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Phasor Measurement Units (PMUs) are devices that take three phase voltages as inputs and output A/B/C phase magnitudes, angles, frequencies, and time stamp data that correlates to these outputs. PMU functionality is typically built into protection relays which are used to protect sensitive areas of the power grid such as transformers and substations. PMU’s then become useful tools that can provide critical insight into the power grid, and may have applications in feedback controls as a sensor.

The main goal of this project was to obtain the delay time inherent in SEL-421 and SEL-487 PMU hardware. To test these units I needed to construct a test bench of hardware and software for signal generation, signal monitoring, signal amplification, data acquisition, data parsing, and calculation software to analyze the results of my tests. My research focuses on a signals and systems approach to testing this hardware. By inputting various signals such as phase ramps (frequency steps), amplitude steps, amplitude modulation and phase modulation I am able to determine characteristics of the PMU hardware such as delay time. By inputting a frequency spectrum of phase modulation signals I was able to calculate the transfer function and obtain a bode plot for the SEL 421 which also yields characteristics of the PMU hardware. These results are a critical part of a much larger grid protection project, and the accuracy of these results are paramount.