A phasor measurement unit (PMU) is a device which measures the electrical waves on an electricity grid using a common time source for synchronization. Time synchronization allows synchronized real-time measurements of multiple remote measurement points on the grid. The resulting measurement is known as a synchro-phasor. PMUs are considered to be one of the most important measuring devices in the future of power systems. PMU can be a dedicated device or the PMU function can be incorporated into a protection relay based on the client preference.

The PMU data is collected either on-site or at centralized location using Phasor Data Concentrator (PDC). The data is then transmitted to a regional monitoring system which is maintained by the utilities.

The technology has the potential to change the economics of power delivery by allowing increased power flow over existing lines.

This technology is a powerful tool for the utility to measure the state of the electrical system and manage the power quality