This chapter addresses the theoretical foundation of a field-proven real-time steady-state stability tool (The commercial name of this tool is Siemens Spectrum Power QuickStab. The software is owned by Siemens AG, Germany, and is seamlessly integrated with the Spectrum Power SCADA/EMS platform and SIGUARD ® Dynamic Security Assessment suite) that quickly and reliably quantifies and visualizes the risk of blackout due to instability. The approach is inspired from Paul Dimo's steady-state stability analysis method and uses the Bruk-Markovic reactive power stability criterion in the REI Nets framework to determine how far the power system is from a state where voltages may collapse and generators may lose synchronism. The technique derives its speed and robustness from Dimo's sound approximations and simplifying assumptions, which are analyzed and substantiated. Metrics that quantify the distance to instability and to the security margin are also discussed, along with innovative tools that extract and visualize essential information from the large amount of computational results.
IntroductionModern transmission networks must sustain megawatt (MW) transfers that can be quite different from those for which they were planned. This is because energy transactions across multi-area systems may cause parallel flows, excessive network loadings, and low bus voltages. Under certain conditions, such degraded states may lead to blackouts-but how to quantify the risk of blackout? How to do it quickly in real time, using input from the most recent state estimate and displaying the results before the immediately next state estimation cycle, so that the operator could make truly online, split-second decisions? And how to extract essential information from large amounts of data and computational results and present it in formats that can be instantly understood and relied upon?