Cable defect detection method and device and readable storage medium

Abstract

The invention discloses a cable defect detection method and device and a readable storage medium. The method comprises the following steps: acquiring impedance characteristics of a to-be-detected cable; determining a target component to be connected with the to-be-tested cable based on the impedance characteristics; in response to completion of connection between the target component and the to-be-detected cable, detecting a connection point between the target component and the to-be-detected cable to obtain a detection signal; and determining defect information of the cable based on the detection signal. The technical problem that cable defects cannot be detected is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of cable detection, and in particular to a method, a device and a readable storage medium for detecting defects of a cable. Background Art

[0002] At present, with the development of urbanization, high-voltage cables have gradually become important power transmission equipment. After long-term operation, high-voltage cables will produce irreversible local defects under the influence of factors such as electric field, temperature, and external force damage, such as damage to the shielding layer and degradation of the main insulation material. As the number of cables put into operation increases, the laying and replacement becomes more and more complicated, and the difficulty of detecting and locating local defects in cables gradually increases. Traveling wave signals are applied to the detection of high-voltage cables due to their fast transmission speed.

[0003] In the related art, the existing methods mainly use high-frequency signals to inject into the cable, such as injecting video signals containing time domain characteristics and frequency domain characteristics. According to the transmission line theory, when a high-frequency signal encounters a damaged point, it will be reflected due to the mismatch between the characteristic impedance of the damaged point and the impedance of the normal point. At the same time, the fast speed of the traveling wave signal will cause a detection blind spot in the detection process. The propagation speed of the signal too fast will cause the signal to be unable to detect the damage defects close to the signal generation section during the generation process. When the signal is close to the signal generation point, because the duration of the signal is longer than the reflection time of the first section of the signal, when the signal has not been completely generated, the reflected signal enters the sampling device at the same time as the incident signal, resulting in signal superposition, affecting detection and positioning. After replacing the measuring end, the reflected signals of the fault point and the terminal will be superimposed due to the close distance between them, and the fault situation cannot be correctly evaluated. Therefore, there is a technical problem that cable defects cannot be detected.

[0004] With respect to the above-mentioned technical problem of being unable to detect cable defects, no effective solution has been proposed so far. Summary of the invention

[0005] The embodiments of the present invention provide a method, a device and a readable storage medium for detecting defects of a cable, so as to at least solve the technical problem that the defects of the cable cannot be detected.

[0006] According to one aspect of an embodiment of the present invention, a method for detecting defects in a cable is provided. The method may include: obtaining an impedance characteristic of a cable to be tested; determining a target component to be connected to the cable to be tested based on the impedance characteristic; in response to the target component being connected to the cable to be tested, detecting a connection point between the target component and the cable to be tested to obtain a detection signal; and determining defect information of the cable based on the detection signal.

[0007] Optionally, based on the impedance characteristics, determining a target component to be connected to the cable under test includes: determining a length threshold of the target component based on the impedance characteristics; obtaining the length of an initial component to be connected to the cable under test; and determining the initial component as the target component in response to the length of the initial component being greater than the length threshold.

[0008] Optionally, before determining the defect information of the cable based on the detection signal, the cable defect detection method also includes: obtaining multiple initial detection signals; comparing the multiple initial detection signals with a time range threshold to obtain a comparison result; in response to the comparison result being that the initial detection signal meets the time range threshold, determining the initial detection signal as the detection signal.

[0009] Optionally, determining defect information of the cable based on the detection signal includes: acquiring an incident signal; and determining the defect information of the cable based on the incident signal and the detection signal.

[0010] Optionally, based on the incident signal and the detection signal, the defect information of the cable is determined, including: extracting spectral characteristics of the incident signal and the detection signal, wherein the spectral characteristics include at least time domain characteristics and frequency domain characteristics; based on the spectral characteristics, respectively determining energy values ​​of the incident signal and the detection signal; based on the energy values, determining the defect information.

[0011] Optionally, based on the energy value, the defect information is determined, including: analyzing the energy value using a defect recognition strategy to obtain the defect information, wherein the defect recognition strategy is a rule for determining the defect information.

[0012] According to another aspect of an embodiment of the present invention, a device for detecting defects of a cable is also provided. The device may include: a first acquisition unit, used to acquire the impedance characteristics of the cable to be tested; a first determination unit, used to determine the target component to be connected to the cable to be tested based on the impedance characteristics; a second acquisition unit, used to detect the connection point between the target component and the cable to be tested in response to the target component and the cable to be tested being connected, and obtain a detection signal; a second determination unit, used to determine the defect information of the cable based on the detection signal.

[0013] According to another aspect of an embodiment of the present invention, a computer-readable storage medium is also provided, the computer-readable storage medium including a stored program, wherein when the program is executed by a processor, the device where the storage medium is located is controlled to execute the cable defect detection method in an embodiment of the present invention.

[0014] According to another aspect of an embodiment of the present invention, a processor is provided, which is used to run a program, wherein the method for detecting defects of a cable in an embodiment of the present invention is executed when the program is run.

[0015] According to another aspect of the embodiments of the present invention, a computer program product is provided, which includes computer instructions, and when the computer instructions are executed by a processor, the method for detecting defects of a cable in the embodiments of the present invention is implemented.

[0016] In an embodiment of the present invention, the impedance characteristics of the cable to be tested are obtained; based on the impedance characteristics, the target component to be connected to the cable to be tested is determined; in response to the target component being connected to the cable to be tested, the connection point between the target component and the cable to be tested is detected to obtain a detection signal; based on the detection signal, the defect information of the cable is determined. In other words, according to the impedance characteristics of the cable to be tested, the embodiment of the present invention does not determine the target component to be connected to the cable to be tested, and then determines the defect information of the cable according to the detection signal. The technical problem of being unable to detect cable defects is solved, and the technical effect of detecting cable defects is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0018] Figure 1 is a flow chart of a method for detecting defects of a cable according to an embodiment of the present invention;

[0019] Figure 2 is a flow chart of a method for detecting near-point defects of high-voltage cables based on time-frequency domain reflection according to an embodiment of the present invention;

[0020] Figure 3 is a schematic diagram of a specific connection between signal injection and acquisition according to an embodiment of the present invention;

[0021] Figure 4 is a schematic diagram of a device for detecting defects of a cable according to an embodiment of the present invention. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings 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 should fall within the scope of protection of the present invention.

[0023] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, functional component or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, functional components or devices.

[0024] According to an embodiment of the present invention, an embodiment of a method for detecting defects in a cable is provided. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0025] Figure 1 is a flow chart of a method for detecting defects in a cable according to an embodiment of the present invention. Figure 1 As shown, the method may include the following steps:

[0026] Step S101, obtaining the impedance characteristics of the cable to be tested.

[0027] In the technical solution provided in the above step S101 of the present invention, the impedance characteristic of the cable to be tested may also be referred to as the characteristic impedance of the cable to be tested, and the cable to be tested may also be referred to as a high-voltage cable.

[0028] In this embodiment, the impedance characteristics of the cable to be tested are obtained. For example, a special impedance test instrument is used to test the impedance characteristics of the cable to be tested. These instruments can generally measure parameters such as resistance, inductance and capacitance of the cable, thereby obtaining the impedance characteristics of the cable. This is only an illustrative example, and does not limit the specific method for obtaining the impedance characteristics of the cable to be tested.

[0029] Step S102: determining a target component to be connected to the cable to be tested based on the impedance characteristics.

[0030] In the technical solution provided in the above step S102 of the present invention, the target component may at least include lead wires.

[0031] In this embodiment, after the impedance characteristics of the cable to be tested are obtained in step S101, the target component to be connected to the cable to be tested is determined according to the impedance characteristics. For example, the target component is selected by determining the length of each component according to the impedance characteristics. This is only an illustrative example and does not limit the specific method of determining the target component to be connected to the cable to be tested.

[0032] For example, it is necessary to select according to the characteristic impedance of the high-voltage cable to be detected. In general, the characteristic impedance of the lead wire needs to be as close as possible to the high-voltage cable. The characteristic impedance of the high-voltage cable can be measured by an impedance tester or other existing devices. And the lead wire is selected, and its length L needs to satisfy the following formula (1):

[0033] L≥1.2v·T p (1)

[0034] Where v is the propagation speed of the detection signal center frequency, T p It is the duration of the detection signal. Since the detection signal contains different frequencies, the wave speed of the signal will change during the transmission process. Therefore, the length of the lead wire needs to have a certain threshold to prevent the sampling signal from being superimposed.

[0035] Step S103, in response to the target component and the cable to be tested being connected, detecting the connection point between the target component and the cable to be tested to obtain a detection signal.

[0036] In the technical solution provided in the above step S103 of the present invention, the detection signal at least includes a time-frequency domain detection signal.

[0037] In this embodiment, after the target component to be connected to the cable to be tested is determined in step S102, the target component is connected to the cable to be tested.

[0038] For example, in the detection process, two wires need to be connected to the cable core and the cable metal sheath to form a detection model that conforms to the transmission line model. Therefore, in the process of signal access, it is also necessary to select a wire that can meet the requirements of tight connection between the two wires on the core and the metal sheath. And considering that the contact surface is incomplete when using clip-type connections such as alligator clips, metal woven bags can be used to wrap to increase the contact surface, reduce contact point emission, and ensure stable signal transmission.

[0039] Optionally, after the target component is connected to the cable to be tested, the connection point between the target component and the cable to be tested is detected to obtain a detection signal. For example, a time domain pulse signal of a shorter duration is used to detect the reflection degree of the connection point, and the reflection of the connection point is observed to obtain a detection signal. This is only an illustrative example and does not limit the specific method of obtaining the detection signal.

[0040] For example, since the time-frequency domain detection signal needs to maintain the time domain and frequency domain characteristics, it needs a certain duration. However, the time domain signal used in the time domain reflection technology has a smaller duration requirement than the time-frequency domain signal, and a shorter duration signal can be used for preliminary detection. Therefore, a shorter duration time domain pulse signal can be used to detect the reflection degree of the connection point, observe the reflection of the connection point, and make corresponding judgments as the reflection signal of the subsequent detection sampling signal. The duration of the time-frequency domain detection signal needs to be considered. As for the duration, due to the need to ensure the time domain characteristics and frequency domain characteristics, and considering the sampling capability of the digital oscilloscope, the continuous range T P The following formula (2) must be satisfied:

[0041]

[0042] Where L is the length of the lead wire and v is the propagation speed of the center frequency of the detection signal.

[0043] Step S104: Determine defect information of the cable based on the detection signal.

[0044] In the technical solution provided in the above step S104 of the present invention, the defect information may at least include the cable end near-point damage location information.

[0045] In this embodiment, after the detection signal is obtained in step S103, the defect information of the cable is determined according to the detection signal. For example, the screened detection signal is injected and the incident and reflected signals are collected using a digital oscilloscope, and the signal is processed after storage to detect and locate the damage of the cable near the cable head end.

[0046] For example, when the time-frequency domain characteristic signal is periodically input, the signal can be a linear frequency modulation signal with a Gaussian envelope. After the signal is injected, the oscilloscope can collect continuous incident signals and reflected signals. Since the characteristics of the two signals are similar, the overall collected signal can be extracted. For example, the Wigner-Ville distribution can be used as an extraction scheme, which can represent the time domain characteristics and frequency domain characteristics of the signal in the form of a matrix. The time-frequency domain matrix W of the incident signal is r (t,ω), the time-frequency matrix W of the reflected signal s (t,ω), we get a spectrum diagram containing both time domain features and frequency domain features, and finally we can use the mutual correlation coefficient C sr The calculation formula is as shown in the following formula (3) and formula (4):

[0047]

[0048] In the above formula, E s and E rThe energy of the incident signal and the reflected signal are respectively used for the normalization of the entire Csr curve. Specifically, the cross-correlation curve of the time-frequency energy of the incident signal and the entire sampling signal is calculated, where the normalized cross-correlation coefficient is 1 is the signal time center of the incident signal, and the second peak is the time center of the first reflected signal. From this, the time difference Δt between the incident and reflected signals can be obtained, which is processed by the following formula (5):

[0049]

[0050] Where L is the length of the lead-out line. According to the above formula (5), the distance S between the fault point and the cable head end can be calculated according to the electromagnetic wave velocity, and the damaged part of the high-voltage cable outer sheath can be located, that is, the damage of the cable close to the cable head end.

[0051] It should be noted that the above embodiments can be implemented by a cable defect detection device.

[0052] In the above steps S101 to S104 of the present invention, the impedance characteristics of the cable to be tested are obtained; based on the impedance characteristics, the target component to be connected to the cable to be tested is determined; in response to the target component being connected to the cable to be tested, the connection point between the target component and the cable to be tested is detected to obtain a detection signal; based on the detection signal, the defect information of the cable is determined. In other words, according to the impedance characteristics of the cable to be tested, the embodiment of the present invention does not determine the target component to be connected to the cable to be tested, and then determines the defect information of the cable according to the detection signal. The technical problem of being unable to detect cable defects is solved, and the technical effect of detecting cable defects is achieved.

[0053] The above method of this embodiment is further introduced below.

[0054] As an optional implementation method, based on the impedance characteristics, a target component to be connected to the cable to be tested is determined, including: based on the impedance characteristics, determining a length threshold of the target component; obtaining the length of an initial component to be connected to the cable to be tested; in response to the length of the initial component being greater than the length threshold, determining the initial component as the target component.

[0055] In this embodiment, the length threshold of the target component is determined according to the impedance characteristics. For example, the propagation speed of the center frequency of the detection signal and the duration of the detection signal are determined according to the impedance characteristics, thereby determining the length threshold of the target component.

[0056] For example, v represents the propagation speed of the detection signal center frequency, T p Indicates the duration of the detection signal. The length threshold can be 1.2v·T p .

[0057] Optionally, after determining the length threshold, the length of the initial component is compared with the length threshold. When the length of the initial component is greater than the length threshold, it indicates that the initial component meets the length requirement. Based on this, the initial component can be determined as the target component.

[0058] As an optional implementation method, before determining the defect information of the cable based on the detection signal, the cable defect detection method also includes: obtaining multiple initial detection signals; comparing the multiple initial detection signals with a time range threshold to obtain a comparison result; in response to the comparison result being that the initial detection signal meets the time range threshold, determining the initial detection signal as a detection signal.

[0059] In this embodiment, multiple initial detection signals are obtained. For example, a digital oscilloscope is used to simultaneously collect the waveform of the incident signal while receiving the reflected detection signal.

[0060] Optionally, after obtaining multiple initial detection signals, the multiple initial detection signals are compared with a time range threshold to obtain a comparison result; when the comparison result is that the initial detection signal meets the time range threshold, it means that the initial detection signal is a valid signal, based on which, the initial detection signal can be determined as a detection signal.

[0061] For example, for the duration, due to the need to ensure the time domain characteristics and frequency domain characteristics, and taking into account the sampling capability of the digital oscilloscope, the continuous range TP needs to satisfy the aforementioned formula (2), that is, when the continuous range of the initial detection signal satisfies the aforementioned formula (2), the initial detection signal can be determined as the detection signal.

[0062] As an optional implementation manner, determining the defect information of the cable based on the detection signal includes: acquiring an incident signal; and determining the defect information of the cable based on the incident signal and the detection signal.

[0063] In this embodiment, the incident signal is acquired, for example, by collecting the waveform of the incident signal through a digital oscilloscope.

[0064] Optionally, after the incident signal is acquired, the defect information of the cable is determined according to the incident signal and the detection signal. The specific determination method is as follows.

[0065] As an optional implementation method, based on the incident signal and the detection signal, the defect information of the cable is determined, including: extracting the spectral characteristics of the incident signal and the detection signal, wherein the spectral characteristics include at least time domain characteristics and frequency domain characteristics; based on the spectral characteristics, respectively determining the energy values ​​of the incident signal and the detection signal; based on the energy values, determining the defect information.

[0066] In this embodiment, the frequency spectrum features of the incident signal and the detection signal are extracted. For example, Wigner-Ville distribution can be used as an extraction scheme, which can represent the time domain features and frequency domain features of the signal in the form of a matrix. The time-frequency domain matrix W of the incident signal is r (t,ω), the time-frequency matrix W of the reflected signal s (t,ω).

[0067] Optionally, the energy values ​​of the incident signal and the detection signal are determined respectively according to the spectrum characteristics. The determination method may be as shown in the aforementioned formula (4), which will not be described in detail here.

[0068] Optionally, after the energy value is determined, defect information is determined according to the energy value. The specific determination method is as follows.

[0069] As an optional implementation manner, determining defect information based on the energy value includes: analyzing the energy value using a defect recognition strategy to obtain the defect information, wherein the defect recognition strategy is a rule for determining the defect information.

[0070] In this embodiment, the energy value is analyzed using a defect recognition strategy to obtain defect information. For example, the defect recognition model may be the aforementioned formula (5), which will not be described in detail here.

[0071] For example, after injecting the time-frequency domain detection signal and collecting it, the time-frequency domain feature decomposition and mutual correlation coefficient calculation method are used to calculate the distance between the signal generation end and the damage. Finally, the lead-out line length is subtracted to obtain the cable end near-point damage location information.

[0072] It should be noted that the above embodiments can be implemented by a cable defect detection device.

[0073] In this embodiment, the impedance characteristics of the cable to be tested are obtained; based on the impedance characteristics, the target component to be connected to the cable to be tested is determined; in response to the target component being connected to the cable to be tested, the connection point between the target component and the cable to be tested is detected to obtain a detection signal; based on the detection signal, the defect information of the cable is determined. In other words, according to the impedance characteristics of the cable to be tested, the embodiment of the present invention does not determine the target component to be connected to the cable to be tested, and then determines the defect information of the cable according to the detection signal. The technical problem of being unable to detect cable defects is solved, and the technical effect of detecting cable defects is achieved.

[0074] The technical solution of the embodiment of the present invention is illustrated below in conjunction with preferred implementation modes.

[0075] At present, with the development of urbanization, high-voltage cables have gradually become important power transmission equipment. After long-term operation, high-voltage cables will produce irreversible local defects under the influence of factors such as electric field, temperature, and external force damage, such as damage to the shielding layer and degradation of the main insulation material. As the number of cables put into operation increases, the laying and replacement becomes more and more complicated, and the difficulty of detecting and locating local defects in cables gradually increases. Traveling wave signals are applied to the detection of high-voltage cables due to their fast transmission speed.

[0076] In the related art, the existing methods mainly use high-frequency signals to inject into the cable, such as injecting video signals containing time domain characteristics and frequency domain characteristics. According to the transmission line theory, when a high-frequency signal encounters a damaged point, it will be reflected due to the mismatch between the characteristic impedance of the damaged point and the impedance of the normal point. At the same time, the fast speed of the traveling wave signal will cause a detection blind spot in the detection process. The propagation speed of the signal too fast will cause the signal to be unable to detect the damage defects close to the signal generation section during the generation process. When the signal is close to the signal generation point, since the duration of the signal is longer than the reflection time of the first section of the signal, when the signal has not been completely generated, the reflected signal enters the sampling device at the same time as the incident signal, resulting in signal superposition, affecting detection and positioning. After replacing the measuring end, the fault point and the terminal will cause the reflected signals of the two to be superimposed due to the close distance, and the fault situation cannot be correctly evaluated. Therefore, there is a technical problem that cable defects cannot be detected. For the above-mentioned technical problem of being unable to detect cable defects, no effective solution has been proposed.

[0077] However, the embodiment of the present invention proposes a method for detecting defects near high-voltage cables based on time-frequency domain reflection, measuring the characteristic impedance of the measured cable; then selecting a lead wire that matches the impedance of the high-voltage cable to access the aluminum sheath and core of the cable, and performing a preliminary test on the contact point after reliable connection to ensure that the impedance mismatch at the contact point will not affect the detection of defects near the cable; then screening the detection signal, including parameters such as signal duration. After completing the above preparations, the signal generator and the digital oscilloscope can be connected to the impedance-matched lead wire, and then the screened detection signal can be injected and the incident and reflected signals can be collected using a digital oscilloscope. After storage, the signal is processed to detect and locate the damage of the cable near the head end of the cable. The technical problem of being unable to detect cable defects is solved, and the technical effect of detecting cable defects is achieved.

[0078] The embodiments of the present invention are further described below.

[0079] Figure 2 is a flow chart of a method for detecting near-point defects of high-voltage cables based on time-frequency domain reflection according to an embodiment of the present invention. Figure 2 As shown, the transmission line inspection collaborative method includes the following steps:

[0080] Step S201, selecting a lead wire with impedance matching for a high-voltage cable.

[0081] In this embodiment, the selection is made according to the detected characteristic impedance of the high-voltage cable. Generally, the characteristic impedance of the lead wire needs to be as close to that of the high-voltage cable as possible, and the characteristic impedance of the high-voltage cable can be measured by an impedance tester or other existing devices. In addition, the lead wire is selected, and its length L needs to satisfy the aforementioned formula (1), which will not be repeated here.

[0082] Optionally, since the detection signal contains different frequencies, the wave velocity of the signal will change during the transmission process, so the length of the lead wire needs to have a certain threshold to prevent the sampling signal from being superimposed.

[0083] Optionally, in a high-voltage cable system, in order to ensure the stability and efficiency of signal transmission, a lead wire is usually used for impedance matching. The lead wire refers to a conductor that connects the cable system and other devices or systems for transmitting signals or power.

[0084] Optionally, in a high-voltage cable system, the main function of the lead wire is to connect the cable system and the terminal equipment to ensure the quality and stability of signal transmission. In order to achieve impedance matching, the characteristic impedance of the lead wire is usually matched with the characteristic impedance of the cable system to reduce signal reflection and loss.

[0085] Optionally, the selection of the lead wire depends on the characteristic impedance and transmission requirements of the cable system. Common lead wire types include coaxial cable, twisted pair, balanced line, etc., and the appropriate lead wire can be selected for impedance matching according to the specific situation.

[0086] Optionally, for the method of selecting the lead-out line for impedance matching of the high-voltage cable, a lead-out line that matches the impedance of the high-voltage cable is used, and it needs to meet certain length requirements to avoid impedance discontinuity reflection signals at the connection between the lead-out line and the high-voltage cable detection.

[0087] Step S202, connecting the impedance-matched lead wire of the high-voltage cable.

[0088] In this embodiment, since two wires need to be connected to the cable core and the cable metal sheath respectively during the detection process to form a detection model that conforms to the transmission line model, it is also necessary to select wires that can ensure that the two wires are tightly connected to the core and the metal sheath respectively during the signal access process.

[0089] Optionally, considering that the contact surface may be incomplete when using clip-type connections such as alligator clips, a metal woven bag may be used to wrap the connection to increase the contact surface, reduce contact point emission, and ensure stable signal transmission.

[0090] Optionally, for the access method of the lead-out line of the high-voltage cable impedance matching, a clamp-type connection plus copper mesh wrapping is adopted to ensure reliable connection of the connection end.

[0091] Step S203: preliminary test of reliable connection.

[0092] In this embodiment, since the time-frequency domain detection signal needs to maintain the time-domain and frequency-domain characteristics, a certain duration is required. However, the time-domain signal used in the time-domain reflectometry technique has a shorter duration requirement than the time-frequency domain signal, and a signal with a shorter duration can be used for preliminary detection.

[0093] Optionally, a time domain pulse signal with a shorter duration is used to detect the reflection degree of the connection point, and the reflection condition of the connection point is observed, which can also be used as a basis for making corresponding judgments on the reflection signal condition of the subsequent detection sampling signal.

[0094] Optionally, as a preliminary test method for reliable connection, a time domain signal of shorter duration is used to evaluate the reflection condition of the lead-out connection end, and a preliminary judgment is made as to whether the reflection signal of the connection section will interfere with the defect detection at the near-point end of the cable.

[0095] Step S204: screening the time-frequency domain detection signal.

[0096] In this embodiment, the duration needs to ensure the time domain characteristics and frequency domain characteristics, and considering the sampling capability of the digital oscilloscope, the duration range T P The above formula (2) needs to be satisfied and will not be elaborated here.

[0097] Optionally, the time domain feature refers to a change feature of a signal over time, including the amplitude, frequency, phase, etc. of the signal. Common time domain features include mean, variance, standard deviation, peak value, waveform factor, etc.

[0098] Optionally, the frequency domain feature refers to the change feature of the signal in frequency. By performing Fourier transform on the signal, the spectrum of the signal can be obtained, thereby obtaining the energy distribution of the signal at different frequencies. Common frequency domain features include spectrum center, spectrum bandwidth, spectrum average, spectrum peak, etc.

[0099] Optionally, time domain features and frequency domain features can be converted to each other. A time domain signal can be converted to a frequency domain signal by performing Fourier transform on the signal, and vice versa. In signal processing and feature extraction, time domain features and frequency domain features are often used in combination to more comprehensively describe the characteristics of the signal.

[0100] Alternatively, a digital oscilloscope is an instrument used to measure and display the waveform of electrical signals. It converts analog signals into digital signals and displays them in digital form. Digital oscilloscopes usually have high resolution, high sampling rate, multiple trigger modes and automatic measurement functions, which can accurately capture and analyze various waveforms.

[0101] Step S205, detecting damage at a point close to the head end of the high voltage cable.

[0102] In this embodiment, Figure 3 is a schematic diagram of a specific connection between signal injection and acquisition according to an embodiment of the present invention, such as Figure 3 As shown, firstly, it is necessary to properly connect the signal generator 301 , the digital oscilloscope 302 , the impedance-matched signal lead wire 304 and the cable under test, and the cable under test includes a metal sheath 303 and a cable core 305 .

[0103] Optionally, since the digital oscilloscope needs to collect the waveform of the incident signal while receiving the reflected detection signal, in order to facilitate the subsequent comparison of the characteristics and attenuation degree of the incident signal and the reflected signal, the signal generator and the digital oscilloscope can be connected to the signal lead wire at the same time. For the other end of the signal lead wire, one lead wire is connected to a copper conductor of the cable core, and the other lead wire can be connected to the metal sheath of the high-voltage cable. For the access method, the copper mesh wrapping method can be used to increase the contact area of ​​the signal to ensure a reliable electrical connection. After the detection device is connected, the test can be started.

[0104] Optionally, the signal processing and detection analysis after input and acquisition are as follows: When the time-frequency domain characteristic signal is periodically input, the signal can adopt a linear frequency modulation signal with a Gaussian envelope. After the signal is injected, the oscilloscope can collect continuous incident signals and reflected signals. Since the characteristics of the two signals are similar, the overall acquired signal can be feature extracted. For example, the Wigner-Ville distribution can be used as an extraction scheme, which can represent the time domain characteristics and frequency domain characteristics of the signal in the form of a matrix. The time-frequency domain matrix W of the incident signal r (t,ω), the time-frequency matrix W of the reflected signal s (t,ω), and a spectrum diagram containing both time domain features and frequency domain features is obtained. Finally, the mutual correlation coefficient C of the above formula (3) and formula (4) can be used sr The calculation formula determines the energy of the incident signal and the reflected signal.

[0105] Optionally, for the signal injection and acquisition structure of the high-voltage cable near-end damage detection signal, an impedance-matched lead wire is added between the detection device and the cable, and it is ensured that the connecting end of the lead wire has a good electrical connection.

[0106] Optionally, for the processing method of the high-voltage cable near-end damage detection signal, after injecting the time-frequency domain detection signal and collecting it, the time-frequency domain feature decomposition and mutual correlation coefficient calculation method are used to calculate the distance between the signal generation end and the damage, and finally the lead-out line length is subtracted to obtain the cable end near-end damage positioning information.

[0107] Optionally, by calculating the cross-correlation curve between the time-frequency energy of the incident signal and the entire sampling signal, the normalized cross-correlation coefficient is 1, which is the signal time center of the incident signal, and the second wave peak is the time center of the first reflected signal. The time difference Δt between the incident and reflected signals can be obtained. The distance S between the fault point and the cable head end can be calculated according to the electromagnetic wave velocity through the above formula (5), and the damaged part of the high-voltage cable outer sheath can be located.

[0108] Optionally, the incident signal refers to a signal that enters the second medium at a certain angle when propagating from one medium to another medium.

[0109] Optionally, a reflected signal is a signal in which part of the energy of an incident signal is reflected back to the original medium when the incident signal reaches the boundary of a second medium. The relationship between the incident signal and the reflected signal can be described by the reflectivity, which is the ratio of the intensity of the reflected signal to the intensity of the incident signal. The reflectivity depends on the refractive index of the two media and the angle of incidence.

[0110] Optionally, the present invention provides a time-frequency domain reflection measurement method for leading out an impedance matching line at the head end. After the impedance matching line is led out, the lead-out line is used to increase the transmission distance of the time-frequency domain signal, increase the time difference between the incident signal and the reflected signal, avoid detection and positioning problems caused by the superposition of the incident signal and the reflected signal, increase the detection range of the time-frequency domain reflection method, and reduce the detection blind area.

[0111] In this embodiment, the characteristic impedance of the measured cable is measured; then, a lead wire that matches the impedance of the high-voltage cable is selected to access the aluminum sheath and core of the cable, and after reliable connection, a preliminary test is performed on the contact point to ensure that the impedance mismatch at the contact point will not affect the detection of defects near the cable; then the detection signal is screened, including parameters such as signal duration. After completing the above preparations, the signal generator and the digital oscilloscope can be connected to the impedance-matched lead wire, and then the screened detection signal can be injected and the digital oscilloscope can be used to collect the incident and reflected signals, and the signal is processed after storage to detect and locate the damage of the cable near the cable head end. The technical problem of being unable to detect cable defects is solved, and the technical effect of detecting cable defects is achieved.

[0112] According to an embodiment of the present invention, a device for detecting defects of a cable is also provided. It should be noted that the device for detecting defects of a cable can be used to execute the method for detecting defects of a cable in the method embodiment.

[0113] Figure 4 Schematic diagram of a cable defect detection device according to an embodiment of the present invention. Figure 4 As shown, the cable defect detection device 400 may include: a first acquisition unit 401 , a first determination unit 402 , a second acquisition unit 403 and a second determination unit 404 .

[0114] The first acquisition unit 401 is used to acquire the impedance characteristics of the cable to be tested.

[0115] The first determining unit 402 is configured to determine a target component to be connected to the cable to be tested based on the impedance characteristics.

[0116] The second acquisition unit 403 is used to detect the connection point between the target component and the cable to be tested in response to the target component and the cable to be tested being connected, and obtain a detection signal.

[0117] The second determining unit 404 is configured to determine defect information of the cable based on the detection signal.

[0118] Optionally, the first determination unit 402 may include: a first determination module, used to determine a length threshold of the target component based on the impedance characteristics; a first acquisition module, used to acquire the length of an initial component to be connected to the cable under test; and a second determination module, used to determine the initial component as a target component in response to the length of the initial component being greater than the length threshold.

[0119] Optionally, the cable defect detection device 400 may further include: a third acquisition unit, used to acquire multiple initial detection signals; a comparison unit, used to compare the multiple initial detection signals with a time range threshold to obtain a comparison result; and a third determination unit, used to determine the initial detection signal as a detection signal in response to the comparison result being that the initial detection signal meets the time range threshold.

[0120] Optionally, the second determination unit 404 may include: a second acquisition module, used to acquire the incident signal; and a third determination module, used to determine the defect information of the cable based on the incident signal and the detection signal.

[0121] Optionally, the third determination module may include: an extraction submodule, used to extract spectral features of the incident signal and the detection signal, wherein the spectral features include at least time domain features and frequency domain features; a first determination submodule, used to determine the energy values ​​of the incident signal and the detection signal respectively based on the spectral features; and a second determination submodule, used to determine defect information based on the energy values.

[0122] Optionally, the second determination submodule may also be used to analyze the energy value using a defect recognition strategy to obtain defect information, wherein the defect recognition strategy is a rule for determining the defect information.

[0123] In this embodiment, the impedance characteristics of the cable to be tested are obtained; based on the impedance characteristics, the target component to be connected to the cable to be tested is determined; in response to the target component being connected to the cable to be tested, the connection point between the target component and the cable to be tested is detected to obtain a detection signal; based on the detection signal, the defect information of the cable is determined. In other words, according to the impedance characteristics of the cable to be tested, the embodiment of the present invention does not determine the target component to be connected to the cable to be tested, and then determines the defect information of the cable according to the detection signal. The technical problem of being unable to detect cable defects is solved, and the technical effect of detecting cable defects is achieved.

[0124] According to an embodiment of the present invention, there is further provided a computer-readable storage medium, the storage medium comprising a stored program, wherein the program executes the method for detecting defects of a cable in the method embodiment.

[0125] According to an embodiment of the present invention, a processor is further provided. The processor is used to run a program, wherein the method for detecting defects of a cable in the method embodiment is executed when the program is run.

[0126] According to an embodiment of the present invention, a computer program product is further provided. The computer program product includes computer instructions. When the computer instructions are executed by a processor, the method for detecting defects of a cable in the method embodiment is implemented.

[0127] The serial numbers of the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0128] In the above embodiments of the present invention, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0129] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. Among them, the device embodiments described above are only schematic. For example, the division of units can be a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of units or modules, which can be electrical or other forms.

[0130] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed over multiple units. Some or all of the units may be selected according to actual needs to achieve the purpose of the present embodiment.

[0131] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0132] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent functional component, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software functional component, which is stored in a storage medium and includes several instructions for a computer device (which can be a personal computer, server or network device, etc.) to perform all or part of the steps of the methods of each embodiment of the present invention. The aforementioned storage medium includes: U disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), mobile hard disk, disk or optical disk, etc., which can store program codes.

[0133] The above are only preferred embodiments of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for detecting defects in a cable, characterized in that: include: Obtain the impedance characteristics of the cable to be tested; Based on the impedance characteristics, determining a target component to be connected to the cable to be tested; In response to the target component and the cable to be tested being connected, detecting a connection point between the target component and the cable to be tested to obtain a detection signal; Based on the detection signal, defect information of the cable is determined.

2. The method according to claim 1, characterized in that: Determining a target component to be connected to the cable to be tested based on the impedance characteristic includes: Determining a length threshold of the target component based on the impedance characteristic; Obtaining the length of an initial component to be connected to the cable under test; In response to the length of the initial component being greater than the length threshold, the initial component is determined as the target component.

3. The method according to claim 1, characterized in that Before determining the defect information of the cable based on the detection signal, the method further includes: obtaining a plurality of initial detection signals; Comparing the plurality of initial detection signals with a time range threshold to obtain a comparison result; In response to the comparison result being that the initial detection signal meets the time range threshold, the initial detection signal is determined as the detection signal.

4. The method according to claim 1, characterized in that Determining defect information of the cable based on the detection signal includes: Obtaining an incident signal; The defect information of the cable is determined based on the incident signal and the detection signal.

5. The method according to claim 4, characterized in that Determining the defect information of the cable based on the incident signal and the detection signal includes: Extracting frequency spectrum features of the incident signal and the detection signal, wherein the frequency spectrum features at least include time domain features and frequency domain features; Based on the frequency spectrum characteristics, respectively determine energy values ​​of the incident signal and the detection signal; Based on the energy value, the defect information is determined.

6. The method according to claim 5, characterized in that Based on the energy value, determining the defect information includes: The energy value is analyzed using a defect identification strategy to obtain the defect information, wherein the defect identification strategy is a rule for determining the defect information.

7. A device for detecting defects in a cable, characterized in that: include: A first acquisition unit, used to acquire the impedance characteristics of the cable to be tested; A first determining unit, configured to determine a target component to be connected to the cable to be tested based on the impedance characteristic; A second acquisition unit is used for detecting a connection point between the target component and the cable to be tested in response to the target component and the cable to be tested being connected, so as to obtain a detection signal; The second determining unit is used to determine defect information of the cable based on the detection signal.

8. A computer-readable storage medium, characterized in that: The computer-readable storage medium includes a stored program, wherein when the program is executed by a processor, the device where the storage medium is located is controlled to execute the method according to any one of claims 1 to 6.

9. A processor, characterized in that: The processor is used to run a program, wherein the program executes the method according to any one of claims 1 to 6 when running.

10. A computer program product, characterized in that The computer program product comprises computer instructions, which implement the method according to any one of claims 1 to 6 when executed by a processor.

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