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GATE 2022 EE – Question 15

Power Systems · Symmetrical components, Symmetrical and unsymmetrical fault analysis · 1 mark · Multiple choice

The valid positive, negative and zero sequence impedances (in p.u.), respectively, for a 220 kV, fully transposed three-phase transmission line, from the given choices are

  1. $1.1,\ 0.15$ and $0.08$
  2. $0.15,\ 0.15$ and $0.35$
  3. $0.2,\ 0.2$ and $0.2$
  4. $0.1,\ 0.3$ and $0.1$

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Show answer and explanation

Correct answer: (B) $0.15,\ 0.15$ and $0.35$

Explanation

For a fully transposed transmission line (a static, symmetric network) the positive and negative sequence impedances are equal, and the zero sequence impedance is larger, typically 2 to 3.5 times the positive sequence value. Only option B satisfies this.