Analysis of PMU response under voltage fluctuations in distribution grids

Phasor Measurement Units (PMUs) are currently used for the monitoring of the electrical quantities mainly in the transmission networks. Nevertheless, they are expected to become an important element also in the monitoring of the dynamic and complex scenario of the future smart distribution grids. The IEEE standard C37.118.1 defines the measurements, the indices and the methods to evaluate synchrophasors, frequency and ROCOF (Rate Of Change Of Frequency) under steady-state and dynamic conditions. The compliance to this standard ensures the interoperability between the PMUs provided from different vendors. The test signals defined in the standard C37.118.1 mainly reflect operating conditions that can occur in the transmission networks. On the other hand, the electrical signals that can be measured in the distribution networks may be different and these different scenarios should be kept into account when a PMU is purposely engineered for the needs of the electric distribution grids. Several international standards describe the voltage characteristics of electricity supplied by distribution systems and consider some operating conditions that are not included in the synchrophasor standard. The aim of this paper is to highlight, through an appropriate test setup, the performance of the PMUs under one of such unexpected conditions, namely the voltage fluctuations that give rise to the disturbance commonly known as light flicker.