Reliability Modeling and Simulation of Electric Substations – A Case Study

The main objective of power transmission and distribution companies is to provide reliable power with minimal Customer Interruptions (CI) and Customer Interruption Minutes (CMI). For these companies, processes and tools that accurately predict the reliability and availability is very important. Studies have shown that the Reliability Block Diagram (RBD) simulation methodology provides more precise results than other methods. Also, the use of field data produces specific and more accurate results than using generalized failure rates for the substation equipment. In this paper, we present how the RBD technique is used to develop precise reliability models for 120 substations using field data. Failure data from over 7000 pieces of equipment was collected, and Weibull distribution was used to create hazard functions for the models. Since substation equipment is repairable, the Restoration Factor (RF) played an essential role in the reliability analysis. A mixed analysis is used to calculate the RF. This paper presents the procedure and methodology used to develop the reliability models, perform a Monte Carlo Simulation, and calculate the CI and CMI for each substation. In addition, the case study shows how unique modeling and statistical methods can be used to perform reliability assessments when individual equipment failure data is not available.