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'''Accelerated life testing for reliability improvement: a case study on Moulded Case Circuit Breaker (MCCB) mechanism '''

Santosh B. Rane, Prathamesh R. Potdar, Suraj Rane

Abstract

MCCB plays a critical role in electricity distribution, and its failure may be costly and hazardous. According to Conseil International des Grands Réseaux Électriques (CIGRE) report CIGRE SC13 (High voltage circuit breaker reliability data for use in system reliability studies, CIGRE Publication, Paris, 1991), it is explored that majority of the circuit breaker failures (90%) occurred due to the failure of the mechanism. In this study, MCCB mechanism is under development stage due to which failure data of mechanism is not available to predict reliability. Therefore, it is essential to assess and improve reliability of MCCB mechanism to know and achieve higher reliability. This paper demonstrates the process of reliability assessment and improvement of the MCCB mechanism by using Boolean algebra and Accelerated Life Test (ALT). Further, Weibull distribution is selected for reliability prediction based on comparison with other distributions. Reliability of mechanism is compared with before improvement and after improvement conditions. In reliability testing, ALT is used, and the result shows that frequency of latch link failure is maximum due to denting and distortion of link. Further, few improvement measures are proposed based on design and manufacturing aspects, and results of suggested measures shows improvement in MCCB mechanism reliability from 72.44 to 95.06%. The design for reliability approach can be implemented rigorously if the failures identified at the development stage of the product, which helps to reduce the considerable losses in the future.

Keywords:- Fault Tree Analysis (FTA), ALT, Reliability modeling, Bollean algebra, Weibull distribution, Reliability of mechanism

Cite this article as:- Rane, S.B., Potdar, P.R. & Rane, S. Int J Syst Assur Eng Manag (2019) 10: 1668. https://doi.org/10.1007/s13198-019-00914-6