Intelligent measurement method for performance diagnosis of electronic molded case circuit breakers

Abstract

This invention discloses a performance diagnosis method for intelligent electronic molded case circuit breakers, relating to the field of electrical measurement technology. Addressing the problem that existing methods only determine whether the tripping time is acceptable at one or a few current points and cannot pinpoint degraded sub-components, this method measures the tripping time deviation from the set tripping time at multiple test current multiples divided into inverse-time and instantaneous tripping sections. It obtains the deviation pattern as the deviation changes with the current multiple and extracts trend and abrupt change terms. Based on the pattern characteristics, performance degradation is attributed to the electronic tripping unit, mechanical operating mechanism, or main contacts: consistent deviations across all sections are attributed to the electronic unit; increasing deviations towards the instantaneous tripping section are attributed to the mechanical mechanism; and only instantaneous or discrete deviations are attributed to the main contacts. Maintenance suggestions for sub-components are generated. This method upgrades diagnosis from simply determining whether a component is acceptable to identifying the specific location of degradation, with the attribution supported by physical mechanisms and providing guidance for maintenance.

Description

Technical Field

[0001] This invention relates to the field of electrical measurement technology, and in particular to a method for intelligent measurement and performance diagnosis of electronic plastic-cased circuit breakers. Background Technology

[0002] Molded case circuit breakers are critical protective electrical devices in low-voltage power distribution systems. Their tripping performance, i.e., time-current characteristics, directly affects the reliability of short-circuit and overload protection. Electronic molded case circuit breakers replace the traditional thermal-magnetic tripping with an electronic tripping unit, where tripping is timed by the electronic unit according to the current magnitude. Early testing often involved verifying whether the tripping time fell within tolerance at the rated point or a few current points during factory or periodic inspections.

[0003] To evaluate the performance of in-service circuit breakers, the current mainstream approach is to use testing equipment to measure their time-current characteristics or to perform fault diagnosis on the circuit breakers. The latter often employs methods such as vibration and multi-information fusion, and is more commonly used for vacuum circuit breakers and high-voltage circuit breakers.

[0004] However, when the tripping performance of an electronic molded case circuit breaker begins to degrade, existing methods often only indicate that the tripping time is off or unqualified, but it is impossible to determine which sub-component is malfunctioning: is it a drift in the timing or current sampling of the electronic tripping unit, a jamming of the operating mechanism causing slower breaking, or burnt-out or poor contact of the main contacts? The maintenance solutions for these three causes are completely different: the electronic unit requires replacement of the electronic board, the mechanical mechanism requires repair of the transmission, and the main contacts require repair or replacement; without identifying the cause, the only option is to return the entire circuit breaker to the factory or blindly disassemble and inspect it.

[0005] Therefore, the existing methods only determine whether the tripping time is qualified at one or a few current points and cannot point out the problems of degraded sub-components, which is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To address the problem that existing methods in the aforementioned background technology only determine whether the tripping time is qualified at one or a few current points and cannot identify degraded sub-components, this invention provides a smart measurement method for performance diagnosis of electronic plastic-cased circuit breakers.

[0007] The method includes: Step S0, initially acquiring the set-time current characteristics of the tested electronic molded case circuit breaker, and several preset test current multiples divided into inverse-time and instantaneous tripping sections, and initializing the diagnostic results; Step S1, for each test current multiple, injecting a test current corresponding to that test current multiple into the tested circuit breaker, and measuring the actual tripping time of the tested circuit breaker at that test current multiple; Step S2, for each test current multiple, obtaining the set tripping time at that test current multiple based on the set-time current characteristics, calculating the tripping time deviation of the actual tripping time relative to the set tripping time, and obtaining the deviation pattern of the tripping time deviation changing with the test current multiple; Step S3, extracting the pattern characteristics from the deviation pattern. The characteristics of this mode include a trend term for the tripping time deviation as a multiple of the test current, and a sudden change term for the tripping time deviation in the instantaneous tripping section relative to the inverse-time section; Step S4, based on the characteristics of this mode, the performance degradation of the circuit breaker under test is attributed to at least one sub-component among the electronic tripping unit, the mechanical operating mechanism, and the main contacts: when the tripping time deviation is in the same direction and similar in magnitude in the inverse-time section and the instantaneous tripping section, it is attributed to the electronic tripping unit; when the tripping time deviation increases from the inverse-time section to the instantaneous tripping section, it is attributed to the mechanical operating mechanism; when the tripping time deviation increases abruptly or discretely only in the instantaneous tripping section, it is attributed to the main contacts; Step S5, based on the attribution results, a performance diagnosis conclusion and sub-component maintenance suggestions for the circuit breaker under test are generated and output.

[0008] The present invention also provides a computer-readable storage medium, a performance diagnostic device for an electronic plastic-cased circuit breaker, and a computer program product thereon, wherein the computer program stored thereon or contained therein implements the above-described method when executed by a processor.

[0009] The beneficial effects of this invention are as follows: First, by measuring the tripping time deviation point by point under multiple test current multiples divided into inverse-time and instantaneous tripping sections, a deviation pattern is obtained that shows the deviation changes with the current multiple. This upgrades the circuit breaker's degradation information from a few isolated pass / fail judgments to an observable and quantifiable pattern, providing a basis for distinguishing degradation sub-causes. Second, by attributing performance degradation to the electronic tripping unit, mechanical operating mechanism, or main contacts based on the deviation pattern characteristics, the diagnosis is upgraded from pass / fail to determining where the degradation occurred, directly pointing to the maintenance of specific sub-components and avoiding the need for the entire unit to be returned to the factory or blind disassembly and inspection. Third, since each sub-causal attribution is further substantiated by verifiable physical quantities, the attribution is supported by physical mechanisms and can be cross-verified by independent physical quantities, making the diagnostic conclusions credible and interpretable. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the overall process of the circuit breaker performance diagnosis method according to an embodiment of the present invention; Figure 2This is a schematic diagram of the module structure of the circuit breaker performance diagnostic device and test circuit according to an embodiment of the present invention; Figure 3 This is a schematic diagram illustrating the division of test current multiples and the setting of tripping time according to an embodiment of the present invention; Figure 4 This is a schematic diagram of an attribution decision tree based on deviation pattern characteristics to attribute performance degradation to sub-components according to an embodiment of the present invention. Figure 5 This is a schematic diagram of pattern feature extraction according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the three types of sub-component attribution criteria according to an embodiment of the present invention; Figure 7 This is a schematic diagram of the degradation factorization process according to an embodiment of the present invention. Figure 8 This is a schematic diagram of the end-to-end execution process of the method according to a specific embodiment of the present invention. Detailed Implementation

[0011] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. The specific rated current, test current multiples, tripping times, deviations, and threshold values ​​used in the following embodiments are illustrative examples and do not constitute a limitation on the scope of protection of this invention. Those skilled in the art can adjust the corresponding parameters according to the model of the circuit breaker under test and the actual operating conditions; the adjusted implementation methods still fall within the scope of protection of this invention.

[0012] The set-time current characteristic described in this invention refers to the factory-set correspondence between the current multiple and the tripping time of the circuit breaker under test. The test current multiple refers to the multiple of the test current relative to the rated current of the circuit breaker under test; the inverse-time zone refers to the overload protection zone where the current multiple is close to the rated current and the tripping time significantly shortens as the current increases; the instantaneous tripping zone refers to the short-circuit protection zone where the current multiple far exceeds the rated current and the circuit breaker trips almost instantaneously. The tripping time deviation refers to the difference between the measured tripping time and the set tripping time at the same test current multiple. The electronic tripping unit refers to an electronic component that samples the main circuit current and issues a tripping command at regular intervals according to the set-time current characteristic; the mechanical operating mechanism refers to a transmission mechanism that drives the contacts to separate after receiving the tripping command; the main contacts refer to the contacts in the main circuit that switch the current.

[0013] like Figure 1As shown, the method of this invention begins with step S0. In step S0, the set-time current characteristics of the circuit breaker under test are acquired for the first time, along with several preset test current multiples, and the diagnostic results are initialized to empty. Figure 3 As shown, the various test current multiples are divided into inverse-time and instantaneous tripping sections. For example, 1.5, 2, and 3 times the rated current fall within the inverse-time section, while 6 and 10 times fall within the instantaneous tripping section. The set tripping time corresponding to each test current multiple is obtained from the set-time current characteristics. The set-time current characteristics can be obtained from the model catalog or nameplate of the circuit breaker under test, which is well known to those skilled in the art and will not be elaborated here.

[0014] In step S1, for each test current multiple, a test current corresponding to that test current multiple is injected into the circuit breaker under test, and the actual tripping time at that test current multiple is measured. For example... Figure 2 As shown, in one implementation, a test current corresponding to the test current multiple is injected into the main circuit of the circuit breaker under test by a current booster, and the application time of the test current is recorded. An interruption of the main circuit current of the circuit breaker under test is detected, and the moment of interruption is taken as the tripping time. The difference between the tripping time and the application time is taken as the measured tripping time under the test current multiple. The measured tripping time refers to the time elapsed from energization to disconnection of the circuit breaker under the test current. Each test current multiple is applied sequentially, with sufficient intervals between adjacent applications to allow the circuit breaker to reset and dissipate heat, avoiding heat accumulation that could affect subsequent measurements.

[0015] In step S2, for each test current multiple, the set tripping time at that test current multiple is obtained based on the set time-current characteristics. The tripping time deviation between the measured tripping time and the set tripping time is calculated, resulting in a deviation pattern of the tripping time deviation as a function of the test current multiple. The deviation pattern refers to a curve or sequence composed of the tripping time deviations of each test current multiple and the test current multiple, reflecting the change of deviation with the current multiple. For a circuit breaker in good working order, the tripping time deviations at each test current multiple are very small, and the deviation pattern approximates a flat line close to zero. However, when a certain sub-component degrades, the deviation pattern will exhibit a shape unique to that sub-component, which is the basis for distinguishing factors in this invention.

[0016] In step S3, mode features are extracted from the deviation pattern. These mode features refer to several quantities characterizing the shape of the deviation pattern, including a trend term for the tripping time deviation changing with the test current multiple, and a sudden change term for the tripping time deviation in the instantaneous tripping section relative to the inverse time section. For example... Figure 5As shown, in one implementation, a linear fit is performed on the tripping time deviation against the test current multiple, and the slope of the fitted value is taken as the trend term: the trend term characterizes whether the deviation increases overall with the current multiple; the difference between the mean of the tripping time deviation at each test current multiple in the instantaneous tripping section and the mean of the tripping time deviation at each test current multiple in the relative inverse time-limited section is taken as the mutation term: the mutation term characterizes whether the deviation changes abruptly in the instantaneous tripping section relative to the inverse time-limited section. The trend term refers to the slope of the linear fit; the mutation term refers to the difference between the mean deviations of the two sections. The trend term and the mutation term together represent the characteristics of a deviation pattern as two comparable numbers, facilitating subsequent attribution according to criteria.

[0017] In step S4, based on the characteristics of this mode, the performance degradation of the circuit breaker under test is attributed to at least one sub-component among the electronic trip unit, mechanical operating mechanism, and main contacts. For example... Figure 6 As shown, the key to this invention lies in the fact that the three types of degradation factors each have characteristics in their deviation modes, which can be used to distinguish them. First, when the electronic trip unit degrades, since the trip timing is almost entirely determined by the electronic unit and its influence on each current multiple is in the same direction and is relatively equal, the trip time deviation in the inverse time limit section and the instantaneous trip section is in the same direction and has a similar magnitude. The deviation mode is approximately a horizontal line that has been shifted as a whole. Based on this, when the trip time deviations under each test current multiple have the same sign and the range of each trip time deviation does not exceed the preset consistency threshold, it is attributed to the electronic trip unit. Furthermore, when each trip time deviation is approximately the same constant, it is determined to be the delay drift of the electronic unit. When each trip time deviation is approximately proportional to the corresponding set trip time, it is determined to be the current sampling drift of the electronic unit.

[0018] Secondly, when the mechanical operating mechanism degrades, since the mechanism's action time is approximately a constant time added after tripping, and the set tripping time of the instantaneous tripping section is already very short, this constant additional time becomes prominent. Therefore, the tripping time deviation increases from the inverse-time section to the instantaneous tripping section, and the deviation pattern is an upward sloping line. Accordingly, when the tripping time deviation increases from the inverse-time section to the instantaneous tripping section, and the slope of the trend term exceeds the preset increasing slope threshold, it is attributed to the mechanical operating mechanism; and the average value of the tripping time deviation under each test current multiple in the instantaneous tripping section is used as the estimated value of the additional action time of the mechanical operating mechanism. Third, when the main contacts degrade (e.g., ablation, increased contact resistance), since their effects are mainly manifested in the instantaneous tripping section where the current is large, heating and arcing are intensified, the tripping time deviation only increases or becomes discrete in the instantaneous tripping section. Therefore, when the sudden change exceeds the preset sudden change threshold, or when the dispersion of the tripping time deviation under each test current multiple in the instantaneous tripping section exceeds the preset dispersion threshold, it is attributed to the main contacts. In conjunction with the voltage drop of the main circuit of the circuit breaker under test during the test current application, when the voltage drop exceeds the preset voltage drop threshold, it is confirmed that the cause is attributed to the main contacts.

[0019] The reason the cause can be attributed to a sub-component in this way is that the electronic unit, mechanical mechanism, and main contact play different roles in the tripping process, and their respective influence on the tripping time varies with the current multiple: the electronic unit operates throughout the entire process and has a relatively consistent impact on each multiple; the mechanical mechanism adds a fixed amount of time at the end, making it more prominent in the short instantaneous segment of the tripping time; the problem with the main contact relies on the heat and arcing of the large current and only manifests in the instantaneous segment. These three patterns can be represented as three modes of deviation: overall translation, upward sloping line, and instantaneous abrupt change. From these, the sub-cause can be deduced. When multiple modes of characteristics are superimposed, each mode's characteristics can be applied to its corresponding sub-component, thus attributing the cause to multiple sub-components.

[0020] In step S5, performance diagnostic conclusions and sub-component maintenance recommendations for the circuit breaker under test are generated and output based on the attribution results. For example... Figure 7 As shown, when the cause is attributed to a single sub-component, maintenance recommendations are output for that sub-component. For example, if the cause is attributed to the electronic trip unit, calibration or replacement of the electronic board is recommended; if the cause is attributed to the mechanical operating mechanism, overhaul of the transmission mechanism is recommended; and if the cause is attributed to the main contacts, repair or replacement of the contacts is recommended. When the cause is attributed to multiple sub-components, maintenance recommendations for each sub-component are output in descending order of the trip time deviation magnitude, allowing maintenance personnel to address the sub-components with the greatest impact first. When the trip time deviation at each test current multiple does not exceed the preset qualified threshold, a diagnostic conclusion that the tested circuit breaker's performance is qualified is output. The performance diagnostic conclusion refers to whether the tested circuit breaker's performance is qualified and the determination of degraded sub-components; the sub-component maintenance recommendations refer to the maintenance measures given for degraded sub-components.

[0021] Further explanation of the three types of sub-factor deviation modes: The delay drift of the electronic trip unit causes the deviation to appear as a horizontal line attached to a non-zero value; the current sampling drift causes the deviation to be proportional to the set trip time, with a slightly larger absolute deviation in the inverse-time zone (longer set time) and a slightly smaller absolute deviation in the instantaneous zone (shorter set time), but both satisfy the electronic unit characteristics of having the same sign for each multiple and a range not exceeding the consistency threshold; the deviation of the mechanical operating mechanism is an upward-sloping line from the inverse-time zone to the instantaneous trip zone, with the slope determined by the additional mechanical action time; the deviation of the main contacts is concentrated in the instantaneous trip zone and is discrete between points due to different arcing conditions each time. These three modes have different characteristics, which can be used to attribute performance degradation to the corresponding sub-components. The attribution determination path is as follows: Figure 4 As shown.

[0022] To improve diagnostic accuracy, this method can also perform the following steps: First, temperature correction: The set-time current characteristic is usually given based on a certain reference ambient temperature. When the test ambient temperature deviates from this reference temperature, the set tripping time is first corrected according to the circuit breaker's temperature coefficient, and then the tripping time deviation is calculated to avoid misjudging the ambient temperature difference as degradation. Second, repeated measurement: Each test current multiple is measured several times, and the median is taken as the measured tripping time to suppress random errors in a single measurement. Third, trend tracking: The deviation patterns obtained from previous diagnoses are archived over time. When the deviation level corresponding to a certain sub-component continues to increase over time, it indicates that the sub-component is degrading rapidly, and maintenance can be arranged in advance.

[0023] All preset thresholds involved in this method can be objectively calibrated according to the model of the circuit breaker under test: the preset consistency threshold can be taken as the statistical upper quantile of the range of tripping time deviations of qualified circuit breakers of the same model, typically taking several percentage points of the set tripping time order of magnitude; the preset increasing slope threshold can be calibrated by the boundary of the trend term slope under normal wear and jamming conditions of the mechanical mechanism; the preset abrupt change threshold and the preset discrete threshold can be calibrated by the statistical boundary of the instantaneous tripping section deviation under normal and ablation conditions of the main contacts; the preset qualified threshold is taken as a percentage of the set tripping time according to the relevant standard's provisions on tripping time tolerance, for example, 10%. After each threshold is calibrated, it can still be finely adjusted according to the model of the circuit breaker under test and the operating conditions.

[0024] In engineering implementation, the application of test current and the detection of tripping moment are completed by the measurement and control hardware in conjunction with the current booster. The calculation of deviation modes, the extraction of mode characteristics, and the attribution of sub-factors are completed in real time by the processor. The time consumption of a single circuit breaker's multi-multiple diagnostic round mainly depends on the relatively long tripping waiting time in the inverse time section, while the instantaneous tripping section is very fast. Sufficient heat dissipation intervals are arranged between each multi-multiple test to avoid the impact of heat accumulation. The entire process can be made into a one-click diagnostic on the circuit breaker tester, which allows maintenance personnel to automatically complete multi-multiple tests and sub-factor diagnostics with a single setup.

[0025] This method can also be used in conjunction with the digital twin on the equipment side: the deviation patterns, pattern characteristics and attribution results of each circuit breaker's previous diagnoses are reported as the health record of the circuit breaker's twin; when the twin predicts that a certain sub-component is about to degrade to the point of affecting protection reliability, preventive maintenance can be arranged in conjunction with the diagnostic conclusions of this method.

[0026] like Figure 2 As shown, the present invention also provides a performance diagnostic device for an electronic plastic-cased circuit breaker corresponding to the above method, which includes a memory and a processor. The memory stores a computer program, which, when executed by the processor, implements the steps of the above method. Figure 2The device is schematically divided into a test current control module, a tripping time measurement module, a deviation and mode characteristic calculation module, a sub-cause attribution module, and a conclusion output module according to the functions it performs. This division is only a schematic division in terms of logical function. Each module works with the current booster and the main circuit of the circuit breaker under test to perform the above steps S1, S2, S3, S4, and S5. The specific processing is the same as the above method, so it will not be repeated.

[0027] The present invention also provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the steps of the above-described method; and a computer program product containing a computer program that, when executed by a processor, also implements the steps of the above-described method. The electronic device carrying the above-described program can be a circuit breaker detector, an industrial control computer, or an embedded measurement and control device, etc., which can be selected by those skilled in the art according to deployment needs, and will not be elaborated upon here.

[0028] As a specific example, such as Figure 8 As shown, taking an electronic plastic-cased circuit breaker with a rated current of 100 amps as an example, the complete execution process of the method described in this invention is explained. Step S0 involves selecting test current multiples of 1.5, 2, 3, 6, and 10 times the rated current, where 1.5, 2, and 3 times fall within the inverse-time zone, and 6 and 10 times fall within the instantaneous tripping zone. The set tripping times corresponding to each multiple are found to be approximately 60 seconds, 20 seconds, 8 seconds, 0.10 seconds, and 0.04 seconds, respectively, based on the set time-current characteristics. The preset consistency threshold is set to 0.03 seconds, and the preset incremental slope threshold and preset abrupt change threshold are set according to the following deviation levels. The preset qualified threshold is 10% of the set tripping time at each point.

[0029] In the first degradation scenario, step S1 sequentially injects test currents of various multiples, and the measured tripping time deviation from the set tripping time is approximately +0.05 seconds, +0.05 seconds, +0.06 seconds, +0.05 seconds, and +0.05 seconds at five multiples, respectively. The deviation pattern obtained in step S2 is approximately a flat line located near +0.05 seconds. Step S3 extracts pattern features: the linear fitting slope is close to zero, and the trend term is very small; the difference between the mean deviations of the instantaneous tripping segment and the inverse time-limited segment is close to zero, and the abrupt change term is very small. Step S4 determines that: the five deviations have the same sign and the range is only 0.01 seconds, not exceeding the consistency threshold of 0.03 seconds, and is attributed to the electronic tripping unit; since each deviation is approximately the same constant of +0.05 seconds, it is further determined to be a delay drift of the electronic tripping unit. Step S5 outputs the diagnostic conclusion "Electronic trip unit delay drift" and maintenance recommendation "Calibrate or replace the electronic trip board".

[0030] In contrast, under the second degradation scenario, the tripping time deviations at the five multiples are approximately +0.01 seconds, +0.02 seconds, +0.03 seconds, +0.06 seconds, and +0.09 seconds, respectively. The deviation pattern is an upward sloping line from the inverse time limit segment to the instantaneous tripping segment. Step S3 shows that the slope of the trend term is significantly positive and exceeds the increasing slope threshold. Step S4 attributes this to the mechanical operating mechanism and uses the average deviation of the instantaneous tripping segment of approximately 0.075 seconds as an estimate of the additional action time of the mechanical mechanism. Step S5 recommends overhauling the transmission mechanism. In the third degradation scenario, the deviations at the three points in the inverse time limit section are all small, while the deviations at the 6x and 10x points in the instantaneous tripping section suddenly increase to positive 0.12 seconds and positive 0.20 seconds, respectively, and are discrete from each other. The mutation terms exceed the mutation threshold, the dispersion exceeds the dispersion threshold, and the voltage drop of the main circuit is too large during the test. Step S4 attributes this to the main contact, and step S5 suggests repairing or replacing the main contact.

[0031] Furthermore, if the tested circuit breaker is in good working order, and the tripping time deviations at the five multiples are approximately +0.005 seconds, -0.004 seconds, +0.003 seconds, -0.002 seconds, and +0.003 seconds respectively, all not exceeding the preset acceptable threshold of 10% of the set tripping time at each point, then the trend term and abrupt change term are very small, and none of the sub-factor criteria are hit. Step S5 directly outputs the diagnostic conclusion that the tested circuit breaker is in good working order, without providing any maintenance suggestions for sub-components. As can be seen from the comparison of the above four scenarios, this method can not only identify degraded sub-components when the circuit breaker degrades, but also correctly judge it as qualified when the circuit breaker is in good working order, without falsely reporting degradation.

[0032] In contrast, if the multi-current multiple deviation mode and sub-cause attribution of this invention are not adopted, and the existing single-point acceptance judgment is used instead: in the above three degradation scenarios, the existing method can only determine non-compliance when the tripping time deviates from the tolerance at a certain current point. However, because it only focuses on isolated points and does not consider the entire pattern of deviation changing with the current multiple, it cannot distinguish whether the degradation is in the electronic unit, mechanical mechanism, or main contacts, leading to the only option of returning the entire circuit breaker to the factory or blindly disassembling and inspecting it. It is evident that the construction of the multi-current multiple deviation mode and the three types of sub-cause attribution based on pattern characteristics upgrade the diagnostic conclusion from acceptance or non-acceptance to determining where the degradation occurred, an effect that the existing method does not possess.

[0033] The test current multiples used in this method are not limited to the five mentioned above and can be increased or decreased according to the protection configuration of the circuit breaker under test. However, at least several multiples should be taken in both the inverse time section and the instantaneous tripping section to extract trend and abrupt change terms. The trend term of the deviation mode can also be characterized by other shape quantities such as piecewise slope. In some boundary cases, this method is handled as follows: when the circuit breaker fails to trip within a reasonable time under a certain test current multiple, the deviation at that point is recorded as the timeout upper limit and marked separately to avoid the fitting being biased by abnormal points; when multiple degradation factors are superimposed and the deviation mode shows a superimposed shape of translation, rise and instantaneous abrupt change, the criteria of each sub-component are hit and attributed to multiple sub-components respectively; when the test ambient temperature deviates significantly from the reference temperature of the set time current characteristic, the set tripping time is first corrected for temperature before calculating the deviation to avoid misjudging the ambient temperature difference as degradation.

[0034] To more clearly illustrate the physical laws underlying this method, the following analysis examines why the three types of factors exhibit different deviation patterns. The electronic trip unit is responsible for sampling the main circuit current and timing it according to the set time current characteristics; the tripping time is almost entirely determined by it. Once its timing reference or current sampling drifts, the tripping timing for each current multiple will shift in the same direction, thus the deviation is consistent across all segments. The mechanical operating mechanism only acts after receiving the tripping command; its action time is relatively fixed and added after the tripping. In the inverse-time segment, the set tripping time is several seconds or even longer, making this additional time negligible. However, in the instantaneous tripping segment, the set tripping time has been shortened to the millisecond level, making the same additional time significant; therefore, the deviation increases towards the instantaneous tripping segment. The main contacts experience more intense electrodynamic forces, arcing, and heating under high current. Disconnection anomalies caused by contact erosion or increased contact resistance are mainly triggered in the instantaneous tripping segment, and the randomness of each arcing causes the deviation to be discrete; therefore, the deviation only increases or becomes discrete in the instantaneous tripping segment.

[0035] The tripping time can be detected in several ways: it can be detected by detecting the abrupt change in the main circuit current of the circuit breaker under test from present to absent; it can also be detected by detecting the state reversal of the auxiliary contacts of the circuit breaker; or it can be detected by detecting the starting point of the vibration signal of the tripping mechanism. Regardless of the method used, as long as the breaking time of the circuit breaker can be stably given, the measured tripping time can be obtained by subtracting it from the application time of the test current. The application time is based on the moment when the current booster output reaches the target test current.

[0036] The reason these three types of sub-factors deserve separate diagnosis is that their maintenance strategies and costs differ significantly: drift in electronic trip units can often be resolved by calibration or replacement of the electronic board; jamming in mechanical operating mechanisms requires repair of transmission components; and burning of main contacts necessitates repair or replacement of the contacts and cleaning of the contact chamber. If the sub-factors are not identified and only the non-compliance is acknowledged, maintenance personnel must either troubleshoot item by item or replace the entire unit, which is both time-consuming and wasteful. This method directly identifies the cause in the sub-component, making maintenance targeted and effective.

[0037] The above mechanism also foresees the applicable boundaries of this method: the more concentrated the degradation of the tested circuit breaker is in a certain sub-component, and the more distinct the characteristics of its deviation mode, the more accurate the attribution of this method will be; when the degradation is slight, all multiple deviations are very small, the deviation mode is close to the zero line, and the characteristics of each mode do not exceed the corresponding threshold, this method judges the performance as qualified based on the preset qualified threshold without forcibly attributing it, and therefore will not treat measurement noise as degradation. Therefore, this method can locate the degraded sub-component while not giving false degradation conclusions for intact circuit breakers, and has good applicable boundaries.

[0038] It should be noted that there is a predictable causal relationship between the technical effects and technical means in the electrical measurement and diagnostic scenarios addressed by this invention. Therefore, the effects are explained above using causal reasoning: measuring the tripping time deviation at multiple current multiples and connecting them into a deviation pattern transforms the circuit breaker's degradation from an isolated point into an observable pattern across the entire circuit—a direct result of multi-point measurement; attributing the degradation to three shapes—overall translation, upward diagonal line, and instantaneous abrupt change—leads the attribution to three sub-components: the electronic unit, the mechanical mechanism, and the main contacts—a direct result of attribution based on physical laws; further substantiated by independent physical quantities such as constant / proportional, additional operating time, and main circuit voltage drop, the attribution can be cross-verified—a direct result supported by physical mechanisms. The above causal chain is established without relying on a specific prototype, and those skilled in the art can implement and verify this invention based on the description in the specification.

[0039] When multiple sub-components of a circuit breaker under test degrade simultaneously, its deviation pattern is a superposition of the various sub-factor patterns. For example, the deviation pattern of electronic trip unit delay drift superimposed on mechanical operating mechanism jamming appears as a diagonal line that rises as a whole and then slopes upwards towards the instantaneous trip section. In this case, the translation amount of the electronic trip unit can be estimated first using the common baseline of the inverse time section deviation, and then subtracted from the deviations at each point. Then, the trend term and abrupt change term are extracted from the subtracted deviation to distinguish between the mechanical operating mechanism and the main contacts, thereby separating the superimposed deviation pattern into the contributions of each sub-component and attributing them separately. This process of first subtracting the common mode and then distinguishing the differential mode is consistent with the idea of ​​attributing the deviation pattern according to shape in this invention.

[0040] This method determines the division between the inverse-time and instantaneous tripping sections based on the inflection point of the current characteristic of the circuit breaker under test: before this inflection point, the tripping time shortens significantly with increasing current, which is the inverse-time section; after this inflection point, the tripping time tends to a very short, approximately constant value, which is the instantaneous tripping section. The test current multiple should be taken from several values ​​in each section, and should cover as much of the vicinity of the inflection point as possible, so that both trend terms and abrupt changes can be stably extracted.

[0041] This method does not conflict with existing time-current characteristic testing equipment; on the contrary, it can be used to measure the actual tripping time. Existing testing equipment excels at accurately measuring tripping time at various current multiples. Based on the measured tripping time, this invention further calculates the tripping time deviation, extracts mode characteristics, and attributes them to factors. Therefore, this method can be implemented independently or used as a diagnostic enhancement for existing time-current characteristic testing equipment, making it easy to integrate into existing testing systems.

[0042] To suppress measurement errors, each test current multiple can be measured repeatedly, and the median is taken as the measured tripping time for that multiple. When fitting the trend term, the deviation at each point is weighted according to its measurement repeatability, so that points with good repeatability contribute more. The entire set of multi-multiple tests and sub-factor diagnosis can be integrated into a one-click process on the circuit breaker tester: after the maintenance personnel clamp the circuit breaker under test into the main circuit, the instrument automatically applies each multiple of test current, measures the tripping time, calculates the deviation mode, extracts mode characteristics and attributes the cause, and finally provides performance diagnosis conclusions and sub-component maintenance suggestions on the screen, without the need for manual point-by-point interpretation.

[0043] This method can be used for both offline testing (where the circuit breaker is removed from the power distribution system and diagnosed on a testing platform) and in-service testing with bypass capabilities (where a test current is applied to the circuit breaker without affecting power supply). The steps are the same for both offline and in-service testing; the only difference is the method of applying the test current. For multi-pole circuit breakers, test currents can be applied to each pole separately and diagnosed individually. The diagnostic conclusion for the entire circuit breaker is then derived by combining the attribution results of each pole.

[0044] It should be noted that the diagnostic accuracy of this method relies on the precision of the tripping time measurement: the measurement resolution between the tripping moment and the application moment should be better than the order of magnitude of the tripping time deviation to be distinguished. For example, when the tripping time deviation in the instantaneous tripping section is on the order of milliseconds, the time measurement resolution should ideally reach sub-milliseconds. At this precision, the three types of degradation sub-modes can be stably distinguished due to the shape differences in their deviation modes, making the attribution conclusions reliable. Those skilled in the art can set the order of magnitude of the tripping time for each section of the circuit breaker under test, and select appropriate time resolution measurement and control hardware and current boosters to enable this method to be implemented on electronic plastic-cased circuit breakers of different models and rated currents.

[0045] In summary, this method, based on observable deviation patterns, supported by interpretable physical mechanisms, and guaranteed by configurable measurement and control hardware, advances the performance diagnosis of electronic molded case circuit breakers from a rough acceptance judgment to a precise sub-component location. This facilitates integration into existing maintenance and repair processes and helps improve the reliability and efficiency of low-voltage power distribution system protection. It has positive practical significance for the intelligent operation and maintenance of electronic molded case circuit breakers.

[0046] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for intelligent measurement and performance diagnosis of electronic plastic-cased circuit breakers, characterized in that, The method includes: step S0, first acquiring the set-time current characteristics of the electronic plastic case circuit breaker under test, as well as a number of preset test current multiples divided into inverse time-limited sections and instantaneous tripping sections, and initializing the diagnostic results; Step S1: For each test current multiple, inject a test current corresponding to that test current multiple into the circuit breaker under test, and measure the actual tripping time of the circuit breaker under test at that test current multiple. Step S2: For each test current multiple, obtain the set tripping time under the set time current characteristics, calculate the tripping time deviation of the measured tripping time relative to the set tripping time, and obtain the deviation pattern of the tripping time deviation as the test current multiple changes. Step S3: Extract mode features from the deviation mode. The mode features include the trend term of the tripping time deviation as a multiple of the test current, and the abrupt change term of the tripping time deviation in the instantaneous tripping section relative to the inverse time section. Step S4: Based on the mode characteristics, attribute the performance degradation of the circuit breaker under test to at least one sub-component among the electronic trip unit, mechanical operating mechanism, and main contacts: When the tripping time deviation is in the same direction and similar in magnitude in the inverse time limit section and the instantaneous tripping section, it is attributed to the electronic tripping unit. When the tripping time deviation increases from the inverse time limit section to the instantaneous tripping section, the cause is attributed to the mechanical operating mechanism; When the tripping time deviation increases or becomes discrete only in the instantaneous tripping section, it is attributed to the main contacts; Step S5: Generate the performance diagnosis conclusion and sub-component maintenance recommendations for the circuit breaker under test based on the attribution results, and output the performance diagnosis conclusion and sub-component maintenance recommendations.

2. The method according to claim 1, characterized in that, Step S1 involves injecting a test current corresponding to a multiple of the test current into the circuit breaker under test and measuring the actual tripping time, including: injecting a test current corresponding to a multiple of the test current through the main circuit of the circuit breaker under test from the current booster and recording the application time of the test current; The interruption of the main circuit current of the circuit breaker under test is detected, and the moment when the main circuit current is interrupted is taken as the tripping moment; The difference between the tripping time and the application time is taken as the measured tripping time under the test current multiple.

3. The method according to claim 1, characterized in that, Step S3 extracts pattern features, including: performing a linear fit on the test current multiple with the tripping time deviation, and taking the slope obtained from the fit as the trend term; The difference between the mean of the tripping time deviation at each test current multiple in the instantaneous tripping section and the mean of the tripping time deviation at each test current multiple in the relative inverse time-limited section is taken as the mutation term.

4. The method according to claim 1, characterized in that, In step S4, attributing the cause to the electronic trip unit includes: when the trip time deviations under each test current multiple have the same sign and the range of each trip time deviation does not exceed a preset consistency threshold, the cause is attributed to the electronic trip unit. Among them, when the deviation of each tripping time is approximately the same constant, it is further determined to be the delay drift of the electronic tripping unit; When the deviation of each tripping time is approximately proportional to the corresponding set tripping time, it is further determined to be a current sampling drift of the electronic tripping unit.

5. The method according to claim 1, characterized in that, In step S4, attributing the cause to the mechanical operating mechanism includes: when the tripping time deviation increases from the inverse time limit segment to the instantaneous tripping segment, and the slope of the trend term exceeds a preset increasing slope threshold, the cause is attributed to the mechanical operating mechanism. The average value of the tripping time deviation under each test current multiple in the instantaneous tripping section is used as the estimated value of the additional action time of the mechanical operating mechanism.

6. The method according to claim 1, characterized in that, In step S4, attributing the cause to the main contact includes: when the mutation exceeds a preset mutation threshold, or when the dispersion of the tripping time deviation under each test current multiple in the instantaneous tripping section exceeds a preset dispersion threshold, the cause is attributed to the main contact. In conjunction with the voltage drop in the main circuit of the circuit breaker under test during the application of the test current, when the voltage drop exceeds the preset voltage drop threshold, the cause is confirmed to be attributed to the main contacts.

7. The method according to claim 1, characterized in that, Step S5 generates performance diagnostic conclusions and sub-component maintenance recommendations, including: When the cause is attributed to a single sub-component, maintenance recommendations are output for that sub-component. When the cause is attributed to multiple sub-components, the sub-components are sorted in descending order of their tripping time deviation magnitude, and maintenance recommendations for each sub-component are output sequentially. When the tripping time deviation at each test current multiple does not exceed the preset qualified threshold, the test circuit breaker will output a diagnostic conclusion that its performance is qualified.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the method of any one of claims 1 to 7.

9. A performance diagnostic device for an electronic plastic-cased circuit breaker, characterized in that, It includes a memory and a processor, wherein the memory stores a computer program that, when executed by the processor, implements the method of any one of claims 1 to 7.

10. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by a processor, it implements the method of any one of claims 1 to 7.

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