What is positive to negative sequence coupling and negative to positive sequence coupling ?

[EddyWirbelstrom]

When calculating voltage imbalance, what is the positive to negative sequence coupling ( Z12 ) and negative to positive sequence coupling ( Z21 ) at the point of common coupling, in relation to unbalanced voltage ? How is it determined ?
The utility has only provided positive ( Z1 ) , negative ( Z2 ) and zero ( Zo ) sequence impedance at the point of common coupling.
If both Utility ( source ) and load were balanced, there would only be positive sequence currents and voltages.

 

[mparenteau]

Mutual coupling...

Mike

 

[7anoter4]

See:
EPRI AC Transmission Line Reference Book—200 kV and Above, Third Edition
Chapter 2: Electrical Characteristics of Conductor Configurations and Circuits