Area angle can monitor cascading outages with synchrophasors

We monitor the severity of multiple line outages inside an area of the power system according to the limitations on a bulk power transfer through the area when the outages occur. The monitoring combines together synchrophasor measurements around the border of the area to form an angle across the area that can be tracked in real time. This is an approach based on physical principles to extract actionable information by suitably combining synchrophasor measurements. We show the capabilities of the method on a model of the WECC system on an area with approximately 500 lines.