1
GATE EE 2007
+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
2
GATE EE 2006
+2
-0.6
A generator feeds power to an infinite bus through a double circuit transmission line. A 3 phase fault occurs at the middle point of one of the lines. The infinite bus voltage is 1 pu, the transient internal voltage of the generator is 1.1 pu and the equivalent transfer admittance during fault is 0.8 pu. The 100 MVA generator has an inertia constant of $$5$$ MJ/MVA and it was delivering 1.0 pu power prior of the fault with rotor power angle of $${30^ \circ }\,\,$$. The system frequency is 50Hz.

The initial accelerating power (in pu) will be

A
1.0
B
0.6
C
0.56
D
0.4
3
GATE EE 2006
+2
-0.6
A generator feeds power to an infinite bus through a double circuit transmission line. A $$3$$ phase fault occurs at the middle point of one of the lines. The infinite bus voltage is $$1$$ pu, the transient internal voltage of the generator is $$1.1$$ pu and the equivalent transfer admittance during fault is $$0.8$$ pu. The 100 MVA generator has an inertia constant of $$5$$ MJ/MVA and it was delivering $$1.0$$ pu power prior of the fault with rotor power angle of $${30^ \circ }\,\,$$. The system frequency is 50Hz.

If the initial accelerating power is $$X$$ pu, the initial acceleration in elect deg/sec2, and the inertia constant in MJ-sec/elect deg respectively will be

A
$$31.4$$$$X,$$ $$18$$
B
$$1800$$ $$X,$$ $$0.056$$
C
$$X/1800,$$ $$0.056$$
D
$$X/31.4,$$ $$18$$
4
GATE EE 2005
+2
-0.6
A generator with constant 1.0 p.u. terminal voltage supplies power through a step-up transformer of 0.12 p.u. reactance and a double-circuit line to an infinite bus bar as shown in the figure. The infinite bus voltage is maintained at 1.0 p.u. Neglecting the resistances and susceptances of the system, the steady state stability power limit of the system is 6.25 p.u. If one of the double-circuit is tripped, the resulting steady state stability power limit in p.u. will be
A
12.5
B
3.125
C
10.0
D
5.0
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