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GATE 2015 EE – Question 54

Power Systems · Symmetrical components, Symmetrical and unsymmetrical fault analysis · 2 marks · Multiple choice

A sustained three-phase fault occurs in the power system shown in the figure. The current and voltage phasors during the fault (on a common reference), after the natural transients have died down, are also shown. Where is the fault located?

Two generators connected through a double-circuit transmission line, with bus P on the left, bus S on the right, and the two parallel lines carrying currents $I_1$, $I_2$, $I_3$, $I_4$. A phasor diagram shows $V_1$, $V_2$ and the four currents.
  1. Location P
  2. Location Q
  3. Location R
  4. Location S

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Show answer and explanation

Correct answer: (B) Location Q

Explanation

During a fault, the currents on both sides of the fault flow towards it. The phasor diagram shows the current on line Q reversed relative to the others, which points to a fault on that line at location Q. This matches the official key.