Partial discharge detection method and system for high-low voltage switch cabinet

Abstract

The invention relates to the technical field of partial discharge detection, in particular to a partial discharge detection method and system for a high-low voltage switch cabinet, and the method comprises the steps: obtaining electromagnetic wave signals and power system voltage data of each sensor position in real time; acquiring a partial discharge period in each detection window according to the electromagnetic wave maximum value of all the sensors in each power frequency period in each detection window, the distance between the electromagnetic wave maximum value and the voltage wave crest and the voltage wave trough of the power system, and the electromagnetic wave signal difference between the sensors; and according to the dispersion degree of the electromagnetic wave maximum values of all the sensors under each partial discharge period in each detection window, the electromagnetic wave signal frequency domain energy of each partial discharge period and the proportion of the partial discharge period in each detection window, obtaining the existence confidence of each detection window, and judging whether partial discharge exists under the current detection window or not. According to the invention, by analyzing the distinguishing characteristics of the partial discharge and the electromagnetic interference in the electromagnetic wave signals at multiple positions, the detection precision of the partial discharge is improved.

Description

Technical Field

[0001] The present application relates to the technical field of partial discharge detection, and in particular to a partial discharge detection method and system for high and low voltage switchgear. Background Art

[0002] High- and low-voltage switchgear is a complete set of electrical equipment used to connect high- and low-voltage cables in power systems. Its primary functions include power distribution, control, and circuit protection, and it is widely used in substations, distribution systems, and renewable energy power plants. Voltage conversion is achieved through transformers, with components such as master switches, circuit breakers, and contactors integrated into the high- and low-voltage compartments. Insulation breakdown is a common problem in high- and low-voltage switchgear. This failure can not only cause circuit breakers to trip, impacting residential electricity use, but in severe cases, can also damage electrical equipment, threatening the safe operation of the power grid.

[0003] Partial discharge is an electrical fault phenomenon that precedes insulation breakdown in high- and low-voltage switchgear. The UHF method, which effectively detects partial discharge by measuring the electromagnetic waves generated during the discharge process, is a commonly used technical means within the industry for detecting partial discharge in high- and low-voltage switchgear. High- and low-voltage switchgear utilizes a large number of connected devices of varying types and quantities, and their corresponding operating states vary in complexity. This results in a significant amount of electromagnetic interference in the switchgear's electromagnetic environment. This, in turn, causes the electromagnetic wave signals obtained by the UHF method to be mixed with a significant amount of interference signals, resulting in a decrease in the accuracy of partial discharge detection. Furthermore, when using a single UHF sensor to detect partial discharge in high- and low-voltage switchgear, the impact of the location of the partial discharge on the electromagnetic wave signal strength is ignored. Consequently, when the location of the partial discharge in the high- and low-voltage switchgear is far from the detection point, the accuracy of partial discharge detection decreases. Summary of the Invention

[0004] In order to solve the above technical problems, the purpose of this application is to provide a partial discharge detection method and system for high and low voltage switchgear. The technical solutions adopted are as follows: In a first aspect, an embodiment of the present application provides a method for detecting partial discharge of a high-voltage and low-voltage switchgear, the method comprising the following steps: Real-time acquisition of electromagnetic wave signals from each sensor location in the high and low voltage switchgear, as well as voltage data from the power system where the high and low voltage switchgear are located; the entire detection process is treated as a detection window for every preset number of power frequency cycles; Obtaining a first eigenvalue of each sensor in each detection window based on the maximum value of the electromagnetic wave signal of each sensor in each power frequency cycle in each detection window, and the distance between the moment of the maximum value of the electromagnetic wave signal and the moment of the peak or trough of the power system voltage; The comprehensive interference value of each detection window is obtained based on the average level of the first eigenvalues ​​of all sensors in each detection window, and the third eigenvalue of each power frequency cycle in each detection window is obtained based on the difference between the maximum values ​​of the electromagnetic wave signals of all two arbitrary sensors in each power frequency cycle in each detection window, thereby obtaining each partial discharge cycle in each detection window; Based on the degree of dispersion of the electromagnetic wave maximum values ​​of all sensors in each partial discharge cycle within each detection window, and the electromagnetic wave signal frequency domain energy corresponding to the sensor with the largest electromagnetic wave signal maximum value in each partial discharge cycle, the partial discharge factor of each partial discharge cycle in each detection window is obtained. Combined with the proportion of partial discharge cycles in each detection window, the existence confidence of each detection window is obtained, and then it is determined whether partial discharge exists in the high and low voltage switchgear in the current detection window.

[0005] Preferably, the calculation formula for the first eigenvalue of each sensor in each detection window is: Where, represents the first eigenvalue of the k-th sensor in the p-th detection window; Indicates the number of power frequency cycles in the pth detection window; It represents the minimum value of the absolute difference between the phase of the electromagnetic wave of the k-th sensor in the t-th power frequency cycle within the p-th detection window and the phase corresponding to the power system power frequency voltage peak and trough; express The maximum value of represents the maximum value of the electromagnetic wave signal of the kth sensor in the tth power frequency cycle within the pth detection window; wherein the electromagnetic wave phase of each sensor in each power frequency cycle refers to the phase of the power system voltage at the moment when the maximum value of the electromagnetic wave signal of each sensor in each power frequency cycle occurs.

[0006] Preferably, the comprehensive interference value of each detection window refers to the average value of the first eigenvalues ​​of all sensors in each detection window.

[0007] Preferably, the third eigenvalue of each power frequency cycle in each detection window refers to the sum of the second eigenvalues ​​between all arbitrary two sensors in each power frequency cycle in each detection window.

[0008] Preferably, the calculation formula for the second eigenvalue between any two sensors at each power frequency cycle in each detection window is: Where, is the second eigenvalue between the i-th and j-th sensors under the u-th power frequency cycle in the p-th detection window, represents the comprehensive interference value of the p-th detection window; and are the maximum values ​​of the electromagnetic wave signals of the i-th and j-th sensors in the u-th power frequency cycle within the p-th detection window, respectively.

[0009] Preferably, each partial discharge period within each detection window refers to a power frequency period in which the third characteristic value within each detection window is greater than a preset discharge threshold.

[0010] Preferably, the calculation formula for the partial discharge factor of each partial discharge cycle in each detection window is: Where, represents the partial discharge factor under the sth partial discharge cycle in the pth detection window; The coefficient of variation of the maximum electromagnetic wave signal of all sensors under the sth partial discharge cycle in the pth detection window; represents an exponential function with the natural constant e as the base; represents the energy of the frequency bin numbered n in the frequency spectrum sequence of the maximum partial discharge signal under the sth partial discharge cycle within the pth detection window; N represents the total number of frequency bins in the frequency spectrum sequence of the maximum partial discharge signal; is the number of the frequency interval; wherein the maximum partial discharge signal under each partial discharge cycle refers to the electromagnetic wave signal corresponding to the sensor with the largest electromagnetic wave signal maximum value within each partial discharge cycle; the method for obtaining each frequency interval and its number in the frequency spectrum sequence of the maximum partial discharge signal under each partial discharge cycle is: evenly divide the frequency range where the frequency spectrum sequence of the maximum partial discharge signal of each partial discharge cycle is located into a preset number of frequency intervals, and number each frequency interval in ascending order of frequency.

[0011] Preferably, the calculation formula for the existence confidence of each detection window is: Where, Indicates the confidence level of the existence of the p-th detection window; It represents the ratio of the number of all partial discharge cycles to the number of all power frequency cycles in the pth detection window; represents the number of partial discharge cycles in the pth detection window; It represents the partial discharge factor under the sth partial discharge cycle in the pth detection window.

[0012] Preferably, the specific process of judging whether there is partial discharge in the high and low voltage switch cabinets under the current detection window is: when the existence confidence of the current detection window of the high and low voltage switch cabinets is greater than the preset existence threshold, it is determined that there is partial discharge in the high and low voltage switch cabinets under the current detection window; otherwise, it is determined that there is no partial discharge in the high and low voltage switch cabinets under the current detection window.

[0013] In a second aspect, an embodiment of the present application also provides a partial discharge detection system for high and low voltage switchgear, comprising a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, the system implements the steps of any one of the above-mentioned partial discharge detection methods for high and low voltage switchgear.

[0014] This application has at least the following beneficial effects: The present application installs multiple ultra-high frequency sensors at different locations of high and low voltage switchgear and analyzes the electromagnetic wave signal characteristics of each sensor to construct a comprehensive interference value for evaluating the electromagnetic interference intensity within each detection window. By analyzing the distinguishing characteristics of the electromagnetic interference signal and the partial discharge signal in the high and low voltage switchgear in the time domain, a third characteristic value is constructed, and the power frequency period in which the partial discharge signal may exist in each detection window is preliminarily obtained, thereby narrowing the search range of the partial discharge signal and improving the accuracy of partial discharge signal detection. By analyzing the variation characteristics between the partial discharge degree and the frequency of the collected electromagnetic wave signal, the collected signals of different frequency bands are weighted, and the frequency domain energy of the sensor is weighted according to the distance between the sensor and the partial discharge location to construct a partial discharge factor, thereby improving the accuracy of partial discharge detection. Finally, by constructing an existence confidence level to evaluate the possibility that the pending partial discharge signal in each detection window is a true partial discharge signal, the impact of the electromagnetic interference signal on the detection of the partial discharge signal is reduced, and the detection accuracy of partial discharge in high and low voltage switchgear is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions and advantages of the embodiments of the present application or the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0016] Figure 1 A flowchart of a method for detecting partial discharge of a high- and low-voltage switchgear according to an embodiment of the present application; Figure 2 A flowchart for obtaining the existence confidence of each detection window provided in one embodiment of the present application. DETAILED DESCRIPTION

[0017] To further illustrate the technical means and effectiveness of this application's implementation of the intended invention, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effectiveness of a partial discharge detection method and system for high- and low-voltage switchgear proposed in this application. In the following description, references to "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics of one or more embodiments may be combined in any suitable manner.

[0018] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0019] The following describes in detail a method and system for detecting partial discharge of high and low voltage switchgear provided by the present application with reference to the accompanying drawings.

[0020] See also Figure 1 , which shows a flowchart of a method for detecting partial discharge of a high and low voltage switchgear provided by one embodiment of the present application, the method comprising the following steps: Step 1: Acquire electromagnetic wave signals at each sensor location in the high and low voltage switchgear in real time, as well as voltage data of the power system where the high and low voltage switchgear are located; and use a preset number of power frequency cycles in the entire detection process as a detection window.

[0021] In this embodiment, a UHF sensor is installed inside each of the six metal casings of the high and low voltage switchgear to collect electromagnetic wave signals at the locations of each UHF sensor within the switchgear. In this embodiment, the signal collection frequency is 8 GHz. A voltmeter is used to collect real-time voltage data from the power system where the high and low voltage switchgear resides. The power frequency of this voltage data is 50 Hz. This collected power system voltage data is used as input for a voltage zero-crossing detection method to determine the starting point of the power frequency cycle and obtain different power frequency cycles. Each power frequency cycle is 0.02 seconds. From the time each UHF sensor begins data collection, every X power frequency cycles is considered a detection window. In this embodiment, X is 500. The voltage zero-crossing detection method is well known, and the detailed process is not detailed here. For ease of description, the UHF sensors will be referred to as sensors.

[0022] Step 2: Obtain the first characteristic value of each sensor in each detection window based on the maximum value of the electromagnetic wave signal of each sensor in each power frequency cycle in each detection window, and the distance between the moment of the maximum value of the electromagnetic wave signal and the moment of the peak or trough of the power system voltage.

[0023] Partial discharges in high and low voltage switchgear occur over short and random periods of time. This application aims to analyze electromagnetic wave signals, obtain the power frequency period in which the partial discharge signals occur, and improve the ability to detect weak partial discharge signals under strong electromagnetic interference.

[0024] High and low voltage switchgear undergoes partial discharge due to the action of external voltage. Partial discharge generally occurs at places with high instantaneous voltage, where the electric field strength is large and the probability of dielectric breakdown is high. The electric field strength generated at the corresponding troughs and peaks of the power frequency voltage is the largest, so the risk of partial discharge is greater. As a result, partial discharge of high and low voltage switchgear usually occurs near the peaks and troughs of the power frequency voltage waveform.

[0025] In this embodiment, the phase of the power system voltage at the moment when the maximum value of the electromagnetic wave signal of each sensor in each power frequency cycle is obtained is recorded as the electromagnetic wave phase of each sensor in each power frequency cycle, where the phase range is 0°~360°. In the power system power frequency voltage of this embodiment, the phases corresponding to the peak and trough are 90° and 270°, respectively.

[0026] As a preferred embodiment, based on the distance between the moment when the electromagnetic wave signal of each sensor in each power frequency cycle in each detection window is at its maximum value and the moment when the power system voltage peaks or troughs, as well as the maximum value of the electromagnetic wave signal of each sensor in each power frequency cycle in each detection window, the first characteristic value of each sensor in each detection window is obtained to characterize the intensity of electromagnetic interference in the electromagnetic wave signal of each sensor in each detection window.

[0027] In this embodiment, the first eigenvalue of the kth sensor in the pth detection window is recorded as , its specific expression is: Where, represents the first eigenvalue of the k-th sensor in the p-th detection window; represents the number of power frequency cycles in the pth detection window, and its value in this embodiment is 500; It represents the minimum value of the absolute difference between the phase of the electromagnetic wave of the k-th sensor in the t-th power frequency cycle within the p-th detection window and the phase corresponding to the power system power frequency voltage peak and trough; express The maximum value of , in this embodiment, is 90°, the purpose of which is to control the calculation range of the first eigenvalue; It represents the maximum value of the electromagnetic wave signal of the kth sensor in the tth power frequency cycle within the pth detection window.

[0028] The larger the value is, the farther the phase of the electromagnetic wave of the kth sensor in the tth power frequency cycle within the pth detection window is from the peak or trough of the power frequency voltage of the power system, and the smaller the possibility of partial discharge in this power frequency cycle. The larger the value of , the greater the electromagnetic interference intensity to which the kth sensor is subjected during the tth power frequency cycle within the pth detection window. The larger the value of , the greater the electromagnetic interference intensity to which the electromagnetic wave signal of the kth sensor in the pth detection window is subjected.

[0029] Step 3: Obtain the comprehensive interference value of each detection window based on the average level of the first eigenvalues ​​of all sensors in each detection window, and obtain the third eigenvalue of each power frequency cycle in each detection window based on the difference in the maximum value of the electromagnetic wave signals of all two arbitrary sensors under each power frequency cycle in each detection window, thereby obtaining each partial discharge cycle in each detection window.

[0030] Furthermore, in order to obtain the comprehensive impact intensity of electromagnetic interference in the time period of each detection window, the first eigenvalue of all sensors in the p-th detection window is obtained, and the average of all the first eigenvalues ​​is recorded as the comprehensive interference value of the p-th detection window, which reflects the degree of influence of the electromagnetic interference in the high and low voltage switchgear in the p-th detection window on the partial discharge detection of all sensors.

[0031] Furthermore, the electromagnetic interference generated by components within high- and low-voltage switchgear can be approximated as white noise, with sensors at different locations being similarly affected. When partial discharge occurs within the switchgear, the electromagnetic waves generated by the partial discharge experience varying degrees of attenuation when reaching sensors at different locations, due to the varying distances between the partial discharge locations. This results in significant differences in the amplitudes of the electromagnetic waves received by different sensors for the same partial discharge signal. Considering that the amplitudes of the high-frequency harmonics of the interference signal generated by changes in the operating state of the high- and low-voltage switchgear are smaller than those of the partial discharge signal, the greater the difference in the amplitudes of the electromagnetic waves between sensors within each power frequency cycle, the more likely partial discharge has occurred within that corresponding power frequency cycle.

[0032] As a preferred embodiment, based on the comprehensive interference value of each detection window and the difference in the maximum value of the electromagnetic wave signal of any two sensors in each power frequency cycle in each detection window, a second characteristic value between any two sensors in each power frequency cycle in each detection window is obtained, which is used to characterize the degree of difference in the electromagnetic wave amplitude of any two sensors in each power frequency cycle in each detection window.

[0033] In this embodiment, the second eigenvalues ​​of the i-th and j-th sensors in the u-th power frequency cycle within the p-th detection window are recorded as , its specific expression is: Where, is the second eigenvalue between the i-th and j-th sensors under the u-th power frequency cycle in the p-th detection window, represents the comprehensive interference value of the p-th detection window; and are the maximum values ​​of the electromagnetic wave signals of the i-th and j-th sensors in the u-th power frequency cycle within the p-th detection window, respectively.

[0034] The larger the value is, the greater the impact of electromagnetic interference in the pth detection window on partial discharge detection. In order to prevent the influence of strong interference signals when obtaining partial discharge signals, the comprehensive interference value is used as the calculation weight to improve the detection capability of weak partial discharge in the detection window. The larger the value is, the greater the difference in electromagnetic wave intensity between the i-th and j-th sensors in the u-th power frequency cycle within the p-th detection window, and the greater the probability of partial discharge between the i-th and j-th sensors in this power frequency cycle.

[0035] Furthermore, the second eigenvalues ​​between all arbitrary two sensors in the u-th power frequency cycle in the p-th detection window are calculated, and the sum of all the second eigenvalues ​​is recorded as the third eigenvalue of the u-th power frequency cycle in the p-th detection window. The obtained third eigenvalue reflects the degree of difference in the overall electromagnetic wave intensity between all sensors in the u-th power frequency cycle in the p-th detection window. The larger the value, the greater the probability of partial discharge in the u-th power frequency cycle in the p-th detection window.

[0036] Furthermore, the power frequency period in which partial discharge exists within the p-th detection window is obtained, specifically: the average value of the third eigenvalues ​​of all power frequency periods within the p-th detection window is calculated, the obtained average value is recorded as the preset discharge threshold, the power frequency period in which the third eigenvalue is greater than the preset discharge threshold is recorded as the partial discharge period within the p-th detection window, and the electromagnetic wave signal of each sensor within the partial discharge period is recorded as the pending partial discharge signal.

[0037] At this point, all partial discharge cycles within the pth detection window are obtained.

[0038] Step 4: Based on the degree of dispersion of the maximum electromagnetic wave values ​​of all sensors in each partial discharge cycle in each detection window, and the frequency domain energy of the electromagnetic wave signal corresponding to the sensor with the largest electromagnetic wave signal maximum value in each partial discharge cycle, the partial discharge factor of each partial discharge cycle in each detection window is obtained. Combined with the proportion of partial discharge cycles in each detection window, the existence confidence of each detection window is obtained, and then it is determined whether partial discharge exists in the high and low voltage switchgear in each detection window.

[0039] Furthermore, during each partial discharge cycle, the larger the electromagnetic wave amplitude of a sensor, the closer the sensor is to the current partial discharge location. Consequently, the electromagnetic wave signal of that sensor during that partial discharge cycle more accurately reflects the severity of the partial discharge during that partial discharge cycle. Therefore, the electromagnetic wave signal corresponding to the sensor with the largest maximum electromagnetic wave signal during each partial discharge cycle is recorded as the maximum partial discharge signal for that partial discharge cycle.

[0040] The longer a single partial discharge in high- and low-voltage switchgear lasts, the lower the frequency of the electromagnetic waves generated by the discharge current. To increase the weight of the signal's lower-frequency components in the calculation, an FFT algorithm is used to obtain the spectrum sequence of the maximum partial discharge signal during each partial discharge cycle. The frequency range of each spectrum sequence is evenly divided into N frequency intervals, and the frequency intervals are numbered from smallest to largest. The energy within each frequency interval is also calculated. The specific method for calculating the frequency domain signal energy is well known; in this embodiment, N is set to 4.

[0041] The distance between the PD location and the sensor significantly influences the assessment of PD severity. During a single PD cycle, when the PD location is closer to a sensor, it is further away from other sensors. The electromagnetic wave signal of the sensor closer to the PD location is more likely to reflect the severity of the local amplification, and therefore, the electromagnetic wave signal of this sensor should be assigned a higher weight to improve the reliability of the PD severity assessment. Therefore, the greater the coefficient of variation of the maximum electromagnetic wave signal of all sensors within a single PD cycle, the greater the weight assigned to the maximum PD signal within that PD cycle.

[0042] Based on the above characteristics, as a preferred embodiment, the partial discharge factor for each partial discharge cycle in each detection window is obtained according to the degree of dispersion of the maximum electromagnetic wave values ​​of all sensors in each partial discharge cycle in each detection window, and the frequency domain energy of the electromagnetic wave signal corresponding to the sensor with the largest maximum electromagnetic wave signal in each partial discharge cycle. This is used to characterize the possibility that the pending partial discharge signal in each partial discharge cycle in each detection window is a true partial discharge signal.

[0043] In this embodiment, the partial discharge factor under the sth partial discharge cycle in the pth detection window is recorded as , its specific expression is: Where, represents the partial discharge factor under the sth partial discharge cycle in the pth detection window; The coefficient of variation of the maximum electromagnetic wave signal of all sensors under the sth partial discharge cycle in the pth detection window; represents an exponential function with the natural constant e as the base; represents the energy of the frequency bin numbered n in the frequency spectrum sequence of the maximum partial discharge signal under the sth partial discharge cycle within the pth detection window; N represents the total number of frequency bins in the frequency spectrum sequence of the maximum partial discharge signal, and in this embodiment, the value is 4; is the frequency interval number.

[0044] By numbering each frequency interval, high-frequency energy is weakened and low-frequency energy is amplified. Moreover, the coefficient of variation is used to set a larger weight for the electromagnetic wave energy of sensors closer to the partial discharge location. This makes the calculated partial discharge factor more able to reflect the possibility that the pending partial discharge signal within the partial discharge cycle is a real partial discharge signal. The larger the value of , the more likely the undetermined partial discharge signal under the sth partial discharge cycle in the pth detection window is to be a true partial discharge signal.

[0045] Furthermore, for partial discharge detection in high- and low-voltage switchgear, the more power frequency cycles within the detection window containing partial discharge signals, the higher the frequency of partial discharge within the detection window, and the more severe the partial discharge. Furthermore, the greater the partial discharge signal energy within the corresponding power frequency cycle, the greater the charge released by the partial discharge, and the more severe the partial discharge.

[0046] As a preferred embodiment, based on the partial discharge factor of each partial discharge cycle in each detection window and the proportion of partial discharge cycles in each detection window, the existence confidence of each detection window is obtained to measure the possibility that the pending partial discharge signal in each detection window is a real partial discharge signal. The flow chart for obtaining the existence confidence of each detection window is as follows: Figure 2 shown.

[0047] In this embodiment, the existence confidence of the pth detection window is recorded as , its specific expression is: Where, Indicates the confidence level of the existence of the p-th detection window; It represents the ratio of the number of all partial discharge cycles to the number of all power frequency cycles in the pth detection window; represents the number of partial discharge cycles in the pth detection window; It represents the partial discharge factor under the sth partial discharge cycle in the pth detection window.

[0048] Furthermore, the presence confidence level of normally operating high and low voltage switchgear in 10,000 detection windows is obtained, and the maximum value is recorded as the preset presence threshold. If the presence confidence level of the high and low voltage switchgear in the current detection window is greater than the preset presence threshold, it is determined that partial discharge exists in the high and low voltage switchgear in the current detection window; otherwise, it is determined that no partial discharge exists in the high and low voltage switchgear in the current detection window.

[0049] Based on the same inventive concept as the above method, an embodiment of the present application also provides a partial discharge detection system for high and low voltage switchgear, comprising a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, the steps of any one of the above-mentioned methods for partial discharge detection of high and low voltage switchgear are implemented.

[0050] It should be noted that the order in which the embodiments of the present application are presented is for illustrative purposes only and does not necessarily represent the superiority or inferiority of the embodiments. Furthermore, the foregoing descriptions of specific embodiments of this specification are provided. Furthermore, the processes depicted in the accompanying drawings do not necessarily require the specific order or sequential sequence shown to achieve the desired results. In certain embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0051] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments.

[0052] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A method for detecting partial discharge of high and low voltage switchgear, characterized in that: The method comprises the following steps: Real-time acquisition of electromagnetic wave signals from each sensor location in the high and low voltage switchgear, as well as voltage data from the power system where the high and low voltage switchgear are located; the entire detection process is treated as a detection window for every preset number of power frequency cycles; Obtaining a first eigenvalue of each sensor in each detection window based on the maximum value of the electromagnetic wave signal of each sensor in each power frequency cycle in each detection window, and the distance between the moment of the maximum value of the electromagnetic wave signal and the moment of the peak or trough of the power system voltage; The comprehensive interference value of each detection window is obtained based on the average level of the first eigenvalues ​​of all sensors in each detection window, and the third eigenvalue of each power frequency cycle in each detection window is obtained based on the difference between the maximum values ​​of the electromagnetic wave signals of all two arbitrary sensors in each power frequency cycle in each detection window, thereby obtaining each partial discharge cycle in each detection window; Based on the degree of dispersion of the electromagnetic wave maximum values ​​of all sensors in each partial discharge cycle within each detection window, and the electromagnetic wave signal frequency domain energy corresponding to the sensor with the largest electromagnetic wave signal maximum value in each partial discharge cycle, the partial discharge factor of each partial discharge cycle in each detection window is obtained. Combined with the proportion of partial discharge cycles in each detection window, the existence confidence of each detection window is obtained, and then it is determined whether partial discharge exists in the high and low voltage switchgear in the current detection window.

2. A method for detecting partial discharge of a high and low voltage switchgear as claimed in claim 1, characterized in that: The calculation formula of the first eigenvalue of each sensor in each detection window is: Where, represents the first eigenvalue of the k-th sensor in the p-th detection window; Indicates the number of power frequency cycles in the pth detection window; It represents the minimum value of the absolute difference between the phase of the electromagnetic wave of the k-th sensor in the t-th power frequency cycle within the p-th detection window and the phase corresponding to the power system power frequency voltage peak and trough; express The maximum value of represents the maximum value of the electromagnetic wave signal of the kth sensor in the tth power frequency cycle within the pth detection window; wherein the electromagnetic wave phase of each sensor in each power frequency cycle refers to the phase of the power system voltage at the moment when the maximum value of the electromagnetic wave signal of each sensor in each power frequency cycle occurs.

3. The method for detecting partial discharge of a high and low voltage switchgear according to claim 1, wherein: The comprehensive interference value of each detection window refers to the average value of the first eigenvalues ​​of all sensors in each detection window.

4. The method for detecting partial discharge of a high and low voltage switchgear according to claim 1, wherein: The third eigenvalue of each power frequency cycle in each detection window refers to the sum of the second eigenvalues ​​between all arbitrary two sensors in each power frequency cycle in each detection window.

5. A method for detecting partial discharge of a high and low voltage switchgear as claimed in claim 4, characterized in that: The calculation formula for the second eigenvalue between any two sensors at each power frequency cycle in each detection window is: Where, is the second eigenvalue between the i-th and j-th sensors under the u-th power frequency cycle in the p-th detection window, represents the comprehensive interference value of the p-th detection window; and are the maximum values ​​of the electromagnetic wave signals of the i-th and j-th sensors in the u-th power frequency cycle within the p-th detection window, respectively.

6. A method for detecting partial discharge of a high and low voltage switchgear as claimed in claim 1, characterized in that: Each partial discharge period within each detection window refers to a power frequency period in which the third characteristic value within each detection window is greater than a preset discharge threshold.

7. The method for detecting partial discharge of a high and low voltage switchgear as claimed in claim 1, wherein: The calculation formula of the partial discharge factor of each partial discharge cycle in each detection window is: Where, represents the partial discharge factor under the sth partial discharge cycle in the pth detection window; The coefficient of variation of the maximum electromagnetic wave signal of all sensors under the sth partial discharge cycle in the pth detection window; represents an exponential function with the natural constant e as the base; represents the energy of the frequency bin numbered n in the frequency spectrum sequence of the maximum partial discharge signal under the sth partial discharge cycle within the pth detection window; N represents the total number of frequency bins in the frequency spectrum sequence of the maximum partial discharge signal; is the number of the frequency interval; wherein the maximum partial discharge signal under each partial discharge cycle refers to the electromagnetic wave signal corresponding to the sensor with the largest electromagnetic wave signal maximum value within each partial discharge cycle; the method for obtaining each frequency interval and its number in the frequency spectrum sequence of the maximum partial discharge signal under each partial discharge cycle is: evenly divide the frequency range where the frequency spectrum sequence of the maximum partial discharge signal of each partial discharge cycle is located into a preset number of frequency intervals, and number each frequency interval in ascending order of frequency.

8. The method for detecting partial discharge of a high and low voltage switchgear according to claim 1, wherein: The calculation formula for the existence confidence of each detection window is: Where, Indicates the confidence level of the existence of the p-th detection window; It represents the ratio of the number of all partial discharge cycles to the number of all power frequency cycles in the pth detection window; represents the number of partial discharge cycles in the pth detection window; It represents the partial discharge factor under the sth partial discharge cycle in the pth detection window.

9. The method for detecting partial discharge of a high and low voltage switchgear as claimed in claim 1, wherein: The specific process of determining whether partial discharge exists in the high-voltage and low-voltage switchgear cabinets in the current detection window is as follows: when the existence confidence level of the high-voltage and low-voltage switchgear cabinets in the current detection window is greater than a preset existence threshold, it is determined that partial discharge exists in the high-voltage and low-voltage switchgear cabinets in the current detection window; otherwise, it is determined that no partial discharge exists in the high-voltage and low-voltage switchgear cabinets in the current detection window.

10. A partial discharge detection system for high and low voltage switchgear, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that: When the processor executes the computer program, the steps of the partial discharge detection method for a high- and low-voltage switchgear are implemented as described in any one of claims 1 to 9.

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