Among steady-state techniques, one of the most common methods for evaluating voltage stability is through the venerable P-V curve, also known as the “knee” curve.  This method is used to identify the real power, or megawatt, margin to the point when the transmission grid is no longer able to support voltages, a state the industry has referred to as “voltage collapse.”  Many analysts have long suspected that the P-V curve at best provided an approximate indicator, and that there was a lot more it was not capturing.  Recent indications from near voltage collapse events seem to confirm that there is indeed a lot more, which may perhaps require a re-thinking of the whole process of using steady-state methods for voltage analysis.