A Novel Markov Model for Protective Relay Reliability

Microprocessor-based protective relay has risen to the ‘technology of choice’ with regard to power system protection due to its monitoring capability, self-checking capability, event recording capability, communication capability, capability for remote interrogation and setting application, and multiple setting groups. However, the existing Markov reliability model for protective relays does not reflect the state of the art of microprocessor-based relays. And the complexity of the Markov model limits its application in the wide range of relay studies. Therefore, this article establishes the general state-transition diagrams of protected components and relays, and a novel Markov model of a protection/component system by taking account of monitoring, self-checking, routine tests, common-cause failures, human error, operation of back-up protection, relay failure to operations and relay mal-trips. The study results of the sensitivity analysis and comparison analysis demonstrate the rationality and superiority of the novel model.