Distance Relay

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yaoyaodes

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Can anyone explain to me the 9.2t. I am so confused about the distance relay topic.
 

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For Relay A, the primary impedances for the required distance settings are:
  • the Z1 setting is 80% of impedance 1-2, or 0.8(4 + j20) ohms = 3.2 + j16 ohms.
  • the Z2 setting is 120% of impedance 1-2, or 1.2(4+l20) ohms = 4.8 + j24 ohms.
  • the Z3 setting is 100% of impedance 1-2 plus 120% impedance 2-3, or 1(4 + j20) ohms + 1.2(6 + j24) ohms, for a total of 11.2 + j48.8 ohms.
Since the question asks for the result for each setting in secondary impedance, not primary impedance, you need to divide each of these by the primary-to-secondary impedance ratio, which is the VT ratio/CT ratio, or (600/1)/(200/5), or 15.

Thus, the answer is B
 
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