Distributed monitoring system for voltage dip classification over distribution grid

The installation of Power Quality (PQ) meters is becoming mandatory in many countries to face the problems introduced by the increasing number of renewable energy sources with intermittent generation. Unfortunately, the current situation is unbalanced: PQ meters are installed on High Voltage (HV) transmission lines and sometimes on Medium Voltage (MV) lines, while the highest number of renewable generators is connected to Low Voltage (LV) grid. In this paper, a novel measurement system for the analysis of voltage dips is proposed. If compared with existing similar systems, the proposed distributed measuring system has the following new characteristics: it is composed of a network of PQ meters on HV, MV and also on LV lines; it uses a heterogeneous communication infrastructure to interconnect meters; it has a cost-effective network-based time synchronization instead of costly GPS solutions; it implements a distributed algorithm to determine the origin of PQ problems. This novel approach overcomes scalability issue, which currently is limiting a larger penetration of PQ systems. The proposed distributed system for monitoring of voltage dips has been deployed in a real distribution grid in Italy. The paper reports analyses on data collected during an entire year. Voltage dips have been correlated and analyzed thanks to the time synchronization of the system.