Calculation of negative sequence impedance (in %) for Generator

Rating of 3phase generator is as follows- MVA-605MVA Rated pf=0.85 lag Rated voltage- 20 KV Rated current-17465 Direct Axis Synchronous reactance(Xd)= 193% Quadrature axis synchronous reactance (Xq)= 234% Negative Sequence reactanceX2= 19.4% Zero Sequence reactance = 12.6% Resistance of stator winding per phase = 0.00131 ohm This 3 phase Generator is connected with three single phase transformers. Rating for R phase transformer is as follows- MVA-200MVA Voltage ratio= 21KV/420KV Vector group- YNd1 Short circuit impedance(positive sequence) = 13.5% Zero sequence impedance= 13.5% whereas Ratings of other Y and B transformer are same . which is as follows MVA-200MVA Voltage ratio- 20KV/400KV HV current = 873.6 LV current =10083 Vector Group-YNd1 Short circuit impedance (positive sequence )= 14.5% Short circuit impedance (zero sequence )=14.5% HV side of these transformers are connected with Grid .calculate negative sequence impedance of generator in % because of unbalance in transformer rating.