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3-winding transformer model in ETAP (impedance)

3-winding transformer model in ETAP (impedance)

3-winding transformer model in ETAP (impedance)

As you may know, in ETAP there's no a "typical data" button available when modelling a three-winding transformer. I want to model a 23/0.4/4.16 kV of 3 MVA.

Would it be ok to model three different two-winding transformer (23/0.4, 23/4.16 and 0.4/4.16 kV) in order to have typical values between sides? If not, which IEC/IEEE reference can I look to have some reference values?


RE: 3-winding transformer model in ETAP (impedance)

J&P has some values, but also explains that choices of winding arrangement and configuration can significantly change the numbers. For instance a transformer with two identical LV windings and HV-LV at 16% can be designed to have either LV-LV of 4% or 28%. Hard to define "typical"!

RE: 3-winding transformer model in ETAP (impedance)

Use of typical values for a three-winding transformer is risky because there is such a possible range. I'd try to get the transformer data from the manufacturer. I've been able to do this for some very old transformers - at least for US transformers. If this is a new transformer, ask potential suppliers to give you a ballpark quote with estimated impedances.

RE: 3-winding transformer model in ETAP (impedance)

In case of three winding transformers, test reports and GTP normally furnish three impedances - HV-LV-1, HV-LV2 and LV1-LV2. From these three impedances one can calculate H,L1 &L2 impedance values for use in short circuit current calculations.

RE: 3-winding transformer model in ETAP (impedance)

No you can't do that. I know tertiary deltas can have a range of impedances. Like what was said earlier, I have used the test reports for modeling.

If you can't explain it to a six year old, you don't understand it yourself.

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