What does a phasor measurement unit (PMU) measure?

A phasor measurement unit (PMU) is designed to measure electrical waves on an electricity grid by capturing their phase angle and magnitude in real-time. This ability allows PMUs to provide synchronized measurements of voltage and current from multiple points on the grid, which is essential for monitoring the health and stability of the power system. The data obtained through PMUs facilitates better decision-making in grid management, as it helps in identifying system disturbances and improves situational awareness for operators.

In contrast, while measuring voltage levels is crucial in substations, this function is typically performed by other instruments such as voltage transformers. Similarly, assessing load demand can be done using different types of metering and monitoring devices, which focus specifically on consumption patterns rather than real-time wave measurements. Current fluctuations in power lines can be measured using specific sensors, but PMUs provide a comprehensive overview by focusing on the waveform characteristics rather than just fluctuations. Thus, the unique functionality of PMUs in analyzing electrical waves makes the first option the most appropriate response.