Cable partial discharge monitoring method and system, program product and storage medium

Abstract

The invention provides a cable partial discharge monitoring method and system, a program product and a storage medium, and relates to the technical field of electrical variable measurement, and aims to capture a pulse current signal generated during cable discharge, perform time calibration on the discharge pulse current signal, measure the time difference of signals monitored at different positions, and combine the signal propagation speed to determine the partial discharge of a cable. Therefore, the specific position of discharge is locked. In a power frequency period, a PRPD atlas is constructed according to the amplitude and frequency of a discharge pulse current signal and corresponding power frequency phase information, then a statistical moment, phase symmetry and a polarity effect on each coordinate axis are calculated based on the atlas, and feature vectors are formed and input into a preset mode recognition model. And the model outputs a judgment result containing the discharge point position and the specific defect type by comparing with a preset monitoring parameter threshold value for the specific defect type. And direction reference is provided for subsequent maintenance and repair work, blind troubleshooting is avoided, the maintenance and repair efficiency is improved, and the cost is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of measuring electrical variables, and in particular to a cable partial discharge monitoring method, system, program product, and storage medium. Background Art

[0002] Power cables are crisscrossed throughout urban areas, across mountainous terrain, and elsewhere, carrying the crucial mission of transmitting large amounts of electrical energy. However, in actual operation, cables and their connectors are often affected by a variety of factors, including variations in material quality, inconsistent construction techniques, complex and changing operating environments, potential damage from external forces, and performance degradation over time. Insulation breakdown is a common occurrence. Given the high voltage levels and large transmission capacity of power systems, such incidents often result in significant economic losses and severely impact the stability and safety of power supply. Therefore, effective monitoring of cable operating conditions is crucial.

[0003] In the past, monitoring partial discharge (PD) in cables was typically accomplished by installing conventional electrical signal detection devices at regular intervals along the cable. These devices primarily detect subtle changes in the electromagnetic field surrounding the cable to detect potential discharge signals. In practice, the detection devices are arranged at predetermined intervals and then kept in continuous operation, receiving real-time electromagnetic field signals from the surrounding cable. When abnormal fluctuations in the electromagnetic field signal are detected, a simple amplitude and frequency analysis is performed on the abnormal signal. By comparing it to a pre-set amplitude range and the frequency range of common discharge signals, a determination is made as to whether PD has occurred. If a discharge is detected, the approximate time period of the abnormal signal and the corresponding detection device location are recorded, providing a rough estimate of the interval within which PD may have occurred.

[0004] More importantly, existing technologies only provide information on the occurrence of partial discharge (PD) problems. This means that they can only perform follow-up work after the problem occurs, but are unable to conduct in-depth analysis in advance on where on the cable the PD problem will occur, nor can they accurately determine the cause of the PD. This results in a lack of direction for subsequent maintenance and repair work, impacting the cost and efficiency of maintenance and repair. Summary of the Invention

[0005] The present application provides a cable partial discharge monitoring method, system, program product and storage medium, which are used to provide a direction reference for subsequent maintenance and repair work, avoid blind investigation, improve the efficiency of maintenance and repair, and reduce costs.

[0006] In the first aspect, the present application provides a cable partial discharge monitoring method, comprising: obtaining a discharge pulse current signal through a high-frequency pulse current sensor deployed on the grounding wire of the cable joint of the cable; obtaining power frequency phase information through a power frequency phase transformer deployed on the cable; based on a double-end pulse time difference positioning method, using the discharge pulse current signal to calculate the position of the discharge point of the cable, wherein the power frequency phase information is used to perform time calibration on the discharge pulse current signal; within each power frequency cycle, the discharge pulse current signal is used as a coordinate axis according to its amplitude, frequency and corresponding power frequency phase information to construct a PRPD spectrum; based on the PRPD spectrum, the statistical moment, phase symmetry and polarity effect of the PRPD spectrum on each coordinate axis are calculated; the characteristic vector composed of the statistical moment, phase symmetry and polarity effect is input into a preset pattern recognition model; when at least one of the statistical moment, phase symmetry or polarity effect exceeds the monitoring parameter threshold preset for a specific defect type, a judgment result is output, and the judgment result includes the position of the discharge point and the specific defect type.

[0007] By adopting the above technical solution, the high-frequency pulse current sensor deployed on the grounding wire of the cable joint captures the pulse current signal generated when the cable discharges, and the power frequency phase transformer deployed on the cable is used to time calibrate the discharge pulse current signal. Based on the double-end pulse time difference positioning method, the time difference of the signals monitored at different positions is measured, combined with the signal propagation speed, to lock the specific location where the discharge occurs. Within the power frequency cycle, the amplitude, frequency and corresponding power frequency phase information of the discharge pulse current signal are used to construct a PRPD spectrum. Then, based on the spectrum, the statistical moment, phase symmetry and polarity effect on each coordinate axis are calculated, and the characteristic vector is input into the preset pattern recognition model. The model compares with the preset monitoring parameter threshold for the specific defect type and outputs the judgment result including the discharge point location and the specific defect type. It provides a directional reference for subsequent maintenance and repair work, avoids blind investigation, improves the efficiency of maintenance and repair, and reduces costs.

[0008] In combination with some embodiments of the first aspect, in some embodiments, a discharge pulse current signal is obtained by a high-frequency pulse current sensor deployed on the grounding wire of the cable connector of the cable; after the step of obtaining the power frequency phase information by an power frequency phase transformer deployed on the cable, the method also includes: extracting the pulse amplitude distribution of the discharge pulse current signal; generating a phase coding sequence based on the extracted pulse amplitude distribution; and using the phase coding sequence to perform phase coding modulation on the discharge pulse current signal.

[0009] By adopting the above technical solution, the pulse amplitude distribution of the discharge pulse current signal is first extracted. Based on the extracted pulse amplitude distribution, a phase coding sequence is generated to distinguish it from other interference signals. Finally, the phase coding sequence is used to perform phase coding modulation on the discharge pulse current signal. In the complex electromagnetic environment where cables are densely laid, the modulated signal carries specific coding information. Even if the electromagnetic fields of surrounding cables affect each other and cause crosstalk, its coding characteristics can remain relatively independent during transmission and are not easily confused by interference signals, ensuring that work such as partial discharge analysis based on this digital signal can be carried out normally and accurately.

[0010] In combination with some embodiments of the first aspect, in some embodiments, before the step of performing phase-coding modulation on the discharge pulse current signal using a phase-coding sequence, the method further includes: generating a predefined pseudo-random sequence as a pilot code through a field programmable gate array deployed on a ground wire of a cable connector of the cable; obtaining a discharge pulse current signal containing the pilot code, and obtaining a discharge pulse current signal not containing the pilot code; subtracting the discharge pulse current signal not containing the pilot code from the discharge pulse current signal containing the pilot code to obtain an extracted pilot code; comparing the extracted pilot code with the pilot code to obtain a damage index; if the damage index is lower than a preset damage threshold, executing the step of performing phase-coding modulation on the discharge pulse current signal using a phase-coding sequence; if the damage index is not lower than the preset damage threshold, extracting a preset number of crosstalk frequency points in the phase-coding sequence, and performing phase shift on the crosstalk frequency points, the crosstalk frequency point being a point where the difference between the extracted pilot code and the pilot code is greater than a threshold, and executing the step of performing phase-coding modulation on the discharge pulse current signal using a phase-coding sequence.

[0011] By employing the above technical solution, a field-programmable gate array (FPGA) deployed on the ground wire of the cable connector generates a predefined pseudo-random sequence as a pilot code, providing a reliable reference standard for subsequent signal integrity assessment. Next, the discharge pulse current signal containing the pilot code and the discharge pulse current signal excluding the pilot code are obtained and subtracted to obtain the extracted pilot code. This operation accurately separates the pilot code portion. By comparing it with the original pilot code, a damage index is obtained, which intuitively reflects the degree of signal interference. If the damage index is below a preset damage threshold, the signal quality is acceptable and modulation using a phase-coded sequence can be performed. If the damage index is not below the preset damage threshold, a preset number of crosstalk frequencies in the phase-coded sequence are extracted and phase-shifted to correct for coding errors that may be caused by interference. This method effectively verifies signal reliability in complex cable operating environments where the collected signal is often a mixture of interference and true discharge signals, preventing signal modulation due to erroneous coding sequences and preventing interference signals from masquerading as legitimate signals and infiltrating subsequent processes. This ensures that the diagnostic model receives accurate input and the accuracy of the monitoring results.

[0012] In combination with some embodiments of the first aspect, in some embodiments, the step of subtracting the discharge pulse current signal that does not contain the pilot code from the discharge pulse current signal that contains the pilot code to obtain the extracted pilot code specifically includes: determining that the discharge pulse current signal that contains the pilot code is the first half-wave signal within the power frequency cycle, and the discharge pulse current signal that does not contain the pilot code is the second half-wave signal that corresponds to the first half-wave signal within the power frequency cycle; performing mirror processing on the second half-wave signal to obtain a mirror signal; and subtracting the mirror signal from the first half-wave signal to obtain the extracted pilot code.

[0013] By employing the above technical solution, the discharge pulse current signal containing the pilot code is determined to be the first half-wave signal within the power frequency cycle, and the discharge pulse current signal without the pilot code is determined to be the second half-wave signal corresponding to the first half-wave signal within the power frequency cycle. This division is based on the periodicity and correlation of the signals within the power frequency cycle. The second half-wave signal is mirrored, utilizing the symmetry of the signal within the cycle. The processed mirror signal and the first half-wave signal are theoretically as similar as possible, with the exception of the pilot code. The pilot code is then extracted by subtracting the mirror signal from the first half-wave signal. This takes into account the inherent characteristics of the signal within the same cycle, reduces the impact of the difference between the two signals caused by the randomness of the cable discharge signal itself, more accurately extracts the pilot code, and avoids deviations in damage index calculation due to inaccurate extraction.

[0014] In combination with some embodiments of the first aspect, in some embodiments, the step of subtracting the discharge pulse current signal that does not contain the pilot code from the discharge pulse current signal that contains the pilot code to obtain the extracted pilot code specifically includes: obtaining the trend characteristics of the parameters in the historical discharge pulse current signal that change over time; matching the current trend characteristics with the trend category statistical information to determine the most matching historical trend category; constructing a predicted discharge pulse current signal waveform within a preset time period in the future based on the historical average change of the most matching historical trend category; subtracting the discharge pulse current signal that contains the pilot code from the predicted discharge pulse current signal waveform point by point to obtain a difference signal, and using the difference signal as the pilot code.

[0015] By adopting the above technical solution, the trend characteristics of the parameters in the historical discharge pulse current signal changing over time are obtained, and the current trend characteristics are matched with the trend category statistical information to determine the most matching historical trend category, which is equivalent to finding the most similar reference template for the current signal in historical experience. Based on the historical average changes of the most matching historical trend category, a predicted discharge pulse current signal waveform within a preset time period in the future is constructed. This allows the constructed waveform to fit the development trend of actual discharge and is more in line with the actual discharge law of the cable. Finally, the discharge pulse current signal containing the pilot code is subtracted point by point from the predicted discharge pulse current signal waveform to obtain the difference signal as the pilot code. This can more accurately extract the pilot code and avoid the deviation of the subtraction result caused by the randomness of the signal, thereby calculating the damage index, avoiding the erroneous triggering of the phase offset operation, and improving the signal quality and the accuracy of cable partial discharge monitoring.

[0016] In conjunction with some embodiments of the first aspect, in some embodiments, based on the double-end pulse time difference positioning method, the step of calculating the position of the discharge point of the cable using the discharge pulse current signal specifically includes: calculating the time difference between the discharge pulse current signals; and calculating the position of the discharge point using a double-end positioning formula based on the time difference and the wave velocity of the discharge pulse current signal; wherein the double-end positioning formula is: Where, is the distance from the discharge point to the reference point, is the wave velocity of the discharge pulse current signal, is the time difference, is the position of the reference point.

[0017] By adopting this technical solution, the time difference between the discharge pulse current signals is first calculated. Based on this time difference and the wave velocity of the discharge pulse current signal, the discharge point position is calculated using a two-terminal positioning formula. This abstract signal propagation time and speed information is converted into specific spatial position information. In other words, the distance from the discharge point to the reference point is accurately determined, thereby determining the location of the cable discharge point.

[0018] In combination with some embodiments of the first aspect, in some embodiments, within an industrial frequency cycle, the discharge pulse current signal is used as coordinate axes according to its amplitude, frequency and corresponding industrial frequency phase information, and before the step of constructing a PRPD spectrum, the method also includes: performing noise reduction processing on the discharge pulse current signal.

[0019] By adopting the above technical solution, the discharge pulse current signal is subjected to noise reduction processing, which can remove various types of noise interference mixed in the signal, such as environmental electromagnetic noise and clutter generated by equipment operation, making the signal waveform purer and closer to the actual discharge situation.

[0020] In a second aspect, the present application provides a cable partial discharge monitoring system, which 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 includes computer instructions, and the one or more processors call the computer instructions to enable the cable partial discharge monitoring system to perform the method described in the first aspect and any possible implementation of the first aspect.

[0021] In a third aspect, the present application provides a computer program product comprising instructions, which, when run on a cable partial discharge monitoring system, enables the cable partial discharge monitoring system to execute the method described in the first aspect and any possible implementation of the first aspect.

[0022] In a fourth aspect, the present application provides a computer-readable storage medium comprising instructions, which, when executed on a cable partial discharge monitoring system, causes the cable partial discharge monitoring system to execute the method described in the first aspect and any possible implementation of the first aspect.

[0023] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages: 1. The high-frequency pulse current sensor deployed on the grounding wire of the cable joint captures the pulse current signal generated when the cable discharges, and the power frequency phase transformer deployed on the cable is used to time calibrate the discharge pulse current signal. Based on the double-ended pulse time difference positioning method, the time difference of the signals monitored at different positions is measured, combined with the signal propagation speed, to lock the specific location where the discharge occurs. Within the power frequency cycle, the amplitude, frequency and corresponding power frequency phase information of the discharge pulse current signal are used to construct a PRPD spectrum. Then, based on the spectrum, the statistical moment, phase symmetry and polarity effect on each coordinate axis are calculated, and the characteristic vector is input into the preset pattern recognition model. The model compares with the preset monitoring parameter threshold for the specific defect type, and outputs the judgment result including the discharge point location and the specific defect type. It provides a directional reference for subsequent maintenance and repair work, avoids blind investigation, improves the efficiency of maintenance and repair, and reduces costs.

[0024] 2. A field-programmable gate array (FPGA) deployed on the ground wire of the cable connector generates a predefined pseudo-random sequence as a pilot code, providing a reliable reference for subsequent signal integrity assessment. Next, the discharge pulse current signal containing the pilot code and the discharge pulse current signal excluding the pilot code are obtained and subtracted to obtain the extracted pilot code. This operation accurately separates the pilot code portion. By comparing it with the original pilot code, a damage index is obtained, which directly reflects the degree of signal interference. If the damage index is below the preset damage threshold, the signal quality is acceptable and modulation using a phase-coded sequence can be performed. If the damage index is not below the preset damage threshold, a preset number of crosstalk frequencies in the phase-coded sequence are extracted and phase-shifted to correct for coding errors that may be caused by interference. This method effectively verifies signal reliability in complex cable operating environments where the collected signal is often a mixture of interference and true discharge signals, preventing signal modulation due to erroneous coding sequences and preventing interference signals from masquerading as legitimate signals and infiltrating subsequent processes. This ensures that the diagnostic model receives accurate input and ensures the accuracy of monitoring results.

[0025] 3. Obtain the trend characteristics of the parameters in the historical discharge pulse current signal that change over time, and match the current trend characteristics with the trend category statistical information to determine the most matching historical trend category, which is equivalent to finding the most similar reference template for the current signal in historical experience. Based on the historical average change of the most matching historical trend category, construct the predicted discharge pulse current signal waveform within the preset time period in the future. This allows the constructed waveform to fit the development trend of the actual discharge and is more in line with the actual discharge law of the cable. Finally, the discharge pulse current signal containing the pilot code is subtracted point by point from the predicted discharge pulse current signal waveform to obtain the difference signal as the pilot code. This can more accurately extract the pilot code and avoid the deviation of the subtraction result caused by the randomness of the signal, thereby calculating the damage index and avoiding the erroneous triggering of the phase offset operation, thereby improving the signal quality and the accuracy of cable partial discharge monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 1 is a flow chart of a cable partial discharge monitoring method according to an embodiment of the present application; Figure 2 This is a schematic diagram of an exemplary application scenario of the cable partial discharge monitoring method in an embodiment of the present application; Figure 3 is a schematic diagram of a discharge pulse current signal in an embodiment of the present application; Figure 4 This is a schematic diagram of the PRPD spectrum in the embodiment of the present application; Figure 5 is another schematic diagram of the PRPD spectrum in the embodiment of the present application; Figure 6 is another schematic diagram of the PRPD spectrum in the embodiment of the present application; Figure 7 is another schematic diagram of the PRPD spectrum in the embodiment of the present application; Figure 8 is another schematic diagram of the PRPD spectrum in the embodiment of the present application; Figure 9 This is another flow chart of the cable partial discharge monitoring method according to an embodiment of the present application; Figure 10 This is another flow chart of the cable partial discharge monitoring method according to an embodiment of the present application; Figure 11 This is another flow chart of the cable partial discharge monitoring method according to an embodiment of the present application; Figure 12 This is another flow chart of the cable partial discharge monitoring method according to an embodiment of the present application; Figure 13 It is a schematic diagram of an exemplary hardware structure of the cable partial discharge monitoring system in an embodiment of the present application. DETAILED DESCRIPTION

[0027] The terms used in the following examples of the present application are for the purpose of describing specific embodiments only and are not intended to limit the present application. As used in the specification and appended claims of the present application, the singular expressions "a," "an," "said," "above," "the," and "this" are intended to include plural expressions as well, unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used in the present application refers to and encompasses any or all possible combinations of one or more of the listed items.

[0028] In the following, the terms "first" and "second" are used for descriptive purposes only and should not be understood to imply or suggest relative importance or implicitly indicate the number of the technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of this application, unless otherwise specified, "plurality" means two or more.

[0029] See also Figure 1 , Figure 1 1 is a flow chart of a cable partial discharge monitoring method according to an embodiment of the present application; S101. Obtain a discharge pulse current signal through a high-frequency pulse current sensor deployed on a ground wire of a cable connector of a cable; and obtain power frequency phase information through a power frequency phase transformer deployed on the cable. The discharge pulse current signal represents the instantaneous pulse current variation signal generated when a partial discharge occurs in the cable. This signal is acquired by a high-frequency pulse current sensor to analyze the cable's discharge condition. Power frequency phase information, which refers to the phase angle of the power frequency alternating current within a cycle, plays an important role in analyzing electrical phenomena related to power frequency alternating current. For example, this step assists in the subsequent processing of the discharge pulse current signal.

[0030] See also Figure 2 ; Figure 2 This is a schematic diagram of an exemplary application scenario of the cable partial discharge monitoring method in an embodiment of the present application; It's important to note that when a partial discharge occurs in a cable, the resulting pulse current forms a loop through the ground wire. Current changes in the ground wire can effectively reflect the discharge. High-frequency pulse current sensors are deployed on the ground wire at the cable connector. Here, they can most directly and effectively capture these transient, pulsed current changes. For example, if a partial discharge occurs at a weak point in the insulation within the cable, the discharge current will inevitably flow into the ground wire. A high-frequency pulse current sensor installed on the ground wire can keenly sense this change and output a corresponding electrical signal for subsequent analysis, enabling monitoring of cable discharge conditions.

[0031] The function of a power-frequency phase transformer is to obtain phase information of the power-frequency alternating current in a cable. This principle is based on electromagnetic induction, coupling with the power-frequency current in the cable to obtain the corresponding phase information. Therefore, it needs to be deployed directly on the cable and establish a close electromagnetic connection with the power-frequency current in the cable. Only in this way can it accurately sense the phase changes of the AC current and convert them into electrical signals for subsequent processing, thereby accurately obtaining power-frequency phase information.

[0032] See also Figure 3 , Figure 3 is a schematic diagram of a discharge pulse current signal in an embodiment of the present application; S102, calculating the position of the discharge point of the cable using the discharge pulse current signal based on a double-ended pulse time difference positioning method, wherein the power frequency phase information is used to perform time calibration on the discharge pulse current signal; Among them, the two-end pulse time difference positioning method is a method for determining the position of the discharge point based on the time difference of the discharge pulse current signal detected simultaneously at both ends of the cable. It utilizes the relatively fixed propagation speed of the discharge pulse in the cable and accurately locates the position of the discharge point by calculating the relationship between the time difference and parameters such as the propagation speed.

[0033] Specifically, after obtaining the discharge pulse current signal, the two-end pulse time difference positioning method is used to simultaneously capture and record the arrival time of the discharge pulse current signal at both ends of the cable (or at different known detection points). Since the discharge pulse current signal propagates at a certain speed in the cable, by measuring the time difference between the received signals at both ends, combined with known parameters such as the pulse propagation speed in the cable and the cable length, and applying the corresponding mathematical formula, the location of the discharge point on the cable can be calculated. The power frequency phase information plays a role in time calibration of the discharge pulse current signal. In actual power systems, the power frequency AC power will have a certain impact on the detected pulse signal time. Calibration using the power frequency phase information can make the result of calculating the discharge point location based on the time difference more accurate.

[0034] It's important to note that since the discharge pulse current signal in the cable coexists and is interrelated with the power-frequency AC power, which has a fixed frequency and periodicity, its phase information can serve as a stable time reference. First, using a power-frequency AC cycle (20ms for 50Hz AC) as the time reference, it is divided into multiple phase intervals. For example, 0-360 degrees can be equally divided into several smaller intervals (e.g., 10-degree intervals). When a discharge pulse current signal is detected, the corresponding power-frequency phase information is recorded. Assuming a discharge pulse current signal is detected at a certain moment, and the acquired power-frequency phase information indicates a 180-degree position (corresponding to a specific time point within a cycle), it can be determined that the discharge pulse occurred at this specific phase of the power-frequency AC power. Because the phase variations of power-frequency AC power are regular and known, this corresponding phase information allows for more precise location of the discharge pulse current signal on the time axis.

[0035] In some specific embodiments, step S102 specifically includes: S1021, calculating the time difference between discharge pulse current signals; It should be noted that the discharge pulse current signals mentioned here refer to discharge pulse current signals from different locations. Specifically, they are comparisons of discharge pulse current signals obtained at different cable joints. The purpose is to calculate the time difference between each pair of discharge pulse current signals distributed at different cable joint locations.

[0036] S1022. Calculate the position of the discharge point using a double-end positioning formula based on the time difference and the wave velocity of the discharge pulse current signal; the double-end positioning formula is: Where, is the distance from the discharge point to the reference point, is the wave velocity of the discharge pulse current signal, is the time difference, is the position of the reference point.

[0037] As can be seen, the time difference between the discharge pulse current signals is calculated first. Based on the time difference and the wave velocity of the discharge pulse current signal, the double-end positioning formula is used to calculate the position of the discharge point. The abstract signal propagation time and speed information is converted into specific spatial position information. In other words, the distance from the discharge point to the reference point is accurately determined, thereby determining the position of the cable discharge point.

[0038] S103, within a power frequency cycle, using the discharge pulse current signal according to its amplitude, frequency and corresponding power frequency phase information as coordinate axes to construct a PRPD spectrum; Among them, the PRPD map is the Phase Resolved Partial Discharge map, which is a map that comprehensively displays the amplitude, frequency and corresponding power frequency phase information of the partial discharge signal. By reflecting the relationship between these parameters on different coordinate axes, it can intuitively reflect the characteristics and laws of cable partial discharge, which helps to analyze the insulation status of the cable.

[0039] Specifically, within one power frequency cycle, the amplitude of the discharge pulse current signal is used as one coordinate axis, the frequency is used as another coordinate axis, and the corresponding power frequency phase information is used as the third coordinate axis. Each detected discharge pulse current signal is marked in this three-dimensional coordinate system according to its actual amplitude, frequency, and the corresponding power frequency phase information when it occurs. Many such marking points constitute the PRPD spectrum.

[0040] S104, calculating the statistical moment, phase symmetry, and polarity effect of the PRPD spectrum on each coordinate axis based on the PRPD spectrum; Among them, statistical moments in the context of PRPD spectra refer to some characteristic quantities, such as mean and variance, calculated by applying mathematical statistical methods to the distribution of each data point in the spectrum. These statistical moments can reflect the statistical characteristics of partial discharge signals in terms of amplitude, frequency, etc. from different angles, which helps to analyze the stability and discreteness of the discharge.

[0041] Phase symmetry refers to the degree of symmetry of the distribution of partial discharge signals at different phases in the PRPD spectrum. It can reflect whether there are certain regularity or symmetry characteristics in the discharge process inside the cable, which is of great significance for determining the type of discharge.

[0042] The polarity effect refers to the differences in amplitude and frequency of positive and negative polarity discharge pulses during partial discharge due to factors such as the cable's internal structure and electric field distribution. By analyzing the polarity effect, we can further understand the electrical state of the cable and possible defects.

[0043] Specifically, based on the constructed PRPD spectrum, the statistical moments are calculated using corresponding mathematical statistical formulas. For example, the mean amplitude is calculated by adding up the amplitude data of all discharge pulse current signals in the spectrum and dividing it by the total number of data points; the variance is obtained by calculating the average of the sum of the squares of the differences between each amplitude data and the mean. For phase symmetry, by comparing the distribution of discharge pulses in different phase regions in the spectrum, such as whether the number and amplitude of discharge pulses at the same phase angle in the positive and negative half-cycles are similar, the phase symmetry is quantified using the symmetry-related algorithm. The calculation of the polarity effect distinguishes the positive and negative polarity of the discharge pulse, and separately counts the amplitude, frequency and other parameters of the discharge pulse under positive and negative polarity, and then compares and analyzes the differences between the two, such as calculating the ratio of the total positive polarity amplitude to the total negative polarity amplitude, etc., in order to determine the specific situation of the polarity effect. Through these calculations, the various characteristics of cable partial discharge can be fully grasped.

[0044] S105, inputting the feature vector composed of the statistical moment, phase symmetry and polarity effect into a preset pattern recognition model; The eigenvector here refers to a vector formed by combining the calculated statistical moments, phase symmetry, and polarity effects, which are parameters reflecting the characteristics of cable partial discharge. It can comprehensively represent the comprehensive characteristics of cable partial discharge and serve as input data for subsequent pattern recognition models, facilitating model classification, judgment, and other operations.

[0045] The preset pattern recognition model refers to a machine learning model or rule-based intelligent judgment model that has been trained in advance with a large amount of cable partial discharge data and can determine whether the cable has specific defects and the type of defects based on the input feature vector. Common ones include neural network models and support vector machine models.

[0046] Specifically, the previously calculated statistical moments, phase symmetry, and polarity effects are combined in a specific order to form a feature vector. This feature vector is then input into a pre-set pattern recognition model. The model analyzes and processes this input feature vector based on its learned rules and algorithms. By comparing and matching the feature vectors in the training data, the model determines whether the current cable partial discharge condition meets the characteristics of a certain defect type, thereby preparing for the subsequent output of the judgment result.

[0047] See also Figure 4 , Figure 4 This is a schematic diagram of the PRPD spectrum in the embodiment of the present application; In the figure, q is the amplitude and t is the frequency. It should be noted that the power frequency phase information mentioned above can be used as an important reference in the time dimension, and here 20ms is usually used as the reference time for a power frequency cycle.

[0048] The distribution range of the discharge amplitude is greater than the preset amplitude distribution range threshold, and the standard deviation of the discharge time interval is greater than the preset time interval standard deviation threshold, indicating that the discharge time interval is unstable. By calculating the ratio of the total amplitude of the positive and negative polarity discharge pulses, the result is in an extremely small fluctuation range close to 1 (such as [0.9, 1.1]), indicating that the amplitude difference characteristics of the positive and negative polarity discharge pulses are not significant (that is, the polarity effect is not obvious), and the discharge signal distribution can be detected at all phases of the entire power frequency cycle. At this time, according to the established discharge type judgment rules, it can be determined that the discharge situation belongs to the "free metal particle suspension discharge" type.

[0049] See also Figure 5 , Figure 5 is another schematic diagram of the PRPD spectrum in the embodiment of the present application; The standard deviation of the amplitude of the discharge pulse is less than the preset amplitude stability standard deviation threshold, indicating that the amplitude of the discharge pulse is in a relatively stable state, and the absolute value of the time interval difference between adjacent discharges is less than the preset time interval difference threshold, which means that the time intervals of adjacent discharges are basically consistent. However, in the case of asymmetric suspended metal bodies, the difference between the amplitude means of positive and negative polarity discharge pulses in the same phase interval is greater than the preset polarity amplitude difference threshold, that is, there is an obvious polarity difference in the signals detected by the positive and negative half-waves. Combining these characteristics and according to the corresponding judgment logic, it can be classified as the "fixed metal body suspension discharge" type.

[0050] See also Figure 6 , Figure 6 is another schematic diagram of the PRPD spectrum in the embodiment of the present application; The statistical value of the number of discharges is less than the preset threshold value of the number of discharges. The repeatability of the discharge condition in the cycle is measured by calculating the correlation coefficient of the number of discharge pulses in adjacent cycles. The correlation coefficient is less than the preset repeatability correlation coefficient threshold, indicating that the repeatability of the discharge cycle is low. The standard deviation of the discharge amplitude is greater than the preset amplitude dispersion standard deviation threshold, indicating that the discharge amplitude is relatively dispersed. However, the standard deviation of the discharge phase is less than the preset phase stability standard deviation threshold, which means that the discharge phase can remain relatively stable. At the same time, by calculating the ratio of the total amplitude of the positive and negative polarity discharge pulses, the result is in a very small fluctuation range close to 1, indicating that there is no significant difference between the positive and negative polarity discharge pulses (that is, the polarity effect is not obvious). Then, according to the existing classification basis, it can be determined that this discharge condition corresponds to the "solid insulation internal air gap" type.

[0051] See also Figure 7 , Figure 7 is another schematic diagram of the PRPD spectrum in the embodiment of the present application; When the spectrum shows that the standard deviation of the discharge amplitude is greater than the preset amplitude dispersion standard deviation threshold, it indicates that the discharge amplitude has a large dispersion, and the standard deviation of the discharge time interval is greater than the preset time interval standard deviation threshold, which means that the discharge time interval is unstable. By calculating the ratio of the total amplitude of the positive and negative polarity discharge pulses, the result is in an extremely small fluctuation range close to 1, that is, the difference characteristics of the positive and negative polarity discharge pulses in related aspects are not obvious. According to the relevant judgment criteria, it can be inferred that the discharge situation belongs to the "insulating surface surface discharge" type.

[0052] See also Figure 8 , Figure 8 is another schematic diagram of the PRPD spectrum in the embodiment of the present application; The statistical value of the number of discharges is greater than the preset discharge number threshold, and the standard deviation of the discharge amplitude is less than the preset amplitude dispersion standard deviation threshold, indicating that the dispersion of the discharge amplitude is small, and the absolute value of the difference in discharge time intervals is less than the preset time interval difference threshold, which means that the discharge time intervals are relatively uniform, and by calculating the ratio of the sum of the amplitudes of the positive and negative polarity discharge pulses, the result is greater than the preset polarity amplitude ratio threshold, indicating that the polarity effect of the discharge is very significant. At the same time, the proportion of the number of discharge pulses in each phase interval to the total number of pulses is statistically analyzed, and it is found that the proportion of the number of discharge pulses in the negative half cycle of the power frequency phase is greater than the preset negative half cycle proportion threshold, that is, the discharge phenomenon only occurs in the negative half cycle of the power frequency phase. According to the corresponding judgment rules, it can be determined that this situation corresponds to the "tip discharge" type.

[0053] S106. When at least one of the statistical moment, phase symmetry, or polarity effect exceeds a preset monitoring parameter threshold for a specific defect type, a judgment result is output, where the judgment result includes the location of the discharge point and the specific defect type.

[0054] Among them, the monitoring parameter threshold refers to the critical value set in advance for different specific defect types through a large number of experiments, data analysis and practical experience, which is used to measure whether characteristic parameters such as statistical moments, phase symmetry and polarity effects exceed the normal range. When these parameters exceed the corresponding threshold, it means that the cable may have corresponding specific defects.

[0055] Specifically, after the preset pattern recognition model processes the input feature vector, it outputs relevant judgment information. This information then compares the statistical moment, phase symmetry, and polarity effect to see if at least one parameter exceeds the preset monitoring parameter threshold for the specific defect type. If a parameter exceeds the threshold, the final judgment result, combined with the previously calculated discharge point location information, is combined to form the final judgment result, clearly indicating the specific cable defect type and discharge point location, providing an accurate basis for subsequent repair and maintenance.

[0056] It can be seen that the high-frequency pulse current sensor deployed on the grounding wire of the cable joint captures the pulse current signal generated when the cable discharges, and the power frequency phase transformer deployed on the cable is used to time calibrate the discharge pulse current signal. Based on the double-end pulse time difference positioning method, by measuring the time difference of the signals monitored at different positions and combining the signal propagation speed, the specific location where the discharge occurs is locked. Within the power frequency cycle, the amplitude, frequency and corresponding power frequency phase information of the discharge pulse current signal are used to construct a PRPD spectrum. Then, based on the spectrum, the statistical moment, phase symmetry and polarity effect on each coordinate axis are calculated, and the characteristic vector is input into the preset pattern recognition model. The model compares with the preset monitoring parameter threshold for the specific defect type and outputs the judgment result including the discharge point location and the specific defect type. It provides a directional reference for subsequent maintenance and repair work, avoids blind investigation, improves the efficiency of maintenance and repair, and reduces costs.

[0057] In actual use, since the high-frequency pulse current sensor is deployed on the ground wire of the cable joint of the cable, it will cause an additional problem, that is, there are multiple cables at the cable joint, and there may also be a scenario where the cables are densely laid; therefore, the electromagnetic fields of multiple cables affect each other, making the high-frequency pulse current sensor extremely susceptible to crosstalk from the electromagnetic fields of surrounding cables, causing the transmitted discharge pulse current signal to be mixed with interference components, resulting in the discharge pulse current signal being easily confused during subsequent analysis.

[0058] See also Figure 9 , Figure 9 This is another flow chart of the cable partial discharge monitoring method according to an embodiment of the present application; In some embodiments, after step S101, the method further includes: S201, extracting the pulse amplitude distribution of the discharge pulse current signal; Among them, the pulse amplitude distribution refers to the distribution pattern of the amplitude corresponding to each pulse in the discharge pulse current signal within a certain range, such as the number of pulses in different amplitude intervals. Extracting it can help further analyze the characteristics of the discharge and subsequently generate related coding sequences and other operations.

[0059] S202, generating a phase coding sequence according to the extracted pulse amplitude distribution; In some embodiments, the amplitude is divided into several levels from small to large, and each level corresponds to a fixed phase value (such as 0 degrees, 90 degrees, 180 degrees, etc.); in the second step, according to the order in which the pulses appear in the discharge pulse current signal, the amplitude level of each pulse is queried in turn, and the corresponding phase value is obtained according to the encoding rule, and these phase values ​​are recorded in sequence to form an initial phase encoding sequence.

[0060] In some embodiments, such as the Gray code encoding algorithm or the differential encoding algorithm, key information such as the amplitude range and pulse frequency in the pulse amplitude distribution is used as input parameters of the algorithm for initialization configuration; in the second step, the encoding algorithm is run by writing a program or using existing algorithm implementation tools, allowing the algorithm to generate a phase coding sequence based on the input parameters and its own logic.

[0061] S203 , using a phase coding sequence to perform phase coding modulation on the discharge pulse current signal.

[0062] Among them, phase coding modulation refers to a signal processing method that uses the generated phase coding sequence to adjust and change the phase of the discharge pulse current signal. In this way, the coding information is integrated into the signal, so that during the subsequent transmission process, even if the signal is affected by crosstalk from the electromagnetic field of the surrounding cables, it can be accurately identified and restored due to its unique phase coding characteristics, thereby ensuring the accuracy and reliability of signal transmission.

[0063] Specifically, the generated phase coding sequence is applied to the discharge pulse current signal for phase coding modulation. In terms of hardware implementation, this can be accomplished through a dedicated phase modulation circuit. The discharge pulse current signal is input into the phase modulation circuit. The circuit adjusts the phase of the input signal pulse by pulse based on the phase information in the phase coding sequence. For example, by changing the phase delay or advance of the signal, the phase of the signal is matched with the phase value in the coding sequence, thereby achieving phase coding modulation. At the software implementation level, the discharge pulse current signal is digitized using a digital signal processing algorithm. The phase data of the signal is calculated and modified by the algorithm according to the phase change rules specified by the phase coding sequence. The processed digital signal is then converted back to an analog signal (if an analog signal form is required for subsequent transmission). Phase coding modulation of the discharge pulse current signal is completed. The modulated signal has coding characteristics that can resist electromagnetic crosstalk and can be transmitted more reliably in complex electromagnetic environments.

[0064] As can be seen, the pulse amplitude distribution of the discharge pulse current signal is first extracted. Based on the extracted pulse amplitude distribution, a phase coding sequence is generated to distinguish it from other interference signals. Finally, the phase coding sequence is used to perform phase coding modulation on the discharge pulse current signal. In the complex electromagnetic environment of densely laid cables, the modulated signal carries specific coding information. Even if the electromagnetic fields of surrounding cables interact and cause crosstalk, its coding characteristics can remain relatively independent during transmission and are not easily confused by interference signals, ensuring that tasks such as partial discharge analysis based on this digital signal can be carried out normally and accurately.

[0065] In actual use, the discharge pulse current signal used in the above embodiment is often a mixture of multiple interference signals and the real signal. This results in an erroneous coding sequence generated by extracting signal features according to existing techniques. Subsequent signal modulation using this erroneous coding sequence can cause interference signals to mix in and masquerade as legitimate signals, resulting in a decrease in the ability to distinguish the discharge pulse current signal.

[0066] See also Figure 10 , Figure 10 This is another flow chart of the cable partial discharge monitoring method according to an embodiment of the present application; In some other embodiments, before step S203, the method further includes: S301, generating a predefined pseudo-random sequence as a pilot code by a field programmable gate array deployed on a ground wire of a cable connector of a cable; The predefined pseudo-random sequence refers to a binary sequence that appears random but is actually repeatable and is generated according to a specific algorithm.

[0067] Pilot code refers to a specific coding sequence used for synchronization and channel estimation in communication systems. By comparing it with the corresponding part in the received signal, the degree of signal damage can be assessed.

[0068] It's important to note that when a partial discharge occurs in a cable, the resulting pulse current forms a loop through the ground wire. The current signal on the ground wire carries the most original and direct information about the discharge. By deploying the FPGA on the ground wire, the predefined pseudo-random sequence (pilot code) it generates can immediately establish a close correlation with this original discharge signal. Because the pilot code is subsequently compared with the corresponding portion of the received signal to assess the severity of signal impairment, generating it on the ground wire ensures that its embedding into the discharge pulse current signal is as close to the source as possible. This maximizes the correlation between the pilot code and the actual discharge signal, making subsequent signal impairment assessment based on this correlation more accurate and reliable.

[0069] S302, obtaining a discharge pulse current signal including a pilot code, and obtaining a discharge pulse current signal not including a pilot code; The discharge pulse current signal containing the pilot code refers to a composite signal obtained by superimposing the pilot code on the original discharge pulse current signal, and is used to evaluate the signal damage program.

[0070] The discharge pulse current signal without the pilot code refers to an original pulse current signal only generated by cable discharge, which is used for subsequent signal subtraction operation to extract the pilot code.

[0071] After generating the pilot code and injecting it into the cable connector ground wire, it is necessary to separately collect the discharge pulse current signals with and without the pilot code to analyze interference during signal transmission. For example, these two signals can be collected in a time-sharing manner within a power frequency cycle after the pilot code is injected.

[0072] S303, subtracting the discharge pulse current signal that does not contain the pilot code from the discharge pulse current signal that contains the pilot code to obtain an extracted pilot code; Specifically, the discharge pulse current signal containing the pilot code is subtracted point by point from the discharge pulse current signal without the pilot code. Since the main difference between these two signals is whether they contain the pilot code, the subtraction result primarily retains the pilot code portion while partially offsetting the effects of the original discharge signal and background noise. To improve extraction accuracy, the subtracted signal can be digitally filtered and enhanced.

[0073] S304, comparing the extracted pilot code with the pilot code to obtain a damage index; The impairment index is a quantitative indicator obtained by comparing the extracted pilot code with the original pilot code. It is used to assess the degree of interference to the signal during transmission. A higher impairment index indicates more severe signal damage.

[0074] After extracting the pilot code, it is necessary to compare it with the original pilot code and calculate the damage index to determine whether the signal quality meets the requirements of subsequent processing. For example, this step is performed each time the pilot code is extracted.

[0075] Specifically, the extracted pilot code is compared point by point with the original pilot code, and the difference between the two is calculated. Common comparison methods include calculating the mean square error (MSE), normalized cross-correlation coefficient (NCC), or bit error rate (BER). Based on the comparison results, a quantitative impairment index is generated. For example, when using the mean square error as the impairment index, a smaller value indicates that the signal is closer to the original state and the impairment is less.

[0076] In some specific embodiments, the extracted pilot code and the original pilot code are normalized to make their amplitude range consistent; the sum of the squares of the differences between the corresponding points of the two is calculated and divided by the number of sample points to obtain the mean square error as the damage index S305: If the damage index is lower than the preset damage threshold, execute step S203; The preset damage threshold is a pre-set damage index critical value used to determine whether the signal quality is acceptable. When the damage index is lower than the threshold, it indicates that the signal quality is good and subsequent phase coding modulation can continue.

[0077] S306. If the damage index is not lower than the preset damage threshold, extract a preset number of crosstalk frequency points from the phase coding sequence and perform phase shift on the crosstalk frequency points. The crosstalk frequency points are points where the difference between the extracted pilot code and the pilot code is greater than the threshold, and execute step S203.

[0078] Among them, the crosstalk frequency point refers to the specific frequency point in the signal spectrum where the interference signal energy is concentrated. These frequency points usually correspond to the interference frequency of the electromagnetic field of the surrounding cables.

[0079] Phase shift refers to adjusting the phase of a signal at a specific frequency. This introduces additional phase changes to offset the effects of crosstalk and improve the signal's anti-interference capability.

[0080] If the damage index is not lower than the preset damage threshold, the signal is subject to severe interference and the phase coding sequence needs to be optimized to enhance its anti-interference capability. For example, this step is performed when strong electromagnetic interference is detected in an area with dense cable laying.

[0081] Specifically, the difference between the extracted pilot code and the original pilot code is first spectrally analyzed to identify frequencies where the difference exceeds a preset threshold. These frequencies are considered crosstalk frequencies. A preset number of crosstalk frequencies are then selected from the phase-coded sequence, and phase offset adjustments are performed on the phase-coded sequence at these frequencies. This adjusted phase-coded sequence has enhanced anti-interference capabilities, effectively suppressing crosstalk at specific frequencies and ensuring the proper functioning of subsequent phase-coded modulation.

[0082] In some specific embodiments, a frequency point with an amplitude greater than a preset threshold is found as a crosstalk frequency point; in the third step, the phase value of the corresponding frequency point in the phase coding sequence is modified according to a preset offset rule (such as a 90-degree phase offset for each crosstalk frequency point), which is not limited here.

[0083] As can be seen, a field-programmable gate array (FPGA) deployed on the ground wire of the cable connector generates a predefined pseudo-random sequence as a pilot code, providing a reliable reference standard for subsequent signal integrity assessment. Next, the discharge pulse current signal containing the pilot code and the discharge pulse current signal excluding the pilot code are obtained and subtracted to obtain the extracted pilot code. This operation accurately separates the pilot code portion. By comparing it with the original pilot code, a damage index is obtained, which intuitively reflects the degree of signal interference. If the damage index is below the preset damage threshold, the signal quality is acceptable and the phase-coded sequence modulation step can be performed. If the damage index is not below the preset damage threshold, a preset number of crosstalk frequencies in the phase-coded sequence are extracted and phase-shifted to correct for coding errors that may be caused by interference. This method effectively verifies signal reliability in complex cable operating environments where the collected signal is often a mixture of interference and true discharge signals, preventing signal modulation due to erroneous coding sequences and preventing interference signals from masquerading as legitimate signals and infiltrating subsequent processes. This ensures that the diagnostic model receives accurate input and the accuracy of the monitoring results.

[0084] In the above embodiment, in step S303, the extracted pilot code is obtained by subtracting the discharge pulse current signal without the pilot code from the discharge pulse current signal including the pilot code. Figures 4 to 8 The cable discharge signal is random, which causes the result obtained by the existing signal subtraction operation to be mixed with the part caused by the difference in the discharge signal in addition to the pilot code, resulting in deviation in the calculation of the damage index.

[0085] See also Figure 7 , Figure 7 is another schematic diagram of the PRPD spectrum in the embodiment of the present application; In some embodiments, step S303 specifically includes: S401, determining that the discharge pulse current signal including the pilot code is a first half-wave signal within the power frequency cycle, and the discharge pulse current signal not including the pilot code is a second half-wave signal within the power frequency cycle corresponding to the first half-wave signal; The power frequency cycle refers to a complete cycle of the alternating current in the power system, which is usually 50 Hz and corresponds to a period of 20 ms.

[0086] The first half-wave signal refers to a positive half-wave or negative half-wave signal within the power frequency period, depending on the system configuration. In this step, it specifically refers to the half-wave signal containing the pilot code.

[0087] The second half-wave signal refers to another half-wave signal adjacent to the first half-wave signal within the power frequency cycle, that is, if the first half-wave is a positive half-wave, the second half-wave is a negative half-wave, and vice versa, and this half-wave signal does not contain a pilot code.

[0088] Specifically, the starting position of the power frequency cycle is determined by detecting the zero-crossing point of the power frequency voltage, dividing a complete power frequency cycle into two half-waves. Depending on the system configuration, one half-wave (e.g., the positive half-wave) is selected as the first half-wave signal containing the pilot code, and the other half-wave (e.g., the negative half-wave) is selected as the second half-wave signal excluding the pilot code. This division method utilizes the periodicity and symmetry of the power frequency signal, providing a foundation for subsequent mirror processing and signal subtraction.

[0089] S402, performing mirror processing on the second half-wave signal to obtain a mirror signal; The mirror processing refers to performing polarity inversion and time axis mirroring operations on the second half-wave signal so that it is theoretically as similar as possible to the components of the first half-wave signal except for the pilot code.

[0090] Specifically, the polarity of the second half-wave signal is inverted, multiplying the amplitude of all sampling points by -1. Then, a mirroring operation is performed on the time axis to align the inverted signal with the first half-wave signal. In theory, this processed mirror signal should be essentially identical to the first half-wave signal in all components (such as discharge pulse characteristics and background noise) except for the pilot code, thus facilitating accurate extraction of the pilot code.

[0091] S403: Subtract the mirror signal from the first half-wave signal to obtain an extracted navigation code.

[0092] It can be seen that the discharge pulse current signal containing the pilot code is determined to be the first half-wave signal within the power frequency cycle, and the discharge pulse current signal without the pilot code is determined to be the second half-wave signal corresponding to the first half-wave signal within the power frequency cycle. This division is based on the periodicity and correlation of the signals within the power frequency cycle. Mirroring the second half-wave signal utilizes the symmetry of the signal within the cycle, ensuring that the processed mirror signal and the first half-wave signal are theoretically as similar as possible, with the exception of the pilot code. The extracted pilot code is then subtracted from the mirror signal from the first half-wave signal. This considers the inherent characteristics of the signal within the same cycle, reduces the impact of the difference between the two signals caused by the randomness of the cable discharge signal, and more accurately extracts the pilot code, avoiding deviations in damage index calculation due to inaccurate extraction.

[0093] Although the above embodiments can solve the above problems, there are some special cases, such as Figure 8In the tip discharge type, there is a greater difference between the half-wave signal and the half-wave signal, so the above embodiment cannot solve the previous problem well.

[0094] See also Figure 8 , Figure 8 is another schematic diagram of the PRPD spectrum in the embodiment of the present application; In some embodiments, step S303 specifically includes: S501, obtaining trend characteristics of parameters in historical discharge pulse current signals changing over time; The historical discharge pulse current signal refers to the discharge pulse current signal data collected over a period of time and stored in the system's historical database. The trend characteristics of parameter changes over time refer to feature vectors extracted from the historical discharge pulse current signal that reflect the temporal variation patterns of signal parameters (such as amplitude, frequency, and phase). Examples include rising edge slope, attenuation coefficient, and periodic variation patterns.

[0095] Specifically, the system retrieves discharge pulse current signal data from a historical database over a specific time period and performs feature extraction on each signal cycle. Extracted parameters include, but are not limited to, pulse amplitude, pulse width, pulse interval, and spectral characteristics. These parameters are then analyzed for patterns of change over time, such as whether they exhibit periodicity, linear growth, or decay. These patterns are then quantified into trend feature vectors for subsequent trend category matching.

[0096] S502: Match the current trend feature with the trend category statistical information to determine the most matching historical trend category; The current trend feature refers to the time-varying trend feature vector of parameters extracted from the currently acquired discharge pulse current signal. Trend category statistics refer to a pre-established database of historical trend features, derived through classification and statistics. This database contains multiple trend categories and their statistical features (such as mean, variance, and center vector).

[0097] In some embodiments, trend category statistical information is loaded into memory to form a category feature library; the Euclidean distance between the current trend feature vector and each category center vector is calculated; and the category with the smallest distance is selected as the most matching historical trend category.

[0098] S503: constructing a predicted discharge pulse current signal waveform within a future preset time period based on the historical average change of the most matching historical trend category; The most matching historical trend category refers to the historical trend category that is determined through trend feature matching and is most similar to the current signal trend.

[0099] The historical average change refers to the average change pattern and statistical characteristics of the historical discharge pulse current signal parameters within a certain period of time under the historical trend category.

[0100] The predicted discharge pulse current signal waveform within a preset time period in the future refers to the prediction result of the discharge pulse current signal waveform within a period of time in the future based on the historical average change.

[0101] After determining the most matching historical trend category, it is necessary to construct a predicted discharge pulse current signal waveform within a preset time period in the future based on the historical average change of the category for subsequent navigation code extraction.

[0102] Specifically, the historical average change parameters that best match the historical trend category are obtained from trend category statistics, such as amplitude change rate, frequency drift, and phase variation patterns. Based on these parameters, a time series prediction model (such as an ARIMA model or LSTM neural network) is used to extrapolate the discharge pulse current signal waveform within a preset future duration. To improve prediction accuracy, the prediction results can be corrected based on the current signal's real-time status.

[0103] In some embodiments, the average amplitude, frequency, and phase change parameters of the most matching category over the past multiple periods are extracted from the trend category statistical information; these parameters are used to perform time series prediction using the ARIMA model to obtain parameter prediction values ​​within a future preset time period; and based on the predicted parameter values, the discharge pulse current signal waveform within the future preset time period is synthesized.

[0104] S504 , subtracting the discharge pulse current signal including the pilot code from the predicted discharge pulse current signal waveform point by point to obtain a difference signal, and using the difference signal as the pilot code.

[0105] The discharge pulse current signal containing the pilot code refers to the discharge pulse current signal actually collected and superimposed with the pilot code.

[0106] The predicted discharge pulse current signal waveform refers to a predicted waveform of the discharge pulse current signal within a preset time period in the future, which is constructed based on historical trends.

[0107] The difference signal refers to the signal obtained by subtracting the discharge pulse current signal containing the pilot code from the predicted discharge pulse current signal waveform point by point, which mainly includes the pilot code and random noise not captured by the prediction model.

[0108] Specifically, the discharge pulse current signal containing the pilot code is subtracted point by point from the predicted discharge pulse current signal waveform. Because the predicted waveform is constructed based on historical trends and reflects the key characteristics of the discharge signal, these characteristics are offset after the subtraction. The pilot code, as additional information superimposed on the original signal, is retained in the difference signal. To improve the purity of the pilot code extraction, the difference signal can be bandpass filtered to remove random noise.

[0109] It can be seen that obtaining the trend characteristics of the parameters in the historical discharge pulse current signal over time and matching the current trend characteristics with the trend category statistical information to determine the most matching historical trend category is equivalent to finding the most similar reference template for the current signal in historical experience. Based on the historical average change of the most matching historical trend category, a predicted discharge pulse current signal waveform within a preset time period in the future is constructed. This allows the constructed waveform to fit the development trend of actual discharge and is more in line with the actual discharge law of the cable. Finally, the discharge pulse current signal containing the pilot code is subtracted point by point from the predicted discharge pulse current signal waveform to obtain the difference signal as the pilot code. This can more accurately extract the pilot code and avoid the deviation of the subtraction result caused by the randomness of the signal, thereby calculating the damage index and avoiding the erroneous triggering of the phase offset operation, thereby improving the signal quality and the accuracy of cable partial discharge monitoring.

[0110] The following introduces the cable partial discharge monitoring system 1300 provided in an embodiment of the present application. Figure 13 Schematic diagram of an exemplary hardware structure of a cable partial discharge monitoring system 1300 provided in an embodiment of the present application.

[0111] In some embodiments, the cable partial discharge monitoring system 1300 is a computer device or the cable partial discharge monitoring system 1300 includes a computer device. The computer device includes a processor, a memory, and a network interface connected via a system bus. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program, and a database. The internal memory provides an environment for the operation of the operating system and computer program in the non-volatile storage medium. The database of the computer device is used to store 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, and in some embodiments, the network interface can also be a wireless network interface. When the computer program is executed by the processor, the method in the embodiment of the present application is implemented.

[0112] Those skilled in the art will understand that Figure 13The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than shown in the figure, or combine certain components, or have a different component arrangement.

[0113] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

[0114] As used in the above embodiments, the term “when” may be interpreted to mean “if” or “after” or “in response to determining that” or “in response to detecting that”, depending on the context. Similarly, the phrases “upon determining that” or “if (stated condition or event) is detected” may be interpreted to mean “if determining that” or “in response to determining that” or “upon detecting (stated condition or event)” or “in response to detecting (stated condition or event)”, depending on the context.

[0115] In the above embodiments, all or part of the embodiments can be implemented using software, hardware, firmware, or any combination thereof. When implemented using software, all or part of the embodiments can be implemented 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, the processes or functions described in the embodiments of this application are generated in whole or in part. 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, optical fiber, digital subscriber line) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that can be accessed by a computer, or a data storage device such as a server or data center that integrates one or more available media. The available medium can be magnetic media (e.g., floppy disk, hard disk, tape), optical media (e.g., DVD), or semiconductor media (e.g., solid-state drive).

[0116] Those skilled in the art will appreciate that all or part of the process steps in the above-described method embodiments can be implemented by a computer program instructing the relevant hardware. The program can be stored in a computer-readable storage medium, and when executed, the program can include the process steps in the above-described 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 cable partial discharge monitoring method, characterized in that: include: A discharge pulse current signal is obtained by a high-frequency pulse current sensor deployed on the ground wire of the cable connector of the cable; Obtaining power frequency phase information through a power frequency phase transformer deployed on the cable; Based on the double-ended pulse time difference positioning method, the position of the discharge point of the cable is calculated using the discharge pulse current signal, wherein the power frequency phase information is used to perform time calibration on the discharge pulse current signal; In a power frequency cycle, the discharge pulse current signal is used as coordinate axes according to its amplitude, frequency and corresponding power frequency phase information to construct a PRPD spectrum; Based on the PRPD spectrum, calculating the statistical moment, phase symmetry and polarity effect of the PRPD spectrum on each coordinate axis; Inputting a feature vector composed of the statistical moment, the phase symmetry, and the polarity effect into a preset pattern recognition model; When at least one of the statistical moment, the phase symmetry or the polarity effect exceeds a monitoring parameter threshold preset for a specific defect type, a judgment result is output, where the judgment result includes the position of the discharge point and the specific defect type.

2. The method according to claim 1, characterized in that The discharge pulse current signal is obtained by a high-frequency pulse current sensor deployed on the ground wire of the cable connector of the cable; After the step of obtaining power frequency phase information by using a power frequency phase transformer deployed on the cable, the method further includes: extracting a pulse amplitude distribution of the discharge pulse current signal; generating a phase coding sequence according to the extracted pulse amplitude distribution; The phase coding sequence is used to perform phase coding modulation on the discharge pulse current signal.

3. The method according to claim 2, characterized in that Before the step of performing phase coding modulation on the discharge pulse current signal using the phase coding sequence, the method further includes: generating a predefined pseudo-random sequence as a pilot code by a field programmable gate array deployed on a ground wire of a cable connector of the cable; obtaining a discharge pulse current signal including the pilot code, and obtaining a discharge pulse current signal not including the pilot code; subtracting the discharge pulse current signal that does not contain the pilot code from the discharge pulse current signal that contains the pilot code to obtain the extracted pilot code; Comparing the extracted pilot code with the pilot code to obtain a damage index; If the damage index is lower than a preset damage threshold, performing the step of using the phase coding sequence to perform phase coding modulation on the discharge pulse current signal; If the damage index is not lower than the preset damage threshold, a preset number of crosstalk frequency points in the phase coding sequence are extracted, and phase shift is performed on the crosstalk frequency points, where the crosstalk frequency point is a point where the difference between the extracted pilot code and the pilot code is greater than a threshold, and the step of performing phase coding modulation on the discharge pulse current signal using the phase coding sequence is performed.

4. The method according to claim 3, characterized in that The step of subtracting the discharge pulse current signal not containing the pilot code from the discharge pulse current signal containing the pilot code to obtain the extracted pilot code specifically includes: Determining that the discharge pulse current signal including the pilot code is a first half-wave signal within a power frequency cycle, and the discharge pulse current signal not including the pilot code is a second half-wave signal within the power frequency cycle corresponding to the first half-wave signal; performing mirror processing on the second half-wave signal to obtain a mirror signal; The mirror signal is subtracted from the first half-wave signal to obtain the extracted pilot code.

5. The method according to claim 3, characterized in that The step of subtracting the discharge pulse current signal not containing the pilot code from the discharge pulse current signal containing the pilot code to obtain the extracted pilot code specifically includes: Obtain the trend characteristics of the parameters in the historical discharge pulse current signal changing with time; Matching current trend characteristics with trend category statistics to determine the best matching historical trend category; Constructing a predicted discharge pulse current signal waveform within a future preset time period based on the historical average change of the most matching historical trend category; The discharge pulse current signal including the pilot code is subtracted point by point from the predicted discharge pulse current signal waveform to obtain a difference signal, and the difference signal is used as the pilot code.

6. The method according to claim 1, characterized in that The step of calculating the position of the discharge point of the cable using the discharge pulse current signal based on the double-ended pulse time difference positioning method specifically includes: Calculating the time difference between the discharge pulse current signals; The discharge point position is calculated using a double-end positioning formula based on the time difference and the wave velocity of the discharge pulse current signal; wherein the double-end positioning formula is: Where, is the distance from the discharge point to the reference point, is the wave velocity of the discharge pulse current signal, is the time difference, is the position of the reference point.

7. The method according to claim 1, characterized in that Before the step of constructing a PRPD spectrum by using the discharge pulse current signal according to its amplitude, frequency and the corresponding power frequency phase information as coordinate axes within each power frequency cycle, the method further includes: The discharge pulse current signal is subjected to noise reduction processing.

8. A cable partial discharge monitoring system, characterized in that: The cable partial discharge monitoring system 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 includes computer instructions, and the one or more processors call the computer instructions to enable the cable partial discharge monitoring system to perform the method according to any one of claims 1 to 7.

9. A computer program product comprising instructions, characterized in that When the computer program product is run on a cable partial discharge monitoring system, the cable partial discharge monitoring system is enabled to perform the method according to any one of claims 1 to 7.

10. A computer-readable storage medium comprising instructions, characterized in that: When the instruction is executed on a cable partial discharge monitoring system, the cable partial discharge monitoring system is caused to execute the method according to any one of claims 1 to 7.

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