Evaluation of Power System Reliability Incorporating Protection System Miscoordination

Document Type : Research Article


1 Faculty of Electrical and Computer Engineering, University of Birjand, Birjand, Iran

2 University of Birjand, Faculty of Engineering, Birjand, Iran

3 University of Zanjan


The operation of protection systems has a considerable impact on power system reliability. The main reason for cascading outages is protection system misoperation. Protection systems affect power system reliability from two perspectives: First, incorrect operation of the protection system due to the failure of any of its components that causes failure to operate or undesired tripping. Second is the incorrect operation of the protection system due to the incorrect setting of relays. In the second case, the protection system is healthy, and incorrect operation is only the result of the erroneous setting of relays. In this paper, an analysis of power system reliability regarding failure and incorrect settings of the protection system is paid. This paper proposes an eight-state Markov model for a transmission line and its protection system incorporating protection system miscoordination distingue from failure to operate and undesired trip. The situation of network lines in the period of simulation time has been determined by the sequential Monte Carlo method, and are calculated the reliability indices such as Loss of Load Probability (LOLP), Loss of Load Expectation (LOLE), Expected Energy Not Supplied (EENS), and Expected Frequency of Load Curtailment (EFLC). The proposed model is applied to a 6-bus IEEE RBTS network, and the reliability indices are calculated and compared from both perspectives to show the importance of the proposed model.


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