Assessment of RMS computation in terms of power quality event detection

In this paper, work on assessment of root-mean-square (RMS) computation recommended in the IEC Standards for power quality event detection with respect to various signal parameters. Correctness of the RMS computation in the standard IEC 61000-4-30, has been tested for power system frequency deviations, point-on-wave changes and phase differences between the fundamental frequency and harmonics in cases of both no harmonics and with harmonics. It has been shown that point-on-wave has negligible effect on RMS errors; however, frequency deviations and phase differences can significantly effect the RMS error, upto 0.3% even in the case of a single harmonic presence. It is recommended that the RMS computation method given in the IEC Standard 61000-4-30 should be assessed based on signal composition for the correctness of power quality event detection.