Connection of a plant with arc furnaces to the Andalucian network

The connection of electrical arc furnaces to the network has always been a cause for concern for technicians in electricity companies due to the specific characteristics of these types of installations. Out of the various installations that are in existence, the arc furnace is the one that causes the most disturbances: this is because it generates harmonics, both in intensity and voltage, causes imbalances between phases and above all, causes flicker. For this reason electricity companies have shown concern about the rules that fix the restrictions on the emission limits for connecting these disturbing loads. As far as flicker is concerned, these limits are defined by two basic indexes in accordance with IEC criteria. These indexes are as follows: Pst, that evaluates the degree of flicker over short periods of time, and Plt for longer periods of time. In this paper measurements have been carried out in a steel plant and have been compared to the theoretical calculations and actual observance of the phenomena. The results lead us to think that the current limits for the said two indexes may be too strict, as, in a specific margin above the established limits of flicker indexes, no visual effect can be perceived