Method and device for determining damage length of electrical tree in cable and electronic equipment

Abstract

The invention discloses a method and device for determining the damage length of an electric tree in a cable and electronic equipment. The method comprises the following steps: acquiring an effective value of an externally applied voltage of a cable in a target time period, and a current value of multiple times of partial discharge generated by the cable under the externally applied voltage in the target time period; based on the effective value of the externally applied voltage and the current values of the multiple partial discharges, determining an externally applied voltage difference corresponding to two adjacent partial discharges in the multiple partial discharges in the target time period; determining a partial discharge initial voltage and a partial discharge final voltage in the target time period based on an externally applied voltage difference corresponding to two adjacent partial discharges in multiple partial discharges in the target time period; and determining the damage length of the electrical tree in the cable based on the current values of the multiple times of partial discharge, the partial discharge initial voltage and the partial discharge final voltage. The technical problem that it is difficult to accurately and non-destructively evaluate the damage length of the electrical tree in the cable is solved.

Description

Technical Field

[0001] The present invention relates to the field of electric power, and in particular, to a method, device, and electronic device for determining the damage length of electrical tree in a cable. Background Art

[0002] As a key medium for power transmission and equipment connection in the power grid, power cables are directly related to the safety and stability of the power system. Inevitably, there are minor defects in the production and installation of power cables, which may deteriorate the insulation performance of power cables over time. In particular, partial discharge phenomena will induce the growth of electrical trees, weaken the cable insulation, and ultimately may cause cable breakdown, leading to serious safety accidents. In the prior art, there are limited non-destructive evaluation methods for the length of electrical trees, making it difficult to meet the requirements of precise monitoring.

[0003] For the above problems, no effective solution has been proposed yet. Summary of the Invention

[0004] Embodiments of the present invention provide a method, device, and electronic device for determining the damage length of electrical tree in a cable, so as to at least solve the technical problem of difficult to accurately and non-destructively evaluate the damage length of electrical tree in a cable.

[0005] According to one aspect of the embodiments of the present invention, a method for determining the damage length of electrical tree in a cable is provided, including: obtaining the effective value of the applied voltage of the cable during a target time period, and the current values of multiple partial discharges generated by the cable under the applied voltage during the target time period; determining the voltage difference of the applied voltage corresponding to two adjacent partial discharges among the multiple partial discharges during the target time period based on the effective value of the applied voltage and the current values of the multiple partial discharges; determining the partial discharge inception voltage and the partial discharge extinction voltage during the target time period based on the voltage difference of the applied voltage corresponding to two adjacent partial discharges among the multiple partial discharges during the target time period; and determining the damage length of the electrical tree in the cable based on the current values of the multiple partial discharges, the partial discharge inception voltage, and the partial discharge extinction voltage.

[0006] Optionally, determining the applied voltage difference corresponding to two adjacent partial discharges among the multiple partial discharges within the target time period based on the effective value of the applied voltage and the current values of the multiple partial discharges includes: obtaining a phase distribution spectrogram of the current values of the multiple partial discharges based on the current values of the multiple partial discharges; determining the phases corresponding to the current values of the multiple partial discharges based on the phase distribution spectrogram; determining the applied voltage values corresponding to the phases corresponding to the current values of the multiple partial discharges based on the effective value of the applied voltage and the phases corresponding to the current values of the multiple partial discharges; and determining the applied voltage difference corresponding to two adjacent partial discharges among the multiple partial discharges based on the applied voltage values corresponding to the phases corresponding to two adjacent partial discharges among the multiple partial discharges.

[0007] Optionally, determining the partial discharge inception voltage and the partial discharge extinction voltage within the target time period based on the applied voltage difference corresponding to two adjacent partial discharges among the multiple partial discharges within the target time period includes: classifying the applied voltage differences corresponding to two adjacent partial discharges among the multiple partial discharges to obtain a classification center; determining the characteristic values of the applied voltage differences corresponding to two adjacent partial discharges among the multiple partial discharges based on the classification center; and determining the partial discharge inception voltage and the partial discharge extinction voltage within the target time period based on the characteristic values.

[0008] Optionally, classifying the applied voltage differences corresponding to two adjacent partial discharges among the multiple partial discharges to obtain a classification center includes: randomly selecting an applied voltage difference as an initial center from the applied voltage differences corresponding to two adjacent partial discharges among the multiple partial discharges; denoting the applied voltage differences among the applied voltage differences corresponding to two adjacent partial discharges among the multiple partial discharges whose distances from the initial center are less than a first threshold as an initial set; determining the distance vectors of the applied voltage differences in the initial set from the initial center, and obtaining the offset vector of the initial set based on the distance vectors of the applied voltage differences in the initial set from the initial center; updating the initial center based on the offset vector and updating the initial set until the offset vector corresponding to the updated initial center is less than a second threshold, taking the updated initial center as the target center and the updated initial set as the target set, where the second threshold is less than the first threshold; and iterating the steps of obtaining the target center and the target set until all the applied voltage differences corresponding to two adjacent partial discharges among the multiple partial discharges are classified to obtain the classification center.

[0009] Optionally, determining the partial discharge inception voltage and the partial discharge extinction voltage within the target time period based on the eigenvalue includes: taking the eigenvalues with opposite signs and similar absolute values in the eigenvalues as eigenvalue pairs to obtain a first eigenvalue pair and a second eigenvalue pair, where the absolute value of the first eigenvalue pair is greater than the absolute value of the second eigenvalue pair; determining the average value of the absolute values of the two eigenvalues in the first eigenvalue pair to obtain a first average value, and determining the average value of the absolute values of the two eigenvalues in the second eigenvalue pair to obtain a second average value; determining the partial discharge inception voltage and the partial discharge extinction voltage within the target time period based on the first average value and the second average value.

[0010] Optionally, determining the damage length of the electrical tree in the cable based on the current values of the multiple partial discharges, the partial discharge inception voltage, and the partial discharge extinction voltage includes: determining the maximum amplitude of the discharge amount of the multiple partial discharges based on the current values of the multiple partial discharges; determining the damage length of the electrical tree in the cable based on the maximum amplitude, the partial discharge inception voltage, and the partial discharge extinction voltage.

[0011] According to another aspect of the present invention, there is provided an apparatus for determining the damage length of an electrical tree in a cable, including: an acquisition module for acquiring the effective value of the applied voltage of the cable within a target time period, and the current values of multiple partial discharges generated by the cable under the applied voltage within the target time period; a first determination module for determining the difference in the applied voltage corresponding to two adjacent partial discharges among the multiple partial discharges within the target time period based on the effective value of the applied voltage and the current values of the multiple partial discharges; a second determination module for determining the partial discharge inception voltage and the partial discharge extinction voltage within the target time period based on the difference in the applied voltage corresponding to two adjacent partial discharges among the multiple partial discharges within the target time period; a third determination module for determining the damage length of the electrical tree in the cable based on the current values of the multiple partial discharges, the partial discharge inception voltage, and the partial discharge extinction voltage.

[0012] According to still another aspect of the present invention, there is provided a computer-readable storage medium, where the computer-readable storage medium includes an executable program stored therein, and when the executable program runs, it controls the device where the computer-readable storage medium is located to execute the method for determining the damage length of an electrical tree in a cable as described in any one of the above.

[0013] According to another aspect of the present invention, there is provided an electronic device, including: a memory storing an executable program; a processor for running the program, wherein when the program runs, it executes the method for determining the damage length of the electrical tree in the cable according to any one of the above.

[0014] According to another aspect of the present invention, there is provided a computer program product including a computer program, and when the computer program is executed by a processor, it implements the steps of any one of the methods for determining the damage length of the electrical tree in the cable.

[0015] In the embodiments of the present invention, by adopting the method of determining the damage length of the electrical tree in the cable based on the partial discharge sequence, by obtaining the effective value of the applied voltage of the cable within the target time period and the current values of multiple partial discharges generated under the applied voltage, and combining the mean shift clustering algorithm, the purpose of accurately determining the damage length of the electrical tree in the cable is achieved, thereby realizing the technical effect of accurately evaluating the health state of the cable, and further solving the technical problem of being difficult to accurately and non-destructively evaluate the damage length of the electrical tree in the cable. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings described herein are used to provide a further understanding of the present invention, form a part of this application, and the schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0017] Figure 1 is a flowchart of a method for determining the damage length of the electrical tree in the cable according to an embodiment of the present invention;

[0018] Figure 2 is a schematic diagram of a method for evaluating the damage length of the electrical tree of a power cable based on the partial discharge sequence according to an alternative embodiment of the present invention;

[0019] Figure 3 is a frequency distribution histogram of the voltage difference between two adjacent discharges of the cable under test according to an alternative embodiment of the present invention;

[0020] Figure 4 is the partial discharge inception voltage V I of the cable under test and the partial discharge extinction voltage V X ;

[0021] Figure 5 is the relationship between the maximum amplitude of the partial discharge amount of the cable under test, the length of the electrical tree, and V I -V X ;

[0022] Figure 6Comparison between the actual length and the estimated length of the electrical tree in the cable under test according to an alternative embodiment of the present invention;

[0023] Figure 7 Structural block diagram of a device for determining the damage length of an electrical tree in a cable according to an embodiment of the present invention. Detailed implementation manners

[0024] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0025] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily need to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order different from those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0026] First, some nouns or terms that appear in the process of describing the embodiments of the present application are applicable to the following explanations:

[0027] Electrical tree: An electrical tree is a physical and chemical phenomenon that occurs in high-voltage insulating materials, commonly found in the insulation layer of power cables, especially in cross-linked polyethylene insulating materials. During the long-term operation of high-voltage cables, due to the existence of tiny voids, bubbles or impurities inside, these defects will trigger partial discharge phenomena under the action of a strong electric field. The high-energy electrons and ions generated by partial discharge will further cause material degradation, forming fine discharge channels, which look like tree branches microscopically, so they are called electrical trees. The formation and development of electrical trees will cause the performance of the cable insulation material to deteriorate gradually, and may eventually lead to insulation breakdown, thus affecting the service life of the cable and the safe operation of the power system. The growth rate and final length of electrical trees are related to factors such as the operating voltage of the cable, material properties, temperature, humidity, and the activity level of partial discharge. Therefore, monitoring and evaluating the growth of electrical trees is of great significance for preventing power cable failures.

[0028] Partial discharge inception voltage: The partial discharge inception voltage and the partial discharge extinction voltage are two key parameters describing the characteristics of partial discharge activities, mainly used to evaluate the partial discharge behavior and insulation performance of insulating materials under high-voltage electric fields. The partial discharge inception voltage refers to the voltage at which partial discharge phenomena are first observed in the insulating material when the applied voltage is gradually increased. This voltage value indicates that the electric field inside the insulating material begins to be uneven or the electric field strength at the defect reaches the threshold sufficient to trigger partial discharge. The magnitude of the partial discharge inception voltage depends on the characteristics of the insulating material, the nature of the defects contained, and the surrounding environmental conditions such as temperature and humidity.

[0029] Partial discharge extinction voltage: The partial discharge extinction voltage refers to the voltage at which the partial discharge phenomena disappear in the insulating material when the applied voltage is gradually decreased. In other words, when the applied voltage drops below the extinction voltage, the partial discharge activity stops. The determination of the partial discharge extinction voltage can help understand the voltage range of partial discharge activities and the conditions for the insulating material to restore its original electrical performance. By comparing the inception voltage and the extinction voltage, the damage degree and repair ability of partial discharge to the insulating material can be evaluated.

[0030] Mean shift clustering algorithm: The mean shift clustering algorithm is a density-based unsupervised machine learning method mainly used for clustering analysis and pattern recognition. Different from other clustering algorithms such as K-means, the mean shift algorithm does not require pre-setting the number of clusters. Instead, it automatically finds the high-density regions of data points through an iterative process, thereby determining the cluster centers and the number of clusters. Its core idea is to use the local average value (i.e., the mean) of data points to estimate the center of the high-density region of data points, and then through a series of iterations, make the data points continuously move towards the center of the high-density region.

[0031] According to an embodiment of the present invention, an embodiment of a method for determining the damage length of electrical tree in a cable is provided. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order than here.

[0032] Figure 1 is a flowchart of a method for determining the damage length of electrical tree in a cable according to an embodiment of the present invention, as Figure 1 shown, the method includes the following steps:

[0033] Step S102, obtain the effective value of the applied voltage of the cable during the target time period, and the current values of multiple partial discharges generated by the cable under the applied voltage during the target time period.

[0034] As an alternative embodiment, the execution entity of the method in this embodiment can be a terminal or a server for determining the damage length of electrical tree in a cable. When applied to a terminal, it can easily realize the determination of the damage length of electrical tree in a cable. When applied to a server, it can call the rich computing resources of the server and can more accurately determine the damage length of electrical tree in a cable. Among them, the types of the above-mentioned terminals can be various. For example, it can be a mobile terminal with certain computing capabilities, or a fixed computer device with recognition capabilities, etc. The types of the above-mentioned servers can also be various. For example, it can be a local server or a virtual cloud server. According to the computing power, it can be a single computer device or a computer cluster integrated by multiple computer devices.

[0035] As an alternative embodiment, various methods can be used to obtain the effective value of the applied voltage of the cable during the target time period, and the current values of multiple partial discharges generated under the applied voltage of the cable during the target time period. For example, the data already collected by the cable data acquisition system can be directly obtained, or the cable data can be collected in real time through high-precision voltage and current sensors. Through the cable data acquisition system or high-precision voltage and current sensors, the effective value of the applied voltage and the current values of multiple partial discharges can be obtained accurately and in real time, so as to determine the damage length of the electrical tree in the cable without damaging the cable, based on the effective value of the applied voltage and the current values of multiple partial discharges.

[0036] Among them, the target time period can be a short time length, which can be determined according to the experimental situation or the actual situation. For example, the target time period can be 1 second. The applied voltage of the cable during the target time period can be the voltage originally applied across the cable, or the voltage actively applied across the cable to determine the damage length of the electrical tree in the cable. Under the applied voltage, due to the existence of the electrical tree in the cable, partial discharge will occur. Under the continuous applied voltage, that is, the applied voltage during the target time period, the partial discharge will not occur continuously, but will occur intermittently multiple times during the target time period.

[0037] Step S104, based on the effective value of the applied voltage and the current values of multiple partial discharges, determine the difference in the applied voltage corresponding to two adjacent partial discharges among the multiple partial discharges during the target time period.

[0038] As an alternative embodiment, when determining the applied voltage difference corresponding to two adjacent partial discharges among multiple partial discharges within a target time period based on the effective value of the applied voltage and the current values of multiple partial discharges, a phase distribution spectrogram of the current values of multiple partial discharges can be obtained based on the current values of multiple partial discharges; based on the phase distribution spectrogram, the phases corresponding to the current values of multiple partial discharges can be determined; based on the effective value of the applied voltage and the phases corresponding to the current values of multiple partial discharges respectively, the applied voltage values corresponding to the phases corresponding to the current values of multiple partial discharges can be determined; based on the applied voltage values corresponding to the phases corresponding to two adjacent partial discharges among multiple partial discharges respectively, the applied voltage difference corresponding to two adjacent partial discharges among multiple partial discharges can be determined. Among them, the applied voltage difference corresponding to two adjacent partial discharges among multiple partial discharges within the target time period can be the applied voltage difference corresponding to every two adjacent partial discharges among multiple partial discharges, or can be the applied voltage difference corresponding to most of the adjacent two partial discharges among multiple partial discharges. Since the partial discharge phenomenon has a short duration, a single partial discharge usually only lasts for a few nanoseconds from the start to the end, and it is difficult to accurately determine the phase at which each partial discharge occurs by directly observing the current values of multiple partial discharges. Through the analysis of the phase distribution spectrogram, converting the current values into a phase distribution spectrogram can more accurately determine the phases corresponding to the occurrences of multiple partial discharges, so as to combine with the effective value of the applied voltage to determine the applied voltage values corresponding to the occurrences of multiple partial discharges, and further determine the applied voltage difference corresponding to two adjacent partial discharges among multiple partial discharges. Through the above method, the correlation between the partial discharge event and the applied voltage can be captured more accurately, so as to more accurately determine the applied voltage difference corresponding to two adjacent partial discharges among multiple partial discharges within the target time period based on the correlation between the partial discharge event and the applied voltage.

[0039] Step S106, based on the applied voltage difference corresponding to two adjacent partial discharges among multiple partial discharges within the target time period, determine the partial discharge inception voltage and the partial discharge extinction voltage within the target time period.

[0040] As an alternative embodiment, when determining the partial discharge inception voltage and the partial discharge extinction voltage within a target time period based on the applied voltage differences corresponding to two adjacent partial discharges among multiple partial discharges within the target time period, the applied voltage differences corresponding to two adjacent partial discharges among multiple partial discharges can be classified to obtain classification centers; based on the classification centers, characteristic values of the applied voltage differences corresponding to two adjacent partial discharges among multiple partial discharges are determined; and based on the characteristic values, the partial discharge inception voltage and the partial discharge extinction voltage within the target time period are determined. For example, the mean shift clustering algorithm can be used to classify the applied voltage differences corresponding to two adjacent partial discharges among multiple partial discharges to obtain classification centers, thereby determining the characteristic values of the applied voltage differences corresponding to two adjacent partial discharges among multiple partial discharges, and the characteristic values are the values of the applied voltage differences corresponding to the classification centers. For instance, after classifying the applied voltage differences corresponding to two adjacent partial discharges among multiple partial discharges, 4 classification centers are obtained, and the corresponding values of the applied voltage differences are 3.1 kV, -2.9 kV, 6.7 kV, and -7.0 kV respectively, then the characteristic values of the applied voltage differences corresponding to two adjacent partial discharges among multiple partial discharges are 3.1 kV, -2.9 kV, 6.7 kV, and -7.0 kV respectively. Among them, the mean shift clustering algorithm can automatically discover the density changes of the data, thereby more accurately determining the classification centers corresponding to the applied voltage differences, that is, the characteristic values corresponding to the applied voltage differences, and using the characteristic values to represent a class of applied voltage differences with the same characteristics, thereby reducing the difficulty of determining the partial discharge inception voltage and the partial discharge extinction voltage within the target time period based on the applied voltage differences.

[0041] As an alternative embodiment, when classifying the applied voltage differences corresponding to two adjacent partial discharges among multiple partial discharges to obtain classification centers, an applied voltage difference can be randomly selected from the applied voltage differences corresponding to two adjacent partial discharges among multiple partial discharges as the initial center; the applied voltage differences among the applied voltage differences corresponding to two adjacent partial discharges among multiple partial discharges whose distances from the initial center are less than a first threshold are recorded as the initial set; the distance vectors between the applied voltage differences in the initial set and the initial center are determined, and based on the distance vectors between the applied voltage differences in the initial set and the initial center, the offset vector of the initial set is obtained; based on the offset vector, the initial center is updated, and the initial set is updated until the offset vector corresponding to the updated initial center is less than a second threshold, the updated initial center is used as the target center, and the updated initial set is used as the target set, where the second threshold is less than the first threshold; the steps of iteratively obtaining the target center and the target set are repeated until all the applied voltage differences corresponding to two adjacent partial discharges among multiple partial discharges are classified to obtain classification centers. Through iterative optimization, the classification center that can best represent the characteristics of the applied voltage differences can be found, and it is ensured that the classification centers cover all the applied voltage differences corresponding to two adjacent partial discharges among multiple partial discharges.

[0042] As an alternative embodiment, when determining the partial discharge inception voltage and the partial discharge extinction voltage within a target time period based on eigenvalue, eigenvalue pairs with opposite signs and similar absolute values in the eigenvalues can be used as the first eigenvalue pair and the second eigenvalue pair, where the absolute value of the first eigenvalue pair is greater than that of the second eigenvalue pair; determine the average value of the absolute values of the two eigenvalues in the first eigenvalue pair to obtain the first average value, and determine the average value of the absolute values of the two eigenvalues in the second eigenvalue pair to obtain the second average value; based on the first average value and the second average value, determine the partial discharge inception voltage and the partial discharge extinction voltage within the target time period. For example, after obtaining 4 classification centers, 4 eigenvalues can be obtained. Among them, the four eigenvalues can be divided into two pairs of eigenvalue pairs with opposite signs and similar absolute values. By obtaining the average value of the absolute values of the eigenvalue pairs, a more accurate partial discharge inception voltage and partial discharge extinction voltage can be further obtained. For example, when the 4 eigenvalues are 3.1 kV, -2.9 kV, 6.7 kV, and -7.0 kV respectively, 3.1 kV and -2.9 kV can be regarded as an eigenvalue pair with opposite signs and similar absolute values, that is, the second eigenvalue pair, and 6.7 kV and -7.0 kV can be regarded as another eigenvalue pair with opposite signs and similar absolute values, that is, the first eigenvalue pair. After obtaining the average value of the absolute values of the two eigenvalue pairs respectively, the following formula can be used to determine the partial discharge inception voltage and the partial discharge extinction voltage within the target time period:

[0043]

[0044] In the formula, dV1 is the first average value, that is, the average value of the absolute values of the two eigenvalues in the first eigenvalue pair; dV2 is the second average value, that is, the average value of the absolute values of the two eigenvalues in the second eigenvalue pair, where the absolute value of the first eigenvalue pair is greater than that of the second eigenvalue pair; V I is the partial discharge inception voltage within the target time period; V X is the partial discharge extinction voltage within the target time period.

[0045] Step S108: Determine the damage length of the electrical tree in the cable based on the current values of multiple partial discharges, the partial discharge inception voltage, and the partial discharge extinction voltage.

[0046] As an alternative embodiment, when determining the damage length of the electrical tree in the cable based on the current values of multiple partial discharges, the partial discharge inception voltage, and the partial discharge extinction voltage, the maximum amplitude of the discharge quantity of multiple partial discharges can be determined based on the current values of multiple partial discharges; based on the maximum amplitude, the partial discharge inception voltage, and the partial discharge extinction voltage, the damage length of the electrical tree in the cable can be determined. By combining the current value of the partial discharge and the effective value of the applied voltage, the health state of the cable can be evaluated more comprehensively, and the damage length of the electrical tree in the cable can be determined more accurately. For example, the following formula can be used to determine the damage length of the electrical tree in the cable:

[0047]

[0048] In the formula, Q is the maximum amplitude of the discharge quantity of multiple partial discharges; V I is the partial discharge inception voltage; V X is the partial discharge extinction voltage; ε0 is the vacuum permittivity.

[0049] Through the above steps, the partial discharge phenomenon of the cable under the applied voltage can be effectively monitored. By analyzing the relationship between the current value of the partial discharge and the effective value of the applied voltage, the damage degree of the internal electrical tree of the cable can be accurately evaluated, providing important data support for the safe operation of the power system.

[0050] Combining the above embodiments and alternative embodiments, an alternative implementation manner is provided. In this alternative implementation manner, an evaluation method for the damage length of the electrical tree of a power cable based on a partial discharge sequence is proposed. Figure 2 is a schematic diagram of an evaluation method for the damage length of the electrical tree of a power cable based on a partial discharge sequence according to an alternative implementation manner of the present invention, as Figure 2 shown, the method includes the following processes.

[0051] S1. Obtain the difference in the applied voltage of the partial discharge sequence.

[0052] Obtain the effective value of the applied voltage and the phase-resolved partial discharge (PRPD) spectrum of the partial discharge signal, and calculate the difference in the applied voltage between every two adjacent discharges of the partial discharge according to the phase at which the discharge occurs.

[0053] Among them, the preprocessing of the partial discharge PRPD spectrum includes:

[0054] S1.1. Installation of the measuring device and setting of the test system; connect the power cable to the partial discharge test system, record the discharge data through a computer and generate a PRPD spectrum, and remove the noise signal in the discharge data to obtain a denoised partial discharge PRPD spectrum.

[0055] S1.2. Obtain the applied voltage data during partial discharge; obtain the discharge phase φ according to the denoised partial discharge PRPD spectrogram, and combine the sine AC voltage formula and the effective value U0 of the applied voltage to obtain the applied voltage value during partial discharge.

[0056] S1.3. Based on the applied voltage value during partial discharge, subtract the applied voltage value at the previous adjacent discharge from the applied voltage value at the current discharge to obtain the difference in applied voltage between two adjacent partial discharges. For example, after obtaining the difference in applied voltage between two adjacent partial discharges, the frequency distribution histogram of the applied voltage difference can be used to preliminarily reflect the frequency distribution law of the applied voltage difference. Figure 3 It is the frequency distribution histogram of the voltage difference between two adjacent discharges of the cable under test according to an optional embodiment of the present invention, as Figure 3 shown.

[0057] S2. Obtain the partial discharge inception voltage and the partial discharge extinction voltage.

[0058] Classify the differences in applied voltage between every two adjacent partial discharges based on the mean shift clustering algorithm, and extract the central points of the differences in applied voltage as characteristic quantities ±dV1, ±dV2; based on the central points of the final differences in applied voltage, obtain the partial discharge inception voltage and the partial discharge extinction voltage through corresponding formulas. Figure 4 It is the partial discharge inception voltage V I of the cable under test and the partial discharge extinction voltage V X , as Figure 4 shown, where the partial discharge inception voltage and the partial discharge extinction voltage in each target time period represent a point in Figure 4 , that is, a value of the partial discharge inception voltage and the partial discharge extinction voltage is obtained every 1 second.

[0059] S2.1. Randomly select a difference in applied voltage between two adjacent partial discharges as the central point.

[0060] S2.2. Denote the points whose distance from the central point among all the differences in applied voltage between two adjacent partial discharges is less than 0.1U0 as set M.

[0061] S2.3. Obtain the distance vector between each point in set M and the central point, and obtain the offset vector corresponding to the central point of set M based on the distance vector.

[0062] S2.4. Move the central point along the direction of the offset vector by a distance equal to the modulus of the offset vector.

[0063] S2.5. Repeat S2.2, S2.3, and S2.4 until the modulus of the offset vector is less than 0.01U0, and remember the central point at this time.

[0064] S2.6. Repeat S2.1 to S2.5 until the applied voltage differences between two adjacent discharges of all partial discharges are classified, and the remembered center points are used as the characteristic values of the voltage differences.

[0065] S2.7. Based on the characteristic values of the voltage differences, use the following formula to obtain the partial discharge inception voltage and the partial discharge extinction voltage:

[0066]

[0067] In the formula, dV2 is the average value of the absolute values of the characteristic values with the largest absolute value among the characteristic values classified in S2.7; dV1 is the average value of the absolute values of the characteristic values with the smallest absolute value among the characteristic values classified in S2.7, V I is the partial discharge inception voltage, V X is the partial discharge extinction voltage.

[0068] S3. Determine the length of the electrical tree inside the power cable insulation.

[0069] Based on the maximum amplitude of the partial discharge quantity, the partial discharge inception voltage and the partial discharge extinction voltage, determine the length of the internal electrical tree of the cable under test according to the following formula:

[0070]

[0071] In the formula, Q is the maximum amplitude of the partial discharge quantity, V I is the partial discharge inception voltage, V X is the partial discharge extinction voltage, and ε0 is the vacuum permittivity.

[0072] Figure 5 is the relationship between the maximum amplitude of the partial discharge quantity of the cable under test, the length of the electrical tree and V I -V X as shown in Figure 5 shown, the length of the electrical tree increases with time, indicating that the longer the time for applying the applied voltage at both ends of the cable, the more times of partial discharge, and the longer the length of the electrical tree in the cable, that is, the higher the degree of damage to the cable. Figure 6 is the comparison between the actual length and the estimated length of the electrical tree of the cable under test according to the optional embodiment of the present invention, as shown in Figure 6 shown, although the curve of the actual length of the electrical tree is smoother and the estimated length is more fluctuating, the actual length value of the electrical tree of the cable under test is relatively close to the estimated length value, indicating that it is reliable to determine the damage length of the electrical tree in the cable by using the optional embodiment of the present invention.

[0073] According to an embodiment of the present invention, there is provided a device for determining the damage length of an electrical tree in a cable, Figure 7The structural block diagram of a device for determining the damage length of electrical tree in a cable according to an embodiment of the present invention is as follows. Figure 7 As shown, the device includes: an acquisition module 702, a first determination module 704, a second determination module 706, and a third determination module 708. The device will be described below.

[0074] The acquisition module 702 is configured to acquire the effective value of the applied voltage of the cable during the target time period, and the current values of multiple partial discharges generated under the applied voltage of the cable during the target time period. The first determination module 704 is connected to the above acquisition module 702 and is configured to determine the applied voltage difference corresponding to two adjacent partial discharges among the multiple partial discharges during the target time period based on the effective value of the applied voltage and the current values of the multiple partial discharges. The second determination module 706 is connected to the above first determination module 704 and is configured to determine the partial discharge inception voltage and the partial discharge termination voltage during the target time period based on the applied voltage difference corresponding to two adjacent partial discharges among the multiple partial discharges during the target time period. The third determination module 708 is connected to the above second determination module 706 and is configured to determine the damage length of the electrical tree in the cable based on the current values of the multiple partial discharges, the partial discharge inception voltage, and the partial discharge termination voltage.

[0075] It should be noted here that the above acquisition module 702, first determination module 704, second determination module 706, and third determination module 708 correspond to steps S102 to S108 in the embodiment. The examples and application scenarios implemented by the multiple modules and the corresponding steps are the same, but are not limited to the content disclosed in the above embodiment.

[0076] As an optional embodiment, the above first determination module 704 includes: a first obtaining unit, a first determination unit, a second determination unit, and a third determination unit. Among them, the first obtaining unit is configured to obtain the phase distribution spectrogram of the current values of the multiple partial discharges based on the current values of the multiple partial discharges. The first determination unit is connected to the above first obtaining unit and is configured to determine the phases corresponding to the current values of the multiple partial discharges based on the phase distribution spectrogram. The second determination unit is connected to the above first determination unit and is configured to determine the applied voltage values corresponding to the phases corresponding to the current values of the multiple partial discharges based on the effective value of the applied voltage and the phases corresponding to the current values of the multiple partial discharges. The third determination unit is connected to the above second determination unit and is configured to determine the applied voltage difference corresponding to two adjacent partial discharges among the multiple partial discharges based on the applied voltage values corresponding to the phases corresponding to two adjacent partial discharges among the multiple partial discharges.

[0077] As an alternative embodiment, the above-mentioned second determination module 706 includes: a classification unit, a fourth determination unit, and a fifth determination unit. Among them, the classification unit is configured to classify the applied voltage differences corresponding to two adjacent partial discharges among multiple partial discharges to obtain a classification center; the fourth determination unit is connected to the above-mentioned classification unit and is configured to determine the eigenvalue of the applied voltage differences corresponding to two adjacent partial discharges among multiple partial discharges based on the classification center; the fifth determination unit is connected to the above-mentioned fourth determination unit and is configured to determine the partial discharge initiation voltage and the partial discharge termination voltage within the target time period based on the eigenvalue.

[0078] As an alternative embodiment, the above-mentioned classification unit includes: a selection subunit, a marking subunit, a first obtaining subunit, an updating subunit, and an iterative subunit. Among them, the selection subunit is configured to randomly select an applied voltage difference as an initial center from the applied voltage differences corresponding to two adjacent partial discharges among multiple partial discharges; the marking subunit is connected to the above-mentioned selection subunit and is configured to mark the applied voltage differences with a distance less than the first threshold from the initial center among the applied voltage differences corresponding to two adjacent partial discharges among multiple partial discharges as an initial set; the first obtaining subunit is connected to the above-mentioned marking subunit and is configured to determine the distance vector between the applied voltage differences in the initial set and the initial center, and obtain the offset vector of the initial set based on the distance vector between the applied voltage differences in the initial set and the initial center; the updating subunit is connected to the above-mentioned first obtaining subunit and is configured to update the initial center based on the offset vector and update the initial set until the offset vector corresponding to the updated initial center is less than the second threshold, take the updated initial center as the target center, and the updated initial set as the target set, where the second threshold is less than the first threshold; the iterative subunit is connected to the above-mentioned updating subunit and is configured to iterate the steps of obtaining the target center and the target set until all the applied voltage differences corresponding to two adjacent partial discharges among multiple partial discharges are classified to obtain the classification center.

[0079] As an alternative embodiment, the above-mentioned fifth determination unit includes: a second obtaining subunit, a third obtaining subunit, and a determination subunit. Among them, the second obtaining subunit is configured to use the eigenvalues with opposite signs and similar absolute values in the eigenvalues as eigenvalue pairs to obtain a first eigenvalue pair and a second eigenvalue pair, where the absolute value of the first eigenvalue pair is greater than the absolute value of the second eigenvalue pair; the third obtaining subunit is connected to the above-mentioned second obtaining subunit and is configured to determine the average value of the absolute values of the two eigenvalues in the first eigenvalue pair to obtain a first average value, and determine the average value of the absolute values of the two eigenvalues in the second eigenvalue pair to obtain a second average value; the determination subunit is connected to the above-mentioned third obtaining subunit and is configured to determine the partial discharge initiation voltage and the partial discharge termination voltage within the target time period based on the first average value and the second average value.

[0080] As an alternative embodiment, the above-mentioned third determination module 708 includes: a sixth determination unit and a seventh determination unit. Among them, the sixth determination unit is configured to determine the maximum amplitude of the discharge amount of multiple partial discharges based on the current values of the multiple partial discharges; the seventh determination unit is connected to the sixth determination unit and is configured to determine the damage length of the electrical tree in the cable based on the maximum amplitude, the partial discharge inception voltage, and the partial discharge termination voltage.

[0081] According to an embodiment of the present invention, there is provided a computer-readable storage medium, where the computer-readable storage medium includes an executable program stored therein. When the executable program runs, it controls the device where the computer-readable storage medium is located to execute the method for determining the damage length of the electrical tree in the cable described in any one of the above.

[0082] According to an embodiment of the present invention, there is provided an electronic device, including: a memory storing an executable program; a processor configured to run the program. When the program runs, it executes the method for determining the damage length of the electrical tree in the cable described in any one of the above.

[0083] According to an embodiment of the present invention, there is provided a computer program product, including a computer program, where when the computer program is executed by a processor, it implements the steps of the method described in any one of the above.

[0084] The serial numbers of the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0085] In the above embodiments of the present invention, the descriptions of the respective embodiments have their own emphases. For parts not detailed in a certain embodiment, reference may be made to the relevant descriptions of other embodiments.

[0086] In several embodiments provided in the present application, it should be understood that the disclosed technical content can be implemented in other ways. Among them, the device embodiments described above are merely illustrative. For example, the division of the units can be a logical function division, and there can be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed couplings or direct couplings or communication connections to each other can be through some interfaces, and the indirect couplings or communication connections of the units or modules can be in an electrical or other form.

[0087] The units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they can be located in one place or distributed to multiple units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0088] In addition, in each embodiment of the present invention, each functional unit can be integrated into one processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of a software functional unit.

[0089] If the above-mentioned integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in each embodiment of the present invention. The aforementioned storage medium includes: various media that can store program codes, such as USB flash drives, read-only memories (ROMs), random access memories (RAMs), mobile hard disks, magnetic disks, or optical discs.

[0090] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for determining the damage length of electrical tree in a cable, characterized in that: include: Acquire the effective value of the externally applied voltage of the cable within a target time period, and the current values ​​of multiple partial discharges generated by the cable under the externally applied voltage within the target time period; Determining, based on the effective value of the externally applied voltage and the current values ​​of the multiple partial discharges, the externally applied voltage difference corresponding to two adjacent partial discharges in the multiple partial discharges within the target time period; Determining a partial discharge start voltage and a partial discharge termination voltage within the target time period based on the applied voltage difference corresponding to two adjacent partial discharges among the multiple partial discharges within the target time period; The damaged length of the electrical tree in the cable is determined based on the current values ​​of the multiple partial discharges, the partial discharge start voltage and the partial discharge termination voltage.

2. The method according to claim 1, characterized in that: The step of determining the difference in externally applied voltage corresponding to two adjacent partial discharges in the multiple partial discharges within the target time period based on the effective value of the externally applied voltage and the current values ​​of the multiple partial discharges comprises: Based on the current values ​​of the multiple partial discharges, obtaining a phase distribution spectrum of the current values ​​of the multiple partial discharges; Based on the phase distribution spectrum, determining the phases corresponding to the current values ​​of the multiple partial discharges respectively; Determining the externally applied voltage values ​​corresponding to the phases corresponding to the current values ​​of the multiple partial discharges based on the effective value of the externally applied voltage and the phases corresponding to the current values ​​of the multiple partial discharges; Based on the externally applied voltage values ​​corresponding to the phases corresponding to two adjacent partial discharges in the multiple partial discharges, the externally applied voltage difference corresponding to the two adjacent partial discharges in the multiple partial discharges is determined.

3. The method according to claim 1, characterized in that The determining of the partial discharge start voltage and the partial discharge termination voltage within the target time period based on the externally applied voltage difference corresponding to two adjacent partial discharges among the multiple partial discharges within the target time period comprises: classifying the externally applied voltage differences corresponding to two adjacent partial discharges among the multiple partial discharges to obtain a classification center; determining, based on the classification center, a characteristic value of the applied voltage difference corresponding to two adjacent partial discharges among the multiple partial discharges; The partial discharge start voltage and the partial discharge termination voltage within the target time period are determined based on the characteristic value.

4. The method according to claim 3, characterized in that The step of classifying the externally applied voltage differences corresponding to two adjacent partial discharges among the multiple partial discharges to obtain a classification center includes: randomly selecting an externally applied voltage difference from the externally applied voltage differences corresponding to two adjacent partial discharges in the multiple partial discharges as an initial center; Recording the externally applied voltage differences corresponding to two adjacent partial discharges in the multiple partial discharges, whose distance from the initial center is less than a first threshold, as an initial set; Determining a distance vector between the externally applied voltage difference in the initial set and the initial center, and obtaining an offset vector of the initial set based on the distance vector between the externally applied voltage difference in the initial set and the initial center; Based on the offset vector, the initial center is updated, and the initial set is updated until the offset vector corresponding to the updated initial center is less than a second threshold, and the updated initial center is used as the target center and the updated initial set is used as the target set, wherein the second threshold is less than the first threshold; The steps of iterating to obtain the target center and the target set are performed until the externally applied voltage differences corresponding to two adjacent partial discharges in the multiple partial discharges are classified to obtain the classification center.

5. The method according to claim 3, characterized in that: The determining the partial discharge start voltage and the partial discharge termination voltage within the target time period based on the characteristic value includes: Taking eigenvalues ​​of opposite sign and similar absolute value among the eigenvalues ​​as eigenvalue pairs, to obtain a first eigenvalue pair and a second eigenvalue pair, wherein the absolute value of the first eigenvalue pair is greater than the absolute value of the second eigenvalue pair; Determine an average value of the absolute values ​​of the two eigenvalues ​​in the first eigenvalue pair to obtain a first average value, and determine an average value of the absolute values ​​of the two eigenvalues ​​in the second eigenvalue pair to obtain a second average value; The partial discharge start voltage and the partial discharge termination voltage within the target time period are determined based on the first average value and the second average value.

6. The method according to any one of claims 1 to 5, characterized in that The determining the damage length of the electrical tree in the cable based on the current values ​​of the multiple partial discharges, the partial discharge start voltage and the partial discharge termination voltage comprises: Determining a maximum amplitude of discharge amounts of the multiple partial discharges based on current values ​​of the multiple partial discharges; The damage length of the electrical tree in the cable is determined based on the maximum amplitude, the partial discharge inception voltage, and the partial discharge termination voltage.

7. A device for determining the damaged length of electrical branches in a cable, characterized in that: include: An acquisition module, used to acquire an effective value of an externally applied voltage of the cable within a target time period, and current values ​​of multiple partial discharges generated by the cable under the externally applied voltage within the target time period; A first determination module is used to determine the externally applied voltage difference corresponding to two adjacent partial discharges in the multiple partial discharges within the target time period based on the effective value of the externally applied voltage and the current values ​​of the multiple partial discharges; A second determination module, configured to determine a partial discharge start voltage and a partial discharge termination voltage within the target time period based on the applied voltage difference corresponding to two adjacent partial discharges among the multiple partial discharges within the target time period; The third determination module is used to determine the damage length of the electrical tree in the cable based on the current values ​​of the multiple partial discharges, the partial discharge start voltage and the partial discharge termination voltage.

8. A computer-readable storage medium, characterized in that: The computer-readable storage medium includes a stored executable program, wherein when the executable program is run, the device where the computer-readable storage medium is located is controlled to execute the method for determining the damaged length of electrical trees in a cable according to any one of claims 1 to 6.

9. An electronic device, characterized in that: include: A memory storing an executable program; A processor is used to run the program, wherein the program, when running, executes the method for determining the damaged length of electrical branches in a cable as claimed in any one of claims 1 to 6.

10. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

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