This is what IEEE Std 1207-2004 (see Sec 7.1.4, p63) says about the use of computer simulation for stability studies:
"Computerized simulations of turbine governing systems may be used to predict the performance of the system under the expected operating conditions. By properly simulating the turbine, the water passages, the generator, the turbine governing system, and the connected electrical load, the performance of the actual system can be predicted within a reasonable tolerance. If simulated stability studies are done early enough in the design process of the hydroelectric generating unit, there may be time to revise the design of one or more constraints to achieve the desired performance level. Simulated stability studies can also be used to predict the ideal tuning of the turbine governing system. This greatly reduces the amount of time required to tune the unit in the field."