  We use synchrophasor measurements of the complex voltage and current at both
ends of multiple transmission lines that connect areas of a power system to
monitor the online voltage collapse margin. A new reduction is used to reduce
the multiple transmission lines to a single line equivalent and determine how
to combine the synchrophasor measurements. Generator reactive power limits can
be accommodated. The results show that this methodology can capture the effect
of multiple contingencies inside the transmission corridors, giving awareness
to the operators about the severity of contingencies with respect to voltage
stability.
