Given three unbalanced line currents \(I_a = 0 + j12\) A, \(I_b = 5 - j10\) A and \(I_c = -10 - j5\) A. Find the negative sequence component of \(I_c\) in amperes.
A\(3.12\angle -14.3^\circ\)
B\(3.12\angle 14.3^\circ\)
C\(2.25\angle -14.3^\circ\)
D\(2.25\angle 14.3^\circ\)
#82📜 EE Pre-Board August 2015📘 PowerhouseEasy
Fault level means
AVoltage at the point of fault
BFault current
CFault power factor
DFault MVA
#83📜 EE Pre-Board August 2015📘 PowerhouseEasy
When a line to ground fault occurs, the current in a faulted phase is 300 A. What is the zero sequence current in this case?
AZero
B100 A
C200 A
D300 A
#84📜 EE Pre-Board August 2015📘 PowerhouseMedium
A 5-MVA, 13.8 kV/480 V, 5% impedance transformer is tapped at a 13.8 kV line where the Thevenin’s equivalent impedance is 0.5 Ω. Determine the fault current at the primary for a three-phase fault at the secondary.
A10,500 A
B4,200 A
C6,050 A
D3,300 A
#85📜 EE Pre-Board March 2016📘 PowerhouseEasy
In a circuit breaker, the time duration from the instant of the fault to the extinction of the arc is known as
AOperating time
Btotal clearing time
CLag time
Dlead time
#86📜 EE Pre-Board March 2016📘 PowerhouseEasy
What is the device function number for overcurrent relay?
A27
B67
C50
D51
#87📜 EE Pre-Board March 2016📘 PowerhouseHard
A synchronous generator having a subtransient reactance of 0.15 pu and operating at 5 percent above its rated voltage supplies a synchronous motor having a 0.20 pu subtransient reactance. The motor is connected to the generator by a transmission line and a transformer of total reactance 0.305 pu. A sudden three-phase fault occurs at the generator terminals. Determine the per unit subtransient fault current.
A–j7.079 pu
B–j8.0789 pu
C–j9.079 pu
D–j10.079 pu
#88📜 EE Pre-Board March 2016📘 PowerhouseMedium
The positive, negative, and zero sequence reactances of a 20-MVA, 13.2 kV synchronous generator are 0.3 pu, 0.2 pu and 0.1 pu, respectively. The generator is solidly grounded and is not loaded. A line to ground fault occurs on phase a. Neglecting all the resistances, determine the positive sequence component of the fault current.
A4,374A
B1,458A
C2,525 A
D7,576A
#89📜 EE Pre-Board March 2016📘 PowerhouseEasy
A balance delta connected load draws 100 A line current form a balanced 3- phase supply. Determine the zero sequence components of the currents.
A−50 − j86.6
B50 − j86.6
C86.6 − j50
D0
#90📜 EE Pre-Board March 2016📘 PowerhouseHard
The sequence components of the phase c current of a 3-phase system are as follows: \(I_{c0} = 0\), \(I_{c1} = 18.4\angle 88.4^\circ\), \(I_{c2} = 3.23\angle 48.2^\circ\). Find the phase b current in amperes.
A\(19.24\angle -218^\circ\)
B\(18\angle 42^\circ\)
C\(18\angle -42^\circ\)
D\(19.24\angle 218^\circ\)
#91📜 EE Pre-Board March 2017📘 PowerhouseEasy
What is the IEEE device function number 50?
AAC time overcurrent relay
Binstantaneous overcurrent relay
CAC circuit breaker
DDifferential protective relay
#92📜 EE Pre-Board March 2017📘 PowerhouseMedium
In a 3-phase, 4-wire system the currents in the a, b, and c lines under an abnormal condition of loading are \(I_a = 100\angle 30^\circ\) A, \(I_b = 50\angle 300^\circ\) A and \(I_c = 30\angle 180^\circ\) A. Find the zero sequence current.
A\(18.3\angle 6.81^\circ\) A
B\(17.3\angle 3.15^\circ\) A
C\(6.71\angle 5.4^\circ\) A
D\(27.29\angle 4.69^\circ\) A
#93📜 EE Pre-Board March 2017📘 PowerhouseEasy
The per unit value of 2 ohm resistor at 100 MVA base and 10 KV base voltage is
A4 pu
B2 pu
C0.5 pu
D0.2 pu
#94📜 EE Pre-Board March 2017📘 PowerhouseEasy
For a single line to ground fault, the zero sequence current is given by j3 pu. The current carried by the neutral during the fault is
Aj1 pu
Bj3 pu
Cj9 pu
Dj6 pu
#95📜 EE Pre-Board August 2017📘 PowerhouseMedium
Given three unbalanced line currents \(I_a = 0 + j12\) A, \(I_b = 5 - j10\) A and \(I_c = -10 - j5\) A. Find the negative sequence component of \(I_c\) in amperes.
A\(2.25\angle 105.7^\circ\)
B\(2.25\angle -134.3^\circ\)
C\(2.25\angle -14.3^\circ\)
D\(3.12\angle -14.3^\circ\)
#96📜 EE Pre-Board August 2017📘 PowerhouseEasy
The per-unit reactances of a synchronous generator are \(X_d = 1.1\), \(X_d' = 0.24\) and \(X_d'' = 0.15\). The generator is operating without load at 5 percent above rated voltage when a three-phase short circuit occurs at its terminals. What is the per unit subtransient fault current?
A4.375 pu
B0.955 pu
C6.67 pu
D7.0 pu
#97📜 EE Pre-Board August 2017📘 PowerhouseEasy
In a short circuit study, the positive, negative and zero sequence impedances are 0.25 pu, 0.25 pu and 0.3 pu, respectively. The base MVA is 100. Determine the fault current for a three-phase fault at the 115 kV level.
A3,000 A
B2,008 A
C1,506 A
D502 A
#98📜 EE Pre-Board March 2018📘 PowerhouseEasy
MHO relay is used for
Arectifier
Bcircuit breaker
Ctransmission lines
Dfeeders
#99📜 EE Pre-Board March 2018📘 PowerhouseMedium
Three unbalanced 3-phase currents are given as follows: \(I_a = 10\angle -30^\circ\) A, \(I_b = 0\), \(I_c = 10\angle -150^\circ\) A. Find the positive sequence component of \(I_a\).
A\(3.34\angle 150^\circ\) A
B\(3.34\angle -150^\circ\) A
C\(3.34\angle 30^\circ\) A
D\(3.34\angle -30^\circ\) A
#100📜 EE Pre-Board March 2018📘 PowerhouseEasy
The per unit impedance of a circuit element is 0.30. If the base kV and base MVA are halved, then the new value of the per unit impedance of the circuit element will be
