Which problem arises in a three-phase power transformer when D-Y vector group windings experience unequal impedance loading?

💡 Explanation

When a D-Y transformer with unequal impedance loading experiences imbalances, zero-sequence currents circulate generating an unbalanced core flux because the delta winding's impedance differs per phase. Therefore, core overheating is caused, rather than harmonic amplification, system resonance, or voltage sag, requiring alternative conditions/setups.

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