Wire impedance

[Fuselink]

II need to calculate the impedance for 3-1/c #1/0 RW90 wires in steel conduit. This is the secondary of 240V single phase transformer. I have the values for 3-1/c wires and somebody told me that for 2 wire the impedance will double!
I can’t find any reference to this to back it up and he says it’s based on experience. Any idea how I can calculate this.
Thank you

 

[cuky2000]

Will be double only for single phase applications since the return conductor should be counted for the total length.

For three phase applications, the current in the return conductor is reducced to be zero for balance conditions with not significant harmonics.

 

[Fuselink]

So, this means that for SLG fault study I need use double the impedance and for LL faults the 3C model will work right?
As I mentioned, transformer secondary is 120/240v.
I am not sure if SKM will consider this automatically or I need to pt two cables inseries to double up impedance?

 

[cuky2000]

The way that SKM work is using the symetrical components. For SLG fault in three phase systems, the fault current is the one that flows in the sequence impedances plus three times the ground impedance in series.