Harmonics in MV and LV distribution systems: present and future levels

Slow but progressive changes in the nature of loads connected to the electric system have been witnessed for some years. Moreover, the large scale dissemination of these new disturbing loads may increase the `background noise´ level of the system and increases the risk of producing harmonic disturbances in all points of the system, especially at the connection points of reactive power compensation capacitors. In a first stage, the paper proposes an analysis of harmonic disturbances in distribution and transmission systems from sample readings made in MV/LV and HV/MV substations representing French Substations at large. The second part of the study consists of identifying these disturbing sources at different levels: domestic customer; MV/LV substation; and HV/MV substation. A statistical computation model of harmonic disturbances is then created from measurement results. It is used to identify the level of harmonics in any system with the knowledge of the number of domestic customers fed by this system