A one-phase, distribution-level phasor measurement unit for post-event analysis

Phasor measurement units (PMUs) are devices which provide near real-time synchronized data (synchrophasor data) at widely separated points across the power grid and are mainly installed at the transmission level. The widespread installation of PMUs across the power grid is gradually becoming a reality - and promises new capabilities to significantly improve real time knowledge of the power grid's operating state. Archived synchrophasor data provides a wealth of high-fidelity data to aid power system model sustainability analyses and to reconstruct unusual power system events. While the PMU device concept is well known in the power industry, the challenges of designing and implementing a PMU which integrates field measurements to deliver Global Positioning System (GPS) synchronized phasor data to the power industries' networks are not as well known or understood. This paper describes the steps, challenges, and reasoning involved in building a single-phase, distribution-level PMU. Our efforts have provided a fundamental understanding of a PMU's inner workings and direction to future efforts to improve PMU performance.

I. Introduction

PHASOR Measurement Units (PMUs) are devices which sample substation voltages and currents through power and current transformers. The device then performs signal processing computations to generate voltage and current phasors referenced to the global positioning system's broadcast timing signal. The phasors are time-stamped using information embedded in the GPS signal. The appeal of PMUs lies in the capacity to generate phasor data at locations separated by 1000s of miles, in a window of time smaller than 1 µs, which, for anticipated power system applications, is effectively simultaneous. Additionally, each PMU in the system assigns an identical time stamp to the phasor measured in that 1 µs window. This enables phasors derived from measurements at thousands of locations across the system to be transmitted and assembled to provide a synchronized snapshot of the system's state at given time.