Method and device for positioning hidden trouble defect of power cable based on reconstructed broadband impedance spectroscopy, electronic equipment and storage medium

Abstract

The invention discloses a method and a device for positioning a hidden defect of a power cable based on a reconstructed broadband impedance spectrum, electronic equipment and a storage medium. According to the method, a healthy broadband impedance spectrum is reconstructed by measuring a head end broadband characteristic impedance spectrum when the tail end of a to-be-detected cable is open-circuited and short-circuited, then a digital lock-in amplifier algorithm is used for analyzing an open-circuit impedance spectrum and the reconstructed healthy impedance spectrum respectively, and the defect is positioned by comparing the difference value of analysis results. According to the scheme, the propagation coefficient rule and the impedance spectrum reference value of a healthy cable do not need to be accurately known, the limitation of an existing FFT method and an existing IT method is solved, high-precision positioning of weak hidden danger defects of the cable is achieved, and the frequency domain reflection method based on the broadband impedance spectrum has more practical operation performance and is suitable for preventive maintenance of an electric power system.

Description

Technical Field

[0001] The present disclosure relates to the field of electrical engineering, and in particular, to a method, device, electronic device, and storage medium for locating hidden dangers and defects of power cables based on reconstructed broadband impedance spectra. Background Art

[0002] The frequency domain reflectometry is a cable fault diagnosis technology developed in recent years, which has the potential to identify weak faults in power cables. Among them, 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 research objects of the frequency domain reflectometry are the cable's beginning impedance spectrum (BIS) and reflection coefficient spectrum (RCS). During testing, the cable end needs to be kept open or shorted. The analysis paradigm is to design an algorithm for a test result. In the existing analysis algorithms, the fast Fourier transform (FFT) or integral transform (IT) method is mainly used to analyze the cable impedance spectrum. However, both methods have obvious defects.

[0004] When the FFT method analyzes the tested impedance spectrum alone, the positioning step size obtained is limited by the selected time window and sampling rate, and the accuracy is insufficient when locating smaller 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, smaller defects can be located. However, the IT method has two practical application obstacles: the kernel function used in the integral transform needs to accurately know the propagation coefficient law of the ideal healthy cable with frequency, and the reference value of the impedance spectrum of the healthy cable needs to be known.

[0006] For cables in standby, the healthy impedance spectrum can be obtained through prior testing; but for cables that have been in service, this reference value cannot be obtained, and only the structural parameters and electrical parameters of the ideal healthy cable can be relied on for calculation. In actual operation, it is difficult to accurately know all the parameters affecting the impedance spectrum of the healthy cable, which will significantly affect the accuracy of the final test results.

[0007] Therefore, there is an urgent need for a new solution that can overcome the above disadvantages and achieve precise positioning of small hidden dangers and defects in power cables without accurately knowing the parameters of the healthy cable. Summary of the Invention

[0008] The present disclosure proposes a solution for locating hidden dangers and defects of power cables based on reconstructed broadband impedance spectra, which can achieve precise positioning of small defects without accurately knowing the parameters of the healthy cable.

[0009] According to an embodiment of the present disclosure, a method for locating potential defects in a power cable based on reconstructed broadband impedance spectrum is proposed, including:

[0010] 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 open , and 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 short - circuited short ;

[0011] Based on the measured broadband characteristic impedance spectra Z open and Z short , reconstruct the healthy broadband impedance spectrum R - Zh of the power cable to be measured according to the following formula:

[0012] R - Zh(i)=[(1 / N)*∑ i A(i)]*[(exp(B(i)) + 1) / (exp(B(i)) - 1)],

[0013] where N is the total number of data points in the impedance spectrum, i is the serial number, i = 1, 2,..., N, A(i)=sqrt(Z open (i)*Z short (i)), sqrt represents the square - root operation, B(i)=log[1+(2*A(i)) / (Z open (i)-A(i))];

[0014] Obtain a reference pseudo - frequency for determining the frequency interval of impedance spectrum analysis according to the relative permittivity of the main insulation layer of the cable to be measured;

[0015] Based on the reference pseudo - frequency, determine the reference frequency list corresponding to each data point to be analyzed in the interval to be analyzed and located of the cable to be measured;

[0016] Using the reference frequency list, adopt the digital lock - in amplifier algorithm to analyze the broadband characteristic impedance spectrum Z at the head end open and the reconstructed healthy broadband impedance spectrum R - Zh as pseudo - time - domain signals respectively, and obtain the corresponding analysis results;

[0017] Locate potential defects according to the difference between the analysis result corresponding to the broadband characteristic impedance spectrum Z at the head end open and the analysis result corresponding to the healthy broadband impedance spectrum R - Zh.

[0018] In some embodiments, the reference pseudo - frequency f 0 is obtained according to the following formula:

[0019] f 0 =2*sqrt(epsilon) / (c*N 0 ),

[0020] 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.

[0021] In some embodiments, the reference frequency list F corresponding to each data point to be analyzed in the positioning interval to be analyzed is determined according to the following formula:

[0022] F = [l 1 *N 0 *f 0 :f 0 :l 2 *N 0 *f 0 ,

[0023] 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.

[0024] In some embodiments, using the reference frequency list, the impedance spectrum is analyzed by the digital lock-in amplifier algorithm, including: for the k-th data point to be analyzed,

[0025] select cos(w k t) as the first reference signal, multiply it with the impedance spectrum being currently analyzed and obtain the X component through low-pass filtering, where w k is the k-th frequency in the reference frequency list;

[0026] select sin(w k t) as the second reference signal, multiply it with the impedance spectrum being currently analyzed and obtain the Y component through low-pass filtering;

[0027] According to the X and / or Y components, obtain the analysis result corresponding to the k-th data point to be analyzed.

[0028] In some embodiments, according to the difference between the analysis result corresponding to the broadband characteristic impedance spectrum Z open at the head end and the analysis result corresponding to the healthy broadband impedance spectrum R-Zh, potential hidden defects are located, including:

[0029] Calculate the difference R = DLIA(Z open ) - DLIA(R - Zh),

[0030] where DLIA(Z open ) is the analysis result corresponding to the head - end broadband characteristic impedance spectrum Z open , and DLIA(R - Zh) is the analysis result corresponding to the healthy broadband impedance spectrum R - Zh;

[0031] Identify the peak points in the waveform diagram of the difference R;

[0032] Determine the location of potential hidden defects according to the abscissa corresponding to the peak points.

[0033] According to an embodiment of the present disclosure, a device for locating potential hidden defects of a power cable based on a reconstructed broadband impedance spectrum is also proposed, including:

[0034] An open - circuit and short - circuit impedance measurement unit, configured to measure the head - end broadband characteristic impedance spectrum Z open when the end of the cable under test is open - circuited, and measure the head - end broadband characteristic impedance spectrum Z short when the end of the cable under test is short - circuited;

[0035] An impedance spectrum reconstruction unit, configured to reconstruct the healthy broadband impedance spectrum R - Zh of the power cable under test based on the measured head - end broadband characteristic impedance spectra Z open and Z short according to the following formula:

[0036] R - Zh(i)=[(1 / N)*∑i A(i)]*[(exp(B(i)) + 1) / (exp(B(i)) - 1)],

[0037] where N is the total number of data points in the impedance spectrum, i is the serial number, i = 1, 2,..., N, A(i)=sqrt(Z open (i)*Z short (i)), sqrt represents the square - root operation, B(i)=log[1+(2*A(i)) / (Z open (i)-A(i))];

[0038] A reference pseudo - frequency calculation unit, configured to obtain a reference pseudo - frequency for determining the frequency interval of impedance spectrum analysis according to the relative permittivity of the main insulation layer of the cable under test;

[0039] A reference frequency list calculation unit, configured to determine a reference frequency list corresponding to each data point to be analyzed in the analysis and location interval of the cable under test based on the reference pseudo - frequency;

[0040] The digital lock-in amplifier algorithm analysis unit is used to utilize the reference frequency list and respectively analyze the head-end broadband characteristic impedance spectrum Z open and the reconstructed healthy broadband impedance spectrum R-Zh as pseudo-time domain signals to obtain corresponding analysis results;

[0041] The hidden danger positioning unit is used to locate hidden danger defects according to the difference between the analysis result corresponding to the head-end broadband characteristic impedance spectrum Z open and the analysis result corresponding to the healthy broadband impedance spectrum R-Zh.

[0042] In some embodiments, the reference pseudo-frequency calculation unit obtains the reference pseudo-frequency f according to the following formula 0 :

[0043] f 0 = 2*sqrt(epsilon) / (c*N 0 )

[0044] 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.

[0045] In some embodiments, the reference frequency list calculation unit determines 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:

[0046] F = [l 1 *N 0 *f 0 :f 0 :l 2 *N 0 *f 0 ,

[0047] 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 . Here, 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.

[0048] In some embodiments, the digital lock-in amplifier algorithm analysis unit uses the reference frequency list and analyzes the impedance spectrum by means of the digital lock-in amplifier algorithm, including: for the k-th data point to be analyzed,

[0049] select cos(ω k t) as the first reference signal, multiply it with the impedance spectrum currently being analyzed, and obtain the X component through low-pass filtering, where ω k is the k-th frequency in the reference frequency list;

[0050] select sin(ω k t) as the second reference signal, multiply it with the impedance spectrum currently being analyzed, and obtain the Y component through low-pass filtering;

[0051] Obtain the analysis result corresponding to the k-th data point to be analyzed according to the X and / or Y components.

[0052] In some embodiments, the potential hazard location unit locates potential hazard defects according to the difference between the analysis result corresponding to the head-end broadband characteristic impedance spectrum Z open and the analysis result corresponding to the healthy broadband impedance spectrum R-Zh, including:

[0053] Calculate the difference R = DLIA(Z open ) - DLIA(R-Zh),

[0054] where DLIA(Z open ) is the analysis result corresponding to the head-end broadband characteristic impedance spectrum Z open , and DLIA(R-Zh) is the analysis result corresponding to the healthy broadband impedance spectrum R-Zh;

[0055] Identify the peak points in the waveform diagram of the difference R;

[0056] Determine the location where potential hazard defects exist according to the abscissa corresponding to the peak points.

[0057] According to an embodiment of the present disclosure, an electronic device is provided. The device 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.

[0058] 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.

[0059] The solution for locating potential defects in power cables based on broadband characteristic impedance spectrum proposed in this disclosure measures the broadband characteristic impedance spectrum at the head end when the cable end is open and short - circuited, reconstructs the healthy broadband impedance spectrum, enabling the elimination of the need to obtain the impedance spectrum reference value of an actual healthy cable. This solves the problem of the traditional IT method's dependence on the parameters of healthy cables, greatly improving the applicability of the method for in - service cables. By combining the digital lock - in amplifier (DLIA) algorithm to analyze the impedance spectrum and calculating the reference frequency list through the reference pseudo - frequency with a custom - defined frequency interval, the defect of the FFT method being limited by the time window and sampling rate is overcome. This allows the positioning step size to be flexibly adjusted and provides a stronger anti - interference ability, thus significantly improving the recognition sensitivity of weak potential defects. In addition, the method of this solution for locating defects by calculating the difference between the broadband characteristic impedance spectrum at the head end and the analysis result of the reconstructed healthy broadband impedance spectrum avoids the complexity of directly calculating the propagation coefficient, making the method more convenient to apply in actual engineering. Experimental results prove that compared with the existing FFT and IT methods, this solution can more accurately identify and locate weak potential defects in cables, has significant advantages, realizes the precise positioning of potential defects in power cables under limited parameter conditions, and provides technical support for the preventive maintenance of power systems.

[0060] Other features and advantages of the technical solution proposed in this disclosure are described in detail below. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] The drawings here are incorporated into the specification and form a part of this specification, showing embodiments consistent with this specification, and are used together with the specification to explain the principles of this specification.

[0062] Figure 1 The flowchart of the method for locating potential defects in power cables based on the reconstructed broadband impedance spectrum according to an embodiment of this disclosure is shown.

[0063] Figure 2 The schematic diagram of the broadband characteristic impedance spectrum at the head end when the cable end is open and the broadband characteristic impedance spectrum at the head end when the cable end is short - circuited obtained according to an exemplary embodiment of this disclosure is shown.

[0064] Figure 3 The schematic diagram of the reconstructed healthy broadband impedance spectrum according to an exemplary embodiment of this disclosure is shown.

[0065] Figure 4a 、 Figure 4b and Figure 4c The schematic diagrams of analyzing and locating potential cable faults according to an exemplary embodiment of this disclosure and the schematic diagram of analyzing and locating potential cable faults using the existing technology are shown respectively.

[0066] Figure 5 The schematic diagram of the structure of an electronic device shown in at least one embodiment of this disclosure. Detailed Implementation Manner

[0067] Here, exemplary embodiments will be described in detail, and examples thereof are shown in the accompanying drawings. When the following description refers to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementation manners described in the following exemplary embodiments do not represent all implementation manners consistent with the present disclosure. On the contrary, they are merely examples of devices and methods consistent with some aspects of the present disclosure as detailed in the appended claims.

[0068] Embodiments of the present disclosure can be applied to a computer system / server, which can operate together with many other general-purpose or special-purpose computing system environments or configurations. Examples of well-known computing systems, environments, and / or configurations suitable for use with the 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, network personal computers, small computer systems, large computer systems, and distributed cloud computing technology environments including any of the above systems, and so on.

[0069] The computer system / server can be described in the general context of computer system-executable instructions, such as program modules, executed by the computer system. Generally, program modules can include routines, programs, object programs, components, logic, data structures, and so on, which perform specific tasks or implement specific abstract data types. The computer system / server can be implemented in a distributed cloud computing environment, where tasks are executed by remote processing devices linked through a communication network. In a distributed cloud computing environment, program modules can be located on local or remote computing system storage media including storage devices.

[0070] Figure 1 The flowchart of a method for locating cable hidden danger defects according to an embodiment of the present disclosure is shown. As Figure 1 shown, the method includes Step 1 to Step 6.

[0071] Step 1: Measure the broadband characteristic impedance spectrum Z open of the first end when the end of the cable to be measured is open-circuited, and measure the broadband characteristic impedance spectrum Z short of the first end when the end of the cable to be measured is short-circuited.

[0072] For the open-circuit measurement, place the end of the cable to be measured in an open-circuit state, that is, disconnect the core wire and the ground wire at the end of the cable. Then, at the first end of the cable, use a precision impedance analyzer for measurement. The analyzer selects multiple discrete frequency points within a preset frequency range and measures the input impedance value at the first end of the cable at each frequency point, so as to obtain the broadband characteristic impedance spectrum Z open of the first end.

[0073] For short - circuit measurement, place the end of the cable under test in a short - circuit state, that is, reliably connect the core wire at the end of the cable to the ground wire. Then, also at the head end of the cable, use a precision impedance analyzer to measure the input impedance value at the head end of the cable at the same discrete frequency points, and obtain the broadband characteristic impedance spectrum Z of the head end. short .

[0074] The measured impedance spectrum Z open and Z short are both sequences of discrete points, and each sequence contains multiple frequency points and their corresponding impedance values.

[0075] Step 2: Based on the measured broadband characteristic impedance spectrum Z of the head end open and Z short , reconstruct the healthy broadband impedance spectrum R - Zh of the power cable under test according to the following formula:

[0076] R - Zh(i) = [(1 / N) * ∑ i A(i)] * [(exp(B(i)) + 1) / (exp(B(i)) - 1)],

[0077] where N is the total number of data points in the impedance spectrum, i is the serial number, i = 1, 2,..., N, A(i) = sqrt(Z open (i) * Z short (i)), sqrt represents the square - root operation, and B(i) = log[1+(2 * A(i)) / (Z open (i) - A(i))].

[0078] In the above formula, A(i) is the geometric mean of the corresponding points of the open - circuit and short - circuit broadband characteristic impedance spectra at the head end. [(1 / N) * ∑ i A(i)] calculates the average value of A at all frequency points as the overall scaling factor. B(i) = log[1+(2 * A(i)) / (Zopen(i) - A(i))] is used to transform the relationship between the open - circuit impedance Z open (i) and A(i) to the logarithmic domain.

[0079] By simultaneously using the open - circuit and short - circuit measurement results, the direct dependence on the reference spectrum of a healthy cable is avoided, and A(i) is used as a hybrid characterization of the open - circuit and short - circuit impedance characteristics. Further, through exponential and logarithmic transformations, a non - linear mapping relationship between the impedance spectrum and the physical characteristics of the cable is established.

[0080] Through the above reconstruction, the problem that the traditional IT method requires a reference spectrum of a healthy cable is solved, and the inference of the healthy state is realized without relying on an external reference, laying a foundation for subsequent defect location.

[0081] Reconstructed healthy broadband impedance spectrum R-Zh and Z open and Z short Have the same frequency point distribution.

[0082] Step 3, according to the relative permittivity of the main insulation layer of the cable to be measured, obtain the reference pseudo-frequency for determining the frequency interval of impedance spectrum analysis.

[0083] The reference pseudo-frequency is the key parameter in this embodiment for determining the frequency interval of impedance spectrum analysis, laying a foundation for subsequent processing of the impedance spectrum as a pseudo-time domain signal. When designing this parameter, the inventor considered both the physical characteristics of the cable and the requirements of analysis accuracy.

[0084] 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 will affect 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 can be measured by a special permittivity tester.

[0085] In some embodiments, the reference pseudo-frequency f is obtained according to the following formula 0 :

[0086] f 0 = 2*sqrt(epsilon) / (c*N 0 ),

[0087] 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.

[0088] 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, which can be used to control the analysis accuracy. The larger N 0 , the smaller the reference pseudo-frequency, and a more refined analysis result can be obtained.

[0089] In practical applications, the appropriate relative permittivity value can be selected according to the cable type, and the 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 not only considers the influence of the main insulation medium of the cable on the propagation of electromagnetic waves, but also can flexibly control the analysis accuracy through the setting of N 0 .

[0090] 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.

[0091] 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 is generated. The positioning interval to be analyzed is a section of the interval selected within the length range of the cable to be measured, which 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 parameter that can be selected by the user, and 1 / N 0 meter is used as the sampling step of the interval.

[0092] In some embodiments, the reference frequency list can be calculated according to the following formula:

[0093] F = [l 1 *N 0 *f 0 :f 0 :l 2 *N 0 *f 0 ,

[0094] 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 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.

[0095] The method for generating the reference frequency list proposed in this embodiment ensures that the subsequent digital lock-in amplifier analysis can cover the entire interval to be analyzed while maintaining an appropriate frequency resolution.

[0096] Different from the FFT method which is limited by the frequency range and frequency step of the impedance spectrum itself, in this embodiment, the positioning interval to be analyzed can be flexibly set according to actual needs, and accurate analysis of this interval can be achieved 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.

[0097] In practical applications, the starting and ending points of the interval to be analyzed and located 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 analyzed per meter 0 , 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 a denser analysis result.

[0098] Step 5: Using the reference frequency list, the digital lock-in amplifier algorithm is adopted to analyze the broadband characteristic impedance spectrum Z at the head end open and the reconstructed healthy broadband impedance spectrum R-Zh as pseudo-time domain signals to obtain corresponding analysis results.

[0099] 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.

[0100] A digital lock-in amplifier (DLIA) is a high-precision measuring device used to extract weak signals at 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 the X and Y components) of the input signal, which is particularly suitable for applications 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.

[0101] For the input signal Vin(t), when the first reference signal cos(wt) is used, the following can be obtained through multiplication by a multiplier:

[0102] Vmix1(t) = V w / 2 * [cos(phi) + cos(2wt + phi)] + delta,

[0103] 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. The Vmix1(t) signal is low-pass filtered to obtain the low-frequency quantity V w / 2 * cos(phi), denoted as X.

[0104] Similarly, when the second reference signal sin(wt) is used, after passing through a multiplier and a low-pass filter, the low-frequency quantity V w / 2 * sin(phi) is obtained, denoted as Y.

[0105] The output result of a digital lock-in amplifier is usually a complex result X + jY, where j is the imaginary unit.

[0106] 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:

[0107] Z = sqrt(X^2 + Y^2), theta = arctan(Y / X).

[0108] The above is the basic principle of the digital lock-in amplifier algorithm.

[0109] The greatest advantage of the digital lock-in amplifier in extracting frequency components lies in its anti-interference ability and the ability to allow users to determine the frequency list by themselves.

[0110] According to some embodiments of this embodiment, for the k-th data point to be analyzed in the positioning interval to be analyzed, cos(w k t) is selected as the first reference signal, multiplied by the broadband characteristic impedance spectrum Z char and passed through a low-pass filter to obtain the X component, where w k is the frequency corresponding to the i-th data point to be analyzed in the reference frequency list; sin(w k t) is selected as the second reference signal, multiplied by the broadband characteristic impedance spectrum Z char and passed through a low-pass filter to obtain the Y component; according to the X and / or Y components, the analysis result corresponding to the k-th data point to be analyzed is obtained.

[0111] In some examples, the real part (i.e., the X component) output by the digital lock-in amplifier algorithm can be used as the analysis result for subsequent processing; in other examples, the imaginary part (i.e., the Y component) output by the digital lock-in amplifier algorithm can be used as the analysis result; in other embodiments, the amplitude Z extracted based on the real part X and the imaginary part Y can be used as the analysis result. When analyzing each impedance spectrum, the same result selection criteria are adopted.

[0112] All the frequencies in the reference frequency list are sequentially used to perform the above processing on the head-end broadband characteristic impedance spectrum Z open , and the analysis result sequence corresponding to the reference frequency list obtained is DLIA(Z open ). All the frequencies in the reference frequency list are also sequentially used to perform the above processing on the reconstructed healthy broadband impedance spectrum R-Zh, and the analysis result sequence corresponding to the reference frequency list obtained is also DLIA(R-Zh).

[0113] Step 6, according to the head-end broadband characteristic impedance spectrum Z openThe difference between the corresponding analysis result and the analysis result corresponding to the healthy broadband impedance spectrum R-Zh is used to locate potential hidden defects.

[0114] The broadband characteristic impedance spectrum Z at the head end open The corresponding analysis result DLIA(Z open ) and the analysis result DLIA(R-Zh) corresponding to the healthy broadband impedance spectrum R-Zh are two corresponding sequences. The abscissas of the sequences correspond to each position point in the interval to be analyzed and located.

[0115] In some embodiments, the difference R = DLIA(Z open ) - DLIA(R-Zh) can be calculated, where DLIA(Z open ) is the analysis result corresponding to the broadband characteristic impedance spectrum Z at the head end open , and DLIA(R-Zh) is the analysis result corresponding to the healthy broadband impedance spectrum R-Zh; peak points are identified in the waveform diagram of the difference R; the positions with potential hidden defects are determined according to the abscissas corresponding to the peak points.

[0116] By calculating the difference between the two analysis results, systematic errors and background interference can be effectively eliminated. This differential processing method enhances the signal-to-noise ratio, making it easier to identify weak potential hidden defect signals. Since the defect points will interfere with the impedance characteristics, the defects can be manifested as obvious peaks in the difference waveform. Compared with traditional methods, the peaks obtained according to this embodiment are sharper and more prominent, effectively improving the detection sensitivity.

[0117] In this embodiment, by using the open-circuit and short-circuit impedance spectra to reconstruct the healthy impedance spectrum, the dependence on the parameters of healthy cables in traditional methods is solved. At the same time, combined with the flexible frequency point selection and high anti-interference ability of the digital lock-in amplifier algorithm, the positioning accuracy and sensitivity of cable potential hidden defects are significantly improved. Experiments prove that this method can accurately locate weak defects without the need to accurately know the propagation coefficient law of healthy cables, providing a practical and efficient technical means for the preventive maintenance of power systems and having high engineering application value.

[0118] The following gives an application example of the present disclosure.

[0119] In this example, a precision impedance analyzer TH285-030 is used on-site to measure a cable with a length of 180 m. To verify the effectiveness of this solution, a weak potential hidden defect is set at a distance of 80 m from the head end of the cable.

[0120] During the measurement, 1601 discrete frequency points are selected in the frequency range of 1 - 30 MHz. The broadband characteristic impedance spectra Z open and Z short at the head end of the cable are measured respectively under the open-circuit and short-circuit conditions at the end, and the test results are as Figure 2as shown

[0121] Based on the measurement results, the healthy broadband impedance spectrum is reconstructed using the method proposed in the present disclosure, such as Figure 3 the Z h (cal) shown therein (i.e., the impedance spectrum R-Zh). Figure 3 The measured open-circuit fault impedance spectrum Z f (exp) (i.e., Z open ) is also shown therein.

[0122] Subsequently, the hidden defect location analysis is respectively performed using the DLIA method, the traditional FFT method, and the IT method according to the present disclosure. In the DLIA analysis, the relative permittivity of the main insulation of the cable to be measured is set to 2.3.

[0123] The location results show that, as Figure 4a shown, the method according to the present disclosure can accurately locate the fault at 80 m, with obvious peaks and accurate positions. In contrast, although the FFT result ( Figure 4b ) can identify the fault location, the amplitude is small and the identification effect is not significant. Similarly, the IT method result ( Figure 4c ) gives an identification peak smaller than that of the present disclosure because it is difficult to accurately obtain the true parameters of the cable system to be measured in actual tests.

[0124] The above application examples verify the correctness and feasibility of the method for locating hidden defects in power cables based on the reconstructed broadband impedance spectrum proposed in the present disclosure, as well as its superiority in practical applications. Through simple impedance spectrum measurement and calculation, accurate location of cable hidden defects can be achieved without relying on reference data of healthy cables.

[0125] The present disclosure also proposes a device for locating hidden defects in power cables based on the reconstructed broadband impedance spectrum, including:

[0126] An open-circuit and short-circuit impedance measurement unit for measuring the broadband characteristic impedance spectrum Z open of the head end when the end of the cable to be measured is open-circuited, and measuring the broadband characteristic impedance spectrum Z short of the head end when the end of the cable to be measured is short-circuited;

[0127] An impedance spectrum reconstruction unit for reconstructing the healthy broadband impedance spectrum R-Zh of the power cable to be measured based on the measured broadband characteristic impedance spectra Z open and Z short according to the following formula:

[0128] R-Zh(i) = [(1 / N) * ∑ i A(i)] * [(exp(B(i)) + 1) / (exp(B(i)) - 1)],

[0129] where N is the total number of data points in the impedance spectrum, i is the serial number, i = 1, 2, …, N, A(i) = sqrt(Z open (i)*Z short (i)), sqrt represents the square root operation, B(i) = log[1+(2*A(i)) / (Z open (i)-A(i))];

[0130] A reference pseudo-frequency calculation unit, configured to 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 to be measured;

[0131] 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;

[0132] A digital lock-in amplifier algorithm analysis unit, configured to use the reference frequency list and adopt the digital lock-in amplifier algorithm to analyze the head-end broadband characteristic impedance spectrum Z open and the reconstructed healthy broadband impedance spectrum R-Zh as pseudo-time domain signals respectively to obtain corresponding analysis results;

[0133] A hidden danger positioning unit, configured to locate hidden danger defects according to the difference between the analysis result corresponding to the head-end broadband characteristic impedance spectrum Z open and the analysis result corresponding to the healthy broadband impedance spectrum R-Zh.

[0134] For other details and features of this embodiment, please refer to the relevant descriptions above.

[0135] 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 locating hidden danger defects of a power cable based on a reconstructed broadband impedance spectrum according to any embodiment or implementation manner of the present disclosure when executing the computer instructions.

[0136] 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 hidden danger defects of a power cable based on a reconstructed broadband impedance spectrum according to any embodiment or implementation manner of the present disclosure.

[0137] 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 memory, CD-ROM, optical memory, etc.) that contain computer-usable program code.

[0138] Each embodiment in this specification is described in a progressive manner. For the same or similar parts among the embodiments, reference can be made to each other. Each embodiment focuses on the differences from other embodiments. In particular, for the embodiment of the data processing device, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can refer to the partial description of the method embodiment.

[0139] The above describes specific embodiments of this specification. 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 embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0140] 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 rather 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. Moreover, although the features may 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 variation of the sub-combination.

[0141] 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 requiring such separation in all embodiments, and it should be understood that the program components and systems described may generally be integrated together in a single software product or packaged into multiple software products.

[0142] Accordingly, 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 processing depicted in the drawings is 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.

[0143] The above are only the preferred embodiments of one or more embodiments of this specification, and are 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 of protection of one or more embodiments of this specification.

Claims

1. A method for locating hidden defects of power cables based on reconstructed broadband 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 ; Based on the measured broadband characteristic impedance spectrum Z of the first end open and Z short , the healthy broadband impedance spectrum R-Zh of the power cable to be tested is reconstructed according to the following formula: R-Zh(i)=[(1 / N)*∑i A(i)]*[(exp(B(i))+1) / (exp(B(i))-1)], Where N is the total number of data points in the impedance spectrum, i is the number, i = 1, 2, ..., N, A (i) = sqrt (Z open (i)*Z short (i)), sqrt represents the square root operation, B(i) = log[1+(2*A(i)) / (Z open (i)-A(i))]; 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, a digital lock-in amplifier algorithm is used to respectively convert the broadband characteristic impedance spectrum Z open The reconstructed healthy broadband impedance spectrum R-Zh is analyzed as a pseudo time domain signal to obtain the corresponding analysis results; According to the broadband characteristic impedance spectrum Z open The difference between the corresponding analysis results and the analysis results corresponding to the healthy broadband impedance spectrum R-Zh is used to locate hidden defects.

2. 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.

3. The method according to claim 2, 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.

4. The method according to claim 1, characterized in that: Using the reference frequency list, the impedance spectrum is analyzed using a digital lock-in amplifier algorithm, including: for the kth data point to be analyzed, Select cos(w k t) as the first reference signal, multiplied by the impedance spectrum currently analyzed and filtered through a low pass filter to obtain the X component, w k is the kth frequency in the reference frequency list; Select sin(w k t) as a second reference signal, multiplied with the impedance spectrum currently analyzed and obtained by low-pass filtering to obtain 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.

5. The method according to claim 1, characterized in that According to the broadband characteristic impedance spectrum Z open The difference between the corresponding analysis results and the analysis results of the healthy broadband impedance spectrum R-Zh can locate hidden defects, including: Calculate the difference R = DLIA (Z open )-DLIA(R-Zh), Among them, DLIA (Z open ) is the broadband characteristic impedance spectrum Z of the first end open The corresponding analysis results, DLIA(R-Zh) are the analysis results corresponding to the healthy broadband impedance spectrum R-Zh; Identify the peak point in the waveform of the difference R; Determine the location of the hidden defect based on the horizontal coordinate corresponding to the peak point.

6. A device for locating hidden defects of power cables based on reconstructed broadband 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 ; Impedance spectrum reconstruction unit, used to reconstruct the broadband characteristic impedance spectrum Z of the head end based on the measurement open and Z short , the healthy broadband impedance spectrum R-Zh of the power cable to be tested is reconstructed according to the following formula: R-Zh(i)=[(1 / N)*∑ i A(i)]*[(exp(B(i))+1) / (exp(B(i))-1)], Where N is the total number of data points in the impedance spectrum, i is the number, i = 1, 2, ..., N, A (i) = sqrt (Z open (i)*Z short (i)), sqrt represents the square root operation, B(i) = log[1+(2*A(i)) / (Z open (i)-A(i))]; 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 and adopt the digital lock-in amplifier algorithm to respectively analyze the broadband characteristic impedance spectrum Z of the first end open The reconstructed healthy broadband impedance spectrum R-Zh is analyzed as a pseudo time domain signal to obtain the corresponding analysis results; The hidden danger location unit is used to locate the hidden danger according to the broadband characteristic impedance spectrum Z of the head end. open The difference between the corresponding analysis results and the analysis results corresponding to the healthy broadband impedance spectrum R-Zh is used to locate hidden defects.

7. The device according to claim 6, characterized in that The reference pseudo frequency calculation unit obtains 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.

8. The device according to claim 7, characterized in that The reference frequency list calculation unit determines the reference frequency list F corresponding to each to-be-analyzed data point in the to-be-analyzed positioning interval 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.

9. The device according to claim 6, characterized in that The digital lock-in amplifier algorithm analysis unit uses the reference frequency list and a digital lock-in amplifier algorithm to analyze the impedance spectrum, including: for the kth data point to be analyzed, Select cos(w k t) as the first reference signal, multiplied by the impedance spectrum currently analyzed and filtered through a low pass filter to obtain the X component, w k is the kth frequency in the reference frequency list; Select sin(w k t) as a second reference signal, multiplied with the impedance spectrum currently analyzed and obtained by low-pass filtering to obtain 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.

10. The device according to claim 6, characterized in that The hidden danger location unit is based on the broadband characteristic impedance spectrum Z of the head end open The difference between the corresponding analysis results and the analysis results of the healthy broadband impedance spectrum R-Zh can locate hidden defects, including: Calculate the difference R = DLIA (Z open )-DLIA(R-Zh), Among them, DLIA (Z open ) is the broadband characteristic impedance spectrum Z of the first end open The corresponding analysis results, DLIA(R-Zh) are the analysis results corresponding to the healthy broadband impedance spectrum R-Zh; Identify the peak point in the waveform of the difference R; Determine the location of the hidden defect based on the horizontal coordinate corresponding to the peak point.

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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