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In a 3-phase, 4-wire unbalanced system, the magnitude of zero sequence current is __________ the current in the neutral wire. 

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HPCL Engineer Electrical 01 Nov 2022 Official Paper
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  1. half of
  2. one-third
  3. twice
  4. three times

Answer (Detailed Solution Below)

Option 2 : one-third
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Detailed Solution

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The correct answer is option 2):(one third)

Concept:

  • In a 3-phase 4 wire unbalanced system, the magnitude of the zero-sequence component is one-third current in the neutral wire.
  • Negative sequence currents are involved when an unbalanced fault occurs in the system.
  • Zero sequence currents are involved when an unbalanced ground fault occurs in the system.
  • For an unbalanced fault with paths for zero sequence currents, at the point of fault both negative and zero sequence voltages are maximum.
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