I have quite a simple system. Contains one substation, feeder pillar and 3 houses. I have calculated the short circuit current that the transfromer in the substation can deliver but is there any one that can help me with finding the equations to calculate the short circuit current level supplied by the cables and house.

Short circuit calculation..
1. compute the PU (per unit ) value of utility source (puZs)
puZs=kva base/utility Short Circuit KVA

2. Compute PU for Tranformer Source (puZt)
puZt = % Z of transformer/100

3. Compute PU value of feeder line
Cable impedanceXlength /1000/m

Convert cable impedance form ohm to PU (pu Zc)
puZc = impedance in ohms/kvsqrX kv base/1000

4. Draw impedance Diagram
5. Draw simplified diagram with values
6. Add the total PU impedance (puZt)
7. Compute short circuit current

Isc = PU Voltage/puZt X base KVAx1000/1.73xbase voltage