Reliability Assessment of Industrial Circuit Breakers with Design Enhancements

Reliability of circuit breakers are critical to ensure safe operation of the power system when a fault occurs. Over the past decade regulatory changes and customer requirements are compelling manufacturers to build more reliable systems and are mandating uses of methodologies like self-test so that the breakers can verify during operation that they have the capability to isolate a fault. The paper models the major components within the circuit breaker, identifies the critical components from a reliability perspective and explains how new design enhancements improve the reliability of circuit breakers. The study uses Weibull distribution for the components and uses Reliability functions in Mathematica to numerically calculate the importance of each component in the circuit breaker from its contribution to the overall breaker reliability. Using the design enhancements, it is observed that the mean time to failure of the breaker increases by 2.46 years and the unavailability of loads is reduced by 23% for a simple test system.