As the power system undergoes change, so must its measurement systems. The grid is currently in a state of rapid change with the proliferation of power electronic devices at all levels of the power system: generation, transmission, distribution, and load. A commonality among these devices is their tendency to manipulate voltage and current waveforms and alter their behavior within an electrical cycle. This behavior has already begun to reveal the limitations of today’s most advanced wide-area monitoring system based on synchrophasor measurements provided by phasor measurement units (PMUs). Though synchrophasors will continue to be useful in many applications, some emerging use cases require measurements that can more accurately represent underlying voltage and current waveforms.
The objective of this guide is to help readers use their existing measurement systems effectively while navigating the significant changes that the power system is undergoing. To accomplish this objective, the capabilities and limitations of PMUs are described. Where synchrophasors are insufficient, this document describes how point-on-wave (POW) measurements can meet application needs. POW measurements result from the conversion of an analog input signal to digital samples, allowing them to accurately reflect non-sinusoidal signals. This document contains descriptions of PMU and POW technology and the use cases for which each is well-suited. The document also highlights key considerations for expanding a measurement system to enable applications based on POW technology.