Power System(Transmission & Distribution)-04:

77)   Where the radial systems are generally employed?

a. Where power is generated at low voltage
b. Where power is generated at high voltage
c. Where power is generated at low voltage and substation is located at the centre of the load
d. Where power is generated at high voltage and substation is located at the centre of the load

78)   What is the main advantage of ring main system over radial system?

i. Voltage drop in the feeder is less.
ii. Power factor is higher.
iii. Supply is more reliable.

Which among the above statements are correct?

a. i and ii only
b. ii and iii only
c. i and iii only
d. i, ii and iii

79)   The null point of a uniformly loaded distributor feed at equal voltage at both ends lies at

a. Mid point
b. Either end
c. Two third distance from one end
d. One fourth distance from one end

80)   In a distribution system, which of the following items shares the major cost?

a. Conductors
b. Earthing systems
c. Distribution transformer
d. Insulators

81)   Which type of distribution is preferred in residential areas?

a. Single phase, two wire
b. Three phase, three wire
c. Three phase, four wire
d. Two phase, four wire

82)   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.

83)   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

84)   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

85)   A three wire dc distribution makes available how many voltages?

a. One
b. Two
c. Three
d. All of these

86)   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

 

87)   What will be the pd at point B if a pd of 300 V is maintained at a point A, for a 2 wire dc distributor cable AB if 2 km long and supplies loads of 100A, 150A, 200A, and 50A suited at 500m, 1000m, 1600m, and 2000m from the feeding point A. Each conductor has a resistance of 0.01 Ω per 1000 m.

a. 288 V
b. 287.6 V
c. 295.36 V
d. 291.2 V

 

88)   What is the loss factor in a distribution system?

a. 0.3 * load factor + 0.7 (load factor)²
b. 0.5 * (load factor)
c. Load factor
d. 0.7 * load factor + 0.3 (load factor)²

 

89)   A 2 wire dc street mains AB, 600 m long is fed from both ends at 220 V. Loads of 20 A, 40 A, 50 A and 30 A are tapped at distances 100m, 250m, 400m and 500m from the end A. If the area of cross section of distributor is 1 cm², what will be the minimum consumer voltage? If ? = 1.7 * 10^-6 Ω cm.

a. 220 V
b. 215.69 V
c. 218.36 V
d. 222.58 V

 

90)   A distribution system is shown in figure with load currents as marked. The two ends of the feeder are fed by voltage sources such that V_p = V_q = 3 V, the value of the voltage V_p for a minimum voltage of 220 V at any point along the feeder is

a. 225.89 V
b. 222.89 V
c. 220.0 V
d. 228.58 V

91)   A uniformly loaded dc distributor is fed at both ends with equal voltages. In comparison to a similar distributor fed at one end only, what will be the maximum voltage drop?

a. One fourth
b. Half
c. One third
d. One sixth

92)   A uniformly loaded dc distributor is fed at both ends with equal voltages. In comparison to a similar distributor fed at one end only, what will be the drop at the midpoint be?

a. One fourth
b. Half
c. One third
d. One sixth

93)   Installation of capacitors at suitable locations and of optimum size in a distribution system results in

i. Improved voltage regulation.
ii. Reduction in distribution power losses.
iii. Reduction of kVA rating of distribution transformers.

Which among the above statements are correct?

a. i only
b. i and ii only
c. iii only
d. All of these

94)   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)
e. None of these

95)   Why are the boosters inserted in the circuit?

a. Reduce current
b. Increase current
c. Reduce voltage drop
d. Compensate for voltage drop

96)   Why is the floating neutral in a three phase supply considered as undesirable?

a. High voltage across the load
b. Low voltage across the load
c. Unequal line voltages across the load
d. None of above

97)   A 300m ring distributor has loads as shown in the fig. The distances are in metres. The resistance of each conductor is 0.2 W per 1000 metres and loads are tapped off at B, C, D. If the distributor is fed at A at 240 V, what will be the voltage at B?

a. 220.6 V
b. 236.9 V
c. 240.6 V
d. 235.97 V

98)   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

99)   Which type of loads use 3 phase 4 wire ac system of distribution?

a. Balanced
b. Unbalanced
c. Both (a) and (b)
d. None of these

100)   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°

101)   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

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