CL WADHWA bits solutions (120-124)

Lesson 21 of 21 • 45 upvotes • 14:59mins

Anvesh Sameer

120. If Ia1 is the positive sequence current of an alternator and Z1, Z2 and Z0 are the sequence impedances of the alternator. The drop produced by the current Ia1 will be: (a) Ia1 Z1 (b) Ia1 (Z1 + Z2) (c) Ia1 (Z1 + Z2 + Z0) (d) Ia1 (Z2 + Z0). 121. For the system shown in diagram below, a line-to-ground fault on the line side of the transformer is equivalent to: (a) A line-to-ground fault on the generator side of the transformer (b) A line-to-line fault on the generator side of the transformer (c) A double line-to-ground on the generator side of the transformer (d) A 3-phase fault on the generator side of the transformer. × F

    122. The positive sequence component of voltage at the point of fault is zero when it is a: (a) 3-phase fault (b) L-L fault (c) L-L-G fault (d) L-G fault. 123. Tick out the correct statement: (a) The negative and zero sequence voltages are maximum at the fault point and decrease towards the neutral (b) The negative and zero sequence voltages are minimum at the fault point and increase towards the neutral (c) The negative sequence is maximum and zero sequence minimum at the fault point and decrease and increase respectively towards the neutral. (d) None of the above. 124. For complete protection of a 3-phase line: (a) Three-phase and three-earth fault relays are required (b) Three-phase and two-earth fault relays are required (c) Two-phase and two-earth fault relays are required (d) Two-phase and one-earth fault relays are required.