Study On The Reliability Of Residual Current Protection Of CM2L MCCB

Residual current circuit breaker(viz. moulded case circuit breaker with residual current protection) is a type of new low-voltage safe protection device, it can offer not only overload and short circuit protection but also avoid the electric shock and fire accident.The study on the reliability of residual current circuit breaker is very important for improving the product quality,as it is related to the people's life and estate.This paper mainly study the reliability of CM2L residual current protection.The reliability check of residual current circuit breaker mainly aims at its working characteristics and the mode of failure.The residual current circuit breaker is a kind of protector that operates infrequently. The residuil current breaker has three failure modes, reject-operation failure, wrong-operation failure and operation failure.The reliability check should consider this characteristic and the three failure modes.The reliability test of residual current circuit breaker is devided into two parts,residual current protection test and operation rebiliability test.For the failure of wrong-operation and reject-operation,the success ratio R is applied as reliability check of residual current protection;for operation failure,the failure ratioλis the criterion of operation reliability.The rake of the failure ratio and success ratio are qualified in this paper.This reliability compliance test plan is put forward in this paper through study the CM2L residual current circuit breaker. According to the sample theory,the reliability compliance test is put forward.The reliability test device of residual current breaker is developed according to the reliability test plan.The device can do the residual current protection test and operation test.So the reliability study can be processed.Based on this,the application of comprehensive reliability analysis in the operation mechanisim of the residual current circuit breaker is discussed and the points during design,manufacturing and usage of the mechanisim have been noted to avoid errors during design and production.Also,improvement has been worked out aimed at various failure modes. Reliability design and reliability growth test have been done for the breaker. And according to FMEA analysis and the result of the reliability test, the emphatically do reliability design and test to the charging spring and link,and get the result same as the analysis through the reliability growth test, the level of operation reliability has improved from sub-grade 4 to grade 3.