Intelligent inspection and maintenance method and system suitable for ultra-high voltage fast circuit breaker

Abstract

This application relates to the field of circuit breaker technology, specifically to an intelligent inspection and maintenance method and system applicable to ultra-high voltage fast circuit breakers. The method includes: acquiring the coil current waveform and the three-phase current transient waveform at the moment of fault clearing for each operational event of the circuit breaker under test within each evaluation cycle, as well as the SF6 gas pressure at each moment within the evaluation cycle; obtaining the performance degradation degree for each operational event; screening out abnormal events within the evaluation cycle; obtaining the mechanical degradation degree characterizing the decline in mechanical performance; calculating the insulation leakage degree characterizing the degradation in insulation sealing performance; calculating the contact erosion degree characterizing the loss of contact electrical life; and using a pre-constructed hidden Markov model to deduce the health status of the circuit breaker under test, thereby generating targeted inspection and maintenance strategies. This application improves the predictability and accuracy of ultra-high voltage fast circuit breaker operation and maintenance, thereby ensuring the long-term safe and stable operation of the ultra-high voltage transmission network.

Description

Technical Field

[0001] This application relates to the field of circuit breaker technology, specifically to an intelligent inspection and maintenance method and system applicable to ultra-high voltage fast circuit breakers. Background Technology

[0002] Ultra-high voltage fast circuit breakers are crucial control and protection devices in high-voltage power grids. Their main functions are to close and interrupt load currents during normal grid operation and to quickly disconnect fault currents when short-circuit faults occur, ensuring the safe and stable operation of the power system. During long-term service and frequent operation, irreversible physical degradation of their internal components is inevitable.

[0003] Since circuit breaker failures are often the result of multi-physical field coupling evolution, for example, mechanical jamming of the operating mechanism not only leads to increased action delay, but the abnormal vibrations it causes can also disrupt the balance of the gas chamber flange, causing instantaneous leakage of SF6 gas. Slower action further prolongs the arc burning time, exacerbating the physical wear of the main contacts. However, current inspection and maintenance of ultra-high voltage circuit breakers mainly rely on traditional periodic maintenance or passive response modes based on single-dimensional threshold over-limit alarms. Periodic maintenance cannot reflect the dynamic degradation trend of equipment under actual complex operating conditions, which may lead to over-maintenance or neglect. Threshold over-limit alarm modes cannot capture the gradual process in the early stages of degradation, lack the ability to predict the development trend of faults, and cannot quantify the deep coupling and causal relationship between the three dimensions of mechanics, insulation, and contacts, making it difficult to formulate scientific and accurate predictive inspection and maintenance strategies. Summary of the Invention

[0004] To address the aforementioned technical issues, an intelligent inspection and maintenance method and system suitable for ultra-high voltage fast circuit breakers are provided to resolve existing problems.

[0005] The solution to the technical problem presented in this application is to provide an intelligent inspection and maintenance method and system applicable to ultra-high voltage fast circuit breakers, including the following steps: In a first aspect, embodiments of this application provide an intelligent inspection and maintenance method applicable to ultra-high voltage fast circuit breakers, the method comprising the following steps: The coil current waveform and the three-phase current transient waveform at the moment of fault clearing of the circuit breaker under test are obtained for each operating event in each evaluation cycle, as well as the SF6 gas pressure at each moment in the evaluation cycle; wherein, a complete closing and opening operation process is defined as an operating event. For each operation event, the waveform characteristic deviation of the coil current waveform is evaluated to characterize the mechanical degradation of a single operation, and the execution degradation degree of each operation event is obtained; abnormal events are screened out from the evaluation period; by the trend and average level of the execution degradation degree under each evaluation period, the mechanical degradation degree characterizing the degradation of mechanical execution performance is obtained. The overall decay characteristics of SF6 gas pressure during each assessment period were evaluated, as well as the difference between SF6 gas pressure and normal level after an abnormal event occurred. The insulation leakage degree, which characterizes the degradation of insulation sealing performance, was calculated. The arc energy accumulation effect is evaluated by measuring the transient waveforms of the three-phase current at the moment of fault cut-off under all operating events in each evaluation cycle, and the contact ablation degree, which characterizes the loss of contact electrical life, is calculated. Based on mechanical degradation, insulation leakage, and contact erosion, a pre-built hidden Markov model is used to deduce the health status of the circuit breaker under test, so as to generate targeted inspection and maintenance strategies.

[0006] Preferably, obtaining the execution degradation degree of each operation event includes: Obtain the reference coil current waveform of the circuit breaker in the non-degraded state when it performs closing and opening operations; for each operation event of the circuit breaker under test, analyze the degree to which the coil current waveform deviates from the reference coil current waveform, and calculate the current deviation for each operation event; Obtain the troughs in the coil current waveform, select the trough corresponding to the minimum trough value, and define it as the effective trough; analyze the degree of shift of the effective trough of the coil current waveform relative to the reference coil current waveform, and calculate the execution delay of each operation event; The degree of performance degradation for each operation event is positively correlated with the current deviation and the execution delay.

[0007] Preferably, the calculation process for the current deviation is as follows: The coil current waveform includes the opening coil current waveform and the closing coil current waveform; the reference coil current waveform includes the reference opening coil current waveform and the reference closing coil current waveform. For each operation event of the circuit breaker under test, the difference between the trip coil current waveform and the reference trip coil current waveform is calculated as the trip current deviation, and the difference between the closing coil current waveform and the reference closing coil current waveform is calculated as the closing current deviation. The maximum value of the trip current deviation and the closing current deviation is selected as the current deviation for each operation event.

[0008] Preferably, the calculation process for the execution delay is as follows: the interval between the start time of the coil current waveform and the corresponding time of the effective trough is counted as a proportion of the total duration of the entire coil current waveform, which is taken as a relative proportion; for each operation event, the difference between the relative proportions of the opening coil current waveform and the reference opening coil current waveform is taken as the opening shift value; the difference between the relative proportions of the closing coil current waveform and the reference closing coil current waveform is taken as the closing shift value; the maximum value between the opening shift value and the closing shift value is selected as the execution delay for each operation event.

[0009] Preferably, the step of filtering out abnormal events from the evaluation period includes: selecting operation events in each evaluation period where the current deviation is greater than a preset first threshold and the execution delay is greater than a preset second threshold, and defining them as abnormal events.

[0010] Preferably, the calculation process of the mechanical degradation degree is as follows: linearly fitting the performance degradation degree of all operating events of the circuit breaker under test in each evaluation period, calculating the slope of the fitted line as the degradation change rate; calculating the average value of all performance degradation degrees of the circuit breaker under test in each evaluation period; the mechanical degradation degree is positively correlated with the average value and the degradation change rate.

[0011] Preferably, the calculation process for the insulation leakage degree is as follows: For each evaluation period, the SF6 gas pressure at each moment is converted to the equivalent pressure value at standard temperature. Curve fitting is performed on the equivalent pressure values ​​at all moments, and the mean of the slope of the tangent line of the fitted curve at all moments is calculated. This is then negatively mapped to the curve as the pressure decay rate. The time within a preset time window following an abnormal event is defined as an abnormal time; the time in each assessment period other than the abnormal time is defined as a normal time; the difference between the mean of the equivalent pressure values ​​of all abnormal times in each assessment period and the mean of the equivalent pressure values ​​of all normal times is calculated as the relative difference. The insulation leakage degree is positively correlated with the relative difference and the pressure attenuation rate.

[0012] Preferably, the calculation process for the contact erosion degree is as follows: for each operation event, extract the mean value of the effective current of the three-phase current transient waveform at the moment of fault clearing, and calculate the energy loss value of each operation event according to the empirical formula for electrical wear; obtain the rated arc energy that the circuit breaker contacts can withstand; calculate the sum of the energy loss values ​​of all operation events in each evaluation period, and use the ratio of this sum to the rated arc energy as the contact erosion degree of the circuit breaker under test in each evaluation period.

[0013] Preferably, the deduction of the health status of the circuit breaker under test includes: forming an observation vector from the mechanical degradation degree, insulation leakage degree, and contact erosion degree of the circuit breaker under test in each evaluation cycle; splicing the observation vectors of the circuit breaker under test in multiple consecutive evaluation cycles to form a multi-dimensional time-series observation sequence, and inputting it into a pre-constructed hidden Markov model to deduce the health status of the circuit breaker under test.

[0014] Secondly, embodiments of this application also provide an intelligent inspection and maintenance system suitable for ultra-high voltage fast circuit breakers, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it implements the steps of any of the above-described intelligent inspection and maintenance methods for ultra-high voltage fast circuit breakers.

[0015] This application has at least the following beneficial effects: This application, by deeply analyzing the morphological deviations and timing characteristics of coil current waveforms, reflects the microscopic anomalies of a single operation, accurately capturing the minute mechanical jamming phenomenon in the initial stage of core startup. Furthermore, by combining the static absolute degradation depth reflected by the average performance degradation degree within the evaluation period and the dynamic deterioration rate reflected by the changing trend, it obtains the mechanical degradation degree characterizing the decline in mechanical performance. This reflects both the current degree of degradation and captures the accelerating trend of degradation, effectively filtering out random errors from single operations and accurately quantifying the degree of decline in mechanical performance effectiveness caused by transmission link fatigue or lubrication drying. The application also calculates the insulation leakage degree characterizing insulation sealing performance degradation. Its beneficial effect lies in innovatively decoupling two different physical mechanisms of insulation gas leakage, examining both long-term slow leakage caused by natural aging and, by extracting the pressure step drop after a mechanical anomaly, accurately capturing the transient leakage caused by mechanical anomaly vibration disrupting the dynamic seal balance. Finally, the application calculates the contact ablation degree characterizing contact electrical life loss. Its beneficial effects lie in extracting the cumulative effect of arcing energy represented by the actual interrupting current of each action, rather than simply counting the number of actions. This allows for a fair and scientific quantification of the severe losses from interrupting huge short-circuit currents and the slight wear from interrupting small load currents, accurately reflecting the actual damage to the contacts from each interruption. Based on mechanical degradation, insulation leakage, and contact erosion, a pre-built Hidden Markov Model is used to deduce the health status of the circuit breaker under test, generating targeted inspection and maintenance strategies. Its beneficial effects lie in the comprehensive evaluation from multiple dimensions such as mechanical jamming, insulation leakage, and contact erosion. By utilizing the time-series modeling capability of the Hidden Markov Model, the temporal correlation of the degradation process is fully explored, enabling the identification of early stages and transition trends of degradation. This achieves a shift from "blind periodic maintenance" to "lean condition maintenance," reducing maintenance costs and significantly improving the predictability and accuracy of ultra-high voltage fast circuit breaker operation and maintenance, thereby ensuring the long-term safe and stable operation of the ultra-high voltage transmission network. Attached Figure Description

[0016] The intelligent inspection and maintenance method applicable to ultra-high voltage fast circuit breakers of this application will be further described in detail below with reference to the accompanying drawings.

[0017] Figure 1 A flowchart illustrating the steps of an intelligent inspection and maintenance method for ultra-high voltage fast circuit breakers provided in this application embodiment; Figure 2 A flowchart illustrating the steps of the method for obtaining insulation leakage degree provided in this application embodiment. Detailed Implementation

[0018] The following, in conjunction with the accompanying drawings and implementation examples, provides a more detailed description of the intelligent inspection and maintenance method and system for ultra-high voltage fast circuit breakers proposed in this application.

[0019] Please see Figure 1 The document illustrates a flowchart of a method for intelligent inspection and maintenance of ultra-high voltage fast circuit breakers according to an embodiment of this application. The method includes the following steps: Step 1: Obtain the coil current waveform and the three-phase current transient waveform at the moment of fault clearing for each operating event of the circuit breaker under test in each evaluation cycle, as well as the SF6 gas pressure at each moment in the evaluation cycle.

[0020] Circuit breakers are critical devices in power systems, responsible for fault isolation and operation mode switching. Their operational reliability directly affects the safety and stability of the power grid. Over long periods of operation and with frequent use, circuit breakers gradually degrade. If this degradation is not detected and addressed in a timely manner, it can lead to circuit breaker failure to operate or insulation breakdown, potentially causing widespread power outages.

[0021] When the circuit breaker under test performs a closing / opening operation, the complete operation process of the circuit breaker under test performing the closing / opening operation is defined as an operation event; The continuous multiple operation events of the circuit breaker under test are taken as an evaluation cycle; the waveform recording file of the circuit breaker under test for each operation event is captured from the fault recorder; the opening coil current waveform, closing coil current waveform, and three-phase current transient waveform at the moment of fault clearing are analyzed from the waveform recording file for this operation event. It should be noted that the arc current waveform at the moment of fault clearing refers to the actual current waveform flowing through the contact gap of the arc extinguishing chamber from the moment the circuit breaker contacts just opened until the moment the arc was completely extinguished. This waveform is directly extracted from the fault recording file and reflects the current characteristics during the arc combustion process.

[0022] The SF6 gas pressure of the circuit breaker under test is obtained in real time at different times during each evaluation cycle using an online SF6 gas pressure monitoring device. In this embodiment, a single evaluation cycle includes the duration of 10 consecutive operation events of the circuit breaker under test, and the sampling frequency of SF6 gas pressure is 10Hz. As other implementation methods, implementers can set them according to actual conditions.

[0023] Thus, the circuit breaker under test obtains the opening coil current waveform, closing coil current waveform, and three-phase current transient waveform at the moment of fault clearing for each operating event in each evaluation cycle, as well as the SF6 gas pressure at different times in each evaluation cycle.

[0024] Step 2: For the coil current waveform of each operation event, evaluate its waveform characteristic deviation to characterize the mechanical degradation of a single operation and obtain the execution degradation degree of each operation event; and screen out abnormal events from the evaluation period; and obtain the mechanical degradation degree characterizing the degradation of mechanical execution performance by the changing trend and average level of the execution degradation degree under each evaluation period.

[0025] Ultra-high voltage fast circuit breakers face three typical degradation processes during long-term operation: First, mechanical actuation degradation, where aging of the operating mechanism can lead to spring fatigue or grease drying at the transmission linkage, increasing the resistance of the iron core movement. This manifests as delayed opening / closing actions, and in severe cases, may result in interruption failure. Second, insulation sealing degradation, where dynamic sealing structures such as the circuit breaker's tie rods can be subject to long-term mechanical impacts that may cause loosening of the sealing flanges or wear of the dynamic sealing rings, disrupting the sealing balance of the gas chamber and causing SF6 insulation gas leakage, thus reducing insulation performance. Third, contact electrical wear degradation, where each interruption of fault current causes the arc to erode the contacts of the arc-extinguishing chamber, and the degree of erosion is closely related to the magnitude of the interrupting current and the arc burning time. The erosion caused by a single large-current interruption may be equivalent to hundreds of normal operations. These three degradation processes are interconnected and mutually causal.

[0026] Based on the above analysis, regarding the degradation of mechanical actuation, the deviation of the opening / closing coil current waveform is analyzed, and the current deviation for each operating event is calculated, specifically: Obtain the reference tripping coil current waveform and the reference closing coil current waveform when the circuit breaker in the non-degraded state performs closing and tripping operations; It should be noted that after the circuit breaker is assembled and debugged at the factory, before its first commissioning, under rated conditions, five consecutive closing operations and five consecutive opening operations are performed. The coil current waveform of each operation is collected, and the average current at the same sampling point under multiple closing operations is calculated as the reference closing current waveform. The average current at the same sampling point under multiple closing and opening operations is calculated as the reference opening current waveform. As for other implementation methods, the implementer can set them according to the actual situation. When the circuit breaker is first commissioned, all transmission components are brand new and in the best lubrication condition, and are naturally regarded as being in an undegraded state.

[0027] The difference between the trip coil current waveform of the circuit breaker under test and the reference trip coil current waveform in each operating event is calculated as the trip current deviation. The difference between the closing coil current waveform of the circuit breaker under test and the reference closing coil current waveform in each operating event is calculated as the closing current deviation. In this embodiment, the DTW distance between the trip coil current waveform of the circuit breaker under test and the reference trip coil current waveform in each operating event is calculated as the trip current deviation; the DTW distance between the closing coil current waveform of the circuit breaker under test and the reference closing coil current waveform in each operating event is calculated as the closing current deviation; wherein, the calculation of the DTW distance is a known technique and will not be described in detail here.

[0028] The maximum value between the opening current deviation and the closing current deviation is selected as the current deviation for each operation event; It should be noted that the greater the deviation of the opening current or closing current, the more significant the difference between the opening / closing coil current waveform and the undegraded state in terms of current amplitude, transient pulses at the opening positions of each stage of the iron core, and the shape of the back EMF peaks / troughs; the greater the current deviation, the more the mechanical performance of the opening and closing deviates from the undegraded state in this operation event.

[0029] Secondly, during the operation of the circuit breaker, a significant back electromotive force (EMF) dip occurs in the current waveform as the closing / opening action progresses. With equipment aging, the grease in the circuit breaker's transmission linkage dries out or the springs fatigue, leading to increased resistance to core movement. This is reflected in the waveform as a shift in the dip point along the time axis, or a change in the current peak value. Therefore, analyzing the shift of the dip in the opening / closing coil current waveform and calculating the execution delay is crucial. Obtain the valleys in the coil current waveform, and select the valley corresponding to the minimum valley value as the effective valley; In this embodiment, the AMPD (Automatic multiscale-based peak detection) algorithm is used to obtain the valleys. The AMPD algorithm is a well-known technology and will not be described in detail here.

[0030] The relative proportion is the time interval between the start time of the coil current waveform and the corresponding time of the effective trough, which is the proportion of the total duration of the entire coil current waveform. For each operation event, the difference in the relative proportion between the trip coil current waveform and the reference trip coil current waveform is used as the trip shift value; the difference in the relative proportion between the closing coil current waveform and the reference closing coil current waveform is used as the closing shift value. In this embodiment, for each operation event, the difference between the relative proportions of the trip coil current waveform and the reference trip coil current waveform is used as the trip shift value; the difference between the relative proportions of the closing coil current waveform and the reference closing coil current waveform is used as the closing shift value. It should be noted that when the difference is less than 0, the trip shift value or the closing shift value is set to 0.

[0031] The maximum value between the tripping and closing shift values ​​is used as the execution delay for each operation event. It should be noted that a larger relative proportion indicates a later effective trough, a longer core movement time, and greater mechanical resistance. Consequently, a larger value indicates a larger post-opening or post-closing shift, representing the degree of deviation of the proportion of time taken for the core to start and move to the back EMF trough point during a single opening or closing operation relative to the undegraded state. A larger execution delay indicates a more significant mechanical execution delay in this operation, greater core movement resistance, and more severe mechanical degradation.

[0032] Furthermore, the degree of performance degradation is determined using the current deviation and execution delay, specifically as follows: The degree of performance degradation for each operation event is positively correlated with the current deviation and the execution delay. It should be noted that a positive correlation means that the dependent variable increases as the independent variable increases and decreases as the independent variable decreases.

[0033] In this embodiment, the maximum-minimum normalization method is used to normalize the current deviation of all operation events. The sum of the normalized current deviation and the execution delay is used as the execution degradation degree. The maximum-minimum normalization method is a well-known technique and will not be described in detail here.

[0034] It should be noted that the greater the degree of performance degradation, the more severe the decline in the mechanical performance effectiveness of the operation event, that is, the circuit breaker operating mechanism has obvious mechanical degradation problems such as spring fatigue, grease drying, or increased iron core movement resistance.

[0035] Furthermore, the changing trend of the performance degradation degree of the circuit breaker under test in each evaluation period is analyzed, and the mechanical degradation degree is calculated, specifically: Linear fitting is performed on the performance degradation of all operational events of the circuit breaker under test in each evaluation period, and the slope of the fitted line is calculated as the degradation rate. In this embodiment, the least squares method is used for linear fitting. The least squares method is a well-known technique and will not be described in detail here.

[0036] Calculate the average value of all performance degradation of the circuit breaker under test in each evaluation period; The mechanical degradation degree of the circuit breaker under test in each evaluation period is positively correlated with the average value and the rate of degradation change. In this embodiment, the maximum-minimum normalization method is used to normalize the degradation rate of multiple consecutive evaluation periods. The sum of the average value and the normalized degradation rate is taken as the mechanical degradation degree. The maximum-minimum normalization method is a well-known technique and will not be described in detail here. It should be noted that since mechanical degradation is an irreversible process, the degradation degree should not decrease with the number of operations. Therefore, if the degradation rate is negative, it indicates a violation of physical laws, and the degradation rate is forcibly assigned a value of 0.

[0037] It should be noted that the greater the rate of decay change, the faster the mechanical degradation of the ultra-high voltage fast circuit breaker under test. That is, with the increase of the number of operations, the mechanical performance deteriorates at an accelerated rate, and the remaining life of the equipment is shortened at a faster rate. The greater the degree of mechanical degradation, the more severe the degradation caused by mechanical jamming of the circuit breaker. At the same time, the faster the degradation rate, the worse the overall health of the equipment, and the closer it is to failure.

[0038] Thus, the mechanical degradation degree of the circuit breaker under test in each evaluation period is obtained.

[0039] Step 3: Evaluate the overall decay characteristics of SF6 gas pressure within each evaluation period, as well as the difference between SF6 gas pressure and normal level after an abnormal event, and calculate the insulation leakage degree that characterizes the degradation of insulation sealing performance.

[0040] Furthermore, the ultra-high voltage fast circuit breaker is a complex electromechanical-hydraulic coupling system. If the ultra-high voltage fast circuit breaker deteriorates more severely due to mechanical jamming, the distribution of mechanical impact force during opening and closing operations will become unbalanced, resulting in strong abnormal vibrations. The circuit breaker's tie rod and other parts have dynamic sealing structures. Long-term abnormal mechanical impacts can cause the sealing flange to loosen or the dynamic sealing ring to wear, thereby breaking the sealing balance of the gas chamber and causing SF6 insulating gas leakage.

[0041] First, based on the above analysis, abnormal events were selected from each evaluation period, specifically: Operation events in each evaluation period where the current deviation is greater than a preset first threshold and the execution delay is greater than a preset second threshold are defined as abnormal events. It should be noted that when the circuit breaker of this model is in a non-degraded state, the current waveforms of the opening and closing coils of 50 operation events are collected to form a historical dataset. The current deviation of each operation event in the historical dataset is calculated, and the 95th percentile of the current deviation of all operation events in the historical dataset is used as a preset first threshold. Correspondingly, the opening delay value and closing delay value of each operation event in the historical dataset are calculated, and the 95th percentile of the execution delay of all operation events in the historical dataset is used as a preset second threshold. As other implementation methods, the implementer can set them according to the actual situation. The two thresholds are calculated in the non-degraded state and represent the reasonable fluctuation range of the circuit breaker of this model under normal operating conditions. When the current deviation of the circuit breaker under test exceeds the first threshold and the execution delay exceeds the second threshold, it indicates that the mechanical performance of the operation event has significantly deviated from the normal level in the non-degraded state and should be judged as an abnormal event.

[0042] It should be noted that when the current deviation is greater than the preset first threshold, it indicates that the difference between the closing / opening coil current waveform of the circuit breaker and the reference exceeds the limit under this operation event; and when the execution delay is greater than the preset second threshold, it indicates that the degree of backward shift of the closing / opening valley point of the circuit breaker exceeds the limit under this operation event; then the closing / opening action of the circuit breaker under this operation event is abnormal.

[0043] Secondly, the temporal decay characteristics of SF6 gas pressure throughout the entire evaluation period and the pressure difference before and after the abnormal event are analyzed to calculate the insulation leakage rate. The flowchart of the method for obtaining the insulation leakage rate provided in this application embodiment is shown below. Figure 2 As shown, it specifically includes: The SF6 gas pressure at all times during each assessment period is converted to the equivalent pressure value at standard temperature; In this embodiment, the pressure-temperature conversion is performed using the Beattie-Bridgman empirical formula based on the ambient temperature at each moment of SF6 gas pressure collection within each evaluation period. The Beattie-Bridgman empirical formula is a well-known technique and will not be described in detail here.

[0044] The equivalent pressure values ​​at all times within each evaluation period are curve-fitted, and the mean slope of the tangent line of the fitted curve at all times is calculated and negatively mapped to it as the pressure decay rate. In this embodiment, the least squares method is used for curve fitting. The least squares method and the calculation of the tangent slope are well-known techniques and will not be described in detail here. Secondly, the specific process of negative mapping is as follows: the negative of the mean of the tangent slope of the fitted curve at all times is taken as the pressure attenuation rate. When the negative of the mean is negative, the pressure attenuation rate is set to 0. A pressure attenuation rate of 0 indicates that the mean of the tangent slope is on an upward trend or a horizontal trend, reflecting that there is no leakage of insulating gas. If the pressure attenuation rate is greater than 0, it indicates that the mean of the tangent slope is on a downward trend, reflecting that there is leakage of insulating gas.

[0045] For each evaluation cycle, the time within a preset time window after an abnormal event is defined as the abnormal time; and the remaining time in each evaluation cycle, excluding the abnormal time, is defined as the normal time. In this embodiment, the preset time window duration is 1 hour. As for other implementation methods, the implementer can set it according to the actual situation.

[0046] The difference between the mean of the equivalent pressure values ​​at all abnormal times within each assessment period and the mean of the equivalent pressure values ​​at all normal times is taken as the relative difference. In this embodiment, the absolute value of the difference between the mean of the equivalent pressure values ​​at all abnormal times within each evaluation period and the mean of the equivalent pressure values ​​at all normal times is calculated, and the ratio of this difference to the mean of the equivalent pressure values ​​at all normal times is used as the relative difference.

[0047] The insulation leakage degree, relative difference, and pressure attenuation rate of the circuit breaker under test were all positively correlated in each evaluation period. In this embodiment, the pressure attenuation rate of multiple evaluation cycles is normalized using the maximum-minimum normalization method, and the sum of this normalization and the relative difference is taken as the insulation leakage degree.

[0048] If all operational events within each evaluation period are not abnormal events, the relative difference is assigned a value of 0; if all operational events within each evaluation period are abnormal events, the value of the circuit breaker model at the time of manufacture is used. The rated SF6 gas pressure at standard temperature is used as the equivalent pressure value at normal times; the absolute value of the difference between the mean of the equivalent pressure values ​​at all abnormal times in each evaluation period and the rated SF6 gas pressure is calculated, and the ratio of this to the rated SF6 gas pressure is used as the relative difference.

[0049] It should be noted that the greater the pressure decay rate, the faster the pressure drops, reflecting the aging and leakage of the circuit breaker's sealing rings; the greater the relative difference, the significantly lower the pressure at abnormal times compared to normal times, and the greater the impact of the circuit breaker's operational degradation on insulation gas leakage, reflecting that the sealing structure has been severely damaged and that mechanical impact has a very significant impact on sealing performance; the greater the insulation leakage, the more severe the insulation leakage.

[0050] Thus, the insulation leakage of the circuit breaker under test in each evaluation period is obtained.

[0051] Step 4: Evaluate the arc energy accumulation effect by analyzing the transient waveforms of the three-phase current at the moment of fault disconnection under all operational events in each evaluation cycle, and calculate the contact erosion degree, which characterizes the loss of contact electrical life. Based on the mechanical degradation degree, insulation leakage degree, and contact erosion degree, use a pre-built hidden Markov model to deduce the health status of the circuit breaker under test, so as to generate targeted inspection and maintenance strategies.

[0052] Furthermore, the degree of electrical wear of the arc-extinguishing chamber contacts of an ultra-high voltage fast circuit breaker depends not only on the number of operating operations, but also on the magnitude of the current interrupted during each operation and the duration of arc burning. For example, the contact erosion caused by interrupting a 50kA short-circuit current may be hundreds or thousands of times greater than that caused by interrupting a normal load current. Therefore, based on the transient waveform of the three-phase current at the moment of fault interruption, the arc burning situation characterized by the interrupting current during the circuit breaker's opening and closing process is analyzed, and the contact erosion degree is calculated, specifically as follows: For each operation event, the mean value of the effective current of the three-phase current transient waveform at the moment of fault clearing is extracted, and the energy loss value of each operation event is calculated based on the empirical formula of electrical wear. It should be noted that the effective value of current and the empirical formula for electrical wear are well-known technologies and will not be elaborated here.

[0053] Obtain the rated arc energy that the circuit breaker contacts can withstand; In this embodiment, the number of permissible breaking times under the rated breaking current is found in the circuit breaker's operation manual. A manual short-circuit breaking test is performed on the circuit breaker, and the arc energy is recorded. The product of the arc energy measured in the test and the number of permissible breaking times is taken as the rated arc energy. The acquisition of the rated arc energy is a well-known technique and will not be described in detail here.

[0054] Calculate the sum of energy loss values ​​for all operating events within each evaluation period, and use the ratio of this sum to the rated arc energy as the contact erosion degree of the circuit breaker under test in each evaluation period. It should be noted that the larger the energy loss value, the larger the current cut off and the longer the arcing time, resulting in greater damage to the contacts; the larger the contact erosion degree, the more severe the contact erosion of the circuit breaker under test and the shorter the remaining electrical life.

[0055] Furthermore, the physical degradation process of ultra-high voltage fast circuit breakers is a continuous but unobservable "latent process." The mechanical degradation, insulation leakage, and contact erosion rates calculated from the three dimensions of mechanical jamming, insulation leakage, and contact erosion are the explicit observed values ​​of this latent process in external multi-physics fields. Therefore, this embodiment uses a hidden Markov model to probabilistically extrapolate this time-dependent latent degradation to assess the state of the circuit breaker under test, specifically: The mechanical degradation, insulation leakage, and contact erosion of the circuit breaker under test in each evaluation period are used to form an observation vector. The observation vectors of the circuit breaker under test in multiple consecutive evaluation periods are spliced ​​together to form a multi-dimensional time series observation sequence, which is then input into a pre-built hidden Markov model to deduce the health status of the circuit breaker under test. In this embodiment, the observation vectors of the circuit breaker under test in five consecutive evaluation cycles are spliced ​​together to form a multi-dimensional time-series observation sequence. As another implementation method, the implementer can set it according to the actual situation.

[0056] Hidden Markov Models (HMMs) are a well-known technique and will not be elaborated upon here. Secondly, the training process for HMMs is as follows: The health status of circuit breakers is divided into four implicit states: no degradation, slight degradation, moderate degradation, and critical risk. Collect historical data of multiple circuit breakers of the same model throughout their entire lifecycle, including a complete data sequence from commissioning to decommissioning. For each circuit breaker, record an observation vector and its corresponding health status label at each evaluation period. Based on this, use the Baum-Welch algorithm to iteratively update the model parameters until convergence, and output the parameters of the trained Hidden Markov Model. The Baum-Welch algorithm is a well-known technique and will not be elaborated upon here.

[0057] Based on the deduced health status, corresponding inspection and maintenance strategies are formulated, specifically as follows: When the deduced health status is no degradation, continue routine online monitoring without manual intervention; when the deduced health status is slightly degraded, increase the monitoring frequency; when the deduced health status is moderately degraded, it is recommended to arrange planned power outages for maintenance; when the deduced health status is at critical risk, it is recommended to immediately apply for an emergency power outage, and carry out forced isolation and disassembly overhaul of the circuit breaker or complete replacement of the arc-extinguishing chamber, etc.

[0058] Based on the same inventive concept as the above methods, this application also provides an intelligent inspection and maintenance system suitable for ultra-high voltage fast circuit breakers, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it implements the steps of any one of the above-described intelligent inspection and maintenance methods suitable for ultra-high voltage fast circuit breakers.

Claims

1. An intelligent inspection and maintenance method applicable to ultra-high voltage fast circuit breakers, characterized in that, The method includes the following steps: The coil current waveform and the three-phase current transient waveform at the moment of fault clearing of the circuit breaker under test are obtained for each operating event in each evaluation cycle, as well as the SF6 gas pressure at each moment in the evaluation cycle; wherein, a complete closing and opening operation process is defined as an operating event. For each operation event, the waveform characteristic deviation of the coil current waveform is evaluated to characterize the mechanical degradation of a single operation, and the execution degradation degree of each operation event is obtained; abnormal events are screened out from the evaluation period; by the trend and average level of the execution degradation degree under each evaluation period, the mechanical degradation degree characterizing the degradation of mechanical execution performance is obtained. The overall decay characteristics of SF6 gas pressure during each assessment period were evaluated, as well as the difference between SF6 gas pressure and normal level after an abnormal event occurred. The insulation leakage degree, which characterizes the degradation of insulation sealing performance, was calculated. The arc energy accumulation effect is evaluated by measuring the transient waveforms of the three-phase current at the moment of fault cut-off under all operating events in each evaluation cycle, and the contact ablation degree, which characterizes the loss of contact electrical life, is calculated. Based on mechanical degradation, insulation leakage, and contact erosion, a pre-built hidden Markov model is used to deduce the health status of the circuit breaker under test, so as to generate targeted inspection and maintenance strategies.

2. The intelligent inspection and maintenance method for ultra-high voltage fast circuit breakers as described in claim 1, characterized in that, The process of obtaining the execution degradation degree for each operation event includes: Obtain the reference coil current waveform of the circuit breaker in the non-degraded state when it performs closing and opening operations; for each operation event of the circuit breaker under test, analyze the degree to which the coil current waveform deviates from the reference coil current waveform, and calculate the current deviation for each operation event; Obtain the troughs in the coil current waveform, select the trough corresponding to the minimum trough value, and define it as the effective trough; analyze the degree of shift of the effective trough of the coil current waveform relative to the reference coil current waveform, and calculate the execution delay of each operation event; The degree of performance degradation for each operation event is positively correlated with the current deviation and the execution delay.

3. The intelligent inspection and maintenance method for ultra-high voltage fast circuit breakers as described in claim 2, characterized in that, The calculation process for the current deviation is as follows: The coil current waveform includes the opening coil current waveform and the closing coil current waveform; the reference coil current waveform includes the reference opening coil current waveform and the reference closing coil current waveform. For each operation event of the circuit breaker under test, the difference between the trip coil current waveform and the reference trip coil current waveform is calculated as the trip current deviation, and the difference between the closing coil current waveform and the reference closing coil current waveform is calculated as the closing current deviation. The maximum value between the opening current deviation and the closing current deviation is selected as the current deviation for each operation event.

4. The intelligent inspection and maintenance method for ultra-high voltage fast circuit breakers as described in claim 3, characterized in that, The calculation process for the execution delay is as follows: the interval between the start time of the coil current waveform and the corresponding time of the effective trough is used as the proportion of the total duration of the entire coil current waveform, and this proportion is used as the relative proportion; for each operation event, the difference between the relative proportion of the trip coil current waveform and the reference trip coil current waveform is used as the trip shift value; the difference between the relative proportion of the closing coil current waveform and the reference closing coil current waveform is used as the closing shift value. The maximum value between the opening and closing shift values ​​is selected as the execution delay for each operation event.

5. The intelligent inspection and maintenance method for ultra-high voltage fast circuit breakers as described in claim 4, characterized in that, The step of filtering out abnormal events within the evaluation period includes: selecting operation events in each evaluation period where the current deviation is greater than a preset first threshold and the execution delay is greater than a preset second threshold, and defining them as abnormal events.

6. The intelligent inspection and maintenance method for ultra-high voltage fast circuit breakers as described in claim 1, characterized in that, The calculation process of the mechanical degradation degree is as follows: linearly fit the performance degradation degree of all operating events of the circuit breaker under test in each evaluation period, calculate the slope of the fitted line as the degradation change rate. Calculate the average value of all performance degradation of the circuit breaker under test in each evaluation period; the mechanical degradation is positively correlated with the average value and the rate of decay change.

7. The intelligent inspection and maintenance method for ultra-high voltage fast circuit breakers as described in claim 1, characterized in that, The calculation process for the insulation leakage is as follows: For each evaluation period, the SF6 gas pressure at each moment is converted to the equivalent pressure value at standard temperature. Curve fitting is performed on the equivalent pressure values ​​at all moments, and the mean of the slope of the tangent line of the fitted curve at all moments is calculated. This is then negatively mapped to the curve as the pressure decay rate. The time within a preset time window following an abnormal event is defined as an abnormal time; the time in each assessment period other than the abnormal time is defined as a normal time; the difference between the mean of the equivalent pressure values ​​of all abnormal times in each assessment period and the mean of the equivalent pressure values ​​of all normal times is calculated as the relative difference. The insulation leakage degree is positively correlated with the relative difference and the pressure attenuation rate.

8. The intelligent inspection and maintenance method for ultra-high voltage fast circuit breakers as described in claim 1, characterized in that, The calculation process for the contact ablation degree is as follows: for each operation event, extract the mean value of the effective current of the three-phase current transient waveform at the moment of fault clearing, and calculate the energy loss value of each operation event based on the empirical formula for electrical wear. Obtain the rated arc energy that the circuit breaker contacts can withstand; calculate the sum of the energy loss values ​​of all operating events in each evaluation period, and use the ratio of this sum to the rated arc energy as the contact ablation degree of the circuit breaker under test in each evaluation period.

9. The intelligent inspection and maintenance method for ultra-high voltage fast circuit breakers as described in claim 1, characterized in that, The process of deriving the health status of the circuit breaker under test includes: forming an observation vector from the mechanical degradation, insulation leakage, and contact erosion of the circuit breaker under test in each evaluation cycle; splicing the observation vectors of the circuit breaker under test in multiple consecutive evaluation cycles to form a multi-dimensional time-series observation sequence; inputting this sequence into a pre-constructed hidden Markov model to derive the health status of the circuit breaker under test.

10. An intelligent inspection and maintenance system for ultra-high voltage fast circuit breakers, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the intelligent inspection and maintenance method for ultra-high voltage fast circuit breakers as described in any one of claims 1-9.

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