A method and apparatus for determining a cable sheath protector fault

Abstract

A cable sheath protector fault determination method and device relate to the technical field of cable protector fault detection. The method comprises: acquiring a voltage of a measured cable sheath loop in a preset time period to obtain a voltage time sequence, and determining a pulse reference time point according to the voltage time sequence; analyzing the voltage time sequence to obtain an effective echo starting time; determining an echo search window according to the effective echo starting time, identifying all local extreme points of the voltage time sequence in the echo search window, taking the largest local extreme point as a main candidate feature point, and taking the second largest local extreme point as a backup feature point; calculating time intervals between the main candidate feature point and the backup feature point and the pulse reference time point, and selecting the main candidate feature point or the backup feature point as an echo feature point according to the time intervals; and calculating a distance between a test point and an impedance abnormal point according to the echo feature point. The technical solution provided in the application can improve the accuracy of protector fault detection.

Description

Technical Field

[0001] This application relates to the technical field of cable protector fault detection, specifically to a method and equipment for determining faults in cable sheath protectors. Background Technology

[0002] With the continuous expansion of power systems, power cables are increasingly widely used in transmission networks. The sheath system of power cables, as a crucial component protecting the cable itself, directly impacts the safety and reliability of the entire cable system. When a fault occurs in the cable sheath, it is necessary to promptly and accurately locate the impedance anomaly point for targeted repairs, minimizing power outage time and economic losses.

[0003] Cable sheath protectors are critical devices in cable sheath systems, used to prevent induced voltage and circulating currents in the sheath from harming equipment and personnel. In fault detection of cable sheath protectors, traditional methods primarily rely on monitoring changes in the current within the sheath circuit to determine the fault state. When a ground fault, open circuit fault, or other anomaly occurs in the sheath, the circuit current will exhibit corresponding changes. By analyzing parameters such as the amplitude and frequency of these current signals, a preliminary assessment can be made as to whether a fault exists.

[0004] However, existing fault determination methods for cable sheath protectors based on current monitoring can mainly detect and identify faults, but have limitations in fault location. Although current signals can reflect the overall state changes of the sheath circuit, they lack location-related time information, making it difficult to accurately determine the specific location of impedance anomalies on the cable line. Summary of the Invention

[0005] This application provides a method and equipment for determining faults in cable sheath protectors, which can accurately determine the specific location of the cable sheath protector on the cable line.

[0006] The first aspect of this application provides a method for determining faults in a cable sheath protector, specifically including: The voltage of the cable sheath circuit under test is obtained within a preset time period according to the preset time step, and the voltage time series is obtained. The time point with the largest absolute voltage value in the voltage time series is taken as the pulse reference time point. The blind zone time period is determined based on the pulse reference time point. Starting from the end time of the blind zone time period, the voltage time series is subjected to a first analysis to obtain the candidate echo start time. The voltage time series is then subjected to a second analysis based on the candidate echo start time to obtain the effective echo start time. The echo search window is determined based on the effective echo start time. All local extreme points of the voltage time series are identified in the echo search window. The local extreme point with the largest absolute voltage value is taken as the main candidate feature point, and the local extreme point with the second largest absolute voltage value is taken as the alternative feature point. Calculate the time interval between the main candidate feature point and the alternative feature point and the pulse reference time point, and select the main candidate feature point or the alternative feature point as the echo feature point according to the time interval; The distance between the test point and the impedance anomaly point is calculated based on the pulse reference time point and the echo characteristic point. The test point is the position where the pulse signal is emitted at the pulse reference time point, and the impedance anomaly point is the position where the echo characteristic point is generated on the sheath circuit of the cable under test.

[0007] By employing the above technical solution, the voltage of the tested cable sheath circuit is acquired according to a preset time step to obtain a voltage time series. The time point with the largest absolute voltage value is used as the pulse reference time point, establishing an accurate time reference. By determining the dead zone time period based on the pulse reference time point, and performing the first and second analyses starting from the end of the dead zone time period to obtain the effective echo start time, the influence of interference signals is effectively avoided. By determining the echo search window based on the effective echo start time, all local extreme points are identified, and primary candidate feature points and alternative feature points are set, achieving accurate identification of the echo signal. By calculating the time interval between the primary candidate feature point and alternative feature point and the pulse reference time point, the most suitable echo feature point is selected, ensuring the accuracy of feature point selection. Finally, based on the pulse reference time point and the echo feature points, the distance from the test point to the impedance anomaly point is calculated, achieving accurate location of the cable sheath protector fault.

[0008] Optionally, the step of performing a first analysis on the voltage time series starting from the end of the blind zone time period to obtain the candidate echo start time includes: Starting from the end of the blind zone time period, the noise standard deviation is calculated in the noise segment of the voltage time series, and the noise standard deviation is multiplied by a first multiplier factor to obtain a first detection threshold. The noise segment is the last preset proportion of the preset time period. The system searches for the first time point in the voltage time series where the absolute voltage value is greater than the first detection threshold. If a time point exceeding the first detection threshold is found, the time point is used as the candidate echo start time. If no time point exceeding the first detection threshold is found, the search is repeated according to the second detection threshold to obtain the candidate echo start time. The second detection threshold is the noise standard deviation multiplied by a second multiplier factor, and the second multiplier factor is less than the first multiplier factor.

[0009] By adopting the above technical solution, the noise standard deviation is calculated in the noise segment of the voltage time series and multiplied by a first multiplier factor to obtain the first detection threshold. This establishes an adaptive detection mechanism based on the actual signal noise level, avoiding the problem that a fixed threshold cannot adapt to changes in noise levels under different test environments. By searching for the first time point where the absolute voltage value is greater than the first detection threshold, starting from the end of the dead zone time period, as the echo start time, the true echo signal start position can be effectively identified. When the signal quality is poor and a time point exceeding the first detection threshold cannot be found, this application uses a smaller second multiplier factor to construct a second detection threshold and searches again. This achieves dynamic adjustment of the detection sensitivity, ensuring that the candidate echo start time can be accurately obtained under different signal strength conditions, thus improving the reliability and adaptability of echo signal detection.

[0010] Optionally, the second analysis of the voltage time series based on the candidate echo start time to obtain the effective echo start time includes: Determine whether a preset number of voltage sampling points in the voltage time series after the candidate echo start time meet the signal continuity condition; if the candidate echo start time is obtained based on a first detection threshold, then the signal continuity condition is that the voltage of the preset number of voltage sampling points all exceeds the first detection threshold; if the candidate echo start time is obtained based on a second detection threshold, then the signal continuity condition is that the voltage of the preset number of voltage sampling points all exceeds the second detection threshold. If the signal continuity condition is not met, the candidate echo start time is determined to be noise interference, and the search continues to the next candidate echo start time and the signal continuity condition verification is performed again. If the signal continuity condition is met, then the candidate echo start time is determined to be the valid echo start time.

[0011] By employing the above technical solution, the system determines whether a preset number of voltage sampling points after the candidate echo start time meet the signal continuity condition, effectively distinguishing between the real echo signal and occasional noise interference. When the voltages of all preset number of voltage sampling points exceed the first or second detection threshold, it indicates that the signal has continuous characteristics and conforms to the physical characteristics of a real echo signal. If the signal continuity condition is not met, the candidate echo start time is determined to be noise interference, and the search continues for the next candidate echo start time, avoiding the problem of single-point noise pulses being misidentified as the start point of the echo signal. Through this signal continuity verification mechanism, this application can accurately screen out the real and valid echo start time, eliminating the influence of transient noise and random interference on echo signal identification, and improving the accuracy and reliability of echo start time determination.

[0012] Optionally, after identifying all local extrema of the voltage time series in the echo search window, selecting the local extrema with the largest absolute voltage value as the primary candidate feature point, and the local extrema with the second largest absolute voltage value as the alternative feature points, the method further includes: Calculate the signal-to-noise ratio of each local extremum point, and filter the local extremum points whose signal-to-noise ratio is lower than a preset signal-to-noise ratio threshold to obtain the filtered local extremum points. The new absolute voltage values ​​of the local extrema after each filtering process are recalculated, and the main candidate feature points and the alternative feature points are updated based on the new absolute voltage values.

[0013] By employing the above technical solution, the signal-to-noise ratio (SNR) of each local extremum point can be calculated, enabling quantitative evaluation of signal quality and identification of feature points severely affected by noise. When the SNR falls below a preset threshold, the system automatically filters the corresponding local extremum points, effectively removing noise components and improving signal purity and reliability. After filtering, the absolute voltage value of the local extremum points is recalculated, and the selection of primary and alternative feature points is dynamically updated accordingly, ensuring that the selected feature points possess both significant signal amplitude characteristics and good signal quality. This SNR-oriented filtering optimization strategy effectively suppresses the influence of adverse factors such as electromagnetic interference and system noise in the measurement environment, improving the accuracy and stability of feature point identification. This method achieves adaptive optimization of signal processing, enabling the fault location system to maintain good detection performance in complex field environments, significantly improving the accuracy and reliability of fault location.

[0014] Optionally, the step of calculating the time interval between the primary candidate feature point and the alternative feature point and the pulse reference time point, and selecting the primary candidate feature point or the alternative feature point as the echo feature point based on the time interval, includes: Calculate the first time interval between the primary candidate feature point and the pulse reference time point, and the second time interval between the alternative feature point and the pulse reference time point; Determine whether the first time interval is within a preset effective time interval range, wherein the effective time interval range is determined based on the expected fault distance range of the sheath circuit of the cable under test; If the first time interval is within the effective time interval range, then the main candidate feature point is selected as the echo feature point; If the first time interval is not within the effective time interval range, then it is determined whether the second time interval is within the effective time interval range. If the second time interval is within the effective time interval range, then the candidate feature point is selected as the echo feature point. If the second time interval is not within the effective time interval range, then the location of the impedance anomaly point is output as uncertain.

[0015] By employing the above technical solution, the time interval between the primary candidate feature point and the alternative feature point and the pulse reference time point is calculated. Combined with the expected fault distance range of the tested cable sheath circuit, an effective time interval range is set, thus verifying the validity of the candidate feature points. This method uses a hierarchical judgment strategy, prioritizing the primary candidate feature point. When its time interval does not meet the effective range, it automatically switches to the alternative feature point for verification, ensuring the reliability and rationality of feature point selection. The setting of the effective time interval range is based on the physical characteristics of the tested cable sheath circuit and the expected fault range, effectively eliminating false feature points caused by signal interference, multiple reflections, and other factors. When neither candidate feature point meets the effective time interval requirement, the system outputs an uncertain impedance anomaly location result, avoiding erroneous fault location judgments. This intelligent feature point screening mechanism significantly improves the accuracy and reliability of fault location and reduces the risk of misjudgment.

[0016] Optionally, calculating the distance from the test point to the impedance anomaly point based on the pulse reference time point and the echo characteristic point includes: Calculate the total propagation time from the pulse reference time point to the echo feature point; Based on the total propagation time and the preset voltage propagation speed, the distance between the test point and the impedance anomaly point is calculated. The preset voltage propagation speed represents the propagation rate of the voltage pulse signal in the sheath circuit medium of the cable under test.

[0017] By employing the above technical solution, the total propagation time is obtained by calculating the time difference between the pulse reference time point and the echo characteristic point. This total propagation time accurately reflects the time consumed by the pulse signal to complete the entire propagation process from transmission to reception of the reflected signal in the sheath circuit of the cable under test. Furthermore, the total propagation time is used in conjunction with a preset voltage propagation speed, which is determined based on the dielectric characteristics and structural parameters of the sheath circuit of the cable under test, taking into account the actual propagation characteristics of the signal in a specific cable medium. By converting the round-trip propagation time into a one-way propagation distance, the precise physical distance between the test point and the impedance anomaly point can be obtained. This solution fully utilizes the propagation characteristics of the time-domain reflected signal, transforming time-domain information into spatial-domain information. This avoids the problem of inaccurate positioning that cannot be achieved by traditional methods such as current monitoring alone, significantly improving the accuracy and reliability of fault location for cable sheath protectors. It provides clear location guidance for subsequent maintenance work and effectively reduces the time cost and manpower investment in fault diagnosis.

[0018] Optionally, after calculating the distance from the test point to the impedance anomaly point, the method further includes: The current change trend of the sheath protector in the sheath circuit of the cable under test is monitored, and current data at multiple time points are collected within a preset monitoring period to form current time series data; The leakage current result is obtained by comparing the current timing data with a preset leakage current threshold. The number of actions of the sheath protector within a preset time window is counted. The number of actions is the cumulative number of times the sheath protector's protection actions are triggered. If the leakage current result is that there is no leakage current and the number of actions is less than a preset action number threshold, the sheath protector is determined to be operating normally. If the leakage current result is that there is leakage current or the number of actions exceeds or equals the preset action number threshold, the sheath protector is determined to be faulty. Based on the leakage current results and the number of operations, the fault mode of the cable sheath protector is determined, and a comprehensive fault diagnosis report including the fault mode and the distance between the test point and the impedance anomaly point is output.

[0019] By adopting the above technical solution, after spatially locating the fault, a multi-dimensional fault diagnosis mechanism is established by collecting current time-series data within a preset monitoring period and comparing it with a preset leakage current threshold, combined with the statistical analysis of the number of actions of the sheath protector. This mechanism, through dual criteria of leakage current detection and action frequency analysis, can comprehensively reflect the operating status of the sheath protector. It can not only identify leakage current anomalies caused by insulation degradation but also detect frequent actions caused by mechanical faults. By jointly judging the leakage current results with the action frequency threshold, a clear judgment standard is formed: "no leakage current and normal action frequency" is judged as normal operation, and "leakage current or abnormal action frequency" is judged as a fault, avoiding misjudgments that may be caused by a single indicator. The final comprehensive fault diagnosis report integrates the fault mode judgment results and precise distance information, providing maintenance personnel with complete information on the fault type and location, significantly improving the pertinence and efficiency of fault handling, achieving a qualitative leap from "fault discovery" to "fault understanding" and then to "precise handling," and greatly reducing the maintenance cost and power outage risk of the power system.

[0020] In a second aspect, this application provides a cable sheath protector fault determination device, which includes: one or more processors and a memory; the memory is coupled to the one or more processors, and the memory is used to store computer program code, the computer program code including computer instructions, and the one or more processors call the computer instructions to cause the cable sheath protector fault determination device to perform the method as described in the first aspect and any possible implementation thereof.

[0021] Thirdly, this application provides a computer program product containing instructions that, when run on a cable sheath protector fault determination device, cause the cable sheath protector fault determination device to perform the method described in the first aspect and any possible implementation thereof.

[0022] Fourthly, this application provides a computer-readable storage medium including instructions that, when executed on a cable sheath protector fault determination device, cause the cable sheath protector fault determination device to perform the method described in the first aspect and any possible implementation thereof. Attached Figure Description

[0023] Figure 1 This is a system architecture diagram of a cable sheath protector fault determination system provided in an embodiment of this application; Figure 2 This is a flowchart illustrating a method for determining faults in a cable sheath protector provided in an embodiment of this application. Figure 3This is an exemplary hardware structure diagram of a cable sheath protector fault determination device provided in an embodiment of this application. Detailed Implementation

[0024] To enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0025] In the description of the embodiments of this application, the words "for example" or "for instance" are used to indicate examples, illustrations, or explanations. Any embodiment or design that is described as "for example" or "for instance" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design options. Rather, the use of the words "for example" or "for instance" is intended to present the relevant concepts in a specific manner.

[0026] In the description of the embodiments of this application, the term "multiple" means two or more. For example, multiple systems means two or more systems, and multiple screen terminals means two or more screen terminals. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. The terms "comprising," "including," "having," and variations thereof all mean "including but not limited to," unless otherwise specifically emphasized.

[0027] Figure 1 An architecture for a cable sheath protector fault determination system is shown. For example... Figure 1 As shown, the system architecture may include a signal acquisition device 011, a network 012, and an electronic device 013. The network 012 provides a data transmission link between the signal acquisition device 011 and the electronic device 013. The network 012 may include various connection types, such as wired or wireless communication links or fiber optic cables.

[0028] Signal acquisition device 011 can send time-domain reflection signal data and cable parameter information to electronic device 013 via network 012. Signal acquisition device 011 is mainly responsible for sending test pulse signals to the sheath circuit of the cable under test, acquiring time-domain reflection echo signals, obtaining basic cable parameters, and initiating fault detection data transmission requests according to preset rules.

[0029] Signal acquisition device 011 is hardware, which can be a test device with time domain reflectance testing and signal acquisition functions, including but not limited to basic components such as pulse generator, signal acquisition device, time domain reflectometer, and cable tester.

[0030] Electronic device 013 is responsible for receiving time-domain reflection signal data and cable parameter information and performing comprehensive analysis and processing, including core functions such as echo signal preprocessing, pulse reference time point identification, effective echo start time determination, echo feature point extraction, and fault distance calculation. Electronic device 013 can adaptively execute fault location algorithms based on echo signal characteristics and cable propagation characteristics, calculate the optimal feature point selection strategy, and combine it with preset judgment rules to ultimately achieve accurate determination of the fault location of the cable sheath protector. These analysis and processing results can be used to improve the accuracy and detection efficiency of cable fault location.

[0031] It should be noted that electronic devices can be either hardware or software. When an electronic device is hardware, it can be implemented as a distributed cluster of multiple electronic devices or as a single electronic device. When an electronic device is software, it can be implemented as multiple software programs or software modules (e.g., multiple software programs or software modules used to provide distributed processing) or as a single software program or software module. No specific limitations are set here.

[0032] It should be understood that Figure 1 The number of signal acquisition devices 011, network 012, and electronic devices 013 shown is merely illustrative. Depending on implementation needs, there can be any number of signal acquisition devices 011, network 012, and electronic devices 013. In particular, if the time-domain reflection signal data does not need to be transmitted remotely, the above system architecture may exclude network 012 and include only signal acquisition devices 011 or electronic devices 013.

[0033] This application provides a method for determining faults in cable sheath protectors, referencing... Figure 2 , Figure 2 This is a flowchart illustrating a method for determining faults in a cable sheath protector according to an embodiment of this application, including steps S101 to S105, as follows: S101: Obtain the voltage of the cable sheath circuit under test within a preset time period according to the preset time step, and obtain the voltage time series. Take the time point with the largest absolute voltage value in the voltage time series as the pulse reference time point.

[0034] In the embodiments of this application, the preset time step represents a fixed time interval for voltage sampling in the time domain, such as collecting voltage data once every 1 microsecond or 10 microseconds, to ensure that the time domain resolution of the voltage signal meets the accuracy requirements of fault detection.

[0035] Specifically, the voltage of the cable sheath circuit under test is continuously sampled according to a preset time step. Starting from the beginning of the preset time period, a voltage value is recorded after each time step until the end of the preset time period. All sampled voltage values ​​are arranged in chronological order to form a voltage time series. The absolute value of each voltage value in the voltage time series is calculated, that is, negative voltages are converted into corresponding positive values. The entire voltage time series is traversed, and the magnitude of all voltage absolute values ​​is compared one by one. The sampling point with the largest absolute voltage value is found, and the time corresponding to the sampling point is determined as the pulse reference time point.

[0036] S102: Determine the blind zone time period based on the pulse reference time point. Starting from the end of the blind zone time period, perform a first analysis on the voltage time series to obtain the candidate echo start time. Perform a second analysis on the voltage time series based on the candidate echo start time to obtain the effective echo start time.

[0037] In this embodiment, the blind time period refers to the time interval after the pulse signal is transmitted where the effective echo signal cannot be accurately detected due to factors such as system response and near-end reflection. For example, the first tens of microseconds after the pulse reference time point, which is used to avoid misidentifying the transmitted pulse itself or near-end interference as a fault echo signal.

[0038] Specifically, the start and end times of the blind zone time period are determined by extending a preset blind zone time length backward from the pulse reference time point. Starting from the end time of the blind zone time period, the noise standard deviation is calculated in the noise segment of the voltage time series. The noise standard deviation is multiplied by a first multiplier factor to obtain a first detection threshold, where the noise segment is the last preset proportion of the preset time period. Starting from the end time of the blind zone, the first time point in the voltage time series with an absolute voltage value greater than the first detection threshold is searched. If a time point exceeding the first detection threshold is found, this time point is taken as the echo start time. If no time point exceeding the first detection threshold is found, a second detection threshold is used to re-search for candidate echo start times. The second detection threshold is the noise standard deviation multiplied by a second multiplier factor, and the second multiplier factor is less than the first multiplier factor. It is then determined whether a preset number of voltage sampling points in the voltage time series after the candidate echo start time meet the signal continuity condition. The signal continuity condition is that the voltage of all preset number of voltage sampling points exceeds either the first or the second detection threshold. If the signal continuity condition is not met, the candidate echo start time is determined to be noise interference, and the search continues to the next candidate echo start time to re-verify the signal continuity condition. If the signal continuity condition is met, the candidate echo start time is determined to be a valid echo start time.

[0039] Based on the above embodiments, as an optional embodiment, the step of performing a first analysis on the voltage time series to obtain the candidate echo start time, starting from the end of the blind zone time period, may specifically include the following steps: S201: Starting from the end of the blind zone time period, calculate the noise standard deviation in the noise segment of the voltage time series, multiply the noise standard deviation by the first multiplier factor to obtain the first detection threshold, and the noise segment is the last preset proportion of the preset time period.

[0040] In the embodiments of this application, the noise segment represents the time interval in the voltage time series that is mainly composed of environmental noise and system noise. It is usually selected as the last preset proportion of a preset time period, such as the last 10% of the entire measurement time period, to provide clean noise statistical characteristics for calculating the detection threshold.

[0041] Specifically, subsequent signal analysis and processing begin from the end of the blind zone time period. The time range of the noise segment is located within the voltage time series; that is, a corresponding time interval is truncated from the end of the preset total time period according to a preset ratio. The voltage values ​​of all voltage sampling points within the noise segment are extracted, and the average value of these voltage values ​​is calculated. Then, the squared difference between each voltage value and the average value is calculated. All squared differences are summed and divided by the number of sampling points minus one. Finally, the square root of the result is taken to obtain the noise standard deviation. The calculated noise standard deviation is multiplied by a first multiplier factor to obtain the first detection threshold.

[0042] S202: Search for the first time point in the voltage time series where the absolute value of the voltage is greater than the first detection threshold. If a time point exceeding the first detection threshold is found, the time point is used as the candidate echo start time. If no time point exceeding the first detection threshold is found, the search is performed again according to the second detection threshold to obtain the candidate echo start time. The second detection threshold is the noise standard deviation multiplied by the second multiplier factor, and the second multiplier factor is less than the first multiplier factor.

[0043] In this embodiment, the second detection threshold represents an alternative detection standard used when the first detection threshold is too strict and fails to detect a valid echo signal. It is obtained by multiplying the noise standard deviation by a smaller second multiple factor, and is used to improve the detection sensitivity of weak echo signals.

[0044] Specifically, starting from the end of the blind zone period, the absolute voltage value of each sampling point in the voltage time series is checked sequentially, and each absolute voltage value is compared with a first detection threshold. If the first sampling point with an absolute voltage value greater than the first detection threshold is found during the search, the search is immediately stopped, and the time corresponding to that sampling point is determined as the candidate echo start time. If no case is found where the absolute voltage value exceeds the first detection threshold after traversing all sampling points from the end of the blind zone to the end of the preset time period, the noise standard deviation is multiplied by a second multiplier factor to obtain a second detection threshold, where the value of the second multiplier factor is less than the value of the first multiplier factor. Starting again from the end of the blind zone period, the same search method is used to find the time point in the voltage time series where the first absolute voltage value is greater than the second detection threshold, and the searched time point is determined as the candidate echo start time.

[0045] Based on the above embodiments, as an optional embodiment, the step of performing a second analysis on the voltage time series according to the candidate echo start time to obtain the effective echo start time may specifically include the following steps: S301: Determine whether a preset number of voltage sampling points in the voltage time series after the candidate echo start time meet the signal continuity condition; if the candidate echo start time is obtained based on the first detection threshold, then the signal continuity condition is that the voltage of the preset number of voltage sampling points all exceeds the first detection threshold; if the candidate echo start time is obtained based on the second detection threshold, then the signal continuity condition is that the voltage of the preset number of voltage sampling points all exceeds the second detection threshold.

[0046] In this embodiment, signal continuity is a verification criterion used to distinguish between real echo signals and random noise interference. By checking whether the voltage amplitude of multiple consecutive sampling points after the candidate echo start time continuously exceeds the detection threshold, it is ensured that the detected signal has the continuity characteristics that an echo signal should have, rather than occasional noise spikes.

[0047] Specifically, starting from the sampling point corresponding to the candidate echo start time, a preset number of consecutive voltage sampling points are extracted sequentially, for example, 5 or 10 consecutive sampling points are extracted as verification samples. For each extracted voltage sampling point, the absolute value of its voltage is calculated and compared with the corresponding detection threshold. The detection threshold is selected according to the method of determining the candidate echo start time, choosing either a first detection threshold or a second detection threshold. If the candidate echo start time is obtained by searching using the first detection threshold, the first detection threshold is used during verification; if the candidate echo start time is obtained by searching using the second detection threshold, the second detection threshold is used during verification. It is checked whether the absolute voltage value of each sampling point in the preset number of voltage sampling points exceeds the corresponding detection threshold. Only when the absolute voltage values ​​of all sampling points exceed the detection threshold is the signal continuity condition considered met.

[0048] S302: If the signal continuity condition is not met, the candidate echo start time is determined to be noise interference, and the search continues to the next candidate echo start time and the signal continuity condition is verified again; if the signal continuity condition is met, the candidate echo start time is determined to be a valid echo start time.

[0049] In the embodiments of this application, the effective echo start time represents the start time of the real echo signal confirmed after signal continuity verification, which is different from the false signal trigger point that may be caused by random noise, and provides a reliable time reference for subsequent distance measurement calculation.

[0050] Specifically, if the absolute voltage value of any one of the preset number of voltage sampling points does not exceed the corresponding detection threshold, the signal corresponding to the current candidate echo start time is determined to be noise interference rather than a true echo signal. Starting from the next sampling point after the current candidate echo start time, the search method described above continues to search for the next time point in the remaining part of the voltage time series where the absolute voltage value exceeds the detection threshold, and this time point is taken as a new candidate echo start time. The signal continuity condition verification is repeated for the new candidate echo start time to check whether the voltage of the subsequent preset number of sampling points all exceed the corresponding detection threshold. The above search and verification process is repeated until a candidate echo start time that meets the signal continuity condition is found, or the entire valid time range is searched. When the absolute voltage values ​​of the preset number of voltage sampling points all exceed the corresponding detection threshold, it is confirmed that the current candidate echo start time corresponds to a true echo signal, and this time point is officially determined as a valid echo start time.

[0051] S103: Determine the echo search window based on the effective echo start time, identify all local extreme points of the voltage time series in the echo search window, and take the local extreme point with the largest absolute voltage value as the main candidate feature point and the local extreme point with the second largest absolute voltage value as the alternative feature point.

[0052] In this embodiment, the echo search window represents a time range set based on the effective echo start time, used to limit the search area for echo signal feature points, avoiding the introduction of irrelevant signal interference due to a global search across the entire voltage time series. The primary candidate feature point and the alternative feature point represent the locations of the largest and second largest voltage amplitudes in the echo signal, respectively, providing crucial reference points for subsequent echo signal analysis and distance calculation.

[0053] Specifically, starting from the effective echo start time, a preset time length is extended to form an echo search window. This time length is determined based on the typical duration and signal characteristics of the echo signal, for example, extending the time interval by 10 to 50 sampling points, ensuring that the window range covers the complete echo signal without including excessive background noise. Within the defined echo search window, all voltage sampling points are traversed. By comparing the voltage values ​​of each sampling point with its adjacent sampling points, all local extrema, including local maxima and local minima, are identified. For a local maximum, its voltage value is greater than the voltage values ​​of the preceding and following sampling points; for a local minimum, its voltage value is less than the voltage values ​​of the preceding and following sampling points. The absolute voltage values ​​of all local extrema are calculated and sorted in descending order of absolute voltage value. The local extrema with the largest absolute voltage value is determined as the primary candidate feature point, and the local extrema with the second largest absolute voltage value is determined as the alternative feature points.

[0054] Based on the above embodiments, as an optional embodiment, S103: after identifying all local extreme points of the voltage time series in the echo search window, and taking the local extreme point with the largest absolute voltage value as the main candidate feature point and the local extreme point with the second largest absolute voltage value as the candidate feature point, the method further includes updating the main candidate feature point and the candidate feature point, which may specifically include the following steps: S401: Calculate the signal-to-noise ratio of each local extremum point, and filter the local extremum points whose signal-to-noise ratio is lower than the preset signal-to-noise ratio threshold to obtain the filtered local extremum points.

[0055] In this embodiment, the signal-to-noise ratio (SNR) represents the ratio of the signal intensity to the background noise intensity at a local extremum point, used to evaluate the reliability of the extremum point as a valid feature point. The filtered local extremum points represent high-quality extremum points retained after SNR screening, eliminating false extremum points that may be caused by noise and improving the accuracy of feature point identification.

[0056] Specifically, for each local extremum identified within the echo search window, voltage sampling points within a preset range around the extremum are selected as the signal region, for example, 3 to 5 sampling points before and after the extremum. The average absolute voltage value of all sampling points within the signal region is calculated as the signal strength of the extremum. A time period outside the echo search window is selected as the noise reference region. This region should be outside the influence range of the echo signal, typically selecting several sampling points before the effective echo start time. The standard deviation or root mean square value of the absolute voltage values ​​of all sampling points within the noise reference region is calculated as the background noise intensity. The signal strength of each local extremum is divided by the background noise intensity to obtain the signal-to-noise ratio (SNR) of that extremum. The SNR of each local extremum is compared with a preset SNR threshold, which is determined based on the application scenario and accuracy requirements, typically set to a value range of 3 to 10. For local extremums with an SNR lower than the preset SNR threshold, they are determined to be false extremums caused by noise interference, removed from the local extremum list, and the filtering process is completed to obtain the filtered local extremums.

[0057] S402: Recalculate the new absolute voltage values ​​of the local extrema after each filtering process, and update the main candidate feature points and alternative feature points based on the new absolute voltage values.

[0058] In this embodiment, the new absolute voltage value represents the corrected voltage amplitude of the local extremum point after filtering, and this value may change due to signal processing during the filtering process. The updated primary candidate feature points and alternative feature points are re-determined based on a high-quality set of extremum points filtered by signal-to-noise ratio, ensuring that the selected feature points have higher signal reliability and measurement accuracy.

[0059] Specifically, for each local extremum retained after signal-to-noise ratio filtering, its voltage value in the voltage time series is reacquired. Since filtering may smooth or denoise the original voltage signal, the absolute voltage value of each retained extremum needs to be recalculated to reflect the true signal strength after filtering. All filtered local extrema are sorted in descending order of their new absolute voltage values, forming a new priority sequence. From the rearranged sequence, the local extremum with the largest new absolute voltage value is re-identified as the updated primary candidate feature point, replacing the previously identified primary candidate feature point. The local extremum with the second largest new absolute voltage value is re-identified as the updated alternative feature point, replacing the previously identified alternative feature point.

[0060] S104: Calculate the time interval between the main candidate feature point and the alternative feature point and the pulse reference time point, and select the main candidate feature point or alternative feature point as the echo feature point according to the time interval.

[0061] In this embodiment, the echo feature point represents the key time node finally selected from the main candidate feature point and alternative feature point for fault distance calculation. This feature point corresponds to the characteristic time in the time domain of the echo signal reflected back from the fault location.

[0062] Specifically, the time differences between the primary candidate feature point and the alternative feature point and the pulse reference time point are calculated to obtain the corresponding time intervals. These time intervals reflect the signal propagation time from the start of the echo signal to each candidate feature point.

[0063] The effective time interval range is determined based on the length of the cable sheath loop under test, the dielectric properties, and the expected fault distance range. The lower limit of this range typically corresponds to the signal propagation time at the nearest possible fault location, while the upper limit corresponds to the signal propagation time at the farthest possible fault location.

[0064] The time interval of the primary candidate feature point is compared with the effective time interval range. If the time interval is within the effective range, it indicates that the time delay corresponding to the primary candidate feature point conforms to the physical expectation and has high credibility. Therefore, the primary candidate feature point is selected as the echo feature point.

[0065] If the time interval of the primary candidate feature point exceeds the valid time interval range, it is further determined whether the time interval of the alternative feature points falls within this range. If the time interval of the alternative feature points falls within the valid range, the alternative feature points are selected as echo feature points, implementing a feature point switching mechanism. If the time interval of the alternative feature points also exceeds the valid range, it indicates that none of the currently identified feature points meet the physical constraints, resulting in an uncertain location of the system output impedance anomaly. This prompts the operator to adjust the measurement parameters or check the measurement environment.

[0066] Based on the above embodiments, as an optional embodiment, S104: the step of calculating the time interval between the main candidate feature point and the candidate feature point and the effective echo start time, and selecting the main candidate feature point or the candidate feature point as the echo feature point according to the time interval, may specifically include the following steps: S501: Calculate the first time interval between the primary candidate feature point and the pulse reference time point, and the second time interval between the candidate feature point and the pulse reference time point; determine whether the first time interval is within the preset effective time interval range, the effective time interval range being determined based on the expected fault distance range of the cable sheath circuit under test.

[0067] In this embodiment, the first time interval represents the time difference between the primary candidate feature point and the pulse reference time point, and the second time interval represents the time difference between the alternative feature point and the pulse reference time point. These two time intervals are used to quantify the echo signal propagation time delay corresponding to different candidate feature points.

[0068] Specifically, a first time interval is obtained by calculating the difference between the time position of the primary candidate feature point and the time position of the pulse reference time point. This time interval reflects the propagation time from the start of the echo signal to the arrival of the primary candidate reflected signal. Similarly, a second time interval is obtained by calculating the difference between the time position of the candidate feature point and the time position of the pulse reference time point. This time interval provides a time reference for the candidate schemes.

[0069] The effective time interval range is determined based on the length of the cable sheath loop, the dielectric properties, and the expected fault distance range. The lower limit of this range typically corresponds to the signal propagation time at the nearest possible fault location, while the upper limit corresponds to the signal propagation time at the farthest possible fault location. For example, for a cable with an expected fault distance range of [L_min, L_max] and a signal propagation speed of v, the effective time interval range can be set to [2×L_min / v, 2×L_max / v], where the coefficient 2 considers the round-trip propagation process of the signal from the test end to the impedance anomaly point and back.

[0070] The first time interval is compared with the effective time interval range. If the first time interval is within the effective range, it indicates that the time delay corresponding to the main candidate feature point meets the physical constraints of the tested cable sheath circuit and has high reliability. If the first time interval exceeds the effective range, it is further determined whether the second time interval is within the range to decide whether to use the candidate feature point as the final echo feature point.

[0071] S502: If the first time interval is within the effective time interval range, then the main candidate feature point is selected as the echo feature point; if the first time interval is not within the effective time interval range, then it is determined whether the second time interval is within the effective time interval range. If the second time interval is within the effective time interval range, then the alternative feature point is selected as the echo feature point; if the second time interval is not within the effective time interval range, then the location of the output impedance anomaly point is uncertain.

[0072] In this embodiment of the application, the final echo feature point is determined by a hierarchical judgment logic to ensure that the selected feature point meets the physical constraints of the sheath circuit of the cable under test.

[0073] Specifically, the first step is to determine whether the first time interval is within the valid time interval range. If the first time interval is within the valid time interval range, it indicates that the time delay corresponding to the primary candidate feature point meets the physical constraints of the expected fault distance range, and has high reliability and accuracy. Therefore, the primary candidate feature point is selected as the echo feature point. The primary candidate feature point usually corresponds to the time node with the largest amplitude or the most obvious signal characteristics in the echo signal, and its reliability is relatively high.

[0074] If the first time interval is not within the valid time interval range, it indicates that the primary candidate feature point may correspond to signals from noise interference, multiple reflections, or other non-target fault locations, and is not suitable for fault location calculation. In this case, the backup mechanism is activated to further determine whether the second time interval is within the valid time interval range.

[0075] If the second time interval is within the valid time interval range, it indicates that the candidate feature point meets the physical constraints and can be used as a reliable time reference. Therefore, the candidate feature point is selected as the echo feature point. This candidate switching mechanism can effectively cope with the situation of failure to identify the main feature point and improve the robustness of the system.

[0076] If the second time interval is also not within the valid time interval range, it indicates that none of the currently identified candidate feature points meet the physical constraints of the tested cable sheath circuit. This may be due to improper measurement parameter settings, poor signal quality, or complex fault types. In this case, the uncertain location of the system output impedance anomaly reminds the operator to readjust the measurement parameters, check the test connections, or use other testing methods for fault location.

[0077] S105: Calculate the distance from the test point to the impedance anomaly point based on the pulse reference time point and the echo characteristic point. The test point is the position where the pulse signal is emitted at the pulse reference time point, and the impedance anomaly point is the position where the echo characteristic point is generated on the sheath circuit of the cable under test.

[0078] Specifically, the total propagation time T_total = t_echo - t_pulse is obtained by calculating the difference between the time position of the echo feature point and the time position of the pulse reference time point, where t_echo is the time coordinate corresponding to the echo feature point and t_pulse is the time coordinate corresponding to the pulse reference time point. This total propagation time reflects the time consumed for the pulse signal to complete the entire propagation process from transmission to reception of the reflected signal in the sheath circuit of the cable under test. Based on the total propagation time and the preset voltage propagation speed, the distance between the test point and the impedance anomaly point is calculated using the distance calculation formula D = (T_total × v) / 2, where v is the preset voltage propagation speed, and the coefficient 2 is used to convert the round-trip propagation time into a one-way propagation distance. The voltage propagation speed is determined according to the dielectric characteristics and structural parameters of the sheath circuit of the cable under test, and is usually a certain proportion of the speed of light. Through this calculation method based on time difference and propagation speed, the physical distance between the test point and the impedance anomaly point is obtained.

[0079] Based on the above embodiments, as an optional embodiment, S105: the step of calculating the distance from the test point to the impedance anomaly point based on the pulse reference time point and the echo characteristic point may specifically include the following steps: S601: Calculate the total propagation time from the pulse reference time point to the echo characteristic point.

[0080] In this embodiment, the total propagation time represents the complete time period from the transmission of the pulse signal to the reception of the reflected echo signal from the impedance anomaly point, including the total round-trip time of the pulse signal propagating from the test point to the impedance anomaly point and the reflected signal returning from the impedance anomaly point to the test point.

[0081] Specifically, the total propagation time is obtained by calculating the difference between the time position of the echo feature point and the time position of the pulse reference time point. Let t_pulse be the time coordinate corresponding to the pulse reference time point and t_echo be the time coordinate corresponding to the echo feature point, then the total propagation time T_total = t_echo - t_pulse. This calculation process obtains the total propagation time required for the pulse signal to complete round-trip propagation in the sheath loop of the cable under test through direct time subtraction.

[0082] S602: Calculate the distance from the test point to the impedance anomaly point based on the total propagation time and the preset voltage propagation speed.

[0083] In the embodiments of this application, voltage propagation speed represents the propagation rate of voltage pulse signal in the sheath circuit medium of the cable under test, which is usually determined according to the medium characteristics and structural parameters of the cable, and is the propagation speed of light in that specific cable medium.

[0084] Specifically, the distance between the test point and the impedance anomaly point is calculated using the formula D = (T_total × v) / 2, where D is the one-way distance from the test point to the impedance anomaly point, T_total is the total propagation time, and v is the preset voltage propagation speed. Since the total propagation time includes the round-trip time of the pulse signal from the test point to the impedance anomaly point and the reflected signal from the impedance anomaly point back to the test point, it needs to be divided by a factor of 2 to convert the round-trip propagation time into a one-way propagation distance. Through this mathematical calculation, the actual physical distance between the test point and the impedance anomaly point is obtained.

[0085] Based on the above embodiments, as an optional embodiment, S105: after the step of calculating the distance from the test point to the impedance anomaly point, the process of determining the fault type of the sheath protector is further included, which may specifically include the following steps: S701: Monitors the current change trend of the sheath protector in the sheath circuit of the cable under test, and collects current data at multiple time points within a preset monitoring period to form current time sequence data.

[0086] In this embodiment of the application, the current timing data represents a set of current measurement values ​​of the sheath protector arranged in chronological order within a preset monitoring period. This data set reflects the current change pattern and dynamic characteristics of the sheath protector over a continuous time period. For example, the current value is collected once every minute within a 24-hour monitoring period to form a timing sequence containing 1440 data points.

[0087] Specifically, measuring devices such as current sensors or current transformers are installed at the sheath protector in the sheath circuit of the cable under test. A preset start and end time for the monitoring cycle is set, for example, continuous monitoring for 24 or 72 hours. Within the monitoring cycle, current data is collected at preset sampling intervals, such as recording the instantaneous current value of the sheath protector every 30 seconds, 1 minute, or 5 minutes. The current measurement value at each time point is associated with its corresponding timestamp, and all current data points are arranged and combined in chronological order to form a current data set with time-series characteristics.

[0088] S702: Compare the current timing data with the preset leakage current threshold to obtain the leakage current result.

[0089] In this embodiment of the application, the leakage current result represents the conclusion of whether there is abnormal leakage current in the sheath protector after comparing and analyzing the current timing data with the preset leakage current threshold. The result is usually a binary state, that is, there is leakage current or there is no leakage current. For example, when the current value of the sheath protector is detected to continuously exceed the preset threshold of 30mA, the leakage current result is that there is leakage current.

[0090] Specifically, the current measurement value corresponding to each time point is extracted from the current time-series data, and each current measurement value is compared with a preset leakage current threshold. The preset leakage current threshold is determined according to the technical specifications and safety standards of the sheath protector, for example, set to a specific value such as 10mA, 30mA, or 50mA. For each sampling point in the current time-series data, a comparison operation is performed: if the current measurement value is greater than the preset leakage current threshold, then the time point is determined to have leakage current. The number of time points exceeding the preset leakage current threshold within the entire monitoring period is counted, and the proportion of time points exceeding the threshold to the total number of sampling points is calculated. The final leakage current result is determined according to preset judgment rules. For example, when the proportion exceeding the threshold is greater than 5% or the continuous time exceeding the threshold exceeds a preset duration, the output leakage current result is that leakage current exists; otherwise, the output leakage current result is that leakage current does not exist.

[0091] S703: Count the number of actions of the sheath protector within a preset time window. The number of actions is the cumulative number of times the protection action of the sheath protector is triggered. If the leakage current result is that there is no leakage current and the number of actions is less than the preset action number threshold, the sheath protector is determined to be operating normally. If the leakage current result is that there is leakage current or the number of actions exceeds or equals the preset action number threshold, the sheath protector is determined to be faulty.

[0092] In this embodiment, the number of actions represents the cumulative count of state switching or action responses that occur when the sheath protector performs its protection function within a preset time window. This value reflects the working frequency and response activity of the sheath protector during the monitoring period. For example, if the sheath protector performs 15 protection actions within a week, then the number of actions is 15.

[0093] Specifically, a preset time window is set with a start and end time, such as a continuous monitoring period of 24 hours, one week, or one month. By monitoring the status signals or action indication signals of the sheath protector, the moment each protection action is triggered is identified, including the complete process of the sheath protector switching from normal to protection mode and returning to normal mode. All protection action events detected within the preset time window are counted to obtain a cumulative number of actions. The counted number of actions is compared with a preset action count threshold, and the leakage current result obtained in the previous steps is also retrieved. A joint judgment logic is executed: when the leakage current result shows no leakage current and the number of actions is less than the preset action count threshold, the sheath protector's operating status is judged as normal operation; when the leakage current result shows leakage current or the number of actions is equal to or exceeds the preset action count threshold, the sheath protector's operating status is judged as faulty.

[0094] S704: Determines the fault mode of the cable sheath protector based on leakage current results and number of operations, and outputs a comprehensive fault diagnosis report including the fault mode and the distance from the test point to the impedance anomaly point.

[0095] In the embodiments of this application, the fault mode represents a specific fault type classified according to different abnormal state characteristics of the sheath protector. The mode describes the specific manifestation and fault mechanism of the fault in the sheath protector, such as leakage current fault mode caused by insulation aging, frequent operation fault mode caused by mechanical wear, or intermittent fault mode caused by poor electrical contact.

[0096] Specifically, multiple fault mode classification rules are established based on different combinations of leakage current results and the number of operations. When the leakage current result indicates the presence of leakage current and the number of operations is within the normal range, the fault mode is identified as an insulation performance degradation fault, indicating that the internal insulation material of the sheath protector is aging or damaged, leading to continuous leakage. When the leakage current result indicates no leakage current but the number of operations exceeds the preset operation threshold, the fault mode is identified as a mechanical operation abnormality fault, indicating that the mechanical components of the sheath protector are oversensitive or malfunctioning. When the leakage current result indicates the presence of leakage current and the number of operations simultaneously exceeds the preset operation threshold, the fault mode is identified as a composite severe fault, indicating that the sheath protector has both insulation and mechanical problems. The distance data between the test point and the impedance anomaly point is obtained, calculated using time-domain reflection or impedance measurement methods. A comprehensive fault diagnosis report data structure is constructed, with the identified fault mode as the main diagnostic conclusion written in the report title section, and the distance information as fault location data written in the location analysis section. The report records in detail the statistical analysis results of the leakage current time sequence data, the specific statistical values ​​of the number of operations, the judgment basis of the fault mode, and the logical process. Add fault severity rating information, and conduct quantitative assessments based on the degree of leakage current exceeding the limit and the degree of abnormality in the number of operations. Finally, integrate and format the information according to a standardized fault diagnosis report format, and output a complete comprehensive fault diagnosis report that includes fault mode classification, precise distance location, detailed detection data, analysis process, and handling recommendations.

[0097] The following describes an exemplary cable sheath protector fault determination device provided in an embodiment of this application. Figure 3 This is an exemplary hardware structure diagram of a cable sheath protector fault determination device provided in an embodiment of this application.

[0098] In some embodiments, the cable sheath protector fault determination device is a computer device or includes a computer device in the cable sheath protector fault determination device. The computer device includes a processor, memory, and a network interface connected via a system bus. The processor of the computer device provides computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores an operating system, computer programs, and a database. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage medium. The database of the computer device stores data. The network interface of the computer device is used to communicate with other external terminals or servers via a network connection. In some embodiments, the network interface can be a wired network interface; in some embodiments, the network interface can also be a wireless network interface. When the computer program is executed by the processor, it implements the methods in the embodiments of this application.

[0099] Those skilled in the art will understand that Figure 3 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0100] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0101] As used in the above embodiments, depending on the context, the term "when..." can be interpreted as meaning "if...", "after...", "in response to determining...", or "in response to detecting...". Similarly, depending on the context, the phrase "when determining..." or "if (the stated condition or event) is interpreted as meaning "if determining...", "in response to determining...", "when (the stated condition or event) is detected", or "in response to detecting (the stated condition or event)".

[0102] In the above embodiments, implementation can be achieved entirely or partially through software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented entirely or partially in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., solid-state drive), etc.

[0103] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. This program can be stored in a computer-readable storage medium, and when executed, it can include the processes described in the above method embodiments. The aforementioned storage medium includes various media capable of storing program code, such as ROM or random access memory (RAM), magnetic disks, or optical disks.

Claims

1. A method for determining faults in a cable sheath protector, characterized in that, The method includes: The voltage of the cable sheath circuit under test is obtained within a preset time period according to the preset time step, and the voltage time series is obtained. The time point with the largest absolute voltage value in the voltage time series is taken as the pulse reference time point. The blind zone time period is determined based on the pulse reference time point. Starting from the end time of the blind zone time period, the voltage time series is subjected to a first analysis to obtain the candidate echo start time. The voltage time series is then subjected to a second analysis based on the candidate echo start time to obtain the effective echo start time. The echo search window is determined based on the effective echo start time. All local extreme points of the voltage time series are identified in the echo search window. The local extreme point with the largest absolute voltage value is taken as the main candidate feature point, and the local extreme point with the second largest absolute voltage value is taken as the alternative feature point. Calculating the time interval between the main candidate feature point and the alternative feature point and the pulse reference time point, and selecting the main candidate feature point or the alternative feature point as the echo feature point according to the time interval, includes: calculating a first time interval between the main candidate feature point and the pulse reference time point, and a second time interval between the alternative feature point and the pulse reference time point; Determine whether the first time interval is within a preset effective time interval range, wherein the effective time interval range is determined based on the expected fault distance range of the sheath circuit of the cable under test; If the first time interval is within the effective time interval range, then the main candidate feature point is selected as the echo feature point; If the first time interval is not within the effective time interval range, then it is determined whether the second time interval is within the effective time interval range. If the second time interval is within the effective time interval range, then the candidate feature point is selected as the echo feature point. If the second time interval is not within the effective time interval range, then the location of the output impedance anomaly point is uncertain. The distance between the test point and the impedance anomaly point is calculated based on the pulse reference time point and the echo characteristic point. The test point is the position where the pulse signal is emitted at the pulse reference time point, and the impedance anomaly point is the position where the echo characteristic point is generated on the sheath circuit of the cable under test.

2. The method for determining faults in a cable sheath protector according to claim 1, characterized in that, The first analysis of the voltage time series, starting from the end of the blind zone time period, to obtain the candidate echo start time includes: Starting from the end of the blind zone time period, the noise standard deviation is calculated in the noise segment of the voltage time series, and the noise standard deviation is multiplied by a first multiplier factor to obtain a first detection threshold. The noise segment is the last preset proportion of the preset time period. The system searches for the first time point in the voltage time series where the absolute voltage value is greater than the first detection threshold. If a time point exceeding the first detection threshold is found, the time point is used as the candidate echo start time. If no time point exceeding the first detection threshold is found, the search is repeated according to the second detection threshold to obtain the candidate echo start time. The second detection threshold is the noise standard deviation multiplied by a second multiplier factor, and the second multiplier factor is less than the first multiplier factor.

3. The method for determining faults in a cable sheath protector according to claim 2, characterized in that, The second analysis of the voltage time series based on the candidate echo start time to obtain the effective echo start time includes: Determine whether a preset number of voltage sampling points in the voltage time series after the candidate echo start time meet the signal continuity condition; if the candidate echo start time is obtained based on a first detection threshold, then the signal continuity condition is that the voltage of the preset number of voltage sampling points all exceeds the first detection threshold; if the candidate echo start time is obtained based on a second detection threshold, then the signal continuity condition is that the voltage of the preset number of voltage sampling points all exceeds the second detection threshold. If the signal continuity condition is not met, the candidate echo start time is determined to be noise interference, and the search continues to the next candidate echo start time and the signal continuity condition verification is performed again. If the signal continuity condition is met, then the candidate echo start time is determined to be the valid echo start time.

4. The method for determining faults in a cable sheath protector according to claim 1, characterized in that, After identifying all local extrema of the voltage time series in the echo search window, and selecting the local extrema with the largest absolute voltage value as the primary candidate feature point and the local extrema with the second largest absolute voltage value as alternative feature points, the process further includes: Calculate the signal-to-noise ratio of each local extremum point, and filter the local extremum points whose signal-to-noise ratio is lower than a preset signal-to-noise ratio threshold to obtain the filtered local extremum points. The new absolute voltage values ​​of the local extrema after each filtering process are recalculated, and the main candidate feature points and the alternative feature points are updated based on the new absolute voltage values.

5. The method for determining faults in a cable sheath protector according to claim 1, characterized in that, The calculation of the distance from the test point to the impedance anomaly point based on the pulse reference time point and the echo characteristic point includes: Calculate the total propagation time from the pulse reference time point to the echo feature point; Based on the total propagation time and the preset voltage propagation speed, the distance between the test point and the impedance anomaly point is calculated. The preset voltage propagation speed represents the propagation rate of the voltage pulse signal in the sheath circuit medium of the cable under test.

6. The method for determining faults in a cable sheath protector according to claim 1, characterized in that, After calculating the distance from the test point to the impedance anomaly point, the method further includes: The current change trend of the sheath protector in the sheath circuit of the cable under test is monitored, and current data at multiple time points are collected within a preset monitoring period to form current time series data; The leakage current result is obtained by comparing the current timing data with a preset leakage current threshold. The number of actions of the sheath protector within a preset time window is counted. The number of actions is the cumulative number of times the sheath protector's protection actions are triggered. If the leakage current result is that there is no leakage current and the number of actions is less than a preset action number threshold, the sheath protector is determined to be operating normally. If the leakage current result is that there is leakage current or the number of actions exceeds or equals the preset action number threshold, the sheath protector is determined to be faulty. Based on the leakage current results and the number of operations, the fault mode of the cable sheath protector is determined, and a comprehensive fault diagnosis report including the fault mode and the distance between the test point and the impedance anomaly point is output.

7. A fault determination device for cable sheath protectors, characterized in that, The cable sheath protector fault determination device includes: one or more processors and a memory; the memory is coupled to the one or more processors, the memory is used to store computer program code, the computer program code including computer instructions, and the one or more processors call the computer instructions to cause the cable sheath protector fault determination device to perform the method as described in any one of claims 1-6.

8. A computer program product containing instructions, characterized in that, When the computer program product is run on the cable sheath protector fault determination device, the cable sheath protector fault determination device performs the method as described in any one of claims 1-6.

9. A computer-readable storage medium comprising instructions, characterized in that, When the instruction is executed on the cable sheath protector fault determination device, the cable sheath protector fault determination device performs the method as described in any one of claims 1-6.

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