An Evaluation of the Extent of Correlation Between Interharmonic and Voltage Fluctuation Measurements

The existence of a general correlation between measured interharmonics and measured lamp flicker would be very significant. Present measurement and emission limitation standards for voltage fluctuations are based exclusively on the 60 W incandescent lamp's response to amplitude modulation of the power frequency. As use of incandescent lamps declines, the need increases to broaden voltage fluctuation quantification beyond lamp flicker. Amplitude modulation of the power frequency is mathematically equivalent to interharmonics summed with the power frequency. This, with the existence of international standards for measuring interharmonics, has suggested interharmonics as a possible basis for characterizing voltage fluctuations more broadly. Moreover, interharmonic measurements may be inherently extendable to quantify the effects of voltage fluctuations on devices other than incandescent lamps. However, any new method that offers advantages in broadening voltage fluctuation measurement must be capable of matching the results of present practices. Therefore, interharmonic measurements must first be demonstrated to be generally correlated to currently accepted flicker severity measurements. The correlation between these measurements is explored in this paper. It is concluded that by using the techniques in this paper, measured lamp flicker and measured interharmonics are correlated to a large extent for most industrial loads.