ground fault return path within a distribution system

[Tfret]

Hello, I need to better understand the return path of ground fault current within a complex factory power distribution system. Will fault current only return to the source transformer ground connection? Our system has multiple large transformers with grounded secondaries. Could some current travel to other transformer grounds connections?

 

[zbang]

Assuming that no ungrounded leads of any transformer secondaries connect (which would generally be a Bad Thing), only one SDS/transformer can supply current to a single fault on it's secondary side*, but the fault current will to return to that source over all possible paths (in proportion to their impedance).

So yes, depending on how the wires are routed, fault current from transformer A could get as far as one end of the bonding jumper in transformer B but won't enter the transformer windings.

* a line-to-line fault between different SDSs is a whole 'nother matter.

 

[Tfret]

So the fault current is only going to return to the transformer that sourced it (through what ever paths that may be)? Is that correct?

 

[GoldDigger]

So the fault current is only going to return to the transformer that sourced it (through what ever paths that may be)? Is that correct?

That is an absolutely correct realization.
In extreme cases some of those paths even go through a different transformer to get there.
But the current at both ends of the winding in question must be identical unless the fault is within the winding.

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