1
GATE EE 2018
Numerical
+1
-0.33
The series impedance matrix of a short three-phase transmission line in phase coordinates is $$\left[ {\matrix{ {{Z_s}} & {{Z_m}} & {{Z_m}} \cr {{Z_m}} & {{Z_s}} & {{Z_m}} \cr {{Z_m}} & {{Z_m}} & {{Z_s}} \cr } } \right]$$.

If the positive sequence impedance is (1 + 𝑗 10) $$\Omega$$, and the zero sequence is (4 + 𝑗 31) $$\Omega$$, then the imaginary part of Zm (in $$\Omega$$) is ______(up to 2 decimal places).
2
GATE EE 2018
Numerical
+1
-0.33
The positive, negative and zero sequence impedances of a 125 MVA, three-phase, 15.5 kV, star-grounded, 50 Hz generator are 𝑗0.1 pu, j0.05 pu and j0.01 pu respectively on the machine rating base. The machine is unloaded and working at the rated terminal voltage. If the grounding impedance of the generator is j0.01 pu, then the magnitude of fault current for a b-phase to ground fault (in kA) is __________ (up to 2 decimal places).
3
GATE EE 2014 Set 1
+1
-0.3
Three phase to ground fault takes place at locations $${F_1}$$ and $${F_2}$$ in the system shown in the figure.

If the fault takes place at location $${F_1}$$, then the voltage and the current at bus A are $${V_F1}$$ and $${{\rm I}_{F1}}$$ respectively. If the fault takes place at location $${F_2}$$, then the voltage and the current at bus A are $${V_{F2}}$$ and $${{\rm I}_{F2}}$$ respectively.

The correct statement about voltages and currents during faults at $${F_1}$$ and $${F_2}$$ is

A
$${V_{F1}}$$ leads $${{\rm I}_{F1}}$$ and $${V_{F2}}$$ leads $${{\rm I}_{F2}}$$
B
$${V_{F1}}$$ leads $${{\rm I}_{F1}}$$ and $${V_{F2}}$$ lags $${{\rm I}_{F2}}$$
C
$${V_{F1}}$$ lags $${{\rm I}_{F1}}$$ and $${V_{F2}}$$ leads $${{\rm I}_{F2}}$$
D
$${V_{F1}}$$ $${{\rm I}_{F1}}$$ and $${V_{F2}}$$ lags $${{\rm I}_{F2}}$$
4
GATE EE 2014 Set 1
+1
-0.3
A 2-bus system and corresponding zero sequence network are shown in the figure.

The transformers T1 and T2 are connected as

A
B
C
D
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