GATE Electrical Engineering (EE) 2016 Shift 2 Solved Paper

A $50\mathit{M}\mathit{V}\mathit{A},10\mathit{k}\mathit{V},50\mathit{H}\mathit{z}$, star-connected, unloaded three-phase alternator has a synchronous reactance of 1 p.u. and a sub-transient reactance of $0.2\mathit{p}.\mathit{u}.$ If a 3-phase short circuit occurs close to the generator terminals, the ratio of initial and final values of the sinusoidal component of the short circuit current is ________.