A cutset area concept for phasor monitoring

We show how to combine together voltage angle phasor measurements at several buses to measure the angle stress across an area of the power system that is called a cutset area. The angle across the cutset area is a weighted average of the angles measured at buses at the borders of the cutset area. The angle across the cutset area is based on circuit theory and it responds to power flow through the area and to line trips inside the cutset area. The angle across the cutset area gives stress information that is specific to the cutset area and is a generalization of the angle difference between two buses. The concepts are illustrated with several choices of cutset areas in a 225 bus model of the Western North American power system.