In this paper, a new flickermeter, designed to calculate flicker severity by using lamp illumination as its input, which complies with the lEC flickermeter for the analysis of flicker in the electricity system caused by iron and steel (I&S) plants, is described. According to the lEC Standard 61000-4-15, flicker is calculated from the voltage and based on the assumption that this voltage feeds an incandescent lamp. In this research work, a system measuring illumination of the lamps has been developed and the illumination of three different types of bulbs, incandescent lamp, compact fluorescent lamp (CFL) and light emitting diode (LED) lamp with the same input voltage, has been investigated. Based on the results, lEC flickermeter algorithm, which is designed based on the incandescent lamp assumption, has been updated to compute flicker severity for any kind of lamp and a new illumination-based flickermeter based on the lEC Standard has been developed. The measurement accuracy of the developed flickermeter has been tested and verified with the test signals recommended in the lEC Standard using actual lamp illumination inputs. Then the developed system has been used to measure the flicker severities of the incandescent lamp, CFL and LED lamp driven by a point of common coupling voltage supplying an I&S plant operating electric arc furnace plants reduced to 230V level. The results have shown that although the flicker severity limits are exceeded when an incandescent lamp is used, with the CFL limits are still exceeded but much lower flicker severity is obtained and the flicker severity computed from the illumination of the LED lamp is much below the limits.