Power system harmonics issues in some end user facilities

The paper presents a few issues generated in low voltage distribution grids at the end user's level, by power system harmonics. The introductory section presents shortly harmonics sources, their analysis, effects and measurement methods, appealing mainly to the limits depicted in the specific standards. The following section presents two case studies of power electronics equipment drawing high distorted currents and having as consequence a high harmonic content. The first one represents a residential equipment supplied by a switch mode power supply, analyzed in laboratory conditions. The second, a variable speed drive, has been analyzed in an industrial environment, i.e. in real conditions. As a conclusion, harmonic measurements and analysis make possible the choice or the design of retrofitting mitigation countermeasures, capable to alleviate harmonics effects.