Phase jumps in PMU signal generators

The understanding of the word “phase” has changed over the years, and power engineers in particular have a different understanding than some others. The matter was examined in a 1946 paper by the Dutch engineer Balth. van der Pol. In the paper, he highlighted a problem with the ordinary definition, but he did not explain it in detail. In our work with phasor measurement units, we have encountered the problem. This paper explains what is going on, and examines ways around it. We examine the question of testing devices such as phasor measurement units, and show that some workers have failed to observe the effects of what we call the “van der Pol problem.” It is suggested that the PMU standard be amended to allow PMUs to show that they can perform well under changing conditions.