1
GATE EE 2004
+2
-0.6
A $$3$$-phase generator rated at $$110$$ MVA, $$11$$ kV is connected through circuit breakers to a transformer. The generator is having direct axis sub-transient reactance $$X'{'_d} = 19\% ,\,\,$$ transient reactance $$X{'_d} = 26\% \,\,$$ and synchronous reactance $$=130$$%. The generator is operating at no load and rated voltage when a three phase short circuit fault occurs between the breakers and the transformer. The magnitude of initial symmetrical rims current in the breakers will be
A
$$4.44$$ kA
B
$$22.20$$ kA
C
$$30.39$$ kA
D
$$38.45$$ kA
2
GATE EE 2003
+2
-0.6
A 20-MVA, 6.6-kV, 3-phase alternator is connected to a 3-phase transmission line. The per unit positive sequence, negative sequence and zero sequence impedance of the alternator are j0.1, and j0.04 respectively. The neutral of the alternator is connected to ground through an inductive reactor of j0.05 p.u. The per unit positive, negative and zero sequence impedances of the transmission line are j0.1 and j0.3 respectively. All per unit values are based on the machine ratings. A solid ground fault occurs at one phase of the far end of the transmission line. The voltage of the alternator neutral with respect to ground during the fault is
A
513.8 V
B
889.9 V
C
1112.0 V
D
642.2 V
3
GATE EE 2003
+2
-0.6
A three-phase alternator generating unbalanced voltages is connected to an unbalanced load through a 3-phase transmission line as shown in figure. The neutral of the alternator and the star point of the load are solidly grounded. The phase voltages of the alternator are
$${E_a} = 10\angle {0^ \circ }V,\,\,\,{E_b} = 10\angle - {90^ \circ }V,\,\,{E_c} = 10\angle {120^ \circ }\,\,V.\,\,\,\,$$ The positive sequence component of the load current is
A
$$1.310\angle - {107^ \circ }A\,$$
B
$$0.332\angle - {120^ \circ }A\,$$
C
$$0.996\angle - {120^ \circ }A\,$$
D
$$3.510\angle - {81^ \circ }A\,$$
4
GATE EE 2002
+2
-0.6
A generator is connected to a transformer which feeds another transformer through a short feeder. The zero sequence impedance values are expressed in pu on a common base and are indicated in figure. The Thevenin equivalent zero sequence impedance at point B is
A
0.8 + j0.6
B
0.75 + j0.22
C
0.75 + j0.25
D
1.5 + j0.25
EXAM MAP
Medical
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