Abstract
This paper discusses a novel method for protection of a bulk power system against voltage instability. In the discussed approach, a region of interest is defined and the system is protected against voltage collapse using synchronized wide-area power-flow measurements. As will be explained, synchronized measurements of Intelligent Electronic Devices can be used for creation of a Wide-Area Loss-Index which shows proximity of a system to voltage collapse. It will be shown that the required measurements for protection of a system need to be taken from critical points, including bulk generations and loads inside a region of interest, as well as its borders.