A method and system for precise location of cable faults based on waveform analysis

Abstract

This invention belongs to the field of cable repair technology, specifically disclosing a method for precise cable fault location based on waveform analysis. The method includes: applying a high-voltage pulse to the cable under test to cause the fault point to puncture and discharge, generating vibration and electromagnetic signals; planning a travel route based on the polarity of the electromagnetic signals to ensure the probe travels directly above the cable; displaying the vibration and electromagnetic signal waveforms simultaneously on a screen; extracting the waveform start time to calculate the time difference and estimating the distance between the probe and the fault point; determining the fault point's orientation based on the phase and intensity of the electromagnetic signals; guiding the probe to gradually approach the fault point; and confirming the directly above position and calculating the burial depth when the time difference reaches its minimum stable value. The system includes a high-voltage pulse generator, a signal acquisition probe, and a display and control host. This invention achieves path planning, anti-interference positioning, de-auditory judgment, and depth measurement, significantly improving the efficiency and accuracy of cable fault location.

Description

Technical Field

[0001] This invention belongs to the field of cable repair technology, and specifically relates to a method and system for accurate cable fault location based on waveform analysis. Background Technology

[0002] Accurate fault location in cables is crucial for ensuring the safe and stable operation of power systems. Buried cables, due to their long-term underground burial, are susceptible to insulation aging and mechanical damage caused by environmental factors and external forces. When a cable fault occurs, quickly and accurately locating the fault point is essential for shortening power outage time, reducing economic losses, and improving power supply reliability. However, the highly concealed nature of buried cables and the complex laying environment make accurate fault location a technical challenge in power operation and maintenance.

[0003] Chinese Patent Publication No. CN110133441A discloses a system and method for locating faults in underground cables. The system includes an underground cable fault detection device, an underground cable pathfinding and ranging device, and an underground cable fault location device. The fault detection device obtains the resistance value of the target cable through a resistance measuring device and determines the fault type (grounding fault, open circuit fault, low resistance fault, or high resistance fault) based on the resistance value. The pathfinding and ranging device emits pulse signals through a low-voltage pulse generator or a high-voltage pulse generator and obtains the reflected signal from the fault point for preliminary distance measurement. The fault location device uses an audio current generator, a DC generator, a step voltage detection device, or an acoustic-magnetic synchronous receiver to accurately locate the fault point for different types of faults. However, in the accurate location process, the operator relies solely on the equipment's indication to move along the cable's direction, lacking effective means of planning the cable path. In actual operation, due to unclear paths or complex terrain, the operator may deviate from directly above the cable, leading to low location efficiency or even location failure. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a method for accurate cable fault location based on waveform analysis.

[0005] This invention provides a method for accurate cable fault location based on waveform analysis, comprising the following steps: Step 1: Connect the output terminal of the high-voltage pulse generator to the core wire of the cable under test, apply a high-voltage pulse signal to the cable under test, so that the high-voltage pulse signal breaks down the cable fault point, forming a pulse discharge to generate vibration signal and electromagnetic signal; Step 2: Place the signal acquisition probe on the ground above the path of the cable being tested, and plan the path of the signal acquisition probe based on the polarity of the electromagnetic signal to ensure that the signal acquisition probe always travels directly above the cable. Step 3: Move the signal acquisition probe along the travel route until the display control host displays both vibration and electromagnetic signals, and plots the vibration signal waveform and electromagnetic signal waveform on the same display screen; Step 4: Extract the start time of the electromagnetic signal waveform and the start time of the vibration signal waveform Calculate the time difference And based on the propagation speed of the vibration signal in the soil medium Estimate the distance between the current position of the signal acquisition probe and the cable fault point. ; Step 5: Determine the location of the cable fault point relative to the signal acquisition probe based on the phase angle characteristics of the electromagnetic signal waveform and the trend of signal intensity change. Step 6: Move the signal acquisition probe according to the distance estimated in Step 4 and the orientation determined in Step 5. Observe the amplitude changes of the vibration signal waveform and electromagnetic signal waveform during the movement. When the amplitude of both waveforms gradually increases, it indicates that the signal acquisition probe is approaching the cable fault point. Step 7: When the time difference between the electromagnetic signal waveform and the vibration signal waveform displayed on the control host is... When the minimum stable value is reached, the location is confirmed to be the ground position directly above the cable fault point; Step 8: Record the minimum time difference and combine it with the propagation speed. Calculate the burial depth of the cable fault point.

[0006] A further approach is to determine the amplitude of the high-voltage pulse signal in step 1 through the following steps: Step 1.1: Obtain the rated voltage level and insulation withstand characteristics of the cable under test, and estimate the breakdown voltage threshold range of its fault point; Step 1.2: Initially set the output amplitude of the high-voltage pulse generator to a safe voltage value lower than the lower limit of the breakdown voltage threshold range, and apply a test pulse to the cable under test; Step 1.3: Monitor the electromagnetic signal on the ground above the cable path in real time using a signal acquisition probe, and determine whether the cable fault point has been broken down based on whether electromagnetic signals caused by discharge are detected. Step 1.4: If no electromagnetic signal is detected, gradually increase the amplitude of the high-voltage pulse signal by a preset step size, and repeat the test pulse after each increase until the signal acquisition probe detects a clear electromagnetic signal waveform, indicating that the cable fault point has been broken down. Step 1.5: Record the amplitude of the high-voltage pulse signal at this time as the standard test amplitude in the subsequent precise positioning process.

[0007] A further proposed solution is that, in step 2, the route planning process includes the following steps: Step 2.1: Determine the estimated path based on the laying path data of the cable under test; Several sampling points are set along the estimated path of the cable under test, and the signal acquisition probe is moved. At the sampling points, the signal acquisition probe is moved in a direction perpendicular to the estimated path, and the polarity change of the electromagnetic signal is observed in real time. Step 2.2: When the polarity of the electromagnetic signal reverses, record the critical position point of the polarity reversal, and determine the critical position point as the position directly above the critical position on the other side of the cable; Step 2.3: Based on the critical position points determined at each sampling point, a curve fitting algorithm is used to generate a smooth path curve on the other side of the cable under test as the travel route of the signal acquisition probe.

[0008] A further approach is that the route planning also includes determining the actual path of the cable under test, including: At the sampling point, move the signal acquisition probe along a direction perpendicular to the estimated path. When the polarity of the electromagnetic signal reverses for the first time, record the first critical point. Then, when moving along the route closer to the current sampling point, record the second critical point when the polarity of the electromagnetic signal reverses for the second time. Take the midpoint of the line connecting the first critical point and the second critical point as the point directly above the cable. Record multiple points directly above the cable and fit them into a curve to represent the actual route of the cable under test.

[0009] A further solution is that, in step 5, determining the orientation of the cable fault point relative to the signal acquisition probe includes: Step 5.1: Compare the phase of the current electromagnetic signal waveform with the pre-recorded reference phase directly above the cable, and determine the left and right offset direction of the signal acquisition probe relative to the cable based on the phase deviation direction; Step 5.2: Move the signal acquisition probe along the actual route of the cable, compare the electromagnetic signal strength at the two positions before and after, and determine whether the fault point is located in front of or behind the signal acquisition probe based on the trend of intensity change. Step 5.3: Based on the judgment results of Step 5.1 and Step 5.2, generate the azimuth information of the fault point relative to the current position of the signal acquisition probe.

[0010] A further solution is the time difference mentioned in step 7. The criteria for determining whether a minimum stable value has been reached include: As the signal acquisition probe moves along the actual path of the cable, the time difference If the time difference continues to decrease until a certain point where it begins to increase, then the time difference at that point is... This is the minimum stable value.

[0011] A further step is to include, in step 7, confirming the location of the ground directly above the cable fault point, further including: The time difference At the minimum stable value location, the signal acquisition probe is moved horizontally a preset length along a direction perpendicular to the actual cable path. If the phase angle of the electromagnetic signal waveform flips by 180° and the amplitude of the vibration signal waveform reaches its maximum value, then the time difference is considered to be... The minimum stable value is located on the ground directly above the cable fault point.

[0012] A second aspect of the present invention provides a cable fault precise location system based on waveform analysis, wherein the above-mentioned cable fault precise location method includes: A high-voltage pulse generator is connected to the core wire of the cable under test. It is used to apply a high-voltage pulse signal to the core wire of the cable under test to break down the fault point of the cable and form a pulse discharge, generating vibration signal and electromagnetic signal. The signal acquisition probe has a built-in accelerometer and an electromagnetic induction sensor for synchronously acquiring vibration and electromagnetic signals. The signal filtering and amplification unit is connected to the signal acquisition probe and is used to filter and amplify the acquired vibration signal and electromagnetic signal respectively. The analog-to-digital conversion unit, connected to the signal filtering and amplification unit, is used to convert the filtered and amplified analog signal into a digital signal. The FPGA signal processing unit, connected to the analog-to-digital converter unit, is used for real-time processing of digital signals and extraction of signal features; The display control host is connected to the high-voltage pulse generator and the signal acquisition probe respectively. It is used to control the output of high-voltage pulse signals, receive vibration signals and electromagnetic signals, and draw the waveforms of vibration signals and electromagnetic signals. The power supply unit is connected to the signal acquisition probe, signal filtering and amplification unit, analog-to-digital conversion unit, FPGA signal processing unit, and display control host, respectively, and is used to provide working power.

[0013] A further embodiment is that the display control host includes: The path planning module is used to plan the travel route of the signal acquisition probe based on the polarity characteristics of the electromagnetic signal, ensuring that the signal acquisition probe always travels directly above the cable. The waveform display module is used to display vibration signal waveforms and electromagnetic signal waveforms on the same display screen. The time difference calculation module is used to extract the start time of the electromagnetic signal waveform and the start time of the vibration signal waveform, and to calculate the time difference. And based on the preset propagation speed of the vibration signal in the soil medium Estimate the distance between the current position of the signal acquisition probe and the cable fault point. ; The orientation analysis module is used to determine the orientation of the cable fault point relative to the signal acquisition probe based on the phase angle characteristics of the electromagnetic signal waveform and the trend of signal intensity change. The guidance module is used to generate movement guidance information based on the estimated distance and determined orientation, and to monitor the amplitude changes of vibration signal waveform and electromagnetic signal waveform during movement; The positioning confirmation module is used to determine the time difference between the electromagnetic signal waveform and the vibration signal waveform. Check whether t has reached the minimum stable value and confirm the ground location directly above the cable fault point; The depth calculation module is used to calculate the burial depth of cable fault points.

[0014] A further embodiment is that the path planning module includes: The sampling point setting unit is used to set several sampling points along the estimated path direction of the cable under test; The mobile guidance unit is used to guide the operator to move the signal acquisition probe at the sampling point in a direction perpendicular to the estimated path; The polarity monitoring unit is used to monitor the polarity changes of the electromagnetic signal waveform in real time during vertical movement. The positioning unit is used to record the first critical point when the polarity of the electromagnetic signal reverses for the first time, and to record the second critical point when the polarity of the electromagnetic signal reverses for the second time while moving along the route close to the current sampling point. The midpoint of the line connecting the first critical point and the second critical point is taken as the point directly above the cable. The path fitting unit is used to generate the actual route path of the cable under test by using a curve fitting algorithm based on the position directly above the cable determined at each sampling point.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention applies a high-voltage pulse signal to the cable under test, causing a pulse discharge at the fault point and releasing vibration and electromagnetic signals. The display and control host shows the waveforms of both signals simultaneously. The operator extracts the start time of both waveforms, calculates the time difference, and estimates the distance between the probe and the fault point by combining this with the vibration signal propagation speed. As the probe approaches the fault point, the time difference continuously decreases. When it reaches a minimum stable value, it confirms that the probe is directly above the fault point, and the burial depth is calculated. This invention achieves dual positioning of the fault point's planar location and burial depth, providing accurate parameters for excavation and maintenance, and avoiding resource waste and project delays caused by blind excavation.

[0016] This invention utilizes changes in the polarity of electromagnetic signals to accurately map the actual route of a cable during route planning. Operators set sampling points along the estimated path, and at each sampling point, the probe is moved horizontally along a direction perpendicular to the estimated path to observe changes in the polarity of the electromagnetic signal. When the polarity reverses twice, two critical points are recorded; the midpoint of the line connecting these two points is the point directly above the cable on that cross-section. After recording multiple points directly above the cable, a curve representing the actual cable route is fitted to the data. This invention accurately determines the position directly above the cable through the principle of polarity reversal, avoiding positioning failures or inefficiencies caused by path deviations.

[0017] This invention compares the current electromagnetic signal phase with a pre-recorded reference phase, determines the left or right offset of the probe based on the phase deviation direction, and adjusts it in real time to ensure it travels directly above the cable. Simultaneously, it compares the electromagnetic signal strength at previous and subsequent positions along the path, determining the fault point's location based on intensity changes. Combining the left / right offset with the forward / backward orientation generates complete location information. The operator moves the probe according to the guidance and observes the amplitude changes of the two waveforms; a gradual increase in amplitude indicates approaching the fault point. This invention achieves quantitative judgment and guided approach to the fault point's location, significantly improving positioning efficiency and accuracy. Attached Figure Description

[0018] The following figures are for illustrative purposes only and are not intended to limit the scope of the invention, wherein: Figure 1 : Schematic diagram of the positioning method of the present invention; Figure 2 : A schematic diagram of electromagnetic signal waveforms and vibration signal waveforms displayed on the same screen; Figure 3 : Schematic diagram of the route determination; Figure 4 : Schematic diagram showing the actual route of the cable; Figure 5 Electrical schematic diagram of a cable fault precise location system.

[0019] In the diagram: 1. Cable; 2. Route; 3. Sampling point; 4. Estimated path; 5. First critical point; 6. Second critical point; 7. Point directly above the cable; 8. Actual route. Detailed Implementation

[0020] To make the objectives, technical solutions, design methods, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0021] Example 1 like Figure 1As shown, this embodiment provides a method for accurate cable fault location based on waveform analysis, including the following steps: Step 1: Connect the output of the high-voltage pulse generator to the core wire of the cable under test. Based on the rated voltage level and insulation withstand characteristics of the cable under test, estimate the breakdown voltage threshold range of its fault point. Initially set the output amplitude of the high-voltage pulse generator to a safe voltage value lower than the lower limit of this threshold range, and apply a test pulse to the cable under test. Monitor the electromagnetic signal on the ground above the cable path in real time using a signal acquisition probe. If no electromagnetic signal caused by discharge is detected, gradually increase the amplitude of the high-voltage pulse signal by a preset step size, and repeat the test pulse application after each increase until the signal acquisition probe detects a clear electromagnetic signal waveform. This indicates that the cable fault point has been broken down by the high-voltage pulse, forming a pulse discharge, and simultaneously generating vibration and electromagnetic signals. Record the high-voltage pulse signal amplitude at this time as the standard test amplitude in the subsequent precise location process.

[0022] Step 2: Place the signal acquisition probe on the ground above the path of the cable being tested. Plan the probe's path based on the polarity of the electromagnetic signal to ensure it always travels directly above the cable. The specific path planning process is as follows: like Figure 3 As shown, the estimated path 3 is determined based on the laying path data of the cable under test 1. To demonstrate the technical effectiveness of the path planning in this embodiment, it is assumed that the estimated path 3 deviates significantly from the actual cable. Several sampling points 3 are set along the direction of the estimated path 4. At each sampling point 3, the signal acquisition probe is moved horizontally in a direction perpendicular to the estimated path (the direction of the dashed arrow in the figure), and the polarity change of the electromagnetic signal waveform is observed in real time. It should be noted that during the pulse discharge process, the current propagates along the core wire of the cable under test. According to the right-hand screw rule, the current will generate a magnetic field around the cable. When the signal acquisition probe is located directly above the cable, the magnetic field sensed by the electromagnetic induction sensor inside it is perpendicular to the cable direction. When the probe moves horizontally from one side of the cable to the other, the initial oscillation direction of the electromagnetic signal waveform changes from positive to negative polarity, or from negative to positive polarity. Therefore, by monitoring the polarity change of the electromagnetic signal waveform during the vertical movement, when the polarity reverses, it can be determined that the probe has crossed from one side of the cable to the other. Based on the critical position points determined at each of the three sampling points, a curve fitting algorithm is used to generate a smooth path curve on the other side of the cable under test as the travel path 2 of the signal acquisition probe. To further improve accuracy, the actual route 8 of the cable is used as the travel path of the signal acquisition probe, such as... Figure 4 As shown, when the polarity of the electromagnetic signal reverses for the first time, this critical position point is recorded as the first critical point 5; along... Figure 4Moving along the path opposite to the dashed arrow, when the electromagnetic signal polarity reverses for the second time, this critical point is recorded as the second critical point 6. The midpoint of the line connecting the first critical point 5 and the second critical point 6 is the point 7 directly above the cable on this cross-section. Repeating the above operation, recording the point 7 directly above multiple sampling points, and using a curve fitting algorithm to generate the actual route path 8 of the cable under test. Continue referring to... Figure 3 and Figure 4 Although the predicted path 4 has deviated from cable 1, the above method can still accurately fit the travel route 2 and the actual route 8 of the cable.

[0023] Step 3: Move the signal acquisition probe along the route planned in Step 2. During the movement, the display control host continuously receives and displays the electromagnetic signal waveforms. When the probe moves close enough to the fault point (usually within tens of meters), the display control host begins to simultaneously display the vibration signal waveform acquired by the accelerometer and the electromagnetic signal waveform acquired by the electromagnetic induction sensor, plotting both waveforms on the same display screen. Figure 2 As shown, operators can visually observe the relative positional relationship between the two waveforms.

[0024] Step 4: Extract the start time of the electromagnetic signal waveform and the start time of the vibration signal waveform Calculate the time difference = - Because the propagation speed of electromagnetic signals in the soil medium is much higher than that of vibration signals, this time difference is proportional to the distance from the signal acquisition probe to the fault point. Based on the preset propagation speed of vibration signals in the soil medium... Estimate the distance between the current position of the signal acquisition probe and the cable fault point. .

[0025] Step 5: Determine the orientation of the cable fault point relative to the signal acquisition probe based on the phase angle characteristics and signal intensity change trend of the electromagnetic signal waveform. Specifically, compare the phase of the current electromagnetic signal waveform with the pre-recorded reference phase directly above the cable, and determine the left or right offset direction of the probe relative to the cable based on the phase deviation direction; move the signal acquisition probe along the actual cable path, compare the electromagnetic signal intensity at the two positions before and after, and determine whether the fault point is located in front of or behind the probe based on the intensity change trend; combine the left and right offset direction and the front and back orientation judgment results to generate complete orientation information of the fault point relative to the current position of the probe.

[0026] Step 6: Based on the distance estimated in Step 4 and the orientation determined in Step 5, move the signal acquisition probe in the direction that decreases the distance. During the movement, observe the amplitude changes of the vibration signal waveform and the electromagnetic signal waveform. When the amplitude of both waveforms gradually increases, it indicates that the signal acquisition probe is approaching the cable fault point. The operator can continuously adjust the movement direction according to the amplitude change trend to ensure gradual approach to the fault point.

[0027] Step 7: When the time difference between the electromagnetic signal waveform and the vibration signal waveform displayed on the control host is... The minimum stable value is reached when the signal acquisition probe moves along the actual path of the cable. If it continues to decrease until a certain position is reached, then it begins to increase; the position corresponding to that position... This is the minimum stable value. To further verify, at this minimum stable value location, the signal acquisition probe is moved horizontally a preset length in a direction perpendicular to the actual cable route. If the phase angle of the electromagnetic signal waveform flips by 180° and the amplitude of the vibration signal waveform reaches its maximum value, then this location is confirmed to be the ground position directly above the cable fault point.

[0028] Step 8: Record the minimum time difference confirmed in Step 7. By combining the propagation speed of vibration signals in the soil medium, the burial depth of the cable fault point is calculated. This depth information provides accurate construction parameters for subsequent excavation and repair.

[0029] Example 2 Building upon Example 1, this example provides a waveform analysis-based precise cable fault location system for executing the method of Example 1. Figure 5As shown, the system includes a high-voltage pulse generator, a signal acquisition probe, a signal filtering and amplification unit, an analog-to-digital converter, an FPGA signal processing unit, a display and control host, and a power supply unit. The high-voltage pulse generator is electrically connected to the core wire of the cable under test and applies a high-voltage pulse signal to the core wire to break down the cable fault point, forming a pulse discharge and generating vibration and electromagnetic signals. The signal acquisition probe incorporates an accelerometer and an electromagnetic induction sensor, used to synchronously acquire vibration and electromagnetic signals, respectively. The accelerometer converts the vibration signal into an electrical signal, and the electromagnetic induction sensor converts changes in the magnetic field into an electrical signal. The signal filtering and amplification unit is electrically connected to the signal acquisition probe and filters and amplifies the acquired vibration and electromagnetic signals, respectively, filtering out high-frequency noise and background interference, and adjusting the amplification factor according to the field environment to ensure the effective signal reaches a suitable amplitude. The analog-to-digital converter is electrically connected to the signal filtering and amplification unit and converts the filtered and amplified analog signal into a digital signal for subsequent digital processing. The FPGA signal processing unit is electrically connected to the analog-to-digital converter unit for real-time processing of digital signals, including digital filtering, feature extraction, and waveform triggering, ensuring real-time signal processing with high speed and reliability. The display control host is connected to the high-voltage pulse generator and signal acquisition probe, controlling the output of the high-voltage pulse signal, receiving vibration and electromagnetic signals, and plotting the two waveforms on the same display screen. The display control host integrates a microcontroller (MCU) and corresponding functional modules. The power supply unit is connected to the signal acquisition probe, signal filtering and amplification unit, analog-to-digital converter unit, FPGA signal processing unit, and display control host, providing a stable power supply to ensure the normal operation of each unit.

[0030] In this embodiment, the display control host includes a path planning module, a waveform display module, a time difference calculation module, a azimuth analysis module, a guidance module, a positioning confirmation module, and a depth calculation module. Specifically, the path planning module is used to plan the travel route of the signal acquisition probe based on the polarity characteristics of the electromagnetic signal, ensuring that the probe always travels directly above the cable. This path planning module further includes a sampling point setting unit, a movement guidance unit, a polarity monitoring unit, a positioning unit, and a path fitting unit. The sampling point setting unit is used to set several sampling points along the estimated path direction of the cable under test; the movement guidance unit is used to guide the operator to move the signal acquisition probe at the sampling points in a direction perpendicular to the estimated path; the polarity monitoring unit is used to monitor the polarity change of the electromagnetic signal waveform in real time during vertical movement; the positioning unit is used to record the first critical point when the electromagnetic signal polarity reverses for the first time, and then, when moving along the route closer to the current sampling point, records the second critical point when the electromagnetic signal polarity reverses for the second time, and takes the midpoint of the line connecting the first and second critical points as the point directly above the cable; the path fitting unit is used to generate the actual route of the cable under test using a curve fitting algorithm based on the cable's position directly above each sampling point. The waveform display module displays the vibration and electromagnetic signal waveforms on the same screen for intuitive observation and analysis by operators. The time difference calculation module extracts the start time of the electromagnetic and vibration signal waveforms, calculates the time difference, and estimates the distance between the current position of the signal acquisition probe and the cable fault point based on the preset propagation speed of the vibration signal in the soil. The orientation analysis module determines the orientation of the cable fault point relative to the signal acquisition probe based on the phase angle characteristics and signal intensity change trends of the electromagnetic signal waveform. This module determines left-right offset through phase comparison and front-back orientation through intensity trends, ultimately synthesizing complete orientation information. The guidance module generates movement guidance information based on the estimated distance and determined orientation, and monitors the amplitude changes of the vibration and electromagnetic signal waveforms during movement, providing real-time prompts to operators to adjust the movement direction. The positioning confirmation module determines whether the time difference between the electromagnetic and vibration signal waveforms has reached the minimum stable value and confirms the ground position directly above the cable fault point. This module determines the minimum value point through monitored trends and performs dual verification at this point using phase reversal and maximum amplitude. The depth calculation module records the minimum time difference, calculates the burial depth of the cable fault point based on the propagation speed, and displays the depth information on the screen. Through the collaborative work of the above modules, this system achieves fully automated guidance and precise positioning throughout the entire process, from path planning, distance estimation, orientation determination to final location and depth calculation.

[0031] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for precise cable fault location based on waveform analysis, characterized in that, Includes the following steps: Step 1: Connect the output terminal of the high-voltage pulse generator to the core wire of the cable under test, apply a high-voltage pulse signal to the cable under test, so that the high-voltage pulse signal breaks down the cable fault point, forming a pulse discharge to generate vibration signal and electromagnetic signal; Step 2: Place the signal acquisition probe on the ground above the path of the cable being tested, and plan the path of the signal acquisition probe based on the polarity of the electromagnetic signal to ensure that the signal acquisition probe always travels directly above the cable. Step 3: Move the signal acquisition probe along the travel route until the display control host displays both vibration and electromagnetic signals, and plots the vibration signal waveform and electromagnetic signal waveform on the same display screen; Step 4: Extract the start time of the electromagnetic signal waveform and the start time of the vibration signal waveform Calculate the time difference And based on the propagation speed of the vibration signal in the soil medium Estimate the distance between the current position of the signal acquisition probe and the cable fault point. ; Step 5: Determine the location of the cable fault point relative to the signal acquisition probe based on the phase angle characteristics of the electromagnetic signal waveform and the trend of signal intensity change. Step 6: Move the signal acquisition probe according to the distance estimated in Step 4 and the orientation determined in Step 5. Observe the amplitude changes of the vibration signal waveform and electromagnetic signal waveform during the movement. When the amplitude of both waveforms gradually increases, it indicates that the signal acquisition probe is approaching the cable fault point. Step 7: When the time difference between the electromagnetic signal waveform and the vibration signal waveform displayed on the control host is... When the minimum stable value is reached, confirm that the location is the ground position directly above the cable fault point; Step 8: Record the minimum time difference and combine it with the propagation speed. Calculate the burial depth of the cable fault point.

2. The method for precise cable fault location based on waveform analysis according to claim 1, characterized in that, The amplitude of the high-voltage pulse signal in step 1 is determined through the following steps: Step 1.1: Obtain the rated voltage level and insulation withstand characteristics of the cable under test, and estimate the breakdown voltage threshold range of its fault point; Step 1.2: Initially set the output amplitude of the high-voltage pulse generator to a safe voltage value lower than the lower limit of the breakdown voltage threshold range, and apply a test pulse to the cable under test; Step 1.3: Monitor the electromagnetic signal on the ground above the cable path in real time using a signal acquisition probe, and determine whether the cable fault point has been broken down based on whether electromagnetic signals caused by discharge are detected. Step 1.4: If no electromagnetic signal is detected, gradually increase the amplitude of the high-voltage pulse signal by a preset step size, and repeat the test pulse after each increase until the signal acquisition probe detects a clear electromagnetic signal waveform, indicating that the cable fault point has been broken down. Step 1.5: Record the amplitude of the high-voltage pulse signal at this time as the standard test amplitude in the subsequent precise positioning process.

3. The method for precise cable fault location based on waveform analysis according to claim 2, characterized in that, In step 2, the route planning process includes the following steps: Step 2.1: Determine the estimated path based on the laying path data of the cable under test; Several sampling points are set along the estimated path of the cable under test, and the signal acquisition probe is moved. At the sampling points, the signal acquisition probe is moved in a direction perpendicular to the estimated path, and the polarity change of the electromagnetic signal is observed in real time. Step 2.2: When the polarity of the electromagnetic signal reverses, record the critical position point of the polarity reversal, and determine the critical position point as the position directly above the critical position on the other side of the cable; Step 2.3: Based on the critical position points determined at each sampling point, a curve fitting algorithm is used to generate a smooth path curve on the other side of the cable under test as the travel route of the signal acquisition probe.

4. The method for precise cable fault location based on waveform analysis according to claim 3, characterized in that, The planning of the travel route also includes determining the actual path of the cable to be tested, including: At the sampling point, move the signal acquisition probe along a direction perpendicular to the estimated path. When the polarity of the electromagnetic signal reverses for the first time, record the first critical point. Then move along the route closer to the current sampling point. When the polarity of the electromagnetic signal reverses for the second time, record the second critical point. Take the midpoint of the line connecting the first critical point and the second critical point as the point directly above the cable. Record multiple points directly above the cable and fit them into a curve to represent the actual route of the cable under test.

5. The method for precise cable fault location based on waveform analysis according to claim 4, characterized in that, In step 5, determining the orientation of the cable fault point relative to the signal acquisition probe includes: Step 5.1: Compare the phase of the current electromagnetic signal waveform with the pre-recorded reference phase directly above the cable, and determine the left and right offset direction of the signal acquisition probe relative to the cable based on the phase deviation direction; Step 5.2: Move the signal acquisition probe along the actual route of the cable, compare the electromagnetic signal strength at the two positions before and after, and determine whether the fault point is located in front of or behind the signal acquisition probe based on the trend of intensity change. Step 5.3: Based on the judgment results of Step 5.1 and Step 5.2, generate the azimuth information of the fault point relative to the current position of the signal acquisition probe.

6. The method for precise cable fault location based on waveform analysis according to claim 5, characterized in that, The time difference mentioned in step 7 The criteria for determining whether a minimum stable value has been reached include: As the signal acquisition probe moves along the actual path of the cable, the time difference If the time difference continues to decrease until a certain point where it begins to increase, then the time difference at that point is... This is the minimum stable value.

7. The method for precise cable fault location based on waveform analysis according to claim 6, characterized in that, Step 7, confirming the ground location directly above the cable fault point, also includes: The time difference At the minimum stable value location, the signal acquisition probe is moved horizontally a preset length along a direction perpendicular to the actual cable path. If the phase angle of the electromagnetic signal waveform flips by 180° and the amplitude of the vibration signal waveform reaches its maximum value, then the time difference is considered to be... The minimum stable value is located on the ground directly above the cable fault point.

8. A precise cable fault location system based on waveform analysis, characterized in that, The method for accurately locating cable faults according to any one of claims 1-7 includes: A high-voltage pulse generator is connected to the core wire of the cable under test. It is used to apply a high-voltage pulse signal to the core wire of the cable under test to break down the fault point of the cable and form a pulse discharge, generating vibration signal and electromagnetic signal. The signal acquisition probe has a built-in accelerometer and an electromagnetic induction sensor for synchronously acquiring vibration and electromagnetic signals. The signal filtering and amplification unit is connected to the signal acquisition probe and is used to filter and amplify the acquired vibration signal and electromagnetic signal respectively. The analog-to-digital conversion unit, connected to the signal filtering and amplification unit, is used to convert the filtered and amplified analog signal into a digital signal. The FPGA signal processing unit, connected to the analog-to-digital converter unit, is used for real-time processing of digital signals and extraction of signal features; The display control host is connected to the high-voltage pulse generator and the signal acquisition probe respectively. It is used to control the output of high-voltage pulse signals, receive vibration signals and electromagnetic signals, and draw the waveforms of vibration signals and electromagnetic signals. The power supply unit is connected to the signal acquisition probe, signal filtering and amplification unit, analog-to-digital conversion unit, FPGA signal processing unit, and display control host, respectively, and is used to provide working power.

9. A cable fault precise location system based on waveform analysis according to claim 8, characterized in that, The display control host includes: The path planning module is used to plan the travel route of the signal acquisition probe based on the polarity characteristics of the electromagnetic signal, ensuring that the signal acquisition probe always travels directly above the cable. The waveform display module is used to display vibration signal waveforms and electromagnetic signal waveforms on the same display screen. The time difference calculation module is used to extract the start time of the electromagnetic signal waveform and the start time of the vibration signal waveform, and to calculate the time difference. And based on the preset propagation speed of the vibration signal in the soil medium Estimate the distance between the current position of the signal acquisition probe and the cable fault point. ; The orientation analysis module is used to determine the orientation of the cable fault point relative to the signal acquisition probe based on the phase angle characteristics of the electromagnetic signal waveform and the trend of signal intensity change. The guidance module is used to generate movement guidance information based on the estimated distance and determined orientation, and to monitor the amplitude changes of vibration signal waveform and electromagnetic signal waveform during movement; The positioning confirmation module is used to determine the time difference between the electromagnetic signal waveform and the vibration signal waveform. Check whether t has reached the minimum stable value and confirm the ground location directly above the cable fault point; The depth calculation module is used to calculate the burial depth of cable fault points.

10. A cable fault precise location system based on waveform analysis according to claim 9, characterized in that, The path planning module includes: The sampling point setting unit is used to set several sampling points along the estimated path direction of the cable under test; The mobile guidance unit is used to guide the operator to move the signal acquisition probe at the sampling point in a direction perpendicular to the estimated path; The polarity monitoring unit is used to monitor the polarity changes of the electromagnetic signal waveform in real time during vertical movement. The positioning unit is used to record the first critical point when the polarity of the electromagnetic signal reverses for the first time, and to record the second critical point when the polarity of the electromagnetic signal reverses for the second time while moving along the route close to the current sampling point. The midpoint of the line connecting the first critical point and the second critical point is taken as the point directly above the cable. The path fitting unit is used to generate the actual route path of the cable under test by using a curve fitting algorithm based on the position directly above the cable determined at each sampling point.

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