1
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
$$3.510\angle - {81^ \circ }A\,$$
2
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
3
GATE EE 2001
+2
-0.6
A $$50$$ Hz alternator is rated $$500$$ $$MVA,$$ $$20$$ $$kV,$$ with $${X_d} = 1.0$$ per unit and $$X'{'_d} = 0.2$$ per unit. It supplies a purely resistive load of $$400$$ $$MW$$ at $$20$$ $$kV.$$ The load is connected directly across the generator terminals when a symmetrical fault occurs at the load terminals. The initial rms current in the generator in per units is
A
$$7.22$$
B
$$6.4$$
C
$$3.22$$
D
$$2.2$$
4
GATE EE 2000
+2
-0.6
The severity of line-to-ground and three phase faults at the terminals of an unloaded synchronous generator is to be same. If the terminal voltage is
$$1.0$$ p.u. and $${Z_1} = {Z_2} = j0.1\,\,$$ p.u.,
$$\,{Z_0} = j0.05\,\,\,\,\,$$ p.u., for the alternator, then the required inductive reacttance for neutral grounding is
A
$$0.0166$$ p.u.
B
$$0.05$$ p.u.
C
$$0.1$$ p.u.
D
$$0.15$$ p.u.
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