Operational reliability evaluation of stepped current protection based on real-time operational conditions of power system

This paper proposes that the real-time operational conditions of power system such as the power system´s operation modes, the configurations of relay protection and the types of short-circuit occurred to power system have critical influences on operational reliability of protection, and operational reliability of stepped current protection installed on transmission lines will be evaluated in this paper. Firstly, this paper considers percentage of operational operation of protection as operational reliability evaluation indicator of stepped current protection, and builds the model of distribution of operational operation probability of protection. Then, based on this model, this paper derives the algorithm to calculate percentage of operational operation of protection. Above all, this paper also proposes a new method to evaluate operational reliability of protection based on ranges of percentage of operational operation of stepped current protection I, II and III. Lastly, this new method can be used to evaluate operational reliability of stepped current protection simply and effectively, testified by an example.