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GATE 2015 EE – Question 52

Power Systems · Per-unit quantities, Bus admittance matrix, Gauss-Seidel and Newton-Raphson load flow methods · 2 marks · Multiple choice

Determine the correctness or otherwise of the following Assertion [a] and the Reason [r].

Assertion: Fast decoupled load flow method gives approximate load flow solution because it uses several assumptions.

Reason: Accuracy depends on the power mismatch vector tolerance.

  1. Both [a] and [r] are true and [r] is the correct reason for [a].
  2. Both [a] and [r] are true but [r] is not the correct reason for [a].
  3. Both [a] and [r] are false.
  4. [a] is false and [r] is true.

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Correct answer: (D) [a] is false and [r] is true.

Explanation

The fast decoupled method uses simplifications only in the Jacobian, which affects how fast it converges. It stops when the power mismatch falls below the tolerance, so it reaches the same accurate solution as a full load flow, and its accuracy depends on that tolerance. So the assertion is false and the reason is true.