Fault Analysis MCQs

Power System MCQs

1. When all the three phases are short-circuited, it gives rise to_____.

a. Zero fault current

b. Symmetrical fault current

c. Asymmetrical fault current

d. Both (b) and (c)

2. The zero sequence reactance will be more than the positive sequence reactance, if the equipment is:________.

a. Generator

b. Transformer

c. Transmission line

d. Both (b) and (c)

3. The sequence networks for three-phase faults are connected in______.

a. Series

b. Parallel

c. Series opposition 

d. None of the above

4. The base impedance and base voltage for a given power system are 10 ohm and 400 V respectively. The base kVA and the base current will be respectively_____.

a. 4 kVA and 400 A

b. 16 kVA and 40 A

c. 4 kVA and 16 A

d. 16000 kVA and 40 A

5. In a line to ground fault on a system, the fault current is 1500 A. The zero sequence current is_____.

a. 500 A

b. 750 A

c. 0 A

d. 1500 A

6. In a practical sequence, currents were measured during a fault:________.

a. LLG fault 

b. L-G fault

c. Both (a) and (b)

d. 3-ф fault

7. Symmetrical faults can be analysed using______.

a. Thevenin's theorem on per phase basis

b. Bus admittance matrix

c. Symmetrical components

d.  Both (a) and (b)

8. In short circuit studies of a large power system network______.

a. Both series resistances of lines and load currents are neglected

b. Both series resistances of the lines and load currents are taken into consideration

c. The series resistances of lines are considered, while load currents are neglected

d. The series resistances of lines are neglected, while load currents are not neglected

9. Consider the following statements:

1. The positive and negative sequence components of voltage in a balanced 3-ф system are zero and only zero sequence component is present

2. The zero sequence current flows only where neutral return path is available

3. For a line to line fault, the sequence networks are connected in series

Which of the above statement(s) is/are true?

a. 2 only

b. 1 and 2 only

c. 2 and 3 only

d. 1 and 3 only

10. A three-phase transformer having zero-sequence impedance of Z₀ and neutral grounded with impedance Zₙ has the zero-sequence network as shown in the below figure.

The connections of its windings are____.

a. Star-delta

b. Star-star

c. Delta-star with neutral grounded

d. Star-star with neutrals grounded