Power System - II (3150911) MCQs

MCQs of Unsymmetrical Fault Analysis

Showing 21 to 30 out of 31 Questions
21.
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
(a) j1 pu
(b) j3 pu
(c) j9 pu
(d) j6 pu
Answer:

Option (c)

22.
When a fault occurs in a power system the zero sequence component of current becomes zero. The type of fault is
(a) 3-phase to ground fault
(b) Line to line fault
(c) Double line to ground fault
(d) Line to ground fault
Answer:

Option (b)

23.
The following sequence currents were recorded in a power system under a fault condition Ipositive = j1.923 pu, Inegative = – j0.8 pu, Izero = – j1.246 pu.The fault is
(a) Line to ground
(b) Line to line
(c) Line to line to ground
(d) Three-phase
Answer:

Option (c)

24.
Which of the network gets affected by the method of neutral grounding?
(a) Zero sequence network
(b) Positive sequence network
(c) Negative sequence network
(d) All of above
Answer:

Option (a)

25.
Zero sequence current flows in a transmission line when there is
(a) Double line to ground fault
(b) An over voltage in a line caused by charged load
(c) Line to line fault
(d) Fault across all the lines
Answer:

Option (a)

26.
Zero sequence fault currents are absent when the fault is
(a) Single line to ground
(b) Line to line
(c) Double line to ground
(d) Any of above
Answer:

Option (b)

27.
When a line to ground fault occurs, the current in faulted phase is 100 A.  Zero sequence current in this case will be
(a) Zero
(b) 33.3 A
(c) 66.6 A
(d) 100 A
Answer:

Option (b)

28.
Star connected, 3 phase, 11kV, 25 MVA alternator with its neutral grounded through 0.033 pu reactance has positive, negative and zero sequence reactance of 0.2 pu, 0.1 pu and 0.1 pu respectively. A single line to ground fault on one of its terminal would result in a fault MVA
(a) 150 MVA
(b) 125 MVA
(c) 100 MVA
(d) 50 MVA
Answer:

Option (a)

29.
The severity of line to ground and three phase fault at the terminal of an unloaded synchronous generator is to be the same. If terminal voltage is 1 pu and Z1= Z2=j0.1 pu, Z0= j0.05 pu for the alternator, then the required inductive reactance for neutral grounding is
(a) 0.0166 pu
(b) 0.05 pu
(c) 0.1 pu
(d) 0.15 pu
Answer:

Option (b)

30.
When a 50 MVA, 11 kV, 3-phase generator is subjected to a three phase fault, the fault current is -j5 pu. When it is subjected to a line to line fault, positive sequence current is -j4 pu. Positive sequence and negative sequence reactances are respectively
(a) j0.2 pu and j0.05 pu
(b) j0.2 pu and j0.25 pu
(c) j0.25 pu and j0.25 pu
(d) j0.05 pu and j0.05 pu
Answer:

Option (a)

Showing 21 to 30 out of 31 Questions