Where to find typical values fot transformer impedances?

[basghari]

Hi everybody,

I'm trying to write some codes to simulate a 30MVA, 138kV three-phase three-winding transformer. For writing a simulation program similar to BCTRAN in EMTP, positive and zero sequence short circuit impedances of transformer in addition to its magnetic curve are needed. Since the code will be revised later, I just need a very rough estimate of these values so that my results seem reasonable. I have looked all over the web, IEEE standards and different textbooks but with no success to find any typical values for these impedances. Can anybody tell me to where to look for these values?

 

[rbulsara]

Contact some of the manufacturers of such transformers. For example ABB or GE etc. Speak to their engineering group, I am sure they can help you out.

30MVA would not be a off-he shelf unit and I doubt if you will find catalog cuts for such a unit. Best you can have if someone here working with utilities can provide values of the existing units of the comparable ratings that they know of.

 

[rbulsara]

SKM program gives a typcial (default) value of Z as 7.1% (R=0.2736 and X=7.095) and typcial X/R ratio as 25. If this is of any help. It calculates zero seq R and X same as the positive seq.

The program has separate field to accept neutral impedance data.

 

[dpc]

IEEE Red Book (IEEE 141)

 

[MJJBEE]

There is also an ANSI standard for transformers however at those sizes you can get a lot of different values depending on how you write the spec.