Incorporating protection systems into composite power system reliability assessment

Protection systems are indispensable for electric power generation, transmission, and distribution systems. In recent years, more and more research efforts have been devoted to consider protection system failures and their impact on composite power systems when performing reliability assessment. Protection systems were designed in the past using electromechanical and hardwired relay logic. With the emergence of microprocessor-based protective relays and more advanced communication technologies, legacy protection panels with stand-alone relays have been gradually replaced by modern panels with multifunctional, smart, and communicative Intelligent Electronic Devices (IEDs). These changes result in increasing complexity and cyber-physical interdependencies and thus novel evaluation methodologies are needed. In this paper, major publications in protection system reliability modeling are reviewed and summarized. The difficulties and challenges of incorporating protection systems into composite power system reliability assessment are discussed. Possible future research directions are suggested. This paper is written with the expectation to stimulate more discussion and research on this topic as well as encourage more applications.