Method and device for locating hidden defects of power cable based on reconstructed broadband impedance spectrum, electronic equipment and storage medium

Abstract

A method, device, electronic equipment and storage medium for locating power cable hidden defects based on reconstructed broadband impedance spectrum are disclosed. The method reconstructs a healthy broadband impedance spectrum by measuring the broadband characteristic impedance spectrum of the cable end when it is open-circuited and short-circuited, analyzes the open-circuit impedance spectrum and the reconstructed healthy impedance spectrum respectively using a digital lock-in amplifier algorithm, and locates the defects by comparing the difference between the analysis results. The scheme does not need to accurately know the propagation coefficient law and impedance spectrum reference value of the healthy cable, solves the limitations of the existing FFT method and IT method, realizes high-precision positioning of the weak hidden defects of the cable, makes the frequency domain reflection method based on the broadband impedance spectrum have more practical operation performance, and is suitable for preventive maintenance of the power system.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of electrical engineering, and particularly relates to a method and device for locating defects in power cables based on reconstructed broadband impedance spectrum, electronic equipment and storage medium. BACKGROUND

[0002] Frequency domain reflectometry is a cable fault diagnosis technology developed in recent years, which has the potential to identify weak faults in power cables. The cable impedance spectrum is the main object of study in frequency domain reflectometry. Through frequency domain reflectometry, potential defects in power cables can be detected in advance to avoid the loss caused by the development of serious faults, which is of great significance to the operation and inspection of cables.

[0003] Currently, the main research objects of frequency domain reflectometry are the first end impedance spectrum (BIS) and the reflection coefficient spectrum (RCS) of the cable. During testing, the end of the cable needs to be kept open or short-circuited. The analysis paradigm is to design an algorithm for a test result. In existing analysis algorithms, 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] FFT method analyzes the impedance spectrum of the test alone, and the positioning step obtained is limited by the selected time window and sampling rate, which is insufficient in positioning smaller defects.

[0005] IT method needs to analyze the healthy impedance spectrum and the test impedance spectrum together. By comparing the difference between the integral transform analysis results of the two impedance spectra, smaller defects can be located. However, IT method has two practical application obstacles: the kernel function used in integral transform needs to accurately know the propagation coefficient law of the ideal healthy cable with frequency variation, and the impedance spectrum reference value of the healthy cable needs to be known.

[0006] For cables in service, the healthy impedance spectrum can be obtained by prior testing; but for cables already in service, this reference value cannot be obtained, and only the structural parameters and electrical parameters of the ideal healthy cable can be used for calculation. In actual operation, it is difficult to accurately know all the parameters that affect 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-mentioned defects and accurately locate small defects in power cables without accurately knowing the parameters of the healthy cable. SUMMARY

[0008] The present disclosure proposes a scheme for locating defects in power cables based on reconstructed broadband impedance spectrum, which can accurately locate small defects without accurately knowing the parameters of the healthy cable.

[0009] According to one embodiment of the present disclosure, a method for locating hidden defects of power cable based on reconstructed broadband impedance spectrum is proposed, comprising:

[0010] measuring the broadband characteristic impedance spectrum Z of the head end of the to-be-tested cable when the end of the to-be-tested cable is open-circuited open , and measuring the broadband characteristic impedance spectrum Z of the head end of the to-be-tested cable when the end of the to-be-tested cable is short-circuited short ;

[0011] based on the measured broadband characteristic impedance spectrum Z open and Z short , reconstructing the health broadband impedance spectrum R-Zh of the to-be-tested power cable according to the following formula:

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

[0013] wherein 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 square root operation, and B(i) = log[1 + (2 * A(i)) / (Z open (i) - A(i))];

[0014] obtaining 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 to-be-tested cable;

[0015] determining a reference frequency list corresponding to each to-be-analyzed data point in the to-be-analyzed positioning interval of the to-be-tested cable based on the reference pseudo-frequency;

[0016] using the reference frequency list, using a digital lock-in amplifier algorithm to analyze the broadband characteristic impedance spectrum Z open and the reconstructed health broadband impedance spectrum R-Zh as pseudo-time domain signals respectively, and obtaining corresponding analysis results;

[0017] locating hidden defects according to the difference between the corresponding analysis results of the broadband characteristic impedance spectrum Z open of the head end and the corresponding analysis results of the health broadband impedance spectrum R-Zh.

[0018] In some embodiments, the reference pseudo-frequency f0 is obtained according to the following formula:

[0019] f0 = 2 * sqrt(epsilon) / (c * N0),

[0020] wherein epsilon is the relative dielectric constant of the main insulation layer of the to-be-tested cable, c is the speed of light, and N0 is the number of data points per meter analyzed.

[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 = [l1*N0*f0:f0:l2*N0*f0],

[0023] wherein [l1*N0*f0:f0:l2*N0*f0] represents an arithmetic sequence from l1*N0*f0 to l2*N0*f0 with a step size of f0, wherein l1 and l2 are the start point and the end point of the positioning interval to be analyzed, and f0 is a reference pseudo-frequency.

[0024] In some embodiments, the impedance spectrum is analyzed by using the reference frequency list and a digital lock-in amplifier algorithm, including:

[0025] selecting cos(w k t) as a first reference signal, multiplying the impedance spectrum currently analyzed by the first reference signal, and obtaining an X component by low-pass filtering, w k being the kth frequency in the reference frequency list;

[0026] selecting sin(w k t) as a second reference signal, multiplying the impedance spectrum currently analyzed by the second reference signal, and obtaining a Y component by low-pass filtering;

[0027] obtaining an analysis result corresponding to the kth data point to be analyzed according to the X and / or Y component.

[0028] In some embodiments, according to the analysis result corresponding to the wideband characteristic impedance spectrum Z open and the difference between the analysis result corresponding to the healthy wideband impedance spectrum R-Zh and the analysis result corresponding to the healthy wideband impedance spectrum R-Zh, the hidden defect is located, including:

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

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

[0031] identifying a peak point in a waveform diagram of the difference R;

[0032] determining the location of the hidden defect according to the abscissa corresponding to the peak point.

[0033] According to one embodiment of the present disclosure, an apparatus for locating a hidden defect in a power cable based on a reconstructed wideband impedance spectrum is also proposed, comprising:

[0034] an open-circuit short-circuit impedance measurement unit for measuring a first-end wideband characteristic impedance spectrum Z of the to-be-tested power cable when a terminal end of the to-be-tested power cable is in open circuit open , and measuring a first-end wideband characteristic impedance spectrum Z of the to-be-tested power cable when the terminal end of the to-be-tested power cable is in short circuit short ;

[0035] an impedance spectrum reconstruction unit for reconstructing a health wideband impedance spectrum R-Zh of the to-be-tested power cable based on the measured first-end wideband characteristic impedance spectrum 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] wherein N is a total number of data points in the impedance spectrum, i is a number, i = 1, 2, …, N, A(i) = sqrt(Z open (i)*Z short (i)), sqrt represents a square root operation, and B(i) = log[1+(2*A(i)) / (Z open (i)-A(i))];

[0038] a reference pseudo-frequency calculation unit for obtaining a reference pseudo-frequency used for determining an analysis frequency interval of the impedance spectrum according to a relative dielectric constant of a main insulation layer of the to-be-tested power cable;

[0039] a reference frequency list calculation unit for determining, based on the reference pseudo-frequency, a reference frequency list corresponding to each to-be-analyzed data point in a to-be-analyzed positioning interval of the to-be-tested power cable;

[0040] a digital lock-in amplifier algorithm analysis unit for using the reference frequency list to analyze, as pseudo-time-domain signals, the first-end wideband characteristic impedance spectrum Z open and the reconstructed health wideband impedance spectrum R-Zh by using a digital lock-in amplifier algorithm, to obtain corresponding analysis results;

[0041] a hidden danger positioning unit for positioning a hidden defect according to a difference between the corresponding analysis result of the first-end wideband characteristic impedance spectrum Z open and the corresponding analysis result of the health wideband impedance spectrum R-Zh.

[0042] In some embodiments, the reference pseudo-frequency calculation unit obtains the reference pseudo-frequency f0according to the following formula:

[0043] f0= 2*sqrt(epsilon) / (c*N0),

[0044] Wherein, 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.

[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 = [l1*N0*f0:f0:l2*N0*f0],

[0047] Wherein, [l1*N0*f0:f0:l2*N0*f0] represents an arithmetic sequence from l1*N0*f0 to l2*N0*f0 with a step size of f0, wherein l1 and l2 are the start point and end point of the positioning interval to be analyzed, and f0 is the reference pseudo-frequency.

[0048] In some embodiments, the digital lock-in amplifier algorithm analysis unit analyzes the impedance spectrum using the digital lock-in amplifier algorithm with the reference frequency list, including:

[0049] Selecting cos(w k t) as the first reference signal, multiplying it with the impedance spectrum being analyzed, and obtaining the X component by low-pass filtering, w k is the kth frequency in the reference frequency list;

[0050] Selecting sin(w k t) as the second reference signal, multiplying it with the impedance spectrum being analyzed, and obtaining the Y component by low-pass filtering;

[0051] According to the X and / or Y components, the analysis result corresponding to the kth data point to be analyzed is obtained.

[0052] In some embodiments, the hidden danger positioning unit positions the hidden defect 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.

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

[0054] Wherein, 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] Identifying the peak point in the waveform graph of the difference R;

[0056] Determining the location of the hidden defect according to the abscissa corresponding to the peak point.

[0057] According to one embodiment of the present disclosure, an electronic device is provided, the device comprising a memory for storing computer instructions executable on a processor, and the processor for implementing the method of any one of the above when executing the computer instructions.

[0058] According to one embodiment of the present disclosure, a computer readable storage medium is provided, having stored thereon a computer program, the program being executed by a processor to implement the method of any one of the above.

[0059] The scheme for locating power cable hidden defects based on wideband characteristic impedance spectrum proposed by the present disclosure solves the problem of dependence on healthy cable parameters of the traditional IT method by measuring the wideband characteristic impedance spectrum of the head end when the cable end is open-circuited and short-circuited, and reconstructing the healthy wideband impedance spectrum, greatly improving the applicability of the method on the served cable, and combining the digital lock-in amplifier (DLIA) algorithm to analyze the impedance spectrum, and calculating the reference frequency list through the self-defined frequency interval reference pseudo-frequency, overcoming the defects of the FFT method limited by the time window and the sampling rate, so that the positioning step can be flexibly adjusted, and has stronger anti-interference ability, thereby significantly improving the identification sensitivity of weak hidden defects. In addition, the method of the present scheme for locating defects by calculating the difference between the wideband characteristic impedance spectrum of the head end and the analysis result of the reconstructed healthy wideband impedance spectrum avoids the complexity of directly calculating the propagation coefficient, making the method more convenient to apply in actual engineering. Experimental results show that, compared with the existing FFT and IT methods, the present scheme can more accurately identify and locate weak hidden defects in the cable, has significant advantages, and realizes accurate positioning of power cable hidden defects under limited parameters, providing technical support for preventive maintenance of the power system.

[0060] Other features and advantages of the technical solutions proposed by the present disclosure are described in detail below. BRIEF DESCRIPTION OF DRAWINGS

[0061] The drawings herein are incorporated into the specification and form a part of the specification, show embodiments consistent with the present disclosure, and together with the specification serve to explain the principles of the present disclosure.

[0062] Figure 1 A flowchart of a method for locating power cable hidden defects based on reconstructed wideband impedance spectrum according to one embodiment of the present disclosure is shown.

[0063] Figure 2 A schematic diagram of the wideband characteristic impedance spectrum of the head end when the cable end is open-circuited and the wideband characteristic impedance spectrum of the head end when the end is short-circuited, obtained according to one exemplary embodiment of the present disclosure, is shown.

[0064] Figure 3 A schematic diagram of a reconstructed broadband impedance spectrum is shown.

[0065] Figure 4a 、 Figure 4b and Figure 4c A schematic diagram of analyzing and locating a cable hidden fault according to one example embodiment of the present disclosure and a schematic diagram of analyzing and locating a cable hidden fault using prior art are shown, respectively.

[0066] Figure 5 is a structural schematic diagram of an electronic device shown in at least one embodiment of the present disclosure. DETAILED DESCRIPTION

[0067] The example embodiments will be described in detail herein with reference to the attached drawings. The description of the example embodiments is intended to apply to all alternative embodiments, unless otherwise indicated. It is to be understood that other example embodiments can be utilized and structural or procedural changes can be made without departing from the scope of the present disclosure. The following detailed description is not to be understood as limiting the broad teachings of the present disclosure.

[0068] Embodiments of the present disclosure can be applied to a computer system / server, which can operate in a networked environment using a plurality of other general purpose or special purpose computer systems and / or configurations. Examples of well-known computer systems, environments, and / or configurations that can be suitable for use with 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, minicomputer systems, mainframe computer systems, and distributed cloud computing environments that include any of the above systems or devices, and the like.

[0069] The computer system / server can be described in the general context of computer system-executable instructions, such as program modules, being executed by a computer system. Generally, program modules can include routines, programs, objects, components, logic, data structures, and the like, that perform particular tasks or implement particular abstract data types. Computer system / server can operate in a distributed cloud computing environment where tasks are performed by remote processing devices that are linked through a communications network. In a distributed cloud computing environment, program modules can be located in local or remote computer system storage media including memory storage devices.

[0070] Figure 1 A flowchart of a method of locating a cable hidden defect according to one embodiment of the present disclosure is shown. As shown in Figure 1 , the method includes steps 1-6.

[0071] Step 1, measure the open-circuit end of the cable under test open , and measure the short-circuit end of the cable under test short .

[0072] For open-circuit measurement, the end of the cable under test is placed in open-circuit state, i.e. the core wire of the cable end is disconnected from the ground. Then at the head end of the cable, a precision impedance analyzer is used to measure the input impedance value at each of the multiple discrete frequency points in the preset frequency range, thus obtaining the head-end wideband characteristic impedance spectrum Z open .

[0073] For short-circuit measurement, the end of the cable under test is placed in short-circuit state, i.e. the core wire of the cable end is reliably connected to the ground. Then at the head end of the cable, a precision impedance analyzer is used to measure the input impedance value at each of the same multiple discrete frequency points, thus obtaining the head-end wideband characteristic impedance spectrum Z short .

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

[0075] Step 2, based on the measured head-end wideband characteristic impedance spectrum Z open and Z short , reconstruct the health wideband 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 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 head-end wideband characteristic impedance spectrum, [(1 / N)*∑ i A(i)] calculates the average value of A at all frequency points as the overall scaling factor, and B(i) = log[1+(2*A(i)) / (Zopen(i)-A(i))] is used to convert the relationship between the open-circuit impedance Z open (i) and A(i) to the logarithmic domain.

[0079] By using the open circuit and short circuit measurement results simultaneously, the direct dependence on the healthy cable reference spectrum is avoided, and by using A(i) as a mixed representation of the open circuit and short circuit impedance characteristics, a nonlinear mapping relationship between the impedance spectrum and the physical characteristics of the cable is further established through exponential and logarithmic transformation.

[0080] The above reconstruction solves the problem of the need for a healthy cable reference spectrum in the traditional IT method, and realizes the inference of the healthy state without relying on external references, laying the foundation for subsequent defect positioning.

[0081] The reconstructed healthy broadband impedance spectrum R-Zh has the same frequency point distribution as Z open and Z short .

[0082] Step 3: According to the relative dielectric constant of the main insulation layer of the cable to be measured, a reference pseudo-frequency for determining the impedance spectrum analysis frequency interval is obtained.

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

[0084] The main insulation layer is the most important insulation part in the cable, used to isolate the conductor and the shielding layer, and its relative dielectric constant will affect the propagation characteristics of electromagnetic waves in the cable. In practical applications, the relative dielectric constant of the main insulation layer of the cable can be obtained by consulting the product technical manual, or measured by a special dielectric constant tester.

[0085] In some embodiments, the reference pseudo-frequency f0 is obtained according to the following formula:

[0086] f0 = 2 * sqrt(epsilon) / (c * N0),

[0087] where epsilon is the relative dielectric constant of the main insulation layer of the cable to be measured, c is the speed of light, and N0 is the number of data points per meter analyzed.

[0088] The reference pseudo-frequency f0 calculated according to this embodiment is directly proportional to the square root of the relative dielectric constant epsilon, and inversely proportional to the number of data points per meter analyzed N0. The number of data points per meter analyzed N0 is a user-selectable parameter that can be used to control the accuracy of the analysis. The larger N0 is, the smaller the reference pseudo-frequency is, and a more detailed analysis result can be obtained.

[0089] In practical applications, appropriate relative permittivity values can be selected according to the cable type, and appropriate number of data points per meter can be selected according to the required positioning accuracy to obtain an ideal analysis effect. The reference pseudo-frequency calculated according to the embodiment not only takes into account the influence of the cable main insulation medium on electromagnetic wave propagation, but also enables flexible control of analysis accuracy through the setting of N0.

[0090] Step 4, determining 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.

[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 selected interval in the length range of the cable to be measured, which is used to determine which section of the cable to analyze. In practical applications, the positioning interval to be analyzed can be selected according to factors such as operation and maintenance requirements, fault prediction, etc. The number of data points per meter N0 is a user-selectable parameter, and 1 / N0 meters is used as the sampling step size.

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

[0093] F = [l1*N0*f0:f0:l2*N0*f0],

[0094] The above formula indicates that the reference frequency list F is an arithmetic sequence from l1*N0*f0 to l2*N0*f0 with a step size of f0, where l1 and l2 are the start and end points of the positioning interval to be analyzed, and f0 is the reference pseudo-frequency.

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

[0096] Unlike the FFT method, which is limited by the frequency range and frequency step size of the impedance spectrum, the present embodiment can flexibly set the positioning interval to be analyzed according to actual requirements, and achieve accurate analysis of the interval through a reasonably constructed reference frequency list. Each frequency in the reference frequency list will serve as a reference frequency for 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 start and end points of the positioning interval to be analyzed can be flexibly selected according to factors such as cable length and the location of the section of interest. At the same time, as analyzed above, by adjusting the number of data points per meter N0, a balance between analysis accuracy and computational load can be achieved. For example, when a suspicious section needs to be analyzed more finely, the N0 value can be appropriately increased to obtain denser analysis results.

[0098] Step 5, using the reference frequency list, the digital lock-in amplifier algorithm is used to 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, and the corresponding analysis results are obtained.

[0099] This embodiment processes the impedance spectrum as a pseudo-time domain signal and analyzes it using a digital lock-in amplifier algorithm. The basic principle of the digital lock-in amplifier is introduced below.

[0100] Digital lock-in amplifier (DLIA) is a high-precision measurement device used to extract weak signals of specific frequencies from complex signal environments. It generates quadrature reference signals for phase locking and digital processing, enabling accurate measurement of signal amplitude and phase in high-noise environments. Dual-channel DLIA has two independent input channels that can simultaneously measure the quadrature components (such as X and Y components) of input signals, making it particularly suitable for applications such as precision optical measurement, material property research, and high-sensitivity sensor signal processing.

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

[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 multiplier. Low-pass filtering the Vmix1(t) signal gives the low-frequency quantity V w / 2*cos(phi), denoted as X.

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

[0105] The output of the 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 biggest advantage of the digital lock-in amplifier in extracting frequency components is the anti-interference ability and the ability to determine the frequency list by the user.

[0110] According to some embodiments of the present embodiment, for the kth 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 the X component is obtained by low-pass filtering, w k is the frequency corresponding to the ith 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 the Y component is obtained by low-pass filtering; and the analysis result corresponding to the kth data point to be analyzed is obtained according to the X and / or Y components.

[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 standard is used.

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

[0113] Step 6, according to the difference between the analysis result corresponding to the broadband characteristic impedance spectrum Z open and the analysis result corresponding to the healthy broadband impedance spectrum R-Zh, the hidden defect is located.

[0114] The analysis result DLIA(Z open ) corresponding to the broadband characteristic impedance spectrum Z open and the analysis result DLIA(R-Zh) corresponding to the healthy broadband impedance spectrum R-Zh are one-to-one corresponding two sequences, and the abscissa of the sequence corresponds to each position point in the positioning interval to be analyzed.

[0115] In some embodiments, a difference value R = DLIA(Z open )-DLIA(R-Zh) can be calculated, where DLIA(Z open ) is the analysis result of the wideband characteristic impedance spectrum Z open of the first end, and DLIA(R-Zh) is the analysis result of the wideband impedance spectrum R-Zh corresponding to the healthy cable.

[0116] By calculating the difference value of the two analysis results, the system error and background interference can be effectively eliminated. This differential processing method enhances the signal-to-noise ratio, making it easier to identify weak hidden defect signals. Since the defect point will interfere with the impedance characteristics, the defect can be represented as a clear peak in the difference waveform. Compared with the traditional method, the peak obtained according to the present embodiment is more sharp and significant, effectively improving the detection sensitivity.

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

[0118] An application example of the present disclosure is given below.

[0119] This example uses a precision impedance analyzer TH285-030 to measure a cable with a length of 180 m on site. To verify the effectiveness of the present scheme, a weak hidden defect is set at a distance of 80 m from the first end of the cable.

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

[0121] Based on the measurement results, the method proposed in the present disclosure is used to reconstruct the healthy wideband impedance spectrum, as shown in Figure 3 Z h (cal) (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 in

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

[0123] The positioning results show that, as shown in FIG. 6, the method according to the present disclosure can accurately locate the fault at 80 m, and the peak value is obvious and the position is accurate. In contrast, the FFT result (FIG. 7) can identify the fault position, but the amplitude is small and the identification effect is not significant. Similarly, the identification peak value given by the IT method result (FIG. 8) is smaller than the identification result of the present disclosure, because it is difficult to accurately obtain the real parameters of the cable system under test in actual test. Figure 4a Figure 4b ) can identify the fault position, but the amplitude is small and the identification effect is not significant. Similarly, the identification peak value given by the IT method result (FIG. 8) is smaller than the identification result of the present disclosure, because it is difficult to accurately obtain the real parameters of the cable system under test in actual test. Figure 4c

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

[0125] The present disclosure also proposes an apparatus for locating the hidden defects of the power cable based on the reconstructed broadband impedance spectrum, comprising:

[0126] an open-circuit short-circuit impedance measurement unit, configured to measure the broadband characteristic impedance spectrum Z open of the first end of the cable under test when the end of the cable under test is open-circuited, and measure the broadband characteristic impedance spectrum Z short of the first end of the cable under test when the end of the cable under test is short-circuited;

[0127] 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 broadband characteristic impedance spectra Z open and Z short of the first end of the cable under test according to the following formula:

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

[0129] wherein 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, and B(i) = log[1+(2*A(i)) / (Z open (i)-A(i))];

[0130] ​​A reference pseudo-frequency calculation unit is configured to obtain a reference pseudo-frequency used for determining an impedance spectrum analysis frequency interval according to a relative dielectric constant of a main insulation layer of the cable to be measured.

[0131] A reference frequency list calculation unit is configured to determine a reference frequency list corresponding to each data point to be analyzed in a 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 is configured to analyze the first-end wideband characteristic impedance spectrum Z open and the reconstructed healthy wideband impedance spectrum R-Zh as pseudo-time domain signals by using the reference frequency list and a digital lock-in amplifier algorithm respectively to obtain corresponding analysis results.

[0133] A hazard positioning unit is configured to position a hidden defect according to a difference between the corresponding analysis result of the first-end wideband characteristic impedance spectrum Z open and the corresponding analysis result of the healthy wideband impedance spectrum R-Zh.

[0134] Other details and features of the embodiment can be found in the above related descriptions.

[0135] Figure 5 The electronic device provided in the at least one embodiment of the present disclosure includes a memory and a processor, the memory is configured to store computer instructions executable on the processor, and the processor is configured to implement the method for positioning a hidden defect of a power cable based on a reconstructed wideband impedance spectrum according to any embodiment or implementation of the present disclosure when the computer instructions are executed.

[0136] The at least one embodiment of the present disclosure also provides a computer readable storage medium having a computer program stored thereon, the program being executed by a processor to implement the method for positioning a hidden defect of a power cable based on a reconstructed wideband impedance spectrum according to any embodiment or implementation of the present disclosure.

[0137] Those skilled in the art should understand that one or more embodiments of the present disclosure can be provided as a method, a system or a computer program product. Therefore, one or more embodiments of the present disclosure can be in the form of a completely hardware embodiment, a completely software embodiment or an embodiment combining software and hardware aspects. Moreover, one or more embodiments of the present disclosure can be in the form of a computer program product implemented on one or more computer usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer usable program code.

[0138] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the data processing device embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0139] The foregoing has described specific embodiments of this specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps described in the claims may be performed in a different order than that shown in the embodiments and may still achieve the desired results. Furthermore, the processes depicted in the drawings do not necessarily require the specific or sequential order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0140] While this specification contains numerous specific implementation details, these should not be construed as limiting the scope of any invention or the scope of the claims, but rather are primarily intended to describe features of specific embodiments of a particular invention. Certain features described in the various embodiments herein may also be implemented in combination in a single embodiment. Conversely, various features described in a single embodiment may also be implemented separately in various embodiments or in any suitable sub-combination. Furthermore, while features may function in certain combinations as described above and even initially claimed in this way, one or more features from a claimed combination may be removed from that combination in some cases, and a claimed combination may refer to a sub-combination or a variation thereof.

[0141] Similarly, although the operations are depicted in a specific order in the accompanying drawings, this should not be construed as requiring these operations to be performed in the specific order shown or sequentially, or requiring all illustrated operations to be performed to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous. Furthermore, the separation of various system modules and components in the above embodiments should not be construed as requiring such separation 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.

[0142] Thus, specific embodiments of the subject matter have been described. Other embodiments are within the scope of the appended claims. In some cases, the actions recited in the claims may be performed in a different order and still achieve the desired result. Furthermore, the processes depicted in the drawings are not necessarily shown in a specific order or sequence to achieve the desired result. In some implementations, multitasking and parallel processing may be advantageous.

[0143] The above description is only the preferred embodiment of one or more embodiments of the specification, and is not used to limit one or more embodiments of the specification. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of one or more embodiments of the specification should be included in the protection range of one or more embodiments of the specification.

Claims

1. A method for locating hidden defects in power cables based on reconstructed broadband impedance spectrum, characterized in that, include: Measurement of the broadband characteristic impedance spectrum Z at the beginning of the cable under test with the end open-circuited. open And measure the broadband characteristic impedance spectrum Z at the beginning of the cable under test when it is short-circuited. short ; Based on the measured broadband characteristic impedance spectrum Z at the beginning open and Z short The healthy broadband impedance spectrum R-Zh of the power cable under test 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 index, i=1,2,…,N, and 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))]; Based on the relative permittivity of the main insulation layer of the cable under test, a reference pseudo-frequency is obtained to determine the frequency interval for impedance spectrum analysis. Based on the reference pseudo-frequency, determine the reference frequency list corresponding to each data point to be analyzed in the analysis positioning interval of the cable under test; Using the aforementioned reference frequency list, a digital lock-in amplifier algorithm is employed to analyze the broadband characteristic impedance spectrum Z at the beginning of the circuit. open The reconstructed healthy broadband impedance spectrum R-Zh is used as a pseudo-time domain signal for analysis, and the corresponding analysis results are obtained. Based on the broadband characteristic impedance spectrum Z at the beginning 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 potential defects; The reference pseudo-frequency f0 is obtained according to the following formula: f0 = 2*sqrt(epsilon) / (c*N0), Where epsilon is the relative permittivity of the main insulation layer of the cable under test, c is the speed of light, and N0 is the number of data points analyzed per meter; And determine the reference frequency list F corresponding to each data point in the analysis interval according to the following formula: F = [l1* N0* f0: f0 : l2* N0* f0], Wherein, [l1* N0* f0: f0 : l2* N0* f0] represents an arithmetic sequence from l1* N0* f0 to l2* N0* f0 with a step size of f0, where l1 and l2 are the start and end points of the positioning interval to be analyzed, and f0 is the reference pseudo-frequency.

2. The method according to claim 1, characterized in that, Using the aforementioned reference frequency list, an impedance spectrum analysis is performed using a digital lock-in amplifier algorithm, including: for the k-th data point to be analyzed, Select cos(w) k t) is used as the first reference signal, multiplied by the impedance spectrum currently being analyzed, and then low-pass filtered to obtain the X component, w k The kth frequency in the reference frequency list; Choose sin(w) k t) is used as the second reference signal, multiplied with the impedance spectrum currently being analyzed, and then filtered through a low-pass filter to obtain the Y component; Based on the X and / or Y components, the analysis results corresponding to the kth data point to be analyzed are obtained.

3. The method according to claim 1, characterized in that, Based on the broadband characteristic impedance spectrum Z at the beginning 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 potential defects, including: Calculate the difference R = DLIA(Z) open )- DLIA(R-Zh), Among them, DLIA(Z) open Z is the broadband characteristic impedance spectrum at the beginning. open The corresponding analysis results, DLIA(R-Zh) are the analysis results corresponding to the healthy broadband impedance spectrum R-Zh; Identify peak points in the waveform of the difference R; The location of potential defects can be determined by the x-coordinate corresponding to the peak point.

4. A device for locating hidden defects in power cables based on reconstructed broadband impedance spectrum, characterized in that, include: The open-circuit and short-circuit impedance measurement unit is used to measure the broadband characteristic impedance spectrum Z at the beginning of the cable under test when the end is open-circuited. open And measure the broadband characteristic impedance spectrum Z at the beginning of the cable under test when it is short-circuited. short ; Impedance spectrum reconstruction unit for using the measured first-end broadband characteristic impedance spectrum Z open and Z short The healthy broadband impedance spectrum R-Zh of the power cable under test 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 index, i=1,2,…,N, and 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))]; The reference pseudo-frequency calculation unit is used to obtain the reference pseudo-frequency for determining the frequency interval of impedance spectrum analysis based on the relative permittivity of the main insulation layer of the cable under test. The reference frequency list calculation unit is used to determine the reference frequency list corresponding to each data point to be analyzed in the analysis positioning interval of the cable under test based on the reference pseudo-frequency. The digital lock-in amplifier algorithm analysis unit is used to analyze the first-end broadband characteristic impedance spectrum Z using the reference frequency list and a digital lock-in amplifier algorithm. open The reconstructed healthy broadband impedance spectrum R-Zh is used as a pseudo-time domain signal for analysis, and the corresponding analysis results are obtained. The hazard location unit is used to locate hazards based on the broadband characteristic impedance spectrum Z at the beginning. 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 potential defects; 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 permittivity of the main insulation layer of the cable under test, c is the speed of light, and N0 is the number of data points analyzed per meter; The reference frequency list calculation unit determines the reference frequency list F corresponding to each data point in the analysis interval according to the following formula: F = [l1* N0* f0: f0 : l2* N0* f0], Wherein, [l1* N0* f0: f0 : l2* N0* f0] represents an arithmetic sequence from l1* N0* f0 to l2* N0* f0 with a step size of f0, where l1 and l2 are the start and end points of the positioning interval to be analyzed, and f0 is the reference pseudo-frequency.

5. The apparatus according to claim 4, characterized in that, The digital lock-in amplifier algorithm analysis unit uses the reference frequency list to analyze the impedance spectrum using a digital lock-in amplifier algorithm, including: for the k-th data point to be analyzed, Select cos(w) k t) is used as the first reference signal, multiplied by the impedance spectrum currently being analyzed, and then low-pass filtered to obtain the X component, w k The kth frequency in the reference frequency list; Choose sin(w) k t) is used as the second reference signal, multiplied with the impedance spectrum currently being analyzed, and then filtered through a low-pass filter to obtain the Y component; Based on the X and / or Y components, the analysis results corresponding to the kth data point to be analyzed are obtained.

6. The apparatus according to claim 4, characterized in that, The hazard location unit is based on the broadband characteristic impedance spectrum Z at the beginning. 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 potential defects, including: Calculate the difference R = DLIA(Z) open )- DLIA(R-Zh), Among them, DLIA(Z) open Z is the broadband characteristic impedance spectrum at the beginning. open The corresponding analysis results, DLIA(R-Zh) are the analysis results corresponding to the healthy broadband impedance spectrum R-Zh; Identify peak points in the waveform of the difference R; The location of potential defects can be determined by the x-coordinate corresponding to the peak point.

7. An electronic device, characterized in that, The device includes a memory and a processor, the memory being used to store computer instructions executable on the processor, and the processor being used to implement the method of any one of claims 1 to 3 when executing the computer instructions.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the method according to any one of claims 1 to 3.

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