Considering the present energy generation scenario where a large number of hydro power plants (HPP) in Brazil have been in operation for quite some time now, and therefore need careful attention in order to have their useful life extended, the present work aims to identify critical component faults that cannot be observed by the current monitoring system present in the power plant under study, and accordingly suggest updates in this system. Therefore, the developed method initially proposes a detailed study of the current hydro generator components using two techniques: Functional Tree (FT) and Internal Block Diagram (IBD), the latter from Systems Modelling Language (SysML). The results obtained with these techniques indicate the functions of all hydrogenerator components and the interfaces between them. Next, the method proposes the use of the Failure Modes and Symptoms Analysis (FMSA) technique, in order to analyze if the monitoring technologies present in the system under study can properly diagnose and prognose any fault in an optimized way. The results obtained through the application of FMSA were able to identify the weak points of the current monitoring system and therefore contributed to the addition of new monitoring points in the plant that will maximize the confidence interval in both the diagnosis and prognosis processes.