Hello im doing a study of arc flash in an industrial environment, using IEEE std 1584 2018.
The network in question has an almost completely radial structure with mostly overcurrent relays.
Im trying to test for arc flash on the LV conductor of transformers.

The transformers used to transform HV (10kV) to LV (400V) are quite large, open air, oil based and have very large electrical gaps between the LV phases, around 15 to 20 cm( 8 to 10 inches). For measurement data see the attached file.

The problem is that the IEEE standard has a standard and max gap at much less than that for LV equipment. The simulation software im using only allows for a gap of 72mm at 400V. With the large gaps leads to the arching current being much smaller than the short circuit current, so much infact that the protection will take over 7 seconds to open the circuit, leading to massive amounts of incident energies. To fix this alot of protection plans would have to be redone.

The thing im mainly wondering about is if there is a real possibility that there could occurre a sustaining arc between the LV conducters when they have such a large gap between them?
I have read an IEEE report, ARC FLASH TESTING OF TYPICAL 480V Utlilty equipment, talking about the unlikeliness of arcs sustaining at so low voltages with that large gaps, but that was for a different kind of transformer. There is not much experience about arc flash here in Norway so i was curious if anyone here had any thoughts and or experience about the situation. The IEEE is not a law in Norway, but it is a recommendation.

Although I referenced "Pad Mounted" transformers, the same issue exists so I made this a formal survey question for this week. We will see where it goes.