Survey of harmonic distortion in LV and MV networks: results and corrective strategies

Harmonic distortion has become a main concern in electric distribution systems and consequently many efforts have been devoted to develop methodologies to analyze the problem and to evaluate the behavior and the impact that different appliances have on voltage distortion. In Europe, the Directive 85/374 recognized electricity as a commodity and hence the need to guarantee a minimum level of quality standards. The technical specification for power quality in the distribution networks, particularly with reference to the limits of voltage distortion, are defined in the European Standard EN 50160 that can be assumed as a reference. The AEM Torino organized a measurement survey, with several on-site measurements, to monitor the situation of the MV and LV distribution networks with respect to some different power quality aspects. Particularly, during this survey, the phase current and voltage, the active and reactive power, the total harmonic distortion (THD) and the 5^th harmonic of voltage and current have been monitored in different locations of the networks. In this paper a summary of the main results of the survey on the situation of the AEM MV and LV distribution systems, mainly with reference to the voltage distortion aspects, is presented. In this framework, the impact of public lighting on the voltage distortion of the LV distribution network is investigated and several remedies are discussed both from the analytical and the experimental point of view