A multi-parameter monitoring method and system of a smart circuit breaker applied to a smart grid

Abstract

The application belongs to the technical field of circuit breaker monitoring, and provides a multi-parameter monitoring method and system of an intelligent circuit breaker applied to a smart grid; after a historical intelligent circuit breaker is tripped due to line fault protection and automatically performs reclosing, a historical current monitoring period is set, the current on the fault line is analyzed for change, whether it is a transient fault or a suspected permanent fault is judged, the time-space persistence of the threshold current is quantified through a fault type identification value, the preliminary layering of the fault type is realized, the suspected permanent fault can be quickly locked, and the transient fault is avoided from being misjudged as a permanent fault that needs long-term isolation; when the suspected permanent fault is judged, the current change on the fault line is reanalyzed and identified from the current decay characteristic dimension, whether it is a closing excitation inrush current or a permanent fault is judged, the circuit breaker mis-tripping caused by the inrush current is avoided, the fault section can be accurately located and isolated, and the secondary fault caused by the trial power-on operation is avoided.

Description

Technical Field

[0001] This invention belongs to the field of circuit breaker monitoring technology, specifically a multi-parameter monitoring method and system for smart circuit breakers applied to smart grids. Background Technology

[0002] With the rapid development of smart grids, smart circuit breakers, as core equipment for grid fault protection, have multi-parameter monitoring capabilities that directly affect the reliability of grid operation and the efficiency of power supply restoration.

[0003] However, during the reclosing operation of smart circuit breakers, traditional smart circuit breakers primarily determine the fault type based on the current amplitude threshold after reclosing. But transient faults (such as lightning interference or tree branch contact) and suspected permanent faults (such as cable insulation aging or poor equipment contact) exhibit overlapping current characteristics: transient faults may generate short-term over-threshold currents due to the reclosing impact, while permanent faults may initially show brief attenuation characteristics. This "fuzzy range" easily leads to misjudgment—misjudging a transient fault as a permanent fault will trigger unnecessary line isolation, prolonging the user's power outage time; misjudging a permanent fault as a transient fault may cause secondary faults due to reclosing failure, expanding the scope of the accident.

[0004] When a smart circuit breaker supplies power to inductive equipment with an iron core (such as a distribution transformer or a step-up transformer), the closing transient process can induce deep magnetic saturation of the iron core, causing the excitation current to surge several to more than ten times its rated value, forming a closing inrush current. This inrush current exhibits a "surge followed by decay" characteristic over time, similar to the current decay characteristics of a permanent fault. Traditional single-parameter threshold methods are difficult to effectively distinguish between the two, often resulting in inrush current being misjudged as a permanent fault, leading to erroneous circuit breaker tripping, or permanent faults being misjudged as inrush current, causing delayed isolation, severely affecting the timeliness of equipment protection and power restoration.

[0005] Therefore, the present invention provides a method and system for multi-parameter monitoring of smart circuit breakers applied to smart grids. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, at least one technical problem raised in the background art is solved.

[0007] The technical solution adopted by this invention to solve its technical problem is: a multi-parameter monitoring method for intelligent circuit breakers applied to smart grids, comprising: After the historical intelligent circuit breaker trips due to line fault protection and automatically performs reclosing, a historical current monitoring cycle is set to analyze the changes in current on the faulty line and determine whether it is a transient fault or a suspected permanent fault. When a suspected permanent fault is identified, the current changes on the faulty line are re-analyzed and identified from the perspective of current decay characteristics to determine whether it is a closing excitation inrush current or a permanent fault, and to determine the permanent fault analysis cycle. The current decay during the permanent fault analysis period is analyzed to obtain the current decay analysis period corresponding to the permanent fault. Stability analysis was performed on the current decay analysis period within multiple permanent fault analysis cycles to obtain the permanent fault current analysis time.

[0008] As a further aspect of the present invention, the process of analyzing the changes in current on the faulty line is as follows: The set historical current monitoring period is divided into historical current monitoring points, and the current of each historical current monitoring point is obtained as the single-time point current value. The single-time point current value is compared with the single-time point current threshold. The single-time point current value that exceeds the single-time point current threshold is extracted as the threshold-exceeding single-time current value, and the corresponding historical current monitoring point is taken as the historical current threshold-exceeding point.

[0009] As a further aspect of the present invention, the process for determining whether a fault is transient or suspected to be permanent is as follows: The number of consecutive historical current exceeding the threshold is counted, and the ratio with the historical current monitoring points is calculated to obtain the fault type identification value; If the historical current over-threshold duration value is greater than the historical current over-threshold duration threshold value, it is suspected to be a permanent fault. If the historical current over-threshold duration is less than or equal to the historical current over-threshold duration threshold, it is considered a transient fault.

[0010] As a further aspect of the present invention, the process of re-analyzing and identifying current changes on the faulty line is as follows: Extract the threshold-exceeding single-hour current values ​​corresponding to consecutive historical current threshold-exceeding points, and sort them according to the order of acquisition time to obtain the historical consecutive threshold-exceeding single-hour current sequence. The largest single-time current value exceeding the threshold within the historical continuous single-time current sequence is selected as the current threshold peak value, and the corresponding historical current threshold point is selected as the historical current threshold peak point. The historical current exceeding the threshold peak point is taken as the starting point of the analysis, and multiple historical current exceeding the threshold points after the starting point are used as comparison points for analysis. After extracting the starting point of the analysis, the first and second points are compared with the current values ​​of the single-time points that exceed the threshold, and the difference between the current exceeding the threshold and the peak value is calculated. The absolute value is then compared with the current threshold at the single time point to obtain the unit current attenuation amplitude value. Extract the first and second comparison points after the analysis starting point to obtain the over-threshold single-time current value corresponding to each comparison point, and calculate the difference between the first and second comparison points after the analysis starting point and the over-threshold single-time current value. Take the absolute value and then calculate the ratio with the single-time current threshold to obtain the unit current attenuation amplitude value.

[0011] As a further aspect of the present invention, the process for determining whether the fault is a closing excitation inrush current or a permanent fault is as follows: Based on the method of obtaining the unit current attenuation amplitude value, the remaining comparison points are calculated and processed to obtain multiple unit current attenuation amplitude values, and the average value of the sum is calculated to obtain the average current attenuation amplitude. The ratio of the interval between adjacent historical current exceeding the threshold to the duration of the historical current monitoring cycle is calculated to obtain the historical threshold interval duration ratio. The ratio of the current decay amplitude of each unit to the historical over-threshold interval duration is calculated to obtain the unit current decay rate ratio. The average value of the summation of the current decay rate ratios of all units is used to calculate the suspected permanent fault analysis value. If the suspected permanent fault analysis value is less than or equal to the suspected permanent fault analysis threshold, then the corresponding historical current monitoring period will be used as the permanent fault analysis period.

[0012] As a further aspect of the present invention, the process of analyzing current decay during the permanent fault analysis period is as follows: Within the permanent fault analysis period, the historical current over-threshold peak point is used as the starting analysis point for the current decay analysis period. Multiple historical current threshold points after the historical current threshold peak point are extracted, and adjacent historical current threshold points are combined into a termination analysis group to obtain multiple termination analysis groups. Extract the unit current decay amplitude value corresponding to each group of termination analysis, compare the magnitudes, and select the smallest unit current decay amplitude value.

[0013] As a further aspect of the present invention, the extraction process for the current decay analysis period is as follows: If the minimum unit current decay amplitude value corresponds to a historical current threshold point that is later in the time dimension within the termination analysis group, and is the last historical current threshold point in the historical continuous threshold single-time current sequence, then the historical current threshold peak point and the last historical current threshold point in the historical continuous threshold single-time current sequence constitute the current decay analysis period. If the minimum unit current decay amplitude value corresponds to a historical current over-threshold point in the time dimension within the termination analysis group, and is not the last historical current over-threshold point in the historical continuous over-threshold single-time current sequence, then the termination analysis group corresponding to the minimum unit current decay amplitude value is taken as the current decay analysis group. Extract historical current threshold points within the current decay analysis group, and take the later historical current threshold points in the time dimension as suspected decay stabilization starting points. Combine the adjacent historical current threshold points after the suspected decay stabilization starting points into a group of suspected decay stabilization analysis groups. The standard deviation and mean of the unit current attenuation amplitude values ​​corresponding to the suspected attenuation stability analysis group are calculated respectively to obtain the standard deviation and mean of the suspected attenuation amplitude. The standard deviation and mean of the suspected attenuation amplitude are then substituted into the formula for calculating the coefficient of variation to obtain the suspected attenuation stability analysis value. If the suspected attenuation stability analysis value is less than or equal to the suspected attenuation stability analysis threshold, then the later historical current exceeding the threshold point in the time dimension within the current attenuation analysis group will be used as the termination analysis point, and combined with the starting analysis point, to form the current attenuation analysis period. If the suspected attenuation stability analysis value is greater than the suspected attenuation stability analysis threshold, then the historical current exceeding the threshold point in the time dimension within the current attenuation analysis group will not be the termination analysis point. Instead, the termination analysis group after the current attenuation analysis group in the time dimension will be selected as the current attenuation analysis group. The analysis will be performed again in the same way as the method for obtaining the suspected attenuation stability analysis value, until the obtained suspected attenuation stability analysis value is less than or equal to the suspected attenuation stability analysis threshold. The termination analysis point will then be determined and combined with the starting analysis point to form the current attenuation analysis period.

[0014] As a further aspect of the present invention, the process of performing stability analysis on the current decay analysis period within multiple permanent fault analysis cycles is as follows: Extract the duration corresponding to each current decay analysis period as the current decay analysis duration; The average current decay analysis time is calculated by averaging all current decay analysis times. The standard deviation of all current decay analysis times is calculated to obtain the standard deviation of current decay analysis times; The standard deviation and mean of the current decay analysis time were calculated using the coefficient of variation formula to obtain the stable analysis value of the decay time.

[0015] As a further aspect of the present invention, the process for obtaining the permanent fault current analysis time is as follows: If the attenuation duration stability analysis value is less than or equal to the attenuation duration stability analysis threshold, then the average of all current attenuation analysis durations is calculated to obtain the permanent fault current analysis time. If the attenuation duration stability analysis value is greater than the attenuation duration stability analysis threshold, the average of the maximum current attenuation analysis duration and the minimum current attenuation analysis duration is selected to obtain the permanent fault current analysis time.

[0016] A multi-parameter monitoring system for smart circuit breakers applied to smart grids includes the following modules: Fault type judgment module: After the historical intelligent circuit breaker trips due to line fault protection and automatically performs reclosing, the historical current monitoring cycle is set to analyze the changes in current on the fault line and determine whether it is a transient fault or a suspected permanent fault. Permanent Fault Analysis Module: When a suspected permanent fault is identified, the current changes on the faulty line are re-analyzed and identified from the perspective of current decay characteristics to determine whether it is a closing excitation inrush current or a permanent fault, and to determine the permanent fault analysis cycle. Attenuation period extraction module: Analyzes the current attenuation within the permanent fault analysis period to obtain the current attenuation analysis period corresponding to the permanent fault; Analysis Time Acquisition Module: Performs stability analysis on the current decay analysis period within multiple permanent fault analysis cycles to obtain the permanent fault current analysis time.

[0017] The beneficial effects of this invention are as follows: 1. This invention, after a historical intelligent circuit breaker trips due to a line fault and automatically performs reclosing, sets a historical current monitoring cycle to analyze the changes in current on the faulty line, determining whether it is a transient fault or a suspected permanent fault. It quantifies the spatiotemporal persistence of the over-threshold current through fault type identification values, achieving preliminary stratification of fault types. This allows for rapid identification of suspected permanent faults, avoiding misjudging transient faults as permanent faults requiring long-term isolation. When a suspected permanent fault is identified, the current changes on the faulty line are re-analyzed and identified from the perspective of current decay characteristics to determine whether it is a closing excitation inrush current or a permanent fault, preventing circuit breaker tripping due to inrush current. This allows for precise location and isolation of the faulty section, avoiding secondary faults caused by trial power-on operations.

[0018] 2. Within the permanent fault analysis cycle, this invention extracts the current decay analysis period corresponding to the permanent fault, accurately capturing the entire decay process of the fault current from transient impact to steady-state constant current. Moreover, the intelligent circuit breaker can accurately perform isolation operations, avoiding secondary damage to equipment caused by isolation that is too early or too late. Stability analysis is performed on the current decay analysis period within multiple permanent fault analysis cycles to select the permanent fault current analysis time. The current permanent fault current analysis time is then adjusted based on the permanent fault current analysis time, which can improve the accuracy of timing control for reclosing or isolation operations. In permanent faults, by accurately isolating the time point, the power outage time in non-faulty sections is reduced. Attached Figure Description

[0019] The invention will now be further described with reference to the accompanying drawings.

[0020] Figure 1This is a flowchart of the steps of a multi-parameter monitoring method for smart circuit breakers applied to smart grids according to the present invention. Figure 2 This is a flowchart of a multi-parameter monitoring system for intelligent circuit breakers applied to smart grids, according to the present invention. Detailed Implementation

[0021] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments. Example

[0022] When a short-circuit fault occurs on a section of a smart grid line, the smart circuit breakers on that line will trip due to the fault and automatically reclose. To quickly restore power, it's necessary to analyze the fault current to determine whether it's a transient fault (successful reclosing) or a permanent fault (failed reclosing). However, during this judgment process, when the smart circuit breaker closes and supplies power to inductive equipment with iron cores (distribution transformers, step-up transformers, iron-core reactors, etc.), the transformer core experiences deep magnetic saturation during the closing transient, causing the excitation current to surge several to more than ten times its rated value. This inrush current interferes with the determination of whether the fault is transient or permanent. Therefore, please refer to [further details needed]. Figure 1 As shown in the embodiment of the present invention, a multi-parameter monitoring method for smart circuit breakers applied to smart grids includes the following steps: Step 1: After the historical intelligent circuit breaker trips due to line fault protection and automatically performs reclosing, set the historical current monitoring cycle, analyze the changes in current on the faulty line, and determine whether it is a transient fault or a suspected permanent fault. In some embodiments, the set historical current monitoring period is divided into historical current monitoring points, wherein the time interval between adjacent historical current monitoring points is equal. Obtain the current at each historical current monitoring point as a single-time point current value; The single-time point current value is compared with the single-time point current threshold. The single-time point current value that exceeds the single-time point current threshold is extracted as the threshold-exceeding single-time current value, and the corresponding historical current monitoring point is taken as the historical current threshold-exceeding point. It is understandable that the single-time point current threshold means that for each historical current monitoring point divided into equal intervals after reclosing, the pre-set critical judgment value used to determine whether the single-time point current value collected by the monitoring point belongs to the abnormal fault current is the benchmark threshold parameter of the entire fault judgment logic. The number of consecutive historical current exceeding the threshold is counted, and the ratio with the historical current monitoring points is calculated to obtain the fault type identification value; It is understandable that the fault type identification value represents an index that comprehensively reflects the abnormal characteristics of the fault current. Specifically, the larger the fault type identification value, the longer the abnormal current lasts in the time dimension; the smaller the fault type identification value, the shorter the abnormal current lasts in the time dimension. If the historical current over-threshold duration value is greater than the historical current over-threshold duration threshold, it indicates that the abnormal current has a relatively long duration in the time dimension, which is suspected to be a permanent fault. If the historical current over-threshold duration value is less than or equal to the historical current over-threshold duration threshold, it indicates that the abnormal current has a short duration in the time dimension and is a transient fault.

[0023] Step 2: When a suspected permanent fault is identified, the current changes on the faulty line are re-analyzed and identified from the perspective of current decay characteristics to determine whether it is a closing excitation inrush current or a permanent fault, and to determine the permanent fault analysis cycle. In some embodiments, the threshold-exceeding single-hour current values ​​corresponding to consecutive historical current threshold-exceeding points are extracted and sorted according to the order of acquisition time to obtain a historical consecutive threshold-exceeding single-hour current sequence. The largest single-time current value exceeding the threshold within the historical continuous single-time current sequence is selected as the current threshold peak value, and the corresponding historical current threshold point is selected as the historical current threshold peak point. The historical current exceeding the threshold peak point is taken as the starting point of the analysis, and multiple historical current exceeding the threshold points after the starting point are used as comparison points for analysis. For example, after extracting the first and second comparison points after the starting point of the analysis, the current values ​​of the first and second points that exceed the threshold are compared respectively, and the difference between the current exceeding the threshold peak value is calculated. The absolute value is then compared with the current threshold value at the single point of time to obtain the unit current attenuation amplitude value. Extract the first and second comparison points after the analysis starting point to obtain the over-threshold single-time current value corresponding to each point, and calculate the difference between the first and second comparison points after the analysis starting point and the over-threshold single-time current value corresponding to each point. Take the absolute value and then calculate the ratio with the single-time current threshold to obtain the unit current attenuation amplitude value. Based on the method of obtaining the unit current attenuation amplitude value, the remaining comparison points are calculated and processed to obtain multiple unit current attenuation amplitude values, and the average value of the sum is calculated to obtain the average current attenuation amplitude. The ratio of the interval between adjacent historical current exceeding the threshold to the duration of the historical current monitoring cycle is calculated to obtain the historical threshold interval duration ratio. The ratio of the current decay amplitude of each unit to the historical over-threshold interval duration is calculated to obtain the unit current decay rate ratio. The average value of the summation of the current decay rate ratios of all units is used to calculate the suspected permanent fault analysis value. It is understandable that the meaning of the suspected permanent fault analysis value is: by quantifying the current decay time efficiency characteristics, it is essentially a mapping of the decay dynamic characteristics of the fault current in the time dimension. Specifically, if the suspected permanent fault analysis value is larger, it indicates that the current decays faster and is a closing excitation inrush current; if the suspected permanent fault analysis value is smaller, it indicates that the current decays slower and is a permanent fault. If the suspected permanent fault analysis value is greater than the suspected permanent fault analysis threshold, it indicates that the current decay rate is relatively fast, which is displayed as a closing excitation inrush current signal, and the corresponding historical current monitoring period is used as the closing excitation inrush current analysis period. If the suspected permanent fault analysis value is less than or equal to the suspected permanent fault analysis threshold, it indicates that the current decay rate is slow, which is displayed as a permanent fault signal, and the corresponding historical current monitoring period is used as the permanent fault analysis period.

[0024] The specific solution of this invention is as follows: After the historical intelligent circuit breaker trips due to line fault protection and automatically performs reclosing, a historical current monitoring cycle is set to analyze the changes in current on the faulty line and determine whether it is a transient fault or a suspected permanent fault. The spatiotemporal persistence of the over-threshold current is quantified by the fault type identification value to achieve preliminary stratification of fault types. Suspected permanent faults can be quickly identified, avoiding the misjudgment of transient faults as permanent faults that require long-term isolation. When it is determined to be a suspected permanent fault, the current changes on the faulty line are re-analyzed and identified from the perspective of current decay characteristics to determine whether it is a closing excitation inrush current or a permanent fault, avoiding circuit breaker tripping due to inrush current. The faulty section can be accurately located and isolated, avoiding secondary faults caused by trial power-on operations. Example

[0025] Please see Figure 1 As shown in the embodiment of the present invention, a multi-parameter monitoring method for smart circuit breakers applied to smart grids includes the following steps: Step 3: Analyze the current decay within the permanent fault analysis period and extract the current decay analysis period corresponding to the permanent fault. In some embodiments, during the permanent fault analysis period, the historical current over-threshold peak point is used as the starting analysis point for the current decay analysis period. Multiple historical current threshold points after the historical current threshold peak point are extracted, and adjacent historical current threshold points are combined into a termination analysis group to obtain multiple termination analysis groups. Extract the unit current decay amplitude value corresponding to each group of termination analysis, compare the magnitudes, and select the minimum unit current decay amplitude value. For example, if the minimum unit current decay amplitude value corresponds to a historical current threshold point that is later in the time dimension within the termination analysis group, and is the last historical current threshold point in the historical continuous threshold single-hour current sequence, then the historical current threshold peak point and the last historical current threshold point in the historical continuous threshold single-hour current sequence constitute the current decay analysis period. For example, if the minimum unit current decay amplitude value corresponds to a historical current over-threshold point in the time dimension within the termination analysis group, and is not the last historical current over-threshold point in the historical continuous over-threshold single-time current sequence, then the termination analysis group corresponding to the minimum unit current decay amplitude value is taken as the current decay analysis group. Extract historical current over-threshold points within the current decay analysis group, and use the later historical current over-threshold points in the time dimension as suspected decay stabilization starting points; Based on the suspected attenuation stabilization starting point, adjacent historical current exceeding the threshold points after the suspected attenuation stabilization starting point are grouped into a suspected attenuation stabilization analysis group; The mean value of the unit current attenuation amplitude corresponding to each group of suspected attenuation stability analysis is calculated to obtain the mean value of suspected attenuation amplitude. The standard deviation of the unit current attenuation amplitude value corresponding to each group of suspected attenuation stability analysis is calculated to obtain the standard deviation of the suspected attenuation amplitude. By substituting the standard deviation and mean of the suspected attenuation amplitude into the formula for calculating the coefficient of variation, the suspected attenuation stability analysis value is obtained. If the suspected attenuation stability analysis value is less than or equal to the suspected attenuation stability analysis threshold, it indicates that the fault current has changed from transient attenuation to steady-state constant current. The historical current exceeding the threshold point in the time dimension within the current attenuation analysis group is taken as the termination analysis point, and combined with the starting analysis point, a current attenuation analysis period is formed. If the suspected attenuation stability analysis value is greater than the suspected attenuation stability analysis threshold, it indicates that the fault current characteristic has changed from transient attenuation to steady-state constant current. The historical current exceeding the threshold point in the time dimension within the current attenuation analysis group is not the termination analysis point. Instead, the termination analysis group after the current attenuation analysis group in the time dimension is selected as the current attenuation analysis group. The analysis is then performed again in the same way as the suspected attenuation stability analysis value is obtained, until the obtained suspected attenuation stability analysis value is less than or equal to the suspected attenuation stability analysis threshold. The termination analysis point is then determined and combined with the starting analysis point to form the current attenuation analysis period.

[0026] Step 4: Perform stability analysis on the current decay analysis period within multiple permanent fault analysis cycles to obtain the permanent fault current analysis time; In some embodiments, the duration corresponding to each current decay analysis period is extracted as the current decay analysis duration; The average current decay analysis time is calculated by averaging all current decay analysis times. The standard deviation of all current decay analysis times is calculated to obtain the standard deviation of current decay analysis times; The standard deviation and mean of the current decay analysis time were calculated using the coefficient of variation formula to obtain the stable analysis value of the decay time. If the attenuation duration stability analysis value is less than or equal to the attenuation duration stability analysis threshold, it indicates that the duration of the current attenuation analysis period within multiple permanent fault analysis cycles is relatively stable. The permanent fault current analysis time is obtained by averaging all the current attenuation analysis durations. If the stable analysis value of the decay duration is greater than the stable analysis threshold of the decay duration, it indicates that the duration of the current decay analysis period in multiple permanent fault analysis cycles is relatively fluctuating. The average of the maximum and minimum current decay analysis durations is selected to obtain the permanent fault current analysis time.

[0027] The specific solution of this invention is as follows: within the permanent fault analysis cycle, the current decay analysis period corresponding to the permanent fault is extracted, and the entire decay process of the fault current from transient impact to steady-state constant current is accurately captured. Moreover, the intelligent circuit breaker can accurately perform isolation operation to avoid secondary damage to the equipment caused by isolation too early or too late. Stability analysis is performed on the current decay analysis period within multiple permanent fault analysis cycles to select the permanent fault current analysis time. The current permanent fault current analysis time is adjusted according to the permanent fault current analysis time, which can improve the accuracy of the timing control of reclosing or isolation operation. In permanent faults, the power outage time of non-faulty sections is reduced by accurately isolating the time point. Example

[0028] Based on the same inventive concept as the multi-parameter monitoring method for smart circuit breakers applied to smart grids in the foregoing embodiments, such as Figure 2 As shown, this application provides a multi-parameter monitoring system for smart circuit breakers applied to smart grids, wherein the system specifically includes: Fault type judgment module: After the historical intelligent circuit breaker trips due to line fault protection and automatically performs reclosing, the historical current monitoring cycle is set to analyze the changes in current on the fault line and determine whether it is a transient fault or a suspected permanent fault. Permanent Fault Analysis Module: When a suspected permanent fault is identified, the current changes on the faulty line are re-analyzed and identified from the perspective of current decay characteristics to determine whether it is a closing excitation inrush current or a permanent fault, and to determine the permanent fault analysis cycle. Attenuation period extraction module: Analyzes the current attenuation within the permanent fault analysis period to obtain the current attenuation analysis period corresponding to the permanent fault; Analysis Time Acquisition Module: Performs stability analysis on the current decay analysis period within multiple permanent fault analysis cycles to obtain the permanent fault current analysis time.

[0029] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A multi-parameter monitoring method for smart circuit breakers applied to smart grids, characterized in that: include: After the historical intelligent circuit breaker trips due to line fault protection and automatically performs reclosing, a historical current monitoring cycle is set to analyze the changes in current on the faulty line and determine whether it is a transient fault or a suspected permanent fault. When a suspected permanent fault is identified, the current changes on the faulty line are re-analyzed and identified from the perspective of current decay characteristics to determine whether it is a closing excitation inrush current or a permanent fault, and to determine the permanent fault analysis cycle. The current decay during the permanent fault analysis period is analyzed to obtain the current decay analysis period corresponding to the permanent fault. Stability analysis was performed on the current decay analysis period within multiple permanent fault analysis cycles to obtain the permanent fault current analysis time.

2. The method for multi-parameter monitoring of intelligent circuit breakers applied to smart grids according to claim 1, characterized in that: The process of analyzing the changes in current on the faulty line is as follows: The set historical current monitoring period is divided into historical current monitoring points, and the current of each historical current monitoring point is obtained as the single-time point current value. The single-time point current value is compared with the single-time point current threshold. The single-time point current value that exceeds the single-time point current threshold is extracted as the threshold-exceeding single-time current value, and the corresponding historical current monitoring point is taken as the historical current threshold-exceeding point.

3. The method for multi-parameter monitoring of intelligent circuit breakers applied to smart grids according to claim 2, characterized in that: The process for determining whether a fault is transient or suspected to be permanent is as follows: The number of consecutive historical current exceeding the threshold is counted, and the ratio with the historical current monitoring points is calculated to obtain the fault type identification value; If the historical current over-threshold duration value is greater than the historical current over-threshold duration threshold value, it is suspected to be a permanent fault. If the historical current over-threshold duration is less than or equal to the historical current over-threshold duration threshold, it is considered a transient fault.

4. The multi-parameter monitoring method for smart circuit breakers applied to smart grids according to claim 1, characterized in that: The process of re-analyzing and identifying current changes on faulty lines is as follows: Extract the threshold-exceeding single-hour current values ​​corresponding to consecutive historical current threshold-exceeding points, and sort them according to the order of acquisition time to obtain the historical consecutive threshold-exceeding single-hour current sequence. The largest single-time current value exceeding the threshold within the historical continuous single-time current sequence is selected as the current threshold peak value, and the corresponding historical current threshold point is selected as the historical current threshold peak point. The historical current exceeding the threshold peak point is taken as the starting point of the analysis, and multiple historical current exceeding the threshold points after the starting point are used as comparison points for analysis. After extracting the starting point of the analysis, the first and second points are compared with the corresponding single-time current values ​​that exceed the threshold. The difference between the current exceeding the threshold and the peak value is calculated. The absolute value is then compared with the single-time current threshold to obtain the unit current attenuation amplitude value. Extract the first and second comparison points after the analysis starting point to obtain the over-threshold single-time current value corresponding to each comparison point, and calculate the difference between the first and second comparison points after the analysis starting point and the over-threshold single-time current value. Take the absolute value and then calculate the ratio with the single-time current threshold to obtain the unit current attenuation amplitude value.

5. The method for multi-parameter monitoring of intelligent circuit breakers applied to smart grids according to claim 4, characterized in that: To determine whether the fault is an inrush current during closing or a permanent fault, the process for determining the analysis period for permanent faults is as follows: Based on the method of obtaining the unit current attenuation amplitude value, the remaining comparison points are calculated and processed to obtain multiple unit current attenuation amplitude values, and the average value of the sum is calculated to obtain the average current attenuation amplitude. The ratio of the interval between adjacent historical current exceeding the threshold to the duration of the historical current monitoring cycle is calculated to obtain the historical threshold interval duration ratio. The ratio of the current decay amplitude of each unit to the historical over-threshold interval duration is calculated to obtain the unit current decay rate ratio. The average value of the summation of the current decay rate ratios of all units is used to calculate the suspected permanent fault analysis value. If the suspected permanent fault analysis value is less than or equal to the suspected permanent fault analysis threshold, then the corresponding historical current monitoring period is taken as the permanent fault analysis period.

6. The multi-parameter monitoring method for smart circuit breakers applied to smart grids according to claim 5, characterized in that: The process of analyzing current decay during the permanent fault analysis period is as follows: Within the permanent fault analysis period, the historical current over-threshold peak point is used as the starting analysis point for the current decay analysis period. Multiple historical current threshold points after the historical current threshold peak point are extracted, and adjacent historical current threshold points are combined into a termination analysis group to obtain multiple termination analysis groups. Extract the unit current decay amplitude value corresponding to each group of termination analysis, compare the magnitudes, and select the minimum unit current decay amplitude value.

7. A multi-parameter monitoring method for smart circuit breakers applied to smart grids according to claim 6, characterized in that: The extraction process for the current decay analysis period is as follows: If the minimum unit current decay amplitude value corresponds to a historical current threshold point that is later in the time dimension within the termination analysis group, and is the last historical current threshold point in the historical continuous threshold single-time current sequence, then the historical current threshold peak point and the last historical current threshold point in the historical continuous threshold single-time current sequence constitute the current decay analysis period. If the minimum unit current decay amplitude value corresponds to a historical current over-threshold point in the time dimension within the termination analysis group, and is not the last historical current over-threshold point in the historical continuous over-threshold single-time current sequence, then the termination analysis group corresponding to the minimum unit current decay amplitude value is taken as the current decay analysis group. Extract historical current threshold points within the current decay analysis group, and take the later historical current threshold points in the time dimension as suspected decay stabilization starting points. Combine the adjacent historical current threshold points after the suspected decay stabilization starting points into a group of suspected decay stabilization analysis groups. The standard deviation and mean of the unit current attenuation amplitude values ​​corresponding to the suspected attenuation stability analysis group are calculated respectively to obtain the standard deviation and mean of the suspected attenuation amplitude. The standard deviation and mean of the suspected attenuation amplitude are then substituted into the formula for calculating the coefficient of variation to obtain the suspected attenuation stability analysis value. If the suspected attenuation stability analysis value is less than or equal to the suspected attenuation stability analysis threshold, then the later historical current exceeding the threshold point in the time dimension within the current attenuation analysis group will be used as the termination analysis point, and combined with the starting analysis point, to form the current attenuation analysis period. If the suspected attenuation stability analysis value is greater than the suspected attenuation stability analysis threshold, then the historical current exceeding the threshold point in the time dimension within the current attenuation analysis group will not be the termination analysis point. Instead, the termination analysis group after the current attenuation analysis group in the time dimension will be selected as the current attenuation analysis group. The analysis will be performed again in the same way as the method for obtaining the suspected attenuation stability analysis value, until the obtained suspected attenuation stability analysis value is less than or equal to the suspected attenuation stability analysis threshold. The termination analysis point will then be determined and combined with the starting analysis point to form the current attenuation analysis period.

8. The multi-parameter monitoring method for smart circuit breakers applied to smart grids according to claim 1, characterized in that: The process of performing stability analysis on the current decay analysis period within multiple permanent fault analysis cycles is as follows: Extract the duration corresponding to each current decay analysis period as the current decay analysis duration; The average current decay analysis time is calculated by averaging all current decay analysis times. The standard deviation of all current decay analysis times is calculated to obtain the standard deviation of current decay analysis times; The standard deviation and mean of the current decay analysis time were calculated using the coefficient of variation formula to obtain the stable analysis value of the decay time.

9. A multi-parameter monitoring method for intelligent circuit breakers applied to smart grids according to claim 8, characterized in that: The process for obtaining the permanent fault current analysis time is as follows: If the attenuation duration stability analysis value is less than or equal to the attenuation duration stability analysis threshold, then the average of all current attenuation analysis durations is calculated to obtain the permanent fault current analysis time. If the attenuation duration stability analysis value is greater than the attenuation duration stability analysis threshold, the average of the maximum current attenuation analysis duration and the minimum current attenuation analysis duration is selected to obtain the permanent fault current analysis time.

10. A multi-parameter monitoring system for intelligent circuit breakers applied to smart grids, characterized in that: Includes the following modules: Fault type judgment module: After the historical intelligent circuit breaker trips due to line fault protection and automatically performs reclosing, the historical current monitoring cycle is set to analyze the changes in current on the fault line and determine whether it is a transient fault or a suspected permanent fault. Permanent Fault Analysis Module: When a suspected permanent fault is identified, the current changes on the faulty line are re-analyzed and identified from the perspective of current decay characteristics to determine whether it is a closing excitation inrush current or a permanent fault, and to determine the permanent fault analysis cycle. Attenuation period extraction module: Analyzes the current attenuation within the permanent fault analysis period to obtain the current attenuation analysis period corresponding to the permanent fault; Analysis Time Acquisition Module: Performs stability analysis on the current decay analysis period within multiple permanent fault analysis cycles to obtain the permanent fault current analysis time.

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