A power cable fault locator and a control method thereof

Abstract

The application relates to the technical field of electrical detection equipment, and particularly provides a power cable fault locator and a control method thereof. The fault locator comprises a detection host, a signal emission probe, a receiving probe and a moving part, and the detection host is internally provided with a pulse reflection mode and a step voltage mode. In the pulse reflection mode, the detection host emits a pulse detection signal to the inside of a cable to be detected through the signal emission probe, the receiving probe receives a reflected pulse signal, and the detection host obtains a preliminary fault positioning point of the power cable according to the pulse reflection signal. In the step voltage mode, the detection host emits a detection current through the signal emission probe, obtains a step voltage signal sequence, and the detection host obtains a final fault positioning point according to the step voltage signal sequence. The application combines the pulse reflection method and the step voltage method, is favorable for realizing high-precision on-site positioning of various cable faults, takes into account portability and detection precision, and improves cable fault repair efficiency.

Description

Technical Field

[0001] This invention relates to the field of electrical testing equipment technology, and more specifically, to a power cable fault locator and its control method. Background Technology

[0002] Power cables are an important component of power transmission and distribution systems. During operation, they are prone to faults such as short circuits, grounding, and wire breaks due to external damage, insulation aging, and moisture. Quickly locating the fault point is crucial to ensuring power supply.

[0003] Currently, cable fault location instruments used in the industry are mainly divided into two types: desktop and simple portable. Desktop fault location instruments have high detection accuracy, but they are large and heavy, require an external power supply, and cannot be used for on-site detection in complex outdoor terrains (such as mountains and suburbs). Simple portable location instruments are small and easy to carry, but their detection principle is simple. They can only locate obvious faults such as short circuits and open wires, and cannot locate hidden faults such as high-resistance grounding and insulation aging. In addition, their detection accuracy is low, and the fault location error is often more than 5 meters, requiring maintenance personnel to further excavate and investigate, which increases the time and cost of emergency repairs.

[0004] Therefore, it is necessary to develop a portable power cable fault locator that balances portability and detection accuracy to improve the efficiency of cable fault repair. Summary of the Invention

[0005] Based on this, in order to achieve high-precision on-site location of various cable faults while considering portability and detection accuracy, and to improve the efficiency of cable fault repair, this invention provides a power cable fault locator and its control method, the specific technical solution of which is as follows: A power cable fault locator includes a detection host, a signal transmitting probe, a receiving probe, and a moving part. The detection host has built-in pulse reflection mode and step voltage mode. In the pulse reflection mode, the signal transmitting probe is clamped at both ends of the cable to be tested. The detection host transmits a pulse detection signal into the cable to be tested through the signal transmitting probe. The receiving probe receives the reflected pulse signal and feeds it back to the detection host. The detection host obtains the preliminary fault location point of the power cable based on the pulse reflection signal. In the step voltage mode, the signal transmitting probe is connected to the grounding end of the cable under test. The detection host transmits a detection current through the signal transmitting probe and moves the receiving probe through the moving part to obtain the step voltage signal sequence and feed it back to the detection host. The detection host obtains the final fault location point based on the step voltage signal sequence.

[0006] The power cable fault locator, by setting up dual modes of pulse reflection and step voltage, can cover various cable faults such as short circuit, open circuit, high resistance grounding, and insulation aging, eliminating detection blind spots and solving the problem of limited detection types of existing instruments. At the same time, it adopts a handheld and portable design, which is suitable for complex terrains such as outdoor mountainous areas and suburbs, and takes into account both portability and detection accuracy.

[0007] In summary, the power cable fault locator combines the pulse reflection method and the step voltage method, which is conducive to achieving high-precision on-site location of various cable faults, while taking into account portability and detection accuracy, and improving the efficiency of cable fault repair.

[0008] Preferably, the detection host includes: The mode switching module is used to respond to user input mode switching commands and switch detection modes. The data processing module is used to process the received reflected pulse signal and step voltage signal sequence; The fault detection module is used to detect and locate cable fault points based on the processed reflected pulse signal and step voltage signal sequence.

[0009] Preferably, the data processing module obtains the propagation speed and reflection time of the received reflected pulse signal and sends them to the fault detection module. The fault detection module obtains the distance between the fault point and the detection point based on the propagation speed and reflection time of the pulse signal to obtain a preliminary fault location point.

[0010] Preferably, the data processing module further obtains the maximum value of the step voltage signal intensity based on the received step voltage signal sequence and sends it to the fault detection module, and the fault detection module obtains the final fault location point based on the maximum value of the step voltage signal intensity.

[0011] A control method for a power cable fault locator, applied to the aforementioned power cable fault locator, includes the following steps: S1, In pulse reflection mode, the signal transmitting probe is clamped at both ends of the cable to be tested. The detection host transmits a pulse detection signal into the cable to be tested through the signal transmitting probe. The receiving probe receives the reflected pulse signal and feeds it back to the detection host. The detection host obtains the preliminary fault location point of the power cable based on the pulse reflection signal. S2, in step voltage mode, the signal transmitting probe is connected to the grounding end of the cable under test. The detection host transmits the detection current through the signal transmitting probe and moves the receiving probe through the moving part to obtain the step voltage signal sequence and feed it back to the detection host. The detection host obtains the final fault location point based on the step voltage signal sequence.

[0012] Preferably, the specific method for obtaining the preliminary fault location point of a power cable based on the pulse reflection signal includes the following steps: S11, obtain the pulse propagation speed and ambient temperature of the cable model corresponding to the cable under test under standard operating conditions, correct the pulse propagation speed according to the ambient temperature, and obtain the actual propagation speed of the pulse signal. S12, obtain the transmission time of the pulse detection signal and the reception time of the reflected pulse signal, and obtain the reflection time based on the transmission time and reception time; S13. Obtain the distance between the fault point and the detection point based on the actual propagation speed and reflection time, and obtain the preliminary fault location point based on the distance.

[0013] Preferably, the specific method for obtaining the reflection time based on the transmission time and the reception time includes the following steps: S121, Based on the power cable fault locator, test a standard calibration cable section of known length to obtain the actual round-trip time of the pulse signal in the standard calibration cable section; S122, obtain the standard round-trip time of the signal based on the length of the standard calibration cable segment and the actual propagation speed of the pulse signal, and obtain the total time offset of the system based on the actual round-trip time of the signal and the standard round-trip time of the signal. S123, obtain the reflection time based on the transmission time, reception time, and total system time offset.

[0014] Preferably, the specific method for obtaining the step voltage signal sequence includes the following steps: S21, obtain the absolute lateral distance between the receiving probe and the initial fault location point, and obtain the distance attenuation coefficient based on the absolute lateral distance; S22, obtain the overall transimpedance gain of the power cable fault locator, obtain the expected step voltage amplitude based on the detection current amplitude, the overall transimpedance gain and the distance attenuation coefficient, and obtain the step voltage signal sequence based on the expected step voltage amplitude; Among them, the distance attenuation coefficient is used to characterize the physical law that the step voltage decreases exponentially with the distance from the initial fault location point.

[0015] Preferably, the specific method for obtaining the expected step voltage amplitude includes the following steps: S221, obtain the real-time working height of the receiving probe above the ground and the ground clearance at which the coupling step voltage of the receiving probe is optimal, and obtain the operating height compensation value based on the real-time working height and ground clearance to compensate for the influence of the change in the height of the receiving probe on the pulse signal receiving strength. S222 obtains the basic step voltage amplitude by multiplying the detected current amplitude by the transimpedance gain of the whole machine, and compensates and corrects the basic step voltage amplitude according to the distance attenuation coefficient and the operating height compensation value to obtain the expected step voltage amplitude.

[0016] Preferably, the operating height compensation value is expressed as: 1 - height attenuation coefficient × (real-time working height - ground clearance) / ground clearance. Attached Figure Description

[0017] The invention will be further understood from the following description taken in conjunction with the accompanying drawings. The components in the drawings are not necessarily drawn to scale, but rather the emphasis is on illustrating the principles of the embodiments. In different views, the same reference numerals designate corresponding parts.

[0018] Figure 1 This is a schematic diagram of the overall structure of a power cable fault location device according to one embodiment of the present invention; Figure 2 This is a block diagram of the system composition and signal transmission of a power cable fault locator according to an embodiment of the present invention; Figure 3 This is a schematic diagram illustrating the working principle of the pulse reflection mode of a power cable fault locator in one embodiment of the present invention; Figure 4 This is a schematic diagram illustrating the working principle of the step mode of a power cable fault locator in one embodiment of the present invention. Figure 5 This is a schematic diagram of the panel structure of the detection host in one embodiment of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to its embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of protection of the invention.

[0020] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly attached to the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0022] In this invention, "first" and "second" do not represent a specific quantity or order, but are merely used to distinguish names.

[0023] like Figures 1-5 As shown, an embodiment of the present invention provides a power cable fault locator, including a detection host, a signal transmitting probe, a receiving probe, and a moving component. The detection host has built-in pulse reflection mode and step voltage mode.

[0024] As a preferred technical solution, the detection host includes a mode switching module, a data processing module, and a fault detection module.

[0025] The mode switching module is used to switch the detection mode in response to the user's input mode switching command; the data processing module is used to process the received reflected pulse signal and step voltage signal sequence; the fault detection module is used to detect and locate the cable fault point based on the processed reflected pulse signal and step voltage signal sequence.

[0026] Specifically, this power cable fault locator is a portable power cable fault locator, suitable for on-site fault location of medium and low voltage power cables of 10kV and below. It has a handheld portable design, weighs ≤2kg, and has dimensions of 20cm×10cm×5cm. It adopts a combination design of detection host, signal transmitting probe, receiving probe, and handheld telescopic rod, and combines the dual detection principles of pulse reflection method and step voltage method to achieve high-precision location of various cable faults.

[0027] In the pulse reflection mode, the signal transmitting probe is clamped at both ends of the cable to be tested. The detection host transmits a pulse detection signal into the cable to be tested through the signal transmitting probe. The receiving probe receives the reflected pulse signal and feeds it back to the detection host. The detection host obtains the preliminary fault location point of the power cable based on the pulse reflection signal.

[0028] In the step voltage mode, the signal transmitting probe is connected to the grounding end of the cable under test. The detection host transmits a detection current through the signal transmitting probe and moves the receiving probe through the moving part to obtain the step voltage signal sequence and feed it back to the detection host. The detection host obtains the final fault location point based on the step voltage signal sequence.

[0029] The data processing module obtains the propagation speed and reflection time of the received reflected pulse signal and sends them to the fault detection module. The fault detection module obtains the distance between the fault point and the detection point based on the propagation speed and reflection time of the pulse signal to obtain a preliminary fault location point. Simultaneously, the data processing module also obtains the maximum step voltage signal strength based on the received step voltage signal sequence and sends it to the fault detection module. The fault detection module obtains the final fault location point based on the maximum step voltage signal strength.

[0030] Specifically, the main unit is the core of the instrument. It uses an aluminum alloy shell and has a built-in fault detection module, data processing module, display screen, and rechargeable lithium battery. The front has a high-definition LCD screen and simple operation buttons, which can display the fault type, fault point distance, and detection waveform. It has two built-in detection modes (pulse reflection mode and step voltage mode) that can be switched with one button.

[0031] The signal transmitting probe connects to the detection host via a data cable and can be clipped onto the terminals at both ends of the cable to transmit detection pulse signals into the cable. It is compatible with cable terminals of different specifications. The moving part is a handheld telescopic rod, and the receiving probe has a magnetic design that attaches to the top of the handheld telescopic rod. It is used to receive reflected pulse signals and step voltage signals generated by cable fault points. The probe has a built-in high-sensitivity sensor that can capture weak signals.

[0032] The handheld telescopic pole is made of telescopic carbon fiber material with a telescopic range of 0.5m-2m, making it easy to adjust the position of the receiving probe in complex outdoor terrain (such as ditches and green belts) without having to bend over or climb. The rechargeable lithium battery is a high-capacity fast-charging lithium battery with a capacity of 10000mAh and a battery life of ≥8 hours. It supports fast charging and can also be used as an emergency power bank to power mobile phones and other devices.

[0033] The magnetic receiving probe can be replaced with a clamp-on receiving probe to be suitable for fault detection in overhead cable sections; the high-definition LCD screen can be equipped with Bluetooth projection function to project the detection data to mobile phones / tablets for easy viewing by multiple people; based on the large-capacity lithium battery, a solar charging panel can be added to be suitable for long-term emergency repairs outdoors without charging conditions; the pulse reflection method can be replaced with the time domain reflection method (TDR) to further improve the detection accuracy of high-resistance grounding faults.

[0034] In summary, the power cable fault locator, by setting up dual modes of pulse reflection and step voltage, can cover various cable faults such as short circuits, open circuits, high-resistance grounding, and insulation aging, eliminating detection blind spots and solving the problem of limited detection types in existing instruments. At the same time, its handheld and portable design is suitable for complex terrains such as outdoor mountains and suburbs, balancing portability and detection accuracy.

[0035] In summary, the power cable fault locator combines the pulse reflection method and the step voltage method, which is conducive to achieving high-precision on-site location of various cable faults, while taking into account portability and detection accuracy, and improving the efficiency of cable fault repair.

[0036] An embodiment of the present invention also provides a control method for a power cable fault locator, applied to the aforementioned power cable fault locator, comprising the following steps: S1, in pulse reflection mode, the signal transmitting probe is clamped at both ends of the cable to be tested. The detection host transmits a pulse detection signal into the cable to be tested through the signal transmitting probe. The receiving probe receives the reflected pulse signal and feeds it back to the detection host. The detection host obtains the preliminary fault location point of the power cable based on the pulse reflection signal.

[0037] Specifically, in pulse reflection mode (suitable for cable faults such as short circuits, open circuits, and high-resistance grounding), the signal transmitting probe is first clamped onto the terminals at both ends of the faulty cable. The detection host is then turned on and switched to pulse reflection mode. The detection host then transmits a high-frequency pulse signal into the cable through the transmitting probe. The signal propagates inside the cable and generates a reflected signal when it encounters a fault point. The reflected pulse signal is then received by the receiving probe and transmitted to the detection host for data analysis. Finally, the data processing module calculates the distance between the fault point and the detection point based on the propagation speed and reflection time of the pulse signal, with a positioning accuracy of ±0.5 meters. The detection waveform and fault distance are displayed on the screen to obtain the preliminary fault location point.

[0038] S2, in step voltage mode, the signal transmitting probe is connected to the grounding end of the cable under test. The detection host transmits the detection current through the signal transmitting probe and moves the receiving probe through the moving part to obtain the step voltage signal sequence and feed it back to the detection host. The detection host obtains the final fault location point based on the step voltage signal sequence.

[0039] Specifically, in step voltage mode (suitable for on-site excavation and location of cable grounding faults): after determining the approximate distance to the fault point through pulse reflection mode, the signal transmitting probe is connected to the cable grounding end, and the system is switched to step voltage mode; then, the signal transmitting probe emits a weak, constant detection current to the ground, generating a step voltage at the fault point; maintenance personnel hold a telescopic pole and move the receiving probe close to the ground, the receiving probe captures the step voltage signal sequence on the ground, and displays the signal strength on the detection host; when the receiving probe moves directly above the fault point, the step voltage signal strength reaches its maximum value, and the detection host issues an audible and visual alert, achieving precise location of the fault point.

[0040] In one embodiment, the specific method for obtaining the preliminary fault location point of a power cable based on the pulse reflection signal includes the following steps: S11: Obtain the pulse propagation speed and ambient temperature of the cable model corresponding to the cable under test under standard operating conditions, correct the pulse propagation speed according to the ambient temperature, and obtain the actual propagation speed of the pulse signal.

[0041] The propagation speed of a high-frequency pulse signal in a specific type of cable depends on the cable's insulation material, structure, and other factors. This pulse propagation speed is the pulse propagation speed of the corresponding cable model at a standard temperature of 25°C. It can be pre-stored in the instrument's database and retrieved by the user when selecting the cable model; it is a factory calibration constant.

[0042] The correction of pulse propagation speed based on ambient temperature is as follows: First, a temperature correction coefficient is obtained to compensate for the deviation in pulse propagation speed caused by the change in the dielectric constant of the cable insulation when the ambient temperature deviates from the standard 25℃. Generally, when the ambient temperature is higher than 25℃, the temperature correction coefficient is slightly less than 1, and when it is lower than 25℃, the temperature correction coefficient is slightly greater than 1. Then, the actual propagation speed is obtained by multiplying the temperature correction coefficient by the pulse propagation speed. For example, the temperature correction coefficient = 1 - insulation medium temperature coefficient × (real-time ambient temperature - standard ambient temperature). The insulation medium temperature coefficient is determined by the cable insulation material and is pre-stored in the database according to the cable model. The typical value is 0.0002-0.0005 / ℃, that is, for every 1℃ increase in temperature, the wave velocity decreases by approximately 0.02% to 0.05%.

[0043] S12, obtain the transmission time of the pulse detection signal and the reception time of the reflected pulse signal, and obtain the reflection time based on the transmission time and reception time.

[0044] For the transmission time, the high-precision timing circuit inside the host can latch the time at the rising edge of the pulse transmission drive signal as the timing start point; the high-sensitivity sensor of the receiving probe captures the weak reflected signal, amplifies it and sends it to the threshold comparison circuit, triggering the timing circuit to latch the current time as the receiving time.

[0045] As a preferred technical solution, the specific method for obtaining the reflection time based on the transmission time and the reception time includes the following steps: S121, Based on the power cable fault locator, a standard calibration cable section of known length is tested to obtain the actual round-trip time of the pulse signal in the standard calibration cable section.

[0046] S122, obtain the standard round-trip time of the signal based on the length of the standard calibration cable segment and the actual propagation speed of the pulse signal, and obtain the total time offset of the system based on the actual round-trip time of the signal and the standard round-trip time of the signal.

[0047] S123, obtain the reflection time based on the transmission time, reception time, and total system time offset.

[0048] For example, reflection time = reception time - transmission time - total system time offset. This total system time offset integrates all fixed time delays independent of fault distance, used to compensate for fixed time delays caused by hardware circuitry and probe coupling. Generally, the total time offset covers the following error sources: inherent signal delays in the pulse transmission drive circuit, receiver amplification circuit, and timing circuit; signal transmission delays in the connection line between the host and probe, and contact coupling delays between the probe and cable terminals; fixed offsets in the reflected pulse trigger time caused by probe sensitivity fluctuations and ambient noise.

[0049] S13. Obtain the distance between the fault point and the detection point based on the actual propagation speed and reflection time, and obtain the preliminary fault location point based on the distance.

[0050] Specifically, this distance is equal to (actual propagation speed × reflection time) / 2, which represents the actual distance from the signal transmission point to the cable fault point (such as a short circuit point, break point, or high-resistance grounding point). Thus, by correcting the high-frequency electromagnetic pulse signal using ambient temperature and obtaining the reflection time by coupling the transmission time, reception time, and total system time offset, this invention can adapt to complex and variable outdoor working conditions, ensuring high accuracy even in a portable form factor.

[0051] To enhance dynamic compensation capabilities in strong electromagnetic environments, the system can acquire the real-time signal-to-noise ratio (SNR) of the current reflected signal, the standard SNR reference value, and the SNR-time offset coefficient. Based on these parameters, an SNR compensation value is obtained to dynamically correct trigger time lag caused by electromagnetic interference. Specifically, the real-time SNR of the current reflected signal, which is the ratio of the peak amplitude of the reflected pulse signal to the effective value of the background noise, directly reflects the strength of electromagnetic interference and signal quality in the current environment. This value is calculated in real-time by the host signal processing module. Simultaneously with capturing the reflected pulse, the peak signal amplitude and the noise floor amplitude are measured to calculate the real-time SNR.

[0052] The standard signal-to-noise ratio (SNR) baseline value is the factory-calibrated ideal environmental SNR, typically set to 20, corresponding to a standard laboratory environment free from strong electromagnetic interference. The SNR-time offset coefficient represents the lag in the reflected pulse trigger time for each 1% decrease in the SNR. Generally, with a fixed rising edge slope for the reflected pulse, a lower SNR results in slower effective rising edges due to noise superposition, causing the signal to reach the trigger threshold later. This leads to an overestimation of the measured reception time, necessitating the deduction of this lag. This SNR-time offset coefficient can be calibrated at the factory using a programmable noise source to inject interference of varying intensities under multiple SNR conditions. This calibration matches typical values ​​for different cable types and fault types and is pre-stored in the system.

[0053] For example, the signal-to-noise ratio (SNR) compensation value = SNR - time offset coefficient × (1 - current real-time SNR of reflected signal / standard SNR reference value), and the reflection time = reception time - transmission time - total system time offset - SNR compensation value. In this way, by dynamically compensating for the reflection time in a strongly coupled electromagnetic environment, a two-layer time error compensation system is created, including both fixed system offset and dynamic SNR offset, further improving fault location accuracy.

[0054] In one embodiment, the specific method for obtaining the step voltage signal sequence includes the following steps: S21, obtain the absolute lateral distance between the receiving probe and the initial fault location point, and obtain the distance attenuation coefficient based on the absolute lateral distance.

[0055] Among them, the distance attenuation coefficient is used to characterize the physical law that the step voltage decreases exponentially with the distance from the initial fault location point.

[0056] For example, the distance attenuation coefficient = exp(-soil signal attenuation coefficient × absolute lateral distance). The soil signal attenuation coefficient characterizes the attenuation rate of the step voltage signal propagating in the soil, and its dimension is per meter (m). -1 The higher the value, the faster the signal attenuates with distance; the drier the soil and the higher the resistivity, the higher the value. 3-4 typical soil parameters can be pre-stored in the system, such as those for wetlands, clay, sandy soil, and gravelly soil. Generally, for wetlands, the distance is approximately 0.2-0.5m. -1 Dry sandy soil, approximately 1.0-1.5m. -1 .

[0057] The absolute lateral distance is the absolute value of the lateral distance between the current lateral position of the receiving probe and the initial fault location point. Generally, the step voltage signal is strongest directly above the fault point and attenuates symmetrically to both sides; therefore, the absolute value is used to represent the distance deviation.

[0058] S22, obtain the overall transimpedance gain of the power cable fault locator, obtain the expected step voltage amplitude based on the detection current amplitude, the overall transimpedance gain and the distance attenuation coefficient, and obtain the step voltage signal sequence based on the expected step voltage amplitude.

[0059] In step voltage mode, the detection current amplitude is a constant, weak detection current injected into the grounding terminal of the faulty cable by the detection host through the signal transmission probe, which serves as the excitation source for generating the step voltage. Due to the extreme fluctuations in outdoor soil resistivity, constant current excitation is used instead of constant voltage excitation to ensure the stability of the signal energy injected into the ground and avoid drastic fluctuations in signal strength caused by changes in soil impedance.

[0060] For the transimpedance gain of the entire instrument, the reference value can be derived by back-calculating the actual step voltage amplitude directly above the fault point under the condition of a known constant excitation current. Specifically, a simulated fault grounding electrode can be pre-buried in a standard soil test trench, and the transmitting probe of the locator can be connected to the grounding electrode with the rated excitation current set. Then, the receiving probe can be fixed at the height above the ground where the step voltage effect is optimal, placed directly above the fault point, and the actual step voltage on the ground surface can be measured using a metrology-grade standard potential meter as a true reference. Next, the measured step voltage displayed on the instrument host can be read, and the transimpedance gain of the entire instrument can be adjusted by correcting the digital potentiometer or firmware parameters so that the deviation between the actual step voltage on the ground surface and the measured step voltage is less than 1%. Finally, the probe can be moved back and forth by 0.5m, 1m, and 2m in the vertical direction to verify the matching degree of the attenuation curve, ensuring that the error between the expected value and the measured value is ≤2% in the entire search range. After verification, the final value of the transimpedance gain of the entire instrument can be fixed in the detection host.

[0061] The overall transimpedance gain integrates the signal amplification / attenuation ratio across the entire link from the ground step voltage to the final sampling voltage of the host, with the dimension of ohms. The integrated hardware factors include, but are not limited to, the electric field coupling sensitivity of the magnetic receiver probe, the voltage amplification factor of the signal amplification circuit, the signal loss of the connecting cables, and the baseline value of the coupling efficiency between the probe and the ground.

[0062] As a preferred technical solution, the specific method for obtaining the expected step voltage amplitude includes the following steps: S221: Obtain the real-time working height of the receiving probe above the ground and the ground clearance at which the coupling step voltage of the receiving probe is optimal. Obtain the operating height compensation value based on the real-time working height and the ground clearance to compensate for the influence of changes in the receiving probe height on the pulse signal reception strength.

[0063] For example, the operating height compensation value is expressed as: 1 - height attenuation coefficient × (real-time operating height - ground clearance) / ground clearance.

[0064] The height attenuation coefficient is a dimensionless small constant that quantifies the signal strength attenuation percentage when the probe's height deviates from the optimal height by 1%. It can be calibrated at the factory through standard tests at different heights. Generally, the height attenuation coefficient is between 0.3 and 0.5, meaning that for every 100% deviation of the height from the optimal value, the signal attenuates by 30% to 50%.

[0065] A distance sensor facing the ground can be installed at the end of the telescopic pole, corresponding to the installation position of the receiving probe. This sensor transmits height data back to the main detection unit in real time, thus obtaining the real-time working height of the receiving probe above the ground. The optimal ground clearance for the receiving probe to couple step voltage is generally set at 0.5m.

[0066] S222 obtains the basic step voltage amplitude by multiplying the detected current amplitude by the transimpedance gain of the whole machine, and compensates and corrects the basic step voltage amplitude according to the distance attenuation coefficient and the operating height compensation value to obtain the expected step voltage amplitude.

[0067] The baseline step voltage amplitude determines the theoretical maximum signal reference value directly above the fault point. The final expected step voltage amplitude is positively correlated with the product of the baseline step voltage amplitude, the distance attenuation coefficient, and the operating height compensation value. Thus, by acquiring the baseline step voltage amplitude, and using the initial fault location point obtained through pulse reflection mode as the center, the theoretically detectable step voltage signal strength at different probe positions is calculated. Then, the expected signal curve on the screen is generated, and finally, it is compared in real time with the measured step voltage signal strength. This guides maintenance personnel to find the signal peak and achieve precise location of the cable fault.

[0068] Before or between each test, the system automatically scans the electromagnetic noise level of the current environment and obtains the average amplitude of the background electromagnetic noise through the detection host, which is the noise floor voltage when there is no effective step voltage signal. The noise floor voltage is subtracted from the expected step voltage amplitude in advance to avoid environmental noise being superimposed on the measured step signal, which could cause the system to misjudge the signal as reaching its peak and trigger the audible and visual alert prematurely.

[0069] The system uses the initial fault location point as the center and calculates the expected step voltage amplitude at each location within a certain search range, such as ±3 meters. A symmetrical peak expectation curve is then plotted on the LCD screen. When maintenance personnel move the probe, the screen synchronously displays the measured step signal curve and moves towards the peak value, following the curve. In this way, guided operations can be achieved based on the generated expectation curve.

[0070] When the measured step voltage signal is not less than 0.95 times the expected step voltage amplitude, and the current position is within the allowable range of the preliminary fault location point, the system determines that the probe is directly above the fault point and triggers an audible and visual alarm.

[0071] In summary, the present invention has the following beneficial effects: 1. Handheld and portable design, lightweight, no external power supply required, suitable for complex terrains such as outdoor mountains and suburbs, dual detection modes achieve fault point location accuracy of ±0.5 meters, far exceeding that of existing portable instruments; 2. Dual modes of pulse reflection and step voltage cover various cable faults such as short circuit, open circuit, high resistance grounding, and insulation aging, eliminating detection blind spots and solving the problem of limited detection types in existing instruments; 3. High-precision positioning eliminates the need for further manual excavation and inspection, directly locating the fault point, shortening cable fault repair time, and significantly reducing excavation and labor costs; 4. One-click mode switching and audio-visual fault point prompts allow grassroots maintenance personnel to operate the instrument without professional training, lowering the barrier to entry for instrument use; 5. A 10000mAh high-capacity lithium battery provides ≥8 hours of battery life, supports fast charging and emergency charging, meeting the power supply needs for long-term outdoor emergency repairs, while an anti-interference module ensures detection accuracy in strong electromagnetic environments.

[0072] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0073] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A power cable fault locator, comprising a detection host, a signal transmitting probe, a receiving probe, and a moving component, characterized in that, The detection host has built-in pulse reflection mode and step voltage mode; In the pulse reflection mode, the signal transmitting probe is clamped at both ends of the cable to be tested. The detection host transmits a pulse detection signal into the cable to be tested through the signal transmitting probe. The receiving probe receives the reflected pulse signal and feeds it back to the detection host. The detection host obtains the preliminary fault location point of the power cable based on the pulse reflection signal. In the step voltage mode, the signal transmitting probe is connected to the grounding end of the cable under test. The detection host transmits a detection current through the signal transmitting probe and moves the receiving probe through the moving part to obtain the step voltage signal sequence and feed it back to the detection host. The detection host obtains the final fault location point based on the step voltage signal sequence.

2. The power cable fault locator according to claim 1, characterized in that, The detection host includes: The mode switching module is used to respond to user input mode switching commands and switch detection modes. The data processing module is used to process the received reflected pulse signal and step voltage signal sequence; The fault detection module is used to detect and locate cable fault points based on the processed reflected pulse signal and step voltage signal sequence.

3. The power cable fault locator according to claim 2, characterized in that, The data processing module obtains the propagation speed and reflection time of the received reflected pulse signal and sends them to the fault detection module. The fault detection module obtains the distance between the fault point and the detection point based on the propagation speed and reflection time of the pulse signal to obtain the preliminary fault location point.

4. The power cable fault locator according to claim 3, characterized in that, The data processing module also obtains the maximum value of the step voltage signal intensity based on the received step voltage signal sequence and sends it to the fault detection module. The fault detection module obtains the final fault location point based on the maximum value of the step voltage signal intensity.

5. A control method for a power cable fault locator, applied to the power cable fault locator as described in any one of claims 1-4, characterized in that, Includes the following steps: S1, In pulse reflection mode, the signal transmitting probe is clamped at both ends of the cable to be tested. The detection host transmits a pulse detection signal into the cable to be tested through the signal transmitting probe. The receiving probe receives the reflected pulse signal and feeds it back to the detection host. The detection host obtains the preliminary fault location point of the power cable based on the pulse reflection signal. S2, in step voltage mode, the signal transmitting probe is connected to the grounding end of the cable under test. The detection host transmits the detection current through the signal transmitting probe and moves the receiving probe through the moving part to obtain the step voltage signal sequence and feed it back to the detection host. The detection host obtains the final fault location point based on the step voltage signal sequence.

6. The control method for a power cable fault location instrument according to claim 5, characterized in that, The specific method for obtaining the preliminary fault location point of a power cable based on pulse reflection signals includes the following steps: S11, obtain the pulse propagation speed and ambient temperature of the cable model corresponding to the cable under test under standard operating conditions, correct the pulse propagation speed according to the ambient temperature, and obtain the actual propagation speed of the pulse signal. S12, obtain the transmission time of the pulse detection signal and the reception time of the reflected pulse signal, and obtain the reflection time based on the transmission time and reception time; S13. Obtain the distance between the fault point and the detection point based on the actual propagation speed and reflection time, and obtain the preliminary fault location point based on the distance.

7. The control method for a power cable fault location instrument according to claim 6, characterized in that, The specific method for obtaining the reflection time based on the transmission and reception times includes the following steps: S121, Based on the power cable fault locator, test a standard calibration cable section of known length to obtain the actual round-trip time of the pulse signal in the standard calibration cable section; S122, obtain the standard round-trip time of the signal based on the length of the standard calibration cable segment and the actual propagation speed of the pulse signal, and obtain the total time offset of the system based on the actual round-trip time of the signal and the standard round-trip time of the signal. S123, obtain the reflection time based on the transmission time, reception time, and total system time offset.

8. The control method for a power cable fault location instrument according to claim 7, characterized in that, The specific method for obtaining the step voltage signal sequence includes the following steps: S21, obtain the absolute lateral distance between the receiving probe and the initial fault location point, and obtain the distance attenuation coefficient based on the absolute lateral distance; S22, obtain the overall transimpedance gain of the power cable fault locator, obtain the expected step voltage amplitude based on the detection current amplitude, the overall transimpedance gain and the distance attenuation coefficient, and obtain the step voltage signal sequence based on the expected step voltage amplitude; Among them, the distance attenuation coefficient is used to characterize the physical law that the step voltage decreases exponentially with the distance from the initial fault location point.

9. The control method for a power cable fault location instrument according to claim 8, characterized in that, The specific method for obtaining the expected step voltage amplitude includes the following steps: S221, obtain the real-time working height of the receiving probe above the ground and the ground clearance at which the coupling step voltage of the receiving probe is optimal, and obtain the operating height compensation value based on the real-time working height and ground clearance to compensate for the influence of the change in the height of the receiving probe on the pulse signal receiving strength. S222 obtains the basic step voltage amplitude by multiplying the detected current amplitude by the transimpedance gain of the whole machine, and compensates and corrects the basic step voltage amplitude according to the distance attenuation coefficient and the operating height compensation value to obtain the expected step voltage amplitude.

10. The control method for a power cable fault location instrument according to claim 9, characterized in that, The operating height compensation value is expressed as: 1 - height attenuation coefficient × (real-time working height - ground clearance) / ground clearance.

Images