Frequency Compliance of MV Voltage Sensors for Smart Grid Application

With the advent of smart grid paradigm, medium voltage (MV) distribution networks have experienced great structural changes that, with the massive deployment of distributed generation, impose the network monitoring in a wider frequency range, up to some kilohertz, to evaluate power quality (PQ) phenomena and to ensure proper operation. Classical voltage instrument transformers (VT) with primary rated voltages higher than a few tens of kilovolt are typically usable in a limited range around power frequency, and thus for accurate measurements up to some kilohertz new types of MV sensors should be needed. Nevertheless, the massive replacement of VTs in a short time is not convenient from an economic point of view. In order to delay the transition to new types of transducers, without limiting the possibility to monitor PQ, if the VTs are characterized in a wider frequency range, then their systematic deviations could be compensated with suitable digital signal processing techniques. Therefore, in this paper, a calibration setup, intended to be employed both in laboratory as well as on-site, for the verification of frequency compliance of MV voltage sensors for smart grid application is presented. A comparison with the Italian National Metrology Institute Laboratory reference system is also described.