Research On The Reliability Of An Air Circuit Breaker

In the low-voltage distribution system, air circuit breaker (ACB) is used to cut off the failure circuit to prevent the whole power distribution circuit and electric equipment from the damage of dynamothermal and dielectric performance of the failure current when overcurrent, short circuit, imbalance, overvoltage, undervoltage and other abnormal conditions occur. The reliability of ACB is very important to the operation of whole low-voltage power distribution system, and the research on reliability has good social and economic value.The reliability theory of ACB is studied in this paper. Based on reliability theoretical research and according to the relevant standards, the requirements of application and main failure modes, this paper sets the mechanical operation failure rate and protection success rate as reliability assessment indexs. Meanwhile, according to the failure statistics of one ACB model, we found that operating mechanism failure, hard-to-rotate drawer handle, burnout of secondary terminal are the key improving point for the reliability analysis. This paper conducts reliability analysis research on these three main failure modes.This paper determines the test condition and method of ACB and defines test parameter, test index, test environment and condition, test cycle, test device and so on.Through analysis on the operating principle of ACB, this paper determines reliability test method on the aspects of mechanical operation stress latitude, environmental influence stress latitude, dieletric stress latitude. Moreover, we edit reliability test standard to provide the foundation of improving and increasing the reliability of ACB.This paper introduces reliability test devices of various ACBs, especially the principle and stucture of reliability test device (of secondary terminal make and break performance) which conducts the reliability test, records and analyses the test process. Main problems which affect product reliability are found after analyzing the reliability of test results:break failure of operating mechanism, hard-to-rotate drawer handle, unreliable secondary terminal make and break performance. By means of data statistics and analysis, we conclude the method of improving reliability.Not only product reliability is improved through reliability study of ACB, but also achieving reliability improvement and editing reliability test standard of ACB, which lays a good foundation for the defining of contents and requirements of other types of ACB.