A Waveform Distortion Evaluation Method Based on a Simple Half-Cycle RMS Calculation

This paper presents a simple and efficient power-quality (PQ) evaluation method based on the half-cycle root-mean-square (H-RMS) calculation, which can be easily applied to waveform distortions processed from instantaneous values. PQ disturbances, especially related to voltage magnitude variations, can be generally divided into two categories by the measuring method: One is the rms-based PQ events, which include voltage sag, swell, undervoltage, overvoltage, and interruption, which are defined by the magnitude variations in terms of rms values. The other is the instantaneous value-based PQ events, which include transient, noise, harmonics, interharmonics, and flicker (or voltage fluctuation), some of which are assessed by the raw data or processed through frequency analysis and filtering. According to the fundamental characteristic and definition of each PQ event, the acquired signal data should be processed through the different routes. This study shows that the H-RMS-based measuring process can be usefully applied to quantify the instantaneous value-based PQ events, especially in regards to waveform distortions, such as harmonic distortion and flicker, which can be assessed by the IEC flicker severity index (Pst) and the equivalent 10-Hz flicker index (ΔV₁₀).