A Phasor Measurement Unit (PMU) measures the electrical waves on a smart grid to determine the system’s state. The IEEE C37.118 specification describes the standards used for measurement, the method of quantifying measurements, test and certification requirements for verifying accuracy, and the data transmission format and protocol for real-time data communication. Data is usually streamed in this format over UDP/IP or across a serial link.
Reference:
Smart Grid Interoperability Maturity Model
Interoperability and Decision-Maker's Checklist