A cable defect detection device based on two-way coupled frequency domain reflection

Abstract

The application provides a cable defect detection device based on double-path coupling frequency domain reflection and belongs to the technical field of power cable detection. The device comprises a general control module, a double-path coupling signal generator, a first coupler, a second coupler, a first signal comparator and a second signal comparator. The general control module is electrically connected with the double-path coupling signal generator. The input end of the first coupler is connected with the double-path coupling signal generator, the coupling port of the first coupler is connected with a cable to be detected, the output end of the first coupler is connected with the input end of the first signal comparator, the output end of the first signal comparator is connected with the input end of the second signal comparator, the input end of the second coupler is connected with the double-path coupling signal generator, the output end of the second coupler is connected with the second signal comparator, and the output ends of the first signal comparator and the second signal comparator are electrically connected with the general control module. The double-path signal comparison structure is used to overcome the phase ambiguity problem of single-path measurement, and the accuracy and reliability of cable defect detection are significantly improved.

Description

Technical Field

[0001] This invention relates to the field of power cable testing technology, and in particular to a cable defect detection device based on dual-path coupling frequency domain reflection. Background Technology

[0002] With the continuous upgrading of infrastructure, power cables play a vital role in modern power transmission and distribution systems. However, throughout the entire lifecycle of cables, from production and installation to operation, various factors, such as installation defects, external damage, and harsh environmental conditions, can impair their insulation performance. These hidden dangers may gradually develop into partial discharge, ultimately leading to the serious consequence of insulation failure. Therefore, accurately locating these localized damage points on the cable is not only a key means of preventing power line faults but also a necessary guarantee for ensuring the safe and reliable operation of the power network.

[0003] Current technologies used for cable fault location include impedance measurement, partial discharge detection, and traveling wave reflection. Among these, the traveling wave reflection method is favored due to its ease of implementation and low hardware requirements. The basic idea of ​​this method is to transmit a low-voltage single-pulse signal to one end of the cable. When the signal propagates along the cable and encounters a fault point or impedance discontinuity, it is reflected. By analyzing the time delay between the transmitted and reflected pulses and based on the propagation speed of electromagnetic waves in the medium, the location of the fault can be calculated.

[0004] However, the traveling wave reflection method has significant drawbacks. The energy contained in a single pulse is limited, and when encountering large or multiple fault points, the reflected signal becomes very weak, reducing the effectiveness of location. Simultaneously, the single pulse signal has poor resistance to environmental noise interference; in environments with complex electromagnetic interference, the useful reflected signal is easily drowned out by noise, affecting location accuracy. The high-frequency components in the pulse attenuate drastically during long-distance transmission, making it difficult to detect minute insulation defects. Furthermore, in cable networks with multiple branches, reflected signals from different paths can overlap, potentially causing signal confusion and increasing location errors. In summary, the application of this method is often limited to short-distance and simple fault scenarios, making it difficult to meet the higher requirements of modern power systems for high precision and detection under complex conditions.

[0005] Furthermore, using single-channel frequency domain reflection to determine the defect location has significant limitations. Due to the non-uniqueness of the reflected signal phase, it is often impossible to accurately determine the true phase of the reflected signal. For example, when the phase difference between the reflected signal R1 and the incident signal S1 is Δθ1, the real part of the reflected signal R1 can be expressed by the following formula:

[0006]

[0007] in,

[0008] However, due to the periodicity and symmetry of the cosine function, this representation method has multiple possible solutions. That is, when the phase difference Δθ1 is a certain value, the real part of the reflected signal can correspond to multiple phase states. This phenomenon makes it impossible to uniquely determine the phase of the reflected signal by relying solely on a single signal, thus leading to phase ambiguity and affecting the accuracy of defect location. Summary of the Invention

[0009] To overcome the shortcomings of the prior art, the purpose of this invention is to provide a cable defect detection device based on dual-channel coupled frequency domain reflection. By utilizing a dual-channel signal comparison structure, the phase ambiguity problem of single-channel measurement is overcome, significantly improving the accuracy and reliability of cable defect detection.

[0010] To achieve the above objectives, the present invention provides the following solution:

[0011] A cable defect detection device based on dual-channel coupled frequency domain reflection includes a central control module, a dual-channel coupled signal generator, a first coupler, a second coupler, a first signal comparator, and a second signal comparator. The central control module is electrically connected to the dual-channel coupled signal generator. The input terminal of the first coupler is connected to the dual-channel coupled signal generator, the coupling port of the first coupler is connected to the cable under test, the output terminal of the first coupler is connected to the input terminal of the first signal comparator, and the output terminal of the first signal comparator is connected to the input terminal of the second signal comparator. The input terminal of the second coupler is connected to the dual-channel coupled signal generator, and the output terminal of the second coupler is connected to the second signal comparator. The output terminals of both the first and second signal comparators are electrically connected to the central control module.

[0012] Preferably, the dual-channel coupled signal generator is controlled by the master control module to generate associated test signal S1 and reference signal S2, and both test signal S1 and reference signal S2 are sinusoidal sweep signals.

[0013] Preferably, the first coupler is used to inject the test signal S1 into the cable under test and separate the reflected signal R1 generated by the defect, and the first coupler outputs the test signal S1 and the reflected signal R1 to the first signal comparator respectively.

[0014] Preferably, the first signal comparator is used to compare the amplitude and phase between the test signal S1 and the reflected signal R1, and outputs the amplitude difference and phase difference information between the test signal S1 and the reflected signal R1. The phase difference calculation formula is as follows:

[0015]

[0016] in, The phase of the reflected signal R1, The phase of the test signal S1.

[0017] Preferably, the second signal comparator is used to compare the phases of the reference signal S2 and the reflected signal R1, and outputs the phase difference information between the reference signal S2 and the reflected signal R1, as shown in the formula:

[0018]

[0019] in, The phase of the reference signal S2.

[0020] Preferably, the master control module, based on the phase difference Δθ1 output by the first signal comparator, decomposes the reflected signal R1 into real and imaginary parts along the phase direction of the test signal S1, which are expressed as follows:

[0021] Real part:

[0022] Virtual part:

[0023] The amplitude of the reflected signal R1 is determined by the magnitudes of the real and imaginary components and the phase difference Δθ1, using the following formula:

[0024]

[0025] Where |R1| is the amplitude of the reflected signal R1; and by combining the known amplitude of the test signal S1, the amplitude difference between the test signal S1 and the reflected signal R1 is obtained.

[0026] Preferably, the second coupler is used to transmit the reference signal S2 to the second signal comparator.

[0027] Preferably, the master control module determines the phase of the reflected signal R1 based on the phase difference information output by the first signal comparator and the phase difference information output by the second signal comparator, combined with the phase characteristics of the preset test signal S1 and reference signal S2. The specific process is as follows:

[0028] First, the same reflected signal R1 is decomposed along the direction of the reference signal S2 to obtain the real part and the imaginary part;

[0029] Secondly, the preset phase difference between the test signal S1 and the reference signal S2 Given the quantities, the relationship can be established as follows:

[0030] Δθ2=Δθ1+Δθ;

[0031] Finally, by comparing the real and imaginary parts of the decomposition along the directions of the test signal S1 and the reference signal S2, the phase difference is verified to eliminate the phase ambiguity caused by the non-uniqueness of the cosine function resulting from single-path measurement, thereby determining the phase information of the reflected signal R1.

[0032] Preferably, the same reflected signal R1 is decomposed along the direction of the reference signal S2, and the real and imaginary parts are obtained as follows:

[0033] Real part:

[0034] Virtual part:

[0035] Where |R1| is the amplitude of the reflected signal R1, and Δθ2 is the phase difference between the reference signal S2 and the reflected signal R1.

[0036] Preferably, the master control module uses the phase of the verified reflected signal R1, combined with the amplitude of the reflected signal R1, to perform windowing function processing and inverse Fourier transform on the spectral characteristics of the reflected signal to obtain the time-domain reflection characteristics, and combines this with the propagation speed of electromagnetic waves in the cable under test to determine the location of the cable defect.

[0037] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0038] In the device provided by this invention, a dual-channel coupled signal generator is controlled by a central control module to generate associated test signal S1 and reference signal S2. A first coupler injects S1 into the cable under test, separates the reflected signal R1, and outputs S1 and R1 to a first signal comparator. A second coupler transmits S2 to a second signal comparator, which simultaneously receives R1 from the first coupler. The first signal comparator compares the amplitude and phase of S1 and R1. The second signal comparator compares the phase of S2 and R1. The two comparators transmit the results to the central control module, which comprehensively analyzes the two comparison information and uses the dual comparison results to accurately determine the spectral characteristics of the reflected signal R1, thereby calculating the location of the cable defect. This invention utilizes a dual-channel signal comparison structure to simultaneously compare the reflected signal with two signals, a test signal and a reference signal, which have a known phase difference. This effectively solves the phase ambiguity problem of single-channel measurement, enables accurate determination of the amplitude and phase of the reflected signal, greatly improves measurement accuracy and anti-interference capability, breaks through the distance limitations of traditional methods, and allows for highly sensitive non-destructive testing of minute defects in long cables, providing reliable technical support for cable maintenance. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a structural block diagram of a cable defect detection device based on dual-path coupling frequency domain reflection according to the present invention.

[0041] Figure 2 This is a schematic diagram illustrating the principle of using dual-channel coupled signals to determine the reflected signal in this invention.

[0042] Explanation of reference numerals in the attached figures:

[0043] 1. Main control module; 2. Dual-channel coupled signal generator; 3. First coupler; 4. Cable under test; 5. First signal comparator; 6. Second coupler; 7. Second signal comparator. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0046] like Figure 1 As shown, this invention provides a cable defect detection device based on dual-channel coupled frequency domain reflection, including a main control module 1, a dual-channel coupled signal generator 2, a first coupler 3, a second coupler 6, a first signal comparator 5, and a second signal comparator 7; the main control module 1 is electrically connected to the dual-channel coupled signal generator 2; the input terminal of the first coupler 3 is connected to the dual-channel coupled signal generator 2, the coupling port of the first coupler 3 is connected to the cable under test 4, the output terminal of the first coupler 3 is connected to the input terminal of the first signal comparator 5, and the output terminal of the first signal comparator 5 is connected to the input terminal of the second signal comparator 7; the input terminal of the second coupler 6 is connected to the dual-channel coupled signal generator 2, and the output terminal of the second coupler 6 is connected to the second signal comparator 7; the output terminals of the first signal comparator 5 and the second signal comparator 7 are both electrically connected to the main control module 1.

[0047] The specific working principle of the device is as follows: the dual-channel coupled signal generator 2 is controlled by the main control module 1 to generate associated test signal S1 and reference signal S2, and both test signal S1 and reference signal S2 are sinusoidal sweep frequency signals.

[0048] The first coupler 3 is used to inject the test signal S1 into the cable under test 4 and separate the reflected signal R1 generated by the defect. The first coupler 3 outputs the test signal S1 and the reflected signal R1 to the first signal comparator 5 respectively.

[0049] The first signal comparator 5 is used to compare the amplitude and phase between the test signal S1 and the reflected signal R1, and outputs the amplitude difference and phase difference information between the test signal S1 and the reflected signal R1. The phase difference calculation formula is as follows:

[0050]

[0051] in, The phase of the reflected signal R1, The phase of the test signal S1.

[0052] The second signal comparator 7 is used to compare the phases of the reference signal S2 and the reflected signal R1, and outputs the phase difference information between the reference signal S2 and the reflected signal R1, as shown in the formula:

[0053]

[0054] in, The phase of the reference signal S2.

[0055] like Figure 2 As shown, the master control module 1, based on the phase difference Δθ1 output by the first signal comparator 5, decomposes the reflected signal R1 into real and imaginary parts along the phase direction of the test signal S1, which are expressed as follows:

[0056] Real part:

[0057] Virtual part:

[0058] The amplitude of the reflected signal R1 is determined by the magnitudes of the real and imaginary components and the phase difference Δθ1, using the following formula:

[0059]

[0060] Where |R1| is the amplitude of the reflected signal R1; and by combining the known amplitude of the test signal S1, the amplitude difference between the test signal S1 and the reflected signal R1 is obtained.

[0061] The second coupler 6 is used to transmit the reference signal S2 to the second signal comparator 7.

[0062] In addition, the overall control module 1 determines the phase of the reflected signal R1 based on the phase difference information output by the first signal comparator 5 and the phase difference information output by the second signal comparator 7, combined with the phase characteristics of the preset test signal S1 and reference signal S2. The specific process is as follows:

[0063] First, the same reflected signal R1 is decomposed along the direction of the reference signal S2 to obtain the real and imaginary parts:

[0064] Real part:

[0065] Virtual part:

[0066] Where |R1| is the amplitude of the reflected signal R1, and Δθ2 is the phase difference between the reference signal S2 and the reflected signal R1.

[0067] Secondly, the preset phase difference between the test signal S1 and the reference signal S2 Given the quantities, the relationship can be established as follows:

[0068] Δθ2=Δθ1+Δθ;

[0069] Finally, by comparing the real and imaginary parts of the decomposition along the directions of the test signal S1 and the reference signal S2, the phase difference is verified to eliminate the phase ambiguity caused by the non-uniqueness of the cosine function resulting from single-path measurement, thereby determining the phase information of the reflected signal R1.

[0070] Based on the above, the main control module 1 uses the phase of the verified reflected signal R1, combined with the amplitude of the reflected signal R1, to perform windowing function processing and inverse Fourier transform on the spectral characteristics of the reflected signal to obtain the time-domain reflection characteristics, and combines the propagation speed of electromagnetic waves in the cable under test 4 to determine the location of the cable defect.

[0071] In order to further improve the reliability and accuracy of the detection results, based on the accurate measurement of amplitude and phase, the following data processing method is adopted:

[0072] For amplitude, the average of the two signals is used for optimization. If the amplitudes measured by the two signals differ significantly, the measurement result is discarded and the measurement is repeated.

[0073] For phase, the quality of phase data is judged by the range utilization rate, and different processing strategies are adopted.

[0074] As mentioned above, the present invention generates a signal with a preset phase difference using a dual-channel coupled signal generator 2. The test signal S1 and reference signal S2 are injected into the cable and transmitted to the second signal comparator 7 via the first coupler 3 and the second coupler 6, respectively. The first signal comparator 5 outputs... The output of the second signal comparator 7 The main control module 1 performs phase verification using Δθ2 = Δθ1 - Δθ, eliminating phase ambiguity in single-channel measurements. However, in practical applications, environmental noise, hardware drift, and other factors may cause fluctuations in the measurement data. To further improve the reliability of the detection results, this invention introduces range utilization analysis to screen the amplitude and phase data. The screening rules are applicable to scenarios including, but not limited to, amplitude-only and phase-only, amplitude-only and phase-only, amplitude-only and phase-only, and amplitude-only and phase-only. The following uses amplitude-only and phase-only as a typical scenario, referring to... Figure 1 The specific filtering rules are as follows:

[0075] Let β be the distribution range of the phase measurement value within its range. Two scaling factors α1 and α2 are set, where 0 < α1 < α2, to evaluate the data quality. The specific evaluation indicators are: low data quality when β < α1 or β > 1-α1; medium data quality when α1 ≤ β < α2 or 1-α2 < β ≤ 1-α1; and high data quality when α2 ≤ β ≤ 1-α2. Let the quality of the data corresponding to the two measured phase values ​​be β1 and β2, respectively. Then, the phase data is processed as follows:

[0076] (1) When the data quality β1 is in the low quality range, i.e. β1<α1 or β1>1-α1, the data of that channel is considered unreliable and the measurement result of that channel is completely discarded. Only the measurement result of the other channel is used as the final phase value. If the data quality β2 is in the low quality range, only the measurement result of the other channel is used as the final phase value.

[0077] (2) When both β1 and β2 are in the range of high data quality, i.e. α2≤β1≤1-α2 and α2≤β2≤1-α2, the two data are considered to be reliable, and the arithmetic mean of the two measurement results is used as the final phase value.

[0078] (3) In other cases, such as when both channels are in the range of medium data quality, i.e. α1≤β<α2 or 1-α2<β≤1-α1, or when one channel is in the range of high quality and the other is in the range of medium quality, a weighted average can be performed based on the specific values ​​of β1 and β2, and a larger weight can be assigned to the channel with higher quality to obtain the final phase value.

[0079] Based on the above filtering rules, scenarios with one amplitude channel and one phase channel, two amplitude channels and one phase channel, and two amplitude channels and two phase channels can be adapted in this way: the quality judgment criteria and processing principles for single / multi-channel amplitude / phase are completely reused, only the number of channels is adjusted, low-quality channels are discarded and high-quality channel results are retained first, and redundancy verification is triggered when multiple channels are of low quality.

[0080] Therefore, this invention utilizes a dual-channel signal comparison structure to effectively solve the phase ambiguity problem of single-channel measurement by synchronously comparing the reflected signal with two test and reference signals with a known phase difference. This enables accurate determination of the amplitude and phase of the reflected signal, greatly improving measurement accuracy and anti-interference capability. It also breaks through the distance limitations of traditional methods and can perform high-sensitivity non-destructive testing on minute defects in long cables, providing reliable technical support for cable maintenance.

[0081] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A cable defect detection device based on dual-path coupled frequency domain reflection, characterized in that, The system includes a central control module, a dual-channel coupled signal generator, a first coupler, a second coupler, a first signal comparator, and a second signal comparator. The central control module is electrically connected to the dual-channel coupled signal generator. The input terminal of the first coupler is connected to the dual-channel coupled signal generator, the coupling port of the first coupler is connected to the cable under test, the output terminal of the first coupler is connected to the input terminal of the first signal comparator, and the output terminal of the first signal comparator is connected to the input terminal of the second signal comparator. The input terminal of the second coupler is connected to the dual-channel coupled signal generator, and the output terminal of the second coupler is connected to the second signal comparator. The output terminals of both the first and second signal comparators are electrically connected to the central control module. The master control module, based on the phase difference information output by the first signal comparator and the phase difference information output by the second signal comparator, combines a preset test signal. S 1 and reference signal S The phase characteristics of 2 are used to determine the reflected signal. R The phase of 1, specifically the process is as follows: First, for the same reflected signal R 1. Along the reference signal S Decompose the 2nd direction to obtain the real and imaginary parts; Secondly, test signal S 1 and reference signal S 2 preset phase difference Given the quantities, the relationship can be established as follows: ； Finally, by comparing along the test signal S 1 and reference signal S The real and imaginary parts of the two-directional decomposition are used to verify the phase difference, thereby eliminating phase ambiguity caused by the non-uniqueness of the cosine function resulting from single-path measurement, and thus determining the reflected signal. R Phase information of 1; The master control module also utilizes the verified reflected signal. R 1 phase, combined with reflected signal R The amplitude of 1 is used to process the spectral characteristics of the reflected signal by a windowing function and inverse Fourier transform to obtain the time-domain reflection characteristics. The location of the cable defect is then determined by combining the propagation speed of electromagnetic waves in the cable under test.

2. The cable defect detection device based on dual-path coupled frequency domain reflection according to claim 1, characterized in that, The dual-channel coupled signal generator is controlled by the main control module to generate associated test signals. S 1 and reference signal S 2, and the test signal S 1 and reference signal S Both are sinusoidal sweep frequency signals.

3. The cable defect detection device based on dual-path coupled frequency domain reflection according to claim 2, characterized in that, The first coupler is used to convert the test signal S 1. Inject the signal into the cable under test and separate the reflected signal generated by the defect. R 1, and the first coupler outputs test signals respectively. S 1 and reflected signal R 1 to the first signal comparator.

4. The cable defect detection device based on dual-path coupled frequency domain reflection according to claim 3, characterized in that, The first signal comparator is used to compare the test signal. S 1 and reflected signal R The amplitude and phase between 1 and 2 are determined, and a test signal is output. S 1 and reflected signal R The amplitude difference and phase difference information of 1, the phase difference calculation formula is: ； in, For reflected signals R Phase 1, For test signal S Phase 1.

5. A cable defect detection device based on dual-path coupled frequency domain reflection according to claim 4, characterized in that, The second signal comparator is used to compare the reference signal. S 2 and reflected signals R Phase 1, and output reference signal. S 2 and reflected signals R The phase difference information of 1 is given by the formula: ； in, Reference signal S Phase 2.

6. The cable defect detection device based on dual-path coupled frequency domain reflection according to claim 5, characterized in that, The master control module is based on the phase difference output by the first signal comparator. , will reflect the signal R 1. Along the test signal S The phase direction of 1 is decomposed into real and imaginary parts, which are represented as follows: Real part: ; Virtual part: ; The magnitudes of the real and imaginary components and the phase difference Determine the reflected signal R The amplitude of 1 is given by the formula: ； in, For reflected signals R The amplitude of 1; combined with the test signal S Given the amplitude, obtain the test signal. S 1 and reflected signal R The amplitude difference is 1.

7. A cable defect detection device based on dual-path coupled frequency domain reflection according to claim 6, characterized in that, The second coupler is used to transmit a reference signal. S 2 to the second signal comparator.

8. The cable defect detection device based on dual-path coupled frequency domain reflection according to claim 1, characterized in that, For the same reflected signal R 1. Along the reference signal S Decomposing the 2nd direction yields the real and imaginary parts as follows: Real part: ; Virtual part: ; in, For reflected signals R The amplitude of 1, Reference signal S 2 and reflected signals R A phase difference of 1.

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