Reliability Analysis Of Permanent Magnetic Actuator Based On Bootstrap Method And Performance Degradation

As a kind of switching device,the reliability of the circuit breaker directly affects the stability of power system.The operating mechanism occupies an important position in the circuit breaker,so its reliability is attracting more and more attention.Using bi-stable permanent magnetic actuator in vacuum circuit breaker as the research object,this paper develops its reliability research from the lifetime and performance degradation,and establishes its reliability distribution model from the parameters which can characterize its reliability,providing reference for the reliability evaluation of permanent magnetic actuator.In order to establish the reliability model of permanent magnetic actuator,this paper develops a series of reliability tests for the research object according to the relevant standards of reliability test.Seven sets of bi-stable permanent magnetic actuator are selected in the no-substitute fixed time life test to observe and record the fault condition and failure time of actuator,combining with the historical data of actuator manufacturer,it analyzes the failure information of actuator using failure mode effect analysis.Temperature test is carried out in three temperature levels according to the national standard to measure and record the changes of closing retention with the temperature.By analyzing the test data,it draws a conclusion that the closing retention decreases with the temperature oppositely.When the temperature is less than a certain value,closing retention decreases slowly,and it decreases rapidly above the value,which results in the failure of actuator.Based on the failure mechanism and failure mode of the bi-stable permanent magnetic actuator,a least-square estimation model in Weibull distribution about actuator is established.The goodness of fit test verifies that actuator lifetime data applies to the selected distribution model.Then this model is used to calculate the life test data,obtaining a reliability distribution model of actuator,and interval estimation of the maximum likelihood theory is used to verify the model parameters.Aiming at the few test data of actuator,this paper adopts the Bootstrap method,which is commonly used in the reliability analysis of small samples,to increase the samples’ quantity.The reliability of the permanent magnetic actuator is calculated by comparing the samples data with that of the test data.As a kind of high reliability and long life products,the working process of permanent magnetic actuator conforms to a certain degradation path.By analyzing the degradation path of each parameter during the life test,the parameters which can represent the reliability of actuator are selected.Using the pseudo failure lifetime data obtained from the degradation path,another reliability distribution model is obtained.By comparing the model with that obtained from the lifetime test data,the result shows that the model from the performance degradation data is consistent with the reliability distribution model of the test data.