A cable defect detection device and method based on phase-shift coupling frequency domain reflection

Abstract

The application discloses a kind of cable defect detection device and method based on phase shift coupling frequency domain reflection, belong to power cable detection technical field, including general control module, signal generator, phase shifter, first coupler, second coupler, first signal comparator and second signal comparator;Signal generator generates original sweep signal;Phase shifter is used to carry out phase shift processing to original sweep signal;First coupler is used to receive test signal, and it is input to be measured cable and separate out reflected signal, after test signal is output to first signal comparator, reflected signal is output to first signal comparator and second signal comparator;Second coupler is used to receive reference signal, and reference signal is input to second signal comparator.The application uses above-mentioned one kind of cable defect detection device and method based on phase shift coupling frequency domain reflection, by introducing phase shifter to construct two-way comparison architecture, effectively overcome phase ambiguity, improve detection precision and reliability.

Description

A cable defect detection device and method based on phase-shifted coupling frequency domain reflection Technical Field

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

[0002] With the advancement of infrastructure modernization, power cables have become a core component of modern power transmission and distribution networks. However, during cable manufacturing, laying, and long-term operation, construction defects, mechanical impacts, and complex environmental factors can easily lead to insulation damage. Such hidden dangers may trigger partial discharge or even evolve into insulation breakdown accidents. Therefore, accurately locating local defects in cables is not only a key technology for preventing line faults but also an important support for ensuring the reliable operation of the power grid.

[0003] Currently, cable defect location technologies mainly include impedance methods, partial discharge methods, and traveling wave methods. Among them, the traveling wave method is widely used due to its ease of operation and low hardware requirements. Its principle is to inject a unipolar low-voltage pulse signal into the cable end, using the reflected wave generated by the defect or impedance mismatch point for location. The defect location is calculated by measuring the time difference between the incident and reflected waves and combining this with the electromagnetic wave propagation speed.

[0004] However, the traveling wave method has significant drawbacks: single-pulse signals have low energy, and the reflected signal attenuates rapidly in scenarios with large or multiple defects, leading to decreased positioning accuracy; single pulses have poor anti-interference capabilities, and noise in complex electromagnetic environments easily drowns out the effective signal; high-frequency pulses attenuate severely over long distances, making it difficult to detect micron-level insulation defects; furthermore, signal reflections in multi-branch cable networks can easily cause aliasing interference, leading to increased positioning errors. These limitations make it only suitable for short-distance, single-defect scenarios, and it is difficult to meet the requirements of modern power systems for high-precision and complex environment detection.

[0005] Determining defect location using single-channel frequency domain reflection 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 test signal S2 is Δθ1, the real part of the reflected signal R1 can be expressed by the following formula:

[0006]

[0007] in,

[0008]

[0009] 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

[0010] The purpose of this invention is to provide a cable defect detection device and method based on phase-shifted coupling frequency domain reflection. By introducing a phase shifter to construct a dual-path comparison architecture, phase ambiguity can be effectively overcome, and detection accuracy and reliability can be improved.

[0011] To achieve the above objectives, this invention provides a cable defect detection device based on phase-shifted coupling frequency domain reflection, comprising a central control module, a signal generator, a phase shifter, a first coupler, a second coupler, a first signal comparator, and a second signal comparator. The signal generator generates an original swept frequency signal; the phase shifter performs phase-shifting processing on the original swept frequency signal; the first coupler receives a test signal and inputs it into the cable under test to separate the reflected signal, then outputs the test signal to the first signal comparator and the reflected signal to the first and second signal comparators; the second coupler receives a reference signal and inputs the reference signal to the second signal comparator; the first signal comparator outputs information characterizing the amplitude relationship and phase difference between the test signal and the reflected signal; the second signal comparator outputs information characterizing the amplitude relationship and phase difference between the reference signal and the reflected signal; the central control module controls the signal generator to generate a signal and comprehensively processes the two signals.

[0012] This invention provides a cable defect detection method based on phase-shifted coupling frequency domain reflection, comprising the following steps:

[0013] S1. The main control module controls the signal generator to generate the original sweep frequency signal. The original sweep frequency signal is processed by the phase shifter to form a test signal S2, which is input into the first coupler. The other signal forms a reference signal S1, which is input into the second coupler.

[0014] S2. The first coupler inputs the test signal S2 into the cable under test and separates the reflected signal R1. Then, the test signal S2 is output to the first signal comparator, and the reflected signal R1 is simultaneously output to the first signal comparator and the second signal comparator.

[0015] S3, The second coupler inputs the reference signal S1 into the second signal comparator;

[0016] S4. The first signal comparator compares the amplitude and phase of the test signal S2 and the reflected signal R1, and outputs information characterizing the amplitude relationship and phase difference between the test signal S2 and the reflected signal R1; the second signal comparator compares the amplitude and phase of the reference signal S1 and the reflected signal R1, and outputs information characterizing the amplitude relationship and phase difference between the reference signal S1 and the reflected signal R1.

[0017] S5, the main control module comprehensively analyzes the two comparison information, and uses the known phase difference between the test signal S2 and the reflected signal R1, as well as the comparison result with the reflected signal R1, to accurately determine the spectral characteristics of the reflected signal R1 and calculate the defect location.

[0018] Preferably, S5 specifically includes the following operations:

[0019] S5.1 The main control module determines the precise phase spectrum characteristics of the reflected signal R1 based on the phase difference information output by the first signal comparator, the phase difference information output by the second signal comparator, and the preset known phase difference.

[0020] S5.2 The main control module calculates the amplitude spectrum characteristics of the reflected signal R1 based on the amplitude relationship information output by the first signal comparator and / or the second signal comparator and the determined precise phase spectrum characteristics.

[0021] S5.3 The main control module processes the determined spectral characteristics of the reflected signal R1 to obtain the time-domain reflection characteristics, and calculates the defect location by combining the propagation speed of electromagnetic waves in the cable.

[0022] Preferably, in step S5.1, the amplitude and phase spectrum characteristics of the reflected signal R1, the test signal S2, and the reference signal S1 are used to accurately calculate the reflection phase of the reflected signal R1. The reflected signal R1 is then decomposed into real and imaginary parts along the direction of the test signal S2, as shown below:

[0023]

[0024] in, The phase of the reflected signal R1, The phase of the test signal S2;

[0025] A reference signal S1 is introduced, and a predetermined known phase difference is ensured between the test signal S2 and the reference signal S1. The reflected signal R1 is decomposed into real and imaginary parts along the direction of the reference signal S1, as shown below:

[0026]

[0027] in, The phase of the reference signal S1;

[0028] The phase difference between the two paths measured separately is as follows:

[0029]

[0030] Where Δθ1 is the phase difference of the test path and Δθ2 is the phase difference of the reference path;

[0031] Substituting the pre-defined known phase difference Δθ into formulas (5) and (6), we have the following relationship:

[0032] Δθ2=Δθ1+Δθ (7);

[0033] The results are obtained by cross-checking according to formula (7). The precise value eliminates phase ambiguity caused by the non-uniqueness of the cosine function resulting from single-path measurements.

[0034] Preferably, in step S5.2, the amplitude and phase spectrum characteristics of the reflected signal R1 are used to accurately calculate the reflection amplitude of the reflected signal R1. The reflected signal R1 is then decomposed into real and imaginary parts along the direction of the test signal S2, as shown below:

[0035]

[0036] in, The phase of the reflected signal R1, The phase of the test signal S2.

[0037] Preferably, the data processing method in S5.3 is as follows:

[0038] For amplitude, the average value of the two signals is used for optimization. If the amplitude measured by the two signals is significantly different, the measurement result is discarded and the measurement is repeated.

[0039] For phase, the quality of the phase data is assessed and different processing strategies are adopted. The applicable scenarios for these processing strategies include, but are not limited to, one amplitude path and one phase path, one amplitude path and two phase paths, two amplitude paths and one phase path, and two amplitude paths and two phase paths. The following is a typical scenario with one amplitude path and two phase paths, and the specific filtering rules are as follows:

[0040] 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:

[0041] (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.

[0042] (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.

[0043] (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.

[0044] 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.

[0045] Therefore, the present invention adopts the above-mentioned cable defect detection device and method based on phase-shifted coupling frequency domain reflection. By introducing a phase shifter to construct a dual-path comparison architecture, phase ambiguity is effectively overcome, and detection accuracy and reliability are improved.

[0046] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0047] Figure 1 is a schematic diagram of the structure of a cable defect detection device based on phase-shifted coupling frequency domain reflection according to the present invention;

[0048] Figure 2 is a schematic diagram of the principle of the cable defect detection method based on phase-shifted coupling frequency domain reflection of the present invention, which uses phase-shifted coupling signal to accurately determine the reflected signal. Detailed Implementation

[0049] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0050] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0051] Example 1

[0052] As shown in Figure 1, this invention provides a cable defect detection device based on phase-shifted coupling frequency domain reflection, including a central control module, a signal generator, a phase shifter, a first coupler, a second coupler, a first signal comparator, and a second signal comparator. The signal generator generates an original sweep frequency signal, which is a sinusoidal sweep frequency signal. The phase shifter performs phase shifting processing on the original sweep frequency signal, ensuring a preset known phase difference between the test signal and the reference signal. The first coupler receives the test signal and inputs it into the cable under test to separate the reflected signal. The test signal is then output to the first signal comparator, and the reflected signal is output to both the first and second signal comparators. The second coupler receives the reference signal and inputs it to the second signal comparator. The first signal comparator outputs information characterizing the amplitude relationship and phase difference between the test signal and the reflected signal; the second signal comparator outputs information characterizing the amplitude relationship and phase difference between the reference signal and the reflected signal. The central control module controls the signal generator to generate signals and integrates the two signals.

[0053] This invention provides a cable defect detection method based on phase-shifted coupling frequency domain reflection, comprising the following steps:

[0054] S1. The main control module controls the signal generator to generate the original sweep frequency signal. The original sweep frequency signal is processed by the phase shifter to form a test signal S2, which is input into the first coupler. The other signal forms a reference signal S1, which is input into the second coupler.

[0055] S2. The first coupler inputs the test signal S2 into the cable under test and separates the reflected signal R1. Then, the test signal S2 is output to the first signal comparator, and the reflected signal R1 is simultaneously output to the first signal comparator and the second signal comparator.

[0056] S3, The second coupler inputs the reference signal S1 into the second signal comparator;

[0057] S4. The first signal comparator compares the amplitude and phase of the test signal S2 and the reflected signal R1, and outputs information characterizing the amplitude relationship and phase difference between the test signal S2 and the reflected signal R1; the second signal comparator compares the amplitude and phase of the reference signal S1 and the reflected signal R1, and outputs information characterizing the amplitude relationship and phase difference between the reference signal S1 and the reflected signal R1.

[0058] S5, the main control module comprehensively analyzes the two comparison signals, using the known phase difference between the test signal S2 and the reflected signal R1, and the comparison result with the reflected signal R1, to accurately determine the spectral characteristics of the reflected signal R1 and calculate the defect location. Specifically, this includes the following operations:

[0059] S5.1 The main control module determines the precise phase spectrum characteristics of the reflected signal R1 based on the phase difference information output by the first signal comparator, the phase difference information output by the second signal comparator, and the preset known phase difference, so as to eliminate phase ambiguity.

[0060] The reflection phase of the reflected signal R1 is accurately calculated using the amplitude and phase spectrum characteristics of the reflected signal R1, the test signal S2, and the reference signal S1. The principle of accurately determining the reflected signal using a phase-shifted coupling signal is shown in Figure 2. The reflected signal R1 is decomposed into real and imaginary parts along the direction of the test signal S2, as shown below:

[0061]

[0062] in, The phase of the reflected signal R1, The phase of the test signal S2.

[0063] A reference signal S1 is introduced, and a predetermined known phase difference is ensured between the test signal S2 and the reference signal S1. The reflected signal R1 is decomposed into real and imaginary parts along the direction of the reference signal S1, as shown below:

[0064]

[0065] in, The phase of the reference signal S1;

[0066] The phase difference between the two paths measured separately is as follows:

[0067]

[0068] Where Δθ1 is the phase difference of the test path and Δθ2 is the phase difference of the reference path;

[0069] Substituting the pre-defined known phase difference Δθ into formulas (5) and (6), we have the following relationship:

[0070] Δθ2=Δθ1+Δθ (7);

[0071] The results are obtained by cross-checking according to formula (7). The precise value eliminates the phase ambiguity caused by the non-uniqueness of the cosine function resulting from single-path measurement, ensuring that the phase information of the reflected signal R1 has unique determinism.

[0072] S5.2 The main control module calculates the amplitude spectrum characteristics of the reflected signal R1 based on the amplitude relationship information output by the first signal comparator and / or the second signal comparator and the determined precise phase spectrum characteristics.

[0073] The amplitude and phase spectrum characteristics of the reflected signal R1 are used to accurately calculate the reflected amplitude of the reflected signal R1. The principle of accurately determining the reflected signal using phase-shifted coupling signal is shown in Figure 2. The reflected signal R1 is decomposed into real and imaginary parts along the direction of the test signal S2, as shown below:

[0074]

[0075] in, The phase of the reflected signal R1, The phase of the test signal S2.

[0076] S5.3 The main control module processes the determined spectral characteristics of the reflected signal R1 to obtain the time-domain reflection characteristics, and calculates the defect location by combining this with the propagation speed of electromagnetic waves in the cable. Based on accurate measurements of amplitude and phase, to further improve the reliability and accuracy of the detection results, the following data processing method is used:

[0077] For amplitude, the average value of the two signals is used for optimization. If the amplitude measured by the two signals is significantly different, the measurement result is discarded and the measurement is repeated.

[0078] For phase data, the quality of the phase data is assessed, and different processing strategies are adopted. These strategies are applicable to scenarios including, but not limited to, one amplitude path and one phase path, one amplitude path and two phase paths, two amplitude paths and one phase path, and two amplitude paths and two phase paths. The following section uses one amplitude path and two phase paths as a typical scenario, referring to Figure 1, and outlines the specific filtering rules as follows:

[0079] 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:

[0080] (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.

[0081] (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.

[0082] (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.

[0083] 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.

[0084] Therefore, the present invention adopts the above-mentioned cable defect detection device and method based on phase-shifted coupling frequency domain reflection. By introducing a phase shifter to construct a dual-path comparison architecture, phase ambiguity is effectively overcome, and detection accuracy and reliability are improved.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A cable defect detection device based on phase-shifted coupling frequency domain reflection, characterized in that: It includes a central control module, a signal generator, a phase shifter, a first coupler, a second coupler, a first signal comparator, and a second signal comparator; the signal generator generates the original sweep frequency signal; The phase shifter is used to perform phase shifting processing on the original sweep frequency signal; the first coupler is used to receive the test signal and input it into the cable under test to separate the reflected signal, and then output the test signal to the first signal comparator, and output the reflected signal to the first signal comparator and the second signal comparator; the second coupler is used to receive the reference signal and input the reference signal to the second signal comparator; the first signal comparator is used to output information characterizing the amplitude relationship and phase difference between the test signal and the reflected signal; The second signal comparator is used to output information characterizing the amplitude relationship and phase difference between the reference signal and the reflected signal; The master control module controls the signal generator to generate signals and integrates the two information streams.

2. A cable defect detection method based on phase-shifted coupling frequency domain reflection, characterized in that: Includes the following steps: S1. The main control module controls the signal generator to generate the original sweep frequency signal. The original sweep frequency signal is processed by the phase shifter to form a test signal. The input is sent to the first coupler, and the other path forms a reference signal. The input is sent to the second coupler; S2, the first coupler will input the test signal. Input the cable under test and separate the reflected signal Then the test signal The output is sent to the first signal comparator, and the reflected signal is... Simultaneously output to the first signal comparator and the second signal comparator; S3, the second coupler will use the reference signal Input the second signal comparator; S4, the first signal comparator compares the test signal. and reflected signals The amplitude and phase of the signal are determined, and the output characterizes the test signal. With reflected signal Information on the amplitude relationship and phase difference between them; The second signal comparator compares the reference signal. and reflected signals The amplitude and phase of the signal are determined, and a characteristic of the reference signal is output. With reflected signal Information on the amplitude relationship and phase difference between them; S5, the main control module comprehensively analyzes the two comparison information channels and uses the test signal. With reference signal The known phase difference and its relationship with the reflected signal The comparison results accurately determine the reflected signal. The spectral characteristics were analyzed and the defect location was calculated.

3. The cable defect detection method based on phase-shifted coupling frequency domain reflection according to claim 2, characterized in that: S5 specifically includes the following operations: S5.1, the main control module determines the reflected signal based on the phase difference information output by the first signal comparator, the phase difference information output by the second signal comparator, and a preset known phase difference. The precise phase spectrum characteristics; S5.2, the main control module calculates the reflected signal based on the amplitude relationship information output by the first signal comparator and the second signal comparator and the determined precise phase spectrum characteristics. The amplitude spectrum characteristics; S5.3, the main control module for the determined reflected signal The spectral characteristics are processed to obtain the time-domain reflection characteristics, and the location of the defect is calculated by combining the propagation speed of electromagnetic waves in the cable.

4. The cable defect detection method based on phase-shifted coupling frequency domain reflection according to claim 3, characterized in that: S5.1 uses reflected signals Test signal and reference signal Accurate calculation of the amplitude and phase spectrum characteristics of the reflected signal The reflected phase will reflect the signal. Along the test signal The direction is decomposed into real and imaginary parts, as shown below: (Real part) (1); (Imaginary part) (2); where, For reflected signals phase, For test signal Phase; Introducing a reference signal And ensure the test signal With reference signal There is a preset known phase difference between them. , will reflect the signal Along the reference signal The direction is decomposed into real and imaginary parts, as shown below: (Real part) (3); (Imaginary part) (4); where, Reference signal The phase of the two paths was measured separately; the phase difference between the two paths was: （5）； (6); among which, To test the phase difference of the path, The phase difference of the reference path; the preset known phase difference Substituting into formulas (5) and (6), we have the following relationship: (7); According to formula (7), we can verify the results. The precise value eliminates phase ambiguity caused by the non-uniqueness of the cosine function resulting from single-path measurements.

5. The cable defect detection method based on phase-shifted coupling frequency domain reflection according to claim 4, characterized in that: S5.2 uses reflected signals Test signal and reference signal Accurate calculation of the amplitude and phase spectrum characteristics of the reflected signal The amplitude of the reflection will reflect the signal. Along the test signal The direction is decomposed into real and imaginary parts, as shown below: (Real part) (8); (Imaginary part) (9); where, For reflected signals phase, For test signal The phase.

6. The cable defect detection method based on phase-shifted coupling frequency domain reflection according to claim 5, characterized in that: The data processing method in S5.3 is as follows: For amplitude, the average value of the two signals is used for optimization. If the amplitude difference between the two signals is large, the measurement result is discarded and the measurement is repeated. For phase, the quality of the phase data is judged and different processing strategies are adopted, as shown below: Let... Two scaling factors are set for the distribution range of phase measurements within their range. and ,in To assess the quality of the data; the specific assessment indicators are: or The quality of the data was low at that time. or The quality of the data is moderate. The data quality is high; let the quality of the data corresponding to the two measured phase values ​​be respectively... and In processing phase data: (1) When the quality of the data It is in the range of low data quality, that is or If the data from that path is deemed unreliable, its measurement result is completely discarded, and only the measurement result from another path is used as the final phase value; if the data quality... If the quality is in the low quality range, then only the measurement result of the other path is used as the final phase value; (2) when both paths are in the low quality range... and All are in the high data quality range, that is and When both data streams are considered reliable, the arithmetic mean of the two measurement results is used as the final phase value; (3) In other cases, such as when both streams are in the range of moderate data quality, i.e. or and or When the quality range is sometimes high and sometimes medium, it can be based on and The specific values ​​are weighted and averaged, and a larger weight is assigned to the higher-quality pathways to obtain the final phase value.

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