A Method to Simplify the Markov Model of Protective Systems

The state space approach is a common method for conducting reliability assessment of protective systems. However, as more factors affecting the reliability of protective relay are considered, the system Markov model is becoming more and more complex and its solving efficiency is decreasing. To avoid this, a method to simplify the Markov model of protective system is proposed in this paper. Based on the continuous-time Markov process (CTMP), the theory underlying the state space approach, the method illustrates that the duration of the protective system in the switching states can be neglected. In other words, the protection switching state can be ignored when developing a Markov model of protective system. This method is applied to two existing models, one for a protection/component system and the other for redundant protective systems. The study results show that the method significantly reduces the complexity of the Markov model and improves the solving efficiency without reducing the capability of Markov model to describe the reliability of protective systems.