Methods, devices, electronic equipment, and storage media for locating hidden defects in cables based on broadband characteristic impedance spectra.

Abstract

A method, apparatus, electronic device, and storage medium for locating hidden defects in cables based on broadband characteristic impedance spectra are disclosed. The method includes: measuring the broadband characteristic impedance spectrum at the beginning of the cable under test when it is open-circuited and short-circuited; calculating the characteristic impedance spectrum based on the open-circuit and short-circuit impedance spectra; obtaining a reference pseudo-frequency based on the relative permittivity of the main insulation layer of the cable under test; determining a reference frequency list based on the reference pseudo-frequency; analyzing the characteristic impedance spectrum using a digital lock-in amplifier analysis algorithm; and determining the location of hidden defects in the cable based on the analysis results. This method does not require obtaining parameters such as the propagation coefficient law and impedance spectrum reference values ​​of healthy cables, overcoming the limitations of existing FFT and IT methods. It achieves high-precision location of subtle hidden defects in cables, making the frequency domain reflection method based on broadband impedance spectra more practical in operation, suitable for preventive maintenance of power systems, and possessing greater field application capabilities.

Description

Technical Field

[0001] This disclosure relates to the field of electrical engineering, and in particular to a method, apparatus, electronic device, and storage medium for locating hidden defects in cables based on broadband characteristic impedance spectrum. Background Technology

[0002] Frequency domain reflection has the potential to identify minor faults in power cables, with cable impedance spectrum being the primary research object. By using frequency domain reflection, potential hidden defects in power cables can be detected in advance, preventing them from developing into serious faults and causing potential losses. This is of great significance for the operation and maintenance inspection of cables.

[0003] Currently, the main research objects of the frequency domain reflection method are the head-end impedance spectrum (BIS) and reflection coefficient spectrum (RCS) of cables. During testing, the cable ends need to be kept open or short-circuited. The analytical paradigm is to design an algorithm based on a single test result. Among the publicly available analytical algorithms, the Fast Fourier Transform (FFT) or Integral Transform (IT) methods are mainly used to analyze cable impedance spectra. However, both of these methods have their own drawbacks.

[0004] The impedance spectrum analyzed by FFT alone is affected by the selected time window and sampling rate, and it is lacking in locating smaller hidden defects.

[0005] The IT method requires combining the analysis of healthy impedance spectra and test impedance spectra. By comparing the differences in the integral transformation results of the two impedance spectra, more minute defects can be located. However, the kernel function used in the integral transformation requires accurate knowledge of the propagation coefficient of the ideal healthy cable as a function of frequency, as well as the impedance spectrum of the healthy cable, which presents practical problems. For cables awaiting service, pre-testing is possible. However, for cables already in service, testing is not feasible. The ideal cable impedance spectrum can only be calculated based on all structural and electrical parameters of the ideal healthy cable, but this is very difficult in practice because every parameter affecting the impedance spectrum of the healthy cable cannot be accurately known, which will affect the final test results.

[0006] Therefore, a technical solution is needed that can locate even the smallest cable defects and overcome the drawbacks of existing methods. Summary of the Invention

[0007] This disclosure proposes a scheme for locating potential defects in power cables based on broadband characteristic impedance spectrum, which can achieve precise location of minute defects without needing to know the propagation coefficient and impedance spectrum of healthy cables.

[0008] According to one embodiment of this disclosure, a method for locating hidden defects in cables based on broadband characteristic impedance spectrum is proposed, including:

[0009] 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 ;

[0010] The broadband characteristic impedance spectrum Z of the cable under test is calculated using the following formula. char :

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

[0012] Among them, Z open (i) represents the broadband characteristic impedance spectrum at the beginning of the spectrum Z. open The i-th data point in Z short (i) represents the broadband characteristic impedance spectrum at the beginning of the spectrum Z. short The i-th data point in Z char (i) represents the broadband characteristic impedance spectrum Z char The i-th data point in the array, where sqrt represents the square root operation;

[0013] 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.

[0014] 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;

[0015] Using the aforementioned reference frequency list, the broadband characteristic impedance spectrum Z of the cable under test is analyzed based on a digital lock-in amplifier algorithm. char As a pseudo-time domain signal, the analysis result DLIA(Z) is obtained. char );

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

[0017] In some implementations, the broadband characteristic impedance spectrum Z at the beginning of the cable under test with the end open-circuited is measured. open And measure the broadband characteristic impedance spectrum Z at the beginning of the cable under test when it is short-circuited. short ,include:

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

[0019] The impedance values ​​at the cable head end at various discrete frequency points are measured when the cable end under test is open-circuited, and the broadband characteristic impedance spectrum Z at the head end is obtained. open ;

[0020] The impedance values ​​at the cable head end at various discrete frequency points when the cable end under test is short-circuited are measured to obtain the broadband characteristic impedance spectrum Z at the head end. short .

[0021] In some implementations, the reference pseudo-frequency f0 is obtained according to the following formula:

[0022] f0=2*sqrt(epsilon) / (c*N0),

[0023] 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.

[0024] In some implementations, the reference frequency list F corresponding to each data point in the analysis interval is determined according to the following formula:

[0025] F = [l1*N0*f0:f0:l2*N0*f0],

[0026] 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.

[0027] In some implementations, the broadband characteristic impedance spectrum Z of the cable under test is analyzed using the reference frequency list and a digital lock-in amplifier analysis algorithm. char As a pseudo-time domain signal, the analysis result DLIA(Z) is obtained. char This includes: for the k-th data point to be analyzed,

[0028] Select cos(w) k t) is used as the first reference signal, and the broadband characteristic impedance spectrum Z char Multiply and then pass through a low-pass filter to obtain the X component, w k The kth frequency in the reference frequency list;

[0029] Choose sin(w) k t) is used as the second reference signal, along with the broadband characteristic impedance spectrum Z. char Multiply and then pass through a low-pass filter to obtain the Y component;

[0030] Based on the X and / or Y components, the analysis results corresponding to the kth data point to be analyzed are obtained.

[0031] In some implementations, according to DLIA(Z) char Determining the location of potential defects in cables includes:

[0032] In DLIA(Z) charIdentify peak points in the waveform diagram;

[0033] The location of potential defects can be determined by the x-coordinate corresponding to the peak point.

[0034] According to one embodiment of this disclosure, a device for locating hidden defects in cables based on broadband characteristic impedance spectrum is also proposed, comprising:

[0035] 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 ;

[0036] The broadband characteristic impedance calculation unit is used to calculate the broadband characteristic impedance spectrum Z of the cable under test according to the following formula. char :

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

[0038] Among them, Z open (i) represents the broadband characteristic impedance spectrum at the beginning of the spectrum Z. open The i-th data point in Z short (i) represents the broadband characteristic impedance spectrum at the beginning of the spectrum Z. short The i-th data point in Z char (i) represents the broadband characteristic impedance spectrum Z char The i-th data point in the array, where sqrt represents the square root operation;

[0039] 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.

[0040] 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.

[0041] The digital lock-in amplifier algorithm analysis unit is used to analyze the broadband characteristic impedance spectrum Z of the cable under test based on the digital lock-in amplifier analysis algorithm using the reference frequency list. char As a pseudo-time domain signal, the analysis result DLIA(Z) is obtained. char );

[0042] Hazard location unit, used to locate hazards based on DLIA(Z) char Determine the location of potential defects in the cable.

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

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

[0045] The impedance values ​​at the cable head end at various discrete frequency points are measured when the cable end under test is open-circuited, and the broadband characteristic impedance spectrum Z at the head end is obtained. open ;

[0046] The impedance values ​​at the cable head end at various discrete frequency points when the cable end under test is short-circuited are measured to obtain the broadband characteristic impedance spectrum Z at the head end. short .

[0047] In some embodiments, the reference pseudo-frequency calculation unit is used to calculate the reference pseudo-frequency f0 according to the following formula:

[0048] f0=2*sqrt(epsilon) / (c*N0),

[0049] 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.

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

[0051] F = [l1*N0*f0:f0:l2*N0*f0],

[0052] 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.

[0053] According to one embodiment of this disclosure, an electronic device is provided, the device including a memory and a processor, the memory being used to store computer instructions executable on the processor, the processor being used to implement the method as described in any of the preceding claims when executing the computer instructions.

[0054] According to one embodiment of the present disclosure, a computer-readable storage medium is provided having a computer program stored thereon that, when executed by a processor, implements the method as described in any of the preceding claims.

[0055] This disclosure presents a scheme for locating potential defects in power cables based on broadband characteristic impedance spectra. By analyzing the impedance spectra measured under open-circuit and short-circuit conditions, the characteristic impedance spectrum is calculated without requiring knowledge of the propagation coefficient and impedance spectrum of healthy cables, overcoming the limitation of the IT method, which requires extensive information on healthy cable parameters in practical applications. Compared to the FFT method, this scheme is not limited by time windows and sampling rates, enabling higher accuracy in location. By using the characteristic impedance spectrum as a pseudo-time-domain signal for analysis with a digital lock-in amplifier, this scheme can effectively identify and locate even minute potential defects. The scheme is simple to operate, requiring only measurements under open-circuit and short-circuit conditions, facilitating its widespread application in practical engineering. Furthermore, experimental verification shows that this scheme significantly outperforms existing FFT and IT methods in locating potential defects in power cables, demonstrating strong practical value.

[0056] Other features and advantages of the technical solutions proposed in this disclosure are described below. Attached Figure Description

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

[0058] Figure 1 A flowchart of a method for locating potential defects in cables according to an embodiment of the present disclosure is shown.

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

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

[0061] Figure 4a , Figure 4b and Figure 4c The diagrams show an analysis of potential faults in a positioning cable according to an exemplary embodiment of the present disclosure and an analysis of potential faults in a positioning cable using existing technology.

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

[0063] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0064] This disclosure can be applied to computer systems / servers that can operate with a wide range of 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 computer systems / servers 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 PCs, minicomputer systems, mainframe computer systems, and distributed cloud computing environments that include any of the above systems, etc.

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

[0066] Figure 1 A flowchart illustrating a method for locating potential defects in cables according to an embodiment of this disclosure is shown. Figure 1 As shown, the method includes steps 1 to 6.

[0067] Step 1: 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 .

[0068] For open-circuit measurements, the end of the cable under test is placed in an open-circuit state, meaning the core wire at the cable end is disconnected from the ground wire. Then, a precision impedance analyzer is used to measure the impedance at the cable's beginning. The analyzer selects multiple discrete frequency points within a preset frequency range, measuring the input impedance at each frequency point to obtain the broadband characteristic impedance spectrum Z at the cable's beginning. open .

[0069] For short-circuit measurements, the end of the cable under test is placed in a short-circuit state, that is, the core wire at the end of the cable is reliably connected to the ground wire. Then, at the beginning of the cable, a precision impedance analyzer is used to measure the input impedance value at the same discrete frequency points to obtain the broadband characteristic impedance spectrum Z at the beginning of the cable. short .

[0070] The measured impedance spectrum Z open and Z short All are discrete point sequences, each containing multiple frequency points and their corresponding impedance values.

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

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

[0073] Among them, Z open (i) represents the broadband characteristic impedance spectrum at the beginning of the spectrum Z. open The i-th data point in Z short (i) represents the broadband characteristic impedance spectrum at the beginning of the spectrum Z. short The i-th data point in Z char (i) represents the broadband characteristic impedance spectrum Z char The i-th data point in the array is represented by sqrt, which denotes the square root operation.

[0074] According to this embodiment, the broadband characteristic impedance spectrum Z at the beginning of the circuit is obtained under both open-circuit and short-circuit conditions. open and Z short Then, the broadband characteristic impedance spectrum Z of the cable under test can be calculated. char For each frequency point, the open-circuit impedance value Z at that frequency point can be taken. open (i) and short-circuit impedance value Z short (i) Multiply the two and take the square root to obtain the characteristic impedance value Z at that frequency. char (i). The broadband characteristic impedance spectrum Z of the cable under test is composed of the characteristic impedance values ​​at all frequency points. char .

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

[0076] Step 3: Based on the relative permittivity of the main insulation layer of the cable under test, obtain the reference pseudo-frequency for determining the frequency interval of impedance spectrum analysis.

[0077] The reference pseudo-frequency is a key parameter used in this embodiment to determine the frequency interval for impedance spectrum analysis, laying 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 required analytical accuracy when designing this parameter.

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

[0079] In some implementations, the reference pseudo-frequency f0 is obtained according to the following formula:

[0080] f0=2*sqrt(epsilon) / (c*N0),

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

[0082] According to this embodiment, the reference pseudofrequency f0 is proportional to the square root of the relative permittivity epsilon and inversely proportional to the number of data points N0 analyzed per meter. The number of data points N0 analyzed per meter is a user-selectable parameter that can be used to control the accuracy of the analysis. The larger N0 is, the smaller the reference pseudofrequency, and the more refined the analysis results can be obtained.

[0083] In practical applications, a suitable relative permittivity value can be selected based on the cable type, and the appropriate number of analysis data points per meter can be chosen in conjunction with the required positioning accuracy to obtain ideal analysis results. The reference pseudo-frequency calculated according to this embodiment considers both the influence of the cable's main insulation medium on electromagnetic wave propagation and allows for flexible control of analysis accuracy through the setting of N0.

[0084] Step 4: 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.

[0085] After obtaining the reference pseudo-frequency, the analysis range can be determined based on the actual condition of the cable under test, and a list of reference frequencies corresponding to each data point to be analyzed can be generated. The analysis range is a selected interval within the length of the cable under test, used to determine which segment of the cable to analyze. In practical applications, the analysis range can be selected based on factors such as maintenance requirements and fault prediction. The number of data points analyzed per meter, N0, is a user-selectable parameter, and 1 / N0 meters is used as the sampling step size of the interval.

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

[0087] F = [l1*N0*f0:f0:l2*N0*f0],

[0088] 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.

[0089] The reference frequency list generation method proposed in this embodiment ensures that the entire range to be analyzed can be covered during subsequent analysis of the digital lock-in amplifier, while maintaining an appropriate frequency resolution.

[0090] Unlike the FFT method, which is limited by the frequency range and frequency step size of the impedance spectrum itself, this embodiment allows for flexible setting of the analysis interval according to actual needs, and achieves accurate analysis of this 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.

[0091] In practical applications, the start and end points of the analysis area can be flexibly selected based on factors such as cable length and the location of the section of interest. Furthermore, as analyzed above, by adjusting the number of data points N0 analyzed per meter, a balance can be struck between analytical accuracy and computational load. For example, when a more detailed analysis of a suspicious section is required, the value of N0 can be appropriately increased to obtain denser analysis results.

[0092] Step 5: Using the aforementioned reference frequency list, and based on the digital lock-in amplifier analysis algorithm, analyze the broadband characteristic impedance spectrum Z of the cable under test. char As a pseudo-time domain signal, the analysis result DLIA(Z) is obtained. char ).

[0093] This embodiment processes the impedance spectrum as a pseudo-time-domain signal and analyzes it using a digital lock-in amplifier algorithm. The basic principles of a digital lock-in amplifier are introduced below.

[0094] A digital lock-in amplifier (DLIA) is a high-precision measurement device used to extract weak signals of specific frequencies from complex signal environments. It achieves phase locking and digital processing by generating orthogonal reference signals, enabling accurate measurement of signal amplitude and phase against high-noise backgrounds. A dual-channel DLIA has two independent input channels, allowing simultaneous measurement of the orthogonal components (such as X and Y components) of the input signal. It is particularly suitable for applications requiring simultaneous processing of multiple signal sources or complex vector analysis, such as precision optical measurement, materials property research, and signal processing for high-sensitivity sensors.

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

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

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

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

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

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

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

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

[0103] The biggest advantage of digital lock-in amplifiers in extracting frequency components lies in their anti-interference capabilities and the ability for users to define their own frequency list.

[0104] According to some implementation methods of this embodiment, for the k-th data point to be analyzed, cos(w) is selected. k t) is used as the first reference signal, and the broadband characteristic impedance spectrum Z char Multiply and then pass through a low-pass filter to obtain the X component, w k The k-th frequency in the reference frequency list; select sin(w) k t) is used as the second reference signal, along with the broadband characteristic impedance spectrum Z. char Multiply the components and pass them through a low-pass filter to obtain the Y component; based on the X and / or Y components, obtain the analysis result corresponding to the k-th data point to be analyzed.

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

[0106] The broadband characteristic impedance spectrum Z was then compared using all frequencies from the reference frequency list in sequence. char After performing the above processing, the final analysis result sequence corresponding to the reference frequency list is obtained, namely DLIA(Z). char ).

[0107] Step 6, according to DLIA(Z) char Determine the location of potential defects in the cable.

[0108] DLIA(Z char ) is a discrete sequence of the same length as the reference frequency list, and the horizontal axis of the sequence corresponds to each location point in the positioning interval to be analyzed.

[0109] In some implementations, in DLIA(Z) char Identify peak points in the waveform diagram; determine the location of potential defects based on the horizontal coordinates corresponding to the peak points.

[0110] When a cable has a hidden defect, the impedance characteristics at the defect location will differ from those at the normal location. This difference will manifest as a sudden change in the waveform in the DLIA analysis results, thus forming an identifiable peak. According to this implementation method, hidden defects in cables can be accurately located.

[0111] The method for locating hidden defects in cables based on broadband characteristic impedance spectra proposed in this embodiment combines and analyzes the impedance spectra under open-circuit and short-circuit conditions at the cable end. This eliminates the need to know the propagation coefficient and impedance spectrum of healthy cables, overcoming the limitations of the IT method in practical applications. For cables that have been in service for many years, obtaining accurate health status parameters has become a major bottleneck in engineering practice due to various complex factors. This embodiment avoids this problem, making the frequency domain reflection method based on broadband impedance spectra truly practical. Furthermore, this embodiment uses a digital lock-in amplifier analysis algorithm to process the characteristic impedance spectrum, which is not limited by time windows and sampling rates, overcoming the limitation of the positioning step size in the FFT method. In addition, according to this embodiment, the positioning accuracy can be flexibly controlled by reasonably setting the number of data points analyzed per meter.

[0112] This embodiment is simple to operate, requiring only the measurement of impedance spectra under two end states, making it easy to promote and apply in practical engineering. Through the design of the reference pseudo-frequency and the construction of the reference frequency list, the analysis interval can be freely selected and precise positioning achieved.

[0113] The following is an application example of this disclosure.

[0114] This example demonstrates the use of a TH285-030 precision impedance analyzer to measure a 160m length of cable in the field. To verify the effectiveness of this approach, a minor, potential defect was introduced 60m from the cable's beginning.

[0115] During the measurement, 1601 discrete frequency points were selected within the frequency range of 1–30 MHz. The broadband characteristic impedance spectra Zopen and Zshort of the cable head were measured successively under open-circuit and short-circuit conditions. The test results are as follows: Figure 2 As shown. Based on the measured open-circuit impedance spectrum and short-circuit impedance spectrum, the broadband characteristic impedance spectrum Zchar of the cable under test is calculated as follows. Figure 3 As shown, that is Figure 3 Zh(cal), and Figure 3 The Zf(exp) shown is the measured open-circuit fault impedance spectrum, i.e., the broadband characteristic impedance spectrum Zopen.

[0116] Given a relative permittivity of 2.3 for the main insulation of the cable under test, a reference pseudo-frequency is calculated based on the relative permittivity, and a reference frequency list is constructed. Then, a digital lock-in amplifier analysis algorithm is used to analyze the broadband characteristic impedance spectrum. The analysis results based on the embodiments proposed in this disclosure are as follows: Figure 4a As shown, a significant peak appeared at 60m, accurately indicating the location of the defect.

[0117] For comparison, the same cable was analyzed using both the FFT and IT methods. Figure 4b As shown, the FFT analysis results are almost unable to identify the location of the fault. Figure 4c As shown, due to the inability to accurately obtain the true parameters of the cable system under test, the identification peak value given by the IT method is significantly smaller than that of this scheme. This experimental result strongly demonstrates the significant advantages of the embodiments proposed in this disclosure in practical engineering applications—it does not rely on difficult-to-obtain healthy cable parameter information, but only measures the characteristics of the cable itself under open and short circuit states to achieve high-precision location of minor hidden defects, making the frequency domain reflection method based on broadband impedance spectrum a practical tool for preventive maintenance of power systems.

[0118] The experimental results above verify the feasibility of this scheme and demonstrate that it has better defect identification and localization capabilities than existing technologies.

[0119] This disclosure also proposes a device for locating hidden defects in cables based on broadband characteristic impedance spectrum, comprising:

[0120] 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 ;

[0121] The broadband characteristic impedance calculation unit is used to calculate the broadband characteristic impedance spectrum Z of the cable under test according to the following formula. char :

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

[0123] Among them, Z open (i) represents the broadband characteristic impedance spectrum at the beginning of the spectrum Z. open The i-th data point in Z short (i) represents the broadband characteristic impedance spectrum at the beginning of the spectrum Z. short The i-th data point in Z char (i) represents the broadband characteristic impedance spectrum Z char The i-th data point in the array, where sqrt represents the square root operation;

[0124] 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.

[0125] 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.

[0126] The digital lock-in amplifier algorithm analysis unit is used to analyze the broadband characteristic impedance spectrum Z of the cable under test based on the digital lock-in amplifier analysis algorithm using the reference frequency list. char As a pseudo-time domain signal, the analysis result DLIA(Z) is obtained. char );

[0127] Hazard location unit, used to locate hazards based on DLIA(Z) char Determine the location of potential defects in the cable.

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

[0129] Figure 5 An electronic device provided in at least one embodiment of the present disclosure includes a memory and a processor. The memory is used to store computer instructions that can be executed on the processor. The processor is used to implement the method for locating hidden defects in cables based on broadband characteristic impedance spectrum as described in any embodiment or implementation of the present disclosure when executing the computer instructions.

[0130] At least one embodiment of this disclosure also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method for locating hidden defects in cables based on broadband characteristic impedance spectrum as described in any embodiment or implementation of this disclosure.

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

[0132] The various embodiments in this specification are described in a progressive manner. 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.

[0133] 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.

[0134] 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.

[0135] 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.

[0136] 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.

[0137] The above description is merely a preferred embodiment of one or more embodiments of this specification and is not intended to limit the scope of one or more embodiments of this specification. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of one or more embodiments of this specification should be included within the scope of protection of one or more embodiments of this specification.

Claims

1. A method for locating hidden defects in cables based on broadband characteristic 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 ; The broadband characteristic impedance spectrum Z of the cable under test is calculated using the following formula. char : = sqrt(Z open (i)*Z short (and)), Among them, Z open (i) represents the broadband characteristic impedance spectrum at the beginning of the spectrum Z. open The i-th data point in Z short (i) represents the broadband characteristic impedance spectrum at the beginning of the spectrum Z. short The i-th data point in Z represents the broadband characteristic impedance spectrum char The i-th data point in the array, where sqrt represents the square root operation; 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, wherein 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; Based on the aforementioned pseudo-frequency, a list of reference frequencies corresponding to each data point in the analysis interval of the cable under test is determined, wherein the list of reference frequencies F corresponding to each data point in the analysis interval is determined 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; For the k-th data point to be analyzed, the reference signal corresponding to the k-th frequency in the reference frequency list is selected, and the broadband characteristic impedance spectrum Z of the cable under test is analyzed based on the digital lock-in amplifier analysis algorithm. char As a pseudo-time domain signal, the analysis result DLIA(Z) is obtained. char ); According to DLIA(Z) char Determine the location of potential defects in the cable, including in DLIA (Z) char The peak points are identified in the waveform diagram, and the location of potential defects is determined based on the horizontal coordinate of the peak points.

2. The method according to claim 1, characterized in that, 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 ,include: Select a preset number of discrete frequency points within a preset frequency range; The impedance values ​​at the cable head end at various discrete frequency points are measured when the cable end under test is open-circuited, and the broadband characteristic impedance spectrum Z at the head end is obtained. open ; The impedance values ​​at the cable head end at various discrete frequency points when the cable under test is short-circuited are measured to obtain the broadband characteristic impedance spectrum Z at the cable head end. short .

3. The method according to claim 1, characterized in that, For the k-th data point to be analyzed, the reference signal corresponding to the k-th frequency in the reference frequency list is selected, and the broadband characteristic impedance spectrum Z of the cable under test is analyzed based on the digital lock-in amplifier analysis algorithm. char As a pseudo-time domain signal, the analysis result DLIA(Z) is obtained. char This includes: for the k-th data point to be analyzed, Select cos(w) k t) is used as the first reference signal, and the broadband characteristic impedance spectrum Z char Multiply and then pass through a low-pass filter 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, along with the broadband characteristic impedance spectrum Z. char Multiply and then pass 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.

4. A device for locating hidden defects in cables based on broadband characteristic 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 ; The broadband characteristic impedance calculation unit is used to calculate the broadband characteristic impedance spectrum Z of the cable under test according to the following formula. char : = sqrt(Z open (i)*Z short (and)), Among them, Z open (i) represents the broadband characteristic impedance spectrum at the beginning of the spectrum Z. open The i-th data point in Z short (i) represents the broadband characteristic impedance spectrum at the beginning of the spectrum Z. short The i-th data point in Z represents the broadband characteristic impedance spectrum char The i-th data point in the array, where sqrt represents the square root operation; 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 pseudo-frequency calculation unit is used to calculate the reference pseudo-frequency f0 according to the following formula: f0 = 2*sqrt(epsilon) / (c*N0), Where epsilon is the relative 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 is used to determine the reference frequency list corresponding to each data point in the analysis positioning interval of the cable under test based on the reference pseudo-frequency. The reference frequency list calculation unit is used to determine the reference frequency list F according to the following formula: F = [l1* N0* f0: f0 : l2* N0* f0], 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; The digital lock-in amplifier algorithm analysis unit is used to analyze the broadband characteristic impedance spectrum Z of the cable under test based on the digital lock-in amplifier analysis algorithm using the reference frequency list. char As a pseudo-time domain signal, the analysis result DLIA(Z) is obtained. char ); Hazard location unit, used to locate hazards based on DLIA (Z char Determine the location of potential defects in the cable, including in DLIA (Z) char The peak points are identified in the waveform diagram, and the location of potential defects is determined based on the horizontal coordinate of the peak points.

5. The apparatus according to claim 4, characterized in that, The open-circuit and short-circuit impedance measurement unit is used for: Select a preset number of discrete frequency points within a preset frequency range; The impedance values ​​at the cable head end at various discrete frequency points are measured when the cable end under test is open-circuited, and the broadband characteristic impedance spectrum Z at the head end is obtained. open ; The impedance values ​​at the cable head end at various discrete frequency points when the cable under test is short-circuited are measured to obtain the broadband characteristic impedance spectrum Z at the cable head end. short .

6. An electronic device, characterized in that, The device includes a memory and a processor, the memory being used to store computer instructions that can run 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.

7. 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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