Model tests for hydraulic turbines and storage pumps are regulated by the IEC 60193 standard. Measurements concerning the dynamic behaviour are explicitly dealt with, and the standard cautions that some amount of uncertainty with regard to transposing model results to the prototype machine. Larger discrepancies are said to become possible if there is some dynamic interaction between the machine and the surrounding system (water conduit, electric grid).


However, as some kind of interaction occurs in every plant, a more specific wording would be desirable; actually the state of the art is already more developed. It would be necessary to distinguish between purely local flow features und others that interact with the system. Among researchers this distinction has been known since decades, in particular for the regular part-load pulsation of the Francis turbines, but has not been adopted for practical use.


For some hydraulic pulsation phenomena the transferability between the reduced scale model and the prototype is notoriously poor. One example is the pulsation at high partial load, occurring frequently at the model but quite rarely at the plant. Another example is the high-load instability which may occur at the prototype but not during the model test.