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Power Systems
Z-Bus Building Algorithm
The prefault ...
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The prefault voltage is 1.05 p.u. and prefault load current is neglected. For a bolted three-phase short circuit at bus 1 use Zbus to calculate the contribution to the fault current from the transmission line.

Zbus matrix is given as, Zbus=+j[0.115650.045800.045800.13893]p.u.

A
-j 2.079 p.u.
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B
-j4.074 p.u.
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C
-j0.512 p.u.
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D
0. p.u.
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Solution

The correct option is A -j 2.079 p.u.
The voltage at buses 1 and 2 during the fault are,
E1=(1−Z11Z11)VF=0
E2=(1−Z21Z11)VF=(1−j0.04580j0.11565)1.05∠0∘=0.6342∠0∘ p.u,

I21=E2−E1j(Xline+Xy1+Xy2)=0.6342−0j0.3050=−j2.079 p.u.

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