A method of measuring the length of corrosion on a copper shield of a cable and related apparatus

Abstract

The application discloses a cable copper shielding corrosion length measurement method and related equipment, based on the traditional TFDR detection principle, the traditional single signal injection measurement strategy is improved, and a double frequency measurement method and corresponding signal processing technology are used to measure the cable copper shielding corrosion length. The double frequency measurement method measures the cable twice, calculates the corrosion degree of the cable copper shielding corrosion defect under the two measurements according to the reflection signals of the two measurements, and then calculates the corrosion length of the cable copper shielding corrosion defect according to the corrosion degree calculation results of the two times, so that the accurate evaluation of the cable copper shielding corrosion defect length is realized. The measurement method can realize the accurate positioning of the cable copper shielding corrosion defect, ensure that the corrosion defect can be found in time and its position can be determined, and can accurately evaluate the corrosion length of the copper shielding corrosion defect and determine the severity of the cable copper shielding corrosion.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power equipment state detection and its application, and particularly relates to a cable copper shielding corrosion length measurement method and related equipment. BACKGROUND

[0002] With the development of power technology and the improvement of power supply requirements, cables are widely applied to urban power transmission and distribution lines. However, the long-buried cable line is extremely prone to corrosion of the copper shielding due to environmental influences. Once the copper shielding layer is corroded, the speed of cable insulation deterioration is suddenly accelerated, and ultimately leads to cable failure and interruption of power supply. Therefore, the copper shielding corrosion detection of the cable line is crucial in the daily operation and maintenance of the cable.

[0003] At present, the popular cable line copper shielding corrosion detection methods mainly include a reflectometer method, a neutral line resistance method and a surface voltage method. Among the three methods, the reflectometer method is favored due to its fast detection speed and high efficiency. The time-frequency domain reflectometer (TFDR) method in the reflectometer method is widely applied in the detection of cable copper shielding corrosion defects due to its high sensitivity and high positioning accuracy. However, the existing TFDR method can only realize high-precision positioning and lacks the ability to estimate the length of the copper shielding corrosion defect, which seriously affects the efficiency of cable operation and maintenance. SUMMARY

[0004] The application provides a cable copper shielding corrosion length measurement method and related equipment, which solves the problem that the existing TFDR method can only realize high-precision positioning and lacks the ability to estimate the length of the copper shielding corrosion defect.

[0005] To achieve the above object, the application provides the following technical scheme:

[0006] A cable copper shielding corrosion length measurement method, comprising:

[0007] injecting Chirp signals into the cable twice and sequentially measuring the reflection signals of the two Chirp signals;

[0008] calculating the corrosion degrees of the cable copper shielding corrosion defects under the two measurements according to the measurement results of the two reflection signals;

[0009] calculating the corrosion length of the cable copper shielding corrosion defect according to the corrosion degree calculation results of the two times;

[0010] wherein the center frequency of the injected Chirp signal in the second measurement is twice that in the first measurement, and the interval time between the two measurements is greater than twice the length of the injected signal propagating from the beginning of the cable to the end.

[0011] Preferably, the calculation of the corrosion degree of the cable is specifically:

[0012] According to the first measurement result, a time-frequency cross correlation analysis method is used to calculate a time-frequency cross correlation curve corresponding to the first measurement result; according to a time corresponding to an extreme value on the time-frequency cross correlation curve, an injection signal time and an arrival time of a rust defect reflection signal are determined. The injection signal time is recorded as 0 time, and the arrival time of the rust defect reflection signal is recorded as t p time.

[0013] 0 time and t p time are taken as starting points, respectively, the injection signal and the rust defect reflection signal are extracted from the first measurement result, and the length of the extracted signal is consistent with the length of the injection signal preset by the signal generating device;

[0014] Fourier transform is performed on the extracted injection signal and reflection signal to obtain a frequency spectrum of the injection signal and a frequency spectrum of the rust defect reflection signal;

[0015] The frequency spectrum of the rust defect reflection signal is divided by the frequency spectrum of the injection signal to obtain a frequency spectrum ratio;

[0016] According to the frequency spectrum ratio and a frequency spectrum ratio-rust degree equation, a first measurement rust degree of the cable copper shielding rust defect is obtained.

[0017] The same calculation process as the first measurement result is used for the second measurement result to calculate a second measurement rust degree of the cable copper shielding rust defect.

[0018] Preferably, the frequency spectrum ratio-rust degree equation is:

[0019]

[0020] wherein P sr is the frequency spectrum ratio, e is a natural constant, A p is a rate of change of an attenuation coefficient of a cable intact part with respect to an angular frequency, l a is a distance between the cable copper shielding rust defect and a measurement point; and ω is a central angular frequency of the injection signal during measurement.

[0021] Preferably, the calculation method of the rate of change of the attenuation coefficient of the cable intact part with respect to the angular frequency A p is as follows:

[0022] An intact cable of a certain type with a length of l x is obtained, the cable end is kept open, a Chirp signal is injected at the cable head, and a measured reflection signal is obtained;

[0023] According to the measurement results of the reflected signal, a time-frequency cross correlation analysis method is used to calculate a time-frequency cross correlation curve corresponding to the reflected signal; according to the time corresponding to the extreme value on the time-frequency cross correlation curve, the injection signal time and the arrival time of the cable end reflected signal are determined. The injection signal time is recorded as 0 time, and the arrival time of the cable end reflected signal is recorded as t pe time.

[0024] The injection signal and the cable end reflected signal are extracted from the measurement results, respectively, with 0 time and t pe time as the starting point, and the length of the extracted signal is consistent with the length of the injection signal preset by the signal generating device;

[0025] The Wigner-Ville distribution of the extracted injection signal and the cable end reflected signal is calculated respectively to obtain the time-frequency distribution of the injection signal and the cable end reflected signal, and then the change rate A p of the attenuation coefficient with respect to the angular frequency is calculated.

[0026] Preferably, the calculation formula of the change rate A p of the attenuation coefficient of the cable intact part with respect to the angular frequency is:

[0027]

[0028] Where ω is the central angular frequency of the injection signal at the time of measurement, l x is the cable length, Ws(t, ω) is the time-frequency component of the injection signal, and Wr(t, ω) is the time-frequency component of the reflected signal.

[0029] Preferably, the calculation formula of the cable corrosion length according to the two corrosion degree calculation results is:

[0030]

[0031] C r2 is the corrosion degree of the second measurement, C r1 is the corrosion degree of the first measurement, ω is the central angular frequency of the Chirp signal at the time of the first measurement, and K s is the change rate of the phase coefficient of the copper shielding corrosion defect cable segment with respect to the angular frequency.

[0032] Preferably, the calculation method of the change rate K s of the phase coefficient of the copper shielding corrosion defect cable segment with respect to the angular frequency is:

[0033]

[0034] Where v sp is the wave velocity of the copper shielding corrosion defect cable segment.

[0035] A cable copper shielding corrosion length measurement system comprises

[0036] The signal acquisition module is configured to continuously emit twice Chirp signals to the cable and acquire reflected signals of the twice Chirp signals.

[0037] The corrosion degree calculation module is configured to calculate the corrosion degree of the cable according to the twice reflected signals.

[0038] The corrosion length calculation module is configured to calculate the corrosion length of the cable according to the calculation results of the twice corrosion degrees.

[0039] In the twice measurement, the center frequency of the Chirp signal injected in the second measurement is twice that in the first measurement, and the interval time between the twice measurements is greater than twice the time length for the injected signal to propagate from the first end to the second end of the cable.

[0040] The computer device comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor implements the steps of the cable copper shielding corrosion length measurement method when executing the computer program.

[0041] The computer readable storage medium stores a computer program, and the computer program implements the steps of the cable copper shielding corrosion length measurement method when executed by a processor.

[0042] Compared with the prior art, the present application has the following beneficial effects: the cable copper shielding corrosion length measurement method of the present application is based on the TFDR principle, improves the traditional single signal injection measurement strategy, and measures the cable copper shielding corrosion length by using the double frequency measurement method and the corresponding signal processing technology. The double frequency measurement method measures the cable twice, calculates the corrosion degree of the cable corrosion defect under the twice measurement according to the twice reflected signals obtained by the twice measurement, and then calculates the corrosion length of the cable according to the calculation results of the twice corrosion degrees, so as to realize accurate evaluation of the length of the copper shielding corrosion defect. The measurement method can realize accurate positioning of the copper shielding corrosion defect, ensure that the corrosion defect can be discovered in time and its position can be determined, and can accurately estimate the length of the corrosion defect, significantly expand the performance and application scenarios of the existing TFDR technology. The present application provides more detailed state information for cable operation and maintenance, and has important practical value in engineering. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 is a device model diagram for measuring the present application;

[0044] Figure 2 is a flowchart of the measurement method of the embodiment of the present application;

[0045] Figure 3is the first measurement result in the specific embodiment and its time-frequency cross-correlation curve;

[0046] Figure 4 is the second measurement result in the specific embodiment and its time-frequency cross-correlation curve;

[0047] Figure 5 is a flow chart of a cable copper shielding corrosion length measurement method of the present application;

[0048] Figure 6 is a block diagram of a cable copper shielding corrosion length measurement system of the present application. DETAILED DESCRIPTION

[0049] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.

[0050] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative labor are within the scope of protection of the present application.

[0051] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0052] In the description of the embodiments of the present application, it should be noted that if the terms "upper", "lower", "horizontal", "inner" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship when the product of the present application is used, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second" and the like are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0053] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly inclined. For example, "horizontal" only means that its direction is relatively more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined.

[0054] In the description of the embodiments of the present application, it also needs to be explained that, unless otherwise explicitly specified and limited, if the terms "arrange", "install", "connect", "connect" appear, they should be understood in a broad sense, for example, they can be fixedly connected, or can be detachably connected, or integrally connected; can be mechanically connected, or can be electrically connected; can be directly connected, or can be indirectly connected through an intermediate medium, or can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0055] In order for those skilled in the art to better understand the technical solutions of the present application, the present application will be further described in detail below with reference to the drawings.

[0056] As Figure 5 shown, the present application provides a cable copper shielding corrosion length measurement method, comprising:

[0057] S101 injects two Chirp signals into the cable, and measures the reflection signals of the two Chirp signals;

[0058] S102 calculates the corrosion degree of the cable copper shielding corrosion defect under the two measurements according to the two measurement results, respectively;

[0059] S103 calculates the corrosion length of the cable copper shielding corrosion defect according to the corrosion degree calculation results of the two times;

[0060] Among them, the center frequency of the Chirp signal injected in the second measurement of the two measurements is twice that of the first measurement, and the interval time between the two measurements is greater than twice the length of the injected signal from the cable head end to the end.

[0061] Specifically:

[0062] The measurement device as Figure 1 shown is used to measure the device, and the measurement device comprises a signal generating device, a data acquisition device and a T-shaped connecting terminal. The T-shaped connecting terminal connects the signal generating device, the data acquisition device and the measured cable, the signal generating device generates Chirp signal, injects into the measured cable, propagates along the measured cable, and partially reflects at the defect to generate reflection signal; the data acquisition device collects and saves the injected signal of the signal generating device and the reflection signal generated by the defect.

[0063] The measurement method comprises: a double frequency measurement method, a corrosion degree calculation method and a corrosion length calculation method.

[0064] The aforementioned double frequency measurement method is characterized in that, when detecting copper shield corrosion defects in a cable, two consecutive measurements are performed. In the two measurements, the center frequency of the injected chirp signal in the second measurement is twice that in the first measurement, and the interval between the two measurements is greater than twice the time it takes for the injected signal to propagate from the beginning to the end of the cable.

[0065] The aforementioned method for calculating corrosion degree is characterized by the following specific calculation steps:

[0066] Step S1: Obtain the results of the first measurement;

[0067] Step S2: Calculate the time-frequency cross-correlation curve of the measurement results using time-frequency cross-correlation analysis. Based on the time-frequency cross-correlation curve, the injection signal time is the time corresponding to the extreme point of the time-frequency cross-correlation curve for the injected signal portion, denoted as time 0. The arrival time of the corrosion defect reflection signal is the time t corresponding to the extreme point of the time-frequency cross-correlation curve for the corrosion defect reflection signal portion. p ;

[0068] Step S3: At time 0 and t respectively p Starting from the first measurement result, the injection signal and the corrosion defect reflection signal are extracted, and the extracted length is consistent with the injection signal length preset by the signal generating device.

[0069] Step S4: Perform Fourier transform on the extracted injection signal and corrosion defect reflection signal respectively to obtain the spectrum of the injection signal and the spectrum of the corrosion defect reflection signal;

[0070] Step S5: Divide the spectrum of the reflected signal from the corrosion defect by the spectrum of the injected signal to obtain the spectrum ratio, denoted as P. sr ;

[0071] Step S6: Substitute the spectral ratio into the spectral ratio-corrosion degree equation to calculate the corrosion degree C. r1 The equation for the spectral ratio and corrosion degree is:

[0072]

[0073] Step S7: Obtain the second measurement result. Repeat steps S2 to S6 for the second measurement result and calculate the corrosion degree C of the second measurement. r2 .

[0074] The spectral ratio-corrosion degree equation in step S6 is characterized by A in the equation. p The attenuation coefficient of the intact portion of the cable changes with respect to angular frequency. The attenuation coefficient-angular frequency characteristic curve of the cable can be obtained by referring to the cable's instruction manual or through measurement and calculation. ais the distance between the measurement points of the corrosion defect; ω is the center angular frequency of the injected signal, ω = 2πf, wherein f is the center frequency of the injected signal.

[0075] The rate of change A of the attenuation coefficient of the intact part of the cable with respect to the angular frequency p characterized in that the rate of change A of the attenuation coefficient of the intact part of the cable with respect to the angular frequency p The cable model is related to the cable model, which can be obtained through the cable manual or measured by measuring the same model cable, and the specific calculation steps are as follows:

[0076] Step M1: Obtain a cable of the same model as the measured cable with a length of l x The first end of the cable is connected to the measuring device of the application, and the end is open.

[0077] Step M2: Use the measuring device of the application to inject a Chirp signal with a center angular frequency of ω into the cable, and collect the reflected signal.

[0078] Step M3: According to the method of step S2 and step S3, the injected signal s h (t) and the reflected signal r h (t) at the end of the cable are extracted.

[0079] Step M4: The extracted injected signal s h (t) and the reflected signal r h (t) at the end of the cable are calculated respectively, and the time-frequency components of the injected signal s h (t) and the end reflected signal r h (t) are obtained, denoted as W s (t, ω) and W r (t, ω), and the rate of change of the attenuation coefficient with respect to the angular frequency is calculated, and the formula is as follows:

[0080]

[0081] The distance l a between the measurement points of the corrosion defect a is calculated by the wave speed v p of the cable and the arrival time t p of the reflected signal, and the wave speed of the cable is a constant and can be obtained from the cable manual, and the calculation formula of the distance l a is as follows:

[0082]

[0083] The rust length calculation method is characterized by utilizing twice measured rust degrees and a rust degree-rust length calculation formula to calculate the rust length of the cable copper shielding defect, and the rust degree-rust length calculation formula is:

[0084]

[0085] The rust degree-rust length calculation formula is characterized by K s being a rate of change of the phase coefficient with respect to the angular frequency of the cable copper shielding rust defect section, the rate of change of the phase coefficient with respect to the angular frequency K s can be calculated by the wave velocity v sp of the cable of the copper shielding rust section, and v sp can be calculated by an existing finite element simulation modeling calculation method, and the rate of change of the phase change coefficient K s is related to the wave velocity v sp .

[0086]

[0087] After the above method and design are adopted, the present application has at least the following advantages:

[0088] The cable copper shielding rust detection and rust length measurement method and device provided by the present application can realize accurate positioning of the copper shielding rust defect, ensure that the rust defect can be found in time and its position is determined, can accurately estimate the length of the rust defect, provide information on the rust severity for the operation and maintenance personnel, and help the operation and maintenance personnel to judge the severity of the defect and the maintenance level.

[0089] Embodiment:

[0090] The measurement device and the specific implementation example connection model adopted by the present application are shown in Figure 1 , which includes a signal generating device, a data acquisition device and a T-shaped connection terminal, and the computer shown in the figure is used for data processing and equipment control. The T-shaped connection terminal connects the signal generating device, the data acquisition device and the measured cable according to the topology shown in Figure 1 , the length of the measured cable is 250m, the position of the rust defect is set at 50m, and the length of the rust defect is 0.4m.

[0091] The device is used for twice frequency measurement of the cable. The first measurement injected Chirp signal has a time length of 200ns, a center frequency of 40MHz and a bandwidth of 40MHz, and the first measurement result is shown in Figure 3 ; the second measurement injected Chirp signal has a time length of 200ns, a center frequency of 80MHz and a bandwidth of 40MHz, and the second measurement result is shown in Figure 4, the interval between the two measurements is 1s.

[0092] The time-frequency cross-correlation curves of the two measurement signals are calculated respectively by using the time-frequency cross-correlation analysis method, such as the correlation curves in Figure 3 and Figure 4 The arrival time t p of the reflected signal is 0.591μs.

[0093] The cable type used in the embodiment is YJV-10kV single-core 35mm 2 , and the rate of change of the attenuation coefficient of the cable with respect to the angular frequency A p is 1.325×10 -10 s / (m·rad), the rate of change of the phase constant of the copper shielding rust defect section with respect to the angular frequency K s is 9.1656×10 -9 s / m, and the wave velocity of the cable v p is 169m / s. According to the calculation formula of the distance l a , the distance l a of the copper shielding distance measurement point is 49.94m, the actual defect setting position is 50m away from the measurement point, and the positioning error is-0.12%.

[0094] The injected signal and the reflected signal of the rust defect in the two measurement results are extracted, the rust degree measurement results of the two times are calculated by using the spectrum ratio-rust degree equation, the first rust degree measurement result C r1 of the rust is 0.1686, and the second rust degree measurement result C r2 is 0.2045. Further, the rust length of the copper shielding rust is calculated to be 0.3990m by using the rust degree-rust length equation, the actual setting length of the rust defect is 0.4m, and the length estimation error is-0.25%.

[0095] As shown in Figure 6 , the present application provides a cable copper shielding rust length measurement system, comprising:

[0096] A signal acquisition module is configured to inject two Chirp signals into the cable and acquire reflected signals of the two Chirp signals.

[0097] A rust degree calculation module is configured to calculate the rust degree of the cable copper shielding rust defect under the two measurements according to the two reflected signals.

[0098] A rust length calculation module is configured to calculate the rust length of the cable copper shielding rust defect according to the rust degree calculation results of the two times.

[0099] The second measurement injects a Chirp signal with a center frequency twice that of the first measurement, and the interval between the two measurements is greater than twice the time it takes for the injected signal to travel from the beginning of the cable to the end.

[0100] The terminal device provided by the embodiment includes a processor, a memory, and a computer program stored in the memory and executable on the processor. The processor implements the steps in each of the above method embodiments when executing the computer program. Alternatively, the processor implements the functions of each module / unit in each of the above device embodiments when executing the computer program.

[0101] The computer program can be divided into one or more modules / units, which are stored in the memory and executed by the processor to complete the present application.

[0102] The terminal device can be a desktop computer, a notebook computer, a palm computer, a cloud server, and the like. The terminal device can include, but is not limited to, a processor and a memory.

[0103] The processor can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, and the like.

[0104] The memory can be used to store the computer program and / or modules. The processor implements various functions of the terminal device by running or executing the computer program and / or modules stored in the memory, and calling data stored in the memory.

[0105] The modules / units integrated in the terminal device, if realized in the form of software function units and sold or used as independent products, can be stored in a computer readable storage medium. Based on such understanding, all or part of the processes in the above-mentioned embodiment methods can also be completed by a computer program instructing related hardware, and the computer program can be stored in a computer readable storage medium. When the computer program is executed by a processor, the steps of the above-mentioned various method embodiments can be implemented. The computer program includes computer program code, which can be in the form of source code, object code, executable files or some intermediate forms, etc. The computer readable medium can include any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal and software distribution medium, etc. It should be noted that the content included in the computer readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction, for example, in some jurisdictions, according to legislation and patent practice, the computer readable medium does not include electrical carrier signals and telecommunication signals.

[0106] Although the embodiments of the present application are described above in conjunction with the drawings, the present application is not limited to the above-mentioned specific embodiments and application fields, and the above-mentioned specific embodiments are only illustrative and guiding, but not limiting. Those skilled in the art can make many forms under the guidance of the specification without departing from the scope protected by the claims of the present application, and these all belong to the protection of the present application.

Claims

1. A method for measuring the corrosion length of copper shielding in cables, characterized in that, include: Two chirp signals were injected into the cable, and the reflected signals of the two chirp signals were measured sequentially. Based on the measurement results of the two reflected signals, the corrosion degree of the copper shield corrosion defects of the cable under the two measurements was calculated respectively; The corrosion length of the copper shield corrosion defect in the cable was calculated based on the results of the two corrosion degree calculations. Among them, the center frequency of the injected Chirp signal in the second measurement was twice that of the first measurement, and the interval between the two measurements was greater than twice the time it took for the injected signal to propagate from the beginning to the end of the cable. The specific calculation of cable corrosion degree is as follows: Based on the initial measurement results, time-frequency cross-correlation analysis was used to calculate the corresponding time-frequency cross-correlation curve. The arrival times of the injected signal and the corrosion defect reflection signal were determined based on the times corresponding to the extreme values ​​on the time-frequency cross-correlation curve. The injection signal time was recorded as time 0, and the arrival time of the corrosion defect reflection signal was recorded as... t p time; At time 0 and t p Starting from the first measurement result, the injection signal and the reflection signal of the corrosion defect are extracted, and the extracted length is consistent with the injection signal length preset by the signal generating device. Fourier transforms were performed on the extracted injection and reflection signals to obtain the spectrum of the injection signal and the spectrum of the reflection signal from the corrosion defect. The spectral ratio is obtained by dividing the spectrum of the reflected signal from the corrosion defect by the spectrum of the injected signal. The corrosion degree of the first measurement of corrosion defects in the copper shield of the cable was obtained based on the spectrum ratio and the spectrum ratio-corrosion degree equation. The same calculation process as the first measurement was used to calculate the corrosion degree of the cable copper shield corrosion defect in the second measurement. The equation for the spectral ratio and corrosion degree is: in This is the spectral ratio. It is a natural constant. The rate of change of the attenuation coefficient of the intact portion of the cable with respect to angular frequency. This refers to the distance between measurement points and the copper shield corrosion defect in the cable. ω The center angular frequency of the signal injected during measurement. The degree of corrosion of the copper shielding of the cable; The formula for calculating the cable corrosion length based on the results of two corrosion degree calculations is as follows: The degree of corrosion was measured for the second time. This is the first measurement of corrosion. The center angular frequency of the Chirp signal injected during the first measurement. This represents the rate of change of the phase coefficient of a copper-shielded cable segment with corrosion defects as a function of angular frequency.

2. The method for measuring the corrosion length of cable copper shielding according to claim 1, characterized in that, The rate of change of the attenuation coefficient of the intact section of the cable with respect to angular frequency The calculation method is as follows: Get a bar of length A certain type of intact cable, with the cable end kept open, a Chirp signal is injected into the cable head and the reflected signal is measured; Based on the measurement results of the reflected signal, the time-frequency cross-correlation curve corresponding to the reflected signal is calculated using the time-frequency cross-correlation analysis method. The injection signal time and the arrival time of the reflected signal at the cable end are determined based on the times corresponding to the extreme values ​​on the time-frequency cross-correlation curve. The injection signal time is recorded as time 0, and the arrival time of the reflected signal at the cable end is recorded as... t pe time; At time 0 and t pe Starting from a certain time, the injected signal and the reflected signal from the end of the cable are extracted from the measurement results. The extracted length is consistent with the injected signal length preset by the signal generator. For the extracted injected signal and the cable end reflected signal, their Wigner-Ville distributions are calculated to obtain the time-frequency distributions of the injected signal and the cable end reflected signal. Then, the rate of change of the attenuation coefficient with respect to the angular frequency is calculated. .

3. The method for measuring the corrosion length of cable copper shielding according to claim 2, characterized in that, The rate of change of the attenuation coefficient of the intact section of the cable with respect to angular frequency The calculation formula is: in, The center angular frequency of the signal injected during measurement. Let Ws(t, ω) be the cable length, Ws(t, ω) be the time-frequency component of the injected signal, and Wr(t, ω) be the time-frequency component of the reflected signal.

4. The method for measuring the corrosion length of cable copper shielding according to claim 1, characterized in that, Rate of change of phase coefficient with respect to angular frequency in copper-shielded corroded cable segments The calculation method is as follows: in, The wave velocity is the wave velocity of the copper-shielded cable segment with corrosion defects.

5. A system for measuring the corrosion length of a cable copper shield, characterized in that, A method for measuring the corrosion length of a cable copper shield according to any one of claims 1-4 includes: Signal acquisition module: used to continuously transmit two chirp signals to the cable and acquire the reflected signals of the two chirp signals; Corrosion Calculation Module: Calculates the corrosion degree of the cable based on the two reflected signals; Rust length calculation module: Calculates the rust length of the cable based on the results of two rust degree calculations; Among the two measurements, the center frequency of the injected Chirp signal in the second measurement was twice that of the first measurement, and the interval between the two measurements was greater than twice the time it took for the injected signal to propagate from the beginning to the end of the cable.

6. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method for measuring the corrosion length of the copper shield of a cable as described in any one of claims 1 to 4.

7. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the method for measuring the corrosion length of the copper shield of a cable as described in any one of claims 1 to 4.

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