This document contains the details of the standard IEEE C37.118 - 2005 which defines synchronized phasor measurements used in power system applications. It provides a method to quantify the measurement, tests to be sure the measurement conforms to the definition, and error limits for the test. It also defines a data communication protocol, including message formats for communicating this data in a real-time system. Explanation, examples, and supporting information are also provided.
More Information on this standard can be found here.