# Power Systems Questions and Answers – Distribution Systems – 2

This set of Power Systems Questions and Answers for Aptitude test focuses on “Distribution Systems – 2”.

1. For the given circuit diagram for the substation the voltage between the two outer conductors is
__________

Explanation: The maximum voltage levels between the two outer conductors is double the supply fed to it and the its rms is √2 V.

2. For the given circuit diagram for the substation fed with 315 kV, the voltage between the two outer conductors is ____________
a) 445.5 kV
b) 890 kV
c) 630 kV
d) 223 kV

Explanation: The maximum voltage levels between the two outer conductors are double the supply fed to it and its rms is √2V.
Voltage between the two outer conductors is √2*315 kV = 445.5 kV.

3. If a 2-wire ac single phase distribution system operating at ‘P’ MW and ‘V’ kV, operating at the power factor of 0.8, then the current in the outer wire in kA is ______
a) 0.8P/V
b) 1.131P/V
c) 1.88P/V
d) 0.088P/V

Explanation: I = P/(√2 V Cos Ø) = 0.88P/V.

4. If a 2-wire ac single phase distribution system operating at ‘30’ MW and ‘315’ kV, operating at the power factor of 0.8, then the current in the outer wire in kA is _____
a) 0.0838
b) 83.8
c) 8.38
d) 1.131

5. For a 2-wire ac single phase distribution system operating at ‘30’ MW and ‘315’ kV, operating at the power factor of 0.8 having 15Ω of resistance of each wire, then the copper loss at the substation in kW will be ___________
a) 210.67
b) 105.33
c) 240.87
d) 108.27

Explanation: Current in the line,
Power losses = 2*I2*R = 2*83.822*15 = 210.673 kW.
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6. For a 2-wire ac single phase distribution system operating at ‘30’ MW and ‘315’ kV, operating at the power factor of 0.8 having 15Ω of resistance of each wire, then the power received at the consumer end will be ____________
a) 29.79 MW
b) 29.895 MW
c) 29.76 MW
d) 29 MW

Explanation: Current in the line,
Power losses = 2*I2*R = 2*83.822*15 = 210.673 kW
Power received = 30-210.67 = 29.79 MW.

7. For a 2-wire ac single phase distribution system operating at ‘P’ MW and ‘V’ kV, operating at the power factor of 0.8. The copper losses of the system will be proportional to ___________

8. The maximum rms voltage between one phase and ground neutral for a three phase 4-wire ac system will be ____________
a) 221.32 kV
b) 313 kV
c) 442 kV
d) 127 kV

Explanation: The maximum rms phase voltage = Vph/√2 = 313/√2 = 221.32 kV.

9. The maximum rms voltage between one phase and ground neutral for a three phase 4-wire ac system will be ___________________
a) 171.46 kV
b) 242.5 kV
c) 221 kV
d) 127 kV

Explanation: The maximum rms phase voltage = Vph/√2 = 420/√(2*3) = 221.32 kV.

10. For the circuit diagram as depicted in the figure, the current per phase under balanced condition with a consumer end load of 90 kW, 414V operating at a power factor of 0.65 is ___________
a) 157.66 A
b) 152 A
c) 111.4 A
d) 193.1 A

Explanation: Current per phase in the line, I = P/(√2 V/√3 CosØ) = 90000/(√2*414/√3*0.65) = 157.66 A.

Sanfoundry Global Education & Learning Series – Power Systems.

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