scottf-
in the case of Rct=4Ohm, Usat would be 340V resulting in
ALF = 340V/1/(4+15)=18 (5P18) for Zx=15VA
My point is, Rct has to be taken into account. Depending on its value compared to the external burden its impact might be large.
Please note you have include the internal burden (Rct) for calculation of the saturation at another burden as specified. For Class 5P.. and 10P.. CTs the result will be lower as given above!
Proceed as follows:
- retrieve the sec. winding resistance Rct from testreport or manufacturers...