An unbalanced three-phase circuit is one that contains at least one source or load that does not possess three-phase symmetry. A source with the three source-function magnitudes unequal and/or the successive phase displacements different from 120° can make a circuit unbalanced. Similarly, a three-phase load with unequal phase impedance values can make a circuit unbalanced.

The single-phase equivalent circuit technique of analysis does not work for unbalanced three-phase circuits. General circuit analysis techniques like mesh analysis or nodal analysis will have to be employed for analysing such circuits.

9.4.1 Unbalanced Y–Y Circuit

Y–Y connection is typically used in the last mile in a power system, ...

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