A cylinder rotor generator delivers 0.5 pu power in the steady – state to an infinite bus through a transmission line of reactance 0.5 pu. The generator no-load voltage is 1.5 pu and the infinite bus voltage is 1 pu. The inertia constant of the generator is 5 MW – s / MVA and the generator reactance in 1 pu. The critical clearing angle, in degrees, for a three – phase dead short circuit fault at the generator terminal is
1. 53.5
2. 60.2
3. 70.8
4. 79.6