X/R ratio 1

[lsuengineer]

I am trying to calculate the fault current on the low side of a transformer. The Transformer parameters are 69kV high side to 12.47kV low side, 40/55/67MVA, 11% impedance. With all of this said how does the X/R ratio figured into the equation?

And what is the "K" factor of a transformer?

 

[dpc]

The X/R ratio of the system (with the transformer dominating) will determine the maximum possible asymmetrical current. It does not have a big impact on the symmetrical current.

Transformer X/R is not generally available directly, but can be computed from the transformer impedance and transformer losses, if known.

"K" factor is a measure of the transformer's ability to handle harmonic currents without overheating.

 

[dgbpeakpwr]

If you need a number, for some preliminary calculations, I recently was given a quote on an identical transformer with an X/R around 27.

are you working on a project in san deigo?