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3. A 60 Hz synchronous generator has a transient reactance of 0.3 per unit and inertia constant 5 MJ/MVA, connected to an infinite bus as shown in Figure 8. Resistances are neglected and reactance are marked on the diagram on a common MVA base. The generator is delivering real power P.= 0.8 per unit and Q=0.074 per unit to the infinite bus at a voltage of = 1.000° per unit. 1 E' X,= 0.2 GBE G₁ Xa=0.3 F Xu-03 X₁ -0.3 Figure 8 V=1.0 8 a) A temporary three-phase fault occurs at the sending end to the line at point F. When the fault is cleared, both lines are intact. Compute the critical clearing angle Do and the critical fault clearing time Oo. (10 marks) b) A three-phase fault occurs at the middle of one of the lines, the fault is cleared, and the faulted line is isolated. Determine the critical clearing angle Do. (10 marks)