A cable fault detection method and a portable cable fault detector

Abstract

The present invention discloses a cable fault detection method and a portable cable fault detector. The method includes the following steps: S1: grounding the metal sheaths at both ends of the cable line, disassembling the interconnection part of the interconnection middle box, and short-circuiting the metal sheaths at both ends of each phase cable head; S2: sending a low-voltage pulse and recording the reflected waveform; S3: releasing a high-voltage pulse so that the cable fault point is instantly broken down to form a high-voltage fault; S4: sending another low-voltage pulse within the duration of the high-voltage fault at the fault point, recording the reflected waveform at the fault point; S5: comparing the two reflected waveforms to obtain the location of the fault point. The present invention measures the fault point through an improved secondary pulse method, with a small ranging error and positioning accuracy that meets on-site needs. It effectively identifies the type of low-voltage cable fault and accurately identifies the location of the fault, greatly reducing the time for fault finding, alleviating the pressure on fault maintenance personnel, shortening the troubleshooting time, and improving economic and social benefits.

Description

Technical Field

[0001] The present invention relates to the field of cable fault detection, and in particular to a cable fault detection method and a portable cable fault detector. Background Art

[0002] Cables are important media for transmitting electrical signals and information. They are mainly and widely used in the fields of electricity, national defense, construction, transportation, communications, automobiles, and chemicals. The normal operation of cable systems provides an important basic guarantee for modern industrial production and social operations.

[0003] With the increasing intelligence of power grids, power cables are widely used in urban underground grids and submarine transmission networks. However, as cables age, the probability of failure increases. Factors such as installation wear during cable line construction and long-term corrosion in the application environment pose a risk of cable failure. Troubleshooting requires significant manpower and material resources. Failure to promptly correct a fault can result in significant economic losses and negative social impacts.

[0004] To ensure the basic safety of urban power supply, purely manual inspections are far from meeting actual needs, and the level of cable fault detection needs to be gradually improved. Traditional cable detection is mainly offline detection, such as time domain reflectometry. This method is a great improvement over manual inspection, but its disadvantage is that it can only be detected offline, that is, the power must be turned off before fault location and detection can be performed. This method affects normal production and life, and the timeliness of detection is greatly reduced. At the same time, offline detection is difficult to perform batch cable inspections. For residential electricity use, offline detection must be performed under the premise of powering off the cable. This requires the power supply department to cut off the power supply to a certain area for fault detection, which inevitably causes large economic losses. For flashover faults that occur during cable operation, the time of occurrence is uncertain and cannot be reproduced during offline detection, which poses a hidden danger to cable operation. Summary of the Invention

[0005] In response to the problem of inaccurate detection of cable fault points in the prior art, the present invention provides a cable fault detection method and a portable cable fault detector. Based on the pulse reflection, the fault ranging and positioning device for underground line breakage, mixed lines (short circuit), and severe insulation defects can determine the precise location of the cable fault point based on the approximate location of the cable fault point analyzed by the cable fault tester host.

[0006] The following are the technical solutions of the present invention.

[0007] A cable fault detection method comprises the following steps:

[0008] S1: Ground the metal sheaths at both ends of the cable line, remove the interconnection part of the interconnection middle box, and short-circuit the metal sheaths at both ends of each phase cable head;

[0009] S2: Send a low-voltage pulse and record the reflected waveform;

[0010] S3: Release high-voltage pulses, causing the cable fault point to be instantly broken down, forming a high-voltage fault;

[0011] S4: Send another low-voltage pulse during the duration of the high-voltage fault at the fault point and record the reflected waveform at the fault point;

[0012] S5: Compare the two reflected waveforms to obtain the location of the fault point.

[0013] By comparing the waveforms of the two low-voltage pulse measurements and aligning them with the starting point, it can be found that the waveforms before the cable fault point overlap well, while the waveform curves after the fault point diverge.

[0014] Preferably, result verification is also included: adjusting the pulse width of the low-voltage pulse and the high-voltage pulse, repeating steps S2-S5 several times, and recording whether the position of the fault point obtained each time is within the error range. If not, an error is reported.

[0015] Preferably, after the error is reported, the location of the fault point is detected using an acoustic-magnetic synchronization method.

[0016] Preferably, the acoustic-magnetic synchronization method for detecting the position of the fault point includes: adjusting the discharge spherical gap to a certain position, and then raising the voltage until the spherical gap automatically discharges. When the fault point breaks through and discharges, the propagation time difference between the sound and the magnetic field multiplied by the propagation speed of the sound is the distance between the fault point and the detection point.

[0017] The present invention also provides a portable cable fault detector, comprising:

[0018] The operation box is used by operators to ground the metal sheaths at both ends of the cable line, dismantle the interconnection part of the interconnection intermediate box, and short-circuit the metal sheaths at both ends of each phase cable head;

[0019] The low-voltage pulse unit is used to send a low-voltage pulse to the cable under test and record the reflected waveform; it is also used to send another low-voltage pulse during the duration of the high-voltage fault at the fault point and record the reflected waveform at the fault point;

[0020] High-voltage pulse unit, used to release high-voltage pulses, causing the cable fault point to be instantly broken down to form a high-voltage fault;

[0021] The processing unit is connected to the low-voltage pulse unit and the high-voltage pulse unit, and is used to compare the two reflected waveforms to obtain the location of the fault point; the display is connected to the processing unit and is used to display information;

[0022] The operation panel is connected to the display and the processing unit and is used to input operation instructions.

[0023] Preferably, the processing unit includes an MSP430 single-chip microcomputer and its working circuit.

[0024] Preferably, the portable cable fault detector is also used to: adjust the pulse width of the low-voltage pulse and the high-voltage pulse, repeatedly run the low-voltage pulse unit and the high-voltage pulse unit several times, and record whether the position of the fault point obtained each time is within the error range. If it is not within the error range, an error is reported.

[0025] Preferably, it also includes an acoustic-magnetic receiving unit, which is used for: after the operator adjusts the discharge spherical gap to a certain position and increases the voltage to the point where the spherical gap automatically discharges, when the fault point breaks through and discharges, the acoustic-magnetic receiving unit multiplies the propagation time difference between the sound and the magnetic field by the propagation speed of the sound to obtain the distance between the fault point and the detection point.

[0026] Traditional secondary pulse wiring maintains the same wiring pattern at the cross-connection box, with one end of the cable's metal sheath grounded. Because the impedance of the cables changes at the interconnection points, the transmitted pulse waves become complex, affecting the waveforms at the three joints and at the fault location, thus interfering with the interpretation of the results. Measurement results from the improved secondary pulse location method show minimal ranging error and satisfactory positioning accuracy.

[0027] The substantial benefits of this invention include: Using an improved secondary pulse method to measure fault points, the ranging error is minimal, and the positioning accuracy meets on-site requirements. It effectively identifies the type and location of low-voltage cable faults. By using secondary pulse reflections to identify a variety of common fault types, such as cable breaks, short circuits, and severe insulation failures, it significantly reduces fault-finding time, alleviates the pressure on repair personnel, shortens troubleshooting time, and improves economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a flow chart of a method according to an embodiment of the present invention;

[0029] Figure 2 It is a system block diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions will be clearly and completely described below in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0031] It should be understood that in various embodiments of the present invention, the size of the sequence number of each process does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0032] It should be understood that in the present invention, "include" and "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products or apparatuses.

[0033] It should be understood that in the present invention, "multiple" refers to two or more. "And / or" is only a description of the association relationship of associated objects, indicating that three relationships can exist. For example, and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. "Contains A, B and C", "Contains A, B, C" means that A, B, and C are all included, "Contains A, B or C" means that one of A, B, and C is included, and "Contains A, B and / or C" means that any one, any two, or any three of A, B, and C are included.

[0034] The technical solution of the present invention is described in detail below with reference to specific embodiments. The embodiments may be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0035] The main electrical positioning technologies include pulse reflection method, impulse current method, time of arrival method, amplitude-frequency mapping method and phase difference method. Among them, pulse reflection method and impulse current method are the most commonly used positioning methods.

[0036] 1) Low-voltage pulse reflection method: This method uses the reflection of radio waves in transmission lines to measure distance by measuring the time difference between the transmitted pulse and the reflected pulse at the fault point. It is primarily used to detect low-resistance and open-circuit faults in cables, as well as standard measurements of the entire cable length. It has high measurement accuracy and is widely used. However, it cannot measure high-resistance or flashover faults.

[0037] Working Principle: During testing, a low-voltage pulse is injected into the cable. This pulse propagates along the cable to an impedance mismatch point, such as a short circuit, fault point, or intermediate joint. The pulse is reflected and sent back to the measurement point where it is recorded by the instrument. The time difference between the transmitted pulse and the reflected pulse on the waveform is Δt, which corresponds to the time it takes for the pulse to travel between the measurement point and the impedance mismatch point. Given the pulse velocity v in the cable, the distance L to the impedance mismatch point can be calculated using the following formula:

[0038] L=v·Δt / 2 (1)

[0039] By identifying the polarity of the reflected pulse, the nature of the fault can be determined. The reflected pulse of an open circuit fault has the same polarity as the transmitted pulse, while the reflected pulse of a short circuit fault has the opposite polarity to the transmitted pulse. As shown in formula (1), the wave velocity of the pulse in the cable is critical for accurately calculating the fault distance. When the wave velocity value of the cable is unknown, the following method can be used for measurement: If the length of the cable under test is known, the wave velocity in the cable can be calculated based on the time Δt between the transmitted pulse and the reflected pulse at the cable terminal: v = 2·L / Δt2) Pulse voltage method: The pulse voltage method first breaks down the cable fault under a DC or pulse high voltage signal, and then measures the distance by recording the time required for the discharge pulse to travel back and forth between the measurement point and the fault point. It includes DC high voltage flashover measurement method (direct flashover method) and impulse high voltage flashover measurement method (impact flashover method). A major advantage of the pulse voltage method is that it does not need to burn through high resistance and flashover faults, and directly uses the instantaneous pulse signal generated by the fault breakdown. The test speed is fast and the measurement process is also simplified. It is a major advancement in cable fault testing technology.

[0040] Therefore, the low-voltage pulse method has a clear waveform, making it easier for engineers to identify faults, but it is only applicable to low-resistance faults. The pulse voltage method, on the other hand, is applicable to a variety of faults, but its waveform is more difficult to identify. Combining these two techniques results in the secondary pulse method, which is an improvement on this method.

[0041] Example:

[0042] A cable fault detection method comprising: Figure 1 The following steps are shown:

[0043] S1: Ground the metal sheaths at both ends of the cable line, remove the interconnection part of the interconnection middle box, and short-circuit the metal sheaths at both ends of each phase cable head;

[0044] S2: Send a low-voltage pulse and record the reflected waveform;

[0045] S3: Release high-voltage pulses, causing the cable fault point to be instantly broken down, forming a high-voltage fault;

[0046] S4: Send another low-voltage pulse during the duration of the high-voltage fault at the fault point and record the reflected waveform at the fault point;

[0047] S5: Compare the two reflected waveforms to obtain the location of the fault point.

[0048] By comparing the waveforms of the two low-voltage pulse measurements and aligning them with the starting point, it can be found that the waveforms before the cable fault point overlap well, while the waveform curves after the fault point diverge.

[0049] This embodiment also includes result verification: adjusting the pulse width of the low-voltage pulse and the high-voltage pulse, repeating steps S2-S5 several times, and recording whether the position of the fault point obtained each time is within the error range. If not, an error is reported.

[0050] In this embodiment, after an error is reported, the location of the fault point is detected using an acoustic-magnetic synchronization method.

[0051] In this embodiment, the acoustic-magnetic synchronization method is used to detect the location of the fault point, including: adjusting the discharge spherical gap to a certain position, and then increasing the voltage until the spherical gap automatically discharges. When the fault point breaks through and discharges, the distance between the fault point and the detection point is obtained by multiplying the propagation time difference between the sound and the magnetic field by the propagation speed of the sound.

[0052] The principle and key technologies of secondary pulse ranging: Under the action of a sufficiently high pulse voltage, a high-resistance fault generates a short-circuit emission when an arc passes through it, resulting in a waveform with the same characteristics as a short-circuit test. That is, the polarity of the test pulse is opposite to the waveform of the echo pulse at the fault point. When the voltage reaches a certain value, when the voltage is very high and the field strength is sufficiently strong, a small number of free electrons in the dielectric collide and dissociate under the action of the electric field. The free electrons collide with neutral molecules, become excited and dissociate, and generate new electrons and positive ions. This means that the cable fault point suddenly fails, the voltage at the fault point drops sharply to near zero, and the current suddenly increases, generating a discharge arc. According to arc theory, the apparent resistance of this arc is very small, which can be considered a low-resistance or short-circuit fault.

[0053] The key technology of the secondary pulse method is to avoid the fault point being reflected by the multi-step voltage reflection wave and the inherent large cosine oscillation waveform generated by the fault point during the high-voltage fault. The instrument then sends another pulse during the duration of the high-voltage fault at the fault point to record the reflected pulse at the fault point.

[0054] By displaying the two measured waveforms simultaneously on the screen and aligning them with the starting point, it is clear that the waveforms begin to overlap completely before the fault point. Once the waveform passes the fault point, it diverges significantly. Furthermore, the inflection point at the fault point is very distinct, a typical waveform for a short-circuit fault echo, which effectively explains the fault distance. Almost all high-impedance faults exhibit this single characteristic waveform.

[0055] First, a low-voltage pulse is transmitted to the faulty cable. As long as the ground resistance at the fault point is at least five times greater than the cable's wave impedance, the faulty cable is considered an open circuit with respect to the low-voltage pulse. The pulse will not be reflected at high-resistance or flashover faults. The reflected waveform received at the pulse release end is equivalent to that of a cable with good core insulation. Only when the tested cable is not fully grounded will the low-voltage pulse transmitted by the IRG be reflected at the terminal, allowing the total line length to be calculated. To accurately locate the fault, a surge voltage generator (SSG) is required to deliver a high-voltage pulse, causing a transient breakdown at the fault point. This changes the cable's resistance, and the resulting low-voltage pulse is then reflected back to the near end from the breakdown point. Comparing the two curves allows the fault's precise location to be determined.

[0056] When the applied pulse signal is transmitted from the initial end of the cable to the terminal, it encounters an obstacle (impedance mismatch point), which may be a wire connection or a break in the cable, and reflects the pulse wave back to the initial end. The fault location formula that can be obtained is:

[0057] s is the distance to the fault point, v is the velocity of the pulse wave in the cable medium, t0 is the time when the pulse is emitted, and t1 is the time when the reflected pulse arrives.

[0058] The calculation formula of the cable's wave impedance is:

[0059]

[0060] Where: L0 is the inductance per unit length of the cable, and C0 is the capacitance per unit length of the cable.

[0061] After pre-locating the fault point using the secondary pulse method, the discharge spherical gap is adjusted to a specific position and the voltage is increased until the gap automatically discharges. The oscilloscope or the sound of the discharge can be used to determine whether the fault point has broken down and discharged. When the fault point breaks down and discharges, the sound of the spherical gap discharge is loud and crisp. Surveyors can then carry an acoustic-magnetic receiver to the calculated location for detection. The precise location of the fault point can be determined based on the sound intensity and frequency of the magnetic field signal.

[0062] In order to improve the accuracy of cable main insulation fault location through the improved secondary pulse method, the metal sheaths at both ends of the cable line are grounded, the interconnection part of the interconnection intermediate box is dismantled, and the metal sheaths at both ends of each phase cable head are short-circuited.

[0063] Traditional secondary pulse wiring maintains the same wiring pattern at the cross-connection box, with one end of the cable's metal sheath grounded. Because the impedance of the cables changes at the interconnection points, the transmitted pulse waves become complex, affecting the waveforms at the three joints and at the fault location, thus interfering with the interpretation of the results. Measurement results from the improved secondary pulse location method show minimal ranging error and satisfactory positioning accuracy.

[0064] This embodiment also provides a portable cable fault detector, comprising:

[0065] The operation box is used by operators to ground the metal sheaths at both ends of the cable line, dismantle the interconnection part of the interconnection intermediate box, and short-circuit the metal sheaths at both ends of each phase cable head;

[0066] The low-voltage pulse unit is used to send a low-voltage pulse to the cable under test and record the reflected waveform; it is also used to send another low-voltage pulse during the duration of the high-voltage fault at the fault point and record the reflected waveform at the fault point;

[0067] High-voltage pulse unit, used to release high-voltage pulses, causing the cable fault point to be instantly broken down to form a high-voltage fault;

[0068] The processing unit is connected to the low-voltage pulse unit and the high-voltage pulse unit, and is used to compare the two reflected waveforms to obtain the location of the fault point; the display is connected to the processing unit and is used to display information;

[0069] The operation panel is connected to the display and the processing unit and is used to input operation instructions.

[0070] In this embodiment, the processing unit includes an MSP430 single chip microcomputer and its working circuit.

[0071] In this embodiment, the portable cable fault detector is also used to: adjust the pulse width of the low-voltage pulse and the high-voltage pulse, repeatedly run the low-voltage pulse unit and the high-voltage pulse unit several times, and record whether the position of the fault point obtained each time is within the error range. If it is not within the error range, an error is reported.

[0072] In this embodiment, an acoustic-magnetic receiving unit is also included. The acoustic-magnetic receiving unit is used to: after the operator adjusts the discharge spherical gap to a certain position and increases the voltage to the point where the spherical gap automatically discharges, when the fault point breaks through and discharges, the acoustic-magnetic receiving unit multiplies the propagation time difference between the sound and the magnetic field by the propagation speed of the sound to obtain the distance between the fault point and the detection point.

[0073] Specifically, the portable cable fault detector of this embodiment is as follows: Figure 2As shown, the system utilizes a keyboard circuit, logic circuit, cable detection circuit, LCD display circuit, alarm circuit, data storage circuit, and an MSP430 single-chip microcomputer control system. All ICs in this system operate at 3.3V DC. Two test modes are designed for this system: standard test and custom test.

[0074] Standard test:

[0075] First, enter the core value via the keyboard, then access the cable detection interface. The MSP430 cable detection circuit sends a signal to the logic circuit, which then sends the result to the MSP430 microcontroller, which in turn sends the data to the storage circuit. After the test is complete, the data in the data storage circuit is read for judgment, and the error alarm circuit is activated and displayed.

[0076] Custom detection:

[0077] Due to the difference in standard detection, there is no need to enter the core value for custom detection, and there is no need to worry about one line corresponding to multiple lines or one line corresponding to the alarm. Other cables are tested according to the current detection cable. If there is any difference, the alarm circuit will be turned on and the error result will be displayed.

[0078] During system testing, the pulse generation circuit primarily transmits pulse signals to the cable. A key aspect of pulse generation circuit design is the ability to adjust the pulse width. Because this design requires flexible pulse width adjustment, a programmable device is used to generate pulses. The use of a programmable device ensures flexibility and convenience in pulse generation, resulting in a clean pulse waveform.

[0079] Theoretically, the adjustable range of the pulse width of the pulse generating circuit designed in this scheme is from one programmable clock cycle to N clock cycles, and the pulse width can be flexibly adjusted.

[0080] Due to the cable's resistance and the associated noise interference, the fault traveling wave signal in the cable will be weakened. If it is smaller than the sampling resolution, the acquisition circuit will have difficulty collecting it. Therefore, the transmitted pulse signal also has a significant impact on the fault traveling wave signal. Therefore, it is necessary to design a pulse receiving circuit at the sampling circuit point. Its main purpose is to amplify the fault traveling wave signal and reduce external interference on the fault traveling wave signal, allowing the sampling circuit to collect a complete fault traveling wave signal.

[0081] The amplifier circuit is used to amplify the weakened fault traveling wave signal to an appropriate amplitude for subsequent sampling circuit collection. At the same time, in order to eliminate the influence of the pulse generation circuit on the amplifier as the main component of the amplifier circuit, a clamping process is performed before the amplifier, that is, the input of the amplifier is limited.

[0082] The generation of detection pulses, sampling by the ADC08100, and the asynchronous FIFO data buffer constitute a high-speed A / D data acquisition system. This requires high-speed time coordination of various signals, which requires a special clock unit to coordinate so that the circuit operates at the correct time.

[0083] In the FPGA, this clock module can be easily customized to generate the A / D sampling clock, the asynchronous memory read and write clock, and the pulse generation module count clock. All clocks are synchronized by a high-speed clock, and the entire system runs synchronously with the same start signal, thus ensuring sampling timing requirements.

[0084] After the DSP program is started, the system clock unit and AD unit should be initialized first. After the clock and AD unit initialization is completed, in order to ensure that CAN communication and reading and writing are normal, a self-test is performed. If the results are normal, it waits for the upper computer to execute instructions.

[0085] After receiving a command to execute a task, the system matches the host and local numbers in the command. If the results match, the command is executed. If the results do not match, a second judgment is made. This second judgment determines whether it is the designated main command and executes the joint tester test process according to the designated conditions. Otherwise, no judgment is made and the task is not executed. The system continues to wait for information from the upstream computer.

[0086] In order to explore the accuracy of the improved secondary pulse method and the traditional secondary pulse connection method in measuring cable main insulation faults, we conducted two tests according to the scheme in Table 1. In the tests, a 110kV line terminal main insulation short-circuit fault was simulated.

[0087] Table 1 Comparison of experimental schemes

[0088] Positioning method Grounding mode Traditional secondary pulse connection mode The cross-connection remains unchanged, and one end of the metal sheath is grounded Improved secondary pulse method The cross-connected metal sleeves are short-circuited and the metal sleeves at both ends of the cable are grounded.

[0089] Traditional secondary pulse wiring involves maintaining the same wiring pattern at the cross-connection box, with one end of the cable's metal sheath grounded. This changes the impedance of the cables at the interconnection points, complicating the pulse transmission wave. This affects the waveforms at the three connectors and at the fault location, thus interfering with the interpretation of the results.

[0090] The improved secondary pulse location method shows that the fault location is 2.32 km away, with a ranging error of 6.83%. This accuracy generally meets the needs of the site. Accurately locating cable faults requires the use of methods such as step pressure and synchronous acousto-magnetic methods.

[0091] The substantial effects of this embodiment include:

[0092] The improved secondary pulse method is used to measure fault points, achieving minimal ranging error and accurate positioning that meets on-site requirements. This method effectively identifies the type and location of low-voltage cable faults. By using secondary pulse reflections to identify common fault types such as cable breaks, short circuits, and severe insulation failures, it significantly reduces fault-finding time, alleviates the pressure on maintenance personnel, shortens troubleshooting time, and improves economic and social benefits.

[0093] The new cable fault detection theory - the secondary pulse method is adopted. Not only is the waveform clear and easy to judge, but it can also provide a method with high measurement accuracy and high speed for high resistance and flashover faults, so it has a wide range of applications.

[0094] The cable fault detection device boasts advantages in terms of accuracy and speed in fault identification using test pulses. It is also portable, reducing labor burden and significantly improving the efficiency of fault finding and repair. Furthermore, the device's design takes into account its ability to handle complex cable faults, ensuring it meets mechanical strength requirements.

[0095] Based on the advanced secondary pulse cable detection method, it is easy for staff to judge the fault and the time of finding the fault is greatly shortened, which reduces the economic losses caused by power outages and has great economic benefits.

[0096] With the improvement of the accuracy of cable fault location, the excavation area of the direct buried cable fault point will be greatly reduced, which can reduce the amount of engineering work and reduce cost expenditure.

[0097] Through the description of the above implementation methods, technical personnel in the relevant field can understand that for the convenience and simplicity of description, only the division of the above-mentioned functional modules is used as an example. In actual applications, the above-mentioned functions can be distributed and completed by different functional modules as needed, that is, the internal structure of the specific device can be divided into different functional modules to complete all or part of the functions described above.

[0098] In the embodiments provided in this application, it should be understood that the disclosed structures and methods can be implemented in other ways. For example, the embodiments of the structure described above are merely illustrative. For example, the division of modules or units is only a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another structure, 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 an indirect coupling or communication connection through some interface, structure or unit, which can be electrical, mechanical or other forms.

[0099] Units described as separate components may or may not be physically separate, and components shown as units may be one physical unit or multiple physical units, that is, they may be located in one place or distributed in multiple places. Some or all of the units may be selected according to actual needs to achieve the purpose of the present embodiment.

[0100] In addition, the functional units in the embodiments of the present application 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 units may be implemented in the form of hardware or software functional units.

[0101] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a readable storage medium. Based on this understanding, the technical solution of the embodiment of the present application is essentially 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 product, which is stored in a storage medium and includes several instructions for enabling a device (which can be a single-chip microcomputer, chip, etc.) or a processor (processor) to execute all or part of the steps of the various embodiments of the present application. The aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0102] The above content is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A cable fault detection method, characterized in that: The following steps are involved: S1: Ground the metal sheaths at both ends of the cable line and short-circuit the metal sheaths at both ends of each phase cable head by removing the interconnection part of the interconnection middle box; S2: Send a low-voltage pulse and record the reflected waveform; S3: Release high-voltage pulses, causing the cable fault point to be instantly broken down, forming a high-voltage fault; S4: Send another low-voltage pulse during the duration of the high-voltage fault at the fault point and record the reflected waveform at the fault point; S5: Compare the two reflected waveforms to obtain the location of the fault point.

2. A cable fault detection method according to claim 1, characterized in that: It also includes result verification: adjusting the pulse width of the low-voltage pulse and the high-voltage pulse, repeating steps S2-S5 several times, and recording whether the position of the fault point obtained each time is within the error range. If not, an error is reported.

3. A cable fault detection method according to claim 2, characterized in that: After the error is reported, the location of the fault point is detected using an acoustic-magnetic synchronization method.

4. A cable fault detection method according to claim 3, characterized in that: The acoustic-magnetic synchronization method for detecting the location of the fault point includes: adjusting the discharge spherical gap to a certain position, then increasing the voltage until the spherical gap automatically discharges. When the fault point breaks through and discharges, the distance between the fault point and the detection point is obtained by multiplying the propagation time difference between the sound and the magnetic field by the propagation speed of the sound.

5. A portable cable fault detector, characterized in that: include: The operation box is used by operators to ground the metal sheaths at both ends of the cable line and short-circuit the metal sheaths at both ends of each phase cable head by dismantling the interconnection part of the interconnection middle box; The low-voltage pulse unit is used to send a low-voltage pulse to the cable under test and record the reflected waveform; it is also used to send another low-voltage pulse during the duration of the high-voltage fault at the fault point and record the reflected waveform at the fault point; High-voltage pulse unit, used to release high-voltage pulses, causing the cable fault point to be instantly broken down to form a high-voltage fault; The processing unit is connected to the low-voltage pulse unit and the high-voltage pulse unit to compare the two reflected waveforms and obtain the location of the fault point; a display connected to the processing unit and configured to display information; The operation panel is connected to the display and the processing unit and is used to input operation instructions.

6. A portable cable fault detector according to claim 5, characterized in that: The processing unit includes an MSP430 single chip microcomputer and a working circuit thereof.

7. The portable cable fault detector according to claim 5, characterized in that: The portable cable fault detector is also used to: adjust the pulse width of the low-voltage pulse and the high-voltage pulse, repeatedly run the low-voltage pulse unit and the high-voltage pulse unit several times, and record whether the position of the fault point obtained each time is within the error range. If it is not within the error range, an error is reported.

8. The portable cable fault detector according to claim 7, characterized in that: It also includes an acoustic-magnetic receiving unit, which is used to: after the operator adjusts the discharge spherical gap to a certain position and increases the voltage to the point where the spherical gap automatically discharges, when the fault point breaks through and discharges, the acoustic-magnetic receiving unit multiplies the propagation time difference between the sound and the magnetic field by the propagation speed of the sound to obtain the distance between the fault point and the detection point.

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