The original electric transmission grids were designed to deliver power from a predictable set of power generators to predictable locations over a period of decades.  Engineers could model flows on the grid and how they change when plants or lines go out.  In a competitive generation industry, generators are allowed to change their output levels from existing plants every 10 minutes and to sell to loads far away physically from the generator.  This can dramatically alter the direction of power flows over the transmission system over the course of hours.  In the August 14, 2003 blackout, more than 530 generating units at 260 power plant locations shut down.  Abnormalities started just after 1 p.m. and concluded with a massive northeast blackout at 4:13 p.m.  The high-speed cascading lasted about 12 seconds while thousands of individual events occurred automatically.  A wide-area monitoring system could have helped operators see the abnormalities that started earlier that afternoon.  Common time stamps now available through Global Positioning Systems (GPS) allow submicrosecond timestamping of the difference between voltage phase angles at widely separated substations.  GPS also offers the means to reference power system frequency (60 Hertz here) to a very precise frequency standard.  The system now being used to make about 30 measurements per second of these complex values of voltage phase angles and frequencies is called a phasor data system or phasor measurement unit.  Mike Ingram said utilities in the east are working together to collect, share, and display all these measurements over fiber optic systems to their transmission system operators in the Eastern Interconnect Phasor Project.