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Equipment Ground Conductor (EGC) on delta system with a grounding transformer

rockman7892

Electrical
Apr 7, 2008
1,168
On an industrial or renewable site that is served from the Delta side of an interconnection transformer and has a grounding transformer (wye -delta) for sourcing ground fault current and limiting overvoltage, is an equipment ground conductor (EGC) as required by NEC still appliable to this system to carry fault current from equipment back to the neutral of the grounding transformer?

Similarly to how the NEC requires and EGC on typical wye systems to carry fault current would this still be applicable on a delta system with a grounding transformer? I would think yes since the intent would still be to provide a path for fault current back to its source.

For example is there was a L-G fault in the delta winding in the transformer, and EGC would be needed to carry fault current from fault location, to transformer ground, along the EGC back to the source at the grounding transformer. Am i looking at this correct?
 
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Yes.
However you may be overlooking the safety aspect of equipment grounding conductors.
A fault to an ungrounded equipment enclosure such as a motor frame or a junction box will typically energize the enclosure to about1/1.73 of line to line voltage.
The source is the capacity to ground of the system.
While there will seldom be enough current to do serious damage, there will often be enough current to be lethal.
The Equipment Grounding Conductor limits the current on the surface of equipment.
Don't look for a loop-hole on EGCs.
There isn't any.
Even an ungrounded system (delta or single phase) and also high resistance grounded systems must have EGCs.
 

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