1
GATE EE 2021
MCQ (Single Correct Answer)
+2
-0.67

Suppose $I_A, I_B$ and $I_C$ are a set of unbalanced current phasors in a three-phase system. The phase-B zero-sequence current $I_{B 0}=0.1 \angle 0^0$ p.u. If phase-A current $I_A=1.1 \angle 0^0$ p.u and phase- $C$ current $I_C=\left(1 \angle 120^0+0.1\right)$ p.u., then $I_B$ in p.u is

A

$1 \angle 240^{\circ}-0.1 \angle 0^{\circ}$

B

$1.1 \angle 240^{\circ}-0.1 \angle 0^{\circ}$

C

$1.1 \angle-120^{\circ}+0.1 \angle 0^{\circ}$

D

$1 \angle-120^{\circ}+0.1 \angle 0^{\circ}$

2
GATE EE 2018
MCQ (Single Correct Answer)
+2
-0.67
The positive, negative and zero sequence impedances of a three phase generator are Z1, Z2 and Z0 respectively. For a line-to-line fault with fault impedance Zf, the fault current is If1 = kIf, where If is the fault current with zero fault impedance. The relation between Zf and k is
A
$${Z_f} = {{\left( {{Z_1} + {Z_2}} \right)\left( {1 - k} \right)} \over k}$$
B
$${Z_f} = {{\left( {{Z_1} + {Z_2}} \right)\left( {1 + k} \right)} \over k}$$
C
$${Z_f} = {{\left( {{Z_1} + {Z_2}} \right)k} \over {1 - k}}$$
D
$${Z_f} = {{\left( {{Z_1} + {Z_2}} \right)k} \over {1 + k}}$$
3
GATE EE 2017 Set 1
Numerical
+2
-0
The positive, negative and zero sequence reactances of a wye-connected synchronous generator are 0.2 pu, 0.2 pu, and 0.1 pu, respectively. The generator is on open circuit with a terminal voltage of 1 pu. The minimum value of the inductive reactance, in pu, required to be connected between neutral and ground so that the fault current does not exceed 3.75 pu if a single line to ground fault occurs at the terminals is _______ (assume fault impedance to be zero). (Give the answer up to one decimal place)
Your input ____
4
GATE EE 2016 Set 1
Numerical
+2
-0
A 30 MVA, 3-phase, 50Hz, 13.8 kV, star-connected synchronous generator has positive, negative and zero sequence reactances, 15%, 15% and 5% respectively. A reactance (Xn) is connected between the neutral of the generator and ground. A double line to ground fault takes place involving phases ‘b’ and ‘c’, with a fault impedance of j0.1 p.u. The value of Xn (in p.u.) that will limit the positive sequence generator current to 4270 A is __________.
Your input ____

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