Power Systems (DC Transmission and Distribution)

1. If in a d.c. 2-wire feeder, drop per feeder conductor is 2%, transmission efficiency of
the feeder is ........................... percent.
(a) 98
(b) 94
(c) 96
(d) 99

2. Transmitted power remaining the same, if supply voltage of a dc 2-wire feeder is increased by 100 percent, saving in copper is .......................... percent.
(a) 50
(b) 25
(c) 100
(d) 75

3. A uniformly-loaded d.c. distributor is fed at both ends with equal voltages. As compared
to a similar distributor fed at one end only, the drop at middle point is
(a) one-half
(b) one-fourth
(c) one-third
(d) twice.

4. In a d.c. 3-wire distributor using balancers and having unequal loads on the two sides
(a) both balancers run as motors
(b) both balancers run as generators
(c) balancer connected to heavily-loaded side runs as a motor
(d) balancer connected to lightly-loaded side runs as a motor.

5. As compared to a dc 2-wire distributor, a 3-wire distributor with same maximum voltage
to earth uses only...................... percent of copper.
(a) 66.7
(b) 33.3
(c) 31.25
(d) 150

6. In a d.c. 3-wire distribution system, balancer fields are cross-connected in order to
(a) make both machines run as unloaded motors.
(b) equalize voltages on the positive and negative outers
(c) boost the generated voltage
(d) balance loads on both sides of the neutral.

Answers
1. (c) 2. (a) 3. (b) 4. (d) 5. (c) 6. (a)

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