Intelligent cable detection system design and detection method

Abstract

The invention discloses a detection system design and a detection method of an intelligent cable, and belongs to the technical field of cable detection, a broadband impedance spectroscopy method is taken as a basic principle, a vector voltammetry method and a digital frequency synthesis technology are combined, detection system hardware design is carried out by adopting a modularization thought, and cable broadband impedance spectroscopy test software is developed by utilizing Qt Company; by analyzing a cable broadband impedance spectroscopy mechanism, a cable test system design scheme based on vector voltammetry is provided, and a cable broadband impedance spectroscopy measurement method based on FFT is provided according to system characteristics. In order to verify the effectiveness of the detection system, a test platform is built in a laboratory and on site for testing, cables in different operation states are tested, analysis is carried out according to a measured cable broadband impedance spectrum and a diagnosis function based on generalized integral transformation, and the designed cable detection system can effectively detect the operation states of the cables. And fault and defect positioning is realized, and the method has the advantages of low cost and high performance.

Description

Technical Field

[0001] The invention discloses an intelligent cable detection system design and detection method, belonging to the technical field of cable detection. Background Art

[0002] At present, the commonly used cable fault testing methods include lightning shock wave detection method, high-voltage continuous wave detection method, low-voltage fault analysis method, etc. The lightning shock wave detection method applies a high-voltage pulse to the fault area to generate a shock wave that is transmitted to the defect point, and locates the fault point by measuring the reflected wave; the high-voltage continuous wave detection method: generates a high-voltage continuous wave on the cable, and locates the fault point using the propagation time and speed of the wave; the low-voltage fault analysis method: performs low-voltage excitation on the fault line and collects signals, from which the fault characteristics are analyzed to determine the fault location. Combining the above methods, the use of cable fault detection equipment can detect and diagnose cables for fault location. Currently, common equipment includes multimeters, cable fault pre-diagnosis instruments, coordinate non-destructive fault measuring instruments, etc. These devices can perform long-distance and high-precision fault detection on cables.

[0003] However, with the continuous development of the power system, the types and categories of cables are increasing, which brings great challenges to cable fault testing. Different types of cables require different test schemes and equipment for fault diagnosis and testing. Therefore, the detection of different types of cables often requires the use of multiple devices and tools; cable faults are difficult to show on the surface. In order to obtain clearer fault information, testers must conduct detailed inspections, but because the internal conductor spacing of cable faults is very small, the external insulation layer is very thick, and the detection resistance is very large, it is very difficult to detect and diagnose cable faults; due to the complex causes of cable faults, as the cable is used for a longer time and eroded by external factors, cable faults continue to occur frequently, especially in places where urban cable layouts are more concentrated, the fault frequency is higher.

[0004] In response to the above problems, cable fault detection methods have developed towards intelligence, and many new non-destructive testing technologies have emerged, such as acoustic emission, laser beam pulse method, and low-frequency electric field emission method. These technologies can locate and detect cable faults with less time and less equipment; using machine learning and artificial intelligence technology, a large amount of data can be analyzed and processed, from which the laws and patterns of cable faults can be learned and refined, and then cable faults can be predicted and prevented. This can improve the efficiency and accuracy of cable fault location. Summary of the invention

[0005] The purpose of the present invention is to provide an intelligent cable detection system design and detection method to solve the problem of poor cable detection effect in the prior art.

[0006] A design method for an intelligent cable detection system comprises designing a hardware system and designing a software system, wherein the hardware system comprises an excitation system and a core circuit in sequence, and the software system comprises a host computer and algorithm processing in sequence; the excitation system comprises a sine sweep signal generation and a signal conditioning circuit in sequence, and the core circuit comprises a cable DUT to be tested and an I / V conversion circuit in sequence, and analog signals are respectively generated after the signal conditioning circuit and after the I / V conversion circuit to an acquisition card, and the acquisition card generates a digital signal after processing the analog signal and sends it to the host computer, and the host computer feeds back the generation of the sine sweep signal through an STM32 main control system, and calls the algorithm processing to process the digital signal at the same time.

[0007] The hardware system is provided with a test cable, which includes a cable head end and a cable end, and the acquisition module is provided with three lines.

[0008] The first line connects the main control module and the DDS module in sequence through the data transmission line. The DDS module is connected to the sweep signal and the power divider in sequence through the signal line, and the incident signal is input to the head end of the cable. The second line starts from the head end of the cable and connects to the IV conversion circuit through the signal line, and inputs the output signal to the acquisition module. The third line generates a branch from the power divider to input the input reference signal into the acquisition module.

[0009] The software system includes a C++-based main control module and a UI-based host computer interface module.

[0010] The C++-based main control module includes a system control module and an analysis and processing module. The system control module includes a high-speed acquisition card control module, a sweep frequency excitation control module, an acquisition end control module and an abnormal state processing module. The analysis and processing module sequentially performs signal data acquisition, restores signal effective value, signal amplitude angle change, and generates impedance spectrum data.

[0011] The UI-based upper computer interface module includes a function setting module and a measurement display module. The function setting module sequentially performs sweep step setting, bandwidth setting, impedance spectrum data storage, and historical test playback. The measurement display module includes a system status display module, an acquisition end display module, an impedance spectrum waveform display module, and a positioning result display module.

[0012] The control process of the STM32 master control system includes: the upper computer performs initial configuration, starts the frequency sweep command, sends instructions to the lower computer, and the lower computer is initialized at the same time, receives the command of the upper computer and completes the operation, feedbacks the status and displays it, the upper computer receives the real-time status of the lower computer, processes the detection data, and returns to start the frequency sweep command if the frequency sweep is not completed. If the frequency sweep is completed, a broadband impedance spectrum is generated, and the broadband impedance spectrum is processed and analyzed, and the information of the broadband impedance spectrum is displayed.

[0013] An intelligent cable detection method, using the intelligent cable detection system design method, includes S1, for a cable with a length of l, the input impedance at a distance x from the head end is Z(x):

[0014]

[0015] In the formula, γ and Z 0 are the propagation coefficient and characteristic impedance of the cable, Γ L is the reflection coefficient at the terminal.

[0016] S2. For a cable with a length of l and a single defect, the fault location is l away from the head end. a The impedance Z(l a ) and the impedance Z(0) at the head end are:

[0017]

[0018] In the formula, Γ L1 , Γ L2 Z(l a ) and the reflection coefficient of Z(0), R f The distance from the head end is l a The fault resistance at || represents the parallel connection of two devices, Z L is the load impedance.

[0019] S3. Expand the input impedance and reflection coefficient spectrum at the head end of the cable with a defect as follows:

[0020]

[0021] Compared with the prior art, the present invention has the following beneficial effects: the cable detection system designed by the present invention can effectively detect the operating status of the cable and locate faults and defects, and has the advantages of low cost and high performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of an intelligent cable detection system;

[0023] Figure 2 It is a schematic diagram of the hardware system;

[0024] Figure 3 It is a schematic diagram of the software system;

[0025] Figure 4 It is the control flow chart of the main control system;

[0026] Figure 5 This is the correlation diagram between short circuit fault and broadband impedance spectrum;

[0027] Figure 6This is the correlation diagram between open circuit fault and broadband impedance spectrum;

[0028] Figure 7 This is the correlation diagram between high resistance fault and broadband impedance spectrum;

[0029] Figure 8 This is the correlation diagram between low-resistance fault and broadband impedance spectrum;

[0030] Fig. 9 This is the broadband impedance amplitude spectrum of a short circuit fault at 100m of the cable;

[0031] Fig.10 This is the diagnostic function curve diagram of a short circuit fault at 100m of the cable;

[0032] Fig.11 This is the broadband impedance amplitude spectrum of a low-resistance fault at 200m of the cable;

[0033] Fig.12 This is the diagnostic function curve diagram of a low-resistance fault at 200m of the cable;

[0034] Fig.13 This is the broadband impedance amplitude spectrum of the cable with aging fault at 200m;

[0035] Fig.14 This is the diagnostic function curve diagram of the aging fault at 200m of the cable;

[0036] Fig.15 This is the broadband impedance amplitude spectrum of the intact cable at 300m;

[0037] Fig.16 This is the diagnostic function curve of the intact cable at 300m;

[0038] Fig.17 This is the broadband impedance amplitude spectrum of cable fault detection at site A;

[0039] Fig.18 It is the diagnostic function curve diagram of cable fault detection at site A;

[0040] Fig.19 This is the test result diagram of cable fault detection at site B. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention is described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, but 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.

[0042] A design method for an intelligent cable detection system comprises designing a hardware system and designing a software system, wherein the hardware system comprises an excitation system and a core circuit in sequence, and the software system comprises a host computer and algorithm processing in sequence; the excitation system comprises a sine sweep signal generation and a signal conditioning circuit in sequence, and the core circuit comprises a cable DUT to be tested and an I / V conversion circuit in sequence, and analog signals are respectively generated after the signal conditioning circuit and after the I / V conversion circuit to an acquisition card, and the acquisition card generates a digital signal after processing the analog signal and sends it to the host computer, and the host computer feeds back the generation of the sine sweep signal through an STM32 main control system, and calls the algorithm processing to process the digital signal at the same time.

[0043] The hardware system is provided with a test cable, which includes a cable head end and a cable end, and the acquisition module is provided with three lines.

[0044] The first line connects the main control module and the DDS module in sequence through the data transmission line. The DDS module is connected to the sweep signal and the power divider in sequence through the signal line, and the incident signal is input to the head end of the cable. The second line starts from the head end of the cable and connects to the IV conversion circuit through the signal line, and inputs the output signal to the acquisition module. The third line generates a branch from the power divider to input the input reference signal into the acquisition module.

[0045] The software system includes a C++-based main control module and a UI-based host computer interface module.

[0046] The C++-based main control module includes a system control module and an analysis and processing module. The system control module includes a high-speed acquisition card control module, a sweep frequency excitation control module, an acquisition end control module and an abnormal state processing module. The analysis and processing module sequentially performs signal data acquisition, restores signal effective value, signal amplitude angle change, and generates impedance spectrum data.

[0047] The UI-based upper computer interface module includes a function setting module and a measurement display module. The function setting module sequentially performs sweep step setting, bandwidth setting, impedance spectrum data storage, and historical test playback. The measurement display module includes a system status display module, an acquisition end display module, an impedance spectrum waveform display module, and a positioning result display module.

[0048] The control process of the STM32 master control system includes: the upper computer performs initial configuration, starts the frequency sweep command, sends instructions to the lower computer, and the lower computer is initialized at the same time, receives the command of the upper computer and completes the operation, feedbacks the status and displays it, the upper computer receives the real-time status of the lower computer, processes the detection data, and returns to start the frequency sweep command if the frequency sweep is not completed. If the frequency sweep is completed, a broadband impedance spectrum is generated, and the broadband impedance spectrum is processed and analyzed, and the information of the broadband impedance spectrum is displayed.

[0049] An intelligent cable detection method, using the intelligent cable detection system design method, includes S1, for a cable with a length of l, the input impedance at a distance x from the head end is Z(x):

[0050]

[0051] In the formula, γ and Z 0 are the propagation coefficient and characteristic impedance of the cable, Γ L is the reflection coefficient at the terminal.

[0052] S2. For a cable with a length of l and a single defect, the fault location is l away from the head end. a The impedance Z(l a ) and the impedance Z(0) at the head end are:

[0053]

[0054] In the formula, Γ L1 , Γ L2 Z(l a ) and the reflection coefficient of Z(0), R f The distance from the head end is l a The fault resistance at || represents the parallel connection of two devices, Z L is the load impedance.

[0055] S3. Expand the input impedance and reflection coefficient spectrum at the head end of the cable with a defect as follows:

[0056]

[0057] This test system has two main application scenarios in cable fault measurement: one is to pre-check cables that may have defects and faults to prevent power outages caused by cable faults; the other is to detect and locate the faults of cables that have already caused power outages in order to quickly troubleshoot the faults. This system is particularly important for buried cables that need to be excavated for repair.

[0058] For the above application scenarios, the following technical problems need to be solved: establish a faulty cable model based on the equivalent distributed parameter circuit model of the cable transmission line, and extract the distance factor in the fault model to achieve fault location; design a suitable detection system solution, starting from the hardware and software parts, to achieve cable impedance spectrum acquisition and cable fault location; design a portable system to improve detection efficiency. This system overcomes the difficulties of previous cable detection systems such as being bulky and difficult to carry, and complex to operate. It is light, integrated and easy to carry, and will be promoted to a certain extent in the research of cable fault non-destructive detection and location technology.

[0059] In order to meet the needs of broadband impedance spectrum measurement, the detection system is designed in combination with the voltammetry measurement principle. The modular approach is adopted to divide the platform into main control module, DDS module and acquisition module according to function. The control module communicates with the host computer through serial port communication, parses relevant instructions, and controls each functional module to complete the test, while providing real-time feedback on the working status of each functional module. The DDS module is responsible for generating the sweep signal. The acquisition module consists of a power divider, IV conversion circuit, and high-speed acquisition card, and communicates with the host computer system through the serial port.

[0060] Qt Company was used to develop the cable broadband impedance spectrum test software. In the whole system, the main control program is mainly responsible for real-time control of the single-chip microcomputer and acquisition card, completing the frequency sweep and acquisition of the signal, and completing the preprocessing and transformation of the impedance spectrum data. In order to better realize the visualization of the cable broadband impedance spectrum, the human-computer interaction interface was designed and developed based on Qt software.

[0061] To verify the effectiveness of the detection system, tests were carried out in the laboratory, and the broadband impedance spectrum of the cable was measured and analyzed in combination with the diagnostic function based on the generalized integral transform. To further test the practicality and reliability of the broadband impedance spectrum detection system for cables, tests were carried out on the actual site, and maintenance personnel dug cable trenches to verify the accuracy of the positioning test. According to laboratory and field tests, the results of the cable detection system were consistent with expectations, and it can effectively detect the operating status of the cable, accurately identify different types of cable faults and defects, and locate faults and defects.

[0062] A schematic diagram of an intelligent cable detection system Figure 1 As shown, it includes designing a hardware system and designing a software system. The hardware system includes an excitation system and a core circuit in sequence, and the software system includes a host computer and algorithm processing in sequence. The excitation system includes a sine sweep signal generation and a signal conditioning circuit in sequence, and the core circuit includes a cable DUT to be tested and an I / V conversion circuit in sequence. The signal conditioning circuit and the I / V conversion circuit generate analog signals to an acquisition card respectively, and the acquisition card generates a digital signal after processing the analog signal and sends it to the host computer. The host computer feeds back the sine sweep signal generation through the STM32 main control system, and calls the algorithm processing to process the digital signal.

[0063] The hardware system diagram is as follows: Figure 2 As shown, a test cable is provided in the hardware system, and the test cable includes a cable head end and a cable end. The acquisition module is provided with three lines. The first line connects the main control module and the DDS module in sequence through the data transmission line, and the DDS module connects the sweep signal and the power divider in sequence through the signal line, and inputs the incident signal into the cable head end. The second line starts from the cable head end, connects the IV conversion circuit through the signal line, and inputs the output signal into the acquisition module. The third line generates a branch from the power divider to input the input reference signal into the acquisition module.

[0064] Software system diagram Figure 3 As shown, the software system includes a C++-based main control module and a UI-based upper computer interface module. The C++-based main control module includes a system control module and an analysis and processing module. The system control module includes a high-speed acquisition card control module, a sweep frequency excitation control module, an acquisition end control module, and an abnormal state processing module. The analysis and processing module sequentially performs signal data acquisition, restores signal effective value, signal amplitude angle change, and generates impedance spectrum data.

[0065] The UI-based upper computer interface module includes a function setting module and a measurement display module. The function setting module sequentially performs sweep step setting, bandwidth setting, impedance spectrum data storage, and historical test playback. The measurement display module includes a system status display module, an acquisition end display module, an impedance spectrum waveform display module, and a positioning result display module.

[0066] The control flow chart of the main control system is as follows: Figure 4 As shown in the figure, the control process of the STM32 main control system includes: the host computer performs initial configuration, starts the frequency sweep command, sends instructions to the slave computer, and the slave computer is initialized at the same time, receives the command of the host computer and completes the operation, feedbacks the status and displays it, the host computer receives the real-time status of the slave computer, processes the detection data, and returns to start the frequency sweep command if the frequency sweep is not completed. If the frequency sweep is completed, a broadband impedance spectrum is generated, and the broadband impedance spectrum is processed and analyzed, and the information of the broadband impedance spectrum is displayed.

[0067] The correlation diagram between short circuit fault and broadband impedance spectrum is shown in the figure below: Figure 5 As shown in the figure, the correlation diagram between open circuit fault and broadband impedance spectrum is as follows Figure 6 As shown in the figure, the correlation diagram between high resistance fault and broadband impedance spectrum is as follows Figure 7 As shown in the figure, the correlation diagram between low resistance fault and broadband impedance spectrum is as follows Figure 8 As shown, it can be observed that the broadband impedance spectrum of the cable carries fault information. Therefore, in the detection system, the cable impedance spectrum is obtained to further detect and locate the cable fault.

[0068] The detection method of the present invention specifically includes S1. For a cable with a length of l, the input impedance at a distance x from the head end is Z(z):

[0069]

[0070] In the formula, γ and Z 0 are the propagation coefficient and characteristic impedance of the cable, Γ L is the reflection coefficient at the terminal.

[0071] S2. For a cable with a length of l and a single defect, the fault location is l away from the head end. a The impedance Z(la ) and the impedance Z(0) at the head end are:

[0072]

[0073] In the formula, Γ L1 , Γ L2 Z(l a ) and the reflection coefficient of Z(0), R f The distance from the head end is l a The fault resistance at || represents the parallel connection of two devices, Z L is the load impedance.

[0074] S3. Expand the input impedance and reflection coefficient spectrum at the head end of the cable with a defect as follows:

[0075]

[0076] In experiment 1, a cable with a total length of 300m had a short circuit fault at 100m and there was an intermediate joint at 200m. The broadband impedance amplitude spectrum of the short circuit fault at 100m is as follows: Fig. 9 As shown in the figure, the diagnostic function curve of the short circuit fault at 100m of the cable is as follows Fig.10 shown.

[0077] In experiment 2, a low-resistance fault occurred at 200m of a cable with a total length of 300m, and the end of the cable was open-circuited. The broadband impedance amplitude spectrum of the low-resistance fault at 200m of the cable is as follows: Fig.11 As shown in the figure, the diagnostic function curve of the low resistance fault at 200m of the cable Fig.12 shown.

[0078] Experiment 3: The total length of the cable is 300m. There is a 3m heat-aged cable area at 200m, and the end of the cable is open-circuited. The broadband impedance amplitude spectrum of the aging fault at 200m is as follows: Fig.13 As shown in the figure, the diagnostic function curve of the cable aging fault at 200m is as follows Fig.14 shown.

[0079] Experiment 4: A complete cable with a total length of 300m and an open end. The broadband impedance amplitude spectrum of the complete cable at 300m is as follows: Fig.15 As shown in the figure, the diagnostic function curve of the intact cable at 300m is as follows Fig.16 shown.

[0080] For Experiment 1, Experiment 2, and Experiment 3, the positioning results are analyzed as shown in Table 1.

[0081] Table 1 Analysis of positioning results

[0082]

[0083] Combined with Table 1, it can be seen that in laboratory tests, the "mutation peaks" formed by different types of faults have different characteristics. The cable fault location is realized by combining the "mutation peak" position. The detection system measures accurately and efficiently, and the maximum positioning error does not exceed 0.4%, which meets the test requirements.

[0084] A broadband impedance amplitude spectrum of on-site cable fault detection is shown in Fig.17 As shown, the diagnostic function curve of cable fault detection at site A is as follows Fig.18 As shown; the detection results of the cable fault detection on site B are shown in Fig.19 As shown, the black curve is the integral transformation result of the normal cable. Total reflection occurs at the terminal open circuit, and a mutation peak is formed at 352 meters. The red curve is a low-resistance fault set at position 1. In addition to the negative polarity mutation peak formed at 48 meters, multiple distortion peaks appear between 48 and 100 meters. This is due to the impedance mismatch between the cable and the test detection system, which causes part of the signal to reflect back and forth between the beginning of the cable and position 1. The blue curve is a low-resistance fault set at position 2, which forms a negative polarity mutation peak at 132 meters; the green curve is a low-resistance fault set at position 3, which forms a negative polarity mutation peak at 215 meters; the yellow curve is a low-resistance fault set at position 4, which forms a negative polarity mutation peak at 268 meters. The test results are close to the reference results, and the positioning error does not exceed 3%.

[0085] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features may be replaced by equivalents, and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A design method for an intelligent cable detection system, characterized in that: It includes designing a hardware system and designing a software system. The hardware system includes an excitation system and a core circuit in sequence, and the software system includes a host computer and algorithm processing in sequence. The excitation system includes a sine frequency sweep signal generation and a signal conditioning circuit in sequence, and the core circuit includes a cable DUT to be tested and an I / V conversion circuit in sequence. The signal conditioning circuit and the I / V conversion circuit generate analog signals to an acquisition card respectively. The acquisition card processes the analog signal and generates a digital signal to the host computer. The host computer feeds back the sine frequency sweep signal generation through the STM32 main control system, and calls the algorithm processing to process the digital signal.

2. The method for designing an intelligent cable detection system according to claim 1, characterized in that: The hardware system is provided with a test cable, which includes a cable head end and a cable end, and the acquisition module is provided with three lines.

3. The method for designing an intelligent cable detection system according to claim 2, characterized in that: The first line connects the main control module and the DDS module in sequence through the data transmission line. The DDS module is connected to the sweep signal and the power divider in sequence through the signal line, and the incident signal is input to the head end of the cable. The second line starts from the head end of the cable and connects to the IV conversion circuit through the signal line, and inputs the output signal to the acquisition module. The third line generates a branch from the power divider to input the input reference signal into the acquisition module.

4. The method for designing an intelligent cable detection system according to claim 3, characterized in that: The software system includes a C++-based main control module and a UI-based host computer interface module.

5. The method for designing an intelligent cable detection system according to claim 4, characterized in that: The C++-based main control module includes a system control module and an analysis and processing module. The system control module includes a high-speed acquisition card control module, a sweep frequency excitation control module, an acquisition end control module and an abnormal state processing module. The analysis and processing module sequentially performs signal data acquisition, restores signal effective value, signal amplitude angle change, and generates impedance spectrum data.

6. The method for designing an intelligent cable detection system according to claim 5, characterized in that: The UI-based upper computer interface module includes a function setting module and a measurement display module. The function setting module sequentially performs sweep step setting, bandwidth setting, impedance spectrum data storage, and historical test playback. The measurement display module includes a system status display module, an acquisition end display module, an impedance spectrum waveform display module, and a positioning result display module.

7. The method for designing an intelligent cable detection system according to claim 6, characterized in that: The control process of the STM32 master control system includes: the upper computer performs initial configuration, starts the frequency sweep command, sends instructions to the lower computer, and the lower computer is initialized at the same time, receives the command of the upper computer and completes the operation, feedbacks the status and displays it, the upper computer receives the real-time status of the lower computer, processes the detection data, and returns to start the frequency sweep command if the frequency sweep is not completed. If the frequency sweep is completed, a broadband impedance spectrum is generated, and the broadband impedance spectrum is processed and analyzed, and the information of the broadband impedance spectrum is displayed.

8. An intelligent cable detection method, characterized in that: A method for designing an intelligent cable detection system according to any one of claims 1 to 7 is used, comprising S1, for a cable with a length of l, the input impedance at a distance x from the head end is Z(x): Where γ and Z0 are the propagation coefficient and characteristic impedance of the cable, respectively. L is the reflection coefficient at the terminal.

9. An intelligent cable detection method according to claim 8, characterized in that: Including S2, for a cable with a length of l and a single defect, the fault location is l away from the head end a The impedance Z(l a ) and the impedance Z(0) at the head end are: In the formula, Γ L1 , Γ L2 Z(l a ) and the reflection coefficient of Z(0), R f The distance from the head end is l a The fault resistance at || represents the parallel connection of two devices, Z L is the load impedance.

10. An intelligent cable detection method according to claim 9, characterized in that: Including S3, the input impedance and reflection coefficient spectrum at the head end of the cable containing a defect is expanded to:

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