Maximum Loadability Index Adapted for Dynamic Scenarios to Anticipate the Voltage Collapse Events

Power systems frequently operate near their stability limits due to progressively increasing demand and severe disturbances that alter their topology. These events can trigger accelerated voltage degradation, leading to voltage collapse due to insufficient reactive power support. This article presents an adaptation of the Maximum Load Index (MLI) for dynamic scenarios, using real-time complex impedance monitoring to anticipate collapse in response to topological and load variations. To ensure rigorous methodological validation, an hierarchical approach is adopted, encompassing three test power systems: 1) An electrical system consisting of four buses and two generators (4BUSES), where a progressive load increase until collapse (load ramp) is exclusively simulated to isolate the node-saddle bifurcation phenomenon and demonstrate the fundamental validity of the MLI without the interference of complex controllers; 2) The Bonneville Power Administration (BPA) system; and 3) The Nordic power system (NORDIC). In these latter two complex systems, the study focuses on severe contingencies triggered by transmission line disconnections. These events lead to long-term voltage instability driven by the contradictory action between generator Overexcitation