Leonardo ENERGY's 5th webcast, by Stefan Fassbinder, expert on Power Quality with Deutsches Kupferinstitut. This webcast is based on a live webinar held last December. It is the first in a series of 3 introducing the subject of harmonics. Harmonic currents arise from the use of non-linear loads such as the proliferation of electronic devices that has been introduced over the last 20 years. Harmonic currents produced by these loads have serious effects on installations, depending, to some extent, on the system of earthing employed. This presentation describes these detrimental effects and makes suggestions for remedial measures.