GE MiCOM P847 relay Phasor Measurement Unit forms part of GE’s system monitoring and control. The devices is used to measure power system data in real time and report to the PDC (Phasor Data Concentrator) for visualization, data storage and most importantly for running a variety of ‘on line’ and ‘off line’ applications in systems analysis and control. The ultimate goal is to run the system economically and preserve system stability following major disturbances.