Shortfall of Power Quality Indices

Firstly, this paper addresses the characteristics and causes of various power quality disturbance. Then, various power quality indices and the indices specially focusses on voltage sags are critically reviewed to highlight their shortfalls. The need of development of power quality indices, similar to the total harmonic distortion (T.H.D), power factor (p.f.), telephone influence factor (TIF), etc., for non-periodic, non-sinusoidal and variable load have been asserted. The various shortfalls of the estimation of single event index, such as, magnitude and duration, have also been incorporated in the discussion. The need to consider phase angle jump in the development of voltage sag index has been advocated. Finally, the various shortfalls of power acceptability curves, site index, and system index have been discussed and need of the development of acceptability curves for the three-phase load and rotating field have also been revealed.