1
GATE EE 2012
MCQ (Single Correct Answer)
+2
-0.6
A cylindrical 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 is $$1$$ pu. The critical clearing angle, in degrees, for a three-phase dead short circuit fault at the generator terminal is
A
$$53.5$$
B
$$60.2$$
C
$$70.8$$
D
$$79.6$$
2
GATE EE 2009
MCQ (Single Correct Answer)
+2
-0.6
A $$500$$ $$MW,$$ $$21$$ $$kV,$$ $$50$$ $$Hz,$$ $$3$$-phase, $$2$$-pole synchronous generator having a rated $$p.f.=$$$$0.9,$$ has a moment of inertia $$\,\,27.5\,\, \times \,\,{10^3}\,\,kg\,\,{m^2}.\,\,$$ The inertia constant $$(H)$$ will be
A
$$2.44$$ s
B
$$2.71$$ s
C
$$4.88$$ s
D
$$5.42$$ s
3
GATE EE 2008
MCQ (Single Correct Answer)
+2
-0.6
A lossless single machine infinite bus power system is shown below:

The synchronous generator transfers $$1.0$$ per unit of power to the infinite bus. The critical clearing time of circuit breaker is $$0.28$$ s. If another identical synchronous generator is connected in parallel to the existing generator and each generator is scheduled to supply $$0.5$$ per unit of power, then the critical clearing time of the circuit breaker will

A
Reduce to $$0.14$$ s
B
Reduce but will be more than $$0.14$$ s
C
Remain constant at $$0.28$$ s
D
Increase beyond $$0.28$$ s
4
GATE EE 2007
MCQ (Single Correct Answer)
+2
-0.6
Consider a synchronous generator connected to an infinite bus by two identical parallel transmission lines. The transient reactance $$x'$$ of the generator $$0.1$$ pu. Due to some previous disturbance, the rotor angle $$(d)$$ is undergoing an undamped oscillation, with the maximum value of $$\delta \left( t \right)$$ equal to $$\,{130^ \circ }\,.$$ One of the parallel lines trip due to relay mal-operation at an instant $$\,\,\,\,\,$$ when $$\,\delta \left( t \right)\,\, = {130^ \circ }\,\,$$ as shown in the figure. The maximum value of the per unit line reactance $$x,$$ such that the system does not lose synchronism subsequent to this tripping is
A
0.87
B
0.74
C
0.67
D
0.54
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