Failure Analysis of Protective Devices in Power Distribution Systems for Reliability Purpose

This paper presents the reliability study of failure rate, mean time to failure (MTTF), and failure mechanism of protective devices installed in power distribution systems of the provincial electricity authority (PEA) of Thailand during the period from 1997 to 2005. Such protective devices include 27 breakers, 109 reclosers, 2,151 fuses, and 79 switches (disconnecting, airbreak and loadbreak switches). According to the Kolmogorov-Smirnov test on failure data, the lifetime of these devices can be described by the Weibull distribution. As a result, their failure rate and MTTF are estimated based on Weibull distribution properties. Finally, failure mechanism of the above protective devices is discussed for improving the reliability of distribution systems