# Power Systems Questions and Answers – Distribution Systems – 1

This set of Power Systems Multiple Choice Questions & Answers (MCQs) focuses on “Distribution Systems – 1”.

1. A transmission and distribution engineer needed to design the sub transmission substation. The tapping component needed will be _______________
a) feeder
b) distributor
c) transmitter
s) tap-changing transformer

Explanation: For the sub transmission level, there is no tapping at various level does not take place. For this a feeder is used.

2. While designing the distribution to locality of one lac population with medium dense load requirement, we can employ ___________
b) parallel system
c) ring main system
d) any of the mentioned

Explanation: A radial system is used for the medium requirement of loading and a medium dense population as it becomes easier to install and operate.

3. A _________ distribution system is more reliable than the ______ distribution system.
b) parallel, ring
d) ring, parallel

Explanation: A parallel distribution system has two end feeding and an alternative of parallel line, so in case there is a fault, the isolator can isolate the faulty part and let the healthy system operate.

4. For the figure shown, having a 2-wire dc system where mid point is earthed, having resistance of 20 ohms, with a power transmitted of 5 MW at the voltage level of 440 kV.
The power loss of the distribution system will be ___________

a) 5165 W
b) 515 kW
c) 10330 W
d) 2583 W

Explanation: I = P/V = 5000000/440000 = 11.36 A
Power loss = 2I2*R = 2* 11.362*20 = 5165 W.

5. For the figure shown, having a 2-wire dc system where mid point is unearthed, having resistance of 20 ohms, with a power transmitted of 5 MW at the voltage level of 440 kV.
The power loss of the distribution system will be ___________

a) 5165 W
b) 515 kW
c) 10330 W
d) 2583 W

Explanation: I = P/V = 5000000/440000 = 11.36 A
Power loss = I2*R = 2* 11.362*20 = 2583 W.

6. A DC 2-wire system with mid-point earthed having cross-sectional area of each conductor be ‘a’ and resistance ‘R1’. If the DC tow wire replaces the system, then the ratio of volume of each conductor V1/V2 will be ___________
a) ¼
b) ½
c) 4
d) 2

Explanation: Let the power losses remain constant over the systems, then
2P2R/V2 = 2P2R1/2*V2
or, R = R1/4;
As R = lρ/a;
a1 = a/4;
So, V1/V1 = 1/4.
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7. While designing the distribution sub stations by the designer, it is required to use the _______ for the discrete power tapping.
a) distributor
b) power transformer
c) distribution transformer
d) feeder

Explanation: For the discrete tapping of the power the consumer level it is the distributor which is employed at the sub stations and consumer levels.

8. A DC 2-wire system with mid-point earthed having cross-sectional area of each conductor be ‘a’ and resistance ‘R1’. If this is replaced by monopolar system, then saving of copper will be ______
a) ½
b)b¼
c) 2
d) 4

Explanation: Let the power losses remain constant over the systems, then
2P2R/V2 = 2P2R1/V2
or, R1 = R
As R = lρ/a;
a1 = a
So, V1/V1 = a1*2l/a1 = 1/2.

9. For the single phase 2-wire system, the maximum voltage between the outer wires and earth is ______________
a) V/√2
b) √2V
c) V
d) 2V

Explanation: The midpoint voltage will be V/√2.

10. For the given distribution system the maximum voltage at the midpoint will be ________
a) 155.6 V
b) 311.12 V
c) 622 V
d) 220 V

Explanation: Vmax = V/√2 = (440/2)/√2 = 155.6 V.

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