Research On The Reliability Of Vacuum Circuit Breaker

Circuit breakers play a dual role of control and protection in the power supply and distribution system, and its reliability level directly determines the safety level of the power system. Because of its unique advantages of high performance and no pollution, vacuum circuit breaker has taken the dominant position in the field of medium voltage. With the merit of simple structure and lower energy consumption, permanent magnetic actuator (PMA) is becoming the ideal operating mechanism for vacuum circuit breaker. Now, the vacuum circuit breaker with PMA has been widely used in our country, and its reliability has received great attention in each department, so it has extremely important significance to study the reliability of vacuum circuit breaker with PMA.In this paper,12kV indoor vacuum circuit breakers with PMA are taken as the research object to carry out the reliability research, and the aim is to find out the design weakness and effective reliability evaluation method of vacuum circuit breaker, and to provide reference for vacuum circuit breaker reliability enhancement.Firstly, the basic concept in the theory of vacuum circuit breaker reliability and the reliability study of circuit breaker at home and abroad are introduced. Then the structure and operating process of vacuum circuit breaker and PMA are analyzed. According to function, structure and working environment, a lot of reliability problems existing in the operation at the scene are obtained in this analysis.The program of the vacuum circuit breaker reliability test is made according to the related reliability and circuit breaker standards, and the test failure criterion is also determined. At the same time, six vacuum circuit breakers are selected to carry out the test, and the failure situation in the test is recorded, and the mechanical characteristic parameters are on the track record in the test process. The test results show that the closing and opening times along with circuit breaker operation times have a smaller scatters, and the closing and opening speed and has the downward trends, and the closing bounce time is on the rise in the test process. Part of the circuit breaker closing bounce time is gradually beyond the technical requirements.Based on the reliability test data and history fault information of vacuum circuit breaker, the failure mode and effects analysis combined with the fault tree analysis is used to carry on the qualitative analysis of the vacuum circuit breaker reliability, and the main failure modes and failure mechanism of vacuum circuit breaker are achieved.According to the obtained failure modes and the physical background of the reliability distribution model, the Weibull distribution is selected as the hypothesis model for the life analysis of vacuum circuit breaker, and the rationality of the model selection is verified by the goodness-of-fit method. Then the Weibull distribution evaluation is deduced by the maximum likelihood estimation under the condition of timing truncation test, and the vacuum circuit breaker reliability estimation model is obtained by the method of iterative according to the test data. Then the reliability quantitative characteristics of vacuum circuit breaker with PMA in the test are calculated. Qualitative and quantitative analysis results can provide effective support for the design, improvement and maintenance of vacuum circuit breaker.