I´m woring on a project where I´m using a "3 phase Star-Auto transformer wíth tertiary".
With the following data:
H: 415 kV 500 MVA, L: 145 kV 500 MVA, T:21 kV 140 MVA
H-L 12,7 % @500 MVA
H-T: 10,5 % @140 MVA
L-T: 5,8 % @140 MVA
Which is configured like this in PSCAD:
When doing some tests on fault current levels on the tertiary winding side I can not seem to get the values correct. When only feeding the transformer from the HV side (415 kV 10000 MVA) I get appr. 77 kA on the 21 kV side, expected value is appr. 32 kA.
If using 1.125 pu (3x0.375) on H-T I get the excepted value 32 kA.
What am I doing wrong, is the model correct? Have I entered the values incorrect?