Hello,
I'm trying to calculate the winding-pair X/R ratios of a three-wound 132/22/22kV, 200/100/100MVA transformer. This is required in my ETAP model.
The datasheet provides the winding-pair Z's, but not the winding-pair Load Losses, only the resistances of the individual windings.
Theoretically the winding-pair load losses would be calculated during the impedance test. How can the individual winding resistances be used to calculate the equivalent winding-pair resistances, or winding-pair load losses, bearing in mind the three windings have different rated powers Sr.
IEC 60076-8 explains how equivalent individual winding impedances and load losses can be calculated using the winding-pair values, using delta-star transformation. This transformation can theoretically be done in reverse, but the base power usage is unclear to me.
The normal X/R ratio equation includes Sr, but for a three-winding transformer there are at least two winding base power, so which should be used?
Any help's much appreciated.