The recent world-wide rash of power systems blackouts has provided an added impetus to wide-scale deployment of phasor measurement units (PMUs). Initial applications of PMUs in the late 1980s and 1990s were isolated due to the limited infrastructure availability and lack of computational support for extensive processing of the networked information. Today, networks of hundreds of PMUs are in place and more are planned. The recognition that networks of PMUs can provide greater power system reliability is based on their ability to give direct access to the state of the power system at any given instant. 2006 IEEE.