I want to calculate the decaying time of asymmetrical short circuit current.So I need x/r ratio.Should I only use zero sequence impedance or all sequence impedances for a L-G fault to calculate the x/r ratio?
The XR Ratio of a transformer is the imaginery portion (j), of the impedance divided by the Real part. In your case considerations are: are you trying to calculate it as a network sequence or separate line entities, this makes a difference of what will result. Typically the best way to calculate this is: at the point of the Fault itself, you would use the Thevinin Equivalent, but are you trying to find the fault of the resultant phase currents at the fault location or somehow the network which is not very accurate?
You have to used all sequence impedance (Z+, Z-, Z0), of LG fault to calculate fault impedance Z, and as resistance is constant could find X/R ratio accurately..
Hi
You can calculate x/r by two voltage source (DC & AC) and a multimeter.
By dc source you can caculate (( r )). Because we have any reactance in dc source.
In next level, by ac voltage source you can get (( z )).
So by having Z & r you can caculate x/r.