Help with Fault Current calculations, single-phase

[Volta]

I am trying to figure out the available fault current at the fourth point on a system. I haven't done this before, can you check my work?
Long post, sorry. Aaaand, I'm not great with significant digits either, so rounding errors are expected. :blink:

Given:
Infinite POCO primary (13.2kV);
167 kVA transformer, pad-mounted;
1.9% Impedance;
240/120 volt secondary.
Calling that point X1.

Lateral is 4" PVC, containing 2 sets of 3/0 THW, calling it 61' of conductor length.
Feeds a bussed wireway, 2' long, so for simplicity I am adding that to my first length and calling it 63' of paralleled 3/0 and ignoring the 24" of ferrous wireway. Calling that point X2.

Service 'tap' is one set 3/0 cu through meter to fusible disconnect, maybe RK5 fuses, 200 amps. Figuring it is 8' to the line side of switch, calling that point X3.

From load of service disconnect 2" PVC through basement to MLO Sqd QO panel. Using 250 kcmil compact aluminum, figuring that to be 35' of conductor. Calling that point X4.

So, for X1 (transformer secondary-
FLA = (167 x 1000) / 240 = 695.8
Multiplier = 100 / 1.9 = 52.63
IscX1 = 695.8 x 52.63 = 36620 L-L
IscX1n = 36620 x 1.5 = 54930 L-N.

Q1: That is my first (known :roll point of confusion- can this be right? For a L-N fault I can see the impedance as 50% of full winding, but do I still use the voltage of the full (240)? Or is that why 1.5 can be a multiplier?


For X2 (lateral to bussed wireway)-
From IEEE Std 241-1990 (Gray Book) via Cooper Bussmann the 'C' value for 3/0 cu in non-magnetic conduit is 13923.
'f' factor L-L = 2 x 63 x 36620 / 2 (sets) x 13923 x 240 = .6904
Multiplier = 1 / (1 + .6904) = .5916
IscX2 = 36620 x .5916 = 21663 L-L
'f' factor L-N = 1.5 x 2 x 63 x 36620 / 2 (sets) x 13923 x 240 x .5 = 2.0713
Multiplier = 1 / (1 + 2.0713) = .3256
IscX2n = .3256 x 54930 = 17885 L-N.

Q2: Is it expected that L-N starts higher, then drops below L-L due to lower voltage?


For X3 (service disconnect)-
'f' factor L-L = 2 x 8 x 36620 / 13923 x 240 = .0519
Multiplier = 1 / (1 + .0519) = .9507
IscX3 = 21663 x .9507 = 19627 L-L
'f' factor L-N = 1.5 x 2 x 8 x 21663 / 13923 x 240 x .5 = .3112
Multiplier = 1 / (1 + .3112) = .7627
IscX3n = .7627 x 17885 = 13641 L-N.


Lastly, for the panel I must install a breaker in, location X4-
'f' factor L-L = 2 x 35 x 19627 / 12862 ('C' of 250 kcmil al) x 240 = .2225
Multiplier = 1 / (1 + .2225) = .8180
IscX4 = 19627 x .818 = 13582 L-L
'f' factor L-N = 1.5 x 2 x 35 x 19627 / 12862 x 240 x .5 = 1.3352
Multiplier = 1 / (1 + 1.3352) = .4282
IscX4n = .4282 x 13641 = 5841 L-N.

Whew!
Am I on the right track? :dunce:

 

[bob]

Every thing matched except

IscX3n = 15271 L-N.

IscX4 = 14582 L-L

IscX4n = 9876 L-N.
Results from fault current program.

 

[Volta]

Every thing matched except

IscX3n = 15271 L-N.

IscX4 = 14582 L-L

IscX4n = 9876 L-N.
Results from fault current program.

Thanks! I know this is a lot to enter, I appreciate the feedback. In trying to find my errors I do see where the result for 'f' factor for X4 is shown as half what it should be, as if I had considered it L-N rather than L-L.
It does seem that the math following uses the correct .4450 rather than the .2225, and I don't see yet otherwise how my values came out below your program.
I also can't find the problem on those last two neutral calcs.
Any ideas?

...
For X3 (service disconnect)-
'f' factor L-L = 2 x 8 x 36620 / 13923 x 240 = .0519
Multiplier = 1 / (1 + .0519) = .9507
IscX3 = 21663 x .9507 = 19627 L-L
'f' factor L-N = 1.5 x 2 x 8 x 21663 / 13923 x 240 x .5 = .3112
Multiplier = 1 / (1 + .3112) = .7627
IscX3n = .7627 x 17885 = 13641? L-N.


Lastly, for the panel I must install a breaker in, location X4-
'f' factor L-L = 2 x 35 x 19627 / 12862 ('C' of 250 kcmil al) x 240 = .2225 should be .4450
Multiplier = 1 / (1 + .2225) = .8180 use .4450 = .6920
IscX4 = 19627 x .818 use .6920 = 13582 L-L somehow that was already figured that way, still 1000 under your result...
'f' factor L-N = 1.5 x 2 x 35 x 19627 / 12862 x 240 x .5 = 1.3352
Multiplier = 1 / (1 + 1.3352) = .4282
IscX4n = .4282 x 13641 = 5841? L-N.
....