Voltage stability assessment for real-time operation

Network voltage stability is represented by nodal conditions associated with the maximum active and reactive power flow that can be transmitted from generators to loads. An analytical assessment tool is derived, based on a simple but sound mathematical background, modelling a straightforward physical characterisation of the phenomena. Comprehensive and meaningful indices are introduced. They indicate the MVA margin to the maximum, the region of operation, the relative importance among buses, the loading ranking of the buses, the sensitivity to control actions, and a measure of difficulty for power transmission. Numerical results are presented for the Itaipu bulk transmission network in the S/SE of Brazil immediately before a voltage stability blackout in April 1997. Computational efficiency is no burden for real time operation including contingency analysis