Fault Current for Multiple Transformers in Single-Phase App

dear,

definitely, fault currents at secondary out put terminals will be cumulative of individual fault currents of 3 transformers of 167 kva. Simple reaon, at any junction point,

I = I1+I2+I3. wether it is normal load current or fault current.

so,

at secondary out put terminal, fuse shall be to suit 3*167kva = 501 kva.

while, secondary out of each 3 transformers shall be to suit 167 kva.

I would think you would be want to use the lesser fault value to insure safety of the residence but if your concerned with the equipment then place a fault on both sides one slightly greater in value before the transformer group and one just after before the actual connection to the residential drop.

For the coordination study, it depends on where the fuses are installed. The fuses that are installed in the common circuits of the primary and secondary sides, the sum of the faults currents through the individual transformers should be considered. However, in this case, you must use the fuses (or other protection) for the individual transformers, because the fuse installed in the common circuits doesn't protect the individual transformers. For the individual transformer protection coordination, you have to consider the fault currents through the individual transformers.

- MS

exactly and this value should reflect the individual value of the transformer in it connection before and after so that both side are protected additionally for greater safety the collective neutral loops of the collective (transformer groups) should be fused as well to prevent damage from feed back along the neutral lines during inclement weather many time while attempting to divide and multiply windings the neutral side is ignored and this is a serious mistake