# Power Systems Questions and Answers – Inductance of a Single-Phase Two-Wire Line – 2

This set of Power Systems Interview Questions and Answers focuses on “Inductance of a Single-Phase Two-Wire Line – 2”.

1. A 10 MVA, 11 kV alternators has positive, negative and zero sequence reactance of 25%, 40%, 10% respectively. The resistance that must be placed in the neutral such that zero sequence of fault current for a single phase to ground fault will not exceed the rated line current in pu is ______
a) 0.22
b) 0.11
c) 0.16
d) 0.97

Explanation:

2. A 10 MVA, 11 kV alternator has positive, negative and zero sequence reactance of 25%, 40%, 10% respectively. The resistance that must be placed in the neutral such that fault current for a single phase to ground fault will not exceed the rated line current in pu is _____________
a) 0.97
b) 0.22
c) 0.87
d) 0.45

Explanation:

3. A 10 MVA, 11 kV alternator has positive, negative and zero sequence reactance of 25%, 40%, 10% respectively. The resistance that must be placed in the neutral such that fault current for a single phase to ground fault will not exceed the rated line current in ohms is __________
a) 11.7
b) 12.8
c) 2.66
d) 5.2

Explanation:

4. (I) Unsymmetrical spacing configurations cause the line interference.
(II) Unsymmetrical spacing causes the voltage induction in the communication lines.
a) (I) and (II) are valid
b) Only (I) is valid
c) Only (II) is valid
d) Both are invalid

Explanation: Both the statements are correct as the unsymmetrical spacing causes the unbalanced voltage generation.

5. (I) Unsymmetrical spacing configurations cause the line interference.
(II) Unsymmetrical spacing causes the voltage induction in the communication lines.
The above problems can be eliminated by ________
a) transposition
b) parallel lines
c) three phase
d) all of the mentioned

Explanation: Transposition meaning exchange of conductors will cause the net voltage induced in the other lines to be zero as the net inductance remains constant.
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6.Transposition is the mean to balance ____________
a) Inductance
b) Voltage
c) Current
d) All of the mentioned

Explanation: Transposition primarily balances the inductances in the line thus causing a constant inductance throughout the line.

7. Over the length of one transposition cycle of a power line, the total flux linkages of a nearby telephone line are zero for the unbalanced three phase currents.
a) True
b) False

Explanation: For an unbalanced supply, there will be non zero flux zero flux linkages in the telephone lines.

8. Over the length of one transposition cycle of a power line, the total flux linkages of a nearby telephone line are zero for the balanced three phase currents.
a) The above statement is valid
b) The above statement is invalid
c) It can’t be concluded
d) The above statement is valid for all conditions.

Explanation: Its valid only with balanced systems.

Sanfoundry Global Education & Learning Series – Power Systems.