Reliability assessment and improvement of air circuit breaker (ACB) mechanism by identifying and eliminating the root causes

Abstract

Air circuit breakers (ACBs) are widely used as electro-mechanical devices to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to isolate a fault condition by interrupting current flow and if it fails to function, then it may cause a major accident. The major functions in ACB relies on mechanical drives and linkages, hence assessing the reliability of these drives and links is of key importance. This paper demonstrates the process of assessment as well as improvement of Reliability of ACB by exploring and eliminating the root causes of failures based on various relevant tools. Reliability assessment of existing and improved ACB mechanism was carried out by using Lifetime distribution. Root causes were analyzed using FTA, Ishikawa diagram, CE Matrix, and Pareto chart. After analyzing various causes, the root cause of failures in ACB was malfunctioning of unidirectional bearing. Elimination of root cause increased the reliability from 17.61 to 87.82 % for 20,000 operations. The drastic increase in reliability of ACB after eliminating the root cause of failure served its purpose effectively and helped in securing a strong position in market. This research deals with reliability improvement of ACB that can cut-off/supply electricity from the substation. Improving reliability of such product reduces these possible risks and indirectly helps the society particularly in critical areas like Hospitals, Airports, Process industries, etc.