In power system planning and operation procedures, bulk power system reliability assessment plays an important role. The current practice of such assessment generally assumes that protection systems are perfect, and the effects of protection system hidden failures are ignored. Recent research, however, shows that protection system hidden failures have been recognized as a contributing factor to power system cascading outages. To evaluate bulk power system reliability considering the impact of protection system hidden failures, this paper proposes a systematic methodology that is based on a breakeroriented system network model including detailed substation configurations and protection system schemes. An analysis of hidden failures in major protection system components is conducted. Based on the results of this analysis, this study focuses on the effects of hidden failures in circuit breaker trip mechanisms (CBTMs). The probabilistic model of the CBTM is built, and a hidden failure effects analysis procedure is developed to obtain contingences resulting from CBTM hidden failures. Such contingencies as well as other contingencies resulting from independent outages and common-mode outages are subjected to a security-constrained adequacy evaluation approach to evaluate system reliability. The proposed methodology is demonstrated with a breaker-oriented 24- substation reliability test system. Evaluation results show that protection system hidden failures downgrade the system reliability level due to the fact that they lead to the outages of undamaged equipment following initial system disturbances.
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