1
GATE EE 2006
+2
-0.6
For a power system the admittance and impedance matrices for the fault studies are as follows. \eqalign{ & {Y_{bus}} = \left[ {\matrix{ { - j8.75} & {j1.25} & {j2.50} \cr {j1.25} & { - j6.25} & {j2.50} \cr {j2.50} & {j2.50} & { - j5.00} \cr } } \right] \cr & {Z_{bus}} = \left[ {\matrix{ {j0.16} & {j0.08} & {j0.12} \cr {j0.08} & {j0.24} & {j0.16} \cr {j0.12} & {j0.16} & {j0.34} \cr } } \right] \cr}The pre-fault voltages are $$1.0$$ $$p.u.$$ at all the buses. The system was unloaded prior to the fault. A solid $$3$$ phase fault takes place at bus $$2.$$ The post fault voltages at buses $$1$$ and $$3$$ in per unit respectively are A $$0.24,0.63$$ B $$0.31, 0.76$$ C $$0.33, 0.67$$ D $$0.67, 0.33$$ 2 GATE EE 2006 MCQ (Single Correct Answer) +2 -0.6 For a power system the admittance and impedance matrices for the fault studies are as follows. \eqalign{ & {Y_{bus}} = \left[ {\matrix{ { - j8.75} & {j1.25} & {j2.50} \cr {j1.25} & { - j6.25} & {j2.50} \cr {j2.50} & {j2.50} & { - j5.00} \cr } } \right] \cr & {Z_{bus}} = \left[ {\matrix{ {j0.16} & {j0.08} & {j0.12} \cr {j0.08} & {j0.24} & {j0.16} \cr {j0.12} & {j0.16} & {j0.34} \cr } } \right] \cr}

The pre-fault voltages are $$1.0$$ $$p.u.$$ at all the buses. The system was unloaded prior to the fault. A solid $$3$$ phase fault takes place at bus $$2.$$

The per unit fault feeds from generators connected to buses $$1$$ and $$2$$ respectively are

A
$$1.20, 2.51$$
B
$$1.55, 2.61$$
C
$$1.66, 2.50$$
D
$$5.00,2.50$$
3
GATE EE 2005
+2
-0.6
The network shown in the given figure has impedances in p.u. as indicated. The diagonal element $$Y22$$ of the bus admittance matrix $${Y_{BUS}}$$ of the network is
A
$$-j$$ $$19.8$$
B
$$+j$$ $$20.0$$
C
$$+j$$ $$0.2$$
D
$$-j$$ $$19.95$$
4
GATE EE 2003
+2
-0.6
The bus impedance matrix of a $$4$$-bus power system is given by $${Z_{bus}} = \left[ {\matrix{ {j0.3435} & {j0.2860} & {j0.2723} & {j0.277} \cr {j0.2860} & {j0.3408} & {j0.2586} & {j0.2414} \cr {j0.2723} & {j0.2586} & {j0.2791} & {j0.2209} \cr {j0.2277} & {j0.2414} & {j0.2209} & {j0.2791} \cr } } \right]$$\$

A branch having an impedance of $$j0.2\Omega$$ is connected between bus $$2$$ and the reference. Then the values of $${Z_{22,new}}$$ and $${Z_{23,new}}$$ of the bus impedance matrix of the modified network are respectively

A
$$j0.5408\,\Omega \,\,\,$$ and $$\,\,\,j0.4586\,\Omega$$
B
$$j0.1260\,\Omega \,\,\,$$ and $$\,\,\,j0.0956\,\Omega$$
C
$$j0.5408\,\Omega \,\,\,$$ and $$\,\,\,j0.0956\,\Omega$$
D
$$j0.1260\,\Omega \,\,\,$$ and $$\,\,\,j0.1630\,\Omega$$
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