The paper describes a study conducted on the control valve and the actuation systems of a Steam Turbine. These devices are of utmost importance, as they rule the machine final power production and rotational speed, thus their accurate modelling is fundamental for a valuable dynamic analysis of the whole system. In particular, a dynamic model developed in the Matlab/Simulink environment is proposed, which supports the analysis of the operational stability of the hydro-mechanical system as well as the failure modes that it may face during operation. The model has been successfully validated through specific field tests conducted on the actuation system at a cogeneration plant located in the General Electric Oil & Gas - Nuovo Pignone facility of Florence. The proposed work also highlights the requirements that new actuation technologies should fulfill in order to meet control valve system performance criteria and is thus useful as both a methodological approach and a "virtual benchmark" allowing to validate in advance any new actuation system. (C) 2017 Elsevier Ltd. All rights reserved.