The aim of this work is to perform a feasibility study on the power line communication for the development of a new generation of interface devices (IDs) for smart grid applications. More in detail, this paper deals with one of the most important issues on this topic which is the communication system. Among the existing communication technologies, the study is focused on power line communications (PLCs). After a analysis of the state of the art in the field, the main aspects are analyzed, concerning the open issues on the use of PLCs, especially for medium voltage (MV) and low voltage (LV) systems. In this work the use of PLC in MV-LV networks is investigated, by means of simulations and experimental tests. These tests are performed in a test power network, which includes a MV overhead power line and a MV/LV transformer. The two ways communication channel is characterized, by transmitting a signal from the MV bus-bars and receiving it from the LV network and vice-versa. In this way the possibility to cross the power transformer is investigated.