Digital measurement of voltage flicker

The author deals with cyclic variations in the envelope of voltage waveforms. European power utilities have done substantial work already in their characterization, based on the effects on visual perception. They have also established a norm for the calculation of an instantaneous flicker level, a short-term severity coefficient, and a long-term severity coefficient. The measurement techniques that they propose are basically designed for analog instrumentation. Digital implementations of the analog design are neither cost effective nor optimal in performance. The author proposes a method for direct calculation of flicker level from digital measurements of voltage waveforms. The direct digital implementation uses a fast Fourier transform (FFT) as the first step in the computation. A pruned FFT, customized for the flicker level computation, is also proposed.>