Overview of key stability concepts applied for real-time operations

This paper discusses a number of background questions meant to set the stage when discussing the issue of real-time stability assessment and monitoring. Why at all real-time stability, to begin with? Which stability aspects are amenable to real-time assessment and monitoring? Could real-time stability assessment and monitoring have helped in the past to avoid blackouts? After a brief overview of frequent obstacles against real-time monitoring, e.g., extensive computation time, extensive modeling, complex result presentation, the paper addresses the intrinsic difficulty in quantifying the stability limit, or limits, and discusses a metric predicated on the concepts of steady-state stability reserve and safe operating margin.