The dual-redundant relay protection system is a basic configuration requirement in 220 kV and above transmission networks
which plays a key role in secure and reliable operation of power systems. This paper presents a five-state space model of the dual-redundant relay protection systems operating in four working conditions for relay protection systems composed of two main protection systems
a far backup protection system and a local backup protection system. On the basis of the five-state space model
a state transfer matrix is developed to determine the relationship between the fault removal probability
the failure rate and the fault probability
the maintenance rate between different working states in accordance with the analytical principles of Markov state space. Finally
an actual transmission network is taken as a case in point to show the importance and crucial role of the dual-redundant relay protection system. This work is supported by Guangdong Provincial Natural Science Foundation of China(No. S2013010012431)
Special Funds for Public Research and Capacity-building of Guangdong Province(No. 2014A010106026)and China Southern Power Grid Company Limited(No. K-GD2014-194).