How to find the transformer sequence impedance
- Thread starter nan_david
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barbeer
Senior Member
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- Pinellas County, FL
I personally can think of quite a few better things to do at 10:36 than worry about the transformers whosa whatsi! 
Sleep is at the top of the list.
Sleep is at the top of the list.
wirenut1980
Senior Member
- Location
- Plainfield, IN
Data sheets might be needed, but before you hunt for them consider this. Positive sequence and negative sequence impedances are generally equal for transformers. And I believe you can use the %Z (converted to per unit) for this value depending on what the units are that the modeling program is asking for.
Zero sequence impedance is infinite if the transformer has a delta winding. If both windings are wye connected, I think it might be the same as the positive sequence value as well unless there is a neutral resistor installed.
What are the imedance units of measure the program is asking for?
Zero sequence impedance is infinite if the transformer has a delta winding. If both windings are wye connected, I think it might be the same as the positive sequence value as well unless there is a neutral resistor installed.
What are the imedance units of measure the program is asking for?
Thanks for your advice...Currently I'm doing the hands on calculation, have not using the software yet. For my own calculation, I all use PU...
So for the wye wye connection transformer with neutral to ground resistor on secondary side, how can I find its zero sequence impedance? Pls advice...
BTW, could you please also advice how to find the postive-, negative- and zero sequence impedance of the generator(Wye connection without neutral to ground resistor)? Thanks
So for the wye wye connection transformer with neutral to ground resistor on secondary side, how can I find its zero sequence impedance? Pls advice...
BTW, could you please also advice how to find the postive-, negative- and zero sequence impedance of the generator(Wye connection without neutral to ground resistor)? Thanks
beanland
Senior Member
- Location
- Vancouver, WA
Transformer Impedance
Transformer Impedance
Generally, manufacturers can provide the nominal percent impedance for the transformer. Values are ususally in percent. In most cases, they provide the positive-sequence impedance. For most delta-wye transformers, this is the zero-sequence impedance as well. For wye-wye three-leg core transformers, the zero sequence impedance can be very different from the positive sequence and the manufacturer will need to provide.
Transformer Impedance
Generally, manufacturers can provide the nominal percent impedance for the transformer. Values are ususally in percent. In most cases, they provide the positive-sequence impedance. For most delta-wye transformers, this is the zero-sequence impedance as well. For wye-wye three-leg core transformers, the zero sequence impedance can be very different from the positive sequence and the manufacturer will need to provide.
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