Zig Zag Transformer Ohms Per Phase

[Blackberry77]

Perhaps I am missing something but I am having a hard time understanding the theory behind the equations in IEEE Std C62.92.4. I have done a calculation below but one would think that lower ohms per phase would result in lower ground fault current as the zig zag provides a lower impedance path and redirects more current to the phases during a ground fault. However, the equations below would not indicate that lower the desired ground fault current would reduce the zig zag ohms per phase. Modelling this in ETAP, it would agree me with my thought process of lower ohms per phase = less ground fault current. Thoughts?

System Voltage - 44 kV
Using 100 MVA base

Base Ohms = (44000)^2/100000000 = 19.36 Ohms
Base Amps = 100000000/(44000)*(1.732) = 1313 Amps
Three Phase Fault Duty = 6.4 kA
Three Phase Fault MVA = 44000*1.732*6400 = 415 MVA
Z1=Z2=100/415 = 0.241 PU
Desired Ground Fault Current = 770 A
Ground Fault Current Ig = 770/1313 = 0.586 PU
Io = 0.586/3 = 0.195 PU
Z(total) = 1.0/0.195 = 5.128 PU
Z(total) - 2Z(1) = 5.128 - 0.241 - 0.241 = 4.646 PU
Zo = 19.36*4.646 = 89.95 Ohms Per Phase
Short Time Rating = (44000/3)*(770) = 11.3 MVA