Redundant design of relay protection system for power plant unit with synchronous generator

Redundant design of protection systems shall reduce the probability of inappropriate operation of relay protection schemes. In this paper, an approach for analysis of relay protection system by means of Fault Tree Analysis (FTA) is presented. Methods based on FTA are widely used for reliability evaluations of different types of systems in areas like nuclear power engineering. The purpose for creating the model was to form a basis for relay protection system reliability evaluation and comparison of results in case of application of electro-mechanical devices and digital devices. The presented approach and results can be used for selection of structure of redundant schemes. If particular input data for exact types of equipment is used, the results can form an objective basis for design evaluation. In the presented paper is presented general input data, not binding any producer of electrical equipment. The indicated results have demonstrative value and are not related to utilization of particular type of equipment. The developed model was used for calculation of the probability of failure for protection system based on electromechanical and digital devices.