Adoption of IEC 61000-4-15. Voltage fluctuations on electric power systems sometimes give rise to noticeable illumination changes from lighting equipment. This phenomenon is often referred to as flicker, lamp flicker, and sometimes voltage flicker. This recommended practice provides specifications for measurement of this phenomenon and recommends acceptable levels for 120 V, 60 Hz and 230 V, 50 Hz AC electric power systems. It does not make any flicker emission specifications for certification of individual products manufactured for use on these systems.