A method for predicting the remaining electrical life of a miniature circuit breaker

Abstract

The present invention discloses a method for predicting the remaining electrical life of a miniature circuit breaker, comprising: determining a rigid closing angle in a closing process as a characteristic quantity for evaluating operating performance based on the operating principle of a mechanical operating system of a miniature circuit breaker; performing an electrical life test on the miniature circuit breaker and calculating the rigid closing angle according to the closing torque collected by a torque sensor; determining the influence of arc erosion on the mechanical operating system based on a failure mechanism of the miniature circuit breaker, and converting the influence of arc erosion on the mechanical operating system into a change in the rigid closing angle in combination with the calculation of the rigid closing angle; establishing a miniature circuit breaker electrical performance degradation model based on a Winner process based on the rigid closing angle change law, and estimating the parameters of the miniature circuit breaker electrical performance degradation model; and realizing the prediction of the remaining electrical life of the miniature circuit breaker based on the estimated parameters of the miniature circuit breaker electrical performance degradation model; the present invention establishes a model to facilitate and accurately predict the remaining electrical life by analyzing the degradation law of the effective characteristic quantity rigid closing angle with life.

Description

Technical Field

[0001] The invention relates to the technical field of electrical equipment, and in particular to a method for predicting the remaining electrical life of a miniature circuit breaker. Background Art

[0002] Miniature circuit breakers are protection devices in low-voltage switchgear and are widely used in homes, industrial buildings and power distribution systems. When a fault occurs in a power line, the miniature circuit breaker can automatically cut off the fault circuit to protect the power line and power equipment.

[0003] The interior of a miniature circuit breaker is mainly composed of a contact arc extinguishing system, a mechanical operating system, and an overcurrent protection system. Each action of the miniature circuit breaker will cause an arc to be generated between the moving and static contacts, ablating the contact material. When the cumulative erosion of the contacts reaches a certain level, the miniature circuit breaker cannot be reliably connected, resulting in the end of the circuit breaker's life and threatening the safe operation of the power distribution system.

[0004] There are many studies on the reliability and remaining life prediction of switching electrical appliances. The literature "Zhao Chengchen, Li Kui, Hu Bokai, et al. Prediction of the remaining electrical life of low-voltage circuit breakers under variable stress conditions [J]. Proceedings of the CSEE, 2022, 42(21): 8004-8016." analyzes the influence of arc on contact erosion under different currents and proposes three methods for predicting the remaining electrical life of low-voltage circuit breakers under variable stress conditions.

[0005] However, in fact, the relevant research on the performance degradation and remaining life prediction of miniature circuit breakers is still immature. The use of arc current and break voltage for life prediction requires real-time data collection, and it is difficult to reflect the internal situation of the circuit breaker. And due to the limitation of the assembly method of the miniature circuit breaker, it is difficult to disassemble and measure the contact weight during the experiment. Therefore, a method for predicting the remaining electrical life of miniature circuit breakers is urgently needed. Summary of the invention

[0006] In order to overcome the shortcomings of the above technologies, the present invention provides a method for predicting the remaining electrical life of a miniature circuit breaker. By analyzing the rigidity and angle degradation during the closing process, an electrical performance degradation model of the miniature circuit breaker based on the Wiener process is established, thereby predicting the remaining electrical life of the miniature circuit breaker.

[0007] The technical solution adopted by the present invention to overcome its technical problems is: a method for predicting the remaining electrical life of a miniature circuit breaker proposed in the present invention comprises constructing a mechanism motion model based on analyzing the operating principle of a mechanical operating system of a miniature circuit breaker; obtaining the mechanism motion law of a closing process based on the mechanism motion model, selecting the rotation angle required for the handle of the mechanical operating system of the miniature circuit breaker to rotate to the contact between the moving and static contacts during the closing process, namely, the rigid closing angle, as a characteristic quantity for evaluating the operating performance; performing an electrical life test on the miniature circuit breaker and calculating the rigid closing angle according to the closing torque collected by the torque sensor; determining the influence of arc erosion on the mechanical operating system based on the failure mechanism of the miniature circuit breaker, and converting the influence of arc erosion on the mechanical operating system into a change in the rigid closing angle in combination with the calculation of the rigid closing angle; establishing a miniature circuit breaker electrical performance degradation model based on a winner process based on the change law of the rigid closing angle, and estimating the parameters of the miniature circuit breaker electrical performance degradation model; and predicting the remaining electrical life of the miniature circuit breaker based on the estimated miniature circuit breaker electrical performance degradation model.

[0008] Furthermore, the mechanism motion law of the closing process is a planar four-bar linkage motion, as shown in formula (1):

[0009] (1),

[0010] in, is the angle between handle BC and X axis, is the angle between the U-shaped connecting rod CD and the X-axis, For rod 3 and x The angle of the axis, l BC , l DF , l CD and l CF They correspond to the lengths of the handle, lock, U-shaped connector and two fixed points CF in the mechanical operating system of the miniature circuit breaker.

[0011] Further, the electrical life test of the miniature circuit breaker is performed and the rigid closing angle is calculated according to the closing torque collected by the torque sensor, specifically including:

[0012] Conduct electrical life test, use torque sensor at intervals to The miniature circuit breaker handle is rotated at a constant angular velocity to collect the closing torque;

[0013] Monitor the connection state of the moving and static contacts to obtain the closing time t;

[0014] The angular velocity of the torque sensor is determined by the closing time t and the torque sensor Calculate the angle of rigid connection .

[0015] Furthermore, the determination of the influence of arc erosion on the mechanical operating system based on the failure mechanism of the miniature circuit breaker specifically includes:

[0016] Each break k The single contact thickness is accumulated to obtain the cumulative contact thickness loss Δ of each section. H As shown in formula (2) and formula (3),

[0017] (2),

[0018] (3),

[0019] In the formula, m j Indicates the miniature circuit breaker j The random contact quality loss caused by the first action, The cumulative contact quality loss after K openings is: j Indicates the first j Second break, ρ Indicates the contact material density, S Represents the area of ​​the contact loss region after breaking, where the cumulative contact thickness loss of each section obeys the normal distribution with unchanged mean and standard deviation.

[0020] Furthermore, the calculation of the rigid-closing angle converts the influence of arc erosion on the mechanical operating system into a rigid-closing angle change, including: calculating the rigid-closing angle for each k opening and closing times based on the movement law of the mechanical operating system and the cumulative contact thickness loss of each section, thereby obtaining the rigid-closing angle change.

[0021] Furthermore, the electrical performance degradation model of the miniature circuit breaker is as shown in formula (4):

[0022] (4),

[0023] in, is the cumulative degradation of the rigid angle as time t increases, is the standard Brownian motion, , are the parameters of the miniature circuit breaker electrical performance degradation model.

[0024] Furthermore, the maximum likelihood estimation method is used to estimate the model parameters of the miniature circuit breaker electrical performance degradation model. The estimation formula is shown in formula (5):

[0025] (5),

[0026] In the formula, k is the cumulative number of closing and opening of the miniature circuit breaker in each section, N is the number of measurements, ΔY i For the i The degenerate increment of the just-closed angle during the first measurement, is the degradation model parameter The estimated value of is the degradation model parameter The estimated value of is an estimate of the failure threshold.

[0027] Furthermore, the remaining electrical life of the miniature circuit breaker is predicted based on the estimated miniature circuit breaker electrical performance degradation model, specifically including: when the cumulative degradation amount of the rigid closing angle is Y ( t ) has not yet reached the failure threshold L When , L 0 is the current accumulated degradation amount obtained by measuring the rigid closing angle. The electrical life probability density function at the current degradation moment is shown in formula (6). The electrical life reliability function of the miniature circuit breaker at the current moment is shown in formula (7). The electrical life expectation and variance of the miniature circuit breaker at the current moment can be expressed as shown in formula (8).

[0028] (6),

[0029] (7),

[0030] (8),

[0031] Where F(·) is the standard normal distribution function.

[0032] The beneficial effects of the present invention are:

[0033] 1. According to the operating principle of the mechanical operating system of the miniature circuit breaker, the mechanical operating system is simplified into a mechanism motion model, so as to determine the rigid closing angle as the characteristic quantity, laying a good foundation for the subsequent prediction of the remaining electrical life of the miniature circuit breaker;

[0034] 2. By analyzing the impact of arc erosion on the mechanical operating system, the rigid closing angle of contacts with different thicknesses is obtained. The electrical performance degradation model of the miniature circuit breaker based on the winner process is established according to the change law of the rigid closing angle, and the remaining electrical life of the miniature circuit breaker at different stages is accurately predicted;

[0035] 3. The closing torque is obtained through the torque sensor, which facilitates the calculation of the rigid closing angle, which can not only reflect the status of the moving and static contacts inside the circuit breaker, but also facilitate the acquisition of characteristic quantities. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1It is a schematic flow chart of a method for predicting the remaining electrical life of a miniature circuit breaker of the present invention;

[0037] Figure 2 is a cross-sectional schematic diagram of the mechanical operating system of the miniature circuit breaker of the present invention;

[0038] Figure 3 It is the operating mechanism and simplified schematic diagram of the miniature circuit breaker of the present invention;

[0039] Figure 4 It is the handle operating torque waveform collected during the closing process of the present invention;

[0040] Figure 5 This is a graph showing the changing trend of the rigid closing angle during the electrical life test of the sample in Example 1 of the present invention;

[0041] Figure 6 is the probability density curve of Example 1 of the present invention;

[0042] Figure 7 It is the reliability curve of Example 1 of the present invention.

[0043] In the figure, 1-handle, 2-U-shaped connecting rod, 3-jump buckle, 4-lock buckle, 5-center bracket, 6-contact lever, 7-contact spring, 8-static contact, 9-moving contact, 10-torsion spring 1, 11-torsion spring 2. DETAILED DESCRIPTION

[0044] In order to facilitate those skilled in the art to better understand the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The following is only exemplary and does not limit the protection scope of the present invention.

[0045] S1. Construct a mechanism motion model based on the analysis of the operating principle of the mechanical operating system of the miniature circuit breaker.

[0046] like Figure 2 Shown is a cross-sectional schematic diagram of the mechanical operating system of a miniature circuit breaker.

[0047] The mechanical operating system of the miniature circuit breaker mainly includes a handle 1, a U-shaped connecting rod 2, a trip buckle 3, a lock buckle 4, a center bracket 5 and a contact lever, and includes two torsion springs, namely a torsion spring 10 and a torsion spring 2 11, and a contact spring 7.

[0048] The torsion spring 10 is located below the handle 1, and the two ends of the torsion spring 1 act on the handle and the housing respectively. During the closing process, the torsion spring provides a full clockwise resistance to the handle 1, and plays a counterclockwise power role during the opening process, so that the handle quickly returns to its initial position.

[0049] According to the analysis of the operating principle of the mechanical operating system of the miniature circuit breaker, the following Figure 3The mechanism motion model shown in the figure. AB and BC of the mechanism operation model correspond to the handle 1, CD corresponds to the U-shaped connecting rod 2, DE corresponds to the jump buckle 3, DF corresponds to the lock buckle 4, FK and KG correspond to the contact lever 6, HJ corresponds to the contact spring 7, I corresponds to the static contact, and G corresponds to the moving contact.

[0050] S2, and based on the mechanism motion model, the mechanism motion law of the closing process is obtained, so that the handle rotation angle of the mechanical operating system of the miniature circuit breaker during the closing process, that is, the rigid closing angle, is selected as the characteristic quantity for evaluating the operating performance.

[0051] The mechanical operating system moves in the form of a planar four-bar linkage during the closing process. The structure of the mechanical operating system is based on the four-bar motion characteristics to obtain the mechanism motion law. The mechanism motion law is shown in formula (1).

[0052] (1),

[0053] In the formula, θ 1 For handle BC and x The angle of the axis, θ 2 CD and x The angle of the axis, θ 3 For rod 3 and x The angle of the axis, l BC , l DF , l CD and l CF They correspond to the lengths of the handle, lock, U-shaped connector and two fixed points C and F in the mechanical operating system of the miniature circuit breaker.

[0054] It should be noted that AB and BC are on the same mechanical part, and their rotation angles are the same. In order to facilitate calculation, the angle between BC and the x-axis is selected.

[0055] During the closing process of the mechanical operating system, the rotation angle of the operating mechanism when the moving and static contacts touch, that is, the closing angle, can effectively reflect the movement performance of the mechanism. θ 1 The angle of rigid connection can be calculated, that is θ 1 Initial value and contact moment of moving and static contacts θ 1 The difference is taken as the characteristic quantity to analyze the degradation law of the rigid angle with the life span, and a model is established to obtain the remaining life span.

[0056] S3, for the electrical life test of the miniature circuit breaker, a torque sensor is used to collect the closing torque of the mechanism and calculate the rigid closing angle.

[0057] S31, conduct electrical life test, and use torque sensor to collect the closing torque of the mechanism life at intervals.

[0058] Torque sensor The miniature circuit breaker handle is rotated at a constant angular velocity to close the circuit breaker, and the closing torque is collected.

[0059] S32, calculating the rigid closing angle according to the torque signal.

[0060] By monitoring the connection state of the moving contact 9 and the stationary contact 8, the closing time is obtained. t。

[0061] S33, through the closing time t and the angular velocity of the torque sensor Calculate the angle of rigid connection .

[0062] In one embodiment, a direct current is connected between the moving contact and the stationary contact to collect the voltage change between the moving contact and the stationary contact. When the moving contact and the stationary contact are not connected, the voltage is the power supply voltage; when the moving and stationary contacts are in contact, the circuit is connected and the voltage step becomes 0. Figure 3 As shown in the figure, the operating torque of the handle is 175N, and the time when the voltage step of the contact signal becomes 0 is the closing time t. And the closing angle is obtained through the angular velocity of the torque sensor.

[0063] S4, based on the failure mechanism of miniature circuit breaker, the influence of arc erosion on the mechanical operating system is determined, and combined with the calculation of rigid closing angle, the influence of arc erosion on the mechanical operating system is converted into the change of rigid closing angle.

[0064] S41, Determine the impact of arc erosion on mechanical operating systems based on the failure mechanism of miniature circuit breakers.

[0065] During the actual service of the miniature circuit breaker, the breaking circuit causes the arc to continuously erode the contact. When the cumulative erosion of the contact reaches a certain level, the miniature circuit breaker cannot be reliably connected, and eventually the moving and static contacts cannot be reliably contacted. Therefore, the influence of arc erosion on the single wear thickness of the contact of the mechanical operating system is determined, so as to analyze the influence of the single wear thickness of the contact on the performance degradation model. Affected by the arc starting phase angle, the single contact mass loss is random, resulting in the contact thickness under a single arc erosion not being uniformly reduced, and having randomness. Therefore, the single contact thickness loss is accumulated in segments. The cumulative contact thickness loss of each segment obeys the normal distribution, and the mean and standard deviation remain unchanged. Among them, the influence of the single wear thickness of the contact on the performance degradation model is analyzed, that is, each breaking kThe single contact thickness is accumulated to obtain the cumulative contact thickness loss Δ of each section. H As shown in formula (2) and formula (3).

[0066] (2),

[0067] (3),

[0068] In the formula, m j Indicates the miniature circuit breaker j The random contact quality loss caused by the first action, The cumulative contact quality loss after K openings is: j Indicates the first j Second break, ρ Indicates the contact material density, S It indicates the area of ​​contact loss after disconnection, which is generally a constant value.

[0069] S42, converting the influence of arc erosion on the mechanical operating system into a change in the rigid closing angle.

[0070] The rigid closing angles of the contacts with different thicknesses are calculated according to formula (1), and the rigid closing angle changes are obtained according to the rigid closing angles of the contacts with different thicknesses.

[0071] S5, based on the change law of the rigid closing angle, a miniature circuit breaker electrical performance degradation model based on the winner process is established, and the parameters of the miniature circuit breaker electrical performance degradation model are estimated.

[0072] S51, based on the change law of the rigid closing angle, a miniature circuit breaker electrical performance degradation model based on the winner process is established.

[0073] The electrical performance degradation model of the miniature circuit breaker is shown in formula (4):

[0074] (4),

[0075] in, is the cumulative degradation of the rigid angle as time t increases, is the standard Brownian motion, , are the parameters of the miniature circuit breaker electrical performance degradation model.

[0076] S52, the maximum likelihood estimation method is used to estimate the model parameters, and the estimation formula is shown in formula (5):

[0077] (5),

[0078] In the formula, kis the cumulative number of closing and opening of the miniature circuit breaker in each section, and N is the number of measurements, that is, the number of measurements when the closing angle changes Δ Y i For the i The degenerate increment of the just-closed angle during the first measurement, is the degradation model parameter The estimated value of is the degradation model parameter The estimated value of is an estimate of the failure threshold.

[0079] S6, predicting the remaining electrical life of the miniature circuit breaker based on the estimated electrical performance degradation model of the miniature circuit breaker.

[0080] S61, when the cumulative degradation of the just closed angle Y ( t ) has not yet reached the failure threshold L That is, the estimated value of the failure threshold of formula (5), let ，L 0 is the current accumulated degradation amount obtained by measuring the rigid closing angle, and the electrical life probability density function at the current degradation moment is shown in formula (6).

[0081] (6),

[0082] S62, the electrical life reliability function of the miniature circuit breaker at the current moment is as shown in formula (7).

[0083] (7),

[0084] Where F(·) is the standard normal distribution function.

[0085] S63, the expected electrical life of the miniature circuit breaker at the current moment and variance It can be expressed as shown in formula (8).

[0086] (8)

[0087] It should be noted that the calculation of the variance can provide a prediction margin for the prediction of the expected electrical life according to the prediction accuracy.

[0088] Taking the remaining electrical life prediction of three miniature circuit breakers according to the miniature circuit breaker remaining electrical life prediction method of the present application as an example, the technical solution of the present invention is explained as follows.

[0089] S1 ’ , establish the kinematic relationship of the mechanism, and substitute the component sizes of the three miniature circuit breakers into formula (1).

[0090] S2 ’ , conduct electrical life tests of three miniature circuit breakers at rated current, and collect the closing torque of the circuit breaker through the torque sensor every 100 times.

[0091] S3 ’ , the rigid closing angle of the miniature circuit breaker is calculated according to the closing torque. The corresponding relationship between the operation times of the three miniature circuit breakers and the calculated rigid closing angle is as follows: Figure 4 shown.

[0092] S4 ’ The electrical performance degradation model (4) of the miniature circuit breaker based on the Winner process is estimated by using formula (5). The parameter estimation values ​​of each test piece are shown in Table 1.

[0093] Table 1

[0094] parameter Sample 1 Sample 2 Sample 3 <![CDATA[ µ 1 Estimated value]]> 0.005 2 0.004 9 0.004 5 <![CDATA[ σ 1 Estimated value]]> 0.038 9 0.039 8 0.043 7

[0095] S5 ’ , and conduct electrical life prediction at different stages.

[0096] Take the electrical life prediction of sample 1 at different stages as an example.

[0097] The probability density calculated by the estimated degradation model parameters The curve is as Figure 5 shown.

[0098] .

[0099] Reliability Function of Electrical Performance Degradation Model , the curve is as Figure 6 shown.

[0100] .

[0101] The remaining electrical life of sample 1 was predicted at different stages, and the results are shown in Table 2.

[0102] Table 2

[0103] Stage (life span / times) Actual remaining battery life (times) Predicted remaining battery life (times) Relative error (%) 1-500 2 397 2 206 7.97% 501-1000 1 897 1 811 4.53% 1001-1500 1 397 1 344 3.79% 1501-2000 897 865 3.57% 2001-2500 397 383 3.53%

[0104] It can be seen from Table 2 that the prediction results of the remaining electrical life of the miniature circuit breaker at different stages are all less than 8%, which meets the engineering requirements.

[0105] It should be noted that: in other embodiments, the steps of the corresponding method are not necessarily performed in the order shown and described in this specification. In some other embodiments, the steps included in the method may be more or less than those described in this specification. In addition, a single step described in this specification may be decomposed into multiple steps for description in other embodiments; and multiple steps described in this specification may be combined into a single step for description in other embodiments.

Claims

1. A method for predicting the remaining electrical life of a miniature circuit breaker, characterized in that: include: The mechanism motion model is constructed based on the analysis of the operating principle of the mechanical operating system of the miniature circuit breaker; The mechanism motion law of the closing process is obtained based on the mechanism motion model, and the rotation angle required for the handle of the mechanical operating system of the miniature circuit breaker to rotate to the contact between the moving and static contacts during the closing process, namely the rigid closing angle, is selected as the characteristic quantity for evaluating the operating performance. Conduct electrical life test on miniature circuit breaker and calculate the rigid closing angle according to the closing torque collected by the torque sensor, and conduct electrical life test, specifically including: Use torque sensors at intervals to The miniature circuit breaker handle is rotated at a constant speed to collect the closing torque. Monitor the connection state of the moving and static contacts to obtain the closing time t, The angular velocity of the torque sensor is determined by the closing time t and the torque sensor Calculate the angle of rigid connection ; The influence of arc erosion on the mechanical operating system is determined based on the failure mechanism of the miniature circuit breaker, including: k The single contact thickness is accumulated to obtain the cumulative contact thickness loss Δ of each section. H As shown in formula (1) and formula (2), （1）， （2）， In the formula, m j Indicates the miniature circuit breaker j The random contact quality loss caused by the first action, The cumulative contact quality loss after K openings is: j Indicates the first j Second break, ρ Indicates the contact material density, S represents the area of ​​contact loss after breaking, where the cumulative contact thickness loss of each section follows a normal distribution with constant mean and standard deviation; Combined with the calculation of the rigid closing angle, the influence of arc erosion on the mechanical operating system is converted into the rigid closing angle change, specifically including: based on the movement law of the mechanical operating system and the cumulative contact thickness loss of each section, the rigid closing angle for each breaking k times is calculated, thereby obtaining the rigid closing angle change; Based on the change law of the rigid closing angle, the electrical performance degradation model of the miniature circuit breaker based on the Winner process is established, and the parameters of the electrical performance degradation model of the miniature circuit breaker are estimated; The remaining electrical life of the miniature circuit breaker is predicted based on the estimated electrical performance degradation model of the miniature circuit breaker.

2. A method for predicting the remaining electrical life of a miniature circuit breaker according to claim 1, characterized in that: The mechanism motion law of the closing process is a planar four-bar linkage motion, as shown in formula (3): （3）， in, is the angle between handle BC and X axis, is the angle between the U-shaped connecting rod CD and the X-axis, For rod 3 and x The angle of the axis, l BC , l DF , l CD and l CF They correspond to the lengths of the handle, lock, U-shaped connector and two fixed points CF in the mechanical operating system of the miniature circuit breaker.

3. A method for predicting the remaining electrical life of a miniature circuit breaker according to claim 1, characterized in that: The electrical performance degradation model of the miniature circuit breaker is shown in formula (4): （4）， in, is the cumulative degradation of the rigid angle as time t increases, is the standard Brownian motion, , are the parameters of the miniature circuit breaker electrical performance degradation model.

4. A method for predicting the remaining electrical life of a miniature circuit breaker according to claim 3, characterized in that: The maximum likelihood estimation method is used to estimate the model parameters of the miniature circuit breaker electrical performance degradation model. The estimation formula is shown in formula (5): （5）， In the formula, k is the cumulative number of closing and opening of the miniature circuit breaker in each section, N is the number of measurements, Δ Y i For the i The degenerate increment of the just-closed angle during the first measurement, is the degradation model parameter The estimated value of is the degradation model parameter The estimated value of is an estimate of the failure threshold.

5. A method for predicting the remaining electrical life of a miniature circuit breaker according to claim 4, characterized in that: The method of predicting the remaining electrical life of the miniature circuit breaker based on the estimated electrical performance degradation model of the miniature circuit breaker specifically includes: When the cumulative degradation of the rigid angle Y ( t ) has not yet reached the failure threshold L When , L 0 is the current accumulated degradation amount obtained by measuring the rigid closing angle. The electrical life probability density function at the current degradation moment is shown in formula (6). The electrical life reliability function of the miniature circuit breaker at the current moment is shown in formula (7). The electrical life expectation and variance of the miniature circuit breaker at the current moment can be expressed as shown in formula (8), （6）， （7）， （8）， Where F(·) is the standard normal distribution function.

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