Synchronization requirements of a Power Quality measurement system for the distribution grid

Power Quality (PQ) measurement is becoming more and more important at distribution level due to the increasing presence of renewable energy sources with an intermittent generation. Some regulatory frameworks in Europe - as the Italian regulation - are starting to address this issue, and the installation of PQ meters is becoming mandatory in HV/MV substations. The measurements data provided by the PQ meters placed in HV/MV grid can be correlated to identify the source of the disturbances only if the measurements instruments are time synchronized. The Italian regulation requires the PQ meters have to be synchronized using a GPS receiver, with a time synchronization uncertainty below 20 ms. The paper investigates the synchronization requirements of a power quality measurement system in order to propose a cost-effective network based time reference instead of costly GPS solutions. Some real examples from a field test area in Italy are used as input for parameters definition.