Switchgear and Protection MCQ PDF Download

61. The reflection coefficient at the load end of a short-circuited line is

(a) zero.
(b) 1 ∠0°
(c) 1 ∠90°
(d) 1 ∠180°

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62. A short length of cable between the dead end tower and the power transformer

(a) reduces the steepness of the wave under certain conditions only.
(b) always reduces the steepness of the incident wave.
(c) steepness of the incident wave remains unaffected.

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63. The insulation strength of an EHV transmission line is mainly governed by

(a) load power factor.
(b) switching overvoltages.
(c) harmonics.
(d) corona.

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64. Which of the following neutral systems will require the lightning arrester of least voltage rating ?

(a) Insulated.
(b) Solidly earthed.
(c) Resistance earthed.
(d) Reactance earthed.

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65. Petersan coil is used for

(a) grounding of system neutral.
(b) to reduce fault current.
(c) connecting two interconnected systems
(d) for shunt compensation of transmission lines.

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66. Which one of the following grounding methods is used to reduce the tower footing resistance where earth resistance is low?

(a) Single driven rod.
(b) Multiple rods.
(c) Counter poises.
(d) Plates.

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68. Tower footing resistance of a transmission tower should be

(a) as high as possible.
(b) as low as possible.
(c) moderately high.
(d) moderately low.

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69 The method of neutral grounding affects the

(a) positive-sequence network.
(b) negative-sequence network.
(c) zero-sequence network.
(d) both positive and zero-sequence networks.

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70. The earth transformer is used to

(a) avoid the harmonics in the transformers.
(b) provide artificial neutral earthing where neutral point is not accessible.
(c) improve stability, pf the system.
(d) measure the voltage.

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71. The positive, negative and zero-sequence impedances of a solidly grounded system under steady-state condition always follow the relations

(a) Zo < Z1 < Z2
(b) Z1 > Z2 > Zo
(c) Z1 < Z2 < Z3
(d) Zo > Z1 > Z2

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72. In an isolated neutral system, when a single line to ground fault occurs

(a) persistent arcing grounds will be developed.
(b) voltage in the healthy phases rise to full line value causing insulation breakdown.
(c) the capacitive current in the faulty phase rises to 3 times its normal value.
(d) all of the above.

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73. The voltage of a transmission line can be controlled by

(a) excitation control.
(b) using induction regulator.
(c) reactive VAR injection methods.
(d) any of the above.

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74. The voltage of a particular bus is regulated by controlling the

(a) active power of the bus.
(b) reactive power of the bus.
(c) phase angle.
(d) phase angle and reactive power.

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Switchgear and Protection MCQ PDF Download

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