Zero seq. and positive seq. impedance of single phase line

[Uquresh1]

The positive seq. impedance and the zero seq. impedance for a single phase line are the same.??
recently i got some data for the line impedances for distribution lines. A single phase line has been tapped off from a 3-phase line. The single phase line's zero sequence impedance is not the same as its positive seq. impedance, which I thought is usually the case.

 

[bacon4life]

What sort of definition are you using for sequence components? I am confused how you can have more than one impedance for only one path.

 

[odlanor]

Fortescue demonstrated that any set of N unbalanced phasors — that is, any such "polyphase" signal — could be expressed as the sum of N symmetrical sets of balanced phasors known as symmetrical components.
Conclusion:
It is applied only to three-phase(polyphase) system

 

[davidbeach]

If all you have is one phase conductor and one neutral conductor you have only one impedance. Add in a second phase conductor and you have a 3-phase system with a "series open" fault and all three sequnce impedance, simplified slightly by negative and positive having the same value. That series open fault along with what ever else you want to analyze will make it lots of fun. ;-)

 

[stevenal]

If you are looking at a fault on the tap line to find current at the three phase source, treat the tap line impedance like you would treat fault impedance. 3* the tap line impedance would be added to your zero sequence circuit.

 

[pwrtran]

Uquresh1

You cannot separate single phase from 3-phase even you are interested in Z0 on a single phase lateral. It is still from a 3-phase system. There is no much difference between a 3-phase and a single phase in terms of zero sequence impedance calculation if you stand at the fault location looking back into the system. You may have a larger Z1 (single phase lateral taking off from a 3phase transformer), but the Z0 will be determined by your first upstream 3-phase transformer's winding configuration.