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

Abstract

The application 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, which comprises the following steps: acquiring electromagnetic wave signals and power system voltage data of each sensor position in real time; acquiring partial discharge periods in each detection window according to the maximum electromagnetic wave of each power frequency cycle of all sensors in the detection window, the distance between the maximum electromagnetic wave and the power system voltage peak and valley, and the electromagnetic wave signal difference between the sensors; acquiring the existence confidence of each detection window according to the discrete degree of the maximum electromagnetic wave of all sensors in each partial discharge period of each detection window, the electromagnetic wave signal frequency energy of each partial discharge period, and the proportion of the partial discharge period in each detection window; and judging whether there is partial discharge in the current detection window. The application improves the detection accuracy of the partial discharge by analyzing the distinguishing features of the partial discharge and electromagnetic interference in the electromagnetic wave signals of multiple positions.

Description

Technical Field

[0001] This application relates to the field of partial discharge detection technology, specifically to a method and system for partial discharge detection in high and low voltage switchgear. Background Technology

[0002] High and low voltage switchgear are complete sets of electrical equipment in power systems that connect high-voltage or low-voltage cables. They primarily perform power distribution, control, and circuit protection functions, and are widely used in substations, power distribution systems, and new energy power plants. They achieve voltage conversion through transformers and integrate high-voltage and low-voltage compartments through components such as main control switches, circuit breakers, and contactors. Insulation breakdown is one of the common faults in high and low voltage switchgear. When insulation breakdown occurs in high and low voltage switchgear, it not only causes circuit breaker tripping, affecting residential power supply, but in severe cases, it can also damage power equipment and threaten 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 ultra-high frequency (UHF) method, by measuring the electromagnetic waves generated during the discharge process, can effectively detect partial discharge and is a commonly used technique in the industry for detecting partial discharge in high and low voltage switchgear. However, high and low voltage switchgear involves a large variety and number of connected devices, and their corresponding operating states are complex, resulting in significant electromagnetic interference in the electromagnetic environment. This leads to a high level of interference in the electromagnetic wave signals acquired by the UHF method, causing a decrease in the detection accuracy of partial discharge. Furthermore, when using a single UHF sensor to detect partial discharge in high and low voltage switchgear, the influence of the partial discharge location on the electromagnetic wave signal strength is ignored. Consequently, when the partial discharge location in the high and low voltage switchgear is far from the detection point, the detection accuracy of partial discharge will also decrease. Summary of the Invention

[0004] To address the aforementioned technical problems, the purpose of this application is to provide a method and system for detecting partial discharge in high and low voltage switchgear. The specific technical solution adopted is as follows:

[0005] In a first aspect, embodiments of this application provide a method for detecting partial discharge in high- and low-voltage switchgear, the method comprising the following steps:

[0006] The electromagnetic wave signals of each sensor location in the high and low voltage switchgear are acquired in real time, as well as the voltage data of the power system in which the high and low voltage switchgear is located; the entire detection process is divided into a detection window of a preset number of power frequency cycles.

[0007] Based on the maximum value of the electromagnetic wave signal of each sensor in each power frequency cycle within each detection window, and the distance between the time when the maximum value of the electromagnetic wave signal is located and the time when the voltage peak or trough of the power system, the first characteristic value of each sensor in each detection window is obtained.

[0008] The comprehensive interference value of each detection window is obtained based on the average level of the first characteristic value of all sensors in each detection window. The third characteristic value of each power frequency cycle in each detection window is obtained by combining the difference of the maximum electromagnetic wave signal of any two sensors in each power frequency cycle in each detection window. Thus, each partial discharge cycle in each detection window is obtained.

[0009] Based on the dispersion of the maximum electromagnetic wave values ​​of all sensors in each partial discharge cycle within each detection window, and the frequency domain energy of the electromagnetic wave signal corresponding to the sensor with the maximum electromagnetic wave signal value in each partial discharge cycle, the partial discharge factor of each partial discharge cycle within 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, thereby determining whether there is partial discharge in the high and low voltage switchgear under the current detection window.

[0010] Preferably, the formula for calculating the first feature value of each sensor within each detection window is: In the formula, This represents the first feature value of the k-th sensor within the p-th detection window; This represents the number of power frequency cycles within the p-th detection window; It represents the minimum absolute difference between the electromagnetic wave phase of the k-th sensor in the t-th power frequency cycle within the p-th detection window and the corresponding phases of the peak and trough of the power frequency voltage of the power system. express The maximum value; This represents the maximum electromagnetic wave signal value of the k-th sensor within the p-th detection window during the t-th power frequency cycle; where 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 electromagnetic wave signal of each sensor in each power frequency cycle is located.

[0011] Preferably, the comprehensive interference value of each detection window refers to the average of the first feature values ​​of all sensors within each detection window.

[0012] Preferably, the third characteristic value of each power frequency cycle within each detection window refers to the sum of the second characteristic values ​​between any two sensors under each power frequency cycle within each detection window.

[0013] Preferably, the formula for calculating the second characteristic value between any two sensors under each power frequency cycle within each detection window is as follows: In the formula, Let be the second characteristic value between the i-th and j-th sensors under the u-th power frequency cycle within the p-th detection window. This represents the overall interference value of the p-th detection window; and These are the maximum electromagnetic wave signals of the i-th and j-th sensors during the u-th power frequency cycle within the p-th detection window, respectively.

[0014] Preferably, each partial discharge cycle within each detection window refers to the power frequency cycle within each detection window where the third characteristic value is greater than a preset discharge threshold.

[0015] Preferably, the formula for calculating the partial discharge factor of each partial discharge cycle within each detection window is as follows: In the formula, This represents the partial discharge factor during the s-th partial discharge cycle within the p-th detection window. The coefficient of variation represents the maximum value of the electromagnetic wave signal of all sensors in the p-th detection window during the s-th partial discharge cycle. This represents an exponential function with the natural constant e as its base. This represents the energy of the frequency interval numbered n in the spectral sequence of the maximum partial discharge signal under the s-th partial discharge cycle within the p-th detection window; N represents the total number of frequency intervals in the spectral sequence of the maximum partial discharge signal. The frequency interval is numbered; where 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 value under each partial discharge cycle; the method for obtaining each frequency interval and its number in the spectrum sequence of the maximum partial discharge signal under each partial discharge cycle is as follows: the frequency range in which the spectrum sequence of the maximum partial discharge signal under each partial discharge cycle is located is evenly divided into a preset number of frequency intervals, and each frequency interval is numbered in ascending order of frequency.

[0016] Preferably, the formula for calculating the existence confidence of each detection window is: In the formula, This represents the confidence level of the existence of the p-th detection window; This represents the ratio of the number of all partial discharge cycles to the number of all power frequency cycles within the p-th detection window; This represents the number of partial discharge cycles within the p-th detection window; This represents the partial discharge factor during the s-th partial discharge cycle within the p-th detection window.

[0017] Preferably, the specific process for determining whether there is partial discharge in the high- and low-voltage switchgear under the current detection window is as follows: when the confidence level of the presence of the high- and low-voltage switchgear under the current detection window is greater than the preset presence threshold, it is determined that there is partial discharge in the high- and low-voltage switchgear under the current detection window; otherwise, it is determined that there is no partial discharge in the high- and low-voltage switchgear under the current detection window.

[0018] Secondly, embodiments of this application also provide a partial discharge detection system for high and low voltage switchgear, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it implements the steps of any of the above-described partial discharge detection methods for high and low voltage switchgear.

[0019] This application has at least the following beneficial effects:

[0020] This application utilizes multiple ultra-high frequency sensors installed at different locations within high- and low-voltage switchgear. By analyzing the electromagnetic wave signal characteristics of each sensor, a comprehensive interference value is constructed to assess the electromagnetic interference intensity within each detection window. Furthermore, by analyzing the time-domain differences between electromagnetic interference signals and partial discharge signals in the high- and low-voltage switchgear, a third characteristic value is constructed, preliminarily obtaining the power frequency period of potential partial discharge signals within each detection window. This narrows the search range for partial discharge signals and improves the accuracy of partial discharge signal detection. By analyzing the variation characteristics between the degree of partial discharge and the frequency of the acquired electromagnetic wave signals, the acquired signals of different frequency bands are weighted, and the frequency domain energy of the sensors is weighted according to the distance between the sensors and the partial discharge location, a partial discharge factor is constructed, further improving the accuracy of partial discharge detection. Finally, by constructing an existence confidence level, the likelihood that the undetermined partial discharge signal within each detection window is a real partial discharge signal is assessed, reducing the influence of electromagnetic interference signals when detecting partial discharge signals and improving the detection accuracy of partial discharge in high- and low-voltage switchgear. Attached Figure Description

[0021] To more clearly illustrate the technical solutions and advantages in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A flowchart illustrating the steps of a partial discharge detection method for high and low voltage switchgear, provided in one embodiment of this application;

[0023] Figure 2 A flowchart illustrating the acquisition of the presence confidence of each detection window is provided for one embodiment of this application. Detailed Implementation

[0024] To further illustrate the technical means and effects adopted by this application to achieve the intended purpose of the invention, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a partial discharge detection method and system for high and low voltage switchgear proposed in this application. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0026] The following description, in conjunction with the accompanying drawings, details the specific scheme of the partial discharge detection method and system for high and low voltage switchgear provided in this application.

[0027] Please see Figure 1 The diagram illustrates a flowchart of a partial discharge detection method for high and low voltage switchgear according to an embodiment of this application. The method includes the following steps:

[0028] Step 1: Real-time acquisition of electromagnetic wave signals from the locations of various sensors in the high and low voltage switchgear, as well as voltage data of the power system where the high and low voltage switchgear is located; the entire detection process is divided into a detection window of a preset number of power frequency cycles.

[0029] In this embodiment, an ultra-high frequency (UHF) sensor is installed inside the metal casing of each of the six sides of the high- and low-voltage switchgear to collect electromagnetic wave signals from the locations of the UHF sensors. In this embodiment, the signal acquisition frequency is 8 GHz. Voltage data of the power system to which the high- and low-voltage switchgear is located is collected in real time using a voltmeter. The power frequency of the voltage data is 50 Hz. The collected power system voltage data is used as input to the zero-crossing voltage detection method to determine the starting point of the power frequency cycle, resulting in different power frequency cycles. Each power frequency cycle is 0.02 s. Starting from the beginning of data collection by each UHF sensor, every X power frequency cycles is recorded as a detection window. In this embodiment, X is 500. The zero-crossing voltage detection method is a known technology, and its specific process will not be described in detail. For ease of description, the UHF sensor will be referred to as the sensor below.

[0030] Step 2: Based on the maximum value of the electromagnetic wave signal of each sensor in each power frequency cycle within each detection window, and the distance between the time of the maximum value of the electromagnetic wave signal and the time of the voltage peak or trough of the power system, obtain the first characteristic value of each sensor within each detection window.

[0031] Partial discharges in high- and low-voltage switchgear occur for short periods and are relatively random. This application aims to analyze electromagnetic wave signals to obtain the power frequency period of the partial discharge signal, thereby improving the detection capability of weak partial discharge signals under strong electromagnetic interference.

[0032] Partial discharge occurs in high and low voltage switchgear due to the application of external voltage. Partial discharge usually occurs at points where the instantaneous voltage is high, the electric field strength is large, and the probability of dielectric breakdown is high. The electric field strength is greatest at the troughs and peaks of the power frequency voltage, so the risk of partial discharge is greater. As a result, partial discharge in high and low voltage switchgear usually occurs near the peaks and troughs of the power frequency voltage waveform.

[0033] In this embodiment, the phase of the power system voltage at the moment when the electromagnetic wave signal of each sensor reaches its maximum value in each power frequency cycle is recorded as the electromagnetic wave phase of each sensor in each power frequency cycle, wherein the phase range is 0°~360°. In the power frequency voltage of the power system in this embodiment, the phases corresponding to the peak and the trough are 90° and 270°, respectively.

[0034] In a preferred embodiment, the first characteristic value of each sensor in each detection window is obtained based on the distance between the time when the maximum value of the electromagnetic wave signal of each sensor in each power frequency cycle within each detection window is located and the time when the voltage peak or trough of the power system is located, as well as the maximum value of the electromagnetic wave signal of each sensor in each power frequency cycle within each detection window. This characteristic value is used to characterize the intensity of electromagnetic interference in the electromagnetic wave signal of each sensor in each detection window.

[0035] In this embodiment, the first feature value of the k-th sensor within the p-th detection window is denoted as... Its specific expression is: In the formula, This represents the first feature value of the k-th sensor within the p-th detection window; This represents the number of power frequency cycles within the p-th detection window; in this embodiment, the value is 500. It represents the minimum absolute difference between the electromagnetic wave phase of the k-th sensor in the t-th power frequency cycle within the p-th detection window and the corresponding phases of the peak and trough of the power frequency voltage of the power system. express The maximum value of is 90° in this embodiment, which is intended to control the calculation range of the first feature value. This represents the maximum value of the electromagnetic wave signal from the k-th sensor within the p-th detection window during the t-th power frequency cycle.

[0036] The larger the value, the farther the electromagnetic wave phase of the k-th sensor in the t-th power frequency cycle within the p-th detection window is from the peak or trough of the power frequency voltage in the power system, and the lower the probability of partial discharge within that power frequency cycle. The larger the value, the greater the electromagnetic interference intensity experienced by the k-th sensor during the t-th power frequency cycle within the p-th detection window. The larger the value, the greater the electromagnetic interference intensity experienced by the electromagnetic wave signal of the k-th sensor in the p-th detection window.

[0037] Step 3: Obtain the comprehensive interference value of each detection window based on the average level of the first characteristic value of all sensors in each detection window, and combine the difference of the maximum electromagnetic wave signal of any two sensors in each power frequency cycle in each detection window to obtain the third characteristic value of each power frequency cycle in each detection window, thereby obtaining each partial discharge cycle in each detection window.

[0038] Furthermore, in order to determine the overall impact intensity of electromagnetic interference within the time period of each detection window, the first characteristic value of all sensors in the p-th detection window is obtained, and the average of all the first characteristic values ​​is recorded as the overall interference value of the p-th detection window. This value reflects the degree of influence of electromagnetic interference in the high and low voltage switchgear on the partial discharge detection of all sensors under the p-th detection window.

[0039] Furthermore, the electromagnetic interference generated by the components within the high- and low-voltage switchgear can be approximated as white noise, and the impact on sensors at different locations is similar. When partial discharge occurs in the high- and low-voltage switchgear, the attenuation of the electromagnetic waves generated by the partial discharge varies significantly from the distances between the partial discharge location and the sensors, resulting in large differences in the amplitude of the electromagnetic wave signals received by different sensors for the same partial discharge signal. Considering that the amplitude of the high-frequency harmonic interference signals excited by changes in the operating state of the high- and low-voltage switchgear is smaller than that of the partial discharge signal, the greater the difference in the amplitude of the electromagnetic wave signals between different sensors within each power frequency cycle, the more likely a partial discharge has occurred within that corresponding power frequency cycle.

[0040] As a preferred embodiment, based on the comprehensive interference value of each detection window and the difference in the maximum electromagnetic wave signal values ​​of any two sensors under each power frequency cycle within each detection window, a second characteristic value between any two sensors under each power frequency cycle within each detection window is obtained, which is used to characterize the degree of difference in electromagnetic wave amplitude between any two sensors under each power frequency cycle within each detection window.

[0041] In this embodiment, the second characteristic values ​​of the i-th and j-th sensors under the u-th power frequency cycle within the p-th detection window are denoted as... Its specific expression is: In the formula, Let be the second characteristic value between the i-th and j-th sensors under the u-th power frequency cycle within the p-th detection window. This represents the overall interference value of the p-th detection window; and These are the maximum electromagnetic wave signals of the i-th and j-th sensors during the u-th power frequency cycle within the p-th detection window, respectively.

[0042] The larger the value, the greater the influence of electromagnetic interference in the p-th detection window on partial discharge detection. To prevent strong interference signals from affecting the acquisition of partial discharge signals, the comprehensive interference value is used as the calculation weight to improve the detection capability of weak partial discharges in the detection window. The larger the value, 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. Therefore, the greater the probability of partial discharge between the i-th and j-th sensors in that power frequency cycle.

[0043] Furthermore, the second characteristic value between any two sensors in the u-th power frequency cycle within the p-th detection window is calculated, and the sum of all the second characteristic values ​​is recorded as the third characteristic value in the u-th power frequency cycle within the p-th detection window. The obtained third characteristic value reflects the overall difference in electromagnetic wave intensity among all sensors in the u-th power frequency cycle within the p-th detection window. The larger the value, the greater the probability of partial discharge in the u-th power frequency cycle within the p-th detection window.

[0044] Furthermore, the power frequency cycle of partial discharge within the p-th detection window is obtained by: calculating the average value of the third characteristic value of all power frequency cycles within the p-th detection window, recording the obtained average value as the preset discharge threshold, recording the power frequency cycle with the third characteristic value greater than the preset discharge threshold as the partial discharge cycle within the p-th detection window, and recording the electromagnetic wave signal of each sensor within the partial discharge cycle as the undetermined partial discharge signal.

[0045] Thus, all partial discharge cycles within the p-th detection window are obtained.

[0046] Step 4: Based on the dispersion of the maximum electromagnetic wave values ​​of all sensors in each partial discharge cycle within each detection window, and the frequency domain energy of the electromagnetic wave signal corresponding to the sensor with the maximum electromagnetic wave signal value in each partial discharge cycle, obtain the partial discharge factor for each partial discharge cycle within each detection window. Combined with the proportion of partial discharge cycles in each detection window, obtain the existence confidence of each detection window, and then determine whether there is partial discharge in the high and low voltage switchgear under each detection window.

[0047] Furthermore, within each partial discharge cycle, the larger the amplitude of the sensor's electromagnetic wave, the closer the sensor is to the current partial discharge location. Therefore, the electromagnetic wave signal from the sensor in that corresponding partial discharge cycle more accurately reflects the severity of the partial discharge within that cycle. Thus, the electromagnetic wave signal corresponding to the sensor with the largest maximum electromagnetic wave signal in each partial discharge cycle is recorded as the maximum partial discharge signal for that cycle.

[0048] The longer the duration of a single partial discharge in a high- and low-voltage switchgear, the lower the frequency of the electromagnetic waves generated by the discharge current. To increase the weight of lower frequency components of the signal in the calculation, an FFT algorithm is used to obtain the spectral sequence of the maximum partial discharge signal for each partial discharge cycle. The frequency range of each spectral sequence is uniformly divided into N frequency intervals, and the frequency intervals are numbered from lowest to highest frequency. Simultaneously, the energy within different frequency intervals is obtained. The specific calculation method for the frequency domain signal energy is a known technique; in this embodiment, N is set to 4.

[0049] In assessing the severity of partial discharge, the distance between the partial discharge location and the sensor has a significant impact. Within a single partial discharge cycle, the closer the partial discharge location is to a particular sensor, the farther it is from other sensors. Therefore, the electromagnetic signal from the sensor closer to the partial discharge location better reflects the severity of the partial amplification, and should be given greater weight to improve the reliability of the severity assessment. Consequently, the larger the coefficient of variation of the maximum electromagnetic signal values ​​from all sensors within a single partial discharge cycle, the greater the weight should be assigned to the maximum partial discharge signal within that cycle.

[0050] Based on the above characteristics, as a preferred implementation, the partial discharge factor for each partial discharge cycle within each detection window is obtained according to the dispersion of the maximum electromagnetic wave values ​​of all sensors in each partial discharge cycle within each detection window, and the frequency domain energy of the electromagnetic wave signal corresponding to the sensor with the maximum electromagnetic wave signal value in each partial discharge cycle. This factor is used to characterize the possibility that the undetermined partial discharge signal in each partial discharge cycle within each detection window belongs to a real partial discharge signal.

[0051] In this embodiment, the partial discharge factor in the s-th partial discharge cycle within the p-th detection window is denoted as... Its specific expression is: In the formula, This represents the partial discharge factor during the s-th partial discharge cycle within the p-th detection window. The coefficient of variation represents the maximum value of the electromagnetic wave signal of all sensors in the p-th detection window during the s-th partial discharge cycle. This represents an exponential function with the natural constant e as its base. This represents the energy of the frequency interval numbered n in the spectral sequence of the maximum partial discharge signal under the s-th partial discharge cycle within the p-th detection window; N represents the total number of frequency intervals in the spectral sequence of the maximum partial discharge signal, which is taken as 4 in this embodiment. This is the numbering of the frequency range.

[0052] By numbering each frequency range, high-frequency energy is weakened while low-frequency energy is amplified. Furthermore, by using the coefficient of variation to assign a larger weight to the electromagnetic wave energy of sensors closer to the partial discharge location, the calculated partial discharge factor can better reflect the probability that the undetermined partial discharge signal within the partial discharge cycle is a real partial discharge signal. The larger the value, the more likely the undetermined partial discharge signal in the s-th partial discharge cycle within the p-th detection window is to be a real partial discharge signal.

[0053] Furthermore, for partial discharge detection in high and low voltage switchgear, the more power frequency cycles of partial discharge signals within the detection window, the higher the frequency of partial discharge within the detection window, and the more severe the partial discharge. Simultaneously, the greater the energy of the partial discharge signal within the corresponding power frequency cycle, the greater the amount of charge released by the partial discharge, reflecting a more severe degree of partial discharge.

[0054] In a preferred embodiment, the presence confidence level of each detection window is obtained based on the partial discharge factor of each partial discharge cycle within each detection window and the proportion of each partial discharge cycle within each detection window. This confidence level is used to measure the probability that the undetermined partial discharge signal within each detection window belongs to a real partial discharge signal. The flowchart for obtaining the presence confidence level of each detection window is shown below. Figure 2 As shown.

[0055] In this embodiment, the existence confidence of the p-th detection window is denoted as . Its specific expression is: In the formula, This represents the confidence level of the existence of the p-th detection window; This represents the ratio of the number of all partial discharge cycles to the number of all power frequency cycles within the p-th detection window; This represents the number of partial discharge cycles within the p-th detection window; This represents the partial discharge factor during the s-th partial discharge cycle within the p-th detection window.

[0056] Furthermore, the presence confidence of normally operating high and low voltage switchgear is obtained under 10,000 detection windows, and the maximum value is recorded as the preset presence threshold. When the presence confidence 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 under the current detection window; otherwise, it is determined that there is no partial discharge in the high and low voltage switchgear under the current detection window.

[0057] Based on the same inventive concept as the above method, this application embodiment also provides a partial discharge detection system for high and low voltage switchgear, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it implements the steps of any one of the above-described partial discharge detection methods for high and low voltage switchgear.

[0058] It should be noted that the order of the embodiments described above is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. Furthermore, specific embodiments of this specification have been described above. Additionally, the processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired results. In some implementations, multitasking and parallel processing are possible or may be advantageous.

[0059] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0060] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the principles of this application should be included within the protection scope of this application.

Claims

1. A partial discharge detection method of a high-low voltage switchgear, characterized by, The method includes the following steps: The electromagnetic wave signals of each sensor location in the high and low voltage switchgear are acquired in real time, as well as the voltage data of the power system in which the high and low voltage switchgear is located; the entire detection process is divided into a detection window of a preset number of power frequency cycles. Based on the maximum value of the electromagnetic wave signal of each sensor in each power frequency cycle within each detection window, and the distance between the time when the maximum value of the electromagnetic wave signal is located and the time when the voltage peak or trough of the power system, the first characteristic value of each sensor in each detection window is obtained. The comprehensive interference value of each detection window is obtained based on the average level of the first characteristic value of all sensors in each detection window. The third characteristic value of each power frequency cycle in each detection window is obtained by combining the difference of the maximum electromagnetic wave signal of any two sensors in each power frequency cycle in each detection window. Thus, each partial discharge cycle in each detection window is obtained. Based on the dispersion of the maximum electromagnetic wave values ​​of all sensors in each partial discharge cycle within each detection window, and the frequency domain energy of the electromagnetic wave signal corresponding to the sensor with the maximum electromagnetic wave signal value in each partial discharge cycle, the partial discharge factor of each partial discharge cycle within 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, thereby determining whether there is partial discharge in the high and low voltage switchgear under the current detection window.

2. The partial discharge detection method for high and low voltage switchgear as described in claim 1, characterized in that, The calculation formula of the first characteristic value of each sensor in each detection window is: ; wherein, represents the first characteristic value of the kth sensor in the pth detection window; represents the number of power frequency cycles in the pth detection window; represents the minimum value of the absolute difference between the electromagnetic wave phase of the kth sensor in the pth detection window and the corresponding phase of the power system power frequency voltage crest and trough in the tth power frequency cycle; represents the maximum value of ; and represents the maximum value of the electromagnetic wave signal of the kth sensor in the pth detection window in the tth power frequency cycle; wherein the electromagnetic wave phase of each sensor in each power frequency cycle refers to the phase of the power system voltage at the time when the maximum value in the electromagnetic wave signal of each sensor in each power frequency cycle is located.

3. The partial discharge detection method of a high-low voltage switchgear according to claim 1, characterized in that, The comprehensive interference value of each detection window refers to the average of the first characteristic values ​​of all sensors within each detection window.

4. The partial discharge detection method of a high-low voltage switchgear according to claim 1, characterized in that, The third characteristic value of each power frequency cycle within each detection window refers to the sum of the second characteristic values ​​between any two sensors under each power frequency cycle within each detection window. The calculation formula of the second characteristic value is: ; in the formula, is the second characteristic value between the i th and j th sensors in the u th power frequency cycle within 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.

5. The partial discharge detection method of a high-low voltage switchgear according to claim 1, characterized in that, Each partial discharge cycle within each detection window refers to the power frequency cycle within each detection window where the third characteristic value is greater than the preset discharge threshold.

6. The partial discharge detection method for high and low voltage switchgear as described in claim 1, characterized in that, The calculation formula of the partial discharge factor of each partial discharge cycle in each detection window is: ; wherein, represents the partial discharge factor under the s-th partial discharge cycle in the p-th detection window; represents the coefficient of variation of the maximum electromagnetic wave signal of all sensors under the s-th partial discharge cycle in the p-th detection window; represents an exponential function with a natural constant e as a base; represents the energy of the frequency interval numbered n in the frequency spectrum sequence of the maximum partial discharge signal under the s-th partial discharge cycle in the p-th detection window; N represents the total number of frequency intervals 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 maximum electromagnetic wave signal in each partial discharge cycle; the acquisition method of each frequency interval and its number in the frequency spectrum sequence of the maximum partial discharge signal under each partial discharge cycle is that the frequency range of the frequency spectrum sequence of the maximum partial discharge signal of each partial discharge cycle is uniformly divided into a preset number of frequency intervals, and each frequency interval is numbered in order from small to large.

7. The partial discharge detection method for high and low voltage switchgear as described in claim 1, characterized in that, The formula for calculating the existence confidence of each detection window is as follows: In the formula, This represents the confidence level of the existence of the p-th detection window; This represents the ratio of the number of all partial discharge cycles to the number of all power frequency cycles within the p-th detection window; This represents the number of partial discharge cycles within the p-th detection window; This represents the partial discharge factor during the s-th partial discharge cycle within the p-th detection window.

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

9. 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, it implements the steps of the partial discharge detection method for high and low voltage switchgear as described in any one of claims 1-8.

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