples of well-known computing systems, environments, and / or configurations suitable for use with a computer system / server include, but are not limited to, personal computer systems, server computer systems, thin clients, thick clients, handheld or laptop devices, microprocessor-based systems, set-top boxes, programmable consumer electronics, networked personal computers, minicomputer systems, mainframe computer systems, and distributed cloud computing technology environments including any of the above systems, and the like.

[0065] Computer systems / servers may be described in the general context of computer system executable instructions (such as program modules) executed by a computer system. In general, program modules may include routines, programs, object programs, components, logic, data structures, etc., which perform specific tasks or implement specific abstract data types. Computer systems / servers may be implemented in a distributed cloud computing environment where tasks are performed by remote processing devices linked through a communication network. In a distributed cloud computing environment, program modules may be located on local or remote computing system storage media including storage devices.

[0066] Figure 1 FIG. 1 is a flow chart showing a method for locating hidden defects of a cable according to an embodiment of the present disclosure. Figure 1 As shown, the method includes steps 1 to 6.

[0067] Step 1: Measure the broadband characteristic impedance spectrum Z at the head end when the end of the cable to be tested is open open , and measure the broadband characteristic impedance spectrum Z of the first end when the end of the cable to be tested is short-circuited short .

[0068] For open circuit measurement, place the end of the cable to be tested in an open circuit state, even if the core wire at the end of the cable is disconnected from the ground wire. Then, use a precision impedance analyzer to measure at the head end of the cable. The analyzer selects multiple discrete frequency points within the preset frequency range and measures the input impedance value of the head end of the cable at each frequency point, thereby obtaining the broadband characteristic impedance spectrum Z of the head end. open .

[0069] For short-circuit measurement, the end of the cable to be tested is placed in a short-circuit state, that is, the core wire at the end of the cable is reliably connected to the ground wire. Then, at the head end of the cable, use a precision impedance analyzer to measure the input impedance value of the head end of the cable at the same discrete frequency point to obtain the broadband characteristic impedance spectrum Z of the head end. short .

[0070] The measured impedance spectrum Z open and Z short They are all discrete point sequences, each of which contains multiple frequency points and their corresponding impedance values.

[0071] Step 2: Calculate the broadband characteristic impedance spectrum Z of the cable to be tested according to the following formula: char :

[0072] Z char (i) = sqrt(Z open (i)*Z short (i)),

[0073] Among them, Z open (i) represents the broadband characteristic impedance spectrum Z of the first endopen the i-th data point in short Z(i) represents the leading-end broadband characteristic impedance spectrum Z short the i-th data point in char Z(i) represents the broadband characteristic impedance spectrum Z char the i-th data point in, sqrt represents the square root operation.

[0074] According to this embodiment, after obtaining the leading-end broadband characteristic impedance spectra Z open and Z short in the open-circuit and short-circuit states, the broadband characteristic impedance spectrum Z char of the cable under test can be calculated. For each frequency point, the open-circuit impedance value Z open (i) and the short-circuit impedance value Z short (i) at this frequency point can be taken. After multiplying the two and taking the square root, the characteristic impedance value Z char (i) at this frequency point is obtained. The broadband characteristic impedance spectrum Z char of the cable under test is composed of the characteristic impedance values of all frequency points.

[0075] The obtained broadband characteristic impedance spectrum Z char and Z open and Z short have the same frequency point distribution.

[0076] Step 3: Obtain a reference pseudo-frequency for determining the impedance spectrum analysis frequency interval according to the relative permittivity of the main insulation layer of the cable under test.

[0077] The reference pseudo-frequency is a key parameter in this embodiment for determining the impedance spectrum analysis frequency interval, laying a foundation for subsequent processing of the impedance spectrum as a pseudo-time-domain signal. The inventor considered both the physical characteristics of the cable and the analysis accuracy requirements when designing this parameter.

[0078] The main insulation layer is the most important insulation part in the cable, used to isolate the conductor and the shielding layer. Its relative permittivity affects the propagation characteristics of electromagnetic waves in the cable. In practical applications, the relative permittivity of the main insulation layer of the cable can be obtained by referring to the product technical manual or measured by a special permittivity tester.

[0079] In some embodiments, the reference pseudo-frequency f 0 is obtained according to the following formula:

[0080] f 0 = 2 * sqrt(epsilon) / (c * N 0 ),

[0081] where epsilon is the relative permittivity of the main insulation layer of the cable under test, c is the speed of light, and N0 The number of data points analyzed per meter.

[0082] The reference pseudo-frequency f calculated according to this embodiment 0 is proportional to the square root of the relative permittivity epsilon and inversely proportional to the number of data points N analyzed per meter 0 The number of data points N analyzed per meter 0 is a user-selectable parameter that can be used to control the accuracy of the analysis. The larger N 0 is, the smaller the reference pseudo-frequency is, and a finer analysis result can be obtained.

[0083] In practical applications, an appropriate relative permittivity value can be selected according to the cable type, and an appropriate number of data points analyzed per meter can be selected in combination with the required positioning accuracy requirements to obtain an ideal analysis effect. The reference pseudo-frequency calculated according to this embodiment takes into account both the influence of the main insulation medium of the cable on the propagation of electromagnetic waves and can flexibly control the analysis accuracy through the setting of N 0 is achieved.

[0084] Step 4: Based on the reference pseudo-frequency, determine the reference frequency list corresponding to each data point to be analyzed in the positioning interval to be analyzed of the cable to be measured.

[0085] After obtaining the reference pseudo-frequency, the positioning interval to be analyzed can be determined according to the actual situation of the cable to be measured, and a reference frequency list corresponding to each data point to be analyzed can be generated. The positioning interval to be analyzed is a section selected within the length range of the cable to be measured and is used to determine which section of the cable to specifically analyze. In practical applications, the positioning interval to be analyzed can be selected according to factors such as operation and maintenance requirements and fault prediction. The number of data points N analyzed per meter 0 is a user-selectable parameter, and 1 / N 0 meter is used as the sampling step of the interval.

[0086] In some embodiments, the reference frequency list can be calculated according to the following formula:

[0087] F = [l 1 * N 0 * f 0 : f 0 : l 2 * N 0 * f 0 ,

[0088] The above formula indicates that the reference frequency list F is an arithmetic progression from l 1 * N 0 * f 0 to l 2 * N 0 * f 0 with a step size of f 0 where l1 and l 2 are the start and end points of the positioning interval to be analyzed, and f 0 is the reference pseudo-frequency.

[0089] According to the reference frequency list generation method proposed in this embodiment, it is ensured that the subsequent digital lock-in amplifier analysis can cover the entire interval to be analyzed while maintaining an appropriate frequency resolution.

[0090] Different from the FFT method which is limited by the frequency range and frequency step of the impedance spectrum itself, this embodiment can flexibly set the positioning interval to be analyzed according to actual needs, and achieve precise analysis of this interval through a reasonably constructed reference frequency list. Each frequency in the reference frequency list will be used as the reference frequency for the subsequent digital lock-in amplifier analysis, and the number of final analysis results corresponds to the number of frequencies in the reference frequency list.

[0091] In practical applications, the start and end points of the positioning interval to be analyzed can be flexibly selected according to factors such as cable length and the position of the section of interest. At the same time, as analyzed above, by adjusting the number of data points N 0 per meter analyzed, a balance can be achieved between analysis accuracy and computational complexity. For example, when a more detailed analysis of a certain suspicious section is required, the value of N0 can be appropriately increased to obtain more dense analysis results.

[0092] Step 5, using the reference frequency list, analyze the broadband characteristic impedance spectrum Z char of the cable to be measured as a pseudo-time domain signal based on the digital lock-in amplifier analysis algorithm, and obtain the analysis result DLIA(Z char ).

[0093] In this embodiment, the impedance spectrum is processed as a pseudo-time domain signal and analyzed using the digital lock-in amplifier algorithm. The basic principle of the digital lock-in amplifier is introduced below.

[0094] A digital lock-in amplifier (DLIA) is a high-precision measuring device used to extract weak signals of specific frequencies from a complex signal environment. It generates orthogonal reference signals for phase locking and digital processing, and can accurately measure the amplitude and phase of signals in a high-noise background. The dual-channel DLIA has two independent input channels and can simultaneously measure the orthogonal components (such as X and Y components) of the input signal, which is particularly suitable for application scenarios that require synchronous processing of multiple signal sources or complex vector analysis, such as precision optical measurement, material property research, and signal processing of high-sensitivity sensors.

[0095] For the input signal Vin(t), when using the first reference signal cos(wt), it can be obtained by multiplying through a multiplier:

[0096] Vmix1(t) = V w / 2 * [cos(phi) + cos(2wt + phi)] + delta,

[0097] where Vmix1 is the signal after multiplication, V w is the amplitude of the w-frequency component in Vin(t), phi is the phase of the w-frequency component, and delta is the noise term generated by the multiplication of the multiplier. After low-pass filtering the Vmix1(t) signal, the low-frequency quantity V w / 2 * cos(phi) is obtained and denoted as X.

[0098] Similarly, by using the second reference signal sin(wt), after passing through a multiplier and a low-pass filter, the low-frequency quantity V w / 2 * sin(phi) is obtained and denoted as Y.

[0099] The output result of the digital lock-in amplifier is usually a complex result X + jY, where j is the imaginary unit.

[0100] Based on the complex result X + jY output by the digital lock-in amplifier, the amplitude Z and phase theta of the w-frequency component in Vin(t) can be extracted:

[0101] Z = sqrt(X^2 + Y^2), theta = arctan(Y / X).

[0102] The above is the basic principle of the digital lock-in amplifier algorithm.

[0103] The greatest advantage of the digital lock-in amplifier in extracting frequency components lies in its anti-interference ability and the ability to allow the user to determine the frequency list by themselves.

[0104] According to some embodiments of this embodiment, for the k-th data point to be analyzed, cos(w k t) is selected as the first reference signal, multiplied with the broadband characteristic impedance spectrum Z char and the X component is obtained through low-pass filtering. w k is the k-th frequency in the reference frequency list; sin(w k t) is selected as the second reference signal, multiplied with the broadband characteristic impedance spectrum Z char and the Y component is obtained through low-pass filtering; according to the X and / or Y components, the analysis result corresponding to the k-th data point to be analyzed is obtained.

[0105] In some examples, the real part (i.e., the X component) of the output of the digital lock-in amplifier algorithm can be used as the analysis result for subsequent processing; in some other examples, the imaginary part (i.e., the Y component) of the output of the digital lock-in amplifier algorithm can be used as the analysis result; in some other examples, the amplitude Z extracted based on the real part X and the imaginary part Y can be used as the analysis result.

[0106] Successively use all the frequencies in the reference frequency list for the broadband characteristic impedance spectrum Z char Perform the above processing, and finally obtain an analysis result sequence corresponding to the reference frequency list, that is, DLIA(Z char ).

[0107] Step 6, determine the position of the hidden defects in the cable according to DLIA(Z char ).

[0108] DLIA(Z char ) is a discrete sequence with the same length as the reference frequency list, and the abscissa of this sequence corresponds to each position point in the interval to be analyzed and located.

[0109] In some embodiments, identify the peak points in the waveform diagram of DLIA(Z char ); determine the position where the hidden defects exist according to the abscissa corresponding to the peak points.

[0110] When there are hidden defects in the cable, the impedance characteristics at the defect location will be different from those at the normal position, and this difference will be manifested as a mutation in the waveform in the DLIA analysis result, thus forming recognizable peaks. According to this embodiment, the hidden defects in the cable can be accurately located.

[0111] According to the method for locating hidden defects in a cable based on the broadband characteristic impedance spectrum proposed in this embodiment, by combining and analyzing the impedance spectra in the open-circuit and short-circuit states at the end of the cable, it is not necessary to know the propagation coefficient law and impedance spectrum of a healthy cable, overcoming the limitations of the IT method in practical applications. For cables that have been in service for many years, due to the influence of various complex factors, obtaining accurate healthy state parameters has become the main bottleneck in engineering practice. This embodiment avoids this problem, making the frequency-domain reflectometry based on the broadband impedance spectrum have true practical operation performance. And this embodiment uses the digital lock-in amplifier analysis algorithm to process the characteristic impedance spectrum, which is not limited by the time window and sampling rate, overcoming the problem of limited positioning step size of the FFT method. In addition, according to this embodiment, by reasonably setting the number of data points analyzed per meter, the positioning accuracy can be flexibly controlled.

[0112] This embodiment is simple to operate, only requiring the measurement of the impedance spectra in two end states, which is convenient for popularization and application in actual engineering. Through the design of the reference pseudo-frequency and the construction of the reference frequency list, the interval to be analyzed can be freely selected and accurate positioning can be achieved.

[0113] The following gives an application example of the present disclosure.

[0114] In this example, a precision impedance analyzer TH285-030 is used on-site to measure a cable with a length of 160 m. To verify the effectiveness of the present solution, a weak hidden defect is set at 60 m from the head end of the cable.

[0115] During the measurement, 1601 discrete frequency points are selected in the frequency range of 1 - 30 MHz. The broadband characteristic impedance spectra Zopen and Zshort at the head end of the cable are measured successively under the open-circuit and short-circuit states at the end, and the test results are as Figure 2 shown. According to the measured open-circuit impedance spectrum and short-circuit impedance spectrum, the broadband characteristic impedance spectrum Zchar of the cable to be measured is calculated as shown in Figure 3 shown, that is, Zh(cal) in Figure 3 while Zf(exp) shown in Figure 3 is the measured open-circuit fault impedance spectrum, that is, the broadband characteristic impedance spectrum Zopen.

[0116] Given that the relative permittivity of the main insulation of the cable to be measured is 2.3, the reference pseudo-frequency is calculated according to the relative permittivity and a reference frequency list is constructed, and then the digital lock-in amplifier analysis algorithm is used to analyze the broadband characteristic impedance spectrum. The analysis result according to the embodiment proposed by the present disclosure is as shown in Figure 4a shown, and an obvious peak appears at 60 m, accurately indicating the defect location.

[0117] For comparison, the FFT method and the IT method are respectively used to analyze the same cable. As shown in Figure 4b shown, the analysis result of the FFT method can hardly identify the location of the fault. As shown in Figure 4c shown, due to the inability to accurately know the true parameters of the cable system to be measured, the identification peak given by the IT method is significantly smaller than that of the present solution. This experimental result strongly proves the significant advantage of the embodiment proposed by the present disclosure in practical engineering applications - without relying on the difficult-to-obtain healthy cable parameter information, only by measuring the characteristics of the cable itself under the open-circuit and short-circuit states, the high-precision positioning of weak hidden defects can be achieved, making the frequency-domain reflectometry method based on the broadband impedance spectrum a practical tool for preventive maintenance of power systems.

[0118] The above experimental results verify the feasibility of the present solution and prove that it has better defect identification and positioning capabilities compared with the existing technologies.

[0119] The present disclosure also proposes a device for locating hidden cable defects based on the broadband characteristic impedance spectrum, including:

[0120] An open-circuit and short-circuit impedance measurement unit for measuring the broadband characteristic impedance spectrum Z at the head end of the cable to be measured when the end of the cable to be measured is open-circuitedopen and measure the broadband characteristic impedance spectrum Z of the first end when the end of the cable under test is short-circuited short ;

[0121] A broadband characteristic impedance calculation unit for calculating the broadband characteristic impedance spectrum Z of the cable under test according to the following formula char :

[0122] Z char (i)=sqrt(Z open (i)*Z short (i)),

[0123] wherein, Z open (i) represents the i-th data point in the broadband characteristic impedance spectrum Z of the first end open in, Z short (i) represents the i-th data point in the broadband characteristic impedance spectrum Z of the first end short in, Z char (i) represents the i-th data point in the broadband characteristic impedance spectrum Z char in, sqrt represents the square root operation;

[0124] A reference pseudo-frequency calculation unit for obtaining a reference pseudo-frequency for determining the impedance spectrum analysis frequency interval according to the relative dielectric constant of the main insulation layer of the cable under test;

[0125] A reference frequency list calculation unit for determining a reference frequency list corresponding to each data point to be analyzed in the positioning interval to be analyzed of the cable under test based on the reference pseudo-frequency;

[0126] A digital lock-in amplifier algorithm analysis unit for using the reference frequency list to analyze the broadband characteristic impedance spectrum Z of the cable under test as a pseudo-time domain signal based on the digital lock-in amplifier analysis algorithm to obtain an analysis result DLIA(Z char ); char )

[0127] A hidden danger positioning unit for determining the position of hidden danger defects in the cable according to DLIA(Z char ).

[0128] For other details and features of this embodiment, please refer to the relevant descriptions above.

[0129] Figure 5 An electronic device provided by at least one embodiment of the present disclosure, the device includes a memory and a processor, the memory is used to store computer instructions that can be run on the processor, and the processor is used to implement the method for positioning hidden danger defects in a cable based on a broadband characteristic impedance spectrum according to any embodiment or implementation manner of the present disclosure when executing the computer instructions.

[0130] At least one embodiment of the present disclosure further provides a computer-readable storage medium, on which a computer program is stored, and when the program is executed by a processor, it implements the method for locating cable hidden dangers and defects based on broadband characteristic impedance spectrum according to any embodiment or implementation manner of the present disclosure.

[0131] Those skilled in the art should understand that one or more embodiments of this specification can be provided as a method, a system, or a computer program product. Therefore, one or more embodiments of this specification can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, one or more embodiments of this specification can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0132] The various embodiments in this specification are described in a progressive manner. The same or similar parts among the various embodiments can be referred to each other, and the key point of each embodiment is to illustrate the differences from other embodiments. In particular, for the embodiments of the data processing device, since it is basically similar to the method embodiments, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiments.

[0133] The specific embodiments of this specification are described above. Other embodiments are within the scope of the appended claims. In some cases, the acts or steps recited in the claims can be performed in a different order than in the embodiments and still achieve the desired results. Additionally, the processes depicted in the figures do not necessarily require the particular order or sequential order shown to achieve the desired results. In certain implementations, multitasking and parallel processing are also possible or may be advantageous.

[0134] Although this specification contains many specific implementation details, these should not be construed as limiting the scope of any invention or the scope of what is claimed, but are mainly used to describe the features of specific embodiments of a particular invention. Certain features described in multiple embodiments in this specification can also be combined and implemented in a single embodiment. On the other hand, the various features described in a single embodiment can also be separately implemented in multiple embodiments or implemented in any suitable sub-combination. In addition, although the features can function in certain combinations as described above and are even initially claimed as such, one or more features from the claimed combination can in some cases be removed from the combination, and the claimed combination can be directed to a sub-combination or a variant of the sub-combination.

[0135] Similarly, although the operations are depicted in the drawings in a particular order, this should not be construed as requiring that the operations be performed in the particular order shown or sequentially, or that all illustrated operations be performed to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous. Additionally, the separation of various system modules and components in the above-described embodiments should not be construed as required in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products.

[0136] Thus, particular embodiments of the subject matter have been described. Other embodiments are within the scope of the appended claims. In some cases, the acts recited in the claims can be performed in a different order and still achieve the desired result. Additionally, the processes depicted in the figures are not necessarily in the particular order or sequential order shown to achieve the desired result. In some implementations, multitasking and parallel processing may be advantageous.

[0137] The foregoing is only a preferred embodiment of one or more embodiments of this specification, and is not intended to limit one or more embodiments of this specification. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of one or more embodiments of this specification shall be included within the scope protected by one or more embodiments of this specification.

Claims

1. A method for locating hidden defects of cables based on broadband characteristic impedance spectrum, characterized in that: include: Measure the broadband characteristic impedance spectrum Z at the head end when the end of the cable under test is open open , and measure the broadband characteristic impedance spectrum Z of the first end when the end of the cable to be tested is short-circuited short ; Calculate the broadband characteristic impedance spectrum Z of the cable under test according to the following formula: char : WITH char (i)=sqrt(Z open (i)*From short (and)), Among them, Z open (i) represents the broadband characteristic impedance spectrum Z of the first end open The i-th data point in Z short (i) represents the broadband characteristic impedance spectrum Z of the first end short The i-th data point in Z char (i) represents the broadband characteristic impedance spectrum Z char The i-th data point in , sqrt represents the square root operation; According to the relative dielectric constant of the main insulation layer of the cable to be tested, a reference pseudo frequency for determining the frequency interval of impedance spectrum analysis is obtained; Determine a reference frequency list corresponding to each data point to be analyzed in the positioning interval to be analyzed of the cable to be tested based on the reference pseudo frequency; Using the reference frequency list, the broadband characteristic impedance spectrum Z of the cable to be tested is converted into char As a pseudo time domain signal, the analysis result DLIA(Z char ); According to DLIA(Z char )Determine the location of hidden defects in the cable.

2. The method according to claim 1, characterized in that: Measure the broadband characteristic impedance spectrum Z at the head end when the end of the cable under test is open open , and measure the broadband characteristic impedance spectrum Z of the first end when the end of the cable to be tested is short-circuited short ,include: Selecting a preset number of discrete frequency points within a preset frequency range; Measure the impedance value of the cable head end at each discrete frequency point when the end of the cable to be tested is open, and obtain the broadband characteristic impedance spectrum Z of the head end open ; Measure the impedance value of the cable head end at each discrete frequency point when the end of the cable to be tested is short-circuited, and obtain the broadband characteristic impedance spectrum Z of the head end short .

3. The method according to claim 1, characterized in that The reference pseudo frequency f0 is obtained according to the following formula: f0=2*sqrt(epsilon) / (c*N0), Where epsilon is the relative dielectric constant of the main insulation layer of the cable to be tested, c is the speed of light, and N0 is the number of data points analyzed per meter.

4. The method according to claim 3, characterized in that: Determine the reference frequency list F corresponding to each data point to be analyzed in the positioning interval to be analyzed according to the following formula: F=[l1*N0*f0:f0:l2*N0*f0], Among them, [l1*N0*f0:f0:l2*N0*f0] represents an arithmetic progression from l1*N0*f0 to l2*N0*f0 with a step length of f0, where l1 and l2 are the starting point and end point of the positioning interval to be analyzed, and f0 is the reference pseudo frequency.

5. The method according to claim 1, characterized in that Using the reference frequency list, the broadband characteristic impedance spectrum Z of the cable to be tested is converted into char As a pseudo time domain signal, the analysis result DLIA(Z char ), including: for the kth data point to be analyzed, Select cos(w k t) as the first reference signal, and the broadband characteristic impedance spectrum Z char Multiply and low-pass filter to get the X component, w k is the kth frequency in the reference frequency list; Select sin(w k t) as the second reference signal, and the broadband characteristic impedance spectrum Z char Multiply and low-pass filter to get the Y component; According to the X and / or Y components, the analysis result corresponding to the kth data point to be analyzed is obtained.

6. The method according to claim 1, characterized in that According to DLIA(Z char ) Determine the location of hidden defects in the cable including: In DLIA(Z char ) to identify the peak point in the waveform diagram; Determine the location of the hidden defect based on the horizontal coordinate corresponding to the peak point.

7. A device for locating hidden defects of cables based on broadband characteristic impedance spectrum, characterized in that: include: Open-circuit and short-circuit impedance measurement unit, used to measure the broadband characteristic impedance spectrum Z of the first end when the end of the cable under test is open open , and measure the broadband characteristic impedance spectrum Z of the first end when the end of the cable to be tested is short-circuited short ; The broadband characteristic impedance calculation unit is used to calculate the broadband characteristic impedance spectrum Z of the cable under test according to the following formula char : WITH char (i)=sqrt(Z open (i)*From short (and)), Among them, Z open (i) represents the broadband characteristic impedance spectrum Z of the first end open The i-th data point in Z short (i) represents the broadband characteristic impedance spectrum Z of the first end short The i-th data point in Z char (i) represents the broadband characteristic impedance spectrum Z char The i-th data point in , sqrt represents the square root operation; A reference pseudo-frequency calculation unit, used to obtain a reference pseudo-frequency for determining a frequency interval for impedance spectrum analysis according to a relative dielectric constant of a main insulation layer of a cable to be tested; A reference frequency list calculation unit, used to determine a reference frequency list corresponding to each to-be-analyzed data point in the to-be-analyzed positioning interval of the cable to be tested based on the reference pseudo frequency; The digital lock-in amplifier algorithm analysis unit is used to use the reference frequency list to convert the broadband characteristic impedance spectrum Z of the cable to be tested based on the digital lock-in amplifier analysis algorithm. char As a pseudo time domain signal, the analysis result DLIA(Z char ); Hazard location unit, used according to DLIA (Z char )Determine the location of hidden defects in the cable.

8. The device according to claim 7, characterized in that The open-circuit and short-circuit impedance measurement unit is used for: Selecting a preset number of discrete frequency points within a preset frequency range; Measure the impedance value of the cable head end at each discrete frequency point when the end of the cable to be tested is open, and obtain the broadband characteristic impedance spectrum Z of the head end open ; Measure the impedance value of the cable head end at each discrete frequency point when the end of the cable to be tested is short-circuited, and obtain the broadband characteristic impedance spectrum Z of the head end short .

9. The device according to claim 7, characterized in that The reference pseudo frequency calculation unit is used to calculate the reference pseudo frequency f0 according to the following formula: f0=2*sqrt(epsilon) / (c*N0), Where epsilon is the relative dielectric constant of the main insulation layer of the cable to be tested, c is the speed of light, and N0 is the number of data points analyzed per meter.

10. The device according to claim 9, characterized in that The reference frequency list calculation unit is used to determine the reference frequency list F according to the following formula: F=[l1*N0*f0:f0:l2*N0*f0], Among them, [l1*N0*f0:f0:l2*N0*f0] represents an arithmetic progression from l1*N0*f0 to l2*N0*f0 with a step length of f0, where l1 and l2 are the starting point and end point of the positioning interval to be analyzed, and f0 is the reference pseudo frequency.

11. An electronic device, characterized in that: The device comprises a memory and a processor, wherein the memory is used to store computer instructions executable on the processor, and the processor is used to implement the method according to any one of claims 1 to 5 when executing the computer instructions.

12. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the method according to any one of claims 1 to 5 is implemented.

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