POWER SYSTEMS MCQS SET 06

POWER SYSTEMS MCQS SET 06

DISTRIBUTION SYSTEM OF ELECTRICAL POWER

1. In a dc 3 wire distributor using having unequal loads on the two sides
a. Both balancers operate as generators.
b. Both balancers operate as motors.
c. Balancers connected to the lightly loaded sides operate as a generator.
d. Balancers connected to the heavily loaded sides operate as a generator.
ANSWER: d. Balancers connected to the heavily loaded sides operate as a generator.
 

2. Why are the balancers fields cross connected in a three wire distribution system?
a. Equalise voltage on positive and negative outer
b. Boost the generated voltage.
c. Make both machines operate as unloaded motors.
d. All of these.
ANSWER: a. Equalise voltage on positive and negative outer
 

3. Which distribution system is energised by two or more generating stations or substations?
a. Radial systems.          b. Interconnected systems.
c. Ring main systems.      d. All of these.
ANSWER: b. interconnected systems.
 

4. A three wire dc distribution makes available how many voltages?
a. One           b. Two            c. Three       d. Both (a) and (b)
ANSWER: c. Three
 

5. If the voltage of the system is about 230 V, then what would be the highest and the lowest permissible voltage?
a. 242 and 214 V              b. 240 and 210 V
c. 244 and 216 V              d. 244 and 212 V
ANSWER: c. 244 and 216 V
 

6. What are boosters?
a. Is a high voltage and low circuit machine.
b. Is a series wound dc generator driven by dc shunt motor
c. Is a low voltage and high current generator operating on straight or linear portion of its voltage current characteristics
d. Both (b) and (c).
ANSWER: d. Both (b) and (c)
 

7. Why are the boosters inserted in the circuit?
a. Reduce current.              b. Increase current.
c. Reduce voltage drop.       d. Compensate for voltage drop.
ANSWER: d. Compensate for voltage drop.
 

8. Why are the floating neutral in a three phase supply considered undesirable?
a. High voltage across the load.
b. Low voltage across the load.
c. Unequal line voltages across the load.
d. None of above
ANSWER: c. Unequal line voltages across the load.
 

9. For purely domestic loads which type of distribution is employed?
a. Single phase two wire.            b. 3 phase 3 wire
c. 3 phase 4 wire                           d. None of these
ANSWER: a. Single phase two wire.
 

10. Which type of loads use 3 phase 4 wire ac system of distribution?
a. Balanced        b. Unbalanced      c. Both (a) and (b)          d. None 
ANSWER: b. Unbalanced

11. In a balanced 3 phase, 4 wire ac system the phase sequence is RYB. If the voltage of R phase = 230 ∠ 0° volts, then what will be the B phase?
a. 230 ∠ - 120°     b. 230 ∠ - 90°        c. 230 ∠ - 90°     d. 230 ∠ - 120°
ANSWER: d. 230∠ - 120°
 

12. What are ground detectors?
a. Used for detecting earth faults for all cables.
b. Used for detecting ground faults for underground cables.
c. Used for detecting all types of fault in a underground cables.
d. None of these.
ANSWER: b. Used for detecting ground faults for underground cables.
 

13. An industrial consumer has a load pattern of 2000 kW, 0.8 lag for 12 hours and 1000 kW UPF for 12 hours. What is its load factor?
a. 10.5            b. 0.75            c. 0.6                d. 2.0
ANSWER: b. 0.75