This is a standard for synchronized phasor measurement systems in power systems. It addresses the definition of a synchronized phasor, time synchronization, application of timetags, method to verify measurement compliance with the standard, and message formats for communication with a phasor measurement unit (PMU). In this context, a PMU can be a stand-alone physical unit or a functional unit within another physical unit. This standard does not specify limits to measurement response time, accuracy under transient conditions, hardware, software, or a method for computing phasors.