The X/R ratio for the 1600kVA Trihal transformer can be calculated using the Trihal electrical characteristics (impedance & losses data) given normally in transformer datasheets
(attached )
values given in transformer datasheet:
-Load losses in Watts (at 75 C),
-No-load losses in Watts, and
-rated impedance voltage = Z%.

then calculation of the X/R ratio can be performed as follows:
we can obtain the R% as follows:
-R% = 100 x
[(Full load loss (W)-no load loss (W))/(transformer rated power (kVA)x1000)]

then using the impedance relation: Z = R+jX,
we can calculate X% = √(Z%² - R%²),
hence you can get X%/R% = X/R ratio.

Remarks:
1) Datasheets for both "standard losses" type and "reduced losses" type Trihal transformers are attached .
Also the impedance value shall be clear on transformer nameplate.

2) an example of above calculation has been attached for your reference.

Best regards.

Released for:Schneider Electric Egypt and North East Africa