Phasor Measurement Units (PMUs) are devices used in electrical engineering to measure the electrical waves on an electricity grid. They provide real-time data on voltage and current, helping to monitor the stability and performance of power systems. PMUs use a technology called synchrophasor measurement, which synchronizes data collection across multiple locations using GPS signals. These measurements are crucial for improving the reliability of power systems and preventing outages. By analyzing the data from PMUs, operators can detect disturbances and make informed decisions to maintain grid stability. This technology is essential for modernizing the electrical grid and integrating renewable energy sources like solar power and wind energy.