Three-winding transformer damage curve

[ciy]

Dear all,
There is a three-winding transformer rated:
345/13.8/6.9 kV transformer;
92/54.5/37.5 MVA
The impedance percentage of PS/PT/ST is 16/13/1.9%.
Please advise how to draw its damage curve?
What is the difference between the 2 winding and 3 winding transformer?
Thanks for your help in advance.
Stanley

 

[EverGreen1231]

As to how one would go about drawing this by hand, I don't know; but the main difference in a 2 winding vs. a 3 winding transformer is the fact that the tertiary windings have effects on the 3rd harmonic currents and stabilization of the neutral that you would not have were there only two windings.

 

[cranky108]

What damage are you wanting to protect for? Winding or core?
The windings can be calculated on there own basis (nameplate rating of each winding). I have no idea how to protect the core (a large hunk of steel).

The delta winding is typical to be sized at 35% of the other two windings.

 

[ciy]

Thanks for your reply from Evergreen1231 and cranky108.
The tertiary winding is also Wye connection.
I wonder which damage curve of winding should be concerned?
Secondary winding? Tertiary winding?

 

[cranky108]

All of them.