A synchronous generator or reactance 1.20 p.u. is connected to an infinite bus through transformers and a line of combined reactance of 0.6 p.u.

•The generator no load voltage is 1.20 p.u. and its inertia constant is 4 seconds.

•Line resistance and machine damping is negligible.

•System frequency of 50Hz:

•Calculate the frequency of natural oscillations when the generator is loaded 50%, 75%, 80% and 90% of its maximum power limit respectively.