Evaluation of the impacts of relay coordination on power system reliability

Summary The security and reliability of a power system rely on establishing and maintaining proper coordination among protective relays. In addition to interrupting unnecessary loads, the probability of exposing hidden failures in protection system components such as Circuit Breakers (CBs) may increase as a consequence of miscoordination among relays. In order to evaluate how malfunction of a protection system can degrade the reliability of the system, this paper proposes a new Markov Chain Monte Carlo (MCMC) algorithm. Furthermore, to consider the impact of relay miscoordination on the hidden failure of protection systems, the paper proposes a failure index which is contingent on the magnitude and duration of fault currents. Then, for a sample test system, the reliability indices of SAIDI, EENS, and ECOST are obtained for three scenarios with different relay settings and coordination. The results are then compared to show that how protection miscoordination in medium‐voltage networks degrades the reliability level of the system. Copyright © 2014 John Wiley & Sons, Ltd.