Analysis of voltage dips on Italian distribution network

Abstract

This paper carries out an in-depth analysis of the voltage dips data gathered by Power Quality Instruments (PQI) installed on each Medium Voltage (MV) busbars of substations directly connected to transmission system and owned by e-distribuzione, the largest Distribution System Operator (DSO) in Italy. The set of power quality data used for this work, consists of voltage dips recorded during the years 2016-2020. By using all data concerning the voltage dips, e-distribuzione has conducted a deep analysis of this phenomenon, in terms of categories of dips per intensity and duration, their origin and their distribution and number during the years, taking into account the peculiarity of any considered period. Furthermore, it is presented a comparison between the influence of structural parameters of transmission system and distribution substation elements and scheme, regarding the disturbance propagations due to a voltage dip, and also how coordination of DSO protection system adopted to improve the continuity of supply indexes (SAIDI and SAIFI) influences the characteristics of voltage dips. Lastly, some reflections about the importance of technical interventions into the substations of MV customers directly connected to the distribution network, so called "immunization-oriented", to contrast effectively the disturbances coming from the distribution network, are presented.