Method for diagnosing breakage fault of connecting rod of motor operating mechanism of vacuum circuit breaker

Abstract

The invention discloses a connecting rod fracture fault diagnosis method for a motor operating mechanism of a vacuum circuit breaker, and relates to the field of internal characteristic fault diagnosis of the motor operating mechanism of the circuit breaker. The method specifically comprises the following steps: firstly, constructing motion models of an adams motor operating mechanism in a healthy state and a connecting rod fracture state, and respectively analyzing the evolution of load torque of the operating mechanism under three working conditions of normal, single fracture and full fracture; in the evolution process, the influence of the interphase connecting rod fracture fault on the load torque and the influence on the motor rotation angle and the electromagnetic torque are simulated respectively, and the electromagnetic torque is adopted as a fault inversion characteristic. Then, three-phase current is collected through a sensor to calculate electromagnetic torque, and the deviation degree of the actual electromagnetic torque and the electromagnetic torque reference value in different stages of the whole movement process is calculated; and finally, weighting the deviation degrees of different stages in the whole movement process, and determining the fault type by comparing the threshold ranges of different fault types. According to the invention, early warning of the short-circuit early fault of the connecting rod under motor inching control is realized.

Description

Technical Field

[0001] This invention relates to the field of fault diagnosis of internal characteristics in the operating mechanism of a circuit breaker motor, and specifically to a method for diagnosing connecting rod fracture faults in the operating mechanism of a vacuum circuit breaker motor. Background Technology

[0002] Compared to single-break circuit breakers, vacuum multi-break circuit breakers improve the breaking arc voltage and the dielectric recovery capability of the break. However, if mechanical parts fail, the moving contact of the break may fail to open, affecting the stable operation of the power system. Therefore, to improve the stability and reliability of circuit breaker operation, it is essential to perform inverse analysis of mechanical faults in the transmission components of the motor operating mechanism.

[0003] In recent years, domestic and foreign scholars have focused their research on the inversion of mechanical faults in circuit breakers on three main aspects: the current signal of the opening and closing coils of the operating mechanism, the acceleration vibration signal of the mechanism, and the stroke-time characteristic curve of the circuit breaker contact movement.

[0004] The opening and closing process of a circuit breaker is accompanied by strong mechanical vibrations, and the actions of different components (such as the tripping mechanism, linkage, and contacts) will generate impact responses with characteristic spectra. When problems such as core jamming, coil short circuit, or abnormal switching of auxiliary contacts occur in the mechanism, the amplitude, rise / fall time, or waveform distortion (such as steps or dips) of the current will deviate significantly from the reference. Fault diagnosis establishes a mapping model between current characteristics (such as excitation peak time, holding current steady-state value, tripping time, etc.) and mechanical state parameters to achieve fault identification and location based on the time-frequency characteristics of the current.

[0005] In addition, by capturing vibration signals from key points of the mechanism (such as the base and operating lever) using a high-sensitivity accelerometer, and extracting time-domain (peak value, energy) and frequency-domain (resonant frequency, energy distribution) features, faults such as loose parts, wear, abnormal buffering, or insufficient collision force can be identified.

[0006] Current research still faces challenges such as insufficient robustness of feature extraction, difficulty in diagnosing coupled multi-fault systems, and low accuracy of signal identification in noisy environments. Future trends focus on multi-source information fusion (integrating current, vibration, travel, and even acoustic / temperature signals), utilizing intelligent algorithms such as deep learning to mine deep correlation features, and integrating physical models to improve the interpretability and generalization ability of fault inversion, providing a more reliable basis for circuit breaker condition assessment and predictive maintenance. Summary of the Invention

[0007] To achieve fault diagnosis of internal characteristics of the motor operating mechanism of a vacuum circuit breaker, this invention proposes a method for diagnosing connecting rod fracture faults in the motor operating mechanism of a vacuum circuit breaker, ultimately realizing early warning of connecting rod short circuit faults under motor micro-motion control.

[0008] The specific steps of the method for diagnosing link fracture in the operating mechanism of a vacuum circuit breaker motor are as follows:

[0009] Step 1: Construct motion models of the Adams motor operating mechanism in healthy and linkage fracture states, and analyze the evolution of the load torque of the operating mechanism under three working conditions: normal, single fracture, and full fracture.

[0010] Specifically:

[0011] First, based on Adams dynamic simulation software, a motion model of the motor operating mechanism is established to analyze the evolution of the load torque during the opening motion: from positive to negative (driven by spring force after dead point), abruptly to positive (acting by self-closing force after the contacts just open), and then decreasing to negative (the change in transmission ratio assists in reaching the opening position).

[0012] Specifically, it evolved into:

[0013] When the motor operating mechanism is in the closed holding position, it is subjected to the reaction force of the contact spring. As the motor rotates, it drives the operating mechanism through the dead point. The load torque on the motor shaft changes from positive to negative, and the spring reaction force changes from resistance to power, pushing the operating mechanism to perform the opening movement.

[0014] When the operating mechanism reaches the position where the contact is just separated, the overtravel phase of the operating mechanism ends, the spring reaction force becomes ineffective, the self-closing force begins to act on the moving contact, the load torque changes abruptly from a negative value to a positive value, and the operating mechanism begins to drive the moving contact to move.

[0015] During the movement of the moving contact of the operating mechanism, the load torque gradually decreases due to the change in the transmission ratio between the moving parts until the operating mechanism passes another dead point. The load torque changes from positive to negative, helping the operating mechanism reach the open position and remain stationary.

[0016] Step 2: Simulate the effects of interphase connecting rod fracture fault on load torque, motor rotation angle and electromagnetic torque during the evolution process, and use electromagnetic torque as the fault inversion feature.

[0017] Based on the motion model of the operating mechanism, the impact of interphase link fracture failure on the load torque during the evolution process is analyzed:

[0018] When a single contact breaks, the load torque is reduced by half to about half of the normal value, and only a single contact can be operated. The torque change is similar to normal but the amplitude is reduced. When a complete contact breaks, the load torque is close to zero, the load force cannot be applied to the motor, the mechanism completely fails and cannot open or close.

[0019] Since the load torque cannot be directly measured by measuring instruments during actual opening and closing operations, it is impossible to determine whether the operating mechanism linkage is broken.

[0020] The effect of interphase connecting rod breakage on motor rotation angle is as follows: the three-closed-loop PID control makes the motor rotation angle curves approximately the same under different fault conditions, making it impossible to directly determine the fault.

[0021] The phase-to-phase linkage fracture fault shows significant differences in electromagnetic torque at different stages of tripping (start-up, after dead point, short arc, long arc, and buffer), which can be used as a fault diagnosis feature.

[0022] Specifically:

[0023] During startup, the motor first needs to overcome the spring reaction force. However, due to the failure of the interphase connecting rod, the motor drive shaft experiences less resistance than normal, resulting in a smaller output electromagnetic torque.

[0024] When the operating mechanism passes the dead point, the spring reaction force helps the operating mechanism to open the circuit breaker. The normal operating mechanism outputs a smaller electromagnetic torque than the faulty one.

[0025] When the moving and stationary contacts are just separated, the operating mechanism enters the short arcing stage. At this time, due to the collision, the load torque changes abruptly. The load on the drive shaft of the normal mechanism is twice as much as that of the single-phase linkage failure. The motor of the normal operating mechanism needs a larger electromagnetic torque than that of the failure operating mechanism to reach the speed requirement.

[0026] When the operating mechanism enters the long arcing stage, it needs to slow down to ensure that there is a sufficient longitudinal magnetic field between the contacts. At this time, the self-closing force helps the operating mechanism to decelerate. The self-closing force on the normal operating mechanism is twice that of a single-phase inter-linkage fault, and the required output electromagnetic torque value is smaller.

[0027] During the buffering phase, the electromagnetic torque output under normal and fault conditions gradually decreases, and the mechanism gradually decelerates.

[0028] The electromagnetic torque of the motor operating mechanism with different degrees of interphase linkage faults shows obvious differences at different stages of the opening and closing process. Electromagnetic torque can be used as a fault inversion feature.

[0029] Step 3: Calculate the electromagnetic torque by collecting three-phase current data using sensors, and calculate the deviation between the actual electromagnetic torque and the reference value at different stages of the entire motion process. ;

[0030] Degree of deviation at each stage The calculation formula is:

[0031]

[0032] This represents the actual electromagnetic torque at each stage. This indicates the reference value of the electromagnetic torque at each stage.

[0033] Step 4: Assess the degree of deviation at different stages of the entire movement. Weighting is performed, and the fault type is determined by comparing the threshold ranges of different fault types.

[0034] The weighted values ​​are selected based on the ratio of electromagnetic torque errors between the fault state and the normal state at different stages. The calculation formula is as follows:

[0035]

[0036] In the formula, For the first Weighted values ​​for each stage, For the first The maximum value of electromagnetic torque error in each stage.

[0037] Through multiple sets of repeated experiments, the weighted values ​​of different stages were averaged, and the final selected weights were: 0.1 for the start-up stage, 0.4 for the short arc burning stage, 0.4 for the long arc burning stage, and 0.1 for the buffer stage.

[0038] Table 1 shows the weighted values ​​of the deviation of the upper and lower limits of electromagnetic torque under different fault conditions:

[0039] Table 1

[0040]

[0041] Therefore, the inversion basis for mechanical failures caused by the breakage of the interphase connecting rod in the motor operating mechanism is as follows:

[0042] when This indicates that there is no breakage fault in the interphase connecting rod; when This indicates that the connecting rod between single phases has broken; when This indicates a complete breakage of the interphase connecting rod;

[0043] The collected electromagnetic torque data is weighted by calculating the degree of deviation, and the fault type is determined by comparing the threshold ranges of different fault types.

[0044] The advantages of this invention are:

[0045] 1. This invention proposes and utilizes "electromagnetic torque" as a sensitive inversion feature for connecting rod fracture faults, making the diagnosis more targeted and accurate. Traditional fault diagnosis may focus more on directly measurable signals such as current, speed and position, or indirect signals such as vibration and sound, but these are all indirect signals for electromagnetic torque, and the sensitivity is weak.

[0046] 2. This invention employs a "phased weighted deviation analysis" strategy, effectively solving the problem of key information overload and improving fault resolution and robustness. Existing methods calculate the average deviation value throughout the entire movement process, which leads to the fault characteristic information of key stages (such as start-up, acceleration, contact contact / separation, buffering, etc.) during the opening and closing process being diluted ("overloaded") by data from relatively "normal" stages throughout the entire stroke.

[0047] 3. This invention constructs a fault type and severity quantitative diagnostic framework based on "threshold range comparison". Through model simulation and / or experimental data, a threshold range (upper and lower limits) for the deviation of electromagnetic torque is pre-set for different degrees of interphase link fracture faults. This differs from simple single threshold judgment. Attached Figure Description

[0048] Figure 1 This is a flowchart of the present invention for determining shaft breakage faults in operating mechanisms using electromagnetic torque;

[0049] Figure 2 This is a flowchart of a method for diagnosing the failure of a connecting rod in the motor operating mechanism of a vacuum circuit breaker according to the present invention;

[0050] Figure 3 This is a fault simulation model of the interphase connecting rod mechanism of the present invention;

[0051] Figure 4 This is the load torque curve of the circuit breaker under normal tripping and connecting rod breakage according to the present invention;

[0052] Figure 5 This is the motor rotation angle following curve under different interphase linkage fault conditions according to the present invention;

[0053] Figure 6 These are the electromagnetic output torque curves for different phase-to-phase connecting rod faults according to the present invention;

[0054] Figure 7 This is a physical diagram simulating the fracture fault of the interphase connecting rod of the present invention;

[0055] Figure 8 This is the reference value for the electromagnetic torque in the interphase connecting rod fault of the present invention; Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0057] Traditional fault diagnosis may focus more on directly measurable signals such as current, speed, and position, or indirect signals such as vibration and sound. This invention, through theoretical analysis and model simulation (ADAMS model), discovers that linkage fracture faults cause significant and identifiable differences in electromagnetic torque at different stages of the opening and closing process. Electromagnetic torque directly reflects the torque required for the motor to overcome the load (including abnormal loads caused by linkage failure), thus possessing a natural sensitivity to fractures in such mechanical connections (linkages), and may be more direct and effective in capturing the essence of such faults compared to other signals.

[0058] Secondly, different weights are assigned to the degree of deviation at different stages: for example, stages more sensitive to link breakage (such as near the contact engagement / disengagement point or the load abrupt change point) are given higher weights. This method significantly amplifies the manifestation of faults at critical stages, making the diagnostic results less susceptible to the influence of other relatively normal parts, greatly improving the detection sensitivity of faults (especially early or minor faults) and the ability to distinguish different fault types / severities, thus enhancing the robustness of the system diagnosis. The calculated actual degree of deviation is compared with preset threshold ranges corresponding to different fault types and severity, thereby not only determining whether a fault exists, but also distinguishing the specific type of fault (such as which link breaks) and quantifying the severity of the fault (such as minor cracks, partial fracture, complete fracture).

[0059] Finally, it enables refined fault diagnosis, going beyond a simple "fault / normal" binary judgment, and provides richer information about the nature (type) and severity (degree) of the fault, which is crucial for predictive maintenance and the development of precise repair strategies.

[0060] This invention discloses a fault diagnosis method for connecting rod fracture in the motor operating mechanism of a vacuum circuit breaker. Based on the abnormal characteristics of electromagnetic torque at critical stages of opening and closing (such as contact action points), it adopts stage-weighted deviation analysis technology to overcome the limitations of traditional mean values. By pre-setting a classification threshold library of fault types and severity, it realizes phase-specific location of connecting rod fracture and quantitative diagnosis of crack degree.

[0061] First, motion models of the Adams motor operating mechanism in both healthy and linkage-fractured states are constructed. The load torque and opening / closing stroke curve variations of the operating mechanism under various operating conditions are analyzed. Based on these variations, a linkage fault judgment method is proposed. It is found that the electromagnetic torque of the motor operating mechanism with different degrees of interphase linkage faults exhibits significant differences at different stages of the opening / closing process, and electromagnetic torque can be used as a fault inversion feature. Upper and lower thresholds are set for the deviation of electromagnetic torque from different interphase linkage fracture faults. The deviation between the actual electromagnetic torque and the reference electromagnetic torque value is calculated throughout the entire motion process, and the fault condition is judged based on these values. Finally, to address the issue of data overload caused by averaging deviations, this invention weights the deviations at different stages and determines the fault type by comparing the threshold ranges of different fault types.

[0062] like Figure 1 As shown, the motor control fault detection and handling process adopts a design logic that combines closed-loop iteration and threshold discrimination. The specific execution steps are as follows: After the process starts, the initial configuration of relevant motor control parameters is first completed. After the controller receives the opening and closing command, the motor sensor module collects the operating status information and feeds it back to the main control system. The main control unit first executes the motor control algorithm calculation and simultaneously completes the storage operation of motor current data. Then, it performs a logical judgment on whether the control cycle has ended. If the cycle has not ended, the iterative process of algorithm calculation and data storage is repeated. When the control cycle is completed, the system calculates and outputs the motor electromagnetic torque value. The torque value is then compared with the preset threshold. If the torque does not exceed the threshold range, the process terminates normally. If the torque exceeds the limit, the fault type is identified according to the preset fault discrimination criteria. Finally, the control system outputs the corresponding fault alarm information, and the process ends.

[0063] like Figure 2 As shown, the specific steps are as follows:

[0064] Step 1: Construct motion models of the Adams motor operating mechanism in healthy and linkage fracture states, and analyze the evolution of the load torque of the operating mechanism under three working conditions: normal, single fracture, and full fracture.

[0065] Specifically:

[0066] First, a motion model of the motor operating mechanism is established based on Adams dynamics simulation software, such as... Figure 3 As shown, the evolution of the load torque during the opening motion is analyzed: from positive to negative (driven by spring force after dead point), abruptly to positive (due to self-closing force after the contacts just open), and then decreases to negative (due to the change in transmission ratio assisting in reaching the opening position).

[0067] Specifically, it evolved into:

[0068] The load torque curve of the motor shaft during the opening movement of the motor operating mechanism is shown in Figure 4(a). In the closed holding position, it is subjected to the reaction force of the contact spring with a magnitude of approximately 80 N·m. As the motor rotates, it drives the operating mechanism through the dead point, and the load torque of the motor shaft changes from positive to negative. The spring reaction force changes from resistance to power, pushing the operating mechanism to perform the opening movement.

[0069] When the operating mechanism reaches the position where the contact is just separated, the overtravel phase of the operating mechanism ends, the spring reaction force becomes ineffective, the self-closing force begins to act on the moving contact, the load torque changes abruptly from a negative value to a positive value, approximately 350 N·m, and the operating mechanism begins to drive the moving contact to move.

[0070] During the movement of the moving contact of the operating mechanism, the load torque gradually decreases due to the change in the transmission ratio between the moving parts. Until the operating mechanism passes another dead point, the load torque changes from positive to negative, helping the operating mechanism reach the open position. The operating mechanism is then subjected to a holding force of 22 N·m and remains stationary.

[0071] Step 2: Simulate the effects of interphase connecting rod fracture fault on load torque, motor rotation angle and electromagnetic torque during the evolution process, and use electromagnetic torque as the fault inversion feature.

[0072] Based on the motion model of the operating mechanism, the evolution process is analyzed, such as... Figure 4 As shown, the effect of interphase connecting rod fracture on load torque:

[0073] When a single contact breaks, the load torque is reduced by half to about half of the normal value, and only a single contact can be operated. The torque change is similar to normal but the amplitude is reduced. When a complete contact breaks, the load torque is close to zero, the load force cannot be applied to the motor, the mechanism completely fails and cannot open or close.

[0074] Since the load torque cannot be directly measured by sensors or other measuring instruments during actual opening and closing operations, it is impossible to determine whether the operating mechanism linkage is broken.

[0075] Adams simulation software was used to simulate single-fracture and two-fracture total fracture failures of the interphase connecting rod of the operating mechanism. The load-rotation curves of the connecting rod fracture failure simulation are as follows: Figure 4As shown in (b), due to the breakage of the interphase linkage in the closed holding position, only half the spring reaction force of the normal operating mechanism is transmitted to the drive shaft. This reduces the self-locking capability of the operating mechanism and decreases the load torque that needs to be overcome. As the operating mechanism passes the dead point, the spring reaction force changes from resistance to assistance, again with the assistance being approximately half of the normal value, and the load torque changes from positive to negative. When the operating mechanism completes the overtravel phase, the moving and stationary contacts begin to separate. The self-closing force, in the form of resistance, hinders the opening movement of the mechanism, causing a sudden change in the load torque. Again, due to the breakage of the interphase linkage, the fault torque is only about half of the normal mechanism. During the moving contact movement phase, the load torque gradually decreases with the change in the transmission ratio between the operating mechanisms. When the operating mechanism passes another dead point, the load torque generated by the self-closing force assists the operating mechanism in performing the opening action.

[0076] When both phase-to-phase connecting rods break, neither of the two moving contacts of the operating mechanism can perform the opening operation. Simultaneously, the load torque of the operating mechanism cannot be transmitted to the drive shaft via the transmission chain, resulting in almost no load on the drive shaft. Overall, a complete breakage of the phase-to-phase connecting rods prevents the self-closing force and spring reaction force of the operating mechanism from acting on the motor. Furthermore, the double-broken moving contacts lose their power source, preventing the operating mechanism from completing the opening and closing operations. With a single phase-to-phase connecting rod, only one contact can perform the opening and closing action, and only half the load force of a normal mechanism is applied to the motor.

[0077] Motor rotation angle following curves under different interphase linkage fault conditions are as follows: Figure 5 As shown in the figure, the motor rotation angle curves are approximately the same under different operating conditions. This is due to the effect of the three-loop PID controller. The motor controller outputs different control signals based on the error between the reference angle and the actual angle, thereby causing the motor to output different electromagnetic torques under different fault conditions to correct the motor rotation angle and make the actual motor rotation angle match the reference angle. Therefore, it is not possible to determine whether the mechanism has a fault based on the actual motor rotation angle curve.

[0078] The electromagnetic output torque curves of the motor under different interphase connecting rod fault conditions are as follows: Figure 6 As shown, the electromagnetic torque caused by the phase-to-phase linkage fracture fault varies significantly in each stage of the tripping process (start-up, after dead point, short arc, long arc, and buffer). For example, the short arc torque is high in the normal mechanism and the starting torque is low in the faulty mechanism, which can be used as a fault diagnosis feature.

[0079] As can be seen from the electromagnetic torque curve of the motor output, the electromagnetic torque output of the motor will be different under different fault conditions in order to follow the reference curve. Therefore, the characteristic of electromagnetic torque can be used to invert the fault of the interphase linkage of the motor operating mechanism.

[0080] Specifically:

[0081] During startup, the motor first needs to overcome the spring reaction force. However, due to the failure of the interphase connecting rod, the motor drive shaft experiences less resistance than normal, resulting in a smaller output electromagnetic torque.

[0082] When the operating mechanism passes the dead point, the spring reaction force helps the operating mechanism to open the circuit breaker. The normal operating mechanism outputs a smaller electromagnetic torque than the faulty one.

[0083] When the moving and stationary contacts are just separated, the operating mechanism enters the short arcing stage. At this time, due to the collision, the load torque changes abruptly. The load on the drive shaft of the normal mechanism is twice as much as that of the single-phase linkage failure. The motor of the normal operating mechanism needs a larger electromagnetic torque than that of the failure operating mechanism to reach the speed requirement.

[0084] When the operating mechanism enters the long arcing stage, it needs to slow down to ensure that there is a sufficient longitudinal magnetic field between the contacts. At this time, the self-closing force helps the operating mechanism to decelerate. The self-closing force on the normal operating mechanism is twice that of a single-phase inter-linkage fault, and the required output electromagnetic torque value is smaller.

[0085] During the buffering phase, the electromagnetic torque output under normal and fault conditions gradually decreases, and the mechanism gradually decelerates.

[0086] Step 3: Calculate the electromagnetic torque by collecting three-phase current data using sensors, and calculate the deviation between the actual electromagnetic torque and the reference value at different stages of the entire motion process. ;

[0087] like Figure 7 The diagram shown is a simulated physical image of the phase-to-phase linkage fracture fault of the present invention. After setting the phase-to-phase linkage of the operating mechanism according to single-phase fault and full-phase fault, the opening and closing operations are performed.

[0088] After the mechanism's movement ends, the electromagnetic output torque of the motor can be obtained based on the three-phase stator current collected by the sensors. To meet the displacement requirements of the circuit breaker's moving contacts during different stages of opening and closing, the motor needs to frequently switch between acceleration and deceleration states, and the electromagnetic torque value will also frequently switch between positive and negative values. Thresholds are set for the upper and lower limits of electromagnetic torque deviation in different phase-to-phase linkage fracture faults, such as... Figure 8 As shown, the deviation between the actual electromagnetic torque and the electromagnetic torque reference value is calculated during the entire motion process, and the fault condition is judged based on the value.

[0089] Defining the degree of deviation (Actual torque) Compared with reference value The deviation is used to evaluate the entire motion process. Thresholds are set to distinguish fault types (single fracture, total fracture), based on... The value is used to determine the fault condition. This method can improve the accuracy of circuit breaker fault inversion and enhance equipment reliability.

[0090] Degree of deviation at each stage The calculation formula is:

[0091]

[0092] This represents the actual electromagnetic torque at each stage. This indicates the reference value of the electromagnetic torque at each stage.

[0093] Step 4: Assess the degree of deviation at different stages of the entire movement. Weighting is performed, and the fault type is determined by comparing the threshold ranges of different fault types.

[0094] In existing technology, by setting upper and lower thresholds for the deviation of electromagnetic torque in different phase-to-phase connecting rod fracture faults, the deviation between the actual electromagnetic torque and the reference value during the entire motion process is calculated, and the fault condition is determined based on these values.

[0095] when This indicates that there is no breakage fault in the interphase connecting rod; when This indicates that the connecting rod between single phases has broken; when This indicates a complete breakage of the interphase connecting rod; Indicates the degree of deviation The lower limit of the threshold; Indicates the degree of deviation The upper limit of the threshold;

[0096] The deviation between actual and reference data was selected as the fault characteristic. The average deviation of electromagnetic torque under different fault conditions is shown in Table 1. The table shows that there is overlap between the upper and lower limits of single-phase connecting rod fracture and complete fracture. This is because the load torque caused by the connecting rod fault has different effects on the drive shaft at different operating stages of the motor operating mechanism. During the start-up stage, the operating mechanism does not need to overcome the self-locking force, but only a relatively small spring reaction force. During the buffering stage, the motor needs to decelerate slowly, requiring less acceleration and not a large electromagnetic torque. Therefore, selecting the average deviation as the basis for fault inversion can lead to misjudgment.

[0097] Table 1

[0098]

[0099] To address the issue of data overload caused by averaging deviations, this invention weights the deviation levels for different stages. As can be seen from the motor electromagnetic torque curves under different operating conditions, the fault electromagnetic torque deviates significantly from the normal torque during the short and long arcing stages; therefore, the weights for the short and long arcing stages should be greater.

[0100] The weighted values ​​are selected based on the ratio of electromagnetic torque errors between the fault state and the normal state at different stages. The calculation formula is as follows:

[0101]

[0102] In the formula, For the first Weighted values ​​for each stage, For the first The maximum value of electromagnetic torque error in each stage.

[0103] Through multiple sets of repeated experiments, the weighted values ​​of different stages were averaged, and the final selected weights were: 0.1 for the start-up stage, 0.4 for the short arc burning stage, 0.4 for the long arc burning stage, and 0.1 for the buffer stage.

[0104] Table 2 shows the weighted values ​​of the deviation of the upper and lower limits of electromagnetic torque under different fault conditions:

[0105] Table 2

[0106]

[0107] Therefore, the inversion basis for mechanical failures caused by the breakage of the interphase connecting rod in the motor operating mechanism is as follows:

[0108] when This indicates that there is no breakage fault in the interphase connecting rod; when This indicates that the connecting rod between single phases has broken; when This indicates a complete breakage of the interphase connecting rod;

[0109] The collected electromagnetic torque data is weighted by calculating the degree of deviation, and the fault type is determined by comparing the threshold ranges of different fault types.

[0110] In summary, this invention records the electromagnetic torque of the motor operating mechanism during its tripping motion, sets upper and lower limits for the reference electromagnetic torque of the motor operating mechanism, and detects mechanical faults when the controller detects that the sampled electromagnetic torque exceeds the upper and lower limits of the reference value. Considering the dispersion of the motor operating mechanism's motion, the upper and lower limits are set to fluctuate by 50 N·m above and below the normal electromagnetic output torque of the motor operating mechanism; the deviation between the actual data and the reference data is selected as the fault characteristic, the average deviation of the electromagnetic torque under different fault conditions is calculated, the collected electromagnetic torque data is weighted by calculating the deviation, and the fault type is determined by comparing the threshold ranges of different fault types.

[0111] This method strengthens the feature weights during the arcing period, effectively avoids data interference in non-critical stages, significantly improves the accuracy of single / full fracture fault discrimination, and provides a more reliable intelligent diagnostic solution for circuit breaker mechanism condition monitoring.

[0112] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for diagnosing a fracture failure of a connecting rod of a motor operating mechanism of a vacuum circuit breaker, characterized by, The specific steps are as follows: Step 1: Construct motion models of the Adams motor operating mechanism in healthy and linkage fracture states, and analyze the evolution of the load torque of the operating mechanism under three working conditions: normal, single fracture, and full fracture. First, a motion model of the motor operating mechanism was established based on Adams dynamics simulation software; Then, the evolution of the load torque during the opening motion is analyzed: from positive to negative - i.e., driven by spring force after the dead point, abruptly to positive - i.e., the self-closing force after the contacts just open, and reduced to negative - i.e., the transmission ratio changes to assist in reaching the opening position; Step 2: Simulate the effects of interphase connecting rod fracture fault on load torque, motor rotation angle and electromagnetic torque during the evolution process, and use electromagnetic torque as the fault inversion feature. Step three, through the sensor acquisition three-phase current calculation electromagnetic torque, and calculate the whole movement process in different stages, the actual electromagnetic torque and the deviation degree of electromagnetic torque reference value ; Degree of deviation of each stage The calculation formula is: ； representing the actual electromagnetic torque of each phase, representing the reference value of the electromagnetic torque of each phase; Step four, the deviation degree of different stages in the whole movement process Weighting is performed to determine the fault type by comparing the threshold range of different fault types; The weighted values ​​are selected based on the ratio of electromagnetic torque errors between the fault state and the normal state at different stages. The calculation formula is as follows: ； In the formula, For the first Weighted values ​​for each stage, For the first The maximum value of electromagnetic torque error at each stage; Through multiple sets of repeated experiments, the weighted values ​​at different stages were averaged, and the final selected weights were: The weights assigned to the startup phase are 0.1, the short arc phase is 0.4, the long arc phase is 0.4, and the buffer phase is 0.

1. The collected electromagnetic torque data is weighted by calculating the degree of deviation, and the fault type is determined by comparing the threshold ranges of different fault types. when This indicates that there is no breakage fault in the interphase connecting rod; when This indicates that the connecting rod between single phases has broken; when This indicates a complete breakage of the interphase connecting rod.

2. The method as described in claim 1, characterized in that, In step one, the specific evolution is as follows: When the motor operating mechanism is in the closed holding position, it is subjected to the reaction force of the contact spring. As the motor rotates, it drives the operating mechanism through the dead point. The load torque on the motor shaft changes from positive to negative, and the spring reaction force changes from resistance to power to drive the operating mechanism to perform the opening movement. When the operating mechanism reaches the position where the contact is just separated, the overtravel phase of the operating mechanism ends, the spring reaction force fails, the self-closing force begins to act on the moving contact, the load torque changes abruptly from a negative value to a positive value, and the operating mechanism begins to drive the moving contact to move. During the movement of the moving contact of the operating mechanism, the load torque gradually decreases due to the change in the transmission ratio between the moving parts until the operating mechanism passes another dead point. The load torque changes from positive to negative, helping the operating mechanism reach the open position and remain stationary.

3. The method as described in claim 1, characterized in that, Step two specifically involves: Based on the motion model of the operating mechanism, the impact of interphase link fracture failure on the load torque during the evolution process is analyzed: When a single contact breaks, the load torque is reduced to about half of the normal value, and only a single contact can be operated. The torque change is similar to normal but the amplitude is reduced. When a complete contact breaks, the load torque is close to zero, the load force cannot be applied to the motor, and the operating mechanism completely fails and cannot open or close the circuit. Since the load torque cannot be directly measured by measuring instruments during actual opening and closing operations, it is impossible to determine the fault of the operating mechanism linkage. The effect of interphase connecting rod breakage on motor rotation angle is as follows: the three-closed-loop PID control makes the motor rotation angle curves approximately the same under different fault conditions, making it impossible to directly determine the fault. The phase-to-phase linkage fracture fault shows significant differences in electromagnetic torque at each stage of tripping: startup, after dead point, short arc, long arc and buffer stage, which can be used as a fault diagnosis feature. Specifically: During the startup phase, the motor first needs to overcome the spring reaction force. However, due to the failure of the interphase connecting rod, the motor drive shaft experiences less resistance than normal, resulting in a smaller output electromagnetic torque. When the operating mechanism passes the dead point, the spring reaction force helps the operating mechanism to open the circuit breaker. The normal operating mechanism outputs a smaller electromagnetic torque than the faulty operating mechanism. When the moving and stationary contacts are just separated, the operating mechanism enters the short arc stage. At this time, due to the collision, the load torque changes abruptly. The load on the drive shaft of the normal mechanism is twice as much as that of the single-phase linkage failure. The motor of the normal operating mechanism needs a larger electromagnetic torque than the faulty operating mechanism to meet the speed requirements. When the operating mechanism enters the long arc stage, it needs to slow down to ensure that there is a sufficient longitudinal magnetic field between the contacts. At this time, the self-closing force helps the operating mechanism to decelerate. The self-closing force on the normal operating mechanism is twice that of a single-phase inter-linkage fault, and the required output electromagnetic torque value is smaller. During the buffer phase, the electromagnetic torque output by both normal and faulty components gradually decreases, and the mechanism gradually decelerates. The electromagnetic torque of the motor operating mechanism with different degrees of interphase linkage faults shows obvious differences at different stages of the opening and closing process. Electromagnetic torque can be used as a fault inversion feature.

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