"In the last years the power distribution grid is evolving from a passive isolated model to an active system where different parties need to communicate in a standard and secure way. With the development of the Smart Grids, the Distribution System Operator (DSO) must enhance the ICT (Information and Communication Technology) and security aspects in order to perform grid control and management actions considering the interaction with the Distributed Energy Resources (DERs) and the other actors of this advanced integrated system. The crucial role of standard communication protocols and procedures is easy arguable when it comes in terms of interoperability among deployed devices from different manufacturers, that may spread over areas controlled by different operators. The need to secure smart grid communications from the threats of cyber attacks represents another important dimension that must be addressed: malicious entities can exploit ICT vulnerabilities in Smart Grids to cause damages to grid devices or malfunctions of grid control activities. This work aims at proposing a methodology to assess the security of Smart Grid communications, whose approach is based on the adoption of standard communication and security protocols. To evaluate the effectiveness of the security measures it’s appropriate to test them in an environment as much as possible aligned with the real implementation: the results included in this paper are based on the cyber security experiments over realistic voltage control scenarios in the operation of active grids performed at the RSE PCS-ResTest Lab."