How to observe a superimposed low frequency component on a power frequency signal?

I cannot find a way to observe the 27 Hz component in the Torque graphs of the "power_thermal" file for SSR simulation. The help section associated with this file describes the schematic and concludes that a 27 Hz sub-synchronous component is present and leads to torque amplification. However, there has been no mention of how this mode is to be observed. Please, help me with this problem. Thank you.

Answer 1

[Sabin]

From the doucmentation: "Open the Scope connected to the STG model. Run the simulation. Observe the speed deviations on the top axis of the Scope and the torques transmitted between the shaft's masses on the bottom axis. A peak torque of over 4 pu is observed for T2 between mass 1 (Generator) and mass 2 (LP turbine). The frequency of the oscillations observed in the torques and speed deviations is about 27 Hz."

27 Hz means a period of 0.037 seconds. Looking at the results we can see the frequency is around this value. It is also possible to use a Spectrum Analyzer to get more precise insights.