Time-varying failure rate extraction in electric power distribution equipment

Reliability evaluation of power distribution system is very important to both power utilities and customers. It presents the probabilistic number and duration of interruption such as failure rate, SAIDI, SAIFI, and CAIDI. However, it has a fatal weakness at reliability index because of accuracy of failure rate. In this paper, the time-varying failure rate (TFR) of power distribution system equipment is extracted from the recorded failure data of Korea Electric Power Corporation (KEPCO) in Korea. For TFR extraction, it is used that the fault data accumulated by KEPCO during 10 years. The TFR is approximated to bathtub curve using the exponential (random failure) and Weibull (aging failure) distribution function. In addition, Kaplan-Meier estimation is applied to TFR extraction because of incomplete failure data of KEPCO. Finally, probability plot and regression analysis is applied. It is presented that the extracted TFR is more effective and useful than mean failure rate (MFR) through the comparison between TFR and MFR