Transformer Sequence Networks in Per Unit

Transformer sequence networks in per unit show how three-phase transformers respond to positive-, negative-, and zero-sequence currents. For an ideal Y-Y transformer grounded through neutral impedances, the per-unit sequence networks act much like those of a single-phase ideal transformer when the current is balanced. Balanc...

An ideal Y-Y transformer grounded via neutral impedances has per-unit sequence networks similar to a single-phase transformer when balanced positive or negative-sequence currents flow, negating neutral currents and voltage drops.

Zero-sequence currents from all three phases combine to form a neutral current, causing voltage drops across t...