Cable copper shielding layer damage and damage opening size detection method, system and equipment based on combination of double frequency measurement method and step-by-step evaluation method, and storage medium

Abstract

The invention discloses a cable copper shielding layer damage and damage opening size detection method, system and device based on the combination of a frequency doubling measurement method and a step-by-step evaluation method and a storage medium, and is applied to the technical field of power equipment state detection. Comprising the following steps: respectively acquiring measurement results of a cable to be measured under Chirp signal injection of Gaussian envelopes with single and double center frequencies, and determining the starting time of an injection signal and the arrival time of a reflection signal according to an extreme value in a time-frequency cross correlation curve; extracting an injection signal and a reflection signal by taking the starting time and the arrival time as extraction starting points and the length of the injection signal as an extraction width, and calculating the damage degree according to the spectrum ratio of the reflection signal to the injection signal; and calculating characteristic impedance based on the damage degree, and sequentially determining the size and length of the central angle of the cable copper shielding layer damage port by using a step-by-step evaluation method. According to the invention, effective detection and positioning of copper shield damage and effective estimation of the damage size are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of power equipment status detection, and in particular to a method, system, device and storage medium for detecting damage to a cable copper shielding layer and the size of a damaged opening based on a combination of a double frequency measurement method and a step-by-step evaluation method. Background Art

[0002] As the main energy supply carrier in today's society, it is of great significance to ensure the safety and reliability of its supply. As an important power transmission medium in power consumption centers such as cities and factories, the safety and reliability of cables are highly valued. However, due to process problems in production and processing, as well as environmental impacts during operation, the copper shielding layer of the cable is prone to damage. The damage defects of the copper shielding layer will affect the uniform distribution of the electric field inside the cable, thereby accelerating the aging of the cable, and eventually causing the cable to fail and fail to supply power. Therefore, it is very important to detect the damage of the copper shielding of the cable during the factory testing and daily operation and maintenance of the cable line.

[0003] The existing methods for detecting copper shield damage in cable lines can be divided into reflectometer method and partial discharge detection method; the reflectometer method does not require the application of voltage to the cable and is suitable for non-powered testing; the partial discharge test is suitable for point detection of the cable during operation. However, there are still several problems in the existing detection methods. The time domain reflectometer is convenient and fast, but the sensitivity is low, it is prone to missed detection, and it is impossible to estimate the size of the detected damage defect; the time spectrum reflectometer (TFDR) has a higher sensitivity but is also unable to measure the size of the damaged opening; the partial discharge detection method also has the disadvantage that the defect size cannot be estimated. If the size of the copper shield damage cannot be estimated, it is impossible to judge the severity of the damage, and thus it is impossible to determine whether the cable needs to be repaired.

[0004] To this end, how to provide a cable copper shielding damage and damage opening size detection method, system, equipment and storage medium based on a combination of a double frequency measurement method and a step-by-step evaluation method, which can effectively detect and locate copper shielding damage in cable lines and effectively estimate the size of the copper shielding damage, so as to provide reference suggestions for whether subsequent repairs are needed. This is a problem that technical personnel in this field urgently need to solve. Summary of the invention

[0005] In view of this, the present invention proposes a method, system, device and storage medium for detecting damage to the cable copper shielding layer and the size of the damaged opening based on a combination of a double frequency measurement method and a step-by-step evaluation method.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A method for detecting damage and damage opening size of a cable copper shield layer based on a combination of a double frequency measurement method and a step-by-step evaluation method, comprising:

[0008] Step 1: Obtain the measurement results of the tested cable under the injection of Chirp signals of Gaussian envelopes at single and double center frequencies respectively, and determine the start time of the injected signal and the arrival time of the reflected signal at single and double center frequencies according to the extreme values ​​in the time-frequency cross-correlation curve of the measurement results;

[0009] Step 2: Take the start time and the arrival time as the extraction starting point, the length of the injection signal as the extraction width, extract the injection signal and the reflection signal at single and double center frequencies, and calculate the cable copper shielding layer damage at single and double center frequencies according to the spectrum ratio of the reflection signal and the injection signal;

[0010] Step 3: Based on the damage degree of the cable copper shielding layer at single and double center frequencies, calculate the characteristic impedance of the cable copper shielding layer damage defect, and use the step-by-step evaluation method to determine the central angle size of the cable copper shielding layer damage opening under the characteristic impedance and the length of the damage opening under the cable copper shielding layer damage degree when the central angle size is known.

[0011] Optionally, in step 1, when obtaining measurement results of the cable under test under the injection of chirp signals with single and double center frequencies of Gaussian envelopes, the interval between two measurements should be greater than twice the time required for the pulse to propagate from the first section of the cable to the end of the cable.

[0012] Optionally, in step 2, the cable copper shielding layer damage at single and double center frequencies is calculated based on the spectrum ratio of the reflected signal and the injected signal, as follows:

[0013]

[0014] Among them, M r P is the damage degree of cable copper shielding layer; sr is the spectrum ratio of the reflected signal to the injected signal; α p is the attenuation coefficient of the cable, which has different attenuation coefficients at different center frequencies; l a It is the distance between the first end of the defect and the signal injection point.

[0015] Optionally, the attenuation coefficient of the cable is calculated as follows:

[0016]

[0017] Among them, α p is the attenuation coefficient of the cable; l x The length of a known, defect-free test cable of the same model as the cable to be tested; r(t) The injected signal of a defect-free test cable of known length and the same model as the cable to be tested at single and double center frequencies;r(t) The reflected signal of a defect-free test cable of known length and the same model as the cable to be tested at single and double center frequencies; Compute the spectrum for the Fourier transform.

[0018] Optionally, the distance between the defect head end and the signal injection point is calculated as follows:

[0019] l a =t d ·v p ;

[0020]

[0021] Among them, l a is the distance between the defect head end and the signal injection point; t d v is the time difference between the start time of the injected signal and the arrival time of the reflected signal at single center frequency of the cable under test; p is the wave velocity of the cable to be tested; l x is the length of a known, defect-free test cable of the same model as the cable to be tested; t x When a defect-free test cable with the same model as the cable to be tested and a known length is measured at an injection signal at a single center frequency, the time difference between the arrival time of the reflected signal at the cable end and the start time of the injection signal is determined based on the extreme value in the time-frequency cross-correlation curve of the measurement result.

[0022] Optionally, in step 3, based on the degree of damage to the cable copper shielding layer at single and double center frequencies, the characteristic impedance of the cable copper shielding layer damage defect is calculated as follows:

[0023]

[0024] Among them, Z s Z is the characteristic impedance of the cable copper shielding layer damage defect; p is the characteristic impedance of the defect-free cable; Γ b is the reflection coefficient of the defect; M r1 M is the cable copper shield damage at single center frequency; r2 It is the cable copper shield damage degree at double the center frequency.

[0025] Optionally, in step 3, the size of the central angle of the damaged opening of the cable copper shielding layer under the characteristic impedance and the length of the damaged opening under the damage degree of the cable copper shielding layer are determined in sequence by using a step-by-step evaluation method, specifically:

[0026] Construct a set of cable copper shielding layer damage defects of different sizes and characteristic impedances of cable copper shielding layer damage defects and cable copper shielding layer damage degrees;

[0027] By comparing the characteristic impedance of the cable copper shielding layer damage defect of the tested cable with the reference value, the size of the central angle of the damaged opening of the cable copper shielding layer under the characteristic impedance is obtained;

[0028] When the size of the central angle is known, the damaged opening length of the cable copper shielding layer under the damage degree of the cable to be tested is obtained by comparing the damage degree of the cable copper shielding layer with the reference value.

[0029] The present invention also provides a cable copper shielding layer damage and damage opening size detection method based on a combination of a double frequency measurement method and a step-by-step evaluation method, comprising:

[0030] Time determination module: used to obtain the measurement results of the tested cable under the injection of Chirp signals of Gaussian envelopes of single and double center frequencies, and determine the start time of the injected signal and the arrival time of the reflected signal under single and double center frequencies according to the extreme values ​​in the time-frequency cross-correlation curve of the measurement results;

[0031] Damage calculation module: The start time and arrival time are used as the extraction starting point, and the length of the injection signal is used as the extraction width. The injection signal and the reflection signal at single and double center frequencies are extracted, and the damage degree of the cable copper shielding layer at single and double center frequencies is calculated based on the spectrum ratio of the reflection signal and the injection signal.

[0032] Damage opening size determination module: Based on the damage degree of the cable copper shielding layer at single and double center frequencies, the characteristic impedance of the cable copper shielding layer damage defect is calculated, and the central angle size of the cable copper shielding layer damage opening under the characteristic impedance and the damage opening length of the cable copper shielding layer under the damage degree of the cable copper shielding layer are determined in turn using a step-by-step evaluation method.

[0033] The present invention also provides an electronic device, comprising:

[0034] Memory for storing computer programs;

[0035] The processor is used to implement the steps of a method for detecting the damage of the cable copper shielding layer and the size of the damaged opening based on the combination of the double frequency measurement method and the step-by-step evaluation method when executing the computer program.

[0036] The present invention also provides a computer-readable storage medium, characterized in that a computer program is stored on the computer-readable storage medium, and when the computer program is executed by a processor, the steps of a method for detecting damage to the copper shielding layer of a cable and the size of the damaged opening are implemented based on a combination of a double frequency measurement method and a step-by-step evaluation method.

[0037] It can be seen from the above technical solutions that, compared with the prior art, the present invention proposes a method, system, device and storage medium for detecting the damage and damage size of the cable copper shield layer based on a combination of a double frequency measurement method and a step-by-step evaluation method. Based on the existing time-frequency domain reflectometer (TFDR) principle, by improving the measurement strategy of the traditional TFDR, introducing a new estimation method, using the double frequency measurement method and the step-by-step estimation method to detect the damage of the cable copper shield and measure the size of the copper shield damage, the effective detection and positioning of the copper shield damage of the cable line and the effective estimation of the copper shield damage size are achieved, providing reference suggestions for whether subsequent maintenance is needed. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0039] Figure 1 It is a schematic diagram of the method flow of the present invention.

[0040] Figure 2 It is a schematic diagram of the reference value of characteristic impedance of the copper shielded damaged cable of the present invention.

[0041] Figure 3 It is a contour diagram of the damage degree reference value of the present invention. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] Embodiment 1:

[0044] Embodiment 1 of the present invention discloses a method for detecting the damage and the size of the damaged copper shielding layer of a cable based on a combination of a double frequency measurement method and a step-by-step evaluation method, such as Figure 1 As shown, including:

[0045] Step 1: Obtain the measurement results of the cable under test under the injection of a Gaussian envelope chirp signal at single (first measurement) and double (second measurement) center frequency, and determine the start time of the injection signal and the arrival time of the reflected signal at single and double center frequencies based on the extreme values ​​in the time-frequency cross-correlation curve of the measurement results.

[0046] When obtaining the measurement results of the cable under test under the injection of chirp signals with single and double center frequency Gaussian envelopes, the interval between the two measurements should be greater than twice the time required for the pulse to propagate from the first section of the cable to the end of the cable.

[0047] A time-frequency cross-correlation curve of the measurement results can be obtained according to a time-frequency cross-correlation method.

[0048] Step 2: Take the start time and arrival time as the extraction starting point, the length of the injection signal as the extraction width, extract the injection signal and reflection signal at single and double center frequencies, and calculate the cable copper shielding layer damage at single and double center frequencies based on the spectrum ratio of the reflection signal and the injection signal.

[0049] The spectrum of the reflected signal and the injected signal can be obtained according to Fourier transform.

[0050] According to the spectrum ratio of the reflected signal and the injected signal, the cable copper shield damage at single and double center frequencies is calculated as follows:

[0051]

[0052] Among them, M r P is the damage degree of cable copper shielding layer; sr is the spectrum ratio of the reflected signal to the injected signal; α p is the attenuation coefficient of the cable, which has different attenuation coefficients at different center frequencies; l a It is the distance between the first end of the defect and the signal injection point.

[0053] The calculation method of the attenuation coefficient of the cable is as follows:

[0054]

[0055] Among them, α p is the attenuation coefficient of the cable; l x The length of the defect-free test cable, which is of the same model as the cable to be tested and known, is required to be no less than 30m, and both ends of the cable line are open; r(t) The injected signal of a defect-free test cable of known length and the same model as the cable to be tested at single and double center frequencies; r(t)The reflected signal of a defect-free test cable of known length and the same model as the cable to be tested at single and double center frequencies; Compute the spectrum for the Fourier transform.

[0056] The calculation method of the distance between the first end of the defect and the signal injection point is as follows:

[0057] l a =t d ·v p ;

[0058]

[0059] Among them, l a is the distance between the defect head end and the signal injection point; t d v is the time difference between the start time of the injected signal and the arrival time of the reflected signal at single center frequency of the cable under test; p is the wave velocity of the cable to be tested; l x is the length of a known, defect-free test cable of the same model as the cable to be tested; t x When a defect-free test cable with the same model as the cable to be tested and a known length is measured at an injection signal at a single center frequency, the time difference between the arrival time of the reflected signal at the cable end and the start time of the injection signal is determined based on the extreme value in the time-frequency cross-correlation curve of the measurement result.

[0060] Step 3: Based on the damage degree of the cable copper shielding layer at single and double center frequencies, calculate the characteristic impedance of the cable copper shielding layer damage defect, and use the step-by-step evaluation method to determine the central angle of the damaged opening of the cable copper shielding layer under the characteristic impedance and the length of the damaged opening under the damage degree of the cable copper shielding layer when the central angle is known, and finally achieve the measurement of the damaged opening size.

[0061] Based on the cable copper shield damage at single and double center frequencies, the characteristic impedance of the cable copper shield damage defect is calculated as follows:

[0062]

[0063] Among them, Z s Z is the characteristic impedance of the cable copper shielding layer damage defect; p is the characteristic impedance of the defect-free cable; Γ b is the reflection coefficient of the defect; M r1 M is the cable copper shield damage at single center frequency; r2 It is the cable copper shield damage degree at double the center frequency.

[0064] The step-by-step evaluation method is used to determine the size of the central angle of the cable copper shield damage opening under the characteristic impedance and the length of the damage opening under the cable copper shield damage degree when the size of the central angle is known. Specifically,

[0065] A set of cable copper shielding layer damage defects of different sizes and characteristic impedances of cable copper shielding layer damage defects and cable copper shielding layer damage degrees is constructed, and the characteristic impedances of cable copper shielding layer damage defects and reference values ​​of cable copper shielding layer damage degrees under cable copper shielding layer damage defects of different sizes can be simulated and calculated by finite element method;

[0066] By comparing the characteristic impedance of the cable copper shielding layer damage defect of the tested cable with the reference value, the size of the central angle of the damaged opening of the cable copper shielding layer under the characteristic impedance is obtained;

[0067] When the size of the central angle is known, the damaged opening length of the cable copper shielding layer under the damage degree of the cable to be tested is obtained by comparing the damage degree of the cable copper shielding layer with the reference value.

[0068] Embodiment 2:

[0069] Embodiment 2 of the present invention discloses a specific application of a method for detecting damage to a cable copper shielding layer and the size of a damaged opening based on a combination of a double frequency measurement method and a step-by-step evaluation method, as follows:

[0070] The cable model used is YJV-10kV single-core 35mm2. The length of the tested cable is 250m. The damage occurs at 50m. The central angle of the damage is 240° and the length of the damage is 0.5m.

[0071] In step 1: the time length of the Chirp signal of the Gaussian envelope of single center frequency is 200ns, the center frequency is 40MHz, and the bandwidth is 40MHz. The time length of the Chirp signal of the Gaussian envelope of double center frequency is 200ns, the center frequency is 80MHz, and the bandwidth is 40MHz. The interval between the two measurements is 0.5s. The time-frequency cross-correlation method is used to calculate the time-frequency cross-correlation curve of the measurement signal. According to the maximum value in the curve, the time difference between the arrival time of the reflected signal and the start time of the injected pulse is 0.592μs.

[0072] In step 2: Use the attenuation coefficient calculation formula to calculate the attenuation coefficient α of the cable to be tested p At 40MHz (single center frequency), it is 0.001867m -1 , at 80MHz (double the center frequency) is 0.002831m -1 According to the cable wave velocity calculation formula, the cable wave velocity is calculated as v pis 169 m / s. Further, the distance l from the defect head end to the signal injection point is calculated according to the distance calculation formula from the defect head end to the signal injection point. a The actual defect location is 50m away from the measurement point, and the positioning error is 0.04%. The damage degree at single center frequency is calculated to be 0.1236 using the damage degree measurement calculation formula, and the damage degree at double center frequency is 0.1613. Furthermore, the characteristic impedance calculation formula of the cable copper shielding layer damage defect is used to calculate the characteristic impedance of the cable to be tested to be 47.67Ω.

[0073] In step 3: the characteristic impedance of the cable copper shielding layer damage defect and the reference value of the cable copper shielding layer damage degree under the cable copper shielding layer damage defects of different sizes are simulated and calculated by the finite element method. The contour maps of the characteristic characteristic impedance reference value and the damage degree reference value are as follows: Figure 2 and Figure 3 Using the step-by-step estimation method, we first compare Figure 2 , we can get the central angle of the damaged opening of the cable copper shielding layer to be 236.86°. Furthermore, when the central angle is known to be 236.86°, we can compare Figure 3 , the estimated value of the damaged opening length is 0.5035m. Comparing the actual value and estimated value of the central angle and the damaged opening length, the relative error of the central angle measurement is -1.31%, and the damaged opening length is 0.7%, which proves the measurement accuracy and effectiveness of the present invention.

[0074] Embodiment 3:

[0075] Embodiment 3 of the present invention discloses a cable copper shielding layer damage and damage opening size detection method based on a combination of a double frequency measurement method and a step-by-step evaluation method, comprising:

[0076] Time determination module: used to obtain the measurement results of the tested cable under the injection of Chirp signals of Gaussian envelopes of single and double center frequencies, and determine the start time of the injected signal and the arrival time of the reflected signal under single and double center frequencies according to the extreme values ​​in the time-frequency cross-correlation curve of the measurement results;

[0077] Damage calculation module: The start time and arrival time are used as the extraction starting point, and the length of the injection signal is used as the extraction width. The injection signal and the reflection signal at single and double center frequencies are extracted, and the damage degree of the cable copper shielding layer at single and double center frequencies is calculated based on the spectrum ratio of the reflection signal and the injection signal.

[0078] Damage opening size determination module: Based on the damage degree of the cable copper shielding layer at single and double center frequencies, the characteristic impedance of the cable copper shielding layer damage defect is calculated, and the central angle size of the cable copper shielding layer damage opening under the characteristic impedance and the damage opening length of the cable copper shielding layer under the damage degree of the cable copper shielding layer are determined in turn using a step-by-step evaluation method.

[0079] Embodiment 4:

[0080] Embodiment 4 of the present invention discloses an electronic device, including:

[0081] Memory for storing computer programs;

[0082] The processor is used to implement the steps of a method for detecting the damage of the cable copper shielding layer and the size of the damaged opening based on the combination of the double frequency measurement method and the step-by-step evaluation method when executing the computer program.

[0083] Embodiment 5:

[0084] Embodiment 5 of the present invention discloses a computer-readable storage medium, characterized in that a computer program is stored on the computer-readable storage medium, and when the computer program is executed by a processor, the steps of a method for detecting damage to the copper shielding layer of a cable and the size of the damaged opening are implemented based on a combination of a double frequency measurement method and a step-by-step evaluation method.

[0085] The embodiment of the present invention discloses a method, system, device and storage medium for detecting the damage and damage opening size of the cable copper shield layer based on the combination of the double frequency measurement method and the step-by-step evaluation method. Based on the existing time-frequency domain reflectometer (TFDR) principle, by improving the measurement strategy of the traditional TFDR, introducing a new estimation method, using the double frequency measurement method and the step-by-step estimation method to detect the copper shield damage of the cable and measure the size of the copper shield damage opening, the effective detection and positioning of the copper shield damage of the cable line and the effective estimation of the copper shield damage size are achieved, providing reference suggestions for whether subsequent maintenance is needed.

[0086] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0087] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for detecting the damage and the size of the damaged copper shielding layer of a cable based on a combination of a double frequency measurement method and a step-by-step evaluation method, characterized in that: include: Step 1: respectively obtain the measurement results of the cable to be tested under the injection of Chirp signals of Gaussian envelopes of single and double center frequencies, and determine the start time of the injection signal and the arrival time of the reflected signal under the single and double center frequencies according to the extreme values ​​in the time-frequency cross-correlation curve of the measurement results; Step 2: Taking the start time and the arrival time as the extraction start point and the length of the injection signal as the extraction width, extract the injection signal and the reflection signal at the single and double center frequencies, and calculate the cable copper shielding layer damage at the single and double center frequencies according to the spectrum ratio of the reflection signal and the injection signal; Step 3: Based on the degree of damage of the cable copper shielding layer at the single and double center frequencies, calculate the characteristic impedance of the cable copper shielding layer damage defect, and use a step-by-step evaluation method to determine in turn the size of the central angle of the damaged opening of the cable copper shielding layer under the characteristic impedance and the length of the damaged opening under the degree of damage of the cable copper shielding layer when the size of the central angle is known.

2. According to claim 1, a method for detecting damage to the cable copper shielding layer and the size of the damaged opening based on a combination of a double frequency measurement method and a step-by-step evaluation method, characterized in that: In step 1, when obtaining the measurement results of the cable under test under the injection of Chirp signals with single and double center frequency Gaussian envelopes, the interval between two measurements should be greater than twice the time required for the pulse to propagate from the first section of the cable to the end of the cable.

3. According to claim 1, a method for detecting damage to the cable copper shielding layer and the size of the damaged opening based on a combination of a double frequency measurement method and a step-by-step evaluation method, characterized in that: In step 2, the damage degree of the cable copper shielding layer at the single and double center frequencies is calculated according to the spectrum ratio of the reflected signal and the injected signal, as follows: Among them, M r P is the damage degree of cable copper shielding layer; sr is the spectrum ratio of the reflected signal to the injected signal; α p is the attenuation coefficient of the cable, which has different attenuation coefficients at different center frequencies; l a It is the distance between the first end of the defect and the signal injection point.

4. A method for detecting damage to the cable copper shielding layer and the size of the damaged opening based on a combination of a double frequency measurement method and a step-by-step evaluation method according to claim 3, characterized in that: The calculation method of the attenuation coefficient of the cable is as follows: Among them, α p is the attenuation coefficient of the cable; l x The length of a known, defect-free test cable of the same model as the cable to be tested; r(t) is the injection signal of a defect-free test cable of known length and the same model as the cable to be tested at the single and double center frequencies; r(t) is the reflected signal of a non-defective test cable of known length and the same model as the cable to be tested at the single and double center frequencies; Compute the spectrum for the Fourier transform.

5. The method for detecting damage to the cable copper shielding layer and the size of the damaged opening based on the combination of the double frequency measurement method and the step-by-step evaluation method according to claim 3 is characterized in that: The method for calculating the distance between the defect head end and the signal injection point is as follows: l a =t d ·v p ; Among them, l a is the distance between the defect head end and the signal injection point; t d v is the time difference between the start time of the injected signal and the arrival time of the reflected signal at single center frequency of the cable under test; p is the wave velocity of the cable to be tested; l x is the length of a known, defect-free test cable of the same model as the cable to be tested; t x When a defect-free test cable with the same model as the cable to be tested and a known length is measured at an injection signal at a single center frequency, the time difference between the arrival time of the reflected signal at the cable end and the start time of the injection signal is determined based on the extreme value in the time-frequency cross-correlation curve of the measurement result.

6. A method for detecting damage to the cable copper shielding layer and the size of the damaged opening based on a combination of a double frequency measurement method and a step-by-step evaluation method according to claim 1, characterized in that: In step 3, based on the damage degree of the cable copper shielding layer at the single and double center frequencies, the characteristic impedance of the cable copper shielding layer damage defect is calculated as follows: Among them, Z s Z is the characteristic impedance of the cable copper shielding layer damage defect; p is the characteristic impedance of the defect-free cable; Γ b is the reflection coefficient of the defect; M r1 M is the cable copper shield damage at single center frequency; r2 It is the cable copper shield damage degree at double the center frequency.

7. A method for detecting damage to the cable copper shielding layer and the size of the damaged opening based on a combination of a double frequency measurement method and a step-by-step evaluation method according to claim 1, characterized in that: In step 3, the size of the central angle of the damaged opening of the cable copper shielding layer under the characteristic impedance and the length of the damaged opening under the damage degree of the cable copper shielding layer are determined in sequence by using a step-by-step evaluation method, specifically: Construct a set of cable copper shielding layer damage defects of different sizes and characteristic impedances of cable copper shielding layer damage defects and cable copper shielding layer damage degrees; By comparing the characteristic impedance of the cable copper shielding layer damage defect of the cable to be tested with a reference value, the size of the central angle of the damaged opening of the cable copper shielding layer under the characteristic impedance is obtained; When the size of the center angle is known, the damaged opening length of the cable copper shielding layer under the damage degree of the cable copper shielding layer is obtained by comparing the damage degree of the cable copper shielding layer of the cable to be tested with a reference value.

8. A cable copper shielding layer damage and damage opening size detection system based on a combination of a double frequency measurement method and a step-by-step evaluation method using a cable copper shielding layer damage and damage opening size detection method based on a combination of a double frequency measurement method and a step-by-step evaluation method as described in any one of claims 1-7, characterized in that: include: Time determination module: used to obtain the measurement results of the tested cable under the injection of Chirp signals of Gaussian envelopes of single and double center frequencies, and determine the start time of the injected signal and the arrival time of the reflected signal under the single and double center frequencies according to the extreme values ​​in the time-frequency cross-correlation curve of the measurement results; A damage degree calculation module: taking the start time and the arrival time as the extraction start point, and the length of the injection signal as the extraction width, extracting the injection signal and the reflection signal at the single and double center frequencies, and calculating the damage degree of the cable copper shielding layer at the single and double center frequencies according to the spectrum ratio of the reflection signal and the injection signal; Damage opening size determination module: Based on the damage degree of the cable copper shielding layer at the single and double center frequencies, the characteristic impedance of the cable copper shielding layer damage defect is calculated, and a step-by-step evaluation method is used to sequentially determine the size of the central angle of the damage opening of the cable copper shielding layer under the characteristic impedance and the length of the damage opening under the damage degree of the cable copper shielding layer when the size of the central angle is known.

9. An electronic device, characterized in that: include: Memory for storing computer programs; A processor is used to implement the steps of a method for detecting damage to the cable copper shielding layer and the size of the damaged opening based on a combination of a double frequency measurement method and a step-by-step evaluation method as described in any one of claims 1 to 7 when executing the computer program.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of a method for detecting damage to the copper shielding layer of a cable and the size of the damaged opening based on a combination of a double frequency measurement method and a step-by-step evaluation method as described in any one of claims 1 to 7.

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