A method and system for detecting the closing and opening currents of a circuit breaker in a switchgear

Abstract

The present invention relates to the field of electrical variable measurement, and specifically relates to a method and system for detecting the opening and closing currents of a circuit breaker in a switchgear cabinet, including: when the average current change amplitude is greater than a preset threshold F1, increasing the sampling frequency T1 to the sampling frequency T2, when the current collected at T2 has the same change law as the current collected at T1, collecting the current at T1 again. If the current moment changes from a high-frequency period to a low-frequency period, changing F1 based on the threshold F2 using the similarity of the current change laws in the recently obtained low-frequency and high-frequency periods. If the current moment changes from a low-frequency period to a high-frequency period, changing F2 using the similarity b of the current change laws in the low-frequency and high-frequency periods obtained in the last two times, and reading out and detecting the opening and closing parameters from all the collected opening and closing currents. The present invention can accurately capture the current generated by a short opening and closing action from a large number of interfering currents.

Description

Technical Field

[0001] The present invention relates to the field of electrical variable measurement, and particularly relates to a method and system for detecting the opening and closing currents of a circuit breaker in a switch cabinet. Background Art

[0002] The core function of a circuit breaker is to perform opening and closing operations to achieve load allocation. During the operation of the equipment, the circuit breaker may malfunction and thus require repair and maintenance. The malfunctions include rust, jamming, loose components, inter-turn short circuit of the coil, etc. These malfunctions may cause abnormal opening and closing of the switchgear, and even serious accidents such as refusal to open and refusal to close. The opening and closing action currents of the circuit breaker are important bases for judging whether there are malfunctions and whether timely repair and maintenance are required. Therefore, the detection of the opening and closing currents of the circuit breaker has always been an important part of the detection and maintenance of the circuit breaker.

[0003] The existing current detection method is to use a current sensor to collect the opening and closing currents. However, due to the short opening and closing action time of the circuit breaker, generally in the order of dozens of milliseconds, and due to the interference of the external electromagnetic environment and the internal circuit of the detection device, these interferences may cause false sampling (that is, when there is no opening and closing operation of the circuit breaker, it is misjudged as having an opening and closing action due to interference) or miss the collection of important current data (such as missing the collection of the currents at the start and end time points of the opening and closing action), thereby making it difficult to accurately capture the currents generated by the short opening and closing actions from a large number of interfered currents, and further resulting in unreliable detection results of the opening and closing currents of the circuit breaker. Summary of the Invention

[0004] To solve the above problems, the present invention provides a method and system for detecting the opening and closing currents of a circuit breaker in a switch cabinet.

[0005] The method and system for detecting the opening and closing currents of a circuit breaker in a switch cabinet of the present invention adopt the following technical solutions:

[0006] An embodiment of the present invention provides a method for detecting the opening and closing currents of a circuit breaker in a switch cabinet, the method comprising the following steps:

[0007] Collect the opening and closing currents at a preset frequency T1. When the average change amplitude of the current is greater than a preset threshold F1, increase T1 to a preset frequency T2 and continue to collect the current. When the current collected at T2 has the same change pattern as the current collected at T1, collect the current at T1 again. When the change patterns are different, continue to collect the current at T2;

[0008] Wherein the period of collecting the current at T1 is denoted as the low-frequency period, and the period of collecting the current at T2 is denoted as the high-frequency period;

[0009] When the current time changes from a high-frequency period to a low-frequency period, change F1 by utilizing the similarity of the change rules of the currents in the most recently obtained low-frequency period and the most recently obtained high-frequency period, including: when the similarity of the change rules is greater than a preset threshold F2, the changed F1 is positively correlated with the maximum change amplitude of the current in the most recently obtained high-frequency period; when the similarity of the change rules is less than or equal to the preset threshold F2, the changed F1 is positively correlated with the minimum change amplitude of the current in the most recently obtained high-frequency period;

[0010] When the current time changes from a low-frequency period to a high-frequency period, change F2 by utilizing the similarity b of the change rules of the currents in the two most recently obtained low-frequency periods and the most recently obtained high-frequency period, and the changed F2 is negatively correlated with b;

[0011] Read out the switching parameters from all the collected closing and opening currents and perform detection.

[0012] Preferably, the determination method for the currents collected at T2 and the currents collected at T1 having the same change rule:

[0013] Record the current sequence collected at frequency T2 as the second current sequence, record the current sequence collected at frequency T1 before increasing the frequency to T2 as the first current sequence, and obtain the current difference between the first current sequence and the second current sequence;

[0014] In the second current sequence, starting from the first current data, take out one current data every other current and form a sequence L(1), and obtain the current difference between the first current sequence and L(1);

[0015] In the second current sequence, starting from the first current data, take out one current data every two currents and form a sequence L(2), and obtain the current difference between the first current sequence and L(2);

[0016] And so on, in the second current sequence, starting from the first current data, take out one current data every N1 currents and form a sequence L(N1), and obtain the current difference between the first current sequence and L(N1); N1 is a preset value.

[0017] When the mean value of all the obtained current differences is less than a preset threshold th1, it is determined that the first current sequence and the second current sequence have the same change rule; when the mean value of all the obtained current differences is greater than or equal to the preset threshold th1, it is determined that the first current sequence and the second current sequence do not have the same change rule.

[0018] Preferably, the specific steps for obtaining the similarity of the change rules of the currents in the most recently obtained low-frequency period and the most recently obtained high-frequency period are as follows:

[0019] For the current sequence List1 composed of the currents obtained recently during the low-frequency period and the current sequence List2 composed of the currents obtained recently during the high-frequency period, the current difference between List1 and List2 is denoted as x, and exp(-x) is taken as the similarity of the variation law, where exp() represents the exponential function with the natural constant as the base.

[0020] Preferably, the specific steps for obtaining the maximum variation amplitude of the current obtained recently during the high-frequency period and the minimum variation amplitude of the current obtained recently during the high-frequency period are as follows:

[0021] For the current sequence List2 composed of the currents obtained recently during the high-frequency period, calculate the differences between every two adjacent current data in List2; cluster the differences of all adjacent current data in List2 into several categories, calculate the mean value of all differences in each category, and for the category with the largest mean value of all differences, the mean value of all differences in the category with the largest mean value is taken as the maximum variation amplitude; for the category with the smallest mean value of all differences, the mean value of all differences in the category with the smallest mean value is taken as the minimum variation amplitude.

[0022] Preferably, when the similarity of the variation law is greater than the preset threshold F2, the changed F1 is positively correlated with the maximum variation amplitude of the current obtained recently during the high-frequency period; when the similarity of the variation law is less than or equal to the preset threshold F2, the changed F1 is positively correlated with the minimum variation amplitude of the current obtained recently during the high-frequency period, and the specific formula included is as follows:

[0023] When the similarity of the variation law is greater than the preset threshold F2, take w×f1+(1 - w)×F1 as the changed F1; when the similarity of the variation law is less than or equal to the preset threshold F2, take w×F1+(1 - w)×f2 as the changed F1;

[0024] Where w represents the similarity of the variation law; f1 and f2 represent the maximum variation amplitude and the minimum variation amplitude respectively.

[0025] Preferably, the specific steps for obtaining the similarity b of the variation law of the currents in the low-frequency periods obtained in the most recent two times and the current obtained recently during the high-frequency period are as follows:

[0026] Arrange the currents in the low-frequency periods obtained in the most recent two times in chronological order to obtain the sequence List3, and the sequence List2 composed of the currents obtained recently during the high-frequency period. The similarity of the variation law between List3 and List2 is denoted as b.

[0027] Preferably, the specific formula for changing F2 by using the similarity b of the variation law of the currents in the low-frequency periods obtained in the most recent two times and the current obtained recently during the high-frequency period is as follows:

[0028] The changed F2 is F2×(y - b), where y represents a preset offset coefficient.

[0029] Preferably, reading the switching parameters from all the collected switching currents and performing detection includes the following specific steps:

[0030] Read the start time point and end time point of the switching operation from all the collected switching currents; take the time difference between the end time point and the start time point as the switching parameter, and find the absolute value of the difference between the obtained switching parameter and the switching parameter measured when the circuit breaker left the factory. The ratio of the absolute value to the switching parameter measured when the circuit breaker left the factory is recorded as the parameter abnormality degree. When the parameter abnormality degree is greater than the preset threshold th2, it is determined that the detection result of the circuit breaker is abnormal.

[0031] Preferably, the specific steps for obtaining the current difference are as follows:

[0032] Perform linear normalization processing on any two current sequences respectively, and record the DTW distance between the two linearly normalized current sequences as the current difference.

[0033] Another embodiment of the present invention provides a switching current detection system for a switchgear circuit breaker. The system includes a detection device and a display. The detection device includes a tripping current sensor and a closing current sensor for collecting switching currents, and the display is used to display the switching currents; the detection device also includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of a switching current detection method for a switchgear circuit breaker as described above.

[0034] The beneficial effects of the technical solution of the present invention are:

[0035] The present invention collects switching currents at a preset frequency T1. When the average change amplitude of the current is greater than the preset threshold F1, T1 is increased to the preset frequency T2 and the current is continuously collected. When the current collected at T2 has the same change law as the current collected at T1, the current is collected again at T1. When the change laws are different, the current is continuously collected at T2. During the process, when facing the situation that the current generated during the switching operation exists for a short time, high-frequency sampling and low-frequency sampling are alternately performed to avoid obtaining a large amount of interfering current data that is invalid for the detection of switching currents when continuously sampling current data at high speed, or in other words, it can capture the current generated by the switching operation with a short existence time in a large amount of invalid currents to a certain extent.

[0036] On this basis, when the high-frequency period changes to the low-frequency period in the present invention, the similarity of the current change rules in the recently obtained low-frequency period and the recently obtained high-frequency period is utilized to change F1. The specific adjustment method is that when the similarity of the change rules is greater than the preset threshold F2, the changed F1 is positively correlated with the maximum change amplitude of the current in the recently obtained high-frequency period; when the similarity of the change rules is less than or equal to the preset threshold F2, the changed F1 is positively correlated with the minimum change amplitude of the current in the recently obtained high-frequency period. This process continuously and dynamically changes the preset threshold F1 to dynamically control the timing of switching back to the high-frequency period when in the low-frequency period, making it applicable to the interference situation existing in the collected current, further avoiding the problem of missing the start and end time points of the switching-on and switching-off operations during low-frequency sampling or the problem of false sampling (that is, when there is no switching-on and switching-off operation of the circuit breaker, it is misjudged that there is a switching-on and switching-off operation due to interference), and further ensuring that the current generated by the short switching-on and switching-off operations can be captured from a large number of interfering currents.

[0037] Furthermore, if the current moment changes from the low-frequency period to the high-frequency period, the similarity b of the current change rules in the two most recently obtained low-frequency periods and the most recently obtained high-frequency period is obtained to change F2, and the changed F2 is negatively correlated with b. In this process, by dynamically adjusting F2, F2 approaches or stabilizes at a better value in real time along with the sampling process. The so-called better value refers to being able to determine whether to use a larger current change amplitude (that is, the maximum change amplitude) or a smaller current change amplitude (that is, the minimum change amplitude) to determine the timing of changing from the low-frequency period to the high-frequency period according to the interference situation existing in the current, further avoiding the situation of high-speed high-frequency acquisition of a large number of invalid currents.

[0038] In summary, in this embodiment, F1 and F2 are dynamically and alternately changed according to the current change conditions when switching from the high-frequency period to the low-frequency period and then from the low-frequency period to the high-frequency period, so as to avoid the problem of high-speed high-frequency acquisition of a large number of invalid interfering currents as much as possible, and also avoid the problem of missing the start and end time points of the switching-on and switching-off operations during low-frequency sampling, further ensuring that the current generated by the short switching-on and switching-off operations can be accurately captured from a large number of interfering currents and ensuring the reliability of the current detection result. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained according to these drawings.

[0040] Figure 1The flowchart of the steps of a method for detecting the opening and closing currents of a switch cabinet circuit breaker provided by an embodiment of the present invention;

[0041] Figure 2 The schematic diagrams of the high-frequency period and the low-frequency period when the threshold F1 in an embodiment of the present invention remains unchanged;

[0042] Figure 3 The schematic diagrams of the high-frequency period and the low-frequency period after the threshold F1 in an embodiment of the present invention is changed. Detailed implementation manners

[0043] In order to further elaborate on the technical means and effects adopted by the present invention to achieve the intended invention purpose, the following describes in detail the specific implementation manners, structures, features and effects of a method and system for detecting the opening and closing currents of a switch cabinet circuit breaker proposed according to the present invention in combination with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs.

[0045] The following specifically describes the specific solutions of a method and system for detecting the opening and closing currents of a switch cabinet circuit breaker provided by the present invention in combination with the accompanying drawings.

[0046] Embodiment 1:

[0047] This embodiment provides a system for detecting the opening and closing currents of a switch cabinet circuit breaker. The system at least includes a detection device and a display; the detection device is used to collect the opening and closing currents (opening current and closing current) of the circuit breaker, and the display is used to display the opening and closing currents of the circuit breaker.

[0048] The detection device includes an opening current sensor and a closing current sensor; the opening current sensor adopts an opening and closing design and can be directly clamped on the opening power line of the circuit breaker, with simple installation; the opening current sensor is designed according to the characteristics of the opening operation power line of the circuit breaker and can be easily clamped on the opening operation power line of the circuit breaker; the opening diameter of the opening current sensor is not less than 20 mm.

[0049] The detection device further includes a detection host. The opening current sensor is connected to the detection host through a cable; the cable of the opening current sensor includes a power line and a signal line; the opening current sensor is powered by the detection host through the power line in the cable of the opening current sensor; the output signal of the opening current sensor is a current, which is uploaded to the opening current detection interface of the detection host through the signal line in the cable of the opening current sensor.

[0050] The closing current sensor and the opening current sensor usually adopt current sensors of the same model.

[0051] The interface between the closing current sensor and the detection host is the closing current detection interface, and the rest is the same as that of the opening current sensor.

[0052] Inside the detection host, there are an amplification circuit, an AD circuit, and a power supply module.

[0053] The function of the amplification circuit is to amplify the output current signals of the opening current sensor and the closing current sensor. Since the output current of the current sensor is extremely weak, usually 4~20mA, the signal is too weak and prone to sampling deviation, so amplification is required. The amplification circuit is implemented using an operational amplifier.

[0054] The function of the AD circuit is to sample the analog current signal and convert it into a digital signal.

[0055] The function of the power supply module is to supply power to the detection host and the devices connected to the detection host (such as the opening current sensor, the closing current sensor, etc.). The power supply module uses a wide-input power conversion module, which is compatible with AC85~270V; DC100~380V; the power conversion module converts the input power into the power required by the device: ±5V, 12V, 24V.

[0056] Inside the detection host, there also include a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements a method for detecting the opening and closing currents of a switch cabinet circuit breaker, which is used to collect and detect the opening and closing currents (that is, the opening current and the closing current).

[0057] Embodiment 2:

[0058] As Figure 1 shown, this embodiment provides a method for detecting the opening and closing currents of a switch cabinet circuit breaker, and the method includes:

[0059] Step S201: Collect the opening and closing currents at a preset frequency T1. When the average change amplitude of the current is greater than the preset threshold F1, increase T1 to the preset frequency T2 and continue to collect the current.

[0060] When collecting the opening and closing currents (opening current or closing current), considering that the opening and closing times (opening time or closing time) are relatively short, generally in dozens of milliseconds. For example, in the factory parameters of the circuit breaker in this embodiment, it is marked that: the opening time is 39.20 milliseconds, and the closing time is 69.70 milliseconds. Therefore, in order to capture the opening and closing currents within the short opening and closing times, a high-speed sampling of the current by the current sensor is required.

[0061] However, since it is impossible to determine the specific execution time of the opening and closing operations, the current sampled by the opening and closing current sensors is not necessarily the current during the execution of the opening and closing operations, but includes the current before and after the execution of the operations.

[0062] It should be noted that in this embodiment, there is a delay between when the staff issues the opening and closing signal instructions and when the circuit breaker executes the opening and closing operations. For example, the time occupied by the transmission of the signal instructions, the time occupied by the mechanical components of the circuit breaker to execute the operations, and even the reaction time of the staff, etc., all result in a delay. This delay is generally between 1 second (equal to 1000 milliseconds) and 4 seconds (equal to 4000 milliseconds). Compared with the short opening and closing time, it is impossible to connect the opening and closing current sensors to the current screen at the moment when the circuit breaker executes the opening and closing operations, resulting in most of the collected current being invalid. Therefore, the general practice is to connect the opening and closing current sensors to the current screen in advance, then collect the current in real time, and then extract the opening and closing current during the execution of the opening and closing operations of the circuit breaker from all the collected opening and closing currents. This current is the one to be obtained in this embodiment and is used to detect the current of the circuit breaker.

[0063] Since all the collected opening and closing currents contain a large amount of useless current, that is, the current is still being collected at a high speed before the opening and closing operations are executed or after they are completed. These currents are useless. On the one hand, they will interfere with the subsequent detection process, and on the other hand, they will occupy too much data storage space or transmission time.

[0064] In this embodiment, in order to avoid collecting too many opening and closing currents that interfere with the subsequent detection process, the opening and closing currents are first collected at a preset frequency T1. When the average change amplitude of the current is greater than the preset threshold F1, T1 is increased to the preset frequency T2 and the current is continued to be collected.

[0065] The above T1 is less than T2. In this embodiment, T1 = 0.2 is used as an example for description, which means collecting 0.2 currents per millisecond, that is, sampling one current every 5 milliseconds; T2 equal to 1 is used as an example for description, which means collecting 1 current per millisecond. Where the average change amplitude of the current being greater than the preset threshold F1 indicates that the current has changed significantly, indicating that an opening and closing operation has occurred; on the contrary, when the average change amplitude of the current is not greater than the preset threshold F1, it indicates that the current has not changed significantly, indicating that no opening and closing operation has occurred.

[0066] In summary, in the above process, when no opening and closing operation occurs, less current is collected at a lower sampling frequency. When an opening and closing operation occurs, the current is sampled at a high speed to obtain the detailed change situation of a large amount of current during the execution of the opening and closing operation.

[0067] As an example, the method for obtaining the average change amplitude of the current includes:

[0068] When collecting current at a frequency T1, after collecting each current, obtain the N0 most recently collected current data, and use the difference between the maximum value and the minimum value of these currents as the average current change amplitude.

[0069] In some other examples, the standard deviation of the N0 current data is used as the average current change amplitude.

[0070] In still some other examples, for the N0 current data, find the difference between every two adjacent current data (i.e., the absolute value of the difference), and use the average value of all the differences in the N0 current data as the average current change amplitude.

[0071] In addition, this embodiment is described by taking N0 = 10 as an example. In other embodiments, N0 can be set to other values. This embodiment does not limit it, as long as N0 is greater than or equal to 2.

[0072] Specifically, when the number of the most recently collected current data is less than N0 when collecting current at a frequency T1, then perform the above processing on all the currents collected after starting to collect current at a frequency T1, and obtain the average current change amplitude. If there is only one current collected after starting to collect current at a frequency T1, then use the difference between this current and the current collected at the previous moment as the average current change amplitude. If there is no current collected at the previous moment, then no longer calculate the average current change amplitude, but continue to collect current at a frequency T1.

[0073] In some other embodiments, when the number of the most recently collected current data is less than N0 when collecting current at a frequency T1, no longer calculate the average current change amplitude, but continue to collect current at a frequency T1.

[0074] In addition, this embodiment is described by taking F1 equal to 0.2A as an example (in this embodiment, the amplifier amplifies the output signal of the current sensor by 100 times). In other embodiments, F1 can be set to other values. This embodiment does not make specific limitations.

[0075] Step S202: When the current collected at T2 has the same change pattern as the current collected at T1, collect current at T1 again. When they have different change patterns, continue to collect current at T2; where the time period of collecting current at T1 is recorded as the low-frequency time period, and the time period of collecting current at T2 is recorded as the high-frequency time period.

[0076] When the detection device uses the detection host and the current sensor to collect current, mis-sampling is inevitable. Mis-sampling refers to the situation where, when the circuit breaker has no opening or closing operation, the detection host mistakenly believes that the circuit breaker has an opening or closing action due to interference, and then triggers mis-sampling (that is, in step S101, the sampling frequency T1 is wrongly increased to the preset frequency T2). The interference includes internal interference and external interference. External interference includes: electromagnetic interference from surrounding power equipment, especially electromagnetic interference from high-voltage power equipment at a relatively close distance, interference coupled by other power equipment through power lines or ground wires, etc. Internal interference includes thermal noise of electronic components inside the sensor, amplifier noise, AD current noise, etc. Especially when the output circuit signal of the current sensor is too weak, the interference of these noises will be more obvious. Although some of these interferences can be eliminated by adding a filter circuit, there are still inevitable internal and external interferences on weak signals.

[0077] In this embodiment, when the average change amplitude of the current is greater than the preset threshold F1 and T1 is increased to the preset frequency T2, the current sequence collected at the frequency T2 is recorded as the second current sequence, and the current sequence collected at the frequency T1 before the frequency is increased to T2 is recorded as the first current sequence. When the first current sequence and the second current sequence have the same change law, it indicates that there is no opening or closing action. At this time, the current is collected again at the frequency T1. When the first current sequence and the second current sequence do not have the same change law, it indicates that the current collected at high speed and high frequency has changed significantly. At this time, the current is continuously collected at the frequency T2.

[0078] Then, continue to obtain the second current sequence collected at the frequency T2, and the first current sequence collected at the frequency T1 before the frequency is increased to T2. Similarly, when the first current sequence and the second current sequence have the same change law, it indicates that there is no opening or closing action. At this time, the current is collected again at the frequency T1. When the first current sequence and the second current sequence do not have the same change law, it indicates that the current collected at high speed and high frequency has changed significantly. At this time, the current is continuously collected at the frequency T2.

[0079] And so on, continuously collect current.

[0080] In the above process, the time period of collecting current at the frequency T1 is recorded as the low-frequency period, and the time period of collecting at the frequency T2 is recorded as the high-frequency period. During the whole process of collecting current, the low-frequency period and the high-frequency period appear alternately, which can avoid the mis-sampling problem caused by interference to a certain extent, and then avoid collecting too many invalid current data, which will interfere with the detection process.

[0081] As an optional example, the method for judging that the first current sequence and the second current sequence have the same change law includes:

[0082] Whenever a current data is collected at T2, the obtained second current sequence and the first current sequence are respectively subjected to linear normalization processing, and the DTW distance between the normalized second current sequence and the first current sequence is obtained, which is denoted as the current difference between the first current sequence and the second current sequence.

[0083] The DTW distance is obtained by using the DTW algorithm, which is a well-known technology and will not be specifically described in this embodiment.

[0084] When the difference is less than the preset threshold th1, it is determined that the first current sequence and the second current sequence have the same change law; when the difference is greater than or equal to the preset threshold th1, it is determined that the first current sequence and the second current sequence do not have the same change law.

[0085] In this embodiment, th1 = 0.63 is taken as an example for description. In other embodiments, th1 can be set to other values, which are not specifically limited in this embodiment.

[0086] As a preferred example, the method for judging that the first current sequence and the second current sequence have the same change law includes:

[0087] In the second current sequence, starting from the first current data, one current data is taken out after every other current, and the sequence composed of these current data is denoted as L(1), and the difference between the first current sequence and L(1) is obtained.

[0088] Then, in the second current sequence, starting from the first current data, one current data is taken out after every two currents, and the sequence composed of these current data is denoted as L(2), and the difference between the first current sequence and L(2) is obtained.

[0089] And so on, in the second current sequence, starting from the first current data, one current data is taken out after every N1 currents, and the sequence composed of these current data is denoted as L(N1), and the difference between the first current sequence and L(N1) is obtained.

[0090] Calculate the mean value of all the differences obtained above. When the mean value is less than the preset threshold th1, it is determined that the first current sequence and the second current sequence have the same change law; when the mean value is greater than or equal to the preset threshold th1, it is determined that the first current sequence and the second current sequence do not have the same change law.

[0091] This preferred example can more comprehensively and accurately evaluate the change law of the first current sequence and the second current sequence compared with the above optional example.

[0092] In this embodiment, N1 = 5 is taken as an example for description. In other embodiments, N1 can be set to other values, which are not specifically limited in this embodiment.

[0093] Specifically, when the number of current data in the second current sequence is less than N2, it is no longer determined whether there is the same change pattern, but the current is continuously collected at T2 to avoid the situation where the current data in the second current sequence is too small to obtain the change pattern. In this embodiment, N2 = 5 is taken as an example for description, and in other embodiments, N2 can be set to other values, which is not limited in this embodiment.

[0094] Step S203: If the current time changes from the high-frequency period to the low-frequency period, change F1 by using the similarity of the current change patterns in the recently obtained low-frequency period and the recently obtained high-frequency period, including: when the similarity of the change patterns is greater than the preset threshold F2, the changed F1 is positively correlated with the maximum change amplitude of the current in the recently obtained high-frequency period; when the similarity of the change patterns is less than or equal to the preset threshold F2, the changed F1 is positively correlated with the minimum change amplitude of the current in the recently obtained high-frequency period.

[0095] Regarding the preset threshold F1 used in steps S201 and S202, if the preset threshold F1 is set too large, it will cause the failure to capture the small current fluctuation changes existing during the execution of the switching-on and switching-off operations in a timely manner, resulting in the failure to enter the high-speed sampling state (i.e., still not performing high-speed sampling at T2) when the switching-on and switching-off operations have already started or have not yet ended, so that the start time point and end time point of the switching-on and switching-off operations cannot be clearly shown in the collected current.

[0096] When the preset threshold F1 is set too small, a little interference can trigger high-speed sampling (i.e., performing high-speed sampling at T2), increasing the number of mis-sampling times and introducing invalid current data with more interference, affecting the detection process (such as affecting the judgment of the start time point and end time point of the switching-on and switching-off operations).

[0097] In this embodiment, when the current time changes from the high-frequency period to the low-frequency period, F1 is changed by using the similarity of the current change patterns in the recently obtained low-frequency period and the recently obtained high-frequency period, solving the problem that F1 is set too large or too small as described above, enabling F1 to dynamically adapt to the sampling process, and further ensuring that the influence of current interference on current collection is avoided in real time.

[0098] The process of changing F1 includes: when the similarity of the change patterns is greater than the preset threshold F2, the changed F1 is positively correlated with the maximum change amplitude of the current in the recently obtained high-frequency period; when the similarity of the change patterns is greater than the preset threshold F2, the changed F1 is positively correlated with the minimum change amplitude of the current in the recently obtained high-frequency period.

[0099] On the one hand, the similarity of the variation law is greater than the preset threshold F2, indicating that when the current moment changes from the high-frequency period to the low-frequency period, the current in the high-frequency period is more likely to be in the same state as the current in the previous low-frequency period, that is, the same interference state, and both are in the state where the opening and closing actions are not triggered; at the same time, considering that the current collected in the recently obtained high-frequency period can more detailedly (without loss) show the fluctuating changes of the current limiting under internal and external interferences, so when the similarity of the variation law is large, the maximum change amplitude of the current in the recently obtained high-frequency period can be used to obtain the changed F1.

[0100] The larger the maximum change amplitude of the current in the recently obtained high-frequency period, the more it means that for the upcoming low-frequency period, in the future, a larger preset threshold F1 can be continuously used to judge whether it is necessary to switch from the low-frequency period to the high-frequency period again, and at the same time, there is no need to worry about missing (or not being able to capture) the start time point and end time point of the opening and closing actions; on the contrary, the smaller the maximum change amplitude of the current in the recently obtained high-frequency period, the more it means that for the upcoming low-frequency period, in the future, a smaller preset threshold F1 needs to be used to judge whether it is necessary to switch from the low-frequency period to the high-frequency period again, and at the same time, there is no need to worry about missing (or not being able to capture) the start time point and end time point of the opening and closing actions.

[0101] On the other hand, when the similarity of the variation law is not greater than the preset threshold F2, it indicates that when the current moment changes from the high-frequency period to the low-frequency period, the current in the high-frequency period is more likely to have changed compared to the current in the previous low-frequency period. For example, the internal interference or external interference has changed, or for example, the change caused by the opening and closing actions. When the similarity of the variation law is small, it is more necessary to use the minimum change amplitude of the current in the recently obtained high-frequency period to obtain the changed F1; the smaller the minimum change amplitude, the more it means that for the upcoming low-frequency period, in the future, a smaller preset threshold F1 needs to be used to judge whether it is necessary to switch from the low-frequency period to the high-frequency period again to avoid missing the start time point and end time point of the upcoming opening and closing actions; on the contrary, the larger the minimum change amplitude, the more it means that for the upcoming low-frequency period, in the future, a larger preset threshold F1 can be used to judge whether it is necessary to switch from the low-frequency period to the high-frequency period again to avoid missing the start time point and end time point of the upcoming opening and closing actions.

[0102] For the change from the high-frequency period to the low-frequency period, by utilizing the similarity of the change rules of the current in the recently obtained low-frequency period and the recently obtained high-frequency period to change F1, such that when determining the change from the low-frequency period to the high-frequency period, F1 can be based on the change situation of the current at present, avoiding the situation where after the change from the high-frequency period to the low-frequency period, when switching back to the high-frequency period according to a fixed F1 (or an F1 that is too large or too small), the closing and opening operations cannot be captured in a timely and high-speed manner. For example, avoiding switching to the high-frequency period after the start time point of closing and opening has passed, and for another example, avoiding switching to the high-frequency period prematurely before the start time point of closing and opening arrives.

[0103] Subsequently, each time when changing from the high-frequency period to the low-frequency period, the above method is used to dynamically change the preset threshold F1.

[0104] As an illustrative explanation, Figure 2 Figure 8 is a schematic diagram of a high-frequency period and a low-frequency period (the current is collected every 5 ms in the low-frequency period and every 1 ms in the high-frequency period), and this figure shows a section of opening current collected when the threshold F1 is kept unchanged; Figure 3 Figure 10 is also a schematic diagram of a high-frequency period and a low-frequency period, and this figure shows a section of opening current collected after the threshold F1 is dynamically changed. The points P1 and P3 represent the start time points of the opening operation, and P2 and P4 represent the end time points of the opening operation. Figure 2 The start time point P3 in Figure 12 is not accurate, Figure 3 The start time point P1 in Figure 14 is relatively accurate ( Figure 3 the changed threshold F1 in Figure 16 is 0.06 A). That is to say, as shown in Figure 2 and Figure 3 , when the set threshold F1 cannot adapt to the interference changes in the current, it will cause missing the accurate start time during low-frequency sampling, affecting the subsequent current inspection results.

[0105] As an example, the similarity of the change rules of the current in the recently obtained low-frequency period and the recently obtained high-frequency period includes the following method:

[0106] For the current sequence List1 composed of the current in the recently obtained low-frequency period and the current sequence List2 composed of the current in the recently obtained high-frequency period, the difference between List1 and List2 (the calculation method is step S202) is denoted as x, and exp(-x) is taken as the similarity of the change rules. exp() represents the exponential function with the natural constant as the base.

[0107] As another example, the similarity of the change rules of the current in the recently obtained low-frequency period and the recently obtained high-frequency period includes the following method:

[0108] Perform linear interpolation on F1 so that List1 and List2 have the same length, and then use the Pearson correlation coefficient between List1 and List2 as the similarity of the variation law. Specifically, when the Pearson correlation coefficient is less than 0.1, set the similarity of the variation law to 0.1.

[0109] As an optional example, the method for obtaining the maximum change amplitude of the current in the recently obtained high-frequency period and the minimum change amplitude of the current in the recently obtained high-frequency period includes:

[0110] For the current sequence List2 composed of the current in the recently obtained high-frequency period, calculate the difference (i.e., the absolute value of the difference) between every two adjacent current data in List2. For all the differences obtained from all adjacent current data in List2, the maximum or minimum value among these differences is used as the maximum change amplitude and the minimum change amplitude, respectively.

[0111] As a preferred example, the method for obtaining the maximum change amplitude of the current in the recently obtained high-frequency period and the minimum change amplitude of the current in the recently obtained high-frequency period includes:

[0112] In the above optional example, using the maximum or minimum value among these differences as the maximum change amplitude and the minimum change amplitude respectively, this method cannot reflect the overall change situation of the current.

[0113] In this preferred example, cluster these differences into several categories. For example, use the K-Means clustering algorithm to cluster them into 3 categories. Each category contains several differences. Calculate the mean value of all the differences in each category. For the category with the largest mean value of all the differences, the mean value of all the differences in this category is used as the maximum change amplitude; for the category with the smallest mean value of all the differences, the mean value of all the differences in this category is used as the minimum change amplitude.

[0114] As an optional example, when the similarity of the variation law is greater than the preset threshold F2, the changed F1 is positively correlated with the maximum change amplitude of the current in the recently obtained high-frequency period; when the similarity of the variation law is less than or equal to the preset threshold F2, the changed F1 is positively correlated with the minimum change amplitude of the current in the recently obtained high-frequency period. The method included is:

[0115] When the similarity of the variation law is greater than the preset threshold F2, use the maximum change amplitude as the changed F1. When the similarity of the variation law is less than or equal to the preset threshold F2, use the minimum change amplitude as the changed F1.

[0116] As a preferred example, when the similarity of the variation law is greater than the preset threshold F2, the changed F1 is positively correlated with the maximum variation amplitude of the current in the most recently obtained high-frequency period; when the similarity of the variation law is less than or equal to the preset threshold F2, the changed F1 is positively correlated with the minimum variation amplitude of the current in the most recently obtained high-frequency period. The method included is as follows:

[0117] When the similarity of the variation law is greater than the preset threshold F2, w×f1+(1 - w)×F1 is taken as the changed F1. When the similarity of the variation law is less than or equal to the preset threshold F2, w×F1+(1 - w)×f2 is taken as the changed F1.

[0118] Where w represents the similarity of the variation law; f1 and f2 represent the maximum variation amplitude and the minimum variation amplitude.

[0119] In this preferred example, the current F1 (describing the adjusted threshold F1 during the conversion from the low-frequency period to the high-frequency period in history) is fused with the maximum variation amplitude (or the minimum variation amplitude) to determine the timing of the next conversion from the low-frequency period to the high-frequency period (i.e., the magnitude of the changed F1), which is relatively reliable compared with the above optional example.

[0120] Step S204: If the low-frequency period changes to the high-frequency period, the similarity b of the variation law of the currents in the two most recently obtained low-frequency periods and the most recently obtained high-frequency period is used to change F2, and the changed F2 is negatively correlated with b.

[0121] In the above steps, when changing from the high-frequency period to the low-frequency period, the current change situation in the most recent period (i.e., the most recently obtained low-frequency period and high-frequency period) is used to determine the switching timing from the low-frequency period to the high-frequency period (i.e., changing F1) after entering the low-frequency period.

[0122] In this step, when the low-frequency period changes to the high-frequency period, the similarity b of the variation law of the currents in the two most recently obtained low-frequency periods and the most recently obtained high-frequency period is obtained to change F2, and the changed F2 is negatively correlated with b.

[0123] If the similarity b of the change pattern is large during this process, it indicates that the interference situation (such as internal interference and external interference) remains unchanged when collecting the current according to the changed F1 in step S203. At this time, the value of F2 is decreased, so that it will be easier to switch between the low-frequency period and the high-frequency period with a larger current change amplitude (corresponding to the maximum current change amplitude in step S203) in the subsequent process. When the similarity b of the change pattern is small, it indicates that the interference situation (such as internal interference and external interference, and may also include the current change situation caused by the opening and closing operations) has changed. At this time, the value of F2 is increased, so that it will be easier to switch between the low-frequency period and the high-frequency period with a smaller current change amplitude (corresponding to the minimum current change amplitude in step S203) in the subsequent process.

[0124] In summary, during this process, by dynamically adjusting F2, F2 approaches or stabilizes at a better value in real time along with the sampling process. The so-called better value means that it can be determined whether to switch from the low-frequency period to the high-frequency period with a larger current change amplitude (i.e., the maximum change amplitude) or a smaller current change amplitude (i.e., the minimum change amplitude) based on the interference situation existing in the current, further avoiding the situation of collecting a large amount of invalid current at high speed and high frequency.

[0125] As an example, obtaining the similarity b of the change pattern of the current in the two most recently obtained low-frequency periods and the most recently obtained high-frequency period to change F2 includes:

[0126] The currents in the two most recently obtained low-frequency periods are arranged in chronological order to obtain a sequence List3, and the sequence List2 composed of the currents in the most recently obtained high-frequency period. The similarity of the change pattern between List3 and List2 is denoted as b.

[0127] The changed F2 is F2×(y - b), where y represents an offset coefficient. In this embodiment, y = 1 is used for description. In other embodiments, y can be set to other values, as long as the changed F2 is greater than 0.

[0128] Step S205: Read out the opening and closing parameters from all the collected opening and closing currents and perform detection.

[0129] Collect the current for a preset time length according to the above process. For example, continuously collect the current for 4 seconds. During this preset time length, the circuit breaker has performed an opening (or closing) operation, but currently, the start time point and the end time point of the opening (or closing) are not determined.

[0130] In this embodiment, when collecting current as described above, the start time point and end time point of opening (or closing) the switch will not miss the current at the start time point and end time point due to too low sampling frequency, nor introduce excessive interference of ineffective current limiting due to too high sampling frequency. In this embodiment, the start time point and end time point of opening (or closing) the switch can be obtained according to the following method:

[0131] Display the collected current on a display, and manually read out the start time point and end time point.

[0132] In some other embodiments, the methods for obtaining the start time point and end time point of opening (or closing) the switch include:

[0133] Only retain the current sequences collected during the high-frequency period, and filter these current sequences respectively (for example, filter using a Gaussian filter kernel with a length of 5). For each filtered current sequence, create a window with a length of 9 centered on each current data in the current sequence, obtain the standard deviation of all current data within the window, and record it as the fluctuation amount of each current data. Obtain the fluctuation amounts of all current data in all filtered current sequences, and use the Otsu threshold segmentation algorithm to divide all the fluctuation amounts into two categories. In this embodiment, only retain the category with the largest average fluctuation amount. The current data in this category has a large fluctuation amount, indicating that the current has a large fluctuation, and this fluctuation is caused by the opening and closing operation. In this category, obtain two currents that are in the same current sequence and are the farthest apart in time sequence. The moments corresponding to these two currents are used as the start time point and end time point of opening (or closing) the switch.

[0134] As an example, take the time difference between the end time point and the start time point as the opening and closing parameter, which represents the opening and closing time when the circuit breaker works in the power grid environment after leaving the factory.

[0135] In some other examples, the method for obtaining the opening and closing parameter is:

[0136] For the current collected between the start time point and the end time point, the difference between the maximum value and the minimum value of these currents is used as the opening and closing parameter, which represents the maximum current fluctuation amplitude during the opening and closing operation.

[0137] In other examples, the opening and closing time and the maximum current fluctuation amplitude can be used together as the opening and closing parameter; in other examples, the average value of the current collected between the start time point and the end time point can also be used as the opening and closing parameter.

[0138] Compare the obtained opening and closing parameter with the opening and closing parameter measured when the circuit breaker leaves the factory. For example, when taking the absolute value of the difference between the obtained opening and closing parameter and the opening and closing parameter measured when the circuit breaker leaves the factory, the ratio of this absolute value to the opening and closing parameter measured when the circuit breaker leaves the factory is recorded as the parameter abnormality degree.

[0139] When the switching parameters include multiple values (for example, when including both the switching time and the maximum current fluctuation amplitude), multiple parameter abnormality degrees are obtained respectively (for example, the parameter abnormality degree of the switching time and the parameter abnormality degree of the maximum current fluctuation amplitude).

[0140] When there is a situation where the parameter abnormality degree is greater than the preset threshold th2, it indicates that the detection result of the circuit breaker is abnormal. At this time, an alarm signal is sent, and the maintenance personnel confirm and repair or replace the circuit breaker. In this embodiment, th2 = 10% is taken as an example for description. In other embodiments, th2 can be set to other values, and this embodiment does not make specific limitations.

[0141] In some other embodiments, the current collected between the start time point and the end time point is displayed on the display, and the staff determines whether there is an abnormality according to the current waveform. Although this embodiment requires subjective judgment by the staff, this embodiment is still a conventional means and has greater universality. Therefore, it is taken as an optional embodiment for current detection.

[0142] So far, this embodiment is completed.

[0143] In the above embodiment, the switching current is collected at the preset frequency T1. When the average change amplitude of the current is greater than the preset threshold F1, T1 is increased to the preset frequency T2 and the current is continuously collected. When the current collected at T2 has the same change law as the current collected at T1, the current is collected again at T1. When they have different change laws, the current is continuously collected at T2. When facing the situation where the current generated during the switching operation exists for a short time, this high-frequency sampling and low-frequency sampling are alternately performed to avoid obtaining a large amount of current data with interference but ineffective for the switching current detection when continuously sampling the current data at high speed. Or rather, it can capture to a certain extent the current generated by the switching operation with a short existence time in a large amount of invalid current.

[0144] On this basis, when the high-frequency period changes to the low-frequency period in this embodiment, the similarity of the current change rules in the recently obtained low-frequency period and the recently obtained high-frequency period is used to change F1. The specific adjustment method is that when the similarity of the change rules is greater than the preset threshold F2, the changed F1 is positively correlated with the maximum change amplitude of the current in the recently obtained high-frequency period; when the similarity of the change rules is less than or equal to the preset threshold F2, the changed F1 is positively correlated with the minimum change amplitude of the current in the recently obtained high-frequency period. This process continuously and dynamically changes the preset threshold F1 to dynamically control the timing of switching back to the high-frequency period when in the low-frequency period, so as to adapt to the interference situation existing in the collected current, and further avoid the problem of missing the start and end time points of the switching-on and switching-off operations during low-frequency sampling caused by mis-sampling, and further ensure that the current generated by the short switching-on and switching-off operations can be captured from a large number of interfering currents.

[0145] Furthermore, if the current moment changes from the low-frequency period to the high-frequency period, the similarity b of the current change rules in the two most recently obtained low-frequency periods and the most recently obtained high-frequency period is obtained to change F2, and the changed F2 is negatively correlated with b. If the similarity b of the change rules is large during this process, it indicates that the interference situation has not changed when the changed F1 is used to collect the current. At this time, the value of F2 is reduced, so that it will be easier to switch between the low-frequency period and the high-frequency period with a larger current change amplitude in the future. When the similarity b of the change rules is small, it indicates that the interference situation has changed. At this time, the value of F2 is increased, so that it will be easier to switch between the low-frequency period and the high-frequency period with a smaller current change amplitude in the future. Therefore, during this process, by dynamically adjusting F2, F2 approaches or stabilizes at a better value in real time during the sampling process. The so-called better value means that it can be judged based on the interference situation of the current whether to use a larger current change amplitude (i.e., the maximum change amplitude) or a smaller current change amplitude (i.e., the minimum change amplitude) in the future to determine the timing of changing from the low-frequency period to the high-frequency period, further avoiding the situation of high-speed high-frequency acquisition of a large number of invalid currents.

[0146] In summary, in this embodiment, F1 and F2 are dynamically changed according to the current change situation when switching from the high-frequency period to the low-frequency period and then from the low-frequency period to the high-frequency period, so as to avoid the problem of high-speed high-frequency acquisition of a large number of invalid interfering currents as much as possible, and also avoid the problem of missing the start and end time points of the switching-on and switching-off operations during low-frequency sampling, and further ensure that the current generated by the short switching-on and switching-off operations can be accurately captured from a large number of interfering currents, ensuring the reliability of the current detection result.

[0147] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for detecting the opening and closing current of a switch cabinet circuit breaker, characterized in that: The method comprises the following steps: The opening and closing current is collected at a preset frequency T1. When the average change amplitude of the current is greater than the preset threshold F1, T1 is increased to a preset frequency T2 and the current is continuously collected. When the current collected at T2 has the same change pattern as the current collected at T1, the current is collected again at T1. When the current has different change patterns, the current is continuously collected at T2. The period of time when current is collected at T1 is recorded as the low-frequency period, and the period of time when current is collected at T2 is recorded as the high-frequency period; If the current moment changes from the high-frequency period to the low-frequency period, F1 is changed by using the similarity of the change rules of the current in the most recently obtained low-frequency period and the most recently obtained high-frequency period, including: when the similarity of the change rule is greater than a preset threshold value F2, the changed F1 is positively correlated with the maximum change amplitude of the current in the most recently obtained high-frequency period; when the similarity of the change rule is less than or equal to the preset threshold value F2, the changed F1 is positively correlated with the minimum change amplitude of the current in the most recently obtained high-frequency period; If the current moment changes from a low-frequency period to a high-frequency period, F2 is changed using the similarity b of the current change rules in the two most recent low-frequency periods and the most recent high-frequency period, and the changed F2 is negatively correlated with b; Read out the opening and closing parameters from all the collected opening and closing currents and perform tests; When the similarity of the change rule is greater than the preset threshold value F2, the changed F1 is positively correlated with the maximum change amplitude of the current in the most recent high-frequency period; when the similarity of the change rule is less than or equal to the preset threshold value F2, the changed F1 is positively correlated with the minimum change amplitude of the current in the most recent high-frequency period, and the specific formulas included are as follows: When the similarity of the change rule is greater than the preset threshold value F2, w×f1+(1-w)×F1 is used as the changed F1; when the similarity of the change rule is less than or equal to the preset threshold value F2, w×F1+(1-w)×f2 is used as the changed F1; Among them, w represents the similarity of the change pattern; f1 and f2 represent the maximum and minimum change amplitudes.

2. A method for detecting the opening and closing current of a switch cabinet circuit breaker according to claim 1, characterized in that: The method for judging whether the current collected by T2 has the same variation rule as the current collected by T1 is as follows: Record the current sequence collected at the frequency T2 as the second current sequence, record the current sequence collected at the frequency T1 before the frequency is increased to T2 as the first current sequence, and obtain the current difference between the first current sequence and the second current sequence; In the second current sequence, starting from the first current data, a current data is taken out after every other current and forms a sequence L(1), and the current difference between the first current sequence and L(1) is obtained; In the second current sequence, starting from the first current data, a current data is taken out after every two currents to form a sequence L(2), and the current difference between the first current sequence and L(2) is obtained; Similarly, in the second current sequence, starting from the first current data, a current data is taken out after every N1 currents to form a sequence L(N1), and the current difference between the first current sequence and L(N1) is obtained; N1 is a preset value; When the average of all current differences obtained is less than the preset threshold value th1, it is determined that the first current sequence and the second current sequence have the same variation rule; When the average value of all the current differences obtained is greater than or equal to the preset threshold value th1, it is determined that the first current sequence and the second current sequence do not have the same variation rule.

3. A method for detecting the opening and closing current of a switch cabinet circuit breaker according to claim 1, characterized in that: The specific steps for obtaining the similarity of the current variation rules in the most recently obtained low-frequency period and the most recently obtained high-frequency period are as follows: For the current sequence List1 formed by the current in the most recent low-frequency period, and the current sequence List2 formed by the current in the most recent high-frequency period, the current difference between List1 and List2 is recorded as x, exp(-x) is used as the similarity of the change law, and exp() represents an exponential function with a natural constant as the base.

4. A method for detecting the opening and closing current of a switch cabinet circuit breaker according to claim 1, characterized in that: The specific steps for obtaining the most recent maximum change amplitude of the current in the high-frequency period and the most recent minimum change amplitude of the current in the high-frequency period are as follows: For the current sequence List2 formed by the current in the most recently obtained high-frequency time period, the difference between every two adjacent current data in List2 is calculated; the differences of all adjacent current data in List2 are clustered into several categories, and the mean of all differences in each category is calculated. For the category with the largest mean of all differences, the mean of all differences in the category with the largest mean is used as the maximum change amplitude; for the category with the smallest mean of all differences, the mean of all differences in the category with the smallest mean is used as the minimum change amplitude.

5. A method for detecting the opening and closing current of a switch cabinet circuit breaker according to claim 1, characterized in that: The specific steps for obtaining the similarity b of the current change rules in the two most recently obtained low-frequency periods and the most recently obtained high-frequency period are as follows: The currents obtained in the two most recent low-frequency periods are arranged in chronological order to obtain a sequence List3, and the currents obtained in the most recent high-frequency period constitute a sequence List2. The similarity of the changing rules between List3 and List2 is recorded as b.

6. A method for detecting the opening and closing current of a switch cabinet circuit breaker according to claim 1, characterized in that: The specific formula for changing F2 by using the similarity b of the current change rules in the two most recently obtained low-frequency periods and the most recently obtained high-frequency period is as follows: The changed F2 is F2×(yb), where y represents a preset offset coefficient.

7. A method for detecting the opening and closing current of a switch cabinet circuit breaker according to claim 1, characterized in that: The specific steps of reading the opening and closing parameters from all the collected opening and closing currents and performing detection include the following: The start time point and the end time point of the opening and closing action are read out from all the collected opening and closing currents; the time difference between the end time point and the start time point is used as the opening and closing parameter, and the absolute value of the difference between the obtained opening and closing parameters and the opening and closing parameters measured when the circuit breaker leaves the factory is calculated. The ratio of the absolute value to the opening and closing parameters measured when the circuit breaker leaves the factory is recorded as the parameter abnormality degree. When the parameter abnormality degree is greater than the preset threshold value th2, it is determined that the current detection result obtained by the circuit breaker is abnormal.

8. A method for detecting the opening and closing current of a switch cabinet circuit breaker according to claim 2 or 3, characterized in that: The specific steps for obtaining the current difference are as follows: Linear normalization is performed on any two current sequences respectively, and the DTW distance between any two current sequences after linear normalization is recorded as the current difference.

9. A switch cabinet circuit breaker opening and closing current detection system, the system comprising a detection device and a display, the detection device comprising an opening current sensor and a closing current sensor for collecting opening and closing currents, the display for displaying the opening and closing currents; the detection device also comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method for detecting the opening and closing current of a switch cabinet circuit breaker as described in any one of claims 1 to 8 are implemented.

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