Cable defect identification and positioning method based on broadband impedance spectroscopy

Abstract

The invention specifically relates to a cable defect identification and positioning method based on a broadband impedance spectrum, and belongs to the technical field of power distribution network equipment fault detection. According to the method, the advantages of the frequency domain reflection method and the reflection method are comprehensively considered, whether the parameters of the frequency domain reflection method and the time domain reflection method need to be corrected or not is judged by using the positioning deviation degree, the positioning deviation degree, the fluctuation width and the combined positioning ratio are used as indexes in the correction process, the respective defects of the frequency domain reflection method and the time domain reflection method are eliminated, and the correction accuracy is improved. The advantages are fused, and the corrected parameters are adopted for positioning, so that the accuracy of cable defect positioning and identification is greatly improved.

Description

Technical Field

[0001] This invention specifically relates to a cable defect identification and location method based on broadband impedance spectrum, belonging to the field of power distribution network equipment fault detection technology. Background Technology

[0002] High-voltage cables can be laid underground, avoiding the occupation of urban space and reducing interference from external factors such as severe weather and bird activity, greatly improving the reliability and stability of power supply. However, during laying and operation, cables are susceptible to mechanical damage such as tension, bending, and compression; in addition, manufacturing defects and long-term overload operation can also lead to localized defects in the cables. If defects in the cables are not addressed in a timely manner, they may further evolve into cable faults as the cable continues to operate, causing serious consequences.

[0003] The patent document "A method, system, device and storage medium for assessing the degree of damage to cable shielding" (publication number: CN119667551A) proposes a method for assessing the degree of damage to cable shielding, which can quickly and accurately assess the degree of damage to the metal shielding layer of the cable and the location of the damage.

[0004] The patent document "A method for locating defects in the sheath of high-voltage cables based on the broadband impedance spectrum of the sheath grounding circuit" (publication number: CN117434386A) proposes a method for locating defects in the sheath of high-voltage cables based on the broadband impedance spectrum of the sheath grounding circuit, which can realize rapid and accurate location of defects in the grounding circuit of high-voltage cables under energized conditions.

[0005] The common feature of the aforementioned cable defect detection devices is that they all employ a broadband impedance spectroscopy cable detection method for cable defect detection. However, most existing broadband impedance spectroscopy methods rely heavily on the subjective experience of the measurement personnel for parameter settings, and the resulting spectrum cannot accurately reflect cable defects, thus containing a certain degree of error. Summary of the Invention

[0006] The technical problem to be solved by this invention is: how to improve the accuracy of cable defect identification and location using broadband impedance spectroscopy.

[0007] To solve the above-mentioned technical problems, the technical solution proposed by this invention is: a cable defect identification and location method based on broadband impedance spectrum, comprising the following steps:

[0008] Step 1: Input the initial frequency domain incident signal into the cable to be identified and located for defect. The spatial domain reflection signal generated in the cable by the initial frequency domain incident signal is obtained. ,

[0009] The initial frequency domain incident signal As shown in equation (1),

[0010] (1)

[0011] In equation (1), a is the maximum amplitude of the Gaussian signal, b is the time shift of the Gaussian signal, and c is the pulse width coefficient of the Gaussian signal. This is the upper limit frequency for testing the input cable; p is the Gaussian pulse frequency in the... The ratio of the amplitude at 0 Hz;

[0012] The spatial domain reflected signal As shown in equation (2) below,

[0013] (2)

[0014] In equation (2), It is a modulo operation; It is the inverse Fourier transform; It is the reflection coefficient at the beginning of the cable;

[0015] The initial frequency domain incident signal is calculated according to the following formula (3). Spatial domain waveform generated in the cable ,

[0016] (3)

[0017] In equation (3), It is the speed at which electromagnetic waves propagate in a cable; It is the time shift factor in a Gaussian pulse signal; It is the speed at which electromagnetic waves propagate in a vacuum; It is the relative permittivity of the insulation layer of the cable;

[0018] The spatial domain waveform This is the frequency domain reflection defect location map of the cable, from which the average position of the frequency domain reflection anomaly peak is extracted. ;

[0019] Step 2: Input pulse width into the cable The pulse signal is used to generate a time-domain reflection defect location map of the cable by using the time difference between the reflected signal and the incident signal formed by the pulse signal within the cable. The location of the time-domain impedance mismatch point is extracted from the time-domain reflection defect location map. ;

[0020] Step 3: Calculate the positioning deviation between the frequency domain reflection defect positioning map and the time domain reflection defect positioning map according to the following formula (4). ,

[0021] (4)

[0022] If the positioning deviation Less than or equal to the positioning deviation threshold The positioning deviation threshold This is an empirical value, generally considered to be 0.5, so the average position of the frequency domain abnormal reflection peak is taken. Location of the time-domain impedance mismatch point The average value is used as the result of locating cable defects;

[0023] Conversely, proceed to step 4 below;

[0024] Step 4: Extract the spatial range of frequency domain reflection anomaly peaks from the frequency domain defect localization map. Fluctuation value at the location of the defect in the frequency domain reflection Fluctuation value at the end of the frequency domain reflection positioning cable Extract the spatial range of time-domain reflection impedance mismatch from the time-domain reflection defect location map. Fluctuation value at the location of the defect in the time domain reflection Fluctuation value at the end of the time-domain reflectometry positioning cable ;

[0025] The initial frequency domain incident signal is obtained by the following equation (5). and the pulse width After correction, the corrected frequency domain incident signal is obtained. and corrected pulse width ,

[0026] (5)

[0027] In equation (5), It is the correction pulse width coefficient for Gaussian signals; This is the upper limit frequency of the corrected test for the input cable; It is the fluctuation width between the frequency domain reflection defect location map and the time domain reflection defect location map; It is the joint location ratio between the frequency domain defect location map and the time domain defect location map; L is the length of the cable; It is a length operation;

[0028] The corrected frequency domain incident signal By inputting the data into the cable and repeating step 2, a corrected frequency domain reflection defect location map is obtained. The average position of the corrected frequency domain reflection abnormality peak is then extracted from this map. ;

[0029] The corrected pulse width The pulse signal is input into the cable and the principle of step 3 is repeated to obtain the corrected time-domain reflection defect location map. The location of the corrected time-domain reflection impedance mismatch point is extracted from the corrected time-domain reflection defect location map. ;

[0030] The average position of the corrected frequency domain reflection abnormality peak Location of the mismatch point with the corrected time-domain reflection impedance The average value is used as the result of defect identification and location of the cable.

[0031] The beneficial effects of this invention are: this invention comprehensively considers the advantages of frequency domain reflection method and reflection method, and uses positioning deviation degree To determine whether the parameters of the frequency domain reflectometry and time domain reflectometry need to be corrected, the positioning deviation is used during the correction process. Fluctuation width and joint positioning ratio As an indicator, it eliminates the shortcomings of both frequency domain reflection method and time domain reflection method, integrates their advantages, and uses the modified parameters for positioning, which greatly improves the accuracy of cable defect location and identification. Attached Figure Description

[0032] Figure 1 This is a flowchart from an embodiment of the present invention. Detailed Implementation

[0033] The following description, in conjunction with the accompanying drawings and specific embodiments, further illustrates the cable defect identification and location method based on broadband impedance spectrum according to the present invention.

[0034] Example

[0035] The cable defect identification and location method in this embodiment, such as Figure 1 As shown, it includes the following steps:

[0036] Step 1: Input the initial frequency domain incident signal into the cable to be identified and located for defect. The spatial frequency domain reflection signal generated in the cable by the initial frequency domain incident signal is obtained. ,

[0037] Initial frequency domain incident signal As shown in equation (1),

[0038] (1)

[0039] In equation (1), a is the maximum amplitude of the Gaussian signal, b is the time shift of the Gaussian signal, and c is the pulse width coefficient of the Gaussian signal. This is the upper limit frequency for testing the input cable; p is the Gaussian pulse frequency. The ratio of the amplitude to the 0Hz output value;

[0040] Spatial frequency domain reflection signal As shown in equation (2) below,

[0041] (2)

[0042] In equation (2), It is a modulo operation; It is the inverse Fourier transform; It is the reflection coefficient at the beginning of the cable;

[0043] The initial frequency domain reflection signal is calculated according to the following formula (3). Spatial domain waveforms generated in the cable ,

[0044] (3)

[0045] In equation (3), It is the speed at which electromagnetic waves propagate in a cable; It is the time shift factor in a Gaussian pulse signal; It is the speed at which electromagnetic waves propagate in a vacuum; It is the relative permittivity of the cable's insulation layer;

[0046] Spatial domain waveforms This refers to the frequency domain reflection defect location map of the cable, from which the average position of the frequency domain reflection anomaly peak is extracted. ;

[0047] Step 2: Input pulse width into the cable The pulse signal is used to generate a time-domain reflection defect location map of the cable by measuring the time difference between the reflected signal and the incident signal within the cable. The location of the time-domain reflection impedance mismatch point is then extracted from the time-domain reflection defect location map. ;

[0048] Step 3: Calculate the positioning deviation between the frequency domain reflection defect positioning map and the time domain reflection defect positioning map according to the following formula (4). ,

[0049] (4)

[0050] If the positioning deviation Less than or equal to the positioning deviation threshold Positioning deviation threshold This is an empirical value, generally considered to be 0.5, so the average position of the frequency domain reflection anomaly peak is taken. Location of time-domain reflection impedance mismatch point The average value is used as the result of locating cable defects;

[0051] Conversely, proceed to step 4 below;

[0052] Step 4: Extract the spatial range of frequency domain reflection anomaly peaks from the frequency domain reflection defect localization map. Fluctuation value at the location of the defect in the frequency domain reflection Fluctuation value at the end of the frequency domain reflection positioning cable Extract the spatial range of time-domain reflection impedance mismatch from the time-domain reflection defect location map. Fluctuation value at the location of the defect in the time domain reflection Fluctuation value at the end of the time-domain reflectometry positioning cable ;

[0053] The initial frequency domain incident signal is obtained by the following equation (5). and pulse width After correction, the corrected frequency domain incident signal is obtained. and corrected pulse width ,

[0054] (5)

[0055] In equation (5), It is the correction pulse width coefficient for Gaussian signals; This is the upper limit frequency for the corrected test of the input cable; It is the fluctuation width between the frequency domain reflection defect location map and the time domain reflection defect location map; It is the joint location ratio between the frequency domain reflection defect location map and the time domain reflection defect location map; L is the length of the cable; It is a length operation;

[0056] Correct the frequency domain incident signal The modified frequency domain reflection defect location map is obtained by inputting the cable and repeating the principle of step 2. The average position of the modified frequency domain reflection abnormal reflection peak is then extracted from the modified frequency domain reflection defect location map. ;

[0057] Correct pulse width The pulse signal is input into the cable, and the principle of step 3 is repeated to obtain the corrected time-domain reflection defect location map. The location of the corrected time-domain reflection impedance mismatch point is extracted from the corrected time-domain defect location map.

[0058] Correct the average position of the abnormal reflection peak in the frequency domain reflection. Location of the mismatch point with the corrected time-domain reflection impedance The average value is used as the result of cable defect identification and location.

[0059] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for identifying and locating cable defects based on broadband impedance spectrum, characterized in that: Includes the following steps: Step 1: Input the initial frequency domain incident signal into the cable to be identified and located for defect. The spatial domain reflection signal generated in the cable by the initial frequency domain incident signal is obtained. , The initial frequency domain incident signal As shown in equation (1), （1） In equation (1), a is the maximum amplitude of the Gaussian signal, b is the time shift of the Gaussian signal, and c is the pulse width coefficient of the Gaussian signal. This is the upper limit frequency for testing the input cable; p is the Gaussian pulse frequency in the... The ratio of the amplitude at 0 Hz; The spatial domain reflected signal As shown in equation (2) below, （2） In equation (2), It is a modulo operation; It is the inverse Fourier transform; It is the reflection coefficient at the beginning of the cable; The initial frequency domain incident signal is calculated according to the following formula (3). Spatial domain waveform generated in the cable , （3） In equation (3), It is the speed at which electromagnetic waves propagate in a cable; It is the time shift factor in a Gaussian pulse signal; It is the speed at which electromagnetic waves propagate in a vacuum; It is the relative permittivity of the insulation layer of the cable; The spatial domain waveform This is the frequency domain reflection defect location map of the cable. The average position of the frequency domain reflection anomaly peak is extracted from the frequency domain reflection defect location map. ; Step 2: Input pulse width into the cable The pulse signal is used to generate a time-domain reflection defect location map of the cable by using the time difference between the reflected signal and the incident signal formed by the pulse signal within the cable. The location of the time-domain impedance mismatch point is extracted from the time-domain reflection defect location map. ; Step 3: Calculate the positioning deviation between the frequency domain reflection defect positioning map and the time domain reflection defect positioning map according to the following formula (4). , （4） If the positioning deviation Less than or equal to the positioning deviation threshold The positioning deviation threshold This is an empirical value, generally considered to be 0.5, so the average position of the frequency domain abnormal reflection peak is taken. Location of the time-domain impedance mismatch point The average value is used as the result of locating cable defects; Conversely, proceed to step 4 below; Step 4: Extract the spatial range of frequency domain reflection anomaly peaks from the frequency domain defect localization map. Fluctuation value at the location of the defect in the frequency domain reflection Fluctuation value at the end of the frequency domain reflection positioning cable Extract the spatial range of time-domain reflection impedance mismatch from the time-domain reflection defect location map. Fluctuation value at the location of the defect in the time domain reflection Fluctuation value at the end of the time-domain reflectometry positioning cable ; The initial frequency domain incident signal is obtained by the following equation (5). and the pulse width After correction, the corrected frequency domain incident signal is obtained. and corrected pulse width , （5） In equation (5), It is the corrected pulse width coefficient for Gaussian signals; This is the upper limit frequency of the corrected test for the input cable; It is the fluctuation width between the frequency domain reflection defect location map and the time domain reflection defect location map; It is the joint location ratio between the frequency domain defect location map and the time domain defect location map; L is the length of the cable; It is a length operation; The corrected frequency domain incident signal By inputting the data into the cable and repeating step 2, a corrected frequency domain reflection defect location map is obtained. The average position of the corrected frequency domain reflection abnormality peak is then extracted from this map. ; The corrected pulse width The pulse signal is input into the cable and the principle of step 3 is repeated to obtain the corrected time-domain reflection defect location map. The location of the corrected time-domain reflection impedance mismatch point is extracted from the corrected time-domain reflection defect location map. ; The average position of the corrected frequency domain reflection abnormality peak Location of the mismatch point with the corrected time-domain reflection impedance The average value is used as the result of defect identification and location of the cable.

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