Effects of Protection System Hidden Failures on Bulk Power System Reliability

Protection system hidden failures have been recognized as a contributing factor to power system cascading outages. However, in the current bulk power system reliability assessment practice, protection systems are generally assumed to be perfect, and the effects of hidden failures in protection systems are not taken into account. In this paper, the impact of protection system hidden failures on bulk power system reliability is investigated. A breaker-oriented bulk power system network model is developed to include detailed system substation configurations and associated protection system schemes. Protection system constituents, such as transducers, relays, circuit breakers, may suffer from hidden failures. Hidden failures existing in transducers and relays can be detected by the advanced system real time monitoring and analysis technologies. Thus, the major concern of this work focuses on the analysis of hidden failures in circuit breakers. The hidden failure effects analysis shows that some initial system disturbances can result in the unnecessary outages of intact power system equipment because of hidden failures in circuit breaker trip mechanisms. Contingencies resulting from hidden failure outages are further evaluated by a security-constrained adequacy evaluation methodology to obtain their influence on system reliability. The proposed analysis procedure is demonstrated with a breaker- oriented 24-substation reliability test system, which is developed based on the IEEE 24-bus reliability test system and integrates explicit substation and protection system models in the network model. Evaluation results show that protection system hidden failures downgrade the system reliability level because they lead to the outages of undamaged equipment following initial system disturbances.