Richard Bingham

The last two articles have covered power quality phenomena that occur very quickly (impulsive and oscillatory transients, often measured in microseconds) and those that are somewhat slower but still brief (short-duration rms variations such as sags and swells with a duration of 1–60 cycles). Both types can cause process interruptions or equipment damage.

Last month’s article discussed how harmonic content and the source of those harmonics could be identified by their waveform signatures. Transients also have telltale signatures in many cases. The same laws (Ohm’s and Kirchhoff’s) used for analyzing rms voltage variations such as sags and swells also apply to transient analysis.

Another IEEE Working Group has been meeting to address the problem of recognizing and analyzing the signature of power quality disturbances to identify their source. IEEE P3139 Guide for Power Quality Data Analytics is the first release of the working group’s 20-year effort on the electrical signatures of various utility equipment failures, including waveforms and RMS plots of the voltages and currents.