Transformer Temporary Replacement 1

[nightfox1925]

Can we temporarily replace 5 MVA 34.5KV-Delta/6.6KV-wye Transformer with a 10MVA 69KV-Delta/13.2KV-wye Power?

Based from the transformation ratio, assuming the 10MVA at nominal tap, if 34.5kV is induced at the 69kV primary, this will result to 6.6kV at the secondary. Are there any repercussions to consider?

 

[davidbeach]

I think it should work. The transformer will only have a 5MVA rating at 34.5kV.

 

[waross]

The impedance of the transformer will not change, but the per unit impedance will change in inverse ratio to the rated voltage change. You will be, in effect, rerating the transformer at 50% of the original KVA so the per unit impedance will double from the nameplate value. You may want to review your protection settings.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[nightfox1925]

Thanks waross, that's a good flag. The P.U. Z will change due to changes in the base voltages and so as the short circuit levels.