Impact of Human Error Modeling on Failure Rate and Optimum Routine Test Interval of Protection System

Power systems should have acceptable reliability in order to operate properly. Highly available and dependable protective relays help to obtain the desirable reliability. The relays should be periodically evaluated during specific intervals to achieve the mentioned characteristics. The Routine Test Interval (RTI) should be optimized in order to economically maximize the reliability of the protection system. The failure rate of the relays plays a vital role in determination of the Optimum Routine Test Interval (ORTI). Human error is one of the effective factors in the failure rate of the relays. Therefore, in this paper, a Markov model is proposed to investigate the impact of human error on the failure rate and the ORTI of the protection system. The model is applied for the protection system of power transformer. The obtained results indicated that human error has a significant impact on the increase of protection system failure, the decrease of the desired reliability indices, and the reduction of ORTI of the protection system.