transformer impedance

[bxny]

For a single phase, 285MVA, generator step up transformer (which is part of a 3-phase bank), 23kV - 425kV, how do I calculate the transformer impedance at the minimum and maximum taps? The transformer has an off load tap changer on the high voltage winding.

 

[davidbeach]

You look at the test report and see what the impedances are at those taps. It may be linear, but it may not. There was a thread here not too long ago that you might look up.

 

[bxny]

thankyou, davidbeach

 

[IndianTechEngg1001]

bxny, just a general question. Why you need these impedance? Normally for SC calculation for distribution transformers I have been using %Z.

Is this for protection relay setting purpose?

 

[mgtrp]

Um... %Z is just the per unit impedance converted to a percentage - it's just a different way of expressing the same thing.